GIFT  OF 


A    DICTIONARY 


OF 


ELECTRICAL    WORDS, 


TERMS  AND  PHRASES. 


BY 

EDWIN  J.  HOUSTON,   A.M.,   Ph.D.     (Princeton), 

EMERITUS    PROFESSOR  OF    NATURAL    PHILOSOPHY   AND    PHYSICAL   GEOGRAPHY   IN   THE   CENTRAL 
HIGH  SCHOOL  OF  PHILADELPHIA  ;    PROFESSOR  OF   PHYSICS  IN  THE  FRANKLIN 
INSTITUTE  OF  PENNSYLVANIA  J    ELECTRICIAN   OF  THE  INTER- 
NATIONAL  ELECTRICAL   EXHIBITION, 
ETC.,   ETC. 


FOURTH  EDITION.       WITH  APPENDIX.       GREATLY  ENLARGED, 


NEW  YORK: 

McGRAW    PUBLISHING    COMPANY, 

114  LIBERTY  STREET. 


vt 


Copyright,  1889,  1892,  1894,  1898 

BT 

THB  W.  J.  JOHNSTON  COMPANY 


Appendix  B. 
Copyright,  1898 

BT 

EDWIN  J.  HOUSTON 


PREFACE  TO  THE  FIRST   EDITION. 

fT>HE  rapid  growth  of  electrical  science,  and  the  almost  daily  addition  to  it  of  new 
1  words,  terms  and  phrases,  coined,  as  they  too  frequently  are,  in  ignorance  of 
ihose  already  existing,  have  led  to  the  production  of  an  electrical  vocabulary  that  is 
already  bewildering  in  its  extent.  This  multiplicity  of  words  is  extremely  discourag- 
ing to  the  student,  and  acts  as  a  serious  obstacle  to  a  general  dissemination  of  elec- 
trical knowledge,  for  the  following  reasons  : 

1.  Because,  in  general,  these  new  terms  are  not  to  be  found  ever,  in  the  unabridged 
editions  of  dictionaries. 

2.  The  books  or  magazines,  in  which  they  were  first  proposed,   are  either  inac- 
cessible to  the  ordinary  reader,  or,  if  accessible,   are  often  written  in  phraseology  un- 
intelligible except  to  the  expert. 

3.  The  same  terms  are  used  by  different  writers  in  conflicting  senses. 

4.  The  same  terms  are  used  with  entirely  different  meanings. 

5.  Nearly  all  the  explanations  in  the  technical  dictionaries  are  extremely  brief  as 
regards  the  words,  terms  and  phrases  of  the  rapidly  growing  and  comparatively  new 
science  of  electricity. 

In  this  era  of  extended  newspaper  and  periodical  publication,  new  words  are  often 
-coined,  although  others,  already  in  existence,  are  far  better  suited  to  express  the  same 
ideas.  The  new  terms  are  used  for  a  while  and  then  abandoned  ;  or,  if  retained, 
having  been  imperfectly  denned,  their  exact  meaning  is  capable  of  no  little  ambiguity; 
and,  subsequently,  they  are  often  unfortunately  adopted  by  different  writers  with  such 
varying  shades  of  meaning,  that  it  is  difficult  to  understand  their  true  and  exact 
significance. 

Then  again,  old  terms  buried  away  many  decades  ago  and  long  since  forgotten,  are 
dug  up  and  presented  in  such  new  garb  that  their  creators  would  most  certainly  fail 
to  recognize  them. 

It  has  been  with  a  hope  of  removing  these  difficulties  to  some  extent  that  the  author 
has  ventured  to  present  this  Dictionary  of  Electrical  Words,  Terms  and  Phrases  to  his 
brother  electricians  and  the  public  generally. 

He  trusts  that  this  dictionary  will  be  of  use  to  electricians,  not  only  by  showing  the 
wonderful  extent  and  richness  of  the  vocabulary  of  the  science,  but  also  by  giving  the 
general  consensus  of  opinion  as  to  the  significance  of  its  different  words,  terms  or 
phrases.  It  is,  however,  to  the  general  public,  to  whom  it  is  not  only  a  matter  of 
interest  but  also  one  of  necessity  to  fully  understand  the  exact  meaning  of  electrical 
literature,- that  the  author  believes  the  bo^k  will  be  of  the  greatest  value. 

In  order  to  leave  no  doubt  concerning  the  precise  meaning  of  the  words,  terms  and 
phrases  thus  defined,  the  following  plan  has  been  adopted  of  giving  : 

(i.)  A  concise  definition  of  the  word,  term  or  phrase. 

(2.)  A  brief  statement  of  the  principles  of  the  science  involved  in  the  definition. 

i  — V.JL.    I 


2870 


(3. )  Where  possible  and  advisable,  a  cut  of  the  apparatus  described  or  employed 
in  connection  with  the  word,  term  or  phrase  defined. 

It  will  be  noticed  that  the  second  item  of  the  plan  makes  the  Dictionary  ap- 
proach to  some  extent  the  nature  of  an  Encyclopedia.  It  differs,  however,  from 
an  Encyclopedia  in  its  scope,  as  well  as  in  the  fact  that  its  definitions  in  all  cases 
are  concise. 

Considerable  labor  has  been  expended  in  the  collection  of  the  vocabulary,  for 
which  purpose  electrical  literature  generally  has  been  explored.  In  the  alphabetical 
arrangement  of  the  terms  and  phrases  defined,  much  perplexity  has  arisen  as  to  the 
proper  catch-word  under  which  to  place  them.  It  is  believed  that  part  of  the 
difficulty  in  this  respect  has  been  avoided  by  the  free  use  of  cross  references. 

In  elucidating  the  exact  meaning  of  terms  by  a  brief  statement  of  the  principles 
of  the  science  involved  therein,  the  author  has  freely  referred  to  standard  textbooks  on 
electricity,  and  to  periodical  literature  generally.  He  is  especially  indebted  to  works 
or  treatises  by  the  following  authors,  viz.  :  S.  P.  Thompson,  Larden,  Gumming, 
Hering,  Prescott,  Ayrton,  Ayrton  and  Perry,  Pope,  Lockwood,  Sir  William  Thom- 
son, Fleming,  Martin  and  Wetzler,  Preece,  Preece  and  Sivewright,  Forbes,  Max- 
well, De  Watteville,  J.  T.  Sprague,  Culley,  Mascart  and  Joubert,  Schwendler, 
Fontaine,  Noad,  Smee,  Depretz,  De  la  Rive,  Harris,  Franklin,  Cavallo,  Grove, 
Hare,  Daniell,  Faraday  and  very  many  others. 

The  author  offers  his  Dictionary  to  his  fellow  electricians  as  a  starting  point  only. 
He  does  not  doubt  that  his  book  will  be  found  to  contain  many  inaccuracies,  ambig- 
uous statements,  and  possibly  doubtful  definitions.  Pioneer  work  of  this  character 
must,  almost  of  necessity,  be  marked  by  incompleteness.  He,  therefore,  invites 
the  friendly  criticisms  of  electricians  generally,  as  to  errors  of  omission  and  commis- 
sion, hoping  in  this  way  to  be  able  finally  to  crystallize  a  complete  vocabulary  of 
electrical  words,  terms  and  phrases. 

The  author  desires  in  conclusion  to  acknowledge  his  indebtedness  to  his  friends, 
Mr.  Carl  Hering,  Mr.  Joseph  Wetzler  and  Mr.  T.  C.  Martin,  for  critical  exami- 
nation of  the  proof  sheets ;  to  Dr.  G.  G.  Faught  for  examination  of  the  proofs  of 
the  parts  relating  to  the  medical  applications  of  electricity,  and  to  Mr.  C.  E.  Stump 
for  valuable  aid  in  the  illustration  of  the  book ;  also  to  Mr.  George  D.  Fowle, 
Engineer  of  Signals  of  the  Pennsylvania  Railroad  Company,  for  information  concern- 
ing their  System  of  Block  Signaling,  and  to  many  others. 

EDWIN  J.  HOUSTON. 
CENTRAL  HIGH  SCHOOL,.  PHILADELPHIA,  PA., 
SEPTEMBER,   1889. 


PREFACE  TO  THE  SECOND  EDITION. 

THE  first  edition  of  the  "Dictionary  of  Electrical  Words,  Terms  and  Phrases"  met 
with  so  favorable  a  reception  that  the  entire  issue  was  soon  exhausted. 
Although  but  a  comparatively  short  time  has  elapsed  since  its  publication,  electrical 
progress  has  been  so  marked,  and  so  many  new  words,  terms  and  phrases  have  been 
introduced  into  the  electrical  nomenclature,  that  the  preparation  of  a  new  edition  has 
been  determined  on  rather  than  a  mere  reprint  from  the  old  plates. 

The  wonderful  growth  of  electrical  science  may  be  judged  from  the  fact  that  the 
present  work  contains  more  than  double  the  matter  and  about  twice  the  number  of 
definitions  that  appeared  in  the  earlier  work.  Although  some  of  this  increase  has 
been  due  to  words  which  should  have  been  in  the  first  edition,  yet  in  greater  part  it 
has  resulted  from  an  actual  multiplication  of  the  words  used  in  electrical  literature. 

To  a  certain  extent  this  increase  has  been  warranted  either  by  new  applications  of 
electricity  or  by  the  discovery  of  new  principles  of  the  science.  In  some  cases,  how- 
ever, new  words,  terms  or  phrases  have  been  introduced  notwithstanding  the  fact  that 
other  words,  terms  or  phrases  were  already  in  general  use  to  express  the  same  ideas. 

The  character  of  the  work  is  necessarily  encyclopedic.  The  definitions  are  given 
in  the  most  concise  language.  In  order,  however,  to  render  these  definitions  intel- 
ligible, considerable  explanatory  matter  has  been  added. 

The  Dictionary  has  been  practically  rewritten,  and  is  now,  in  reality,  a  new  book 
based  on  the  general  lines  of  the  old  book,  but  considerably  changed  as  to  order  of 
arrangement  and,  to  some  extent,  as  to  method  of  treatment. 

As  expressed  in  its  preface,  the  author  appreciates  the  fact  that  the  earlier  book 
was  tentative  and  incomplete.  Though  the  wide  scope  of  the  second  edition,  the 
vast  number  of  details  included  therein,  and  the  continued  growth  of  the  electrical 
vocabulary  must  also  necessarily  make  this  edition  incomplete,  yet  the  author  ventures 
to  hope  that  it  is  less  incomplete  than  the  first  edition.  He  again  asks  kindly  criti- 
cisms to  aid  him  in  making  any  subsequent  edition  more  nearly  what  a  dictionary  of 
so  important  a  science  should  be. 

The  order  of  arrangement  in  the  first  edition  has  been  considerably  changed.  The 
initial  letter  under  which  the  term  or  phrase  is  defined  is  in  all  cases  that  of  the  noun. 

For  example,  "Electric  Light "  is  defined  under  the  term  "  Light, 'Electric "  ; 

"  Diameter  of  Commutation  "  under  "Commutation,  Diameter  of ,"  "Alter- 
nating Current  Dynamo-Electric  Machine"  under  "Machine,  Dynamo- Electric. 
Alternating  Current  — —  — . "  As  before,  the  book  has  numerous  cross  references. 

Although  the  arrangement  of  the  words,  terms  and  phrases  under  the  initial  letter 
of  the  first  word,  term  or  phrase,  as,  for  example,  "  Electric  Light "  under  the  letter  E, 
might  possess  some  advantages,  yet,  in  the  opinion  of  the  author,  the  educational  value 


VI 

of  the  work  would  be  thereby  considerably  decreased,  since  to  a  great  extent  such  an 
arrangement  would  bring  together  incongruous  portions  of  the  science. 

Frequent  cross  references  render  it  possible  to  use  the  Dictionary  as  a  text-book  in 
connection  with  lectures  in  colleges  and  universities.  With  such  a  book  the  student  need 
make  notes  only  of  the  words,  terms  or  phrases  used,  and  afterwards,  by  the  use  of  the 
definitions  and  explanatory  matter  connected  therewith,  work  up  the  general  subject 
matter  of  the  lecture.  The  author  has  successfully  used  this  method  in  his  teaching. 

In  order  to  separate  the  definitions  from  the  descriptive  matter,  two  sizes  of  type 
have  been  used,  the  definitions  being  placed  in  the  larger  sized  type. 

In  the  descriptive  matter  the  author  has  not  hesitated  to  quote  freely  from  standard 
electrical  works,  electrical  magazines,  and  periodical  literature  generally.  Among  the 
numerous  works  consulted,  besides  those  to  which  reference  has  already  been  made 
in  the  preface  to  the  first  edition,  he  desires  to  acknowledge  his  indebtedness  espe- 
cially to  "The  Alternating  Current  Transformer,"  by  J.  A.  Fleming  ;  to  various  works 
of  John  W.  Urquhart ;  to  "Modern  Views  of  Electricity,"  by  Prof.  O.  J.  Lodge;  to 
"A  Text-book  of  Human  Physiology,"  by  Landois  &  Sterling;  and  to  "Practical 
Application  of  Electricity  in  Medicine  and  Surgery, "  by  Liebig  &  Rohe. 

The  cuts  or  diagrams  used  in  the  book  have  either  been  drawn  especially  for  the 
work  or  have  been  taken  from  standard  electrical  publications. 

The  chart  of  standard  electrical  symbols  and  diagrams  has  been  taken  from  Prof. 
F.  B.  Crocker's  paper  on  that  subject. 

The  definition  of  terms  used  in  systems  of  electric  railways  have  been  taken 
mainly  from  a  paper  on  "  Standards  in  Electric  Railway  Practice,"  by  O.  T.  Crosby. 

The  author  desires  especially  to  express  his  obligations  to  Prof.  F.  B.  Crocker  of 
the  Electrical  Engineering  Department,  Columbia  College,  New  York,  and  to  Carl 
Hering,  of  Philadelphia,  for  critical  examination  of  the  entire  manuscript  and  for  many 
valuable  suggestions  ;  also  to  The  Electrical  World  and  the  Electrical  Engineer  of  New 
York,  and  to  Prof.  Elihu  Thomson,  Edward  Caldwell,  T.  C.  Martin,  Dr.  Louis  Bell, 
Joseph  Wetzler,  Nikola  Tesla,  Wm.  H.  Wahl,  Prof.  Wm.  D.  Marks,  Prof.  A.  £. 
Dolbear,  C.  W.  Pike,  John  Hoskin,  and  numerous  others,  for  aid  in  connection  with 
new  words  or  phrases.  So  far  as  they  relate  to  the  medical  applications  of  electricity, 
the  proof  sheets  were  revised  by  Dr.  G.  G.  Faught,  of  Philadelphia. 

The  author  desires  to  thank  critics  of  the  first  edition  and  the  electrical  fraternity  in 
general  for  valuable  suggestions.  He  presents  this  second  e  lition  of  his  Dictionary  id  the 
hope  that  it  may  to  some  extent  properly  represent  the  vocabulary  of  electrical  science. 

CENTRAL  HIGH  SCHOOL,  EDWIN  J.   HOUSTON. 

PHILADELPHIA,  May,  1892. 


PREFACE  TO  THE  THIRD  EDITION. 

THE  second  edition  of  the   "Dictionary  of  Electrical  Words,  Terms,  and  Phrases'* 
was  exhausted  in  such  a  comparatively  short  time  that  the  publishers  believed 
that  what  new  matter  might  be  required  for  a  third  edition  could  best  be  added  in 
the  form  of  an  appendix. 

Although  not  quite  two  years  have  elapsed  since  the  issue  of  the  second  edition, 
yet  the  growth  of  electrical  science  has  continued  at  so  rapid  a  pace,  and  new  words, 
terms,  and  phrases  have  of  necessity  been  introduced  so  rapidly,  that  fully  twenty  per 
cent.,  both  of  new  words  and  new  matter,  have  been  found  necessary  for  the  third 
edition.  Had  this  fact  been  known  in  time,  it  might  have  been  better  to  have 
developed  the  additional  matter  throughout  the  text,  rather  than  placing  it  at  the  end 
of  the  book  as  an  appendix. 

Should  a  demand  be  made  for  a  fourth  edition,  the  author  contemplates  re- 
writing and  re-arranging  the  entire  volume.  He  is  thoroughly  aware  of  the  inaccuracies 
and  incompleteness  of  many  of  the  definitions  in  the  second  edition,  and  hopes,  in 
the  event  of  a  demand  for  a  fourth  edition,  to  produce  a  volume  more  nearly  ap- 
proximating to  what  an  electrical  dictionary  should  be.  In  the  meantime,  he  again 
asks  the  kindly  criticisms  of  his  fellow  laborers  in  the  electrical  field  to  aid  him  in  the 
work. 

In  order  to  facilitate  the  use  of  the  cross-references,  all  words,  terms,  and  phrases 
referred  to  in  the  appendix  are  so  marked;  i.  e.,  (See  Appendix — Insulation,  Kilo- 
metric,  of  Cable.}  All  references  not  so  marked  will  be  found  in  the  main  text  of  the 
dictionary. 

The  author  desires  to  express  his  obligations  to  numerous  authors  and  technical 
journals  for  information  as  to  new  words,  terms,  and  phrases,  and  to  the  significance 
generally  given  to  them  in  actual  use  He  desires  especially  to  acknowledge  his 
obligations  to  his  colleague,  Mr.  A.  E.  Kennelly,  and  to  Professors  R.  A.  Fessenden, 
C.  Wellman  Park;  to  Messrs.  C.  P.  Steinmetz,  J.  F.  Kelly,  O.  B.  Shallenberger,  Carl 
Hering,  H.  W.  Frye,  W.  D.  Weaver,  W.  F.  C.  Hasson,  Tbwnsend  Wolcott,  J.  B. 
Cahoon,  and  many  others,  for  reading  of  proof  sheets  and  suggestions. 

The  author  presents  this  third  edition  of  the  Dictionary  with  the  hope  that  it 
may  prove  of  value  to  the  electrical  fraternity. 

EDWIN  J.  HOUSTON. 

PHILADELPHIA,  May,  1894. 


PREFACE  TO  THE  FOURTH  EDITION. 

IN  preparing  the  fourth  edition  of  his'"  Dictionary  of  Electrical 
Words,  Terms  and  Phrases,"  the  author  soon  found  that  the 
recent  marvellous  growth  in  the  electrical  vocabulary  was  such  that 
it  would  be  impossible  to  add,  in  the  shape  of  a  separate  appendix, 
the  new  words,  terms  and  phrases  only,  that  it  was  necessary  to 
introduce  into  the  book.  This  will  be  evident  from  the  fact  that 
the  added  words  exceed  in  number  those  already  contained  in  the 
first,  second  and  third  editions.  Since  it  was  deemed  inadvisable 
by  the  publisher  to  recast  the  entire  book,  the  only  course  left  open 
to  the  author  was  to  alphabetically  arrange  all  the  old  and  new 
words,  and  to  present  them  in  concise  definitions  without  any  ency- 
clopaedic matter,  referring  the  reader  to  the  matter  contained  in 
the  earlier  editions  for  illustration  and  detail. 

It  has  also  been  thought  advisable  to  introduce  a  change  in  the 
manner  of  arrangement,  the  words,  terms  and  phrases  being  alpha- 
betically arranged  according,  either  to  the  word,  or  to  the  first  word 
of  the  term  or  phrase.  This  has  permitted  the  entire  suppression 
of  all  cross  references,  which,  in  view  of  the  author's  past  expe- 
rience, he  believes  will  prove  an  advantage. 

The  author  desires  to  acknowledge  the  very  valuable  assistance 
afforded  him  by  his  colleague,  Dr.  A.  E.  Kennelly,  in  the  prepa- 
ration of  the  matter  for  the  fourth  edition,  both  in  collecting  new 
terms,  as  well  as  in  preparing  the  definitions,  and  reading  the 
proof. 

The  author  trusts,  that  the  fourth  edition  of  his  electrical  Diction- 
ary will  prove  of  benefit  not  only  to  the  electrical  world  but  to  the 
reading  public  generally. 

All  criticisms  will  be  gladly  received. 

EDWIN  J.  HOUSTON. 

PHILADELPHIA,  December,  1897. 


A     DICTIONARY 


OF 


ELECTRICAL 

WORDS,    TERMS    AND    PHRASES. 


A.  or  An.  —  An  abbreviation  sometimes  used 
in  medical  electricity  for  anode.  (See  Anode?) 

A.  C.  C.  —  An  abbreviation  used  in  medical 
electricity  for  Anodic  Closure  Contraction. 
(See  Contraction,  Anodic  Closure?) 

A.  D.  C.  —  An  abbreviation  used  in  medical 
electricity  for  Anodic  Duration  Contraction. 
(See  Contraction,  Anodic  Duration?) 

A.  0.  C.  —  An  abbreviation  used  in  medical 
electricity  for  Anodic  Opening  Contraction. 
(See  Contraction,  Anodic  Opening?) 

Abscissa  of  Rectilinear  Co-ordinates.  —  A 
line  or  distance  cut  off  along  axis  of  abscissas. 

The  abscissa  of  the  point  D,  Fig.  I,  on  the  curve 
O  D  R,  is  the  distance  D  i,  or  its  equal  A  2, 
measured  or  cut  off  on  the  line  A  C,  the  axis  of 
abscissas;  or,  briefly,  A  2,  is  the  abscissa  of  the 
point  D. 

Abscissas,    Axis  of  -  —  One    of   the 

axes  of  co-ordinates  used  for  determining  the 
position  of  points  on  a  curved  line. 

Thus  the  position  of 
the  point  D,  Fig.  I,  on 
the  curved  line  O  D  R, 
is  determined  by  the  per- 
pendicular distances,  D  I 
and  D  2,  of  such  point 
from  two  straight  lines, 
A  B  and  A  C,  called  the 


axes  of  co-ordinates.  AC, 
is  called  the  axis  of  ab- 
scissas,  and  AB,  the  axis  of  ordinates.  The  point 


2 
**•*'/  <* 


A,  where  the  lines  are  considered  as  starting  or 
originating,  is  called  the  point  of  origin,  or,  gen- 
erally, the  origin. 

The  use  of  co-ordinates  was  first  introduced  by 
the  famous  mathematician,  Des  Cartes. 

Absolute. — Complete  in  itself. 

The  terms  absolute  and  relative  are  used  in 
electricity  in  the  same  sense  as  ordinarily. 

Thus,  a  galvanometer  is  said  to  be  calibrated 
absohittly  when  the  exact  current  strengths  re- 
quired to  produce  given  deflections  ai  e  known  ; 
or,  in  other  words,  when  the  absolute  current 
strengths  are  known  ;  it  is  said  to  be  calibrated 
relatively  when  only  the  relative  current  strengths 
required  to  produce  given  deflections  are  known. 

The  word  absolute,  as  applied  to  the  units  em- 
ployed in  electrical  measurements,  was  introduced 
by  Gauss  to  indicate  the  fact  that  the  values  of 
such  units  are  independent  both  of  the  size  of  the 
instrument  employed  and  of  the  value  of  gravity  at 
the  particular  place  where  the  instrument  is 
used. 

The  word  absolute  is  also  used  with  reference 
to  the  fact  that  the  values  of  the  units  could 
readily  be  redetermined  from  well  known  con- 
stants, in  case  of  the  loss  of  the  standards. 

The  absolute  units  of  length,  mass,  and  time 
are  more  properly  called  the  C.  G.  S.  units,  or 
the  centimetre-gramme-second  units.  (See  Units, 
Absolute. ) 

An  absolute  system  of  units  based  on  the  milli- 
gramme, millimetre,  and  second,  was  proposed  by 
Weber,  and  was  called  the  millimetre  milli- 
gramme-second units.  It  has  been  replaced  by 


[Acc, 


the  C.  G.  S.  units.  (See  Units,  Centimetre- 
Gramme-Second.  Units,  Fundamental.') 

Absolute  Block  System  for  Railroads.— 

(See  Block  System  for  Railroads,  Absolute?) 

Absolute  Calibration. — (See  Calibration, 
Absolute?) 

Absolute  Electrometer. — (See  Electrome- 
ter, Absolute?) 

Absolute  Galvanometer. — (See  Galva- 
nometer, Absolute?) 

Absolute  Unit  of  Current. — (See  Current, 
Absolute  Unit  of.) 

Absolute  Unit  of  Electromotive  Force. — 
(See  Force,  Electromotive,  Absolute  Unit 
of.) 

Absolute  Unit  of  Inductance. — (See  -In- 
ductance, Absolute  Unit  of.) 

Absolute  Unit  of  Resistance. — (See  Re- 
sistance, Absolute  Unit  of) 

Absolute  Unit  of  Self-Induction. — (See 
Inducti  n,  Self,  Absolute  Unit  of) 

Absolute  Units. — (See    Units,  Absolute) 

Absolute  Vacuum. — (See  Vacuum,  Ab- 
solute) 

Absorption. — The  taking,  or,  literally, 
drinking  in,  of  one  form  of  matter  by  another, 
such  as  a  gas,  vapor  or  liquid  by  a  solid ;  or 
of  the  energy  of  sound,  light,  heat,  or  elec- 
tricity by  ordinary  matter. 

Absorption,  Acoustic The  taking 

in  of  the  energy  of  sound  waves  produced  by 
one  sounding  or  vibrating  body  by  another 
vibrating  body. 

Acoustic  absorption  may  result  in  the  dissipa- 
tion of  the  absorbed  energy,  as  heat,  or  in  sym- 
pathetic vibrations.  (See  Vibrations,  Sympathetic.) 

Absorption,  Electric The  appar- 
ent soaking  of  an  electric  charge  into  the 
glass  or  other  solid  dielectric  of  a  Leyden  jar 
or  condenser.  (See  Condenser) 

The  capacity  of  a  condenser  varies  with  the 
time  the  condenser  remains  charged  and  with  the 
time  taken  in  charging.  Some  of  the  charge 
acts  as  if  it  soaked  into  the  solid  dielectric,  and 
this  is  the  cause  of  the  residual  charge.  (See 
Charge,  Residual.)  Therefore,  when  the  con- 


denser  is  discharged,  less  electricity  appears  than 
was  passed  in  ;  hence  the  term  electric  absorption. 

Absorption,    Luminous  --  The    ab- 

sorption of  the  energy  of  light  in  its  passage 
through  bodies. 

When  sunlight  falls  on  an  opaque  colored  body, 
such  for  example  as  a  red  body,  all  the  colors  but 
the  reds  are  absorbed.     The  reds  are  then  thrown 
offand  thus  cause  the  color.     In  the  same  manne-  , 
when  sunlight  falls  on  a  transparent  colored  body, 
such  for  example  as  red,  all  colors  but  the  reds  are 
absorbed,  and  the  reds  are  transmitted. 

When  sunlight  falls  on  a  phosphorescent  body, 
a  part  of  the  light  is  absorbed  as  heat  ;   another 
part  is  absorbed  by  the  molecules  being  set  into 
motion  sufficiently  rapid  to  cause  them  to  emit 
light  or  to  become  luminous. 

A  mass  of  glowing  gas  or  vapor  absorbs  waves 
of  light  of  the  same  length  as  those  it  itself  emits. 
This  is  the  cause  of  the  dark  lines  of  the  solar 
spectrum,  called  the  Fraunhoffer  lines. 

The  amount  of  light  absorbed  by  the  glass  globe 
of  an  incandescent  lamp,  according  to  Urquhart, 
is  as  follows,  viz.: 

Clear  glass  .............   10  per  cent. 

Ground  glass  ............   35        " 

Opalescent  glass  ..........   50        " 

Absorption,  Selective  —  --  The  absorp- 
tion of  a  particular  or  selected  character  of 
waves  of  sound,  light,  heat,  or  electricity. 

Absorption,    Thermal   --   —  The    ab- 

sorption of  heat  energy  in  its  passage  through 
a  body. 

The  phenomena  of  thermal  absorption  are 
similar  to  those  of  luminous  absorption.  A  sub- 
stance that  is  transparent  to  heat,  or  which  allows 
heat  waves  to  pass  through  without  absorption, 
is  called  diathermanous,  or  diathermanic,  or 
is  said  to  be  transparent  to  heat. 

Absorptive  Power.  —  (See  Power.  Absorp- 
tive) 

Acceleration.  —  The  rate  of  change  of 
velocity. 

Acceleration  is  thus  distinguished  from  velocity: 
velocity  expresses  in  time  the  rate-  of-  change  of 
position,  as  a  velocity  of  three  metres  per  second; 
acceleration  expresses  in  time  the  rate-of-change 
of  velocity,  as  an  acceleration  of  one  centimetre 
per  second. 

Since  all  matter  is  inert,  and  cannot  change  its 


Ace.] 


condition  of  rest  or  motion  without  the  applica- 
tion of  some  force,  acceleration  is  necessarily  due 
to  some  force  outside  the  matter  itself.  A  force 
may  therefore  be  measured  by  the  acceleration  it 
imparts  to  a  given  mass  of  matter. 

Acceleration  is  positive  when  the  velocity  is  in- 
creasing, and  negative  when  it  is  decreasing. 

Acceleration,  Dimensions  of The 

^alue  of  the  acceleration  expressed  in  terms 
of  the  length  or  of  distance  by  the  time.  (See 
Acceleration,  Unit  of.) 

Acceleration,  Unit  of  — That  ac- 
celeration which  will  give  to  a  body  unit- 
velocity  in  unit-time ;  as,  for  example,  one 
centimetre-per-second  in  one  second. 

Bodies  falling  freely  in  a  vacuum,  and  ap- 
proximately so  in  air,  acquire  an  acceleration 
which  in  Paris  or  London,  at  the  end  of  a  second, 
amounts  to  about  981  centimetres  per  second,  or 
nearly  32.2  ft.  per  second. 

V 
A  =  — ,  or,  in  other  words, 

The  acceleration  equals  the  velocity  divided  by 
the  time. 

But,  since  velocity  equals  the  Distance,  or  the 

Length  traversed  in  a  Unit  of  Time,  V  =  —  . 


TU      r         A        V         T          L 
Therefore,  A  =  -;  =  -=-  =  =  ,  or 


The  acceleration  equals  the  length,  or  the  dis- 
tance passed  through,  divided  by  the  square  of  the 
time  in  seconds. 

These  formulae  represent  the  Dimensions  of 
Acceleration. 

Accumulated  Electricity. — (See  Electri- 
city, Accumulated^) 

Accumulating  Electricity. — (See  Electri- 
city, Accumulating^) 

Accumulation  of  Electricity. — (See  Elec- 
tricity, Accumulation  of.) 

Accumulator. — A  word  sometimes  applied 
to  any  apparatus  in  which  the  strength  of  a 
current  is  increased  by  the  motion  past  it  of  a 
conductor,  the  currents  produced  in  which 
tend  to  strengthen  and  increase  the  current 
which  causes  the  induction. 


[Act. 

The  word  accumulator  is  sometimes  applied  to 
Sir  Wm.  Thomson's  Electric  Current  Accumu- 
lator. 

Current  accumulators  operate  on  the  reaction 
principle  of  dynamo-electric  machines.  In  this 
sense,  therefore,  a  dynamo -electric  machine  is  an 
accumulator.  (See  Machine,  Dynamo-Electric, 
Reaction  Principle  of.) 


Fig.  2.    Barlow's  Wheel. 

The  copper  disc  D,  Fig.  2,  has  freedom  of 
rotation,  on  a  horizontal  axis  at  O,  in  a  magnetic 
field,  the  lines  of  force  of  which,  represented  by 
the  dotted  lines  in  the  drawing,  pass  downward 
perpendicularly  into  the  plane  of  the  paper. 

If,  now,  a  current  from  any  source  be  passed 
in  the  direction  A,  O,  B,  C,  A,  through  the  circuit 
A,  O,  B,  C,  A,  which  is  provided  with  spring 
contacts  at  O,  and  A,  the  disc  will  rotate  in  the 
direction  of  the  curved  arrow.  This  motion  is 
due  to  the  current  acting  on  that  part  of  the  disc 
which  lies  between  the  two  contacts — A  and  O. 
This  apparatus  is  known  as  Barlow's  Wheel. 

If,  when  no  current  is  passing  through  the 
circuit,  the  disc  be  turned  in  the  direction  of  the 
arrow,  a  current  is  set  up  in  such  a  direction  as 
would  oppose  the  rotation  of  the  disc.  (See 
Law,  Lenz's.) 

If,  however,  the  disc  be  turned  in  the  opposite 
direction  to  that  of  the  arrow,  induction  currents 
will  as  before  be  produced  in  the  circuit.  As 
this  rotation  of  the  disc  tends  to  move  the  circuit 
O  A,  towards  the  parallel  but  oppositely  directed 
circuit  B  C,  these  two  circuits  being  parallel  and 
in  opposite  directions  tend  to  repel  one  another, 
and  there  will  thus  be  set  up  induced  currents 
that  tend  to  oppose  the  motion  of  rotation,  and 
the  current  of  the  circuit  will  therefore  increase 
in  strength.  (See  Dynamics,  Electro.)  Should 
then  a  current  be  started  in  the  circuit,  and  the 
original  field  be  removed,  the  induction  will  be 
continued,  and  a  current  which,  up  to  a  certain 
extent,  increases  or  accumulates,  is  maintained  in 
the  circuit  during  rotation  of  the  disc.  (Larden.) 

Barlow's  Wheel,  when  used  in  this  manner,  is 
known  as  Thomson's  Electric  Current  Accumu- 
lator. 


Ace.] 


e 


[Ace. 


Accumulator. — A  word  often  applied  to 
a  Leyden  jar  or  condenser,  which  permits  the 
gradual  collection  from  an  electric  source  of 
a  greater  charge  than  it  would  otherwise  be 
capable  of  containing. 

A  condenser.     (See  Condenser?) 

The  ability  of  a  source  to  accumulate  an  in- 
creased charge  when  connected  to  a  condenser  is 
due  to  the  increased  capacity  which  a  plate  or 
other  conductor  acquires  when  placed  near 
another  plate  or  conductor.  (See  Condenser, 
jfar,  Leyden.) 

Accumulator.    Capacity    of The 

capacity  of  a  condenser,  expressed  in  micro- 
farads.    (See  Condenser,  Capacity  of.) 

Accumulator  or  Condenser ;  Laws  of  Ac- 
cumulation of  Electricity. — Sir  W.  Snow 
Harris,  by  the  use  of  his  Unit-Jar  and  Elec- 
tric Thermometer,  deduced  the  following 
laws  for  the  accumulation  of  electricity,  which 
we  quote  from  Noad's  "  Student's  Text-Book 
of  Electricity,"  revised  by  Preece : 

(I.)  "Equal  quantities  of  electricity  are  given 
off  at  each  revolution  ot  the  plate  of  an  electrical 
machine  to  an  uncharged  surface,  or  to  a  surface 
charged to  any  degree  of  saturation. " 

(2. )  "A  coated  surface  receives  equal  quantities 
of  electricity  in  equal  times  ;  and  the  number  of 
revolutions  of  the  plate  is  a  fair  measure  of  the 
relative  quantities  of  electricity,  all  other  things 
remaining  the  same." 

(3. )  "  The  free  action  of  an  electrical  accumula- 
tion is  estimated  by  the  interval  it  can  break 
through,  and  is  directly  proportional  to  the  quan- 
tity of  electricity." 

(4.)  "  The  free  action  is  inversely  proportional 
to  the  surface/' 

(5.)  "  When  the  electricity  and  the  surface  are 
increased  in  the  same  ratio,  the  discharging  in- 
terval remains  the  same  ;  but  if,  as  the  electricity 
is  increased,  the  surface  is  diminished,  the  dis- 
charging interval  is  directly  as  the  square  of  the 
quantity  of  electricity." 

(6.)  '«  The  resistance  of  air  to  discharge  is  as 
the  square  of  the  density  directly. " 

According  to  some  later  investigations,  the 
quantity  a  plane  surface  can  receive  under  a  given 
density  depends  on  the  linear  b  >und<iry  of  the 
surface  as  well  &>  on  the  area  <>f  ;  he  surface. 

"  The  amount  of  electrical  charge  depends  on 


surface  and  linear  extension  conjointly.  There 
exists  in  every  plane  surface  what  may  be  termed 
an  electrical  boundary,  having  an  important  rela- 
tion to  the  grouping  or  disposition  of  the  electric 
particles  in  regard  to  each  other  and  to  surrounding 
matter.  This  boundary  in  circles  or  globes  is 
represented  by  their  circumferences.  •  In  plane 
rectangular  surfaces,  it  is  by  their  linear  extension 
or  perimeter.  If  this  boundary  be  constant,  their 
electrical  charge  varies  with  the  square  root  of 
the  surface.  If  the  surface  be  constant  the  charge 
varies  with  the  square  root  of  the  boundary.  If 
the  surface  and  boundary  both  vary,  the  charge 
varies  with  the  square  root  of  the  surface  multi- 
plied into  the  square  root  of  the  boundary.'" 

These  laws  apply  especially  to  continuous  sur- 
faces taken  as  a  whole,  and  not  to  surfaces  divided 
into  separate  parts. 

By  electrical  charge  Harris  meant  the  quantity 
sustained  on  a  given  surface  under  a  given  elec- 
trometer indication  ;  by  electrical  intensity,  he 
meant  the  indication  of  the  electrometer  corre- 
sponding to  a  given  quantity  on  a  given  surface. 

(See  Condenser,  Capacity  of.  Capacity,  Elec- 
trostatic. Capacity,  Specific  Inductive. ) 

Accumulators  of  this  character  are  now 
generally  called  Condensers.  (For  more  mcdern 
principles  concerning  their  construction  and 
capacity  see  Condenser.  Condenser,  Capacity  of.} 

Accumulator,  Secondary  or  Storage 
Cell Two  inert  plates  partially  sur- 
rounded by  a  fluid  incapable  of  acting  chem- 
ically on  either  of  them  until  after  the  passage 
of  an  electric  current,  when  they  become 
capable  of  furnishing  an  independent  electric 
current. 

This  use  of  the  term  accumulator  is  the  one 
most  commonly  employed.  A  better  term  for 
such  a  cell  is  a  secondary  or  storage  cell.  (See 
Cell,  Secondary  or  Storage.) 

Commercially,  an  accumulator  consists  of  a 
single  jar  and  its  electrolyte,  in  which  a  single 
set  of  positive  and  negative  plates  is  properly 
placed. 

Accumulator,     Water-Dropping  - 

An  apparatus  devised  by  Sir  W.  Thomson  for 
increasing  the  difference  of  potential  between 
two  electric  charges. 

The  tube  X  Y,  Fig.  3,  connects  with  a  reser- 
voir of  water  which  is  maintained  at  the  zero 
potential  of  the  earth.  The  water  escapes  from 


Ach.] 


[Act. 


B' 


Water-Drop- 


the  openings  at  C  and  D,  in  small  drops  and  falls 
on  funnels  provided,  as  shown,  to  receive  the 
separate  drops  and  again  discharge  them. 

The  vessels  A,  A',  and  B, 
H',    which    are    electrically          _X 
connected    as    shown,    are 
maintained  at  a  certain  small  A  ?J|j 
difference    of   potential,    as 
indicated  by  the  respective 
-f-  and  —  signs. 

Under  these  c  i  r  c  u  m  - 
stances,  therefore,  C  and  D, 
will  be  charged  inductively  f'f-3- 
with  charges  opposite  to  &**  Ac™m"ator- 
those  of  A  and  B,  or  with  —  and  -j-  electricities 
respectively.  As  the  drops  of  water  fall  on  the 
funnels,  the  charges  which  the  funnels  thus  con- 
stantly receive  are  given  up  to  B'  and  A',  before 
the  water  escapes.  Since,  therefore,  B,  B',  and 
A,  A',  are  receiving  constant  charges,  the  differ- 
ence of  potential  between  them  must  continually 
increase.  This  apparatus  operates  on  the  same 
principle  as  the  replenisher.  The  drops  of  water 
act  as  the  carriers,  and  A,  A',  and  B,  B',  as  the 
hollow  vessels.  (See  Replenisher.} 

Achromatic.  —  Free  from  false  coloration. 

Images  formed  by  ordinary  lenses  do  not  pos- 
sess the  true  colors  of  the  object,  unless  the  edges 
of  the  lenses  are  cut  off  by  the  use  of  a  diaphragm  ; 
i  e.,  an  opaque  'plate  with  a  central  circular 
opening.  The  edges  of  the  lenses  disperse  the 
light  like  an  ordinary  prism,  and  so  produce  rain- 
bow colored  (prismatic)  fringes  in  the  image. 
The  use  of  an  achromatic  lens  is  to  obviate  this 
false  coloration. 

Achromatizahle.  —  Capable  of  being  freed 
from  false  coloration. 

Achromatize.  —  To  free  from  false  color- 
ation. 

Achromatizing.  —  Freeing  from  false  color- 
ation. 

Acid,  Spent  --  A  battery  acid,  or  other 
acid,  that  has  become  too  weak  for  efficient 
action. 

In  a  voltaic  cell  the  acid  of  the  electrolyte 
becomes  spent  by  combining  with  the  metal  of 
the  positive  plate. 

Acidonieter.  —  A  special  form  of  hydrom- 
eter used  in  determining  the  specific  gravity 
of  the  acid  liquid  in  a  secondary  or  storage 


cell.     (See  Areometer  or  Hydrometer.     Cell. 
Storage!) 

The  scale  on  the  acidometer  tube  is  made  to  in- 
dicate the  density  according  to  the  distance  the 
floating  instrument  sinks  in  the  liquid. 

Aclinic  Line. — (See  Line,  Aclinic?) 

Acoustic  Absorption. — (See  Absorption, 
Acoustic?) 

Acoustic  Engraving. — (See  Engraving, 
Acoustic?) 

Acoustic  Telegraphy. — (See  Telegraphy, 
Acoustic?) 

Acoustic  Tetanus. — (See  Tetanus,  Acous- 
tic'.) 

Acoutemeter,  Electric An  ap- 
paratus for  electrically  testing  the  delicacy  of 
hearing. 

The  Acoutemeter  is  one  of  the  many  applica- 
tions of  Hughes'  sonometer.  It  consists  of  three 
flat  coils  placed  parallel  to  one  another  on  a  grad- 
uated rod,  passing  through  their  axes.  The 
central  coil,  which  is  used  as  the  primary  of  an 
induction  coil,  is  fixed.  The  other  two,  which  are 
employed  as  secondary  coils,  are  movable.  (See 
Sonometer^  Hughes'.  Coil,  Induction.  Micro- 
ph<me.}  A  microphone,  electrical  tuning  fork, 
switches,  plugs,  and  other  accessories,  are  suitably 
placed  and  connected.  The  subject  whose  hear- 
ing is  to  be  tested  is  placed  with  his  back  to  the 
apparatus,  and  with  two  telephone  receivers  tightly 
fixed  to  his  ears.  As  various  sounds  are  produced , 
the  outer  or  movable  coils  are  moved  gradually 
away  from  the  central  coil,  until  no  sound  is 
heard  in  the  telephone  receivers.  This  distance 
is  in  the  inverse  ratio  of  the  delicacy  of  hearing  of 
the  individual. 

Actinic  Photometer. — (See  Photometer, 
Actinic?) 

Actinic  Ray. — (See  Ray,  Actinic?) 

Actinism. — The  chemical  effects  of  light, 
as  manifested  by  the  decomposition  of  various 
substances. 

Under  the  influence  of  the  sun's  light,  the  car- 
bonic acid  absorbed  by  the  leaves  of  plants  is  de- 
composed in  the  living  leaves  into  carbon,  which  is 
retained  by  the  plant  for  the  formation  of  its 
woody  fibre  or  ligneous  tissue,  and  oxygen,  which 
is  thrown  off. 


Act.] 


[Act. 


The  bleaching  of  curtains,  carpets,  and  other 
fabrics  exposed  to  sunlight  is  caused  by  the  actinic 
power  of  the  light.  The  photographic  picture  is 
impressed  by  the  actinic  power  of  light  on  a  plate 
covered  with  some  sensitive  metallic  salt. 

Actinograph. — An  apparatus  for  measur- 
ing and  recording  the  intensity  of  the  chemi- 
cal effects  of  light. 

Actinography. — The  method  of  measuring 
and  recording  the  intensity  of  the  chemical 
effects  of  light. 

Actinometer. — A  word  sometimes  applied 
to  a  pyrheliometer.  (See  Pyrheliometer} 

Actinometer,  Electric  -  — An  appa- 
ratus for  electrically  measuring  the  intensity 
of  the  chemically  active  rays  present  in  any 
luminous  radiation. 

The  rays  from  the  luminous  source  are  per- 
mitted to  fall  on  a  selenium  resistance,  and  their 
intensity  determined  by  the  change  observed  in 
the  resistance  as  indicated  by  the  deflections  of  a 
galvanometer  placed  in  circuit  with  the  selenium 
resistance.  Or,  a  thermo-electric  pile  is  employed, 
and  the  amount  of  heat  present  determined  by  the 
indications  of  a  galvanometer  placed  in  its 
circuit. 


The     action 

cataphoresis.     (See 


Action,    Cataphoric 

of    electric    osmose    or 
Cataphoresis^) 

Action  Currents. — (See  Currents, Action^) 
Action,    Inductive,    Lines     of  — 

Lines  within  the  space,  separating  a  charge 
and  a  neighboring  body,  along  which  elec- 
trostatic inductive  action  takes  place. 

Lines  of  electrostatic  force. 

Lines  of  inductive  action  pass  through  the 
dielectric,  separating  the  two  bodies,  and  termi- 
nate on  the  surfaces  of  the  conductor.  According 
to  the  now  generally  received  notions,  the  elec- 
trostatic charge  exists  in  the  mass  of  the  dielectric, 
and  not  in  that  of  the  conductor.  The  lines  of 
inductive  action  terminate  against  the  surfaces, 
one  at  the  positive,  and  the  other  at  the  negative 
surface.  A  true  E.  M.  F.  exists  in  the  space 
traversed  by  lines  of  inductive  action.  A  con- 
ductor brought  into  this  space  becomes  electri- 
fied, or  is  strained  in  such  a  manner  that  a 
momentary  current  is  produced  by  the  rearrange- 


ment of  the  electrification  brought  about  by 
electrostatic  induction. 

Action,  Local,  of  Dynamo-Electric  Ma- 
chine   The  loss  of  energy  in  a  dy- 
namo-electric machine  by  the  setting  up  of 
eddy  currents  in  its  pole  pieces,  cores,  or 
other  conducting  masses.  (See  Currents, 
Eddy.} 

In  a  dynamo-electric  machine  local  action  i« 
obviated  by  z.  lamination  of  the  pole  pieces,  arma- 
ture core,  etc.  (See  Core,  Lamination  of.) 

Action,   Local,   of  Voltaic    Cell 

An  irregular  dissolving  or  consumption  of  the 
zinc  or  positive  element  of  a  voltaic  battery,  by 
the  fluid  or  electrolyte,  when  the  circuit  is 
open  or  broken,  as  well  as  when  closed,  or  in 
regular  action. 

Local  action  is  due  to  small  particles  of  such 
impurities  as  carbon,  iron,  arsenic,  or  other 
negative  elements,  in  the  positive  plate.  These 
impurities  form  with  the  positive  element  minute 
voltaic  couples,  and  thus  direct  the  corrosive 
action  of  the  liquid  to  portions  of  the  plate  near 
them.  Local  action  causes  a  waste  of  energy. 
It  may  be  avoided  by  the  amalgamation  of  the 
zinc.  (See  Zinc,  Amalgamation  of.) 

Action,  Magne-Crystallic  , A   term 

proposed  by  Faraday  to  express  differences 
in  the  action  of  magnetism  on  crystalline 
bodies  in  different  directions. 

A  needle  of  tourmaline,  if  hung  with  its  axis 
horizontal,  is  no  longer  paramagnetic,  as  usual, 
but  diamagnetic.  The  same  is  true  of  a  crystal 
of  bismuth.  Faraday  concluded  from  these  ex- 
periments that  a  force  existed  distinct  from  either 
the  paramagnetic  or  the  diamagnetic  force.  He 
called  this  the  magne -cry  stallic  force. 

Plucker  infers  from  these  phenomena  that  a 
definite  relation  exists  between  the  ultimate  form 
of  the  particles  of  matter  and  their  magnetic  be- 
havior. The  subject  may  be  regarded  as  yet 
somewhat  obscure.  (See  Polarity,  Diamagnetic. ) 

Action  of  a  Current  on  a  Magnetic  Pole. 

— (See  Current,  Action  of,  on  a  Magnetic 
Pole.) 
Action,   Refreshing,  of  Current 

The  restoration,  after  fatigue,  of  muscular  and 
nervous  excitability  obtained  by  the  action  of 


Act.] 


9 


[Aer. 


voltaic  alternatives.     (See  Alternatives,  Vol- 
taic?) 

Activity. — The  work  done  per  second  by 
any  agent.  (This  term  is  but  seldom  used.) 

Work-per-second,  or,  as  generally  termed 
in  the  United  States,  Power,  or  Rate  of 
Doing  Work.  (See  Power?) 

Activity,  Unit  of A  rate  of  work- 
ing that  will  perform  one  unit  of  work  per 
second. 

In  C.  G.  S.  units,  the  activity  of  one  erg  per 
second. 

The  C.   G.  S.  unit  of  activity  is  very  small. 
One  Watt,  the  practical  unit  of  activity  or  power, 
is   equal  to   ten  million  ergs   per  second.     (See 
Waft.) 

The  unit  of  activity  generally  used  for  mechan- 
ical power  is  the  horse-power,  or  746  watts. 
^See  Horse-Power.) 

Actual  Cautery.— (See  Cautery,  Actual.) 
Acute  Angle. — (See  Angle,  Acute?) 
Adapter. — A  screw  nozzle  fitted  to  an  elec- 
tric lamp,  provided  with  a  screw  thread  to  en- 
able it  to  be  readily  placed  on  a  gas  bracket 
or  chandelier  in   place   of  an  ordinary  gas 
burner. 

Adherence. — The  quality  or  property  of 
adhering.  (See  Adhesion?) 

Adherence,  Magnetic Adhesion  be- 
tween surfaces  due  to  magnetic  attraction. 

Magnetic  adhesion  has  been  applied,  among 
other  things,  to  a  brake  action  on  car  wheels, 
either  by  causing  them  to  adhere  directly  to  the 
track  or  to  a  brake- block. 

Adhesion. — The  mutual  attraction  which 
exists  between  unlike  molecules.  (See  At- 
traction, Molecular?) 

The  phenomena  of  adhesion  are  due  to  the 
mutual  attraction  of  dissimilar  molecules. 

Adhesion,  Electric Adhesion  be- 
tween surfaces  due  to  the  attraction  of  unlike 
electrostatic  charges. 

Molecular  adhesion  must  be  distinguished  from 
the  attraction  which  causes  a  piece  of  dry  and 
warmed  writing  paper,  that  has  been  rubbed  by  a 
piece  of  india-rubber,  to  stick  to  a  papered  wall. 
In  this  latter  case  the  attraction  between  the  wall 


and  the  paper  is  due  to  the  mutual  attraction  of 
two  dissimilar  electrostatic  charges.  Molecular 
adhesion  must  also  be  distinguished  from  the  at- 
traction of  opposite  magnetic  poles. 

Adhesion,  Galvanoplastic The  ad- 
hesion of  a  galvanoplastic  deposit  or  coating 
to  surfaces  subjected  to  electroplating.  (See 
Plating,  Electro?) 

Adiathermancy. — Opacity  to  heat. 

A  substance  is  said  to  be  diathermanous  when 
it  is  transparent  to  heat.  Clear,  colorless  crys- 
tals of  rock  salt  are  very  transparent  both  to  light 
and  to  heat.  Rock  salt,  covered  with  a  layer  or 
deposit  of  lampblack  or  soot,  is  quite  transparent 
to  heat.  An  adiathermanous  body  is  one  which 
is  opaque  to  h*eat. 

Heat  transparency  varies  not  only  with  differ- 
ent substances,  but  also  with  the  nature  of  the 
source  from  which  the  heat  is  derived.  Thus,  a 
substance  may  be  opaque  to  heat  from  a  non- 
luminous  source,  such  as  a  vessel  filled  with  boil- 
ing water,  while  it  is  comparatively  transparent 
to  heat  from  a  luminous  source,  such  as  an  incan- 
descent solid  or  a  voltaic  arc. 

A  similar  difference  exists  as  regards  transpar- 
ency to  light.  A  colorless  glass  will  allow  light 
of  any  color  to  pass  through  it.  A  blue  glass  will 
allow  blue  light  to  pass  freely  through  it,  but  will 
completely  prevent  the  passage  of  any  red  light; 
and  so  with  other  colors. 

Adiathermauic. — Possessing  the  quality  of 
adiathermancy.  (See  Adiathermancy?) 

Adjustable  Condenser. — (See  Condenser, 
Adjustable?) 

Adjuster,  Cord A  device  for  ad- 
justing the  length  of  a  pendant  cord. 

Adjustment. — Such  a  regulation  of  any 
apparatus  as  will  enable  it  to  properly  perform 
its  functions. 

JEpinus'  Condenser. — (See  Condenser, 
jEpinus'?) 

Aerial  Cable. — (See  Cable,  Aerial?) 

Aerial  Cable,  Suspending  Wire  of — 
(See  Wire,  Suspending,  of  Aerial  Cable?) 

Aerial  Line. — (See  Line,  Aerial?) 

Aerolites. — A  name  sometimes  given  to 
meteorites. 

Meteorites    are    masses   of  solids   which   pass 


Aff.] 


10 


[Ago. 


through  the  upper  portions  only  of  the  earth's 
atmosphere  on  their  approach  to  the  orbit  of  the 
earth,  or  which  fall  through  the  air  on  the  earth's 
surface  from  the  sky.  They  are  luminous  at 
night  and  are  followed  by  a  train  of  fire.  The 
luminosity  is  due  to  heat  produced  by  friction 
through  the  air.  Meteors  frequently  burst  from 
the  sudden  expansion  of  their  outer  portions. 

Some  meteorites  are  composed  of  nearly  pure 
iron  alloyed  with  nickel.  The  majority  of  them, 
however,  are  merely  stones  or  oxidized  sub- 
stances. Their  average  velocity  is  about  26  miles 
a  second. 

Affinity,  Chemical Atomic  attrac- 
tion. 

The  force  which  causes  atoms  to  unite  and 
form  chemical  molecules. 

Atomic  or  chemical  attraction  generally  results 
in  a  loss  of  the  characteristic  qualities  or  proper- 
ties which  distinguish  one  kind  of  matter  from 
another.  In  this  respect  chemical  affinity  differs 
from  adhesion,  or  the  force  which  holds  unlike 
molecules  together.  (See  Adhesion.  Attraction, 
Molecular.1)  If,  for  example,  sulphur  is  mixed 
with  lampblack,  no  matter  how  intimate  the 
mixture,  the  separate  particles,  when  examined 
by  a  magnifying  glass,  exhibit  their  peculiar  color, 
lustre,  etc.  If,  however,  the  sulphur  is  chemi- 
cally united  with  the  carbon,  a  colorless,  transpar- 
ent, mobile  liquid,  called  carbon  bisulphide,  re- 
sults, that  possesses  a  disagreeable,  penetrating 
odor. 

Chemical  affinity,  or  atomic  combination,  is  in 
fluenced  by  a  variety  of  causes,  viz.: 

(I.)  Cohesion.  Cohesion,  by  binding  the  mole- 
cules more  firmly  together,  opposes  their  mutual 
atomic  attraction. 

A  solid  rod  of  iron  will  not  readily  burn  in  the 
flame  of  an  ordinary  lamp;  but,  if  the  cohesion  be 
overcome  by  reducing  the  iron  rod  to  filings,  it 
burns  with  brilliant  scintillations  when  dropped 
into  the  same  flame.  In  this  case  the  increase  of 
surface  and  the  increased  temperature  of  the 
smaller  particles  also  contribute  to  the  result. 

(2.)  Solution.  Solution,  by  giving  the  molecules 
greater  freedom  of  motion,  favors  their  chemical 
combination. 

(3.)  Heat.  Heat  sometimes  favors  atomic  com- 
bination possibly  by  decreasing  the  cohesion,  and, 
possibly,  by  altering  the  electrical  relations  of  the 
atoms.  If  too  great,  heat  may  produce  decom- 
position. There  is  for  most  substances  a  critical 


temperature  below  which  chemical  combination 
will  not  take  place.     (See  Thermolysis.} 

(4.)  Light.  Decomposition,  or  the  lessening  of 
chemical  affinity,  through  the  agency  of  light,  is 
called  Actinism.  Light  also  causes  the  direct 
combination  of  substances.  A  mixture  of  equal 
volumes  of  hydrogen  and  chlorine  unites  explo- 
sively when  exposed  to  the  action  of  full  sunlight. 
(See  Actinism.) 

(5. )  Electricity.  An  electric  spark  will  cause 
an  explosive  combination  of  a  mixture  of  oxygen 
and  hydrogen.  Electricity  also  produces  chemi- 
cal decomposition.  (See  Electrolysis.) 

Helmholtz  accounts  for  the  electro-chemical 
attraction  of  oxygen  for  zinc  by  supposing  that  all 
substances  possess  a  definite  amount  of  attraction 
for  electricity,  and  that  the  attraction  of  zinc  in 
this  respect  exceeds  that  of  copper  and  the  other 
metals.  He  thus  regards  the  zinc  as  attracting 
its  electric  charge  rather  than  as  attracting  the 
oxygen.  Since  both  zinc  and  copper  are  dyad 
metals,  this  view,  as  will  be  seen,  is  at  variance 
with  later  views. 

Chemical  affinity  may  be  caused  by  the  opposite 
attractions  of  electrical  charges  naturally  possessed 
by  the  atoms  of  matter.  This  would  appear  to  be 
rendered  probable  by  the  law  of  electro-chemical 
equivalence.  (See  Equivalence,  Electro-Chemical, 
Law  of.  Electricity,  Atom  of.) 

After  Currents. — (See  Currents,  After  ^ 

Aging   of  Alcohol,   Electric (See 

Alcohol,  Electric  Aging  of.) 

Agonal. — Pertaining  to  the  agone.  (See 
Agone?) 

Agone. — A  line  connecting  places  on  the 
earth's  surface  where  the  magnetic  needle 
points  to  the  true  geographical  north. 

The  line  of  no  declination  or  variation  of 
a  magnetic  needle.  (See  Needle,  Magnetic, 
Declination  of) 

As  all  the  places  on  the  earth  where  the  mag- 
netic needle  points  to  the  true  north  may  be  ar- 
ranged on  a  few  lines,  it  will  be  understood  that 
the  pointing  of  the  magnetic  needle  to  the  true 
geographical  north  is  the  exception  and  not  the 
rule.  In  many  places,  however,  the  deviation 
from  the  true  geograpical  north  is  so  small  that 
the  direction  of  the  needle  may  be  regarded  as. 
approximately  due  north. 

Agonic. — Pertaining  to  the  agone. 


Air.J 


11 


[Ala. 


Air-Blast  for  Commutators. — An  inven- 
tion of  Prof.  Elihu  Thomson  to  prevent  the 
injurious  action  of  destructive  flashing  at  the 
commutator  of  a  dynamo-electric  machine. 

A  thin,  forcible  blast  of  air  is  delivered  through 
suitable  tubes  at  points  on  the  three-part  commu- 
tator cylinder  of  the  Thomson -Houston  dynamo, 
where  the  collecting  brushes  bear  on  its  surface. 
The  effect  is  to  blow  out  the  arc  or  prevent  its  for- 
mation and  thus  avoid  its  destructive  action  on 
the  commutator  segments.  The  use  of  the  air- 
blast  also  permits  the  free  application  of  oil,  thus 
further  avoiding  wear. 


Fig.  4.    Air -Blast  on  Commuta 

The  blast-nozzles  are  shown  at  B8,  B8,  Fig.  4, 
near  the  collecting  brushes. 

The  air-supply  is  obtained  from  a  blower  at- 
tached directly  to  the  shaft  of  the  machine.  Its 
construction  and  operation  will  be  readily  under- 
stood from  an  inspection  of  Fig.  5,  in  which  the 


Fig,  3.      The  Thomson  Blower, 

top   is    removed   for  ready   examination   of  the 
interior  parts. 

Air  Churning. — (See  Churning,  Air.) 

Air  Condenser. — (See  Condenser,  Air) 

Air  Field.— (See  Field,  Air) 

Air-Gap.— (See  Gap,  Air) 

Air-Line  Wire. — (See  Wire,  Air-Line^) 

Air  Magnetic  Circuit. — (See  Circuit,  Air 
Magnetic?) 

Air-Pump. — (See  Pump,  Air.) 

Air-Pump,  Geissler's  Mercurial 

(See  Pump,  Air,  Geissler's  Mercurial) 


Air-Pump,  Mechanical (See  Pump, 

Air,  Mechanical) 

Air-Pump,  Mercurial (See  Pump, 

Air,  Mercurial^ 

Air-Pump,  Sprengel's  Mercurial 

(See  Pump,  Air,  Sprengefs  Mercurial^) 

Air-Space  Cut-Out.— (See  Cut-Out,  Air- 
Spaced) 

Alarm,  Burglar A  device,  generally 

electric,  for  automatically  announcing  the 
opening  of  a  door,  window,  closet,  drawer,  or 
safe,  or  the  passage  of  a  person  through  a 
hallway,  or  on  a  stairway. 

Electric  burglar-alarm  devices  generally  consist 
of  mechanism  for  the  operation  of  an  automatic 
make  and -break  bell  on  the  opening  or  closing  of 
an  electric  circuit.  The  bell  may  either  continue 
ringing  only  while  the  contact  remains  closed,  or, 
may,  by  the  throwing  on  of  a  local  circuit  or 
battery,  continue  ringing  until  stopped  by  some- 
non-automatic  device,  such  as  a  hand-switch. 

The  alarm-bell  is  stationed  either  in  the  house 
when  occupied,  or  on  the  outside  when  the  house 
is  temporarily  vacated,  or  may  connect  directly 
with  the  nearest  police  station. 

Burglar-alarm  apparatus  is  of  a  variety  of 
forms.  Generally,  devices  are  provided  by  means 
of  which,  in  case  of  house  protection,  an  annunci- 
ator shows  the  exact  part  where  an  entrance  has 
been  attempted.  (See  Annunciator,  Burglar- 
Alarm.)  Switches  are  provided  for  disconnecting 
all  or  parts  of  the  house  from  the  alarm  when  so  • 
desired,  as  well  as  to  per- 
mit windows  to  be  partly 
raised  for  purposes  of  ven- 
tilation without  sounding 
the  alarm.  A  clock  is  fre- 
quently connected  with  the 
alarm  for  the  purpose  of 
automatically  disconnect- 
ing any  portion  of  the 
house  at  or  for  certain  in- 
tervals of  time. 

Fig.  6  shows  a  burglar-  Fig.  6.  Burglar-Alarm 
alarm  with  annunciator,  Annunciator. 

switches,  switch-key,  cut-off,  and  clock. 

Alarm,  Burglar,  Central-Station 

A  burglar-alarm,  the  contact  points  of  which  .1 
are  placed  in  the  places  to  be  protected,  and  . 


Ala.] 


12 


[Ala. 


connected  by  suitable  circuits  with    alarms 
placed  in  a  centrally  located  station. 

In  a  system  of  central-station  burglar-alarms,  a 
number  of  houses,  factories,  banks,  etc.,  are  all 
connected  telegraphically  with  the  nearest  police 
station,  or  other  central  station,  constantly  pro- 
vided with  police  officers.  A  series  of  contacts  are 
placed  on  doors,  windows,  safes  and  money  draw- 
ers, and  connected  with  alarms  and  annunciators 
placed  in  the  central  station.  An  unauthorized 
entrance,  therefore,  is  automatically  telegraphed 
to  the  central  station  and  its  exact  location  indi- 
cated on  the  annunciator.  Systems  of  central- 
station  fire-alarms  are  constructed  on  a  similar 
plan. 


Alarm,  Electric 


— An  automatic  de- 


vice by  which  attention  is  called  to  the  occur- 
rence of  certain  events,  such  as  the  opening 
of  a  door  or  window;  the  stepping  of  a  person 
on  a  mat  or  staircase;  the  rise  or  fall  of  tem- 
perature beyond  a  given  predetermined  point; 
or,  a  device  intended  to  call  a  person  to  a  tel- 
egraphic or  telephonic  instrument. 

Electric-alarms  are  operated  by  means  of  the 
ringing  of  an  electro-magnetic  or  mechanical  bell, 


Fig.  ?.    Electrically  Started  Mechanical  Alarm, 

which  is  electrically  called  into  action  by  either 
closing  or  opening  an  electric  circuit,  generally 
the  former. 

Electric-alarms  may  be  divided  into  two  classes, 
Tiz.: 

(I.)  Mechanically  operated  alarms,  or  those  in 


which  the  alarm  is  given  by  clock-work,  started 
by  means  of  an  electric  current. 

(2.)  Those  in  which  the  alarm  is  both  set  in  ac- 
tion and  operated  by  an  electric  current. 

In  Fig.  7  is  shown  the  general  construction  of 
an  electrically  started  mechanical  alarm.  The 
attraction  of  the  armature  B,  by  the  electro-mag- 
net A,  moves  the  armature  lever  pivoted  at  C, 
and  thus  releases  the  catch  e,  and  permits  the 
spring  or  weight  connected  with  the  clock  move- 
ment to  set  it  in  motion  and  strike  the  bell. 

Electrically  actuated  alarm-bells  are  generally 
of  the  automatic  make-and -break  form.  The 
striking  lever  is  operated  by  the  attraction  of  the 
armature  of  an  electro-magnet,  and  is  provided 
with  a  contact-point,  so  placed  that  when  the 
hammer  is  drawn  away  from  the  bell,  by  the  ac- 
tion of  a  spring,  on  the  electro-magnet  losing  its 
magnetism,  a  contact  is  made,  but  when  the  ham- 
mer is  drawn  towards  the  bell  the  contact  is  open- 
ed. When,  therefore,  the  hammer  strikes  the 
bell,  the  circuit  is  opened,  and  the  electro-magnet 
releases  its  armature,  permitting  a  spring  to  again 
close  the  contact  by  moving  the  striking  lever 
away  from  the  bell.  Once  set  into  action,  these 
movements  are  repeated  while  there  is  battery 
power  sufficient  to  energize  the  magnet. 

In  Fig.  8,  in  which  is  shown  an  electrically  ac- 
tuated alarm-bell,  the  battery  terminals  are  con- 


Fig:  8.    Automatic  Make-and-Break. 

-ected  with  the  right  and  left  hand  binding-posts, 
P  and  M.  The  hammer,  K,  is  connected  with  a 
striking  lever,  which  forms  part  of  the  circuit, 
and  which  is  attached  to  the  armature  of  the  elec 
tro-magnet  e.  A  metallic  spring,  g,  bears  against 
the  armature  when  the  latter  is  away  from  the 
magnet,  but  does  not  touch  the  armature  when 
it  is  moved  towards  the  magnet.  A  small  spring 
draws  the  lever  away  from  the  magnet  when  no 
current  is  passing.  The  movements  of  the  arma- 


Alii. 


13 


[Ale. 


ture  thus  automatically  open  and  close  the  circuit 
of  the  electro-magnet. 

This  form  of  make-and-break  is  called  an  auto- 
matic make-and-break. 

Alarm,  Electrically  Operated An 

alarm  that  is  maintained  in  operation  by  the 
electric  current.  (See  Alarm,  Electric?) 

Alarm,  Electro-Mechanical  -  — A 
mechanically  operated  alarm  that  is  started 
or  set  in  operation  by  means  of  an  electric 
current.  (See  Alarm,  Electric?) 

Alarm,  Fire,  Automatic An  in- 
strument for  automatically  telegraphing  an 
alarm  from  any  locality  on  its  increase  in  tem- 
perature beyond  a  certain  predetermined  point. 

Fire-alarms  are  operated  by  thermostats,  or  by 
means  of  mercurial  contacts;  i.  e.,  a  contact 
closed  by  the  expansion  of  a  column  of  mercury. 
(See  Thermostat.  Contact,  Mercurial.) 

In  systems  of  fire-alarm  telegraphs,  the  alarm 
is  automatically  sounded  in  a  central  police  sta- 
tion and  in  the  district  fire-engine  house.  (See 
Telegraphy,  Fire-Alarm. ) 

Alarm,  Mercurial  Temperature 

An  instrument  for  automatically  telegraphing 
an  alarm  by  means  of  a  mercurial  contact  on 
a  predetermined  change  of  temperature. 

The  action  of  mercurial  contacts  is  dependent 
on  the  fact  that,  as  the  mercury  expands  more 
than  glass  by  the  action  of  heat,  the  mercury  level 
reaches  a  contact-point  placed  in  a  glass  tube  and 
thus  completes  the  circuit  through  its  own  mass, 
which  forms  the  other  or  movable  contact. 
Sometimes  both  contacts  are  placed  on  opposite 
sides  of  a  tube  and  are  closed  when  the  mercury 
reaches  them. 

Mercurial  temperature  or  thermo>tat  alarms 
are  employed  in  hot-houses,  incubators,  tanks 
and  buildings  for  the  purpose  of  maintaining  a 
uniform  temperature. 

Alarm,  Telegraphic  -  —An  alarm-bell 
for  calling  the  attention  of  an  operator  to 
a  telegraphic  instrument  when  the  latter  is  of 
the  non-acoustic  or  needle  type. 

In  acoustic  systems  of  telegraphy  the  sounds 
themselves  are  generally  sufficient. 

Alarm,  Telephonic An  alarm-bell 

for  calling  a  correspondent  to  the  receiving 
telephone. 


These  alarms  generally  consist  of  magneto- 
electric  bells.  (See  Bell,  Magneto- Electric.} 

Alarm,  Temperature An    electric 

alarm  automatically  operated  on  a  change  of 
temperature.  (See  Alarm,  Fire,  Automatic.} 

Alarm,  Thermostat An  electric 

alarm  that  is  thrown  into  action  by  a  thermo- 
stat. (See  Thermostat?) 

Alarm,  Water  or    Liquid  Level  — 

A  device  for  electrically  sounding  an  alarm 
when  a  water  surface  varies  materially  from 
a  given  level. 

An  electric  bell  is  placed  in  a  circuit  that  is  au- 
tomatically closed  or  broken  by  the  movement  of 
contact-points  operated  by  the  change  of  liquid 
level. 

A  form  of  electric  alarm  for  a  water-level  is 
shown  in  Fig.  9.  The  float  is  provided  with 
contacts  for  closing  an  electric  circuit,  when  it 
either  rings  a  bell,  or,  by  its  action  on  some  form 
of  automatic  cut-off,  stops  the  water. 


Fig.  ?.         Water-Level  Alarm.        Fig.  10. 

When  arranged  with  a  double  float,  as  shown 
in  Fig.  10,  the  alarm  may  be  made  to  signal 
either  a  too  high  or  a  too  low  water  level. 

Alarm,  Yale-Lock-Switch   Burglar  - 
— An   apparatus   whereby  the  opening  of  a 
door  by  an  authorized  party  provided  with  the 
regular  key  will  not  sound  an  alarm,  but  any 
other  opening  will  sound  such  alarm. 


Fig.  zi.    Yale-Lock-Suritch. 

A  Yale-lock  burglar-alarm  switch  is  shown  in 
Fig.  ii. 

Alcohol,  Electric  Aging1  of A  pro- 
cess for  the  rapid  aging  of  alcohol,  by  ex- 


Ale. 


14 


[All. 


posing  it  to  the  action  of  electrically  produced 
-ozone. 

Instead  of  the  ordinary  process  of  aging  alco- 
•hol,  by  exposing  it  in  partially  closed  vessels  to 
the  action  of  air,  it  is  exposed  to  the  action  of 
ozone,  electrically  produced. 

The  ozone  employed  is  obtained  in  substan- 
tially the  usual  way  by  the  passage  of  a  rapid 
succession  of  electric  sparks  through  air. 

Alcohol,  Electric  Rectification  of  — 

A  process  whereby  the  bad  taste  and  odor  of 
alcohol,  due  to  the  presence  of  aldehydes, 
are  removed  by  the  electrical  conversion  of 
the  aldehydes  into  true  alcohols  through  the 
addition  of  hydrogen  atoms. 

An  electric  current  sent  through  the  liquid 
between  zinc  electrodes  liberates  oxygen  and  hy- 
drogen irom  the  decomposition  of  the  water. 
"The  nascent  or  atomic  hydrogen  converts  the 
aldehydes  into  alcohol  and  deprives  the  pro- 
ducts of  their  fusel  oil,  while  the  oxygen  forms 
insoluble  zinc  oxide. 

Algebraic  Co-efficient. — (See  Co-efficient, 
Algebraic?) 

Algebraic  Notation.— (See  Notation,  Al- 
gebraic?) 

All-Night  Arc  Lamp.— (See  Lamp,  All- 
Night  Arc.} 

All-Night  Electric  Lamp. — (See  Lamp, 
All-Night  Arc.} 

Allotropic.— Pertaining  to  allotropy.  (See 
Allotropy.} 

Allotropic  State.— (See  State,  Allotropic}. 

Allotropy. — A  variation  of  the  physical 
properties  of  an  elementary  substance  with- 
out change  of  composition  of  its  molecules. — 
(See  State,  Allotropic} 

Alloy. — A  combination,  or  mixture,  of  two 
or  more  metallic  substances. 

Alloys  in  most  cases  appear  to  be  true  chemi- 
cal compounds.  In  a  few  instances,  however, 
they  may  form  simple  mixtures. 

The  composition  of  a  few  important  alloys  is 
here  given: 

Solder,  plumber's;  Tin  66  parts,  Lead  34  parts. 

Pewter,  hard;  Tin  92  parts,  Lead  8  parts. 

Britannia  metal;  Tin  100  parts,  Antimony  8 
parts,  Copper  4  parts,  Bismuth,  I  part. 


Type  metal;  Lead  80,  Antimony  20  parts. 
Brass,  white;  Copper  65,  Zinc  35  parts. 
Brass,  red;  Copper  90,  Zinc  10  parts. 
Speculum  metal;  Copper  67,  Tin  33  parts. 
Bell  metal;  Copper  78,  Tin  22  parts. 
Aluminium  bronze;  Copper  90,  Aluminium  10 
parts. 

Alloy. — To  form  a  combination  or  mixture 
of  two  or  more  metallic  substances. 

Alloy,  German  Silver An  alloy 

employed  for  the  wires  of  resistance  coils, 
consisting  of  50  parts  of  copper,  25  of  zinc, 
and  25  of  nickel. 

German  silver  wire  is  suitable  for  resistance 
coils,  because  its  resistance  varies  but  slightly  with 
changes  of  temperature.  It  is  cheaper  than  plati- 
num-silver alloy,  and  is  therefore  employed  ex- 
tensively. Platinum  silver  alloy,  however,  has 
more  resistance  for  a  given  size  of  wire,  and  its  re- 
sistance varies  somewhat  less  than  German  silver 
with  changes  of  temperature,  and  is  therefore  used 
where  greater  accuracy  is  desired. 

Alloy,  Palladium An  alloy  of  pal- 
ladium with  other  metals. 

Palladium  forms  a  number  of  useful  alloys  with 
various  metals.  Some  of  the  palladium  alloys  are 
as  elastic  as  steel,  are  unaffected  by  moisture  or 
ordinary  corrosive  agencies,  and  are  entirely  de- 
void of  paramagnetic  properties;  that  is  to  say, 
they  cannot  be  magnetized  after  the  manner  ot' 
iron. 

These  properties  have  been  utilized  bv  their 
discoverer,  Paillard,  in  their  employment  for  the 
hair-springs,  escapements  and  balance  wheels  of 
watches,  in  order  to  permit  the  watches  to  be  car- 
ried into  strong  magnetic  fields  without  any  ap- 
preciable effects  on  the  rate  of  the  watch.  A 
number  of  careful  tests  made  by  the  author,  by 
long  continued  exposure  of  watches,  thus  pro- 
tected by  the  Paillard  alloys,  in  extraordinary 
fields,  show  that  the  protection  thus  given  the 
watches  enables  them  to  be  carried  into  the  strong- 
est possible  magnetic  fields  without  appreciably 
affecting  their  rate. 

The  Paillard  palladium  alloys  have  the  follow- 
ing composition,  viz. : 

Alloy  No.  i. 

Palladium 60  to  75  parts. 

Copper 15  to  25       " 

Iron   I  to    5      " 


All.] 


15 


[Alp. 


Alloy  No.  2. 

Palladium 50  to  75  parts. 

Copper 201030      " 

Iron 5  to  20      " 

Alloy  No.  j. 

Palladium 651075  " 

Copper 15*025  " 

Nickel  I  to    5  " 

Gold I  to    2j  " 

Platinum ^  to    2  " 

Silver 3  to  10  " 

Steel i  to    5  " 

Alloy  No.  4. 

Palladium 45  to  50  " 

Silver 20  to  25  " 

Copper 15  to  25  " 

Gold 2  to    5  " 

Platinum 2  to    5  " 

Nickel 2  to    5  " 

Steel 2  to    5  " 

The  great  value  of  the  palladium  alloys,  when 
employed  for  the  hair-springs  of  watches,  arises 
not  only  from  their  non-magnetizable  properties, 
and  their  inoxidizability,  but  particularly  from  the 
fact  that  their  elasticity  is  approximately  the  same 
for  comparatively  wide  ranges  of  temperature. 

Alloy,  Platinum-Silver An  alloy 

consisting  of  one  part  of  platinum,  and  two 
parts  of  silver. 

Platinum  silver  alloy  is  now  extensively  em- 
ployed for  resistance  coils  from  the  fact  that 
changes  in  temperature  of  the  alloy  produce  but 
comparatively  small  changes  in  its  electrical  re- 
sistance. (See  Alloy,  German  Silver.) 

Alphabet,  Telegraphic  — An  arbi- 
trary code  consisting  of  dots  and  dashes, 
sounds,deflections  of  a  magnetic  needle,  flashes 
of  light,  or  movements  of  levers,  following  one 
another  in  a  given  predetermined  order,  to 
represent  the  letters  of  the  alphabet  and  the 
numerals. 

Alphabet,  Telegraphic :  International 

Code The  code  of  signals  for  letters, 

etc.,  employed  in  England  and  on  the  Euro- 
pean continent  generally. 

Similar  symbols  are  employed  for  the  numerals 
and  the  punctuation  marks. 

It  will   be   observed   that  it  is  mainly  in  the 


characters  of  the  American  Morse,  in  which  spaces 
are  used,  that  the  Continental  characters  differ 
from  the  American.  This  is  due  to  the  use  of  the 
needle  instrument,  with  which  a  space  cannot  well 
be  represented.  A  movement  or  deflection  of  the 


Single 
Needle 


Single 

/Needle 


O 


t     _ 


a  . — 
b    __.« 
c    _,_ 

d     . 


f    .. VN/- 

g    —         '/* 

h       ....  ,      NXNX 

•         ~.  ^ 

J* ^/// 

k A/ 

I        . S/xx 

m  __  —        // 

International  Telegraphic  Code. 

needle  to  the  left  signifies  a  dot ;  a  movement  to 
the  right,  a  dash. 

Alphabet,   Telegraphic :  Morse's 

Various  groupings  of  dots  and  dashes,  or 
deflections  of  a  magnetic  needle  to  the  right 
and  left,  which  represent  the  letters  of  the 
alphabet  or  other  signs. 

In  the  Morse  alphabet  dots  and  dashes  are  em- 
ployed in  recording  systems,  and  sounds,  of 
varying  intervals,  corresponding  to  the  dots  and 
dashes,  in  the  sounder  system. 

A  dash  is  equal  in  length  of  time  to  three  dots. 
The  space  between  the  separate  characters  of  a 
single  letter  is  equal  to  one  dot,  except  in  the 
American  Morse,  in  which  the  following  letters 
contain  longer  spaces:  C,  O,  R,  Y,  and  Z.  The 
lengthened  spaces  are  equal  to  two  dots.  L  is 
one  and  a  half  times  the  length  of  T. 

The  sound  produced  by  the  down  stroke  of  the 
sounding  lever  in  the  Morse  sounder  is  readily 
distinguishable  from  the  up  stroke.  When  these 
differences  are  taken  in  connection  with  the  inter- 
vals between  successive  sounds  there  is  no  diffi- 
culty in  reading  by  sound. 

(For  methods  of  receiving  the  alphabet,  see 
Sounder,  Morse  Telegraphic.  Recorder,  Morse. 
Recorder,  Bain's  Chemical.  Recorder,  Siphon. 
Relay.  Magnet,  Receiving.)  In  the  net  die  tele- 
graph, the  code  is  similar  to  that  used  in  the  Morse 
Alphabet.  (See  Telegraphy,  Single-Needle.) 


Alt.] 


16 


[Alt. 


AMERICAN  MORSE  CODE. 
ALPHABET. 


a 

b 

c  --    - 

d 

e  - 
i 


k 

1  

m 


I 

2 

3 

4 

c 


n 

o  -  - 

P 

q 

r  -    -- 
s 

u 

V 

w 

X 

y    ..     .. 


&    .      ... 

NUMERALS. 


6  - 


PUNCTUATION    MARKS. 

Period Interrogation  . 

Comma Exclamation . 

Printing  Single  Needle 

t  x//// 

2  xx    /// 

3  x  x  v    // 


4 

5 
6 
7 

8 
9 
10 


x   x  x  x 
x    x   \   x   \ 
/  \   \    x    x 
//x   x  x 
///xx 


_____        ///// 


Period  ------  XX     xx     xx 

Comma         ----  .^  \/\/\/ 

Interrogation  ______  xx   //xx 

Exclamation  __  1  __  _  .  //xx// 

Colon  ------  ///xxx 

Semicolon     ------  /x  /x  /x 

Alteration  Theory  of  Muscle  or  Nerve 
Current—  (See  Theory,  Alteration,  of 
Muscle  or  Nerve  Current?) 

Alternating  Arc.—  (See  Arc,  Alternat- 
ing.} 

Alternating  Current  Circuit.—  (See  Cir- 
cuit, Alternating  Current?) 


Alternating    Current    Condenser.— (See 

Condenser,  Alternating  Current?) 

Alternating  Current  Dynamo-Electric 
Machine. — (See  Machine,  Dynamo-Electric, 
Alternating  Current?) 

Alternating  Current  Electric   Motor.— 

(See  Motor,  Electric,  Alternating  Current?) 

Alternating  Currents. — (See  Currents, 
Alternating?) 

Alternating  Currents,  Distribution  of 
Electricity  by  —  —(See  Electricity,  Dis- 
tribution of,  by  Alternating  Currents?) 

Alternating  Discharge. — (See  Dischange, 
Alternating?) 

Alternating  Dynamo-Electric  Machine. — 

(See  Machine,  Dynamo-Electric,  Alternat- 
ing Current?) 

Alternating    Electrostatic    Field.— (See 

Field,  Alternating  Electrostatic.} 

Alternating  Electrostatic  Potential. — 
(See  Potential,  Alternating  Electrostatic?) 

Alternating  Field. — (See  Field,  Alternat- 
ing?) 

Alternating  Influence  Machine,  Wims- 
hurst's  —  — (See  Machine,  Wimshurst's 
Alternating  Influence?) 

Alternating  Magnetic  Field. — (See  Field, 
Alternating  Magnetic?) 

Alternating  Magnetic  Potential. — (See 
Potential,  Alternating  Magnetic.} 

Alternating  Potential. — (See  Potential, 
Alternating?) 

Alternating  Primary  Currents. — (See 
Currents,  Alternating  Primary?) 

.Alternating  Secondary  Currents. — (See 
Currents,  Alternating  Secondary?) 

Alternation. — A  change  in  direction  or 
phase. 

Alternations. — Changes  in  the  direction  of 
a  current  in  a  circuit. 

A  current  that  changes  its  direction  300  times 
•per  second  is  said  to  possess  300  alternations  per 
second. 

Alternations,  Complete A  change 

in  the  direction  of  a  current  in  a  circuit  from  its 


Alt] 


[Amnu 


former  direction  and  back  again  to  that 
direction.  A  complete  to-and-fro  change. 

Complete  alternations  are  sometimes  indicated 
by  the  symbol  ~. 

Alternations,  Frequency  of — A 

phrase  employed  to  denote  the  number  of  al- 
ternations per  second. 

Alternative  Path. — (See  Path,  Alterna- 
tive^) 

Alternatives,  Voltaic A  term  used 

in  medical  electricity  to  indicate  sudden  re- 
versals in  the  polarity  of  the  electrodes  of  a 
voltaic  battery. 

An  alternating  current  from  a  voltaic  bat- 
tery, obtained  by  the  use  of  a  suitable  com- 
mutator. 

Sudden  reversals  of  polarity  produce  more 
energetic  effects  of  muscular  contraction  than  do 
simple  closures  or  completions  of  the  circuit. 

The  muscular  contraction  produced  by  a  voltaic 
current  is  much  stronger  when  the  direction  of  the 
current  is  rapidly  reversed  by  means  of  a  com- 
mutator than  when  the  current  is  more  slowly 
broken  and  the  poles  then  reversed. 

The  effect  of  voltaic  alternatives  is  to  produce 
quick  contractions  that  are  in  strong  contrast  to 
the  prolonged  contractions  that  result  from  the 
faradic  current.  In  the  faradic  machine,  the 
reversals  are  so  rapid  that  the  muscle  fails  to 
return  to  rest  before  it  is  again  contracted. 

Voltaic  alternatives  are  sometimes  indicated  by 
the  contraction  V.  A. 

Alternator. — A  name  commonly  given  to 
an  alternate  current  dynamo.  (See  Machine, 
Dynamo-Electric,  Alternating  Current?) 

Alternator,  Compensated  Excitation  of 

An  excitation  of  an  alternating  current 

dynamo-electric  machine,  in  which  the  field  is 
but  partially  excited  by  separate  excitement, 
the  remainder  of  its  exciting  current  being 
derived  from  the  commuted  currents  of  a 
small  transformer  placed  in  the  main  circuit 
of  the  machine. 

The  object  of  compensated  excitation  of  an 
alternator  is  to  render  the  machine  self-governing. 

Amalgam. — A  combination  or  mixture 
of  a  metal  with  mercury. 

Amalgam,  Electric  — A  substance 


with  which  the  rubbers  of  the  ordinary  fric- 
tional  electric  machines  are  covered. 

Electric  amalgams  are  of  various  compositions. 
The  following  formula  produces  an  excellent 
amalgam  : 

Melt  together  five  parts  of  zinc  and  three  of 
tin,  and  gradually  pour  the  molten  metal  into 
nine  parts  of  mercury.  Shake  the  mixture  until 
cold,  and  reduce  to  a  powder  in  a  warm  mortar. 
Apply  to  the  cushion  by  means  of  a  thin  layer  of 
stiff  grease. 

Mosaic  gold,  or  bisulphide  of  tin,  and  powdered 
graphite,  both  act  as  good  electric  amalgams. 

An  electric  amalgam  not  only  acts  as  a  con- 
ductor to  carry  off  the  negative  electricity,  but, 
being  highly  negative  to  the  glass,  produces  a  far 
higher  electrification  than  would  mere  leather  or 
chamois. 

Amalgamate. — To  form  into  an  amalgam. 

Amalgamating. — Forming  into  an  amal- 
gam. 

Amalgamation. — The  act  of  forming  into 
an  amalgam,  or  effecting  the  combination  of 
a  metal  with  mercury. 

Amalgamation  of  Zinc  Plates  of  Voltaic 
Cell.— (See  Plates,  Zinc,  of  Voltaic  Cell, 
Amalgamation  of.) 

Amber. — A  resinous  substance,  generally 
of  a  transparent,  yellow  color. 

Amber  is  interesting  electrically  as  being  be- 
lieved to  be  the  substance  in  which  the  proper- 
ties of  electric  attractions  and  repulsions,  imparted 
by  friction  or  rubbing,  were  first  noticed.  It  was 
called  by  the  Greeks  rj\.EM.Tpov,  from  which  the 
word  electricity  is -derived.  This  property  was 
mentioned  by  the  Greek,  Thales  of  Miletus,  600 
B.  c.,  as  well  as  by  Theophrastus. 

American  System   of  Telegraphy.— (See 

Telegraphy,  American  System  of.) 

American  Twist-Joint. — (See  Joint, 
American  Twist.) 

American  Wire  Gange. — (See  Gauge, 
Wire,  American?) 

Ammeter. — A  form  of  galvanometer  in 
which  the  value  of  the  current  is  measured 
directly  in  amperes.  (See  Galvanometer!) 

An  ampere-meter  or  ammeter  is  a  commercial 
form  of  galvanometer  in  which  the  deflection*  of 


A  ill  ill. 


18 


[Amp. 


a  magnetic  needle  are  calibrated  or  valued  in  am- 
peres. As  a  rule  the  coils  of  wire  in  an  ammeter 
are  of  lower  resistance  than  in  a  voltmeter.  The 
magnetic  needle  is  deflected  from  its  zero  position 
by  the  field  produced  by  the  current  whose  strength 
in  amperes  is  to  be  measured.  This  needle  is  held 
in  the  zero  position  by  the  action  of  a  magnetic 
field,  either  of  a  permanent  or  an  electro-magnet, 
by  the  action  of  a  spring,  or  by  a  weight  under  the 
influence  of  gravity.  There  thus  exist  a  variety 
of  ammeters,  viz. :  permanent -magnet  ammeters, 
electro-magnetic  ammeters,  spring  ammeters  and 
gravity  ammeters. 

In  the  form  originally  devised  by  Ayrton  and 
Perry,  the  needle  came  to  rest  almost  imme- 
diately, or  was  dead-beat  in  action.  (See  Damp- 
ing.') It  moved  through  the  field  of  a  permanent 
magnet.  The  instrument  was  furnished  with  a 
number  of  coils  of  insulated  wire,  which  could 
be  connected  either  in  series  or  in  multiple-arc  by 
means  of  a  commutator,  thus  permitting  the  scale 
reading  to  be  verified  or  calibrated  by  the  use  of  a 
single  voltaic  cell.  (See  Circuits,  Varieties  of. 
Commutatoi .  Calibration,  Absolute.  Calibra- 
tion, Relative.)  In  this  case  the  coils  were 
turned  to  series,  and  a  plug  pulled  out,  thus  intro- 
ducing a  resistance  of  one  ohm. 

c 


Fig.  12.     Ayrton  and  Perry  Ammeter. 

Fig.  12  represents  an  ampere-meter  devised  by 
Ayrton  and  Perry.  A  device  called  a  commutator 
for  connecting  the  coils  either  in  series  or  parallel 
is  shown  at  C.  Binding-posts  are  provided  at 
P,  PS,  and  S.  The  dynamo  terminals  are  con- 
nected at  the  posts  P,  PS,  and  the  current  will 
pass  only  when  the  coils  are  in  multiple,  thus 
avoiding  accidental  burning  of  the  coils.  In  this 
case  the  entire  current  to  be  measured  passes 
through  the  coils  so  coupled.  The  posts  S  and 
PS,  are  for  connecting  the  single  battery  cell  cur- 
vent. 

A  great  variety  of  ampere-meters,  or  ammeters, 
have  been  devised.  They  are  nearly  all,  how- 


ever, constructed  on  essentially  the  same  general 
principles. 

Commercial  ammeters  are  made  in  a  great  va- 
riety of  forms.  When  the  currents  to  be  meas- 
ured are  large,  as  is  generally  the  case  in  electric 
light  or  power  stations,  they  consist  of  a  coil  of 
insulated  wire,  often  of  a  single  turn,  or  even  of 
but  a  part  of  a  turn,  having  a  balanced  core  of 
iron  or  steel  capable  of  moving  freely  within  it. 

Ammeter,      Electro-Magnetic A 

form  of  ammeter  in  which  a  magnetic  needle  is 
moved  against  the  field  of  an  electro-magnet 
by  the  field  of  the  current  it  is  measuring. 
(See  Ammeter.) 

Ammeter,  Gravity A  form  of  am- 
meter in  which  a  magnetic  needle  is  moved 
against  the  force  of  gravity  by  the  field  of  the 
current  it  is  measuring.  (See  Ammeter?) 

Ammeter,       Magnetic- Yane An 

ammeter  in  which  the  strength  of  a  magnetic 
field  produced  by  the  current  that  is  to  be 
measured  is  determined  by  the  repulsion  ex- 
erted between  a  fixed  and  a  movable  iron 
vane,  placed  in  said  field  and  magnetized 
thereby.  (See  Voltmeter,  Magnetic-  Vane.) 

Ammeter,     Permanent-Magnet A 

form  of  ammeter  in  which  a  magnetic  needle 
is  moved  against  the  field  of  a  permanent  mag- 
net by  the  field  of  the  current  it  is  measuring. 
(See  Ammeter?) 

Ammeter,  Reducteur  for (See  Re- 

ducteur,  or  Shunt  for  Ammeter?) 

Ammeter,  Spring A  form  of  am- 
meter in  which  a  magnetic  needle  is  moved 
against  the  action  of  a  spring  by  the  field  of 
the  current  it  is  measuring.  (See  Ammeter) 

Amorphous. — Having  no  definite  crys- 
talline form. 

Mineral  substances  have  certain  crystalline 
forms,  that  are  as  characteristic  of  them  as  are  the 
forms  of  animals  or  plants.  Under  certain  cir- 
cumstances, however,  they  occur  without  definite 
crystalline  form,  and  are  then  said  to  be  amor- 
phous solids. 

Amperage. — The  number  of  amperes  pass- 
ing in  a  given  circuit. 

The  current  strength  in  any  circuit  as  indi- 
cated by  an  ampere-meter  placed  in  the  circuit. 


Amp.] 


19 


[Amp. 


Ampere. — The  practical  unit  of  electric 
current. 

Such  a  rate-of-flow  of  electricity  as  trans- 
mits one  coulomb  per  second. 

Such  a  current  (or  rate-of-flow  or  trans- 
mission of  electricity)  as  would  pass  with  an 
electromotive  force  of  one  volt  through  a  cir- 
cuit whose  resistance  is  equal  to  one  ohm. 

A  current  of  such  a  strength  as  would 
deposit  .005084  grain  of  copper  per  second. 

A  current  of  one  ampere  is  a  current  of  such 
definite  strength  that  it  would  flow  through  a  cir- 
cuit of  a  certain  resistance  and  with  a  certain 
electromotive  force.  (See  Force,  Electromotive, 
Volt.  Resistance.  Ohm.) 

Since  the  ohm  is  the  practical  unit  of  resistance, 
and  the  volt  the  practical  unit  of  electromotive 
force,  the  ampere,  or  the  practical  unit  of  current, 
is  the  current  that  would  flow  through  unit  resist- 
ance, under  unit  pressure  or  electromotive  force. 

To  make  this  clearer,  take  the  analogy  of  water 
flowing  through  a  pipe  under  the  pressure  of  a 
column  of  water.  That  which  causes  the  flow  is 
the  pressure  or  head ;  that  which  resists  the  flow 
is  the  friction  of  the  water  against  the  pipe,  which 
will  vary  with  a  number  of  circumstances.  The 
rate-of-flow  may  be  represented  by  so  many  cubic 
inches  of  water  per  second. 

As  the  pressure  or  head  increases,  the  flow  in- 
creases proportionally;  as  the  resistance  increases, 
the  flow  diminishes. 

Electrically,  electromotive  force  corresponds  to 
the  pressure  or  head  of  the  water,  and  resistance 
to  the  friction  of  the  water  and  the  pipe.  The 
ampere,  which  is  the  unit  rate-of-flow ptr  second, 
may  therefore  be  represented  as  follows, 

Tp 

viz. :      C  =  — ,  as  was  announced  by  Ohm  in  his 
R 

law.     (See  Law  of  Ohm.) 

This  expression  signifies  that  C,  the  current  in 
amperes,  is  equal  to  E,  the  electromotive  force  in 
volts,  divided  by  R,  the  resistance  in  ohms. 

We  measure  the  rate-of-flow  of  liquids  as  so 
many  cubic  inches  or  cubic  feet  per  second — that  is, 
in  units  of  quantity.  We  measure  the  rate-of-flow 
of  electricity  as  so  much  electricity  per  second. 
The  electrical  unit  of  quantity  is  called  the  Coul- 
omb. (See  Coulomb.']  The  coulomb  is  such  a 
quantity  as  would  pass  in  one  second  through  a 
circuit  in  which  the  rate-of-flow  is  one  ampere. 

An  ampere  is  therefore  equal  to  one  coulomb  per 
second. 


The  electro-magnetic  unit  of  current  is  such  a 
current  that,  passed  through  a  conducting  wire 
bent  into  a  circle  of  the  radius  of  one  centimetre, 
would  tend  to  move  perpendicular  to  its  plane  a 
unit  magnetic  pole  held  at  its  centre,  and 
sufficiently  long  to  practically  remove  the  other 
pole  from  its  influence,  with  unit  force,  *'.  e.,  the 
force  of  one  dyne.  (See  Dyne.)  The  ampere,  or 
practical  electro-magnetic  unit,  is  one-tenth  of 
such  a  current ;  or,  in  other  words,  the  absolute 
unit  of  current  is  ten  amperes. 

An  ampere  may  also  be  defined  by  the  chemical 
decomposition  the  current  can  effect  as  measured 
by  the  quantity  of  hydrogen  liberated,  or  metal 
deposited. 

Defined  in  this  way,  an  ampere  is  such  a  cur- 
rent as  will  deposit  .00111815  gramme,  or 
.017253  grain,  of  silver  per  second  on  one  of  the 
plates  of  a  silver  voltameter,  from  a  solution  of 
silver  nitrate  containing  from  15  to  30  per  cent,  of 
the  salt  (See  Voltameter),  or  which  will  decompose 
.00009326  gramme,  or  .001439  grain  of  dilute 
sulphuric  acid  per  second,  or  pure  sulphuric  acid 
at  59  degrees  F.  diluted  with  about  15  per  cent,  of 
water,  that  is,  dilute  sulphuric  acid  of  Sp.  Gr.  of 
about  i.i.  The  present  scientific  and  commercial 
practice  is  to  take  the  ampere  to  be  such  a  current 
as  will  deposit  4  024  grammes  of  silver  in  one  hour. 

Ampere  Arc. — (See  Arc,  Ampere?) 
Ampere-Feet. — (See  Feet,  Ampere.) 
Ampere-Hour. — (See  Hour,  Ampere?) 

Ainpdre-Meter. — An  ammeter.  (See  Am- 
meter?) 

Ampere-Meter,  Balance  or  Neutral  Wire 

An  ampere-meter  placed  in  the  cir- 
cuit of  the  neutral  wire,  in  the  three-wire  sys- 
tem of  electric  distribution,  for  the  purpose  of 
showing  the  excess  of  current  passing  over 
one  side  of  the  system  as  compared  with  the 
other  side,  when  the  central  wire  is  no  longer 
neutral. 

Ampere-Minute. — (See  Minute,  Ampere?) 
Ampdre  Ring. — (See  Ring,  Ampere?) 
Ampere-Second. — (See  Second,  Ampere?) 
Ampdre  Tap. — (See  Tap,  Ampere?) 
Ampere-Turn. — (See  Turn,  Ampere?) 

Ampere-Turn,  Primary (See  Turn, 

Ampere,  Primary?) 


Amp.] 


20 


[Ane. 


Ampere-Turn,     Secondary 

Turn,  Ampere,  Secondary?) 


—  (See 


of  a 


Ampere-  Volt.  —  A  watt,  or  the 
horse-power. 

This  term  is  generally  written  volt-ampere. 
(See  Volt-Ampere.} 

Ampere-Winding.  —  (See  Winding,  Am- 
pere) 

Ampere's  Rule  for  Effect  of  Current  on 
Needle.  —  (See  Rule,  Ampere's,  for  Effect  of 
Current  on  Needle.} 

Ampere's  Theory  of  Magnetism.  —  (See 
Magnetism,  Ampere  s  Theory  of.) 

Amperian  Currents.  —  (See  Currents,  Am- 
perian.) 

Amplitude  of  Vibration  or  Ware.  —  (See 
Vibration  or  Wave,  Amplitude  of.) 

Ammunition-Hoist,  Electric  --  —  An 
electrically  operated  hoist  for  raising  ammu- 
nition to  the  deck  of  a  ship. 

In  the  electric  ammunition-hoist  the  electric 
motor  which  moves  the  hoist  is  made  to  follow  the 
motions  of  the  operator's  hand,  both  as  regards 
direction  and  speed.  The  motion  of  a  crank,  or 
wheel,  causes  a  switch  to  start  an  electric  motor  in 
a  certain  direction,  which  tends  to  close  the  switch, 
thus  necessitating  a  race  between  the  operator 
and  the  motor.  Should  the  operator  begin  to 
close  the  switch  more  slowly,  the  m  tor  will  over- 
take him,  will  partially  close  the  switch,  and  thus 
lower  the  speed  of  the  motor. 

Analogous  Pole.  —  (See  Pole,  Analogous) 

Analysis.  —  The  determination  of  the  com- 
position of  a  compound  substance  by  separ- 
ating it  into  the  simple  or  elementary  sub- 
stances of  which  it  is  composed. 

Analysis,  Electric  --  The  determin- 
ation of  the  composition  of  a  substance  by 
electrical  means. 

Various  processes  have  been  proposed  for  elec- 
tric analysis;  they  consist  essentially  in  decompos- 
ing the  substance  by  means  of  electric  currents, 
and  are  either  qualitative  or  quantitative.  (See 
Electrolysis.) 

Analysis,  Electrolytic  --  A  term 
sometimes  used  instead  of  electric  analysis. 
(See  Analysis,  Electric) 

Analysis,   Qualitative  --  A   chemical 


analysis  which  merely  ascertains  the  kinds  of 
elementary  substances  present. 

Analysis,  Quantitative A  chemical 

analysis  which  ascertains  the  relative  propor- 
tions in  which  the  different  components  enter 
into  a  compound. 

Analyzable. — Separable  into  component 
parts. 

Analyze. — To  separate  into  component 
parts. 

Analyze,  Electrically To  separate 

electrically  into  component  parts. 

Analyzer,  Electric A  gridiron   of 

metallic  wires  which  is  transparent  to  electro- 
magnetic waves,  when  its  length  is  perpendic- 
ular to  them,  but  opaque  to  them — /'.  e., 
possessing  the  ability  to  reflect  them — when 
rotated  90  degrees  from  its  former  position. 

The  electric  analyzer,  it  will  be  observed,  is 
analogous  to  an  analyzer  for  polarized  light.  A 
reflecting  surface,  for  example,  being  able  to  re- 
flect polarized  light  in  a  given  position,  and  unable 
to  reflect  it  when  rotated  90  degrees  from  such 
position,  is  capable  of  acting  as  an  analyzer  lor 
polarized  light. 

Analyzer,  Gray's,  Harmonic  Telegraphic 

An  electro-magnet,  the  armature  of 

which  consists  of  a  steel  ribbon  stretched  in 
a  metallic  frame  and  capable  through  regula- 
tion, as  to  tension,  by  means  of  a  screw,  of 
being  tuned  to  a  certain  note. 

The  steel  ribbon  is  thrown  into  vibration  when- 
ever pulsations  from  the  transmitting  instruments 
are  sent  over  the  line  corresponding  to  the  rate  t.f 
motion  of  the  ribbon,  but  is  not  set  into  vibration 
by  any  others.  If,  therefore,  a  number  of  different 
analyzers,  tuned  to  different  notes,  are  placed  on 
the  same  line,  each  will  be  operated  only  by  the 
pulsations  sent  into  the  line  corresponding  to  its 
rate  of  motion,  and  thus  multiple  transmission  in 
the  same  direction  is  possible.  In  order  to- 
strengthen  the  tones  of  the  analyzers,  each  is  pro- 
vided  with  a  resonant  air  column.  (See  Reson- 
ator. Telegraphy,  Multiplex.) 

Analyzing. — Separating  into  component 
parts. 

Anelectric. — A  word  formerly  applied  to 
bodies  (conductors)  which  it  was  believed 
could  not  he  electrified  by  friction. 


Aue.] 


21 


[Ani. 


This  term  is  now  obsolete.  Conductors  are 
•easily  electrified,  when  insulated. 

Anelectrotonic  State.— (See  State,  Anelec- 
trotonic?) 

Anelectrotonic  Zone. — (See  Zone,  Anelec- 
trotonic^) 

Anelectrotonns. — In  electro-therapeutics, 
the  decreased  functional  activity  which  occurs 
in  a  nerve  in  the  neighborhood  of  the  anode, 
or  positive  electrode,  when  applied  therapeu- 
tically.  (See  Electrotonus) 

Anemometer,  Electric An  appa- 
ratus to  electrically  record  or  indicate  the  direc- 
tion and  intensity  of  the  wind. 

In  the  electric  recording  anemometer,  the  force 
or  velocity  of  the  wind,  or  both,  are  recorded  on 
a  moving  sheet  of  paper,  on  which  the  time  is 
marked,  so  that  the  exact  time  of  any  given 
change  is  known. 

Anemoscope. — An  instrument  which  indi- 
cates, but  does  not  measure  the  intensity  or 
record  the  direction  of  the  wind. 

The  word  is  often,  though  improperly,  used  in- 
terchangeably for  anemometer. 

Angle. — The  deviation  in  direction  between 
two  lines  or  planes  that  meet. 

Angles  are  measured  by  arcs  of  circles.  The 
angle  at  B  A  C,  Fig.  13,  is  the  deviation  of  the 
straight  line  A  B,  from  A 
C.  In  reading  the  let- 
tering of  an  angle  the 
letter  placed  in  the  mid- 
dle indicates  the  angle 
referred  to.  Thus  B  A 
C,  means  the  angle  be- 
tweenABandAC;  B  A 


B 


A  C 

Fig.  fj.    Angles. 
D,  the  angle  between  B  A  and  A  D.    Angles  are 
valued  in  degrees,  there  being  360  degrees  in  an 
entire  circumference  or  circle.     Degrees  are  in- 
dicated thus:  90°,  or  ninety  degrees. 

Angle,  Acute An  angle  whose  value 

is  less  than  a  right  angle  or  90  degrees. 

B  A  E,  or  E  A  D,  in  Fig.  13,  is  an  acute  angle. 

Angle,  Complement  of What  an 

angle  needs  to  make  its  value  90  degrees,  or  a 
right  angle. 

Thus  in  Fig.  13,  B  A  E,  is  the  complement  of 
the  angle  E  A  D.  since  B  AE4-EAD  =  o/> 
degrees. 


Angle,  Obtnse  — An  angle  whose 

value  is  greater  than  a  right  angle  or  90 
degrees. 

E  A  C,  Fig.  13,  is  an  obtuse  angle. 

Angle  of  Declination  or  Variation. — (See 
Declination,  Angle  of.  Variation,  Angle  of.) 

Angle  of  Difference  of  Phase  Between 
Alternating  Currents  of  Same  Period. — 
(See  Phase,  Angle  of  Difference  of,  Between 
Alternating  Currents  of  Same  Period?) 

Angle  of  Dip. — (See  Dip.  Dip  or  Incli- 
nation, Angle  of?) 

Angle  of  Inclination. — (See  Dip  or  Incli- 
nation, Angle  of.) 

Angle  of  Lag  of  Dynamo-Electric  Ma- 
chine.— (See  Lag,  Angle  of,  of  Dynamo- 
Electric  Machine?) 

Angle  of  Lead. — (See  Lead,  Angle  of) 

Angle  of  Variation. — (See  Variation, 
Angle  of.) 

Angle,  Plane An  angle  contained 

between  two  straight  lines. 

Angle,  Solid An  angle  contained 

between  two  surfaces. 

Angle,  Supplement  of What  an 

angle  needs  to  make  its  value  180  degrees,  or 
two  right  angles. 

Thus  in  Fig.  13,  E  A  C,  is  the  supplement  of 
E  A  D,  because  EAD-fEAC  =  i8o  degrees, 
or  two  right  angles. 

Angle,  Unit  -  —An  angle  of  57.29578° 
or  57°  17'  44.8"  nearly. — (See  Velocity,  An- 
gular?) 

Angular  Currents. — (See  Currents,  An- 
gular?) 

Angular  Velocity.— (See  Velocity,  Angu- 
lar?) 

Animal  Electricity. — (See  Electricity, 
Animal?) 

Animal  Magnetism. — (See  Magnetism, 
Animal?) 

Anion. — The  electro-negative  radical  of  a 
molecule. 

Literally,  the  term  ion  signifies  a  group  of 
wandering  atoms.  An  anion  is  that  group  of 
atoms  of  an  electrically  decomposed  or  electro ly zed 


Ani.] 


22 


[Ann. 


molecule  which  appears  at  the  anode.  (See 
Electrolysis.  Anode. ) 

As  the  anode  is  connected  with  the  electro- 
positive terminal  of  a  source,  the  anion  is  the 
electro-negative  radical  or  group  of  atoms,  and 
therefore  appears  at  the  electro-positive  terminal. 

A  kathion,  or  electro-positive  radical,  appears 
at  the  kathode,  which  is  connected  with  the 
electro-negative  terminal  of  the  battery.  Oxygen 
and  chlorine  are  anions.  Hydrogen  and  the 
metals  are  kathions. 

Anisotropic  Conductor. — (See  Conductor, 
Anisotropic?) 

Anisotropic  Medium. — (See  Medium, 
Anisotropic?) 

Annealing,  Electric A  process 

for  annealing  metals  in  which  electric  heating 
is  substituted  for  ordinary  heating. 

Annual  Inequality  of  Earth's  Magnet- 
Ism. — (See  Inequality,  Annual,  of  Earth's 
Magnetism. 

Annual   Variation  of  Magnetic  Needle. 

— (See  Needle,  Magnetic,  Annual  Variation 
of.} 

Annunciator,  Burglar-Alarm An 

annunciator  used  in  connection  with  a  system 
of  burglar-alarms.  (See  Alarm,  Burglar?) 

Annunciator  Clock,  Electric  — 

(See  Clock,  Electric  Annunciator?) 

Annunciator  Drop. — (See  Drop,  Annun- 
ciator?) 

Annunciator    Drop,  Automatic 

(See  Drop,  Automatic  Annunciator?) 
Annunciator,    Electro-Magnetic  — 

An  electric  device  for  automatically  indicating 
the  points  or  places  at  which  one  or  more 
electric  contacts  have  been  closed. 

The  character  of  the  annunciator  depends,  of 
course,  on  the  character  of  the  places  at  which 
these  points,  places  or  stations  are  situated. 

Annunciators  are  employed  for  a  variety  of 
purposes.  In  hotels  they  are  used  for  indicating 
the  number  of  a  room  the  occupant  of  which 
desires  some  service,  which  he  signifies  by  push- 
ing a  button,  thus  closing  an  electric  circuit. 
This  is  indicated  or  announced  on  the  annuncia- 
tor by  the  falling  of  a  drop,  on  which  is  printed  a 
number  corresponding  with  the  room,  and  by  the 


ringing  of  a  bell  to  notify  the  attendant.  The  num- 
ber is  released  by  the  movement  of  the  armature 
of  an  electro-magnet.  The  drops  are  replaced  in 
their  former  position  by  some  mechanical  device 
operated  by  the  hand.  In  the  place  of  a  drop  a 


Fig.  14.    Electro- Magnetic  Annunciator. 

needle  is  sometimes  u<ed,  which,  by  the  attraction 
of  the  armature  of  an  electro-magnet,  points  to 
the  number  signaling. 

Annunciators  for  houses,  burglar-alarms,  fire- 
alarms,  elevators,  etc.,  are 
of  the  same  general  con- 
struction. 

Annunciators  are  general- 
ly operated  by  electro-mag, 
netic  attraction  or  repulsion, 
and  are  therefore  some- 
times called  electro-magnetic 
annunciators. 

Fig.  14  shows  an  annun- 
ciator suitable  for  use  in 
hotels. 

The  numbers  28  and  85 
are  represented  as  having 
been  dropped  by  the  closing 
of  the  circuit  connected 
with  them. 

Annunciator,    Eleva- 
tor   An  annuncia- 
tor   connected    with    an 
Fig.  15.   Elevator     elevator  to    indicate   the 

Annunciator.  n  .         .. 

floor  signaling. 

One  form  of  elevator  annunciator  is  shown  in 
Fig.  15. 


Ann.] 


23 


[Ann, 


Annunciator,       Fire-Alarm An 

annunciator  used  in  connection  with  a  system 
of  fire-alarms. 

Annunciator,    Gravity-Drop An 

annunciator  whose  signals  are  operated  by 
the  fall  of  a  drop. 


Fig.  z6.    Gravity-Drop  Annunciator. 

A  form  of  gravity-drop  annunciator  is  shown 
in  Fig.  16.  The  armature  mechanism  for  the 
release  of  the  drop  will  be  understood  by  an  in- 
spection of  the  drawing. 

Annunciator,  Hotel An  annun- 
ciator connected  with  the  different  rooms  of  a 
hotel. 

A  hotel-annunciator  is  generally  provided  with 
a  return  bell  and  guest-call. 

Annunciator,  House An  annun- 
ciator connected  with  the  rooms  of  a  house. 

Annunciator,  Needle An  annun- 
ciator, the  indications  of  which  are  given  by 
the  movements  of  a  needle  instead  of  the  fall 
of  a  drop. 

A  form  of  needle-annunciator  is  shown  in 
Fig.  17. 

Annunciator,  Oral    or  Speaking    Tube 

An  annunciator  electrically  operated 


by  means  of  a  puff  of  breath  transmitted 
through  an  ordinary  speaking  tube. 

The  oral-annunciator  is  a  contrivance  whereby 
a  central  office  is  placed  in  communication  with  a 
number  of  speaking  tubes  coming  from  different 
points  in  a  hotel  or  other  place.  A  person 
in  any  room,  who  wishes  to  communicate 
with  the  central  office,  blows  through  the 
speaking  tube  in  his  room,  and  thus,  by 
effecting  an  electric  contact,  rings  a  bell  and 
operates  a  drop  at  the  annunciator,  thus  indicat- 
ing the  exact  tube  at  which  the  attendant  is  to 
receive  the  message.  The  attendant  can  thus  be 
placed  in  easy  communication  with  each  of  the 
rooms  whose  speaking  tubes  connect  with  the 
annunciator. 

Annunciator,  Pendulum  or  Swinging 

—  An  annunciator,  the  indicating  arm  of 
which  consists  of  a  pendulous.or  swinging  arm, 


Fig.  17.    Needle-Annunciator. 

which,  when  at  rest,  points  vertically  down- 
ward, and  which  is  moved  to  the  right  or  left 
by  the  action  of  the  current. 

Pendulous,  or  swinging-annunciators  are  gen- 
erally so  arranged  as  to  need  no  replacement. 


Ann.] 


[App. 


On  the  cessation  of  the  current  the  indicator  arm 
drops  vertically  downward. 

A  relay  is  preferably  used  with  pendulum- 
annunciators,  since  the  rapid  makes  and  breaks 
of  the  current  by  the  bell  alarm  interfere  with 
their  satisfactory  action. 

Anodal.  —  Pertaining  to  the  anode.  (See 
Anode?) 

Anodal  Diffusion.  —  (See  Diffusion,  Ano- 


Anode. —  The  conductor  or  plate  of  a  de- 
composition cell  connected  with  the  positive 
terminal  of  a  battery,  or  other  electric  source. 

That  terminal  of  an  electric  source  out  of 
which  the  current  flows  into  the  liquid  of  a 
decomposition  cell  or  voltameter  is  called  the 
anode. 

That  terminal  of  an  electric  source  into 
which  the  current  flows  from  a  decomposition 
cell  or  voltameter  is  called  the  kathode. 

The  anode  is  connected  with  the  carbon  or 
positive  terminal  of  a  voltaic  battery,  and  the 
kathode  with  the  zinc,  or  negative  terminal. 
Theretore  the  word  anode  has  been  used  to 
signify  the  positive  terminal  of  an  electric  source, 
and  kathode,  the  negative  terminal,  and  in  this 
sense  is  employed  generally  in  electro-thera- 
peutics. It  is  preferable,  however,  to  restrict  the 
use  of  the  words  anode  and  kathode  to  those 
terminals  of  a  source  at  which  electrolysis  is 
taking  place. 

The  terms  anode  and  kathode  in  reality  refer 
to  the  electro-receptive  devices  through  which 
the  current  flows.  S.nce  it  is  assumed  that  the 
current  flows  out  of  a  source  from  its  positive 
pole  or  terminal,  and  back  through  the  source  at 
its  negative  pole  or  terminal,  the  pole  of  any 
device  which  is  connected  with  the  positive  pole 
of  a  source  is  the  part  or  place  at  which  the 
current  enters  and  flows  through  it,  and  that 
connected  with  the  negative  pole,  the  part  at 
which  it  leaves.  Hence,  probably,  the  change 
in  the  use  of  the  words  already  referred  to. 

Since  the  anion,  or  the  electro  negative  radical, 
appears  at  the  anode,  it  is  the  anode  of  an  electro- 
plating bath,  or  the  plate  connected  with  the 
positive  terminal  of  the  source,  that  is  dissolved. 

When  the  term  anode  was  first  proposed  by 
Farauay,  voltaic  batt  ries  were  the  only  available 
electric  source,  and  the  term  referred  only  to  the 


positive  terminal  of  a  voltaic  battery  when 
placed  in  an  electrolyte. 

Anodic. — Pertaining  to  the  anode.  (See 
Anode?) 

Anodic  Electro-Diagnostic  Reactions. — 

(See  Reactions,  Kathodic  and  Anodic  Elec- 
tro-Diagnostic?) 

Anodic  Opening  Contraction. — (See  Con- 
tration,  Anodic  Opening?) 

Anomalous  Magnet. — (See  Magnet,  An- 
omalous?) 

Anomalous  Magnetization. — (See  Mag- 
netization, Anomalous?) 

Anti-Induction  Cable (See  Cable, 

Anti-Induction?) 

Anti-Induction  Conductor.  —  (See  Con- 
ductor, Anti-Induction?) 

Antilogous  Pole. — (See  Pole,  Antilogous?) 

Anvil. — The  front  contact  of  a  telegraphic 
key  that  limits  its  motion  in  one  direction. 
(See  Key,  Telegraphic?) 

Aperiodic  Galvanometer. — (See  Galva- 
nometer, Aperiodic?) 

Apparatus,    Faradic-Induction  - 

An  induction  coil  apparatus  for  producing 
faradic  currents. 

A  voltaic  battery  is  connected  with  the  primary 
of  an  induction  coil,  and  its  current  rapidly 
broken  by  an  automatic  break,  or  by  a  hand 
break.  The  alternating  or  faradic  currents  thus 
produced  in  the  secondary  coils  are  used  for 
electro-therapeutic  purposes.  (See  Coil,  Induc- 
tion.") 

Faradic  induction  apparatus  is  made  in  a  great 
variety  of  forms.  They  all  operate,  however,  on 
essentially  the  same  principles. 

Apparatus,    Faradic,    Magneto-Electric 

A  small  magneto-electric  machine 

employed  in  electro-therapeutics  for  producing 
faradic  currents. 

Magneto-electric  faradic  machines  consist  essen- 
tially  of  a  coil  of  wire  wrapped  on  an  armature 
core  that  is  rotated  before  the  poles  of  permanent 
magnets.  No  commutator  is  employed,  since  it  is 
desired  to  obtain  rapidly  alternating  currents. 

Apparatus,  Interlocking  -  — Devices 
for  mechanically  operating  from  a  distant  signal 


App.] 


[Arc. 


tower,  railroad  switches  and  semaphore  signals 
for  indicating  the  position  of  such  switches, 
by  means  of  a  system  of  interlocking  levers, 
so  constructed  that  the  signals  and  the 
switches  are  so  interlocked  as  to  render  it 
impossible,  after  a  route  has  once  been  set  up 
and  a  signal  given,  to  clear  a  signal  for  a 
route  that  would  conflict  with  the  one  previ- 
ously set  up.  (See  Block  System  for  Rail- 
roads^) 

Apparatus,  Magneto-Electric  Medical 
A  term  applied  to  small  magneto- 
electric  machines  employed  in  medical  elec- 
tricity for  the  production  of  uncommuted 
or  faradic  currents.  (See  Apparatus,  Fara- 
dic,  Magneto- Electric?) 

Apparatus,  Registering,  Electric 

Devices  for  obtaining  permanent  records  by 
electrical  means. 

Apparatus,  Registering,  Telegraphic 

— A  name  sometimes  given  to  a  telegraphic 
recorder.  (See  Recorder,  Chemical,  Bain's. 
Recorder,  Morse.  Recorder,  Siphon?) 

Apparent    Co-efficient    of    Induction. — 

(See  Induction,  Apparent  Co-efficient  of.) 

Arago's  Disc. — (See  Disc,  Arago's?) 

Arc. — A  voltaic  arc.     (See  Arc,   Voltaic:) 

Arc. — To  form  a  voltaic  arc. 

A  dynamo-electric  machine  is  said  to  arc  at  the 
commutator,  when  the  current,  passes  as  visible 
sparks  across  the  spaces  between  adjacent  seg- 
ments. 

This  action  at  the  commutator  is  more  gener- 
ally called  sparking  or  burning. 

Arc,  Alternating A  voltaic  arc 

formed  by  means  of  an  alternating  current. 

In  order  to  avoid  the  extinction  of  the  arc  a 
certain  number  of  alternations  per  second  is  nec- 
essary. The  alternating  arc  produces  a  loud 
singing  noise.  At  very  high  frequencies,  how- 
ever, the  noise  disappears. 

The  alternating  arc,  not  possessing  a  fixed  posi- 
tive crater,  requires  to  be  covered  by  a  good 
reflector  to- throw  the  light  downward. 

Arc,  Ampere  —  — A  single  conductor 
bent  in  an  arc  of  a  circle,  and  used  in  electric 
balances  for  measuring  the  electric  current. 


Arc  Blow-Pipe.— (See  Blow-Pipe,  Elec- 
tric Arc.} 

Arc,    Compound An     arc     formed 

between  more  than  two  .eparate  electrodes. 

Arc,  Counter   Electromotive    Force    of 

An  electromotive  force  generally  be- 
lieved to  be  set  up  on  the  formation  of  a 
voltaic  arc,  opposed  in  direction  to  the  electro- 
motive force  maintaining  the  arc.  (See  Force, 
Electromotive,  Counter?] 

This  counter  electromotive  force  is  believed  to 
have  its  origin  partly  in  the  energy  absorbed  at 
the  crater  of  the  positive  carbon,  where  the  car- 
bon is  volatilized,  and  given  out  at  the  nipple  on 
the  negative  carbon,  where  it  is  deposited  or 
solidified.  It  is  to  be  noted  in  this  connection 
that  the  apparent  resistance  of  the  carbon  voltaic 
arc  is  not  directly  proportional  to  the  length  of 
the  arc. 

Arc,  Electric A  term  sometimes 

used  for  the  voltaic  arc.  (See  Arc,  Voltaic?) 

Arc,  Frying  of—  — A  frying  sound  at- 
tending the  formation  of  a  voltaic  arc  when 
the  carbons  are  too  near  together. 

The  cause  of  the  frying  sound  is  probably  the 
same  as  that  of  hissing.  (See  Arc,  Hissing  of  .) 

Arc,  Hissing  of A  hissing  sound 

attending  the  formation  of  voltaic  arcs  when 
the  carbons  are  too  near  together. 

The  cause  of  the  hissing  is  not  entirely  under- 
stood. Prof.  Elihu  Thomson  suggests  that  it  is 
due  to  a  too  rapid  volatilization  of  the  carbons. 

Arc  Lamp. — (See  Lamp,  Arc.} 
Arc  Lamp,   Electric  —       — (See   Lamp, 
Electric  Arc.) 

Arc  Lamp,  Triple  -Carbon  Electric  — 

— (See  Lamp,  Arc,  Triple  Carbon  Electric.) 
Arc  Lighting. — (See  Lighting,  Arc.) 

Arc,  Metallic A  voltaic  arc  formed 

between  metallic  electrodes. 

When  the  voltaic  arc  is  formed  between  metallic 
electrodes  instead  of  carbon  electrodes,  a  flaming 
arc  is  obtained,  the  color  of  which  is  characteristic 
of  the  burning  metal ;  thus  copper  forms  a  brill- 
iant green  arc.  The  metallic  arc,  as  a  rule  is 
much  longer  than  an  arc  with  the  same  current 
taken  between  carbon  electrodes. 

Arc  Micrometer. — (See  Micrometer,  Arc.) 


Arc.] 


26 


[Arc. 


Arc,  Noisy A  voltaic  arc,  the 

maintenance  of  which  is  attended  by  frying, 
hissing,  or  spluttering  sounds. 

Arc,  Quiet A  voltaic  arc  which  is 

maintained  without  sensible  sounds. 

Arc,  Roaring  of—  — A  roaring  sound 
attending  the  formation  of  a  voltaic  arc  when 
the  carbons  are  too  near  together  and  a  very 
powerful  current  is  used. 

Arc,  Simple  —  — An  arc  formed  be- 
tween two  electrodes. 

Arc,  Spluttering  of A  spluttering 

sound  attending  the  formation  of  a  voltaic 
arc. 

Prof.  Elihu  Thomson  suggests  that  the  cause  of 
spluttering  is  due  to  the  presence  of  impurities  in 
the  carbons,  or  from  the  sudden  evolution  of  gas 
from  insufficiently  baked  carbons. 

Arc,  Voltaic The  brilliant  arc  or 

bow  of  light  which  appears  between  the  elec- 
trodes or  terminals,  generally  of  carbon,  of  a 
sufficiently  powerful  source  of  electricity,  when 
separated  a  short  distance  from  each  other. 

The  source  of  light  of  the  electric  arc  lamp. 

It  is  tailed  the  voltaic  arc  because  it  was  first 
obtained  by  the  use  of  the  battery  invented  by 
Volta.  The  term  arc  was  given  to  it  from  the 
shape  of  the  luminous  bow  or  arc  formed  between 
the  carbons. 

To  form  the  voltaic  arc  the  carbon  electrodes 
are  first  placed  in  contact  and  then  gradually 
separated.  A  brilliant  arc  of  flame  is  formed  be- 
tween them,  which  consists  mainly  of  volatilized 
carbon.  The  electrodes  are  consumed,  first,  by 
actual  combination  with  the  oxygen  of  the  air; 
and,  second,  by  volatilization  under  the  combined 
influence  of  the  electric  current  and  the  intense 
heat. 

As  a  result  of  the  formation  of  the  arc,  a  crater 
is  formed  at  the  end  of  the  positive  carbon,  and 
appears  to  mark  the  point  out  of  which  the 
greater  part  of  the  current  flows. 

The  crater  is  due  to  the  greater  volatilization 
of  the  electrode  at  this  point  than  elsewhere. 
It  marks  the  position  of  highest  temperature  of  the 
electrodes,  and  is  the  main  source  of  the  light  of 
the  arc. "  When,  therefore,  the  voltaic  arc  is  em- 
ployed for  the  purposes  of  illumination  with 
vertically  opposed  carbons,  the  positive  carbon 
should  be  made  the  upper  carbon,  so  that  the 


focus  of  greatest  intensity  of  the  light  may  be 
favorably  situated  for  illumination  of  the  space 
below  the  lamp.  When,  however,  it  is  desired  to 
illumine  the  side  of  a  building  above  an  arc  lamp, 
the  lower  carbon  should  be  made  positive. 

The  positive  carbon  is  consumed  about  twice  as 
rapidly  as  the  negative,  both  because  the  negative 
oxygen  attacks  the  points  of  the  positive  carbon, 
and  because  the  positive  carbon  suffers  the  most 
rapid  volatilization. 

The  electric  current  passes  through  the  space 
occupied  by  the  voltaic  arc  because — 

(I.)  The  heated  arc  is  a  partial  conductor  of 
electricity. 

(2.)  Because  small  charges  of  electricity  are 
Carried  bodily  forward  from  the  positive  to  the 
negative  carbon  through  the  space  of  the  voltaic 
arc,  by  means  of  the  minute  particles  which  are 
volatilized  at  the  positive  electrode. 

S.  P.  Thompson  has  shown  that  the  tempera- 
ture of  the  light-emitting  surface  of  the  carbon  is 
the  temperature  of  the  volatilization  of  carbon, 
and  is  therefore  constant. 

Dr.  Fleming  found  that  "  A  rise  of  potential 
along  the  arc  takes 
place  very  suddenly, 
just  in  the  neighbor- 
hood of  the  crater." 

The   crater    in  the 
end  of  the  positive  car- 
bon is  seen  in  Fig.  18. 
On  the  opposed  end 
of  the  negative  carbon 
a  projection  or  nipple 
is  formed  by   the  de- 
posit of  the  electrical- 
ly volatilized  carbon. 
Fig.  18.    Voltaic  Arc.        The  rounded    masses 
or  globules  that  appear  on  the  surface  of  the  elec- 
trodes are  due  to  deposits  of  molten  foreign  mat- 
ters in  the  carbon. 

The  carbon,  both  of  the  crater  and  its  opposed 
nipple,  is  converted  into  pure,  soft  graphite. 

Arc,  Voltaic,  Resistance    of The 

resistance  offered  by  the  voltaic  arc  to  the 
passage  of  the  current. 

As  in  all  other  conductors,  the  ohmic  resistance 
of  the  arc  increases  with  its  length,  and  decreases 
with  its  area  of  cross-section.  The  apparent 
resistance,  however,  is  not  directly  proportional 
to  the  length.  An  increase  of  temperature  de- 
creases the  resistance  of  the  voltaic  arc. 


Arc.] 


27 


[Arm. 


The  total  apparent  resistance  of  the  voltaic  arc 
is  composed  of  two  parts,  viz.: 

(I.)  The  true  ohmic  resistance.  (See  Resist- 
ance, Ohmic.) 

(2.)  The  counter  electromotive  force,  or  spuri- 
ous resistance.  (See  Resistance,  Spurious.} 


Arc,  Watt 


— A  voltaic  arc,  the  elec- 


tric power  of  which  is  equal  to  a  given  number 
of  watts. 

The  ordinary  long-arc,  as  employed  in  arc 
lighting,  has  a  difference  of  potential  of  about  45 
volts  and  a  current  strength  of  about  10  amperes. 
It  is,  therefore,  a  45O-watt  arc. 

Arch,  Auroral  —  —The  archlike  form 
sometimes  assumed  by  the  auroral  light.  (See 
Aurora  Borealis?) 

Arcing. — Discharging  by  means  of  voltaic 
arcs.  (See  Arc,  Voltaic?) 

Arcing  at  the  commutator  of  a  dynamo-electric 
machine  not  only  prevents  the  proper  operation 
of  the  machine,  but  eventually  leads  to  the  de- 
struction of  the  brushes  and  the  commutator. 

Areometer,  Bead  —  — A  form  of  are- 
ometer suitable  for  rapidly  testing  the  density 
of  the  liquid  in  a  storage  cell. 

The  bead  areometer  consists  of  a  glass  tube, 
open  at  both  top"  and  bottom,  containing  a  few 
glass  beads,  so  weighted  as  to  float  at  liquid 
densities  such  as  1.105,  1.170,  1.190 
and  1. 200.  To  use  the  instrument, 
it  is  immersed  in  the  liquid  of  the 
storage  cell,  and  then  withdrawn. 
The  finger  being  kept  in  the  upper 
opening,  the  liquid  does  not  escape 
through  the  small  opening  at  the 
bottom.  The  density  is  then  ascer- 
tained by  noting  the  beads  that 
float. 

Areometer  or  Hydrometer. 

— An  instrument  for  determin- 
ing the  specific  gravity  of  a  liquid. 
A  common  form  of  hydrometer 
consists,  as  shown  in  Fig.  19,  of  a 
closed  glass  tube,  provided  with  a 
bulb,   and  filled  at  the  lower  end 
with  mercury  or  shot,  so  as  to  in- 
sure its    vertical    position    when  Fig.  19.    Hv- 
floating  in  a  liquid.     When  placed       drometer. 
in  different  liquids,  it  floats  with  part  of  the  tube 
out  of  the  liquid.     The   lighter  the  liquid,  the 
2— Vol.  1 


smaller  is  the  portion  that  remains  out  of  the 
liquid  when  the  instrument  floats.  The  specific 
gravity  is  determined  by  observing  the  depth  to 
which  the  instrument  sinks  when  placed  in  different 
liquids,  as  compared  with  the  depth  it  sinks  when 
placed  in  water. 

Areometry. — The  measurement  of  specific 
gravity  by  means  of  an  areometer. 

Argaud  Burner,  Electric  Hand-Lighter 
(See  Burner,  Argand,  Electric  Hand- 
Lighter^) 

Argand  Burner,  Electric  Plain-Pendant 
— (See  Burner,  Plain  Pendant,  Argand, 
Electric?) 

Argand  Burner,  Electric  Ratchet-Pen- 
dant —  — (See  Burner,  Ratchet-Pendant, 
Argand,  Electric?) 

Argyroinetry. — The  art  of  determining 
the  weight  of  electrolytically  deposited  silver. 
(See  Balance,  Plating?) 

Arm,  Balance One  of  the  resist- 
ances of  an  electric  balance.  (See  Arms, 
Bridge  or  Balance.  Bridge,  Electric?) 

Arm,  Bridge  -. —  — A  bridge  arm.  (See 
Arms,  Bridge  or  Balance?) 

Arm,  Cross  —  — A  horizontal  beam  at- 
tached to  a  pole  for  the  support  of  the  in- 
sulators for  telegraph,  electric  light  or  other 
electric  wires. 

A  telegraphic  arm.  (See  Arm,  Tele- 
graphic?) 

Arm,  Rocker An  arm  on  which  the* 

brushes  of  a  dynamo  or  motor  are  mounted 
for  the  purpose  of  shifting  their  position  on 
the  commutator. 

Arm,  Semaphore  -  —The  movable 
arm  of  the  signal  apparatus  employed  in  block 
systems  for  railroads,  for  the  purpose  of  in- 
forming engineers  of  trains  of  the  condition 
of  the  road  as  regards  other  trains. 

In  the  absolute  block  system,  as  used  on  some 
roads,  there  are  two  positions  for  the  semaphore 
arm,  viz.: 

(I.)  For  Danger — when  in  a  horizontal  position, 
or  at  90  degrees  with  the  vertical  supporting  pole. 

(2.)  Clear — when  dropped  below  the  horizontal 
position  through  an  angle  of  75  degrees. 

In  the  Permissive  Block  System,  a  third  position 


Arm.] 


28 


[Arm. 


intermediate  between  the  ist  and  the  2d,  or  at  an 
angle  of  37  degrees  30  minutes  with  the  horizontal 
position,  is  used  for  caution.  (See  Block  System 
for  Railroads.} 

Arm,  Signal A  semaphore  arm. 

(See  Arm,  Semaphored) 

Arm,  Telegraphic A  cross-arm 

placed  on  a  telegraphic  pole  for  the  support 
of  the  insulators. 

These  arms  are  generally  called  cross-arms. 

Armature. — A  mass  of  iron  or  other 
magnetizable  material  placed  on  or  near  the 
pole  or  poles  of  a  magnet. 

In  the  case  of  a  permanent  magnet,  the  arma- 
ture, when  used  as  a  keeper,  is  of  soft  iron  and  is 
placed  directly  on  the  magnet  poles.  In  this  case 
it  preserves  or  keeps  the  magnetism  by  closing 
the  lines  of  magnetic  J orce  of  the  magnet  through 
the  soft  iron  of  the  armature,  and  is  then  called  a 
keeper,  (See  Force,  Magnetic,  Lines  of.) 

In  the  case  of  an  electro-magnet,  the  armature 
is  placed  near  the  poles,  and  is  moved  toward 
them  whenever  the  magnet  is  energized  by  the 
passage  of  the  current  through  the  magnetizing 
coils.  This  movement  is  made  against  the  action 
of  a  spring  or  weights,  so  that  on  the  loss  of 
magnetism  by  the  magnet,  the  armature  moves 
from  the  magnet  poles.  (See  Magnet,  Permanent. 
Magnet,  Keeper  of. ) 

When  the  armature  is  of  soft  iron  it  moves  to- 
ward the  magnet  on  the  completion  of  the  circuit 
through  its  coils,  no  matter  in  what  direction 
the  current  flows,  and  is  then  called  a  non-polar- 
ized armature.  (See  Armature,  Non-Polarized.} 

When  made  of  steel,  or  of  another  electro-mag- 


Fig,  20.     Bi-polar  Armature. 

net,  it  moves  from  or  toward  the  poles,  accord- 
ing to  whether  the  poles  of  the  armature  are  of 
the  same  or  of  a  different  polarity  from  those  of 
the  magnet.  Such  an  armature  is  called  a 
polarized  armature.  (Sec  Armature,  Polarized.) 


Armature,  Bi-polar An  armature 

of  a  dynamo-electric  machine  the  polarity  of 
which  is  reversed  twice  in  every  revolution 
through  the  field  of  the  machine. 

A  form  of  bi-polar  armature  is  shown  in  Fig.  20. 
The  word  bi-polar  armature  is  not  generally 
employed.  The  term  applies  rather  to  the  field- 
magnet  poles  than  to  the  armature. 

Armature  Bore. — (See  Bore,  Armature.) 

Armature  Bore,  Elliptical  —  — (See 
Bore,  Elliptical  Armature?) 

Armature  Chamber. — (See  Chamber, 
Armature?) 


Armature    Coils,   Dynamo 


—(See 


Coils,  Armature,  of  Dynamo-Electric  Ma- 
chine?) 

Armature  Core,  Dynamo  -  — (See 

Core,  Armature,  of  Dynamo-Electric  Ma- 
chine?) 

Armature,  Cylindrical  -  — A  term 
sometimes  applied  to  a  drum  armature. 
(See  Armature,  Drum.  Armature,  Dy- 
namo-Electric Machine?) 

Armature,  Cylindrical  Ring. — A  ring 
armature  with  a  core  in  the  shape  of  a  com- 
paratively long  cylinder. 

Armature,  Disc —  — An  armature  of  a 
dynamo-electric  machine,  in  which  the  arma- 
ture coils  consist  of  flat  coils,  supported  on 
the  surface  of  a  disc.  (See  Armature,  Dy- 
namo-Electric Machine?) 

Armature,  Dissymmetrical  Induction  of 

Any  induction  produced  in  the  arma- 
ture of  a  dynamo-electric  machine  that  is  un- 
equal in  amount  on  opposite  halves,  or  in  sym- 
metrically disposed  portions  of  the  armature. 

Dissymmetrical  induction  in  the  armature  may 
cause  annoying  or  injurious  sparking  at  the  com- 
mutator. It  may  arise — 

( i  )  From  a  lack  of  symmetry  in  the  amount  of 
the  armature  windings. 

(2.)  From  a  lack  of  symmetry  in  the  arrange- 
ment of  the  armature  windings  on  the  armature 
core. 

(3. )  From  a  lack  of  symmetry  of  the  pole  pieces 
of  the  machine. 

(4.)  From  an  improper  position  of  the  brushes 


Arm.] 


Arm. 


as  regards  the  neutral  point  on  the  commutator, 
causing  a  temporary  short-circuiting  of  one  or 
more  of  the  armature  coils. 

Armature,  Drum An  armature  of 

a  dynamo-electric  machine,  in  which  the 
armature  coils  are  wound  longitudinally  over 
the  surface  of  a  cylinder  or  drum.  (See 
Armature,  Dynamo-Electric  Machine^ 

A  form  of  drum-armature  is  shown  in  Fig.  21. 


Fig.  21.    Drum- Armature. 

Armature,     Dynamo-Electric     Machine 

The  coils  of  insulated  wire  together 

with  the  iron  armature  core,  on  or  around 
which  the  coils  are  wound. 

That  part  of  a  dynamo-electric  machine  in 
which  the  differences  of  potential  which 
cause  the  useful  currents  are  generated. 

Generally,  that  portion  of  a  dynamo-elec- 
tric machine  which  is  revolved  between  the 
pole  pieces  of  the  field  magnets. 

The  armature  of  a  dynamo-electric  machine 
usually  consists  of  a  series  of  coils  of  insulated 
wire  or  conductors,  wrapped  around  or  grouped 
on  a  central  core  of  iron.  The  movement  of 
these  wires  or  conductors  through  the  magnetic 
field  of  the  machine  produces  an  electiic  cur- 
rent by  means  of  the  electromotive  forces  so  gen- 
erated. Sometimes  the  field  is  rotated  ;  some- 
times both  armature  and  field  rotate. 

The  armatures  of  dynamo-electric  machines 
are  of  a  great  variety  of  forms.  They  may  for 
convenience  be  arranged  under  the  following 
heads,  viz.: 

Cylindrical  or  drum-armatures,  disc-arma- 
tures, pole-or-radial  armatures,  ring  armatures, 
(utd spherical-armature*.  For  further  particulars 
see  above  terms.  Armatures  are  also  Divided 


into  classes  according  to  the  character  of  the 
magnetic  field  through  which  they  move — viz.: 
unipolar,  bipolar,  and  multipolar  armatures. 

The  English  sometimes  use  the  word  cylindrical 
armature  as  a  synonym  of  ring-armature. 

A  unipolar-armature  is  one  whose  polarity  is 
never  reversed.  A  bipolar-armature  is  one  in 
which  the  polarity  is  reversed  twice  in  every 
rotation;  multipolar  armatures  have  their  po- 
larity reversed  a  number  of  times  in  every  rota- 
tion. 

The  term  armature  as  applied  to  a  dynamo- 
electric  machine  was  derived  from  the  fact  that 
the  iron  core  acts  to  magnetically  connect  the 
two  poles  of  the  field  magnets  in  the  same 
manner  that  an  ordinary  armature  connects  the 
poles  of  a  magnet. 

Armature,  Flat  Ring A  ring-arma- 
ture with  a  core  in  the  shape  of  a  short  cylin- 
drical ring. 

Armature,  Girder  -  — An  armature 
with  an  H  -shaped  or  girder-like  core.  ^ 

An  H -shaped  armature. 

Armature,  Intensity  —  — An  old  term 
for  an  armature  with  coils  of  many  turns  and 
of  a  comparatively  high  resistance. 

Armature,  Lamination  of  Core  of— 
— A  division  of  the  iron  core  of  the  armature 
of  a  dynamo-electric  machine  or  motor,  so  as 
to  avoid  the  formation  of  eddy-currents 
therein.  (See  Core,  Lamination  of.  Cur- 
rents, Eddy?) 

Armature,  Multipolar  —  — A  dynamo- 
electric  machine  armature  whose  polarity  is 
reversed  more  than  twice  during  each  rotation 
in  the  field  of  the  machine. 

Armature,  Neutral  —  — A  non-polarized 
armature.  (See  Armature,  Non-Polarized^ 

Armature,  Neutral-Relay A  relay 

armature,  consisting  of  a  piece  of  soft  iron, 
which  closes  a  local  circuit  whenever  its  elec- 
tro-magnet receives  an  impulse  over  the  main 
line.  (See  Armature,  Polarized?) 

This  term  is  applied  in  contradistinction  to  a 
polarized  relay  armature. 

Armature,    Non-Polarized     — An 

armature  of  soft  iron,  which  is  attracted  toward 
the  poles  of  an  electro-magnet  on  the  como1" 


Arm.] 


30 


[Arm. 


tion  of  the  circuit,  no  matter  in  what  direc- 
tion the  current  passes  through  the  coils. 

The  term  non-poiarized  is  ustd  in  contradistinc- 
tion to  polarized  armature.  (See  Armature, 
Polarized. ) 

Th  non-polanztd  armature  of  a  relay  magnet 
is  generally  called  the  netitral -relay  armature. 

Armature  of  a  Cable,  or  Cable-Armature. 

— A  term  sometimes  employed  for  the  sheath- 
ing or  protecting  coat  of  a  cable. 

The  term  armor  sheathing  or  coating  is  prefer- 
able. 

Armature  of  a  Condenser,  or  Condenser 
Armature. — A  term  sometimes  applied  to 
the  metallic  plates  of  a  condenser  or  Leyden 
jar. 

The  use  of  this  term  is  unnecessary  and  iU- 
advised.  The  term  coating  or  plate  would  appear 
to  be  preferable. 

Armature  of  Holtz  Machine,  or  Holtz- 
Machine  Armature. — The  pieces  of  paper 
that  are  placed  on  the  stationary'  plate  of  the 
Holtz  and  other  similar  electrostatic  induction 
machines. 

Armature  Pockets. — (See-Poc6ets,  Arma- 
ture.) 

Armature,  Polarized An  armature 

which  possesses  a  polarity  independent  of 
that  imparted  by  the  magnet  pole  near  which 
it  is  placed. 

In  permanent  magnets  the  armatures  are  made 
of  soft  iron,  and  therefore,  by  induction,  become 
of  a  polarity  opposite  to  that  of  the  magnet  poles 
that  lie  nearest  them.  They  have,  therefore,  only 
a  motion  of  atiraction  toward  such  poles.  (See 
Induction,  Magnetic. ) 

In  electro-magnets  the  armatures  may  either  be 
made  of  soft  iron,  in  which  case  they  are  attracted 
only  on  the  passage  of  the  current;  or  they  may 
be  formed  of  permanent  steel  magnets,  rr  may  be 
electro- magnets  themselves,  in  which  case  the  pas- 
sage of  the  current  through  the  coils  of  the  elec- 
tro-magnet, or  electro- magnets,  may  cause  either 
attraction  or  repulsion,  according  as  the  adjacent 
poles  are  of  opposite  polarity  or  are  of  the  same 
polarity. 

Armature.  Pole  —  — An  armature  the 
coils  of  which  are  wound  on  separate  poles 


that  project  radially  from  the  periphery  of  a 
disc,  drum  or  ring. 

A  pole-armature  showing  the  arrangement  of 


Fig.  22.    Pole-Armature. 

the  coils  and  their  connection  to  the  commutator 
segments  is  seen  in  Fig.  22. 

Armature,  Quantity An  old  term 

for  an  armature  wound  with  but  a  few  coils 
of  comparatively  low  resistance. 

Armature,  Radial  -  —A  term  some- 
times used  instead  of  pole-armatune.  (See 
Armature,  Pole.) 

Armature,  Ring:  —      —A  dynamo-electric 
machine  armature,   the   coils  of  which  are 
wound  on  a  ring-shaped  core. 
c 


Fig.  23.     Ring-Armaturt, 

A  ring-armature  is  shown  in  Fig.  23,  together 
with  the  disposition  of  the  coils  and  their  connec- 
tion to  the  segments  of  the  commutator. 

Armature,  Shuttle A  variety  of 

drum  armature  in  which  a  single  coil  of 
wire  is  wound  in  an  H-shaped  groove  formed 
in  a  bobbin  shaped  core. 

The  old  form  of  Siemens-armature. 

Armature,  Single-Loop A  closed 

conducting  circuit  consisting  of  a  single  loop, 
capable  of  revolving  in  a  magnetic  field  so  as 
to  cut  its  lines  of  force. 

Armature,  Spider. — (See  Spider,  Arma- 
ture) 


Arm.] 


31 


[A.rr. 


Armature,  Spherical 


— A  dynamo- 


electric  machine  armature,  the  coils  of  which 
are  wound  on  a  spherical  iron  core. 

The  Thomson-Houston  dynamo,  which  is  the 
only  machine  employing  an  armature  of  this  type, 
has  its  armature  formed  by  wrapping  three  coils 
of  insulated  wire  on  a  core  of  iron  so  shaped  as 
to  insure  an  approximately  spherical  armature 
when  wrapped. 

Armature,  Toothed-Ring An  ar- 
mature, the  core  of  which  is  in  the  shape  of 
a  ring,  provided  with  a  number  of  teeth  in  the 
spaces  between  which  the  armature  coils  are 
placed. 

Armature,  Unipolar  —  — A  dynamo- 
electric  machine  armature  whose  polarity  is 
not  reversed  during  its  rotation  in  the  field 
of  the  machine. 

Armature,  Ventilation  of A  pro- 
cess for  insuring  the  free  passage  of  air 
through  the  armature  of  a  dynamo-electric 
machine  in  order  to  prevent  overheating. 

Armor  of  Cable. — (See  Cable,  Armor  of.) 

Armored  Cable. — (See  Cable,  Armored?) 

Armored  Conductor. — (See  Conductor, 
Armored.} 

Arms,  Bridge  or  Balance The 

electric  resistances,  in  the  electric  balance  or 
bridge.  (See  Bridge,  Electric?) 


J'o 

Fig.  24..    Arms  of  Balance. 

An  unknown  resistance,  such,  for  example,  as 
D,  Fig.  24,  is  measured  by  proportioning  the 
known  resistances,  A,  C  ana  B,  so  that  no  current 
flows  through  the  galvanometer  G,  across  the 
circuit  9r  bridge  M  G  N. 

Arms,  Proportionate The  two  re- 
sistances or  arms  of  an  electric  bridge  whose 
relative  or  proportionate  resistances  only  are 
required  to  be  known  in  order  to  determine, 


in  connection  with  a  known  resistance,  the 
value  of  an  unknown  resistance  placed  in  the 
remaining  arm  of  the  bridge. 

Thus  is  Fig.  24,  A  and  B,  are  the  proportionate 
arms. 

Arrangement  or  Device,  Electromotive 
A  term  sometimes  employed  to  rep- 
resent a  dynamo-electric  machine,  voltaic  cell 
or  other  electric  source,  by  means  of  which 
electromotive  force  can  be  produced. 

Electric  sources  do  not  produce  electric  cur- 
rents, but  differences  of  potential  or  electro- 
motive force.  Electric  sources  are  therefore  very 
properly  termed  electromotive  devices. 

Arrester,  Lightning A  device  by 

means  of  which  the  apparatus  placed  in  any 
electric  circuit  is  protected  from  the  destruc- 
tive effects  of  a  flash  or  bolt  of  lightning. 

In  the  phenomena  of  lateral  induction  and 
alternative  path,  we  have  seen  the  tendency  of  a 
disruptive  discharge  to  take  a  short-cut  across  an 
intervening  air  space,  rather  than  through  a 
longer  though  better  conducting  path.  Most 
lightning  arresters  are  dependent  for  their  opera- 
tion on  this  tendency  to  lateral  discharge.  (See 
Induction,  Lateral.  Path,  Alternative.) 

A  form  of  lightning  arrester  is  shown  in  Fig.  25. 


Fig.  25.   Comb  Lightning- Arrester. 

The  line  wires,  A  and  B,  are  connected  by  two 
metallic  plates  to  C  and  D,  respectively. 

These  plates  are  provided  with  points,  as  shown, 
and  placed  near  a  third  plate,  connected  to  the 
ground  by  the  wire  G.  Should  a  bolt  strike  the 
line,  it  is  discharged  to  the  earth  through  the 
wire  G. 

Various  forms  are  given  to  lightning  arresters 
of  this  type.  The  projections  are  sometimes  placed 
on  the  ground  connected  plate  as  well  as  on  the 
plates  connected  to  line  wires.  This  form  is 
sometimes  called  a  comb  arrester,  or  protector. 


Arr.J 


32 


[Ast. 


Arrester,    Lightning,    Comb    —      — A 

term  sometimes  applied  to  a  lightning  ar- 
rester in  which  both  the  line  and  ground 
plates  are  furnished  with  a  series  of  teeth, 
like  those  on  a  comb.  (See  Arrester,  Light- 
ning) 

Arrester,  Lightning,  Counter-Electro- 
motive Force  —  — A  lightning  arrester, 
in  which  the  passage  of  the  discharge  through 
the  instruments  to  be  protected  is  opposed 
by  a  counter-electromotive  force,  generated 
by  induction  on  the  passage  of  the  discharge 
of  the  bolt  to  earth. 

The  counter-electromotive  force  lightning  ar- 
rester is  an  invention  of  Professor  Elihu  Thomson. 

It  assumes  a  variety  of  forms.  In  the  shape 
shown  in  Fig.  26,  the  line  circuit  of  the  dynamo, 


Fig.  26.     Counter-Electromotive  Force  Lightning 
Arrester. 

D,  has  one  end  connected  to  ground,  and  the 
other  end  has  two  conducting  paths  to  ground. 
One  of  these  paths  is  through  the  ordinary  comb- 
protector  at  P,  by  the  ground  plate  E;  this  cir- 
cuit includes  a  few  turns 
of  wire  C'.  The  other 
path  is  through  a  corres- 
ponding coil  C,  either 
interior  or  exterior  to  C', 
so  as  to  be  within  its  in- 
ductive field.  As  will  be 
seen  from  the  figure,  C,  is 
~Fig.  27.  Counter-Elec.  connected  through  the 
tromotive  Force  Light-  machine  to  the  ground. 
tiing  Arrester.  The  induction  coils  C 

and  C',    are    thoroughly    insulated    from     each 
other. 

Should  a  lightning  flash  or  other  static  discharge 
pass  through  the  circuit  C',  which  is  of  compara- 
tively low  self-induction,  a  counter-electromotive 
force  is  produced  in  the  other  coil  C,  which 
protects  the  line  circuit. 


In  the  form  of  lightning  arrester  shown  in 
Fig.  27,  the  coil  in  the  path  of  the  direct  light- 
ning discharge  is  formed  into  an  exterior  mesh  or 
net  work  surrounding  the  dynamo  to  be  pro- 
tected. In  this  case,  the  coils  of  the  dynamo  act 
as  the  secondary  coils  in  which  the  counter  elec- 
tromotive force  is  set  up. 

Arrester,  Lightning,  Transformer  - 

— A  form  of  lightning  arrester  designed  for 
the  protection  of  transformers. 

The  Thomson  arrester  for  transformers  oper- 
ates on  the  same  principle  as  his  arc-line  pro- 
tector. In  the  latter  the  arc,  when  formed, 
is  blown  out  by  the  action  of  the  field  of  an 
electro-magnet.  This  arc  is  formed  on  curved 
metallic  bows,  one  of  which  is  connected  to  line 
and  the  other  to  earth.  The  arc  is  formed  at  the 
smallest  interval  between  the  bows,  and  is  extin- 
guished by  being  driven  by  action  of  a  magnetic 
field  toward  greatest  interval. 

Arrester  Plate  of  Lightning  Protector. — 

(See  Plate,   Arrester,   of  Lightning   Pro- 
tector^) 

Arrester  Plates. — (See  Plates,  Arrester?) 

Articulate  Speech. — (See  Speech,  Articu- 
late^ 

Artificial  Carbons. — (See  Carbons,  Arti- 
ficial) 

Artificial  Illumination. — (See  Illumina- 
tion, Artificial.) 

Artificial  Line.— (See  Line,  Artificial) 
Artificial   Magnet. — (See   Magnet,  Arti- 
ficial) 

Asphyxia. — Suspended  respiration,  result- 
ing eventually  in  death,  from  non-aeration  of 
the  blood. 

In  cases  of  insensibility  by  an  electric  shock  a 
species  of  asphyxia  is  sometimes  brought  about. 
This  is  due,  probably,  to  the  failure  of  the  nerves 
and  muscles  that  carry  on  respiration.  The  exact 
manner  in  which  death  by  electrical  shock  results 
is  not  known.  (See  Death,  Electric.) 

Assymrnetrical  Resistance. — (See  Resist- 
ance, Assymmetrical?) 

Astatic. — Possessing  no  directive  power. 

Usually  applied  to  a  magnetic  or  electro-mag, 
netic-device  which  is  free  from  any  tendency  to 
take  a  definite  position  on  account  of  the  earth's 
magnetism. 


Ast.] 


33 


[Ato. 


Astatic  Circuit.— (See  Circuit,  Astatic?) 
Astatic  Couple. — See  Couple,  Astatic?) 
Astatic  Galvanometer. — (See  Galvanom- 
eter, Astatic.) 

Astatic  Needle. — (See  Needle,  Astatic?) 

Astatic  Pair. — (See  Pair,  Astatic) 

Astatic  System. — (See  System,  Astatic) 

Astronomical  Meridian. — (See  Meridian, 
Astronomical?) 

Asymptote  of  Curve. — (See  Curve,  Asymp- 
tote of) 

Atmosphere,  An A  unit  of  gas  or 

fluid  pressure  equal  to  about  1 5  pounds  to  the 
square  inch. 

At  the  level  of  the  sea  the  atmosphere  exerts  a 
pressure  of  about  15  pounds  avoirdupois,  or, 
more  accurately,  14.73  pounds,  on  every  square 
inch  of  the  earth's  surface.  This  value  has  there- 
fore been  taken  as  a  unit  of  fluid  pressure. 

For  more  accurate  measurements  pounds  to  the 
square  inch  are  employed. 

In  the  metric  system  of  weights  and  measures 
an  atmosphere  is  considered  equal  to  1,033 
grammes  per  square  centimetre. 

Atmospheric  pressures  are  measured  by  instru- 
ments called  Manometers.  (See  Manometer.) 

Atmosphere,  Residual  —  —The  traces 
of  air  or  other  gas  remaining  in  a  space  which 
has  been  exhausted  of  its  gaseous  contents 
by  a  pump  or  other  means. 

It  is  next  to  impossible  to  remove  all  traces  of 
air  trom  a  vessel  by  any  known  form  of  pump  or 
oiher  appliance.  (See  Vacuum,  Absolute.) 

Atmosphere,   The — The  ocean  of  ' 

air  which  surrounds  the  earth. 

The  atmosphere  is,  approximately,  composed, 
by  weight,  of  oxygen  23  parts,  and  nitrogen  77 
parts.  Besides  these  there  are  from  4  to  6  parts 
in  10,000  of  carbonic  acid  gas  (or  about  a  cubic 
inch  of  carbonic  acid  to  a  cubic  foot  of  air),  and 
varying  proportions  of  the  vapor  of  water. 

1  he  oxygen,  nitrogen  and  carbonic  acid  form 
the  constant  ingredients  of  the  atmosphere,  the 
vapor  of  water  the  variable  ingredient.  There 
are  in  most  localities  a  number  of  other  variable 
ingredients  present  as  impurities. 

Atmospheric  Electricity. — (See  Electric- 
ity, Atmospheric) 


Atmospheric  Electricity,  Origin  of 

— (See  Electricity,  Atmospheric,  Origin  of) 

Atom. — The  smallest  quantity  of  elemen- 
tary or  simple  matter  that  can  exist. 
An  ultimate  particle  of  matter. 

Atom  means  that  which  cannot  be  cut.  It  is 
generally  believed  that  material  atoms  are  abso- 
lutely unalterable  in  size,  shape,  weight  and  den- 
sity ;  that  they  can  neither  be  cut,  scratched, 
flattened,  nor  distorted  ;  and  that  they  are  un- 
affected in  size,  density,  or  shape,  by  heat  or 
cold,  or  by  any  known  physical  force. 

Although  almost  inconceivably  small,  atoms 
nevertheless  possess  a  definite  size  and  mass. 
According  to  Sir  William  Thomson,  the  smallest 
visible  organic  particle,  1-4000  of  a  millimetre  in 
diameter,  will  contain  about  30,000,000  atoms. 

Atom,  Closed-Magnetic  Circuit  of  — 

(See  Circuit,  Closed-Magnetic,  of  Atom?) 

Atom,  Gramme  -  — Such  a  number 
of  grammes  of  any  elementary  substance  as  is 
numerically  equal  to  the  atomic  weight  of 
the  substance. 

The  gramme-atom  of  a  substance  represents 
the  number  of  calories  required  to  raise  the  tem- 
perature of  one  gramme  ot  that  substance  through 
I  degree  C.  (See  Heat,  Atomic.  Calorie.)  Thus, 
in  the  case  of  chlorine,  whose  atomic  weight  is 
35.5,  its  gramme-atom  is  35.5  ;  consequently 
35.5  small  calories  of  heat  would  be  required  to 
raise  one  gramme-atom  of  chlorine  through  I 
degree  C. 

Atom  of  Electricity. — (See  Electricity, 
Atom  of.) 

Atom,  Yortex  —  — A  number  of  particles 
of  the  universal  ether  moving  in  the  manner 
of  a  vortex  ring. 

The  theory  of  vortex  atoms,  so  formed  from 
vortex  rings,  was  propounded  by  Sir  William 
Thomson  in  order  to  explain  how  a  readily  mov- 
able substance,  like  the  universal  ether,  could  be 
made  to  possess  the  properties  of  a  rigid  solid.  If 
it  be  granted  that  a  vortex  motion  has  once  been 
imparted  to  the  universal  ether,  Thomson  shows 
that  such  rings  would  be  indestructible.  (See 
Matter,  Thomson's  Hypothesis  of.) 

Atomic  Attraction.  —  (See  Attraction, 
Atomic?) 


Ato.] 


34 


[Att. 


Atomic  Capacity. — (See  Capacity,  Atom- 
ic?) 

Atomic  Currents. — (See  Currents,  Atom- 
ic.} 

Atomic  Energy. — (See  Energy,  Atomic?) 
Atomic  Heat.— (See  Heat,  Atomic?) 

Atomic  or  Molecular  Induced  Currents. 

— (See    Currents,   Induced,    Molecular     or 
Atomic?) 

Atomic  Weight. — (See  Weight,  Atomic.} 

Atomicity. — The  combining  capacity  of 
the  atoms. 

The  relative  equivalence  of  the  atoms  or 
their  atomic  capacity. 

The  elementary  atoms  do  not  always  combine 
atom  for  atom.  Some  single  atoms  of  certain 
elements  will  combine  with  two,  three,  four,  or 
even  more  atoms  of  another  element. 

The  value  of  the  atomic  capaciiy  of  an  atom  is 
also  called  its  quantivalence  or  valency. 
Elements  whose  atomic  capacity  is — 

One,     are  called  Monads,     or  Univalent. 
Two,         "  Dyads,        "  Bivalent. 

Three,       "  Triads,        "  Trivalent. 

Four,         "  Tetrads,       "  OuaJiivalent. 

Five,         "  Pentads,      "  Quinquivalent 

Six,  "  Hexads,      "  Sexivalent. 

Seven,       "  Heptads,    "  Septivalent. 

Atomization. — The  act  of  obtaining  liquids 
in  a  spray  of  finely  divided  particles. 

In  most  cases  the  term  is  not  literally  correct, 
as  each  of  the  smallest  particles  so  obtained  usu- 
ally consist  of  many  thousands  of  atoms. 

Atomize. — To  separate  into  a  fine  spray  by 
means  of  an  atomizer.,  (See  Atomizer?) 

Atomizer. — An  apparatus  for  readily  ob- 
taining a  finely  divided  jet  or  spray  of  liquid. 

A  jet  of  steam,  or  a  blast  of  air,  is  driven  across 
the  open  end  of  a  tube  that  dips  below  the  surface 
of  the  liquid  to  be  atomized.  The  partial  vacuum 
so  formed  draws  up  the  liquid,  which  is  then 
blown  by  the  current  into  a  fine  spray. 

Attract. — To  draw  together. 
Attracted-Disc  Electrometer. — (See  Elec- 
trometer, Attracted-Disc} 

Attracting1. — Drawing  together. 


Attraction. — Literally  the  act  of  drawing 
together. 

In  science  the  name  attraction  is  given  to  a 
series  of  unknown  causes  which  effect,  or  are  as- 
sumed to  effect,  the  drawing  together  of  atoms, 
molecules  or  masses. 

Attraction  and  repulsion  underlie  nearly  all 
natural  phenomena.  While  their  effects  are  well 
known,  it  is  doubtful  if  anything  is  definitely 
known  of  their  true  causes. 

Since  attraction,  pure  and  simple,  necessitates 
the  belief  in  action  at  a  distance,  an  action  which 
is  now  generally  discredited,  we  must,  strictly 
speaking,  regard  the  term  attraction  as  being  but 
a  convenient  substitution  of  the  effect  for  the 
cause. 

It  would  appear  much  more  reasonable  to  re- 
gard the  effects  of  attraction  as  produced  by  a 
true  push  exerted  from  the  outside  of  the  bodies. 
According  to  this  notion,  two  mas-ses  of  matter 
undergoing  attraction  are  pushed  together  rather 
than  drawn  or  attracted  together. 

It  has  been  suggested  that  gravitation  may  per- 
haps be  an  effect  of  a  longitudinal  motion  or  vibra- 
tory thrust  in  the  universal  ether.  If  this  is  the 
case,  and  the  ether  is  sensibly  incompressible,  the 
velocity  of  gravitation,  it  would  appear,  should  be 
almost  infinite. 

Attraction,  Atomic The  attraction 

which  causes  the  atoms  to  combine.  (See 
Affinity,  Chemical.} 

In  the  opinion  of  Lodge,  atomic  attraction  is 
the  result  of  the  attraction  of  dissimilar  charges  of 
electricity  possessed  by  all  atoms,  which  are  capa- 
ble  of  uniting  or  entering  into  chemical  combi- 
nation. (See  Electricity,  Atom  of.} 

Attraction,  Capillary  -  — The  molec- 
ular attractions  that  are  concerned  in 
capillary  phenomena.  (See  Capillarity?) 

Attraction,  Electro-Dynamic The 

mutual  attraction  of  electric  currents,  or  of 
conductors  through  which  electric  currents 
are  passing.  (See  Dynamics,  Electro.} 

Attraction,  Electro-Magnetic The 

mutual  attraction  of  the  unlike  poles  of 
electro-magnets.  (See  Magnet,  Electro.\ 

Attraction,  Electrostatic  — The 

mutual  attraction  exerted  between  unlike 
electric  charges,  or  bodies  possessing  unlike 
~'ectric  charges. 


Att.] 


35 


[Aur. 


For  example,  the  pith  hall  supported  on  an  in- 
sulated string  is  attracted,  as  shown  at  A,  Fig.  28, 


•  Fig,  28.     Electrostatic 
Attraction. 


Fig.  29.     Electrostatic 
Repulsion. 


by  a  bit  of  sulphur  which  has  been  briskly  rubbed 
by  a  piece  of  silk.  As  soon,  however,  as  the  ball 
touches  the  sulphur  and  receives  a  charge,  it  is 
repelled,  as  shown  at  B,  Fig.  29. 

These  attractions  ai  d  repulsions  are  due  to  the 
effects  of  electrostatic  induction.  (See  Induction, 
Elfctrostatic. ) 


Attraction,  Magnetic 


— The  mutual 


attraction    exerted    between    unlike    magnet 
poles. 

Magnetic  attractions  and  repulsions  are  best 
shown  by  means  of  the  magnetic  needle  N  S, 
Fig.  30.  The  N.  pole  of  an  approached  magnet 


Fig.  30.      Magnetic  Attraction. 

attracts  the  S.  pole  of  the  needle  but  repels  the 
N.  pole. 

The  laws  of  magnetic  attraction  and  repulsion 
may  be  stated  as  follows,  viz.: 

(i.)  Magnet  poles  of  the  same  name  repel  each 
other;  thus,  a  north  pole  repels  another  north 
pole,  a  south  pole  repels  another  south  pole. 


(2.)  Magnet  poles  of  unlike  names  attract  each 
other;  thus  a  north  pole  5 

attracts  a  south  pole,  or 
a  south  pole  attracts  a  N= 
north  pole. 

A  small  bar  magnet,        Fig.  31.    floating 
N  S,  Fig.  31,  laid  on  the  Magnet. 

top  of  a  light  vessel  floating  on  the  surface  of  a 
liquid,  may  be  readily  employed  to  illustrate  the 
laws  of  magnetic  attraction  and  repulsion. 

Attraction,  Mass  —  — The  mutual  at- 
traction exerted  between  masses  of  matter. 
(See  Gravitation^) 

Attraction,  Molar A  term  some- 
times employed  for  mass  attraction. 

Gravitation  is  an  example  of  mass  attraction, 
where  the  mass  of  the  earth  attracts  the  mass  of 
some  body  placed  near  it.  (See  Gravitation.) 

Attraction,  Molecular  —  —The  mutual 
attraction  exerted  between  neighboring 
molecules. 

The  attraction  of  like  molecules,  or  those  of  the 
same  kind  of  matter,  is  called  Cohesion  ;  that  of 
unlike  molecules,  Adhesion. 

The  tensile  strength  of  iron  or  steel  is  due  to 
the  cohesion  of  its  molecules.  Paint  adheres  to 
wood,  or  ink  to  paper,  by  cohesion  or  the  attrac- 
tion between  tne  unlike  molecules. 

Attraction  of  Gravitation. — A  term  gen- 
erally applied  to  the  mutual  attraction  be- 
tween masses.  (See  Gravitation) 

Attractions  and  Repulsions  of  Currents. 

— (See  Currents,  Attractions  and  Repulsions 
of.} 

Audiphone.— A  thin  plate  of  hard  rubber 
held  in  contact  with  the  teeth,  and  maintained 
at  a  certain  tension  by  strings  attached  to  one 
of  its  edges,  for  the  purpose  of  aiding  the 
hearing. 

The  plate  is  so  held  that  the  sound-waves  from 
a  speaker's  voice  impinge  directly  against  its  flat 
surface.  It  operates  by  means  of  some  of  the 
waves  being  transmitted  to  the  ear  directly 
through  the  bones  of  the  head. 

The  audiphone  is  sometimes  called  a  denti- 
ph<ma. 

Aural  Electrode. — (See  Electrode,  Aural.} 
Aurora  Australis. — The  Southern  Light. 
A  name  given  to  an  appearance  in  the  south- 


Aur.] 


36 


[Aut. 


ern  heavens  similar  to  that  of  the  Aurora 
Borealis.  (See  Aurora  Borealis} 

Aurora  Borealis. — The  Northern    Light. 

Luminous  sheets,  columns,  arches,  or  pillars 
of  pale,  flashing  light,  generally  of  a  red  color, 
seen  in  the  northern  heavens. 

The  auroral  light  assumes  a  great  variety  of  ap- 
pearances, to  which  the  terms  auroral  arch,  bands, 
coronas,  curtains  and  streamers  are  applied. 

The  exact  cause  of  the  aurora  is  not  as  yet 
known.  It  would  appear,  however,  beyond  any 
reasonable  doubt,  that  the  auroral  flashes  are  due 
to  the  passage  of  electrical  discharges  through  the 
upper,  and  therefore  rarer,  regions  of  the  atmos- 
phere. The  intermittent  flashes  of  light  are  prob- 
ably due  to  the  discharges  being  influenced  by  the 
earth's  magnetism. 

Auroras  are  frequently  accompanied  by  mag- 
netic storms.  (See  Storm,  Magnetic. ) 

The  occurrence  of  auroras  is  nearly  always 
simultaneous  with  that  of  an  unusual  number  of 
sun  spots.  Auroras  are  therefore  probably  con- 
nected with  outbursts  of  the  solar  energy.  (See 
Spots,  Sun.) 

The  auroral  light  examined  by  the  spectroscope 
gives  a  spectrum  characteristic  of  luminous  gaseous 
matter,  i.  e.,  contains  a  few  bright  lines;  but,  ac- 
cording to  S.  P.  Thompson,  this  spectrum  is  pro- 
duced by  matter  that  is  not  referable  with  cer- 
tainty to  that  of  any  known  substance. 

Whatever  may  be  the  exact  cause  of  auroras, 
their  appearance  is  almost  exactly  reproduced  by 
the  passage  of  electric  discharges  through  vacua. 

Aurora  Polaris. — A  general  term  some- 
times applied  to  aurora  in  the  neighborhood 
of  either  pole,  or  in  either  the  northern  or 
the  southern  hemisphere. 

Auroral  Arch. — (See  Arch,  Auroral} 
Auroral  Bauds. — (See  Bands,  Auroral} 
Auroral     Coronae. — (See     Corona,    Au- 
roral?) 

Auroral  Curtain. — (See  Curtain,  Au- 
roral.} 

Auroral  Flashes. — (See  Flashes,  Auroral.} 
Auroral  Light — (See  Light,  Auroral} 
Auroral    Storm.— (See  Storm,  Auroral} 
Auroral  Streamer. — (See  Streamer,  Au- 
roral} 
Auroras     and    Magnetic    Storms,   Peri- 


odicity of 


— Observed  coincidences  be- 


tween the  occurrence  of  auroras,  magnetic 
storms,  and  sun-spots. 

The  occurrence  of  auroras,  or  magnetic  storms, 
at  periods  of  about  eleven  years  apart,  corre- 
sponds to  the  well-known  eleven-year  sun-spot 
period. 

The  period  also  agrees  with  a  variation  in  the 
magnetic  declination  of  any  place,  which,  accord- 
ing to  Sabine,  occurs  once  in  every  eleven  years. 

Austral  Magnetic  Pole. — (See  Pole,  Mag- 
netic, Austral} 

Autographic  Telegraphy.  —  (See  Teleg- 
raphy, Autographic} 

Automatic  Annunciator  Drop.  —  (See 
Drop,  Annunciator,  Automatic} 

Automatic  Bell. — vSee  Bell,  Automatic 
Electric} 

Automatic  Contact  Breaker. — (See  Con- 
tact Breaker,  Automatic} 

Automatic  Cut-Out. — (See  Cut-Out,  Au- 
tomatic} 

Automatic  Cut-Out  for  Multiple-Connect- 
ed Electro-Receptive  Devices. — (See  Cut- 
Out,  Automatic,  for  Multiple-Connected 
Electro-Receptive  Devices.) 

Automatic  Cut-Out  for  Series-Connected 
Electro-Receptive  Devices. — (See  Cut-Out, 
Automatic,  for  Series-Connected  Electro-Re- 
ceptive Devices.) 

Automatic  Drop.  —  (See  Drop,  Auto- 
matic} 

Automatic  Electric  Burner. — (See Burn- 
er, Automatic  Electric} 

Automatic  Electric  Safety  System  for 
Railroads. — (See  Railroads,  Automatic  Elec- 
tric Safety  System  for} 

Automatic  Fire-Alarm.  —  (See  Alarm, 
Fire,  Automatic} 

Automatic  Gas  Cut-Off.  —  (See  Cut-Off, 
Automatic  Gas} 

Automatic  Indicator.  —  (See  Indicator, 
Automatic} 

Automatic  Make-and-Break. — (See  Make- 
and-Break,  Automatic} 

Automatic  Oiler. — (See  Oiler,  Automatic} 


Aut.] 


37 


[B.  A,  U. 


Automatic  Paper-Winder. — (See  Winder, 
Telegraphic  Paper.} 

Automatic  Regulation. — (See  Regulation, 
Automatic.) 

Automatic  Regulator. — (See  Regulator, 
Automatic.} 

Automatic  Search-Light.  —  (See  Light, 
Search,  Automatic.} 

Automatic  Switch  for  Incandescent  Elec- 
tric Lamp. — (See  Switch,  Automatic,  for 
Incandescent  Electric  Lamp.} 

Automatic  Telegraphy.  —  (See  Teleg- 
raphy, Automatic!) 

Automatic  Telephone  Switch.  —  (See 
Switch,  Telephone,  Automatic?) 

Automatic  Time  Cut-Outs.— (See  Cut- 
Out,  Automatic  Time.} 

Automatic  Yariable  Resistance. — (See 
Resistance,  Variable,  Automatic?) 

Automatically  Regulable. — (See  Regula- 
ble, Automatically?) 

Automobile  Torpedo. — (See  Torpedo,  Au- 
tomobile?) 

Average  or  Mean  Electromotive  Force. — 
(See  Force,  Electromotive,  Average,  or 
Mean?) 

Axes  of  Co-ordinates. — (See  Co-ordinates, 
Axes  of?) 

Axial  Magnet. — (See  Magnet,  Axial?) 

Axis,    Magnetic The  line  around 

which  a  magnetic  needle,  free  to  move,  but 
which  has  come  to  rest  in  a  magnetic  field, 
can  be  turned  without  changing  the  set  or 
direction  in  which  it  has  come  to  rest. 

Axis,  Magnetic,  of  a  Straight  Needle  — 
— A  straight  line  drawn  through  the  magnet, 
joining  its  poles. 


25  30  35 


The  magnetic  axis  of  a  straight  needle  may  be 
regarded  as  a  straight  line  passing  through  the 
poles  of  the  needle  and  its  point  of  support. 

The  magnetic  axis  may  not  correspond  with 
the  geometric  axis  of  the 
needle.  This  leads  to 
an  error  in  reading  the 
true  direction  in  which 
the  needle  is  pointing, 
which  must  be  cor- 
rected. Thus,  the  nee- 
dle N  S,  Fig.  32,  points 
to  31  degrees  on  the 
scale.  In  reality,  if  the 
magnetic  axis  of  the 
needle  lies  in  the  line 
N'  S',  the  true  deflec- 
tion of  the  needle  is  only 
28  degrees. 


32.     Magnetic 
Axis. 


Axis  of  Abscissas.— (See  Abscissas,  Axis 
of?) 

Axis  of  Ordinates.— (See  Ordinates,  Axis 
of?) 

Azimuth. — In  astronomy,  the  angular  dis- 
tance between  an  azimuth  circle  and  the 
meridian. 

The  azimuth  of  a  heavenly  body  in  the  North- 
ern Hemisphere  is  measured  on  the  arc  of  the 
horizon  intercepted  between  the  north  point  of 
the  horizon  and  the  point  where  the  great  circle 
that  passes  through  the  heavenly  body  cuts  the 
horizon. 

Azimuth  Circle.— (See   Circle,  Azimuth?) 

Azimuth  Compass. — (See  Compass,  Azi- 
muth?) 

Azimuth,  Magnetic  —  — The  arc  inter- 
cepted on  the  horizon  between  the  magnetic 
meridian  and  a  great  circle  passing  through 
the  observed  body. 


B. — A  contraction  used  in  mathematical 
writings  for  the  internal  magnetization,  or  the 
magnetic  induction,  or  the  number  of  lines  of 
force  per  square  centimetre  in  the  magnetized 
material. 

This  contraction  for  internal  magnetization  is, 


in  most  mathematical  treatises,  printed  in  bold- 
faced type. 

B.  A.  Ohm.— (See  Ohm,  B.  A?) 

B.  A.  U. — A  contraction  sometimes  em- 
ployed for  the  British  Association  unit  or  ohm. 


B.  W.  G. 


38 


[Bal. 


B.  W.  G. — A  contraction  for  Birmingham 
wire  gauge.  (See  Gauge,  Birmingham 
Wire.) 

A  contraction  sometimes  used  for  the  new 
British  wire  gauge. 

Back  Electromotive  Force.— (See  Force, 
Electr emotive,  Sack.) 

Back-Stroke  of  Lightning-. — (See  Light- 
ning, Back-Stroke  of.) 

Bain's  Chemical  Recorder. — (See  Re- 
corder, Chemical,  Bain's.) 

Bain's  Printing  Solution. — (See  Solution, 
Bain's  Printing) 

Balance  Arms. — (See  Arms,  Bridge  or 
Balance?) 

Balance,  Bi-fllar  Suspension An 

instrument  similar  in  construction  to  Cou- 
lomb's torsion  balance,  but  in  which  the 
needle  is  hung  by  two  separate  fibres  instead 
of  by  a  single  one.  (See  Balance,  Coulomb's 
Torsion.  Suspension,  Bi-filar) 

Balance,  Centi-Ampdre An  am- 
meter in  the  form  of  a  balance,  whose  scale  is 
graduated  to  give  direct  readings  in  centi- 
amperes. 

Ampere  balances  giving  readings  in  various 
decimals  or  multiples  of  amperes  have  been  de- 
vised by  Sir  William  Thomson.  The  strength  of 
current  passing  is  determined  by  the  action  on  a 
movable  ring  or  coil,  placed  between  iwo  fixed 
rings  or  coils. 

The  movable  ring  is  in  a  horizontal'  plane 
nearly  midway  between  the  two  fixed  rings. 
The  fixed  rings  are  traversed  by  the  current 
in  opposite  directions,  so  that  one  attracts 
and  the  other  repels  the  movable  ring.  The 
movable  ring  is  attached  to  one  end  of  a  horizon- 
tal balance  arm,  and  a  similar  movable  ring,  also 
provided  with  attracting  and  repellinlg  fixed  rings, 
is  attached  to  the  opposite  end  of  the  balance  arm. 
In  order  to  avoid  disturbance  of  horizontal  com- 
ponents of  terrestrial,  or  of  local  magnetic  force, 
the  current  is  sent  in  the  same  direction  through 
the  two  movable  rings.  The  balancing  is  effected 
by  means  of  a  weight,  sliding  on  a  nearly  hori- 
zontal arm  attached  to  the  balance.  A  counter- 
poise weight  is  used  in  connection  with  the  sliding 
weight. 


A  standard   Thomson    centi-ampere    balance 
is  shown  in  Fig.  33.     In  measuring  a  current, 


•*%"•  33-      Centi-Amptre.  Balance. 

the  weight  is   moved  along  the  scale  until  the 
balance  comes  to  rest. 


Balance,  Composite 


— A    balance 


form  of  ammeter  devised  by  Sir  William  Thom- 
son, which  can  be  used  for  an  ampere-meter,  a 
watt-meter,  or  a  volt-meter,  according  to  the 
manner  in  which  its  sets  of  fine  and  coarse 
wire  coils  are  connected.  (See  Balance, 
Centi- Ampere) 

Balance,  Coulomb's  Torsion An 

apparatus  to  measure  the  force  of  electric  or 
magnetic  repulsion  between  two  similarly 
charged  bodies,  or  between  two  similar  mag- 
net poles,  by  opposing  to  such  force  the  tor- 
sion of  a  thin  wire. 

The  two  forces  balance  each  other  ;  hence  the 
origin  of  the  name. 


F'ff"  34'    Coulomb's  Torsion  Balance. 

Fig.   34  represents  a  Coulomb    torsion  bal- 
ance, adapted  to  the  measurement  of  .the  force 


Bal.] 


39 


[Bal. 


of  electrostatic  repulsion.  A  delicate  needle  of 
shellac,  having  a  small  gilded  pith  ball  at  one  of 
its  ends,  is  suspended  by  a  fine  metallic  wire.  A 
proof -plane  i  B,  is  touched  to  the  electrified  surface 
whose  charge  is  to  be  measured,  and  is  then 
placed  as  shown  in  the  figure.  (See  Plane,  Proof.) 
There  is  a  momentary  attraction  of  the  needle, 
anu.  .u^"-  a  repulsion,  which  causes  the  needle  to 
be  moved  a  cer+ain  distance  from  the  ball  on  the 
proof-plane.  This  distance  is  measured  in  degrees 
on  a  graduated  circle  a  a,  marked  on  the  instru- 
ment. The  force  of  the  repulsion  is  calculated  by 
determining  the  amount  of  torsion  required  to 
move  the  needle  a  certain  distance  toward  the 
ball  of  the  electrified  proof-plane. 

This  torsion  is  obiained  by  the  movement  of  the 
torsion  head  D,  the  amount  of  which  motion  is 
measured  on  a  graduated  circle  at  D.  The 
measurement  is  based  on  the  fact  that  the  force  re- 
quired to  twist  a  wire  is  proportional  to  the  angle 
of  torsion. 

Balance,  Deci-Ampere An  ammeter 

in  the  form  of  a  balance,  whose  scale  is 
graduated  to  give  direct  readings  in  deci- 
amperes.  (See  Balance,  Centi- Ampere?) 

Balance,  Deka- Ampere — An  am- 
meter in  the  form  of  a  balance,  whose  scale  is 
graduated  to  give  direct  readings  in  deka- 
amperes.  (See  Balance,  Centi-Ampere?) 

Balance,  Electric  — A  term  fre- 
quently used  for  Wheatstone's  electric  bridge. 
(See  Bridge,  Electric?) 

The  electric  bridge  is  sometimes  called  a  balance 
because,  when  in  use  in  measuring  resistances, 
one  resistance  or  set  of  resistances  balances  an- 
other resistance  or  set  of  resistances. 

Balance,  Hekto-AmpSre An  am- 
meter in  the  form  of  a  balance,  whose  scale 
is  graduated  to  give  direct  readings  in  hekto- 
amperes.  (See  Balance,  Centi- Ampere.} 

Balance  Indicator. — (See  Indicator,  Bal- 
ance.} 

Balance,     Induction,     Hughes'  — 

An  apparatus  for  the  detection  of  the  presence 
of  a  metallic  or  conducting  substance  by  the 
aid  of  induced  electric  currents. 

Hughes'  induction  balance  is  shown  in  Fig.  35. 

A,  B,  C  and  D  are  bobbins,  wound  with  about 
300  feet  of  No.  32  copper  wire.  The  coils  ar« 


connected  as  shown,  A  and  B,  in  the  circuit  of  a 
battery,  and  C  and  D,  in  the  circuit  of  a  telephone. 
The  coils,  A  and  B,  and  C  and  D,  are  placed  at 


Fig  33.     Hughes'  Induction  Balance. 

such  a  distance  apart  as  to  prevent  any  mutual 
induction  occurring  between  them.  The  coils 
are  so  joined  that  the  direction  of  the  induction 
of  A,  on  C,  is  opposite  to  that  of  B,  on  D. 

The  coils,  A  and  B,  then  act  as  primaries,  and  C 
and  D,  as  secondaries.  In  the  battery  circuit  is  an 
interrupter  I,  which  is  caused  to  continually  make 
and  break  the  circuit. 

The  coils  are  so  adjusted  that  the  opposing 
secondary  coils  produce  but  little  noise  to  one 
listening  at  the  telephone.  This  can  readily  be 
done  by  the  adjusting  of  a  single  pair  of  coils. 

If  a  angle  coin  or  mass  of  metal  be  introduced 
between  either  A  and  C,  or  B  and  D,  or  even 
above  one  of  the  coils,  as  at  d,  the  balance 
will  be  disturbed,  since  some  of  the  induction  is 
now  expended  in  producing  electric  currents  in 
the  interposed  metal,  and  a  sound  will  therefore 
be  heard  in  the  telephone.  But  if  precisely  similar 
metals  are  placed  in  similar  positions,  between  A 
and  C,  and  B  and  D,  no  sound  is  heard  in  the 
telephone,  since  the  inductive  effects  due  to  the 
two  metals  are  the  same. 

The  slightest  difference,  however,  either  in 
composition,  size  or  position,  destroys  the  balance, 
and  causes  a  sound  to  be  heard  in  the  telephone. 

A  spurious  coin  is  thus  readily  detected  when 
compared  with  a  genuine  coin. 

A  somewhat  similar  instrument  has  been  em- 
ployed to  detect  and  locate  a  bullet  or  other  for- 
eign metallic  substance  in  the  human  body. 

In  order  to  determine  the  amount  of  the  dis- 
turbance, an  instrument  called  a  sonometer  is 
used  (See  Sonometer,  Hughes1),  in  which  a  single 
secondary  coil,  placed  in  the  circuit  of  a  telephone, 
slides  on  a  graduated  bar  between  two  fixed 
primary  coils,  so  wound  as  to  exert  equal  and  op- 
posite inductions  on  the  secondary.  When,  there- 
fore,  the  secondary  is  exactly  in  ihe  middle  of  the 


Bal.] 


40 


[Bal. 


graduated  bar,  and  consequently  exactly  midway 
between  the  two  fixed  primary  coils,  no  sounds  are 
heard  in  the  telephone,  but  when  moved  to  one 
side  or  the  other  the  sounds  are  heard.  Switches 
are  so  arranged  that  the  telephone  can  be  readily 
switched  from  the  induction  balance  to  the  tele- 
phone, or  vice  versa.  When,  therefore,  a  metallic 
disc  is  placed  in  one  of  the  coils  of  the  induction 
balance,  and  a  noise  is  heard  in  the  telephone, 
the  coil  of  the  sonometer  is  shifted  so  that  the 
noise  heard  in  this  telephone  is  judged  by  the 
ear  to  be  equal,  and  the  comparison  can  then  be 
made  by  means  of  simple  calculations. 

The  following  table  gives,  in  arbitrary  values, 
the  results  of  various  experiments  as  to  the  sensi- 
tiveness in  this  respect  of  discs  of  different 
metals,  of  various  sizes  and  shapes  : 

Silver,  chemically  pure 125 

Gold 117 

Silver,  commercial 115 

Aluminium 112 

Copper ico 

Zinc 80 

Bronze 75 

Tin 74 

Iron,  ordinary . ,  53 

German  silver 50 

Iron,  pure 40 

Copper,  alloyed •'..-,  40 

Lead 58 

Antimony 35 

Bismuth 10 

Zinc,  alloyed 6 

Carbon 2 

— {Fleming.} 

An  inspection  of  this  table  shows  that  the  values 
found  for  different  metals  do  not  correspond  with 
their  electric  conducting  power,  although,  roughly 
speaking,  the  best  conductors  stand  at  the  top  of 
the  table,  and  the  worst  at  the  bottom.  The 
effects  appear  to  be  dependent  for  their  action  on 
the  phenomena  of  magnetic  screening,  for — 

(i.)  If  slots  are  cut  in  the  middle  of  the  plate 
its  disturbing  action  is  either  removed  or  very 
much  decreased. 

(2.)  If  a  flat  coil  of  copper  wire  replaces  a  disc 
of  metal  no  effect  is  produced  on  the  induction 
balance  when  its  ends  are  open,  but  when  closed 
the  coil  acts  just  like  a  disc,  or  continuous  plate 
of  metal. 

(3.)  The  difference  between  various  metals  in- 


serted as  discs  in  the  induction  balance  is  less  at 
'  high  speeds  of  reversal  than  at  low  speeds. 

Balance,  Kilo-Ampere — An  am- 
meter in  the  form  of  a  balance,  whose  scale  is 
graduated  to  give  direct  readings  in  kilo-am- 
peres. (See  Balance,  Centz- Ampere.) 

Balance  of  Induction  in  Cable.— (See 
Induction,  Balance  of,  in  Cable!, 

Balance,  Plating  -  — An  automatic 
device  for  disconnecting  the  current  from 
the  article  to  be  plated,  as  soon  as  a  certain 
increase  in  weight  has  been  obtained. 

The  objects  to  be  plated  are  suspended  at  one 
end  of  a  balance,  and  when  a  certain  increase  in 
weight  has  been  gained,  the  balance  tips  and 
breaks  the  circuit.  Edison's  electric  meter  is 
based  on  this  principle. 

Balance,   Thermic,    or  Bolometer. — An 

apparatus  constructed  on  the  principle  of  the 
differential  galvanometer,  devised  by  Professor 
Langley  for  determining  small  differences  of 
temperature.  (See  Galvanometer,  Differen- 
tial^ 

A  coil  composed  of  two  separately  insulated 
wires,  wound  together,  is  suspended  in  a  mag- 
netic field,  and  has  a  current  sent  through  it. 
Under  normal  conditions,  this  current  separates 
into  two  equal  parts,  and  runs  through  the  wires 
in  opposite  directions.  It  therefore  produces  no 
sensible  field,  and  suffers  no  deflection  by  the  field 
in  which  it  is  suspended. 

Any  local  application  of  heat  producing  a  dif- 
ference in  temperature  in  these  coils,  causing  a 
difference  in  resistance,  prevents  this  equality.  A 
field  is  therefore  produced  in  the  suspended  coil, 
which,  though  extremely  small,  is  rendered  meas- 
urable by  means  of  the  powerful  field  produced 
in  the  coil,  within  which  the  double  coil  is  sus- 
pended. 

Differences  of  temperature  as  small  as  one- 
fourteen  thousandth  of  a  degree  Fahrenheit  are 
detected  by  the  instrument. 

Balance,  Wheatstone's  Electric A 

name  often  given  to  the  electric  bridge  or 
balance.  (See  Bridge,  Electric!) 

Balanced-Metallic  Circuit. — (See  Circuit, 
Balanced-Metallic!) 

Balanced  Resistances. — (See  Resistances, 
Balanced!) 


Bui.] 


41 


[Bar. 


Balata. — An  insulating  material. 
Balata,  when  prepared  for  use  as  an  insulating 
material,  is  somewhat  like  gutta-percha. 


indicate   the  peculiarities  of  distribution  of  the 
charge  thereon. 


Ball,  Electric  Time 


— A  ball,  sup- 


ported in  a  prominent  position  on  a  tall  pole, 
and  caused  to  fall  at  the  exact  hour  of  noon, 
or  at  any  other  predetermined  time,  for  the 
purpose  of  thus  giving  correct  time  to  an 
entire  neighborhood. 

The  release  of  the  ball  is  effected  by  the  closing 
of  an  electric  circuit,  either  automatically,  or 
through  the  agency  of  an  observer. 

Ball,  Fire A  term  sometimes  ap- 
plied to  globular  lightning.  (See  Lightning, 
Globular?) 

Ball  Lightning.— (See  Lightning,  Sail.) 
Ballistic  Curve.— (See  Curve,  Ballistic?) 

Ballistic  Galvanometer. — (See  Galva- 
nometer, Ballistic.} 


Balloon,    Electric 


— A    balloon,   or 


air  ship,  provided  with  electric  power  so  as 
to  be  able  to  be  steered  or  moved  against  the 
direction  of  the  wind. 

Electric  balloons  have  been  moved  against  the 
wind  and  steered  with  a  certain  amount  of  success, 
by  the  use  of  electric  motors  driven  by  storage 
batteries.  All  thr.t  is  needed  to  make  aerial  navi- 
gation a  commercial  success  is  the  ability  to  ob- 
tain great  power  with  a  small  weight.  The  storage 
battery  does  this  to  a  limited  extent. 

Bearing  in  mind  the  high  efficiency  of  the  elec- 
tric motor,  it  would  appear  that  the  problem  of 
successful  aerial  navigation  will  be  solved  when 
the  discovery  is  made  of  means  for  directly  con- 
verting the  chemical  potential  energy  of  coal  into 
electrical  energy. 

Balloon  Signaling  for  Military  Pur- 
poses.—  (See  Signaling,  Balloon,  for  Mil- 
itary Purposes?) 

Balls,  Pith—  —Two  balls  of  pith,  sus- 
pended by  conducting  threads  of  cotton  to 
insulated  conductors,  employed  to  show  the 
electrification  of  the  same  by  their  mutual 
repulsion.' 

The  pith  balls  connected  with  the  insulated 
cylinder  A  B,  Fig.  36,  not  only  show  the  electri- 
fication of  the  cylinder,  but  serve  also  to  roughly 


Fig.  36.    Pith  Ball  Cylinder. 

Bands,        Auroral Approximately 

parallel  streaks  of  light  sometimes  seen 
during  the  prevalence  of  the  aurora.  (See 
Aurora  B  area  Us.) 

Bank  of  Lamps.— (See  Lamps,  Bank  of.) 
Banked  Battery.— (See  Battery,  Banked.) 

Bar,  Detorsion  —  —A  bar  placed  in  a 
magnetic  instrument  called  a  declinometer  for 
the  purpose  of  removing  the  torsion  of  the 
suspending  thread  of  the  magnet. 

The  detorsion  _>ar  of  the  declinometer  is  gen- 
erally made  of  gun  metal  of  the  same  weight  as 
that  of  the  suspended  magnet.  A  small  magnet 
is  placed  in  a  rectangular  aperture  in  the  middle 
of  the  bar. 

Bar  Electro-Magnet.— (See  Mag-net, 
Electro,  Bar.) 

Barad. — A  unit  of  pressure  proposed  by 
the  British  Association. 

One  barad  equals  one  dyne  per  square  cen/<- 
metre. 

Barometer. — An  apparatus  for  measuring 
the  pressure  or  weight  of  the  atmosphere. 

Barometric  Column. — (See  Column,  Baro- 
metric.) 


— Omnibus     bars.      (See 


Bars,    Bus  — 

Bars,  Omnibus?) 

Bars,    Krizik's Cores    of    various 

shapes,  provided  for  solenoids,  in  which  the 
distribution  of  the  metal  in  the  bar  is  so  pro- 
portioned as  to  insure  as  nearly  as  possible  a 
uniform  attraction  or  pull  while  in  different 
positions  in  the  solenoid. 


Bar.] 


42 


[Bat. 


Krizik's  bars  of  various  shapes  are  shown  in 
ig-  37-     It  will  be  observed  that  in  all  cases  the 


f'f-  37-      Krizik's  Bars.' 

mass  of  metal  is  greater  toward  the  middle  of 
the  core  than  near  the  ends. 

When  a  core  of  uniform  diameter  is  drawn  into 
a  solenoid,  the  attraction  or  pull  is  not  uniform  in 
strength  for  different  positions  of  the  bar.  When 
the  bar  is  just  entering  the  solenoid,  the  pull  is 
strongest ;  as  soon  as  the  end  passes  the  middle  of 
the  core  the  attraction  decreases,  until,  when  the 
centres  of  the  bar  and  core  coincide,  the  motion 
ceases,  since  both  ends  of  the  solenoid  attract 
equally  in  opposite  directions.  By  proportioning 
the  bars,  as  shown  in  the  figure,  a  fairly  uniform 
pull  for  a  considerable  length  may  be  obtained. 

Bars,      Negative-Omnibus  — The 

bus-bars  that  are  connected  with  the  negative 
terminal  of  the  dynamos.  (See  Bars,  Omni- 
bus.) 

Bars,  Neutral-Omnibus The  bus- 

bars  that  are  connected  with  the  neutral 
dynamo  terminal  in  a  three-wire  system  of 
distribution. 

Bars,  Omnibus Heavy  bars  of  con- 
ducting material  connected  directly  to  the 
poles  of  dynamo-electric  machines,  in  electric 
incandescent  light  or  electric  railway  installa- 
tions, and  therefore  receiving  the  entire  current 
produced  by  the  machine. 

Main  conductors  common  to  two  or  more 
dynamos  in  an  electrical  generating  plant. 

The  terms  bus  and  omnibus  bars  refer  to  the 
fact  that  the  entire  or  whole  current  is  carried  by 
them. 

Bars,  Positive-Omnibus  —  —The  bus- 
bars that  are  connected  with  the  positive 
terminal  of  the  dynamos. 

i>ath,  Bi-polar  —  — An  electro-thera- 
peutic bath,  the  current  applied  to  which 
enters  at  one  part  of  the  tub,  and  leaves  at 
another  part. 


The  electrodes  for  the  bi-polar  bath  consist  of 
suitably  shaped  copper  plates,  generally  called 
shovel  electrodes. 

Bath,  Copper—  — An  electrolytic  bath 
containing  a  readily  electrolyzable  solution 
of  a  copper  salt,  and  a  copper  plate  acting  as 
the  anode,  and  placed  in  the  liquid  near  the 
object  to  be  electro-plated,  which  forms  the 
kathode.  (See  Plating,  Electro?) 

The  sulphate,  the  cyanide  and  the  acetate  of  cop- 
per are  used  for  copper  baths.  The  use  of  the  sul- 
phate is  objectionable.  The  cyanide  is  expensive. 
The  acetate  is  therefore  very  generally  employed. 
Wahl  gives  the  following  formula  for  a  copper 
bath,  viz. : 

Water i, coo  parts. 

Acetate  of  copper,  crystal- 
lized          20    " 

Carbonate  of  soda ao    " 

Bisulphite  of  soda 20    " 

Cyanide  of  potassium  (pure)         20    " 

Bath,  Electro-Plating-  — Tanks  con- 
taining metallic  solutions  in  which  articles 
are  placed  so  as  to  be  electro-plated.  (See 
Plating,  Electro?) 

Strictly  speaking  a  plating  bath  includes  not 
only  the  vessel  and  its  metallic  solution,  but  also 
the  metallic  plate  acting  as  the  anode  and  the 
article  to  be  plated  forming  the  kathode. 

Bath,  Electro-Therapeutic A  bath 

furnished  with  suitable  electrodes  and  used 
in  the  application  of  electricity  to  curative 
purposes. 

Such  baths  should  be  used  only  under  the  advice 
of  a  regular  physician. 

Bath,    Gold An   electrolytic    bath 

containing  a  readily  electrolyzable  solution  of 
a  gold  salt  and  a  gold  plate  acting  as  the 
anode,  and  placed  in  the  liquid  opposite  the 
object  to  be  plated,  which  forms  the  kathode. 
(See  Plating,  Electro?) 

Electro  gilding  may  be  accomplished  either  with 
or  without  the  aid  of  heat.  Hot  gilding  appears 
to  give  a  smoother  and  cleaner  deposit. 

The  following  is  a  fairly  good  solution  for  a 
gold  bath: 

Water 1,000  parts. 

Cyanide  of  potassium,  pure. .        20     " 

Gold  10     " 

— (Wahl.) 


Bat.] 


43 


[Bat. 


The  gold  is  first  converted  into  neutral  chloride 
by  dissolving  it  in  25  parts  of  pure  hydrochloric 
acid  to  which  12.5  parts  of  pure  nitric  acid  has 
been  added.  When  the  gold  is  completely  dis- 
solved, the  liquid  is  heated  until  of  a  dark  red 
color,  in  order  to  expel  any  excess  of  acid. 

Bath,  Head,  Electric A  variety 

of  electric  breeze,  applied  therapeutically  to 
the  head  of  the  patient. 

The  patient  is  placed  on  an  insulating  stool  and 
connected  with  one  pole  of  an  electrostatic  induc- 
tion machine,  the  other  pole  of  which  is  con- 
nected to  a  circle  of  insulated  points  suspended 
over  the  head. 


Bath,  Hydro-Electric 


— A    bath    in 


which  electro-therapeutic  treatment  is  given 
by  applying  one  electrode  to  the  metallic  lining 
of  the  tub,  and  the  other  electrode  to  the  body 
of  the  bather. 

Bath,      Multipolar-Electric  — An 

electro-therapeutic  bath,  in  .which  more  than 
two  electrodes  are  employed. 

It  is  not  clear  that  the  multipolar- electric  bath 
possesses  any  decided  advantages  over  the  bi-polar 
bath. 

Bath,  Nickel An  electrolytic  bath 

containing  a  readily  electrolyzable  salt  of 
nickel,  a  plate  of  nickel  acting  as  the  anode 
of  a  battery  and  placed  in  the  liquid  near  the 
object  to  be  coated,  which  forms  the  kathode. 
(See  Plating,  Electro^ 

The  double  sulphate  of  nickel  and  ammonium 
(from  5  to  8  parts  dissolved  in  100  parts  of  water) 
is  used  for  the  bath.  Some  prefer  to  add 
sulphate  of  ammonium  and  citric  acid  to  the  above 
solution. 

Bath,  Shower,  Electric A  shower 

bath  in  which  the  falling  drops  carry  electric 
charges  to  the  patient  subjected  thereto. 

The  water  is  rendered  slightly  alkaline.  One 
pole  is  immersed  in  the  alkaline  water  and  the 
other  connected  to  a  metallic  stool  on  which  the 
patient  is  placed. 

Bath,  Silver An  electrolytic  bath 

containing  a  readily  electrolyzable  salt  of 
silver  and  a  plate  of  silver  acting  as  the 
anode  of  an  electric  source  and  placed  in  the 
liquid  near  the  object  to  be  coated,  which 
forms  the  kathode.  vSee  ^fating.  Electro.} 


The  double  cyanide  of  silver  and  potassium 
is  the  salt  usually  employed  in  the  silver  bath. 

The  following  bath  is  recommended  by  Rose- 
leur: 

Water 1,000  parts. 

Cyanide  of  potassium  (pure)        50     " 
Pure  silver 25     " 

The  silver  (granulated)  is  treated  with  pure  nitric 
acid  (43  degrees  Beaume)  and  converted  into 
nitrate  of  silver.  The  solution  is  then  heated  to 
dryne^s  and  subsequently  fused.  The  fused  nitrate 
so  obtained  is  dissolved  in  fifteen  times  its  weight 
of  distilled  water  and  treated  with  a  solution  of 
cyanide  of  potassium  (10  per  cent,  of  the  cyanide), 
by  means  of  which  silver  cyanide  is  thrown  down 
as  a  precipitate.  This  precipitate  is  then  sepa-- 
rated  and  washed.  It  is  added  to  the  i,coo  parts 
of  water,  dissolved,  and  the  cyanide  of  potassium 
afterward  added,  thus  forming  the  double  cyan- 
ide required  for  the  bath. 

Bath,  Stripping1  —  — A  bath  for  remov- 
ing an  electro-plating  of  gold,  silver,  or  other 
metal,  either  by  simple  dipping  or  by  electric 
action. 


Bath,  Ungilding 


-A  stripping  bath 


suitable  for  the  removal  of  a  coating  of  gold. 
(See  Bath,  Stripping^ 

Bath,  Unipolar-Electric  —  —An  electro- 
therapeutic  bath,  the  water  of  which  forms 
one  of  the  electrodes  of  the  source,  and  the 
other  electrode  is  attached  to  a  metallic  rod 
fixed  at  a  convenient  height  above  the  tub. 

The  bath  tub  is  formed  of  non-conducting  sub- 
stances. The  terminals  of  the  electrode  con- 
nected with  the  water  terminate  in  metal  plates 
located  at  suitable  points  in  the  tub.  The  cur- 
rent  is  applied  by  the  patient  making  and  break- 
ing contact  at  the  vertical  metal  rod  with  his 
hands. 

The  unipolar-electric  bath  is  employed  instead 
of  local  galvanization  where  it  is  desired  to  limit 
the  application  to  especial  organs  or  particular 
parts  of  the  body.  In  general  galvanization  the 
patient  is  placed  on  an  electrode  of  large  sur- 
face, formed  of  a  large  sponge- covered  metallic 
plate,  on  which  he  sits  or  rests.  This  electrode  is 
connected  with  the  kathode  of  the  battery.  The 
anode  is  connected  with  a  large  sponge  electrode, 
which  is  moved  regularly  over  the  body  of  the 
patient;  sometimes  the  moistened  hand  of 'the 
operator  is  used  in  place  of  the  sponge  electrode. 


Bat.] 


[Bat. 


Bath,  Unsilvering  —  — A  stripping  bath 
suitable  for  the  removal  of  a  coating  of  silver. 
(See  Bath,  Stripping^ 

Bathometer. — An  instrument  invented  by 
Siemens  for  obtaining  deep-sea  soundings 
without  the  use  of  a  sounding  line. 

The  bathometer  depends  for  its  operation  on 
the  varied  attraction  of  the  earth  for  a  suspended 
weight  in  parts  of  the  ocean  differing  in  depth. 
As  the  vessel  passes  over  deep  portions  of  the 
ocean,  the  solid  land  of  the  bottom,  being  further 
from  the  ship,  exerts  a  smaller  attraction  than  it 
would  in  shallow  parts,  where  it  is  nearer;  for, 
although  in  the  deep  parts  of  the  ocean  the  water 
lies  between  the  ship  and  the  bottom,  the  smaller 
density  of  the  water  as  compared  with  the  land 
causes  it  to  exert  a  smaller  attraction  than  in  the 
shallower  parts,  where  the  bottom  is  nearer  the 
ship.  The  varying  attraction  of  the  earth  is 
caused  to  act  on  a  mercury  column,  the  reading 
of  which  is  effected  by  means  of  an  electric  con- 
tact. 

Battery,  Banked  — A  term  some- 
times applied  to  a  battery  from  which  a  num- 
ber of  separate  circuits  are  supplied  with  cur- 
rents. 

The  term  banked -battery  is  sometimes  ap- 
plied to  a  multiple  arc  connected  battery. 

Battery,  Cautery A  term  some- 
times employed  in  electro-therapeutics,  for  a 
multiple  connected  voltaic  battery  adapted  for 
producing  electric  incandescence  for  cautery 
effects. 

Battery,  Closed-Circuit  -  —A  voltaic 
battery  which  may  be  kept  constantly  on 
closed-circuit  without  serious  polarization. 

The  gravity  battery  is  a  closed-circuit  battery. 
As  employed  for  use  on  most  telegraph  lines,  it  is 
maintained  on  a  closed  circuit.  When  an  operator 
wishes  to  use  the  line  he  opens  his  switch,  thus 
breaking  the  circuit  and  calling  his  correspondent. 
Such  batteries  should  not  polarize.  (See  Cell, 
Voltaic,  Polarization  of.) 

Battery,  Connection  of,  for  Quantity 

— A  term,  now  generally  in  disuse,  formerly 
employed  to  indicate  the  grouping  of  voltaic 
cells,  now  known  as  parallel  or  multiple. 

The  arrangement  or  coupling  of  a  number  of 
voltaic  cells  in  multiple  reduces  the  internal  resist- 


ance of  the  battery,  and  thus  permits  a  greater 
current,  or  quantity,  of  electricity  to  pass  ;  hence 
the  origin  of  the  term. 

Battery,  Dynamo The  combina- 
tion or  coupling  together  of  several  separate 
dynamo-electric  machines  so  as  to  act  as  a 
single  electric  source. 

The  dynamos  may  be  connected  to  the  leads 
either  in  series,  in  multiple,  in  multiple-series  or 
in  series-multiple. 

Battery,  Dynamo,  Electric  Machine 

— A  dynamo  battery.  (See  Battery,  Dy- 
namo.) 

Battery,  Electric A  general  term 

applied  to  the  combination,  as  a  single  source, 
of  a  number  of  separate  electric  sources. 

The  separate  sources  may  be  coupled  either  in 
series,  in  multiple,  in  multiple-series,  or  in  series- 
multiple.  (  See  Circuits,  Varieties  of.) 

The  term  battery  is  sometimes  incorrectly  ap- 
plied to  a  single  voltaic  couple  or  cell. 

Battery,  Floating,  De  la  Rive's A 

floating  voltaic  cell,  the  terminals  of  which  are 
connected  with  a  coil  of  insulated  wire,  em- 
ployed to  show  the  attractions  and  repul- 
sions between  magnets  and  movable  electric 
circuits. 

The  cell,  shown  in  Fig.  38,  consists  of  a  vol- 


'f-  3S.    Floating  Cell. 

taic  couple  of  zinc  and  copper,  the  terminals  of 
which  are  connected  to  the  circular  coil  of  insu- 
lated wire,  as  shown,  and  the  whole  floated  by 
means  of  a  cork,  in  a  vessel  containing  dilute  sul- 
phuric acid. 

When  the  current  flows  through  the  coil  in  the 
direction  shown  by  the  arrows,  the  approach  of 
the  N-seeking  pole  of  a  magnet  will  cause  the 
cell  to  be  attracted  or  to  move  towards  the  mag- 
net pole,  since  the  south  face  or  end  of  the  coil  is 
nearer  the  north  pole  of  the  magnet.  If  the  other 


Bat] 

end  were  nearer,  repulsion  would  occur,  the  cell 
turning  round  until  the  south  face  is  nearer  the 
magnet,  when  attraction  occurs. 

This  is,  strictly  speaking,  a  floating  cell,  and 
not  a  battery.  (See  Battery,  Voltaic.} 

Battery,  Galvanic Two  or  more 

separate  voltaic  cells  so  arranged  as  to  form 
a  single  source. 

This  is  more  correctly  called  a  Voltaic  Battery. 
(See  Battery,  Voltaic.) 

Battery,  Gas A  battery  in  which 

the  voltaic  elements  are  gases  as  distinguished 
from  solids. 

The  electrodes  of  a  gas  battery  generally  con- 
sist  of  plates  of  platinum,  or  other  solid  substance 
which  possesses  the  power  of  occluding  oxygen 
and  hydrogen.  The  lower  parts  of  these  plates 
dip  into  dilute  sulphuric  acid,  and  the  upper  parts 
are  respectively  surrounded  by  oxygen  and  hydro- 
gen gas  derived  from  the  electrolytic  decompo- 
sition of  the  dilute  acid. 

A  gas  battery  consisting  of  plates  of  platinum 
dipping  below  into  acid  liquid,  and  surrounded 
in  the  space  above  the  liquid  by  hydrogen  and 
oxygen  H,  H'  and  O,  O',  etc.,  respectively  is 
shown  in  Fig.  39. 


45  [Bat. 

Battery,  Leyden  Jar The  combina- 
tion of  a  number  of  separate  Leyden  jars  so 
as  to  act  as  one  single  jar. 

A  Leyden  jar  battery  is  shown  in  Fig.  40, 


Fig.  39.     Gas  Battery. 

In  charging  this  battery  an  electric  current  is 
sent  through  it  until  a  certain  quantity  of  the 
gases  has  been  produced.  If,  then,  the  charging 
current  be  discontinued,  a  current  in  the  oppo- 
site direction  is  produced  by  the  battery.  The 
gas  battery  is  in  reality  a  variety  of  storage  bat- 
tery. (See  Electricity,  Storage  of.  Cell,  Secon- 
dary. Cell,  Storage.) 

Gas  batteries  can  also  be  made  by  feeding  con- 
tinually into  the  cell  a  gas  capable  of  acting  on 
the  positive  elements. 

Battery  Gauge.— (See  Gaug<t,  Battery^ 


Fig.  40,    Leyden  Jar  Battery. 


where  nine  separate  Leyden  jars  are  connected 
as  a  single  jar  by  joining  their  outer  coatings  by 
placing  them  in  the  box  F,  the  bottom  of  which 
is  lined  with  tin  foil.  The  inner  coatings  are 
connected  together  by  the  metal  rods  B,  as 
shown. 

A  discharging  rod  A,  may  be  employed  for 
connecting  the  opposite  coatings.  The  handles 
are  made  of  glass,  or  any  other  good  insulating 
material. 

A  number  of  Leyden  jars  can  be  coupled  in 
series  by  connecting  the  inner  coating  of  the  first 
jar  to  the  outer  coating  of  the  second,  the  inner 
coating  of  the  second  to  the  outer  coating  of  the 
third,  and  so  on.  The  battery  so  obtained  is 
then  discharged  by  connecting  the  outer  coat 
ing  of  the  first  jar  with  the  inner  coating  of  tbe 
last. 

Battery,  Local A  voltaic  battery 

used  at  a  station  on  a  telegraph  line  to 
operate  the  Morse  sounder,  or  the  register- 
ing or  recording  apparatus,  at  that*  point 
only.  (See  Telegraphy,  American  or  Morse 
System  of.) 

The  local  battery  is  thrown  into  or  out  of  action 
by  the  telegraphic  relay.  (See  Relay.) 

Battery,  Magnetic The  combina- 
tion, as  a  single  magnet,  of  a  number  of  sep- 
arate magnets. 

A  magnetic  battery,  or  compound  magnet,  is 


Bat.] 


4C 


[Bat. 


shown  in  Fig.  41.     It  consists  of  straight  bars  of 
steel,  p,  p,  p,  with  their  similar  poles  placed  near 
together     and    inserted     in 
masses  of  soft  iron,  N  and 
S,  as  shown. 

Battery,  Main 

The  battery,  in  a  system 
of  telegraphic  communi- 
cation, that  is  employed 
for  sending  the  signals 
over  the  main  line,  as  dis- 
tinguished from  any  bat- 
tery employed  for  any 
other  particular  work, 
such,  for  example,  as  that 
of  the  local  battery.  (See 

D    ..  T         ,*.  Fig,    AT,      Magnetic 

Battery,  Local.)  s    *' 

~  Battery,  or   Cont- 

Battery,  Multiple-Con-        pound  Magnet. 

nected A  battery  the  single  cells  of 

vhich  are  connected  to  one  another  and  to  the 
mains  or  conductors  in  multiple.  (See  Cir- 
cuit, Multiple) 

Battery,    Open-Circuit A   voltaic 

battery  which  is  normally  on  open-circuit, 
and  which  is  used  continuously  only  for  com- 
paratively small  durations  of  time  on  closed- 
circuit. 

Leclanche'-cells  form  an  excellent  open-circuited 
battery.  They  have  a  comparatively  high  electro- 
motive force,  but  rapidly  polarize.  They  cannot 
therefore  be  economically  used  for  furnishing 
currents  continuously  for  long  durations  of  time. 
When  left  on  open-circuit,  however,  they  readily 
depolarize.  They  therefore  form  an  excellent 
battery  for  such  work  as  annunciator  bells,  burg- 
lar alarms,  etc.,  where  the  current  is  only 
required  for  short  periods  of  time,  separated  by 
comparatively  long  intervals  of  rest.  (See  Cell, 
Voltaic,  Leclanche.) 

Battery  Plates  of  Secondary  or  Storage 

Cell,  Forming  of (See  Plates  of 

Secondary  or  Storage  Cell,  Forming  of.) 

Battery,  Plunge • — A  number  of 

separate  voltaic  cells  connected  so  as  to  form 
a  single  cell  or  electric  source,  the  plates  of 
which  are  so  supported  on  a  horizontal  bar 
as  to  be  capable  of  being  simultaneously 
placed  in,  or  removed  from,  the  exciting 
liquid. 


The  plunge  battery  shown  in  Fig.  42,  consists 


Fig.  42.    Plunge  Battery, 

of  a  number  of  zinc-carbon  elements  immersed  in 
an  electrolyte  of  dilute  sulphuric  acid,  or  in  elec- 
tropoion  liquid,  contained  in  separate  jars,  J,  J. 
(See  Liquid,  Electropoion.) 

The  mode  of  support  to  the  horizontal  bar 
will  be  understood  from  an  inspection  of  the 
drawing. 

Battery,  Primary The  combina- 
tion of  a  number  of  separate  primary  cells  so 
as  to  form  a  single  source. 

The  term  primary  battery  is  used  in  order  to 
distinguish  it  from  secondary  or  storage  battery. 
(See  Cell,  Secondary.  Cell,  Storage.) 

Battery,  Secondary The  combina- 
tion of  a  number  of  separate  secondary  or 
storage  cells,  so  as  to  form  a  single  electric 
source.  (See  Electricity,  Storage  of.) 

Battery,  Selenium  —  —The  combina- 
tion of  a  number  of  separate  selenium  cells  so 
as  to  form  an  electric  source.  (See  Cell, 
Selenium.) 

Battery,  Series-Connected A  bat- 
tery, the  separate  cells  of  which  are  con- 
nected to  one  another  and  to  the  line  or 
conductor  in  series.  (See  Circuit,  Series.) 

Battery  Solution. — (See  Solution,  Bat- 
tery.) 

Battery,  Split A  voltaic  battery 

connected  in  series,  but  having  one  of  its 
middle  plates  connected  with  the  ground. 

By  the  employment  of  the  device  of  a  split- 
battery,  the  poles  of  the  battery  are  maintained 
at  potentials  differing  in  opposite  directions  from 
the  potential  of  the  earth. 

Battery,  Storage  —  — A  number  of 
separate  storage  cells  connected  so  as  to 
form  a  single  electric  source. 


Bat.] 


[Bel. 


A  cell  of  a  storage  battery  is  shown  in  Fig. 


43- 


Fig.  43.     Storage  Battery. 

Battery,  Storage,  Element  of A 

single  set  of  positive  and  negative  plates  of  a 
storage  cell  connected  so  as  to  be  ready  for 
placing  in  the  acid  liquid  of  the  jar  or  cell. 

A  term  sometimes  applied  to  one  of  the 
storage  cells  in  a  storage  battery. 

This  latter  use  of  the  term  element  is  unfortu- 
nate, since  from  the  analogous  case  of  a  primary 
•cell,  an  element  would  consist  of  a  single  plate, 
either  positive  or  negative,  and  not  of  both.  That 
is,  every  voltaic  couple  consists  of  two  elements, 
the  positive  and  the  negative. 

Battery,    Thermo A   term    often 

applied  to  a  thermo-electric  battery.  (See 
Battery,  Thermo- Electric?) 

Battery,     Thermo-Electric The 

combination,  as  a  single  thermo-electric  cell, 
of  a  number  of  separate  thermo-electric  cells 
or  couples.  (See  Couple,  Thermo-Electric?} 

Battery,  Voltaic The  combina- 
tion, as  a  single  source,  of  a  number  of  sepa- 
rate voltaic  cells. 

Battery,  Water A  battery  formed 

of  zinc  and  copper  couples  immersed  in  an 
electrolyte  of  ordinary  water. 

Any  voltaic  couple  can  be  used,  the  positive 
element  of  which  is  slightly  acted  on  by  water. 
When  numerous  couples  are  employed  consider- 
able difference  of  potential  can  be  obtained. 

Water  batteries  are  employed  for  charging 
electrometers.  They  are  not  capable  of  giving 
any  considerable  current,  owing  to  their  great  in- 
ternal resistance. 


Bead  Areometer  or  Hydrometer. — (See 
Areometer,  Bead.} 

Bec-Carcel. — The  Carcel,  or  French  unit 
of  light.  (See  CarceZ.) 

Bell,  Automatic;Electric An  elec- 
tric bell  furnished  with  an  automatic  contact- 
breaker.  (See  Contact-Breaker,  Automatic.) 

A  form  of  automatic-electric  bell  is  shown  in 
Fig.  44.  The  relation  of  the  electro-magnet,  its 
armature  and  the  bell 
lever,  will  be  readily 
understood  from  an  in- 
spection of  the  draw- 
ing. 

Bell,  Call 

An  electric  bell  used 
to  call  the  attention 
of  an  operator  to  the 
fact  that  his  corre- 
spondent wishes  to 
communicate  with 
him. 

Bell,  Circular 

— A  bell  so  construct- 
ed that  all  its  moving 
parts  are  contained  in  Fig.  44,   Automatic  Electric 
the  gong.  Bell.* 

Bell,  Continuous-Sounding  Electric 

— An  electric  bell,  which,  on  the  completion 
of  the  circuit,  continues  striking  until  stopped 
either  by  hand  or  automatically. 

On  the  completion  of  the  circuit,  the  attraction 
of  an  armature  throws  a  catch  off  from  a  lever, 
and  thus  permits  the  lever  to  fall  and  complete  a 
contact  and  allows  the  current  to  ring  the  bell;  or 
the  bell  is  rung  by  clockwork,  which  is  thrown 
into  action  by  the  passage  of  a  current  through  an 
electro-magnet.  (See  Bell,  Electro-Mechanical.) 

Bell,    Differential     Electric An 

electric  bell,  the  magnetizing  coils  of  which 
are  differentially  wound. 

Differential  winding  is  ot  advantage  where  a 
very  strong  current  is  required,  as  this  winding 
decreases  the  sparking  at  the  contacts,  on  the 
opening  of  the  circuit. 

Bell,  Electro-Magnetic,  Siemens-Arma- 
ture Form A  form  of  electro-mag« 


Bel.] 


48 


[Bel. 


netic  bell  in  which  the  movements  of  the  bell 
armature  are  obtained  by  the  reversal  of 
polarity  that  takes  place  when  alternating  cur- 
rents are  pass-  fi^^ 

\_b 


ed  through  the 
coils  of  a  sim- 
ple, single  coil, 
Siemens  -  arma- 

F*&.  45*  Siemens- Armature  Form 
The       details  of  Electro-Magnetic  Cell. 

will  be  readily  understood  from  an  examination 
of  Fig.  45. 

Bell,  Electro-Mechanical A  bell, 

the  striking  apparatus  of  which  is  driven  by 
a  weight  or  spring,  called  into  action  by  the 
movement  of  the  armature  of  an  electro- 
magnet. (See  Alarm,  Electric?) 

Bell,  Extension-Call A  device  for 

prolonging  the  sound  of  a  magneto  call. 

An  alarm  bell  is  automatically  connected  with 


Fig.  46.    Extension-Call  Bell. 

the  circuit  of  a  local  battery  by  means  of  the  cur- 
rent  generated  by  the  magneto-call,  and  continues 
sounding  after  the  current  of  the  magneto  call 
has  ceased. 

A  form  of  extension-call  bell  is  shown  in  Fig.  46. 

Bell,  Indicating— An  electric  bell 

in  which,  in  order  to  distinguish  between 
different  bells  in  the  same  office,  a  number 
is  displayed  by  each  bell  when  it  rings. 

Bell,  Magneto-Electric An  electric 

bell,  the  curre.it  employed  to  operate  or 
strike  which  is  obtained  by  the  motion  of  a 
magneto-electric  machine. 

Bell,  Night In  a  telephone  ex- 
change, a  bell,  switched  into  connection  with 
the  shunted  circuit  of  an  annunciator  case,  and 
intended,  by  its  constant  ringing,  to  call  the 
attention  of  the  night  operator  to  the  falling 
of  a  drop. 


Bell,  Relay,  Electric An  electric 

bell  m  which  a  relay  magnet  is  employed  to 
switch  a  local  battery  into  the  circuit  of  the 
sounding  apparatus  of  the  bell. 

The  relay  bell  is  suitable  for  use  when  the  bell 
to  be  sounded  is  situated  at  a  great  distance.  A? 
the  current  from  the  line,  when  this  is  long,  is 
too  weak  to  ring  the  bell,  it  throws  irito  action  a 
local  battery  by  the  action  of  a  relay. 

Relay  bells  were  used  in  the  early  forms  ol 
acoustic  telegraphs  as  employed  in  England  with 
relay  sounders. 

The  dots  and  dashes  of  the  Morse  alphabet  were 
indicated  by  the  sounds  of  two  bells,  a  tap  on 
one  bell  indicating  a  dot,  and  a  tap  on  the  other 
a  dash.  This  system  is  now  practically  aban- 
doned. 

Bell-Shaped  Magnet.— (See  Magnet,  Bell- 
Shaped?] 

Bell,  Shunt,  Electric An  electric 

bell,  the  magnetizing  coils  of  which  are  placed 
on  the  line  in  shunt. 

In  the  case  of  shunt-connected  electric  bells, 
one  of  the  bells  must  make  and  break  the  circuit 
for  all  the  rest.  The  series-connected  electric 
bell  is  used  where  the  distance  between  the  sepa- 
rate bells  is  great,  in  order  to  save  the  expense  of 
multiple  connections. 

In  most  cases,  where  a  number  of  electric  bells 
are  to  be  simultaneously  sounded,  connection  in 
multiple  is  adopted. 

Bell,  Single-Stroke  Electric An 

electric  bell  that  gives  a  single  stroke  only  for 
each  make  of  the  circuit. 


-.-.  ,- 


47'     Single-Stroke  Bell. 


Since  the  bell  gives  a  single  stroke  for  each 
completion  of  the  circuit,  its  use  permits  of  ready 
communication  between  any  two  places  by  any 


Bel.] 


49 


[Bla. 


system  of  prearranged  signals.  A  buzzer  may  be 
used  for  the  same  purpose.  A  form  of  single- 
stroke  bell  is  shown  in  Fig.  47.  On  completing  the 
c  rcuit,  the  current,  through  its  coils,  attracts  the 
armature  and  causes  a  single  stroke  of  the  bell. 

Bell,  Telephone-Call  -  —A  call  bell 
used  to  call  a  correspondent  to  the  telephone. 

The  telephone-call  bell  is  generally  a  magneto- 
electric  bell. 

Bell,  Trembling1 A  name  some- 
times given  to  a  vibrating  or  an  automatic 
make-and-break  bell.  (See  Make-and-Break, 
Automatic) 

Bell,  Vibrating A  trembling  bell. 

(See  Bell,  Trembling) 

Bias  of  Relay  Tongue. — (See  Tongue, 
Relay,  Bias  of.) 

Bichromate  Yoltaic  Cell.— (See  Cell,  Vol- 
taic, Bichromate^ 

Bi-fllar  Suspension. — (See  Suspension, 
Bi-filar) 

Bi-fllar  Suspension  Balance. — (See  Bal- 
ance, Bi-filar  Suspension) 

Bi-fllar  Winding.— (See  Winding,  Bi- 
filar) 

Binary  Compound. — (See  Compound,  Bi- 
nary^ 

Binding  Coils. — (See  Coils,  Binding) 

Binding-Post.— (See  Post,  Binding?) 

Binding-Screw. — (See  Screw,  Binding) 

Binding  "Wire  for  Telegraph  Lines. — (See 
Wire,  Binding,  for  Telegraph  Lines?) 

Biology,  Electro  —  —That  branch  of 
electric  science  which  treats  of  the  electric 
conditions  of  living  animals  and  plants,  and 
the  effects  of  electricity  upon  them. 

Electro-Biology  includes : 

(i.)  Electro-Physiology. 

(2.)  Electro-Therapy,  or  Electro-Therapeutics. 

Bioplasm. — Any  form  of  living  matter  pos- 
sessing the  power  of  reproduction. 

Bioscopy,  Electric The  determina- 
tion of  the  presence  of  life  or  death  by  the 
passage  of  electricity  through  the  nerves  and 
muscles. 

Bi-polar. — Having  two  poles. 


Bi-polar  Armature.  —  (See  Armature* 
Bi-polar) 

Bi-polar  Bath. — (See  Bath,  Bi-polar) 

Birmingham  Wire  Gauge". — (See  Gauge, 
Wire,  Birmingham) 

Bi-Telephone.— (See  Telephone,  Bi) 

Bitite. — A  variety  of  insulating  material. 

Black  Electro-Metallurgical  Deposit. — 
(See  Deposit,  Black  Electro-Metallurgical) 

Black  Lead. — A  variety  of  carbon  em- 
ployed in  various  electrical  processes. 

Black  lead  is  also  termed  plumbago  or  graphite. 
(See  Plumbago.  Graphite.} 

The  term  black  lead  is  a  misnomer,  since  the 
substance  is  carbon  and  not  lead.  The  term  is  an 
old  one,  and  is  still  very  generally  used. 

Blasting,  Electric The  electric 

ignition  of  powder  or  other  explosive  material 
in  a  blast.  (See  Fuse,  Electric) 

The  current  required  for  the  ignition  of  the 
fuse  is  generally  obtained  by  means  of  a  magneto- 
electric  machine.  In  the  form  of  magneto-blast- 
ing machine,  shown  in  Fig.  48,  the  movement 


Fig.  48.    Magneto- Blasting  Machine. 

of  the  handle  shown  at  the  top  of  the  figure 
causes  the  rapid  rotation  of  a  cylindrical  armature 
constructed  on  the  Wheatstone  and  Siemens  prin- 
ciple. The  magnets  are  of  iron,  and  are  furnished 


Ble.J 


50 


[Boa, 


with  coils  of  insulated  wire.  On  the  rotation  of 
the  armature  the  current  developed  therein  in- 
creases the  field  of  the  field  magnet,  and,  when 
of  the  proper  degree  of  intensity,  is  thrown  into  the 
outer  circuit,  and  ignites  the  fuse. 

Bleaching,  Electric  —  —Bleaching  pro- 
cesses in  which  the  bleaching  agents  are 
liberated,  as  required,  by  the  agency  of  electro- 
lytic decomposition. 

In  the  process  of  Naudin  and  Bidet,  the  cur- 
rent  from  a  dynamo-electric  machine  is  passed 
through  a  solution  of  common  salt  between  two 
closely  approached  electrodes.  The  chlorine  and 
sodium  thus  liberated  react  on  each  other  and 
form  sodium  hypochloride,  which  is  drawn  off 
by  means  of  a  pump  and  used  for  bleaching. 
(See  Electrolysis.} 


Block,     Branch 


— A     device     em- 


ployed in  electric  wiring  for  taking  off  a  branch 
from  a  main  circuit.     (See  Wiring?} 

A  form  of  branch-block,  with  its  fuses  attached, 
is  shown  in  Fig.  49. 


Fig.  49.   Branch-Block. 

Block,    Cross-Over A   device    to 

permit  the  safe  crossing  of  one  wire  over 
another  in  molding  or  cleat  wiring. 

Block,  Fuse A  block  containing 

a  safety  fuse  or  fuses  for  incandescent  light 
circuits.  (See  Fuse,  Safety?) 

Block  System  for  Railroads.— (See  Rail- 
roads, Block  System  for?) 

Block  Wire.— (See  Wire,  Block.} 

Blow-Pipe,  Electric  —  — A  blow-pipe 
in  which  the  air-blast  is  obtained  by  a  stream 
of  air  particles  produced  at  the  point  of  a 


charged    conductor    by    a    convection    dis- 
charge. 

The  candle  flame,  Fig.  50,  is  blown  in  the  di- 

P 


Fig.  JO.     Convection  Blow-Pipe. 

rection  of  the  stream  of  air  particles  passing  off 
from  the  point  P.  (See  Convection,  Electric.} 

Blow-Pipe,  Electric- Arc — A  de- 
vice of  Werdermann  for  cutting  rocks,  or 
other  refractory  substances,  in  which  the  heat 
of  the  voltaic  arc  is  directed,  by  means  of  a 
magnet,  or  a  blast  of  air,  against  the  substance 
to  be  cut. 

The  carbons  are  placed  parallel,  so  as  to  readily 
enter  the  cavity  thus  cut  or  fused.  This  inven- 
tion has  never  been  introduced  into  extensive 
practice. 

In  the  welding  process  of  Benardos  and 
Olzewski,  the  welding  temperature  is  obtained  by 
means  of  an  electric  arc  taken  between  two  suit- 
ably shaped  electrodes. 

In  the  electric-arc 
blow  -  pipe,  shown  in 
Fig.  51,  the  voltaic  arc, 
taken  between  two  ver- 
tical carbon  electrodes, 
is  deflected  into  a  hori- 
zontal position  under  the 
influence  of  the  inclined 
poles  of  a  powerful  elec- 
tro-magnet. 

The  highly  heated  car- 
bon vapor  which  consti- 
tutes the  voltaic  arc  is  deflected  by  the  magnet  in 
the  same  direction  as  would  be  any  other  mov- 
able circuit  or  current. 

Board,     Cross-Connecting In    a 

system  of  telegraphic  or  telephonic  communL 
cation,  a  board  to  which  the  line  terminals  are 
run  before  entering  the  switchboard,  so  as  to 


Fig.  ^  i.    Electric- Arc 
Blow-Pipe. 


Boa.] 


51 


[Boa. 


readily  place  any  subscriber  in  connection 
with  any  desired  section  of  the  switchboard. 

Board,  Fuse A  board  of  slate  or 

other  incombustible  material  on  which  all 
the  safety  fuses  in  an  installation  are  as- 
sembled. 

The  fuse  hoard  is  used  for  avoiding  accidents 
from  the  firing  of  the  fuses. 

Board,  Hanger  • A  form  of  board 

provided  for  the  ready  placing  or  removal  of 
an  arc  lamp  from  a  circuit. 


.  5S.    Hanger-Board. 

A  hanger-board  contains  a  switch  or  cut-out  for 
the  ready  opening  or  closing  of  the  circuit.  A 
form  of  hanger-board  is  shown  in  Fig.  52. 

Board,  Key Any  board  to  which 

are  connected  electric  keys  or  switches. 

Board,  Legging-Key A  key  board 

employed  for  the  purpose  of  legging  an 
operator  into  a  circuit  connecting  two  or  more 
subscribers.  (See  Leg.) 

Board,  Multiple  Switch A  board 

to  which  the  numerous  circuits  employed  in 
systems  of  telegraphy,  telephony,  annunciator 
or  electric  light  and  power  circuits  are  con- 
nected. 

Various  devices  are  employed  for  closing  these 
circuits,  or  for  connecting  or  cross-connecting 
them  with  one  another,  or  with  neighboring  cir- 
cuits. 

A  multiple  switchboard,  for  example,  for  a  tele- 
phone exchange,  will  enable  the  operator  to  con- 
nect any  subscriber  on  the  line  with  any  other 
subscriber  on  that  line,  or  on  another  neighbor- 


ing line  provided  with  a  multiple  switchboard. 
To  this  end  the  following  parts  are  necessary: 

(l.)  Devices  whereby  each  lineentering  the  ex- 
change can  readily  have  inserted  in  its  circuit  a 
loop  connecting  it  with  another  line.  This  is 
accomplished  by  placing  on  the  switchboard  a 
separate  spring-Jack  connection  for  each  sepa- 
rate line.  This  connection  consists  essentially 
of  one  or  two  springs  made  of  any  conducting 
mefal,  which  are  maintained  in 
metallic  contact  when  the  plug 
key  is  not  inserted,  but  which  are 
readily  separated  from  one  another 
by  the  introduction  of  the  plug, 
ke)',  Fig.  53,  the  terminals,  a  and 
b,  of  which  are  insulated  from, 
each  other,  and  are  connected  to 
the  ends  of  a  loop  coming  from 
another  line.  As  the  key  is  in-  Fiff'S3'g  P*ug" 
serted,  the  metallic  spring  or 
springs  of  the  spring-jack  are  separated  and  the 
metallic  pieces,  a  and  b,  are  brought  into  good 
sliding  contact  therewith,  thus  introducing  the 
loop  into  the  circuit.  (See  Spring-  Jack?) 

(2.)  As  many  separate  annunciator-drops  as 
there  are  separate  subscribers.  These  are  pro* 
vided  so  as  to  notify  the  Central  Office  of  the  par- 
ticular subscriber  who  desires  a  connection. 
Alarm-bells  to  call  the  operator's  attention  to  the 
calling  subscriber,  or  to  the  falling  of  a  drop,  are 
generally  added.  (See  'Bell,  Call.) 

(3.)  Connecting  cords  and  keys  for  connecting 
the  operator's  telephone,  and  means  for  ringing 
subscribers'  bells,  and  clearing  out  drops. 


Fig.  S4-    Multiple  Switchboard  for  Electric  Light. 

In  Multiple  Switchboards  for  the  Electric  Light 
or  Distributing  Switches,  spring-jack  contacts  are 
connected  with  the  terminals  of  different  circuits. 


Boa.] 


[Bod. 


and  plug  switches  with  the  dynamo  terminals. 
By  these  means,  any  dynamo  can  be  connected 
with  any  circuit,  or  a  number  of  circuits  can  be 
connected  with  the  same  dynamo,  or  a  number 
of  separate  dynamos  can  be  placed  in  the  same 
circuit  without  interference  with  the  lights. 

Board,  Switch A  board  provided 

with  a  switch  or  switches,  by  means  of  which 
electric  circuits  connected  therewith  may  be 
opened,  closed,  or  interchanged. 

Board,  Switch,  Telegraphic  ;  — A 

device  employed  at  a  telegraph  station  by 
means  of  which  any  one  of  a  number  of  tele- 
graph instruments,  in  use  at  that  station,  may 
be  placed  in  or  removed  from  any  line  con- 
nected with  the  station,  or  by  means  of  which 
one  wire  may  be  connected  to  another. 

The  ability  to  readily  connect  one  wire  with 
another  is  of  use  in  case  of  interruption  to  tele- 
graph lines,  in  which  case  a  through  circuit  may 
be  made  up  of  sections  of 
different  circuits. 

In  the  switchboard  shown 
hi  Fig.  55,  the  upper  left- 
hand  binding  post  is  con- 
nected to  earth;  the  four 
remaining  binding  -  posts 


m 


are  connected  to  two  sepa-  Fig.  ss-     Telegraphic 
rate  instruments  — the  sec-  Switchboard. 

ond  and  third  from  the  top  to  one  instrument, 
and  the  fourth  and  fifth  to  another  instrument. 
The  four  posts  at  the  top  of  the  figure  are  con- 
nected  to  two  lines  running  east  and  west. 

Various  connections  are  made  by  the  insertion 
of  plug  keys  in  the  various  openings. 

Board,    Switch,    Trunking   — A 

switchboard  in  which  a  few  subscribers  only 
are  connected  with  the  operator,  thus  enabling 
him  to  obtain  any  other  subscriber  by  means 
of  trunk  wires  extending  to  the  other  sections. 
(See  Wire,  Trunk) 

Boat,  Electric  —A  boat  provided 

with  electric  motive  power. 

Electric  power  has  been  applied  both  to  ordi- 
nary vessels  and  to  submarine  torpedo  boats. 

Boat,  Submarine  Electric A  boat 

capable  of  being  propelled  and  steered  while 
entirely  under  water. 

The  motive  power  of  such  boats  is  generally 


electricity.  The  requisite  buoyancy  is  obtained 
by  means  of  an  air  chamber.  Artificial  ventila- 
tion is  maintained,  the  fresh  air  requisite  for 
breathing  being  derived  from  a  compressed  air 
cylinder. 

Boat,  Torpedo  — A  boat  used  for 

carrying  and  discharging  torpedoes.  (See 
Torpedo) 

Bobbin,  Electric An  insulated  coil 

of  wire  for  an  electro-magnet. 

Body,  Charged A  body  containing 

an  electric  charge. 

Charges  are  bound  or  free.  (See  Charge, 
Bound.  Charge^  free.) 

Body,  Electrified — A  body  con- 
taining an  electric  charge. 

Body,    Human,    Resistance    of 

The  resistance  which  the  human  body  offers  to 
the  passage  of  an  electric  current. 

The  resistance  of  the  human  body  to  the  passage 
of  a  current  varies  with  the  time.  The  re- 
sistance rapidly  decreases  after  a  short  time. 

"The  resistance  diminishes  because  of  the  con- 
duction of  water  in  the  epidermis  under  the  action 
of  the  constant  current  and  the  congestion  of  the 
cutaneous  blood  vessels  in  consequence  of  the 
stimulation. "  (Landois  and  Stirling.) 

The  resistance  also  varies  markedly  with  the 
condition  of  the  surface,  the  condition  of  the  skin, 
and  with  the  shape,  area,  position  and  material 
of  the  electrodes  by  which  the  current  is  led  into 
and  carried  out  of  the  parts.  It  very  seldom  is 
less  than  l,ooo  ohms  under  the  most  favorable 
conditions,  and  with  ordinary  contacts  is  many 
times  that  amount. 

The  muscles  offer  nearly  nine  times  the  resist- 
ance in  a  direction  transverse  to  the  fibres  than 
longitudinally  to  them.  (Hermann.) 

The  resistance  of  the  epidermis  is  greater  than 
that  of  any  other  tissue  of  the  body. 

The  human  body  probably  possesses  a  true 
assymmetrical  resistance;  that  is  to  say,  when 
taken  after  the  current  has  been  passing  for  some 
time,  its  resistance  is  different  in  different  direc- 
tions. This  variation  in  the  apparent  resistance 
is  believed  by  some  to  be  due  to  polarization 
effects. 

Body,  Insulated  — A  body  sup- 
ported on  an  insulator,  or  non-conductor  of 
electricity. 


Fig.  Sb,    Electric 
Body-  Protector. 


Bod.] 

Body-Protector,  Electric A  de- 
vice for  protecting  the  human  body  against  the 
accidental  passage  of  an  electric  discharge. 

To  protect  the  human  body  from  the  acciden- 
tal passage  through  it  of  dangerous  electric  cur- 
rents, Delany  places  a  light,  flexible,  conducting 
wire,  A  A  B  L  L,  in  the  posi- 
tion shown  in  Fig.  56,  for 
the  purpose  of  leading  the 
greater  part  of  the  current 
around  instead  of  through 
the  body.     The   body-pro- 
tector thus  provides  a  by- 
path, or  shunt  of  low  resist- 
ance, around  the  body,  and 
protects  it  from  the  effects 
of  an  accidental  discharge. 
The  resistance  of  the  con- 
tacts of  the  protecting  conductor  with  the  skin 
may  interfere  somewhat  with  the  efficacy  of  the 
device.     Inside  insulating  shoe-soles  for  lessening 
the  danger    from    accidental   contacts   through 
grounded  circuits  have  also  been  proposed. 

Boiler-Feed,  Electric   — A  device 

for  automatically  opening  a  boiler-feed  appar- 
atus electrically  when  the  water  in  the  boiler 
falls  to  a  certain  predetermined  point. 

Boiling  of  Secondary  or  Storage  Cell. — 
(See  Cell,  Secondary,  or  Storage,  Boiling  of.) 

Bole.— A  unit,  seldom  or  uc/er  used,  pro- 
posed by  the  British  Association. 

One  bole  is  equal  to  one  gramme-kine.  (See 
Kine.) 

Bolometer. — An  apparatus  devised  by 
Langley  for  measuring  small  differences  of 
temperature. 

A  thermal  balance.  (See  Balance,  Ther- 
mic?) 

Bombardment,  Molecular  •  —The 

forcible  rectilinear  projection  from  the  nega- 
tive electrode,  of  the  gaseous  molecules  of  the 
residual  atmospheres  of  exhausted  vessels  on 
the  passage  of  electric  discharges.  (See 
Matter,  Radiant,  or  Ultra-Gaseous!) 

BonsaKte. — An  insulating  substance. 

Bore,  Armature •  — The  space  pro- 
vided between  the  pole  pieces  of  a  dynamo 
or  motor  for  the  rotation  of  the  armature*, 


53  [Box. 

Boreal  Magnetic  Pole.— (See  Pole,  Mag' 
netic,  Boreal.} 

Bot. — A  term  sometimes  used  as  a  con- 
traction for  Board  of  Trade  unit  of  electric 
supply,  or  the  energy  contained  in  a  current 
of  i  ,000  amperes  flowing  in  one  hour  under  a 
pressure  of  one  volt. 

The  term  appears  inadmissible.  If  used  at  all, 
it  should  be  B.  O.  T.  The  usage  of  giving  the 
names  of  distinguished  dead  electricians  to  new 
units  is  a  good  one,  and  should  be  followed  here. 

Boucherize. — To  subject  to  the  boucheriz- 
ing  process.  (See  Boucherizing!) 

Boucherizing. — A  process  for  the  preser- 
vation of  wooden  telegraph  poles,  by  inject- 
ing a  solution  of  copper  sulphate  into  the 
pores  of  the  wood.  (See  Pole,  Telegraphic!) 

Bound  Charge. — (See  Charge,  Bound!) 

Box  Bridge. — (See  Bridge,  Box!) 

Box,  Cable  • — A  box  placed  on  a 

large  terminal  pole  and  provided  to  receive  the 
separate  conductors  where  the  air-line  wires 
join  a  cable. 

The  wires  are  distributed  in  the  cable  box  so 
as  to  be  readily  attached  to  the  air-line  wires. 

Box,  Cooling,  of  Hydro-Electric  Ma- 
chine. — A  box  provided  in  Armstrong's 
hydro-electric  machine  for  the  steam  to  pass 
through  before  leaving  the  nozzle. 

In  passing  through  the  cooling-box  some  of  the 
steam  suffers  condensation.  The  cooling-box, 
therefore,  always  contains  some  water,  the  pres- 
ence of  which  seems  to  be  necessary  to  the  opera- 
tion of  the  machine. 

Box,  Distributing,  of  Conduit.— A  name 
generally  applied  to  a  handhole  of  a  conduit 
(See  Handhole  of  Conduit!) 

Box,  Distribution,  for  Arc  Light  Cir- 
cuits.— A  de'vice  by  means  of  which  arc 
and  incandescent  lights  may  be  simultane- 
ously employed  on  the  same  line  from  a  con- 
stant-current dynamo-electric  machine  or 
other  source  of  constant  currents. 

A  portion  of  the  line  circuit,  whose  difference 
of  potential  is  sufficient  to  operate  the  electro- 
receptive  device,  as,  for  example,  an  incandescent 
lamp,  is  divided  into  such  a  number  of  multiple 


Box.] 


54 


[Box. 


.circuits  as  will  provide  a  current  of  the  requisite 
strength  for  each  of  the  devices.  For  example,  if 
the  normal  current  on  the  line  is  seven  amperes, 
then  each  of  the  seven  multiple-connected  electro- 


-  S7-     Series-Multiple  Circuit. 
receptive  devices  shown  in  Fig.  57  will  have  a  cur- 
rent  of  one  ampere  passing  through  it,  provided 
the  resistance  of  each  branch  is  the  same,, 

In  order  to  protect  the  remaining  devices  from 
variations  in  the  current  on  the  extinguishment  of 
any  of  the  devices,  automatic  cut-outs  are  pro- 
vided, which  divert  the  current  thus  cut  off 
through  a  resistance  equivalent  to  that  of  the 
device. 

A  variety  of  distribution  boxes  are  in  use.  (See 
Circuits,  Varieties  of.} 

Box,    District-Call    —A    box    by 

means  of  which  an  electric  signal  is  auto- 
matically sent  over  a  telegraphic  line  and 
received  by  an  electro-magnetic  device  at  the 
other  end  of  the  line. 


Fig.  58.    District  Cull  Box. 
A  system  of  district  calls  includes  a  number  of 
call  boxes  connected  by  telegraphic  lines  with  a 
central  station.     A  wheel,  or  its  equivalent,  set  in 


motion  by  the  pulling  of  a  lever,  makes  and 
breaks  an  electric  circuit  and  sends  over  the  line 
a  succession  of  electric  impulses  of  varying  length, 
separated  from  one  another  by  varying  intervals 
of  time.  These  impulses  may  be  received  at  the 
central  station  as  a  series  of  dots  and  dashes,  or 
may,  by  means  of  a  Morse  sounder,  produce  suc- 
cessive sounds.  By  pulling  the  lever  or  handle 
through  different  distances,  different  signals  may 
be  sent  to  the  central  station  and  serve  as  calls  for 
various  services,  such  as  messenger  boys,  fire 
alarm,  police,  special,  etc. 

The  general  appearance  of  a  four-call  district 
box  is  shown  in  Fig.  58.  In  order  to  transmit 
a  call  for  any  particular  one  of  these  four  services 
the  handle  is  pulled  until  it  comes  opposite  to  the 
letters  indicating  the  required  service,  and  is  then 
released.  The  service  required  is  then  indicated 
at  the  receiving,  or  central  station,  through  the 
varying  signals  sent  over  the  line  by  the  move- 
ment of  the  break-wheel,  on  the  release  of  the 
handle. 

Box,  Fire-Alarm  Signal A  signal 

box  provided  for  the  purpose  of  automatically 
sending  an  alarm  of  fire. 

The  fire-alarm  box  shown  in  Fig.  59,  operates 


Fig.  JQ.    Fire- Alarm  Signal-Box. 

on  the  same  principle  as  the  district  call  box.  The 
movement  of  the  handle  in  the  direction  of  the 
arrow  drives  a  wheel  that  makes  and  breaks  a 
circuit  at  certain  intervals. 

The  fire-alarm    signal    boxes    are    connected 


Box.] 


55 


[Box. 


either  with  a  central  station,  or  with  the  engine 
houses  of  the  district  in  which  the  alarm  is 
sounded,  or  with  both. 

Box,  Fire- Alarm  Telegraph An 

automatic-call  signal-box  employed  for  send- 
ing an  alarm  of  fire  to  a  central  station. 

A  form  of  fire-alarm  telegraph  box  is  shown  in 
Fig.  60.  It  consists  essentially  of  a  circuit-breaker 


Fig.  bO.  Fire- Alarm  Telegraph  Box. 
that  is  moved  by  pulling  down  a  lever.  The 
release  of  the  lever  repeats  the  signal  to  the  fire 
department  at  the  central  station  a  certain  number 
of  times.  The  box  also  contains  a  relay  bell, 
lightning  arrester  and  signal-bell  key. 

Box,  Fishing1 A  term  sometimes 

used  instead  of  junction  box.  (See  Box, 
Junction.} 

Box,  Flush A  box  or  space,  flush 

with  the  surface  of  a  road-bed,  provided  in  a 
system  of  underground  wires  or  conduits, 
to  facilitate  the  introduction  of  the  conduct- 
ors into  the  conduit,  or  for  the  examination 
of  the  conductors. 

Box,  Fuse The  box  in  which  the 

fuse-wire  of  a  safety-fuse  is  placed. 

The  fuse-box  should  be  formed  of  moisture- 
proof^  "ncombustible;  insulating  materials. 

Box,    Junction A   moisture-proof 

box  provided  in  a  system  of  underground  con- 


the  feeders  and  the  mains,  and  from  which 
the  current  is  distributed  to  the  individual 
consumer.  (See  Feeder.  Main,  Electric?) 

A  form  of  junction  box  for  coupling  lengths  of 
conductors  is  shown  in  Fig.  6l. 

Box,  Patrol  Alarm An  automatic- 
signal  call-box  provided  for  use  on  the  out- 
side of  buildings.  . 

The  call-box  is  placed  inside  a  box,  the  outer 
door  of  which  is  furnished  with  a  Yale  lock. 


Fig.  bl.     Junction  Box. 

ductors  to  receive  the  terminals  of  the  feed- 
ers, in   which  connection   is  made  between 


Ftg.62.    Patrol  Box. 

A  form  of  patrol  box  is  shown  in  Fig.  62. 

Box,  Resistance A  box  containing 

a  number  of  separate  coils  of  known  resist- 
ances employed  for  determining  the  value  of 
an  unknown  resistance,  and  for  other  pur- 
poses. (See  Bridge,  Electric,  Box  Form  of.) 

Box-Sounding  Relay.— (See  Relay,  Box- 

Sounding?) 

Box-Sounding  Telegraphic  Relay.— (See 

Relay,  Box-Sounding  Telegraphic^) 

Box,  Splice A  box  provided  for 

holding  splice  joints  and  loops,  and  so  ar- 
ranged as  to  be  readily  accessible  for  exami- 
nation, re-arrangmg,  cross-connecting,  etc. 

Splice-boxes  vary  in  shape  and  construction 
according  to  the  purposes  for  which  they  are 
designed. 

Box,  Splice,  Four-way A  splice- 
box  piovided  with  four  ways  or  tubular  con- 
duits. 

Box,    Splice,   Two- Way A  splice- 


Box.J 


56 


[Bra. 


box  provided  with  but  two  tubular  conduits  or 
ways. 

Box,    Tumbling A    rotating   box 

in  which  metallic  articles  that  are  to  be 
electroplated  are  placed  so  as  to  be  polished 
by  attrition  against  one  another. 

Boxing  the  Compass. — (See  Compass, 
Boxing  the?) 

Bracket,  Lamp,  Electric A  de- 
vice similar  to  a  bracket  for  a  gas  burner  for 
holding  or  supporting  an  electric  lamp. 


Fig.  63.    Lamp  Bracket,      Fig.  6  4.      Lamp  Bracket. 
Lamp  brackets  are  either  fixed  or  movable. 


Fig.  6f.    Lamp  Bracket,  Movable  Arms. 

Those  shown  in  Figs.  63  and  64  are  fixed.  That 
shown  in  Fig.  65  is  movable. 

Bracket,  Telegraphic A  support 

or  cross  piece  placed  on  a  telegraph  pole 
for  the  support  of  the  insulators  of  tele- 
graphic lines. 

Telegraphic  insulators  are  supported  either  on 
wooden  arms,  or  on  iron  or  metal  brackets. 

Fig.  66  shows  a  form  of  iron  bracket.  Fig.  67 
shows  a  form  of  wooden  arm. 


Fig.  67.     Telegraphic 
Cross-Ann. 


Fig.  66.    Telegraphic 
Bracket. 

Various  well  known  modifications  of  these 
shapes  are  in  common  use.  (For  details,  see  Pole% 
Telegraphic.) 


Braid,  Tubular A  braid  of  fibrous 

insulating  material,  woven  in  the  form  of  a 
tube,  and  provided  for  drawing  over  a  splice 
after  two  wires  have  been  connected. 

Braided  Wire.— (See  Wire,  Braided^ 

Brake,  Electro-Magnetic A  brake 

for  car  wheels,  the  braking  power  for  which 
is  either  derived  entirely  from  electro-magnet- 
ism, or  is  thrown  into  action  by  electro-mag- 
netic devices. 

Electro-magnetic  car  brakes  are  of  a  great  va- 
riety of  forms.  They  may,  however,  be  arranged 
in  two  classes,  viz. : 

(l.)  Those  in  which  magnetic  adhesion,  or  the 
magnetic  attraction  of  the  brake  to  the  wheels,  is 
employed. 

(2.)  Ordinary  brake  mechanism  in  which  the 
force  operating  the  brake  is  thrown  into  action  by 
an  electro-magnet. 

Brake,  Friction A  name  some- 
times given  to  a  Prony  brake.  (See  Brake, 
Prony?) 

Brake,  Magneto-Electric  — : A  device 

for  checking  the  swing  of  a  galvanometer,  in 
which  a  slight  inverse  current  is  sent  through 
the  coils  of  the  galvanometer. 

The  Frey  magneto -electric  brake,  as  shown  in 
Fig.  68,  consists  of  a  small  coil,  connected  by  a 


Fig.  68.   Electric  Brake. 

contact-key  with  the  galvanometer  terminals.  A 
small  adjustable  magnet  coil  is  provided  for 
regulating  the  action  of  the  inverse  current.  To 
avoid  disturbance,  the  brake  is  placed  at  least 
4  or  5  feet  from  the  galvanometer.  Manipulation 
of  the  ordinary  galvanometer  key  attains  the  same 
end  in  a  much  simpler  manner. 

Brake,  Prony A  mechanical  de- 
vice for  measuring  the  power  of  a  driving 
shaft. 


JBra. 


57 


An  inflexible  beam,  Fig.  69,  is  provided  at  one 
end  with  a  clamping  device  for  clamping  the 
driving  shaft  or  pulley,  and  at  the  other  end  A, 
with  a  pan  for  holding  weights. 

If  the  brake  be  arranged  as  shown  in  Fig.  69, 
and  the  shaft  rotate  in  the  direction  of  the  arrow, 
the  tendency  will  be  to  carry  the  beam  around 
with  the  shaft,  placing  it  at  some  given  moment 


CD? 


Fig.  69,    Prony  Brake, 

in  the  position  shown  by  the  dotted  line.  If  a 
sufficiently  heavy  weight  be  placed  at  x,  in  a  pan 
hung  at  A,  the  beam  will  assume  a  position  ver- 
tically downwards.  If,  however,  the  torque,  or 


Jfr 


Fig.  70.    Prony  Brake. 

twisting  force  of  the  driving  shaft,  be  balanced  by 
the  weight,  the  bar  will  remain  horizontal.  The 
power  can  then  be  calculated  by  multiplying  the 
weight  in  pounds  by  the  circumference  in  feet  of 
the  circle  of  which  the  bar  is  a  radius,  and  this 
product  by  the  number  of  turns  of  the  driving 
shaft  per  minute.  The  product  will  be  the  num- 


Fig.  71,    Prony  Brake. 

ber  of  foot-pouhds  per  minute,  and,  when  divided  • 
by  33,000,  will  give  the  horse-power. 

Some  modified  forms  of  the  Prony  brake  are 
shown  in  Figs.  70  and  71. 

A  simple  form  of  brake  consists  of  a  cord  passed 
over  the  pulley  of  the  machine  to  be  tested.  A 
weight  is  hung  at  one  end  of  the  cord.  The  other 


end  of  the  cord  is  attached  to  the  top  of  a  spring 
balance,  the  other  end  of  which  is  fastened  to  the 
floor.  A  reading  of  the  spring  balance  is  taken 
while  the  pulley  is  at  rest  and  when  it  is  in  motion, 
and  the  result  calculated. 

Branch. — A  term  applied  to  any  principal 
distributing  conductor  from  which  outlets 
are  taken  or  taps  made. 

Branch-Block.— (See  Block,  Branch) 

Branch  Conductors.— (See  Conductor, 
Branch) 

Branch  Fuse.— (See  Fuse,  Branch.) 

Branch,  Sub A  distributing  con- 
ductor taken  from  a  branch. 

Branding,  Electric A  process 

whereby  the  branding  tool  is  heated  by  elec- 
trical incandescence  instead  of  by  ordinary 
heat. 

The  branding  tool  consists  essentially  of  a  small 
transformer  with  devices  for  regulating  the  cur- 
rent  strength  by  switches  and  choking  coils. 

Brassing,  Electro  —  —Coating  a  sur- 
face with  a  layer  of  brass  by  electro-plating. 
(See  Plating,  Electro) 

The  plating  bath  contains  a  solution  of  copper 
and  zinc  ;  a  brass  plate  is  used  as  an  anode. 

Break. — A  want  of  continuity  in  a  circuit. 

Break,  Circuit  Loop A  device  for 

introducing  a  loop  in  any  part  of  a  line 
circuit. 

A  form  of  circuit  loop-break  is  shown  in  Fig.  72. 


Fig.  J2.     Circuit  Loop  Break. 

It  consists  essentially  of  a  rigid  frame  with  two 
porcelain  or  other  suitable  insulators  for  the  sup. 
port  of  the  loop  wires. 


Bre.] 


58 


[Bri. 


Break-Down  Switch. — (See  Svuitch,Break- 
Down?) 

Break-Induced  Current. — (See  Current, 
Break-Induced?) 

Break,  Mercury A  form  of  circuit 

breaker  operated  by  the  removal  of  a  conduc- 
tor from  a  mercury  surface. 

Mercury  breaks  assume  a  variety  of  forms.  One 
end  of  the  circuit  is  connected  with  the  mercury, 
and  the  other  with  the  conductor. 

Break  Shock. — (See  Shock,  Break\ 

Breaker,  Circuit Any  device  for 

breaking  a  circuit. 

Breaking  the  Primary.— (See  Primary, 
Breaking  the.) 

Breaking  Weight  of  Telegraph  Wires. — 
(See  Wires,  Telegraph,  Breaking  Weight 
of.) 

Breath  Figures.— (See  Figures,  Breath.) 

Breeze,  Electric  —  — A  term  some- 
times employed  in  electro-therapeutics  for  a 
brush  discharge. 

One  of  the  electrodes,  consisting  of  a  single 
point  or  a  number  of  points,  is  held  near  the 
parts  to  be  treated  so  that  the  convective  discharge 
is  received  thereon.  The  other  electrode  is  con- 
nected to  the  body  of  the  patient. 

Breeze,  Electro-Therapeutic An 

electric  breeze.     (See  Breeze,  Electric?) 
Breeze,  Head,  Electro-Therapeutic  - 

— A  form  of  electric  convective  discharge, 
or  electric  breeze,  applied  to  the  head.  (See 
Breeze,  Electric?) 

Breeze,  Static —  — An  electric  breeze 
obtained  by  the  convective  discharge  of  an 
electrostatic  charge. 

Bridge-Anns. — (See  Arms,  Bridge  or 
Balance?) 

Bridge,  Box A  box  of  resistance 

coils  so  arranged  as  to  be  capable  of  being 
used  directly  as  a  Wheatstone  electric  balance. 
(See  Bridge,  Electric,  Box  Form  of.) 

The  commercial  form  of  Wheatstone's 
balance. 

Bridge,  Electric  — A    device    for 

measuring  the  value  of  electric  resistances. 


The  electric  bridge  is  also  called  the  Electric 
Balance. 

This  is  called  a  bridge  because  the  wire  M,  G, 
N,  bridges  or  joins  points  of  equal  potential. 

A,  B,  C  and  D,  Fig.  73,  are  four  electric  re- 
sistances, any  one  of  which  can  be  determined  in 
ohms,  provided  the  absolute  value  of  one  of  the 
others,  and  the  relative  values  of  any  two  of  the 
remaining  three  are  known  in  ohms. 

A  voltaic  battery,  Zn  C,  is  connected  at  Q 
and  P,  so  as  to  branch  at  P,  and  again  unite  at 


Fig.  73.    Electric  Balance. 

Q,  after  passing  through  the  conductor  D  C,  and 
B  A. 

A  sensitive  galvanometer,  G,  is  connected  at 
M  N,  as  shown. 

The  passage  of  a  current  through  any  resistance 
is  attended  by  a  fall  of  potential  proportional  to 
the  resistance.  (^e&  Potential,  Electric.)  If,  then, 
the  resistances  A,  C  and  B,  are  so  proportioned 
to  the  value  of  the  unknown  resistance  D,  that  no 
current  passes  through  the  galvanometer  G,  the 
two  points,  M  and  N,  in  the  two  circuits,  Q  M  P 
and  Q  N  P,  are  at  the  same  potential.  That  is  to 
say,  the  fall  of  potential  along  Q  M  P  and  Q  N  P, 
at  the  points  M  and  N,  is  equal.  Since  the  fall 
of  potential  is  proportional  to  the  resistance,  it 
follows  that 

A  :  B  :  :  C  :  D, 


If  then  we  know  the  values  of  A,  B  and  C,  the 
value  of  D,  can  be  readily  calculated. 

T> 

By  making  the  value  _,  some  simple  ratio,  the 

•  -A. 

value  of  D,  is  easily  obtained  in  terms  of  C. 

The  resistances  A,  B  and  C,  may  consist  of 
coils  of  wire  whose  resistance  is  known.  To 
avoid  their  magnetism  affecting  the  galvanometer 
needle  during  the  passage  of  the  current  through 
them,  they  should  be  made  of  wire  bent  into  two 


Bri.] 


59 


[Bri. 


parallel  wires  and  wrapped  in  coils  called  resist- 
ance coils;  or  a  resistance  box  may  be  used.  (See 
Coil,  Resistance.  £ox,  Resistance.) 

There  are  two  general  forms  of  Wheatstone's 
Bridge,  the  box  form,  and  the  sliding  form. 

Bridge,    Electric,    Armg  of The 

resistances  of  an  electric  bridge  or  balance. 
(See  Bridge,  Electric^ 

Bridge,  Electric,  Box  Form  of 

A  commercial  form  of  bridge  or  balance  in 
which  all  the  known  arms  or  branches'of  the 
bridge,  except  the  unknown  arm,  consist  of 
standardized  resistance  coils,  whose  values  are 
given  in  ohms.  (See  Coil,  Resistance?) 
The  box  form  of  bridge  or  balance  is  shown  in 


ig-  74-    Box  Balance. 


perspective  in  Fig.  74,  and  in  plan  in  Fig.  75. 
The  bridge  arms,  corresponding  to  the  resistances 


Fig:  73.    Box  Balance. 

A  and  B,  of  Fig.  73,  consist  of  resistance  coils  of 
10,  loo  and  1,000  ohms  each,  inserted  in  the 
arms  q  z,  and  q  x,  of  Fig.  75.  These  are 
called  the  proportional  coils.  The  arm  corre- 
sponding to  resistance  C,  of  Fig.  73,  is  composed 
of  separate  resistances  of  i,  2,  2,  5,  10,  10,  20,  50, 
loo,  loo,  200,  500,  1,000,  1,000,  2,000  and  5,000 
ohms.  In  some  forms  of  box  bridges  additional 
decimal  resistances  are  added. 

The  resistance  coils  are  wound,  as  shown  in 
Fig.  76,  after  the  wire  has  been  bent  on  itself  in 
the  middle^  This  is  done  in  order  to  avoid  the 
effects  of  induction,  among  which  are  a  disturb- 
ing action  on  a  galvanometer  used  near  them, 
and  the  introduction  of  a  spurious  resistance  in 
the  coils  themselves.  (See  Resistance^  Spurious.} 
3— Vol.  1 


To  avoid  the  effects  of  changes  of  resistance  oc- 
casioned by  changes  of  temperature,  the  coils  are 
made  of  German  silver,  or,  preferably,  of  alloys 
called  Platinoid  or  Platinum  silver.  Even  when 
these  alloys  are  used,  care  should  be  taken  not  to 
allow  the  currents  to  pass  continuously  through 
the  resistance  coils  longer  than  a  few  moments. 

The  coils,  C,  C',  are  connected  with  one  another 
in  series  by  soldering  their  ends  to  the  short 


Fig.  76.    Resistance  Coils. 

thick  pieces  of  brass,  E,  E,  E,  Fig.  76.  On  the  in- 
sertion  of  the  plug-keys,  at  S,  S,  the  coils  are  cut- 
out by  short-circuiting.  Care  should  be  taken  to 
see  that  the  plug-keys  are  firmly  inserted  and  free 
from  grease  or  dirt,  as  otherwise  the  coil  will  not  be 
completely  cut  out.  As  each  plug-key  is  inserted 
it  should  be  turned  slightly  in  the  opening,  so 
as  to  insure  good  contact. 

The  following  are  the  connections,  viz.:  The 
galvanometer  is  inserted  between  q  and  r,  Fig.  77, 


fig.  77-     Electric  Balance. 

the  unknown  resistance  between  z  and  r;  the  bat- 
tery is  connected  tox  and  z.  A  convenient  pro- 
portion being  taken  for  the  value  of  the  propor- 
tional coils,  resistances  are  inserted  in  the  arm  C, 
until  no  deflection  is  shown  by  the  galvanometer 
G.  The  similarity  between  these  connections  and 
those  shown  in  Fig.  75  will  be  seen  from  an 
inspection  of  Fig.  77.  The  arms,  A  and  B,  corre- 
spond to  q  x  and  q  z,  of  Fig.  75 ;  C,  to  the  arm 


Bri.] 


60 


[Bri. 


x  r,  Fig.  75 ;  and  D,  to  the  unknown  resistance. 
We  then  have  as  before: 

A:B::C:D,orAxD  = 

The  advantage  of  the  simplicity  of  the  ratios,  A 
and  B,  or  10,  100  and  1,000  of  the  bridge  box, 
will  therefore  be  manifest.  The  battery  terminals 
may  also  be  connected  to  q  and  r,  and  the  gal- 
vanometer terminals  to  x  and  z,  without  disturb- 
ing the  proportions. 

Bridge,  Electric,  Commercial  Form  of 

A  name  sometimes  given  to  the  box 

form  of  Wheatstone's  electric  balance.  (See 
Bridge,  Electric,  Box  Form  of.) 

Bridge,  Electric  Duplex An  ar- 
rangement of  telegraphic  circuits  in  the  form 
of  a  Wheatstone  electric  bridge  for  the  pur- 
poses of  duplex  telegraphy.  (See  Teleg- 
raphy, Duplex,  Bridge  Method  of.) 

Bridge,  Electric,  Proportionate  Arms 
of (See  Arms,  Proportionate.) 

Bridge,  Electric,  Slide-Form  of 

A  balance  in  which  the  proportionate  arms  of 
the  bridge  are  formed  of  a  single  thin  wire,  of 
uniform  diameter,  generally  of  German  silver, 
of  comparatively  high  resistance.  The  length 
of  this  wire  is  usually  one  metre ;  hence  this 
apparatus  is  often  called  the  metre  bridge. 

A  Sliding  Contact  Key  slides  over  the  wire;  one 
terminal  of  the  key  is  connected  with  the  galva-> 
nometer  and  the  other  with  the  wire  when  the  key 
is  depressed.  As  the  wire  is  of  uniform  diameter 
the  resistances  of  the  arms,  A  and  B,  Fig.  78,  will 


Eia  ~:—r_,flfc~ 

J""""l 


Fig.  78.    Slide  Bridge. 

be  directly  proportional  to  the  lengths.  A  scale 
placed  near  the  wire  serves  to  measure  these 
lengths.  A  thick  metal  strip  connected  with  the 
slide  wire  has  four  gaps  at  P,  Q,  R  and  S. 

When  in  ordinary  use,  the  gaps  at  P  and  S,  are 
either  connected  by  stout  strips  of  conducting  ma- 
terial  or  by  known  resistances,  in  which  latter  case 
they  act  simply  as  ungraduated  extensions  of  the 
slide  wire,  and,  like  lengthening  the  slide  wire, 
increase  the  sensibility  of  the  instrument. 


The  unknown  resistance  is  then  inserted  in  the 
gap  at  Q,  and  a  known  resistance,  generally  the 
resistance  box,  in  that  at  R.  The  galvanometer 
has  one  of  its  terminals  connected  to  the  metal 
strip  between  Q  and  R,  and  its  other  terminal  to 
the  sliding  key.  The  battery  terminals  are  con- 
nected to  the  metal  strips  between  P  and  Q,  and 
R  and  S,  respectively. 

These  connections  are  more  clearly  seen  in  the 
form  of  bridge  shown  in  Fig.  79.  The  slide  wire, 
w  w,  consists  of  three  separate  wires  each  a  metre 


Fig.JQ.    Slide  Form  of  Bridge. 

in  length,  so  arranged  that  only  one  wire,  or  two 
in  series,  or  all  three  in  series,  can  be  used.  Mat- 
ters being  now  arranged  as  shown,  the  sliding 
key  is  moved  until  no  current  passes  through  the 
galvanometer  when  the  key  is  depressed. 

The  slide  form  of  bridge  is  not  entirely  satis- 
factory, since  the  uncertainty  of  the  spring-con- 
tact causes  a  lack  of  correspondence  between  the 
point  of  contact  and  the  point  of  the  scale  on 
which  the  index  rests. 

The  loss  of  uniformity  in  the  diameter  of  the 
wire,  due  to  constant  use,  causes  a  lack  of  corre- 
spondence between  the  resistance  of  the  wire  and 
its  length.  With  care,  however,  very  accurate 
'  results  can  be  obtained  by  the  slide  form. 

Bridge,  Inductance An  appara- 
tus for  measuring  the  inductance  of  a  circuit 
similar  to  a  Wheatstone  bridge.  (See  Induc- 
tance.) 

Professor  Hughes  employed  an  inductance 
bridge  of  the  following  description: 

Four  resistances,  Q,  S,  R  and  P,  arranged  as 
shown  in  Fig.  80,  form  the  bridge.  The  re- 
sistances, Q,  S  and  R,  consist  of  sections  of  Ger- 
man silver  wire,  one  metre  in  length,  each  of 
the  resistance  of  4  ohms.  P,  is  a  coil  of  wire  pos- 
sessing sensible  inductance.  The  object  of  tha 


Bri.] 


61 


[Bri, 


bridge  is  to  measure  the  value  of  this  inductance. 
I,  is  an  interrupter  placed  in  the  circuit  of  the 
battery  B. 

Suppose  the  interrupter,  I,  be  placed  in  the  tele- 
phone circuit  between  T  and  c.  By  shifting  the 
sliding  contact  so  as  to  alter  the  value  of  R,  a  bal- 


Fig.  So.     Inductance  Bridge. 

ance  can  be  effected  and  silence  obtained  in  the 
telephone. 

Now  remove  the  interrupter  and  place  it  in  the 
battery  circuit  between  b  and  a,  as  shown  in  Fig. 
So.  If  now,  the  interrupter,  I,  be  made  to  rapidly 
interrupt  the  battery  current,  this  balance  is 
destroyed,  and  cannot  be  again  obtained  by  any 
variation  in  the  value  of  the  resistance,  R. 

The  reason  of  this  is  evident.  On  the  closing 
or  opening  of  the  battery  current,  the  inductance 
of  P,  produces  a  counter  electromotive  force  in 
P,  which  produces  differences  of  potential  between 
a  and  c.  If  an  attempt  be  made  to  prevent  this, 


Fig.  St.    Hugkef  Inductance  Bridge. 

by  altering  the  value  of  R,  the  steady  balance  is 
destroyed,'  and  the  telephone  will  be  traversed  by 
a  current  during  the  time  the  currents  have  be- 
come steady.  In  order  to  obtain  a  balance 
during  rapid  alternations  of  the  battery  current, 
Vrofeseor  Hughes  placed  a  pair  of  mutually  in- 


ductive coils  in  the  battery  and  the  telephone 
circuits,  as  shown  in  Fig.  81. 

The  resistances,  Q,  S,  R  and  P,  are  the  same 
as  already  described.  The  mutually  inductive 
coils,  Mx  and  Ms,  are  placed  respectively  in  the 
telephone  and  battery  circuits  in  the  manner 
shown.  The  coil  M2,  in  the  battery  circuit  is 
fixed,  while  that  in  the  telephone  circuit  is  so 
arranged  that  it  can  be  maintained,  with  its  centre 
coincident  with  that  of  Ma,  while  its  axis  can  be 
placed  at  any  desired  angle  with  M8.  When  the 
axes  of  the  coils  are  at  right  angles,  the  inductance 
is  zero.  When  they  are  co-linear,  the  inductance 
is  at  its  maximum. 

When  the  coils  M15  and  M8,  are  in  any  inter- 
mediate position,  the  inductive  electromotive 
force  produced  in  the  telephone  circuit  can,  if 
the  value  of  R,  be  changed,  be  made  to  balance 
the  impulsive  electromotive  force  due  to  the  in- 
ductance of  P,  and  the  value  of  this  latter  can, 
therefore,  be  inferred. 


— An  apparatus  in- 


Bridge,  Magnetic  — 

vented  by  Edison  for  measuring  magnetic 
resistance,  similar  in  principle  to  Wheatstone's 
electric  bridge. 

The  magnetic  bridge  is  based  on  the  fact  that 
two  points  at  the  same  magnetic  potential,  when 
connected,  fail  to  produce  any  action  on  a  mag- 
netic needle.  The  magnetic  bridge  consists,  as 
shown  in  Fig.  82,  of  four  arms  or  sides  made  of 


Fig.  82.    Magnetic  Bridge. 

pure,  soft  iron.  The  poles  of  an  electro-magnet 
are  connected  to  projections  at  the  middle  of 
the  short  side  of  the  rectangle.  By  this  means 
a  difference  of  magnetic  potential  is  main- 
tained at  these  points.  The  two  long  sides  are 
formed  of  two  halves  each,  which  form  the  four 
arms  of  the  balance.  Two  of  these  only  are 
movable. 

Two  curved  bars  of  soft  iron,  of  the  same  area 
of  cross-section  as  the  arms  of  the  bridge,  rest  on 
the  middle  of  the  long  arms,  in  the  arched  shape 
shown.  Their  ends  approach  near  the  too  ot  the 


Bri.j 


[Bru. 


arch  within  about  a  half  inch.  A  space  is  hol- 
lowed out  between  these  ends,  for  the  reception  of 
a  short  needle  of  well-magnetized  hardened  steel, 
suspended  by  a  wire  from  a  torsion  head. 

The  movements  of  the  needle  are  measured  on 
a  scale  by  a  spot  of  light  reflected  from  a  mirror. 

The  electro-magnet  maintains  a  constant  dif- 
ference of  magnetic  potential  at  the  two  shorter 
ends  o.  the  rectangle.  If,  therefore,  the  four 
bars,  or  arms  of  the  bridge,  are  magnetically 
identical,  there  will  be  no  deflection,  since  no 
difference  of  potential  will  exist  at  the  ends  of  the 
bars  between  which  the  needle  is  suspended.  If, 
however,  one  of  the  bars  or  arms  be  moved  even 
a  trifle,  the  needle  is  at  once  deflected,  the  motion 
becoming  a  maximum  when  the  bar  is  entirely 
removed.  If  replaced  by  another  bar,  differing 
in  cross-section,  constitution,  or  molecular  struc- 
ture, the  balance  is  likewise  disturbed. 

The  magnetic  bridge  is  very  sensitive.  It  was 
designed  by  its  inventor  for  testing  the  magnetic 
qualities  of  the  iron  used  in  the  construction  of 
dynamo-electric  machines. 

Bridge  Method  of  Duplex  Telegraphy. — 

(See  Telegraphy,  Duplex,  Bridge  Method 
of.} 

Bridge  Method  of  Quadruples  Teleg- 
raphy.— (See  Telegraphy,  Quadruplex, 
Bridge  Method  of.} 

Bridge,    Metre A    slide   form    of 

Wheatstone's  electric  bridge,  in  which  the 
slide  wire  is  one  metre  in  length.  (See 
Bridge,  Electric,  Slide  Form  of?) 

Bridge,  Resistance A  term  some- 
times applied  to  an  electric  bridge  or  balance. 
(See  Bridge,  Electric?) 

Bridge,    Reversible A   bridge  or 

balance  so  arranged  that  the  proportionate 
coils  can  be  readily  interchanged,  thus  per- 
mitting the  bridge  coils  to  be  readily  tested  by 
reversing. 

Bridge,    Wheatstone's    Electric 

A  name  given  to  the  electric  bridge  or  balance. 
(See  Bridge,  Electric?) 

Bridges. — Heavy  copper  wires  suitably 
shaped  for  connecting  the  dynamo-electric 
machines  in  an  incandescent  light  station  to 
the  bus-rods  or  wires. 


Bright  Dipping.— (See  Dipping,  Bright?) 
Bright    Dipping    Liquid. — (See  Liquid, 
Bright  Dipping?) 

Britannia  Joint. — (See  Joint,  Britannia?] 
Broken  Circuit. — (See  Circuit,  Broken?) 

Bronzing,  Electro  —  — Coating  a  sur- 
face with  a  layer  of  bronze  by  electro-plating. 
(See  Plating,  Electro?) 

The  plating  bath  contains  a  solution  of  tin  and 
copper. 

Brush-and-Spray  Discharge. — (See  Dis- 
charge, Brush-and-Spray?) 

Brush  Discharge.  —  (See  Discharge, 
Brush?) 

Brush  Electrode. — (See  Electrode,  Brush?) 

Brush,  Faradic  • An  electrode  in 

the  form  of  a  brush  employed  in  the  medical 
application  of  electricity. 

The  bristles  are  generally  made  of  nickelized 
copper  wire. 

Brush-Holders  for  Dynamo-Electric  Ma- 
chines.— Devices  for  supporting  the  collecting 
brushes  of  dynamo-electric  machines. 

As  the  brushes  require  to  be  set  or  placed  on 
the  commutator  in  a  position  which  often  varies 
with  the  speed  of  the  machine,  and  with  changes 
in  the  resistance  of  the  external  circuit,  all  brush- 
holders  are  provided  with  some  device  for  moving 
them  concentrically  with  the  commutator  cylin- 
der. 

Brush  Rocker. — (See  Rocker,  Brush?) 

Brush,  Scratch  — A  brush  made 

of  wire  or  stiff  bristles,  etc.,  suitable  for  clean- 
ing the  surfaces  of  metallic  objects  before 
placing  them  in  the  plating  bath. 

Scratch  brushes  are  made  of  various  shapes  and 
are  provided  with  wires  or  bristles  of  varying 
coarseness. 

Some  forms  of  scratch  and  finishing  brushes 
are  shown  in  Fig.  83.  They  are  circular  in  outline 


Fig.  83.     Scratch  Brushes. 

and  are  adapted  for  use  in   connection  with  a 
lathe. 


Bru.J 


63 


[Bui. 


Brush,      Scratch,      Circular 


scratch  brush  of  a  circular  shape,  so  fitted  as 
to  be  capable  of  being  placed  in  a  lathe  and 
set  in  rapid  rotation. 

Brush,  Scratch,  Hand A  scratch 

brush  operated  by  hand,  as  distinguished 
from  a  circular  scratch  brush  operated  by  a 
lathe. 

Brushes,  Adjustment  of  Dynamo-Electric 

Machines Shifting  the  brushes   into 

the  required  position  on  the  commutator 
cylinder,  either  non-automatically  by  hand,  or 
automatically  by  the  current  itself.  (See 
Regulation,  Automatic,  of  Dynamo-Electric 
Machines?) 

Brushes,  Carbon,  for  Electric    Motors 

Plates  of  carbon  for  leading  current 

to  electric  motors.  (See  Brushes  of  Dynamo- 
Electric  Machine?) 

These  are  generally  known  simply  as  brushes. 

Brushes,  Collecting,  of  Dynamo-Electric 

Machine Conducting  brushes  which 

bear  on  the  commutator  cylinder,  and  take  off 
the  current  generated  by  the  difference  of 
potential  in  the  armature  coils.  (See  Brushes 
of  Dynamo-Electric  Machine?) 

Brushes,  Lead  of The  angle  through 

which  the  brushes  of  a  dynamo-electric  ma- 
chine must  be  moved  forward,  or  in  the 
direction  of  rotation,  in  order  to  diminish 
sparking  and  to  get  the  best  output  from 
the  dynamo. 

The  necessity  for  the  lead  arises  from  the  coun- 
ter magnetism  or  magnetic  reaction  of  the  arma- 
ture, and  the  magnetic  lag  of  its  iron  core.  (See 
Lead,  Angle  of.) 

The  position  of  the  brushes  on  the  commutator 
to  insure  the  best  output  is  practically  the  same 
in  a  series  dynamo  for  any  current  strength. 
In  shunt  and  compound  dynamos  it  varies  with 
the  lead. 

Brushes  of  Dynamo-Electric  Machine.— 

Strips  of  metal,  bundles  of  wire,  slit  plates  of 
metal,  or  plates  of  carbon,  that  bear  on  the 
commutator  cylinder  of  a  dynamo-electric 
machine,  and  carry  off  the  current  generated. 
Rotary  brushes  consisting  of  metal  discs  are 
sometimes  employed.  Copper  is  almost  univer- 


Fig,  84.    Brushes. 


sally  used  for  the  brushes  of  dynamo-electric 
machines.  Carbon  brushes  are  often  used  for 
dynamo-electric  motors. 

The  brush  shown  at  B,  Fig.  84,  is  formed  of 
copper  wires,  soldered 
together  at  the  non- 
bearing  end.  A  copper 
plate,  slit  at  the  bear- 
ing end,  is  shown  at  C, 
and  bundles  of  copper 
plates,  soldered  together 
at  the  non-bearing  end, 
are  shown  at  D. 

The  brushes  should 
bear  against  the  com- 
mutator cylinder  with 
sufficient  force  to  pre- 
vent jumping,  and  con- 
sequent burning,  and 
yet  not  so  hard  as  to 
cause  excessive  wear. 

Brushes,  Rotating,  of  Dynamo-Electric 

Machines Discs  of  metal,  employed 

in  place  of  the  ordinary  brushes  for  carry- 
ing off  the  current  from  the  armatures  of 
dynamo-electric  machines. 

Brushing,  Scratch Cleansing  the 

surface  of  an  article  to  be  electroplated,  by 
friction  with  a  scratch  brush. 

Scratch  brushing  is  generally  done  with  the 
brushes  wet  by  various  solutions. 

Buckling. — Irregularities  in  the  shape  of 
the  surfaces  of  the  plates  of  storage  cells,  fol- 
lowing a  too  rapid  discharge. 

Bug. — A  term  originally  employed  in  quad- 
ruplex  telegraphy  to  designate  any  fault  in 
the  operation  of  the  apparatus. 

This  term  is  now  employed,  to  a  limited  extent, 
for  faults  in  the  operation  of  any  electric  appa- 
ratus. 

Bug-Trap. — A  device  employed  to  over- 
come the  "  bug  "  in  quadruplex  telegraphy. 

Bulb,  Lamp  — The  chamber  or 

globe  in  which  the  filament  of  an  incan- 
descent electric  lamp  is  placed. 

The  chamber  or  globe  of  a  lamp  must  be  of 
such  construction  as  to  enable  the  high  vacuum 
necessary  to  the  operation  of  the  lamp  to  be  main- 
tained. 


Bun.]  64 

Bunched  Cable.— (See  Cable,  Bunched!) 
Bunched    Cable,    Straightaway  - 

(See  Cable,  Bunched,  Straightaway!) 

Bunched   Cable,   Twisted    — (See 

Cable,  Bunched,  Twisted!) 

Bunsen  Voltaic  Cell.— (See  Cell,  Voltaic, 
Bunsens!) 

Buoy,  Electric A  buoy  on  which 

luminous  electric  signals  are  displayed. 

Burglar  Alarm.— (See  Alarm,  Burglar!) 

Burglar  Alarm  Annunciator. — (See  An- 
nunciator, Burglar  Alarm!) 

Burglar  Alarm  Contacts.— (See  Contacts, 
Burglar  Alarm!) 

Burglar  Alarm,  Tale  Lock  Switch  for  — 
— (See  Alarm,  Yale-Lock-Switch  Burglar!) 

Burner,  Argand  Electric An  ar- 

gand  gas-burner  that  is  lighted  by  means  of 
an  electric  spark. 

The  argand  electric  burner  assumes  a  variety 
of  forms,  such  as  the  plain-pendant,  the  ratchet- 
pendant  and  the  automatic.  They  are  also  used 
in  systems  of  multiple  gas  lighting. 

Burner,  Argand  Electric,  Automatic 

— An  argand  burner  arranged  for  automatic 
electric  lighting.  (See  Burner,  Automatic- 
Electric!) 

Burner,  Argand  Electric,  Hand-Lighter 

— A     plain-pendant    electric     burner 

adapted  for  lighting  an  argand  gas-burner. 
(See  Burner,  Plain-Pendant  Electric?) 

Burner,  Argand-Electric,  Plain-Pendant 

— A     plain-pendant     electric     burner 

adapted  for  lighting  an  argand  gas  burner. 
(See  Burner,  Plain-Pendant  Electric!) 

Burner,  Argand-Electric,  Ratchet-Pend- 
ant   A  ratchet-pendant  electric  burner 

adapted  for  lighting  an  argand  gas-burner. 
(See  Burner,  Ratchet-Pendant  Electric!) 

Burner,  Automatic-Electric An 

electric  device  for  both  turning  on  the  gas 
and  lighting  it,  and  turning  it  off,  by  alter- 
nately touching  different  buttons. 

The  gas-cock  is  opened  or  closed  by  the  motion 
of  an  armature,  the  movements  of  which  are  con- 
trolled by  two  separate  electro-magnets.  One 
push-button,  usually  a  white  one,  turns  the  gas  on 


[Bur. 


by  energizing  one  of  the  electro-magnets  and, 
at  the  same  time,  lights  it  by  means  ot  a  suc- 
cession of  sparks  from  a  spark  coil.  Another 
push-button,  usually  a  black  one,  turns  the  gas 
off  by  energizing  the  other  electro-magiaet. 
The  turning  on  or  off  of  the  gas  is  accom- 
plished by  positive 
motions.  Automatic 
burners  are  also  made 
with  a  single  button. 

An  Argand  Electric 
Burner  is  shown  in 
Kg.  85. 

Burner,  Electric 
Candle  -  — A 
device  for  electri- 
cally lighting  a  gas 
jet  in  a  burner  sur- 
rounded by  a  por- 
celain tube  in  imita- 
tion of  a  candle. 

Electric  candle  bur- 
ners are  either  simple 
or  ratchet  candle  bur- 
ners. 

Burner,  Hand- 
Lighting  Electric 

A  name  sometimes  applied  to  a  plain- 
pendant  electric  burner.  (See  Burner,  Plain- 
Pendant  Electric!) 


Argand  Electric 
Burner. 


Burner,    Jump-Spark 


-A     term 


sometimes  applied  to  a  gas  burner  in  which 
the  issuing  gas  is  ignited 
by  a  spark  that  jumps  be-  f . 
tween  the  metallic  points 
placed  on  it. 

Jump-spark  burners  are 
used  in  systems  of  multiple 
gas  lighting.  (See  Light- 
ing,  Electric  Gas.) 

Burner,  Plain-Pen- 
dant Electric A 

gas--  burner       provided 

with  a  pendant  for  the 

purpose  of  lighting  the 

gas  by  means  of  a  spark,  Fig.  86.  Plain-pliant 

after  the  gas  has   been  Burner. 

turned  on  by  hand. 

The  gas  is  first  turned  on  by  hand  at  the  ordi- 


Bur.] 


65 


[But. 


nary  key,  and  is  then  lighted  by  pulling  the  pend- 
ant C,  Fig.  86.  A  spark  irom  a  spark  coil  ignites 
the  gas. 

This  is  sometimes  called  an  electric  hund- 
lighting  burner. 

Burner,  Ratchet-Pendant  Candle  Elec- 
tric   A  burner  for  both  lighting  and 

extinguishing  a  candle  gas  jet. 

Burner,   Ratchet-Pendant  Electric  — 

— A  gas-burner  in  which  one  pulling  of  a 
pendant  turns  on  the  gas  and  ignites  it  by 
means  of  an  electric  spark  from  a  spark  coil, 
and  the  next  pulling  of  the  pendant  turns  off 
the  gas. 

A  ratchet-wheel  and  pawl  are  operated  by  the 
motion  of  the  pendant.  The  first  pull  of  the 
pendant  chain  moves  the  ratchet  so  as  to  open  a 
four- way  gas  cock,  and  at  the  same  time  light 
the  gas  at  the  burner  tip  by  a  wipe-spark  from  a 
spark  coil.  On  the  next  pull  ot  the  pendant,  the 
four  way  cock  is  turned  so  as  to  turn  off  the  g?s. 
Alternate  pulls,  therefore,  light  and  extinguish 
the  gas. 

Burner,  Simple  Candle  Electric 

A  plain-pendant  electric  burner.  (See  Bur- 
ner, Plain  Pendant  Electric.) 


Thumb-Cock 

gas- 


Electric 


Burner, 

An  electric 
burner,  in  which 
the  turning  of  an 
ordinary  thumb- 
cock  turns  on  the 
gas,  and  ignites  it 
by  a  spark  pro- 
duced byawiping 
contact  actuated 
by  the  motions  of 
the  thumb-cock. 
A  form  of  thumb- 
cock  burner  is 
shown  in  Fig.  87. 

Burner,     Vi- 
brating -,E  1  e  c  - 

trie    — An     Fig.  87.     Thumb- Cock  Burner. 

electric  gas-burner  in  which  the  gas  is  lighted 
after  it  is  turned  on  by  hand,  by  means  of  the 
spark  from  a  spark  coil  produced  on  the  rapid 


making  and  breaking  of  the  circuit  by  a 
vibrating  contact. 

The  vibrating-electric  burner  has  a  single  elec- 
tro-magnet. It  is  operated  by  means  of  a  button 
or  switch,  and  may  be  used  on  single  lights  or  on 
groups  of  lights.  It  bears  the  same  relation  to 
the  automatic  burner  that  the  plain-pendant 
burner  does  to  the  ratchet  burner. 

Burnetize. — To  subject  to  the  Burnetizing 
process.  (See  Burnetizing^) 

Burnetizing. — A  method  adopted  for  the 
preservation  of  wooden  telegraph  poles  by 
injecting  a  solution  of  zinc  chloride  into  the 
pores  of  the  wood.  (See  Pole,  Telegraphic?) 

Burning  at  Commutator  of  Dynamo. — 

An  arcing  at  the  brushes  of  a  dynamo-elec- 
tric machine,  due  to  their  imperfect  contact, 
or  improper  position,  which  results  in  loss  of 
energy  and  destruction  of  the  commutator 
segments. 

Bus. — A  word  generally  used  instead  of 
omnibus.  (See  Omnibus?) 

Bus-Bars. — (See  Bars,  Bus?) 

Bus-Rod  Wires.— (See  Wires  Bus-Rod^ 

Bus-Wire.— (See  Wire,  Bus.) 

Butt  Joint.— (See  Joint,  Butt.) 

Button,  Carbon  — A  resistance  of 

carbon  in  the  form  of  a  button. 

A  button  of  carbon  is  used  as  an  electric  resist- 
ance in  a  variety  of  apparatus;  its  principal  use, 
however,  is  in  the  transmitting  instrument  of  the 
electric  telephone.  In  the  telephone  transmitter, 
the  button  is  so  placed  between  contact-plates  that 
when  the  plates  are  pre.-sed  together  by  the 
sound-waves,  the  electrical  resistance  is  dec 'eased 
by  a  decrease  in  the  thickness  of  the  carbon  button, 
an  increase  in  its  density,  and  an  increase  in  the 
number  of  points  where  the  carbon  touches  the 
plates.  Rheostats,  or  resistances,  have  been 
made  by  the  use  of  a  number  of  carbon  buttons  or 
discs  piled  one  on  another  and  placed  in  a  glass 
tube.  Discs  of  carbonized  cloth  form  excellent 
resistances  lor  such  purposes. 

Button,    Press A    push    button. 

(See  Button,  Push?) 

Button,  Push A  device  for  closing 


But.] 


66 


[Cab. 


in  electric  circuit  by  the   movement  of  a         Buzzer,  Electric  — A  call,  not  as 

Dutton.  loud  as  that  of  a  bell,  produced  by  a  rapid 

A  button,  when  pushed  by  the  hand,  closes  the 


Fig.  8 8.    Push  Button.         Fig.  89. 


0 

Push  Button. 


contact,  and  thus  completes  a  circuit   in  which 
some  electro- receptive  device  is  placed.     This 

circuit  is  opened  by  a  spring,  p 

on  the  removal  of  the  pressure. 
Some  forms  of  push-buttons  are 
shown  in  Figs.  88,  89  and  90. 

KJloor-push  for  dining-rooms 
and  offices  is  shown  in  Fig. 
90. 

Fig.  88  shows  the  general 
appearance  of  an  ordinary  bell- 
push.  The  arrangement  of  the 

Fig.  oo.    Floor 
interior  spnng  contacts  will  be  Push. 

understood  by  an  inspection  of  Fig.  91. 


Fig.  9  f.    Spring  Contact  of  Bell  Push. 

automatic  make-and-break.    (See  Make-and- 
Break,  Automatic?} 

The  buzzer  is  generally  plrced  inside  a  resonant 


Fig.  92.    Buzzer. 

case  of  wood  in  order  to  strengthen  the  sound  by 
resonance.     A  form  of  buzzer  is  shown  in  Fig.  92. 


C. — An  abbreviation  for  centigrade. 

^hus,  20  degrees  C.  means  20  degrees  of  the 
centigrade  thermometric  scale.  (See  Scale,  Cett' 
tigrade  Thermometer.') 

C. — A  contraction  for  current. 

Generally  a  contraction  for  the  current  in 

E 

amperes,  as  C  =  ™- 

C.  C. — A  contraction  for  cubic  centimetre. 
(See  Weights  and  Measures,  Metric  System 
of-} 

C.  G.  S.  TJnits.~A  contraction  for  centi- 
timetre-gramme-second  units.  (See  Units, 
Centimetre-Gramme-Second.) 


C.  P. — A  contraction  for  candle  power. 
(See  Candle,  Standard.) 

Cable.— An  electric  cable.  (See  Cable, 
Electric^ 

Cable. — To  send  a  telegraphic  dispatch, 
by  means  of  a  cable. 

Cable,  Aerial A  cable  suspended 

in  the  air  from  suitable  poles. 

Cable,  Anti-Induction,  TTaring 

'A  form  of  anti-induction  cable. 

In  the  Waring  an ti- induction  cable  the  separate 
conductors  are  covered  with  a  fibrous  insulator, 
from  which  all  air  and  moisture  is  expelled,  and 
the  fibre  then  saturated  with  an  insulating  ma- 


Cab.] 


67 


[Cab. 


terial  called  ozite.  The  conductors  are  then  pro- 
tected from  the  inductive  effects  of  neighboring 
conductors  by  a  continuous  sheath  of  lead  alloyed 
with  tin. 

Where  the  cables  are  bunched,  the  bunches 
are  sometimes  again  surrounded  by  insulating 
material,  and  the  whole  then  covered  by  a  con- 
tinuous lead  sheathing  ;  generally,  however,  the 
separately  insulated  conductors  are  bunched, 
and  then  covered  by  a  single  sheathing  of  lead 
alloyed  with  tin. 

Cable,  Armature  of  —  —  The  armor  of 
a  cable.  (See  Armature  of  a  Cabled) 

Cable,  Armor  of  -  -  — The  protecting 
sheathing  or  metallic  covering  on  the  outside 
of  a  submarine  or  other  electric  cable. 

Cable,  Armored  —  — An  electric  cable 
provided,  in  addition  to  its  insulating  coat- 
ing, with  a  protective  coating  or  sheathing, 
generally  of  metal  tubing  or  wire. 

Cable-Box.— (See  Box,  Cable^ 

Cable,  Bunched A  cable  contain- 
ing more  than  a  single  wire  or  conductor. 

Some  forms  of  bunched,  lead-covered  cables, 
are  shown  in  Fig.  93. 


Fig.  93.     Bunched  Cables. 

Cable,  Bunched,  Straightaway — 

A  bunched  cable  the  separate  conductors  of 
which  extend  in  the  direction  of  the  length  of 
the  cable  without  any  twisting,  being  placed 
in  successive  layers. 

In  arranging  the  separate  conductors  in  suc- 
cessive layers  an  advantage  is  gained  in  testing 
for  a  given  wire  in  order  to  make  a  loop,  splice, 
or  branch  with  the  next  adjoining  section.  This  is 
rendered  still  easier  by  giving  the  conductors 
of  the  successive  layers  some  distinctive  form  of 
braiding  in  the  fibrous  insulating  material,  or 
some  distinctive  color. 

Cable,    Bunched,    Twisted    — A 

bunched  cable,  the  separate  conductors  of 
which  are  twisted-pairs  placed  in  successive 
layers. 


Each  twisted-pair  of  a  bunched  cable  acts  as  a 
metallic  circuit,  and,  moreover,  possesses  the  ad- 
vantage of  avoiding  the  ill  effects  of  induction,  so 
disadvantageous  in  telephone  circuits. 

In  laying  up  the  twisted-pairs  in  successive 
layers  in  a  bunched  cable,  the  direction  of  twist- 
ing is  reversed  in  each  successive  layer.  This 
form  is  especially  desirable  on  all  long  cable  lines. 

In  the  case  of  twisted  cables  for  telephone  lines, 
the  twists  are  sometimes  made  as  frequent  as  one 
in  every  three  or  four  inches.  In  such  cases  the 
cross-talk  of  induction  is  inappreciable. 

Cable,  Capacity  of The  quantity 

of  electricity  required  to  raise  a  given  length 
of  a  cable  to  a  given  potential,  divided  by  the 
potential. 

The  amount  of  charge  for  a  given  potential 
that  any  single  conductor  will  take  up  with 
the  rest  of  the  conductors  grounded.  (See 
Capacity,  Electrostatic^) 

The  ability  of  a  wire  or  cable  to  permit  a 
certain  quantity  of  electricity  to  be  passed 
into  it  before  acquiring  a  given  difference  of 
potential. 

Before  a  telegraph  line  or  cable  can  transmit  a 
signal  to  its  further  end,  its  difference  of  potential 
must  be  raised  to  a  definite  amount  dependent  on 
the  character  of  the  instruments  and  the  nature  of 
the  system. 

The  first  effect  of  electricity  being  passed  into  a 
line  is  to  produce  an  accumulation  of  electricity 
on  the  line,  similar  to  the  charge  in  a  condenser. 
Cables  especially  act  as  condensers,  and  from  the 
high  specific  inductive  capacity  of  the  insulating 
materials  employed,  permit  considerable  induc- 
tion to  take  place  between  the  core  and  the 
metallic  armor  or  sheathing,  or  the  ground. 

The  capacity  of  a  cable  depends  on  the  capacity 
of  the  wire  ;  i.  e.,  on  its  length  and  surface,  on 
the  specific  inductive  capacity  of  its  insulation, 
and  its  neighborhood  to  the  earth,  or  to  other 
conducting  wires,  casings,  armors,  or  metallic 
coatings.  Submarine  or  underground  cables 
therefore  have  a  greater  capacity  than  air  lines. 

This  accumulation  of  electricity  produces  a  re- 
tardation in  the  speed  of  signaling,  because  the 
wire  must  be  charged  before  the  signal  is  received 
at  the  distant  end,  and  discharged  or  neutralized 
before  a  current  can  be  sent  in  the  reverse  direc- 
tion. This  latter  may  be  done  by  connecting 
each  end  to  earth,  or  by  the  action  of  the  reverse 
current  itself. 


Cab.] 


[Cab. 


The  smaller  the  electrostatic  capacity  of  a  cable, 
therefore,  the  greater  the  speed  of  signaling.  (See 
Retardation. ) 

The  capacity  of  a  cable  is  measured  in  micro- 
farads. (See  farad,  Micro.) 

Cable  Clip.— (See  Clip,  Cable?) 
Cable-Core.— (See  Core  of  Cable?) 

Cable,  Core-Ratio  of The  ratio  be- 
tween the  diameter  of  the  insulation  of  a  cable 
and  the  mean  diameter  of  the  strand. 

D 
The  core-ratio  is  represented  by  -p;  where  D, 

is  the  diameter  of  the  insulation,  and  d,  the  mean 
diameter  of  the  strand.  Should  the  extreme 
diameter  of  the  strand  of  a  cable  be  used  in  cal- 
culations for  insulation  resistance,  inductive  capa- 
city, etc.,  erroneous  values  would  be  obtained. 
The  measured  diameter  of  the  copper  conductor 
is  consequently  decreased  some  five  per  cent.,  and, 
in  this  way,  correct  values  are  approximately 
obtained. — (Clark  dr3  Sabitte.) 

Cable,  Duplex A  conductor  con- 
sisting of  two  separate  cables  placed  parallel 
to  each  other. 

The  duplex  cable  is  used  especially  in  the  al- 
ternating current  system. 

Cable,  Electric •  — The  combination 

of  an  extended  length  of  a  single  insulated 
conductor,  or  two  or  more  separately  insu- 
lated electric  conductors,  covered  externally 
with  a  metallic  sheathing  or  armor. 

Strictly  speaking,  the  word  cable  should  be 
limited  to  the  case  of  more  than  a  single  con- 
ductor. Usage,  however,  sanctions  the  employ- 
ment of  the  word  to  indicate  a  single  insulated 
conductor. 

The  conducting  wire  may  consist  of  a  single 
wire,  of  a  number  of  separate  wires  electrically 
connected,  or  of  a  number  of  separate  wires  in- 
sulated from  one  another. 

An  electric  cable  consists  of  the  following  parts, 
viz.: 

( I .)  The  conducting  wire  or  core. 

(2.)  The  insulating  material  for  separating  the 
several  wires;  and 

(3.)  The  armor  or  protecting  covering,  consist- 
ing of  strands  of  iron  wire,  or  of  a  metallic  coat- 
Ing  or  covering  of  lead. 

As  to  their  position,  cables  are  aerial,  sub- 
marine, or  underground.  As  to  their  purpose, 


they  are  telegraphic,  telephonic,  or  electric  light 
and  power  cables.  As  to  the  number  of  their 
conductors  they  are  single-wire  or  bunched 
cables.  Bunched  cables  are  straightaway  or 
twisted. 
Fig.  94  shows  a  form  of  submarine  cable  the 


Fig.  94.    Electric  Cablt. 

armor  of  which  is  formed  of  strands  of  iron 
wire. 

Cable,  Electric  Light  or  Power 

A  cable  designed  to  distribute  the  electric  cur- 
rent employed  in  electric  light  or  power  sys- 
tems. 

Electric  light  cables  are  generally  tmderground. 
They  may  be  submarine.  (See  Cable,  Electric.} 

•Cable,  Flat A  cable,  the  separate 

conductors  of  which  are  laid-up  side  by  side 
so  as  to  form  a  flat  conductor. 

A  flat  cable  is  suitable  for  house  work  as  being 
less  objectionable  in  appearance  when  placed  on 
the  outside  of  ceilings  or  walls. 

Cable,  Flat  Duplex A  flat,  laid-up 

cable  containing  two  wires. 

Cable-Grip.— (See  Grip,  Cable?) 
Cable-Hanger. — (See  Hanger,  Cable?) 

Cable-Hanger  Tongs.— (See  Tongs,  CaKe- 
Hanger?) 

Cable  Laid-Up  in  Layers. — A  term  applied 
to  a  cable,  all  the  conducting  wires  of  which 
are  in  layers. 


Cab.] 


69 


[Cab. 


Cable  Laid-Up  in  Eeversed  Layers. — A 
term  applied  to  a  cable  in  which  the  conduct- 
ors, in  alternate  layers,  are  twisted  in  opposite 
directions.  (See  Cable,  Bunched,  Straight- 
away^) 

Cable  Laid-Up  in  Twisted  Pairs.— A  term 
applied  to  a  cable  in  which  every  pair  of  wires 
is  twisted  together.  (See  Cable,  Bunched, 
Twisted?) 

Cable  Lead. — (See  Lead,  Cable). 

Cable,  Multiple-Core A  cable  con- 
taining more  than  a  single  core. 

Cable-Protector.— (See  Protector,  Cable.) 

Cable-Scrying. — (See  Serving,  Cable.) 

Cable,  Single-Wire A  cable  con- 
taining a  single  wire  or  conductor 

Cable,  Sub-Aqueous •  — An  electric 

cable  designed  for  use  under  water. 

The  term  submarine  is  more  frequently  em- 
ployed. 

Cable,  Submarine A  cable  designed 

for  use  under  water. 

Submarine  cables  are  either  shallow-water*  or 
deep-sea  cables.  Gutta-percha  answers  admirably 
for  the  insulating  material  of  the  core.  Various 
other  insulators  are  also  used. 

Strands  of  tarred  hemp  or  jute,  known  as  the 
cable- serving,  are  wrapped  around  the  insulated 
core  in  order  to  protect  it  from  the  pressure  of  the 
galvanized  iron  wire  armor  afterwards  put  on. 
To  prevent  corrosion  the  iron  wire  is  covered 
with  tarred  hemp,  galvanized,  or  otherwise 
coated. 

Submarine  cables  are  generally  employed  tor 
telegraphic  or  telephonic  communication.  (See 
Cable,  Electric.) 

Cable,  Submarine,  Deep-Sea A 

submarine  cable  designed  for  use  in  deep 
water. 

This  form  of  cable  is  not  so  heavily  armored  as 
the  shallow-water  submarine  cable. 

Cable,  Submarine,  Shallow- Water 

A  submarine  cable  designed  for  use  in  shallow 
water. 

This  cable  is  provided  with  a  heavier  armor  or 
sheathing  than  a  deeo-sea  cable  to  protect  it 
from  chafing  due  to  the  action  of  the  waves  and 
tides  in  shaiiow  water.  (See  Cable,  Submarine.) 


Cable  Support,  Underground (See 

Support,  Underground  Cable.) 

Cable  Tank.-  (See  Tank,  Cable) 

Cable,  Telegraphic A  cable  de- 
signed to  establish  telegraphic  communication 
between  different  points. 

Telegraphic  cables  may  be  aerial,  submarine, 
or  underground.  (See  Cable,  Electric.) 

Cable,  Telephonic— A  cable  de- 
signed to  establish  telephonic  communication 
between  different  points. 

Telephonic  cables  may  be  aerial,  submarine, 
or  underground.  (See  Cable,  Electric.) 

Cable-Terminal. — (See  Terminal,  Cable.} 

Cable,  Torpedo —A  cable,  in  the 

circuit  of  which  a  torpedo  is  placed.  (See 
Torpedo,  Electric?) 

Cable,  Twisted-Pair A  cable 

containing  a  single  twisted  pair,  suitable  for 
use  as  a  lead  and  return,  thus  affording  a 
metallic  circuit. 

Cable,  Two,  Three,  Four,  etc.,  Conductor 
.  — A  cable  containing  two,  three,  four, 
or  more  separate  conducting  wires. 

Cable,  Underground An  electric 

cable  placed  underground. 

The  conducting  wires  of  an  underground  cable 
are  surrounded  by  a  good  insulating,  water-proof 
substance,  and  protected  by  a  sheathing  or  armor. 
A  coating  of  lead  is  very  generally  employed  for 
the  sheathing  or  armor.  Underground  cables,  in 
order  to  be  readily  accessible,  should  be  placed 
in  an  underground  conduit  or  subway.  (See 
Cable,  Electric.  Conduit^  Underground  Electric. 
Suoway,  Electric.) 

Cable- Worming. — (See  Worming,  Cable) 

Cablegram. — A  message  received  by  means 
of  a  submarine  telegraphic  cable. 

Cables,  Laying-Up The  placing  or 

disposing  of  the  separate  cables  or  conduc- 
tors in  a  bunched  cable. 

The  separate  conductors  in  cables  may  be  laid- 
up  " straightaway  "  or  "twisted."  (See  Cable, 
Bunched^  Twisted.  Cable,  Bunched,  Straight- 
away. ) 

Cabling. — Sending  a  telegraphic  disp^ch 
bv  means  of  a  cable. 


Cal.] 


70 


[Cal. 


Calahan's  Stock  Printer.  —  (See  Printer, 
Stock,  Calahan's) 

Calami  ne,  Electric  --  A  crystalline 
variety  of  silicate  of  zinc  that  possesses  pyro- 
electric  properties.  (See  Electricity,  Pyro) 

Cal-Electricity.—  (See  Electricity,  Cal) 

Calibrate.  —  To  determine  the  absolute 
or  relative  value  of  the  scale  divisions,  or  of 
the  indications  of  any  electrical  instrument, 
such  as  a  galvanometer,  electrometer,  vol- 
tameter, wattmeter,  etc. 

Calibrating.  —  The  act  of  determining  the 
absolute  or  relative  value  of  the  deflections, 
or  indications  of  an  electric  instrument. 

Calibration,  Absolute  --  The  deter- 
mination of  the  absolute  values  of  the  read- 
ing of  an  electrometer,  galvanometer,  volt- 
meter, amperemeter,  or  other  similar  instru- 
ment. 

The  calibration  of  a  galvanometer,  for  ex- 
ample, consists  in  the  determination  of  the  law 
which  governs  its  different  deflections,  and  by 
which  is  obtained  in  amperes,  either  the  absolute 
or  the  relative  currents  required  to  produce  such 
deflections. 

For  various  methods  of  calibration,  see  stan- 
dard works  on  electrical  testing,  or  on  elec- 
tricity. 

Calibration,  Invariable,  of  Galvanom- 
eter --  In  galvanometers  with  absolute 
calibration,  a  method  for  preventing  the  oc- 
currence of  variations  in  the  intensity  of  the 
field  of  the  galvanometer,  due  to  the  neigh- 
borhood of  masses  of  iron,  etc. 

Calibration,  Relative  --  The  deter- 
mination of  the  relative  values  of  the  reading 
of  an  electrometer,  voltmeter,  amperemeter, 
or  other  similar  instrument. 

Caliper,  Mi- 
crometer - 
—  A  name  some- 
times given  to  a 
vernier  wire 
gauge.  (See 
Gauge,  Vernier 


Call-Bell,    Extension (See  Bell, 

Extension  Call) 
Call-Bell,    Magneto-Electric An 

electric  call-bell  operated  by  currents  pro- 
duced by  the  motion  of  a  coil  of  wire  before 
the  poles  of  a  permanent  magnet. 

A  well  known  form  of  magneto  call-bell  is  shown 


Fig,  9S-    Micrometer  Caliper. 

A  form  of  micrometer  caliper  isshown  in  Fig.  qq. 


Fig.  96.    Magneto  Call  Bell. 

in  Fig.  96.  The  armature  is  driven  by  the  rota- 
tion of  the  handle. 

Call-Bell,  Telephone An  electric 

bell,  the  ringing  of  which  is  used  to  call  a 
person  to  a  telephone. 

Call,  Electric  Bell  — An  electric 

bell  sometimes  used  to  call  the  attention  of  an 
operator  to  the  fact  that  his  correspondent 
wishes  to  communicate  with  him,  or  to  notify 
an  attendant  that  some  service  is  desired. 

Call,  Messenger — A  district  call- 
box.  (See  Box,  District  Call) 

Call,  Thermo-Electric An  instru- 
ment for  sounding  an  alarm  when  the  tem- 
perature rises  above,  or  falls  below,  a  fixed 
point. 

In  one  form  of  thermo-electric  call  a  needle  is 
moved  over  a  dial  by  a  simple  thermic  device  and 
rings  a  bell  when  the  temperature  for  which  it 
has  been  se  is  attained.  The  thermo-call  is  appli- 
cable to  the  regulation  of  the  temperature  oi 


Cal.] 


71 


[Cal. 


dwellings,  incubators,  hot  houses,  breweries,  dry- 
ing rooms,  etc. 

Callaud  Yoltaic  Cell.— (See  Cell,  Vol- 
taic, Callaud's.) 

Calling-Drop. — (See  Drop,  Calling.} 

Calorescence.  —  The  transformation  of 
invisible  heat-rays  into  luminous  rays,  when 
received  by  certain  solid  substances. 

The  term  was  proposed  by  Tyndall.  The  light 
from  a  voltaic  arc  is  passed  through  a  hollow 
glass  lens  filled  with  a  solution  of  iodine  in  bisul- 
phide of  carbon. 

This  solution  is  opaque  to  light  but  quite  trans- 
parent to  heat. 

If  a  piece  of  charred  paper,  or  thin  platinum 
foil,  is  placed  in  the  focus  of  these  invisible  rays, 
it  will  be  heated  to  brilliant  incandescence.  (See 
focus.) 

Caloric. — A  term  formerly  applied  to  the 
fluid  which  was  believed  to  be  the  cause  or 
essence  of  heat. 

The  use  of  the  word  caloric  at  the  present  time 
is  very  unscientific,  since  heat  is  now  known  to 
be  an  effect  of  a  wave  motion  and  not  a  material 
thing.  (SeeJfeat.) 

Calorie. — A  heat  unit. 

There  are  two  calories,  the  small  and  the  large 
calorie. 

The  amount  of  heat  required  to  raise  the  tem- 
perature of  one  gramme  of  water  from  o  degree 
C.  to  I  degree  C.  is  called  the  small  calorie. 

The  amount  of  heat  required  to  raise  1,000 
grammes,  or  a  kilogramme,  of  water  from  o  de- 
gree C.  to  I  degree  C.  is  called  the  great  calorie. 
The  first  usage  of  the  word  is  the  commoner. 

This  word  is  sometimes  spelled  calory. 

Calorie,  Great  — The  amount  of 

heat  required  to  raise  the  temperature  of  one 
kilogramme  of  water  from  o  degree  C.  to  I 
degree  C. 

Calorie,    Small The   amount  of 

heat  required  to  raise  the  temperature  of  one 
gramme  of  water  from  o  degree  C.  to  i 
degree  C. 

Calorimeter. — An  instrument  for  measur- 
ing the  amount  of  heat  or  thermal  energy 
contained  or  developed  in  a  given  body. 

Thermometers  measure  temperature  only.     A 


thermometer  plunged  in  a  cup  full  of  boiling 
water  shows  the  same  temperature  that  it  would 
in  a  tub  full  of  boiling  water.  The  quantity  of 
heat  energy  present  in  the  two  cases  is  of  course 
greatly  different,  and  can  be  measured  by  a  cal- 
orimeter only. 

Various  forms  of  calorimeters  are  employed. 

In  order  to  determine  the  quantity  of  heat  in 
a  given  weight  of  any  body,  this  weight  may  be 
heated  to  a  definite  temperature,  such  as  the  boil- 
ing point  of  water,  and  placed  in  a  vessel  con- 
taining ice.  The  quantity  of  ice  melted  by  the 
body  in  cooling  to  the  temperature  of  the  ice,  is 
determined  by  measuring  the  amount  of  water 
derived  from  the  melting  of  the  ice.  Care  must 
be  observed  to  avoid  the  melting  of  the  ice  by  ex- 
ternal heat. 

In  this  way  the  amount  of  heat  required  to 
raise  the  temperature  of  a  given  weight  of  a  body 
a  certain  number  of  degrees,  or  the  capacity  of 
the  body  for  heat,  may  be  compared  with  the 
capacity  of  an  equal  weight  of  water.  This  ratio 
is  called  the  specific  heat.  (See  Heat,  Specific.} 

The  heat  energy,  present  in  a  given  weight  of 
any  substance  at  a  given  temperature,  can  be  de- 
termined by  means  of  a  calorimeter;  for,  since  a 
pound  of  water  heated  1°  F.  absorbs  an  amount 
of  energy  equal  to  772  foot-pounds,  the  energy  can 
be  readily  calculated  if  the  number  of  pounds  of 
water  and  the  number  of  degrees  of  temperature 
are  known.  (See  Heat,  Mechanical  Equivalent 
of-) 

Calorimeter,  Electric An  instru- 
ment for  measuring  the  heat  developed  in  a 
conductor  or  any  piece  of  electrical  apparatus, 
in  a  given  time,  by  an  electric  current. 


Fig.  9?.    Electric  Calorimeter. 

A  vessel  containing  water  is  provided  with  ft 
thermometer  T,   Fig.  97.     The  electric  current 


Cal.] 


72 


[Can, 


passes  for  a  measured  time  through  a  wire  im- 
mersed in  the  liquid. 

The  quantity  of  heat  is  determined  from  the 
increase  of  temperature,  and  the  weight  of  the 
water  heated. 

According  to  Joule,  the  number  of  heat  units 
developed  in  a  conductor  by  an  electric  current 
is  proportional: 

(i.)  To  the  resistance  of  the  conductor. 

(2.)  To  the  square  of  the  current  passing. 

(3.)  To  the  time  the  current  is  passing. 

(See  Heat  Unit,  English.) 

The  heating  power  of  a  current  is  as  the  square 
of  the  current  only  when  the  resistance  remains 
the  same.  (See //<?#/,  Electric.) 

Calorimetric. — Pertaining  to  or  by  means 

of  the  calorimeter. 

Calorimetric  measurement  is  the  measurement 
of  heat  energy  made  by  means  of  the  calorimeter. 
(See  Calorimeter.) 

Calorimetrically. — In  a  Calorimetric  man- 
ner. 

Calorimetric  Photometer. — (See  Photom- 
eter, Calorimetric.) 

Calorimotor. — A  name  applied  to  a  defla- 
grator.  (See  Deflagrator^ 

Calory. — A  term  used  for  calorie. 

Calorie  is  the  preferable  orthography.  (See 
Calorie.) 

Cam,  Electro-Magnetic A  form 

of  magnetic  equalizer,  which  depends  for  its 
operation  on  the  lateral  approach  of  a  suita- 
bly shaped  polar  surface.  (See  Equalizer, 
Magnetic?) 

Cam,  Listening In  a  telephone 

exchange  system,  a  metallic  cam  by  means  of 
which  an  operator  is  placed  in  circuit  with 
a  subscriber. 

Candle. — The  unit  of  photometric  intensity. 

Such  a  light  as  would  be  produced  by  the 
consumption  of  two  grains  of  a  standard 
candle  per  minute. 

An  electric  lamp  of  1 6  candle-power,  or  one  of 
2,ooo  candle-power,  is  a  light  that  gives  respect- 
ively 1 6  or  2,000  times  as  much  light  as  one  stand- 
ard candle. 

Candle  Burner,  Electric (See2?wr- 

ner,  Electric  Candle?) 


Candle,  Electric A   term   applied 

to  the  Jablochkoff  candle,  and  other  similai 
devices.  (See  Candle,  Jablochkoff,) 

Candle,  Foot A  unit  of  illumina- 
tion equal  to  the  illumination  produced  by  a 
standard  candle  at  the  distance  of  I  foot. 

According  to  this  unit,  the  illumination  pro- 
duced by  a  standard  candle  at  the  distance  of 
2  feet  would  be  but  the  one-fourth  of  a  foot- 
candle;  at  3  feet,  the  one-ninth  of  a  foot-candle, 
etc. 

The  advantage  of  the  proposed  standard  lies  in 
the  fact  that  knowing  the  illumination  in  foot- 
candles  required  for  the  particular  work  to  be 
done,  it  is  easy  to  calculate  the  position  and 
intensity  of  the  lights  required  to  produce  the 
illumination. 

Candle,  Jablochkoff An   electric 

arc  light  in  which  the  two  carbon  electrodes  are 
placed  parallel  to  each  other  and  maintained 
a  constant  distance  apart  by  means  of  a  sheet 
of  insulating  material  placed  between  them. 

The  Jablochkoff  electric  candle  consists  of  twa 
parallel  carbons,  separated  by  a  layer  of  kaolin  or 
other  heat-resisting  insulating  material,  as  shown 
in  Fig.  98.  The  current  is  passed  into  and  out  of 
the  carbons  at  one  end  of  the 
candle,  and  forms  a  voltaic  arc  at 
the  other  end.  In  order  to  start 
the  arc,  a  thin  strip  called  the 
igniter,  consisting  of  a  mixture  of 
some  readily  ignitable  substance, 
connects  the  upper  ends  of  the 
carbons. 

An  alternating  current  is  em- 
ployed with  these  candles,  thus 
avoiding  the  difficulty  which  Ft'f'  <>s  Ja~ 
would  otherwise  occur  from  the  *•***'  Candu' 
more  rapid  consumption  of  the  positive  than  the 
negative  carbon.  (See  Current^  Alternating.) 

Candle,  Metre The  illumination  pro- 
duced by  a  standard  candle  at  the  distance  of 
one  metre.  (See  Candle,  Foot?) 

Candle-Power.— (See  Power,  Candle.) 

Candle-Power,  Bated (See  Power, 

Candle,  Rated.) 

Candle -Power,  Spherical (See 

Power,  Candle,  Spherical?) 

Candle,    Standard A  candle    of 


Cao.] 

definite  composition  which,  with  a  given  con- 
sumption in  a  given  time,  will  produce  a  light 
of  a  fixed  and  definite  brightness. 

A  candle  which  burns  120  grains  of  sperma- 
ceti wax  per  hour,  or  2  grains  per  minute,  will 
give  an  illumination  equal  to  one  standard  candle. 

Unless  considerable  care  is  taken,  erroneous  re- 
sults will  be  obtained  from  the  use  of  the  stand- 
ard candle.  According  to  Slingo  and  Brooker 
the  following  are  among  the  most  important 
causes  of  these  errors  : 

(I.)  Defective  forms  of  candle  which  cause  a 
varying  consumption  of  the  material  per  second, 
and  consequently  a  varying  light  for  the  standard 
candle. 

(2. )  Variations  in  the  composition  of  the  sper- 
maceti of  which  the  candle  is  composed.  Sper- 
maceti is  not  a  definite  chemical  compound,  but 
consists  of  a  mixture  of  various  substances ; 
therefore,  even  if  the  consumption  is  maintained 
constant,  the  light-giving  power  is  not  necessarily 
Constant. 

(3.)  Variations  in  the  composition  and  charac- 
ter of  the  wick,  such  as  the  number  and  size  of 
the  threads  of  which  it  is  formed  and  the  closeness 
of  the  strands,  all  of  which  circumstances  influence 
the  amount  of  light  given  off  by  the  candle. 

(4.)  The  light  emitted  in  certain  directions  ra- 
ries  in  a  marked  degree  with  the  shape  of  the 
wick.  The  mere  bending  of  a  wick  may,  there- 
fore,  cause  the  amount  of  light  to  vary  consider- 
ably. 

(5.)  The  light  varies  with  the  thickness  of  the 
wick.  Thick  wicks  give  less  light  than  thin 
wicks. 

(6.)  The  light  given  by  the  standard  candle  va- 
ries with  the  temperature  of  the  testing-room. 
As  the  temperature  rises  the  light  given  by  the 
standard  candle  increases. 

(7.)  Currents  of  air,  by  producing  variations 
in  the  amount  of  melting  wax  in  the  cup  of  the 
candle,  vary  the  amount  of  light  emitted. 

These  difficulties  in  obtaining  a  fixed  amount  of 
light  from  a  standard  candle,  together  with  the 
difficulty  of  comparing  the  feeble  light  of  a  single 
candle  with  the  light  of  a  much  more  powerful 
source,  such  as  an  arc  lamp,  coupled  with  the 
additional  difficulty  arising  from  the  difference  in 
the  colors  of  the  lights,  have  led  to  the  use  of 
other  standards  of  light  than  those  furnished  by 
the  standard  candle. 

Caontchonc.  or  India-Rubber.— A  resin- 


'3  [Cap. 

ous  substance  obtained  from  the  milky  juices 
of  certain  tropical  trees. 

Caoutchouc  possesses  high  powers  of  electric 
insulation,  and  is  used  either  pure  or  combined 
with  sulphur. 

Cap,  Insulator A  covering  or  cap 

placed  some  distance  above  an  insulator,  but 
separated  from  it  by  an  air  space. 

Insulator  caps  are  intended  for  protection  of  the 
insulators  from  injury  by  the  throwing  of  stones 
or  other  malicious  acts.  Insulator  caps  are  gen- 
erally made  of  iron.  They  are  highly  objection- 
able, owing  to  the  facility  they  offer  for  the  ac- 
cumulation of  dust  and  dirt. 

Capacity,   Atomic The   quantiva- 

lence  or  valency  of  an  atom.  (See  Atomi- 
city) 

Capacity,  Dielectric A  term  em- 
ployed in  the  same  sense  as  specific  inductive 
capacity.  (See  Capacity,  Specific  Inductive?) 

Capacity,    Electro-Dynamic    — A 

term  formerly  employed  by  Sir  William 
Thomson  for  self-induction.  (See  Induction, 
Self.} 

Capacity,  Electrostatic The  quan- 
tity of  electricity  which  must  be  imparted  to  a 
given  body  or  conductor  as  a  charge,  in  order 
to  raise  its  potential  a  certain  amount.  (See 
Potential,  Electric?) 

The  electrostatic  capacity  of  a  conductor  is  not 
unlike  the  capacity  of  a  vessel  filled  with  a  liquid 
or  gas.  A  certain  quantity  of  liquid  will  fill  a 
given  vessel  to  a  level  dependent  on  the  size  or 
capacity  of  the  vessel.  In  the  same  manner  a 
given  quantity  of  electricity  will  produce,  in  a 
conductor  or  condenser,  a  certain  difference  of 
electric  level,  or  difference  of  potential,  dependent 
on  the  electrical  capacity  of  the  conductor  or 
condenser. 

Or,  taking  the  analogous  case  of  a  gas-tight 
vessel,  the  quantity  of  gas  that  can  be  forced  into 
such  a  vesssl  depends  on  the  size  of  the  vessel 
and  the  pressure  with  which  it  is  forced  in.  A 
tension  or  pressure  is  thus  produced  by  the  gas 
on  the  walls  of  the  vessel,  which  is  greater  the 
smaller  the  size  of  the  vessel  and  the  greater  the 
quantity  of  gas  forced  in. 

In  the  same  manner,  the  smaller  the  capacity 
of  a  conductor,  the  smaller  is  the  charge  required 


Cap.] 


[Cap. 


to  raise  it  to  a  given  potential,  or  the  higher  the 
potential  a  given  charge  will  raise  it. 

The  capacity  K,  of  a  conductor  or  condenser, 
is  therefore  directly  proportional  to  the  charge  Q, 
and  inversely  proportional  to  the  potential  V;  or, 


From  which  we  obtain  Q  =  KV;  ort 

The  quantity  ef  electricity  required  to  charge  a 
conductor  or  condenser  to  a  given  potential  is 
equal  to  the  capacity  of  the  conductor  or  condenser 
multiplied  by  the  potential  through  which  it  is 
raised. 

Capacity,  Electrostatic,  Unit  of  -- 
Such  a  capacity  of  a  conductor  or  condenser 
that  an  electromotive  force  of  one  volt  will 
charge  it  with  a  quantity  of  electricity  equal 
to  one  coulomb. 

The  farad.     (See  Farad^ 

Capacity  of  Cable.—  (See  Cable,  Capacity 

of-} 

Capacity  of  Condenser.  —  (See  Condenser, 
Capacity  of.) 

Capacity  of  Ley  den  Jar.  —  (See  Jar, 
Leyden,  Capacity  of.) 

Capacity  of  Line.  —  (See  Line,  Capacity 
of.) 

Capacity  of  Polarization  of  a  Toltaio 
Cell.—  (See  Cell,  Voltaic,  Capacity  of  Polar- 
ization of.) 

Capacity,  Safe  Carrying,  of  a  Conductor 
—  •  --  The  maximum  electric  current  the 
conductor  will  carry  without  becoming  unduly 
heated. 

Capacity,  Specific  Inductive  -- 
The  ability  of  a  dielectric  to  permit  induction 
to  take  place  through  its  mass,  as  compared 
with  the  ability  possessed  by  a  mass  of  air  of 
the  same  dimensions  and  thickness,  under 
precisely  similar  conditions. 

The  relative  power  of  bodies  for  trans- 
mitting electrostatic  stresses  and  strains 
analogous  to  permeability  in  metals. 

The  ratio  of  the  capacity  of  a  condenser 
whose  coatings  are  separated  by  a  dielectric 
of  a  given  substance  to  the  capacity  of  a 
simflar  condenser  whose  plates  are  separated 
by  a  plate  or  layer  of  air. 


The  inductive  capacity  of  a  dielectric  is  com- 
pared with  that  of  air. 

According  to  Gordon  and  others,  the  specific 
inductive  capacities  of  a  few  substances,  com. 
pared  with  air,  are  as  follows: 

Air i.oo 

Glass 3-013  to  3.258 

Shellac 2.740 

Sulphur 2.580 

Gutta-percha 2.462 

Ebonite 2.284 

India-rubber 2.220  to  2.497 

Turpentine 2.160 

Petroleum 2.030  to  2.070 

Paraffin  (solid) 1-994 

Carbon  bisulphide 1.810 

Carbonic  acid 1.00036 

Hydrogen 0.99967 

Vacuum 0.99941 

Faraday,  who  proposed  the  term  specific  in* 
ductive  capacity,  employed  in  his  experiments  a 
condenser  consisting  of  a  metallic  sphere  A,  Fig. 
99,  placed  inside  a  large 
hollow  sphere  B. 

The  concentric  space 
between  A  and  B  was  filled 
with  the  substance  whose 
specific  inductive  capacity 
was  to  be  determined. 

Capacity,       Specific 

Magnetic A  term 

sometimes  employed  in 
the  sense  of  magnetic 
permeability. 

Conductibility  for  lines 
of  magnetic  force  in  the 
same  sense  that  specific 
inductive  capacity  is  con- 
ductibility  for  lines  of 
electrostatic  force. 

This  term  has  received 
the  name  of  specific  mag-  "•  "• 
netic  capacity  in  order  to  distinguish  it  from  specific 
inductive  capacity.  The  velocity  of  propagation 
of  waves  in  any  elastic  medium  is  proportional  to 
the  quotient  obtained  by  extracting  the  square 
root  of  the  elasticity  of  the  medium  divided  by 
the  square  root  of  its  density;  or, 

v  =  .|f 


Cap.] 


[Car. 


Similarly,  the  speed  with  which  inductive  waves 
travel  depends  on  the  relation  between  the  elas- 
ticity and  the  density  of  the  medium.  Calling  =^? 

the  electric  elasticity,  then  its  reciprocal,  K,  corre- 
sponds with  the  dielectric  capacity.  The  elec- 
trical density,  //,  corresponds  with  the  magnetic 
permeability.  The  velocity  of  wave  transmission 
is  therefore, 


V  = 


Capacity,  Storage,  of  Secondary  Cell 

— (See  Cell,  Secondary  or  Storage,  Capa- 
city of.) 

Capillarity. — The  elevation  or  depression 
of  liquids  in  tubes  of  small  internal  diameter. 

The  liquid  is  elevated  when  it  wets  the  walls, 
and  depressed  when  it  does  not  wet  the  walls  of 
the  tube. 

The  phenomena  of  capillarity  are  due  to  the 
mutual  attractions  existing  between  the  mole- 
cules of  the  liquid  for  one  another,  and  the 
mutual  attraction  between  the  molecules  of  the 
liquid  and  those  of  the  walls  of  the  tube. 

In  capillarity,  therefore,  the  approximately 
level  surface  caused  by  the  equal  attraction  of  all 
the  molecules  towards  the  earth's  centre  is  dis- 
turbed by  the  unequal  attraction  exerted  on  each 
molecule  by  the  walls  of  the  tube  and  by  the  re- 
maining molecules. 

Capillarity,  Effects  of,  on  Toltaic  Cell 

Effects  caused  by  capillary  action 

which  disturb  the  proper  action  of  a  voltaic 
cell. 

These  effects  are  as  follows: 

(i.)  Creeping,  or  efflorescence  of  salts.  (See 
Creeping,  Electric.  Efflorescence.') 

(2.)  Oxidation  of  contacts  and  consequent  in- 
troduction of  increased  resistance  into  the  battery 
circuit.  The  liquid  enters  the  capillary  spaces 
between  the  contact  surfaces  and  oxidizes  them. 

Capillary. — Of  a  small  or  hair-like  diame- 
ter or  size. 

A  capillary  tube  is  a  tube  of  small  hair-like  di- 
ameter. (See  Capillarity.} 

Capillary  Attraction. — (See  Attraction, 
Capillary) 


Capillary  Contact-Key. — (See  Key,  Cap- 
illary Contact?) 

Capillary  Electrometer.— (See  Electrom- 
eter, Capillary) 

Carbon. — An  elementary  substance  which 
occurs  naturally  in  three  distinct  allotropic 
forms,  viz.:  charcoal,  graphite  and  the  dia- 
mond. (See  Allotropy) 

Carbon-Brushes   for  Electric  Motors. — 

(See  Brushes,  Carbon,  for  Electric  Motors) 

Carbon  Button. — (See  Button,  Carbon) 

Carbon-Clutch  or  Clamp  of  Arc  Lamp. 
— (See  Clutch,  Carbon,  of  Arc  Lamp.] 

Carbon-Electrodes  for  Arc  Lamps. — (See 
Electrodes,  Carbon,  for  Arc  Lamps) 

Carbon-Holders  for  Arc  Lamps.— (See 
Holders,  Carbon,  for  Arc  Lamps) 

Carbon  Points. — (See  Points,  Carbon) 

Carbon  Transmitter  for  Telephones.— 
(See  Transmitter,  Carbon,  for  Telephones) 

Carbonic  Acid  Gas.— (See  Gas,  Carbonic 
Acid) 

Carboning  Lamps. — (See  Lamps,  Carbon- 
ing) 

Carbonizable.— Capable  of  being  carbon- 
ized. (See  Carbonization,  Processes  of) 

Carbonization. — The  act  of  carbonizing. 
(See  Carbonization,  Processes  of) 

Carbonization,      Processes    of 

Means  for  carbonizing  material. 

The  carbonizable  material  is  placed  in  suitably 
shaped  boxes,  covered  with  powdered  plumbago 
or  lamp-black,  and  subjected  to  the  prolonged 
action  of  intense  heat  while  out  of  contact  with 
air. 

The  electrical  conducting  power  of  the  carbon 
which  results  from  this  process  is  increased  by  the 
action  ot  the  heat,  and,  probably,  also,  by  the  de- 
posit in  the  mass,  ot  carbon  resulting  from  the 
subsequent  decomposition  of  the  hydro-carbon 
gases  produced  during  carbonization. 

When  the  carbonization  is  for  the  purpose  of 
producing  conductors  for  incandescent  lamps,  in 
order  to  obtain  the  uniformity  of  conducting 
power,  electrical  homogeneity,  purity  and  high 
refractory  power  requisite,  selected  fibrous  ma- 
terial, cut  or  shaped  in  at  least  one  dimension 


Car.] 

prior  to  carbonization,  must  be  taken,  and  sub- 
jected to  as  nearly  uniform  carbonization  as  pos- 
sible. 

Carbonize. — To  reduce  a  carbonizable  ma- 
terial to  carbon.  (See  Carbonization.  Pro- 
cesses of.) 

Carbonized  Cloth  Discs  for  High  Resist- 
ances.—(See  Cloth  Discs  Carbonized,  for 
High  Resistances^) 

Carbonizer.— Any  apparatus  suitable  for 
reducing  carbonizable  material  to  carbon. 

Carbonizing. — Subjecting  a  carbonizable 
substance  to  the  process  of  carbonization. 
(See  Carbonization,  Processes  of,) 

Carbons,  Artificial Carbons  ob- 
tained by  the  carbonization  of  a  mixture  of 
pulverized  carbon  with  different  carbonizable 
liquids. 

Powdered  coke,  or  gas-retort  carbon,  some- 
times mixed  with  lamp-black  or  charcoal,  is  made 
into  a  stiff  dough  with  molasses,  tar,  or  any  other 
hydro-carbon  liquid.  The  mixture  is  molded 
into  rods,  pencils,  plates,  bars  or  other  desired 
shapes  by  the  pressure  of  a  powerful  hydraulic 
press.  After  drying,  the  carbons  are  placed  in 
crucibles  and  covered  with  lamp-black  or  pow- 
dered plumbago,  and  raised  to  an  intense  heat  at 
which  they  are  maintained  for  several  hours.  By 
the  carbonization  of  the  hydro-carbon  liquids,  the 
carbon  paste  becomes  strongly  coherent,  and  by 
the  action  of  the  heat  its  conducting  power  in- 
creases. 

To  give  increased  density  after  baking,  the 
carbons  are  sometimes  soaked  in  a  hydro-carbon 
liquid,  and  subjected  to  a  re-baking.  This  may 
be  repeated  a  number  of  times. 

Carbons,  Concentric-Cylindrical 

A  cylindrical  rod  of  carbon  placed  inside  a  hol- 
low cylinder  of  carbon  but  separated  from  it 
by  an  air  space,  or  by  some  other  insulating, 
refractory  material. 

Jablochkoff  candles  sometimes  are  made  with  a 
solid  cylindrical  electrode,  concentrically  placed 
in  a  hollow  cylindrical  carbon. 

Carbons,  Cored A  cylindrical  carbon 

electrode  for  an  arc  lamp  that  is  molded 
around  a  central  core  of  charcoal,  or  other 
softer  carbon. 


76 


[Car. 


Much  of  the  unsteadiness  of  the  arc  light  is  due 
to  changes  in  the  position  of  the  arc.  Cored  car- 
bons, it  is  claimed,  render  the  arc  light  steadier, 
by  maintaining  the  arc  always  at  the  softer  carbon 
and  hence  at  the  central  point  of  the  electrode. 

A  core  of  harder  carbon,  or  other  refractory 
material,  is  sometimes  provided  for  the  negative 
carbon. 

Carbons,  Flashed Carbons  which 

have  been  subjected  to  the  flashing  pro- 
cess. (See  Carbons,  Flashing  Process  for.) 

Carbons,  Flashing  Process  for A 

process  for  improving  the  electrical  uniformity 
of  the  carbon  conductors  employed  in  in- 
candescent lighting,  by  the  deposition  of  car- 
bon in  their  pores,  and  over  their  surfaces  at 
those  places  where  the  electric  resistance  is 
relatively  great. 

The  carbon  conductor  or  filament  is  placed  in 
a  vessel  filled  with  the  vapor  of  a  hydrocarbon 
liquid  called  rhigolene,  or  any  other  readily  de- 
composable hydrocarbon  liquid,  and  gradually 
raised  to  electric  incandescence  by  the  passage 
through  it  of  an  electric  current  A  decomposi- 
tion of  the  hydrocarbon  vapor  occurs,  the  car- 
bon resulting  therefrom  being  deposited  in  and  on 
the  conductor. 

As  the  current  is  gradually  increased,  the 
parts  of  the  conductor  first  rendered  incandes- 
cent are  the  places  where  the  electric  resist- 
ance is  the  highest,  these  parts,  therefore,  and 
practically  these  parts  only,  receive  the  deposit 
of  carbon.  As  the  current  increases,  other 
portions  become  successively  incandescent  and 
receive  a  deposit  of  carbon,  until  at  last  the 
filament  glows  with  a  uniform  brilliancy,  in- 
dicative of  its  electric  homogeneity. 

A  carbon  whose  resistance  varies  considerably 
at  different  parts  could  not  be  successfully  em- 
ployed in  an  incandescent  lamp,  since  if  heated 
by  a  current  sufficiently  great  to  render  the  points 
of  comparatively  small  resistance  satisfactorily 
incandescent,  the  temperature  of  the  points  of 
high  resistance  would  be  such  as  to  lower  the  life 
of  the  lamp,  while  if  only  those  portions  were 
safely  heated,  the  lamp  would  not  be  economical. 
The  flashing  process  is  therefore  of  very  great 
value  in  the  manufacture  of  an  incandescent 
lamp. 

The  name  "  flashing  "  was  applied  to  the  pro- 
cess by  reason  of  the  flashing  light  emitted  by  the 


Car.] 


77 


[Cas. 


carbons  when  they  have  been  sufficiently  treated. 
The  process  requires  so  little  time  that  the  dull  red 
which  first  appears  soon  flashes  to  the  full  lumin- 
osity required. 

The  term  "flashing"  is  sometimes  applied  to 
the  electrical  heating  to  incandescence,  while  the 
carbons  are  in  the  lamp  chambers,  and  on  the 
pumps.  This  flashing  is  for  the  purpose  of 
driving  off  all  the  gases  occluded  by  the  carbon, 
so  that  these  gases  may  be  carried  off  by  the 
operation  of  pumping.  This  process  is  more 
properly  called  the  process  for  driving  off  the 
occluded  gases. 

The  carbons  are  sometimes  flashed  in  the  liquid 
itself  instead  of  in  its  vapor. 

Carbons,  Paper  —  — Carbons,  of  textile 
or  fibrous  origin,  obtained  from  the  carboniza- 
tion of  paper. 

The  carbonization  of  paper  is  readily  effected 
by  submitting  the  paper  to  the  prolonged  action 
of  a  high  temperature  while  out  of  contact  with 
air. 

For  this  purpose  the  paper  is  packed  in  retorts 
or  crucibles,  and  covered  with  lamp-black,  or 
powdered  plumbago,  in  order  to  exclude  the  air. 

Since  paper  consists  of  a  plane  of  material  uni- 
formly thin  in  one  direction,  formed  almost  en- 
tirely of  fibres  of  pure  cellulose,  the  greatest 
length  of  which  extends  in  a  direction  nearly  par- 
allel to  that  in  which  the  paper  is  uniformly  thin, 
it  is  clear  that  sheets  of  this  substance,  when  car- 
bonized, should  yield  flexible  carbons  of  unusual 
purity  and  electrical  homogeneity,  since  such 
carbons  are  structural  in  character,  and  are  uni- 
formly affected  by  the  heat  of  carbonization  to  an 
extent  that  would  be  impossible  by  the  carboniza- 
tion of  any  material  in  a  mass. 

Carcase  of  Dynamo-Electric  Machine. — 

(See  Machine,  Dynamo-Electric,  Carcase  of.) 
Carcel.— The  French  unit  of  light.  The 
light  emitted  by  a  lamp  burning  42  grammes 
of  pure  colza  oil  per  hour,  with  a  flame  40 
millimetres  in  height. 

The  bec-carcel.  One  carcel  =  9.5  to  9.6  stand- 
ard candles. 

Carcel  Lamp. — (See  Lamp,  Carcel.) 
Carcel  Standard  Gas  Jet. — (See/<?/,  Gas, 

Carcel  Standard) 
Card,  Compass A  card  used  in  the 

mariner's  compass,  on  which  are  marked  the 


four  cardinal  points  of  the  compass  N,  S,  E 
and  W,  and  these  again  divided  into  thirty- 
two  points  called  Rhumbs.  (See  Compass, 
Azimuth?) 

Cardew  Yoltmeter.  —  (See  Voltmeter, 
Cardew.) 

Carriage,  Pen  —  —The  carriage  in  an 
electric  chronograph  which  holds  the  pen  and 
moves  over  the  sheet  of  paper  on  which  the 
record  is  made.  (See  Chronograph,  Elec- 
tric.) 

Carriers  of  Replenisher. — (See  Replen- 
isher,  Carriers  of.) 
Cascade,  Charging  Leyden  Jars  by 

— A  method  of  charging  jars  or  condensers 
by  means  of  the  free  electricity  liberated  by 
induction  from  one  coating,  when  a  charge  is 
passed  into  the  other  coating. 

The  jars  are  placed  as  shown  in  Fig.  100,  with 
the  inside  coating  of  the  first  jar  connected  with 
the  outside  coating  of  the  one  next  it.  There  is  in 


Fig.  TOO.     Cascade  Charging  of  Leyden  Jars. 

reality  no  increase  in  the  entire  charge  obtained 
in  charging  by  cascade,  since  the  sum  of  the 
charges  given  to  the  separate  jars  is  equal  to 
the  same  charge  given  to  a  single  jar  separately 
charged. 

The  energy  of  the  discharge  in  cascade  can  be 
shown  to  be  less  than  that  of  the  same  charge 
when  confined  to  a  single  jar.  This  ic  of  course 
to  be  expected,  since  it  is  energy  that  <?  charged 
in  the  jar  and  not  electricity,  and,  of  course,  the 
energy  charged  in  the  jar  can  never  exceed  the 
energy  employed  in  charging  the  jar.  There  is 
a  small  loss  for  each  jar,  and  this  increases  ne- 
cessarily with  each  jar  added. 

Cascade,  Connection  of  Electric  Sources 

in A  term  sometimes  used  for  series- 
connection  of  electric  sources. 

The  term  series -connection  is  the  preferable 
one.  (See  Connection,  Series.) 

Case-Hardening,  Electric Super- 
ficially converting  a  piece  of  wire  into  steef 
by  electrically  produced  heat. 


Cas.] 


78 


[Can. 


In  electric  case-hardening,  the  superficial  layers 
of  a  piece  of  iron  are  converted  into  steel  by 
electrically  heating  the  same,  while  surrounded 
by  a  layer  of  case-hardening  flux  and  carbonaceous 
substances  such  as  animal  charcoal,  shavings  of 
horn,  leather  cuttings  or  other  similar  substances. 

In  the  case  of  a  readily  oxidizable  metal  like 
Iron,  oxidation  is  prevented  by  surrounding  the 
metal  by  a  hydrocarbon  gas,  which,  when  suffi- 
ciently heated,  deposits  on  the  surfaces  a  pro- 
tective coating  of  carbon.  This  layer  of  carbon 
gradually  carbonizes  the  iron. 

Case  Wiring. — (See  Wiring,  Case.) 

Cataphoresis.— A  term  sometimes  em- 
ployed in  place  of  electric  osmose.  (See  Os- 
mose, Electric!) 

The  word  cataphoresis  applies  to  the  cases  where 
medicinal  substances,  such  as  iodine,  cocoaine, 
quinine,  etc.,  are  caused  to  pass  through  organic 
tissues  in  the  direction  of  flow  of  an  electric  cur. 
rent,  or  from  the  anode  to  the  kathode.  This 
action  is  probably  due  to  an  electrolytic  action. 

Cataphoric  Action. — (See  Action,  Cata- 
phoric^ 

Catch,  Safety A  wire,  plate,  strip, 

or  box  of  readily  fusible  metal,  capable  of  con- 
ducting, without  fusing,  the  current  ordinarily 
employed  on  the  circuit,  but  which  fuses  and 
thus  breaks  the  circuit  on  the  passage  of  an 
abnormally  large  current. 

Safety -catches  are  generally  placed  on  multiple- 
arc  and  multiple-series  circuits.  (See  Fusc% 
Safety.} 

Catelectrotonus.— An  orthography  some- 
times applied  to  Kathelectrotonus.  (See 

Kathelectrotonus!) 

Cathetometer.— An  instrument  for  the  ac- 
curate measurement  of  vertical  height. 

The  cathetometer  consists  essentially  of  an 
accurately  divided  vertical  rod  which  carries  a 
sliding  support  for  a  telescope.  The  telescope  is 
provided  with  two  spider  lines  at  right  angles  to 
one  another,  so  placed  as  to  be  seen  in  front  of 
the  object  whose  height  is  to  be  measured.  From 
observations  taken  in  different  positions,  the 
measurement  of  the  true  vertical  height  is  readily 
obtained. 

Cathion. — A  term  sometimes  used  instead 
Ot  Kathion. 


More  correctly  written  Kathion.  (See 
Kathion!) 

Cathode. — A  term  sometimes  used  instead 
of  Kathode. 

Catoptrics. — That  branch  of  optics  which 
treats  of  the  reflection  of  light. 

Causty,  Galvano A  term  some- 
times used  for  galvano-cautery.  (See  Cautery, 
Galvano!] 

Cauterization. — The  act  of  cauterizing,  or 
burning  with  a  heated  solid  or  caustic  sub- 
stance. 

Cauterization,  Electric Subject- 
ing to  cauterization  by  means  of  a  wire  elec- 
trically heated.  (See  Cautery,  Electric?) 

Cauterize. — To  subject  to  cauterization,  or 
burning  with  a  heated  solid  or  caustic  sub- 
stance. 

Cauterizer,  Electric A  term  some- 
times applied  to  an  electric  cautery.  (See 
Cautery,  Electric!) 

Cautery,  Actual A  burning  or  sear- 
ing with  a  white-hot  metal. 

Cautery  Battery.— (See  Battery,  Cautery!) 

Cautery,  Electric An  instrument 

used  for  electric  cauterization. 

In  electro-therapeutics,  the  application  ol 
variously  shaped  platinum  wires  heated  to  in- 
candescence by  the  electric  current  in  place 
of  a  knife,  for  removing  diseased  growths,  or 
for  stopping  hemorrhages. 

The  operation,  though  painful  during  applica- 
tion, is  afterward  less  painful  than  that  with  a 
knife,  since  secondary  hemorrhage  seldom  occurs, 
and  the  wound  rapidly  heals. 

Electric  cautery  is  applicable  in  cases  where 
the  knife  would  be  inadmissible  owing  to  the 
situation  of  the  parts  or  their  surroundings. 

Cautery,  Galrano A  term  fre- 
quently employed  in  place  of  electric  cautery. 
(See  Cautery,  Electric!) 

Cautery,  Galvano  Electric An 

electric  cautery.  (See  Cautery,  Electric!) 

Cautery,  Galvano  Thermal A 

term  sometimes  used  for  an  electric  cautery, 
(See  Cautery,  Electric!* 


Cau.  7 


79 


[Cel. 


Cautery-Knife  Electrode. — (See  Electrode, 
Cautery-Knife.) 

Cautery,  Thermal  — A  cautery 

heated  by  heat  other  than  that  of  electric  ori- 
gin, as  distinguished  from  an  electric  cautery. 
(See  Cautery,  Electric?) 

Ceiling  Rose. — (See  Rose,  Ceiling!) 

Cell,  Depositing  — An  electrolytic 

cell  in  which  an  electro-metallurgical  deposit  is 
made.  (See  Metallurgy,  Electro?) 

Cell,  Electrolytic A  cell  or  vessel 

containing  an  electrolyte,  in  which  electrolysis 
is  carried  on. 

An  electrolytic  cell  is  called  a  voltameter  when 
the  value  of  the  current  passing  is  deduced  from 
the  weight  of  the  metal  deposited. 

Cell,  Impulsion A  photo-electric 

cell  whose  sensitiveness  to  light  may  be  re- 
stored or  destroyed  by  slight  impulses  given 
to  the  plates,  such  as  by  blows  or  taps,  or  elec- 
tro-magnetic impulses. 

An  impulsion  cell  may  be  prepared  by  pasting 
pieces  of  tin-foil,  the  opposite  faces  of  which  are 
respectively  polished  and  dull,  on  the  opposite 
faces  of  a  plate  of  glass,  so  as  to  expose  dissimi- 
lar sides  to  the  light,  when  the  cells  are  dipped 
in  alcohol. 

Cell,  Photo-Electric A  cell  capa- 
ble of  producing  differences  of  potential 
when  its  opposite  faces  are  unequally  exposed 
to  radiant  energy. 

Photo-voltaic  cells  are  made  hi  a  variety  of 
forms,  both  with  selenium  and  with  different  me- 
tallic substances.  (See  Cell,  Selenittm.) 

Cell,  Porous A  jar  of  unglazed 

earthenware,  employed  in  double-fluid  voltaic 
cells,  to  keep  the  two  liquids  separated. 

The  use  of  a  porous  cell  necessarily  increases 
the  internal  resistance  of  the  cell,  from  the  de- 
crease it  produces  in  the  area  of  cross  section  of 
liquid  between  the  two  elements.  When  the  bat- 
tery is  dismantled,  the  porous  cells  should  be 
kept  under  water,  otherwise  the  crystallization  of 
the  zinc  sulphate  or  other  salt  is  apt  to  produce 
serious  exfoliation,  or  scaling  off,  or  even  to 
crumble  the  porous  cell. 

A  porous  cell  is  sometimes  called  a  diaphragm, 
but  only  properly  so  when  the  cell  is  reduced  to 
a  single  separating  plate.  (See  Cell,  Voltaic.) 


Cell,  Secondary 


— A  term  sometimes 


used  instead  of  storage  cell. 

The  term  secondary  cell  is  used  in  contradis- 
tinction to  primary  or  voltaic  cell. 

Cell.  Secondary  or  Storage,  Boiling  of 

A   term  sometimes    applied   to   the 

gassing  of  a  storage  cell.  (See  Cell,  Storage, 
Gassing  0f.) 

Cell,  Secondary  or  Storage,  Capacity  of 

The  product  of  the  current  in  am- 
peres, by  the  number  of  hours  the  battery  is 
capable  of  furnishing  said  current,  when 
fully  charged,  until  exhausted. 

The  capacity  of  storage  cells  is  given  in  ampere- 
hours.  A  storage  battery  with  a  capacity  of  1,000 
ampere-hours  can  furnish,  say  a  current  of  fifty 
amperes  for  twenty  hours,  or  a  current  of  one 
hundred  amperes  for  ten  hours ;  or  a  current  of 
twenty-five  amperes  for  forty  hours. 

Cell,  Secondary  or  Storage,  Gassing  of 

An  escape  of  gas  due  to  the  decom- 
position of  water  on  passage  of  too  strong  a 
charging  current. 

Cell,  Secondary  or  Storage,  Renovation 

of The  revivifying  or  recharging  of  a 

run-down,  or  discharged  storage  cell. 

Cell,  Secondary  or  Storage,  Time-Fall 

of  Electromotive  Force  of (See 

Force.  Electromotive  of  Secondary  or 
Storage  Cell,  Time-Fall,  0f.) 

Cell,  Secondary  or  Storage,  Time-Rise 

of  Electromotive  Force  of (See 

Force,  Electromotive  of,  Secondary  or 
Storage  Cell,  Time-Rise,  0f.) 

Cell,  Selenium A  cell  consisting 

of  a  mass  of  selenium  fused  in  between  two 
conducting  wires  or  electrodes  of  platinized 
silver  or  other  suitable  metal. 

A  convenient  manner  of  forming  a  selenium 
cell  is  to  wind  two  separate  spirals  of  platinized 
silver  wire  around  a  cylinder  of  hard  wood,  tak- 
ing care  to  maintain  them  a  constant  distance 
apart,  so  as  to  avoid  contact  between  them.  The 
space  between"  these  wires  is  filled  with  fused  sele- 
nium, which  is  allowed  to  cool  gradually. 

Exposure  to  sunlight  reduces  the  resistance  of 
a  selenium  cell  to  about  one-half  its  resistance  in 


CeL] 


80 


[Cel. 


the  dark,  but  neither  the  resistance  nor  the  reduc- 
tion ratio  long  remains  constant. 

A  selenium  cell  produces  a  difference  of  poten- 
tial, or  electromotive  force,  when  one  of  its  elec- 
trode faces  is  exposed  to  light,  while  the  other  is 
kept  in  darkness. 

According  to  Von  Uljanin,  who  experimented 
with  selenium  melted  in  between  two  parallel 
platinized  plates,  cooled  under  pressure,  and  then 
reduced  from  the  amorphous  to  the  sensitive  crys- 
talline variety  by  gradual  cooling  after  two  or 
three  heatings  in  a  paraffine  bath  up  to  195  de- 
grees, the  following  peculiarities  were  observed: 

(i.)  Exposure  of  one  of  the  electrodes  to  sun- 
light produced  an  electromotive  force  which 
causes  a  current  to  flow  from  the  dark  to  the 
illumined  electrode. 

(2.)  The  maximum  electromotive  force  was 
o.  12  volt. 

(3.)  The  electromotive  force  disappeared  instan- 
taneously and  completely  on  the  darkening  of  the 
electrodes. 

(4.)  A  slight  difference  in  the  electromotive 
force  was  observed  when  the  positive  and  nega- 
tive electrodes  were  alternately  exposed  to  the 
light,  the  maximum  electromotive  force  being 
attained  by  the  exposure  of  the  negative  electrode. 

(5.)  If  both  electrodes  are  similarly  illumined 
the  resulting  current  strength  is  decreased  and 
may  reach  zero. 

(6.)  The  action  of  light  is  instantaneous. 

(7.)  Most  of  the  selenium  cells  experimented 
with  exhibited  an  electromotive  force  of  polariza- 
tion. 

(8.)  The  electromotive  force  of  polarization  is 
diminished  by  exposure  to  light. 

(9.)  The  electrical  resistance  and  sensitive- 
ness to  light  as  regards  the  production  of  an 
electromotive  force  decrease  with  time.  This 
is  probably  due  to  a  gradual  change  in  the  allo- 
tropic  state  of  the  selenium.  (See  State,  Allo- 
tropic.) 

(10.)  The  electromotive  force  produced  is  pro- 
portional  to  the  intensity  of  the  illumination  only 
when  the  obscure  rays  or  heat  rays  are  absent. 

(II.)  Of  different  wave  lengths  the  orange-yel- 
low rays  in  the  diffraction  spectrum,  and  the 
greenish-yellow  in  the  prismatic  ppectrum  pro- 
duced the  greatest  effect. 

Among  some  of  the  more  recent  applications 
of  selenium  cells  are  the  following: 

(I.)  A  selenium  cell  is  so  placed  in  a  circuit 
containing  an  electro-magnet  and  switch,  that  on 


one  of  its  electrodes  being  exposed  to  the  de- 
creased illumination  of  coming  night  it  automat- 
ically turns  on  an  electric  lamp,  and,  conversely, 
on  the  approach  of  daylight,  and  the  consequent 
illumination  of  the  electrode,  turns  it  off. 

(2.)  A  device  whereby  the  presence  of  light, 
as  for  example  that  carried  by  a  burglar,  auto- 
matically rings  an  alarm  and  thus  calls  the  atten- 
tion of  the  watchman  of  the  building. 

Cell,  Standard (See  Cell,  Voltaic, 

Standard?) 

Cell,  Storage  — ' Two  relatively  inert 

plates  of  metal,  or  of  metallic  compounds, 
immersed  in  an  electrolyte  incapable  of  acting 
considerably  on  them  until  after  an  electric 
current  has  been  passed  through  the  liquid 
from  one  plate  to  the  other  and  has  changed 
their  chemical  relations. 

A  single  one  of  the  cells  required  to  form 
a  secondary  battery. 

Sometimes,  the  jar  containing  a  single  cell 
is  called  a  storage  cell. 

This  latter  use  of  the  word  is  objectionable. 

A  storage  cell  is  also  called  an  accumulator. 

On  the  passage  of  an  electric  current  through 
the  electrolyte,  its  decomposition  is  effected  and 
the  electro-positive  and  electro-negative  radicals 
are  deposited  on  the  plates,  or  unite  with  them, 
so  that  on  the  cessation  of  the  charging  current, 
there  remains  a  voltaic  cell  capable  of  generating 
an  electric  current. 

A  storage  cell  is  charged  by  the  passage  through 
the  liquid  from  one  plate  to  the  other  of  an  elec- 
tric current,  derived  from  any  external  source. 
The  charging  current  produces  an  electrolytic  de- 
composition of  the  inert  liquid  between  the 
plates,  depositing  the  electro-positive  radicals,  or 
kathions,  on  the  plate  connected  with  the  negative 
terminal  of  the  source,  and  the  electro-negative 
radicals,  or  onions,  on  the  plate  connected  with 
the  positive  terminal. 

On  the  cessation  of  the  charging  current,  and 
the  connection  of  the  charged  plates  by  a  con- 
ductor outside  the  liquid,  a  current  is  produced, 
which  flows  through  the  liquid  from  the  plate 
covered  with  the  electro-positive  radicals,  to  that 
covered  with  the  electro-negative  radicals,  or  in 
the  opposite  direction  to  that  of  the  charging  cur- 
rent. 

The  simplest  storage  cell  is  Plan  id's  cell,  which, 
as  originally  constructed,  consists  of  two  plates  of 


Cel.J 


81 


[Cel. 


lead  immersed  in  dilute  sulphuric  acid,  H2SO4. 
On  the  passage  of  the  charging  current,  the  plates 
A  and  B,  Fig.  101,  dipped  in  H2SO4,  are  covered 
respectively  with  lead  peroxide,  PbO2,  and  finely 
divided,  spongy  lead.  The  peroxide  is  formed  on 
the  positive  plate,  and  the  metallic  lead  on  the 
negative  plate.  The  acid  and  water  should  have 
a  specific  gravity  of  about  1.170.  When  the  cell 
is  fully  charged  the  acid  solution  loses  its  clear- 
ness and  becomes  milky  in  appearance,  and  the 


Figs.  ioi  and  102,     Storage  Cell. 

specific  gravity  increases  to  1. 195.    This  increase 
is  a  good  sign  of  a  full  charge. 

When  the  charging  current  ceases  to  pass,  the 
cell  discharges  in  the  opposite  direction,  viz., 
from  B'  to  A',  that  is,  from  the  spongy  lead  plate 
to  the  peroxide  plate  through  the  electrolyte,  as 
shown  in  Fig.  102. 

As  a  result  of  this  discharging  current  the  per- 
oxide, PbO8,  on  A',  gives  up  one  of  its  atoms  of 
oxygen  to  the  spongy  lead  on  B',  thus  leaving 
both  plates  coated  with  a  layer  of  PbO,  lead 
monoxide,  or  litharge.  When  this  change  is 
thoroughly  effected,  the  cell  becomes  inert,  and 
will  furnish  no  further  current  until  again  charged 
by  the  passage  of  a  current  from  some  external 
source. 

•  In  order  to  increase  the  capacity  of  the  storage 
cells,  and  thus  prolong  the  time  of  their  discharge, 
the  coating  of  lead  monoxide  thus  left  on  each 
of  the  plates,  when  neutral,  is  made  as  great  as 
possible.  To  effect  this,  a  process  called  '  'forming 
the  plates"  is  employed,  which  consists  in  first 
charging  the  plates  as  already  described,  and 
then  reversing  the  direction  of  the  charging  cur- 
rent,  the  currents  being  sent  through  the  cell  in 
alternately  opposite  directions,  until  a  consider, 
able  depth  of  the  lead  plates  has  been  acted  on. 

It  will  be  noticed  that  during  the  action  of  the 
charging  current,  the  oxygen  is  transferred  from 
the  PbO,  on  one  jjlate,  to  the  PbO,  on  the  other 
plate,  thus  leaving  one  Pb,  and  the  other  PbOg; 
and  that  on  discharging,  one  atom  of  oxygen  is 


transferred  from  the  PbO2,  to  the  Pb,  thus  leav- 
ing both  plates  covered  with  PbO.  In  reality 
this  is  but  the  final  result  of  the  action,  hydrated 
sulphate  of  lead,  PbO,  H2SO4,  being  formed, 
and  subsequently  decomposed.  Other  com- 
pounds are  formed  that  are  but  imperfectly  un- 
derstood. 

In  order  to  decrease  the  time  required  for  form- 
ing, accumulators,  or  secondary  cells,  have  been 
constructed,  in  which  metallic  plates  covered  with 
red  lead  Pb3O4  replace  the  lead  plates  in  the 
original  Plante  cell.  On  charging,  the  Pb3O4 
is  peroxidized  at  the  anode,  i.  e.,  converted  into 
PbO2,  and  deoxidized,  and  subsequently  con- 
verted into  metallic  lead  at  the  kathode.  Or,  in 
place  of  the  above  Pb3O4,  red  lead  is  placed  on 
the  anode  and  PbO,  or  litharge,  on  the  kathode. 

Plates  of  compressed  litharge  have  also  been 
recently  used  for  this  purpose.  Storage  cells  so 
formed  have  a  greater  storage  capacity  per  unit 
weight  than  those  in  which  a  grid  is  employed, 
but  a  higher  resistance. 

In  all  cases  where  a  metal  plate  is  employed 
various  irregularities  of  surface  are  given  to  the 
plates,  in  order  to  increase  their  extent  of  surface 
and  to  afford  a  means  for  preventing  the  separa- 
tion of  the  coatings.  The  metallic  form  thus 
provided  is  known  technically  as  a  grid. 

Unless  care  is  exercised,  the  plates  will  bucklt 
from  the  difference  in  the  expansion  of  the  lead 
and  its  filling  of  oxide.  This  buckling  is  attended 
with  lan  increase  in  the  resistance  of  the  cell  and 
the  gradual  separation  of  the  oxides  that  cover  or 
fill  it. 

Cell,    Thermo-Electrfe A  name 

applied  to  a  thermo-electric  couple.  (See 
Couple,  Thermo-Electric^ 

Cell,  Voltaic The  combination  of 

two  metals,  or  of  a  metal  and  a  metalloid, 
which,  when  dipped  into  a  liquid  or  liquids 
called  electrolytes,  and  connected  outside  the 
liquid  or  liquids  by  a  conductor,  will  produce 
a  current  of  electricity. 

Different  liquids  or  gases  may  take  the  place  of 
the  two  metals,  or  of  the  metal  and  metalloid. 
(See  Battery,  Gas.) 

Plates  of  zinc  and  copper  dipped  into  a  solu- 
tion of  sulphuric  acid  and  water,  and  connected 
outside  the  liquid  by  a  conductor,  form  a  simple 
voltaic  cell. 

If  the  zinc  be  of  ordinary  commercial  purity: 


Cel.] 


[Cel. 


and  is  not  connected  outside  the  liquid  by  a  con- 
ductor, the  following  phenomena  occur: 

(i.)  The  sulphuric  acid  or  hydrogen  sul- 
phate, H,,SO4,  is  decomposed,  zinc  sulphate, 
ZnSO4,  being  formed,  and  hydrogen,  H2,  liber- 
ated. 

(2.)  The  hydrogen  is  liberated  mainly  at  the 
surface  of  the  zinc  plate. 

(3.)  The  entire  mass  of  the  liquid  becomes 
heated. 

If,  however,  the  plates  are  connected  outside 
the  liquid  by  a  conductor  of  electricity,  then  the 
phenomena  change  and  are  as  follows,  viz.: 

(i.)  The  sulphuric  acid  is  decomposed  as  be- 
fore; but, 

(2.)  The  hydrogen  is  liberated  at  the  surface  of 
the  copper  plate  only. 

(3.)  The  heat  no  longer  appears  in  the  liquid 
only,  but  in  all  parts  of  the  circuit. 

(4.)  An  electric  current  now  flows  through  the 
entire  circuit,  and  will  continue  so  to  flow  as  long 
as  there  is  any  sulphuric  acid  to  be  decomposed, 
and  zinc  with  which  to  form  zinc  sulphate. 

The  energy  which  previously  appeared  as  heat 
only,  now  appears  in  part  as  electric  energy. 

Therefore,  although  the  mere  contact  of  the 
two  metals  with  the  liquid  will  produce  a  differ- 
ence of  potential,  it  is  the  chemical  potential 
energy  which  became  kinetic  during  chemical 
combination  that  supplies  the  energy  required  to 
maintain  the  electric  current.  (See  Energy, 
Kinetic.  Energy,  Potential.') 

A  voltaic  cell  consists  of  two  plates  of  different 
metals,  or  of  a  metal  and  a  metalloid  (or  of  two 
gases,  or  two  liquids,  or  of  a  liquid  and  a  gas), 
each  of  which  is  called   a 
voltaic  element,  and  which, 
taken  together,  form  what  is 
called  a  voltaic  couple. 

The  voltaic  couple  dips  in- 
to a  liquid  called  an  electro- 
lyte, which,  as  it  transmits 
the  electric  current,  is  de- 
.,  composed  by  it.  The  ele- 
ments are  connected  outside 
the  electrolyte  by  any  con-  Fig'  103. 
ducting  material. 

Direction  of  the  Current. — In  any  voltaic  cell 
the  current  is  assumed  to  flow  through  the  liquid, 
from  the  metal  most  acted  on  to  the  metal  least 
acted  on,  and  outside  the  liquid,  through  the  out- 
side circuit,  from  the  metal  least  acted  on  to  the 
metal  most  acted  on. 


Voltaic 
Couple. 


In  Fig.  103  a  zinc-copper  voltaic  couple  is 
shown,  immersed  in  dilute  sulphuric  acid.  Here, 
since  the  zinc  is  dissolved  by  the  sulphuric  acid, 
the  zinc  is  positive,  and  the  copper  negative  in 
the  liquid.  The  zinc  and  copper  are  of  opposite 
polarities  out  of  the  liquid. 

There  is  still  a  considerable  difference  of  opinion 
as  to  the  exact  cause  of  the  potential  difference  o. 
the  voltaic  cell.  There  can  be  no  doubt  that  a 
true  contact  force  exists,  but  the  chemical  poten- 
tial energy  of  the  positive  plate  is  the  source 
of  energy  which  maintains  the  potential  differ- 
ence. 

The  difference  in  the  polarity  of  the  zinc  and 
copper  in  and  out  of  the  liquid  is  generally  de- 
nied by  most  of  the  later  writers  on  electricity, 
since  tests  by  a  sufficiently  delicate  electrometer 
show  that  the  entire  zinc  plate  is  negative  and 
the  entire  copper  plate  positive.  Remembering, 
however,  the  convention  as  to  the  direction  of 
the  flow  of  the  current,  since  the  current  flows 
from  the  zinc  to  the  copper  through  the  liquid, 
we  may  still  fairly  regard  the  zinc  as  positive  and 
the  copper  as  negative  in  the  liquid.  It  will  be 
remembered,  that  in  every  source  the  polarity 
within  the  source  is  necessarily  opposite  to  the 
polarity  outside  it.  The  copper  plate  is  there- 
fore called  the  negative  plate,  and  the  wire  con- 
nected to  its  end  out  of  the  liquid,  the  positive 
electrode.  Similarly,  the  zinc  plate  is  called  the 
positive  plate,  and  the  wire  connected  to  it  the 
negative  electrode. 

It  will  of  course  be  understood  that  in  the 
above  sketch  the  current  flows  only  on  the  com- 
pletion of  the  circuit  outside  the  cell;  that  is, 
when  the  conductors  attached  to  the  zinc  and 
copper  plates  are  electrically  connected. 

Amalgamation  of  the  Zinc  Plate. — When  zinc 
is  used  for  the  positive  element,  it  will,  unless 
chemically  pure,  be  dissolved  by  the  electrolyte 
when  the  circuit  is  open,  or  will  be  irregularly 
dissolved  when  the  circuit  is  closed,  producing 
currents  in  little  closed  circuits  from  minute  vol- 
taic couples  formed  by  the  zinc  and  such  impuri- 
ties as  carbon,  lead,  or  iron,  etc.,  always  found 
in  commercial  zinc.  (See  Action,  Local,  of  Vol- 
taic Cell.)  As  it  is  practically  impossible  to  ob- 
tain chemically  pure  zinc,  it  is  necessary  b?  amal- 
gamate the  zinc  plate;  that  is,  to  cover  it  with  a 
thin  layer  of  zinc  amalgam. 

Polarization  of  the  Negative  Plate. — Since  the 
evolved  hydrogen  appears  at  the  surface  of  the 
negative  plate,  the  surface  of  this  plate,  unless 


Cel.] 


83 


[CeL 


means  are  adopted  to  avoid  it,  will,  after  a  while, 
become  coated  with  a  film  of  hydrogen  gas,  or 
as  it  is  technically  called,  will  become  polarized. 
(See  Cell,  Voltaic,  Polarization  of.) 

The  effect  of  this  polarization  is  to  cause  a  fall- 
ing off  or  weakening  of  the  current  produced  by 
the  battery,  due  to  the  formation  of  a  counter  - 
electromotive  force  produced  by  the  hydrogen- 
covered  plate ;  that  is  to  say,  the  negative  plate, 
now  being  covered  with  hydrogen,  a  very  highly 
electro-positive  element,  tends  to  produce  a 
current  in  a  direction  opposed  to  that  of  the 
cell  proper.  (See  Force,  Electromotive,  Coun- 
ter.) 

This  decrease  in  current  strength  is  rendered 
still  greater  by  the  increased  resistance  in  the  cell, 
due  to  the  bubbles  of  hydrogen,  and  to  the  de- 
creased electromotive  force,  due  to  the  increase 
in  the  density  of  the  zinc  sulphate,  in  the  casje  of 
zinc  in  hydrogen  sulphate. 

In  the  case  of  storage  cells,  the  counter-elec- 
tromotive force  of  polarization  is  employed  as  the 
source  of  secondary  currents.  (See  Electricity, 
Storage  of.  Cell,  Secondary.  Cell,  Storage.) 

In  order  to  avoid  the  effects  of  polarization  in 
voltaic  cells,  and  thus  insure  constancy  of  cur- 
rent, the  bubbles  of  gas  at  the  negative  plate  are 
mechanically  carried  off  either  by  roughening  its 
surface,  by  forcing  the  electrolyte  against  the 
plate  as  by  shaking,  or  by  a  stream  of  air;  or  else 
the  negative  plate  is  surrounded  by  some  liquid 
or  solid  substance  which  will  remove  the  hydro- 
gen, by  entering  into  combination  with  it.  (See 
Cell,  Voltaic,  Polarization  of.) 

Voltaic  cells  are  therefore  divided  into  cells 
with  one  or  with  two  fluids,  or  electrolytes,  or 
into: 

(i.)  Single-fluid  cells;  and 

(2.)  Double-fluid  cells. 

Very  many  forms  of  voltaic  cells  have  been  de- 
vised. The  following  are  among  the  more  im- 
portant, viz.  :  Of  the  Single-Fluid  Cells,  the 
Grenet,  Poggendorff,  or  Bichromate,  the  Zinc- 
Copper,  the  Zinc-Carbon  and  the  Smee.  Of  the 
Double-Fluid  Cells,  Grove's,  Bunsen's,  Callaud 
or  Gravity,  DanielPs,  Leclancht,  Siemens-Halske 
and  the  Meidinger. 

Of  all  the  voltaic  cells  that  have  been  devised 
two  only,  viz.,  the  Gravity,  a  modified  Daniell, 
and  the  Leclanche,  have  continued  until  now  in 
very  general  use,  the  gravity  cell  being  used  on 
closed-circuited  lines,  and  the  Leclanche  on  open- 
circuited  lines  ;  the  former  being  the  best  suited 


of  all  cells  to  furnish  the  continuous  constant  cur« 
rents  employed  in  most  systems  of  telegraphy, 
and  the  latter  for  furnishing  the  intermittent  cur- 
rents  required  for  ringing  bells,  operating  aniiun- 
ciators,  or  for  similar  work. 

Cell,  Toltaic,  Absorption  and  Genera- 
tion of  Heat  in (See  Heat,  Absorption 

and  Generation  of,  in  Voltaic  Cell.) 

Cell,  Voltaic,  Bichromate A  zinc- 
carbon  couple  used  with  an  electrolyte 
known  as  electropoion,  a  solution  of  bichro- 
mate of  potash  and  sulphuric  acid  in  water. 
(See  Liquid,  Electropoion^ 

Bichromate  of  sodium  or  chromic  acid  are 
sometimes  used  instead  of  the  bichromate  of 
potassium. 

The  zinc,  Fig.  104,  is  amalgamated  and  placed 
between  two  carbon  plates. 
The  terminals  connected 
with  the  zinc  and  carbon 
are  respectively  negative 
and  positive.  In  the  form 
shown  in  the  figure,  the  zinc 
plate  can  be  lifted  out  of 
the  liquid  when  the  cell  is 
not  in  action. 

The  bichromate  cell  is 
excellent  for  purposes  re- 
quiring strong  currents 
where  long  action  is  not 
necessary.  As  this  cell 
readily  polarizes  it  cannot 
be  advantageously  employ-  Fig.  104..  Bichromate 
ed  continuously  for  any  Cell. 

considerable  period  of  time.  It  becomes  depolar- 
ized, however,  when  left  for  some  time  on  open 
circuit 

The  following  chemical  reaction  probably  takes 
place  when  the  cell  is  furnishing  current,  viz. : 
K2Cr2O7  +  7H2SO4  +  $Zn  = 

K2S04  +3ZnS04  +  Crs3(So4)  +  ;H2O. 

This  cell  gives  an  electromotive  force  of  about 
1.9  volts. 

Cell,  Voltaic,  Bnnsen's A  zinc- 
carbon  couple,  the  elements  of  which  are 
immersed  respectively  in  electrolytes  of  dilute 
sulphuric  and  strong  nitric  acids. 

Bunsen's  cell  is  the  same  as  Grove's,  except 
that  the  platinum  is  replaced  by  carbon.  The 
zinc  surrounds  the  porous  cell  containing  the  car« 


Cel.] 


[Cel. 


bon.    The  polarity  is  as  indicated  in  Fig.  105. 
(See  Cell,  Voltaic,  Grove.) 


Fig.  103.    Bunsen  Cell. 

The  Bunsen  cell  gives  an  electromotive  force 
of  about  1.96  volts. 

Cell,  Voltaic,  Calland's A  name 

sometimes  given  to  the  gravity  cell.  (See 
Cell,  Voltaic,  Gravity!) 

Cell,  Voltaic,  Capacity  of  Polarization  of 

• The  quantity  of  electricity  required 

to  be  discharged  by  a  voltaic  cell  in  order  to 
produce  a  given  polarization.  (See  Cell,  Vol- 
taic, Polarization  of.) 

During  the  discharge  of  a  voltaic  cell  an  electro- 
motive force  is  gradually  set  up  that  is  opposed 
to  that  of  the  cell.  The  quantity  of  electricity 
required  to  produce  a  given  polarization  de- 
pends, of  course,  on  the  condition  and  size  of 
the  plates.  Such  a  quantity  is  called  the  capacity 
of  polarization. 

Cell,   Voltaic,  Closed-Circuit A 

voltaic  cell  that  can  be  left  for  a  considerable 
time  on  a  closed  circuit  of  comparatively 
small  resistance  without  serious  polarization. 

The  term  closed-circuit  voltaic  cell  is  used  in 
contradistinction  to  open-circuit  cell,  and  applies 
to  a  cell  that  can  only  be  kept  on  closed  circuit 
for  a  comparatively  short  time. 

Daniell's  cell  and  the  gravity  cell  are  closed-cir- 
cuit cells.  Leclanchd's  is  an  open-circuit  cell. 

Cell,  Voltaic,  Contact  Theory  of 

A  theory  which  accounts  for  the  production 
of  difference  of  potential  or  electromotive 
force  in  the  voltaic  cell  by  the  contact  of  the 
elements  of  the  voltaic  couple  with  one  an- 
other by  means  of  the  electrolyte. 


The  mere  contact  of  two  dissimilar  substances 
through  the  electrolyte  will  produce  a  difference 
of  potential,  but  the  cause  of  the  current  which  a 
voltaic  cell  is  able  to  maintain  is  the  chemical 
potential  energy  which  becomes  kinetic  during 
combination.  (See  Cell,  Voltaic.  Series,  Contact,) 

Most  authorities  explain  the  difference  of 
potential  produced  by  the  contact  of  different 
metals  by  the  fact  that  the  metals  are  sur- 
rounded by  air.  They  point  out  the  fact  that  the 
order  of  the  metals  in  the  contact-series  is 
almost  identical  with  the  order  of  their  electro- 
chemical  power  as  deduced  from  their  chemical 
.equivalents,  and  their  heat  of  combination  with 
oxygen.  It  would  appear,  therefore,  that  the 
difference  of  potential  between  a  metal  and  the 
air  which  surrounds  it,  is  a  measure  of  the  tend- 
ency of  the  metal  to  become  oxidized. 

The  origin  of  the  electromotive  force  of  a  zinc, 
copper  couple,  in  an  electrolyte  of  hydrogen  sul- 
phate, is  the  superior  affinity  of  the  zinc  for  the 
oxygen,  over  that  of  the  copper  for  the  oxygen. 

Cell,  Voltaic,  Creeping   in The 

formation,  by  efflorescence,  of  salts  on  the  sides 
of  the  porous  cup  of  a  voltaic  cell,  or  on  the 
walls  of  the  vessel  containing  the  electrolyte. 
Paraffining  the  portions  of  the  walls  out  of  the 
liquid,  or  covering  the  surface  of  the  liquid  with 
a  neutral  oil,  obviates  much  of  this  difficulty.  (See 
Efflorescence.) 

Cell,  Voltaic,  Daniell's A  zinc- 
copper  couple,  the  elements  of  which  are  im- 
mersed respectively  in  electrolytes  of  dilute 
sulphuric  acid,  and  a  saturated  solution  of 
copper  sulphate. 

In  the  form  of  Daniell's  cell,  shown  in  Fig.  106, 
the  copper  element  is  made  in  the  form  of  a  cylin- 
der c,  and  is  placed  in  a  porous  cell.  The  cop- 
per cylinder  is  provided  with  a  wire  basket  near 
the  top,  filled  with  crystals  of  blue  vitriol,  or  cop. 
per  sulphate,  so  as  to  maintain  the  strength  of  the 
solution  while  the  cell  is  in  use.  The  zinc  is  in 
the  shape  of  a  cylinder  and  is  placed  so  as  to  sur- 
round the  porous  cell.  This  cell  gives  a  nearly 
constant  electromotive  force. 

The  constancy  of  action  of  Daniell's  cell 
depends  on  the  fact  that  for  every  molecule  ol 
sulphuric  acid  decomposed  in  the  outer  cell,  an 
additional  molecule  of  sulphuric  acid  is  supplied 
by  the  decomposition  of  a  molecule  of  copper  sul. 
phate  in  the  inner  cell.  This  will  be  better  ua- 


Cel.] 


85 


tCel. 


derstood  from  the  following  reactions  which  take 

place,  viz.: 

Zn  +  H8SO4  =  ZnSO4  -f-  Hg 
H,  +  CuS04  =  H8SO4  -f  Cu. 
The  H8SO4,  thus  formed  in  the  inner  cell, 

passes  through  the  porous  cell,  and  the  copper  is 

deposited  on  the  surface  of  the  copper  plate. 


Fig  io(>.     Daniell  s  Cell. 

The  Daniell  cell  gives  an  electromotive  force 
of  about  1.072  volts. 

A  serious  objection  to  this  form  of  cell  arises 
from  the  fact  that  the  copper  is  gradually  de- 
posited over  the  surface  and  in  the  pores  of  the 
porous  cell,  thus  greatly  increasing  its  resistance. 
This  difficulty  is  avoided  in  the  gravity  cell.  (See 
Cell,  Voltaic,  Gravity.) 

Cell,    Yoltaic,    Double-Fluid A 

voltaic  cell  in  which  two  separate  fluids  or  elec- 
trolytes are  employed. 

One  of  the  elements  of  the  voltaic  couple  is 
dipped  into  one  of  the  fluids  and  the  other  ele- 
ment into  the  other  fluid.  In  order  to  Iceep  the 
fluids  separate  and  distinct,  they  are  either  sep- 
arated by  means  of  porous  cells,  or  by  the  action 
of  gravity.  (See  Cell,  Porous.  Cell,  Voltaic, 
Gravity.} 

In  the  double-fluid  cell  the  negative  element  is 
surrounded  by  a  liquid  which  is  capable  of  pre- 
venting polarization  by  combining  chemically 
with  the  substance  that  teilds  to  collect  on  its 
surface.  In  the  Daniell  cell  this  substance  is  the 
same  as  that  of  the  negative  plate.  (See  Cell, 
Voltaic,  Polarization  of.) 

Cell,  Toltaic,  Dry A  voltaic  cell 

in  which  a  moist  material  is  used  in  place  of 
the  ordinary  fluid  electrolyte. 


The  term  dry  cell  is  in  reality  a  misnomer, 
since  all  such  cells  are  moistened  with  liquid 
electrolytes. 

The  dry  cell,  like  other  cells,  is  made  in  a 
variety  of  forms.  The  ab- 
sence of  free  liquid  permits 
the  cell  to  be  closed.  A  well 
known  form  of  dry  cell  is| 
shown  in  Fig.  107. 

Cell,  Toltaic,  Effects  of  I 

Capillarity   in (See 

Capillarity,  Effects  of,  in 
Voltaic  Cell.} 

Cell,  Yoltaic,  Exciting 
Liquid  of The  elec- 
trolyte Of  a  Voltaic  Cell.  pig,  107.  Dry  Cell. 

A  voltaic  cell  may  have  a  single  electrolyte,  in 
which  case  it  is  called  a  single-fluid  cell,  or  it  may 
have  two  electrolytes,  in  which  case  it  is  called  a 
double-fluid  cell. 

Cell,  Yoltaic,  Fuller's  Mercury  Bichro- 
mate    — A  zinc-carbon  couple  im- 
mersed in  an  electrolyte  of  electropoion  liquid. 

The  zinc  is  attached  to  a  copper  rod  by  being 
cast  thereto,  and  is  placed  at  the  bottom  of  a 
porous  cell,  where  it  is  covered  by  a  layer  of 
mercury.  The  carbon  plate  is  placed  in  electro- 


Pig.  108     Fuller's  Mercury  Bichromate  CeU. 
poion  liquid,  diluted  with  water  in  the  proportion 
of  three  of  the  former  to  two  of  the  latter.    The 
zinc  is  generally  placed  in  pure  water,  which 
rapidly  becomes  acid. 

The  mercury  effects  the  continuous  amalgama- 
tion of  the  zinc. 

A  Fuller  mercury  bichromate   cell   is  shown 
in  Fig.  1 08. 


Cel.] 


86 


[CeL 


Cell,  Toltaic,  Gravity A  zinc- 
copper  couple,  the  elements  of  which  are  em- 
ployed with  electrolytes  of  dilute  sulphuric  acid 
or  dilute  zinc  sulphate,  and  a  concentrated 
solution  of  copper  sulphate  respectively. 

The  use  of  a  porous  cell  is  open  to  the  objection 
of  increased  internal  resistance.  Moreover,  the 
porous  cell  is  apt  to  receive  a  coating  of  copper 
which  often  deposits  on  the  cell  instead  of  on  the 
copper  plate.  The  gravity  cell  was  devised  in 
order  to  avoid  the  use  of  a  porous  cell.  As  its 
name  indicates,  the  two  fluids  are  separated  from 
each  other  by  gravity. 

The  copper  plate  is  the  lower  plate,  and  is  sur- 
rounded by  crystals  of  copper  sulphate.     The 
tine,  generally  in  the  form  of  an  open  wheel,  or 
^row-foot,    is    sus- 
pended near  the  top 
of  the    liquid,    as 
shown  in  Fig.  109. 

When  the  cell  is 
set  up  with  sul- 
phuric acid,  the  re- 
actions are  the  same 
as  in  the  Daniell 
cell.  When  copper 
sulphate  and  zinc 
sulphate  alone  are 
used,  zinc  replaces 
the  copper  in  the 

copper       sulphate. 

.„,  ,.         .     .v  Ftg.  fOQ.     The  Gravity  CeU. 

The  action  is  then 

merely  a  substitution  process.    (See  Cell,  Voltaic, 
Daniels.) 

A  dilute  solution  of  zinc  sulphate  is  generally 
used  to  replace  the  dilute  sulphuric  acid.  It 
gives  a  somewhat  lower  electromotive  force,  but 
ensures  a  greater  constancy  for  the  cell. 

Cell,   Voltaic,    Grenet A    name 

sometimes  given  to  the  bichromate  cell.    (See 
Cell,  Voltaic,  Bichromate^ 

Cell,  Voltaic,  Grove A  zinc-plati- 
num couple,  the  elements  of  which  are  used 
with  electrolytes  of  sulphuric  and  nitric  acids 
respectively. 

The  zinc,  Z,  Fig.  no,  is  amalgamated  and 
placed  in  dilute  sulphuric  acid,  and  the  platinum, 
P,  in  strong  nitric  acid  (HNO8)  in  a  porous  cell 
to  separate  it  from  the  sulphuric  acid.  (See  C  ell, 
Porous.)  In  the  Grove  cell  the  current  is  moder- 
ately constant,  since  the  polarization  of  the  plati- 


num  plate  is  prevented  by  the  nitric  acid,  which 

oxidizes  and  thus  removes  the   hydrogen  that 

tends  to  be  liberated  at  its  surface.     The  con- 

stancy of  the  current 

is  not  maintained  for 

any  considerable  time, 

since  the  two   liquids 

are    rapidly     decom- 

posed,  or    consumed, 

zinc  sulphate  forming 

in  the  sulphuric  acid, 

and  water  in  the  nitric 

acid. 

The  chemical  reac- 
tions are  as   follows, 
viz.: 
Zn 


6H 


2NQ 


I  to,     Grove's  Cell. 


H2SO4  = 
ZnS04  +  H8; 
2HNO8= 
4H2O  +  2NO; 
08  =  N8O4. 
Nitrate   of    ammo- 
nium is  sometimes   formed  when  the  nitric  acid 
becomes  dilute  by  decomposition.     The  reaction 
is  as  follows  : 

2HN08  -f-  4H8  =  3H8O  +  NH4NO». 

The  cell  gives  an  electromotive  force  of  1.93 
volts. 

When  the  porous  cell  is  good,  the  resistance  of 
the  Grove  cell  may  be  calculated  according  to 
the  following  formula  of  Ayrton: 


R  = 


3-6  Xd 


ohms, 


where  d,  is  the  distance  in  inches  between  the 
platinum  and  zinc  plates,  and  A,  the  square  inches 
of  the  immersed  portion  of  the  platinum  plate. 

Cell,  Voltaic,  Leclanche* A  zinc- 
carbon  couple,  the  elements  of  which  are  used 
in  a  solution  of  sal-ammoniac  and  a  finely 
divided  layer  of  black  oxide  of  manganese 
respectively. 

The  zinc  is  in  the  form  of  a  slender  rod  and 
dips  into  a  saturated  solution  of  sal-ammoniac^ 
NH4C1. 

The  negative  element  consists  of  a  plate  of  car- 
bon, C,  Fig.  in,  placed  in  a  porous  cell,  in  which 
is  a  mixture  of  black  oxide  of  manganese  and 
broken  gas-retort  carbon,  tightly  packed  around 
the.  carbon  plate.  By  this  means  a  greatly  ex 
tended  surface  of  carbon  surrounded  by  black 


CeL] 

oxide  of  manganese,  MnO8,  is  secured.  The  entire 
outer  jar,  and  the  spaces  inside  the  porous  cell  are 
filled  with  the  solution  of  sal-ammoniac. 


87 


Fig.  TIT.     The  Leclanchi  Cell. 


This  cell,  though  containing  but  a  single  fluid, 
belongs,  in  reality,  to  the  class  or  type  of  double- 
fluid  cells,  being  one  in  which  the  negative  ele- 
ment is  surrounded  by  an  oxidizing  substance, 
the  black  oxide  of  manganese,  which  replaces  the 
nitric  acid  or  copper  sulphate  in  the  other  double- 
fluid  cells. 

This  reaction  is  generally  given : 

Zn  +  4NH4Cl  +  2MnO2  =  ZnCl8  +  2NH4C1 
+  2NH8  4-  Mn808  +  H80. 

This  reaction  is  denied  by  some,  who  believe 
the  following  to  take  place : 

Zn  +  2(NH4C1)  =  ZnCl8  +  2NH,  +  H8. 
The  ZnCl2  and  NH8  react  as  follows : 
ZnCl8  +  2(NH3)  =  2  (NHj)  ZnCl2  +  H8. 

2H  +  2(MnzO2)  =  H8O  -f  Mn2O3; 
or,  possibly,  4.H  -f-  3MnO8  =  Mn2O  -}-  2HtO. 

The  Leclanche  cell  gives  an  electromotive  force 
of  about  1.47  volts.  It  rapidly  polarizes,  and 
cannot,  therefore,  give  a  steady  current  for  any 
prolonged  time.  When  left  on  open  circuit,  how- 
ever, it  quickly  depolarizes. 

Cell,  Toltaic,  Local  Action  of 

(See  Action,  Local,  of  Voltaic  Cell.} 

Cell,  Toltaic,  Meidinger A  zinc- 
copper  couple,  the  elements  of  which  are  em- 
ployed with  dilute  sulphuric  acid,  or  solution 
of  sulphate  of  magnesia,  and  strong  nitric 
acid,  respectively. 

The  Meidinger  cell  is  a  modification  of  the 
Daniell  cell.  The  zinc-copper  couple  is  thus  ar- 
ranged :  Z  Z,  Fig.  112,  is  an  amalgamated  zinc 
ring  placed  near  the  walls  of  the  vessel,  A  A, 
constricted  at  b  b.  The  copper  element,  c,  is 
similarly  placed  with  respect  to  the  walls  of  the 
vessel  d  d.  The  glass  cylinder  h,  filled  with 


[Cel. 

crystals  of  copper  sulphate,  has  a  small  hole  in 
its  bottom,  and  keeps  the  vessel,  d  d,  supplied 
with  saturated  so- 
lution  of  copper 
sulphate,,  The  cell 
is  charged  with  di- 
lute sulphuric  acid, 
or  a  dilute  solution 
of  Epsom  salts,  or 
magnesium  sul- 
phate. 

Cell,    Voltaic, 
Open-Circuit 

A  voltaic 

cell  that  cannot  be 
kept  on  closed  cir- 
cuit, with  a  com- 
paratively small 

resistance,  for  any   Fig.  112.     The  Meidinger  Cell. 

considerable  time  without  serious  polariza- 
tion. 

A  Leclanche'  cell  is  an  open-circuit  cell.  The 
term  open-circuit  cell  is  used  in  contradistinc- 
tion to  closed-circuit  cell,  such  as  the  Daniell. 
(See  Cell,  Voltaic,  Closed-Circuit.) 

Cell,    Voltaic,   Poggendorff  —A 

name  sometimes  given  to  the  Grenet  cell.  (See 
Cell,  Voltaic,  Grenet.} 

Cell,  Voltaic,  Polarization  of The 

collection  of  a  gas,  generally  hydrogen,  on  the 
surface  of  the  negative  element  of  a  voltaic 
cell. 

The  collection  of  a  positive  substance  like  hydro- 
gen on  the  negative  element  or  plate  of  r-  voltaic 
cell  sets  up  a  counter-electromotive  force,  which 
tends  to  produce  a  current  in  the  opposite  direc- 
tion to  that  produced  by  the  cell.  (See  Force, 
Electromotive,  Counter.) 

Polarization  causes  a  decrease  in  the  normal 
current  of  a  voltaic  cell: 

(I.)  On  account  of  the  increased  resistance  of 
the  cell  from  the  bubbles  of  gas  which  form  part 
of  its  circuit. 

(2.)  On  account  of  the  counter -electromotive 
force,  produced  by  polarization. 

There  are  three  ways  in  which  the  ill  effects  of 
the  polarization  of  a  voltaic  cell  can  be  avoided. 
These  are  : 

(i.)  Mechanical.—  The  negative  plate  is  fur- 
nished with  a  roughened  surface  which  enables  th« 


CeU] 


88 


fCel. 


bubbles  of  gas  to  escape  from  the  points  on  such  »ur - 
face  ;  or,  a  stream  of  gas,  or  air,  is  blown  through 
the  liquid  against  the  plate  and  thus  mechanically 
brushes  the  bubbles  off. 

(2.)  Chemical. — The  surface  of  the  negative 
plate  is  surrounded  by  some  powerful  oxidizing 
substance,  such  as  chromic  or  nitric  acid,  which 
is  capable  of  oxidizing  the  hydrogen,  and  thus 
thoroughly  removing  it  from  the  plate. 

The  oxidizing  substance  may  form  th»  entire 
electrolyte,  as  is  the  case  of  the  bichromate  solution 
employed  in  the  zinc-carbon  couple.  Generally, 
however,  it  has  been  found  preferable  to  employ 
a  separate  liquid,  like  nitric  acid,  to  completely 
surround  the  negative  plate,  and  another  liquid  for 
the  positive  plate,  the  two  liquids  being  generally 
kept  from  mixing  by  a  porous  cell,  or  diaphragm. 
Such  cells  are'  called  double-fluid  cells.  (See 
Cell,  Voltaic,  Double- Fluid.) 

(3.)  Electro-Chemical. — This  also  necessitates  a 
double-fluid  cell.  The  negative  element  is  im- 
mersed in  a  solution  of  a  salt  of  the  same  metal  as 
that  forming  the  negative  plate.  Thus,  a  cop. 
per  plate,  immersed  in  a  solution  of  copper  sul 
phate,  cannot  be  polarized,  since  metallic  copper 
is  deposited  on  its  surface  by  the  action  of  the 
hydrogen  which  tends  to  be  liberated  there. 

The  constancy  of  action  of  a  Daniell  cell  depends 
on  a  deposition  of  metallic  copper  on  its  copper 
plate  as  well  as  on  the  formation  of  hydrogen 
sulphate,  and  the  solution  of  additional  copper 
sulphate  from  the  crystallized  salt  placed  in  the 
cell.  (See  Cell,  Voltaic,  Daniell's.) 

Cell,  Voltaic,  Primary,  Exhaustion  of 

The  inability  of  a  primary  voltaic 

cell  to  furnish  any  further  current,  unless 
fresh  electrolyte,  or  fresh  positive  element,  or 
both,  are  supplied  to  it. 

In  the  case  of  exhaustion  of  a  primary  voltaic 
cell  the  stock  of  fresh  energy  is  supplied  to  the 
cell  from  the  chemical  potential  energy  of  the 
positive  element,  or  of  the  electrolyte  or  elec- 
trolytes. (See  Energy,  Chemical  Potential.) 

In  most  voltaic  cells  a  marked  decrease  in  the 
current  strengtk  is  observed  soon  after  the  cir- 
cuit is  closed,  and,  therefore,  long  before  the 
cell  is  exhausted.  This  decrease  is  due— 

(i.)  To  the  increased  internal  resistance  due  to 
the  bubbles  of  hydrogen  on  the  negative  plate. 

(2.)  To  the  counter-electromotive  force  of  po- 
larization,  where  zinc  is  employed  with  an  elec. 
trolyte  of  sulphuric  acid. 


(3.)  To  the  decrease  in  the  electromotive  force 
due  to  an  increase  in  the  density  of  the  zinc  sul- 
phate. 

Cell,  Voltaic,  Secondary,  Exhaustion  of 

The  inability  of  a  secondary  cell  to 

furnish  any  further  current,  unless  fresh 
electro-positive  and  electro-negative  materials 
are  formed  in  it  by  the  passage  of  the 
charging  current. 

In  the  case  of  the  exhaustion  of  a  secondary 
voltaic  cell,  the  stock  of  fresh  energy  supplied 
to  the  cell  is  derived  from  the  electric  energy 
of  the  charging  current.  (See  Energy,  Electric.) 

Cell,  Voltaic,  Siemens-Halske 

A  zinc-copper  couple,  the  elements  of  which 
are  employed  with  dilute  sulphuric  acid  and 
saturated  solution  of  copper  sulphate  respect- 
ively. 

The  Siemens-Halske  cell  is  a  modification  of 
Darnell's.  A  ring  of  zinc,  Z  Z,  Fig,  113,  sur- 


Fig  113'     Siemens- Halskt  Cell. 

rounds  the  glass  cylinder,  c  c.  The  porous 
cell  is  replaced  by  a  diaphragm,  f  f,  of  porous 
paper,  formed  by  the  action  of  sulphuric  acid  on 
a  mass  of  paper  pulp.  Crystals  of  copper  sul- 
phate are  placed  in  the  glass  jar,  c  c,  and  rest 
on  the  copper  plate,  k,  formed  of  a  close  copper 
spiral.  Terminals  are  attached  at  b  and  h.  The 
entire  cell  is  charged  with  dilute  sulphuric  acid. 
The  resistance  of  the  cell  is  high, 

Cell,  Voltaic,  Silver  Chloride A 

zinc  and  silver  couple  immersed  in  electro- 
lytes of  sal-ammoniac  or  common  salt  and 
silver  chloride. 


Cel.] 


89 


[Cel. 


The  zinc  acts  as  the  positive  element,  and  a 
silver  wire,  around  which  a  cylinder  of  fused 
silver  chloride  is  cast,  as  the  negative  element. 
The  zinc,  and  the  silver  wire  and  silver  chloride, 
are  placed  in  a  small  glass  test-tube  and  covered 
with  the  sal-ammoniac  or  common  salt,  and 
the  tube  closed  by  a  cork  of  paraffin,  to  prevent 
the  evaporation  of  the  electrolyte.  When  sal- 
ammoniac  is  used,  the  strength  of  the  solution  is 
that  obtained  by  dissolving  23  grammes  of  pure 
sal-ammoniac  in  I  litre  of  water.  The  silver 
chloride  acts  as  a  depolarizer. 

This  cell  is  used  as  a  standard  cell,  known  as 
De  la  Rue's  standard  cell,  from  its  inventor, 
Warren  De  la  Rue.  Its  electromotive  force  is 
1.068  volts. 

Cell,  Yoltaic,  Simple Any  voltaic 

cell  formed  of  a  single  couple  immersed  in  a 
single  exciting  liquid. 

Cell,  Toltaic,  Single-Fluid A  vol- 
taic cell  in  which  but  a  single  fluid  or  elec- 
trolyte is  used. 

Single-fluid  voltaic  cells  possess  the  disadvan- 
tage of  polarizing  during  action.  This  polariza- 
tion is  due  to  the  electro-positive  element  of  the 
electrolyte  collecting  on  the  surface  of  the  nega- 
tive plate,  or  within  its  mass.  For  example, 
where  dilute  sulphuric  acid  is  the  electrolyte, 
hydrogen  gas  collects  on  the  negative  plate  and 
lowers  the  electromotive  force  produced  by  the 
cell,  by  a  counter-electromotive  force  thereby 
generated.  (See  Force,  Electromotive.  Force, 
Electromotive,  Counter.) 

Cell,  Toltaic,  Since A  zinc-silver 

couple  used  with  an  electrolyte  of  dilute  sul- 
phuric acid,  H2SO4. 

A  form  of  Smee  cell  is  shown  in  Fig.  1 14.  Here 
the  plate  of  silver  is  placed  between  two  zinc 
plates. 

The  silver  plate  is  roughened  and  covered  with 
a  coating  of  metallic  platinum,  in  the  condition 
known  asplatinum  black.  (See  Platinum  Black.) 
This  cell  was  formerly  extensively  employed  in 
tlectro-metallurgy  but  is  now  replaced  by  dynamo- 
tlectric -machines.  (See  Metallurgy,  Electro. 
Machine,  Dynamo-Electric. ) 

A  zinc-carbon  couple  is  sometimes  used  to  re- 
place the  zinc-silver  couple.  A  couple  of  zinc- 
lead  is  also  used,  though  not  very  advanta- 
geously. 


The  Smee  cell  was  one  of  the  earliest  forms 
of  voltaic  cells. 

In  the  zinc-silver  couple  the  chemical  reaction 
that  takes  place   when  the 
cell  is  furnishing  current  is 
as  follows,  viz. : 
Zn  +  H8SO4  ==  ZnSO4 

+  H2. 

The  Smee  cell  gives  an 
electromotive  force  of  about 
.65  volt. 

Cell,  Voltaic,  Stand- 
ard   A  voltaic  cell 

the  electromotive  force  of 
which  is  constant,  and  Fig-  114.  Smee  Cell. 
which,  therefore,  may  be  used  in  the  measure- 
ment of  an  unknown  electromotive  force. 

Absolute  constancy  of  electromotive  force  is 
impossible  to  attain,  but  if  the  current  of  the 
standard  cell  is  closed  but  for  a  short  time  the 
electromotive  force  may  be  regarded  as  practically 
invariable. 

Cell,  Toltaic,  Standard,  Clark's 

The  form  of  standard  cell  shown  in  Fig.  115. 

Latimer  Clark's  standard  cell  assumes  a 
variety  of  forms.  The  H-form  is  arranged  as 
shown  in  Fig.  115.  The  vessel  to  the  left  con- 
tains, at  A,  an  amal- 
gam of  pure  zinc.  The 
other  vessel  contains, 
at  M,  mercury  covered 
with  pure  mercurous 
sulphate,  Hg8  SO4. 
Both  vessels  are  then 
filled,  above  the  level 
of  the  cross  tube,  with 
a  saturated  solution  of 
zinc  sulphate  Z,  Z,  to 
which  a  few  crystals 
of  the  same  are  added. 
Tightly  fitting  corks 

C,  C,  prevent  loss  by  Fig.  sij.    Clark's  Stand- 
evaporation.  *rd  Cell. 

The  voltage  of  this  cell  in  legal  volts  is  1.438 
[i  —0.00077  (*  —  15  degrees  C.)]—(Ayrton.) 

The  value  t,  is  the  temperature  in  degrees  of 
the  centigrade  scale. 

Cell,  Toltaic,  Standard,  Rayleigh's  Form 

of  Clark's A  modified  form  of  Clark's 

cell. 


\\ 


w 


Cel.] 


90 


[Cel. 


Lord  Rayleigh's  form  of  Clark's  standard  cell 
is  shown  in  Fig.  116.  The  electrodes  pass  respect- 
ively through  the  bottom  and  top  of  the  test  tube 
of  glass.  On  the  lower 
electrode  a  layer  of  mer- 
cury, Hg,  is  placed.  On 
this  rests  a  layer  of  mercu- 
rous  sulphate  paste  made 
sufficiently  semi-fluid  with 
a  solution  of  zinc  sulphate 
to  form  an  approximately 
level  surface.  The  zinc, 
Zn,  is  attached  to  the  up- 
per electrode  and  is  im- 
mersed in  this  semi-fluid 
paste. 

The  mercurous  sulphate 
appears  to  act  to  keep  the 
mercury  free  from  impuri- 
ties. 

The  electromotive  force  j 
of  this  cell  has  been  care- 
fully determined  by  Ray-   Fig    Ilt>      Rayieigh<s 
leigh.     Its  value  in  true         Form     of    Clark's 

volts  is  :  Standard  Cell. 

E=  1.435  t1  —  .00077  (t —  15)]  when  t,  is  the 
temperature  in  degrees  Centigrade. 

This  cell  is  often  called  Clark's  normal  element. 

Cell,  Voltaic,  Standard,  De  la  Rue's 

— A  form  of  silver-chloride  cell.     (See  Cell, 
Voltaic,  Silver-Chloride?) 

Cell,  Voltaic,  Stand- 
ard, Fleming's  — 
The  form  of  standard 
cell  shown  in  Fig.  117. 

The  U-tube,  Fig.  117, 
is  connected,  as  shown, 
by  means  of  taps,  with 
two  vessels  filled  with 
chemically  pure  solutions 
of  copper  sulphate  of  sp. 
gr.  i.i  at  15  degrees  C., 
and  zinc  sulphate  of  sp. 
gr.  1.4  at  15  degrees  C. 
respectively.  To  use  the 
cell  the  zinc  rod  Zn,  con- 
nected with  a  wire  pass- 
ing through  a  rubber 
stopper,  is  placed  in  the 
left-hand  branch.  The  tap  A,  is  opened  and 
the  entire  U-tube  is  filled  with  the  denser 
zinc  sulphate  solution.  The  tap  at  C,  is  then 


opened,  and  the  liquid  in  the  right-hand  branch 
above  the  tap  is  discharged  into  the  lower  vessel, 
but,  from  this  part  only.  The  tap  C,  is  then 
closed,  and  the  tap  B,  opened,  and  the  lighter 
copper  sulphate  allowed  to  fill  the  right-hand 
branch  above  the  tap  C.  The  copper  rod  Cu,  fitted 
to  a  rubber  stopper  and  connected  with  a  con- 
ducting wire,  is  then  placed  in  the  copper  solution. 
Tubes  are  provided  at  L  and  M,  for  the  recep- 
tion of  the  zinc  and  copper  rods  when  not  in  use. 
The  copper  rod  is  prepared  for  use  by  freshly 
electro-plating  it  with  copper.  The  electro- 
motive force  of  this  cell  is  1.074  volts.  If  the  line 
of  demarkation  between  the  two  liquids  is  not 
sharp,  the  arms  of  the  vessels  are  emptied,  and 
fresh  liquid  is  run  in. 

Cell,  Voltaic,  Standard,  Lodge's 

A  form  of  standard  Daniell  cell. 

Lodge's  standard  cell  is  shown  in  Fig.  118. 
Through  the  tube  T,  in  a 
wide  mouthed  bottle,  is 
passed  the  glass  tube,  in  the 
mouth  of  which  is  placed  a 
zinc  rod.  To  the  bottom  of 
the  tube  T,  a  small  test-tube 
t,  containing  crystals  of  cop- 
per sulphate,  is  fastened  by 
means  of  a  string  or  rubber 
band.  The  uncovered  end 
of  a  gutta-percha  insulated 
copper  wire  projects  at  the 
bottom  of  t,  through  a  tube 
in  a  tightly  fitting  cork,  and 
forms  the  copper  electrode.  The  bottle  is  partly 
filled  as  shown  with  a  solution  of  zinc  sulphate. 

The  internal  resistance  of  this  cell  is  so  high 
that  it  is  only  employed  in  the  use  of  zero  methods 
with  a  condenser. 

Cell,  Voltaic,  Standard,  Sir  William 
Thomson's  -  — A  form  of  standard 
Daniell  cell. 


Fig.  118.    Lodges 
Form  of  Daniell' s  Cell. 


Fig.  117.    Fleming's 
Standard  Cell. 


Fig.  1 19.     Thomson's  Form  of  Daniell' s  Cell. 

Sir  Wm.  Thomson's  standard  cell  is  shown  in 
Fig.'  119.   A  zinc  disc  is  placed  at  the  bottom  of  the 


Cel.]  1 

cylindrical  vessel  and  a  solution  of  zinc  sulphate 
01  tp.  gr.  1.2  poured  over  it.  By  means  of  the 
funnel  F,  a  half-saturated  solution  of  copper 
sulphate  is  carefully  poured  over  this  and  floats 
on  it  owing  to  its  smaller  density.  The  electro, 
motive  force  of  this  cell  is  1.072  true  -volts  at 
15  degrees  C. 

Cell,  Voltaic,  Standardizing  a De- 

cermining  the  exact  value  of  the  electromotive 
force  of  a  voltaic  cell,  in  order  to  enable  it  to 
be  used  as  a  standard  in  determining  the 
electromotive  force  of  any  other  electric 
source. 

Cell,  Toltaic,  Two-Fluid A  term 

sometimes  employed  in  place  of  double-fluid 
cell.  (See  Cell,  Voltaic,  Double-Fluid) 

Cell,    Toltaic,  Water A    voltaic 

cell  in  which  the  exciting  liquid  is  merely 
water. 

Any  voltaic  couple  can  be  used,  the  positive 
element  of  which  is  acted  on  by  water.  (See 
Battery,  Voltaic.) 

Cell,    Toltaic,     Zinc-Carbon A 

cell  in  which  zinc  and  carbon  form  the  posi- 
tive and  negative  elements  respectively. 

A  name  sometimes  given  to  the  bichro- 
.nate  cell. 

Cell,     Toltaic,    Zinc-Copper A 

cell  in  which  zinc  and  copper  form  the  posi- 
tive and  negative  elements  respectively. 

Cell,  Toltaic  Zinc-Lead —A  zinc- 
lead  couple  sometimes  used,  though  not  very 
advantageously,  to  replace  the  zinc-silver 
couple  in  a  Smee  cell.  (See  Cell,  Voltaic, 
Smee) 

Cells,  Coupled A  number  of  sep- 
arate cells  connected  in  any  way  so  as  to 
(orm  a  single  source. 

Cells,  Toltaic,  Series-Connected 

A  number  of  separate  voltaic  cells  connected 
in  series  so  as  to  form  a  single  source.  (See 
Circuit,  Series) 

Cement-Lined  Conduit  —  (See  Conduit. 
Cement-Lined) 

Cements,      Insulating   — Various 

mixtures  of  gums,  resins  and  other  substances, 
possessing  the  ability  to  bind  two  or  more 
4— Vol.  1 


[Chm 

substances  together  and  yet  to  eleL-traally  in- 
sulate one  from  the  other. 

Centi. — (As  a  prefix) — The  one-hundredth 
part  of. 

Centi-Ampe're. — One-hundredth  of  an  am- 
pere. 

Centi-AmpSre  Balance.— (See  Balance, 
Centi-Ampere) 

Centigrade  Thermometer  Scale.  —  (See 
Scale,  Centigrade  Thermometer)  i 

Centigramme.— The  hundredth  of  a 
gramme 

One  centigramme  equals  0.1544  grains  avoir- 
dupoise.  (See  Weights  and  Measures,  Metric 
System  of.) 

Centilitre.— The  hundredth  of  a  litre. 
One  centilitre  equals  0.6102  of  a  cubic  inch. 
(See  Weights  and  Measures,  Metric  System  of.) 

Centimetre.— The  hundredth  of  a  metre. 
One   centimetre   equals   0.3937   inch.       (See 
Weights  and  Measures,  Metric  System  of.) 

Centimetre-Gramme-Second  TJnits.— (Se« 

Units,  Centimetre-Gramme-Second) 

Central  Galvanization.— (See  Galvaniza- 
tion, Central) 

Central  Station.— (See  Station,  Central) 

Central  Station  Burglar  Alarm.— (See 
Alarm,  Burglar,  Central  Station) 

Central  Station  Lighting.— (See  Light- 
ing, Electric  Central  Station) 

Centre  of  Gravity.— (See  Gravity,  Centre 

Centre  of  Oscillation.— (See  Oscillation, 
Centre  of) 

Centre  of  Percussion. — (See  Percussion, 
Centre  of) 

Centrifugal  Force.— (See  Force,  Centrtfu* 
gal) 

Centrifugal  Governor. — (See  Governor. 
Centrifugal) 

Chain  Lightning.  —  (See  Lightning, 
Chain) 

Chain,  Linked  Magnetic  and  Electric 

A  chain  of  three  links,  the  separate 

links  of  which  consist  of  the  primary  circuit, 


Cha.j 


/Cha, 


the  magnetic  circuit,  and  the  secondary  cir- 
cuit respectively,  of  an  induction  coil. 

The  conception  of  a  linked  magnetic  and  elec- 
tric chain,  in  studying  the  action  of  an  induction 
cofl,  was  first  developed  by  Kapp.  A  linker1 
magnetic  and  electric  chain  is  shown  in  Fig.  120. 


Fig.  1 20.    Linked  Magnetic  and  Electric  Chain. 

li,  in  such  a  case,  the  magnetic  core  or  circuit  is 
of  varying  magnetization,  when  one  of  the  electric 
circuits  has  a  periodic  current  passed  through 
it,  the  various  phenomena  of  the  induction  cofl 
are  produced.  (See  Coil,  Induction.) 

Chain,  Molecular A  polarized  chain 

of  molecules  that  is  supposed  to  exist  in  an 
electrolyte  during  its  electrolytic  decomposi- 
tion, or  in  a  voltaic  cell  on  closing  its  circuit. 
(See  Hypothesis,  Grotthus.) 

Chain  Pull.— (See  Pull,  Cham.) 

Chamber,  Armature The  armature 

bore.  (See  Bore.  Armature?) 

Chamber  of  Lamp. — (See  Lamp,  Cham- 
ber of.) 

Change,  Chemical Any  change  hi 

matter  resulting  from  atomic  combination 
and  the  consequent  formation  of  new  mole- 
cules. 

Some  chemical  changes  are  caused  by  atomic 
combinations  and  the  formation  of  new  molecules. 
They  are  necessarily  attended  by  ?  loss  of  the  spe- 
cific identity  of  the  substances  involved  in  the 
change.  Thus  carbon,  a  black  solid,  combined 
with  sulphur,  a  yellow  solid,  produces  carbon 
disulphide,  a  colorless,  odorous  liquid.  (See 
Atom.) 

Change,  Physical Any  change  hi 

matter  resulting  from  a  change  in  the  relative 
position  of  its  molecules,  without  the  forma- 
tion of  new  molecules. 

Ice,  when  heated,  is  turned  into  water;  steel, 
when  stroked  by  a  magnet,  is  rendered  perma- 
nently magnetic;  a  piece  of  vulcanite  or  hard 


rubber  stroked  by  a  piece  of  cat  skin  becomes 
electrified.  In  all  these  cases,  which  are'instances 
of  physical  changes,  the  substances  retain  their 
specific  identity,  This  is  true  in  all  cases  of  phys- 
ical changes.  (See  Molectile.) 

Changing-over  Switch. — (See  Switch, 
Changing-over^ 

Changing  Switch. — (See  Switch,  Chang- 
ing.) 

Characteristic  Curre. — (See  Curve, 
Characteristic) 

Characteristic  Curve  of  Parallel  Trans- 
former.— (See  Curve,  Characteristic,  of 
Parallel  Transformer?) 

Characteristic  Curve  of  Series  Trans- 
former.— (See  Curve,  Characteristic,  of 
Series  Transformer^ 

Characteristics  of  Sound.— (See  Sound, 
Characteristic  of.) 

Charge ,  Bound The  condition  of 

an  electric  charge  -on  a  conductor  placed  near 
another  conductor,  but  separated  from  it  by 
a  medrum  through  which  electrostatic  induc- 
tion can  take  place.  (See  Induction,  Elec- 
trostatic) 

When  a  charged  conductor  is  placed  near  an- 
other conductor,  but  separated  from  it  by  a  di- 
electric or  medium  through  which  induction  can 
take  place,  a  charge  of  the  opposite  name  is  in- 
duced in  the  neighboring  conductor.  This  charge 
is  so  held  or  bound  on  the  conductor  by  the  mu- 
tual attraction  of  the  opposite  charge  that  it  is 
not  discharged  on  connection  with  the  earth 
unless  both  conductors  are  simultaneously  touched 
by  any  good  conductor.  The  bound  charge  was 
formerly  called  dissimulated  or  latent  electricity. 
(See  Electricity,  Dissimulated  or  Latent.) 

Charge,  Density  of The  quantity 

of  electricity  per  unit  of  area  at  any  point  on 
a  charged  surface. 

Coulomb  used  the  phrase  surface  density  to 
mean  the  quantity  of  electricity  per  unit  of  area 
at  any  point  on  a  surface. 

Charge,  Dissipation  of The  gradual 

but  final  loss  of  any  charge  by  leakage,  which 
occurs  even  in  a  well  insulated  conductor. 

This  loss  is  more  rapid  with  negatively  charged 
conductors,  than  with  those  positively  charged. 


Crookes,  of  England,  has  retained  a  charge  on 
conductors  for  years,  without  appreciable  leakage, 
by  placing  the  conductors  in  vessels  in  which  a 
kigh  vacuum  was  maintained.  (See  Vacuum, 
High.) 

Charge,  Distribution  of The  vari- 
ations that  exist  in  the  density  of  an  electrical 
charge  at  different  portions  of  the  surface  of 
all  insulated  conductors  except  spheres. 

The  density  of  charge  varies  at  different  points 
of  the  surface  of  conductors  of  various  shapes.  It 
is  uniform  at  all  points  on  the  surface  of  a  sphere. 

It  is  greater  at  the  extremities  of  the  longer 
axis  of  an  egg-shaped  body,  and  greatest  at  the 
sharper  end. 

It  is  greater  at  the  corners  of  a  cube  than  at 
the  middle  of  a  side. 

It  is  greatest  around  the  edge  of  a  circular  disc. 

It  is  greatest  at  the  apex  oi  a  cone 

Charge,  Electric The  quantity  of 

electricity  that  exists  on  the  surface  of  an  in- 
sulated electrified  conductor. 

When  such  a  conductor  is  touched  by  a  good 
conductor  connected  with  the  earth,  it  is  dis- 
charged. (See  Condenser.) 

Charge,  Free The  condition  of  an 

electric  charge  on  a  conductor  isolated  from 
any  other  conductor. 

It  is  impossible  to  obtain  a  perfectly  free  charge, 
since  it  is  impossible  to  complete^  isclate  an 
insulated  conductor.  The  charge,  however,  can 
be  comparatively  free. 

The  charge,  on  a  completely  isolatea  conductor 
readily  leaves  it  when  it  is  put  in  contact  with  a 
good  conductor  connected  with  the  ground.  (See 
Charge,  Bound.) 

Charge,   Induced  Electrostatic 

The  charge  produced  by  bringing  a  body 
Into  an  electrostatic  fiel 

In  order  to  obtain  a  permanent  charge,  /.  e.,  a 
charge  which  will  be  maintained  when  the  body 
is  withdrawn  from  an  electrostatic  field,  it  is  nec- 
essary to  connect  the  body  with  the  earth  so  that 
it  may  lose,  or'part  with,  a  charge  of  the  same 
name  as  the  inducing  charge.  Then,  on  the  with- 
drawal of  this  charge,  it  will  possess  a  charge  op- 
posite in  name  to  the  inducing  charge.  (See 
Condenser.) 

Charge,  Influence A  charge  pro- 


[ClUL 

duced  by  electrostatic  induction.  (See  /«« 
duction,  Electrostatic) 

Charge,  Negative According  to  the 

double-fluid  hypothesis,  a  charge  of  negative 
electricity. 

According  to  the  single-fluid  hypothesis, 
any  deficit  of  an  assumed  electrical  fluid. 

Charge,  Positive According  to  the 

double-fluid  hypothesis,  a  charge  of  positive 
electricity. 

According  to  the  single-fluid  hypothesis, 
any  excess  of  an  assumed  electrical  fluid. 

Charge,  Residual The  charge  pos- 
sessed by  a  charged  Leyden  jar  for  a  few 
moments  after  it  has  been  disruptively  dis- 
charged by  the  connection  of  its  opposite 
coatings. 

The  residual  charge  is  probably  due  to  a  species 
of  dielectric  strain,  or  a  strained  position  of  the 
molecules  of  the  glass  caused  by  the  charge. 
Such  residual  charge  is  not  present  in  air  con. 
densers.  In  other  words,  a  Leyden  jar  does  not 
give  up  all  the  electric  energy  charged  in  r;,  on  a 
Single  disruptive  discharge. 

Charge,  Return A  charge  induced 

in  neighboring  conductors  by  a  discharge  oi 
lightning. 

Under  the  influence  of  induction  a  lightning 
stroke  produces  during  its  discharge  an  electric 
shock  in  the  human  body,  or  a  charge  in  neigh- 
boring bodies,  which  is  called  the  back  or  re- 
turn stroke  of  lightning.  (See  Stroke^  Light- 
ning, Back  or  Return.) 

Charged  Body.— (See  Body,  Charged) 

Charging  Accumulators. — Sending  an 
electric  current  into  a  storage  battery  for  the 
purpose  of  rendering  it  an  electric  source. 

There  is,  strictly  speaking,  no  accumulation  of 
electricity  in  a  storage  battery,  such,  for  example, 
as  takes  place  in  a  condenser,  but  a  mere  storage 
of  chemical  energys  which  may  afterward  become 
electric.  (See  Cell,  Storage.) 

Charging  Leyden  Jars  by  Cascade.— (See 

Cascade,  Charging  Leyden  Jars  by) 

Chart,  Inclination A  map  or  chart 

on  which  the  isoclinic  lines  are  marked.  (See 
Map  or  Chartt  Inclination.  Lines. 


Cluu] 


94 


[Chr. 


Chart,  Isodynamic A  map  or  chart 

on  which  the  isodynamic  lines  are  marked. 
(See  Map  or  Chart,  Isodynamic.  Lines, 
Isodynamic?) 

Chart,  Isogonal An  isogonic  chart. 

(See  Map  or  Chart,  Isogonal.) 

Chart,  Isogonic A  map  or  chart 

on  which  the  isogonic  lines  are  marked.  (See 
Map  or  Chart,  Isogonic.  Lines,  Isogonic?) 

Chatterton's  Compound.  —  (See  Com- 
pound, Chatterton 's.) 

Chemical  Change. — (See  Change,  Chem- 
ical?) 

Chemical  Effect.— (See  Effect,  Chemical?) 

Chemical  Equivalent. — (See  Equivalent, 
Chemical?) 

Chemical  Galvano-Cantery. — (See  Cau- 
tery, Galvano-Chemical?} 

Chemical  Phosphorescence. — (See  Phos- 
phorescence, Chemical?) 

Chemical  Photometer. — (See  Photometer, 
Chemical?)  ' 

Chemical  Potential  Energy. — (See  En- 
ergy, Chemical  Potential?) 

Chemical  Recorder,  Bain's (See 

Recorder,  Chemical,  Bains?) 

Chemistry,  Electro That  branch 

of  electric  science  which  treats  of  chemical 
compositions  and  decompositions  effected  by 
the  electric  current.  (See  Electrolysis,  De- 
composition, Electrolytic?) 

That  branch  of  chemistry  which  treats  of 
combinations  and  decompositions  by  means 
of  electricity. 

Electro-chemistry  treats  of  the  formation  of 
new  molecules,  by  the  combination  of  atoms  under 
the  electric  force,  as  well  as  the  decomposition  of 
molecules  by  electricity. 

The  action  of  a  series  of  sparks  passed  through 
air,  in  forming  nitric  acid,  is  an  instance  of  the 
former,  and  electrolytic  decompositions  in  gen- 
eral afford  instances  of  the  latter. 

Chimes,  Electric Bells  rung  by 

the  attractions  and  repulsions  of  electrostatic 
charges. 

The  bells  B  and  B,  Fig.  121,  are  conductively 
connected  to  \hefrime  or  positive  conductor  -4-, 


of  a  frictional  machine.  The  bell  C,  is  insulated 
from  this  conductor  by  means  of  a  silk  thread, 
but  is  connected  with  the  ground  by  the  metallic 
chain.  Under  these 
circumstances  the 
clappers,  1,  1,  insu- 
lated by  silk  threads, 
t,  t,  are  attracted  to 
B,  B,  by  an  induced 
charge  and  repelled 
to  C,  where  they  lose 
their  charge  only  to 
be  again  attracted  to 
B.  B.  In  this  way 
the  bells  will  con- 
tinue  ringing  as  long 


Fig,  lit.  Electric  Chimes. 


as  the  electric  ma- 
chine  is  in  operation. 

Choking  Coil.— (See  Coil,  Choking?) 
Chronograph,  Electric •  — An  elec- 
tric apparatus  for  automatically  measuring 
and  registering  small  intervals  of  time. 

Chronographs,  though  of  a  variety  of  forms, 
generally  register  small  intervals  of  time  by 
causing  a  tuning  fork  or  vibrating  bar  of  steel, 
whose  rate  of  motion  is  accurately  known,  to 
trace  a  sinuous  line  on  a  smoke-blackened  sheet 
of  paper,  placed  on  a  cylinder  driven  at  a  uni- 
form rate  of  motion  by  clockwork.  If  the  fork 
is  known  to  produce,  say,  256  vibrations  per 
second  be  used,  each  sinuous  line  will  represent 
567  part  of  a  second. 


Fig.  122.     Electric  Chronograph. 


An  electro-magnet  is  used  to  make  -marks  on 
the  line  at  the  beginning  and  the  end  of  the 
observation,  and  thus  permit  its  duration  to  be 
measured. 

In  the  form  of  electric  chronograph  shown 


Clir.] 


95 


[Cir. 


in  Fig.  122,  an  electro-magnet,  the  armature  of 
which  carries  a  pen,  is  supported  on  a  carriage 
moved  by  clockwork  over  a  sheet  of  paper 
wrapped  on  a  rotating  cylinder.  A  clock  is  so 
connected  with  the  circuit  of  the  electro-magnet 
that  it  makes  or  breaks  the  circuit  at  the  end  of 
every  second  second,  and  so  moves,  or  displaces, 
the  armature,  as  to  cause  an  elevation  or  depres- 
sion in  the  otherwise  continuous  sinuous  line,  that 
would  be  drawn  on  the  paper  by  the  double 
motion  of  its  rotation  and  the  movement  of  the 
pen-carriage. 

When  it  is  desired  to  know  with  great  precision 
the  exact  time  of  occurrence  of  any  event, 
such,  for  example,  as  the  transit  of  a  star  over  the 
meridian,  the  observer,  who  carries  in  his  hand  a 
push  button,  or  other  form  of  electric  key,  closes 
or  opens  the  circuit  at  the  exact  moment  and  so 
superposes  an  additional  mark  on  the  sinuous 
line.  Since  the  exact  time  of  starting  the  clock 
is  known,  and  the  intervals  between  the  regular 
successive  marks  are  two  seconds  each,  it  is  easy  to 
estimate  from  its  position  between  any  two  such 
marks  the  exact  value  of  the  additional  mark  inter- 
posed. Fig.  122,  taken  from  Young,  shows  a  form 
of  chronograph  by  Warner  &  Swasey.  The  de- 
tails of  this  apparatus  will  be  understood  from 
an  inspection  of  the  drawing. 

Chronograph  Record. — (See  Record, 
Chronograph .) 

Chronoscope,  Electric An  appa- 
ratus for  electrically  indicating,  but  not 
necessarily  recording,  small  intervals  of  time. 

This  term  is  often  used  for  chronograph. 

The  interval  of  time  required  for  a  rifle  ball 
to  pass  between  two  points  may  be  determined 
by  causing  the  ball  to  pierce  two  wire  screens 
placed  a  known  distance  apart.  As  the  screens 
are  successively  pierced,  an  electric  circuit  is 
thus  made  or  broken,  and  marks  are  registered 
electrically  on  any  apparatus  moving  with  a 
known  velocity. 

Cigar-Lighter,     Electric    — (See 

Lighter,  Cigar,  Electric?) 

Cipher  Code.— (See  Code,  Cipher!) 

Circle,  Azimuth  — The    arc   of  a 

great  circle  passing  through  the  point  of  the 
heavens  directly  overhead,  called  the  Zenith, 
and  the  point  directly  beneath,  called  the 

Nadir. 


Circle,  Dipping  — A  term  some- 
times applied  to  an  inclination  compass.  (See 
Compass,  Inclination?) 

Circle,  Galvanic A  term  some- 
times used  for  galvanic  circuit.  (See  Circuit, 
Galvanic?) 

Circle  of  Reference. — The  circle,  by  refer- 
ence to  which  simple  harmonic  motion  may 
be  studied,  by  comparison  with  uniform  mo- 
tion around  such  circuit.  (See  Motion, 
Simple  Harmonic?) 

Circle,  Voltaic A  name  formerly 

employed  for  voltaic  cell  or  circuit.  (See 
Cell,  Voltaic.  Circuit,  Voltaic?) 

Circuit,  Air-Magnetic That  part 

of  the  path  of  a  line  of  magnetic  induction 
which  takes  place  wholly  through  air. 

Circuit,  Alternating  Current A 

circuit  in  which  an  alternating  current  of 
electricity  is  flowing.  (See  Current,  Alter- 
nating?) 

Circuit,  Astatic A  circuit  consist- 
ing of  two  closed  curves  enclosing  equal  sur- 
faces. 


Such    a    circuit    is 
not  deflected  by  the 
action  of  the   earth's 
field.    The  circuit  dis-  > 
posed,    as    shown    in 
Fig.  123,  is  astatic  and  . 
produces    two    equal  ' 
and  opposite  fields  at 
S  and  S'.     (See  Mag. 

A 

1   Ci 
—  |  o 

+j  s' 

—  "    IB 
Fig.  123.    Astatic  Circuit. 

netism,  Ampere's  Theory  of.) 

Circuit,  Balanced-Metallic  —  — A  me- 
tallic circuit,  the  two  sides  of  which  have 
similar  electrical  properties. 

Circuit  Breaker. — (See  Breaker,  Circuit?) 

Circuit,  Broken An  open  circuit. 

A  circuit,  the  electrical  continuity  of  which 
has  been  disturbed,  and  through  which  the 
current  has  therefore  ceased  to  pass. 

Circuit,  Closed A  circuit  is  closed, 

completed,  or  made  when  its  conducting 
continuity  is  such  that  the  current  can  pass. 

Circuit,  Closed  Iron-Magnetic 

The  name  applied  to  the  path  of  any  line 


dr.] 


96 


[Cir. 


of  magnetic  force,  which  takes  place  entirely 
through  iron,  steel,  or  other  paramagnetic  sub- 
stance. 
Circuit,  Closed-Loop  Parallel A 

variety  of  parallel  circuit  in  which  the  lead 
and  the  return  circuit  are  arranged  in  the 
form  of  concentric  circuits,  with  the  recep- 
tive devices  placed  radially  between  them, 

Circuit,  Closed-Magnetic A  mag- 
netic circuit  which  lies  wholly  in  iron  or  other 
substance  of  high  magnetic  permeability. 

All  lines  of  magnetic  force  form  closed  circuits. 
The  term  closed -magnetic  circuit  is  used  in  con- 
tradistinction to  a  divided  circuit,  or  one  in  which 
an  air  gap  exists  in  the  substance  of  high  mag- 


Fig.  124.    Closed-Magnetic  Circuit. 

netic  permeability  forming  the  remainder  of  the 
circuit.  This  introduces  so  high  a  resistance  that 
such  a  circuit  is  sometimes  called  an  open-mag- 
netic circuit.  An  iron  ring,  such  as  shown  in 
Fig.  124,  forms  a  closed-magnetic  circuit. 

Circuit,  Closed-Magnetic,  of  Atom 

A  closed-magnetic  circuit,  or  closed  lines 
of  magnetic  force  supposed  to  lie  entirely  in 
the  atom  itself. 

The  assumption  of  closed  lines  of  magnetic 
force  in  atoms  or  molecules  was  made  in  order  to 
explain  the  original  polarity  of  the  same,  and  to 
account  for  some  of  the  other  phenomena  of 
magnetism. 

When  the  atom  is  subjected  to  a  magnetizing 
force,  such,  for  example,  as  the  field  of  an  electric 
current,  these  closed  lines  of  force  are  assumed 
to  open  out  and  produce  lines  of  polarized  atoms. 
According  to  Lodge,  for  every  single  line  of  force 
produced  by  the  current  passing  through  a  coil 
of  wire  surrounding  an  iron  core,  some  3,000 
lines  of  magnetic  force  are  added  to  it  from  the 
iron.  Therefore  an  iron  core  greatly  increases 
the  magnetic  strength  of  a  hollow  coil  of  wire. 


Circuit,  Closed-Magnetic,  of  Molecule 

— A  closed-magnetic  circuit  assumed  to  lie 
wholly  within  the  molecule. 

As  it  is  not  known  whether  the  assumed  mag- 
netic circuit  lies  within  the  atom  or  the  molecule, 
it  is  called  indifferently  the  closed-atomic  or 
closed-molecular  circuit.  (See  Circuit,  Closed- 
Magnetic^  of  Atom.} 

Circuit,  Completed  —•—  —A  closed 
circuit. 

A  circuit,  the  conducting  continuity  of 
which  is  unbroken. 

A  completed  circuit  is  also  called  a  made  or 
closed  circuit. 

Circuit,  Compound —A  circuit  con- 
taining more  than  a  single  source,  or  more 
than  a  single  electro-receptive  device,  or  both, 
connected  by  conducting  wires. 

The  term  compound  circuit  is  sometimes  ap- 
plied to  a  series  circuit.  (See  Circuit,  Series.) 
The  term,  however,  is  a  bad  one,  and  is  not 
generally  adopted. 

Circuit,  Constant-Current A  cir- 
cuit in  which  the  current  or  number  of  am- 
peres is  maintained  constant  notwithstanding 
changes  occurring  in  its  resistance. 

The  series-circuit,  as  maintained  for  arc-lamps, 
is  a  constant-current  circuit.  (See  Regulation, 
Automatic.') 

Circuit,     Constant-Potential  — A 

circuit,  the  potential  or  number  of  volts  of 
which  is  maintained  approximately  constant. 
The  multiple-arc  or  parallel  circuit  is  an  ap- 
proximately constant-potential  circuit. 

Circuit,  Derivative A  derived  or 

shunt  circuit.     (See  Circuit,  Shunt.) 
Circuit,  Derived 

A  term  applied  to  a  shunt 
circuit. 

If,  in  addition  to  the  galva- 
nometer G,  the  conductor  S, 
Fig.  125,  be  connected  with 
the  circuit  of  the  battery  B,  a 
derived  circuit  will  thus  be 
established,  and  a  current  will 
flow  through  S,  diminishing  tf'  J2S' 
the  current  in  the  galvanom- 
eter. (See  Circuit,  Shunt.) 


Derived 
Circuit. 


dr.] 

Circuit,       Divided-Magnetic A 

magnetic  circuit  which  lies  partly  in  iron,  or 
other  substance    of  high  magnetic    perme- 
ability, and  partly  in  air. 
A  divided-magnetic  circuit  is  shown  in  Fig.  126. 


97 


Fig,  1 2b.    Divided  Magnetic  Circuit. 

Where  the  iron  ring  is  separated  by  the  air  gap, 
a  high  magnetic  resistance  is  introduced,  owing 
to  the  fact  that  the  iron  is  at  these  points  replaced 
by  air,  whose  magnetic  reluctance  is  great. 

Circuit,  Double-Wire •  — A  term 

sometimes  used  for  a  simple  multiple  circuit 
with  two  conductors  or  wires.  (See  Circuit, 
Multiple^ 

The  term  double-wire  circuit  is  used  in  contra- 
distinction to  single-wire  circuit.  (See  Circuit, 
Single- Wire.) 

Circuit,  Earth A  circuit  in  which 

the  ground  or  earth  forms  part  of  the  con- 
ducting path. 

Circuit,  Earth,  Telegraphic 

That  portion  of  a  telegraphic  circuit  which  is 
completed  through  the  earth  or  ground. 

Circuit,  Electric The  path  in 

which  electricity  circulates  or  passes  from  a 
given  point,  around  or  through  a  conducting 
path,  back  again  to  its  starting  point. 

All  simple  circuits  consist  of  the  following 
parts,  viz.: 

(I.)  Of  an  electric  source  which  may  be  a 
voltaic  battery,  a  thermopile,  a  dynamo-electric 
machine,  or  any  other  means  for  producing  elec- 
tricity. 

(2.)  Of  leads  or  conductors  for  carrying  the 
electricity  out  from  the  source,  through  whatever 
apparatuses  placed  in  the  line,  and  back  again  to 
the  source. 

(3.)  Various  electro-receptive  devices,  such  as 
electro-magnets,  electrolytic  baths,  electric 
motors,  electric  heaters,  etc.,  through  which 


[Cir. 

passes  the  current  by  which  they  are  actuated  ot 
operated. 

Circuit,  Electrostatic The  circuit 

formed  by  lines  of  electrostatic  force. 

Lines  of  electrostatic  force,  like  lines  of  mag- 
netic force,  form  closed  circuits.  Hence  the 
origin  of  the  phrase  electrostatic  circuit.  (See 
Force,  Electrostatic,  Lines  of.) 

Circuit,  External That  part  of  a 

circuit  which  is  external  to,  or  outside  the  elec« 
trie  source. 

The  circuit  external  to  the  source  consists  of 
two  distinct  parts,  viz. : 

(I.)  The  conductors  or  leads. 

(2  )  The  electro-receptive  or  translating  de- 
vices. 

It  is  in  the  external  circuit  only  that  useful 
work  is  done  by  the  current. 

Circuit,  Forked A  term  sometimes 

used  in  telegraphy  for  a  number  of  circuits 
that  radiate  from  a  given  central  point. 

Circuit,  Galvanic A  term  some- 
times employed  instead  of  voltaic  circuit. 

The  term  galvanic  in  place  of  voltaic  is  unwar- 
ranted by  the  facts  of  electric  science.  (See  Cir- 
cuit, Voltaic.) 

Galvani  thought  he  had  discovered  the  vital 
fluid  or  source  of  animal  life.  Volta  first  pointed 
out  the  true  explanation  of  the  phenomena  ob- 
served in  Galvani's  frog,  and  devised  means 
for  producing  electricity  in  this  manner.  The 
terms  voltaic  battery,  cell,  circuit,  etc.,  are  there- 
fore preferable. 

Circuit,  Ground A  circuit  in  which 

the  ground  forms  part  of  the  path  through 
which  the  current  passes. 

As  the  ground  is  not  always  a  good  conductor, 
the  terminals  should  be  connected  with  the  gas  or 
water  pipes,  or  with  metallic  plates,  called  ground 
plates.  Such  connection,  or  any  similar  ground 
connection,  is  usually  termed  the  ground  or  earth. 

Circuit,    Ground,   Telegraphic 

An  earth  circuit  used  in  any  system  of  telegra- 
phy. (See  Circuit,  Earth,  Telegraphic?) 

Circuit,  Grounded A  ground  cir- 
cuit. 

Circuit,  Incomplete An  open  oi 

broken  circuit. 


Cir.j 

A  circuit  whose  conducting  continuity  is 
incomplete. 

Circuit,  Inductive Any  circuit  in 

which  induction  takes  place, 

Circuit,  Internal That  part  of  a 

circuit  which  is  included  within  the  electric 
source. 

The  alectric  current  passing  through  the  inter- 
nal  circuit  does  no  useful  work. 

Circuit,  Leg  of One  part  of  a 

twisted  or  metallic  circuit. 

Circuit,  Line The  wire  or  other 

conductors  in  the  main  line  of  any  telegraphic 
or  other  electric  circuit. 

Circuit,  Line,  Telegraphic The 

conductor  or  line  connecting  different  tele- 
graphic stations. 

Circuit,  Local-Battery The  cir- 
cuit, in  a  telegraphic  system,  in  which  is 
placed  a  local  battery  as  distinguished  from  a 
main  battery.  (See  Telegraphy,  American 
or  Morse  System  of.) 

Circuit,  Loop A  term  sometimes 

applied  to  a  circuit  in  parallel  or  multiple-arc. 
(See  Circuit,  Multiple?) 

Circuit  Loop  Break. — (See  Break,  Circuit 
Loop?) 

Circuit,  Made A  completed  circuit. 

A  circuit,  whose  conducting  continuity  is 
unbroken. 

A  made  circuit  is  often  called  a  completed  or 
closed  circuit.  (See  Circuit ',  Closed.) 

Circuit,  Magnetic The  path  through 

which  the  lines  of  magnetic  force  pass. 
All  lines  of  magnetic  force  form  closed  circuits. 


98 


[Cir. 


Fig.  127.    Magnetic  Circuit. 

In  the  bar  magnet,  shown  in  Fig.  127,  part  of 
this  path  is  through  the  air.  In  order  to  reduce 
or  lower  the  resistance  of  a  magnetic  circuit,  iron 


is  often  placed  around  the  magnet.  The  magnet 
is  then  said  to  be  iron-clad. 

The  armature  of  a  magnet  lowers  the  magnetic 
resistance  by  affording  a  better  path  for  the  lines 
of  magnetic  force  than  the  air  between  the 
poles. 

The  magnetic  circuit  always  tries  to  shorten  its 
path,  or  to  render  itself  as  compact  as  possible. 
This  is  seen  in  the  action  of  an  armature  drawn 
towards  a  magnet  pole. 

Circuit,     Main-Battery  —A    term 

sometimes  used  for  line  circuit.  (See  Circuit, 
Line.) 

Circuit,  Metallic A  circuit  in  which 

the  ground  is  not  employed  as  any  part  of  the 
path  of  the  current,  metallic  conductors  being 
employed  throughout  the  entire  circuit. 

Circuit,  Multiple A  compound  cir- 
cuit, in  which  a  number  of  separate  sources 
or  separate  electro-receptive  devices,  or  both, 
have  all  their  positive  poles  connected  to  a 
single  positive  lead  or  conductor,  and  all  their 
negative  poles  to  a  single  negative  lead  or 
conductor. 

The  connection  of  three  Bunsen  cells,  in  mul. 
tiple,  is  shown  in  Fig.  128,  where  the  three  car- 


Fig.  128.     Batteries  connected  in  a  Multiple  Circuit. 

bons,  C,  C,  C,  are  connected  together  so  as  to  form 
the  positive,  or  -J-  terminal  of  the  battery,  and 
the  three  zincs,  Zn,  Zn,  Zn,  are  similarly  con- 
nected together  so  as  to  form  the  negative,  or  — 
terminal. 

The  electromotive  force  is  the  same  as  that  of 
a  single  cell,  or  source.  The  internal  resistance 
of  the  source  is  as  much  less  than  the  resistance  ot 
any  single  source  as  the  area  of  the  combined 
negative  or  positive  plates  is  greater  than  that  of 
any  single  negative  or  positive  plate ;  or,  in  othet 
words,  is  less  in  proportion  to  the  number  of  cells, 
or  other  separate  sources  so  coupled. 

The  connection  of  six  cells  in  multiple  or 
parallel  circuit,  is  shown  in  Fig.  129. 


€ir.J 


99 


[Cir. 


In  the  case  of  the  six  cells,  the  current  would 


be, 


where  E,  is  the  electromotive  force,  r,  the  in- 
ternal, and  r',  the  external  resistance. 


Fig.  129.    &'•*  Cells  Connected  in  Multiple. 

In  the  case  of  voltaic  cells  the  effect  of  multiple 
connection  on  the  internal  resistance  of  the  source 
is  to  increase  the  area  of  cross-section  of  the 
liquid  in  the  direct  proportion  of  the  number  of 
cells  added,  and  consequently  to  decrease  the  re- 
sistance in  the  same  proportion. 

When  strong  or  large  currents  of  low  electro- 
motive force  are  required,  connections  in  multi- 
ple-arc are  generally  employed. 

The  multiple-arc  connection  was  formerly 
called  connection-far -quantity.  This  term  is  now 
abandoned. 

The  total  -resistance  for  the  parallel  circuit  is 
obtained  as  follows:  calling  the  separate  resist- 
ances of  the  separate  electro-receptive  devices, 
R',  R",  R"',  etc.,  etc.,  etc.,  total  resistance, 

p  _  R'  X  R"  X  R'" 

R'  R"  -f-  R"  R'"  4-  R'  R'" 

or,  what  is  the  same  thing,  the  conductivity  is  the 
sum  of  the  reciprocal  of  the  separate  resistances, 
»'.  e. : 

III 
Conductivity  =  -pr-  +  -pir  -f-  ?><-• 

The  joint  resistance  of  only  two  separate  resist- 
ances joined  in  a  multiple-circuit  is  equal  to  the 
product  of  the  separate  resistances  divided  by 
their  sum. 

When  the  separate  resistances  joined  in  multiple 
arc  are  all  of  the  same  value,  the  joint  resistance  is 
equal  to  the  resistance  of  one  of  them  divided  by 
their  number. 


A  term  often 

(See  Circuit,  Mul- 


Circuit,  Multiple-Arc 

used  for  multiple  circuit. 
ttjfr.] 

Circuit,  Multiple-Series  •  — A  com- 
pound circuit  in  which  a  number  of  separate 


sources,  or  separate  electro-receptive  devices, 
or  both,  are  connected  in  a  number  of  sepa- 
rate  groups    in  series,  and  these  separata 
groups  subsequently  connected  in  multiple. 
In  Fig.    130,  a  multiple-series  circuit  of  six 
._ c 


\ 


J 


Fig.  130.     Multiple~Series-Connected  Cells. 

sources  is  shown,  in  which  three  separate  groups 
of  two  series-connected  cells  are  coupled  in  multi. 
pie.  The  current  takes  the  paths  indicated  by  the 
arrows.  The  electromotive  force  of  the  source 
will  be  increased  in  proportion  to  the  number  of 
cells  in  series,  and  the  internal  resistance  de- 
creased in  proportion  to  the  number  in  parallel. 


Fig.  131.    Cells  Connected  in  Multiple- Series. 


-J!L+r'. 

2 

In  Fig.  131,  six  cells  are  arranged  in  two 
groups  of  three  series-connected  cells,  and  these 
three  groups  connected  in  parallel. 

Calling  r,  the  resistance  of  each  separate  cell, 
the  total  resistance  for  the  multiple-series  circuit 
for  a  circuit  containing  three  cells  in  parallel  and 
two  in  series  is, 


R 


2r 
T 


for  three  in  series  and  two  in  parallel, 


If,  therefore,   the   circuit  of  this  battery  be 
closed  by  a  resistance  equal  to  r,  the  current 
would  be  in  the  case  of  Fig.  130, 
2E 


Cir.] 


100 


[Cir. 


Circuit,  Negative  Side  of The  side 

ot  a  circuit  opposite  to  the  positive  side. 
(See  Circuit,  Positive  Side  of.) 

That  side  or  half  of  a  circuit  connected  to  or 
leading  from  the  positive  terminal  of  the  source  of 
CNrrent. 

Circuit,  Open A  broken  circuit. 

A  circuit,  the  conducting  continuity  of 
which  is  broken. 

Circuit,    Open-Iron    Magnetic 

The  path  of  a  line  of  magnetic  induction, 
which  passes  partly  through  iron,  and  partly 
through  an  air  space. 

The  magnetic  circuit  is  always  closed,  that  is 
the  lines  of  magnetic  force  always  form  closed 
paths.  The  term  "open"  is  used  in  contradis- 
tinction only  to  "closed  "  iron  magnetic  circuit, 
in  which  the  entire  path  of  a  line  of  force  passes 
through  iron.  (See  Circuit,  Magnetic.) 

Circuit,  Parallel A  name  some- 
times applied  to  circuits  connected  in  mul- 
tiple. (See  Circuit,  Multiple!) 

Circuit,  Parallel-Tree A  form  of 

parallel  circuit  in  which  the  receptive  devices 
are  placed  in  parallel  between  the  leads  and 
returns,  and  the  branches  and  sub-branches 
arranged  in  a  tree-like  form. 

Circuit,  Positive  Side  of That  side 

of  a  circuit,  bent  in  the  form  of  a  circle,  in 
which,  if  an  observer  stood  with  his  head  in 
the  positive  region,  he  would  see  the  current 
pass  round  him  from  his  right  hand  towards 
his  left.— (Daniell) 

Circuit,  Recoil A  term  sometimes 

applied  to  the  circuit  that  lies  in  the  alterna- 
tive path  of  a  discharge.  (See  Path,  Alter- 
native?) 

Circuit,  Return That  part  of  a 

circuit  by  which  the  electric  current  returns  to 
the  source. 

In  a  multiple-circuit  the  lead  that  is  con- 
nected to  the  negative  terminals  of  the 
separate'  sources. 

Circuit,  Series A  compound  cir- 
cuit in  which  the  separate  sources,  or  the  sep- 
arate electro-receptive  devices,  or  both,  are  so 
placed  that  the  current  produced  in  each,  or 
passed  through  each,  passes  successively 


through  the  entire  circuit  from  the  first  to  the 
last. 

The  six  cells,  shown  in  Fig.  132,  are  connected 
in  series  by  joining  the  positive  pole  of  each  cell 
with  the  negative  pole  of  the  succeeding  cell,  the 
negative  and  positive  poles  at  the  extreme  ends 


Fig.  132.    Series  Circuit. 

being  connected  by  conductors  with  the  external 
circuit. 

The  connection  of  three  Leclanche"  cells  ut 
series  is  clearly  shown  in  Fig.  133.     The  carbons, 

C  +,.  C+ 


Fig.  133.     Voltaic  Cells  Connected  in  Series. 

C,  C,  of  the  first  and  second  cells  are  connected  to 
the  zincs,  Zn,  Zn,  of  the  second  and  third  cells, 
thus  leaving  the  zinc,  Zn,  of  the  first  cell,  and  the 
carbon,  C,  of  the  third  cell,  as  the  terminals  of 
the  battery.  The  direction  of.  the  current  is 
shown  by  the  arrows. 

The  resistance  of  such  a  connection  is  equal  to 
the  sum  of  the  resistances  of  all  of  the  separate 
sources. 

The  electromotive  force  is  equal  to  the  sum  of 
the  separate  electromotive  forces. 

If  the  electromotive  force  of  a  single  cell  is 
equal  to  E,  its  internal  resistance  to  r,  and  the 
resistance  of  the  leads  and  electro-receptive  d«- 
vices  to  r',  then  the  current  in  the  circuit, 


C- 

- 


•F+7" 

If  six  of  such  cells  are  coupled  in  series,  the  cur- 
rent becomes 

_6E_ 
~~6r  + r'' 

If,  however,  the  internal  resistance  of  each  cell  be 
so  small  as  to  be  neglected,  the  formula  becomes 

C  =  — 5 


Cir.] 


101 


[Cir. 


or  the  current  is  six  times  as  great  as  with  one 
cell. 

The  total  resistance  of  the  separate  sources  or 
electro-receptive  devices  of  the  series  circuit  is 
as  follows,  calling  R',  R",  R'",  etc.,  the  separate 
resistance  and  R,  the  total  resistance, 
R  =  R'  +R"  -f-R'",  etc. 

The  series  connection  of  battery  cells  is  used 
on  telegraph  lines,  where  a  high  electromotive 
force  is  required  in  order  to  overcome  a  consider. 
able  resistance  in  the  circuit,  or  in  similar  cases 
where  the  resistance  in  the  external  circuit  is 
great,  on  account  of  a  number  of  electro-receptive 
devices  being  connected  to  the  line  in  series. 

The  series  connection  was  formerly  called 
connection  for  intensity.  The  term  is  now  aban- 
doned. 

Circuit,  Series-Multiple  --  A  com- 
pound circuit,  in  which  a  number  of  separate 
sources,  or  separate  electro-receptive  devices, 
or  both,  are  connected  in  a  number  of  sepa- 
rate groups  in  multiple-arc,  and  these  sepa- 
rate groups  subsequently  connected  in  series. 

In  the  series-  multiple  circuit  the  resistance  of 
each  multiple  group  is  equal  to  the  resistance  of 
a  single  branch  divided  by  the  number  of  branches. 

If,  for  example,  r,  is  the  resistance  of  each  sepa- 
rate branch  of  say  seven  parallel  circuits  in  each 
of  the  separate  groups  of  multiple  circuits,  then 
the  resistance,  R,  of  each  separate  multiple 
group  is— 


The  total  resistance  of  the  series-multiple  cir- 
cuit is  equal  to  the  sum  of  the  resistances  of  the 
separate  multiple  groups.  The  total  resistance  of 
the  three  groups  is  — 

R  =  -  +  I  +  L  =  J1L. 
7777 

An  example  of  the  series-multiple  circuit  is 
shown  in  Fig.  134,  which  is  the  method  adopted 


F'g-  134-     Series-Multii>le  Circuit. 

in  the  use  of  distribution  boxes.  Here  a  number 
c  multiple  -groups  or  circuits  are  connected  with 
each  other  in  series,  as  shown.  (See  Box,  Dis- 
tribution, for  Arc  Light  Circuits. ) 

Circuit,  Short A  shunt,  or  by-path. 


of  comparatively  small  resistance,  around  the 
poles  of  an  electric  source,  or  around  any 
portion  of  a  circuit,  by  which  so  much  of  the 
current  passes  through  the  new  path,  as  vir- 
tually to  cut  out  the  part  of  the  circuit  around 
which  it  is  placed,  and  so  prevent  it  from  re- 
ceiving an  appreciable  current. 

Circuit,  Shunt A  branch  or  add* 

tional  circuit  provided  at  any  part  of  a  cir- 
cuit, through  which  the  current  branches  or 
divides,  part  flowing  through  the  original  cir- 
cuit, and  part  through  the  new  branch. 

A  shunt  circuit  is  in  multiple  circuit  with  the 
circuit  it  shunts. 

In  the  case  of  branch  circuits  each  of  the  cir- 
cuits acts  as  a  shunt  to  the  others.  Any  number 
of  additional  or  shunt  circuits  may  be  thus  pro- 
vided. (See  Laws,  J&rchhojfs.} 

Circuit,  Simple A  circuit  containing 

a  single  electric  source,  and  a  single  electro- 
receptive  device,  connected  by  a  conductor. 

The  term  .simple  circuit  is  sometimes  applied 
to  a  multiple  circuit.  The  term  is  not,  however, 
a  good  one,  and  is  not  in  general  use. 

Circuit,  Single- Wire A  term  some- 
times used  for  a  grounded  circuit.  (See 
Circuit,  Grounded?) 

The  single-wire  circuit  is  sometimes  used  in  the 
distribution  of  incandescent  lamps  in  multiple-arc. 
One  pole  of  the  dynamo  is  put  to  ground,  and  the 
other  pole  to  a  single  wire  or  lead.  The  electro- 
receptive  devices  have  one  of  their  poles  con. 
nected  to  this  lead  and  the  other  pole  to  earth. 
The  single-wire  circuit  is  a  very  objectionable 
circuit  so  far  as  safety  is  concerned. 

It  is  frequently  used,,  however,  in  the  wiring  of 
ships. 

Circuit,  Through A  telephonic  or 

telegraphic  circuit  that  has  been  completed 
through  to  a  given  station  by  cutting  out  inter- 
ruptions or  breaks  in  the  line  by  the  connec- 
tion together  of  sections  of  different  wires. 

Circuit,  Time-Constant  of  •  —The 

time  in  which  a  current  due  to  a  constant 
electromotive  force  will  rise  in  a  conductor 
to  a  definite  fraction  of  its  maximum  value. 

The  rauo  of  the  inductance  of  a  circuit  to 
its  resistance. 


»»'  **»»*•  • 


Cir.J 


102 


[Cle. 


•  The  time  required  from  the  moment  of 
closing  the  circuit,  for  a  current  to  rise  to 


a  value  equal  to 


e— I 


of  the  full  value,  or 


.632  of  the  maximum  value. 

In  the  above,  e,  equals  2.71828,  or  the  base  of 
the  Napierian  system  of  logarithms. 

The  time-constant  is  proportional  to  the  con- 
ductivity of  the  circuit  and  its  formal  resistance. 

Approximately  the  time  constant  of  a  circuit  is 
the  time  from  closing  the  circuit,  in  which  the 
current  rises  to  two-thirds  of  its  maximum  value, 
this  maximum  value  being  determined  by  the 

E 
formula,  C  =  — . 

R 

Thetime-constant  of  a  circuit  may  be  reduced — 

(i.)  By  decreasing  the  self-induction  of  the  cir- 
cuit. 

(2.)  By  increasing  the  resistance. 

In  the  case  of  a  magnetic  conductor  the  time- 
constant  is  proportional  to  a  quantity  (the  perme- 
ability) which  is  determined  by  the  capacity  of 
the  conductor  to  utilize  part  of  the  energy  in 
producing  magnetization  of  its  substance.  —(Flem- 
ing-) 

Circuit,  Yoltaic The  path  through 

which  the  current  flows  out  from  a  voltaic  cell 
or  battery,  through  the  translating  devices 
and  back  again  to  the  cell  or  b-*tery. 

Circuits,  Forked A  term  employed 

in  telegraphy  to  indicate  circuits  that  radiate 
from  any  single  point. 

Forked  circuits  are  employed  in  simultaneously 
transmitting  messages  to  several  stations. 

Circuits,  Varieties  of Conducting 

paths  provided  for  the  passage  oT  an  electric 
current. 

Electric  circuits  may  be  divided,  according  to 
their  complexity,  into — 

(i.)  Simple. 

(2.)  Compound. 

According  to  the  peculiarities  of  their  connec- 
tions, into — 

(i.)  Shunt  or  derived. 

(2.)  Series. 

(3.)  Multiple,  multiple-arc  or  parallel. 

(4.)  Multiple-series. 

(5.)  Series-multiple. 

Either  the  circuits,  the  sources,  or  the  electro- 


receptive  devices  may  be  connected  in  series,  in 
multiple,  in  multiple-series  or  in  series-multiple. 

According  to  their  resistance,  circuits  are 
divided  into— 

(i.)  High-resistance. 

(2.)  Low-resistance. 

According  to  their  relation  to  the  electric 
source,  into — 

(I.)  Internal  circuits. 

(2.)  External  circuits. 

According  to  their  position,  or  the  work  done, 
circuits  are  divided  into  very  numerous  classes; 
thus,  in  telegraphy,  we  have  the  following,  viz.: 

(i.)  The  line -circuit. 

(2.)  The  earth  or  ground  circuit. 

(3.)  The  local-battery  circuit. 

(4.)  The  main -battery  circuit,  etc. 

Circular  Bell.— (See  Bell,  Circular) 
Circular  Units.— (See  Units,  Circular^ 

Circular  Units  (Cross-Sections),  Table 
of (See  Units,  Circular  (Cross- Sec- 
tions), Table  of.) 

Clamp,  Carbon A  carbon  clutch. 

(See  Clutch,  Carbon,  of  Arc  Lamp) 

Clamp  for  Arc  Lamps.— A  clamp  for 
gripping  the  lamp-rod,  /.  e.,  the  rod  that  sup- 
ports the  carbon  electrodes  of  arc  lamps. 
(See  Lamp,  Electric,  Arc) 

Clamp,  Rod A  carbon  clutch.  (See 

Clamp  for  Arc  Lamps) 

Clark's  Compound. — (See  Compound, 
Clark's) 

Clark's    Standard    Yoltaic    Cell.— (See 

Cell,  Voltaic,  Standard,  Clark's) 

Clark's    Standard    Yoltaic    Cell,  Ray- 

leigh's  Form  of (See  Cell,    Voltaic, 

Standard,  Ray  leigh's  Form  of  Clark's) 

Clay  Electrode.— (See  Electrode,  Clay) 

Cleansing,  Fire  —  —The  removal  of 
grease  from  metallic  articles,  that  are  to  be 
electro-plated,  by  subjecting  them  to  the  action 
of  heat. 

This  cleansing  is  for  the  purpose  of  obtaining  a 
uniform,  adherent  coating. 

Clearance-Space.— (See  Stiace.  Clearance) 


Cle.] 


103 


[CIo. 


Clearing-Out  Drops.— (See  Drops,  Clear- 
ing-Out^) 

Cleat,  Crossing A  cleat  so  arranged 

as  to  permit  the  crossing  of  one  pair  of  wires 
under  or  over  another  pair  without  contact 
with  each  other. 

Cleat-Wiring.— (See  Wiring,  Cleat.) 

Cleats,  Electric Suitably  shaped 

pieces  of  wood,  porcelain,  hard  rubber  or 
other  non-conducting  material  used  for  fasten- 
ing and  supporting  electric  conductors  to 
ceilings,  walls,  etc. 

A  simple  form  of  wooden  cleat  is  shown  in 
«3S- 


Fig.  135.     Wooden  Cleat. 

Clepsydra,  Electric An  instrument 

for  measuring  time  by  the  escape  of  water  or 
Other  liquid  under  electrical  control. 

Climbers,  Pole 

— Devices  employed  by 
linemen  for  climbing 
wooden  telegraph  poles. 

A  climber  with  straps 
for  attachment  to  the  leg 
and  foot  is  shown  in  Fig. 
136. 

Clip,  Cable A 

term  sometimes  used  for 
cable  hanger.  (See 
Hanger,  Cabled) 

Clock,  Electric 

— A  clock,  the  works  of 

Which  are  moved,   COn-   Fig.  136.     Climber  and 

trolled,     regulated     or  straps. 

wound,  either  entirely  or  partially,  by  the  elec- 
tric current. 

Electric  clocks  may  be  divided  into  three 
classes,  viz.: 

(i.)  Those  in  which  the  works  are  moved  en- 
tirely or  partially  by  the  electric  current. 

(2.)  Those  which  are  controlled  or  regulated 
by  the  electric  current. 


Fig. 


Controlling 
Clock. 


(3.)  Those  which  are  merely  wound  by  the 

current. 

'  A  clock  moving  independently  of  electric  power 

is  prevented  from  gain- 
ing  or  losing  time,  by 

means   of   a  slight  re- 
tardation or  acceleration 

electrically       imparted. 

The    entire    motion    of 

the    balance    wheel    is 

sometimes  imparted  by 

electricity. 

An  example  of  one  oi 

many  forms  of  controll- 
ing   electric    clocks    is 

shown     in     Fig.     137, 

where  the  split  battery 

(See  Battery,  Split),  P 

N,     is    connected,      as 

shown,   to    the    spring 

contacts  S  and  S'.  In  this  way  currents  are  sent 
into  the  circuit  in  alternately  opposite  directions. 
The  pendulum  bob,  Fig.  138,  of  the  con. 
trolled  clock  is  formed  of  a  hollow  coil  of  insu- 
lated wire,  which  encircles  one  or  both  of  two 
permanent  magnets,  A  and  A',  placed  with  their 
opposite  poles  facing  each  other. 

When  the  pendulum  of  the  controlling  clock  is 
in  the  position  shown  in  Fig.  137,  the  current 
passes  in  the  direction  E  P  Sn  W,  etc.,  and  through 
the  coil  C,  Fig.  138.  When  the  pendulum  of  the 
controlling  clock  is  in  con- 
tact with  S',  the  current 
flows  through  Wn  S'  N  E, 
etc.,  and  through  the  coil 
C  in  the  opposite  direc- 
tion. In  this  manner  a 
slight  motion  forwards  or 
backwards  is  imparted  to 
the  pendulum,  which  is 
thus  kept  in  time  with  the 
controlling  clock. 

Mercury      contacts     are 
sometimes     employed     in 
place  of  the  springs  S  and 
S'.  Induction  currents  may  A. 
also  be  employed. 

Clocks  of  non-electric  ac-   Fig.  138.    Controlled 
tion   may    be    electrically  Clock. 

controlled,  or  correctly  set  at  certain  intervals, 
either  automatically  by  a  central  clock,  or  by  the 
depression  of  a  key  operated  by  hand  from  an 
astronomical  observatory. 


Clo.] 

In  a  system  of  time-telegraphy,  the  controlling 
clock  is  called  the  master  clock,  and  the  con- 
trolled clocks,  the  secondary  clocks. 

Secondary  clocks  are  generally  mere  dials,  con- 


104 


[Clo. 


Fig.  139.    Mechanism  of  Secondary  Clock. 

taining  step-by-step  movements,  for  moving  the 
hour,  minute  and  second  hands,  as  shown  in 
Fig-  139- 

In  Spellier's  clock,  a  series  of  armatures  H, 
Fig.    140,   mounted  on  the  circumference  of  a 


Fig.  r 4.0.    Spellier's  Electric  Clock. 

wheel,  connected  with  the  escapement  wheel, 
pass  successively,  with  a  step-by-step  movement, 
over  the  poles  of  electro-magnets.  On  the  com- 
pletion of  the  circuit,  they  are  attracted  towards 
the  magnet,  and  on  the  breaking  of  the  circuit 
they  are  drawn  away  by  the  fall  of  the  weight  F, 
placed  on  the  lever  D,  pivoted  at  E.  A  pulley  at 
E,  runs  over  the  surface  of  a  peculiarly  shaped 
cog  on  the  escapement  wheel. 

Clock,   Electric  Annunciator A 

clock,  the  hands  or  works  of  which,  at  cer- 
tain predetermined  times,  make  electric  con- 
tacts and  thus  ring  bells,  release  drops,  trace 
records,  etc. 


Clock,  Electrical-Controlling In 

a  system  of  time  telegraphy,  the  master  clock, 
whose  impulses  move  or  regulate  the  second- 
ary clocks.  (See  Clock,  Electric?) 

Clock,  Electrically-Controlled In 

a  system  of  time  telegraphy,  a  secondary 
clock,  that  is  either  driven  or  controlled  by 
the  master  clock.  (See  Clock,  Electric!) 

Clock,  Electrolytic,  Tesla's A  time 

piece  in  which  the  rotation  of  the  wheel  work 
is  obtained  by  the  difference  in  weight  of  the 
two  halves  of  a  delicately  pivoted  and  well- 
balanced  wheel  placed  in  an  electrolytic 
bath. 

In  the  electrolytic  clock  of  Nikola  Tesla,  a  deli- 
cately formed  and  balanced  disc  of  copper  is  sup- 
ported on  a  horizontal  axis  at  right  angles  to  the 
shortest  distance  between  the  two  electrodes,  and 
placed  in  a  bath  of  copper  sulphate.  Its  two 
halves  become  respectively  electro-positive  and 
electro-negative  when  a  current  is  passed  through 
the  bath,  and  consequently  metal  is  deposited  on 
one  half  and  dissolved  from  the  other  half.  The 
rotation  of  the  disc  under  the  influence  of  gravity 
is  caused  to  mark  time. 

An  electrolytic  clock  could  therefore  be  made 
to  answer  roughly  as  an  electric  meter. 

Clock,  Master The  central  or  con- 
trolling clock  in  a  system  of  electric  time-dis- 
tribution, from  which  the  time  is  transmitted 
to  the  secondary  clocks  in  the  circuit.  (See 
Clock,  Electric!) 

Clock,  Secondary Any  clock  in  a 

system  of  time  telegraphy  that  is  controlled 
by  the  master  clock.  (See  Clock,  Electric!) 

Clock,  Self-Winding A  clock  that 

at  regular  intervals  is  automatically  wound  by 
the  action  of  a  small  electro-magnetic  motor 
contained  within  it. 

This  motor  is  usually  run  by  one  or  more  vol- 
taic cells,  concealed  in  the  case  of  the  clock. 

Closed-Circnit. — (See  Circuit,  Closed!) 

Closed-Circuit  Battery. — (See  Battery, 
Closed-Circuit!) 

Closed-Circuit,  Single-Current/  Signal- 
ing   (See  Signaling,  Single-Current, 

Closed-Circuit^ 


CIo.] 


105 


[Coe. 


Closed-Circuit  Thermostat.— (See  Ther- 
mostat, Closed-Circuit) 

Closed-Circuit  Voltaic  Cell.— (See  Cell, 
Voltaic,  Closed-Circuit) 

Closed-Circuit  Voltmeter.— (See  Volt- 
meter, Closed-Circuit) 

Closed-Circuited. — Placed  in  a  closed  or 
completed  circuit. 

A  voltaic  battery,  or  other  source,  is  closed-cir- 
cuited when  its  poles  or  terminals  are  electrically 
connected  with  each  other. 

Closed-Circuited  Conductor. — (See  Con- 
ductor, Closed-Circuited) 

Closed-Circular  Current. — (See  Current, 
Closed-  Circular) 

Closed-Coil  Disc  Dynamo-Electric  Ma- 
chine.— (See  Machine,  Dynamo-Electric, 
Closed-Coil  Disc) 

Closed-Coil  Drum  Dynamo-Electric  Ma- 
chine.— (See  Machine,  Dynamo-Electric, 
Closed-Coil  Drum) 

Closed-Coil  Dynamo-Electric  Machine. — 
(See  Machine,  Dynamo-Electric,  Closed- 
Coil) 

Closed-Coil  Ring  Dynamo-Electric  Ma- 
chine.— (See  Machine,  Dynamo-Electric, 
Closed-Coil  Ring) 

Closed-Iron-Circuit  Transformer.—  (See 
Transformer,  Closed-Iron-Circuit) 

Closed-Loop  Parallel-Circuit.— (See  Cir- 
cuit, Closed-Loop  Parallel) 

Closed-Magnetic  Circuit. — (See  Circuit, 
Closed-Magnetic) 

Closed-Magnetic  Core. — (See  Cqre,  Closed- 
Magnetic) 

Closure. — The  completion  of  an  electric 
circuit. 

Cloth  Discs,  Carbonized,  for  High  Re- 
sistances   Discs  of  cloth  carbonized  by 

heating  to  an  exceedingly  high  temperature 
in  a  vacuum,  or  out  of  contact  with  air. 

After  carbonization  the  discs  retain  their  flex- 
ibility and  elasticity  and  serve  admirably  for  high 
resistances.  When  piled  together  and  placed  in 
glass  tubes,  they  form  excellent  variable  resist* 
ances  when  subjected  to  varying  pressure. 


Cluh-Footed     Magnet.  —  (See     Magnet, 
Club-Footed) 
Clutch,  Carbon,  of  Arc  Lamp A 

clutch  or  clamp  attached  to  the  rod  or  other 
support  of  the  carbon  of  an  arc  lamp,  pro- 
vided for  gripping  or  holding  the  carbon. 
(See  Lamp,  Electric  Arc) 

Clutch  Rod.— (See  Rod,  Clutch) 

Coating,  Metallic A  covering  or 

coating  of  metal,  usually  deposited  from 
solutions  of  metallic  salts  by  the  action  of  an 
electric  current .  (See  Plating,  Electro) 

Coating  of  Condenser. — A  sheet  of  tin 
foil  on  one  side  of  a  Leyden  jar  or  condenser, 
directly  opposite  a  similar  sheet  on  the  other 
side  for  the  purpose  of  receiving  and  collecting 
the  opposite  charges.  (See  Jar,  Leyden. 
Condenser) 

Coatings  of  Leyden  Jar. — The  sheets  of 
tin  foil  or  other  conductor  on  the  opposite 
sides  of  a  Leyden  jar  or  condenser.  (See 
Jar,  Leyden.  Condenser) 

Code,  Cipher A  code  in  which  a 

number  of  words  or  phrases  are  represented 
by  single  words,  or  by  arbitrary  words  or  syl- 
lables. 

The  message  thus  received  requires  the  posses- 
sion of  the  key  to  render  it  intelligible. 

Code,Telegraphic The  pre-arranged 

signals  of  any  system  of  telegraphy.  (See 
Alphabet,  Telegraphic.  Alphabet,  Tele- 
graphic, Morse's.  Alphabet,  Telegraphic, 
International  Code) 

Co-efficient,  Algebraic A  number 

prefixed  to  any  quantity  to  indicate  how 
many  times  that  quantity  is  to  be  taken. 

The  number  3,  in  the  expression  3a,  is  a  co- 
efficient and  indicates  that  the  a,  is  to  be  taken 
three  times,  as  a  -j-  a  -f-  a  =  3a. 

Co-efficient,  Economic,  of  a  Dynamo- 
Electric  Machine The  ratio  between 

the  electrical  energy,  or  the  electrical  horse- 
power of  the  current  produced  by  a  Hvnamo, 
and  the  mechanical  horse-power  expended  in 
driving  the  dynamo. 

The  economic  co-efficient  is  usually  called  the 
efficiency. 


Coe.] 

The  efficiency  may  be  the  commercial  effi- 
ciency, which  is  the  useful  or  available  energy  in 
the  external  circuit  divided  by  the  total  mechan- 
ical energy;  or  it  may  be  the  electrical  efficiency, 
which  is  the  available  electrical  energy  divided 
by  the  total  electrical  energy. 

The  efficiency  of  conversion  is  the  total  elec- 
trical energy  developed,  divided  by  the  total 
mechanical  energy  applied. 

If  M,  equals  the  mechanical  energy, 
W,  the  useful  or  available  electrical  energy, 

and 
w,   the   electrical  energy   absorbed  by  the 

machine,  and 
m,  the  stray  power,   or  the  power  lost  in 

friction,  eddy  currents,  air  friction,  etc. 
Then,  since 


106 


[Coi. 


The  Commercial  Efficiency 
-  W_          W 
=  ~M~~ 


-  w-J-m 
The  Electrical  Efficiency 

W 

W  + w 
The  Efficiency  of  Conversion 

__  \V_4-_w_.      W-f  w 

M~~       w  +  w  +  m* 

Co-efficient  of  Electro-Magnetic  Inertia. 

— (See    Inertia,   Electro-Magnetic,  Co-effi- 
cient of) 

Co-efficient  of  Expansion.— (See  Expan- 
sion, Co-efficient  of) 

Co-efficient  of  Expansion,  Linear 

(See  Expansion,  Linear,  Co-efficient  of) 

Co-efficient  of  Magnetic  Induction.— (See 

Induction,  Magnetic,  Co-efficient  of) 

Co-efficient  of  Magnetization.— (See 
Magnetization,  Co-efficient  of) 

Co-efficient  of  Mutual- Inductance. — (See 
Inductance,  Mutual,  Co-efficient  of) 

Co-efficient  of  Mutual-Induction.— (See 
Induction,  Mutual,  Co-efficient  of) 

Co-efficient  of  Self-Induction.— (See  In- 
duction, Self,  Co-efficient  of) 

Coercitive  Force.— (See  Force,  Coerci- 
tive) 

Coercive  Force. — (See  Force,  Coercive) 

Coil,  Choking A  coil  of  wire  so 


Fig.  14.1.    Choking- 
Coil. 


wound  on  a  core  of  iron  as  to  possess  high 
self-induction. 

Choking-coils  are  used  to  obstruct  or  cut  off  an 
alternating  current  with  a  loss  of  power  less  than 
with  the  use  of  a  mere  ohmic  resistance. 

Fig.  141  shows  a  choking-coil.  It  consists  of 
a  circular  solenoid  of  insulated  wire,  wound 
on  a  core  of  soft  iron  wire.  A  thorough  divis- 
ion of  the  core  is  obtained  by  forming  it  of  coils 
of  insulated  iron  wire.  In  this  way,  no  eddy 
currents  are  produced  in  the  coil.  When  a  simple 
periodic  electromotive  force  is  applied  to  the 
terminals  of  such  a  coil,  if 
the  magnetic  permeability 
of  the  coil  is  constant,  a 
simple  periodic  current  is 
produced,  which  lags  be- 
hind the  phase  of  the  im- 
pressed electromotive  force 
by  a  constant  angle.  If 
the  impressed  electromo- 
tive force  is  sufficiently  great  to  more  than  satu- 
rate the  core,  the  choking  coil  ceases  to  choke 
the  current.  The  higher  the  periodicity  the 
greater  is  the  choking  effect  of  a  given  coil,  or  the 
smaller  the  coil  may  be  made  to  produce  a  given 
effect. 

Since  an  open -magnetic  circuit  requires  a 
greater  current  to  saturate  it  than  a  closed-mag- 
netic circuit,  the  complete  throttling  or  choking 
power  of  such  a  coil  is  increased  by  forming  its 
core  of  a  closed  magnetic  circuit,  i.  e.,  of  a  circuit 
i  n  which  there  is  no  air  space  or  gap .  (See  Circuit, 
Divided- Magnetic.  Circuit,  Closed- Magnetic.) 

Coil,  Electric A  convolution  of  in- 
sulated wire  through  which  an  electric  current 
may  be  passed.  (See  Magnet,  Electro.} 

The  term  coil  is  usually  applied  to  a  number 
of  turns  or  to  a  spool  of  wire. 

Coil,  Impedance A  term  sometimes 

applied  to  a  choking-coil.  (See  Coil,  Chok- 
ing.} 

Such  a  coil  has  a  high  self-induction.  Its  im- 
pedance is  therefore  high.  (See  Induction,  Self. 
Impedance.} 

Coil,  Induction An  apparatus  con* 

sisting  of  two  parallel  coils  of  insulated  wire 
employed  for  the  production  of  currents  by 
mutual  induction.  (See  Induction,  Mutual. 
Induction,  Electro-Dynamic.} 


CoL] 


10  ," 


[Coi. 


A  rapidly  interrupted  battery  current,  sent 
through  a  coil  of  wire  called  the  primary  coil, 
induces  alternating  currents  in  a  coil  of  wire  called 
the  secondary  coil. 

As  heretofore  made,  the  primary  coil  consists  of 
a  few  turns  of  a  thick  wire,  and  the  secondary 
coil  of  many  turns,  often  thousands,  of  fine  wire. 
Such  coils  are  generally  called  Ruhmkorff  coils, 
from  the  name  of  a  celebrated  manufacturer  of 
them. 

In  the  form  of  Ruhmkorff  coil,  shown  in  Fig. 
142,  the  primary  wire,  wound  on  a  core  formed 


Fig.  142.    Ruhmkorff  Coil. 

of  a  bundle  of  soft  iron  wires,  has  its  ends  brought 
out  as  shown  at  f,  f.  The  fine  wire,  forming  the 
secondary  coil,  is  wrapped  around  an  insulated 
cylinder  of  vulcanite,  or  glass,  surrounding  the 
primary  coil.  This  wire  is  very  thin,  and  in  some 
coils  is  over  one  hundred  miles  in  length. 

If  the  core  of  an  induction  coil  were  made  solid 
it  would  heat  considerably  and  therefore  cause  a 
loss  of  energy.  The  core  is  therefore  laminated, 
usually  by  forming  it  of  a  bundle  of  soft  iron  wire. 

Too  great  a  division  of  the  core,  however,  is 
inadvisable,  since,  although  the  eddy  currents 
therein  are  thereby  avoided,  yet,  too  great  a 
division  of  the  core  acts  practically  so  to 
decrease  the  magnetic  permeability  that  the 
greatest  efficiency  cannot  be  obtained. 

The  ends  of  the  secondary  coil  are  connected 
to  the  insulated  pillars  A  and  B. 

The  primary  current  is  rapidly  broken  by 
means  of  a  mercury  break,  shown  at  L  and  M. 

The  commutator,  shown  to  the  right  and  front 
of  the  base,  is  provided  for  the  purpose  of  cutting 
off  the  current  through  the  primary,  or  for  chang- 
ing its  direction.  When  a  battery  which  produces 
a  comparatively  large  current  of  but  a  few  volts 
electromotive  force  is  connected  with  the  pri- 
mary, and  its  current  rapidly  interrupted,  a 
torrent  of  sparks  will  pass  between  A  and  B, 
having  an  electromotive  force  of  many  thousands 
of  times  the  number  of  volts  of  the  primary  cur- 


rent, but  of  a  correspondingly  smaller  current 
strength. 

In  such  cases,  excepting  losses  during  conver. 
sign,  the  energy  in  the  primary  current,  or  C  E, 
is  equal  to  the  energy  in  the  secondary  current, 
or  C'  E'.  As  much  therefore  as  E',  the  electro- 
motive force  of  the  secondary  current,  exceeds  E, 
the  electromotive  force  of  the  primary  current, 
the  current  strength  C',  of  the  secondary,  will  b« 
less  than  the  current  strength  C,  of  the  primary. 
This  is  approximately  true  only,  and  only  in  in. 
duction  coils  possessing  a  closed  magnetic  circuit. 
(See  Transformer.'] 

Fig.  143  shows  diagramatically  the  arrange- 


Fig.  143.     Circuit  Connections  of  Induction  Coil. 

ment  and  connection  of  the  different  parts  of  an 
induction  coil. 

The  core  II',  consists  of  a  bundle  of  soft  iron 
wires,  each  of  which  is  covered  with  a  thin  insu- 
lating layer  of  varnish  or  oxide.  A  primary  wire 
P  P,  consisting  of  a  few  turns  of  comparatively 
thick  wire,  is  wound  around  the.  core,  and  a 
greater  length  of  thin  wire  S  S,  is  wound  upon  the 
primary.  This  is  called  the  secondary.  So  as 
not  to  confuse  the  details  of  the  figure  it  is  repre- 
sented as  a  few  turns. 

The  terminals  of  the  battery  B,  are  connected 
to  the  primary  wire,  through  the  automatic  inter- 
rupter, in  the  manner  shown.  It  will  be  seen  that 
the  attraction  of  the  core  TI',  for  the  vibrating 
armature  H,  will  break  contact  at  the  point  o,  and 
cause  a  continued  interruption  of  the  battery 
current. 

The  condenser  cc',  is  connected  ?s  bl.wwn.  It 
acts  to  diminish  the  sparking  at  the  contact  points 
on  breaking  contact,  and  thus,  by  making  the 
battery  current  more  sudden,  to  make  its  in« 
ductive  action  greater. 

The  reactions  which  take  place  when  a  simple 


Coi.] 


108 


[Coi. 


periodic  electromotive  force  is  impressed  on  the 
primary  of  an  induction  coil  are  substantially 
thus  stated  by  J.  A.  Fleming  : 

(i.)  The  application  of  a  simple  periodic  im- 
pressed electromotive  force  produces  a  simple 
periodic  current,  moving  under  an  effective  elec- 
tromotive force  of  self-induction,  and  brings  into 
existence  a  counter- electromotive  force  of  self- 
induction,  which  cautes  the  primary  current  to 
kg  behind,  by  an  angle  called  the  angle  of  lag. 

(2.)  The  field  around  the  primary,  and,  there- 
fore, the  induction  through  the  secondary,  is  in 
consonance  with  the  primary  current,  and  the  im- 
pressed electromotive  force  in  the  secondary  is 
in  quadrature  with  the  primary  current.  (See 
Consonance.  Quadrature,  In.) 

(3.)  The  secondary-impressed  electromotive 
force  gives  rise  to  a  secondary  current  moving 
under  an  effective  electromotive  force  and  creat- 
ing a  counter  electromotive  force  of  self-induc- 
tion. 

(4.)  This  secondary  current  reacts  in  its  turn 
on  the  primary,  and  creates  what  is  called  the 
back  electromotive  force,  or  the  reacting-induc- 
tive-electromotive  force  of  the  primary  circuit. 

(5.)  There  is  then  a  phase-difference  between 
the  primary  and  secondary-currents,  and  also  be- 
tween the'  primary-impressed  electromotive  force 
and  the  primary  current 

If,   as  in  Fig.  144,   two  electric  circuits    are 


Fig.  144.    Electr-c  and  Magnetic  Link. 

linked  with  a  magnetic  circuit,  and  a  small 
periodic  electromotive  force  be  impressed  on  the 
primary,  the  following  phenomena  occur: 

(I.)  A  periodic  primary  current  is  set  up  in 
the  primary  circuit,  which,  though  of  the  same 
periodic  time  as  the  impressed  electromotive 
force,  differs  from  it  in  phase. 

(2.)  A  wave  of  counter  electromotive  force  is 
produced  in  the  primary  circuit  by  the  inductive 
action,  which  does  not  coincide  either  with  the 
impressed  electromotive  force,  nor  with  the 
primary  current. 

(3.)  A  wave  of  magnetization  is  produced  in 
the  iron  core,  which  lacs  behind  the  primary 


current  by  somewhat  less  than  90  degrees  oi 
phase. 

(4.)  A  wave  of  impressed  electromotive  force 
is  produced  in  the  secondary  circuit,  due  to  and 
measured  by  the  rate  of  change  of  magnetic  in- 
duction in  the  core,  and  lagging  90  degrees,  or 
more,  behind  the  magnetization  wave. 

(5.)  A  wave  of  secondary  current,  lagging  be 
hind  the  secondary  electromotive  force  in  phase 
except  where  the  circuit  consists  of  a  few  turns  o' 
conductor,  or  is  connected  with  an  external  cu  - 
cuit  of  practically  no  inductance. — [Fleming.} 

Coil,    Induction,    Inverted    — An 

induction  coil  in  which  the  primary  coil  is 
made  of  a  long,  thin  wire,  and  the  secondary 
coil  of  a  short,  thick  wire. 

By  the  use  of  an  inverted  coil,  a  current  of  high 
electromotive  force  and  comparatively  small  cur- 
rent strength,  *'.  <•.,  but  of  few  amperes,  is  con- 
verted or  transformed  into  a  current  of  compar- 
atively  small  electromotive  force  and  large  cur- 
rent strength.  For  advantages  of  this  conversion 
see  Electricity,  Distribution  of,  by  Alternating 
Currents. 

Inverted  induction  coils  are  called  converters  oe 
transformers.  (See  Transformer.} 

Coil,    Induction,    Medical    — An 

induction  coil  used  for  medical  purposes. 

A  form  of  induction  coil  used  for  medical  pur« 
poses  is  shown  in  Fig.  145. 


Fig.  t4j.    Medical  Induction  Gat. 

Coil,  Induction,  Microphone Alt 

induction  coil,  in  which  the  variations  in  the 
circuit  of  the  primary  are  obtained  by  means 
of  microphone  contacts.  (See  Microphotie^ 

The  carbon -button  telephone  transmitter  is  a 
microphone  in  its  action,  its  electric  resistance 
varying  with  the  varying  pressure  caused  by  the 
sound  waves.  The  carbon-button  is  in  the  prim- 
ary circuit  of  an  induction  coil,  variations  t» 


Coi.] 


109 


[Coi. 


primary  of  which,  under  the  influence  of  the 
sound  waves,  produce  corresponding  variations 
in  the  currents  induced  in  the  secondary. 

Coil,  Kicking- A  term  sometimes 

applied  to  a  Choking-Coil.  (See  Coil,  Chok- 
ing) 

The  term  kicking-coil  has  arisen  from  the  fact 
that  the  impedance  due  to  self-induction  opposes 
the  starting  or  stopping  of  the  current  somewhat 
in  the  manner  of  an  opposing  kick. 


Coil,  Magnet 


— A   coil  of  insulated 


wire  surrounding  the  core  of  an  electro-mag- 
net, and  through  which  the  magnetizing  cur- 
rent is  passed.  (See  Magnet,  Electro?) 

Coil,  Primary  -  —That  coil  or  con- 
ductor of  an  induction  coil  or  transformer, 
through  which  the  rapidly  interrupted  or  alter- 
nate inducing  currents  are  sent. 

In  the  Ruhmkorff  induction  coil  the  primary 
coil  consists  of  a  comparatively  short  length  of 
thick  wire,  the  secondary  coil  being  formed  of 
a  comparatively  great  length  of  fine  wire.  In 
the  transformer  or  converter,  the  primary  coil 
consists  of  wire  that  is  longer  and  thinner  than 
that  in  the  secondary  coil.  In  other  words,  the 
transformer  or  converter  consists  of  an  inverted 
induction  coil.  (See  Coil,  Induction.  Trans- 
former. ) 

Coil,  Reaction A  magnetizing  coil, 

surrounded  by  a  conducting  covering  or 
sheathing,  which  opposes  the  passage  of 
rapidly  alternating  currents  less  when  directly 
over  the  magnetizing  coil  than  when  a  short 
distance  from  it. 

A  term  often  used  for  choking-coil.  (See 
Coil,  Choking.) 

Coil,  Reaction,  Balanced A  coil 

employed  in  a 
system  of  distri- 
bution by  means 
of  transformers 
for  maintaining 
a  constant  cur- 
rent in  the  sec- 
ondary Circuit,  FiS-  I4<>  Balanced-Reaction  Coil. 

despite  changes  in  the  load  placed  therein. 
A  balanced-reaction  coil  is  shown  in  Fig.  146. 


A  reaction  coil  is  placed  in  the  circuit  of  lamps  in 
series  in  a  constant  potential  system.  The  sheath- 
ing of  this  coil  is  maintained  in  a  balanced  position 
by  the  counter  weight  P,  and  the  spring  S.  If  now 
a  lamp  is  extinguished  in  the  circuit,  the  increase 
of  current,  due  to  decreased  resistance,  causes  the 
sheath  to  be  deflected,  and,  thus  increasing  the 
self-induction  of  the  coil,  reduces  the  lamp  current 
to  its  normal  value. 

Coil,  Resistance A  coil  of  wire 

of  known  electrical  resistance  employed  for 
measuring  resistance. 

In  order  to  avoid  self-induction  and  the  mag- 
netizing effects  of  the  coils  on  the  needles  of  the 
galvanometer  used  in  electric  measurements,  as 
well  as  the  disturbing  effects  of  self-induction,  the 
wire  of  the  resistance  coil  is  doubled  on  itself 
before  being  wound,  and  its  ends  connected 
with  the  brass  bars,  E,  E,  Fig.  147.  The  inser- 


Fig.  147.     Connections  of  Resistance  Coils. 

tion  of  the  plug-key  cuts  the  coil  out  of  the  cir- 
cuit by  short-circuiting.  (See  Box,  Resistance. 
Bridge,  Electric.  Coil,  Resistance,  Standard.} 

The  coils  are  made  of  German  silver,  or  plati- 
noid, the  resistance  of  which  is  not  much 
affected  by  heat. 

Coil,  Resistance,  Standard A  coil 

the  resistance  of  which  is  that  of  the  stand- 
ard ohm  or  some  multiple  or  sub-multiple 
thereof. 

The  standard  ohm,  as  issued  by  the  Electric 
Standards  Committee  of  England,  has  the  form 
shown  in  Fig.  148.  The  coil  of  wire  is  formed  of 
an  alloy  of  platinum  and  silver,  insulated  by  silk 
covering  and  melted  paraffine.  Its  ends  are  sol- 
dered to  thick  copper  rods,  r,  r',  for  ready  con- 
nection with  mercury  cups.  The  coil  is  at  B. 
The  space  above  it,  at  A,  is  filled  with  paraffine. 
A  hole,  at  t,  runs  through  the  coil  for  the  readv 


Coi.l 


no 


[Coi. 


insertion  of  a  thermometer.  The  lower  part  of 
the  coil,  B,  is  immersed  in  water  up  to  the  shoul- 
der of  A,  and  the  water  stirred  from  time  to 


Fig.  14.8.    Standard  Ohm. 

time.  Since  the  coil  is  heated  by  the  current,  sue- 
cessive  observations  should  be  at  least  ten  minutes 
apart.  Only  mild  currents  should  be  passed 
through  the  coils. 

Coil,  Resistance,   Standardized  - 

Resistance  coils  whose  resistances  have  been 
carefully  determined  by  comparison  with  a 
standard  ohm  or  other  standard  coils. 

Coil,  Ruhmkorff A  term  some- 
times applied  to  any  induction  coil,  the 
secondary  of  which  gives  currents  of  higher 
electromotive  force  than  the  primary.  (See 
Coil,  Induction?) 

Coil,  Secondary  -  — That  coil  or  con- 
ductor of  an  induction  coil  or  transformer, 
in  which  alternating  currents  are  induced  by 
the  rapidly  interrupted  or  alternating  currents 
in  the  primary  coil.  (See  Coil,  Induction. 
Transformer^) 

Coil,  Shunt  -  — A  coil  placed  in  a  de- 
rived or  shunt  circuit.  (See  Circuit,  Shunt) 

Coil,  Spark  — A  coil  of  insulated  wire 

connected  with  the  main  circuit  in  a  system 
of  electric  gas-lighting,  the  extra  spark  pro- 


Fig.  I4Q.    Spark  Coil. 

duced  on  breaking  the  circuit  of  which  is  em- 
ployed for  electrically  igniting  gas  jets. 

Spark  coils  are  employed  where  the  number  of 


gas  jets  to  be  simultaneously  lighted  is  not  too 
great.     When  this  number  exceeds  certain  limits, 
the  spark  from  an  induction  coil  is  more  ad  van- 
tageously  used. 
A  spark  coil  is  shown  in  Fig.  149. 

Coils,  Armature,  of  Dynamo-Electric 

Machine The  coils,  strips  or  bars  that 

are  wound  or  placed  on  the  armature  core. 

To  avoid  needless  resistance  the  wire,  or  othe* 
conductor,  of  the  armature  coils,  should  be  as 
short  and  thick  as  will  enable  the  desired  electro- 
motive force  to  be  obtained  without  excessive 
speed  of  rotation. 

The  armature  coils  should  enclose  as  many 
lines  of  force  as  possible  (i.  e.,  they  should  have 
as  nearly  a  circular  outline  as  possible).  In 
drum-armatures,  the  breadth  of  the  armature  is 
frequently  made  nearly  equal  to  its  length,  unless 
other  considerations  prevent. 

When  the  armature  wire  consists  of  rods  or 
bars,  it  should  be  laminated  or  slit  in  planes 
parallel  to  the  lines  of  force  so  as  to  avoid 
eddy  currents.  Other  things  being  equal,  the 


Fig.  Jjo.     Series  Connection  of  Armature  Coils. 

greater  the  number  of  coils,  the  more  uniform 
the  current  generated.  The  separate  coils  should 
be  symmetrically  disposed;  otherwise  irregular  in- 
duction, and  consequent  sparking  at  the  commu- 
tator results. 

The  coils  of  pole-armatures  should  be  wound  near 
the  poles  rather  than  on  the  middle  of  the  cores. 
In  order  to  avoid  undue  heating,  spaces  for 
air  ventilation  are  not  inadvisable.  Various  con- 
nections of  the  armature  coils  are  used. 

In  some  machines  all  the  coils  are  connected  in 
a  closed  circuit.  In  some,  the  coils  are  independ- 
ent of  one  another,  and,  either  for  the  entire 
revolution,  or  for  part  of  a  revolution,  are  on  an 
open  circuit. 


Coi.] 


Ill 


[Col. 


In  alternating  current  dynamos  in  order  to  ob- 
tain the  rapid  reversals  or  alternations  of  current, 
which  in  some  machines  are  as  high  as  12,  coo 
per  minute,  a  number  of  poles  of  alternate  polar- 
ity are  employed.  The  separate  coils  that  are 
used  on  the  armature  may  be  coupled  either  in 
series  or  in  multiple-arc. 

Where  a  comparatively  low  electromotive  force 
is  sufficient,  such  as  for  incandescent  lamps  in 
multiple-arc,  the  separate  coils  are  united  in 
parallel;  but  for  purposes  where  a  considerable 
electromotive  force  is  necessary,  as  for  example, 
in  systems  of  alternate  current  distribution,  with 
converters  at  considerable  distances  from  the 
generating  dynamo,  they  are  often  connected  in 
series,  as  shown  in  Fig.  150. 

Coils,  Binding Coils  of  wire  wound 

on  the  outside  of  the  armature  coils,  and  at 
right  angles  thereto,  to  prevent  the  loosening 
of  the  armature  wires  by  the  action  of  cen- 
trifugal force. 

The  binding  coils  are  generally  made  of  hard 
brass  wire. 

Coils,  Compensating A  term  some- 
times applied  to  the  series  coils  placed  on  a 
shunt-wound  dynamo. 

Coils,  Conjugate  — Two  coils  so 

placed,  as  regards  each  other,  that  an  interrup- 
tion of  the  current  in  one  produces  no  induced 
current  in  the  other. 

When  two  coils  are  conjugate  to  each  other,  the 
lines  of  force  of  one  do  not  pass  through  the  other. 
Consequently  such  coils  can  produce  no  induc- 
tion in  one  another. 

Coils,  Henry's A  number  of  sepa- 
rate induction  coils  so  connected  that  the 
currents  induced  in  the  secondary  wire  of 
the  first  coil,  are  caused  to  induce  currents 
in  the  secondary  wire  of  the  second  coil,  with 
whose  primary  it  is  connected  in  series,  and 
so  on  throughout  all  the  coils. 

A  series  of  three  of  Henry's  coils  is  shown  in 
Fig.  151.  An  intermittent  battery  current  is  sent 

b 


secondary,  d,  of  the  second  coil,  is  connected  with 
the  primary,  e,  of  the  third  coil,  and  the  cur- 
rents finally  induced  in  f,  are  employed  for  any 
useful  purpose,  such  as  the  magnetization  of  a 
bar  of  iron  at  g. 

The  current  in  b,  is  sometimes  called  a  Secon- 
dary Current,  or  a  Current  of  the  Second  Order; 
that  induced  by  this  secondary  current  in  d,  is 
called  a  Tertiary  Current,  or  a  Current  of  the 
Third  Order  y  that  in  f,  a  Current  of  the  Fourth 
Order.  Henry  carried  these  successive  induc- 
tions up  to  currents  of  the  Seventh  Order. 

Henry's  coils  in  reality  consist  of  separate  in- 
duction coils,  connected,  as  above  explained,  in 
series. 

In  Fig.   152,  the  tertiary  current  induced   in 

A 

n 


Fig.  132.     Tertiary  Currents  of  Coils. 
IV,  may  be  employed  to  give  shocks  to  a  person 
grasping  the  handles,  e  and  f. 

Coils,  Proportional Pairs  of  re- 
sistance coils,  generally  of  10,  100  and  1,000 
ohms  each,  forming  the  proportional  arms  of 
the  balance  or  bridge,  and  employed  in  the  box, 
or  commercial  form  of  Wheatstone's  bridge. 
(See  Bridge,  Electric,  Commercial  Form 
of.} 

Cold,  Production  of,  by  Electricity 

— An  absorption  of  energy  and  consequent 
reduction  of  temperature  at  a  thermo-electric 
junction  by  the  passage  of  an  electric  current 
across  such  junction  in  a  certain  direction. 

When  an  electric  current  passes  across  a  thermo- 
electric junction,  the  junction  is  either  heated  or 
cooled.  In  the  case  of  an  antimony-bismuth 
couple,  if  the  current  passes  from  the  antimony 


Fig.  Jjl-    Henry's  Coils. 

into  a,  the  secondary,  b,  of  which  is  connected 
with  the  primary,  c,  of  the  second  coil.     The 


Freezing  of  Water  by  Electricity. 

to  the  bismuth  the  junction  is  heated;  if  it  passes 
from  the  bismuth  to  the  antimony  it  is  cooled. 
In  the  apparatus  shown  in  Fig.  153,  the  antimony- 
bismuth  couple  is  arranged  as  shown  for  the 


Col.] 


112 


[Coin. 


freezing  of  water  by  means  of  the  electric  cur- 
rent. A  and  B,  represent  plates  of  antimony  and 
bismuth  respectively.  A  small  cavity,  at  E,  serves 
to  hold  a  drop  of  water.  When  a  current  has 
passed  in  the  direction  shown  by  the  arrows,  a 
drop  of  water,  previously  cooled  to  the  tempera- 
ture of  melting  ice,  is  solidified  by  the  lowering 
of  the  temperature  at  the  junction. 

Collecting  Brushes  of  Dynamo-Electric 
Machine.  —  (See  Brushes,  Collecting,  of 
Dynamo-Electric  Machine?) 

Collectors,  Electric Devices  em- 
ployed for  collecting  or  taking  off  electricity 
from  a  moving  electric  source. 

Collectors  of  Electric  Frictional  Ma- 
chines.— The  metallic  points  that  collect  the 
charge  from  the  glass  plate  or  cylinder  of  a 
frictional  electric  machine. 

Collectors  of  Dynamo  Electric  Machines. 
— The  brushes  that  rest  on  the  commutator 
cylinder,  and  carry  off  the  current  generated 
on  the  rotation  of  the  armature. 

Collectors  are  properly  called  commutators 
when  they  are  employed  to  cause  an  alternate 
current  to  become  continuous,  or  to  flow  in  one 
and  the  same  direction. 

Colloids. — One  of  the  two  classes  into 
which  substances  are  separated  by  dialysis. 

By  dialysis  bodies  are  separated  'into  crystal- 
loids, or  bodies  capable  of  crystallizing,  and  col- 
loids or  jelly-like  bodies,  incapable  of  crystallizing. 
Colloids  possess  great  cohesion  and  but  slight 
diffusibility.  (See  Dialysis.) 

Colombin. — An  insulating  substance,  con- 
sisting of  a  mixture  of  sulphate  of  barium 
and  sulphate  of  calcium,  placed  between  the 
parallel  carbons  of  the  Jablochkoff  candle. 

Column,  Barometric  — A  column, 

usually  of  mercury,  approximately  30  inches 
in  vertical  height,  sustained  in  a  barometer, 
or  other  tube,  by  the  pressure  of  the  atmos- 
phere. 

The  space  above  the  barometric  column  con- 
tains a  vacuum  known  as  the  Torricellian  vac- 
uum. (See  Vacuum,  Torricellian.) 

Column,  Electric A  term  formerly 

applied  to  a  voltaic  pile.     (See  Pile,  Voltaic?) 
Colza  Oil.— (See  Oil,  Colza?) 


Combination  Gas  Fixtures. — (See  F£x~ 
tures.  Gas,  Combination?) 

Combined  Tangent  and  Sine  Galvanom- 
eter.— (See  Galvanometer,  Combined  Tan~ 
gent  and  Sine?) 

Comb  Lightning  Arrester. — (See  Arrester, 
Lightning,  Comb?) 

Comb  Protector.— (See  Protector,  Comb?) 
Commercial  Efficiency. — (See  Efficiency, 
Commercial?) 

Commercial    Efficiency   of    Dynamo.— 

(See  Efficiency,  Commercial,  of  Dynamo?} 

Commercial  Form  of  Electric  Bridge.— 
(See  Bridge,  Electric,  Commercial  Form  of.) 

Communicator,  Electric A  terra 

formerly  employed  for  a  telegraphic  key.  (See 
Key,  Telegraphic?) 

Commntating  Transformers,  Distribu- 
tion of  Electricity  by  • — (See  Elec- 
tricity, Distribution  of,  by  Commutating 
Transformers?) 

Commutation. — The  act  of  commuting,  as 
of  currents. 

Commutation,  Diameter  of In  a 

dynamo-electric  machine  a  diameter  on  the 
commutator  cylinder  on  one  side  of  which 
the  differences  of  potential,  produced  by  the 
movement  of  the  coils  through  the  magnetic 
field,  tend  to  produce  a  current  in  a  direction 
opposite  to  those  on  the  other  side. 

That  diameter  on  the  commutator  cylinder 
of  an  open-circuited  armature  that  joins  the 
points  of  contact  of  the  collecting  brushes. 

Thus  in  Fig.  154,  the  directions  of  the  induced 
electromotive  forces  are  indicated  by  the  arrows. 
The  diameter  of  commutation  is  therefore  the  line 
n  n'.  The  term  neutral  line  is  also  sometimes 
given  to  this  line.  It  lies  at  right  angles  to  the 
line  of  maximum  magnetization  m  m. 

In  a  closed-circuited  armature,  that  is,  in  an  arm* 
ature  the  coils  of  which  are  connected  in,  a  closed 
circuit,  the  collecting  brushes  rest  on  the  commu- 
tator cylinder  at  the  neutral  line,  or  on  the  diame* 
ter  of  commutation. 

In  an  open-circuited  armature,  however,  where 
the  coils  are  independent  of  each  other,  the 
collecting  brushes  must  be  set  at  m  m,  at  right 
angles  to  the  mutral  line  n  n.  The  term  diame 


Com.] 


113 


[Com. 


ter  of  commutation  is,  therefore,  often  applied  to 
this  second  position.    According  to  this  use  of  the 


Fig.  154*    Diameter  of  Commutation, 

term,  the  diameter  of  commutation  is  that  diameter 
on  the  commutator  which  joins  the  points  of  con- 
tact of  the  collecting  brushes. 

The  neutral  linenn',  Fig.  154,  it  will  be  noticed 
does  not  occupy  a  vertical  position,  but  is  dis- 
placed somewhat  in  the  direction  of  rotation,  thus 
necessitating  the  shifting  of  the  brushes  forward 
in  the  direction  of  rotation.  This  necessary  shift- 
ing of  the  brushes  is  known  technically  as  the 
lead  of  the  brushes.  (See  Lead,  Angle  of.) 

It  will  thus  be  seen  that  the  term  diameter  of 
commutation  is  used  in  two  different  senses. 

In  reality,  the  term  refers  to  the  position  of  cer- 
tain points  on  the  commutator  as  distinguished 
Irom  points  on  the  armature  coils.  On  the  com- 
mutator,  the  diameter  of  commutation  is  the  line 
drawn  through  the  two  commutator  bars  at  which 
the  currents  from  the  two  sides  are  opposed  to 
each  other. 

It  is  evident  that  the  commutator  may  be  inten- 
tionally twisted  with  respect  to  the  armature,  so 
as  to  bring  its  diameter  of  commutation  into  any 
desired  convenient  position. 

Commutation,  Dissymmetry  of 

A  commutation  in  which  the  neutral  line  does 
not  coincide  with  a  diameter  of  the  commu- 
tator. (See  Commutation,  Diameter  of.) 

Commutator. — In  general,  a  device  for 
changing  the  direction  of  an  electric  current. 

Commutator,  Burning-  at  • •  — Arcing 

and  consequent  destructive  action  on  the 
commutator  segments  of  a  dynamo-electric 
machine. 

When  the  arcing  is  pronounced,  the  intense 
heat  soon  'destroys  the  commutator. 

Commutator  Cylinder,  Neutral-Line  of 

(See  Line,  Neutral,  of  Commutator 

Cylinder^ 


Commutator,  Dynamo-Electric  Machine 

That  part  of  a  dynamo-electric  ma- 
chine which  is  designed  to  cause  the  alter- 
nating currents  produced  in  the  armature  to 
flow  in  one  and  the  same  direction  in  the  ex- 
ternal circuit. 

One  end  of  an  armature  coil  is  connected  with 
A',  Fig.  155,  and  the 
other  with  A,  The  brushes 
are  so  set  that  A,  and  A', 
are  in  contact  with  B', 
and  B,  respectively,  as 
long  as  the  current  flows 
in  the  same  direction  in  the 
armature  coil  connected 
therewith,  but  enter  into 
contact  with  B,  and  B',  Fig.  153.  Commutator 
when  the  current  changes  of  Dynamo  -  Electric 
its  direction,  and  continue  Machine. 
in  such  contact  as  long  as  it  flows  in  this  direc- 
tion. By  the  t(se  of  a  commutator  the  (urrent 
will  therefore  flow  throttgh  any  circuit  connected 
with  the  brushes  in  one  and  the  same  constant 
direction. 


Two-part  Commutator 

In  action,  the  commutator  is  subject  to  wear 
from  the  friction  of  the  brushes,  and  the  burning 
action  of  destructive  sparks.  The  rommutator 

A 


Fig.  TS7-     Two-part 
Commutator. 


.     Two-part 
Commutator. 


segments  are,  therefore,  made  of  comparatively 
thick  pieces  of  metal,  insulated  from  one  another 


Com.] 


114 


[Com. 


and  supported  on  a  commutator  cylinder  usually 
placed  oruthe  shaft  of  the  armature. 

The  ends  of  the  armature  coils  are  connected 
to  commutator  strips  or  segments. 

The  number  of  metallic  pieces  or  segments,  A. 
and  A',  on  the  commutator  cylinder  depends  on 
the  number,  arrangement  and  connection  of  the 
armature  coils,   and  on  the 
disposition  of  the  magnetic 
field  of  the  machine. 

Figs.  156,  157  and  158 
show  the  connections  of  an 
armature  coil  to  the  plates  of 
a  two-part  commutator. 

A  four-part  commutator 
for  a  ring-armature,  and  the  **- '5** 

Commutator. 
connections    of    the     coils 

thereto,  are  shown  in  Fig.  159. 

The  commutator  strips  may  either  connect  the 
separate  coils  in  a  closed-circuited  armature,  in 
which  the  coils  are  all  connected  with  one  an- 
other,  or,  in  an  open -circuited  armature,  in  which 
the  separate  coils  are  independent  of  one  another. 

Commutator,  RuhmkoriTs A  name 

given  by  Ruhmkorff  to  a  device  placed  on  his 
induction  coil  for  the  purpose  of  changing  or 
reversing  the  direction  of  the  battery  current 
through  the  primary. 

This  reverser  is  shown  in  Fig.  160.  (See 
Coil,  Ruhmkorff.') 


Fig.  160,    Ruhmkorff's  Commutator 

Two  metallic  strips,  V,  V,  supported  on  a 
cylinder  of  insulating  material,  are  in  contact  with 
the  battery  terminals  A,  and  D,  through  iwo 
vertical  springs  that  b?ar  on  them.  On  a  half 
rotation  of  the  cylinder  by  the  thumb  screw  L, 


the  strips  V,  V,  change  places  as  regards  the  ver- 
tical springs,  and  thus  reverse  the  direction  o{ 
the  battery  current. 

Commuted  Currents.  —  (See  Currents, 
Commuted^ 

Commuter,  Current Any  appa- 
ratus by  means  of  which  electrical  currents, 
flowing  alternately  in  different  directions, 
may  be  caused  to  flow  in  one  and  the  same 
direction. 

A  Commutator. 

Commuting. — Causing  to  flow  in  one  and 
the  same  direction. 

Commuting  Currents.  —  (See  Currents, 
Commuting^ 

Compartment  Manhole  of  Conduit.—  (See 
Manhole,  Compartment,  of  Conduit.) 

Compass,  Azimuth  — A  compass 

used  by  mariners  for  measuring  the  horizon- 
tal distance  of  the  sun  or  stars  from  the  mag- 
netic meridian.  (See  Azimuth,  Magnetic!] 

A  mariner's  Compass. 

A  single  magnetic  needle,  or  several  magnetic 
needles,  are  placed  parallel  to  one  another  on  the 
lower  surface  of  a  card,  called  the  compass  card. 
This  card  is  divided  into  the  four  cardinal  points, 
N,  S,  E  and  W,  and  these  again  subdivided  into 
thirty-two  points  called  Rhumbs. 

In  the  azimuth  compass  these  divisions  are  sup> 
plemented  by  a  further  division  into  degrees. 

A  form  of  azimuth  compass  is  shown  in  Fig. 
l6l.  In  order  to  maintain  the  compass  box  in  a 


Fig.  l6r.    Azimuth  Compass, 

horizontal  position,  despite  the  rolling  of  the  ship, 
the  box,  A  B,  is  suspended  in  the  larger  box,  P 
Q,  on  two  concentric  metallic  circles,  C  D,  and 


Com.j 


115 


E  F,  pivoted  on  two  horizontal  axes  at  right  angles 
to  each  other.  This  kind  of  support  is  technic- 
ally termed  Gimbals.  Sights  G,  H,  are  provided 
for  measuring  the  magnetic  azimuth  of  any  ob- 
ject. 

Compass,  Boxing  the  — —  —Naming. 
Consecutively,  all  the  different  points  or 
thumbs  of  the  compass  from  any  one  of  them. 
(See  Compass,  Points  of.} 

Compass-Card. — (See  Card,  Compass) 

Compass,  Inclination A  magnetic 

needle  moving  freely  in  a  single  vertical  plane; 
and  employed  for  determining  the  angle  of 
dip  at  any  place. 

An  Inclinometer.    (See  Inclinometer) 
A  dipping  circle.     (See  Circle,  Dipping) 
The  needle  M,  Fig.  162,  is  supported  on  knife 


Fig.  ibz      Inclination  Con: past. 

tdges  so  as  to  be  free  to  move  only  in  the  verticat 
plane  of  the  graduated  vertical  circle  C  C.  This 
Circle  is  movable  over  the  horizontal  graduated 
circle  H  II.  In  order  to  determine  the  true  angle 
of  dip,  the  vertical  plane  in  which  the  needle  is 
free  to  move  must  be  placed  exactly  in  the  plane 
of  the  magnetic  meridian. 

To  ascertain  this  plane  the  vertical  circle  is 
moved  until  the  needle  points  vertically  down* 
wards.  It  is  then  in  a  plane  90  degrees  from  tha 
magnetic  meridian.  The  vertical  circle  is  then 
moved  over  the  horizontal  circle  90  degrees,  in 
which  position  it  is  in  the  plane  of  the  magnetic 
meridian,  when  the  true  angle  of  the  dip  is  read  off. 

For  an  explanation  of  the  reason  of  this>  see 


[Com, 

Component,    Horizontal  and    Vertical^    of  thk 
Earth's  Magnetism. 

Compass,  Mariner's A  name  often 

applied  to  an  azimuth  compass.    (See  Com- 
pass, Azimuth?) 

Compass,  Points  of The  thirty-two 

points  into  which  a  compass  card  is  divided. 
Sixteen  of  these  points  are  shown  in  Fig.  163. 


Fig.  163.    Points  of  Compass. 

The  position  of  the  remaining  points  will  be 
readfly  seen  by  an  inspection  of  the  figures. 
These  points  are  as  follows: 


I.  North. 
8.  N.  by  E. 

3.  N.  N.  E. 

4.  N.  E.  by  N. 

5.  N.  E. 

6.  N.  E.  by  E. 

7.  E.  N.  E. 
&  E.  by  N. 
g.  East. 

10.  E.  byS. 

11.  E.  S.  E. 

12.  S.  E.  by  E. 

13.  S.  E. 

14.  S.  E.  by  S 

15.  S.  S.  E. 

16.  S.  by  E. 


17.  South. 

18.  S.  by  W. 

19.  S.  S.  W. 

20.  S.  W.  by  Su 

21.  S.  W. 

22.  S.  W.  by  W. 

23.  W.  S.  W. 

24.  W.  by  S. 

25.  West. 

26.  W.  by  N. 

27.  W.  N.  W. 

28.  N.  W.  by  W. 

29.  N.  W. 

30.  N.  W.  by  N. 

31.  N.  N.  W. 

32.  N.  by  W. 


Boxing  the  Compass  consists  in  naming  all 
these  points  consecutively  from  any  one  of  them. 

The  direction  in  which  the  ship  is  sailing  is  de. 
termined  by  means  of  a  point  fixed  on  the  inside  of 
the  compass  box,  directly  in  the  line  of  the  ves- 
sel's bow. 

Compass,  Rhumbs  of  —  — The  points 
of  a  mariner's  compass.  (See  Compass^ 
Points  of) 


Com.j 


116 


Compensated  Alternator. — (See  Alter- 
nator, Compensated^ 

Compensated  Excitation  of  Alternator. 

— (See  Alternator,  Compensated  Excita- 
tion of.) 

Compensating  Coils. — (See  Coils.  Com- 
pensating.) 

Compensating  Magnet.  —  (See  Magnet, 
Compensating^ 

Complement  of  Angle*— <$&$  Angle,  Com- 
plement of.) 

Completed-Circuit. — (See  Circuit,  Com- 
pleted.) 

Component. — One  of  the  two  or  more  sep- 
arate forces  into  which  any  single  force  may 
be  resolved ;  or,  conversely,  the  separate  forces 
which  together  produce  any  single  resulting 
force. 

When  two  or  more  forces  act  simultaneously  to 
produce  motion  in  a  body,  the  body  will  move 


Ftg.  164.     Composition  of  Forces, 


with  a  given  force  in  a  single  direction  called  the 
resultant.  The  separate  forces,  or  directions  of 
motion,  are  called  the  components. 

Two  forces  acting  simultaneously  on  a  body  at 
A,  Fig.  164,  tending  to  move  it  in  the  direction 


Fff.r6f.   Rttotution  o/Fcne*. 


of  the  arrows,  along  A  B,  and  A  C,  with  intend- 
tiesproportioned  to  the  lengths  of  the  lines  A  B, 
and  A  C,  respectively,  will  move  it  in  the  direc- 
tion A  D.  obtained  by  drawing  B  D,  and  L>  C, 


parallel  to  A  C,  and  A  B,  respectively,  and  then 
drawing  A  D,  through  the  po.nt  of  intersection, 
D.  This  is  called  the  Comrosition  of  Forces. 
A  D,  is  the  resultant  force,  and  A  B  and  A  C, 
are  its  components. 

Conversely,  a  single  force,  acting  in  the  direc- 
tion of  D  B,  Fig.  165,  against  a  surface,  B  C, 
may  be  regarded  as  the  resultant  of  the  two  sep- 
arate forces,  D  E,  and  D  C,  one  parallel  to  C  ±J, 
and  one  perpendicular  to  it.  D  E,  being  parallel 
to  C  B,  produces  no  pressure,  and  the  absolute 
effect  of  the  force  will,  therefore,  be  represented 
by  CD. 

This  separation  of  a  single  force  into  two  or 
more  separate  forces  is  called  the  resolution  of 
forces,  the  force,  D  B,  being  resolved  into  the 
components,  D  E  and  D  C. 

Component  Currents. — (See  Currents, 
Component?) 

Component,  Horizontal,  of  Earth's  Mag- 
netism   That  portion  of  the  earth's 

directive  force  which  acts  in  a  horizontal  di- 
rection. 

That  portion  of  the  earth's  magnetic  force 
which  acts  to  produce  motion  in  a  com- 
pass needle  free  to  move  in  a  horizontal  plane 
only. 

Let  A  B,  Fig.  166,  represent  the  direction  and 
magnitude  of  the  earth's  magnetic  field  on  a  mag- 
netic needle.     The  magnetic  force  will  lie  in  the 
plane  of  the  magnetic   merid- 
ian, which  will  be  assumed  to  _D  A 
be  the  plane  of  the  paper  C  A 
D.    The  earth's  field,  A  B,  can 
be   resolved   into   two  compo-  j 
nents,  AD,  the horizontat com-  j 
ponent,  and  A  C,  the  vertical  j 
component 

In  the  case  of  a  magnetic  ! 
needle,  like  the  ordinary  com-  J 
pass  needle,  which  is  free  to  | 
move  in  a  horizontal  plane  only, 
the  horizontal  component  alone 

directs  the  needle.    A  weight  . 

,.  ,  patients  of  Earth,  t 

is  applied  to  balance  the  vertical       Magnetism. 
component. 

When  the  needle  is  free  to  move  in  a  vertical 
plane,  and  this  plane  corresponds  with  that  of 
the  magnetic  meridian,  the  entire  magnetic  force, 
A  B,  acts  to  place  the  needle,  supposed  to  be 
properly  balanced,  in  the  direction  of  the  lines  of 
force  of  the  earth's  magnetic  field  at  that  point 


Com.] 


117 


[Con. 


Component,  Yertical,  of  Earth's  Magnet- 

ism  -  -  —  That  portion  of  the  earth's 
directive  force  which  acts  in  a  vertical  direc- 
tion. 

In  the  vertical  plane  at  right  angles  to  the  plane 
of  the  magnetic  meridian,  the  vertical  component 
alone  acts,  and  the  needle  points  vertically  down- 
wards, in  no  matter  what  part  of  the  earth  it 
may  be.  In  Fig.  166,  A  C,  is  the  vertical  com- 
ponent of  the  earth's  directive  force. 

Composite  Balance.—  (See  Balance,  Com" 


Composite-Field  Dynamo.  —  (See  Dynamo, 
Composite-Field) 

Composition    of  Forces.  —  (See    Forces, 

Composition  of.) 

Compound  Arc.—  (See  Arc,  Compound?) 

Compound,  Binary  --  In  chemistry, 
a  compound  formed  by  the  union  of  two 
different  elements. 

Water  is  a  binary  compound,  being  formed  by 
the  union  of  two  atoms  of  hydrogen  with  one 
atom  of  oxygen.  Its  composition  is  expressed  in 
the  mical  symbols,  HSO,  which  indicates  that  two 
atoms  of  hydrogen  are  combined,  or  chemically 
united,  with  one  atom  of  oxygen.  Water  is 
therefore  a  binary  compound,  because  it  is  formed 
of  two  different  elementary  substances. 

Compound,  Chatterton's  --  A  com- 
pound for  cementing  together  the  alternate 
coatings  of  gutta-percha  employed  on  a  cable 
conductor,  or  for  filling  up  the  space  between 
the  strand  conductors. 

The  composition  of  Chatterton's  compound  is 
as  follows: 

Stockholm  tar  ........  I  part  by  weight. 

Resin  ...............  I     «'  " 

Gutta-percha  .........  3     "  " 

—(Clark  &>  Saline.) 

Compound  Circuit.  —  (See  Circuit,  Com- 
pound.) 

Compound,  Clark's  --  A  compound 
for  the  outer  casing  of  the  sheathing  of  sub- 
marine cables. 

The  composition  of  Clark's  compound  is  as  fol- 


Mineral  pitch .65  parts  by  weight. 

Silica 30    •'  " 

Tar 5     ««  " 

—(Clark  &»  Sabine.) 

Compound  -  Horseshoe  Magnet. —  (See 
Magnet,  Compound-Horseshoe) 

Compound  Magnet. — (See  Magnet,  Com- 
pound) 

Compound  Radical.^— (See  Radical,  Com- 
pound) 

Compound-Winding  of  Dynamo-Electric 
Machines. — (See  Winding,  Compound,  of 
Dynamo-Electric  Machine.) 

Compound- Wound  Dynamo-Electric  Ma- 
chine.— (See  Machine,  Dynamo-Electric, 
Compound-  Wound) 

Compound-Wound  Motor. — (See  Motor, 
Compound-  Wound) 

Concentration  of  Lines  of  Force. — (See 
Force,  Lines  of,  Concentration  of) 

Concentric  Carbon  Electrodes. — (See 
Electrodes,  Concentric  Carbon) 

Concentric  Cylindrical  Carbons.— (See 
Carbons,  Concentric  Cylindrical) 

Condenser. — A  device  for  increasing  the 
capacity  of  an  insulated  conductor  by  bring- 
ing it  near  another  insulated  earth-connected 
conductor,  but  separated  therefrom  by  any 
medium  that  will  readily  permit  induction  to 
take  place  through  its  mass. 

A  variety  of  electrostatic  accumulator. 

If  the  conductor  A,   Fig.  167,  standing  alone 


f  Air  Condenser. 


Fig.  167. 

and  separated  from  other  conductors,  be  con. 
nected  with  an  electric  machine,  it  will  receive 
only  a  very  small  charge. 


Con.] 


118 


[Con. 


If,  however,  it  be  placed  near  C,  but  separated 
from  it  by  a  dielectric,  such  as  a  plate  of  glass 
B,  and  C,  be  connected  with  the  ground,  A,  will 
receive  a  much  greater  charge.  (See  Dielectric.) 

Suppose,  for  example,  that  A,  be  connected 
«r>th  the  positive  conductor  of  a  frictional  electric 
machine,  it  will  by  induction  establish  a  negative 
Charge  on  the  surface  C,  nearest  it,  and  repel 
a  positive  charge  to  the  earth.  The  presence  of 
these  two  opposite  charges  on  the  opposed  sur- 
faces of  A  and  C,  permits  A,  to  receive  a  fresh 
charge  from  the  machine.  (See  Induction, 
Electrostatic.) 

The  charge  in  a  condenser  in  reality  resides 
on  the  opposite  surfaces  of  the  glass,  or  other 
dielectric  separating  the  metallic  coatings,  as  can 
be  shown  by  removing  the  coatings  after  charg- 
ing. 

The  condenser  resulted  from  the  discovery  of 
the  Leyden  jar.  (See  Jar,  Ley  den.) 

The  capacity  of  a  condenser  is  measured  in 
microfarads.  (See  Farad.) 

In  practice  condensers  are  made  of  sheets  of 
tin  foil,  connected  to  A  and  B,  respectively,  and 
separated  from  one  another  by  sheets  of  oiled 
silk,  paraffined  paper,  or  thin  plates  of  mica,  as 
shown  in  Fig.  168. 


Fig.  1 68.    Condenser. 

A  Leyden  jar  or  condenser  does  not  store  elec- 
tricity any  more  than  a  storage  battery  does. 
The  same  quantity  of  electricity  passes  out  of  the 
opposite  coating  of  the  jar  that  is  passed  into  the 
other  coating.  The  jar,  therefore,  possesses  no 
store  of  electricity.  What  it  really  possesses  is  a 
store  of  electrical  energy. 

According  to  Ayrton,  if  the  capacity  of  a  con. 
denser,  in  farads,  be  F,  and  the  difference  of  po- 
tential, with  which  it  is  charged,  be  V,  volts,  the 
store  of  electric  energy  it  possesses,  or  the  work  it 
Can  do  when  discharged,  is, 

Fx  V* 
Work  =  '•  foot-pounds. 

Condenser,  Adjustable  — A  con- 
denser, the  plates  of  which  can  be  readily 
adjusted  so  as  to  obtain  the  same  capacity 
as  that  of  the  conductor  to  be  measured. 


In  order  to  obtain  a  comparatively  wide  range 
of  adjustability,  a  condenser  is  composed  of  say 
four  separate  sections:  consisting  of  one  of  2 
microfarads,  one  of  I  microfarad  and  two  of  $ 
microfarad,  thus  making  in  all  4  microfai  ads. 

Condenser,  JEpinus A  name  given 

to  an  early  form  of  condenser.  (See  Con- 
denser!) 

Condenser,  Air  — A  condenser  in 

which  layers  of  air  act  as  the  dielectric. 

A  form  of  air  condenser  is  shown  in  Fig.  169. 


Fig.  tbq.    Air  Condenser. 

It  consists  essentially  of  one  set  of  thin  plates  of 
glass  partially  coated  on  both  sides  with  sheets  oi 
tin  foil,  so  as  to  leave  uncoated  a  space  of  about 
one  inch  around  the  edge  of  the  glass.  The  glass 
plates  do  not  act  as  dielectrics,  but  merely  as  sup- 
ports  for  the  tin  foil,  hence  the  foil  on  both  sides 
of  the  plates  is  connected  electrically. 

Another  set  of  plates  alternating  with  the  above 
have  the  tin  foil  placed  over  the  whole  surface  of 
the  glass. 

These  plates  are  placed,  alternately,  over  one 
another  on  a  stand  between  guide  rods  of  vulcan. 
ite  E,  E,  E,  E,  in  the  manner  shown,  and  are 
separated  from  one  another  by  fragments  of  glass 
of  the  same  thickness.  The  plates  with  the  foil 
over  their  entire  surface  are  all  connected  to- 
gether and  to  the  terminal  B,  to  form  the  outer 
coating,  and  the  plates  with  the  foil  over  nearly 
all  their  surfaces  are  all  connected  together  and 
to  the  terminal  A,  to  form  the  inner  coating  of 
the  condenser. 

There  is  thus  formed  a  condenser  in  which 
practically  two  extended  conducting  surfaces  an 


Con.J 


119 


[Con. 


separated  from  each  other  by  a  thin  layer  of  air, 
which  acts  as  the  dielectric. 

Condenser,  Alternating-Current  -- 

A  condenser  suitable  for  use  in  connection  with 
a  system  for  the  distribution  of  electric  energy 
by  means  of  alternating  currents. 

Alternating-current  condensers  must  have  a  very 
thin  dielectric  in  order  to  avoid  too  great  bulk. 
This,  of  course,  introduces  a  difficulty  as  regards 
liability  of  failure  of  insulation,  which  must  be 
carefully  avoided. 

Condenser,  Armature  of  --  (See  Arm- 
ature of  a  Condenser.) 

Condenser,  Capacity  of  --  •  -The  quan- 
tity of  electricity  in  coulombs  a  condenser  is 
capable  of  holding  before  its  potential  in  volts 
is  raised  a  given  amount. 

The  ratio  between  the  quantity  of  electric- 
ity in  coulombs  on  one  coating  and  the  poten- 
tial difference  in  volts  between  the  two  coat- 
ings. —  (Ayrton!) 

The  capacity  is  directly  proportional  to  the 
charge  Q,  and  inversely  proportional  to  the  po- 
tential V,  or, 


or,  since  Q  =  K  V,  the  quantity  of  electricity  re- 
quired to  charge  a  condenser  to  a  given  potential 
is  equal  to  the  capacity  of  the  condenser  multi- 
plied by  the  potential  through  which  it  is  carried. 

The  capacity  of  a  condenser  increases  in  direct 
proportion  to  the  increase  in  the  area  of  its  coat- 
ings. 

When  the  coatings  are  plane  and  parallel  to 
each  other,  the  capacity  of  the  condenser  is  in  the 
inverse  ratio  to  the  distance  between  the  coatings. 

Condenser,  Coating  of  --  (See  Coat- 
ing of  Condenser!) 

Con  denser,  Plate  -  -A  condenser,  the 
metallic  coatings  of  which  are  placed  on 
suitably  supported  plates. 

Condenser,  Poles  of  --  —  (See  Poles  of 

Condenser.} 

Condenser,    Time-Constant    of  -  — 

The  time  in  which  the  charge  of  a  condenser 
tails  to  the  1-2.71828  part  of  its  original 
value. 

Condensers,  Distribution  of  Electricity 
by  Means  of  --  .(See  Electricity,  Distri 


btttion  of  by  Alternating  Currents,  by  means 
of  Condensers .  Electricity,  Distribution  of, 
by  Continuous  Currents,  by  means  of  Con- 
densers.) 

Conduct.— To  pass  electricity  through  con- 
ducting  substances. 

To  determine  the  general  direction  in  which 
electricity  shall  pass  through  the  ether  or 
dielectric  surrounding  the  so-called  conduct- 
ing substance.  (See  Conduction,  Electric!) 

Conductance. — A  word  sometimes  used  in 
place  of  conducting  power. 
Conductivity. 

Conductance,  Magnetic A  word 

sometimes  used  instead  of  magnetic  permea- 
bility. (See  Permeability  Magnetic!) 

The  magnetic  conductance  is  equal  to  the  total 
induction  through  the  circuit  divided  by  the 
magnetizing  force. 

Conducting  Cord.— (See  Cord,  Conduct- 
ing.) 

Conducting,  Electrical Possessing 

the  power  of  passing  electricity  through  any 
conducting  substance. 

Possessing  the  power  of  determining  the 
direction  in  which  electricity  shall  pass  through 
the  ether  surrounding  a  substance,  (See 
Conductor.) 

Conducting  Power.— (See  Power  Con- 
ducting.) 

Conducting  Power  for  Electricity.— (Se* 

Power,  Conducting,  for  Electricity.) 

Conducting  Power  for  Lines  of  Mag 
netic  Force. — (See  Forte,  Magnetic,  Lines 
of,  Conducting  Power  of,) 

Conducting    Power,    Tables   of — 

(See  Power,  Conducting,  Tables  of.) 

Conduction  Current. — (See  Current,  Con- 
duction!) 

Conduction,  Disruptive A  species 

of  conduction  in  which  the  resistance  of  *u* 
conductor  is  suddenly  overcome. 

Disruptive  conduction  is  seen  in  the  disruptive 
discharge  of  a  condenser,  or  Leyden  jar. 

Conduction,      Electric The     s<x 


COIL] 


120 


{Con. 


called  flow  or  passage  of  electricity  through 
a  metallic  or  other  similarly  acting  substance. 

The  ability  of  a  substance  to  determine  the 
direction  in  which  electric  energy  shall  be 
transmitted  through  the  ether  surrounding  it. 

The  ability  of  a  substance  to  determine  the 
direction  in  which  a  current  of  electricity 
passes  from  one  point  to  another. 

When  a  conducting  wire  has  its  ends  connected 
with  an  electric  source,  a  current  of  electricity  is, 
in  common  language,  said  to  flow  through  the  wire, 
and  this  was  formerly  believed  to  be  a  correct 
statement.  According  to  modern  views,  however, 
the  electric  energy  is  believed  to  pass  through  the 
ether  or  other  dielectric  surrounding  the  con- 
ductor,  the  so-called  conductor  forming  merely 
a  sink,  where  the  electrical  energy  dissipates 
itself.  The  conductor  simply  acts  to  direct  the 
current. 

Since,  however,  the  energy  practically  passes 
by  means  of,  and  in  the  general  direction  of  the 
conductor,  there  is  no  objection  in  speaking  of 
the  electricity  as  flowing  through  the  conductor. 

Conduction,  Electric,  Disruptive 

A  conduction  of  electric  energy  which  ac- 
companies a  disruptive  discharge.  (See 
Discharge,  Disruptive.) 

Conduction,  Electric,  Metallic A 

conducting  of  electric  energy  of  the  same  char- 
acter as  that  which  occurs  in  metallic  sub- 
stances. 

Conduction,  Electrolytic A  term 

sometimes  employed  to  indicate  the  passage 
of  electricity  through  an  electrolyte. 

There  is  no  passage  of  electricity  through  an 
electrolyte  in  the  same  sense  as  through  an  ordi- 
nary conductor. 

When,  through  electrolysis,  an  electromotive 
force  is  brought  to  bear  on  a  molecule  of  say 
HC1,  it  is  assumed  by  some  that  the  liberated 
hydrogen  atoms  travel  on  the -whole  in  one  di. 
rection,  and  the  liberated  chlorine  atoms  in  the 
opposite  direction.  The  atoms  thus  moving 
through  the  liquid  may  by  their  electric  charges 
be  assumed  to  convey  electricity,  and  this  fact 
has  given  rise  to  the  term  electrolytic  conduc- 
tion. 

In  electrolytic  conduction  the  charges  are 
necessarily  equal,  but  the  speeds  of  their  motion 
are  unequal.  In  a  given  liquid,  each  atom  has 


its  own  rate  of  motion,  no  matter  T^ith  what  it 
has  been  combined.  Hydrogen  travels  faster 
than  any  other  kind  of  atom.  The  conductivity 
of  a  liquid  depends  on  the  sum  of  the  speeds  with 
which  the  two  opposed  atoms  travel. 

This  assumed  double  stream  of  oppositely  mov 
ing  atoms  is  denied  by  most  physicists.  (Se« 
Hypothesis,  Grotthus.} 

Cond  uctive-Discharge.— (See  Discharge, 
Conductive!) 

Conductivity,  Electric The  recip- 
rocal of  electric  resistance. 

Since  the  conductivity  is  greater  the  less  the  re- 
sistance, the  conductivity  will  be  equal  to  the  recip- 
rocal of  the  resistance,  and  may  be  so  defined.  The 

conductivity  is  therefore  equal  to  -L. 

R  * 

Conductivity,  Equivalent A  con- 
ductivity equal  to  the  sum  of  several  conduc- 
tivities. 

Conductivity  per  Unit  of  Mass.— The  re- 
ciprocal of  the  resistance  of  a  substance  per 
unit  of  mass. 

Conductivity  per  Unit  of  Yolume.— The 

reciprocal  of  the  resistance  of  a  substance 
per  cubic  centimetre  or  per  cubic  inch. 

The  resistance  is  measured  from  one  face  of 
the  cube  to  the  opposite  face. 

Conductivity  Resistance. — (See  Resist- 
ance, Conductivity!) 

Conductivity,  Specific The  par- 
ticular conductivity  of  a  substance  for  elec- 
tricity. 

The  specific  or  particular  resistance  of  a 
given  length  and  unit  of  cross-section  of  a 
substance  as  compared  with  the  same  length 
and  area  of  cross-section  of  some  standard 
substance. 

Conductivity,  Specific  Magnetic 

The  specific  or  particular  permeability  of  a 
substance  to  lines  of  magnetic  force. 

The  specific  magnetic  conductivity  is  measured 
by  the  ratio  of  the  magnetization  produced  to  the 
magnetizing  force  which  produces  it. 

The  specific  magnetic  conductivity  is  the  an- 
alogue of  specific  inductive  capacity,  or  conduc- 
tivity for  lines  of  electrostatic  force.  It  is  also  the 
analogue  for  specific  conducting  power  for  heat* 


Con.] 


121 


[Con. 


Conductor. — A  substance  which  will  per- 
mit the  so-called  passage  of  an  electric  current. 

A  substance  which  possesses  the  ability  of 
determining  the  direction  in  which  electricity 
shall  pass  through  the  ether  or  other  dielec- 
tric surrounding  it. 

Some  electrolytes,  such,  for  example,  as  vari- 
ous mixtures  of  sulphuric  acid  and  water,  possess 
a  true  power  of  conducting  electricity,  and  there- 
fore have  a  specific  resistance.  Generally,  how- 
ever, the  passage  of  the  electrolyzing  current  is 
regarded  as  different  from  that  of  a  current  which 
merely  heats  the  conductor. 

The  space  or  region  around  a  conductor 
through  which  an  electric  current  is  passing  has 
a  magnetic  field  produced  in  it. 

The  term  conductor  is  opposed  to  non-conductor, 
or  a  substance  which  will  not  permit  the  passage 
of  an  electric  current  through  it  after  the  manner 
of  a  conductor. 

The  terms  conductors  and  non-conductors  are 
only  relative.  There  are  no  such  things  as 
either  perfect  conductors  or  perfect  non  con- 
ductors. 

Conductors  in  general,  are  distinguished  from 
electrolytes,  in  that  the  latter  do  not  allow  the 
electricity  to  pass  save  by  undergoing  a  chemical 
decomposition. 

Conductor,  Anisotropic A  con- 
ductor which,  though  homogeneous  in  struc- 
ture like  crystalline  bodies,  has  different 
physical  properties  in  different  directions,  just 
as  crystals  have  different  properties  in  the 
direction  of  their  different  crystalline  axes. 

Anisotropic  conductors  possess  different  powers 
of  electric  conduction  in  different  directions. 
But  in  opposite  directions  along  the  same  axis  their 
conductivity  is  equal.  They  differ  in  this  respect 
from  isotropic  conductors.  (See  Conductor,  Iso- 
tropic.) 


Conductor,  Anti-Induction 


— A  con- 


ductor so  constructed  as  to  avoid  injurious 
inductive  effects  from  neighboring  telegraphic 
or  electric  light  and  power  circuits. 

Such  anti-induction  conductors  sometimes  con- 
sist of  a  conductor  for  constant  currents  and  a 
metallic  shield  surrounding  the  conductor,  and 
designed  to  prevent  induction  from  taking  place 
in  the  wire  itself. 

The  anti-induction  conductor   generally  con- 


sists of  twin  conductors  surrounded  by  ordinary 
insulation  and  sometimes  enclosed  by  some  form 
of  metallic  shield,  in  order  to  prevent  the  action 
of  electrostatic  induction. 

When  a  periodic  current  is  to  be  transmitted 
through  a  conductor,  the  most  effective  way  of 
annulling  its  inductive  effects  on  neighboring  cir- 
cuits is  to  place  the  lead  of  the  conductor  in  the 
axis  of  another  conductor,  used  as  a  return.  In 
other  words,  to  employ  concentric  cylinders,  in- 
sulated from  one  another  and  from  the  earth. 
Under  these  conditions,  calling  the  current  in  one 
direction  positive,  and  in  the  other  direction 
negative,  the  shielding  action  will  be  perfect 
when  the  algebraic  sum  of  the  currents  in  the 
core  and  sheath  are  zero. 

The  same  effect  is  obtained  in  metallic  circuits, 
by  placing  the  leads  parallel  to  the  return,  and 
crossing  and  recrossing  the  wires  repeatedly. 
(See  Connection,  Telephonic  Cross.) 

Elihu  Thomson  renders  ordinary  telephone 
conductors,  arranged  as  single  lines  with  earth 
returns,  free  from  induction  by  means  of  the 
counter-electromotive  force  produced  in  a  coil  of 
wire  by  the  disturbing  cause. 

In  applying  this  system  to  the  case  of  an  elec- 
tric arc  or  power  line  passing  alongside  a  tele- 
phone line,  a  wire  coil,  whose  turns  are  pro- 
portioned in  number  to  the  induction  to  be  bal- 
anced, is  introduced  into  the  electric  light  line 
and  placed  near  another  coil  of  finer  wire  inserted 
as  a  loop  in  the  telephone  circuit.  The  second  coil 
is  placed  parallel  to  or  inclined  at  an  angle  to  the 
first  coil.  In  practice,  the  second  coil  is  inclined 
until  the  counter-induction  set  up  in  the  tele- 
phone wire  is  equal  to  that  produced  in  the  main 
line,  and  silence  is  thus  produced,  so  far  as  in- 
duction is  concerned,  in  the  telephone. 

Conductor,  Armored  • — A  conduc- 
tor provided  with  a  covering  or  sheathing  of 
metal  placed  over  the  insulating  covering  for 
protection  from  abrasion  or  external  wear. 

Armored  conductors  are  used  in  situations 
where  the  conductor  is  exposed  to  abrasion  or 
other  external  wear. 


Conductor,  Branch 


• — A  conductor 


placed  in  a  shunt   circuit.       (See   Circuit, 
Shunt.) 
Conductor,    Closed-Circuited  — A 

conductor  connected  as   a  closed   or  com- 
pleted circuit. 


Con.] 


122 


[Coii. 


Conductor,  Conjugate In  a  system 

of  linear  conductors,  any  pair  of  conductors 
that  are  so  placed  as  regards  each  other  that 
a  variation  of  the  resistance  or  the  electro- 
motive force  in  the  one  causes  no  variation  in 
the  current  of  the  other. 

Conductor,    Earth- Circuited   — A 

conductor  connected  to  the  ground,  or  to  an 
earth-connected  circuit. 

Conductor,  House-Serrice A  term 

employed  in  a  system  of  rrultiple  incan- 
descent lamp  distribution  for  that  portion  of 
the  circuit  which  is  included  between  the  ser- 
vice cut-out  and  the  centre  or  centres  of  dis- 
tribution, or  between  this  cut-out  and  one  or 
more  points  on  house  mains. 

Conductor,  Isotropic A  conduc- 
tor which  possesses  the  same  powers  of  elec- 
tric conduction  in  all  directions. 

An  electrically  homogeneous  conducting 
medium. 

Conductor,  Leakage A  conductor 

placed  on  a  telegraph  circuit  for  the  purpose 
of  preventing  the  disturbing  effects  of  leakage 
into  a  neighboring  line  by  providing  a  direct 
path  for  such  leakage  to  the  earth. 

The  leakage  conductor,  as  devised  by  Varley 
consists  of  a  thick  wire  attached  to  the  telegraph 
pole.  The  lower  end  of  the  conductor  is  grounded, 
and  its  upper  end  projects  above  the  top  of  the 
pole. 

There  exists  some  doubt  in  the  minds  of  expe- 
rienced telegraph  engineers  whether  it  is  well  to 
apply  leakage  conductors  to  telegraphic  or  tele- 
phonic lines  of  over  12  or  15  miles  in  length, 
since  such  conductors  greatly  increase  the  electro- 
static capacity  of  the  line,  and  thus  cause  serious 
retardation. 

Conductor,    Lightning   — A    term 

sometimes  used  for  a  lightning  rod.  (See 
Rod,  Lightning?) 

Conductor,  Open-Circuited A  con- 
ductor arranged  as  an  open  or  broken  circuit. 

Conductor,  Potential  of The  rela- 
tion existing  between  the  quantity  of  elec- 
tricity in  a  conductor  and  its  capacity. 

A  given  quantity  of  electricity  will  raise  the 


potential  of  a  conductor  higher  in  proportion  as 
the  capacity  of  the  conductor  becomes  Jess. 

Conductor,    Potential    of,  Methods    of 

Yarying The  potential  of  a  conductor 

may  be  varied  in  the  following  ways  ? 

(I.)  By  varying  its  electric  charge. 

(2.)  By  varying  its  size  or  shape  without  alter- 
ing its  charge. 

(3.)  By  varying  its  position  as  regards  neigh, 
boring  bodies. 

This  resembles  the  case  of  a  gas  whose  tension 
or  pressure  may  be  varied  as  follows,  viz. : 

(I.)  By  varying  the  quantity  of  gas. 

(2.)  By  varying  the  size  of  the  gas  holder  in 
which  it  is  kept,  and 

(3.)  By  varying  the  temperature. 

Difference  of  potential,  therefore,  corresponds — 

(i.)  With  difference  of  level  in  liquids. 

(2. )  With  difference  of  pressure  in  gases. 

(3.)  With  difference  of  temperature  in  heat 

— (Ayrton.) 

Conductor,  Prime  — The  positive 

conductor  of  a  frictional  electric  or  electro- 
static machine.  (See  Machine,  Frictional 
Electric.} 

Conductor,  To  Short-Circuit  a — 

To  shunt  a  conductor  with  a  circuit  of  com- 
paratively small  resistance. 

Conductor,  Underground An  elec- 
tric conductor  placed  underground  by  actual 
burial  or  by  passing  it  through  underground 
conduits  or  subways. 

Underground  conductors,  though  less  unsightly 
than  the  ordinary  aerial  conductors,  require  to 
be  laid  with  unusual  care  to  render  them  equally 
safe,  since,  when  contacts  do  occur,  all  the  wires 
in  the  same  conduit  are  apt  to  be  simultaneously 
affected,  thus  spreading  the  danger  in  many  dif- 
ferent directions.  They  are,  however,  less  liable  to 
dangers  arising  from  occasional  accidental  crosses 
or  contacts. 

Conductors,   Service Conductors 

employed  in  systems  of  incandescent  lighting 
connected  to  the  street  mains  and  to  the 
electric  apparatus  placed  in  the  separate 
buildings  or  areas  to  be  lighted. 

Conduit,  Cement-Lined  — A  cable 

conduit,  the  separate  ducts  of  which  are  sur- 
rounded by  any  suitable  cement. 


Con.] 


123 


[Con. 


— (See  Man- 


Conduit,  Haudhole  of 

hole  of  Conduit} 
Conduit,  Manhole  of  • 

hole  of  Conduit.} 

Conduit,  Multiple  • •  —A  conduit 

formed  of  concrete  or  other  insulating  mate- 
rial, and  furnished  with  a  number  of  separate 
ducts. 

Conduit,  Open-Box  —A  conduit 

consisting  of  an  open  box  of  wood  placed  in 
a  trench  and  closed  with  a  wooden  cover 
after  the  introduction  of  the  cable. 

Cables  or  wires  may  be  drawn  through  such 
conduits  in  the  usual  manner. 

Conduit,  Rodding  a Introducing  a 

wire  or  rope  into  the  duct  of  a  closed  conduit 
preparatory  to  drawing  the  cable  through. 

Various  methods  are  in  use  for  rodding  a  con- 
duit  One  much,  followed  consists  in  using  sec- 
tions of  gas  pipe,  the  ends  of  which  are  furnished 
with  screw  threads. 

The  sections  are  about  four  feet  in  length.  One 
section  is  pushed  into  the  duct  at  one  manhole 
and  the  successive  sections  are  introduced  into 
the  duct  and  screwed  onto  the  section  in  the  duct 
and  pushed  through  until  a  sufficient  length  is 
obtained  to  reach  the  next  manhole,  a  rope  or 
cable  is  then  pulled  through  from  one  manhole  to 
the  next. 

Conduit,  Underground  Electric  — 

An  underground  passageway  or  space  for 
the  reception  of  electric  wires  or  cables.  (See 
Subway,  Electric} 

Congelation. — The  act  of  freezing,  or  the 
change  of  a  liquid  into  a  solid  on  loss  of  heat, 
or  change  of  pressure. 

Conjugate  Coils. — (See  Coils,  Conjugate) 

Connect. — To  place  or  bring  into  electric 
contact. 

Connecting. — Placing  or  bringing  into  elec- 
tric contact. 

Connection  for  Intensity. — Connection  in 
series.  (See  Connection,  Series?) 

This  term  is  now  nearly  obsolete. 

Connection  for  Quantity. — Connection  in 
multiple.  (See  Connection,  Multiple?) 

This  term  is  now  nearly  obsolete. 
5— Vol.  1 


— (See  Hand-          Connection,  Mercurial 


— A    form 


of  readily  adjustable  connection  obtained  by 
providing  the  poles  of  one  piece  of  electric 
apparatus  with  cups  or  cavities  filled  with 
mercury,  into  which  the  terminals  of  another 
piece  of  apparatus  are  dipped  in  order  to 
place  the  two  in  circuit  with  each  other. 

This  form  of  connection  is  used  particularly 
when  a  very  perfect  contact  or  one  free  from 
friction  is  desired. 

Connection,  Multiple Such  a  con- 
nection of  a  number  of  separate  electric 
sources,  or  electro-receptive  devices,  or  circuits, 
that  all  the  positive  terminals  are  connected 
to  one  main  or  positive  conductor,  and  all  the 
negative  terminals  are  connected  to  one  main 
or  negative  conductor. 

In  the  multiple  connection  of  a  number  of 
electro-receptive  devices,  when  the  devices  are 
connected  as  above  described  to  positive  and 
negative  leads  that  are  maintained  at  a  constant 
difference  of  potential,  the  current  passes  through 
the  devices  from  one  lead  to  the  other  by  branch- 
ing and  flowing  through  as  many  separate  cir- 
cuits as  there  are  separate  receptive  devices, 
and  the  opening  or  closing  of  one  of  these  cir- 
cuits does  not  affect  the  others.  (See  Circuits, 
Varieties  of.} 

Connection,  Multiple-Series Such 

a  connection  of  a  number  of  separate  electric 
sources,  or  separate  electro-receptive  de- 
vices, or  circuits,  that  the  sources  or  devices 
are  connected  in  a  number  of  separate  groups 
in  series,  and  each  of  these  groups  connected 
to  main  positive  and  negative  conductors  or 
leads  in  multiple  arc.  (See  Circuits,  Varie- 
ties of} 

Connection  of  Battery  for  Quantity.— 
(See  Battery,  Connection  of,  for  Quantity} 

Connection  of  Electric  Sources  in  Cas- 
cade.— (See  Cascade,  Connection  of  Electric 
Sources  in} 

Connection  of  Voltaic  Cells  for  Inten- 
sity.— (See  Intensity,  Connection  of  Voltaic 
Cells  for} 

Connection,  Series  -  —The  connec- 
tion of  a  number  of  separate  electric 
sources,  or  electro-receptive  devices,  or  cir- 


Con.] 


124 


[Coil. 


cuits,  so  that  the  current  passes  successively 
from  the  first  to  the  last  in  the  circuit.  (See 
Circuits,  Varieties  of.) 

Connection,  Series-Multiple Such 

a  connection  of  a  number  of  separate  electro- 
receptive  devices,  that  the  devices  are  placed 
in  multiple  groups  or  circuits,  and  these 
separate  groups  connected  with  one  another 
in  series. 

Connection,  Telephonic   Cross  — 

A  device  employed  in  systems  of  telephonic 
communication  for  the  purpose  of  lessening 
the  bad  effects  of  induction,  in  which  equal 
lengths  of  adjacent  parallel  wires  are  alter- 
nately crossed  so  as  to  alternately  occupy  the 
opposite  sides  of  the  circuit. 

Connector. — A  device  for  readily  con- 
necting or  joining  the  ends  of  two  or  more 
wires.  (See  Post,  Binding?) 

Connector,  Double 
A  form  of  bind- 
ing screw  suitable  for 
readily  connecting  two 
wires  together. 

A  form  of  double  con- 
nector is  shown  in  Fig. 
170. 

Conning-  Tower.  — 
(See  Tower,  Conning) 

Consequent  Points. — (See  Points,  Conse- 
quent?) 

Consequent  Poles. — (See  Poles,  Conse- 
quent?) 

Conservation  of  Energy. — (See  Energy, 
Conservation  of.) 

Consonance,  "In  Consonance." — A  term 
employed  to  express  the  fact  that  one  simple 
periodic  quantity,  /.  e.,  a  wave  or  vibration, 
agrees  in  phase  with  another. 

Constant. — That  which  remains  invariable. 

Constant-Current. — (See  Current,  Con- 
stant?) 

Constant-Current  Circuit. — (See  Circuit, 
Constant  Current?)  . 

Constant-Current,  Distribution  of  Elec- 
tricity by  -  —(See  Electricity,  Distri- 
bution of,  by  Constant  Currents?) 


.  170.    Double 
Connector. 


Constant,  Dielectric A  term  some- 
times employed  in  place  of  specific  inductive 
capacity.  (See  Capacity,  Specific  Inductive?) 

Constant,      Galvanometer    — The 

numerical  factor  connecting  the  current  pass- 
ing through  a  galvanometer  with  the  deflec- 
tion produced  by  such  current. 

Sometimes  a  distinction  is  made  between  the 
galvanometer  constant  and  the  reduction  factor, 
the  former  being  used  to  indicate  the  relation 
between  the  current  and  the  geometrical  constant 
of  the  galvanometer,  while  the  latter  is  used  in 
the  sense  just  denned  of  galvanometer  constant. 

Constant  Inductance. — (See  Inductance, 
Constant?) 

Constant  Potential. — (See  Potential, 
Constant?) 

Constant-Potential  Circuit. — (See  Cir- 
cuit, Constant-Potential?) 

Constant,  Time,  of  Electro-Magnet  — — 
— The  time  required  for  the  magnetizing 

p T 

current  to  rise  to  the of  its  final  value. 

e 

Contact-Breaker,    Automatic A 

device  for  causing  an  electric  current  to 
rapidly  make  and  break  its  own  circuit. 

The  spring  c,  Fig.  171,  carries  an  armature  of 
soft  iron,  B,  and  is 
placed  in  a  circuit  in 
such  a  manner  that 
the  circuit  is  closed 
when  platinum  con- 
tacts placed  on  the 
ends  of  D  and  B, 
touch  each  other.  In 
this  case  the  arma- 
ture, B,  is  attracted  to 
the  core  A,  of  the 
electro- magnet,  thus 
breaking  the  circuit 
and  causing  the  magnet  to  lose  its  magnetism. 
The  elasticity  of  the  spring  C,  causes  it  to  fly  back 
and  again  close  the  contacts,  thus  again  energiz- 
ing the  electro-magnet  and  again  attracting  B. 
and  breaking  the  circuit.  The  makes  and  breaks 
usually  follow  each  other  so  rapidly  as  to  produc* 
a  musical  note.  (See  Alarm,  Electric.) 


B  ATTEST 

Fig.  r?r.    Automatic 
Contact   Breaker. 


Contact,  Dotting 


— An  electric  con- 


Con.] 


125 


[Con. 


tact  obtained  by  the  approach  of  one  con- 
tact point  towards  another. 

The  term  dotting  contact  is  used  in  contradis- 
tinction to  a  rubbing  contact.  The  rubbing 
contact  is  generally  to  be  preferred,  since  it  tends 
automatically  to  remove  dust  and  keep  the  con- 
tact surfaces  polished  and  free  from  oxides. 

Contact  Dynamo. — (See  Dynamo,  Con- 
tact) 

Contact  Electricity.  —  (See  Electricity, 
Contact?) 

Contact,  Fire- Alarm A  contact  so 

arranged  that  an  alarm  is  given  when  any 
predetermined  temperature  is  reached. 

Fire-alarm  contacts  are  generally  operated  by 
the  expansion  of  a  metal  or  of  a  conducting  fluid, 
such  as  mercury.  (See  Thermostat.') 

Contact  Force. — (See  Force,  Contact?) 

Contact,  Full-Metallic A  contact. 

which  from  its  small  resistance  establishes  a 
good  or  complete  connection.  (See  Contact, 
Metallic) 

Contact,  Intermittent The  occa- 
sional contact  of  a  telegraphic  or  other  line 
with  other  wires  or  conductors  by  swing- 
ing, or  by  alternate  contraction  or  expansion 
under  changes  of  temperature. 

Contact,   Metallic A  contact  of 

a  metallic  conductor  produced  by  its  coming . 
into  firrr.  connection  with  another  metallic 
conductor. 

Contact,  Partial A  contact  of   a 

telegraphic,  or  other  line,  arising  from  defect- 
ive insulation,  bad  earths,  or  connection  with 
an  imperfect  conductor. 

Contact,  Rolling -A  contact  con- 
nected with  one  part  of  an  electric  circuit, 
that  completes  the  circuit  by  being  rolled  over 
a  conductor  connected  with  and  forming 
another  part  of  the  circuit. 

Rolling  contacts  are  employed  on  electric  rail- 
roads. (See  Railroad,  Electric.) 

Contact,    Rubbing    — A    contact 

effected -by  means  of  a  rubbing  motion. 
Contact  Series. — (See  Series,  Contact) 
Contact,  Sliding A  contact  con- 
nected with  one  Dart  of  a  circuit  that  closes 


or  complete?:  an  electric  circuit  by  being  slid 
over  a  conductor  connected  with  another 
part  of  the  circuit. 

Sliding  contacts  are  employed  in  electric  rail- 
roads, in  rheostats,  switches,  and  a  variety  of  other 
apparatus.  (See  Railroad,  Electric.  Rheostat. 
Key,  Discharge.) 

Contact,  Spring  — A  spring-sup- 
ported contact  connected  with  one  part  of  a 
circuit  that  completes  said  circuit  by  being 
moved  so  as  to  touch  another  contact  con- 
nected with  the  other  part  of  the  circuit. 

The  movement  required  to  bring  the  two  con- 
tacts together  may  be  non-automatic,  as  in  the  case 
of  a  push-button,  or  automatic,  as  in  the  case  of 
a  thermostat.  (See  Button,  Push.  Thermostat) 

Contact  Theory  of  Voltaic  Cell.— (See 
Cell,  Voltaic,  Contact  Theory  of  ) 

Contact,  Vibrating A  spring  con- 
tact, connected  with  one  part  of  a  circuit  and 
so  supported  as  to  be  able  to  vibrate  towards 
and  from  another  contact  connected  with 
another  part  of  the  circuit,  thus  automatically 
closing  and  opening  said  circuit. 

A  vibrating  contact  is  used  in  the  automatic 
contact-breaker  in  which  the  movement  ot  an 
armature  towards  an  electro-magnet  is  caused  to 
break  the  circuit  of  the  coi's  of  the  electro-magnet, 
and,  on  its  movement  away  trom  the  magnet,  to 
close  another  contact  which  again  completes  the 
circuit  of  the  electro-magnet.  (See  Contact 
Breaker,  Automatic) 

Contact,  Wiping  — A  contact  ob- 
tained by  a  wiping  movement  of  one  con- 
ductor against  another. 

The  spark  for  electrically  igniting  a  gas  jet  is 
obtained  by  means  of  a  wiping  contact  of  a  spring 
moved  by  the  motion  of  the  pendant,  (See 
Burner,  Plain- Pendant  Electric) 

Contacts. — A  variety  of  faults  occasioned 
by  the  accidental  contact  of  a  circuit  with  any 
conducting  body. 

The  word  contacts  as  employed  above  is  in  the 
sense  of  accidental  contacts  as  distinguished  from 
predetermined  contacts. 

Contacts  of  an  accidental  character  are  of  the 
following  varieties,  viz.: 

(I.)  Full,  or  metallic,  as  when  the  circuit  is 


Con.] 


126 


[Con. 


accidentally  placed  in  firm  connection  with  an. 
other  metallic  circuit. 

(2.)  Partial,  as  by  imperfect  conductors  being 
placed  across  wires,  or  bad  earths,  or  defective 
insulation. 

(3.)  Intermittent,  as  by  occasional  contacts  of 
swinging  wires,  etc. 

Contacts,  Burglar  •  Alarm  —  —Con- 
tacts fitted  to  windows,  doors,  tills,  steps, 
floors,  etc.,  so  that  a  movement  of  the  parts 
from  their  natural  position  gives  an  alarm  by 
sounding  a  conveniently  located  bell. 

Contacts,  Lamp Metallic  plates  or 

lings  connected  with  the  terminals  of  an  incan- 
descent lampforready  connection  with  the  line. 

Contacts,  Mercurial Electric  con- 
tacts that  are  opened  or  closed  by  the  ex- 
pansion or  contraction  of  a  mercury  column. 

In  the  commonest  forms  of  mercurial  con- 
tacts, on  the  expansion  of  the  mercury  by  heat  it 
reaches  a  contact  point  placed  in  the  tube,  and 
thus  completes  the  circuit  through  it  own  mass. 

Or,  on  contraction  it  breaks  a  contact,  and  thus 
disturbing  an  electric  balance,  sounds  an  alarm. 

Continental  Code  Telegraphic  Alphabet. 
— (See  Alphabet,  Telegraphic*  International 
Code.) 

Continuity  of  Current— (See  Current. 
Continuous) 

Continuous  Current— <See  Czirrent,  Con- 
tinuous) 

Continuous  Current,  Distribution  of 
Electricity  by  — —  — (See  Electricity,  Dis- 
tribution of,  by  Constant  Currents) 

Continuous  Current,  Dynamo-Electric 

Machine (See  Machine,  Dynamo- 

Electric,  Continuous  Current) 

Continuous-Sounding  Electric  Bell. — 
(See  Bell,  Continuous-Sounding  Electric) 

Continuous  Wires  or  Conductors.— (See 
Wires  or  Conductors,  Continuous) 

Contraction,  Anodic  Closure  — —  —The 
muscular  contraction  observed  on  the  closing 
of  a  voltaic  circuit,  the  anode  of  which  is  placed 
over  a  nerve,  and  the  kathode  at  some  other 
part  of  the  body. 

This  term  is  generally  written  A.  C.  C. 


Contraction,  Anodic  Duration 

The  length  of  time  the  muscle  continues  in 
contraction  on  the  opening  or  closing  of  a 
circuit,  the  anode  of  which  is  placed  over  the 
part  contracted. 

This  terra  is  generally  written  A.  D.  C. 

Contraction,   Anodic    Opening 

The  muscular  contraction  observed  on  the 
opening  of  a  voltaic  circuit,  the  anode  of  which 
is  placed  over  a  nerve,  and  the  kathode  at 
some  other  part  of  the  body. 

This  term  is  generally  written  A.  O.  C. 

When  the  anode  is  placed  over  a  nerve  and  a 
weak  current  is  employed,  if  the  circuit  be  kept 
closed  for  a  few  minutes,  it  will  be  noticed  that, 
on  opening  the  circuit  the  contraction  will  be 
much  greater  than  if  it  had  been  opened  after 
being  closed  for  only  a  few  seconds.  The  effect 
of  the  A*  O.  C.  therefore  depends  not  only  on  the 
current  strength,  but  also  on  the  time  during 
which  the  current  has  passed  through  the  nerve. 

Contraction  of  Lines  of  Magnetic  Force. 
— (See  Force,  Magnetic,  Contraction  of 
Lines  of) 

Contractures.  —  In  electro-therapeutics, 
prolonged  muscular  spasms,  or  tetanus,  caused 
by  the  passage  of  electric  currents. 

Contraplex  Telegraphy.— (See  Telegra- 
phy, Contraplex) 

Controlled  Clock.— (See  Clock.  Electric) 
Controller. — A  magnet,  in  the  Thomson- 
Houston  system  of  automatic  regulation, 
whose  coils  are  traversed  by  the  main  cur- 
rent, and  by  means  of  which  the  regulator 
magnet  is  automatically  thrown  into  or  out  of 
the  main  circuit  on  changes  in  the  strength 
of  the  current  passing.  (See  Regulation, 
Automatic) 

Controlling  Clock.— (See  Clock,  Electric) 

Controlling  Magnet.— (See  Magnet,  Con- 
trolling) 

Convection  Currents.— (See Currents.Con- 
vection) 

Con vect ion,  Electric The  air  par- 
ticles, or  air  streams,  which  are  thrown  off 
from  the  pointed  ends  of  a  charged,  insulated 
conductor. 


Con.] 


127 


[Cop. 


Convection  streams,  like  currents  flowing 
through  conductors,  act  magnetically,  and  are 
themselves  acted  on  by  magnets.  The  same  thing 
is  true  of  the  brush  discharge,  of  the  voltaic  arc, 
and  of  convective  discharges  in  vacuum  tubes. 

Convection,  Electrolytic A  term 

proposed  by  Helmholtz  to  explain  the  appa- 
rent conduction  of  electricity  by  an  electro- 
lyte, without  consequent  decomposition. 

Helmholtz  assumes  that  the  atoms  of  oxygen  or 
hydrogen,  adhering  to  the  electrodes  during  elec- 
trolysis, are  mechanically  dislodged  and  diffused 
through  the  liquid,  thus  carrying  off  the  elec- 
tricity by  the  charges  received  while  in  contact 
with  the  electrodes. 

Convection  of  Heat,  Electric (See 

Heat,  Electric  Convection  of.) 

Convection  Streams. — (See  Streams,  Con- 
vection^) 

Convective  Discharge. — (See  Discharge, 
Convective?) 

Conversion,  Efficiency  of,  of  Dynamo  — 
—The  total  electric  energy  developed  by  a 
dynamo,  divided  by  the  total  mechanical 
energy  required  to  drive  the  dynamo.  (See 
Co-efficient,  Economic,  of  a  Dynamo-Electric 
Machine?) 

The  efficiency  of  conversion 

W  -j-  w   _          W  +  w 

M~~     ~~  W  +  w  -f  m, 

where  W,  equals  the  useful  or  available  electrical 
energy,  M,  the  total  mechanical  energy,  w,  the 
electrical  energy  absorbed  by  the  machine,  and 
m,  the  stray  power,  or  the  power  lost  in  friction, 
eddy  currents,  air  friction,  etc. 

Converted  Currents. — (See  Currents, 
Converted?) 

Converter. — The  inverted  induction  coil 
employed  in  systems  of  distribution  by  means 
of  alternating  currents. 

A  term  sometimes  used  instead  of  trans- 
former. (See  Transformer?) 

Converter,  Closed-Iron  Circuit  

A  closed-iron  circuit  transformer.  (See 
Transformer,  Closed-Iron  Circuit?) 

Converter,    Constant-Current    — 

A  constant-current  transformer.  (See  Trans- 
former, Constant-Current.) 


Converter,  Efficiency  of The  effi- 

ciency  of  a  transformer.     (See  Transformer, 
Efficiency  of.) 

Converter  Fuse. — (See  Fuse,  Converter.) 

Converter,  Hedgehog  -  — A  form  of 
transformer.  (See  Transformer,  Hedgehog.) 

Converter,  Multiple  -  — A  multiple 
transformer.  (See  Transformer,  Multiple?) 

Converter,  Open-Iron-Circuit  —  — An 
open-iron-circuit  transformer.  (See  Trans- 
former, Open-Iron-Circuit?) 

Converter,  Series  -  — A  series  trans- 
former. (See  Transformer,  Series.) 

Converter,  Step-down  —  — A  step-down 
transformer.  (See  Transformer,  Step-down.) 

Converter,  Step-up  -  — A  step-up 
transformer.  (See  Transformer,  Step-up?) 

Converter,  Welding  — A  welding 

transformer.  (See  Transformer,  Welding.) 

Converting  Currents. — (See  Currents, 
Converting.} 

Cooling  Box  of  Hydro-Electric  Machine. 
— (See  Box,  Cooling,  of  Hydro-Electric 
Machine?) 

Co-ordinates,  Axes  of The  axes  of 

abscissas  and  ordinates. 

The  two  straight  lines,  usually  perpendicular 
to  each  other,  to  which  distances  representing 
values  are  referred  for  the  graphic  represen- 
tation of  such  values.  (See  Abscissas,  Axes  of.) 

Copper  Bath.— (See  Bath,  Copper.) 
Copper  Plating.— (See  Plating,  Copper.) 
Copper  Ribbon. — A  variety  of  strap  cop- 
per.    (See  Copper,  Strap.) 

Copper,  Strap  -  — Copper  conductors 
in  the  form  of  straps  or  flat  bars. 

Strap  copper  is  used  on  the  armatures  of  some 
dynamos.  Heavy  copper  conductors  for  such 
purposes  are  divided  into  strap  copper  so  as  to 
avoid  eddy  currents.  The  straps  are  placed 
alongside  one  another  and  insulated  by  a  coating 
of  varnish. 

Copper  Wire,  Hard-Drawn (See 

Wire,  Copper,  Hard-Drawn?) 

Copper  Wire,  Soft-Drawn  — (See 

Wire,  Copper,  Soft-Drawn.) 


top.] 


128 


[Cor. 


Copper  Toltameter. — (See  Voltameter, 
Copper.} 

Coppered  Plumbago. — (See  Plumbago, 
Coppered} 

Coppering,  Electro  —  —  Electro-plating 
with  copper.  (See  Plating,  Electro^) 

Cord-Adjuster. — (See  Adjuster,  Cord.} 

Cord,  Conducting A  small  flexible 

cable,  usually  containing  several  conductors 
separated  from  one  another  by  insulating  ma- 
terial. 

Cord,  Electric A  flexible,  insulated 

electric  conductor,  generally  containing  at  least 
two  parallel  wires. 

Electric  cords  are  named  from  the  purposes  for 
which  they  are  employed,  battery  cord*,  dental 
cords,  lamp  cords,  motor  cords,  switch  cords,  etc. 


Fig.  1-72.     Flexible  Cord. 

A  two-conductor  flexible  cord,  in  which  each 
cord  is  composed  of  a  number  of  bare  copper  wires 
placed  parallel  to  and  in  contact  with  one  another, 
is  shown  in  Fig.  i"j2.  The  several  separate  wires 
give  flexibility  to  the  cord. 

Cord,  Pendant A  flexible  conductor 

provided  for  conveying  the  current  to  a  hang- 
ing electric  lamp  supported  by  it. 

Cords,  Telephone  —  —Flexible  con- 
ductors for  use  in  connection  with  a  tele- 
phone. 


Fig.  173.     Telephone  Cords. 

Telephone  cords,  attached  to  an  articulating 
telephone,  are  shown  in  Fig.  173. 


Core,    Armature,    Filamentous 

An  armature  core,  the  iron  of  which  consists 
of  wire. 

Core,  Armature,  H An  armature 

core  in  the  shape  of  the  letter  H,  generally 
known  as  the  shuttle  armature,  and  some- 
times as  the  girder  armature. 

This  form  is  also  called  an  I  armature. 

The  H  armature  core  was  the  form  originally 
given  to  the  Siemens  armature.  In  this  form  a 
single  coil  of  wire  was  secured  on  the  cross-bar 
of  the  H  armature  core,  so  as  to  fill  up  the  entire 
space  inside  the  letter,  and  the  ends  of  the  wire 
connected  to  a  two-part  commutator. 

Core,  Armature,  Lamination  of 

The  subdivision  of  the  core  of  the  armature 
of  a  dynamo-electric  machine  into  separate 
insulated  plates  or  strips  for  the  purpose  of 
avoiding  eddy  or  Foucault  currents. 

This  lamination  must  always  be  perpendicular 
to  the  direction  of  the  eddy  currents  that  would 
otherwise  be  produced.  (See  Currents,  Eddy.) 

Core,  Armature,  of  Dynamo-Electric 
Machine  —  — The  iron  core,  on,  or  around 
which,  the  armature  coils  of  a  dynamo-electric 
machine  are  wound  or  placed. 

The  armature  core  is  laminated  for  the  pur- 
pose of  avoiding  the  formation  of  eddy  or  Fou- 
cault currents. 

In.  drum,  and  in  ring-armatures,  the  laminae 
should  be  in  the  form  of  thin  insulated  discs  or 
plates  of  soft  iron ;  in  pole-armatures  they  should 
be  in  the  form  of  bundles  of  insulated  wires. 

The  iron  in  the  cores  should  be  of  such  an  area 
of  cross-section,  as  not  to  be  readily  oversaturated. 

Core,    Armature,     Radially-Laminated 

An  armature  core,  the  iron  of  which 

consists  of  thin  iron  washers. 

Core,  Armature,  Ribbed A  cylin- 
drical armature  core  provided  with  longi- 
tudinal projections  or  ribs  that  serve  as 
spaced  channels  or  grooves  for  the  reception 
of  the  armature  coils. 

Core,  Armature,  Tangentially-Laminated 

— An  armature  core,  the  iron  of  which 

consists  of  a  coiled  ribbon. 

Core,  Armature,  Ventilation  of 

Means  for  passing  air  through  the  armature 


Cor.J 


129 


[Cou. 


cores  of  dynamo-electric  machines  in  order  to 
prevent  undue  accumulation  of  heat. 

A  properly  proportioned  dynamo-armature 
may  need  no  ventilation,  since  in  such'  the 
amount  of  heat  generated  is  small  as  compared 
with  the  extent  of  the  radiating  surface. 

Since,  however,  in  practice  all  armatures  tend 
to  heat  at  full  load,  especially  in  certain  installa- 
tions in  heated  situations,  ventilation  of  the  ar- 
mature is  desirable. 


Core,    Closed-Magnetic 


— A   mag- 


netic core  so  shaped  as  to  provide  a  complete 
iron  path  or  circuit  for  the  lines  of  magnetic 
force  of  its  field. 


Core,   Laminated 


— A  core   of  iron 


which  has  been  divided  or  laminated,  in  order 
to  avoid  the  injurious  production  of  Foucault 
or  eddy  currents. 

Core,    Lamination   of Structural 

subdivisions  of  the  cores  of  magnets,  arma- 
tures, and  pole-pieces  of  dynamo-electric 
machines,  electric  motors,  or  similar  appa- 
ratus, in  order  to  prevent  heating  and  subse- 
quent loss  of  energy  from  the  production  of 
local,  eddy  or  Foucault  currents. 

These  laminations  are  obtained  by  forming  the 
cores  of  sheets,  rods,  plates,  or  wires  of  iron  in- 
sulated from  one  another. 

The  cores  of  dynamo-electric  machine  arma- 
tures should  be  subdivided  in  planes  at  right 
angles  to  the  armature  coils;  or  in  planes  parallel 
to  the  direction  of  the  lines  of  force  and  to  the 
motion  of  the  armature;  or,  in  general,  in  planes 
perpendicular  to  the  currents  that  would  otherwise 
be  generated  in  them. 

Pole  pieces  should  be  divided  in  planes  per- 
pendicular to  the  direction  of  the  currents  in  the 
armature  wires. 

Magnet  cores  should  be  divided  in  planes  at 
right  angles  to  the  magnetizing  current. 

Core  of  Cable. — The  conducting  wires  of 
an  electric  cable.  (See  Cable,  Electric?) 

Core,  Open-Magnetic Any  mag- 
netic core  so  shaped  that  the  lines  of  magnetic 
force  of-  its  field  complete  their  circuit  partly 
through  iron  and  partly  through  air. 

Core  Ratio  of  Cable. — (See  Cable,  Core 
Ratio  of.) 


Core,  Ring A  hollow,  cylindrical 

core  of  short  length. 

Core,  Ring,  Elongated A  hollow, 

cylindrical  core  of  comparatively  great  length. 

Core,  Solenoid  —A  core  so  arranged 

as  to  be  drawn  into  a  solenoid  on  the  passage 
of  the  current  through  its  coils,  and  to  be 
withdrawn  therefrom,  on  the  stopping  of  the 
current  by  the  action  of  a  spring  or  weight. 
(See  Solenoid.) 

Core,    Stranded,    of    Cable The 

conducting  wire  or  core  of  a  cable  formed  of 
a  number  of  separate  conductors  or  wires  in- 
stead of  a  single  conductor  of  the  same  weight 
per  foot  as  the  combined  conductors. 

Core  Transformer. — (See  Transformer, 
Core. ) 

Cored  Carbons. — (See  Carbons,  Cored.) 

Cored  Electrodes. — (See  Electrodes, 
Cored.) 

Coronae,  Auroral A  crown-shaped 

appearance,  sometimes  assumed  by  the  auro- 
ral light.  (See  Aurora  Borealis) 

Corposant. — A  name  sometimes  given  by 
sailors  to  a  St.  Elmo's  Fire.  (See  Fire,  St. 
Elmo's?) 

Correlation  of  Energy. — (See  Energy, 
Correlation  of) 

Corresponding  Points. — (See  Points,  Cor- 
responding) 

Cosine. — One  of  the  trigonometrical  func- 
tions. (See  Trigonometry) 

Cotangent. — One  of  the  trigonometrical 
functions.  (See  Trigonometry) 

Coulomb. — The  unit  of  electrical  quantity. 

A  definite  quantity  or  amount  of  the  thing 
or  effect  called  electricity. 

Such  a  quantity  of  electricity  as  would  pass 
in  one  second  in  a  circuit  whose  resistance  is 
one  ohm,  under  an  electromotive  force  of 
one  volt. 

The  quantity  of  electricity  contained  in  a 
condenser  of  one  farad  capacity,  when  sub- 
jected to  an  electromotive  force  of  one  volt. 

The  quantity  of  electricity  that  flows  per 
second  past  a  cross-section  of  a  conductor 


Con.] 


130 


[I'ou. 


conveying  an  ampere. — (Ayrton.)  (See  Am- 
pere. Farad.  Volt.) 

Coulomb's  Torsion  Balance. — (See  Bal- 
ance, Coulomb's  Torsion?) 

Coulomb-Volt. — A  Joule,  or  .7373  foot- 
pound. 

The  term  is  generally  written  volt-coulomb. 
(See  Volt-Coulomb.) 

Counter,  Electric  —  — A  device  for 
counting  and  registering  such  quantities  as 
the  number  of  fares  collected,  gallons  of  water 
pumped,  sheets  of  paper  printed,  revolutions 
of  an  engine  per  second,  votes  polled,  etc. 

Various  electric  devices  are  employed  for  this 
purpose.  They  are  generally  electro-magnetic 
in  character. 

Counter-Electromou.  e  Force.  —  (See 
Force,  Electromotive,  Counter.} 

Counter  Electromotive  Force  Lightning 
Arrester. — (See  Arrester,  Lightning,  Coun- 
ter-Electromotive Force!) 

Counter-Electromotive  Force  of  Convec- 
tive  Discharge. — (See  Force,  Electromotive, 
Counter,  of  Convective  Discharged) 

Counter-Electromotive  Force  of  Mutual 
Induction. — (See  Force,  Electromotive, 
Counter,  of  Mutual  Induction?) 

Counter-Electromotive  Force  of  Self-In- 
duction.— (See  Force,  Electromotive,  Coun- 
ter, of  Self -Induction?) 

Counter-Electromotive  Force  of  Self-In- 
duction of  the  Primary.— (See  Force, 
Electromotive,  Counter,  of  Self-induction  of 
the  Primary?) 

Counter-Electromotive  Force  of  Self-in- 
duction of  the  Secondary. — (See  Force, 
Electromotive,  Counter,  of  Self-induction  of 
the  Secondary?) 

Counter-Electromotive  Force  of  the 
Primary. — (See  Force,  Electromotive ; 
Counter,  of  the  Primary?) 

Counter  Inductive  Effect.— (See  Effect, 
Counter  Inductive?) 

Couple. — In  mechanics,  two  equal  parallel 
forces  acting  in  opposite  directions  but  not  in 
the  same  line,  and  tending  to  cause  rotation. 

The  moment,  or  effective  power  of  a  couple,  is 


N; 


equal  to  the  intensity  of  one  of  the  forces  multiplied 
by  the  perpendicular  distance  between  the  direc- 
tions of  the  two  forces. 

Couple,  Astatic  •  — Two  magnets  of 

exactly  equal  strength  so  placed  one  over  the 
other  m  the  same  vertical  plane  as  to  com- 
pletely neutralize  each  other. 

An  astatic  couple  has  no  directive  tendency.  A 
pair  of  magnets  combined  as  an  astatic  couple  is 
called,  an  astatic  needle.  (See  Needle,  Astatic.) 

Couple,  Magnetic  —  —The  couple  which 
tends  to  turn  a  magnetic  needle,  placed  in  the 
earth's  field,  into  the  plane  of  the  magnetic 
meridian. 

If  a  magnetic  needle  is  in  any  other  position 
than  in  the  magnetic  meridian,  there  will  be  two 
parallel  and  equal  forces  acting  at  A  and  B,  Fig. 
174,  in  the  directions  shown  by  the  arrows. 
Their  effect  will  be  to  ro- 
tate the  needle  until  it 
comes  to  rest  in  the  mag- 
netic meridian  N  S. 

The  total  force  acting 
on  either  pole  of  a  needle 
free  to  move  in  any  direc- 
tion, is  equal  to  the 
strength  of  that  pole  mul- 
tiplied by  the  total  inten- 
sity of  the  earth's  field  at 
that  place  ;  or,  if  free  to  move  in  a  horizontal 
direction  only,  is  equal  to  the  intensity  of  the 
earth's  horizontal  component  of  magnetism  at 
that  place,  multiplied  by  the  strength  of  that  pole. 

The  effective  power  or  moment  of  a  magnetic 
couple  is  equal  to  the  force  exerted  on  one  of  the 
poles  multiplied  by  the  perpendicular  distance, 
P  Q,  between  their  directions. 

Couple,  Moment  of  — The  effective 

power  or  force  of  a  couple. 

The  moment  of  a  couple  is  equal  to  the  inten- 
sity of  one  of  the  forces  multiplied  by  the  perpen- 
dicular distance  between  the  direction  of  the 
forces. 

Couple,  Thermo-Electric  —  — Two  dis- 
similar metals  which,  when  connected  at  their 
ends  only,  so  as  to  form  a  completed  electric 
circuit,  will  produce  a  difference  of  potential, 
and  hence  an  electric  current,  when  one  of  the 
ends  is  heated  more  than  the  other. 

Thus  if  a  bar  of  bismuth  be  soldered  to  a  bar 


is 

174.    Magnttic 
Couple. 


Con.] 


131 


[Cre. 


of  antimony  the  combination  will  form  a  thermo- 
elec^ric  couple,  and  the  circuit  so  formed  will 
have  a  current  passing  through  it  when  one  junc- 
tion is  hotter  or  colder  than  the  other. 

There  is,  according  to  Lodge,  a  true  contact 
force,  at  a  thermo-electric  junction,  as  is  shown  by 
the  reversible  heat  effects  produced  when  an 
electric  current  is  passed  across  such  junction ;  for, 
in  one  direction  more  heat  is  produced,  and  in  the 
opposite  direction  less  heat.  This,  as  is  well 
known,  differs  from  the  irreversible  heat  produced 
by  a  current  through  a  homogeneous  metallic 
conductor.  The  reversible  heat  effects,  or  as  they 
are  called  the  Peltier  effects,  may  overpower  and 
conceal  the  heating  effects.  But,  in  addition  to 
these  effects,  since  a  difference  of  potential,  called 
a  Thomson  effect,  exists  in  a  substance  unequally 
heated,  currents  are  so  produced,  and  these  are 
also  influential  in  causing  the  difference  of  poten- 
tial of  a  thermo-electric  couple. 

"  There  are  then,"  says  Lodge,  "in  a  simple 
circuit  of  two  metals  with  their  junctions  at  differ- 
ent temperatures,  altogether  four  E.  M.  Fs.,  one 
in  each  metal,  from  hot  to  cold,  or  vice  versa,  and 
one  at  each  junction,  and  the  current  which  flows 
around  such  a  circuit  is  propelled  by  the  resultant 
of  these  four."  *  *  *  "  These  four  forces, 
two  Thomson  forces  in  the  metals,  and  two  Peltier 
forces  at  their  junctions,  may  some  of  them  help 
and  some  hinder  the  current."  *  *  *  "When- 
ever they  help,  the  locality  is  to  that  extent  cooled; 
whenever  they  hinder,  it  is  to  that  extent 
warmed." 

The  action  of  a  thermo-electric  couple  in  pro- 
ducing a  difference  of  potential  is  therefore  a 
complicated  one,  and  depends  on  Peltier  and 
Thomson  effects,  as  well  as  on  the  thermo-electric 
effect.  (See  Effect,  Peltier.  Effect,  Thomson. 
Effect,  Thermo -Electric.) 

Couple,  Yoltaic—  -  Two  materials, 
usually  two  dissimilar  metals,  capable  of 
acting  as  an  electric  source  when  dipped  in 
an  electrolyte,  or  capable  of  producing  a 
difference  of  electric  potential  by  mere  con- 
tact. 

Liquids  and  gases  are  capable  of  acting  as 
voltaic  couples. 

All  voltaic  cells  have  two  metals,  or  a  metal  and 
a  metalloid,  or  two  gaseous  or  liquid  substances 
which  are  of  such  a  character  that,  when  dipped 
into  the  exciting  fluid  one  only  is  chemically 
acted  on. 


Each  one  of  these  two  substances  is  called  an 
element  of  the  cell,  and  the  two  taken  collectively 
form  a  -voltaic  couple. 

The  elements  of  a  voltaic  couple  may  consist  of 
two  gases  or  two  liquids.  (See  Battery,  Gas.) 

Coupled  Cells.— (See  Cells,  Coupled^ 

Coupler,  Yoltaic  -  —Any  device  by 
means  of  which  voltaic  cells  may  be  readily 
coupled  or  connected  in  different  forms  of 
circuits.  (See  Circuits,  Varieties  of.) 

Coupling  of  Yoltaic  Cells  or  Other 
Electric  Sources.— A  term  indicating  the 
manner  in  which  a  number  of  separate 
electric  sources  may  be  connected  so  as  to 
form  a  single  source.  (See  Circuits,  Varie- 
ties of.) 

Cramp,  Telegrapher's  -  —An  affec- 
tion of  the  hand  of  a  telegrapher  due  to  im- 
moderate and  excessive  use  of  the  same 
muscles,  somewhat  similar  to  the  disease 
known  as  writer's  cramp. 

Telegrapher's  cramp,  like  writer's  cramp,  may 
be  defined  as  a  professional  neurosis  of  co-ordina- 
tion. It  appears  not  only  in  certain  groups  of 
muscles,  but  is  limited  to  such  groups,  only  when 
they  are  performing  certain  complicated  opera- 
tions. For  example,  telegrapher's  cramp  is 
practically  a  paralysis  of  certain  muscles  of  the 
hand  and  wrist  of  the  operator.  These  muscles, 
when  called  on  to  perform  the  somewhat  delicate 
movements  required  in  sending  a  telegraphic  dis- 
patch, are  incapable  of  performing  their  proper 
functions,  but  when  called  on  to  perform  in  part 
other  similar  actions,  provided  all  these  actions 
are  not  required  to  be  used,  appear  to  be  un- 
affected. 

The  ability  of  the  operator  to  send  with  either 
hand  would  lessen  the  liability  to  this  disease. 

Crater  in  Positive  Carbon. — A  depression 
at  the  end  of  the  positive  carbon  of  an  arc 
lamp  which  appears  when  a  voltaic  arc  is 
formed.  (See  Arc,  Voltaic.) 

Creep,  Diffusion  —  — The  flow  of  an 
electric  current  in  portions  of  a  conducting 
substance,  outside  the  parts  that  lie  in  the 
direct  lines  between  the  points  where  the 
terminals  of  the  same  are  applied  to  the  con- 
ducting substance 


t're.J  132 

Creeping,  Electric A  term  some- 
times applied  to  the  creeping  of  a  current. 
(See  Current,  Creeping  of.} 

Creeping  in  Voltaic  Cell.— (See  Cell,  Vol- 
taic, Creeping  in.) 

Creeping  of  Current — (See  Current, 
Creeping  of,  Electric) 

Creeping,  Saline The  formation 

of  salts  by  efflorescence  on  the  walls  of  a  solid 
immersed  in  a  solution  of  a  salt. 

Creosoting. — A  process  employed  for  the 
preservation  of  wood,  as,  for  example,  tele- 
graph poles,  by  injecting  creosote  into  the 
pores  of  the  wood.  (See  Pole,  Telegraphic) 

Crith. — A  term  proposed  by  A.  W.  Hoff- 
man, as  a  unit  of  weight,  or  the  weight  of 
one  litre,  or  cubic  decimetre,  of  hydrogen  at 
O  C.  and  760  mm.  barometric  pressure. 

Critical  Current.  —  (See  Current,  Crit- 
ical) 

Critical  Current  of  a  Dynamo. — (See 
Current,  Critical,  of  a  Dynamo) 

Critical  Distance  of  Lateral  Discharge 
through  Alternative  Path. — (See  Distance, 
Critical,  of  Lateral  Discharge  through 
an  Alternative  Path) 

Critical  Speed  of  Compound-Wound  Dy- 
namo.— (See  Speed,  Critical,  of  Compound- 
Wound  Dynamo) 

Crookes'  Dark  Space. — (See  Space,  Dark, 
Crookes') 

Crookes'  Electric  Radiometer. — (See  Ra- 
diometer, Electric,  Crookes') 
Cross  Arm. — (See  Arm,  Cross) 

Cross-Connecting  Board. — (See  Board, 
Cross-Connecting) 

Cross,  Electric A  connection,  gen- 
erally metallic,  accidentally  established  be- 
tween two  conducting  lines. 

A  defect  in  a  telegraph,  telephone  or  other 
circuit  caused  by  two  wires  coming  into 
contact  by  crossing  each  other. 

A  swinging  or  intermittent  cross  is  caused  by 
wires,  which  are  too  slack,  being  occasional^ 
blown  into  contact  by  the  wind. 


[Cro. 

A  weather  cross  arises  from  defective  action  oi 
the  insulators  in  wet  weather. 

Cross,  Swinging  or  Intermittent 

An  accidental  contact,  generally  metallic, 
caused  by  wires  being  brought  into  occasional 
contact  with  one  another,  or  with  some  other 
conductor,  by  the  intermittent  action  of  the 
wind. 

Cross,  Weather A  contact  or  leak 

occurring  in  a  telegraphic  or  other  line  dur- 
ing wet  weather,  from  the  defective  action  of 
the  insulators. 

Crossing  Cleat— (See  Cleat,  Crossing) 

Crossing,  Live-Trolley —A  device 

whereby  a  trolley  moving  over  a  line  that 
crosses  a  second  line  at  an  angle  is  enabled 
to  maintain  its  electrical  connection  with  the 
line  while  crossing. 

A  live-trolley  crossing  is  necessitated  where  one 
line  of  electric  railway  crosses  another.  The 
upper  line  must,  of  course,  provide  a  space  or 
opening  for  crossing  the  lower  line  at  the  points 
of  intersection.  This  is  effected  in  the  Bagnall 
live-trolley  crossing,  shown  in  Fig.  175,  by  attach- 


Fig-  Z75-     Live-Trolley  Crossing. 

ing  to  the  upper  trolley  wire  a  bridge  piece  of 
light  lathe  casting,  provided  at  its  centre  with  a 
gap  through  which  the  trolley  wire  passes.  This 
bridge  piece  is  insulated  from  the  trolley  wire  by 
means  oi  a  disc  of  insulating  material  at  the  cen- 
tre of  the  bridge,  which  is  provided  with  a  hinged 
curved  lever,  that  in  its  normal  position  rests  un- 
der the  influence  of  gravity  in  the  position  shown 
in  the  figure.  The  passage  of  the  trolley  wheel 
along  the  wire  carries  the  line  under  it  and  thus 
bridges  the  gap,  as  shown  by  the  position  of  the 
dotted  lines. 

Crossing  Wires. — (See  Wires,  Crossing) 

Cross-Over  Block. — (See  Block,  Cross- 
Over) 

Cross-Over,  Trolley  —  — A  device  by 
means  of  which  a  trolley  is  enabled  to  pass 
over  the  points  where  different  lines  cross  one 
another  without  serious  interrunt;nn. 


Cro.] 

A  trolley  cross-over,  for  trolley  lines,  is  shown 
in  Fig.  176. 


[Cur. 


Fig.  176.     Trolley  Cross -Over. 

Crow-foot  Zinc.— (See  Zinc,  Crow-foot?) 

Crucible.  Electric A  crucible  in 

which  the  heat  of  the  voltaic  arc.  or  of  elec 
trie  incandescence,  is  employed  either  to  per- 
form difficult  fusions,  or  for  the  purpose  of 
effecting  the  reduction  of  metals  from  their 
ores  or  the  formation  of  alloys.  (See  Fur- 
nace, Electric?) 

Crystal.— A  solid  body  bounded  by  sym- 
metrically disposed  plane  surfaces, 

A  definite  form  or  shape  is  as  characteristic  of 
an  inorganic  crystalline  substance  as  it  is  of  an 
animal  or  plant,     Each  substance  has  a  form  in 
which  it  generally  occurs.      There  are,  however, 
certain  modifications  of  the  typical  forms  which 
cause  plane  surfaces  to  appear  curved,  and  the 
symmetrical  arrangement  of  the  faces  to  disap 
pear.     These  modifications   often   render  it   ex 
tremely   difficult  to   recognize  the    true  typical 
torm 

'For  the  different  fundamental  crystalline  forms, 
or  systems  of  crystals,  see  any  standard  work  on 
chemistry. 

Crystal.  Hemiliedral  —  -  —A  crystal 
whose  shape  or  form  has  been  modified  by 
the  replacement  of  half  its  edges  or  solid 
angles, 

A  hemihedral  crystal  possesses  different  forms 
at  the  ends  or  extremities  of  its  axes.  Hemi- 
hedral  crystals,  when  unequally  heated,  develop 
electrical  charges. 

Electricity  produced  in  this  way  was  formerly 
C3\\e&  pyro-electricity.  (See  Electricity,  J'yro.) 

Crystal,  Holohedral A  crystal 

whose  shape  or  form  has  been  modified  by 
the  replacement  of  all  its  edges  or  solid 
angles. 

Crystalline  Electro-Metallurgical  De- 
posit.— (See  Deposit.  Crystalline.  Electro- 
Metallurgzcal.) 

Crystallization.— Solidification  from  a  state 
of  solution  or  fusion  in  a  definite  crystalline 
iorm. 


The  crystallization  of  a  dissolved  solid  is  fa- 
vored by  any  cause  that  gives  increased  freedom 
of  movement  to  its  molecules,  such  for  example  as 
solution,  fusion,  sublimation,  or  precipitation. 

Crystallization  by  Electrolytical  Decom- 
position.— The  crystalline  deposition  of  vari- 
ous metals  by  the  passage  of  an  electric  cur- 
rent through  solutions  of 'their  salts  under 
certain  conditions. 

A  strip  of  zinc  immersed  in  a  solution  of  sugar 
of  lead  (acetate  of  lead)  soon  becomes  covered 
with  bright  metallic  plates  of  lead,  that  are  elec- 
trolytically  deposited  by  the  weak  currents  due  to 
minute  voltaic  couples  formed  with  the  zinc  by 
particles  of  iron,  carbon,  or  other  impurities  in 
the  zinc.  The  deposit  assumes  at  times  a  tree- 
like growth,  and  is  therefore  called  a  lead  tree. 
(See  Couple,  Voltaic.) 

Crystallization,  Electro  —  — Crystalli- 
zation effected  during  electrolytic  deposition. 

Crystallize. — To  separate  from  a  liquid 
or  vapor,  in  the  form  of  a  crystalline  solid. 

Crystalloid.— Those  portions  of  a  mixed 
substance  subjected  to  dialysis,  that  are  capa- 
ble of  crystallization.  (See  Dialysis.) 

Cube,  Faraday's  —An  insulated 

room  cubic  in  shape,  covered  on  the  inside 
with  tin  foil,  which,  when  charged  on  the 
outside  gives  no  indications  to  an  observer  on 
the  inside,  though  furnished  with  delicate  in- 
struments. 

Faraday's  cube  illustrates  the  fact  that  an  elec- 
trostatic charge  resides  on  the  outside  of  an  insu- 
lated conductor.  (See  Net,  Faraday's.) 

Cup,  Mercury A  cup  or  cavity 

filled  with  mercury  and  connected  with  the 
pole  of  an  electric  apparatus  for  the  ready 
placing  of  the  same  in  circuit  with  other  elec- 
tric apparatus. 

To  connect  apparatus  it  is  only  necessary  to 
insert  the  free  terminal  of  one  apparatus  in  the 
mercury  cup  of  the  other. 

Cup,  Porous A  porous  cell.  (See 

Cell,  Porous) 

Curb,  Double  -  — A  device  for  in- 
creasing the  speed  of  signaling,  by  means  of 
which  the  line  is  rid  of  its  charge  before  the 
next  signal  is  sent,  by  sending  an  opposite 
charge,  then  another  in  the  same  direction, 


Cur.] 


134 


LCur. 


then  finally  another  in  the  same  direction 
before  connecting  with  the  ground. 

The  effect  of  the  third  charge  is  to  reduce  the 
potential  of  the  line  more  nearly  to  zero  at  the 
end  of  the  signal. 

Curb,  Single  —A  device  for  in- 
creasing the  speed  of  signaling  telegraphic- 
ally by  ridding  the  line  of  its  previous  charge 
by  sending  a  reversed  current  through  it  be- 
fore connecting  with  the  ground. 

In  single-curb  signaling  the  operator  in  dis- 
charging the  line  before  sending  another  signal 
through  it,  before  putting  the  line  to  earth,  re- 
verses the  battery,  and  then  connects  to  earth. 

Current,  Absolute  Unit  of A  cur- 
rent of  10  amperes.  (See  Ampere.  Units, 
Practical!) 

A  current  of  such  a  strength  that  when 
passed  through  a  circuit  of  a  centimetre  in 
length  bent  in  the  form  of  an  arc  of  a  circle 
one  centimetre  in  radius,  will  act  with  the 
force  of  a  dyne  on  a  magnetic  pole  of  unit 
strength,  placed  at  the  centre  of  the  arc. 

The  ampere,  the  practical  unit  of  current,  is 
but  ^5  the  value  of  the  absolute  unit  of  current. 

Current,  Action  of,  on  a  Magnetic  Pole 

An  attraction  or  repulsion  depend- 
ent on  the  name  of  the  pole  and  the  direction 
of  the  current. 

Two  currents  of  electricity  attract  or  repel  each 
other  according  to  the  direction  in  which  they 
are  flowing,  and  the  mutual  positions  of  their 
circuits.  A  current  and  a  magnetic  pole  exert  an 
action  on  each  other  which,  strictly  speaking,  is 
neither  attraction  nor  repulsion,  but  which  is  ro- 
tation, that  may,  however,  be  regarded  as  being 
produced  by  the  combined  action  of  attraction 
and  repulsion. 

Current,  Alternating  —  — A  current 
which  flows  alternately  in  opposite  directions. 

A  current  whose  direction  is  rapidly  re- 
versed. 

The  non-commuted  currents  generated  by  the 
differences  of  potential  in  the  armature  of  a 
dynamo-electric  machine  are  alternating  or 
simple-periodic-currents. 

In  a  characteristic  curve  of  the  electromotive 
forces  of  alternating  currents,  positive  electro- 
motive forces,  or  those  that  would  produce  cur- 


rents in  a  certain  direction,  are  indicated  by 
values  aboz>e  a  horizontal  line,  and  negative  elec- 
tromotive forces,  by  values  be-low  the  line. 

The  curves  ABC,  and  C  D  E,  Fig.  177,  are 

B 


Fig    177-     Curve  of  Electromotive  Forces  of  Alternating 
Currents. 

often  called  phases,  and  represent  the  alternate 
phases  of  the  current. 

Current,  Alternative   —A  voltaic 

alternative.     (See  Alternatives,  Voltaic^ 
Current,    Assumed    Direction   of  Flow 

of The  direction  the  current  is  as- 
sumed to  take,  t.  e.,  from  the  positive  pole  of 
the  source  through  the  circuit  to  the  negative 
pole  of  the  source. 

The  electricity  is  assumed  to  come  out  of  the 
source  at  its  positive  pole,  and  to  return  or  flow 
back  into  the  source  at  its  negative  pole.  This 
convention  as  to  the  direction  of  the  electric  cur- 
rent is  in  accordance  with  the  assumption  of  the 
direction  of  flow  of  lines  of  magnetic  forces. 

The  old  idea'of  a  dual  or  double  current  flowing 
in  opposite  directions  is  still  maintained  by  some, 
(See  Force,  Lines  of,  Direction  of.) 

Current,  Axial In  electro-thera- 
peutics a  current  flowing  in  a  nerve  in  the 
opposite  direction  to  the  normal  impulse  in 
the  nerve. 

Current.  Break-Induced The  cur- 
rent induced  by  a  current  in  its  own,  or  in 
another  circuit,  on  breaking  or  opening  the 
same. 

The  current  induced  in  the  secondary  on 
the  breaking  of  the  primary  circuit. 

The  break-induced  current  set  up  by  a  current 
in  its  own  circuit  is  sometimes  called  the  direct- 
induced  current. 

Lord  Rayleigh  has  shown  that  within  certain 
limits  the  break-induced  current  has  a  greater 
effect  in  magnetizing  steel  needles,  the  smaller 
the  number  of  turns  of  wire  in  the  secondary.  In 


Cur.] 


135 


[Cur. 


the  case  of  a  galvanometer,  it  is  well  known  that 
the  opposite  is  true.  The  deflection  of  the  gal- 
vanometer needle  depends  on  the  strength  of  the 
whole  current.  The  magnetizing  power  depends, 
for  the  greater  part,  on  the  strength  of  the  cur- 
rent at  the  beginning  of  its  formation 

Current.  Closed -Circular  -  -  —A  cur- 
rent flowing  in  a  circular  circuit. 

A  small  closed-circular  current  may  be  replaced 
magnetically  by  a  thin  disc  of  steel,  magnetized  in 
a  direction  perpendicular  to  its  iace,  and  the  edge 
of  which  corresponds  to  the  edge  of  the  circular 
conductor. 

Current-Commuter.  —  (See  Commuter, 
Current?) 

Current.  Conduction —The  current 

that  passes  through  a  metallic  or  other  con- 
ducting substance,  as  contradistinguished 
from  a  current  produced  in  a  non-conductor 
or  dielectric.  (See  Current,  Displacement) 

Current,  Constant A  current  that 

continues  to  flow  m  the  same  direction  for 
some  time  without  varying  m  strength, 

This  term  is  sometimes  used  to  mean  a  con 
tinuous  or  direct  current  in  contradistinction  to 
an  alternating  current,  but  it  ought  to  be  applied 
only  to  unvarying  currents,  such,  for  example  as 
a  constant  current  of  10  amperes. 

Current,  Continuous  -  — An  electric 
current  which  flows  in  one  and  the  same 
direction 

Although  the  term  continuous  current  is  used 
as  synonymous  with  constant  current,  it  is  not 
entirely  so;  a  continuous  current  flows  constantly 
in  the  same  direction  A  constant  current  not 
only  flows  continuously  in  the  same  direction,  but 
maintains  an  approximately  constant  current 
strength 

This  term  continuous  current  is  used  in  the 
opposite  sense  to  alternating  current,  and  in  the 
same  sense  as  a  direct  current. 

Current,   Creeping  of  Electric • 

A  change  in  the  direction  of  path  of  a  current 
from  the  direct  line  between  the  points  of 
connection  with  the  source. 

When  the  terminals  of  any  electric  source  are 
placed  in  contact  with  any  two  points  of  a  metallic 
sheet  of  conducting  material,  the  flow  of  the  cur- 
rent ib  not  confined  to  the  direct  line  between  the 


Critical 
Curve  of  Dynamo 
Current 


points  of  contact,  but  creeps  or  diffuses  into  por- 
tions of  the  conducting  plate  surrounding  this 
direct  line.  (See  Current,  Diffusion  of.) 

In  a  somewhat  similar  manner,  the  current 
is  said  to  creep,  or  to  establish  a  partial  short- 
circuit  around  the  poles  of  a  poorly  insulated 
voltaic  battery,  or  other  electric  source. 

Current,    Critical  — 
—The  current  at  which  a 
certain  result  is  reached, 

Current,  Critical,  of  a 
Dynamo —  —That  value 
of  the  current  at  which  the 
characteristic  curve  begins 
to  depart  from  a  nearly 
straight  line,  —  (Silvanus  Fig  178 
P  Thompson.} 

In  Fig.  178  the  critical 
current  is  shown  in  three  different  cases,  as  oc- 
curring where  the  dotted  vertical  line  cuts  the 
characteristic  curves. 

The  speed  at  which  a  series  dynamo  excites 
itself  is  often  called  the  critical  speed. 

Current,  Demarcation.  -  — A  term 
sometimes  applied  to  an  electric  current  ob- 
tained from  an  injured  muscle. 

"  Every  injury  of  a  muscle  or  nerve  causes  at 
the  point  of  injury  a  dying  surface,  which  behaves 
negatively  to  the  positive  intact  substance."— 
(Landois  &  Stirling.) 

Current  Density.— The  current  of  elec- 
tricity which  passes  in  any  part  of  a  circuit  as 
compared  with  the  area  of  cross-section  of 
that  part  of  the  circuit. 

In  a  dynamo- electric  machine  the  current  den- 
sity in  the  armature  wire  should  not,  according  to 
Silvanus  P.  Thompson,  exceed  2.500  amperes 
per  square  inch  of  area  of  transverse  section  of 
conductor. 

The  current  density  in  a  dynamo  wire,  of 
necessity  depends  on  the  sectional  area  of  the 
coils .  If,  for  example,  a  current  of  50  amperes 
be  safe  in  an  armature  section  of  eight  turns  it 
may  be  safely  increased  to  100  amperes  if  the 
conductors  are  cross-  sectioned  so  as  to  make  but 
four  turns. — (Urquhart.) 

In  electro- plating,  for  every  definite  current 
strength  that  passes  through  the  bath,  or  in  other 
words,  for  a  definite  number  of  coulombs,  a 
definite  weight  of  metal  is  deposited,  the  charac- 


Cur.] 


136 


[Cur: 


ter  of  which  depends  on  the  current  density.  The 
character  of  an  electrolytic  deposit  will  therefore 
depend  on  the  current  density  at  that  part  of  the 
circuit  where  the  deposit  occurs. 

The  following  table  from  Urquhart  gives  the 
practical  working  value  for  the  current  density 
for  electro-metallurgical  deposits  : 

CURRENT   DENSITY    (OR    AMPERES    ON 
CATHODE). 

Amperes 
Solution  of  per  square  foot. 

Copper,  acid  bath 5.0  to  10.0 

Copper,  cyanide  bath 3.0  "     5.0 

Silver,  double  cyanide 2.0  "     5.0 

Gold,  chloride  in  cyanide i.o  "     2.0 

Nickel,  double  sulphate 6.0  "     8.0 

Brass,  cyanide 2.0  "     3.0 

Tin 

Current,     Diacritical  —Such    a 

strength  of  the  magnetizing  current  as  pro- 
duces a  magnetization  of  an  iron  core  equal 
to  half-saturation. 

The  diacritical  current  is  the  current  which, 
flowing  through  the  diacritical  number  of  ampere- 
turns,  will  bring  up  the  magnetism  produced  to 
half -saturation. 

,  The  diacritical  number  of  ampere-turns  is  such 
a  number  of  ampere-turns  as  would  reduce  the 
magnetic  permeability  to  half  its  lull  value. 

Current,  Diffusion  of  -  —A  term  em- 
ployed to  designate  the  difference  in  the 
density  of  current  in  different  portions  of  a 
conductor.  (See  Current.  Creeping  of  ,  Elec- 
tric) 

Current,  Diffusion  of  Electro-Therapeu- 
tic   The  difference  in  the  density  of 

current  in  different  portions  of  the  human 
body  between  the  electro-therapeutic  elec- 
trodes. 

When  the  electrodes  are  placed  at  any  two 
given  points  of  the  human  body,  the  current 
branches  through  various  paths,  extending  in  a 
general  direction  from  one  electrode  to  the  other, 
according  to  the  law  of  branched  or  derived  cir- 
cuits, and  flowing  in  greater  amount,  or  with 
greater  density  of  current,  through  the  relatively 
better  conducting  paths.  (See  Current  Density.') 

This  is  sometimes  called  the  creeping  of  the 
Current.  (See  Current,  Creeping  of  .} 

Current,  Direct  — A  current  con- 


stant in  direction,  as  distinguished  from  an 
alternating  current. 

A  continuous  current. 

Current,  Direct-Induced The  cur- 
rent induced  in  a  circuit  by  induction  on  it- 
self, or  self-induction,  on  breaking  or  opening 
the  circuit.  (See  Currents,  Extra.} 

This  is  called  the  direct-induced  current  because 
its  direction  is  in  the  same  direction  as  the  induc- 
ing current. 

Current,  Direction  of—  —The  direc- 
tion an  electric  current  is  assumed  to  take 
out  from  one  pole  of  any  source  through  the 
circuit  and  its  translating  devices  back  to  the 
source  through  its  other  pole. 

Conventionally,  the  current  is  assumed  to  come 
out  from  the  positive  pole  of  the  source  and  to  go 
back  to  the  source  at  the  negative  pole. 

Current,  Displacement  —  — The  rate 
of  change  of  electric  displacement. 

A  brief  conduction  current  produced  in  a 
dielectric  by  an  electric  displacement.  (See 
Displacement,  Electric?) 

This  is  called  a  displacement  current  in  order 
to  distinguish  it  from  a  conduction  current  in  any 
conductor. 

The  displacement  current  continues  while  the 
displacement  of  electricity  is  going  on.  Dis- 
placement currents  have  all  the  properties  of  con- 
duction currents,  and,  like  the  latter,  produce  a 
magnetic  field;  in  fact,  they  resemble  extremely 
brief  conduction  currents. 

The  difference  between  conducting  substances 
and  dielectrics,  lies  in  the  fact  that  the  conducting 
substances  do  not  possess  an  elastic  force,  en- 
abling them  to  resist  electric  displacement.  In 
other  words,  conducting  substances  possess  no 
electric  elasticity,  and  can  have  no  true  displace- 
ment current  established  in  them.  (See  Elasti- 
city, Electric.} 

A  displacement  current,  like  a  conduction  cur- 
rent, possesses  a  magnetic  field,  or  is  encircled  by 
lines  of  magnetic  force.  (See  Field,  Magnetic,  of 
an  Electric  Current. ) 

Current,  Electric  -  — The  quantity  of 
electricity  which  passes  per  second  through 
any  conductor  or  circuit. 

The  rate  at  which  a  definite  quantity  of  elec- 
tricity passes  or  flows  through  a  conductor  or 
circuit. 


Cur.] 


137 


[Cur. 


The  ratio  existing  between  the  electro- 
motive force,  causing  the  current,  and  the 
resistance  which  may,  for  convenience,  be 
regarded  as  opposing  it,  expressed  in  terms 
of  quantity  of  electricity  per  second. 

The  unit  of  current,  or  the  ampere,  is  equal  to 
one  coulomb  per  second.  (Set  Ampere.  Coulomb.) 

The  word  current  must  not  be  confounded 
with  the  mere  act  of  flowing;  electric  current 
signifies  rate  of  flow,  and  always  supposes  an 
electromotive  force  to  produce  the  current,  and  a 
resistance  to  oppose  it. 

The  electric  current  is  assumed  to  flow  out 
from  the  positive  terminal  of  a  source,  through 
the  circuit  and  back  into  the  source  at  the  nega- 
tive terminal.  It  is  assumed  to  flow  into  the 
positive  terminal  of  an  electro-receptive  device 
such  as  a  lamp,  motor,  or  storage  battery,  and 
out  of  its  negative  terminal;  or,  in  other  words, 
the  positive  pole  of  the  source  is  always  con- 
nected to  the  positive  terminal  of  the  electro-re- 
ceptive  device. 

Professor  Lodge  draws  the  following  com- 
parison between  the  motions  of  ordinary  mat- 
ter, heat  and  electricity:  "Consider  the  modes 
in  which  water  may  be  made  to  move  from  place 
to  p'.ace;  there  are  only  two.  It  may  be  pumped 
along  pipes,  or  it  may  be  carried  about  in  jugs. 
In  other  words,  it  may  travel  through  matter,  or, 
it  may  travel  with  matter.  Just  so  it  is  with  heat, 
also.  Heat  can  travel  in  two  ways:  it  can  flow 
through  matter,  by  what  is  called  'conduction,' 
or,  it  can  travel  with  matter,  by  what  is  called 
'convection.'  There  is  no  other  mode  of  con- 
veyance of  heat."  *  *  *  "For  electricity 
the  same  is  true.  Electricity  can  travel  with 
matter,  or  it  can  travel  through  matter,  by  con- 
vection, or  by  coiMuction,  and  by  no  other  way." 

In  the  above,  the  radiation  of  heat  is  apparently 
lost  sight  of. 

In  the  opinion  of  some,  an  electric  current  con- 
sists of  two  distinct  currents,  one  of  positive  and 
the  other  of  negative  electricity,  flowing  in  oppo- 
site directions.  Each  of  these  currents  is  supposed 
to  be  equal  in  amount  to  the  other. 

The  electric  current  is  now  regarded  as  passing 
through  the  dielectric  surrounding  the  conductor, 
rather  than  through  the  conductor  itself.  (See 
Current,  Electric,  Method  of  Propagation  of, 
Through  a  Circuit.') 

The  current  that  flows  or  passes  in  any  circuit 
is,  in  the  case  of  a  constant  current,  equal  to  the 


electromotive  force,  or  difference  of  potential, 
divided  by  the  resistance,  as — 

c-t 

K 
(See  Law  of  Ohm.) 

Current,  Electric,  Method  of  Propagation 

of,  Through  a  Circuit When  an 

electric  current  is  propagated  through  a  wire 
or  other  conductor,  it  is  not  sent  or  pushed 
through  the  conductor,  like  a  fluid  through 
a  pipe  or  other  conductor,  but  is,  so  to  speak, 
rained  down  on'the  surface  of  the  conductor 
from  the  medium  or  dielectric  surrounding  it. 

Poynting,  who  has  carefully  studied  this  mat- 
ter, remarks  as  follows,  viz.:  "A  space  contain- 
ing electrical  currents  may  be  regarded  as  the 
field  where  energy  is  transformed  at  certain  points 
into  the  electric  or  magnetic  kind,  by  means  of 
batteries,  dynamos,  thermopiles,  etc.,  and  in 
other  parts  of  the  field  this  energy  is  being  again 
transformed  into  heat,  work  done  by  the  electro- 
magnetic forces,  or  any  other  form  yielded  by 
currents. 

"Formerly  the  current  was  regarded  as  some- 
thing traveling  in  the  conductor,  and  the  energy 
which  appeared  at  any  part  of  the  circuit  was 
supposed  to  be  conveyed  thither  through  the 
conductor  by  the  current.  But  the  existence  of  in- 
duced currents  and  electro-magnetic  actions  have 
led  us  to  look  on  the  medium  surrounding  the 
conductor  as  playing  a  very  important  part  in  the 
development  of  the  phenomena.  If  we  believe  in 
the  continuity  of  the  motion  of  energy,  we  are 
forced  to  conclude  that  the  surrounding  _  medium 
is  capable  of  containing  energy,  and  that  it  is 
capable  of  being  transferred  from  point  to  point. 
We  are  thus  led  to  consider  the  problem,  how 
does  the  energy  about  an  electric  current  pass 
from  point  to  point;  by  what  paths  does  it  travel, 
and  according  to  what  laws  ?  Let  us  take  a  spe- 
cific case.  Suppose  a  dynamo  at  one  spot  gen- 
erates an  electric  current,  which  is  made  to  operate 
an  electric  motor  at  a  distant  place.  We  have 
here,  in  the  first  place,  an  absorption  of  energy 
from  the  prime  motor  into  the  dynamo.  We  find 
the  whole  space  bet  ween,  and  around  the  conduct- 
ing wires  magnetized  and  the  seat  of  electro- 
magnetic energy.  We  have  further  a  retrans- 
formation  of  energy  in  the  motor.  The  question 
which  presents  itself  for  solution  is  to  decide  how 
the  energy  taken  up  by  the  dynamo  is  trans- 
mitted to  the  motor,  by  what  path  it  travels 


Cur.] 


138 


[Cur. 


and  according  to  what  laws  ?  Briefly  stated,  the 
tendency  of  recent  views  is  that  this  energy  is 
conveyed  through  the  electro-magnetic  medium 
or  ether,  and  that  the  function  of  the  wire  is  to 
localize  the  direction  or  to  concentrate  the  flow  in 
a  particular  path,  and  thus  provide  a  sink  or  place 
in  which  the  energy  can  be  dissipated.  *  *  *  " 

Taking  again,  for  instance,  the  case  of  the  dis- 
charge of  a  condenser  by  a  conductor.  He  says: 
"Before  the  discharge  we  know  that  the  energy 
resides  in  the  dielectric,  between  the  conducting 
plates.  If  these  plates  are  connected  by  a  wire, 
according  to  these  views,  the  energy  is  transferred 
outwards  along  the  electrostatic,  equipotential  sur- 
faces, and  moves  on  to  the  wire  and  is  there  con- 
verted into  heat.  According  to  this  view  we 
must  suppose  the  lines  of  electrostatic  induction, 
running  from  plate  to  plate,  to  move  outwards,  as 
the  dielectric  strain  lessens,  and  while  still  keep- 
ing their  ends  on  the  plates,  to  finally  converge 
in  on  the  wire  and  be  there  broken  up  and  their 
energy  dissipated  as  heat." 

In  other  words,  some  of  the  energy  of  the  ex- 
panding lines  of  induction  is  changed  into  mag- 
netic energy;  this  energy  is  contained  in  ring- 
shaped  tubes  of  force,  which  expand  outwards 
from  between  the  plates  and  then  contract  on 
some  other  part  of  the  conductor. 

The  time  of  the  discharge,  then,  consists  of  the 
following  steps,  viz. : 

(I.)  The  time  during  which  the  energy  of  the 
charge  is  nearly  all  electrostatic  and  is  repre- 
sented by  the  energy  contained  in  the  lines  or 
tubes  of  electrostatic  induction,  running  from 
plate  to  plate  of  the  condenser. 

(2.)  The  time  during  which  the  discharge  is  at 
its  maximum  and  the  energy  consists  of  two  parts, 
viz.:  energy  associated  with  the  outward  ex- 
panding lines  of  electrostatic  induction,  and  energy 
associated  with  the  closed  lines  or  tubes  of  mag- 
netic force,  which  at  first  are  expanding  and  after- 
wards contracting. 

(3.)  The  time  when  the  energy  has  been  ab- 
sorbed, or  the  period  in  which  the  energy  in  the 
wire  or  the  conductor  has  either  been  dissipated 
in  the  form  of  non -luminous  radiation  or  obscure 
heat. 

(4.)  The  time  during  which  this  non-luminous 
heat  gives  up  its  energy  again  to  the  surrounding 
medium  in  the  shape  of  heat  waves. 

Current,  Electro-Therapeutic  Polarizing1 

The    current    which    produces    the 


phenomena  of  electrotonus.  (See  Electro* 
tonus.) 

Current,  Element  of  — A  term 

employed  in  mathematical  discussions  to  in- 
dicate a  very  small  part  of  a  current  for  ease 
in  considering  its  action  on  a  magnetic  needle 
or  other  similar  body. 

Current,  Faradic  — In  electro- 
therapeutics, the  current  produced  by  an  in- 
duction coil,  or  by  a  magneto-electric  machine. 

A  rapidly  alternating  current,  as  distin- 
guished from  a  uniform  voltaic  current. 

A  voltaic  current  that 'is  rapidly  alternated  by 
means  of  any  suitable  key  or  switch  is  sometimes 
called  a  voltaic  alternative.  The  discharge  from 
a  Holtz  machine  is  sometimes  called  a  Franklinic 
Current.  (See  Alternatives,  Voltaic.  Current^ 
Franklinic?) 

Current  •  Filaments.  —  (See  Filament, 
Current.) 

Current,  Franklinic A  term  some- 
times used  in  electro-therapeutics  for  a  cur- 
rent produced  by  the  action  of  a  frictional 
electric  machine. 

The  term,  Franklinic  current,  is  used  in  con- 
tradistinction to  Faradic  current,  or  that  produced 
by  induction  coils,  or,  in  contradistinction  to  a 
galvanic  or  voltaic  current,  or  that  produced  by 
a  voltaic  battery. 

Current,  Generation  of,  by  Dynamo-Elec- 
tric Machine — The  difference  of 

potential  developed  in  the  armature  coils 
by  the  cutting  of  the  lines  of  magnetic 
force  of  the  field  by  the  coils,  during  the  rota- 
tion of  the  armature. 

• 

If  a  loop  of  wire  whose  ends  are  connected  to 
the  two-part  commutator,  shown  in  Fig.  179,  be 

A 


Fig.  779.     Induction  in  Armature  Loop. 

rotated  in  the  magnetic  field  between  the  magnet 
poles  N  and  S,  in  the  direction  of  the  large  arrow, 
differences  of  potential  will  be  generated  which 


Cur,] 


139 


[Cur. 


will  cause  currents  to  3ow  in  the  direction  indi- 
cated by  the  small  arrows  during  its  motion  past 
the  north  pole  from  the  top  to  the  bottom,  but  in  the 
opposite  direction  during  its  motion  past  the  south 
pole — from  the  bottom  to  the  top.  If,  now,  col- 
lecting brushes  rest  on  the  commutator  in  the 
positions  shown  in  the  Fig.  180.  the  vertical  line 
180° 


Fig.   180.     Action  of  Commutator. 

of  the  gap  between  the  poles  corresponding  with 
the  vertical  gap  between  the  commutator  seg- 
ments, the  currents  generated  in  the  loop  will  be 
caused  to  flow  in  one  and  the  same  direction,  and 
B',  will  become  the  positive  brush,  since  the  end 
of  the  loop  is  connected  with  it  only  so  long  as  it 
is  positive.  As  soon  as  it  becomes  negative,  from 
the  current  in  the  loop  flowing  in  the  opposite 
direction,  the  other  end,  which  is  then  positive, 
is  connected  with  the  positive  brush. 

A  similar  series  of  changes  occur  at  the  nega- 
tive brush  B. 

Theoretically,  the  neutral  points,  where  the 
brushes  rest,  would  be  in  the  vertical  line  coincid- 
ing with  that  of  the  gap  between  the  poles.  An 
inspection  of  the  figure  show ;  that  the  neutral 
line,  or  the  diameter  of  commutation,  is  dis- 
placed in  the  direction  of  rotation.  (See  Commu- 
tation, Diameter  of.)  The  displacement  of  the 
brushes,  so  necessitated,  is  called  the  lead. 

The  cause  of  the  lead  is  the  reaction  that  occurs 
between  the  magnetic  poles  of  the  field  magnets 


Fig   i8r      Cause  of  Lead  of  Brushes, 

and  those(of  the  armature,  the  result  of  which  is 
to  displace  the  field  magnet  poles,  and  to  cause  a 
change  in  the  density  in  the  field.  This  is  shown 
in  Fig,  181.  where  the  density  of  the  lines  of  force 
indicates  the  position  of  the  diameter  of  commu- 


tation as  being  near,  or  at  right  angles  to  the  di- 
ameter of  greatest  average  magnetic  density. 
(See  Lead,  Angle  of.  Lag,  Angle  of.) 

Current-Governor. — (See  Governor,  Cur- 
rent.) 
Current,  Homogeneous  Distribution  of 

Such  a  distribution  of  a  current  through 

any  conductor  in  which  there  is  an  equal 
density  of  current  at  all  portions  of  any 
cross-section  of  the  conductor. 

When  the  flow  of  a  constant  current  is  estab- 
lished in  a  solid  conducting  wire,  there  is  a 
homogeneous  distribution  of  current  in  that  con- 
ductor. 


Current,    Induced 


— The     current 


produced  in  a  conductor  by  cutting  lines  of 
force. 

The  induced  current  results  from  differences  of 
potential  produced  by  electro-dynamic  induction. 
(See  Induction,  Electro- Dynamic.') 

Current  -  Induction.  —  (See  Induction, 
Current?) 

Current,    Intensity    of  •  — An  old 

term  sometimes  employed  to  indicate  the 
current  which  resulted  from  a  considerable 
difference  of  potential,  or  a  great  electromotive 
force. 

This  term  was  also  formerly  used  as  synony- 
mous with  strength  of  current. 

This  use  of  the  term  is  now  abandoned. 

Voltaic  batteries,  connected  in  series  so  as  to 
give  a  considerable  difference  of  potential  were 
spoken  of  as  being  connected  for  intensity. 

This  term  has  also  been  used  for  the  quantity 
of  electricity  conveyed  per  second  across  a  unit 
area  of  cross -section. 

Intensity  of  current  is  more  properly  called 
density  of  current.  (See  Current  Density.} 

Current,  Intermittent A  current 

that  does  not  flow  continually,  but  which  flows 
and  ceases  to  flow  at  intervals,  so  that  elec- 
tricity is  practically  alternately  present  and 
absent  from  the  circuit. 

Current,  Inverse-Secondary  -  —The 
make-induced  current.  (See  Current,  Make- 
Induced) 

Current,  Jacobi's  Unit  of Such 

a  current  that  when  passed  through  a  volta- 
meter will  liberate  a  cubic  centimetre  of 


C«r.J 


140 


[Cur. 


oxygen  and  hydrogen  at  O  degrees  C.  and 
760  mm.  barometric  pressure. 

One  Jacobi's    unit    of  current   equals        * 

10.32 
ampere.     (Obsolete.) 

Current,  Make-Induced  —The 

current  induced  by  a  current  in  its  own  circuit 
on  making  or  closing  the  same. 

The  current  produced  in  the  secondary  of 
an  induction  coil  on  the  making  or  com- 
pletion of  the  circuit  of  the  primary. 

The  make-induced  current  is  also  called  the 
inverse-secondary  current,  because  its  direction 
is  opposite  to  that  of  the  inducing  current. 

Current,  Make  or  Break  Induced,  Dura- 
tion of The  time  during  which  the 

induced  inverse  or  direct -secondary  currents 
continue. 

Blaserna  made  a  number  of  experiments,  which 
he  claims  shows  : 

(I.)  The  greater  the  distance  apart  of  the  pri- 
mary  and  the  secondary,  that  is,  the  less  their 
mutual-induction,  the  less  the  maximum  value  of 
the  secondary  current,  and  the  greater  the  delay 
in  establishing  that  maximum. 

(2.)  The  delay  in  establishing  the  maximum  of 
the  break  or  direct-secondary  current  is  not  as 
great  as  in  the  case  of  the  make,  or  inverse-sec- 
ondary current. 

(3.)  When  the  coils  are  near  together,  the  in- 
duced currents  at  starting  are  established  by  a 
series  of  electric  oscillations. 

(4  )  The  primary  current  establishes  itself  by  a 
series  of  electrical  oscillations. 

(5.)  That  the  interposition  of  dielectric  sub- 
stances, such  as  glass  between  '.he  coils,  Deduces 
the  time  between  tht  making  or  breaking  of  the 
primary  current  and  the  beginning  of  the  sec- 
ondary current.  This  last  conclusion  was  nega- 
tived by  some  experiments  of  Bernstein. 

Blaserna  determined  in  the  case  of  certain  -ex- 
periments the  following  value  for  the  durations  of 
the  secondary  currents  : 

Inverse -secondary  current  lasts  000485  second. 

Direct -secondary  current  lasts  .000275  second. 

Helmholtz  contradicts  the  results  of  Blaserna, 
and  asserts  : 

(i.)  That  no  perceptible  difference  in  the  zero 
points  of  the  currents  is  produced  by  varying 
the  distance  between  the  primary  and  secondary. 

(2  )  That  the  sparks  produced  by  the  breaking 


of  the  primary  last  for  an  appreciable  time,  some 
thing  like  T^5ff  to  ^VTS  of  a  second. 

(3.)  The  duration  of  the  break-spark  is  never 
constant,  but  depends  in  great  part  on  the  amount 
of  platinum  given  off  from  the  contacts  at  each 
spark. 

Current-Meter.— A  form  of  galvanometer. 
(See  Galvanometer.} 

Current,  Momentary  — A  current 

that  continues  to  flow  but  for  a  short  time. 

Current,  Multi-Phase  -  —A  rotating 
current.  (.See  Current,  Rotating.) 

Current,  Muscle In  electro-thera- 
peutics, the  current  flowing  through  a  muscle 

Muscle  currents  are  produced  either  by  stimu 
lation,  or  during  activity  of  a  muscle.  According 
to  L.  Hermann,  uninjured  muscles,  or  perfectly 
dead  muscles,  yield  no  currents,  but  such  cur- 
rents  result  only  from  an  injury,  (See  Current, 
Demarcation , ) 

Current,  Non-Homogeneous  Distribution 

of  •  —Such  a  distribution  of  current  pass- 
ing through  a  conductor  m  which  there  is  an 
unequal  density  of  current  at  all  portions  of 
any  cross-section  of  the  conductor. 

When  a  rapidly  alternating  current  is  passed 
through  any  solid  conductor,  the  current  density 
is  greater  at  the  surface  and  less  towards  the 
centre.     The  current  distribution  in  such  a  con 
ductor  is  non -homogeneous,  and  the  want  of  uni 
formity  of  current  density  is  greater  as  the  rapid 
ity  of  alternation  or  periodicity  is  greater. 

Current,  Outgoing —The  current 

sent  out  over  the  line  from  a  station  provided 
with  a  duple*  or  quadruplex  transmission,  as 
distinguished  from  the  received  current.  (See 
Current,  Received} 

Current,  Periodic  —A  simple 

periodic  current.  (See  Currents,  Simple 
Periodic} 

Current,  Periodic,  Power  of An 

amount  of  work,  per  second,  equal  to  the 
product  of  the  electromotive  force  taken  at 
successive  moments  of  time  during  a  com- 
plete cycle,  multiplied  by  the  current  strength 
taken  at  the  corresponding  moments  during 
the  cycle. 
Since  the  electromotive  force  and  current  in 


Car.] 

/ 

a  periodic  circuit  may  be  represented  by  two 
simple  harmonic  functions,  the  mean  value  of 
the  two,  when  of  different  amplitude  and  phase, 
is  equal  to  the  product  of  their  maximum  value 
by  the  cosine  of  their  difference  of  phase  divided 
by  two. 

Current,  Polarization In  electro- 
therapeutics, the  constant  current  which  when 
passed  through  a  nerve  produces  in  it  the 
electrotonic  st  Ue.  (See  Electrotonus.} 

Current  Pulsating A  pulsatory 

current.  (See  Current,  Pulsatory?) 

Current,  Pulsatory A  current,  the 

strength  of  which  changes  suddenly. 

The  pulsatory  current  usually  consists  of  sudden 
and  distinct  impulses,  or  rushes  of  current,  in 
contradistinction  to  an  undulatory  or  harmonically 
varying  current. 

Current,  Received The  current 

received  from  the  distant  end  of  the  line  at  a 
station  provided  with  a  duplex  or  quadruplex 
transmission  as  distinguished  from  the  out- 
going, current. 

A  term  sometimes  used  in  telegraphy  to 
distinguish  between  currents  that  come  in  over 
the  line  from  a  distant  station,  and  those 
that  are  sent  out  to  a  distant  station. 

Current,  Rectilinear A  current 

flowing  through  straight  or  rectilinear  por- 
tions of  a  circuit. 

In  studying  the  effects  of  the  attractions  or  repul- 
sions produced  by  electric  currents  the  name  ex- 
pressing the  peculiarity  of  shape  of  any  part  of 
the  circuit  is  often  applied  to  the  current  flowing 
through  that  part  of  the  circuit.  Thus  we  speak 
of  a  rectilinear  current,  a  sinuous  current. 

Current,    Reverse-Induced  — The 

current  induced  by  a  current  in  its  own  cir- 
cuit at  the  moment  of  making  or  closing  the 
circuit. 

The  current  induced  in  the  secondary  on 
closing  or  making  the  circuit  of  the  primary. 

This  is  called  the  reverse-induced  current,  be- 
cause its  direction  is  opposite  to  that  of  the  current 
in  the  inducing  circuit. 

Current,  Reversed A  current  whose 

direction  is  changed  at  intervals.  iSee  Cur- 
rent, Alternating.} 


141 


[Cnr. 


Current  Reverser. — (See  Reverser,  Cur- 
rent?) 

Current,  Reversing  a Changing  the 

direction  of  an  electric  current. 

Current,  Rotating A  term  applied 

to  the  current  which  results  by  combin- 
ing a  number  of  alternating  currents,  whose 
phases  are  displaced  with  respect  to  one  an- 
other. 

A  rotating  current  is  sometimes  called  a  poly- 
phase or  multiple-phase  current,  particularly  if 
there  are  three  or  more  currents  combined . 

The  rotating  current  is  employed  by  Tesla, 
Dobrowolsky  and  others  in  a  system  of  distribu- 
tion by  transformers  in  place  of  the  ordinary 
alternating  current.  In  practice,  three  alternating 
current  are  combined.  The  currents  and  their 
combination  are  obtained  by  means  of  a  specially 
constructed  alternator.  When  three  currents  are 
combined  the  displacement  between  each  set  of 
phases  is  120  degrees.  A  rotating  current,  unlike 
an  alternating  current,  possesses,  in  a  certain 
sense,  a  definite  direction  of  flow.  Its  effect  on  a 
magnetic  needle  is  to  cause  rotation.  Hence 
motors  constructed  on  the  principle  of  rotating 
currents  will  start  with  a  load. 

Current,    Rotatory  -  Phase  •  Alternating 

A  term    sometimes   employed  for   a 

rotating  electric  current,  (See  Current,  Ro- 
tating?) 

Current,  Secretion  .  —In  electro- 
therapeutics, a  current  following  stimulation 
of  the  secretory  nerves. 

Current,  Simple-Harmonic A  term 

sometimes  used  instead  of  simple-periodic 
current.  (See  Currents,  Simple  Periodic.} 

Current,  Sinuous A  term  some- 
times applied  to  currents  flowing  through  a 
sinuous  conductor. 

Sinuous  currents  exert  the  same  effects  of  attrac- 
tion or  repulsion  on  magnets,  or  on  neighboring 
circuits,  as  would  a  rectilinear  current  whose 
length  is  that  of  the  axis  of  such  sinuous  current. 

This  can  be  shown  by  approaching  the  circuit 
A'  B',  Fig.  182,  consisting  of  the  sinuous  con- 
ductor A',  and  rectilinear  conductor  B',  to  the 
movable  conductor  A  B  C,  on  which  it  produces 
110  effect.  The  current  A',  therefore,  neutral- 


Cur.] 


142 


[Cur. 


izes  the  effects  of  the  current  B';  or,  it  is  equal  to 
it  in  effect. 


Fig.  182.    Rectilinear  Equivalent  of  Sinuous  Current. 

In  calculating  the  effects  of  sinuous  currents  it 
is  convenient  to  consider  them  as  consisting  of  a 


Fig.  183.    Sinuous  Currents. 

succession  of  short,  straight  portions  at  right  an- 
gles to  one  another,  as  shown  in  Fig.  183. 

Current,  Steady A  current  whose 

Strength  does  not  vary  from  time  to  time. 

In  a  steady  current  the  quantity  of  electricity 
flowing  through  each  unit  of  area  of  the  equi- 
potential  surface  of  the  conductor  is  the  same  for 
each  succeeding  interval  of  time.  Such  a  current 
is  sometimes  called  a  uniformly  distributed  cur- 
rent. 

Current  Streamlets. — (See  Streamlets, 
Current?} 

Current  Strength. — The  product  obtained 
by  dividing  the  electromotive  force  by  the 
resistance. 

The  current  strength  for  a  constant  current 
according  to  Ohm's  law  is  — 


Current  strength  is  proportional  to  the  amount 
of  the  magnetic  or  chemical  (electrolytic)  effects 
it  is  capable  of  producing. 

For  a  simple-periodic  current,  the  current 
strength  necessarily  varies  from  time  to  time. 

The  average  current  strength  of  a  simple, 
periodic  current  is  equal  to  the  average  impressed 
electromotive  force  divided  by  the  impedance. 
(See  Impedance. ) 

The  maximum  current  strength  is  equal  to  the 
maximum  impressed  electromotive  force  divided 
by  the  impedance. 

Current,    to    Transform     a To 

change  the  electromotive  force  of  a  current 
by  its  passage  through  a  converter  or  trans- 
former. 

To  convert  a  current. 

Current,  Transforming  a Chang- 
ing the  electromotive  force  of  a  current  by  its 
passage  through  a  converter  or  transformer. 

Current,    Undulating An   undu- 

latory  current.     (See  Currents,  Undulatory.} 

Current,  Uniformly-Distributed 

A  term  sometimes  employed  in  the  sam: 
sense  as  steady  current.  (See  Current. 
Steady.) 

Current,  Unit  Strength  of Such 

a  strength  of  current  that  when  passed 
through  a  circuit  one  centimetre  in  length, 
arranged  in  an  arc  one  centimetre  in  radius, 
will  exert  a  force  of  one  dyne  on  a  unit  mag- 
net pole  placed  at  the  centre. 

This  absolute  unit  is  equal  to  ten  amperes  or 
practical  units  of  current.  (See  Ampere.) 

Current,    Variable    Period    of 

The  period  which  exists  while  an  electric 
current  is  being  increased  or  decreased  in 
strength,  or  while  it'  is  being  reversed. 

Currents,  Action Physiological  cur- 
rents obtained  during  the  activity  of  a  muscle 
or  nerve. 

Currents,  After In  electro-thera- 
peutics, currents  produced  in  nervous  or 
muscular  tissue  when  a  constant  current, 
which  has  been  flowing  through  the  same, 
has  been  stopped. 

After  currents  are  due  to  internal  polarization. 

Currents,    Alternating-Primary 

The  currents  employed  in  the  primary  of  a 


Cur.] 


143 


[Cur. 


transformer  to  induce  alternating  currents  in 
the  secondary.  (See  Transformer?) 

Currents,  Alternating-Secondary 

The  currents  induced  in  the  secondary  of  a 
transformer  by  the  alternating  currents  in  the 
primary.  (See  Transformer) 

Currents,  Alternating,  Shifting  of  Phase 

of (See  Phase,  Shifting  of,  of  Alter- 
nating Currents?) 

Currents,  Amperian The  electric 

currents  that  are  assumed  in  the  amperian 
theory  of  magnetism  to  flow  around  the  mole- 
cules of  a  magnet.  (See  Magnetism,  Amperes 
Theory  of.) 

The  amperian  currents  are  to  be  distinguished 
from  the  eddy,  Foucault^  or  parasitical  currents,. 
since,  unlike  them,  they  are  directed  so  as  to  pro 
duce  useful  effects.  (See  Currents,  Eddy.) 

It  is  not  believed  that  the  amperian  currents 
are  produced  in  magnetizable  substances  by  the 
act  of  magnetization.  The  atoms  or  molecules 
were  magnetic  originally.  All  the  magnetizing 
force  does  is  to  arrange  the  molecules  or  atoms, 
or  to  set  them  in  one  and  the  same  direction. 

Currents,  Angular Currents  flow- 
ing through  circuits  that  cross  or  are  inclined 
to  one  another  at  any  angle,  (See  Dynamics, 
Electro) 

Currents.  Atomic A  term  some- 
times used  instead  of  molecular  or  amperian 
currents.  (See  Currents,  Amperian) 

Currents,  Attractions    and    Repulsions 

Of The  mutual  attractions  or  repul- 
sions exerted  by  currents  on  one  another 
through  the  interaction  of  their  magnetic 
fields.  (See  Dynamics,  Electro) 

Currents,  Commuted Electric  cur- 
rents that  have  been  caused  to  flow  in  one 
and  the  same  direction.  (See  Commutator) 

Currents,  Commuting  — Causing 

several  currents  to  flow  in  one  and  the  same 
direction. 

Currents,  Component The  two  or 

more  currents  into  which  it  may  be  conceived 
that  a  single  current  can  be  divided,  so  as 
to  produce  the  same  effects  of  attraction  or 
repulsion  that  the  single  current  would  do. 


The  idea  of  component  currents  is  based  on  the 
similar  idea  ot  the  components  of  any  single 
force. 

Currents,  Continuity  of  — The 

freedom  from  variation  in  current  strength  or 
current  direction. 

Currents,  Convection  — Currents 

produced  by  the  bodily  carrying  forward  of 
static  charges  in  convection  streams.  (See 
Streams,  Convection) 

In  a  convection  current,  the  static  charge  is 
bodily  carried  forward. 

Rowland  has  shown  experimentally  that  a 
moving  electric  charge  is  the  equivalent  of  an 
electric  current.  He  rotated  a  gilded  ebonite 
disc  between  two  gilt  glass  discs,  near  which 
were  placed  a  number  of  delicate  magnetic 
needles.  When  certain  rapidity  of  rotation  was 
obtained,  the  discs  were  found  to  affect  the  mag- 
netic needles  the  same  as  would  a  current  of  elec- 
tricity flowing  in  a  circular  conductor,  whose 
form  coincided  with  the  periphery  of  the  disc. 

Currents,  Converted Electric  cur~ 

rents  changed  either  in  their  electromotive 
force  or  in  their  strength,  by  passage  through 
a  converter  or  transformer.  (See  Trans- 
former) 

Currents,  Converting Changing 

the  electromotive  force  of  currents  by  their 
passage  through  a  converter  or  transformer. 
.(See  Transformer) 

Currents,  Diaphragm Electric  cur- 
rents produced  by  forcing  a  liquid  through 
the  capillary  pores  of  a  diaphragm.  (See 
Osmose,  Electric) 


Currents,  Earth 


— Electric  currents 


flowing  through  the  earth,  caused  by  a  differ- 
ence of  potential  at  different  parts. 

The  causes  of  these  differences  of  potential  are 
various  and  are  not  well  understood. 

Currents,  Eddy Useless  currents 

produced  in  the  pole  pieces,  armatures,  field- 
magnet  cores  of  dynamo-electric  machines  or 
motors,  or  other  metallic  masses,  either  by 
their  motion  through  magnetic  fields,  or  by 
variations  in  the  strength  of  electric  currents 
flowing  near  them. 

Sensible  eddy  currents  are  producd  in  the  mass 


Cur.l 


144 


[Cur. 


of  the  conducting  wire  on  the  armature  of  a 
dynamo-electric  machine  when  the  wire  is  com- 
paratively heavy. 

Such  currents  are  called  eddy  currents,  heal 
currents,  Foucault  currents,  or  parasitical  cur- 
rents. They  form  closed -circuits  of  comparatively 
low  resistance,  and  tend  to  cause  undue  heating  of 
armatures  or  pole  pieces.  They  not  only  cause  a 


Fig,  184.    Foucault  Currents  in  Pole  Pieces. 

useless  expenditure  of  energy,  but  interfere  with 
the  proper  operation  of  the  device. 

To  reduce  them  as  far  as  practicable,  the  pole 
pieces,  armature  cores  or  armature  wires,  are 
laminated.  (See  Core,  Lamination  of.) 

These  local  currents  are  perhaps  preferably 
called  Foucault  currents  when  they  take  place 
in  magnetic  cores,  pole  pieces  or  armature 
cores,  and  eddy  currents  when  they  occur  in  the 
armature  wire  or  conductor.  When  the  armature 
conductor  is  made  up  of  copper  bars,  for  exam- 
ple, the  eddy  currents  in  the  latter  are  usually 
considerable. 

Since  Foucault  currents  in  dynamo-electric  ma- 
chine cores  are  due  to  variations  in  the  magnetic 


Foucault  Currents  in  Pole  Pieces. 


strength  of  the  field  magnets,  or  of  the  arma- 
ture, they  will  be  of  greatest  intensity  when  the 
changes  in  the  magnetic  strength  are  the  greatest 
and  most  sudden. 

These  changes  are  most  marked,  and  conse- 
quently the  Foucault  currents  are  strongest  at  those 
corners  of  the  pole  pieces  of  a  dynamo  from  which 
the  armature  is  moved  in  its  rotation,  as  will  be 
seen  from  an  inspection  of  Fig.  184. 

Fig.  185,  shows  Foucault  currents  generated  in 
pole  pieces. 


Currents,    Eddy-Conduction — A 

term  employed  for  ordinary  eddy  currents  in 
conductors,  in  order  to  distinguish  them  from 
eddy-displacement  currents.  (See  Currents, 
Eddy-Displacement.) 

Currents,  Eddy  Deep  Seated Eddy 

currents  set  up  in  the  mass  of  a  conductor  sub- 
jected to  electro-dynamic  induction  in  con- 
tradistinction to  superficially  seated  eddy  cur- 
rents. (See  Currents,  Eddy,  Superficial.) 

Currents,    Eddy-Displacement    — 

Eddy  currents  produced  in  the  mass  of  a 
dielectric  or  insulator,  when  lines  of  magnetic 
or  electrostatic  force  pass  through  the  di- 
electric or  insulator. 

Eddy-displacement  currents  are  produced  in 
a  dielectric  or  non-conductor,  when  it  is  moved 
across  a  magnetic  field,  so  as  to  cut  the  lines  of 
magnetic  force. 

Eddy  displacement  currents  would  also  occur' 
if  a  dielectric  is  subjected  to  varying  electrostatic 
induction. 

Currents,  Eddy,  Superficial Eddy 

currents  produced  in  conducting  substances 
that  are  limited  to  the  outer  layers  thereof. 

The  eddy  currents  produced  by  alternating 
currents  are  superficial  if  the  alternating  currents 
are  sufficiently  rapid.  The  oscillatory  currents  pro- 
duced during  the  discharge  of  a  Leyden  jar  are 
more  superficial  in  proportion  as  the  discharge 
takes  place  rapidly.  When  currents  are  pro- 
duced in  a  magnetizable  body  by  the  discharge 
of  a  Leyden  jar,  they  are  more  and  more  super- 
ficial, as  the  discharge  of  the  jar  is  more  and  more 
rapid.  The  reason  a  slow  discharge  of  a  jar  or 
condenser  produces  a  greater  magnetizing  effect 
is,  because  of  the  checking  or  screening  action 
the  superficial  eddy  currents  exert  on  the  interior 
of  the  mass  of  the  magnetizable  substance  when 
the  discharge  is  very  rapid. 

Currents,  Electrotonic  -  —  In  electro- 
therapeutics, currents  due  to  internal  polariza- 
tion in  the  nerve  fibre  between  the  conduct- 
ing core  of  the  nerves  and  the  enclosing 
sheaths. 

Currents,  Extra Currents  pro- 
duced in  a  circuit  by  the  induction  of  the 
current  on  itself  on  the  opening  or  closing  of 


Cur.] 


145 


the  circuit.  (See  Currents,  Extra.  Induc- 
tion, Self.) 

The  extra  current  induced  on  breaking,  flows 
in  the  same  direction  as  the  original  current  and 
acts  to  strengthen  and  prolong  it.. 

The  extra  current  induced  on  making  or  com- 
pleting a  circuit  flows  in  the  opposite  direction 
to  the  original  current  and  tends  to  oppose  or  re  • 
tard  the  current. 

Both  of  these  currents  are  called  induced  or 
extra,  currents.  The  former  is  called  the  direct- 
induced  current,  and  the  latter  the  reversed-in- 
duced  current.  (See  Current,  Direct-Induced. 
Current,  Reversed-Induced.') 

In  order  to  distinguish  this  induction  from  that 
produced  in  a  neighboring  conductor  by  the  pas- 
sage of  the  electric  current,  it  is  called  selj  -induc- 
tion. (See  Induction,  Self.  Induction,  Mutual.} 

The  effect  on  a  telegraphic  line  of  the  self-in- 
duced or  extra  currents  is  to  decrease  the  speed  ot 
signaling  by  retarding  the  beginning  of  a  signal, 
and  prolonging  its  cessation . 

The  greater  the  number  of  turns  of  wire  in  a 
circuit,  or  magnet,  and  the  greater  the  mass  ot 
iron  in  its  core,  the  greater  the  strength  of  the 
extra  currents. 

Currents,  Foucault A  name  some- 
times applied  to  eddy  currents,  especially  in 
armature  cores.  (See  Currents,  Eddy?) 

Currents,  Heating  Effects  of •  —The 

heat  produced  by  the  passage  of  an  electric 
current  through  any  circuit.  (See  Heat,  Elec- 
tric) 

Currents,  Imbibition  —Currents 

produced  in  tissues  by  the  imbibition  or  ab- 
sorption of  a  fluid. 

Imbibition  currents  are  a  species  of  diaphragm 
currents.  The  absorption  of  a  fluid  at  the 
demarcation  surface  of  an  injured  nerve  or 
muscle,  or  at  the  contracted  portion  of  muscles, 
produces  imbibition  currents. 

Such  currents  are  also  produced  in  plants  by 
the  movement  of  fluids  produced  by  bending  the 
stalk  or  leaves,  or  by  active  movements  of  certain 
sensitive  plants. 

Currents,  Induced-Molecular  or  Atomic 

•  — Currents    induced   in   the   atoms    or 

molecules  of  a  magnetizable  substance  on  its 
being  brought  into  a  magnetic  field. 

These  currents  are  called  induced-molecular 
or  induced-atomic   currents  in  order  to   distin- 


guish them  from  the  molecular,  atomic  or  amperian 
currents,  or  the  currents  which  are  assumed  to  be 
always-  present.  It  is  by  the  presence  of  these 
assumed  induced-molecular  currents  that  the 
phenomena  of  diamagnetism  are  explained  by 
Weber.  (See  Diamagnetism,  Weber's  Theory 
of.) 

Currents,  Local •  — A  name  sometimes 

applied  to  eddy  currents.  (See  Currents, 
Eddy.) 

Currents,   Molecular  or  Atomic 

A  term  sometimes  employed  for  amperian 
currents.  (See  Currents,  Amperian.) 

Currents,  Natural — A  term  some- 
times applied  to  earth  currents.  (See  Cur' 
rents.  Earth?) 

Currents,  Negative A  term  em- 
ployed in  single-needle  telegraphy  for  cur- 
rents sent  over  a  line  in  a  negative  direction 
by  depressing  a  key  that  connects  the  line 
with  the  negative  pole  of  a  battery  and  so 
deflects  the  needle  to  the  left,  (See  Teleg- 
raphy, Single-Needled) 

Currents,  Network  of — A  term 

sometimes  applied  to  a  number  of  shunt  or 
derived  circuits.  (See  Circuit,  Sktmt.  Cir- 
cuit, Derived.  Laws,  Kirchhoff's^) 

Currents  of  Motion. — A  term  sometimes 
employed  in  electro-therapeutics  for  the  cur- 
rents of  electricity  that  traverse  healthy 
muscle  or  nerve  tissue  during  the  sudden  con- 
traction or  relaxation  thereof. 

The  existence  of  these  currents  is  denied  by 
some. 

Currents  of  Rest. — A  term  sometimes  em- 
ployed in  electro-therapeutics  for  the  cur- 
rents of  electricity  that  traverse  healthy 
muscle  or  nerve  tissue  while  the  muscles  are 
passive. 

The  existence  of  these  currents  is  denied  by 
some. 

Currents,  Orders  of Induced  elec- 
tric currents  named  from  the  order  in  which 
they  are  induced,  as  currents  of  the  first, 
second,  third,  fourth,  etc.,  orders. 

An  induced  current  can  be  caused  to  induce  an- 
other current  in  a  neighboring  circuit,  and  this  a 
third  current,  and  so  on.  Such  currents  are  dis- 


Cur.] 


146 


[Car. 


tinguished  by  the  term,  currents  of  the  second, 
third,  fourth,  etc.,  order.  (See  Coils,  Henry's.) 

Currents,  Parasitical A  name 

sometimes  applied  to  eddy  currents.  (See 
Currents,  Eddy?) 

Currents,  Positive •  — A  term  em- 
ployed in  single-needle  telegraphy  for  currents 
sent  over  the  line  in  a  positive  direction  by  de- 
pressing a  key  that  connects  the  line  with 
the  positive  pole  of  a  battery  and  so  deflects 
the  needle  to  the  right.  (See  Telegraphy, 
Single-Needled) 

Currents,  Reversed •  — A  name  some- 
times applied  to  alternating  currents.  (See 
Current,  Alternating?) 

Currents,  Secondary —The  currents 

produced  by  secondary  batteries  in  contra- 
distinction to  the  currents  produced  by 
primary  batteries. 

The  currents  produced  by  the  secondary 
conductor  of  an  induction  coil,  as  distinguished 
from  the  currents  sent  into  the  primaries. 

This  second  use  of  the  term  secondary  current 
is  more  usual. 

Currents,  Self-Induced A  current 

produced  by  self-induction. 

An  extra  current.  (See  Induction,  Self. 
Currents,  Extra?) 

Currents,  Simple  Periodic Cur- 
rents, the  flow  of  which  is  variable,  both  in 
strength  and  duration,  and  in  which  the  flow 
of  electricity,  passing  any  section  of  the  con- 
ductor, may  be  represented  by  a  simple  peri- 
odic curve. 

A  current  of  such  a  nature  that  the  con- 
tinuous variation  of  the  flow  of  electricity 
past  any  area  of  cross-section  of  the  con- 
ductor, or  the  variations  in  the  electromotive 
force  of  which  can  be  expressed  by  a  simple- 
periodic  or  harmonic  curve.  (See  Curve, 
Simple-Harmonic?) 

Alternate  currents  are  simple-periodic  currents. 

The  average  current  strength  of  simple-periodic 
currents  is  equal  to  the  average  impressed  electro- 
motive force  divided  by  the  impedance. 

The  transmission  of  rapidly  varying  or  sim- 
ple-periodic currents  through  conductors  differs 
rery  greatly  from  the  transmission  of  steady  cur- 


rents. With  a  steady  current,  the  current  density 
is  the  same  for  all  areas  of  cross-section  of  the 
conductor.  For  a  rapidly  intermittent  current, 
the  current  density  is  greater  near  the  surface, 
and  when  the  rate  of  intermission  is  sufficiently 
great,  the  current  is  entirely  absent  at  the  centre 
of  the  conductor. 

Lord  Rayleigh  has  shown  that  when  the  rate  ot 
intermission  is  1,050  per  second,  the  effective  re- 
sistance of  a  wire  i6omm.  in  length,  and  30  mm. 
in  diameter,  is  i .  84  times  its  resistance  to  steady 
currents.  He  found  that  the  increase  of  resist- 
ance is  greater  in  the  case  of  conductors  of  great 
diameter  than  in  those  of  small  diameter. 

As  regards  the  character  of  conductor  best 
suited  for  transmitting  rapidly  alternating  cur- 
rents, it  can  be  shown  : 

(I.)  That  for  transmitting  alternate  currents  o< 
moderate  frequency,  say  of  about  1,000  per  sec- 
ond, copper  conductors  should  be  used  in  prefer- 
ence to  rods  of  iron. 

(2.)  That  the  conductor  should  be  in  the  form 
of  thin  strips,  or  if  tubular,  of  thin  walls. 

(3.)  That  the  mere  stranding  of  the  conductor, 
z.  e.,  forming  it  of  separate  insulated  conductors 
connected  in  parallel,  will  be  of  no  effect  in  pre  • 
venting  the  current  from  acting  on  the  outside  of 
the  conductor,  unless  the  conductor  be  arranged 
in  the  form  of  a  cable,  in  which  one  part  forms  a 
lead,  and  another  part  the  return. 

Stephan  draws  the  following  analogy  between 
the  flow  of  alternating  currents  in  a  conductor 
and  the  flow  of  heat  in  a  hot  wire  : 

"  Suppose  a  wire  or  conductor,  uniformly  heated 
from  centre  to  circumference,  be  suddenly  taken 
into  a  space  where  the  temperature  is  high,  the 
outer  portions  of  the  wire  first  rise  in  temperature, 
and  afterwards  the  inner  portions.  In  the  case  of 
a  conductor  of  circular  cross-section,  the  heat 
penetrates  successive  concentric  layers.  The  same 
phenomena  occur  when  an  electromotive  force  is 
suddenly  set  up  between  the  ends  of  a  cylindrical 
conductor.  The  current  gradually  penetrates  the 
conductor  from  the  outside  to  the  centre. 

"  Now  suppose  the  heated  wire  is  carried  into  a 
cooler  space,  the  heat  waves  pass  out  radially 
from  the  centre  towards  the  circumference.  The 
cooling  wire  corresponds  to  the  case  of  a  con- 
ductor in  which  the  external  electromotive  force 
is  suddenly  removed." 

According  to  this  conception,  the  heat  conduct- 
ing power  of  any  substance  corresponds  to  its 
electrical  conducting  power. 


Cur.] 


147 


[Cur. 


According  to  Stephan,  in  the  case  of  a  con- 
ductor of  iron  of  4  mm.  in  diameter,  traversed  by 
an  alternating  current  of  250  alternations  per 
second,  the  current  density  on  the  surface  is  about 
twenty-five  times  as  great  as  that  at  its  axis. 

Where  the  conductor  is  of  non-magnetic  mate- 
rial, the  difference  in  the  current  density  is  not  s>o 
marked. 

Rapidly  intermittent  currents  produce  a  real 
increase  in  the  resistance  of  the  conductor,  which 
must  not  be  confused  with  the  fact  that  the  impe- 
dance is  greater  than  the  ohmic  resistance,  but 
rather  as  an  actual  increase  in  the  rate  at  which 
energy  is  dissipated  per  unit  of  current. 

Since  current  density  is  greatest  at  the  outside 
portions  of  a  conductor,  and  the  central  portions 
are  nearly,  if  not  entirely,  deserted  by  the  cur- 
rent, we  may  regard  the  conductor  as  having 
the  ohmic  resistance  of  a  hollow  cylinder  of  the 
same  diameter  as  the  conductor,  with  a  cor- 
respondingly smaller  area  of  cross-section,  and 
therefore,  of  greater  ohmic  resistance  per  unit  of 
length. 

The  condition  of  affairs  in  the  case  of  a  con- 
ductor in  which  a  current  of  electricity  is  begin- 
ning to  flow,  is  now  very  generally  regarded 
somewhat  as  follows,  viz.: 

The  current  begins  at  the  surface  of  the  con- 
ductor, and  more  or  less  slowly  soaks  through 
towards  the  centre.  If  the  current  is  constant,  the 
current  soon  reaches  the  deepest  layers;  but,  if  it 
is  rapidly  intermittent,  before  it  can  soak  very  far 
into  the  conductor  towards  its  axis,  it  is  turned 
back  towards  the  surface,  and  so  becomes  con- 
fined to  layers  which  will  be  more  and  more  super- 
ficial, as  the  rapidity  of  reversal  increases. 

Therefore,  for  convenience,  we  may  regard  a 
solid  conductor,  through  which  a  rapidly  inter- 
mittent current  of  e'ectricity  is  flowing,  as  being 
practically  converted  into  a  hollow  cylinder  of 
the  same  diameter  as  the  solid  conductor,  the 
area  of  cross -section  of  which  hollow  cylinder 
becomes  smaller  and  smaller,  as  the  rapidity  of 
alternation  is  increased. 

Another,  and  perhaps  the  more  correct  concep 
tion  of  the  condition  of  affairs  in  a  solid  conductor 
traversed  by  a  rapidly  alternating  current  of  elec- 
tricity, has  been  pointed  out  by  Maxwell,  and  after- 
wards by  Heavyside,  Rayleigh  and  Hughes.  This 
conception  is  to  regard  the  central  portions  of  the 
conductor  as  possessing  a  counter  electromotive 
force  greater  than  the  outer  portions.  The  entire 
current  flowing  across  any  section  of  a  conductor 


miy  be  regarded  as  made  up  of  little  current 
streamlets,  parallel  to  one  another. 

The  central  streamlets,  or  filaments,  from  their 
mutual  induction  on  one  another,  experience  a 
greater  resistance  in  reaching  their  full  strength 
than  the  surface  filaments  do.  Taken  in  this 
sense,  we  may  state  generally  that  the  transmis- 
sion of  rapidly  alternating  currents  through  con- 
ductors depends  on  the  inductance,  rather  than 
on  the  resistance;  but  for  steady  currents,  it  de- 
pends more  on  the  resistance  than  on  the  induct- 
ance. 

In  periodic  or  oscillatory  currents,  as  those 
produced  by  the  discharge  of  a  Leyden  jar,  or 
condenser,  the  surface  streamlets  have  a  current 
density  far  greater  than  the  central  streamlets. 

The  true  or  ohmic  resistance  of  the  circuit  is  a 
minimum  when  the  current  is  uniformly  distrib- 
uted through  all  parts  of  the  cross-section  of  the 
conductor,  and  the  dissipation  of  energy  through 
the  generation  of  heat  is  less  than  for  any  other 
distribution. 

The  conception  of  a  periodic  current  flowing 
through  a  conductor,  starting  from  the  surface 
and  gradually  soaking  in  towards  the  centre, 
regards  the  energy  of  an  electric  current — not  as 
being  pushed  through  the  conductor,  as  water 
through  a  pipe,  but  as  actually  being  absorbed  at 
its  surface,  from  the  surrounding  dielectric,  or  as 
being,  so  to  speak,  rained  down  on  the  conductor 
from  the  space  outside  of  it. 

Currents,  Swelling In  electro- 
therapeutics, currents  that  begin  weak  and  are 
gradually  made  stronger  and  then  weaker. 

Currents,  Swelling-Faradic  — A 

term  employed  in  electro-therapeutics  for  fara- 
dic  currents  that  are  caused  to  gradually  in- 
crease in  strength  and  then  to  gradually  de- 
crease to  zero  strength. 

Currents,  Transient Currents  that 

are  but  of  momentary  duration. 

Currents,  Undnlatory  —  — Currents  the 
strength  and  direction  of  whose  flow  gradually 
change. 

The  term  undulatory  currents  is  used  in  con- 
tradistinction to  pulsatory  currents,  in  which  the 
strength  changes  suddenly.  In  actual  practice, 
such  currents  differ  from  undulatory  currents 
more  in  degree  than  in  kind,  since,  when  sent 
into  a  line,  the  effects  of  retardation  tend  to 
obliterate,  to  a  greater  or  less  extent,  the  sudden 


Cur.] 


148 


[Cur. 


differences  in  intensity  on  which  their  pulsatory 
character  depends. 

The  currents  produced  in  the  coils  of  the  Sie- 
mens magneto-electric  key,  in  which  the  me- 
chanical  to-and-fro  motion  of  the  key  sends  elec- 
trical impulses  into  the  line,  are,  in  point  of  fact, 
undulatory  in  character,  when  they  follow  one  an- 
other rapidly. 

The  currents  in  most  dynamo-electric  machines, 
the  number  of  whose  armature  coils  is  compara- 
tively great,  are,  so  far  as  the  variations  in  their 
intensity  or  strength  are  concerned,  undulatory 
in  character  even  when  non-commuted. 

The  currents  on  all  telephone  lines  that  trans- 
mit articulate  speech  are  undulatory.  This  is 
true,  whether  the  transmitter  employed  merely 
varies  the  resistance  by  variations  of  pressure,  or 
actually  employs  makes-and-breaks  that  rapidly 
follow  one  another. — (See  Current,  Pulsatory. 
Current,  Intermittent.') 


The  ballistic  curve  has  a  smaller  vertical  height 
than  the  parabola.     The  projectile  also  has  a 


Curtain,    Auroral 


— A    sheet    of 


auroral  light  having  the  shape  of  a  curtain. 
(See  Aurora  Borealis^) 

Curve,  Asymptote  of A  straight 

line  which  continually  approaches  a  curved 
line,  but  meets  or  becomes  tangent  to  such 
curved  line  only  at  an  infinite  distance. 

In  Fig.  186,  the  curve  C  D,  continually  ap- 
proaches the  asymptote  y  z,  but  never  meets  it. 

It  is  at  first  difficult  to  un- 
derstand how  one  line  can 
continually  approach  an- 
other and  yet  never  meet  it. 
But  it  will  be  readily  under-  _ 
stood  if  it  is  remembered  y  '* 

that  in  all  cases  of  asymp-  Fig-  z86.  Asymptote 
totic  approach  each  advance  "?  Curve- 

becomes  smaller  and   smaller. 

This  mathematical  conception  is  like  a  value 
which,  although  constantly  reduced  to  one-half 
of  its  former  value,  is  nevertheless  never  reduced 
to  zero  or  no  value. 

Curve,  Ballistic The  curve  ac- 
tually described  by  a  projectile  thrown  in 
any  other  than  a  vertical  direction  through 
the  air. 

The  path  of  a  projectile  in  a  vacuum  is  a  para- 
bola— that  is,  the  path  A  E  B,  Fig.  187.  In  air, 
the  effects  of  fluid  resistances  cause  the  projectile 
to  take  the  path  A  C  D,  called  a  ballistic  curve. 


Fig.  l8j.    Ballistic  Curve. 

smaller  vertical  range.  Instead  of  reaching  the 
point  B,  it  continually  approaches  the  perpen- 
dicular E  F. 

Curve,   Characteristic A  diagram 

in  which  a  curve  is  employed  to  represent 
the  ratio  of  certain  varying  values. 

The  electromotive  force  generated  in  the  arma- 
ture coils  of  a  dynamo-electric  machine,  when  the 
magnetic  field  is  of  a  constant  intensity,  is  theo- 
retically proportional  to  thft  speed  of  rotation.  In 
practice  this  is  modified  by  a  number  of  circum- 
stances. 

The  relation  existing  between  the  speed 
and  electromotive  force  may  be  graphically  rep- 
resented by  referring  the  values  to  two  straight 
lines,  one  horizontal  and  the  other  vertical,  called 
respectively  the  axes  of  abscissas  and  ordinates. 
(See  Abscissas,  Axis  of.}  If,  in  a  given  case,  the 
number  of  revolutions 
is  marked  off  along 
the  horizontal  line 
from  the  point  o,  Fig. 
188,  in  distances  from 
o,  proportional  to  the 
number  of  revolu- 
tions, and  the  corre- 
sponding electromo- 
tive forces  are  marked 
off  along  the  vertical  line  in  distances  from  o, 
proportional  to  the  electromotive  forces,  the 
points  where  these  lines  intersect  will  form  the 
characteristic  curve  as  shown  in  Fig.  188. 

Curve,  Characteristic,  of  Parallel  Trans- 
former   A  curve  so  drawn  that  its 

ordinate  and  abscissa  at  any  point  represent 
the  secondary  electromotive  force  and  the  sec- 
ondary current  of  a  multiple  connected  trans- 
former, when  the  resistance  of  the  secondary 
circuit  has  a  certain  definite  value. 

With  a  constant  electromotive  force  in  the  pri 


600 

Revolutions. 

Fig.  z88.     Characteristic 
Curve. 


Car.] 


149 


[Cur. 


mary  circuit,  i.  <?.,  with  the  transformers  in  parallel, 
the  characteristic  curve  is  a  straight  line  parallel 
to  the  axis  of  the  current.  This  curve,  as  shown 
in  Fig.  189,  is  practically  a  straight  line.  The  par- 
allel transformer  will  be 
practically  self- regulating 
under  a  constant  primary 
electromotive  force. 

According  to  Forbes,  if 
a  transformer  has  its  lamp  pfgt  7<y9.  Character- 
load  in  parallel  with  the  istic  of  Parallel  Trans- 
secondary  circuit,  the  ex-  former. 
tinction  of  its  lamps  will  decrease  the  efficiency 
of  the  transformer.  The  efficiency  is  therefore 
less  for  light  loads  than  for  heavy  loads  of  parallel 
lamps  up  to  a  certain  point. 

Curve,  Characteristic,  of  Series  Trans- 
former   A  curve  so  drawn  that  its 

ordinate  and  abscissa  at  any  point  represent 
the  secondary  electromotive  force  and  second- 
ary current  of  a  series-connected  transformer, 
when  the  resistance  of  the  secondary  current 
has  a  certain  definite  value. 

Fig.   190  shows  characteristic  curve  of  a  series 


Fig.  I  go.     Characteristic  of  Series  Transformer. 

transformer.  O  a,  is  drawn  perpendicular  to  the 
line  representing  the  secondary  current,  and  a  b, 
perpendicular  to  O  a,  represents  the  correspond- 
ing secondary  electromotive  force.  The  various 
positions  of  b,  as  different  values  are  given  to  O  a, 
produce  the  elliptic  curve  which  is  the  character- 
istic curve  of  the  series  transformer. 

"  A  series  transformer, "  says  Fleming,  "with 
a  core  sufficiently  large  to  avoid  saturation,  can 
never  be  self-regulating  if  so  used.  It  can  only 
be  made  self-regulating  with  a  non  saturated  core, 
when  working  near  the  extremities  of  its  charac- 
teristic, either  with  a  small  secondary  current 
or  a  low  electromotive  force.  Both  of  these  con- 
ditions are  uncommercial." 


—  A  curve  in  which  the  life  of  an  electric 
lamp  is  represented  by  means  of  abscissas  and 
ordinates  proportional  to  the  life  in  hours  and 
the  candle-power  or  the  volts  respectively. 


Curve,  Logarithmic 


A  curve    in 


which  the  rate  of  increase  or  decrease  of  the 

ordinate  is  proportional  to  the  ordinate  itself. 

On  the  line  O  X,  Fig.  191,  mark  off  the  time 


Curve,  Life,  of  Incandescent  Lamp 


M 
Fig;  iqi.    Logarithmic  Curve. 

in  lengths,   reckoned  from  O.     Represent  the 

current  strength  by  lines  drawn  vertically  to  the 

•p 
time-line.     Let  O  Y,  equal  C  =  fr • 

Applying  the  electromotive  force,  the  current 
grows  in  the  wire  as  represented  by  the  graphic 
curve. 

According  to  Fleming,  the  growth  of  this  cur- 
rent takes  place  according  to  the  following  law, 
viz.:  "The  current  strength  at  any  instant, 
added  to  the  rate  of  growth  of  the  current  strength 
at  that  instant  multiplied  by  the  time-constant,  is 
equal  to  the  current  which  would  exist  if  induc- 
tion were  zero. ' ' 

Curve,  Permeability A  curve  repre- 
senting the  magnetic  permeability  of  a  mag- 
netic substance. 

There  is  a  certain  temperature  for  every  para- 
magnetic substance,  at  which  its  permeability  is 
no  greater  than  that  of  air.  This  temperature 
for  iron  is  reached  at  about  750  degrees  C.;  for 
nickel,  at  about  400  degrees  C. 

Curve,      Simple-Harmonic  — The 

curve  which  results  when  a  simple-harmonic 
motion  in  one  line  is  compounded  with  a  uni- 
form motion  in  a  straight  line,  at  right  angles 
thereto. 

A  harmonic  curve  is  sometimes  called  a  curve 
of  sines,  because  the  abscissas  of  the  curve  are 
proportional  to  the  times,  while  the  ordinates  are 
proportional  to  the  sines  of  the  angles,  which  are 
themselves  proportional  to  the  times. 


Car.] 


150 


[Cut. 


Carres,  Isochasmen Curves  drawn 

on  the  earth's  surface  between  zones  having 
equal  frequency  of  auroral  discharges. 

The  isochasmen  curves  are  nearly  at    right 
angles  to  the  magnetic  meridian. 


Curves,    Magnetic 


— Curved    lines 


showing  the  direction  of  the  lines  of  mag- 
netic force  in  any  field,  formed  by  sprinkling 
iron  filings  on  a  sheet  of  paper  or  glass  held 
in  the  field  of  a  magnet,  and  gently  tapping 
the  support  so  as  to  permit  the  filing*  to  prop- 
erly arrange  themselves.  (See  Figures, 
Magnetic?) 

Cut-In,  To To  introduce  an  electro- 
receptive  device  into  the  circuit  of  an  electric 
source  by  completing  or  making  the  circuit 
through  it. 

Cut-Off,  Automatic  Gas A  device 

for  automatically  cutting  out  the  battery 
from  an  electric  gas-lighting  circuit  on  the 
accidental  grounding  of  the  circuit. 

Unless  the  battery  is  disconnected  from  the  cir- 
cuit on  the  establishing  of  a  ground,  the  battery 
will  polarize  and  soon  become  useless. 


Cut-Out,   A 


— A  device  by  means  of 


which  an  electro-receptive  device  or  loop  may 
be  thrown  out  of  the  circuit  of  an  electric 
source. 

In  any  system  of  light  or  power  distribution,  a 
cut  out  is  generally  placed  outside  a.  building 
into  which  a  loop  or  branch  of  the  main  cux .  '.t 
runs,  so  as  to  permit  that  loop  or  branch  to  be 
readily  disconnected  therefrom.  In  the  same  way 
cut-out  keys  or  switches  are  generally  placed  in 
the  circuit  of  the  loop  and  each  electro-receptive 
device. 

Cut-Out,  Air-Space — A    modified 

form  of  paper  cut-out,  in  which  the  disc  of 
paper  or  mica  is  replaced  by  the  resistance  of 
an  air-space. 

Although  the  resistance  of  an  air-space  is  so 
high  as  to  be  practically  immeasurable,  yet  it  is 
overcome  or  broken  by  a  much  lower  differ- 
ence of  potential  than  an  equal  thickness  of 
paper  or  mica.  (See  Path,  Alternative.  Cut- 
Out,  Film.) 


Cut-Out,  Automatic Any   device 

that  will  automatically  cut-out,  or  remove,  a 
translating  device,  or  an  electric  source,  from 
an  electric  circuit,  whenever  any  predeter- 
mined effect  is  produced. 

Cut-Out,  Automatic,  for  Multiple-Con- 
nected Electro-Receptive  Devices 

A  device  for  automatically  cutting  an  electro- 
receptive  device,  such  as  a  lamp,  out  of  the 
circuit  of  the  leads. 

Automatic  cut-outs  for  incandescent  lamps, 
when  connected  to  the  leads  in  multiple-arc,  con- 
sist of  strips  of  readily  melted  metal  called  safely 
fuses,  which  on  the  passage  of  an  excessive  cur- 
rent fuse,  and  thus  automatically  break  the  cir- 


Fig.  IQ2,     Ceiling  Cut- Out. 

cuit   in    that    particular    branch.      (See 
Safety.) 

A  form  of  ceiling  cut-out,  made  of  porcelain,  is 
shown  in  Fig.  192,  with  the  two  halves  separated 


Fig.  TQ3.    Ceiling  Cut-Out. 

to  show  interior  details,  and  in  Fig.  193,  with  the 
two  halves  placed  together. 


Cut] 


151 


[Cyc. 


Cut-Out,  Automatic,  for  Series-Connected 

Electro-Receptive  Devices A  device 

whereby  an  electro-receptive  device,  such 
as  an  electric  arc  lamp,  is,  to  all  intents  and 
purposes,  automatically  cut  out,  or  removed 
from  the  circuit,  by  means  of  a  shunt  of  low 
resistance,  which  permits  the  greater  part  of 
tne  current  to  flow  past  the  lamp. 

It  will  be  observed  that  the  lamp,  though  still  in 
the  circuit,  is  to  all  practical  intents  cut  out  from 
the  same,  since  the  proportion  of  the  current 
that  now  passes  through  it  is  too  small  to  oper- 
ate it. 

In  most  series  arc  lamps,  cut-outs  are  oper- 
ated by  means  of  an  electro-magnet  placed  in  a 
shunt  circuit  of  high  resistance  around  the  car- 
bons. If  the  carbons  fail  to  properly  feed,  the 
arc  increases  in  length  and  consequently  in  resist- 
ance. More  current  passes  through  the  shunt 
magnet,  until  finally,  when  a  certain  predeter- 
mined limit  is  reached,  the  armature  of  the  elec- 
tro-magnet is  attracted  to  the  magnet  pole  and 
mechanically  completes  the  short  circuit  past  the 
lamp. 

In  some  automatic  cut-outs  the  fusion  of  a 
readily  fused  wire,  placed  in  a  shunt  circuit 
arrunu  the  carbons,  permits  a  spring  to  complete 
the  shor :  circuit. 

The  automatic  cut-out  prevents  the  accidental 
extinguishing  of  any  single  lamp  in  a  series  cir- 
cuit from  extinguishing  the  remaining  lamps  on 
that  circuit. 

Cut-Out,    Automatic     Time  — A 

device  arranged  so  as  to  automatically  cut  out 
a  translating  device,  or  an  electric  source,  from 
a  circuit,  at  the  end  of  a  certain  predetermined 
time. 

Cut-Out,    Duplex A   cut-out    so 

arranged  that  when  one  bar  or  strip  is  fused 
or  melted  by  an  abnormal  current  another  can 
be  immediately  substituted  for  it. 

Cut-Out,  Film A  cut-out  in  which 

a  film,  or  sheet  of  paper  or  mica,  is  interposed 
between  a  line  plate  and  an  earth  plate,  which, 
when  punctured  by  a  spark,  short  circuits  the 
instruments  on  the  line. 

Cut-Out,  Main-Line  — An  auto- 
matic cut-out  placed  on  the  main  line.  (See 
Cut-Out,  Automatic?) 


A  form  of  main-line  cut-out  is  shown  in  Fig. 


Fig.   194.     Main-Line  Cut-Out, 

194.  The  fuses  are  shown  as  attached  to  the  fuse- 
block. 

Cut-Out,  Paper ' A  term  sometimes 

employed  instead  of  film  cut-out.  (See  Cut- 
Out,  Film.} 

Cut-Out,  Kosette A  rosette  for  an 

electrolier,  containing  a  cut-out.  (See  Ro- 
sette} 

Cut-Out,  Spring-Jack A  device 

similar  in  general  construction  to  a  spring- 
jack,  but  employed  to  cut  out  a  circuit. 

An  insulated  plug  is  thrust  between  spring 
contacts,  thus  breaking  the  circuit  by  forcing 
them  apart. 

Cut  Out,  To To  remove  an  elec- 
tro-receptive device  from  the  circuit  of  an 
electric  source  by  disconnecting  or  diverting 
the  circuit  from  it. 

Cutting  Lines  of  Force. — (See  Force, 
Lines  of  Cutting.) 

Cycle. — A  period  of  time  within  which  a 
certain  series  of  phenomena  regularly  recur, 
in  the  same  order. 

Cycle,  Magnetic  — —  — A  single  round 
of  magnetic  changes  to  which  a  magnetizable 


Cyc.] 


152 


[Dam. 


substance,  such  as  a  piece  of  iron,  is  subjected 
when  it  is  magnetized  from  zero  to  a  cer- 
tain maximum  magnetization,  then  decreased 
to  zero,  reversed  and  carried  to  a  negative 
maximum,  and  then  decreased  again  to  zero. 

Cyclical  Magnetic  Variation. — (See  Va- 
riation, Cyclical  Magnetic?) 

Cyclotrope. — A  name  proposed  in  place 
of  transformer  or  converter.  (See  Trans- 
former^) 

Cylinder,  Yortex • — A  number  of 

vortex  stream-lines  grouped  parallel  to  one 
another  about  a  straight  line  which  forms  the 
axis  or  core  of  the  vortex. 

Cylindrical  Armature. — (See  Armature, 
Cylindrical?) 

Cylindrical  Carbon  Electrodes. — (See 
Electrodes,  Cylindrical  Carbon?) 

Cylindrical  Electro-Magnet. — (See  Mag- 
net, Electro,  Cylindrical?) 


Cylindrical  Magnet. — (See  Magnet,  Cyl- 
indrical?) 

Cylindrical  Ring  Armature. — (See  Arm- 
ature, Cylindrical  Ring?) 

Cymogene. — An  extremely  volatile  liquid 
which  is  given  off  from  crude  coal  oil  during 
the  early  parts  of  its  distillation. 

The  two  liquids  which  are  obtained  from  the 
condensation  of  the  vapors  given  off  during  the 
first  parts  of  the  distillation  of  coal  oil  are  called 
cymogene,  and  rhigolene.  These  liquids  are  em- 
ployed on  account  of  their  extreme  volatility  for 
the  artificial  production  of  cold. 

Rhigolene  is  employed  by  some  for  the  treat- 
ment or  flashing  of  the  carbons  used  in  incan  - 
descent  lamps.  (See  Carbons,  Flashing  Process 
for.) 

Cystoscopy,  Electric A  name  given 

to  Hitze's  method  of  ocular  examination 
of  the  human  bladder  by  electric  illumina- 
tion. 


Damped  Magnetic  Needle. — (See  Needle, 
Magnetic,  Damped?) 

Damper. — A  metallic  cylinder  provided  in 
an  induction  coil  so  as  to  partially  or  com- 
pletely surround  the  iron  core,  for  the  purpose 
of  varying  the  intensity  of  the  currents  induced 
in  the  secondary. 

The  metallic  cylinder  acts  as  a  screen  or  shield 
for  the  rapidly  alternating  currents  traversing  the 
field  of  the  primary.  (See  Screening,  Magnetic.") 
As  the  damper  is  pulled  out,  a  greater  length  of 
the  core  is  exposed  to  the  induction. 

Damper. — A  term  sometimes  applied  to  a 
dash-pot  or  other  similar  apparatus  provided 
for  the  purpose  of  preventing  the  too  sudden 
movement  of  a  lever  or  other  part  of  a  device. 
(^tt  Dash-Pot. ) 

Some  form  of  damper  or  dash-pot  is  used  on 
most  electric  arc  lamps,  the  upper  carbon  of 
which  is  fed  by  a  direct  fall. 

The  double  use  of  this  word  is  unfortunate. 

Damping. — The  act  of  stopping  vibratory 
motion  such  as  bringing  a  swinging  mag- 


netic needle  quickly  to  rest,  so  as  to  deter- 
mine the  amount  of  its  deflection,  without 
waiting  until  it  comes  to  rest  after  repeated 
swingings  to  and  fro. 

Damping  devices  are  such  as  offer  resistance 
to  quick  motion,  or  high  velocities.  1  hose  gen- 
erally employed  in  electrical  apparatus  are  either 
air  or  fluid  friction,  obtained  by  placing  vanes 
on  the  axis  of  rotation,  or  by  checking  the  move- 
ments of  the  needle  by  means  of  the  currents  it 
sets  up,  during  its  motion,  in  the  mass  of  any  con- 
ducting metal  placed  near  it.  These  currents,  as 
Lenz  has  shown,  always  tend  to  produce  motion 
in  a  direction  opposed  to  that  of  the  motion  caus- 
ing them.  Bell-shaped  magnets  are  especially 
suitable  for  this  kind  of  damping.  (See  Magnet^ 
Bell- Shaped.) 

The  needle  of  a  galvanometer  is  dead-beat  when 
its  moment  of  inertia  is  so  small  that  its  oscillations 
in  an  intense  field  are  very  quick,  and  the  mirror, 
acting  as  a  vane,  causes  the  movements  to  die  out 
very  rapidly,  and  the  needle  therefore  moves 
sharply  over  the  scale  from  point  to  point  and 
comes  quickly  to  a  dead  stop.  When  the  needle 
or  swinging  coil  is  heavy  and  moves  in  an  intensf 


Dam.] 


153 


[Dea, 


field,  as  in  the  Deprez-d' Arson val  galvanometer, 
the  movements  are  dead-beat. 

Damping  by  means  of  pieces  of  india  rubber  is 
often  applied  to  telephone  diaphragms  to  prevent 
their  excessive  or  continued  vibration. 

Damping,  Electric A  term  some- 
times employed  to  express  a  decrease  in 
the  intensity  of  the  electric  oscillations  pro- 
duced in  a  conductor  by  electric  resonance, 
under  circumstances  where  higher  overtones 
are  set  up  in  the  conductor. 

Daniell's  Toltaic  Cell.— (See  Cell,  Vol- 
taic, Dani ell's.) 

Dark-Space,  Crookes' (See  Space, 

Dark,  Crookes\) 

Dark-Space,  Faraday's (See  Space, 

Dark,  Faraday's.) 

Dash-Pot. — A  mechanical  device  to  prevent 
too  sudden  motion  in  a  movable  part  of  any 
apparatus. 

The  dash-pot  of  an  automatic  regulator,  or  of 
an  arc-lamp,  is  provided  to  prevent  too  sudden 
movements  of  the  collecting  brushes  on  the  com- 
•mutator  cylinder,  or  the  too  sudden  fall  of  the 
upper  carbon.  Such  devices  consist  essentially  of 
a  loose  fitting  piston  that  moves  through  air  or 
glycerine. 

Dash-pots  are  species  of  damping  devices,  and, 
like  the  damping  arrangements  on  galvanometers 
or  magnet  needles,  prevent  a  too  free  movement 
of  the  parts  with  which  they  are  connected.  (See 
Damper.  Damping.) 

Day,  Normal  Magnetic A  day  dur- 
ing which  the  value  of  the  earth's  magnetic 
elements  does  not  vary  greatly  from  their 
mean  value.  (See  Elements,  Magnetic,  of  a 
Place.) 

Day  of  Disturbance,  Magnetic — 

A  day  during  which  the  mean  departure  of 
the  readings  of  a  declinometer  at  any  place, 
from  the  normal  monthly  value  at  that  place, 
is  once  and  a  half  the  average. — (Lloyd.) 

Dead-Beat. — Such  a  motion  of  a  galvanom- 
eter needle  in  which  the  needle  moves  sharply 
over  the  sqale  from  point  to  point  and  comes 
quickly  to  rest.  (See  Damping.) 

Dead-Beat  Discharge.— (See  Discharge, 
Dead-JBeat.) 


Dead-Beat  Galvanometer. — (See  Galva- 
nometer, Dead-Seat.) 

Dead  Dipping. — (See  Dipping,  Dead.) 
Dead  Earth.— (See  Earth,  Dead  or  Total.) 

Dead  Turns  of  Armature  Wire,  or  Dead 

Wire.— (See     Turns,   Dead,   of    Armature 
Wire.) 

Death,  Electric   — Death   resulting 

from    the .  passage   of    an   electric    current 
through  the  human  body. 

The  exact  manner  in  which  an  electric  current 
causes  death  is  not  known.  When  the  current  is 
sufficiently  powerful,  as  in  a  lightning  flash,  or  a 
powerful  dynamo  current,  insensibility  is  prac- 
tically instantaneous. 

Death  may  be  occasioned : 
(i.)  As  the  direct  result  of  physiological  shock. 
(2.)  From  the  action  of  the  current  on  the  res- 
piratory  centres. 

(3.)  From  the  actual  inability  of  the  nerves  or 
muscles,  or  both,  to  perform  their  functions. 

(4.)  From  an  actual  electrolytic  decomposition 
of  the  blood  or  tissues  of  the  body. 

(5.)  From  the  polarization  of  those  parts  of  the 
body  through  which  the  current  passes. 

(6.)  From  an  actual  rupture  of  parts  by  a  dis- 
ruptive discharge. 

The  current  required  to  cause  death  will  de- 
pend on  a  variety  of  circumstances,  among 
which  are: 

(i.)  The  particular  path  the  current  takes 
through  the  body,  with  reference  to  the  vital 
organs  that  may  lie  in  this  path. 

(2.)  The  freedom  or  absence  of  sudden  varia- 
tions of  electromotive  force. 

(3.)  The  time  the  current  continues  to  pass 
through  the  body. 

In  some  fatal  cases,  it  is  probably  the  extra- 
current,  or  the  induced-direct  current  on  break- 
ing, that  causes  death,  since,  as  is  well  known, 
its  electromotive  force  may  be  many  times 
greater  than  that  ot  the  original  current. 

A  comparatively  low-potential  continuous-cur- 
rent, cannot,  therefore,  be  properly  regarded 
as  entirely  harmless,  simply  because  its  electro- 
motive force  is  necessarily  small.  In  the  case  of 
alternating  currents  the  danger  increases  after  a 
certain  point  with  the  number  of  alternations  per 
second.  When,  however,  the  number  of  alter- 
nations per  second  reaches  a  given  number,  the 
danger  decreases  as  the  frequency  of  alternations 


Dec.] 


154 


[Beg. 


increases.     This  was  conclusively  shown  by  the 
independent  investigations  of  Tatum  and  Tesla. 

Decalescence. — A  term  proposed  by  Prof. 
Elihu  Thomson  for  an  absorption  of  sensible 
heat,  which  occurs  at  a  certain  time  during 
the  heating  of  a  bar  of  steel. 

Decalescence  will  thus  be  observed  to  be  the 
reverse  of  recalescence,  which  is  the  phenome- 
non of  the  emission  of  sensible  heat  at  a  certain 
time  during  the  cooling  of  a  heated  bar  of 
steel.  (See  Recalescence) 

Deci  (as  a  prefix). — The  one-tenth. 

Deci-Ampe're. — One-tenth  of  an  ampere. 

Deci-Ampe're  Balance. — (See  Balance, 
Deci- A  mpere) 

Deci-Lux. — The  one-tenth  of  a  lux.  (See 
Lux) 

Declination. — The  variation  of  a  mag- 
netic needle  from  the  true  geographical  north. 
•  The  magnetic  declination  is  east  or  west.  (See 
Needle,  Magnetic,  Declination  of) 

Declination,  Angle  of  -  — The  angle 
which  measures  the  deviation  of  the  mag- 
netic needle  to  the  east 
or  west  of  the  true  geo- 
graphical north. 

The  angle  of  variation 
of  a  magnetic  needle.        w  hx-i — TWi— Jr — IE 

In  Fig.  195,  if  N  S,  rep- 
resents  the  true  north  and 
south  line,  the  angle  of  de- 
clination  is  N  O  A,    and   Fig.  195.    Declination 
the  sign  of  the  variation  is  of  Needle, 

east,  because  the  deviation  of  the  needle  is  to- 
ward the  east.  (See  Needle,  Magnetic,  Declina- 
tion of) 

Declinometer. — A  magnetic  needle  suit- 
ably arranged  for  the  measurement  of  the 
value  of  the  magnetic  declination  or  varia- 
tion at  any  place. 

Decomposition. — In  chemistry  the  separa- 
tion of  a  molecule  into  its  constituent  atoms 
or  groups  of  atoms.  (See  Molecule.  Atom) 

Decomposition,  Electric Chem- 
ical decomposition  by  means  of  an  electric  dis- 
charge or  current. 

This  decomposition  may  result  from  an  increase 


of  temperature  produced  by  the  electric  discharge, 
or  from  the  passage  of  the  current.  In  the  latter 
case  it  is  more  properly  called  electrolytic  decom- 
position. 

Decomposition,  Electric,  Crystallization 

by (See   Crystallization    by  Electro- 

lytical  Decomposition?) 

Decomposition,  Electrolytic The 

separation  of  a  molecule  into  its  constituent 
atoms  or  groups  of  atoms  by  the  action  of 
the  electric  current. 

These  atoms  or  groups  of  atoms  are  either 
electro-positive  or  electro-negative  in  character. 
(See  Electrolysis.  Anion.  Kathion) 

De-energize. — To  deprive  an  electro-recep- 
tive device  of  its  operating  current. 

De-energizing. — Depriving  an  electro- 
receptive  device  of  its  operating  current. 

Deep-Seated  Eddy  Currents. — (See  Cur- 
rents, Eddy,  Deep-Seated?) 

Deep-Water  Submarine  Cable. — (See 
Cable,  Submarine,  Deep-Sea.} 

Deflagration,  Electrical  —  —The  fusion 
and  volatilization  of  metallic  substances  by  the 
electric  current. 

J)eflagrator. — The  name  given  to  a  voltaic 
battery,  of  small  internal  resistance,  employed 
by  Hare  in  the  electric  deflagration  of  metal- 
lic substances. 

Deflection  Method.— (See  Method,  Deflec- 
tion) 

Deflection  of  Magnetic  Needle. — (See 
Needle,  Magnetic,  Deflection  of) 

Degeneration. — Such  a  degeneration  of  the 
muscular  or  cellular  structure  of  any  cell  or 
organ  that  incapacitates  it  from  performing  its 
functions. 

Degeneration  of  Energy. — (See  .Energy, 
Degeneration  of) 

Degeneration,  Partial,  Reaction  of 

— That  form  of  alteration  to  electric  stimula- 
tion, in  which  the  nerves  show  no  abnormal 
reaction  to  electric  stimulation,  while  the 
muscles,  when  directly  stimulated  by  the  con- 
stant current,  exhibit  the  reaction  of  degen- 
eration. (See  Degeneration,  Reaction  of!) 


Deg.] 


155 


[Dep. 


Degeneration,   Reaction   of  — A 

qualitative     and     quantitative    alteration  of 
nerves  and  muscles  to  electric  stimulation. 

According  to  Landois  and  Stirling  the  following 
conditions  characterize  essentially  the  reaction  of 
degeneration:  "The  excitability  of  the  muscles 
is  diminished  or  abolished  for  the  faradic  cur- 
rent, while  it  is  increased  for  the  galvanic  current 
from  the  third  to  the  fifty -eighth  day ;  it  again 
diminishes,  however,  with  variations,  from  the 
seventy-second  to  eightieth  day  ;  the  anodic  clos- 
ing contraction  is  stronger  than  the  kathodic 
closing  contraction."  *  *  *  "The  diminu- 
tion of  the  excitability  of  the  nerves  is  similar  for 
the  galvanic  and  faradic  currents. ' ' 

Deka  (as  a  prefix). — Ten  times. 

Deka-Amp&re. — Ten  amperes. 

Deka-AmpSre  Balance. — (See  Balance, 
Deka- A  mpere?) 

De  la  Rue's  Standard  Yoltaic  Cell.— (See 
Cell,  Voltaic,  Standard,  De  la  Rue's.} 

Deliquescence. — The  solution  of  a  crystal- 
line solid  arising  from  its  absorption  of  vapor 
of  water  from  the  atmosphere. 

Demagnetizable. — Capable  of  being  de- 
prived of  magnetism. 

Demagnetization.— A  process,  generally  di- 
rectly opposite  to  that  for  producing  a  magnet, 
by  means  of  which  the  magnet  may  be  de- 
prived of  its  magnetism. 

A  magnet  may  be  deprived  of  its  magnetism, 
or  be  demagnetized — 

(l.)  By  heating  it  to  redness. 

(2. )  By  touching  to  its  poles  magnet  poles  of  the 
same  name  as  its  own. 

(3.)  By  reversing  the  directions  of  the  motions 
by  which  its  magnetism  was  originally  imparted, 
if  magnetized  by  touch,  by  stroking  it  with  a 
magnet  in  the  opposite  direction  from  that  which 
would  have  to  be  given  in  order  to  produce  the 
magnetization  which  is  to  be  removed  from  it. 

(4.)  By  exposing  it  in  a  helix  to  the  influence  of 
currents  which  will  impart  magnetism  opposite  to 
that  which  it  originally  possessed. 

Avria  claims  that  a  smaller  magnetizing  force  is 
required  to- demagnetize  a  needle  than  is  required 
to  magnetize  it. 

Demagnetization      of      Watches. — (See 

Watches,  Demagnetization  of.) 
6— Vol.  1 


Demagnetize. — To  deprive  of  magnetism. 

Demagnetizing. — Depriving  of  magnetiza- 
tion. 

Demarcation  Current. — (See  Current,  De- 
marcation?) 

Demarcation  Surface.— (See  Surf  ace,  De- 
marcation?) 

Density,  Electric —The  quantity  of 

free  electricity  on  any  unit  of  area  of  surface. 

The  density  is  said  to  be  positive  or  negative 
according  as  to  whether  the  charge  is  positive  or 
negative.  (See  Charge,  Density  of.  Plane, 
Magnetic  Proof.} 

Density,  Magnetic The  strength 

of  magnetism  as  measured  by  the  number  of 
lines  of  magnetic  force  that  pass  through  a 
unit  area  of  cross-section  of  the  magnet,  i.  e., 
a  section  taken  at  right  angles  to  the  lines  of 
force.  (See  Field,  Magnetic?) 

Density  of  Charge. — (See  Charge,  Den- 
sity of.} 

Density  of  Current.  —  (See  Current 
Density?) 

Density  of  Field.— (See  Field,  Density  of.) 

Density,  Surface A  phrase  used 

by  Coulomb  to  mean  the  quantity  of  eiec- 
tricity  per  unit  of  area  at  any  point  on  a  sur- 
face. (See  Charge  Density.  Density, 
Electric?) 

Dental-Mallet,  Electro-Magnetic 

A  mallet  for  filling  tee*1"1,  the  blows  of  which 
are  struck  by  means  of  electrically-driven 
mechanism. 

Electro-magnetism  was  first  employed  for  this 
purpose  by  Bonwill,  of  Philadelphia. 

Dentiphone. — An  audiphone.  (See  Audi- 
phone?) 

Depolarization. — The  act  of  reducing  or 
removing  the  polarization  of  a  voltaic  cell 
or  battery.  (See  Cell,  Voltaic,  Polarization 

Depolarize. — To  deprive  of  polarization. 
Depolarizing. — Depriving  of  polarization. 

Depolarizing  Fluid.— (See  Fluid,  De- 
polarizing?) 


i)ep.J 


156 


[Dev, 


Deposit,     Black,    Electro-Metallurgical 

— A  crystalline  variety  of  electro- 
metallurgical  deposit.  (See  Deposit,  Electro- 
Metallurgical?) 

Deposit,  Crystalline,  Electro-Metallurgi- 
cal    — A  non-adherent,  non-coherent 

film  of  Jectrolytically  deposited  metal.  (See 
Deposit,  Electro-Metallurgical?) 

Deposit,     Electro-Metallurgical 

The  deposit  of  metal  obtained  by  any  electro- 
metallurgical  process. 

To  obtain  a  good  metallic  deposit  the  density 
of  the  current  must  be  regulated  according  to  the 
strength  of  the  metallic  solution  employed. 

Electro -metallurgical  deposits  are  either — 

(l.)  Regnline,  or  flexible,  adherent  and  strongly 
coherent  metallic  films,  deposited  when  neither 
the  current  nor  the  solution  is  too  strong;  or, 

(2.)  Crystalline;  or  non-adherent  and  non-co- 
herent deposits. 

The  crystalline  deposit  may  either  be  of  a  loose, 
sandy  character,  which  is  thrown  down  when  too 
feeble  a  current  is  used  with  too  strong  a  metallic 
solution,  or  it  may  consist  of  a  black  deposit,  which 
is  thrown  down  when  the  current  is  too  strong  as 
compared  with  the  strength  of  the  solution.  This 
latter  character  of  deposit  is  sometimes  technically 
called  burning,  and  takes  place  most  frequently 
at  sharp  corners  and  edges,  where  the  current 
density  is  greatest.  (See  Current  Density.) 

Deposit,  Electro-Metallurgical  Nodular 

A  coherent,  irregular  electro-metal- 
lurgical deposit  which  occurs  whenever  the 
current  density  falls  below  its  normal  value. 
Deposit,  Electro-Metallurgical,  Regnline 

A    flexible,    adherent    and   strongly 

coherent  film  of  metal  electrolytically  de- 
posited. (See  Deposit,  Electro-Metallur- 
gical^) 

Deposit,    Electro-Metallurgical,    Sandy 

A  non-coherent  electro-metallurgical 

deposit  which  occurs  whenever  the  current 
density  exceeds  its  normal  value. 
Depositing  Cell. — (See  Cell,  Depositing?) 
Depositing  Tat— (See  Vat,  Depositing?) 
Deposition,  Electric The  deposit- 
ing   of  a  substance,  generally  a  metal,  by 
the  action  of  electrolysis.     (See  Electrolysis?) 


The  electric  deposition  of  a  metal  on  any  con- 
ducting surface  is  sometimes  called  an  electro- 
metallurgical  deposition.  (See  Metallurgy^ 
Electro.) 

Deprez-d'Arsonval  Galvanometer.— (See 

Galvanometer,  Deprez-d 'Arsonval?) 

Derivative  Circuit— (See  Circuit,  De- 
rivative?) 

Derived  Circuit— (See  Circuit,  Derived.) 
Derived  Units.— (See  Units,  Derived?) 
Destructive  Distillation. — (See  Distilfa* 
tion,  Destructive.) 

Detector  Galvanometer. — (See  Galva- 
nometer, Detector?) 

Detector,  Ground In  a  system 

of  incandescent  lamp  distribution,  a  device 
placed  in  the  central  station,  for  showing  by 
the  candle-power  of  a  lamp  the  approximate 
location  of  a  ground  on  the  system. 

Fig.  196,  shows  a  form  of  ground-detector,  in 


Ffg.  196.     Ground-Detector. 

which  a  small  transformer  is  placed  on  a  board  iu 
connection  with  a  lamp  and  a  two-way  switch. 
One  terminal  of  the  primary  of  the  transformer  is 
put  to  ground,  while  the  other  can  be  connected 
by  means  of  the  switch  to  one  or  the  other  of  the 
two  primary  mains  of  the  distribution  circuit. 
Should  an  earth  exist  on  either  main,  then  when 
the  testing  transformer  has  its  pole  connected  to 
the  other  main,  the  lamp  in  its  secondary  circuit 
will  light  up,  providing  the  leak  is  of  sufficient 
magnitude  to  permit  a  sufficiently  great  current 
to  pass  through  the  primary  circuit. 

Detorsion  Bar. — (See  Bar,  Detorston) 
Device,  Electro-Receptive Various 


Dov.J 


157 


[Dev. 


devices  placed  in  an  electric  circuit,  and 
energized  by  the  passage  through  them  of  the 
electric  current. 

A  translating  device. 

The  following  are  among  the  more  important 
electro-receptive  devices,  viz. : 

(I.)  Electro- magnets. 

(2.)  Electric  motors. 

(3.)  Electro-magnetic  signal  apparatus. 

(4.)  Telegraphic  or  telephonic  apparatus. 

(5.)  An  arc  or  incandescent  lamp. 

(6. )  An  electric  heater. 

(7.)  A  plating  bath  or  voltameter. 

(8.)  An  uncharged  storage  cell. 

(9.)  A  converter  or  transformer. 

ELECTRO-RECEPTIVE  DEVICES. 

Motion  Reproduced. 
(l.)  Electric  motor. 
(2.)  Telpherage  system. 
(3.)  Telephone  receiver. 
(4.)  Telegraphic  apparatus. 
(5.)  Telephote  receiver. 

Radiant  Energy  Produced, 
(6.)  Arc  or  incandescent  electric  lamp. 
(7.)  Electric  heater. 
(8.)  Electric  welder. 
(9.)  Leyden  jar  or  battery. 

Chemical  Decomposition  Effected. 
(10.)  Electrolytic  bath. 
(ll.)  Uncharged  storage  battery. 

Electro-Magnetism  Produced. 
(12.)  Electro-magnet. 

Device,  Feeding,  of  an  Arc  Lamp 

A  device  for  maintaining  the  carbon  electrodes 
of  an  arc  lamp  at  a  constant  distance  apart 
during  their  consumption.  (See  Lamp, 
Electric  Arc,} 

Device,    Magneto-Receptive Any 

device  that  is  capable  of  being  energized 
when  placed  in  a  magnetic  field. 

The  term  magneto-receptive  device  is  used  in 
contradistinction  to  electro-receptive  device.  (See 
Device,  Electro- Receptive.") 

Darice-or  Arrangement,  Electromotive 

A  term  sometimes  employed  instead 
->f  nn  electro  source.  (See  Source,  Electric. 
Arrangement  or  Device.  Electromotive^ 


Derice,  Safety,  for  Arc  Lamps,  or  Series 
Circuits Any  mechanism  which  auto- 
matically provides  a  path  for  the  current 
around  a  lamp,  or  other  faulty  electro-recep- 
tive device  in  a  series  circuit,  and  thus  pre- 
vents the  opening  of  the  entire  circuit  on  the 
failure  of  such  device  to  operate.  (See  Lamp, 
Electric  Arc?) 

Device,  Safety,  for  Multiple  Circuits 

—A  wire,  bar,  plate  or  strip  of  readily 
fusible  metal,  capable  of  conducting,  without 
fusing,  the  current  ordinarily  employed  on  the 
circuit,  but  which  fuses  and  thus  breaks  the 
circuit  on  the  passage  of  an  abnormally  great 
current. 

The  terms  safety-catch,  safety-plug,  safety* 
atrip  and  safety -fuse  are  also  used  for  this  safety 
device.  (See  Fuse,  Safety.} 

Device,  Translating  — -  —A  term  em- 
bracing electro-receptive  and  magneto-recep- 
tive devices.  (See  Device,  Electro-Recefr* 
jive.)  •• 

Translating  devices  are  placed  in  an  electric 
circuit,  and  when  traversed  by  the  current  effect 
a  change,  or  translation  in  the  form  of  the  electric 
energy  whereby  useful  work  is  accomplished. 

Translating  devices  depend  for  their  operation 
on  the  luminous,  heating,  magnetic,  or  chemical 
effects  of  the  current. 

Devices,  Electro-Receptive,  Multiple 
Connected A  connection  of  electro- 
receptive  devices,  in  which  the  positive  poles 
of  a  number  of  separate  devices  are  all  con 
nected  with  a  single  positive  lead  or  conduc- 
tor, and  the  negative  poles  all  connected  with 
a  single  negative  lead  or  conductor. 

The  multiple-arc-connection  of  electro-receptive 
devices  is  suitable  for  constant  potential  circuits.^  or 
those  in  which  the  electromotive  force  is  main- 
tained approximately  constant.  In  such  circuits 
the  energy  absorbed  by  each  device  will  increase 
as  its  resistance  decreases,  since  the  energy  ab- 
sorbed is  proportional  to  the  current  passing. 
(See  Circuits,  Varieties  of.) 

Multiple-arc-connected  electro-receptive  devices 
are  employed  in  incandescent  lamp  distribution. 
Each  device  added  reduces  the  resistance  :,f  the 
entire  circuit. 


Dev.] 


158 


[Dia, 


Deyices,Electro-Receptive,Multiple- Arc- 
Connected  A  term  used  in  place  of 

multiple-connected  electro-receptive  devices. 
(See  Devices,  Electro-Receptive,  Multiple- 
Connected?) 

Devices,  Electro-Receptive,  Multiple- 
Series-Connected  A  connection  of 

electro-receptive  devices  in  which  a  number  of 
separate'  electro-receptive  devices  are  con- 
nected in  groups  in  series,  and  each  of  these 
separate  groups  afterwards  connected  in  mul- 
tiple-arc. 

The  multiplerseries  connection  permits  electro- 
receptive  devices  to  be  placed  on  mains  whose 
electromotive  force  would  be  too  high  to  permit 
a  single  service  to  be  connected  directly  to  them. 
It  is  of  great  value  in  the  distribution  of  incandes- 
cent lamps  by  constant  currents,  since  by  per- 
mitting a  higher  electromotive  force  to  be  em- 
ployed  on  the  main  conductors,  it  reduces  the 
dimensions  of  the  conductors  required  for  the 
economical  distribution  of  the  current.  (See 
Circuit 's,  Varieties  of.) 

Devices,  Electro-Receptive,   Series-Con- 

nectad The  connection  of  electro- 
receptive  devices  in  which  the  devices  are 
placed  consecutively  in  the  circuit,  so  that  the 
current  passes  successively  through  all  of 
them  from  the  first  to  the  last. 

The  series-connection  of  electro-receptive  de- 
vices is  suited  to  constant -current  circuits.  The 
work  done  in  the  device  is  developed  by  the  fall 
of  potential  in  each  device.  This  kind  of  con- 
nection is  used  in  most  systems  of  arc  light  and 
telegraphic  lines.  (See  Circuits,  Varieties  of.) 

Devices,  Electro-Receptive,  Series-Mill- 

tiple-Connected — A  connection  of 

electro-receptive  devices  in  which  a  number 
of  separate  electro-receptive  devices  are  joined 
in  separate  multiple  groups,  and  each  of  these 
groups  subsequently  connected  with  one  an- 
other in  series. 

The  effect  of  series-multiple  connections  is  to 
split  up  the  current  into  a  number  of  separate 
currents  of  smaller  strength,  but  of  the  same 
electromotive  force.  It  is  applicable  to  such  cases 
as  the  combination  of  arc  and  incandescent  lamps 
in  the  same  circuit.  (See  Circuits,  Varieties  of .) 

Devices,      Translating,      Multiple-Con- 


nected 


-A  term   sometimes  used  for 


multiple-connected  electro-receptive  devices. 
(See  Devices,  Electro-Receptive,  Multiple- 
Connected^ 

Devices,  Translating,  Multiple- Arc-Con- 
nected   — A  term  used  in  place  of 

multiple-connected  electro-receptive  devices. 
(See  Devices,  Electro-Receptive,  Multiple* 
Connected?) 

Devices,  Translating,  Multiple-Series- 
Connected — A  term  sometimes  used 

instead  of  multiple-series-connected  electro- 
receptive  devices.  (See  Devices,  Electro- 
Receptive,  Multiple-Series-Connected?) 

Devices,  Translating,  Series-Connected 
— '• -A  term  sometimes  used  for  series- 
connected  electro-receptive  devices.  (See 
Devices,  Electro  -  Receptive,  Series -Con- 
nected?) 

Devices,  Translating,  Series-Multiple- 
Connected  •  — A  term  sometimes  used 

for  series-multiple-connected  electro-recep- 
tive devices.  (See  Devices,  Electro-Recep* 
tive,  Series-Multiple-Connected?) 

Dextrorsal  Helix. — (See  Helix,  Dex- 
trorsal?) 

Dextrorsal  Solenoid. — (See  Solenoid,  Dex» 
trorsal?) 

Diacritical  Current. — (See  Current,  Dia- 
critical.) 

Diacritical  Number. — (See  Number,  Dia- 
critical?) 

Diacritical  Point  of  Magnetic  Satura- 
tion.— (See  Saturation,  Magnetic,  Diacrit- 
ical Point  of.) 

Diagnosis,  Electro. — Diagnosis  by  means 
of  the  exaggeration  or  diminution  of  the  re- 
action of  the  excitable  tissues  of  the  body 
when  subjected  to  the  varying  influences  of 
electric  currents. 

The  electric  current  has  also  been  applied  in 
order  to  distinguish  between  forms  of  paralysis, 
and  as  a  final  test  of  death. 

Diagnostic,  Electro Pertaining  to 

electro-diagnosis.  (See  Diagnosis,  Electro.) 

Diagometer,  Rousseau's An  ap- 
paratus in  which  an  attempt  is  made  to 


Dia.] 


159 


[IKa. 


determine  the  chemical  composition  and  con- 
sequent purity  of  certain  substances  by  their 
electrical  conducting  powers. 

The  arrangement  of  the  apparatus  is  shown  in 
Fig.  197.     A  dry  pile.  A,  has  its  negative,  or  — 


Fig.  ZQ7-     Rousseau's Diagometer. 


terminal,  m',  grounded.  Its  positive,  or  -f-  ter- 
minal is  connected  to  a  delicately  supported,  and 
slightly  magnetized  needle,  M,  terminated  by  a 
conducting  plate,  L.  Opposite  L,  and  at  the  same 
height,  is  a  fixed  plate  of  slightly  larger  size.  The 
needle  M,  when  at  rest  in  the  plane  of  the  magnetic 
meridian,  is  in  contact  at  L,  with  the  fixed  plate. 
If,  therefore,  the  upper  plate  of  the  pile  is  con- 
nected with  the  needle  M,  both  plates  are  similarly 
charged  and  repulsion  takes  place,  the  needle 
coming  to  rest  at  a  certain  distance  from  the  fixed 
plate. 

The  substance  whose  purity  is  to  be  determined 
is  placed  in  the  cup  G,  which  is  connected, 
through  L,  with  the  fixed  plate,  A  branch  wire 
from  the  -f-  terminal  of  the  pile  is  then  dipped  into 
the  substance  in  G,  and  its  purity  determined 
from  the  length  of  time  required  for  the  two  plates 
at  L,  to  be  discharged  through  the  material  in  G. 

It  is  claimed  that  the  instrument  will  detect  the 
difference  between  pure  coffee  and  chicory.  Its 
practical  application,  however,  is  very  doubtful. 

Diagram,       Thernio-Electric  — A 

diagram  in  which  the  thermo-electric  power 
between  different  metals  is  designated  for 
different  temperatures. 

The  differences  of  potential,  produced  by  the 
mere  contact  of  two  metals,  varies,  not  only  with 
the  kind  of  metals,  and  the  physical  state  of  each 
metal,  but  also  with  their  temperature.  This 
difference  of  potential,  maintained  in  conse- 
quence of  the  difference  of  temperature  between 
the  junctions  of  a  thermo-electric  couple,  is  ap- 
proximately proportional  to  the  differences  of 
temperature  of  these  junctions,  if  these  differences 
are  not  great,  and  is  equal  to  the  product  of  such 


differences  of  temperature  and  a  number  depend  ent 
on  the  metals  in  the  couple.     This  number  is 
called  the  thermo-electric  power.     (See    Couple^ 
Thermo-Electric.     Thermo-Electric  Power.) 
'  In  Fig.  198  (after    Tait),  the  thermo-electric 


200°c  2oO°«  300°<!  350°e  400°<!  450°» 


K&5 


Fig.  T<)8.  Thermo- Electric  Diagram. 
power  is  shown  between  lead  and  iron,  and  lead 
and  copper.  The  numbers  at  the  top  of  the  table 
represent  degrees  of  the  centigrade  thermometer. 
Those  at  the  sides  represent  the  differences  of 
potential  in  micro -volts. 

The  thermo-electric  power  of  the  copper-iron 
couple  decreases  from  the  freezing  point  of  water, 
O  degrees  C.,  to  a  temperature  of  274.5  degrees 
C.,  when  it  becomes  zero.  Beyond  that  temper- 
ature the  thermo-electric  power  increa  ,es,  but  in 
the  opposite  direction.  The  point  at  which  this 
occurs  is  called  the  neutral  point. 

Dial  Telegraph.— (See  Telegraphy,  Dial.) 

Dialysis.— The  act  of  separating  a  mixture 
of  crystalloids  and  colloids  by  diffusion 
through  a  membrane. 

If,  for  example,  the  contents  of  a  stomach,  in  a 
case  of  suspected  poisoning,  be  placed  in  a  vessel, 
the  bottom  of  which  is  formed  of  a  sheet  of 
parchment  paper  and  floated  in  water,  the 
crystalloid  or  substances  capable  of  crystalliz- 
ing, will  pass  into  the  water  and  the  colloid,  an 
uncrystallized  ielly-like  substance,  will  remain  in 
the  vessel.  This  process  has  been  used  to  detect 
the  presence  of  poison  in  the  stomach  in  post- 
mortem cases. 

Diamagnetic. — The  property  possessed  by 
substances  like  bismuth,  phosphorus,  anti- 
mony, zinc  and  numerous  others,  of  being 
apparently  repelled  when  placed  between  the 
poles  of  powerful  magnets 

When  diamagnetic  substances  in  the  form  of 
rods  or  bars  are  placed,  as  in  Fig.  199,  between 
the  poles-  of  a  powerful  electro-magnet,  they 
place  themselves  at  right  angles  to  the  poles,  or 
are  apparently  repelled. 

Paramagnetic  substances  like  iron  or  steel,  on 
the  contrary,  come  to  rest  under  similar  circunv 


Dia.] 


160 


[Dia. 


Ftg.  799     Effect  of  Para* 
magnetism. 


stances  in  a  straight    line  joining  the  poles,    at 
right  angles  to  the  position  shown  in  Fig.  199. 

Paramagnetic  substances  are  sometimes  called 
ferro-magnetiC)  or  substances  magnetic  after  the 
manner  of  iron.  This  word  is  unnecessary  and 
ill-advised.  The  term  sidero-magnetic,  which  has 
also  been  proposed  in  place  of  paramagnetic,  is 
also  unnecessary. 

Paramagnetic  substances  appear  to  concentrate 
the  lines  of  magnetic  force  on  them;  that  is,  their 
magnetic  resistance  is 
smaller  than  that  of  the 
air  or  other  medium  in 
which  the  magnet  is 
placed.  They,  there- 
fore, come  to  rest  with 
their  greatest  dimen  • 
sions  in  the  direction  of 
the  lines  of  magnetic 
force. 

Diamiignetic  sub- 
stances  appear  to  have 
a  greater  magnetic  re- 
sistance than  that  of 
the  air  around  them. 
They,  therefore,  come 
to  rest  with  their  least 
dimensions  in  the  direction  of  the  lines  of  mag. 
netic  force. 

The  difference  between  paramagnetic  and  dia. 
magnetic  substances  is  generally  believed  to  be 
due  to  the  varying  resistance  these  substances 
thus  offer  to  lines  of  magnetic  force  as  compared 
•with  that  offered  by  air  or  by  a  vacuum. 

Tyndall  comes  to  the  conclusion  as  the  result  of 
extended  experimentation:  "  That  the  diamag- 
netic  force  is  a  polar  force,  the  polarity  of  dia- 
magnetic  bodies  being  opposed  to  that  of  para- 
magnetic ones  under  the  same  conditions  of 
excitement." 

This  view,  however,  is  not  generally  accepted 
by  scientists. 

Diamagnetistn  is  also  possessed  by  certain  liquid 
and  gaseous  substances. 

Diamagnetic  Polarity. — (See  Polarity, 
Diamagnettc.} 

Diamagnetically. — In  a  diamagnetic  man- 
ner. 

Diamagnetism. — A  term  applied  to  the 
magnetism  of  diamagnetic  bodies.  (See  Dia- 
magnettc?) 


Diamagnetism,  Weber's  Theory  of 

— A  theory  to  account  for  the  phenomena 
of  diamagnetism. 

Weber's  theory  of  diamagnetism,  like  Ampere's 
theory  of  magnetism,  supposes  that  magnetic 
substances  consist  of  originally  magnetized  mole- 
cules or  atoms,  and  that  the  act  of  magnetization 
consists  of  polarizing  these  atoms  or  molecules, 
or  turning  them  in  one  and  the  same  direction. 
That  the  original  condition  of  the  molecules  or 
atoms  is  probably  due  to  the  passage  of  electricity, 
which  continually  circulates  through  their  mass, 
the  atoms  being  supposed  to  possess  perfect  con- 
ductivity. 

Suppose  the  substance  through  whose  mole- 
cules  or  atoms  these  currents  are  flowing  be 
immersed  in  a  magnetic  field.  All  of  the  mole- 
cules or  atoms  which  can  turn  so  as  to  look  along 
lines  of  force  in  the  right  direction  will  have  the 
current  flowing  in  them  thereby  weakened  so  long 
as  they  remain  in  the  field.  When  drawn  out  of 
it,  however,  these  currents  will  regain  their  nor- 
mal strength. 

Suppose  now  the  case  of  a  substance,  in  which 
the  currents  are  normal  but  weak,  immersed  in  a 
strong  magnetic  field.  There  may  thereby  be 
effected  a  complete  reversal  of  the  direction  of 
these  currents,  and  others  may  be  produced 
which  flow  in  the  opposite  direction,  and  which 
will  continue  so  to  flow  as  long  as  the  substance 
remains  in  the  field.  Such  currents  would  then 
be  sufficient  to  explain  the  phenomena  of  diamag- 
netic action. 

An  electric  current  produced  in  a  circuit  near 
which  a  momentary  current  of  electricity  is  sud  • 
denly  brought  has  now  the  opposite  direction  to 
that  which  produces  it,  and  this  momentary  cur- 
rent  would  tend  to  produce  repulsion.  When, 


Fig,  200.     Weber's  Theory  of  Diamagnetism. 
too,  the  circuit  is  drawn  out  of  the  neighborhood 
in  which  another  current  is  flowing,  another  mo 


Dia.] 


161 


[Die. 


mentary  current  is  produced  in  the  same  direc- 
tion. This  produces  attraction. 

Now,  regarding  the  same  phenomena  from  the 
standpoint  of  lines  of  magnetic  force,  when  a 
conductor  through  which  a  current  is  passing  is 
placed  in  a  magnetic  field,  any  increase  in  the 
number  of  lines  of  magnetic  force  passing  through 
it  tends  to  move  the  conductor  out  of  the  magnetic 
field,  while  any  decrease  in  the  number  of  lines 
of  force  tends  to  move  the  conductor  into  the 
field.  To  experimentally  show  the  attractions 
and  repulsions  produced  by  magnetization  or 
demagnetization,  the  following  apparatus  may  be 
employed : 

A  stout  disc  of  copper,  Fig.  200,  is  supported 
on  a  horizontal  arm  in  the  position  shown  in  front 
of  the  pole  of  a  powerful  electro- magnet.  When 
the  current  is  sent  through  the  electro-magnet  the 
disc  of  copper  is  repelled  from  the  magnetic  pole. 
When  the  magnetism  is  being  destroyed  by  the 
opening  of  the  circuit  and  by  the  weakening  of 
the  current,  the  copper  disc  is  attracted. 

Diamagnetometer. — An  apparatus  de- 
signed for  studying  diamagnetism.  (See  Dza- 
magnetism.} 

The  apparatus  for  the  study  of  paramagnetism 
generally  receives  simply  the  name  of  magnet- 
ometer. 

Diamagnets.  —  Diamagnetic  substances 
subjected  to  magnetic  induction  and  formerly 
called  diamagnets  in  contradistinction  to  or- 
dinary magnets. 

Diamagnets  are  supposed  by  some  to  possess  a 
polarity  the  same  as  that  of  the  inducing  pole, 
instead  of  the  opposite  polarity,  as  in  paramagnetic 
substances.  (See  Diamagnetism.') 

Diaphragm. — A  sheet  of  some  solid  sub- 
stance, generally  elastic  in  character  and  cir- 
cular in  shape,  securely  fixed  at  its  edges  and 
capable  of  being  set  into  vibration. 

The  receiving  diaphragm  of  a  telephone  is 
generally  a  thin  plate  or  disc  of  iron,  fixed  at  its 
edges,  placed  near  a  magnet  pole  and  set  into 
vibration  by  variations  in  the  magnetic  strength 
of  the  pole,  due  to  variations  in  the  current  that 
is  passed  over  the  line. 

The  transmitting  diaphragm  of  the  telephone 
or  of  a  phonograph,  consists  of  a  plate  fixed  at  its 
edges  and  set  into  vibration  by  the  sound  waves 
striking  it. 


Diaphragm. — A  term  sometimes  employed 
for  a  plate  form  of  porous  cell. 

Diaphragm  Currents. — (See  Currents, 
Diaphragm.  Cell,  Porous.} 

Diaphragm  of  Voltaic  Cell.-  A  term 
sometimes  used  for  the  porous  cell  of  a 
double  fluid  voltaic  cell  when  in  the  form  of 
a  plate. 

Dice-Box  Insulator.— (See  Insulator, 
Dice-Box.} 

Dielectric. — A  substance  which  permits 
induction  to  take  place  through  its  mass. 

This  word  is  sometimes,  but  improperly,  writ- 
ten Di-Electric. 

The  substance  which  separates  the  opposite 
coatings  of  a  condenser  is  called  the  dielectric. 
All  dielectrics  are  non-conductors. 

All  non-conductors  or  insulators  are  dielectrics, 
but  their  dielectric  power  is  not  exactly  propor- 
tional to  their  non-conducting  power. 

Substances  differ  greatly  in  the  degree  or  ex- 
tent to  which  they  permit  induction  to  take  place 
through  or  across  them.  Thus,  a  certain  amount 
of  inductive  action  takes  place  between  the  insu- 
lated metal  plates  of  a  condenser  across  the  layer 
of  air  between  them. 

A  dielectric  may  be  regarded  as  pervious  to 
rapidly  reversed  periodic  currents,  but  opaque  to 
continuous  currents.  There  is,  however,  some, 
conduction  of  continuous  currents. 

According  to  Swinburne,  there  are  three  species 
of  conduction  that  may  take  place  in  dielectrics, 
all  of  which  produce  a  heating  of  the  dielectric, 
viz.: 

(I.)  Metallic  Condition,  i.  e.,  such  a  conduc- 
tion as  takes  place  in  a  metal.  This  kind  of  con- 
duction arises  from  the  presence  of  metallic  par- 
ticles embedded  in  the  dielectric. 

(2.)  Disruptive  Conduction^  or  a  momentary 
current  accompanying  a  disruptive  discharge. 

(3.)  Electrolytic  Conduction,  or  that  kind  of 
conduction  which  accompanies  the  electrolysis 
of  a  conductor.  This  kind  of  conduction  may 
take  place  in  some  kinds  of  glass. 

Faraday  regarded  the  dielectric  as  the  true  seat 
of  electric  phenomena.  Conducting  substances 
he  considered  as  mere  breaks  in  the  continuity  of 
the  dielectric.  This  is  the  view  now  generally 
held. 

Dielectric  Capacity. — (See  Capacity,  Dt- 
electric?) 


Die. 


162 


[Dim. 


Dielectric     Constant. — (See     Constant, 
Dielectric) 
Dielectric  Density  of  a  Gas. — (See  Gas, 

Dielectric  Density  of) 

Dielectric,  Polarization  of  — —  —A 
molecular  strain  produced  in  the  dielectric  of  a 
Leyden  jar  or  other  condenser,  by  the-attrac- 
tion  of  the  electric  charges  on  its  opposite 
faces,  or  by  the  electrostatic  stress.  (See 
Strain,  Dielectric) 

A  term  formerly  employed  in  place  of 
electric  displacement. 

Faraday,  in  his  study  of  the  action  of  induction, 
in  denying  the  possibility  of  action  at  a  distance, 
thought  that  the  dielectric  through  which  induc- 
tion takes  place  was  polarized,  and  that  in  this 
way  the  induction  was  transmitted  across  the 
intervening  space  between  the  inducing  and  the 
induced  body  by  the  action  of  the  contiguous 
particles  of  the  dielectric. 

The  polarization  of  the  glass  of  a  Leyden  jar, 
and  the  accompanying  strain,  are  seen  by  the 
frequent  piercing  of  the  glass,  and  by  the 
residual  charge  of  the  jar.  (See  Charge,  Resid- 
ual) 

Dielectric  Resistance.— (See  Resistance. 
Dielectric) 

Dielectric  Strain.— (See  Strain,  Dielec- 
tric) 

Dielectric  Strength  of  a  Gas. — (See  Gas, 
Dielectric  Strength  of) 

Dielectric  Stress.— (See  Stress,  Dielec- 
tric) 

Difference  of  Potential.— (See  Potential, 
Difference  of) 

Differential  Electric  Bell.— (See  Bell, 
Differential  Electric) 

Differential  Galvanometer. — (See  Gal- 
vanometer, Differential) 

Differential  Indnctometer. — (See  Indue- 
tometer.  Differential) 

Differential  Method  of  Duplex  Teleg- 
raphy.—(See  Telegraphy,  Duplex,  Differ- 
ential Method  of) 

Differential  Relay.— (See  Relay,  Differ- 
ential. ) 

Differential  Thenno-Pile.— (See  Pile, 
Thermo,  Differential) 


Differential  Voltameter.— (See   Voltam- 
eter, Siemens'  Differential) 
Differentially     Wound     Motor.  —  (See 

Motor.  Differentially  Wound.} 

Diffusion,  Anodal A  term  applied 

to  the  introduction  of  any  drug  into  the  human 
body  by  electricity. 

The  cataphoretic  introduction  of  drugs 
into  the  body.  (See  Cataphoresis) 

A  sponge  or  other  similar  electrode,  saturated 
with  a  solution  of  the  drug,  is  connected  with 
the  anode  of  a  source  and  placed  over  the  part 
to  be  treated  and  its  kathode  connected  to 
another  part  of  the  body  in  a  nearly  direct  line 
with  the  anode  and  the  current  passed, 

Diffusion  Creep.— (See  Creep.  Diffusion) 
Diffusion    of   Electric     Current. — (See 

Current,  Diffusion  of) 

Diffusion  of  Lines  of  Force.— (See  Force, 
Lines  of  Diffusion  of) 

Dimensions  of  Acceleration.— (See  Ac- 
celeration, Dimensions  of) 

Dimensions  of  Units — (See  Units,  Dimen- 
sions of) 

Diminished  Electric  Irritability.— (See 

Irritability,  Electric,  Diminished^ 

Dimmer A  choking  coil,  employed 

in  a  system  of  distribution  by  converters  or 

transformers,  for  regulating  the  potential  of 

the  feeders. 
The  dimmer  consists  essentially  of  a  choking 

coil  wound  around  a  laminated  ring  of  soft  iron, 


Fig.  20  r.     Re  action  Coil  Dimmer. 

and  provided  with  an  envelope  of  heavy  copper. 
The  copper  ring,  by  its  position  as  regards  the 
choking  coil,  adjusts  or  regulates  the  self-induc- 
tion of  the  coil,  and  consequently  regulates  the 
potential  of  the  feeders.  The  dimmer  is  used  in 
theatres  or  similar  situations  to  turn  the  lights  up 
or  down. 


Dio.] 


163 


[Dip. 


The  reaction  coil  or  dimmer  is  shown  in  Fig. 
201.  The  choking  coil  is  wound  on  a  ring  of 
iron.  The  copper  sheath  is  furnished  with  a 
handle  to  permit  its  position  to  be  readily 
changed  with  respect  to  the  coil  of  insulated  wire. 
A  laminated  iron  drum  is  supported  on  bearings 
inside  the  ring.  When  the  sheath  is  over  the 
coil,  the  coil  offers  but  a  small  resistance  to  the 
passage  of  the  current.  When  away  from  it  the 
self-induction  of  the  coil  is  increased. 

Dioptre. — A  unit  of  refracting  power. 

A  lens  of  one  dioptre  has  a  focal  length  of 
one  metre.  One  of  two  dioptres  has  a  focal 
length  of  50  centimetres;  one  of  four  dioptres 
25  centimetres.  This  is  also  spelled  dioptry. 

Dioptric. — Relating  to  dioptrics. 
Dioptrics. — The  science   which  treats  of 
the  refraction  of  light. 

Dioptry. — A  word  sometimes  used  for  di- 
optre. (See  Dioptre?) 

Dip,  Magnetic  —  —The  deviation  of  a 
magnetic  needle  from  a  true  horizontal  posi- 
tion. 

The  inclination  of  the  magnetic  needle  to- 
wards the  earth. 

The  magnetic  needle  shown  in  Fig.  202,  though 


Fig.  202.    Angle  of  Dip. 

supported  at  its  centre  of  gravity,  will  not  retain 
a  horizontal  position  in  all  places  on  the  earth's 
surface. 


In  the  northern  hemisphere  its  north-seeking 
end  will  dip  or  incline  at  an  angle  B  O  C,  called 
the  angle  of  dip.  In  the  southern  hemisphere 
its  south  seeking  end  will  dip. 

The  cause  of  the  dip  is  the  unequal  distance  of 
the  magnetic  poles  of  the  earth  from  the  poles  of 
the  needle. 

The  magnetic  equator  is  a  circle  passing 
around  the  earth  midway  (in  intensity)  between 
the  earth's  magnetic  poles.  There  is  no  dip  at 
the  magnetic  equator.  At  either  magnetic  pole 
the  angle  of  dip  is  90  degrees. 

Dip,  or  Inclination,  Angle  of 

The  angle  which  a  magnetic  needle,  free  to 
move  in  both  a  vertical  and  a  horizontal  plane, 
makes  with  a  horizontal  line  passing  through 
its  point  of  support. 

The  angle  of  dip  of  a  magnetic  needle. 
(See  Inclination,  Angle  of.) 

Diplex  Telegraphy. — (See  Telegraphy, 
Diplex) 

Dipping. — An  electro-metallurgical  process 
whereby  a  deposit  or  thin  coating  of  metal 
is  obtained  on  the  surface  of  another  metal 
by  dipping  it  in  a  readily  decomposable 
metallic  salt. 

Cleansing  surfaces  for  electro-plating  pro- 
cesses by  immersing  them  in  various  acid 
liquors. 

Dipping,  Bright Dipping  in  acid 

liquors  for  the  purpose  of  obtaining  a  bright 
electro-metallurgical  coating. 

Dipping  Circle. — (See  Circle,  Dipping?) 

Dipping,  Dead Dipping  in  acid 

liquors  for  the  purpose  of  obtaining  a  dead  or 
unpolished  surface  on  an  electro-metallurgical 
coating. 

Dipping,  Electro-Metallurgical • 

A  process  for  obtaining  an  electro-metallur- 
gical deposit  on  a  metallic  surface  by  dipping 
it  in  a  solution  of  a  readily  decomposable 
metallic  salt. 

A  bright,  polished  iron  surface,  when  simply 
dipped  into  a  solution  of  copper-sulphate,  re- 
ceives a  coating  of  metallic  copper  from  the  elec- 
trolytic action  thus  set  up. 

This  process  is  known  technically  as  dipping. 
The  term  dipping  is  also  used  in  electro-metal- 
lurgy  to  indicate  the  process  of  cleaning  the 


Dir.] 


164 


[Dis. 


articles,  that  are  to  be  electro-plated,  by  dipping 
them  in  various  acid  or  alkaline  baths. 

Direct  Current. — (See  Current,  Direct?) 

Direct-Current     Electric    Motor. — (See 
Motor,  Electric,  Direct-Current?) 

Direct  Electromotive  Force. — (See  Force, 
Electromotive,  Direct) 

Direct     Excitation. — (See     Excitation, 
Direct.) 

Direct-Induced  Current. — (See  Current, 
Direct-Induced.) 

Direct,  or  Break-Induced  Current • 

— (See  Current,  Direct.  Current,  Break- 
Induced) 

Direct  Working. — (See  Working,  Direct) 

Direction,  Negative,  of  Electrical  Con- 
vection of  Heat A  direction  in  which 

heat  is  transmitted  through  an  unequally 
heated  conductor  by  electric  convection, 
during  the  passage  of  electricity  through  the 
conductor,  opposite  that  of  the  current.  (See 
Heat,  Electric  Convection  of.) 

Direction  of  Lines  of  Force. — (See  Force, 
Lines  of,  Direction  of) 

Direction,  Positive,  of  Electrical  Con- 
vection   of    Heat A    direction    in 

which  heat  is  transmitted  through  an  un- 
equally heated  conductor  by  electric  convec- 
tion, during  the  passage  of  electricity  through 
the  conductor,  the  same  as  that  of  the  cur- 
rent. (See  Heat,  Electric  Convection  of.) 
Direction,  Positive,  Bound  a  Circuit 

In    a  plane  circuit  looked    at  from 

one  side,  a  direction  opposite  to  that  of  the 
hands  of  a  clock. 

This  is  a  convention  which  has  been  made  in 

order  to  conveniently  connect  the  direction  of  the 

electromotive  force  produced  by  induction,  with 

the  direction  of  the  induction. 

Direction,  Positive,  Through  a  Circuit 

In  a  plane    circuit,  looked  at  from 

one  side,  a  direction  through  the  circuit  away 
from  the  observer. 

Directive  Tendency  of  Magnetic  Needle. 
— (See  Needle,  Magnetic,   Directive    Ten- 
dency of.) 
Disc,    Arago's A  disc    of    copper 


or  other  non-magnetic  metallic  substance, 
which,  when  rapidly  rotated  under  a  mag- 
netic needle,  supported  independently  of  the 
disc,  causes  the  needle  to  be  deflected  in  the 
direction  of  rotation,  and,  when  the  velocity 
of  the  disc  is  sufficiently  great,  to  rotate  with  it. 
Such  disc  is  shown  in  Fig.  203  at  b.  The  move- 


Fig.  203.    Arago's  Disc. 

ment  of  the  needle  is  due  to  electric  currents,  in. 
duced  by  the  disc  moving  through  the  field  of  the 
needle  so  as  to  cut  its  lines  of  magnetic  force.  To 
obtain  the  best  results  the  disc  must  move  very 
rapidly,  and  should  be  ^near  the  needle.  More- 
over, the  needle  should  be  powerful. 

This  effect  was  discovered  by  Arago,  in  1824. 
Since  a  magnetic  needle  moving  over  a  metallic 
plate  produces  electric  currents  in  a  direction 
which  tends  to  stop  the  motioi  of  the  needle,  a 
damping  of  the  motion  of  a  magnetic  needle  is 
sometimes  effected  by  causing  it  to  move  near  a 
metal  plate.  The  induced  currents,  which  the 
needle  produces  in  the  plate  by  its  motion  over  it, 
tend  to  retard  the  motion  of  the  needle.  (See 
Damping.  Law,  Lenz's.) 

Disc  Armature. — (See  Armature,  Disc.) 

Disc,    Faraday's A    metallic   disc 

movable  in  a  magnetic  field  on  an  axis 
parallel  to  the  direction  of  the  field. 

Such  a  disc  is  shown  in  Fig.  204,  and  moves, 


Fig.  204..     Faraday's  Disc. 

as  will  be  seen,  so  as  to  cut  the  lines  of  magnetic 
force  at  right  angles. 

The  difference  of  potential  generated  by  the 
motion  of  such  a  disc  may  be  caused  to  produce 
a  current,  by  providing  a  circuit  which  is  com- 
pleted through  the  portion  of  the  disc  that  at  any 


Dis.] 


165 


[Dis. 


moment  of  its  rotation  is  situated  between  spring 
contacts  resting  on  the  axis  of  rotation  and  the 
circumference  of  the  disc,  respectively. 

In  Barlow  s  or  Sturgeon's  wheel,  Fig.  205,  the 


Discharge,    Brush-and-Spray 


—A 


Fig.  2OJ.    Barlow's  Wheel. 

wheel  itself  rotates  in  the  direction  shown,  when 
a  current  is  sent  through  it  in  a  direction  indicated 
by  the  arrows. 

Discharge. — The  equalization  of  the  dif- 
ference of  potential  between  the  terminals  of 
a  condenser  or  source,  on  their  connection  by 
a  conductor. 

The  removal  of  a  charge  from  the  surface 
of  any  charged  conductor  by  connecting  it 
with  the  earth,  or  another  conductor. 

The  removal  of  a  charge  by  means  of  a 
stream  of  electrified  air  particles. 

The  discharge  of  an  insulated  conductor,  a 
cloud,  a  condenser,  or  a  Leyden  battery,  is  oscil- 
latory. The  oscillatory  currents  continue  but  for 
a  short  time.  The  discharge  is  therefore  often 
spoken  of  as  producing  momentary  currents. 

The  discharge  of  a  voltaic  battery,  or  a  stor- 
age battery,  is  nearly  continuous,  and  furnishes  a 
current  which  is  practically  continuous,  as  dis- 
tinguished from  the  momentary  currents  produced 
by  the  discharge  of  a  condenser. 

A  discharge  may  be  alternating,  brush,  brush 
and  spray,  conductive,  convective,  dead-beat, 
disruptive,  flaming,  glow,  lateral,  oscillatory, 
periodic,  stratified,  streaming,  impulsive  and 
periodic. 

Discharge,  Alternating An  elec- 
tric discharge  which  changes  its  direction  at 
regular  intervals  of  time. 

A  periodic  discharge. 

Discharge,  Brush A  faintly  lu- 
minous discharge  that  occurs  from  a  pointed 
positive  conductor. 

The  brush  discharge  is  a  species  of  convective 
discharge.  In  it,  the  streams  of  electrified  air 
particles  assume  the  characteristic  brush  shape. 
(See Discharge,  Convective.) 


form  of  streaming  discharge  obtained  by  in- 
creasing the  frequency  of  the  alternations 
of  a  high  potential  current  which  assumes 
the  appearance  of  a  spray  of  silver-white 
sparks,  or  a  bunch  of  thin  silvery  threads 
around  a  powerful  brush. 

Some  idea  of  the  brush-and-spray   discharge 
may  be  obtained    from    Fig.   206,   taken  from 


Fig.  206.    Brush-and-Spray  Discharge  ( Tesla). 
Tesla,  who  has  carefully  studied  these  phenom- 
ena. 

The  brush-and-spray  discharge  is  best  obtained, 
according  to  Tesla,  by  bringing  the  terminals 
of  a  source  of  rapidly  alternating  electrostatic 
currents  of  high  potential  somewhat  nearer  to- 
gether, when  the  streaming  discharge  has  been 
obtained,  and  preferably  increasing  the  frequency 
of  the  alternations. 

The  brush-and-spray  discharge,  when  power- 
ful, closely  resembles  a  gas  flame  from  gas  escap- 
ing under  great  pressure.  Says  Tesla  :  ' '  But 
they  do  not  only  resemble,  they  are  veritable 
flames,  for  they  are  hot.  Certainly  they  are  not 
as  hot  as  a  gas-burner,  but  they  would  be  so  if  the 
frequency  and  the  potential  would  be  sufficiently 
high." 

The  brush-and-spray  discharge,  at  higher  fre- 
quencies, passes  into  a  form  of  discharge  for  which 
Tesla  has  proposed  no  particular  name.  He  de- 
scribes this  form,  in  a  publication  of  a  lecture 
before  the  American  Institute  of  Electrical  Engi- 
neers, as  follows,  viz. : 

' '  If  the  frequency  is  still  more  increased,  then 
the  coil  refuses  to  give  any  spark  unless  at  com- 
paratively small  distances,  and  the  fifth  typical 
form  of  discharge  may  be  observed  (Fig.  207). 
The  tendency  to  stream  out  and  dissipate  is  then 
so  great  that  when  the  brush  is  produced  at  one 
terminal  no  sparking  occurs,  even  if,  as  I  have  re- 
peatedly tried,  the  hand,  or  any  conducting  ob- 
ject, is  held  within  the  stream  ;  and,  what  is  more 


Dis.] 


166 


[Dis. 


singular,  the  luminous  stream  is  not  at  all  easily 
deflected  by  the  approach  of  a  conducting  body. 

"At  this  stage  the  streams  seemingly  pass  with 
the  greatest  freedom  through  considerable  thick- 
nesses of  insulators,  and  it  is  particularly  interest- 
ing to  study  their  behavior.  For  this  purpose  it 
is  convenient  to  connect  to  the  terminals  of  the 
coil  two  metallic  spheres,  which  may  be  placed  at 
any  desired  distance  (Fig.  208) .  Spheres  are  pref- 


Fig.  207.    Fifth.  Typical  Form  of  Discharge  ( Tcsla). 

erable  to  plates,  as  the  discharge  can  be  better 
observed.  By  inserting  dielectric  bodies  between 
the  spheres,  beautiful  discharge  phenomena  may 
be  observed.  If  the  spheres  be  quite  close  and  a 
spark  be  playing  between  them,  by  interposing  a 
thin  plate  of  ebonite  between  the  spheres  the 
spark  instantly  ceases  and  the  discharge  spreads 
into  an  intensely  luminous  circle  several  inches  in 
diameter,  provided  the  spheres  are  sufficiently 
large.  The  passage  of  the  stream  heats,  and, 
after  a  while,  softens  the  rubber  so  much  that  two 


Fig.  2O8.    Luminous  Discharge  -with  Interposed 
Insulators. 

plates  may  be  made  to  stick  together  in  this  man. 
ner.  If  the  spheres  are  so  far  apart  that  no  spark 
occurs,  even  if  they  are  far  beyond  the  striking 
distance,  by  inserting  a  thick  plate  of  glass  the 
discharge  is  instantly  induced  to  pass  from  the 
spheres  to  the  glass  in  the  form  of  luminous 
streams.  It  appears  almost  as  though  these 


streams  pass  through  the  dielectric.  In  reality 
this  is  not  the  case,  as  the  streams  are  due  to  the 
molecules  of  the  air  which  are  violently  agitated 
in  the  space  between  the  oppositely  charged  sur- 
faces of  the  spheres. 

"When  no  dielectric  other  than  air  is  present, 
the  bombardment  goes  on,  but  is  too  weak  to 
be  visible  ;  by  inserting  a  dielectric  the  indkx> 
live  effect  is  much  increased,  and  besides,  the 
projected  air  molecules  find  an  obstacle  and  the 
bombardment  becomes  so  intense  that  the  streams 
become  luminous.  If  by  any  mechanical  means 
we  could  effect  such  a  violent  agitation  of  the 
molecules  we  could  produce  the  same  phenom- 
enon. A  jet  of  air  escaping  through  a  small 
hole  under  enormous  pressure  and  striking 
against  an  insulating  substance,  such  as  glass, 
may  be  luminous  in  the  dark,  and  it  might  be 
possible  to  produce  phosphorescence  of  the  glass 
or  other  insulators  in  this  manner. 

"  The  greater  the  specific  inductive  capacity  of 
the  interposed  dielectric,  the  more  powerful  the 
effect  pioduced.  Owing  to  this  the  streams  show 
themselves  with  excessively  high  potentials  even 
if  the  glass  be  as  much  as  one  and  one-half  to  .two 
inches  thick.  But  besides  the  heating  due  to  bom- 
bardment, some  heating  goes  on  undoubtedly  in 
the  dielectric,  being  apparently  greater  in  glass 
than  in  ebonite.  I  attribute  this  to  the  greater 
specific  inductive  capacity  of  the  glass  in  conse- 
quence of  which,  with  the  same  potential  differ- 
ence,  a  greater  amount  of  energy  is  taken  up  in  it 
than  in  rubber.  It  is  like  connecting  to  a  battery 
a  copper  and  a  brass  wire  of  the  same  dimen- 
sions. The  copper  wire,  though  a  more  perfect 
conductor,  would  heat  more  by  reason  of  its  tak- 
ing more  current.  Thus  what  is  otherwise  con- 
sidered a  virtue  of  the  glass  is  here  a  defect. 
Glass  usually  gives  way  much  quicker  than  ebo« 
nite  ;  when  it  is  heated  to  a  certain  degree  thfc 
discharge  suddenly  breaks  through  at  one  point, 
assuming  then  the  ordinary  form  of  an  arc." 

Discharge,  Conductive  —  A  dis- 
charge effected  by  leading  the  charge  off 
through  a  conductor  placed  in  contac*  with 
the  charged  body. 

Discharge,  Convective A  dis- 
charge which  occurs  from  the  points  on  the 
surface  of  a  highly  charged  conductor, 
through  the  repulsion  by  the  conductor  of  air 
particles  that  in  this  manner  carry  off  minute 
charges. 


Dis.] 


1C7 


[Dis. 


A  convective  discharge,  though  often  attended 
by  a  feeble  sound,  is  sometimes  called  a  silent 
discharge,  in  order  to  distinguish  it  from  the 
noisy,  disruptive  discharge,  which  is  attended  by 
a  sharp  snap,  or  when  considerable,  by  a  loud 
report. 

A  convective  discharge  is  also  called  a  glow  or 
brush  discharge.  The  latter  is  best  seen  at  the 
small  button  at  the  end  of  the  prime  or  positive 
conductor  of  a  frictional  electric  machine. 

The  positive  discharge  from  a  point  or  small 
rounded  conductor  is  always  brush-shaped;  the 
negative  discharge  is  always  star  shaped. 

In  rarefied  gases,  the  discharge  is  convective  in 
character  and  produces  various  luminous  effects 
of  great  beauty,  the  color  of  which  depends  on 
the  kind  of  gas,  and  the  size,  shape  and  material 
of  the  electrodes,  and  on  the  degree  of  the  vacuum. 
Thus  in  the  rarefied 
space  of  the  vessel  shown 
in  Fig.  209,  the  discharge 
becomes  an  ovoidal  mass 
of  light,  sometimes  called  ] 
the  Philosopher'1  s  Egg. 

When  the  discharges! 
in  rarefied  gases  follow 
one  another  very  rapid- 
ly, alternations  of  light 
and  darkness,  or  stratifi- 
cations, or  stria  are  pro-  ] 
duced. 

The  breadth  of  the 
dark  bands  increases  as 
the  vacuum  becomes 
higher.  The  light  por- 
tions start  at  the  positive 
electrode,  and  are  hotter  | 
than  the  dark  portions. 

The  effects  of  luminous  Fis-sog.  Discharge  i» 
convective  dischargesare  R^efiedAir. 

best  seen  in  exhausted  glass  tubes,  called  Geissler 
lubes,  containing  residual  atmospheres  of  various 
gases.  (See  Tubes,  Geissler.) 

Discharge,  Dead-Beat  —  A  non- 
oscillatory  discharge.  (See  Discharge, 
Oscillatory?) 

Discharge,  Disruptive A  sudden, 

and  more  or  less  complete,  discharge  that 
takes  place  across  an  intervening  non-con- 
ductor or  dielectric. 

A  mechanical  strain  of  the  dielectric  occurs, 
which  suddenly  breaks  down  as  it  were  and  per- 


mits the  discharge  to  pass  as  a  spark,  or  rap^ 
succession  of  sparks. 

In  air,  the  spark,  when  long,  generally  takes 
the  zigzag  path,  as  shown  in  Fig.  210. 

The  sparks  produced  by  disruptive   discharges 
consist  of  heated  gases, 
together  with  portions  of 
the   conductor  that  are 
volatilized  by  the  heat. 

The  discharge  of  a  Ley- 
den  jar  or  condenser  may 
be  disruptive,  as  when 
the  discharging  rod  is 
held  with  one  knob  con- 
nected with  one  coating, 
and  the  other  near  the 
other  coating.  It  may 
be  gradual,  as  when  the 
two  coatings  are  alter- 
nately connected  with  the 
ground.  The  discharge 
of  a  Leyden  jar  as,  in- 
deed, the  disruptive  dis- 
charge in  general,  is  os- 
cillatory. 

The  stress  is  often  suf- 
ficient to  pierce  the  glass. 

Discharge,  Dura- 
tion of The 


Fig.  210.     Disruptive 
Discharge. 


time  required  to  effect  a  complete  disruptive 
discharge. 

The  disruptive  discharge  is  not  instantaneous; 
some  time  is  required  to  effect  it.  Estimates  of 
the  duration  of  a  flash  of  lightning  based  on  the 
duration  of  a  Leyden  jar  discharge,  are  mislead- 
ing  from  the  enormous  difference  in  the  quantity 
and  the  potential  in  the  two  cases.  The  fact  that 
the  disruptive  discharge  is  oscillatory  and  consists 
of  a  number  of  discharges  taking  place  in  alter- 
nately opposite  directions  shows  that  the  discharge 
is  not  instantaneous. 

Leyden  jar  discharges,  are,  however,  accom- 
plished in  very  small  periods  of  time. 

Discharge,  Flaming  — The   white 

and  flaming  arc-like  discharge  that  occurs 
between  the  terminals  of  the  secondary  of  an 
induction  coil,  when,  with  a  great  number  of 
alternations  per  second,  the  current  through 
the  primary  is  increased  beyond  that  required 
for  the  sensitive-thread  discharge.  (See  Dis* 
charge,  Sensitive-  Thread!) 


Dis.] 


168 


[Dis. 


According  to  Tesla  the  flaming  discharge  is 
best  produced  when  the  number  of  alternations  is 
not  too  great  and  certain  relations  between  ca- 
pacity, self-induction  and  frequency  are  observed. 
These  relations  must  be  such  as  will  permit  the 
flow  through  the  circuit  of  the  maximum  current, 
and  thus  may  be  obtained  with  wide  variations  in 
the  frequency.  The  flaming  discharge  develops 
considerable  heat,  and  is  characterized  by  the 
absence  of  the  shrill  note  accompanying  less  pow- 
erful discharges.  This  is  probably  due  to  the 
enormous  frequency. 

Some  idea  of  the  flaming  discharge  may  be  had 


Fig.  211.    Flaming  Discharge  (Tesla). 
from  an  inspection  of  Fig.  211,  taken  from  Tesla. 

Discharge,  Glow A  form  of  con- 

vective  discharge.      (See  Discharge,   Con- 
v&ttve.) 

Discharge,  impulsive A  dis- 
charge produced  in  conductors  by  suddenly 
created  differences  of  potential. 

Impulsive  discharges  are  influenced  more  by  the 
inductance  of  a  conductor  than  by  its  true  ohmic 
resistance.  (See  Inductance.  Resistance,  Ohmic. ) 

A  mass  of  guncotton  simply  ignited  in  the 
open  air,  produces  but  little  effect  on  any  resisting 
object  placed  below  it.  If,  however,  it  be  rapidly 
ignited  by  means  of  a  detonator,  and  is  thus  fired 
with  much  greater  rapidity,  it  may  shatter  any- 
thing placed  beneath  it. 

In  a  similar  manner,  a  rapidly  discharged  cur- 
rent, or  impulsive  discharge,  produces,  through  the 
inductance  of  the  conductor,  a  series  of  effects 
somewhat  similar  to  the  above,  in  which  a  great 
impedance  is  produced  by  a  sudden  change  of 
direction. 

Discharge,    Induced    Currents,    Effects 

Produced    by — Varying    classes   of 

effects  produced  by  the  discharges  of  induced 
currents. 


The  effects  produced  by  discharges  of  induced 
currents  are  classified  by  Fleming  as  follows: 

(l.)  Effects  depending  on  the  entire  quantity  of 
the  discharge. 

a.  Galvanometric  effects. 

If  the  needle  of  the  galvanometer  has  a  period 
or  time  of  oscillation  that  is  long,  as  compared 
with  the  time  of  duration  of  the  discharge,  the  sine 
of  one-half  the  angle  of  deflection  is  proportional 
to  the  whole  quantity  of  the  discharge. 

b.  Electro-chemical  effects. 

The  quantity  of  an  electrolyte  broken  up  is 
proportional  to  the  quantity  of  electricity  which 
passes  through  it. 

(2.)  Effects  depending  on  the  average  of  the 
square  of  the  current  strength  at  any  instant  dur- 
ing the  discharge. 

a.  Heating  effects. 

The  rate  of  dissipation  as  heat,  according  to 
Joule's  law,  is  proportional  to  the  square  of  the 
current  strength  passing. 

b.  Electro-dynamic  effects. 

When  a  discharge  passes  through  a  circuit, 
part  of  which  is  fixed  and  part  movable,  the  forces 
of  attraction  and  repulsion  which  take  place  be- 
tween them  at  any  instant  are  proportional  to 
the  square  of  the  current  strength. 

(3.)  Effects  depending  on  rate  of  change  of 
the  current. 

a.  Physiological  effects. 

The  effect  of  the  discharge  in  producing  physi- 
ological shock  increases  with  the  suddenness  of 
the  discharge.  Of  two  discharges  which  reached 
the  same  maxima  that  which  reached  it  first  would 
produce  the  greatest  physiological  effect.  Recent 
investigations  by  Tesla  and  others  would  appear  to 
partly  disprove  the  above  statement 

b.  Telephonic  effects. 

The  telephone,  like  the  body  of  an  animal,  is 
affected  more  by  the  rate  of  change  than  by  the 
current  strength  at  any  instant. 

c.  Magnetic  effects. 

Rayleigh  has  shown  that  the  magnetic  effects  of 
the  discharge  depend  upon  the  maximum  current 
strength  during  the  discharge,  or  upon  the  initial 
current  strength,  in  cases  where  the  current  dies 
away  gradually.  Since  the  time  required  for  the 
permanent  magnetizing  of  a  steel  wire  is  small 
compared  with  the  duration  of  the  induced  cur- 
rent, the  amount  of  magnetism  acquired  depends 
essentially  on  the  initial  or  maximum  current 
strength  during  the  discharge,  irrespective  of  the 
time  during  which  said  discharge  lasts. 


Dis.J 


169 


[Dis. 


d.  Luminous  effects. 

These  are  also  dependent  in  the  case  of  induced 
discharges  on  the  rate  of  change  of  the  current. 

Discharge-Key. — (See  Key,  Discharged) 


Discharge,   Lateral 


— A  discharge, 


taking  place  on  the  discharge  of  a  Leyden  jar, 
or  other  disruptive  discharge,  between  parts 
of  the  jar  or  conductors,  not  in  the  circuit  of 
the  main  discharge. 

If  a  charged  Leyden  jar  is  placed  on  an  insulat- 
ing stool,  and  is  then  discharged  by  the  discharg- 
ing rod,  the  lateral  discharge  is  seen  as  a  small 
spark  that  passes  between  the  outside  coating  of 
the  jar  and  a  body  connected  ^vith  the  earth  at 
the  moment  of  the  discharge  through  the  rod. 

A  lateral  discharge  is  also  seen  in  the  sparks 
that  can  be  taken  from  a  conductor  in  good  con- 
nection with  the  earth,  by  holding  the  hand  near 
the  conductor,  while  it  is  receiving  large  sparks 
from  a  powerful  machine  in  operation.  These 
discharges  are  due  to  induction. 

If  a  Leyden  jar  be  discharged  by  means  of  a  con- 
ducting wire  bent  as  shown  in  Fig.  212,  in  which 


Fig.    212. 

two  parts  of  the  circuit  are  closely  approached  as  at 
A,  whenever  a  spark  occurs  at  B,  another  spark 
produced  by  a  lateral  discharge  occurs  at  A. 
Although  the  resistance  of  the  metallic  circuit  is 
enormously  less  than  the  resistance  of  the  air 
Bpace  through  which  the  lateral  discharge  occurs, 
yet  the  counter  electromotive  force  produced  in 
the  metallic  circuit  by  the  impulsive  discharge, 
renders  its  resistance  far  greater  than  that  of 
the  air  space.  The  path  of  a  lateral  discharge 
is  called  the  alternative  path.  (See  Path,  Al- 
ternative, ) 

Discharge,  Luminous  Effects  of 

The  luminous  phenomena  attending  and  pro- 
duced by  an  electric  discharge. 

The  luminous  effects  vary  as  to  color,  intensity, 
shape  and  accompanying  acoustic  phenomena 
according  to  a  variety  of  circumstances,  the  prin- 
cipal of  which  are  as  follows,  viz. : 

(i.)  With  the  kind  of  gaseous  medium  through 
which  the  discharge  passes.  Thus,  a  spark  passed 
through  hydrogen  has  a  crimson  or  reddish  color; 


through  carbonic  acid  or  chlorine,  a  greenish 
color. 

(2.)  With  the  density  of  the  medium.  In  a 
partial  vacuum,  the  discharge  from  an  induction 
coil  becomes  an  ovoidal  mass  of  light.  As  the 
vacuum  increases,  the  light  at  first  grows  brighter, 
but  as  a  higher  vacuum  is  reached,  striae  of  al- 
ternate dark  and  light  bands  appear.  Finally, 
with  very  high  vacua  the  discharge  fails  to  pass. 
(See  Discharge,  Convective.') 

(3.)  With  the  nature  of  the  substances  forming 
the  points  from  which  the  discharge  is  taken. 
This  is  due  to  the  partial  volatilization  of  the  ma- 
terial of  the  electrodes. 

(4.)  With  the  kind  of  electricity,  i.  e.,  whether 
positive  or  negative.  A  positive  charge  assumes 
the  shape  of  a  fan;  a  negative  discharge,  that  of 
a  star. 

(5.)  On  the  density  of  the  discharge.  The  in- 
troduction  of  a  Leyden  jar  or  condenser  in  the 
circuit  of  a  Holtz  machine,  for  example,  causes 
the  spark  to  change  from  the  faint  bluish  to  the 
silvery  white. 

(6.)  The  disruptive  discharge  through  air  is  at- 
tended by  snapping  or  crackling  sound,  which,  in 
the  case  of  lightning,  reaches  the  intensity  of  thun- 
der. When  the  disruptive  discharge  takes  place 
through  a  vacuum  a  faint  hissing  sound  is  heard, 
or  all  sound  may  entirely  disappear. 

(7. )  Luminous  effects  resulting  from  molecular 
bombardment  occurring  in  comparatively  high 
vacua.  These  luminous  effects  may  result : 

(a.)  From  actual  incandescence  of  some  refrac- 
tory material  produced  by  the  blows  of  the  mole- 
cules; or, 

(b.)  As  a  result  of  phosphorescence  or  fluores- 
cence due  to  such  blows. 

Canary  glass,  or  glass  stained  by  uranium  oxide, 
fluoresces  and  emits  a  yellowish  green  light;  solu- 
tion of  sulphate  of  quinine  emits  a  bluish  light. 

Discharge,     Non-Oscillatory    — A 

dead-beat  discharge.  (See  Discharge,  Dead- 
Beat.} 

Discharge,  Oscillating A  number 

of  successive  discharges  and  recharges  which 
occur  on  the  disruptive  discharge  of  a  Leyden 
jar,  or  condenser. 

A  discharge  which  periodically  decreases 
by  a  series  of  oscillations. 

A  discharge  which  produces  a  dying-away- 
backwards  and  forwards  current. 


Dis.] 


170 


[Dis 


The  disruptive  discharge  ot  a  Leyden  jar,  or 
condenser,  is  not  effected  by  a  single  rush  of  elec- 
tricity. When  discharged  through  a  compara- 
tively small  resistance,  a  number  of  alternate 
partial  discharges  and  recharges  occur,  which 
produce  true  oscillations  or  undulatory  discharges. 

These  oscillations  are  caused  by  the  induction 
of  the  discharge  on  itself,  and  are  similar  to  the 
self-induction  of  a  current. 

The  existence  of  the  oscillating  discharge  in  the 
case  of  a  Leyden  jar  or  condenser,  proves,  in  the 
opinion  of  some,  that  electricity,  taken  along 
with  matter,  possesses  i  property  similar  to 
inertia. 

Discharge,  Oscillatory A  term 

sometimes  used  for  an  oscillating  discharge. 
(See  Discharge,  Oscillating) 

Discharge,  Periodic  — An  electric 

discharge  which  changes  its  direction  at  reg- 
ular intervals  or  periods. 

An  alternating  discharge. 

Discharge,  Periodically-Decreasing • 

— An  oscillating  discharge  whose  decrease  is 
periodic.  (See  Discharge,  Oscillating?) 

Discharge,  Sensitive-Thread The 

thin,  thread-like  discharge  that  occurs  be- 
tween the  terminals  of  the  secondary  of  an  in- 
duction coil  of  high  frequency. 

The  sensitive-thread  discharge  occurs,  accord- 
ing to  Tesla,  when  the  number  of  alternations  per 


Fig-  2 1 3-    Sensitive-  Thread  Discharge  (  Tesla). 

second  is  high  and  the  current  through  the 
primary  small.  This  discharge  has  the  form  of 
a  thin,  feebly -colored  thread.  Though  very  sensi- 
tive, being  deflected  by  a  mere  breath,  it  is  never- 
theless quite  persistent,  if  the  terminals  be  at 
one-third  of  the  striking  distance  apart.  Tesla 
ascribes  its  extreme  sensitiveness,  when  long,  to 
the  motion  of  suspended  dust  particles  in  the  air. 
The  general  appearance  of  the  sensitive-thread 
discharge  is  shown  in  Fig.  213,  taken  from  Tesla. 


Discharge,  Silent A  name  given 

to  a  convective  discharge  in  order  to  distin- 
guish it  from  the  more  noisy  disruptive  dis- 
charge. 

The  convective  discharge  in  reality  is  attended 
by  a  feeble  sound,  which,  however,  is  quiet  when 
compared  with  the  more  pronounced  sound  of  the 
disruptive  discharge.  (See  Discharge,  Connec- 
tive.} 

Discharge,  Stratified The  form 

of  alternate  light  and  dark  spaces  assumed  by 
the  discharges  of  an  induction  coil  through  a 
partially  exhausted  gas.  (See  Tube,  Strati- 
fication?) 

The  striae  are  explained  by  Curtis  as  follows: 
•'Under  the  influence  of  the  electric  rhythm  of 
the  rapidly  following  discharges  the  molecules 
of  the  residual  gas  collect  in  alternately  dense 
and  rarefied  spaces.  The  light  bands  correspond  to 
the  spaces  where  the  molecules  are  comparatively 
crowded  together,  and  their  concomitant  friction 
produces  the  luminous  disturbance.  The  dark 
spaces  are  where  the  molecules  are  further  apart, 
and  where  their  collisions  are  consequently  lest 
frequent." 

Discharge,  Streaming A  form  as- 
sumed by  the  flaming  discharge  between  the 
terminals  of  the  secondary  of  an  induction 
coil  when  the  frequency  of  the  alternations 
increases  beyond  a  certain  limit,  and  the 
potential  has  consequently  increased. 

The  streaming  discharge  partakes  of  the  general 
characteristics  of  the  flaming  discharge.  Lumi- 
nous streams  pass  in  abundance,  not  only  between 
the  terminals  of  the  secondary,  but,  according  to 
Tesla,  who  has  carefully  studied  these  phe- 
nomena, between  the  primary  and  the  secondary, 
through  the  insulating  dielectric  separating 


Fig.  214.     Streaming  Discharge  (Tesla). 

them.     The  streams  not  only  pass  between  th« 
terminals,  but  also  issue  from  all  points  and  pro- 


Dis.] 


171 


[Dis. 


jections,  as  will  be  seen  from  Fig.  214,  taken  from 
Tesla. 

When  the  streaming  discharge  reaches  a  cer- 
tain higher  limit  it  becomes  a  brush-and  spray 
discharge.  (See  Discharge,  Brush-and- Spray.} 

The  streaming  discharge  obtained  from  an  in- 
duction coil  with  high  frequencies  differs  from  that 
of  an  electrostatic  machine  in  that  it  neither  pos- 
sesses the  violet  color  of  the  positive  static  dis- 
charge nor  the  brightness  of  the  negative,  but  is 
intermediate  in  color. 


--  A  term  some- 
times applied  to  an  oscillatory  discharge.  (See 
Discharge,  Oscillatory^) 

Discharge,    to    Electrically  -  —To 

equalize  differences  of  potential  by  connecting 
them  by  means  of  a  conductor. 

Discharge,  Undulatory  --  A  dis- 
charge, the  strength  and  direction  of  which 
gradually  change.  (See  Currents,  Undu- 


Discharge,     Unidirectional  -  —  An 

electric  discharge  which  takes  place  from  the 
beginning  to  the  end,  in  one  and  the  same  di- 
rection. 

Discharge,  Telocity  of  --  The  time 
required  for  the  passage  of  a  discharge 
through  a  given  length  of  conductor. 

According  to  modern  views  it  is  the  ether  sur- 
rounding the  wire  or  conductor  which  conveys 
the  electric  pulses.  All  the  energy  which  gets  into 
the  conductor  is  dissipated  as  heat. 

The  velocity  of  propagation  of  discharge  of  the 
pulses  produced  by  the  oscillating  discharge  of  a 
Leyden  jar  through  .the  inter-atomic  or  inter- 
molecular  ether,  i.e.,  through  the  fixed  ether  within 
different  substances,  varies  with  the  substance. 
Through  free  ether  the  velocity  is  that  of  light,  or 
185,000  miles  a  second. 

The  velocity  of  discharge  through  long  con- 
ductors or  cables  is  much  lessened  by  incapacity 
of  the  cable,  and  the  effects  of  induction,  and  will 
therefore  vary  in  different  cases.  (See  Retard- 
ation.} 

Discharger,  Universal  -  —An  appa- 
ratus for  sending  the  discharge  of  a  powerful 
Leyden  battery  or  condenser  in  any  desired 
direction. 

The  universal  discharger  consists  es;ent'al'y  of 


metallic  rods,  supported  on  insulated  pillars  and 
capable  of  ready  motion,  both  towards  and  from 
one  another,  as  well  as  in  vertical  and  horizon- 
tal planes.  The  object  which  is  to  receive  the 
discharge  is  placed  on  an  insulated  table  between 
the  rods',  and  the  latter  connected  with  the 
opposite  coatings  of  the  battery  or  condenser, 
when  the  discharge  passes  through  it. 

The  term  universal  discharger  is  sometimes  ap- 
plied to  the  discharging  tongs. 

Discharging,  Electrically  --  —The 
act  of  equalizing  differences  of  potential  by 
connection  with  a  conductor. 

Discharging  Rod.  —  (See  Rod,  Discharg- 


Discharging  Tongs.  —  (See  Tongs,  Dis- 
charging^) 

Disconnect.  —  To  break  or  open  an  electric 
circuit. 

Disconnecter.  —  A  key  or  other  device  for 
opening  or  breaking  a  circuit. 

Disconnecting.  —  The  act  of  opening  or 
breaking  an  electric  circuit. 

Disconnection.  —  A  term  employed  to  des- 
ignate one  of  the  varieties  of  faults  caused 
by  the  accidental  breaking  or  disconnection 
of  a  circuit. 

Disconnections  of  this  kind  may  be  : 

(I.)  Total  ;  as  by  a  switch  inadvertently  lefi 
open;  or  by  the  accidental  breaking  of  a  part  of 
the  circuit. 

(2.)  Partial  ;  as  by  a  dirty  contact;  a  loose,  o 
badly  soldered  joint;  a  poorly  clamped  binding 
screw;  a  loose  terminal,  or  a  bad  earth. 

(3.)  Intermittent;  as  by  swinging  joints,  alter- 
nate expansions  or  contractions  on  changes  oi 
temperature;  the  collection  of  dust  and  dirt  in  dry 
weather,  and  their  washing  out  in  wet  weather. 

Disconnection,       Intermittent  -  — 

Any  fault  in  a  line  which  occurs  at  intervals 
or  intermittently. 

Disconnection,  Partial  --  A  partial 
fault  in  a  line  caused  by  any  imperfect  con- 
tact. 

Disconnection,  Total  ---  A  fault  in 
a  line  occasioned  by  a  complete  break  in  the 
circuit. 

Disguised  Electricity.  —  (See  Electricity,. 
Disguised.) 


Dis.J 


172 


[Dis. 


Disjunctor.— A  device  employed  in  a  sys- 
tem for  tne  distribution  of  electric  energy  by 
means  of  continuous  currents  by  condensers, 
for  the  purpose  of  periodically  reversing  the 
constant  current  sent  over  the  line.  (See 
Electricity,  Distribution  of,  by  Continuous 
Current  by  Means  of  Condensers?) 

Dispersion  Photometer. — (See  Photome- 
ter, Dispersion?) 

Displacement  Current. — (See  Current, 
Displacement?) 

Displacement,  Electric A  displace- 
ment of  electricity  in  a  uniform  and  non- 
crystalline  dielectric  when  lines  of  electro- 
static or  magnetic  force  pass  through  it. 

The  quantity  of  electricity  displaced  in  any 
homogeneous,  non-crystallizable  dielectric, 
by  the  action  of  an  electric  force  through 
the  unit  area  of  cross-section,  taken  perpen- 
dicular to  the  direction  of  the  electric  force. 

Electric  displacement  is  produced  under  an 
elastic  strain,  which  continues  only  while  the  elec- 
tric force  is  acting. 

Displacement,  Electric,  Lines  of  — 

Lines  of  electric  induction  along  which  elec- 
tric displacement  takes  place. 

Displacement,  Electric,  Oscillatory 

— A  displacement  of  electricity  in  a  di- 
electric or  non-conductor  of  an  oscillatory 
character. 

Displacement,    Electric,   Theory  of 

— A  theory  which  regards  the  electricity 
produced  on  an  insulated  conductor,  by  in- 
duction through  a  dielectric,  as  displaced  out 
of  the  dielectric  on  to  the  conductor,  or  into 
the  dielectric  from  the  conductor,  by  the  in- 
fluence of  the  electric  force. 

This  conception  was  introduced  into  science  by 
Maxwell,  after  a  careful  study  of  Faraday's  denial 
of  action  at  a  distance. 

Suppose  a  small  insulated  sphere  to  receive  a 
charge  of  electricity  +  Q.  It  will,  by  induction, 
produce  an  equal  and  opposite  charge  —  Q,  on 
the  inner  surface,  and  a  similar  charge  on  the 
outer  surface  of  the  small  hollow  sphere,  placed 
near  it,  but  separated  by  the  dielectric.  There 
has,  therefore,  been  a  displacement  of  electricity 
throueh  the  dielectric.  The  medium  of  the 


dielectric  has  connected  the  two  bodies,  and  the 
phenomena  have  appeared  by  the  action  of  the 
electric  torce  on  the  substance  of  the  dielectric; 
or,  in  other  words,  there  has  been  no  action  at 
a  distance. 

According  to  this  conception,  an  electric  cur- 
rent, called  a  displacement  current,  exists  in  the 
dielectric,  while  displacement  is  taking  place. 

Displacement  Waves. — (See  Waves,  Dis- 
placement?) 

Disruptive  Electric  Conduction. — (See 
Conduction,  Electric,  Disruptive?] 

Dissimulated   or    Latent    Electricity. — 

(See  Electricity,  Dissimulated  or  Latent?) 
Dissipation    of   Charge. — (See     Charge, 

Dissipation  of?) 

Dissipation    of   Energy. — (See    Energy, 

Dissipation  of.} 

Dissipation  of  Energy,  Hysteresial ' 

— (See  Energy,  Hysteresial,  Dissipation  of. 
Hysteresis.} 

Dissipation,  Specific  Hysteresial  - 
The  specific  loss  of  energy  by  hysteresis  in 
the   case   of    a  particular    substance.     (See 
Hysteresis.} 

Dissociate. — To  separate  a  compound  sub- 
stance into  its  constituents. 

Dissociation. — The  separation  of  a  chemi- 
cal compound  into  its  constituent  parts. 

Dissymmetrical  Induction  of  Armature. 

— (See  Armature,  Dissymmetrical  Induc- 
tion of.} 

Dissymmetrical  Magnetic  Field. — (See 
Field,  Magnetic,  Dissymmetrical.} 

Dissymmetry  of  Commutation. — (See 
Commutation,  Dissymmetry  of.} 

Distance,  Critical,  of  Lateral  Discharge 

Through  an  Alternative  Path The 

distance  at  which  a  discharge  will  take  place 
through  an  air  space  of  given  dimensions,  ii. 
preference  to  passing  through  a  metallic  cir- 
cuit of  comparatively  small  resistance. 

Distance,  Explosive A  term  some- 
times employed  for  sparking  distance.  (See 
Distance,  Sharking?) 

Uist&uce.  syarking The  distance 


Dis.j 


173 


[Dot. 


at  which  electrical  sparks  will  pass  through 
an  intervening  air  space.  (See  Spark,  Length 
of.} 

Distant  Station. — (See  Station,  Distant.} 


Distillation,      Destructive 


—The 


action  of  heat  on  an  organic  substance, 
while  out  of  contact  with  air,  resulting  in  the 
decomposition  of  the  substance  into  simpler 
and  more  stable  compounds. 

The  different  products  resulting  from  destruc- 
tive distillation  may  be  successively  collected  by 
the  ordinary  processes  of  distillation. 

Distillation,  Dry A  species  of  de- 
structive distillation.  (See  Distillation,  De- 
structive.} 

Distillation,  Electric The  dis- 
tillation of  a  liquid  in  which  the  effects  of 
heat  are  aided  by  an  electrification  of  the 
liquid. 

Beccaria  discovered  that  a  liquid  evaporates  more 
rapidly  when  electrified  than  when  unelectrified. 
Crookes  has  shown  that  evaporation  is  aided 
by  negative  electrification,  or  that  evaporation 
takes  place  more  rapidly  at  the  negative  terminal 
during  a  discharge  than  at  the  positive.  (See 
Evaporation,  Electric. ) 

Distributing  Box  of  Conduit. — (See  Box, 
Distributing,  of  Conduit?) 

Distributing  Station. — (See  Station,  Dis- 
tributing.} 
Distributing  Switch  for  Electric  Light. 

— (See   Switch,   Distributing,  for   Electric 
Lights.} 
Bistribution-Box  for  Arc  Light  Circuits. 

— (See  Box,  Distribution,  for  Arc  Light 
Circuits} 

Distribution,  Centre  of In  a  sys- 
tem of  multiple-distribution,  any  place  where 
branch  cut-outs  and  switches  are  located  in 
order  to  control  communication  therewith. 

The  electrical  centre  of  a  system  of  distri- 
bution as  regards  the  conducting  network. 

Distribution  of  Charge. — (See  Charge, 
Distribution  of} 

Distribution  of  Electricity.— (See  Elec- 
tricity, Distribution  of} 


Distribution  of  Electricity  by  Alternat- 
ing Currents (See  Electricity,  Dis- 
tribution of,  by  Alternating  Currents.} 

Distribution  of  Electricity  by  Alternat- 
ing Currents  by  Means  of  Condensers.— 
(See  Electricity,  Distribution  of,  by  Alter- 
nating Currents  by  Means  of  Condensers.} 

Distribution  of  Electricity  by  Caminu- 
tating  Transformers.  —  (See  Electricity, 
Distribution  of,  by  Commutating  Trans- 
formers?) 

Distribution  of  Electricity  by  Constant 
Potential  Circuit. — (See  Electricity,  Multi- 
ple Distribution  of,  by  Constant  Potential 
Circuit} 

Distribution  of  Electricity  by  Contin- 
uous Current  by  Means  of  Transformers. — 
(See  Electricity,  Distribution  of,  by  Contin- 
uous Current  by  Means  of  Transformers.) 

Distribution  of  Electricity  by  Motor- 
Generators.  —(See  Electricity,  Distribution 
of,  by  Motor-Generators} 

Distribution,  Series,  of  Electricity  by 
Constant  Current  Circuit. — (See  Electricity, 
Series  Distribution  of,  by  Constant  Current 
Circuit} 

District  Call-Box.— (See  Box,  District 
Call} 

Diurnal  Inequality  of  Earth's  Magnet- 
ism.— (See  Inequality,  Diurnal,  of  Earth's 
Magnetism?) 

Divided  Magnetic  Circuit. — (See  Circuit, 
Divided  Magnetic} 

Door-Opener,  Electric  — A  device 

for  opening  a  door  from  r.  distance  by  elec- 
tricity. 

Various  devices  consisting  of  electro-magnets, 
acting  against,  or  controlling  springs  or  weights, 
are  employed  for  this  purpose. 

Dosage,    Electro-Therapeutical 

The  apportioning  of  the  amount  of  the  cur- 
rent and  the  duration  of  its  application  to  the 
body  for  the  treatment  of  disease. 

Dosage,  Galvanic  —Electro-thera- 
peutical dosage.  (See  Dosage,  Electro- 
Therapeutical)  . 

Dotting  Contact.— (See  Contact,  Dotting} 


DOU.J 


174 


Double-Break     Knife     Switch.— (See 

Switch,  Double-Break  Knife?) 

Double-Carbon  Arc  Lamp. — (See  Lamp, 
Electric  Arc,  Double-Carbon) 

Double-Cone  Insulator. — (See  Insulator, 
Double-Cone) 

Double-  Connector. — (See  Connector, 
Double) 

Double-Contact  Key.— (See  Key,  Double- 
Contact) 

Double-Cup  Insulator. — (See  Insulator, 
Double-Cup) 

Double-Curb.— (See  Curb,  Double) 

Double-Curb  Signaling.— (See  Signaling, 
Curb,  Double) 

Double-Current  Signaling.— (See  Signal- 
ing, Double-Current) 

Double-Current  Translator. — (See  Trans- 
lator, Double-Current) 

Double-Curr ent  Transmitter. — (See 
Transmitter,  Double-Current) 

Double-Current  Working —The 

employment,  in  systems  of  telegraphy,  by 
means  of  suitable  keys,  of  currents  from 
voltaic  batteries,  in  alternately  opposite 
directions,  thus  increasing  the  speed  of 
signaling.  (See  Working,  Reverse-Current) 

Double-Fluid   Electrical    Hypothesis. — 

(See  Electricity,  Double-Fluid  Hypothesis 
of-) 

Double-Fluid  Voltaic  Cell.— (See  Cell, 
Voltaic,  Double-Fluid) 

Double-Magnet  Dynamo-Electric  Ma- 
chine.— (See  Machine,  Dynamo-Electric, 
Double-Magnet) 

Double-Pen  Telegraphic  Register. — (See 
Register,  Double-Pen,  Telegraphic.) 

D  o  n  b  1  e-Refraction.— (See  Refraction, 
Double) 

Double-Refraction,  Electric. — (See  Re- 
fraction, Double,  Electric) 

Double-Shackle  Insulator. — (See  Insula- 
tor, Double-Shackle) 

Double-Shed  Insulator. — (See  Insulator, 
Double-Shed) 


Double-Tapper  Key.— (See  Key,  Double- 
Tapper) 
Double-Touch,  Magnetization  by 

A  method  for  producing  magnetization  by 
the  simultaneous  touch  of  two  magnet  poles. 
(See  Magnetization,  Methods  of) 

Double-Transmission. — (See  Transmis- 
sion, Double) 

Double-Trolley.— (See  Trolley,  Double) 

Doubler  of  Electricity. — An  early  form  of 
continuous  electrophorus.  (See  Electro- 
phorus) 

Drifting  Torpedo.— (See  Torpedo,  Drift- 
ing) 

Drill,  Electro-Magnetic  — A  drill 

applied  especially  to  blasting  or  mining  opera- 
tions, operated  by  means  of  electricity. 

Drip  Loop.— (See  Loop,  Drip) 
Driven  Pulley.— (See  Pulley,  Driven) 
Driven  Shaft.— (See  Shaft,  Driven) 
Driving  Pulley. — (See  Pulley,  Driving) 
Driving  Shaft.— (See  Shaft,  Driving) 
Driving  Spider. — (See  Spider,  Driving) 

Drop,  Annunciator  — A  movable 

signal  operated  by  an  electro-magnet,  and 
placed  on  an  annunciator,  the  dropping  of 
which  indicates  the  closing  or  opening  of  the 
circuit  with  which  the  electro-magnet  is  con- 
nected. 

The  falling  of  the  drop  may  be  attended  by  the 
sounding  of  a  bell  or  other  alarm,  or,  it  may  give 
a  silent  indication. 

Drop,  Annunciator,  Automatic A 

drop  for  an  annunciator,  which  on  the  closing 
of  a  circuit,  falls  and  holds  the  circuit  closed 
until  the  drop  is  raised. 

Drop,    Annunciator,  Gravity — A 

drop  for  an  annunciator,  acted  on  by  gravity 
when  released  by  the  movement  of  the  arma- 
ture of  an  electro-magnet. 

Drop,  Automatic A  device  for  au- 
tomatically closing  the  circuit  of  a  bell  and 
holding  it  closed  until  stopped  by  resetting  a 
drop. 


JDro.J 


.175 


[Dyn. 


The  automatic  drop  is  especially  applicable  to 
burglar  alarms.  On  the  opening  of  a  door  or 
shutter,  the  closing  of  the  circuit  moves  the 
armature  of  an  elec- 
tro -  magnet,  and, 
by  the  falling  of  a 
drop,  closes  the  cir- 
cuit and  holds 
closed  until  me- 
chanically opened 
by  the  replacing  of 
the  drop.  The 
general  appearance 
of  the  automatic 
drop  is  shown  in 
Fig.  215. 

Drop,   Calling1 

An     an_      Fig.  2  is-    Automatic  Drop. 

nunciator  drop  employed  to  indicate  to  the 
operator  in  a  telegraphic  or  telephonic  system 
that  one  subscriber  wishes  to  be  connected 
with  another. 

Drop  of  Potential. — (See  Potential,  Drop 

of-} 

Drops,  Clearing-  Out — Restoring 

the  drops  of  annunciators  to  their  normal 
position  after  they  have  been  thrown  out  of 
the  same  by  the  closing  of  the  circuits  of  their 
magnets. 

These  clearing-out  devices  as  placed  on  most 
forms  of  annunciators  are  generally  mechanical  in 
operation. 

Drum  Armatur e. — (See  Armature, 
Drum.) 

Drum,  Electro-Magnetic A  drum, 

used  in  feats  of  legerdemain,  operated  by 
an  automatic  electro-magnetic  make  and 
break  apparatus. 

Dry      Distillation.— (See      Distillation, 

Dry.) 

Dry  Electrode.— (See  Electrode,  Dry.) 
Dry  Pile.— (See  Pile,  Dry) 

Dry  Voltaic  Cell.— (See  Cell,  Voltaic, 
Dry.) 

Dub's  Laws.— (See  Laws,  Dub's.) 
Duplex  Cable.— (See  Cable,  Duplex.) 
Duplex  Cut-Ont.— (See  Cut-out,  Duplex) 


Duplex  Flat  Cable.— (See  Cable,  Flat 
Duplex) 

Duplex  Telegraphy. — (See  Telegraphy, 
Duplex^ 

Duplex  Wire.— (See  Wire,  Duplex^ 
Duration    of  Electric   Discharge. — (See 
Discharge,  Duration  of.) 

Duration    of   Make-Induced  Current. — 

(See  Current,  Make  or  Break  Induced,  Du- 
ration of.) 

Dust    Figures,  Lichtenberg's    

(See  Figures,  Lichtenberg's  Dust.) 

Dyad. — A  chemical  element  which  has  two 
bonds  by  which  it  can  unite  or  combine  with 
another  element. 

An  element  whose  atomicity  is  bivalent. 

Dyeing,  Electric The  application 

of  electricity  either  to  the  reduction  or  the 
oxidation  of  the  salts  used  in  dyeing. 

Goppelsroder,  in  his  processes  of  electric  dyeing^ 
forms  and  fixes  ani'.ine  black  on  cloth  as  follows, 
viz.:  the  cloth,  saturated  with  an  aniline  salt,  is 
placed  on  an  insulated  metallic  plate,  inert  to  the 
aniline  salt,  and  connected  with  one  pole  of  a 
battery  or  other  electric  source.  The  other  pole 
is  connected  with  a  metallic  plate  on  which  the 
required  design  is  drawn.  On  the  passage  of  the 
current,  the  design  is  traced  in  aniline  black  on 
the  cloth.  A  minute  or  two  suffices  for  the 
operation. 

A  species  of  electrolytic  writing  is  obtained  on 
cloths  arranged  as  above  by  substituting  a  carbon 
pencil  for  the  metallic  plate.  On  writing  with 
this  pencil,  as  with  an  ordinary  pencil,  the  pas- 
sage of  the  current  so  directed  is  followed  by  the 
deposition  of  aniline  black. 

By  means  of  a  somewhat  similar  process  writ- 
ing  in  white  on  a  colored  ground  is  obtained. 

Dynamic  Electricity. — (See  Electricity, 
Dynamic?) 

Dynamics,  Electro That  branch 

of  electric  science  which  treats  of  the  action 
of  electric  currents  on  one  another  and  on 
themselves  or  on  magnets. 

The  principles  of  electro-dynamics  were  dis- 
covered by  Ampere  in  1821. 

A  convenient  form  of  apparatus,  for  showing 
experimentally  the  action  of  one  current  on 
another,  consists  of  two  upright  metallic  columns 


Dyn.J 


176 


[Dyn. 


or  pillars,  which  support  horizontal  metallic  arms 
containing  mercury  cups,  y,  and  c,  Fig.  216. 


Fig.  2  rb.     Deflection  of  a  Circuit  by  a  Current. 


The  circuit  is  bent  in  the  form  of  a  rectangle, 
circle  or  solenoid,  and  terminates  in  points  that 
dip  in  the  mercury  cups.  The  current  is  led  into 
and  out  of  the  apparatus  at  the  points  -}-  and  — 
at  the  base  of  the  upright  supports. 

When  a  magnet,  or  another  circuit,  is  ap- 
proached to  the  movable  circuit  thus  provided, 
attractions  or  repulsions  are  produced  according 
to  th2  position  of  the  magnet,  or  the  direction  of 
the  currents  in  the  two  circuits. 

If  a  magnet  A  B,  Fig.  217,  be  placed,  as  shown, 


Fig.  217.     Deflection  of  Circuit  by  a  Magnet. 

below  the  movable  circuit  C  C,  the  circuit  will 
tend  to  place  itself  at  right  angles  to  the  axis  of 
the  magnet.  This  movement  is  the  same  as 
would  occur  if  electric  currents  were  circulating 
around  the  magnet  in  the  direction.cf  the  assumed 
Amperian  cur  rents.  It  also  illustrates  the  prin- 
ciple of  the  electric  motor.  (See  Magnetism,  Am- 
pere's Theory  of.) 

Ampere  has  given  the  results  of  his  investigations 
as  to  the  mutual  attractions  and  repulsions  of  cur- 


rents in    the    following    statements,    which  are 
known  as  Ampere's  Laws  : 

(l.)  Parallel  portions  of  a  circuit  attract  one 
another  if  the  currents  in  them  are  flowing  in  the 
same  direction,  and 
repel  one  another  if 
the  currents  are  flow- 
ng  in  opposite  direc- 
tions. 

A  current  flowing 
through  a  spiral  tends 
to  shorten  the  spiral 
from  the  attraction  of 
the  parallel  currents  in  contiguous  turns. 

Similar  poles  of  two  solenoids  repel  each  other, 
as  at  A,  A',  Fig.  218,  because,  when  opposed  to 
each  other,  the  currents  that  produce  these  poles 


A          B 

Fig.  218.     Action  of  Solenoid 

Poles. 


Fig.  2  rq.    Antptre's  Stand. 

are  flowing  in   opposite  directions,  as  may  be 
seen  from  an^inspection  of  the  drawing. 

Dissimilar  solenoid  poles,  on  the  contrary,  at- 
tract each  other  as  at  A,  B,  in  Fig.  218,  since 


c 

Fig.  2  2O.     Electro- Dynamic  Attraction. 

the  currents  which  produce  them  flow  in  the  same 
direction. 

In  Fig.  219,  a  form  of  Ampere's  stand  is  shown, 
in  which  one  of  the  circuits  is  in  the  form  of  the 


177 


[Dyn. 


coil  M  N  ;  its  action  on  the  movable  circuit  C  B, 
is  to  repel  it,  since  the  currents,  as  shown,  are 
flowing  in  an  opposite  direction  in  the  adjacent 
portions  of  the  fixed  and  movable  circuits. 

(2.)  Two  portions  of  a  circuit  intersecting  each 
other  mutually  attract  each  other  when  the  cur- 
rents  in  both  circuits  flow 
either  towards  or  from 
the  point  of  intersection, 
but  repel  each  other  f 
they  flow  in  opposite  di- 
rections from  this  point. 

Thus,  in  Fig.  220,  the    , 
currents  in  both  circuits  P 
P  Q  and  A  B  C  D,  flow 
towards    and   from    the 


Fig.  22T.    Continuous 
Rotation  of  Current. 


point  of  intersection  Y,  and  attract  one  another 
and  cause  a  motion  until  the  two  circuits  are 
parallel. 

If  the  currents  flow  in  opposite  directions  they 
repel  each  other,  and,  if  free  to  move,  will  come 
to  rest  when  parallel  to  each  other  ;  therefore, 
two  portions  of  a  circuit  crossing  each  other  tend 
to  mjve  until  they  are  parallel,  and  their  currents 
are  flowing  in  the  same  direction. 

(3.)  Successive  portions  of  the  circuit  of  the 
same  rectilinear  current,  that  is,  a  current  flowing 
in  the  same  straight  line,  repel  one  another. 

A  circuit  O  A,  Fig.  221,  movable  on  O,  as  a 


Fig .  222.    Mutual  Action  of  Magnetic  Fields. 

centre,  will  be  continuously  rotated  in  the  direc- 
tion of  the  curved  arrow  by  the  rectilinear  cur- 
rent, P  Q;  for,  the  directions  of  the  currents  being 
as  shown  by  the  arrows,  there  will  be  attraction 
in  the  positions  (i)  and  (2),  and  repulsion  in  pe- 
tition (4). 

The  cause  of  the  mutual  attractions  and  repul- 
sions df  electric  circuits  will  readily  appear  from 
a  consideration  of  the  mutual  action  of  their 
magnetic  fields. 

Thus  an  inspection  of  Fig.  222  shows : 


(l.)  That  parallel  currents  flowing  in  the  same 
direction  attract,  because  their  lines  of  force  have 
opposite  directions  in  adjoining  parts  of  the  cir- 
cuit of  these  lines. 

(2.)  That  parallel  currents  flowing  in  opposite 
directions  repel,  because  their  lines  of  force  have 
the  same  directions  in  adjoining  parts  of  the  cir- 
cuit. 

These  laws  may  therefore  be  generalized  thus, 
viz. :  Lines  of  magnetic  force  extending  in  oppo- 
site dirtctions  attract  one  another;  lines  of 
magnetic  force  extending  in  the  same  direction 
repel  one  another. 

Ampere  proved  that  a  circuit,  doubled  on  itself 
so  that  the  current  flows  in  opposite  directions  in 
the  two  parts,  exerts  no  force  on  external  objects. 
This  expedient  is  adopted  in  resistance  coils  to 
prevent  any  disturbance  of  the  galvanometer 
needles.  He  also  showed  that  a  sinuous  circuit, 
or  one  bent  into  zigzags,  produces  the  same  effects 
of  attraction  or  repulsion  as  it  would  if  it  were 
straight.  (See  Coil,  Resistance.} 

The  term  sinuous  current  is  sometimes  applied 
to  the  current  in  a  sinuous  circuit.  (See  Current, 
Sinuous.)  This  must  be  distinguished  from  the 
term  sinusoidal  current,  which  applies  to  fluctua- 
tions in  the  current  and  not  to  peculiarities  in  the 
shape  of  the  conductor. 

When  two  inclined  magnets,  free  to  move,  are 
left  to  their  mutual  attractions  and  repulsions,  they 
gradually  come  to  rest  with  their  axes  parallel  to 
each  other. 

Two  conductors  through  which  electric  cur- 
rents are  flowing  act  on  one  another  as  two 
magnets  would. 

A  conductor  conveying  a  current  of  electricity 
tends  to  rotate  round  a  magnetic  pole.  A  mag- 
netic pole  tends  t._>  rotate  continuously  round  an 
electric  current. 

The  motion  of  a  magnet  near  a  conductor 
produces  an  electromotive  force  in  that  conductor 
provided  the  conductor  cuts  the  lines  offeree. 

A  magnetized  substance  becomes  magnetized 
when  placed  in  a  magnetic  field. 

A  conductor  through  which  a  current  of  elec- 
tricity is  passing  tends  to  wrap  itself  around  a 
neighboring  magnetic  pole.  The  following  ex- 
periments illustrate  this  tendency: 

(i.)  The  experiment  suggested  by  Lodge:  A 
powerful  current  of  electricity  is  passed  through 
some  eight  feet  in  length  of  gold  thread  such  as 
is  employed  for  making  lace.  The  thread  is 
hung  in  a  vertical  position,  near  a  vertical  bar 


178 


magnet.  As  soon  as  the  current  passes,  the 
thread  will  wrap  itself  around  the  bar  magnet, 
one  half  of  it  twisting  itself  round  the  north  pole, 
the  other  half  round  the  south  pole. 

(2.)  The  experiment  suggested  by  Professor  S. 
P.  Thompson:  An  electric  current  is  sent  through 
a  stream  of  mercury  while  it  is  flowing  between 
two  poles  of  a  powerful  electro-magnet;  when 
the  current  is  sent  through  the  magnet,  the 
stream  is  twisted  in  spiral  directions  which  vary, 
either  with  the  direction  of  the  current,  or  with 
the  direction  of  the  magnetic  polarity. 

(3.)  Somewhat  similar  effects  can  be  shown  by 
the  rotation  of  a  stream  cf  gas  round  a  magnetic 
pole  placed  in  an  exhausted  glass  receiver. 

Dynamo. — The  name  frequently  applied  to 
a  dynamo-electric  machine  used  as  a  gener- 
ator. (See  Machine,  Dynamo-Electric?) 

Dynamo  Balancing  Rheostat. — (See 
Rheostat,  Dynamo  Balancing?) 

Dynamo-Battery. — (See  Battery,  Dy- 
namo?) 

Dynamo  Brush  Trimmer. — (See  Trim- 
mer, Dynamo  Brush?) 

Dynamo,      Composite-Field  — A 

dynamo  whose  field  coils  are  series  and 
separately  excited. 

Additional  separately  excited  coils  placed  on 
the  field  of  a  series  wound  dynamo  render  it  self- 
regulating. 

A  composite  dynamo  is  a  form  of  compounded 
dynamo. 

Dynamo,  Compound-Wound. — A  com- 
pound-wound dynamo-electric  machine.  (See 
Machine,  Dynamo-Electric,  Compound- 
Wound?) 

Dynamo,  Contact  —  — A  form  of  dyna- 
mo in  which  the  space  between  the  arma- 
ture and  field  magnet  poles  is  so  reduced  that 
they  actually  touch  one  another. 

In  contact  dynamos  both  field  and  armature 
revolve.  This  form  of  dynamo  has  not  been  very 
successful  in  practice. 

Dynamo-Electric  Machine. — (See  Ma- 
chine, Dynamo-Electric?) 

Dynamo-Electric  Machine,  Alternating 
Current  — (See  Machine,  Dynamo- 
Electric,  Alternating  Current?) 


Dynamo-Electric  Machine  Armature. — 

(See  Armature,  Dynamo-Electric  Machine.} 
Dynamo-Electric      Machine      Armature 
Coils. — (See  Coils,  Armature,  of  Dynamo- 
Electric  Machine?) 

Dynamo-Electric  Machine  Armature 
Core. — (See  Core,  Armature,  of  Dynamo- 
Electric  Machine?) 

Dynamo-Electric  Machine  Battery. — 
(See  Battery,  Dynamo-Electric  Machine?) 

Dynamo-Electric  Machine,  Bi-Polar 

— (See  Machine,  Dynamo-Electric,  Bi- 
Polar?) 

Dynamo-Electric  Machine,  Collecting 

Brushes  of (See  Brushes,  Collecting, 

of  Dynamo-Electric  Machine?) 

Dynamo-Electric    Machine  Commutator 

(See  Commutator,  Dynamo-Electric 

Machine?) 

Dynamo-Electric  Machine,  Compound- 
Wound  -  -  — (See  Machine,  Dynamo- 
Electric,  Compound-  Wound?) 

Dynamo-Electric  Machine,  Generation  of 
Current  by fSee  Current,  Genera- 
tion of,  by  Dynamo-Electric  Machine?) 

Dynamo-Electric  Machine,  Field  Mag- 
nets —  — (See  Magnets,  Field,  of  Dynamo- 
Electric  Machine?) 

Dynamo-Electric  Machine,  Methods  of 
Increasing  the  Electromotive  Force  Gene- 
rated by (See  Force,  Electromotive, 

Generated  by  Dynamo-Electric  Machine, 
Method  of  Increasing?) 

Dynamo-Electric  Machine,  Mouse-Mill, 
Sir  William  Thomson's  -  —(See  Ma- 
chine, Dynamo-Electric,  Mouse-Mill,  Sir 
William  Thomson's?) 

Dynamo-Electric  Machine,  Multipolar 
— (See  Machine,  Dynamo-Electric, 
Multipolar?) 

Dynamo-Electric  Machine,  Pole-Pieces  of 

(See  Pole-Pieces  of  Dynamo-Electric 

Machine?) 

Dynamo-Electric  Machine,  Reversibility 

of (See  Machine,  Dynamo-Electric, 

Reversibility  of?) 


179 


Dynamo-Electric  Machine,  Varieties  of 

— (See  Machine,  Dynamo-Electric, 

Varieties  of.) 

Dynamo,  Inductor A  dynamo- 
electric  machine  fey  alternating  currents  in 
which  the  differences  of  potential  causing  the 
currents  are  obtained  by  magnetic  changes  in 
the  cores  of  the  armature  and  field  coils  by 
the  movement  past  them  of  laminated  masses 
of  iron  inductors. 

The  coils  corresponding  to  the  armature  and 
field  magnets  of  the  ordinary  dynamo  are  sta- 
tionary. The  laminated  masses  of  iron,  employed 
to  cause  magnetic  changes  in  the  cores  of  the  field 
and  armature  coils,  are  fixed  on  an  inductor  wheel 
which  is  rapidly  revolved  in  front  of  them.  The 
magnets  corresponding  to  the  field  magnets  are 
called  the  primary  poles,  and  are  magnetized  by 
an  exciter.  The  magnets  corresponding  to  the 
armature  are  called  the  secondary  poles  and  are 
placed  so  as  to  alternate  with  the  primary  poles. 
The  inductors  are  so  shaped  that  they  carry  the 
magnetism  of  one  pole  of  the  primary  magnet 
to  the  secondary  poles  when  the  inductor  is  in 
one  position,  and  of  the  opposite  pole  when  in  a 
slightly  different  position.  The  inductor  wheel 
therefore  acts  as  a  magnetic  commutator  and 
changes  the  position  of  the  secondary  magnet  as 
it  rotates,  thus  producing  electromotive  force. 
The  number  of  alternations  per  revolution  is 
equal  to  twice  the  number  of  inductors  placed  on 
the  inductor  wheel. 

Dynamo,  Inverted A  dynamo-elec- 
tric machine  in  which  the  armature  bore  or 
chamber  is  placed  below  the  field  magnet 
coils. 

The  term  inverted  is  used  in  contradistinction 
to  the  overtype  dynamo.  (See  Dynamo,  Over- 
type.} 

Dynamo,  Mouse  Mill A  form  of 

dynamo-electric  machine  designed  by  Sir 
William  Thomson  to  act  as  the  replenisher  of 
one  of  his  electrometers.  (See  Replenisher?) 

Dynamo,  Multiphase A  polyphase 

dynamo.  (See  Dynamo,  Polyphase.  Dyna- 
mo, Rotating  Current?) 

Dynamo,  Overtype A  dynamo- 
electric  machine,  the  armature  bore  or  cham- 
ber of  which  is  placed  above  the  field  magnet 
coils  instead  of  below  them  as  in  many  forms. 


The  overtype  form  of  dynamo  possesses  tha 
advantage  of  better  avoiding  magnetic  leakage. 

Dynamo,  Polyphase A  name  some- 
times applied  to  a  rotating  current  dynamo. 
(See  Dynamo,  Rotating  Current?) 

Dynamo,  Pyromagnetic A  name 

sometimes  applied  to  a  pyromagnetic  gen- 
erator. (See  Generator,  Pyromagnetic?) 

Dynamo,    Kotary-Phase A    term 

sometimes  employed  for  a  rotating  current 
dynamo.  (See  Dynamo,  Rotating  Current?) 

Dynamo,    Separately-Excited A 

separately-excited  dynamo-electric  machine. 
(See  Machine,  Dynamo-Electric,  Separ- 
ately-Excited?) 

Dynamo,  Series A   series-wound 

dynamo-  electric 
machine.  (SeeJ/a- 
chine,  Dynamo- 
Electric,  Series- 
Wound?) 

Dynamo,  Shunt 

— A  shunt- 
wound  dynamo- 
electric  machine. 
(See  Machine, 
Dynamo  -  Electric, 
Shunt-  Wound?) 

Dynamograph. 

—  A  term  some- 
times applied  to  a 
type-writing  tele- 
graph that  records 
the  message  in 
type-written  char- 
acters, both  at  the 
sending  and  the 
receiving  ends. 

Dynamometer.  [= 
— A  name  given  to 
a  variety  of  appar-    f,-f.  223,   Parsons'  Dyna- 
atus  for  measuring  mometer. 

the  power  of  an  engine  or  motor. 

In  all  dynamometers  the  strain  on  the  belt  or 
other  moving  part  is  measured,  say  in  pounds, 
and  the  speed  of  the  moving  part  is  also  measured 
in  feet  per  second.  The  product  of  the  strain  in 


180 


pounds  by  the  velocity  in  feet  per  second,  di- 
vided by  550,  will  give  the  horse  power. 

One  of  the  many  forms  of  dynamometers  is 
shown  in  Fig.  223.  It  is  known  as  Parsons'  Dy- 
namometer. 

The  driving  pulley  is  shown  at  A,  and  the 
driven  pulley  at  C.  Weights  hung  at  Q1,  are  va- 
ried so  as  to  maintain  the  axes  of  the  suspended 
pulleys,  D  and  B,  as  nearly  as  possible  at  the 
same  height.  Then  the  tension  Tx  and  T2,  on 
the  sides  O  and  O',  of  the  belts,  will  be  repre- 
sented by  the  following  equation  : 

T    _  T    _  ^  —  Q 
1  1  —  i  i  --  -  —  , 


Since  the  same  current  passes  through  both  tht 
fixed  and  movable  coils,  and  they  both  act  on 
each  other,  the  deflecting  force  here  is  evidently 
proportional  to  the  square  of  the  strength  of  th« 


from  which,  knowing  the  belt  speed,  the  horse 
power  may  be  deduced. 

There  are  several  other  forms  of  dynamometer, 
such  as  the  cradle  dynamometer,  in  which  the 
machine  is  supported  on  knife  edges  and  the 
torque  or  pull  exerted  on  or  by  the  machine  is 
balanced  by  weights  sliding  on  a  lever.  In  these 
dynamometers  the  power  is  transmitted  through 
them  and  they  are  therefore  called  transmission 
dynamometers. 

Dynamometer,  Electro  --  A  form  of 
galvanometer  for  the  measurement  of  electric 
currents. 

In  Siemens'  Electro-Dynamometer,  shown  in 
Fig.  224,  there  are  two  coils  ;  a  fixed  coil,  C,  se- 
cured to  an  upright  support,  and  a  movable  coil, 
L,  consisting  often  of  but  a  single  turn  of  wire. 
The  movable  coil  is  suspended  by  means  of  a 
thread  and  a  delicate  spring,  S,  capable  of  being 
twisted  by  turning  a  milled  screw  -head  through 
an  angle  of  torsion  measured  on  a  scale  by  means 
of  an  index  connected  to  the  screw-head.  The 
two  ends  of  the  movable  coil  dip  into  mercury 
cups  so  connected  that  the  current  to  be  measured 
passes  through  the  fixed  and  movable  coils  in 
series. 

When  ready  for  use  the  movable  coil  is  at  right 
angles  to  the  fixed  coil.  The  current  to  be  meas- 
ured is  then  sent  into  the  coils,  and  their  mutual 
action  tends  to  place  the  movable  coil  parallel  to 
the  fixed  coil  against  the  torsion  of  the  spring,  S. 
The  amount  of  this  force  can  be  ascertained  by 
determining  the  amount  of  torsion  required  to 
bring  the  movable  coil  back  to  its  zero  position. 


Fig,  224..     Siemens'  Electro- Dynamometer, 

current  to  be  measured.  The  deflecting  force, 
and  consequently  the  current  strength,  is  there- 
fore  proportional  to  the  square  root  of  the  angle 
of  torsion,  and  not  directly  to  the  angle  of  tor- 
sion. 

Dyne. — The  unit  of  force. 

The  force  which  in  one  second  can  impart 
a  velocity  of  I  centimetre  per  second  to  a 
mass  of  I  gramme. 

The  dyne  is  the  unit  of  force,  or  a  force  capa- 
ble, after  acting  for  one  second  on  a  mass  of  I 
gramme,  of  giving  it  a  velocity  of  I  centimetre 
per  second.  The  weight  of  a  body  in  dynes,  or  the 
force  with  which  it  gravitates,  is  equal  tj  its 
mass  in  grammes,  multiplied  by  the  acceleration 
imparted  to  it  in  centimetres  per  second.  For 
this  latitude  the  acceleration  is  about  981  centi- 
metres per  second. 


E,] 


181 


[Bad. 


E. — A  contraction  sometimes  used  for 
earth,, 

A  contraction  sometimes  used  for  electro- 
motive force,  or  E.  M.  F.,  as  in  the  well- 
known  formula  for  Ohm's  law, 


E.  M.  D.  P.— A  contraction  for  electro- 
motive difference  of  potential.  (See  Poten- 
tial, Difference  of,  Electromotive^) 

E.  M.  F. — A  contraction  generally  used  for 
electromotive  force.  (See  Force,  Electro- 
motive?) 

Earth. — A  fault  in  a  telegraphic  or  other 
line,  caused  by  accidental  contact  of  the  line 
with  the  ground  or  earth,  or  with  some  con- 
ductor connected  with  the  latter. 

This  is  more  frequently  called  a  ground. 

Earths  are  of  three  kinds,  viz. : 

(I.)  Deader  Total  Earth. 

(2.)  Partial  Earth. 

(3.)  Intermittent  Earth. 

The  term  earth  is  also  applied  to  a  plate  buried 
in  the  ground,  and  intended  to  make  a  good  con- 
tact between  the  earth  and  a  wire  circuit,  which 
is  connected  with  the  plate. 

Earth  Circuit.— (See  Circuit,  Earth?) 

Earth-Circuited  Conductor. — (See  Con- 
ductor, Earth-Circuited?) 

Earth  Currents. — Electric  currents  flow- 
ing through  different  parts  of  the  earth  caused 
by  a  difference  of  potential  at  different  points. 

The  causes  of  these  differences  of  potential  are 
Tarious  and  are  not  well  understood. 

Earth,  Dead  or  Total —A  fault  in 

a  telegraphic  or  other  line  in  which  the  line 
is  thoroughly  grounded  or  connected  with 
the  earth. 

Dead  earth  is  sometimes  called  total  earth. 

Earth-Grounded  Wire.— (See  Wire, 
Earth-  Grounded. ) 

Earth,  Intermittent A  swinging 

earth.  (See  Earth,  Swinging  or  Jntermit- 
tent?) 

Earth  or  Ground. — That  part  of  the  earth 


or  ground  which  forms  part  of  an  electric 
circuit. 

A  circuit  is  put  to  earth  or  ground  when  the 
earth  is  used  for  a  portion  of  the  circuit. 

The  resistance  of  an  earth  connection  may  vary 
in  time  from  the  following  causes,  viz.: 

( I. )  The  corrosion  of  the  ground  plate.  This  is 
especially  apt  to  occur  in  the  case  of  a  copper 
plate. 

(2.)  From  polarization,  a  counter-electro- 
motive force  being  produced,  thus  introducing  a 
spurious  resistance  into  the  circuit.  (See  Resist- 
ance, Spurious.) 

Earth,  Partial A  fault  in  a  tele- 
graphic or  other  line  in  which  the  line  is  in 
partial  connection  with  the  earth. 

The  term  partial  earth  is  used  in  contradistinc- 
tion  to  dead  or  total  earth. 

Earth,  Return A  circuit  in  which 

the  return  current  passes  back  to  the  source 
through  the  earth. 

Earth,  Swinging  or  Intermittent 

— A  fault  in  a  telegraphic  or  other  line  in 
which  the  action  of  the  wind,  or  occasional 
expansion  by  heat,  brings  the  line  into  inter- 
mittent contact  with  the  earth. 

Earth,  Total A  term  sometimes 

used  for  dead  earth.  (See  Earth,  Dead  or 
Total?) 

Ebonite. — A  tough,  hard,  black  substance, 
composed  of  India  rubber  and  sulphur,  which 
possesses  high  powers  of  insulation  and  of 
specific  inductive  capacity. 

Ebonite  is  often  called  vulcanite. 

Vulcanite  rubbed  with  cat-skin  acts  as  one  of 
the  best  known  substances  for  becoming  electri- 
fied by  friction.  For  this  purpose  both  substances 
should  be  thoroughly  dried. 

Economic  Co-efficient  of  Dynamo-Elec- 
tric Machine — (See  Co-efficient,  Economic, 
of  a  Dynamo-Electric  Machine?) 

Eddy  Currents. — (See  Currents,  Eddy.) 

Eddy  Currents,  Deep-Seated (See 

Currents,  Eddy,  Deep-Seated?) 

Eddy  Currents,  Superficial  —  — (See 
Currents,  Eddy,  Superficial?* 


Edd.j 

Eddy-Displacement  Currents. — (See  Cur- 
rents, Eddy-Displacement^ 

Eel,  Electric An  eel  possessing 

file  power  of  giving  powerful  electric  shocks = 

The  gymnotus  electricus. 

The  electricity  is  produced  by  an  organ  ex- 
tending the  entire  length  of 
the  body. 

According  to  Faraday,  the 
shock  given  by  a  specimen 
of  the  animal  examined  by 
him  was  equal  to  that  of  15 
Leyden  jars,  having  a  total 
surface  of  25  square  feet. 
Fig.  225  shows  the  general 
appearance  of  the  animal. 

Effect,  Acheson 

The  increase  in  the  electro- 
motive force  of  the  sec- 
ondary of  a  transformer  by 
the  action  of  the  changes 
in  temperature  of  its  core. 
(See  Electricity,  Cat.) 

Effect,   Chemical  Eel, 

— The  effect  occasioned  by  atomic  combina- 
tion, which  results  in  a  loss  of  those  properties 
or  peculiarities  by  which  the  substances  en- 
tering into  combination  are  ordinarily  recog- 
nized. 

Atomic  combination,  resulting  in  the  for- 
mation of  new  molecules 

The  formation  of  new  molecules  necessitates  the 
possession  by  the  new  substance  of  properties  dis- 
tinct and  separate  from  those  of  its  constituents. 

Black  carbon,  and  yellow  sulphur,  for  example, 
both  solids,  unite  chemically  to  form  a  frans- 
parent  colorless  liquid. 

Chemical  changes  differ  from  physical  changes, 
which  latter  can  occur  in  a  substance  without  the 
formation  of  new  molecules,  and  consequently 
without  the  loss  by  it  of  the  properties  it  ordi- 
narily possesses. 

Thus  a  sheet  of  vulcanite,  electrified  by  friction, 
Still  retains  its  characteristic  density,  shape,  color, 
etc. 

Effect,    Counter-Inductive —The 

opposal  of  current  or  charge  oy  means  of  a 
counter-electromotive  force  produced  by  ui- 
duction. 


Fig.  223.    Electric 


[Eft 


In  the  Thomson  counter-electromotive  force 
lightning  arrester,  a  counter-electromotive  force, 
produced  by  the  inductive  effects  of  the  passag« 
of  the  bolt  to  earth,  protects  the  instrument  by 
opposing  the  passage  of  the  bolt.  (See  Arrester% 
Lightning  Counter-Electromotive  Force.") 

Effect,  Edison An  electric  dis- 
charge which  occurs  between  one  of  the  ter- 
minals of  the  incandescent  filament  of  an 
electric  lamp,  and  a  metallic  plate  placed  near 
the  filament  but  disconnected  therefrom,  as 
soon  as  a  certain  difference  of  potential  is 
reached  between  the  lamp  terminals. 

The  effect  of  the  discharge  is  to  produce  a  cur- 
rent  in  a  circuit  connected  to  one  pole  of  the  lamp 
terminals  and  the  metallic  plate,  as  may  be  shown 
by  means  of  a  galvanometer. 

Effect,  Electrotonic An  altered 

condition  of  excitability  of  a  nerve  produced 
when  in  the  electrotonic  state.  (See  Elec- 
trotonus?) 

Effect,  Faraday The  rotation  of 

the  plane  of  polarization  of  a  beam  of  plane 
polarized  light  by  its  passage  through  a 
magnetic  field. 

Lodge  suggests  the  following  explanation  for 
the  Faraday  effect :  As  is  well  known,  a  strongly 
magnetized  medium  possesses  a  different  magnetic 
susceptibility  to  additional  magnetizing  forces  in 
the  same  direction  than  it  does  in  the  opposite 
direction.  It  therefore  follows  that  the  vibra- 
tions are  resolved  into  two  opposed  circular  com- 
ponents, which  travel  through  the  medium  with 
different  rates  of  velocity,  since  one  tends  to  mag- 
netize it  and  the  other  to  demagnetize  it.  The 
plane  of  rotation  will  therefore  be  rotated. 

He  also  suggests  the  following  explanation  for 
the  Faraday  effect,  viz.:  He  assumes  that  the 
Amperian  molecular  currents  in  such  substances 
as  exhibit  rotation  in  a  magnetic  field  do  not 
consist  of  two  equal  and  opposite  electrical  cur- 
rents,  but  that  one  of  the  currents  is  slightly 
stronger  than  the  other.  Suppose,  for  example, 
that  in  iron  the  positive  Amperian  current  is 
weaker  than  the  negative,  and  that  the  ether  as 
a  whole  is  rotating  with  the  negative  current. 
Any  ethereal  vibration  entering  such  a  medium 
will  begin  to  screw  itself  in  the  direction  opposed 
to  that  of  the  magnetizing  current.  In  copper, 
or  other  similar  substances,  the  rotation  should 
take  place  in  the  opposite  direction. 


Elf. 


183 


[Eff, 


Effect,  Ferranti • — An  increase  in  the 

electromotive  force,  or  difference  of  potential, 
of  mains  or  conductors  towards  the  end  of  the 
same  farthest  from  the  terminals  that  are  con- 
nected with  a  source  of  constant  potential. 

The  Ferranti  effect  refers  to  the  increase  of  the 
electromotive  force  on  the  mains  employed  in 
systems  for  the  transmission  of  electrical  energy 
\y  means  of  alternating  currents.  It  was  found, 
for  example,  in  the  currents  used  on  the 
mains  connected  with  one  of  Mr.  Ferranti's  alter- 
nating dynamos  and  leading  to  the  town  of  Dept- 
ford,  that  instead  of  finding  a  drop  of  potential  at 
the  ends  of  the  mains  farthest  from  the  dynamo, 
as  was  expected,  a  notable  increase  in  the  poten- 
tial occurred.  These  effects  were  observed  dur- 
ing the  laying  of  the  mains.  Testing  the  poten- 
tial by  placing  an  incandescent  lamp  in  the  circuit 
across  the  mains,  the  increase  of  the  potential 
with  the  increase  of  the  length  of  the  main  was 
shown  by  the  increased  brilliancy  of  the  light  of 
the  incandescent  lamp. 

Various  explanations  have  been  given  as  the 
cause  of  the  Ferranti  effect. 

Effect,  Hall  —A  transverse  elec- 
tromotive force,  produced  by  a  magnetic 
field  in  substances  undergoing  electric  dis- 
placement. 

This  transverse  electromotive  force  is  probably 


Fig.  2S(>.    Hall  Effect. 

due  to  magnetic  whirls,  in  a  manner  similar  to 
the  Faraday  effect. 

The  Hall  effect  is  produced  by  placing  a  very 
thin  metallic  strip,  conveying  an  electric  current, 
in  a  strong  magnetic  field. 

Tne  cross  A  B  C  D,  Fig.  226,  is  cut  out  of  a 


gold  leaf  or  other  very  thin  metallic  sheet.  The 
ends  A  and  B,  are  connected  with  the  terminals 
of  a  battery  S,  and  the  ends  C  and  D,  with  the 
galvanometer  G. 

None  of  the  battery  current  can  therefore  flow 
through  the  galvanometer. 

If,  now,  the  metallic  cross  be  placed  in  a  power- 
ful magnetic  field,  the  lines  of  force  of  which  are 
perpendicular  to  the  plane  of  the  cross,  the  deflec- 
tion of  the  galvanometer  needle  will  show  the 
existence  of  a  current,  which,  if  the  battery  cur- 
rent flows  in  the  direction  of  the  arrow,  or  from  A, 
to  B,  and  the  lines  of  magnetic  force  pass  through 
the  paper  from  the  front  to  the  back  of  the  sheet, 
when  the  cross  is  formed  of  gold,  silver,  platinum 
or  tin-foil,  will  flow  through  C  D,  from  C  to  D, 
but  in  the  opposite  direction  if  formed  of  iron. 
These  effects  cease  if  the  conductor  is  increased 
in  thickness  beyond  a  certain  extent. 

As  regards  the  production  of  the  Hall  effect  by 
the  influence  of  a  magnetic  field  on  conductors, 
Mr.  Shelford  Bidwell  suggests  that  since  magnet- 
ism affects  the  conductivity  of  metals  in  a 
complicated  manner,  it  is  possible  that  metallic 
substances  conveying  an  electric  current  in  a 
magnetic  field  are  more  or  less  strained  by  the 
mechanical  forces,  and  that,  therefore,  heat  may 
be  unequally  developed,  and  that  the  resistance 
thus  being  modified  in  places,  there  may  be  pro- 
duced disturbances  of  the  flow  which  may 
rapidly  produce  in  part  a  transverse  electromotive 
force. 

Effect,  Hall,  Real A  transverse  elec- 
tromotive force  produced  in  conductors  con- 
veying electric  currents,  by  magnetic  whirls, 
in  a  manner  similar  to  that  in  which  the  Far- 
aday effect  is  produced.  (See  Effect,  Fara- 
day^ 

Effect,  Hall,  Spurious An  appa- 
rent transverse  electromotive  force  produced 
in  conductors  conveying  electric  currents  in 
magnetic  fields,  by  changes,  produced  by  mag- 
netism, in  the  conductivity  of  the  metals,  and 
the  co'nsequent  production  of  local  distur- 
bances in  the  electrical  flow,  thus  resulting 
in  an  apparent  transverse  electromotive  force. 

Effect,  Impulsion The  restoration 

or  loss  of  sensitiveness  of  a  photo-voltaic  eel' 
to  the  action  of  light,  produced  by  means  of 
an  impulse  such  as  that  of  a  tap  or  blow,  or 
electro-magnetic  impulse. 


Eff.] 


184 


[Eff. 


Effect,  Joule — The  heating  effect 

produced  by  the  passage  of  an  electric  cur- 
rent through  a  conductor,  arising  merely  from 
the  resistance  of  the  conductor. 

The  rate  at  which  this  occurs  is  proportional  to 
the  resistance  of  the  conductor  through  which 
the  current  is  passing  multiplied  by  the  square 
of  the  current.  (See  Heat,  Electric. ) 

Effect,  Kerr A  term  applied  to 

the  electrostatic  optical  effect  discovered  by 
Dr.  Kerr,  viz.,  that  a  beam  of  plane  polarized 
light  is  elliptically  polarized  when  transmitted 
across  an  electrostatic  field. 

The  Kerr  effect  does  not  take  place  in  free  space, 
but  occurs  in  different  senses  or  directions  in  dif- 
ferent media. 

Like  the  Faraday  effect,  the  Kerr  effect  de- 
pends on  the  presence  of  a  dense  medium,  and  the 
direction  of  the  effect  depends  on  the  character  of 
the  medium. 

Effect,  Mordey  — A  term  some- 
times applied  to  a  decrease  in  the  value  of 
hysteresis  in  the  iron  of  a  dynamo  armature  at 
full  load. 

Effect,  Peltier The  heating  ef- 
fect produced  by  the  passage  of  an  electric 
current  across  a  thermo-electric  junction  or 
surface  of  contact  between  two  different  met- 
als. (See  Junction,  Ther mo-Electric.) 

The  passage  of  the  current  across  a  thermo- 
electric junction  produces  either  heat  or  cold.  If 
heat  is  produced  by  its  passage  in  one  direction, 
told  is  produced  by  its  passage  in  the  opposite 
direction.  The  Peltier  effect  may,  therefore, 
mask  the  Joule  effect. 

The  Peltier  effect  is  the  converse  of  the  thermo- 
electric effect,  where  the  unequal  heating  of  metal- 
lic junctions  results  in  an  electric  current.  (See 
Effect,  Joule.  Effect,  Thomson.) 

The  quantity  of  heat  absorbed  or  emitted  by 
the  Peltier  effect  is  proportional  to  the  current 
strength,  and  not,  as  in  the  Joule  effect,  to  the 
square  of  the  current. 

Effect,  Photo-Yoltaic The  change 

in  the  resistance  of  selenium  or  other 
substances  effected  by  their  exposure  to 
light.  The  photo-voltaic  effect  is  seen  in 
the  case  of  the  selenium  cell.  (See  Cell, 
Selenium?) 


Effect,  Seebeck A  term  sometimes 

used  instead  of  thermo-electric  effect.  (See 
Effect,  Thermo-Electric?) 

This  term  has  nearly  passed  out  of  use. 

Effect,  Skin The  tendency  of  alter. 

nating  currents  to  avoid  the  central  portions 
of  solid  conductors  and  to  flow  or  pass  mostly 
through  the  superficial  portions. 

The  so-called  skin  effect  is  more  pronounced 
the  more  frequent  the  alternations. 

Effect,  Thermo-Electric The  pro- 

duction  of  an  electromotive  force  at  a 
thermo-electric  junction  by  a  difference  of 
temperature  between  that  junction  and  the 
other  junction  of  the  thermo-electric  couple. 
(See  Couple,  Thermo-Electric.  Junction, 
Thermo-Electric^) 

Effect,  Thomson The  production  of 

an  electromotive  force  in  unequally  heated 
homogeneous  conducting  substances. 

A  term  also  applied  to  the  increase  or  de- 
crease in  the  differences  of  temperature  in  an 
unequally  heated  conductor,  produced  by  the 
passage  of  an  electrical  current  through  the 
conductor. 

The  Thomson  effects  vary  according  to  whether 
the  current  passes  from  a  colder  to  a  1  otter  part 
of  the  conductor,  or  the  reverse. 

The  Thomson  effects  differ  in  direction  in  differ- 
ent metals,  and  are  absent  in  lead.  Thomson  has 
pointed  out  the  similarity  between  this  species  of 
thermo-electric  phenomena,  and  convection  by 
heat,  or  the  phenomena  of  a  liquid  circulating  in 
a  closed  rectangular  tube,  under  the  influence  of 
differences  of  temperature,  in  -which  the  heated 
fluid  gives  out  heat  in  the  cooler  parts  of  the  cir- 
cuit, and  takes  in  heat  in  the  warmer  parts. 
This  would  presuppose  that  positive  electricity 
carries  heat  in  copper  like  a  real  fluid,  but  that 
in  iron  it  acts  as  though  its  specific  luat  were  a 
negative  quantity,  in  which  respect  it  is  unlike  a 
true  fluid. 

"  We  may  express,"  says  Maxwell,  "  both  the 
Peltier  and  the  Thomson  effects  by  stating  that 
when  an  electric  current  is  flowing  from  places  of 
smaller  lo  places  of  greater  thermo-electric  power, 
heat  is  absorbed,  and  when  it  is  flowing  in  the 
reverse  direction  heat  is  generated,  and  this 
whether  the  difference  of  thermo-electric  power 
in  the  two  places  arises  from  a  difference  in  the 


Eff.] 


185 


[Ele. 


nature  of  the  metals,  or  from  a  difference  of  tem- 
perature in  the  same  metal." 

Effect,     Toltaic A     difference     of 

potential  observed  at  the  point  of  contact  of 
two  dissimilar  metals. 

This  difference  of  potential  was  formerly  as- 
Cribed  to  the  mere  contact  of  dissimilar  metals, 
and  is  even  yet  believed  by  some  to  be  due  to 
such  contact.  It  is,  however,  perhaps  more  ac- 
curately ascribed  to  the  greate-r  affinity  of  oxygen 
of  the  air  for  the  positive  metal  than  for  the 
negative  metal;  that  is,  to  a  chemical  action  on 
the  positive  element  of  a  voltaic  couple. 

Effective  Electromotive  Force.— (See 
Force,  Electromotive,  Effective?) 

Effective  Secondary  Electromotive 
Force. — (See  Force,  Electromotive,  Second- 
ary, Effective?) 

Effects  of  Capillarity  on  Voltaic  Cells. — 
(See  Capillarity ;  Effects  of,  on  Voltaic  Cell?) 

Efficiency,  Commercial — The  useful 

or  available  energy  produced  divided  by  the 
total  energy  absorbed  by  any  machine  or  ap- 
paratus. 

The  Commercial  Efficiency  = 
W  _  W 

~M~       W  +  w  -f-  m, 

when  W  =  the  useful  or  available  energy;  M  = 
the  total  energy;  w,  the  energy  absorbed  by  the 
machine,  and  m,  the  stray  power,  or  power  lost 
in  friction  of  bearings,  etc.,  air  friction,  eddy  cur- 
rents, etc. 

Efficiency,  Commercial,  of  Dynamo 

— The  useful  or  available  electrical  energy  in 
the  external  circuit,  divided  by  the  total 
mechanical  energy  required  to  drive  the 
dynamo  that  produced  it.  (See  Co-efficient, 
Economic,  of  a  Dynamo-Electric  Machine?) 

Efficiency,  Electric The  useful  or 

available  electrical  energy  of  any  source, 
divided  by  the  total  electrical  energy. 

W 

The  electric   efficiency  = _,  where  W, 

W-f-w 

equals  the  useful  or  available  electrical  energy, 
and  w,  the  electrical  energy  absorbed  by  the 
machine.  , 

Efficiency  of  Conversion. — The  ratio  be- 
tween the  energy  present  in  any  result  and 
*he  energy  expended  in  producing  that  result. 


Efficiency  of  Conversion   of  Dynamo. — 

(See  Conversion,  Efficiency  of,  of  Dynamo?) 
Efficiency  of  Transformer. — (See   Trans- 
former, Efficiency  of?) 

Efficiency,  Quantity,  of  Storage  Battery 

The  ratio  of  the  number  of  ampere- 
hours  taken  out  of  a  storage  or  secondary 
battery,  to  the  number  of  ampere-hours  put  in 
the  battery  in  charging  it. 

Efficiency,  Real,  of  Storage  Battery 

— The  ratio  of  the  number  of  watt-hours 
taken  out  of  a  storage  battery,  to  the  number 
of  watt-hours  put  into  the  battery  in  charg- 
ing it. 

Efflorescence. — The  drying  of  crystals  by 
losing  their  water  of  crystallization  and  be- 
coming pulverulent  or  crumbling. 

The  term  is  sometimes  loosely  applied  to 
the  deposition  of  solid  matter  by  the  -crystal- 
lization of  a  salt,  above  the  line  of  the  liquid, 
on  the  surface  of  a  vessel  containing  a  vaporiz- 
able  saline  solution. 

The  liquid,  by  capillarity  in  a  porous  vessel,  or 
by  adhesion  to  the  walls  of  an  impervious  vessel, 
rises  above  the  level  of  the  main  liquid  line,  and, 
evaporating,  deposits  crystals  on  the  vessel. 

This  process  is  technically  called  creeping,  and 
is  often  the  cause  of  much  annoyance  in  voltaic 
cells. 

Egg,  Philosopher's A  name  given 

to  the  ovoidal,  or  egg-shaped  mass  of  light 
that  appears  when  a  convective  discharge  is 
taken  between  two  electrodes  in  a  partial 
vacuum. 

The  philosopher's  egg  is  but  one  of  the  shapes 
assumed  by  the  convective  discharge.  (See  Dis- 
charge, Convective.) 

Elasticity,  Electric The  quotient 

arising  from  dividing  the  electric  stress  by 
the  electric  strain. 

It  can  be  shown  mathematically  that  the  elec- 
tric elasticity  is  equal  to  4,  or  4  x  3. 1416,  divided 
by  the  specific  inductive  capacity. 

Electrepeter. — An  instrument  for  chang- 
ing the  direction  of  an  electric  current. 

The  old  term  for  switch,  key,  or  pole  changer. 
(Obsolete.) 

Electric. — Pertaining  to  electricity. 


Ele.] 


186 


[Ele. 


Electric  Absorption. — (See  Absorption, 
Electric?) 

Electric  Acoutemeter. — (See  Acouteme- 
ter,  Electric?) 

Electric  Actinometer. — (See  Actinomecer ; 
Electric?) 

Electric  Adhesion. — (See  Adhesion,  Elec- 
tric?) 

Electric  Aging  of  Alcohol. — (See  Alco- 
hol, Electric  Aging  of?) 

Electric  Alarm. — (See  Alarm,  Electric?) 

Electric  Alarm  Speaking-Tube  Mouth- 
Piece. — (See  Speaking-Tube  Mouth-Piece, 
Electric  Alarm?) 

Electric  Amalgam. — (See  Amalgam, 
Electric?) 

Electric  Ammunition  Hoist. — (See  Hoist, 
Ammunition,  Electric?) 

Electric  Analysis. — (See  Analysis,  Elec- 
tric?) 

Electric  Analyzer. — (See  Analyzer,  Elec- 
tric?) 

Electric  Anemometer. — (See  Anemome- 
ter, Electric?) 

Electric  Annealing. — (See  Annealing, 
Electric?) 

Electric  Annunciator  Clock. — (See 
Clock,  Electric  Annunciator?) 

Electric  Arc. — (See  Arc,  Electric?) 

Electric  Arc  Blow-Pipe. — (See  Blow- 
Pipe,  Electric  Arc?) 

Electric  Argand  Burner,  Hand-Lighter 
(See  Burner,  Argand  Electric,  Hand- 
Lighter?) 

Electric  Argand  Burner,  Plain-Pendant 

—(See  Bitrner,  Argand  Electric, 

Plain-Pendant?) 

Electric  Argand  Burner,  Ratchet-Pend- 
ant • (See  Burner,  Argand  Electric, 

Ratch  et-Penda  «/.) 

Electric  Balance.  —(Gee  Balance,  Elec- 
tric?) 

Electric  Balloon.— (Gee  Balloon,  Elec- 
tric?) 

Electric  Battery. — (Gee  Battery,  Elec- 
tric?) 


Electric  Bell,  Continuous-Sounding 

— (See  Bell,  Continuous-Sounding  Electric?) 

Electric    Bell,  Differential.— (See  Bell, 
Differential  Electric?) 

Electric    Bell,  Mechanical.— (See  Bell, 
Electro-Mechanical?) 

Electric  Bell  Pull.— (See  Pull,  Bell,  Elec- 
tric?) 

Electric  Bioscopy. — (See  Bioscopy,  Elec- 
tric?) 

Electric  Bi-Polar  Bath.— (See  Bath,  Bi- 
Polar?) 

Electric  Blasting. — (See  Blasting,  Elec- 
tric?) 

Electric     Bleaching. — (See    Bleaching, 
Electric?) 

Electric    Blow-Pipe. — (See    Blow-Pipe, 
Electric?) 

Electric  Boat. — (See  Boat,  Electric?) 
Electric  Bobbin. — (See  Bobbin,  Electric?) 
Electric  Body-Protector. — (See  Body-Pro- 
tector, Electric?) 

Electric  Boiler-Feed. — (See  Boiler-Feed, 
Electric?) 

Electric  Branding. — (See  Branding,  Elec- 
tric?) 

Electric  Breeze. — (See  Breeze,  Electric?) 
Electric  Bridge. — (See  Bridge,  Electric?) 
Electric  Buoy. — (See  Buoy,  Electric?) 
Electric    Burner. — (See    Burner,   Auto- 
matic Electric?) 

Electric  Buzzer. — (See  Buzzer,  Electric?) 
Electric  Cable.— (See  Cable,  Electric?) 
Electric  Calamine. — (See  Calamine,  Elec- 
tric?) 

Electric  Call-Bell.— (See  Bell,  Call.} 
Electric  Calorimeter. — (See  Calorimeter, 
Electric?) 

Electric  Candle.— (See  Candle,  Electric?) 
Electric     Case-Hardening. — (See     Case- 
Hardening,  Electric?) 

Electric  Cauterization. — (See  Cauteriza- 
tion, Electric?) 

Electric     Cauterizer. — (See    Cauterizer, 
Electric?) 


Ele.] 


187 


[Ele. 


Electric  Cautery. — (See  Cautery,  Elec- 
tric^ 

Electric  Charge. —  (See  Charge,  Electric?) 
Electric  Chimes. — (See  Chimes,  Electric?) 

Electric  Chronograph. — (See  Chrono- 
graph, Electric?) 

Electric  Chronoscope. — (See  Chronoscope, 
Electric?) 

Electric  Cigar-Lighter. — (See  Lighter, 
Cigar,  Electric?) 

Electric  Circuit. — (See  Circuit,  Electric.) 

Electric  Cleats.— (See  Cleats,  Electric?) 

Electric  Clepsydra. — (See  Clepsydra,  Elec- 
tric?) 

Electric  Clock.— (See  Clock,  Electric?) 

Electric  Coil.—  (See  Coil,  Electric?) 

Electric  Column. — (See  Column,  Elec- 
tric?) 

Electric  Communicator. — (See  Commu- 
nicator, Electric?) 

Electric  Conducting. — (See  Conducting, 
Electrical?) 

Electric  Conduction. — (See  Conduction, 
Electric.) 

Electric  Convection  of  Heat. — (See  Heat, 
Electric  Convection  of?) 

Electric  Cord.— (See  Cord,  Electric?) 
Electric   Counter. — (See    Counter,  Elec- 
tric?) 

Electric  Creeping. — (See  Creeping,  Elec- 
tric?) 

Electric  Cross. — (See  Cross,  Electric?) 
Electric  Crucible. — (See  Crucible,  Elec- 
tric?) 

Electric  Current. — (See  Current,  Elec- 
tric?) 

Electric  Cystoscopy. — (See  Cystoscopyt 
Electric?) 

Electric  Damping. — (See  Damping,  Elec- 
tric?) 

Electric  Death.— (See  Death,  Electric?) 
Electric     Decomposition. —  (See    Decom- 
position, Electric?) 
7— Vol.  ] 


Electric  Density. — (See  Density,  Elec- 
tric?) 

Electric  Deposition. — (See  Deposition, 
Electric?) 

Electric  Determination  of  Longitude. — 
(See  Longitude,  Electric  Determination 
of.) 

Electric  Displacement. — (See  Displace- 
ment, Electric.) 

Electric  Distillation.— (See  Distillation, 
Electric.) 

Electric  Door-Bell  Pull.— (See  Pull, 
Electric  Door-Bell?) 

Electric     Double-Refraction.  —  i  See 

Double-Refraction,  Electric?) 

Electric  Dyeing. — (See  Dyeing,  Electric?) 

Electric    Dynamometer,  Siemens'. — (See 
Dynamometer,  Electro?) 
Electric  Eel.— (See  Eel,  Electric?) 

Electric  Efficiency. — (See  Efficiency,  Elec- 
tric?) 

Electric  Elasticity. — (See  Elasticity,  Elec- 
tric?) 

Electric  Elevator. — (See  Elevator,  Elec- 
tric?) 

Electric  Endosmose. — (See  Endosmose, 
Electric?) 

Electric  Energy. — (See  Energy,  Electric?) 

Electric  Entropy. — (See  Entropy,  Elec- 
tric?) 

Electric  Escape. — (See  Escape,  Electric?) 

Electric  Etching. — (See  Etching,  Elec- 
tro?) 

Electric  Evaporation. — (See  Evapora- 
tion, Electric?) 

Electric  Excitability  of  Nerve  or  Mus- 
cular Fibre. — (See  Excitability,  Electric, 
of  Nerve  or  Muscular  Fibre?) 

Electric  Exhaustion. — (See  Exhaustion, 
Electric?) 

Electric  Expansion. — (See  Expansion, 
Electric?) 

Electric  Exploder.— (See  Exploder,  Elec- 
tric Mine?) 


Ele.] 


188 


[Ele. 


Electric  Explorer. — (See  Explorer,  Elec- 
tric?) 

Electric  Field.— (See  Field,  Electric) 

Electric    Figures,    Breath  — (See 

Figures,  Electric,  Breath) 

Electric  Figures,  Lichtenberg's  - 
(See  Figures,  Electric,  Lichtenberg's) 
Electric  Fishes. — (See  Fishes,  Electric) 
Electric  Fly.— (See  Fly,  Electric) 
Electric  Flyer. — (See  Flyer,  Electric) 
Electric  Fog.— (See  Fog,  Electric) 
Electric  Force. — (See  Force,  Electric) 
Electric  Furnace. — (See  Furnace,  Elec- 
tric) 

Electric  Fuse. — (See  Fuse,  Electric) 
Electric  Gas-Lighting. — (See  Gas-Light- 
ing, Electric) 

Electric  Gas-Lighting,  Multiple  - 
(See  Gas-Lighting,  Multiple  Electric) 

Electric  Gas-Lighting  Torch.— (See 
Torch,  Electric  Gas-Lighting) 

Electric  Gastroscope. — (See  Gastroscope, 
Electric) 

Electric  Gilding. — (See  Gilding,  Electric) 
Electric  Governor. — (See  Governor,  Elec- 
tric) 

Electric  Hand-Lighter  for  Argand 
Burner. — (See  Burner,  Argand  Electric 
Hand-L  ighter) 

Electric  Head-Bath.— (See  Bath,  Head, 
Electric) 

Electric  Head-Light.— (See  Head-Light, 
Locomotive,  Electric) 

Electric  Heat. — (See  Heat,  Electric) 
Electric  Heater. — (See  Heater,  Electric) 
Electric   Horse  Power. — (See  Power, 
Horse,  Electric) 

Electric  Hydrotasimeter. — (See  Hydro- 
tasimeter,  Electric) 

Electric  Ignition. — (See  Ignition,  Elec- 
tric) 

Electric  Images. — (See  Images,  Electric) 
Electric  Incandescence. — (See  Incandes- 
cence, Electric) 


Electric  Indicator  for  Steamships. — (See 
Indicator,  Electric,  for  Steamships) 

Electric     Indicators. — (See     Indicators, 
Electric^ 

Electric  Inertia. — (See  Inertia,  Electric) 

Electric      Insolation. — (See     Insolation, 
Electric) 

Electric  Installation. — (See  Installation, 
Electric) 

Electric     Insulation. — (See     Insulation, 
Electric) 

Electric    Irritability.— (See  Irritability, 
Electric) 

Electric  Jar. — (See  Jar,  Electric) 

Electric  Jewelry. — (See    Jewelry,   Elec- 
tric) 

Electric    Lamp,    Arc (See  Lamp, 

Electric,  Arc) 

Electric    Lamp-Bracket. — (See   Bracket, 
Lamp,  Electric) 

Electric  Lamp,  Incandescent (See 

Lamp,  Electric,  Incandescent) 

Electric   Lamp,  Semi-Incandescent  — 
— (See  Lamp,  Electric,  Semi-Incandescent) 

Electric  Lamp,  Socket  for. — (See  Socket, 
Electric  Lamp) 

Electric    Launch. — (See   Launch,    Elec- 
tric) 

Electric    Letter-Box. — (See    Letter-Box, 
Electric) 

Electric  Light. — (See  Light,  Electric) 

Electric  Lighting,  Central  Station 

— (See  Station,  Central) 

Electric   Lighting,   Isolated (See 

Lighting,  Electric,  Isolated) 

Electric  Light  or  Power    Cable. — (See 
Cable,  Electric  Light  or  Power) 

Electric  Lock. — (See  Lock,  Electric) 

Electric   Locomotive. — (See  Locomotive, 
Electric) 

Electric  Log. — (See  Log,  Electric) 

Electric  Loom. — (See  Loom,  Electric) 

Electric  Loop. — (See  Loop,  Electric) 

Electric  Machine,  Frictional (See 

Machine,  Frictional  Electric) 


Ele.] 


J89 


[Ele. 


Electric  Main. — (See  Main,  Electric?) 
Electric  Masses. — (See  Masses.  Electric) 
Electric  Measurements. — (See  Measure- 
ments, Electric.) 

Electric     Megaloscope. — (See     Megalo- 
scope,  Electric?) 

Electric  Meter. — (See  Meter.  Electric?) 
Electric  Mine-Exploder.— (See  Mine-Ex- 
ploder, Electro-Magnetic.     Fuse,  Electric?) 

Electric  Motor. — (See  Motor,  Electric?) 

Electric   Motor,  High-Speed (See 

Motor,  Electric,  High-Speed?) 

Electric   Motor,  Low-Speed (See 

Motor,  Electric,  Low-Speed?) 

Electric    Mnltipolar   Bath  -        — (See 
Bath,  Multipolar,  Electric?) 

Electric  Musket. — (See  Musket,  Electric?) 
Electric  Organ. — (See  Organ,  Electric?) 
Electric  Oscillations. — (See  Oscillations, 

Electric?) 

Electric  Osmose. — (See  Osmose,  Electric?) 
Electric     Osteotome. — (See     Osteotome, 

Electric?) 

Electric      Overtones.— (See      Overtones, 
Electric?) 

Electric  Pen.— (See  Pen,  Electric?) 
Electric  Pendant. — (See  Pendant,  Elec- 
tric?) 

Electric   Pendant-Lamps. — (See  Lamps, 
Electric  Pendant?) 

Electric     Pendulum. — (See    Pendulum, 
Electric?) 

Electric   Permeancy. — (See   Permeancy, 
Electric?) 

Electric   Phosphorescence. — (See    Phos- 
phorescence, Electric?) 

Electric  Photometer.— (See  Photometer?) 
Electric  Piano.— (See  Piano,  Electric?) 
Electric  Plow.— (See  Plow,  Electric?) 
Electric  Position-Finder. — (See  Finder, 
Position,  Electric?) 

Electric  Potential. — (See  Potential,  Elec- 
tric?) 


Electric  Power. — (See  Power,  Electric.) 
Electric  Probe. — (See  Probe,  Electric ) 
Electric  Prostration. — (See  Prostration, 
Electric.) 

Electric  Protection. — (See  Protection, 
Electric,  of  Houses,  Ships  and  Buildings.) 

Electric  Protection  of  Metals. — (See 
Metals..  Electrical  Protection  of) 

Electric  Pulse.— (See  Pulse,  Electrical?} 

Electric     Pyrometer,    Siemens'.— (See 

Pyrometer,  Siemens' .  Electric) 

Electric     Radiometer,   Crookes'  — 

(See  Radiometer,  Electric,  Crookes  ) 

Electric  Range-Finder.— (See  Finder, 
Range,  Electric?) 

Electric  Ratchet-Pendant  for  Argand 
Burner. — (See  Burner,  Argand  Electric, 
Ratchet-Pendant.) 

Electric  Ray.— (See  Ray,  Electric?) 

Electric  Reaction  Wheel.— (See  Wheel, 
Reaction,  Electric) 

Electric  Rectification  of  Alcohol. — (See 

Alcohol,  Electric  Rectification  of) 

Electric  Refining  of  Metals. — (See  Metals, 
Electric  Refining  of) 

Electric   Register,    Watchman's  — 

(See  Register,  Watchman's  Electric.) 

Electric  Registering  Apparatus. — (See 
Apparatus,  Registering,  Electric?) 

Electric  Relay-Bell.— (See  Bell.  Relay, 
Electric?) 

Electric  Repulsion. — (See  Repulsion, 
Electric?) 

Electric  Resistance. — (See  Resistance, 
Electric?) 

Electric  Resonance. — (See  Resonance, 
Electric) 

Electric  Retardation.—  (See  Retardation, 
Electric) 

Electric  Rings. — (See  Rings,  Electric) 

Electric  Safety  Lamps. — (See  Lamp, 
Electric  Safety.) 

Electric  Saw. — (See  Saw,  Electric) 


Ele.] 


190 


[Ele. 


Electric  Seismograph. — (See  Seismo- 
graph, Electric.} 

Electric  Shadow. — (See  Shadow,  Elec- 
tric) 

Electric  Shock.— (See  Shock,  Electric} 

Electric  Shower  Bath.— (See  Bath, 
Shower  Electric.} 

Electric  Shunt  Bell.— (See  Bell,  Shunt, 
Electric.} 

Electric  Single-Stroke  Bell.— (See  Bell, 
Single-Stroke  Electric} 

Electric  Siphon. — (See  Siphon,  Electric.} 

Electric  Soldering. — (See  Soldering, 
Electric} 

Electric  Sphygmograph. — (See  Sphygmo- 
graph,  Electrical} 

Electric  Sterilization. — (See  Steriliza- 
tion, Electric} 

Electric  Storm. — (See  Storm,  Electric} 

Electric  Striae. — (See  Sir  ice,  Electric} 

Electric  Submarine  Boat. — (See  Boat, 
Submarine,  Electric} 

Electric  Sunstroke. — (See  Sunstroke, 
Electric} 

Electric  Surgings. — (See  Surgings,  Elec- 
tric} 

Electric  Swaging. — (See  Swaging,  Elec- 
tric} 

Electric  Tanning. — (See  Tanning,  Elec- 
tric.} 

Electric  Target.— (See  Target,  Electric} 

Electric  Teazer.— (See  Teaser,  Electric 
Current} 

Electric  Telehydrobarometer. — (See  7V/- 
ehydrobarometer,  Electric} 

Electric  Tell-Tale  Signal.— (See  Signal, 
Electric  Tell-Tale} 

Electric  Tempering. — (See  Tempering, 
Electric. } 

Electric  Tension. — (See  Tension,  Elec- 
tric} 

Electric  Thermo-Call.— (See  Thermo- 
Call,  Electric} 

Electric  Thermometer. — (See  Thermom- 
eter, Electric} 


Electric      Throwback-Indicator. — ( See 

Indicator,  Electrical  Throwback} 

Electric  Time-Ball.— (See  Ball,  Electric 
Time} 

Electric  Time-Meter.— (See  Meter,  Elec- 
tric Time} 

Electric  Torpedo.— (See  Torpedo,  Elec- 
'  trie} 

Electric  Tower.— (See  Tower,  Electric} 

Electric  Tramway.— (See  Tramway,  Elec- 
tric} 

Electric  Transmitters. — (See  Transmit- 
ter, Electric} 

Electric  Trumpet.— (See  Trumpet,  Elec- 
tric} 

Electric  Turn-Table.— (See  Turn-Table, 
Electric} 

Electric  Typewriter. — (See  Typewriter, 
Electric} 

Electric  Yalve.— (See  Valve,  Electric} 

Electric  Valve  Burner,  Argand  — 
(See  Valve  Burner,  Argand  Electric} 

Electric  Varnish. — (See  Varnish,  Elec- 
tric} 

Electric  Vibrating  Burner. — (See  Burner 
Vibrating,  Electric} 

Electric  Volatilization. — (See  Volatiliza- 
tion, Electric} 

Electric  Water  or  Liquid  Level  Alarm. — 

(See  Alarm,  Water  or  Liquid  Level} 

Electric  Welding.— (See  Welding,  Elec- 
tric} 

Electric  Whirl.— (See  Whirl,  Electric} 

Electric  Whistle,  Automatic  Steam  — 
— (See    Whistle,    Steam,  Automatic    Elec- 
tric} 

Electric  Wood  Mouldings. — (See  Mould- 
ings, Electric  Wood} 

Electric  Work.— (See  Work,  Electric} 

Electrical  Controlling  Clock. — (See 
Clock,  Electrical  Controlling} 

Electrically. — In  an  electrical  manner. 

Electrically  Controlled  Clock.  —  (See 
Clock,  Electrically  Controlled} 


191 


Electrically  Discharge,  To (See 

Discharge,  To  Electrically^) 

Electrically  Discharging. — (See  Dis- 
charging, Electrically!) 

Electrically  Energizing. — (See  Energiz- 
ing, Electrically!) 

Electrically  Operated  Alarm. —  (See 
Alarm,  Electrically  Operated!) 

Electrically  Retarding. — (See  Retard- 
ing,  Electrically') 

Electrician. — One  versed  in  the  principles 
and  applications  of  electrical  science- 

Electrician,  Electro-Therapeutical 

—A  medical  electrician. 

Electrician,  Medical One  skilled 

in  the  application  of  electricity  to  the  human 
body  for  diagnosis  or  curative  purposes. 

A  medicai  electrician  should  possess  a  full 
knowledge,  not  only  of  the  principles  and  appli- 
cations of  electric  science,  but  also  of  physics  and 
chemistry  and  of  the  medical  sciences. 

Electricity. — The  name  given  to  the  un- 
known thing,  matter  or  force,  or  both,  which 
is  the  cause  of  electric  phenomena. 

Electricity,  no  matter  how  produced,  is  oe- 
lieved  to  be  one  and  the  same  thingc 

The  terms  frictional-electridty,  pyro-electricity, 
magneto-electricity,  voltaic  or  galvanic  electricity, 
thermo-electricity,  contact-electricity,  animal  or 
vegetable-electricity,  etc.,  etc.,  though  convenient 
for  distinguishing  iLeir  origin,  have  no  longer 
the  significance  formerly  attributed  to  them  as 
representing  different  kinds  of  the  electric  force. 
(See  Electricity,  Single-Fluid  Hypothesis  of. ) 

Electricity,  Accumulated — Elec- 
tricity collected  in  or  by  means  of  accumula- 
tors. 

Electricity,  Accumulating  — Ob- 
taining successively  increasing  electrical 
charges.  (See  Electricity,  Accumulation  of.) 

Electricity,  Accumulation  of A 

general  term  applied  indifferently  to — 

(i.)  The  gradual  collecting  of  electric 
energy  in  a  Leyden  jar  or  condenser. 

(2.)  The  increase  of  an  electric  charge  by 
the  action  of  various  devices  called  accumu- 
lators. 


(3.)  The  production  of  a  charge  by  the  use 
of  machines  called  influence  machines. 

(4.)  The  collection  of  electric  energy  in  the 
so-called  storage  batteries  or  accumulators. 

Electricity,  Animal  — -  — Electricity 
produced  during  life  in  the  bodies  of  animals. 

All  animals  produce  electricity  during  life.  In 
some,  such  as  the  electric  eel  or  torpedo,  the 
amount  is  comparatively  large.  In  others,  it  is 
small. 

Some  of  these  animals,  when  of  full  size,  are  able 
to  give  very  severe  shocks,  and  use  this  curious 
power  as  a  means  of  defense  against  their  enemies. 

If  the  spinal  cord  of  a  recently  killed  frog  be 
brought  into  contact  with  the  muscles  of  the 
thigh,  a  contraction  will  ensue. — (Matteucci.) 

The  nerve  and  muscle  of  a  frog,  connected 
by  a  water  contact  with  a  sufficiently  delicate 
galvanometer,  show  the  presence  of  a  current 
that  may  last  several  hours.  Du  Bois-Reymond 
showed  that  the  ends  of  a  section  of  muscular 
fibres  are  negative,  and  their  sides  positive,  and 
has  obtained  a  current  by  suitably  connecting 
them. 

In  the  opinion  of  some  electro-therapeutists  no 
electric  current  exists  in  passive,  normal  nerve  or 
muscular  tissue.  In  an  injured  tissue  a  current, 
called  a  demarcation  current,  is  produced.  (See 
Current,  Demarcation.) 

All  muscular  contractions,  however,  apparently 
produce  electric  currents. 

In  electro-therapeutics,  it  is  probable  that 
greater  success  would  accrue  in  practice  if  the 
human  body  were  regarded  as  an  electric  source 
as  well  as  an  electro-receptive  device. 

Electricity,  Atmospheric  —  — The  free 
electricity  almost  always  present  in  the  atmos- 
phere. 

The  following  facts  have  been  discovered  con- 
cerning  atmospheric  electricity,  viz. : 

(i.)  The  free  electricity  of  the  atmosphere  is 
generally  positive,  but  often  changes  to  negative 
on  the  approach  of  fogs  and  clouds. 

(2.)  It  exists  in  greater  quantity  in  the  higher 
regions  of  the  air  than  near  the  earth's  surface. 

(3.)  It  is  stronger  when  the  air  is  still  than 
when  the  wind  is  blowing. 

(4.)  It  is  subject  to  yearly  and  daily  changes 
in  its  intensity,  being  stronger  in  winter  than  ia 
summer,  and  at  the  -nicul -2  of  the  day  than  either 
at  the  Beginning  or  the  close. 


192 


Ulle 


Electricity,  Atmospheric,  Origin  of — - 

—The  exact  cause  of  the  free  electricity  of 
the  atmosphere  is  unknown. 

Peltier  ascribes  the  cause  of  the  free  electricity 
of  the  atmosphere  to  a  negatively  excited  earth, 
which  charges  the  atmosphere  by  induction.  (See 
Induction,  Electrostatic.)  Free  atmospheric  elec- 
tricity has  also  been  ascribed  to  the  evaporation 
of  water;  to  the  condensation  of  vapor;  to  the 
friction  of  the  wind;  to  the  motion  of  terrestrial 
objects  through  the  earth's  magnetic  field;  to  in- 
duction from  the  sun  and  other  heavenly  bodies; 
to  differences  of  temperature;  to  combustion,  and 
to  gradual  oxidation  of  plant  and  animal  life.  It 
is  possible  that  all  these  causes  may  have  some 
effect  in  producing  the  free  electricity  of  the  at- 
mosphere. 

Whatever  is  the  cause  of  the  free  electricity  ol  the 
atmosphere,  there  can  be  but  little  doubt  that  it 
is  to  the  condensation  of  aqueous  vapor  that  the 
high  difference  of  potential  of  the  lightning  flash 
is  due.  (See  Potential,  Difference  of. )  As  the 
clouds  move  through  the  air  they  collect  the  free 
electricity  on  the  surfaces  of  the  minute  drops  of 
water  of  which  they  are  composed,  and  when 
many  thousands  of  these  subsequently  collect  in 
larger  drops  the  difference  of  potential  is  tnor- 
mously  increased  in  consequence  of  the  equally 
enormous  decrease  in  the  surface  of  any  single 
drop  over  the  sum  of  the  surfaces  of  the  drops 
that  have  coalesced  to  form  it. 

Electricity,   Atom  of A   quantity 

of  electricity  equal  in  amount   to   that  pos- 
sessed by  any  chemical  monad  atom. 

Professor  Lodge  points  out  the  fact  that  the 
charge  of  a  monad  atom  of  any  element  is  the 
smallest  charge  a  body  can  possess,  and  is  pessibly 
as  indivisible  as  the  atom  itself.  He  points  out  the 
fact  that  chemical  affinity  or  atomic  attraction  may 
be  due  to  the  electrical  attraction  of  atoms  contain- 
ing unlike  charges;  that  although  the  difference  of 
potential  between  the  atoms  is  small,  probably 
somewhere  between  i  and  3  volts,  the  distances 
separating  them  are  so  very  small  that  their 
mutual  attractive  force  must  be  almost  infinitely 
great. 

As  D'Auria  has  pointed  out,  if  the  centres  of  at- 
traction  of  the  atoms  be  the  centres  of  the 
atoms  themselves,  then  the  atoms,  if  approached 
to  actual  contact,  would  be  separated  from  one 
another  by  a  distance  equal  to  half  th"  sum  of 
their  diameters.  If,  however,  the  centre  ot  at- 


traction be  situated  at  any  point  on  the  surface  of 
the  atoms  the  distance  of  separation  would  be- 
come equal  to  zero,  calling  d,  the  distance  be- 
tween them,  m  and  m1,  their  respective  masses, 
and  S,  a  co-effecient  varying  with  the  substance, 
and  f,  the  force  of  mutual  attraction,  then  : 

f  = 


from  which  we  see  that  the  value  of  fx  becomes 
infinite  when  the  atoms  are  in  contact. 

Electricity,  Cal  — Electricity  pro- 
duced by  changes  of  temperature  in  the  core 
of  a  transformer. 

The  changes  of  temperature  in  the  transformer 
core  can  produce  a  difference  of  potential  in  the 
secondary  circuit  which  increases  the  electro- 
motive force  induced  in  the  secondary  by  the 
variations  in  the  primary.  This  is  sometimes" 
called  ihe  Acheson  effect.  (See  Effect,  Ackeson.) 

Electricity,  Conservation  of  — A 

term  proposed  by  Lippman  to  express  the 
fact  that  when  a  body  receives  an  electric 
charge  in  the  open  air,  the  earth  and  heavenly 
bodies  receive  an  equal  and  opposite  charge, 
thus  preserving  the  sum  of  the  total  positive 
and  negative  electricities  in  the  universe. 

Electricity,    Contact   — Electricity 

produced  by  the  mere  contact  of  dissimilar 
metals. 

The  mere  contact  of  two  dissimilar  metals  re- 
sults ia  the  production  of  opposite  electrical 
charges  on  their  opposed  surfaces,  or  in  a  differ- 
ence of  electric  potential  between  these  surfaces. 
The  cause  of  this  difference  of  potential  is  now 
very  generally  ascribed  to  the  voltaic  couple  being 
surrounded  by  the  atmosphere,  the  oxygen  of 
which  acts  more  energetically  on  the  positive 
element  than  it  does  on  the  negative  element. 

The  mere  contact  of  dissimilar  metals  cannot 
produce  a  constant  electric  current.  An  electric 
current  possesses  kinetic  energy.  To  produce  a 
constant  electric  current,  therefore,  energy  must 
be  expended. 

The  voltaic  pile  through  the  contact  of  dis- 
similar metals  produces  a  difference  of  potential, 
yet  the  cause  of  the  current  is  to  be  found  in 
chemical  action.  (See  Cell,  Voltaic.) 

Electricity,  Disguised  -  —Dissimu- 
lated electricity.  (See  Electricity,  Dissimu- 
lated or  Latent.) 


193 


Ele 


Electricity,  Dissimulated  or  latent 

— The  condition  of  an  electric  charge  when 
placed  near  an  opposite  charge,  as  InaLeyden 
jar  or  condenser. 

In  this  case,  merely  touching  one  of  the 
charged  surfaces  will  not  effect  its  complete  dis- 
charge. 

Electricity  in  the  condition  of  a  bound  charge 
•vvas  formerly  called  latent  electricity.  This  term 
is  now  in  disuse.  Such  a  charge  \z  now  called  a 
bound  charge.  (See  Charge.  Bound.  Charge, 
Free.} 

Electricity,  Distribution  of •  — Va- 
rious combinations  of  electric  sources,  circuits 
and  electro-receptive  devices  whereby  elec- 
tricity generated  by  tha  sources  is  carried  or 
distributed  to  more  or  less  distant  electro- 
receptive  devices  by  means  of  the  various  cir- 
cuits connected  therewith. 

A  number  of  different  systems  for  the  distribu- 
tion of  electricity  exist.  Among  the  most  import- 
ant are  the  following,  viz. : 

(l.)  Direct  or  continuous-current  distribution. 

(2.)  Alternating-current  distribution. 

(3.)  Storage  battery  or  secondary  distribution. 

(4.)  Distribution  by  means  of  condensers. 

(5.)  Distribution  by  means  of  motor-gener- 
ators. 

Electricity,  Distribution  of,  by  Alterna- 
ting- Currents A  system  of  electric 

distribution  by  the  use  of  alternating  currents. 

A  system  of  electric  distribution  in  which 
lamps,  motors,  or  other  electro-receptive  de- 
vices are  operated  by  means  of  alternating 
currents  that  are  sent  over  the  line,  but  which, 
before  passing  through  said  devices,  are  modi- 
fied by  apparatus  called  transformers  or  con- 
verters. 

Such  a  system  embraces  : 

(I.)  An  alternating-current  dynamo-electric 
machine  or  battery  of  machines. 

(2.)  A  conductor  or  line  wire  arranged  in  a 
metallic  circuit. 

(3.)  A  number  of  converters  or  transformers 
whose  primary  coils  are  placed  in  the  circuit  of 
the  line  wire. 

(4.)  A  number  of  electro-receptive  devices 
placed  in  the  circuit  of  the  secondary  coil  of  the 
converter.  (See  Transformer.'] 


Electricity,  Distribution  of,  by  Alterna- 
ting Currents  by  Means  of  Condensers 

• — A  system  of  alternate  current  distribution 
in  which  condensers  are  employed  to  trans- 
form current  of  high  potential  received  from 
an  alternating  current  dynamo  to  currents 
of  low  potential  which  are  ted  to<he  -"nps  o* 
other  electro-receptive  devices, 

In  the  system  of  McElroy  the  conversion  from 
high  to  low  potential  is  obtained  by  making  the 
primary  plates  of  the  condensers  charged  by 
the  dynamo  smaller  than  the  secondary  plates, 
the  ratio  of  the  area  of  the  primary  plates  to  that 
of  the  secondary  plates  being  made  in  accordance 
with  the  ratio  of  conversion  desired. 

Electricity,  Distribution  of,  by  Commnta- 

ting  Transformers A  system  of  elec° 

trical  distribution  in  which  motor-generators 
are  used,  but  neither  the  armature  nor  the 
field  magnets  are  revolved,  a  special  commu- 
tator being  employed  to  change  the  polarity 
of  the  magnetic  circuits. 

Electricity,  Distribution  of,  by  Constant 

Currents A  system  for  the  distribution 

of  electricity  by  means  of  direct,  /.  <?.,  con- 
tinuous, steady  or  non-alternating  currents, 
as  distinguished  from  alternating  currents. 

Distribution  by  means  of  direct  currents  may 
be  effected  in  ?.  number  of  ways  ;  the  most  im- 
portant are: 

(i.)  Distribution  with  constant  current  or 
series  -  distribution . 

(2.)  Distribution  with  constant  potential  or 
multiple-distribution. 

Strictly  speaking,  these,  as,  indeed,  all  systems, 
are  systems  for  the  distribution  of  electric  energy 
rather  than  the  distribution  of  electricity. 

In  a  system  of  series-distribution,  the  electro- 
receptive  devices  are  placed  in  the  main  line  in 
series,  so  that  the  electric  current  passes  succes- 
sively through  each  of  them.  In  such  a  system 
each  device  added  increases  the  total  resistance  of 
the  circuit  so  that  the  total  resistance  is  equal  to 
the  sum  of  the  separate  resistances  on  the  line. 

In  order,  therefore,  to  maintain  the  current 
strength  constant,  independent  of  the  number  of 
devices  added  to  or  removed  from  the  circuit,  the 
electromotive  force  of  the  source  must  increase 
with  each  electro-receptive  device  added,  and  de- 
crease with  each  electro-receptive  device  taken 


Ele.| 


194 


[Ele. 


out-  If  the  number  of  electro-receptive  devices 
be  great,  such  a  circuit  is  necessarily  character- 
ized by  a  comparatively  high  electromotive  force. 

Since  the  current  passes  successively  through 
all  the  electro-receptive  devices,  an  automatic 
safety  device  is  necessary  in  ore]  er  to  automatically 
provide  a  short  circuit  of  comparatively  low  resist- 
ance oast  a  faulty  device,  and  thus  prevent  a 
single  faulty  device  from  invalidating  the  action 
of  all  other  devices  in  the  circuit. 

Arc  lamps  are  usually  connected  to  the  line 
circuit  in  series. 

In  a  system  of  multiple-distribution,  the  electro- 
deceptive  devices  are  connected  to  the  main  line 
or  leads  in  multiple-arc,  or  parallel,  so  that  each 
device  added  decreases  the  resistance  of  the  circuit. 
In  order,  therefore,  to  maintain  a  proper  current 
through  the  electro-receptive  devices,  the  mains 
must  be  kept  at  a  nearly  constant  difference  of 
potential.  The  electro-receptive  devices  employed 
in  such  a  system  of  distribution  are  generally  of 
high  electric  resistance,  so  that  the  introduction  or 
removal  of  a  few  of  the  electro-receptive  devices 
will  not  materially  alter  the  resistance  of  the  whole 
circuit,  and  will  not,  therefore,  materially  affect 
the  remaining  lights. 

In  this  system  automatic  safety  devices,  opera- 
ting by  the  fusion  of  a  readily  melted  alloy  or 
metal,  are  provided  for  the  purpose  of  preventing 
too  powerful  currents  from  passing  through  any 
branch  connected  with  the  main  conductors  or 
leads.  (See  Plug,  fusible.) 

Incandescent  lamps  are  generally  connected 
with  the  main  conductors  or  leads  in  parallel  or 
multiple-arc. 

Distribution  of  incandescent  lamps  by  series 
connections  is  sometimes  employed.  Such  lamps 
arc  usually  of  comparatively  low  resistance,  and 
are  provided  each  with  an  automatic  cut-out, 
which  establishes  a  short  circuit  past  the  lamp  on 
its  failure  to  properly  operate. 

During  the  passage  of  an  electric  current 
through  any  series-distribution  circuit,  energy  is 
expended  in  different  portions  of  the  circuit,  in 
proportion  to  the  resistance  of  these  parts.  In 
any  system,  economy  of  distribution  necessitates 
that  the  energy  expended  in  the  electro-receptive 
devices  must  bear  as  large  a  proportion  as  prac- 
ticable to  the  energy  expended  in  the  source  and 
leads.  In  series-distribution,  this  can  readily  be 
accomplished  even  if  the  resistance  of  the  leads  is 
comparatively  high,  since  the  total  resistance  of 
the  circuit  increases  with  every  electro-receptive 


device  added.  Comparatively  thin  wires  can 
therefore  be  employed  for  a  very  considerable 
extent  of  territory  covered,  without  very  great 
loss. 

In  systems  of  multiple-distribution,  however, 
this  is  impossible  ;  for,  since  every  electro-recep. 
tive  device  added  decreases  the  total  resistance  of 
the  circuit,  unless  the  resistance  o  f  the  leads  is 
correspondingly  decreased  the  economy  becomes 
smaller,  unless  the  resistance  of  the  leads  was  orig=> 
inally  so  low  as  to  be  inappreciable  when  com- 
pared with  the  change  of  resistance. 

In  systems  of  distribution  by  alternating  cur- 
rents this  is  avoided  by  passing  a  current  of  but 
small  strength  and  considerable  difference  of 
potential  over  a  line  connecting  distant  points, 
and  converting  this  current  into  a  current  of  largo 
strength  and  small  difference  of  potential  ai;  tKc 
places  where  it  is  required  for  use. 

Electricity,  Distribution  of,  by  Contin- 
uous Current,  by  Means  of  Condensers 

A  system  of  distribution  devised  by 

Doubrava,  in  which  a  continuous  current  is 
conducted  to  certain  points  in  the  line  where 
a  device  called  a  "  disjunctor  "  is  employed,  to 
reverse  it  periodically,  and  the  reversed  cur- 
rents so  obtained  directly  used  to  charge  con- 
densers in  the  circuit  of  which  induction  coils 
are  used. 

This  method  of  distribution  is  a  variety  of  dis- 
tribution by  means  of  constant  currents. 

The  condensers  are  used  to  feed  incandescent 
lamps  or  other  electro-receptive  devices. 

Electricity,  Distribution  of,  by  Continu- 
ous Current,  by  Means  of  Transformers 

—A  system  for  the  transmission  of  elec- 
tric energy  by  means  of  continuous  or  direct 
currents  that  are  sent  over  the  line  to  suitably 
located  stations  where  motor-dynamos  are 
used  for  transformers. 

The  dynamo  armature  is  used  with  two  sepa- 
rate circuits,  one  of  a  short  and  coarse  wire,  and 
one  of  a  long  fine  wire.  This  construction  will 
permit  the  conversion  of  a  high  to  a  low  potentia. 
or  vice  versa;  or  two  separate  dynamos  can  be 
placed  on  the  same  shaft  and  one  used  as  the 
motor. 

It  is  evident  that  a.  motor  generator  can  be  con- 
structed to  convert  continuous  currents  into  alter- 
nate, or  alternate  currents  into  continuous  cur- 


195 


[Ele. 


rents.    In  this  last  case  the  armature  and  fixed 
circuits  must  be  kept  separate. 

Another  form  of  continuous  current  conversion 
is  effected  by  means  of  the  motion  of  a  commutator 
which  effects  a  rotation  of  magnetic  polarity  in  a 
double- wound  armature  of  fine  and  coarse  wire. 

Electricity,  Distribution  of,  by  Motor 
Generators A  system  of  electric  dis- 
tribution in  which  a  continuous  current  of 
high  potential,  distributed  over  a  main  line,  is 
employed  at  the  points  where  its  electric  en- 
erg)-  is  to  be  utilized  for  driving  a  motor, 
which  in  turn  drives  a  dynamo,  the  current  of 
which  is  used  to  energize  the  electro-recep- 
tive devices. 

This  method  of  distribution  is  a  variety  of  dis- 
tribution by  means  of  continuous  or  direct  cur- 
rents. 

In  another  system  of  distribution  by  means  of 
motor  generators,  the  motor  and  dynamo  are 
combined  in  one  with  a  double-wound  armature, 
the  fine  wire  coils  in  which  receive  the  high  po- 
tential driving  current  and  the  coarse  wire  coils 
lurnish  the  low  potential  current  used  in  the  dis- 
tribution circuits. 

Electricity,  Double  Fluid  Hypothesis  of 
A  hypothesis  which  endeavors  to  ex- 
plain the  causes  of  electric  phenomena  by  the 
assumption  of  the  existence  of  two  different 
electric  fluids. 

The  double  fluid  hypothesis  assumes: 

(i.)  That  the  phenomena  of  electricity  are  due 
to  two  tenuous  and  imponderable  fluids,  the  posi- 
tive and  the  negative. 

(2.)  That  the  particles  of  the  positive  fluid  repel 
one  another,  as  do  also  the  particles  of  the  nega- 
tive fluid;  but  that  the  particles  of  positive  fluid 
attract  the  particles  of  the  negative  and  vice  -versa. 

(3.)  That  the  two  fluids  are  strongly  attracted 
by  matter,  and  when  present  in  it  produce  elec- 
trification. 

(4.)  That  the  two  fluids  attract  one  another  and 
unite,  thus  masking  the  properties  of  each. 

(5.)  That  the  act  of  friction  separates  these 
fluids,  one  going  to  the  rubber  and  the  other  to 
the  thing  rubbed. 

Professor  Lodge  is  disposed  to  favor  the  double 
rather  than  the  single  fluid  hypothesis.  He  states 
in  support  of  this  belief  the  following  facts,  viz. : 

(I.)  An  electric  wind  or  breeze  is  produced 
both  at  the  positive  and  negative  terminals  of  an 


electrical  machine,  and  this  whether  the  point  be 
attached  directly  to  these  terminals,  or  whether 
it  be  held  in  the  hand  of  a  person  near  them. 

(2.)  The  well  known  peculiarities  connected 
with  the  spark  discharge,  seen  in  Wheatstone's 
experiments  on  the  velocity  of  electricity. 

(3.)  An  electrostatic  strain  scarcely  affects  the 
volume  of  the  dielectric,  thus  suggesting  or  show- 
ing a  distorting  stress,  which  alters  the  shape  of 
the  substance  of  the  dielectric,  but  not  its  size. 

(4.)  The  effects  of  electrolysis  in  what  he  as- 
sumes the  double  procession  of  the  atoms  past 
each  other  in  opposite  directions. 

(5.)  The  phenomena  of  self-induction,  or  the 
behavior  of  a  thick  wire  on  an  alternating  current. 

(6.)  The  apparent  absence  of  momentum  in  the 
electric  current,  or  moment  of  inertia  in  an  elec- 
tro-magnet so  far  as  tested. 

Electricity,  Dynamic A  term  some- 
times employed  for  current  electricity  in  con- 
tradistinction to  static  electricity. 

Electricity,  Franklinic  — A  term 

sometimes  employed  in  electro-therapeutics, 
for  the  electricity  produced  by  a  frictional 
or  an  electrostatic-induction  machine.  (See 
Current,  Franklinic^] 

Electricity,  Frictional Electricity 

produced  by  friction. 

This  term  as  formerly  employed  to  indicate 
static  charges  as  distinguished  from  currents,  is 
gradually  falling  into  disuse,  and  the  frictional 
electric  machines  are  being  generally  replaced  by 
continuous-induction  machines,  like  those  of 
Holtz,  Topler-Holtz,  or  Wimshurst. 

The  character  of  the  charge  produced  by  fric- 
tion depends  on  .the  nature  of  the  rubber  as  well 
as  on  that  of  the  thing  rubbed. 

In  the  following  table  the  substances  are  so  ar- 
ranged that  any  one  in  the  list  becomes  positively 
electrified  when  rubbed  by  any  which  follows  it : 

Positive. 
Cat's  fur. 
Polished  glass. 
Wool. 

Cork  at  ordinary  temperatures. 
Coarse  brown  paper. 
Cork  heated. ' 
White  silk. 
Black  silk. 
Shellac. 
Rough  glass. — (Forbes.1) 


Ele.] 


196 


[Ele. 


Negative. 

It  will  be  seen  that  the  character  of  the  charge 
produced  by  friction  depends  on  the  character  of 
the  surfaces  rubbed.  This  is  seen  from  the  fore- 
going table,  where — 

(i.)  The  roughness  of  the  surface,  as  in  the 
case  of  glass,  produces  a  difference  in  the  nature  of 
the  charge;  thus,  rough  glass  is  at  the  bottom  of 
the  table,  and  smooth,  polished  glass  near  the  top. 

(2.)  The  state  of  the  surface  as  shown  by  the 
color.  Black  silk  rubbed  with  white  silk  is  nega- 
tive to  it 

(3.)  The  state  of  the  surface,  as  varied  by  the 
temperature.  Hot  cork  receives  a  negative  charge 
when  rubbed  against  a  piece  of  cold  cork. 

Forbes  has  pointed  out  that  these  differences 
are  probably  due  to  the  change  produced  in  the 
ability  of  the  surface  to  radiate  heat  or  light.  A 
substance  or  body  which  radiates  the  most  light 
or  heat  is  negative.  Thus,  a  hot  body  radiates 
more  heat  than  a  cold  body,  and  is  negative  to  it. 
A  rough  surface  is  negative  to  a  smooth  surface 
because  it  radiates  more  heat  than  a  smooth  sur- 
face. For  the  same  reason  a  black  surface  is  neg- 
ative to  a  white  surface.  In  this  latter  case,  how- 
ever, the  black  surface  is  the  worse  radiator  of 
light. 

The  contact  of  dissimilar  substances  has  long 
been  considered  by  some  as  one  of  the  requisites 
for  the  ready  production  of  electricity  by  friction. 
In  fact,  the  production  of  electricity  by  friction 
has  been  ascribed  as  an  effect  due  to  a  true  contact 
force  at  the  points  of  junction  of  the  rubber  and 
the  thing  rubbed.  Others,  however,  deny  the 
existence  of  a  true  contact  force  of  this  nature. 
(See  Force,  Contact.) 

Electricity,  Galvanic *— A  term  used 

by  some  in  place  of  voltaic  electricity.  (See 
Electricity,  Voltaic?) 

The  use  of  the  term  galvanic  electricity  would 
appear  to  be  less  logical  than  the  word  voltaic, 
since  Volta,  and  not  Galvani,  was  the  first  to  find 
out  the  true  origin  of  the  difference  of  potential 
produced  in  the  voltaic  pile. 

Electricity,  Hertz's  Theory  of  Electro- 
Magnetic  Radiations  or  Waves A 

theory,  now  generally  accepted,  which  regards 
light  as  one  of  the  effects  of  electro-magnetic 
pulsations  or  waves. 

The  recent  brilliant  researches  of  Dr.  Hertz,  of 
Carlsruhe,  show  that  when  an  impulsive  discharge 


is  passing  through  a  conductor,  ether  waves  are 
radiated  or  propagated  in  all  directions  in  the 
space  surrounding  the  conductor,  and  that  these 
waves  are  in  all  respects  similar  to  those  of  light, 
except  that  they  are  much  longer. 

The  electro-magnetic  waves  are  set  up  in  the 
luminiferous  ether,  and  move  through  it  with  the 
same  velocity  as  that  of  light.  Moreover,  electro- 
magnetic waves  possess  the  same  powers  of  reflec- 
tion, refraction,  interference,  resonance,  etc.,  etc., 
as  are  possessed  by  waves  of  light.  (See  Resona- 
tor, Electric.) 

When  an  alternating  or  simple  faradic  current 
or  pulse  of  electricity  is  transmitted  from  one  end 
to  the  other  of  a  long  metallic  conductor,  the 
pulses  are  believed  to  travel  through  the  universal  • 
ether  surrounding  the  conductor  rather  than 
through  the  conductor  itself.  The  velocity  of  this 
propagation  in  free  ether  is  the  same  as  that  of 
light,  and,  indeed,  is  identical  with  that  of  light 
itself.  In  the  inter-atomic  or  inter-molecular 
ether,  whether  of  conductors,  or  of  dielectrics,  the 
velocity  of  propagation  varies  with  the  nature  of 
the  medium. 

The  waves  produced  by  electric  pulses  are  of 
much  greater  length  than  those  of  light. 

According  to  Lodge  a  condenser  of  the  capacity 
of  a  micro-farad,  if  discharged  through  a  coil  hav- 
ing the  self-induction  of  I  ohm,  will  give  rise 
to  waves  in  the  ether  1,200  miles  in  length,  and 
will  possess  a  rate  of  oscillation  equal  to  about  157 
complete  wave-lengths  per  second. 

A  common  pint  Leyden  jar  discharged  through 
an  ordinary  discharging  rod,  will  produce  a  se- 
ries of  waves  about  15  to  20  metres  in  length, 
and  will  possess  a  rate  of  oscillation  equal  to  about 
ten  million  per  second. 

Lodge  calculates  that  in  order  to  obtain  the  short 
waves  requisite  to  influence  the  Tetina  of  the  eye, 
and  thus  produce  light,  the  circuit  in  which  the 
electrical  oscillations  take  place  must  have  at  least 
atomic  dimensions,  and  that  the  phenomena  of 
light  may  therefore  be  due  to  local  oscillations  or 
surgings  in  circuits  of  atomic  dimensions.  (See 
Light,  MaxwelFs  Electro-Magnetic  Theory  of.) 

Electricity,  Latent  —  — A  term  for- 
merly applied  to  bound  electricity. 

Electricity,  Magneto Electricity 

produced  by  the  motion  of  magnets  past  con- 
ductors, or  of  conductors  past  magnets. 

Electricity  produced   by  magneto-electric 


Ele.] 


197 


[Ele. 


induction.  (See  Induction,  Electro-Dyna- 
mic.} 

Electricity,  Multiple-Distribution  of,  by 

Constant  Potential  Circuit  —Any 

system  for  the  distribution  of  continuous  cur- 
rents of  electricity  in  which  the  electro- 
receptive  devices  are  connected  to  the  leads 
in  multiple-arc  or  parallel.  (See  Electricity, 
Distribution  of,  by  Constant  Currents?) 

Electricity,  Natural  Unit  of—  —A 
term  sometimes  used  in  place  of  an  atom  of 
electricity. 

The  natural  unit  of  electricity  is  an  amount 
equal  to  the  charge  possessed  by  any  monad  atom 
of  a  chemical  element. 

The  natural  unit  of  electricity  is  equal  to  the 
hundred  thousand  millionth  of  the  ordinary 
electrostatic  unit,  or  less  than  a  hundred  tril- 
iionth  of  a  coulomb.  (See  Electricity,  Atom  of.) 

Electricity,  Negative One  of  the 

phases  of  electrical  excitement. 

The  kind  of  electric  charge  produced  on 
resin  when  rubbed  with  cotton. 

Electricity,  Photo Electrical  dif- 
ferences of  potential  produced  by  the  action 
of  light. 

Electricity,  Plant Electricity  pro- 
duced in  plants  during  their  growth. 

Electricity,  Positive One  of  the 

phases  of  electric  excitement. 

The  kind  of  electric  charge  produced  on 
cotton  when  rubbed  against  resin. 

Electricity,  Production  of,  by  Light 

— The  production  of  electric  differences  of 
potential  by  the  action  of  light. 

Hallwachs  nas  noticed  that  a  clean  metallic 
plate  becomes  electrified  when  light  falls  upon  it. 

Differences  of  potential  are  produced  in  a 
selenium  cell  when  its  electrodes  are  unequally 
illumined.  A  thermo  cell  is  an  illustration  of  a 
difference  of  potential  produced  by  non-luminous 
radiation. 

Electricity,  Pyro Electricity  de- 
veloped in  certain  crystalline  bodies  by  un- 
equally heating  or  cooling  them. 

Tourmaline,  in  the  crystalline  state,  poscesses 
this  property  in  a  marked  degree.  When  a 
crystal  of  tourmaline  is  heated  or  cooled,  it 


acquires  opposite  electrifications  at  opposite 
ends  or  poles. 

In  the  crystal  of  tourmaline  shown  in  Fig.  227, 
the  end  A,  called  the  analogous  pole,  acquires  a 
positive  electrification, 
and  the  end  B,  called  the 
antilogous  pole,  a  nega- 
tive electrification,  -while 
the  temperature  of  the 
cry  stalls  rising.  While 
cooling,  the  opposite 
electrifications  are  pro- 
duced. 

A  heated  crystal  of 
tourmaline,  suspended  by 
a  fibre,  is  attracted  or 
repelled  by  an  electrified 
body  or  by  a  second 
heated  tourmaline,  in  the  Fis-  227.  Pyro  Electric 
same  manner  as  an  elec-  Crystal. 

trified  body. 

Many  crystalline  bodies  possess  similar  prop- 
erties. Among  these  are  the  ore  of  zinc  known 
as  electric  calamine  or  the  silicate  of  zinc,  bjra- 
cite,  quartz,  tartrate  of  potash,  sulphate  of 
quinine,  etc. 

Electricity,    Radiation     of — The 

radiation  of  electric  energy  by  means  of  elec- 
tro-magnetic waves.  (See  Electricity,  Hertz's 
Theory  of  Electro-Magnetic  Radiations  or 
Waves.) 

Electricity,  Resinous A  term 

formerly  employed  in  place  of  negative  elec- 
tricity. 

It  was  at  one  time  believed  that  all  resinous 
substances  are  negatively  electrified  by  friction. 
This  we  now  know  to  be  untrue,  the  nature  of 
electrification  depending  as  much  on  the  char- 
acter of  the  rubber  as  on  the  character  of  the 
thing  rubbed.  Thus  resins  rubbed  with  cotton, 
flannel  or  silk,  become  negatively  excited,  but  when 
rubbed  with  sulphur  or  gun  cotton,  positively 
excited.  The  te;ms  positive  and  negative  are 
now  exclusively  employed. 

Electricity,  Series  Distribution  of,  by 
Constant  Current  Circuit Any  sys- 
tem for  the  distribution  of  constant  currents 
of  electricity  in  which  the  electro-receptive 
devices  are  connected  to  the  line-wire  or 
circuit  in  series.  (See  Electricity,  Distribu~ 
tion  of,  by  Constant  Currents^ 


Jfle.] 


198 


[Ele. 


Electricity,  Single-Fluid  Hypothesis  of 

A  hypothesis  which  endeavors  to  ex- 
plain the  cause  of  electrical  phenomena  by 
the  assumption  of  the  existence  of  a  single 
electric  fluid. 

The  single-fluid  hypothesis  assumes: 

(i.)  That  the  phenomena  of  electricity  are  due 
to  the  presence  of  a  single,  tenuous,  imponder- 
able fluid. 

(2  )  That  the  particles  of  this  fluid  mutually 
repel  one  another,  but  are  attracted  by  all  matter. 

(3.)  That  every  substance  possesses  a  definite 
capacity  for  holding  the  assumed  electric  fluid, 
and,  that  when  this  capacity  is  just  satisfied  no 
effects  of  electrification  are  manifest. 

(4.)  That  when  the  body  has  less  than  this 
quantity  present,  it  becomes  negatively  excited, 
and  when  it  has  more,  positively  excited. 

(5.)  That  the  act  of  friction  causes  a  redistribu- 
tion of  the  fluid,  part  of  it  going  to  one  of 
the  bodies,  giving  it  a  surplus,  thus  positively 
electrifying  it,  and  leaving  the  other  with  a 
deficit,  thus  negatively  electrifying  it. 

The  single-fluid  hypothesis  has  been  provis- 
ionally accepted  by  some  with  this  modification, 
that  a  negatively  excited  body  is  thought  to  be 
the  one  which  contains  the  excess  of  the  assumed 
fluid,  and  a  positively  excited  body  the  one  which 
contains  the  deficit. 

They  make  this  change  on  account  of  the 
phenomena  observed  in  Crookes'  tube,  where 
the  molecules  of  the  residual  gas  are  observed  to 
be  thrown  off  from  the  negative  and  not  from  the 
positive  terminal.  (See  Tube,  Crookes'.) 

Another  view  considers  electricity  to  be  due  to 
differences  of  ether  pressure,  electricity  being  the 
ether  itself,  and  electromotive  force,  the  differences 
of  ether  pressures.  Positive  electrification  is  as- 
sumed to  result  from  a  surplusage  of  energy,  and 
negative  electrification  from  a  deficit  of  energy. 

At  the  present  time  the  views  of  Hertz  are 
generally  accepted.  (See  Electricity,  Hertz's 
Theory  of  Electro -Magnetic  Radiations  or  Waves.) 

Electricity,  Specific    Heat   of— A 

term  proposed  by  Sir  William  Thomson  to 
indicate  the  analogies  existing  between  the 
absorption  and  emission  of  heat  in  purely 
thermal  phenomena,  and  the  absorption  and 
emission  of  heat  in  thermo-electric  phe- 
nomena, (See  Heat,  Specific^ 
As  we  have  already  seen  heat  iz  either  given 


out  or  absorbed,  when  an  electric  current  passes 
from  one  metal  to  another  across  a  junction  be- 
tween them.  (See  Effect,  Peltier.') 

So,  too,  when  electricity  passes  through  an  un- 
equally heated  wire,  the  current  tends  to  increase 
or  decrease  the  differences  of  temperature,  ac- 
cording to  the  direction  in  which  it  flows,  and 
according  to  the  character  of  the  metal.  (See 
Effect,  Thomson.'] 

" If  electricity  were  a  fluid,"  says  Maxwell, 
"running  through  the  conductor  as  water  does 
through  a  tube,  and  always  giving  out  or  ab- 
sorbing heat  till  its  temperature  is  that  of  the 
conductor,  then  in  passing  from  hot  to  cold  it 
would  give  out  heat,  and  in  passing  from  cold  to 
hot  it  would  absorb  heat,  and  the  amount  of  this 
heat  would  depend  on  the  specific  heat  of  the 
fluid." 

Electricity,  Static A  term  applied 

to  electricity  produced  by  friction. 

The  term  static  electricity  is  properly  em- 
ployed in  the  sense  of  a  static  charge  but  not  as 
static  electricity,  since  that  would  indicate  a  par- 
ticular kind  of  electricity,  and,  as  is  now  gen- 
erally recognized,  electricity,  from  no  matter 
what  source  it  is  derived,  is  one  and  the  same 
thing. 

Electricity,  Storage  of  -  — A  term 
improperly  employed  to  indicate  such  a 
storage  of  energy  as  will  enable  it  to  directly 
reproduce  electric  energy. 

A  so-called  storage  battery  does  not  store  elec- 
tricity, any  more  than  the  spring  of  a  clock  can 
be  said  to  store  time  or  sound.  The  spring  stores 
muscular  energy,  i.  e.,  renders  the  muscular 
kinetic  energy  potential,  which,  again  becoming 
kinetic,  causes  the  works  of  the  clock  to  move 
or  strike. 

In  the  same  way  in  a  so-called  storage  battery, 
the  energy  of  an  electric  current  is  caused  to 
produce  electrolytic  decompositions  of  such  a 
nature  as  independently  to  produce  a  current  on 
the  removal  of  the  electrolyzing  current.  (See 
Cell,  Secondary.  Cell,  Storage.) 

Electricity,  Thermo  -  —Electricity 
produced  by  differences  of  temperature  at  the 
junctions  of  dissimilar  metals. 

If  a  bar  of  antimony  is  soldered  to  a  bar  of  bis- 
muth, and  the  free  ends  of  the  two  metals  are 
connected  by  means  of  a  galvanometer,  an  appli- 
cation of 'neat  to  the  junction,  so  as  to  raise  its 


Ele.J 


199 


[Ele. 


temperature  above  the  rest  of  the  circuit,  will  pro- 
duce a  difference  of  potential,  which,  if  neutral- 
ized, will  cause  a  current  to  flow  across  thejuat- 
tion  from  the  bismuth  to  the  antimony  (against 
the  alphabet,  or  from  B  to  A).  If  the  junction  be 
cooled  below  the  rest  of  the  circuit,  a  current  is 
produced  across  the  junction  from  the  antimony 
to  the  bismuth  (with  the  alphabet,  or  from  A  to  B). 
These  currents  are  called  thermo-electric  currents, 
and  are  proportional  to  the  differences  of  tem- 
perature. 

Even  the  same  metal,  in  different  physical 
states  or  conditions,  such  as  a  wire,  part  of  which 
is  straight  and  the  remainder  bent  into  a  spiral  as 
at  H  C,  Fig.  228,  if  heated  at  F  by  the  flame  of 

F. 


Fig    228.     Tfier  mo- Electricity. 

a  lamp  will  have  a  difference  of  potential  devel- 
oped in  it. 

The  same  thing  may  also  be  shown  by  placing 
»  cylinder  of  bismuth  J,  Fig.  229,  in  a  gap  in  a 

A 


Fig,  22().     Thermo- Electric  Circuit. 

hollow  rectangle  of  copper  A  B,  inside  of  which 
a  magnetic  needle,  M,  is  supported. 

The  rectangle  of  copper  being  placed  in  the 
magnetic  meridian,  on  heating  the  junction  by  the 
flame  of  a  lamp  F,  the  needle  will  be  deflected 
by  a  current  produced  by  the  difference  of  tem- 
perature. 

Thermo-electricity  is  generally  obtained  by 
means  of  the  combination  of  a  thermo-electric 
couple,  in  a  thermo-electric  cell.  (See  Couple, 
Thermo-electric.  Cell,  Thermo- Electric.'] 

Since  the  difference  of  potential  produced  by 
a  single  thermo-electric  couple  is  small,  a  number 
of  such  couples  or  cells  are  generally  connected  in 


series  to  produce  a  thermo-electric  battery.  (See 
Battery,  Thermo-electric. ) 

Electricity,    Unit    Quantity    of 

The  quantity  of  electricity  conveyed  by  unit 
current  per  second. 

The  practical  unit  quantity  of  electricity  is  the 
coulomb,  which  is  the  quantity  conveyed  by  a 
current  of  one  ampere  in  one  second. 

Electricity,   Unit  Quantity  of,  Natural 

The  quantity  of  electricity  pos- 
sessed as  a  charge  by  any  elementary  monad 
atom.  (See  Electricity,  Atom  of.) 

Electricity,  Varieties  of A  classi- 
fication of  electricity  according  to  its  state  of 
rest  or  motion,  or  to  the  peculiarities  of  its 
motion. 

Lodge  classifies  the  different  varieties  of  elec- 
tricity as  follows,  viz. : 

(i.)  Electricity  at  Rest,  or  Static  Electricity. 

This  branch  of  electric  science  treats  of  phenom- 
ena belonging  to  stresses  and  strains  in  insulated 
media,  when  brought  into  the  neighborhood  of 
electric  charges,  together  with  the  modes  of  ex- 
citing such  electric  charges,  and  the  laws  of  their 
interactions. 

(2.)  Electricity  in  Locomotion,  or  Current  Elec- 
tricity. 

This  branch  of  electric  science  treats  of  the  phe- 
nomena produced  in  metallic  conductors,  chem- 
ical compounds  and  dielectric  media,  by  the  pas- 
sage of  electricity  through  them,  and  the  modes 
of  exciting  electricity  into  motion,  together  with 
the  laws  of  its  flow. 

(3.)  Electricity  in  Rotation,  or  Magnetism. 

This  branch  of  electric  science  treats  of  the  phe- 
nomena produced  in  electricity  in  whirling  or 
vortex  motion,  the  manner  in  which  such  whirls 
may  be  produced,  the  strains  and  stresses  which 
they  produce,  and  the  laws  of  their  interactions. 

(4.)  Electricity  in  Vibration,  or  Radiation. 

This  branch  of  electric  science  treats  of  the  study 
of  the  propagation  of  periodic  or  undulatory  dis- 
turbances through  various  kinds  of  media,  the 
laws  regulating  wave  velocity,  wave  length,  re- 
flection, interference,  dispersion,  polarization  and 
other  similar  phenomena  generally  studied  under 
light. 

A  misleading  classification  of  electricity  is 
sometimes  made  according  to  the  sources  which 
produce  it.  This  is  misleading,  since  electricity, 
no  matter  how  produced,  is  one  and  the  same. 


Ele.] 


200 


[Ele. 


The  so-called  varieties  of  electricity  may  be  di- 
vided int'>  different  classes  according  to  the  nature 
of  the  source.  The  principles  of  these  are  as  fol- 
lows : 

(l.)  Frictional- Electricity,  or  that  produced  by 
the  fricti  m  of  one  substance  against  another. 

(2.)  Voltaic-Electricity,  or  that  produced  by 
the  contact  of  dissimilar  substances  under  the  in- 
fluence of  chemical  action. 

(3.)  Thermo-Electricity,  or  that  produced  by 
differences  of  temperature  in  a  thermo  couple. 

(4.)  Pyro-Electricity,  or  that  produced  by  dif- 
ferences of  temperature  in  certain  crystalline 
solids. 

(5.)  Magneto-Electricity,  or  that  produced  by 
the  motion  of  a  conductor  through  the  field  of 
permanent  magnets.  This  is  a  variety  of — 

(6.)  Dynamo-Electricity,  or  that  produced  by 
moving  conductors  so  as  to  cut  lines  of  magnetic 
force. 

(7.)  Vital-Electricity,  or  that  produced  under 
the  influence  of  life  or  accompanying  life. 

Electricity,  Titreous A  term  for- 
merly employed  to  indicate  positive  elec- 
tricity. 

It  was  formerly  believed  that  the  friction  of 
glass  with  other  bodies  always  produces  the 
same  kind  of  electricity.  This,  however,  is  now 
known  not  to  be  the  case. 

The  term  is  now  replaced  by  positive  elec- 
tricity. (See  Electricity,  Resinous.} 

Electricity,  Yoltaic Differences  of 

potential  produced  by  the  agency  of  a  vol- 
taic cell  or  battery. 

Electricity  is  the  same  thing  or  phase  of  energy 
by  whatever  source  it  is  produced. 

Electrics. — Substances  capable  of  becom- 
ing' electrified  by  friction. 

Substances  like  the  metals,  which,  when  held 
in  the  hand  could  not  be  electrified  by  friction 
were  formerly  called  non-electrics. 

These  terms  were  used  by  Gilbert  in  the  early 
history  of  the  science. 

This  distinction  is  not  now  generally  employed 
since  conducting  substances  if  insulated,  may  be 
electrified  by  friction. 

Electriflable. — Capable  of  being  endowed 
with  electric  properties. 

Electrification.— The  act  cf  becoming 
electrified. 

The  production  of  an  electric  charge. 


Electrified  Body.— (See  Body,  Electri- 
fied) 

Electrify. — To  endow  with  electrical  prop- 
erties. 

Electrine. — Relating  to  electrum,  or  am- 
ber. 

Electrization,  Therapeutical — Sub- 
jecting different  parts  of  the  human  body  to 
the  action  of  electric  currents  for  the  cure  of 
diseased  conditions. 

Electro-Biology. — (See  Biology,  Electro) 

Electro-Brassing. — (See  Brassing,  Elec- 
tro) 

Electro-Bronzing. — (See  Bronzing,  Elec- 
tro) 

Electro  -  Capillary  Phenomena. — (See 
Phenomena,  Electro-Capillary) 

Electrocesis. — A  word  proposed  for  cur- 
ing by  electricity. 

Electro-Chemical  Equivalent.  —  (See 
Eqtiivalent,  Electro-Chemical) 

Electro-Chemical  Meter. — (See  Meter, 
Electro-Chemical) 

Electro-Chemical  Telephone. — (See  Tele- 
phone, Electro-Chemical) 

Electro-Chemistry.  —  (See  Chemistry, 
Electro) 

Electro-Chromic  Rings. — (See  Rings, 
Electro-Chromic) 

Electro-Contact  Mine. — (See  Mine,  Elec- 
tro-Contact) 

Electro-Coppering.  —  (See  Coppering, 
Electro) 

Electro-Crystallization. — (See  Crystalli- 
zation, Electro) 

Electrocution. — Capital  punishment  by 
means  of  electricity. 

Electrode. — Either  of  the  terminals  of  an 
electric  source. 

The  term  was  applied  b)  Faraday  to  cither  o* 
the  conductors  placed  in  an  electrolytic  bath  and 
conveying  the  current  into  it,  and  this  is  its  strict 
meaning.  The  terms  pole  or  terminal  apply  to 
the  ends  of  a  break  in  any  electric  circuit. 

Electrode,  Aural  -  — A  therapeutic 
electrode,  shaped  for  the  treatment  of  the 


E!e.] 


201 


[Ele. 


ear.  (See  Electrode.  Electro-Thera- 
peutic^] 

Electrode,    Brush A    therapeutic 

electrode  fashioned  like  a  wire  brush  or  other 
conducting  brush.  (See  Electrode,  Electro- 
Therapeutic^ 

Electrode,  Cautery-Knife A  knife- 
shaped  electrode,  that  is  rendered  incan- 
descent by  the  passage  of  the  electric  cur- 
rent. 

Electrode,  Clay A  therapeutic  elec- 
trode of  clay  shaped  to  fit  the  part  of  the 
body  to  be  treated.  (See  Electrode,  Electro- 
Therapeutic^] 

Electrode,  Disc A  disc-shaped  elec- 
trode employed  in  electro-therapeutics.  (See 
Electrode,  Electro-  Therapeutic?) 

Electrode,  Dry A  therapeutic  elec- 
trode applied  in  a  dry  state.  (See  Electrode, 
Electro-  Therapeutic?) 

Electrode,  Electro-Therapeutic 

In  electro-therapeutics  the  electrode  mainly 
concerned  in  the  treatment  or  diagnosis  of  the 
diseased  parts. 

Either  the  positive  or  the  negative  electrode 
may  be  the  therapeutic  electrode,  and  one  or  the 
other  is  employed  according  to  the  particular 
character  of  the  effect  it  is  desired  to  obtain. 
The  other  electrode  is  placed  at  any  convenient 
and  suitable  part  of  the  body,  and  is  called  the 
indifferent  electrode, 

The  therapeutic  electrode  is  generally  placed 
nearer  the  organ  or  part  to  be  treated  than  the 
indifferent  electrode. 

Electrode-Handle,  Pole-Changing  and 
Interrupting  —  — A  handle  provided  for 
the  ready  insertion  of  electro-therapeutic 
electrodes,  and  provided  with  means  for  inter- 
rupting or  changing  the  direction  of  the  cur- 
rent. 

Electrode,  Illumined  —  — That  elec- 
trode of  a  selenium  cell  which  is  exposed  to 
the  light.  (See  Cell,  Selenium?) 

Electrode,  Indifferent In  electro- 
therapeutics the  electrode  that  is  employed 
merely  to  complete  the  circuit  through  the 
organ  or  part  subjected  to  the  electric  cur- 


rent, and  is  not  directly  concerned  in  the 
treatment  or  diagnosis  of  the  diseased  parts. 
Either  the  positive  or  the  negative  electrode 
may  be  the  indifferent  electrode.  (See  Electrode, 
Electro-  Therapeutic.) 

Electrode,  Moist A  therapeutic- 
electrode  applied  in  a  moist  condition.  (See 
Electrode,  Electro-  Therapeutic?) 

Electrode,  Needle A  therapeutic 

electrode  in  the  shape  of  a  needle,  and  em- 
ployed for  electrolytic  treatment.  (See  Elec- 
trode, Electro-  Therapeutic?) 

Electrode,  Negative The  electrode 

connected  with  the  negative  pole  of  an  elec- 
tric source. 

Electrode,  Non-Illumined — That 

electrode  of  a  selenium  cell  that  is  protected 
from  the  direct  action  of  light.  (See  Cell,  Sel- 
enium?) 

Electrode,   Non- Wasting A  term 

sometimes  applied  to  the  negative  electrode 
of  an  arc-lamp  when  made  of  iridium  or  other 
similar  material. 

Electrode,  Positive The  electrode 

connected  with  the  positive  pole  of  an  electric 
source. 

Electrode,  Rectal A  therapeutic 

electrode,  suitably  shaped  for  the  treatment  of 
the  rectum.  (See Electrode,  Electro-Thera- 
peutic?) 

Electrode,  Sponge  -  — A  moistened 
sponge  connected  to  one  of  the  terminals  of 
an  electric  source  and  acting  as  the  electro- 
therapeutic  electrode. 

Electrode,  TJrethral  -  — An  electro- 
therapeutic  electrode  suitably  shaped  for  the 
treatment  of  the  urethra.  (See  Electrode, 
Electro-  Therapeutic?) 

Electrode,  Vaginal  — An  electro- 
therapeutic  electrode  suitably  shaped  for  the 
treatment  of  the  vagina.  (See  Electrode, 
Electro-  Therapeutic?) 

Electro-Deposi!  s. — (See  Deposits,  Elec- 
tro?) 

Electrodes. — T'"se  terminals  of  an  electric 
source. 

The  positive  electrode  is  sometimes  called  the 


202 


[Ele. 


Anode,  and  the  negative  electrode  the  Kathode. 
No  matter  for  what  purposes  employed,  they  are 
generally  in  electro-therapeutics  termed  electrodes. 
In  precise  use  these  terms  should  be  restricted 
to  the  electrodes  when  used  for  electrolytic  de- 
composition. 

The  electrodes  are  made  of  different  shapes  and 
of  different  materials  according  to  the  character  of 
the  work  the  current  is  to  perform. 

Electrodes,  Carbon,  for  Arc-Lamps  — 
Rods  of  artificial  carbon   employed  in   arc 
lamps. 

These  are  more  properly  called  simply  arc- 
lamp  carbons. 

Arc-lamp  carbons  are  moulded  into  the  shape 
-of  rods,  from  plastic  mixtures  of  carbonaceous 
materials"  and  carbonizable  liquids.  On  the  sub- 
sequent carbonization  of  these  rods  the  ingredients 
are  caused  to  cohere  in  one  solid  mass  by  the  de- 
posit of  carbon  derived  from  the  carbonizable 
materials.  (See  Carbons*  Artificial.') 

Carbons  for  arc-lamps  are  generally  copper- 
coated,  so  as  to  somewhat  decrease  their  resist- 
ance, and  insure  a  more  uniform  consumption. 
Arc-lamp  carbons  are  sometimes  provided  with  a 
central  core  ot  softer  carbon,  which  fixes  the  po- 
sition of  the  arc  and  thus  insures  a  steadier  light. 
(Se'  Zarbons,  Cored.) 

Electrodes,  Cored Carbon  elec- 
trodes of  a  cylindrical  shape  provided  with  a 
central  cylinder  of  softer  carbon. 

The  use  of  cored  electrodes  for  arc  lamps  is 
for  the  purpose  of  steadying  the  light  by  maintain- 
ing the  arc  in  a  central  position.  This  is  effected 
by  the  greater  vaporization  of  the  softer  carbon 
of  the  core. 

Electrodes,  Cylindrical  Carbon  - 
Carbon  cylinders  used  for  electrodes  of  arc- 
lamps,  or  for  battery  plates. 

Electrodes,  Electro-Therapeutic 

Electrodes  of  various  shapes   employed   in 
electro-therapeutics. 

The  electro-therapeutic  electrode,  as  distin- 
guished from  the  indifferent  electrode,  is  especially 
shaped  for  the  particular  purpose  for  which  it  is 
designed. 

When  the  electricity  is  intended  to  affect  the 
skin  or  superficial  portions  of  the  body  only,  it  is 
applied  dry,  and  is  then  generally  metallic.  To 
reach  the  deeper  structures,  such  as  the  muscle 
or  nerve  trunks,  moistened  sponge  electrodes  are 


employed.  Before  their  use  the  skin  should  be 
thoroughly  moistened.  Sponge-electrodes  are 
generally  made  conducting  by  a  solution  of  some 
saline  substance,  such  as  common  salt. 

Electrodes,  Erb's  Standard  Size  of  — 

— Standard  sizes  of  electrodes  generally 
adopted  in  electro-therapeutics. 

The  following  standard  sizes  have  been  pro- 
posed by  Erb,  viz. : 
(i.)  Fine  electrode. ...   ^    centimetre  diameter. 

(2.)  Small        "       2  "  " 

(3.)  Medium  "       7.5  "  " 

(4.)  Large      "       ....6x2         "  " 

(5.)  Very  large  do 8  x  16       "  " 

Electrodes,     Non-Polarizable    — 

Electrodes  employed  in  electro-therapeutics, 
that  are  so  constructed  as  to  avoid  the  effects 
of  polarization. 

Non-polarizable  electrodes  are  obtained  by 
employing  two  amalgamated  zinc  wires,  dipped 
into  saturated  solution  of  zinc  chloride  placed  in 
glass  tubes,  and  closing  the  lower  ends  of  the 
tubes  by  a  piece  of  potter's  clay.  The  contact  of 
an  electrode  so  prepared  with  the  tissues  of  the 
body  does  not  produce  a  polarization. 

Electro-Diagnosis. — (See  Diagnosis,  Elec- 
tro^ 

Electro-Diagnostic. —  (See  Diagnostic, 
Electro?) 

Electro-Dynamic  Attraction. — (See  At- 
traction, Electro-Dynamic?) 

Electro-Dynamic  Capacity. —  (See  Ca- 
pacity, Electro-Dynamic?) 

Electro-Dynamic  Induction. — (See  Induc- 
tion, Electro-Dynamic?) 

Electro-Dynamic  Repulsion. — (See  Re- 
pulsion, Electro-Dynamic?) 

Electro-Dynamics.  —  (See  Dynamics, 
Electro?) 

Electro-Dynamometer. — (See  Dynamom- 
eter, Electro?) 

Electro-Etching. — Electric  etching.  (See 
Etching,  Electro?] 

Electrogenesis. — Results  following  the 
application  of  electricity  to  the  spinal  cord  or 
nerve  after  the  withdrawal  of  the  electrodes. 

Electro-Gilding. — (See  Gilding,  Electro^ 


Ele.] 


203 


[Ele. 


Electro-Kinetics. — (See  Kinetics,  Elec- 
tro?) 

Electrolier. — A  chandelier  for  holding 
electric  lamps,  as  distinguished  from  a  chan- 
delier for  holding  gas-lights. 

Electrology. — That  branch  of  science 
which  treats  of  electricity.  (Obsolete.) 

Electrolysis. —  Chemical  decomposition 
effected  by  means  of  an- electric  current. 

When  an  electric  current  is  sent  through  an 
electrolyte,  i.  e.,  a  liquid  which  permits  the  cur- 
rent to  pass  only  by  means  of  the  decomposition 
of  the  liquid,  the  decomposition  that  ensues  is 
called  electrolytic  decomposition, 

The  electrolyte  is  decomposed  or  broken  up 
into  atoms  or  groups  of  atoms  or  radicals,  called 
ions. 

The  ions  are  of  two  distinct  kinds,  viz. :  The 
electro -positive  ions,  or  kathions,  and  the  electro- 
negative ions,  or  onions. 

Since  the  anode  of  the  source  is  connected  with 
the  electro-positive  terminal,  it  is  clear  that  the 
amons*  or  the  electro-negative  ions,  must  appear 
at  the  anode,  and  the  kathions,  or  electro-positive 
ions,  must  appear  at  the  kathode. 

Hydrogen,  and  the  metals  generally,  are 
kathions.  Oxygen,  chlorine,  iodine,  etc.,  are 
anions. 

The  vessel  containing  the  electrolyte,  in  which 
these  decompositions  take  place,  is  sometimes 
called  an  electrolytic  cell. 

An  electrolytic  cell  is  called  a  voltameter  when 
it  is  arranged  for  measuring  the  current  passing 
by  means  of  the  amount  of  decomposition  it 
effects.  (See  Voltameter.} 

Electrolysis  by  Means  of  Alternating 
Currents. — Electrolytic  decomposition  ef- 
fected by  means  of  alternating  currents. 

When  an  alternating  current  is  passed  through 
dilute  sulphuric  acid,  in  a  voltameter  provided 
with  large  platinum  electrodes,  no  visible  decom- 
position occurs.  If,  however,  the  size  of  the 
electrodes  be  decreased  below  a  certain  point, 
then  visible  decomposition  occurs. 

Verdet  showed  that  when  no  other  break  ex- 
ists in  the  circuit  of  the  alternating  current 
within  the  voltameter,  no  indications  of  elec- 
trolysis are  obtained,  unless  the  alternating 
current  is  very  powerful.  If,  however,  a  break  is 
made  in  the  secondary  circuit,  so  that  the  dis- 


charge has  to  pass  as  a  spark,  then  visible  signs 
of  electrolysis  are  produced  by  comparatively 
feeble  alternating  currents. 

When  electrolysis  occurs  by  means  of  alternat- 
ing currents — 

(i.)  The  gases  collected  at  both  electrodes 
have  the  same  composition. 

(2.)  Where  the  quantities  of  electricity  that  al- 
ternately pass  in  opposite  directions  are  unequal, 
the  electrodes  show  manifest  polarization,  and, 
when  connected  by  a  conductor,  yield  a  current 
like  a  secondary  battery. 

(3.)  The  electrodes  manifest  no  sensible  polari- 
zation where  the  quantities  of  electricity  that  al- 
ternately pass  in  opposite  directions  are  equal. 

Electrolysis,  Faraday's  Laws  of — 

The  principal  facts  of  electrolysis  are  given 
in  the  following  laws: 

(i.)  The  amount  of  chemical  action  in  any 
given  time  is  equal  in  all  parts  of  the  circuit. 

(2.)  The  number  of  ions  liberated  in  a  given 
time  is  proportional  to  the  strength  of  the  cur- 
rent passing.  Twice  as  great  a  current  will 
liberate  twice  as  many  ions.  The  current  may 
be  regarded  as  being  carried  through  the  elec- 
trolyte by  the  ions:  since  an  ion  is  capable  of 
carrying  a  fixed  charge  only  of  -f-  or  —  electri- 
city, any  increase  in  the  current  strength  necessi- 
tates an  increase  in  the  number  of  ions. 

(3.)  When  the  same  current  passes  successively 
through  several  cells  containing  different  elec- 
trolytes, the  weights  of  the  ions  liberated  at  the 
different  electrodes  will  be  equal  to  the  strength 
of  the  current  multiplied  by  the  electro-chemical 
equivalent  of  the  ion.  (See  Equivalence,  Elec- 
tro-Chemical, La-d)  of  .} 

The  chemical  equivalent  is  proportional  to  the 
atomic  weight  divided  by  the  valency.  (See 
Equivalent,  Chemical.} 

The  electro-chemical  equivalent  of  any  element 
is  equal  to  the  weight  in  grammes  of  that  element 
set  tree  by  one  coulomb  of  electricity,  and  is  found 
by  multiplying  the  electro-chemical  of  hydrogen 
by  the  chemical  equivalent  of  that  element.  (See 
Equivalent,  Electro-  Chemical. ) 

Electrolyte,  Polarization  of The 

formation  of  molecular  groups  or  chains,  in 
which  the  poles  of  all  the  molecules  of  any 
chain  are  turned  in  the  same  direction,  viz.: 
with  their  positive  poles  facing  the  negative 
plate,  and  their  negative  poles  facing  the 


Ele.] 


204 


[Ele, 


positive  plate.  (See  Cell,  Voltaic.  Hypoth- 
esis, Grotthus') 

Electrolytic  or  Electrolytical. — Pertain- 
ing to  electrolysis. 

Electrolytic  Analysis. — (See  Analysis, 
Electrolytic) 

Electrolytic  Cell.— (See  Cell,  Electro- 
lytic, Teslas) 

Electrolytic  Clock.— (See  Clock,  Electro- 
lytic) 

Electrolytic  Conduction. — (See  Conduc- 
tion, Electrolytic) 

Electrolytic  Convection. — (See  Convec- 
tion, Electrolytic) 

Electrolytic  Decomposition. — (See  De- 
composition, Electrolytic) 

Electrolytic  Hydrogen. — (See  Hydrogen, 
Electrolytic) 

Electrolytic  Writing.— (See  Writing, 
Electrolytic) 

Electrolytically. — In  an  electrolytic  man- 
ner. 

Electrolyzable. — Capable  of  being  elec- 
trolyzed,  or  decomposed  by  means  of  elec- 
tricity. 

Electrolyzed. — Separated  or  decomposed 
by  means  of  electricity. 

Electrolyzing. — Causing  or  producing 
electrolysis. 

Electro-Magnet. — (See  Magnet,  Electro) 

Electro-Magnetic  Ammeter. — (See  Am- 
meter, Electro-Magnetic) 

Electro-Magnetic  Annunciator.— (See 
Annunciator,  Electro-Magnetic) 

Electro-Magnetic  Attraction. — (See  At- 
traction, Electro-Magnetic) 

Electro-Magnetic  Bell-Call.— (See  Call, 
Bell,  Magneto-Electric) 

Electro-Magnetic  Bell,  Siemens'  Arma- 
ture   (See  Bell,  Electro-Magnetic, 

Siemens'  Armature  Form) 

Electro-Magnetic  Brake. — (See  Brake, 
Electro-Magnetic) 

Electro-Magnetic  Cam. — (See  Cam, 
Electro-*,*  agnetic) 


Electro-Magnetic  Dental-Mallet. — (See 
Dental-Mallet,  Electro-Magnetic) 

Electro-Magnetic     Drill.— (See      Drill, 

Electro-Magnetic) 

Electro-Magnetic  Engine. — (See  Engine, 
Electro-Magnetic) 

Electro-Magnetic  Exploder. — (See  Ex- 
ploder, Electro- Magnetic) 

Electro-Magnetic  Eye. — (See  Eye,  Elec- 
tro-Magnetic) 

Electro-Magnetic  Impulse. — (See  Im- 
pulse, Electro-Magnetic) 

Electro-Magnetic  Induction. — (See  In- 
duction, Electro-Magnetic) 

Electro-Magnetic  Medium. — (See  Me- 
dium, Electro-Magnetic) 

Electro-Magnetic  Meter. — (See  Meter, 
Electro-Magnetic) 

Electro-Magnetic  Momentum  of  Sec- 
ondary Circuit. — (See  Momentum,  Elec- 
tro-Magnetic, of  Secondary  Circuit) 

Electro-Magnetic  Pop-Gun. — (See  Pop- 
Gun,  Electro-Magnetic) 

Electro-Magnetic  Radiation. — (See  Ra- 
diation, Electro-Magnetic) 

Electro-Magnetic  Repulsion. — (See  Re- 
pulsion, Electro-Magnetic) 

Electro-Magnetic  Resonator. — (See  Res- 
onator, Electro- Magnetic) 

Electro-Magnetic  Shunt. — (See  Shunt, 
Electro-Magnetic) 

Electro-Magnetic  Solenoid. — (See  Sole- 
noid, Electro-Magnetic) 

Electro-Magnetic  Strain. — (See  Strain, 
Electro-Magnetic) 

Electro-Magnetic  Stress. — (See  Stress, 
Electro-Magnetic) 

Electro-Magnetic  Theory  of  Light,  Max- 
well's   (See  Light,  Maxwell's  Elec- 
tro-Magnetic Theory  of) 

Electro-Magnetic  Vibrator. — (See  Vi- 
brator, Electro-Magnetic) 

Electro-Magnetic  Voltmeter.— (See  TW/- 
meter,  Electro-Magnetic) 


Ele.] 


205 


[Ele. 


Electro-Magnetic  Units. — (See  Units, 
Electro-Magnetic?) 

Electro-Magnetics.  —  (See  Magnetics, 
Electro?) 

Electro-Massage. — (See  Massage,  Elec- 
tro?) 

Electro-Mechanical  Alarm. —  (See  Alarm, 
Electro-Mechanical?) 

Electro-Mechanical  Gong. — (See  Gong, 
Electro-Mechanical?) 

Electro-Metallurgical  Crystalline  De- 
posit.— (See  Deposit,  Crystalline,  Electro- 
Metallurgical?) 

Electro-Metallurgical  Galvanization.— 

(See  Galvanization,  Electro- Metallurgical?) 

Electro-Metallurgical  Nodular  Deposit. 

— (See      Deposit,     Electro  -  Metallurgical 
Nodular?) 

Electro  -  Metallurgical  Regnline  De- 
posit.—  (See  Deposit,  Electro-Metallurgical 
Reguline?) 

Electro-Metallurgical  Sandy  Deposit. — 

(See  Deposit,  Electro-Metallurgical  Sandy?) 

Electro-Metallurgy.— (See  Metallurgy, 
Electro?) 

Electrometer. — An  apparatus  for  measur- 
ing differences  of  potential. 

Electrometers  operate,  in  general,  by  means 
of  the  attraction  or  repulsion  of  charged  conduc- 
tors on  a  suitably  suspended  needle  or  disc.  As 
no  current  is  required  to  flow  through  the  appa- 
ratus electrometers  are  especially  adapted  to  many 
cases  where  voltmeters  could  not  be  so  readily 
used. 

Electrometer,  Absolute An  elec- 
trometer the  dimensions  of  which  are  such 
that  the  value  of  the  electromotive  force  can 
be  directly  determined  from  the  amount  of 
the  deflection  of  the  needle. 

A  form  of  attracted-disc  electrometer. 
(See  Electrometer,  At  traded- Disc?) 

Electrometer,    Attracted-Disc A 

form   of  electrometer  devised  by  Sir  William 


Thomson,  in  which  the  force  is  measured  by 
the  attraction  between  the  two  discs. 

Thomson's  Attracted-Disc  Electrometer  is 
shown  in  Fig.  230.  It  consists  of  a  plate  C,  sus- 
pended from  the  longer  end  of  a  lever  1,  within  the 
fixed  guard  plate,  or  guard  ring  B,  immediately 
above  a  second  plate  A,  supported  en  an  insulated 
stand,  and  capable  of  a  measurable  approach 


Fig.  230.    Attracted-Dise  Electrometer. 

towards  C,  or  a  movement  away  from  it.  The 
plate,  C,  is  placed  in  contact  with  B,  by  means  of 
a  thin  wire.  By  means  of  this  connection  the 
distribution  of  the  charge  over  the  plate,  C,  is 
uniform.  The  electrostatic  attraction  is  meas- 
ured by  the  attraction  of  the  fixed  disc,  A,  on  the 
movable  disc,  C,  connected  respectively  to  the  two 
bodies  whose  difference  of  potential  is  to  be 
measured.  One  of  these  may  be  the  earth.  The 
fulcrum  of  the  lever  1,  is  formed  of  an  aluminium 
wire,  the  torsion  of  which  is  used  to  measure  the 
force  of  the  attraction;  or,  it  may  be  measured 
directly  by  the  counterpoise  weight  Q. 

This  instrument  is  sometimes  called  an  absolute 
electrometer,  because,  knowing  the  dimensions  of 
the  apparatus,  the  value  of  the  difference  of  poten- 
tial can  be  directly  determined  from  the  amount 
of  the  motion  observed. 


Electrometer,  Capillary An  elec- 
trometer in  which  a  difference  of  potential  is 


Fig.  231.      Capillary  Electrometer 

measured  by    the  movement   of  a  drop  of 
sulphuric  acid  in  a  tube  filled  with  mercury. 


tie.] 


20G 


[Ele. 


A  form  of  capillary  electrometer  is  shown  in 
yi^.  231,  in  which  a  horizontal  glass  tube  with 
a  drop  of  acid  at  B,  has  its  ends  connected  with 
two  vessels  M  and  N,  filled  with  mercury.  If 
a  current  be  passed  through  the  tube,  a  move- 
ment of  the  drop  towards  the  negative  pole 
will  be  observed.  Where  the  electromotive 
force  does  not  exceed  one  volt,  the  amount  of 
the  movement  is  proportional  to  the  electro- 
motive force. 

Electrometer,  Quadrant An  elec- 
trometer in  which  an  electrostatic  charge  is 
measured  by  the  attractive  and  repulsive 
force  of  four  plates  or  quadrants,  on  a  light 
needle  of  aluminium  suspended  within  them. 

The  sectors  or  quadrants  are  of  brass,  and  are 
so  shaped  as  to  form  a  hollow  cylindrical  box 
when  placed  together.  The  four  sectors,  or  quad- 
rants, are  insulated  from  one  another,  but  the 
opposite  ones  are  connected  by  a  conducting  wire, 
as  shown  in  Fig. 
232.  A  light  needle 
of  aluminium,  u, 
maintained  at  some 
constant  potential, 
by  connection  with 
the  inner  coating 
of  a  Ley  den  jar,  is 
suspended,  gener- 
ally by  two  par- 
allel silk  threads, 
so  as  to  freely  swing  inside  the  hollow  box.  This 
needle,  when  at  rest,  is  in  the  position  shown  by 
the  dotted  lines,  with  its  axis  of  symmetry  exactly 
under  one  of  the  slots  or  spaces  between  two 
Apposite  sectors.  (See  Suspension,  Bi-Filar.} 

The  quadrant  electrometer,  shown  in  Fig.  233, 
.ias  one  of  its  quadrants  removed  so  as  to  show 
the  suspended  aluminium  needle. 

A  similar  form  of  instrument  is  shown  in  Fig. 
234,  with  all  the  quadrants  in  place,  and  the 
whole  instrument  covered  by  a  glass  shade. 

To  use  the  quadrant  electrometer  the  pairs  of 
sectors  are  connected  with  the  two  bodies  whose 
difference  of  potential  is  to  be  measured,  and  the 
deflection  of  the  needle  observed,  generally 
through  a  telescope,  by  means  of  a  spot  of  light 
reflected  from  a  mirror  attached  to  the  upper  part 
of  the  needle. 

Sometimes  the  segments  are  made  in  the  shape 
of  a  cylinder,  and  the  needle  in  the  shape  of  a 
suspended  rectangle. 


Electrometer,  Registering 


— An  elec- 


trometer, the  deviations  of    the    needle  of 
which  are  automatically  registered. 


Fig.  232.     Quadrant  Elec- 
trometer. 


Fig.  233.    Quadrant  Electrometer,  Showing  Suspended 
Needle. 

The  registration  of  this  class  of  electrometer  is 
obtained  by  means  of  photography.    The  spot  of 


Fig.  234.     Quadrant  Electromettr. 

light,  reflected  from  the  mirror  ot  the  electrometer, 
falls  on  a  fillet'  of  sensitized  paper,  moved  by 
clockwork. 


Ele. 


207 


[Ele. 


Electromotive   Arrangement  or  Device. 

— (See  Arrangement  or  Device,  Electromo- 
tive?} 

Electromotive  Difference  of  Potential. — 

(See  Potential,  Difference  of  Electromotive?) 

Electromotive  Force. — (See  Force,  Elec- 
tromotive^) 

Electromotive  Force,  Average (See 

Force,  Electromotive,  Average  or  Mean.} 

Electromotive  Force,  Back  or  Counter 
(See  Force,  Electromotive.  Back.) 

Electromotive  Force,  Direct (See 

Force,  Electromotive,  Direct?) 

Electromotive  Force,  Inductive 

(See  Force,  Electromotive,  Inductive?) 

Electromotive  Force,  Secondary-Im- 
pressed   — (See  Force.  Electromotive \ 

Secondary-Impressed?) 

Electromotive  Force,  Simple-Periodic 
— (See  Force,  Electromotive,  Simple- 
Periodic?) 

Electromotive  Force,  Transverse  — 
(See  Force,  Electromotive.  Transverse?) 

Electromotive  Impulse. — (See  Impulse, 
Electromotive?) 

Electro-Motograph. — (See  Motograph, 
Electro?) 

Electro-Muscular. — (See  Muscular,  Elec- 
tro?) 

Electro-Muscular  Excitation. — (See  Ex- 
citation, Electro-Muscular?) 

Electronecrosic. — Pertaining  to  capital 
punishment  by  means  of  electricity. 

Electronecrosis. —  A  word  proposed  for 
capital  punishment  by  means  of  electricity. 

Electro-Negative  Ions. — (See  Ions,  Elec- 
tro-Negative?) 

Electronegatives. — The  atoms  or  radicals 
that  appear  at  the  anode  or  positive  terminal 
during  electrolysis. 

The  anions.     (See  Electrolysis.     Anton?) 

Electro-Nervous  Excitability. — (See  Ex- 
citability, Electro-Nervous?) 

Electro- Nickeling.  —  (See  Nickeling, 
Electro?) 

Electro-Optics. — (See  Optics,  Electro?) 


Electrophanic. — Pertaining  to  capital  pun- 
ishment by  means  of  electricity. 

Electrophanical. — Pertaining  to  capital 
punishment  by  means  of  electricity. 

Electrophauize.  -  To  inflict  capital  pun- 
ishment by  means  of  electricity. 

Electrophany. — Capital  punishment  by 
means  of  electricity. 

The  word  electrophany  would  appear  to  be  far 
preferable  to  the  word  electrocution,  since  it  is  in 
accordance  with  etymological  usage,  while  elec- 
trocution is  not. 

Electrophila. — A  devotee  of  electricity. 

Electrophobia. — A  word  proposed  for  fear 
of  electricity. 

Electrophoric. — Pertaining  to  an  electro- 
phorus.  (See  Electrophorus?) 

Electrophorus. — An    apparatus    for    the 
production  of  electricity 
by   electrostatic    induc- 
tion.     (See    Induction, 
Electrostatic?) 

A  disc  of  vulcanite,  or 
hard  rubber  B,  contained 
in  a  metallic  form,  is  rub- 
bed briskly  by  a  piece  of 
cat's  skin  and  the  insu- 
lated metallic  disc,  A,  is  Fig.  233.  Electrophortts, 
placed  on  the  centre  of  the  Charging. 

vulcanite  disc,  as  shown  in  Fig.  235. 

The  negative  charge  produced  in  B,  by  fric- 
tion, produces  by  induction  a  positive  charge  on 
the  part  of  A,  nearest  it, 
and  a  negative  charge 
on  the  part  furthest  from 
it. 

In  this  condition,  if 
the  disc  be  raised  from 
the  plate  by  means  of  its 
insulating  handle,  as 
shown  in  Fig.  236,  no 
electrical  effects  will  be 
noticed,  since  the  two  op- 
posite and  equal  charges 
unite  and  neutralize  each  Fig.  236.  Electrophorus, 

.,  Tr     i  ,,  Discharging, 

other.     If,   however,  the 

disc  A,  be  first  touched  by  the  finger,  and  then 
raised  from  the  disc  B,  it  will  be  found  to 
itively  charged. 


B 


Kle.] 


208 


[Ele. 


E 1  e  c  t  r  o-Physiology. — (See  Physiology, 
Electro) 

Electropic  Medium. — (See  Medium,  Elec- 
tropic) 

Electro-Plating.— (See  Plating,  Electro) 

Electro-Plating  Bath.— (See  Bath,  Elec- 
tro-Plating) 

Electro-Pneumatic  Signals. — (See  Sig- 
nals, Electro-Pneumatic) 

Electro-Pneumatic  Thermostat.  —  (See 
Thermostat,  Electro-Pneumatic) 

Electropoion  Liquid. — (See  Liquid,  Elec- 
tropoion) 

Electro-Positive  Ions. — (See  Ions,  Elec- 
tro-Positive) 

Eleetropositives. — The  atoms  or  radicals 
that  appear  at  the  kathode  or  negative  termi- 
nal of  any  source  during  electrolysis. 

Thekathions.  (See  Electrolysis.   Kathion) 
E 1  e  c  t  r  o-Prognosis. — (See     Prognosis, 
Electric)  , 

Electro-Puncture. — (See  Puncture,  Elec- 
tro) 

Electro-Receptive  Devices. — (See  Device, 
Electro-Receptive) 

Electro-Receptive  Devices,  Multiple-Arc- 
Connected  (See  Devices,  Electro- 
Receptive,  Multiple- A  re-  Connected) 

Electro-Receptive  Devices,  Multiple-Se- 
ries-Connected —  — (See  Devices,  Elec- 
tro-Receptive, Multiple-Series-Connected) 

Electro-Receptive  Devices,  Series-Con- 
nected   (See  Devices,  Electro-Recep- 
tive, Series-Connected) 

Electro-Receptive  Devices,  Series-Mul- 
tiple-Connected   (See  Devices,  Elec- 
tro-Receptive, Series-Multiple-Connected) 

Electroscope.  —  An  apparatus  for  showing 
the  presence  of  an  electric  charge,  or  for  de- 
termining its  sign,  whether  positive  or  nega- 
tive, but  not  for  measuring  its  amount  or 
value. 

In  the  gold-leaf  electroscope,  two  gold  leaves, 
n,  n,  Fig.  239,  suspended  near  each  other,  show 
by  their  repulsion  the  presence  of  an  electric 
charge.  Two  pith  balls  may  be  used  for  the  same 
purpose. 


The  pith  balls  B,  B,  shown  in  Fig.  237,  form 
a  simple  electroscope.  If  repelled  by  a  charge, 
when  approached  by  a  similar  charge  in  S,  they 
will  at  once  be  still  further  repelled,  as  shown  by 
the  dotted  lines. 

To  use  an  electroscope  for  determining  the  sign  of 


Fig-  237'  Pith  Bal1  Electroscope. 
an  unknown  charge,  the  gold  leaves  or  pith  balls  are 
first  slightly  repelled  by  a  charge  of  known  name, 
as,  for  example,  positive,  applied  to  the  knob  C, 
Fig.  239.  They  are  then  charged  by  the  electrified 
body  whose  charge  is  to  be  determined.  If  they 
are  further  repelled,  its  charge  is  positive.  If 
they  are  first  attracted  and  afterwards  repelled, 
its  charge  is  negative. 

Two  posts  B,  Fig.  239,  connected  with  the 
earth,  increase  the  amount  of  divergence  by  in- 
duction. 

Electroscope,  Condensing, Volta's 

An  electroscope  employed  for  the  detection 
of  feeble  charges,  the  leaves  of  which  are 
charged  by  means  of  a  condenser. 

The   condensing   electroscope,    Fig.     238,    is 
formed  of  two  metallic 
plates,   placed   at  the  G 

top  of  the  instrument, 
and  separated  by  a 
suitable  dielectric. 
The  upper  plate,  P,  is 
removable  by  means 
of  the  insulated  han- 
dle, G. 

To  employ  the  elec 
trdscope,  as  for  exam- 
ple, to  detect  the  free 
charge  in  an  unequal-  Fig.  ^23 8.  ~  Condensing  Elec- 
ly    heated  crystal   of  troscope. 

tourmaline,  the  crystal  is  touched  to  the  lower 
plate,  while  the  upper  plate  is  connected  to  the 
ground  by  the  finger.  On  the  subsequent  re- 
moval of  the  upper  plate  an  enormous  decrease 


Ele.J 


209 


[Ele. 


ensues  in  the  capacity  of  the  condenser,  and  the 
charge  now  raises  the  potential  of  the  lower 
plate,  and  causes  a  marked  divergence  of  the 
leaves  L,  L.  (See  Electricity,  Pyro.) 

Electroscope,  Gold-Leaf An  elec- 
troscope in  which  two  leaves  of  gold  are  used 
to  detect  the  presence  of  an  electric  charge, 
or  to  determine  its  character  whether  positive 
or  negative. 

When  a  charge  is  imparted  to  the  knob  C,  Fig. 
239,  the  gold  leaves  n,  n,  diverge.  This  will  oc- 
cur whether  the  charge  be 
positive  or  negative. 

To  determine  the  char- 
acter of  an  unknown 
charge,  the  leaves  are  first 
caused  to  diverge  by  means 
of  a  known  positive  or  neg- 
ative charge.  The  un- 
known charge  is  then  given 
to  the  leaves.  If  they  di- 


Fig.  23Q.     Gold- Leaf 
Electroscope. 


verge  still  further,  then  the  charge  is  of  the  same 
name  as  that  originally  possessed  by  the  leaves. 
If,  however,  they  first  move  to- 
gether and  are  afterwards  re- 
pelled, the  charge  is  of  the 
opposite  name. 

Electroscope,  Pith -Ball 

-  An  electroscope 
which  shows  the  presence  of 
a  charge  by  the  repulsion  of 
two  similarly  charged  pith 
balls.  (See  Electroscope?) 

Any  two  pith  balls,  suspend- 
ed by  conducting  threads,  but 
insulated  from  the  earth,  will 
serve  as  an  electroscope. 

Electroscope,  Quadrant, 
Henley's An  electro- 
scope sometimes  employed 
to  indicate  large  charges  of 
electricity. 

A  pith  ball  placed  on  a  light 
arm  A,  of  straw  or  other  simi- 
lar material,  Fig.  240,  is  pivoted 
at  the  centre  of  a  graduated 
circle  B'.     The  arm,  C,  is   at-  Fig.  240.   Henley's 
tached  by  means  of  the  screw       Electroscope. 
to  the  prime  conductor  of  an  electric  machine. 
The  similar  charge  imparted   to  A,  by  contact 


with  C,  causes  a  repulsion  which  may  be  meas- 
ured on  the  graduated  arc. 

This  instrument  approaches  the  electrometer  in 
the  character  of  its  operation,  since  by  its  means, 
approximately  correct  measurements  may  be  made 
of  the  value  of  the  repulsion.  It  should  not,  how- 
ever, be  confounded  with  the  quadrant  electrom- 
eter. (See  Electrometer,  Quadrant.') 

Electroscopically. — By  means  of  the  elec- 
troscope. (See  Electroscope?) 

Electroscopy. — The  art  of  determining  the 
kind  of  charge  a  body  possesses,  by  means 
of  an  electroscope. 

Electro  -  Sensibility. — (See  Sensibility, 
Electro?) 

Electro-Silvering. — (See  Silvering,  Elec- 
tro?) 

Electro-Smelting. — (See  Smelting,  Elec- 
tro?) 

Electrostatic  Attraction. — (See  Attrac- 
tion, Electrostatic?) 

Electrostatic  Capacity. — (See  Capacity, 
Electrostatic?) 

Electrostatic  Circuit. — (See  Circuit, 
Electrostatic?) 

Electrostatic  Field.— (See  Field,  Electro- 
static?) 

Electrostatic  Induction. — (See  Induction, 
Electrostatic?) 

Electrostatic  Induction  Machine. — (See 
Machine,  Electrostatic  Induction?) 

Electrostatic  Leakage.— (See  Leakage, 
Electrostatic?) 

Electrostatic  Lines  of  Force. — (See  Force, 
Electrostatic,  Lines  of.) 

Electrostatic  Repulsion. — (See  Repulsion, 
Electrostatic.) 

Electrostatic  Screening.— (See  Screening, 
Electrostatic?) 

Electrostatic  Stress. — (See  Stress,  Elec- 
trostatic.) 

Electrostatic  Units.— (See  Units,  Electro- 
static?) 

Electrostatics.— That  branch  of  electric 
science  which  treats  of  the  phenomena  and 
measurement  of  electric  charges. 


Ele.] 


210 


[Ele. 


The  principles  of  electrostatics  are  embraced 
in  the  following  laws,  viz.: 

(i.)  Charges  of  like  name,  *.  e.,  either  positive 
or  negative,  repel  each  other.  Charges  of  unlike 
name  attract  each  other. 

(2.)  The  forces  of  attraction  or  repulsion  be- 
tween two  charged  bodies  are  directly  propor- 
tional to  the  product  of  the  quantities  of  elec- 
tricity possessed  by  the  bodies  and  inversely 
proportional  to  the  square  of  the  distance  be- 
tween them. 

These  laws  can  be  demonstrated  by  the  use  of 
Coulomb's  torsion  balance.  (See  Balance,  Tor- 
sion.') 

Calling  q,  and  q1,  the  quantities  of  electricity 
possessed  by  the  two  bodies,  and  r,  the  distance 
between  them,  then,  if  f,  is  the  force  exerted  by 
their  mutual  action, 

/•_5(11 
:    r~" 

Electro-Technics.— (See  Technics,  Elec- 
tro) 

Electrothanasing.— Producing  death  by 
electricity. 

Electrothanasis.— A  word  proposed  for 
death  by  electricity. 

The  death  referred  to  here  is  death  other  than 
that  caused  by  capital  punishment. 

Electrothanasise. — To  produce  death  by 
electricity. 

The  death  here  referred  to  is  other  than  that 
caused  by  capital  punishment. 

Electrothanatose. — To  cause  death  by 
electricity. 

Electrothanatosic. — Pertaining  to  capital 
punishment  by  means  of  electricity. 

Eleetrothanatosing.— Causing  death  by 
electricity. 

Electrothanatosis. — A  word  proposed  for 
death  by  electricity. 

The  death  here  referred  to  is  death  other  than 
that  caused  by  capital  punishment. 

Electro-Therapeutic  Bath.— (See  Bath, 
Electro-  Therapeutic) 

Electro-Therapeutic  Breeze.— (See 

Breeze,  Electro-  Therapeutic) 


Electro-Therapeutic  Diffusion  of  Cur- 
rent.— (See  Current,  Diffusion  of,  Electro- 
Therapeutic) 

Electro-Therapeutic  Dosage.— (S  e  e 
Dosage,  Electro-  Therapeutical) 

Electro-Therapeutic  Electrode. — (See 
Electrode,  Electro-  Therapeutic) 

Electro-Therapeutic  Electrodes. — (See 
Electrode,  Electro-  Therapeutic) 

Electro-Therapeutic       Galvanization. — 

(See  Galvanization,  Electro-  Therapeutical) 

Electro-Therapeutic         Head-Breeze. — 

(See  Breeze,  Head,  Electro-  Therapeidic) 

Electro-Therapeutics. — (See  Therapeu- 
tics, Electro) 

Electro-Therapeutist. — (See  Therapeu- 
tist, Electro) 

Electro-Therapy. — (See  Therapy,  Elec* 
tro) 

Electro-Thermal  Meter.— (See  Meter, 
Electro-  Thermal) 

Electro-Tinning. — (See  Tinning,  Elec- 
tro) 

Electrotisic. — Pertaining  to  capital  pun- 
ishment by  means  of  electricity. 

Electrotisiny. — Producing  capital  punish- 
ment by  means  of  electricity. 

Electrotisis. — A  word  proposed  for  capi- 
tal punishment  by  means  of  electricity. 

Electrotonic  Current— (See  Current, 
Electrotonic) 

Electrotonic  Effect.— (See  Effect,  Electro- 
tonic) 

Electrotonic  Excitahility. — (See  Excita- 
bility, Electrotonic) 

Electrotonic  State.— (See  State,  Electro- 
tonic) 

Electrotonus. — A  condition  of  altered 
functional  activity  which  occurs  in  a  nerve 
when  subjected  to  the  action  of  an  electric 
current. 


Ele.j 


211 


[Ele. 


The  electrotonic  state  is  produced  by  the 
passage  through  a  nerve  of  a  constant  current 
called  the  polarizing  current. 

Electrotonus  is  attended  by  the  modification  of 
the  nerve  in  the  following  respects,  viz. : 

(i.)  In  its  electromotive  force. 

(2.)  In  its  excitability. 

The  passage  of  the  constant  current  produces 
a  change  in  the  electromotive  force  of  that  part  of 
the  nerve  traversed  by  the  current. 

This  alteration  in  muscular  excitability  may 
consist  in  either  an  increased  or  a  decreased  func- 
tional activity.  The  decreased  functional  activity 
•ccurs  in  the  neighborhood  of  the  anode,  or  the 
positive  terminal,  and  is  called  the  anelectrotonic 
state.  The  increased  functional  activity  occurs  in 
the  neighborhood  of  the  kathode,  or  the  negative 
terminal,  and  is  called  the  kathelectrotonic  slate. 
(See  Anelectrotonus.  Kathelectrotonus.} 

This  altered  functional  activity  affects  not  only 
the  intra  polar  parts  of  the  nerve,  or  that  part 
between  the  electrodes,  but  also  the  extra-polar 
portions,  or,  in  other  words,  the  remainder  of  the 
nerve. 

The  electrotonic  state  is  characterized  by  two 
varieties,  viz.:  those  in  which  the  electromotive 
force  of  the  nerve  is  decreased,  and  those  in  which 
the  electromotive  force  of  the  nerve  is  increased. 
These  varieties  of  electrotonus  are  called  respec- 
tively the  negative  and  positive  phase  of  electro- 
tonus. (See  Electrotonus,  Negative  Phase  of. 
Electrotonus,  Positive  Phase  of.) 

Electrotonus,  Negative  Phase  of 

A  decrease  in  the  electromotive  force  of  a 
nerve  effected  by  seeding  a  current  through 
the  nerve  in  the  opposite  direction  to  the 
nerve  current.  (See  Current,  Nerve?) 

Electrotonus,  Positive  Phase  of 

An  increase  in  the  electromotive  force  of  a 
nerve  effected  by  sending  a  current  through 
the  nerve  in  the  same  direction  as  the  nerve 
current. 

The  increase  in  the  electromotive  force  not  only 
affects  the  portions  of  the  nerve  in  the  intra-polar 
regions,  but  in  the  extra  polar  regions  as  well. 

Electrotype. — A  type,  cast,  or  impression 
of  an  o,bject  obtained  by  means  of  electro- 
metallurgy. (See  Metallurgy,  Electro.  Elec- 
trotyping^) 

Electrotyping,  or  the  Electrotype  Pro- 


cess   Obtaining    casts    or    copies    of 

objects    by  depositing   metals  in  molds  by 
the  agency  of  electric  currents. 

The  molds  are  made  of  wax,  or  other  plastic 
substance,  rendered  conducting  by  coating  it  with 
powdered  plumbago. 

The  mold  is  connected  with  the  negative 
battery  terminal,  and  placed  in  a  metallic  solu- 
tion, generally  of  copper  sulphate,  opposite  a 
plate  of  metallic  copper,  connected  with  the  posi- 
tive battery  terminal.  As  the  current  passes,  the 
metal  is  deposited  on  the  mold  at  the  kathode, 
and  dissolved  from  the  metallic  plate  at  the 
anode,  thus  producing  an  exact  copy  or  cast  and 
at  the  same  time  maintaining  constant  the  strength 
of  the  bath. 

Electrozemia. — A  word  proposed  for  capi- 
tal punishment  by  means  of  electricity. 

Elect  rum. — A  name  given  by  the  ancienis 
to  various  substances  that  could  be  readily 
electrified  by  friction. 

The  term  electrum  included  a  number  of  sub- 
stances, but  was  applied  mainly  either  to  amber 
or  to  an  alloy  of  gold  and  silver. 

Element. — Any  kind  of  matter  which  can- 
not be  decomposed  into  simpler  matter. 

Matter  that  is  formed  or  composed  of  but 
one  kind  of  atoms. 

Oxygen  and  hydrogen  are  elements  or  varie- 
ties of  elementary  matter.  They  cannot  be  de- 
composed into  anything  but  oxygen  or  hydrogen. 
Water,  on  the  contrary,  is  compound  matter, 
since  it  can  be  decomposed  into  its  constituent 
parts,  oxygen  and  hydrogen. 

There  are  about  seventy  well-known  elements, 
some  of  which  are  very  rare,  occurring  in  ex- 
tremely small  quantities. 

The  evidence  of  the  true  elementary  condition 
of  many  of  the  elements  is  based,  to  a  great  ex- 
tent, on  the  fact  that  so  far  they  have  resisted  all 
efforts  made  to  decompose  them  into  simpler  sub- 
stances. We  should  bear  in  mind,  however,  that 
until  Davy's  use  of  the  voltaic  battery,  potash, 
soda,  and  many  other  similar  compounds  were  re- 
garded as  true  elements.  It  is  not  improbable 
that  many  of  the  now  so-called  elements,  may 
hereafter  be  decomposed  into  simpler  constitu- 
ents. 

The  following  table  gives  the  names,  chemical 


Ele.] 


212 


[Ele, 


symbols,  approximate  atomic  weights  and  equiva- 
lents of  the  principal  elements  : 


Names  ot 
Elements. 

i 
>* 

CA 

Approximate 
Atomic 
Weight. 

Chemical  Equivalent.* 

Al. 
Sb. 
As. 
Ba. 
Be. 
Bi. 
B. 
Br. 
Cd. 
Cs. 
Ca. 
C. 
Ce. 
Cl. 
Cr. 
Co. 
Cu. 
D. 
E. 
F. 
Ga. 
Ge. 
G. 
Au. 
H. 
In. 
I. 
Ir. 
Fe. 
La. 
Pb. 
Li. 
Mg. 
Mn. 
Hg. 
Mo. 
Ni. 
Nb. 
N. 
Os. 
O. 

Pd. 
P. 
Pt. 
K. 
R. 
Rb. 
Ru. 
Sm. 
Sc. 
Se. 
bi. 
Ag. 
Na. 
Sr. 
S. 
Ta. 
Te 
TI. 
Th. 
Sn. 
Ti. 
W. 
U. 
Va. 
Yb. 
Y. 
Zn. 
Zr. 

27. 

120. 

74-9 
136.8 
9.1 
207.5 
10.9 
79.8 
in.  8 
132.6 
40. 

12. 
140.4 

35-4 
52- 
58  9 
63.2 
144.6 
165.9 
19. 
68.9 
72.3 

196.3 
i. 

113.4 
126.6 
192.7 
55-9 
*38.5 
206.5 

7- 
24. 

53-9 
199.7 
95-5 
57-9 
93-8 
14. 
198.5 
to. 
105.7 
31- 
194.4 

39-  » 
104.1 

85.3 
104.3 
150.02 

78!8 
28.3 
107.7 
23. 
87-4 

§a> 
182.1 

128. 
203.7 
233-4. 
117.7 

i83.'« 
238.5 
Si-3 
172.8 
89.8 
64.9 
89.4 

9  >         [compounds 
40  in  eus,   24  in  ic 
24.9  iaous,  15  in  ic 
68.  A 
4.6 
69.2 
3-6 
79.8 

55-9 
66.3 
20 
6 

35.4 
26  mous,  17.3  in  ic 
29-5 
31.6 

19. 

196.  a  in  out,  65.  4  in  ic 

37-8 
126.6 
96.4,  64.2,  48.3 
28  in  ous,  18.6  in  ic 

103.3 
7 

12 

27 

199.7  in  ous,  99.9  in  ic 
28 

'4 

8 

52.9  in  <?«.?,  26.  4  in  if 
6  .  2  in  phosphates 
97.2  in  ous,  48.6111  ic 
39; 
52  in  ous,  34.7  in  ic 
85-3. 
52.1  mous,  34.  7  in  if 

7- 
107.7 

23 
43-7 

203  .  7  in  ous,  67  .  9  in  ic 

58.9  in  ous,  29.4  in  ic 
24  in  ous,  12  in  ic 
9  1  .  8  in  ous 
119.2  in  ous 
17.1  mous 

3*-S 

Caesium  

Chlorine  

Cobalt  

Didymium  

Gallium  

Germamun.  

Gold  

Iodine  

Lead  

Manganese  

Mercury  

Molybdenum  
Nickel  

Silicon  

Thallium  

Tin  

Titanium.......... 

Yttrium  

'  Atomic -weight  divided  by  the  valency. 


Element,  Negative One  of   the 

substances  forming  a  voltaic   couple.     (See 
Couple,  Voltaic.!) 
Element,  Negative,  of  a  Toltaic  Cell 

— That  element  or  plate  of  a  voltaic  cell  into 
which  the  current  passes  from  the  exciting 
fluid  of  the  cell. 

The  plate  that  is  not  acted  on  by  the  elec- 
trolyte during  the  generation  of  current  by 
the  cell 

The  copper  or  carbon  plate,  respectively 
in  a  zinc-copper  or  zinc-carbon  couple. 

It  must  be  carefully  borne  in  mind  that  the 
conductor  attached  to  the  negative  element  of  a 
voltaic  pile  is  the  positive  conductor  or  electrode 
of  the  pile,  since  the  current  that  flows  into  the 
plate  from  the  liquid  or  electrolyte  must  flow  out 
of  the  plate  where  it  projects  beyond  the  liquid. 

Element  of  Current. — (See  Current,  Ele- 
ment of.) 

Element  of  Storage  Battery. — (See  Bat- 
tery, Storage,  Element  of.) 

Element,  Positive That  element  or 

plate  of  a  voltaic  cell  from  which  the  current 
passes  into  the  exciting  fluid  of  the  cell. 

The  element  of  a  voltaic  couple  which  is 
acted  on  by  the  exciting  fluid  of  the  cell. 
(See  Couple,  Voltaic.) 

Element,  Thermo-Electric One  of 

the  two  metals  or  substances  which  form  a 
thermo-electric  couple.  (See  Couple,  Ther- 
mo-Electric.) 

Element,  Voltaic One  of  the  two 

metals  or  substances  which  form  a  voltaic 
couple.  (See  Couple,  Voltaic.) 

Elements,    Electrical    Classification    of 

A  classification  of  the  chemical  ele- 
ments into  two  groups  or  classes  according 
to  whether  they  appear  at  the  anode  or  kathode 
when  electrolyzed. 

The  chemical  elements  may  be  arranged  into 
electro-positive  and  electro-negative  according  to 
whether,  during  electrolysis,  they  appear  at  the 
negative  or  positive  terminal  of  the  source  respec- 
tively. 

The  electro-positive  elements  or  radicals  are 
called  kathions,  and  appear  at  the  kathode  or 
electro-negative  terminal.  The  electro-negative 


Ele.J 


213 


[Ene, 


elements  are  called  onions,  and  appear  at  the 
anode,  or  the  electro-positive  terminal.  (See 
Ions.) 

The  metals  generally  are  electro-positive;  oxy. 
gen,  chlorine,  iodine,  fluorine,  etc.,  are  electro- 
negative. 

Elements,  Magnetic,  of  a  Place 

The  values  of  the  magnetic  intensity,  the  mag- 
netic declination  or  variation,  and  the  mag- 
netic inclination  or  dip  at  any  place. 

Elevator  Annunciator. — (See  Annuncia- 
tor, Elevator?) 

Elevator,  Electric An  elevator 

operated  by  electric  power. 

Elongated  King  Core. — (See  Core,  Ring, 
Elongated?) 

Elongation,  Magnetic An  increase 

in  the  length  of  a  bar  of  iron  on  its  magnetiza- 
tion. 

This  increase  in  length  is  thought  to  greatly 
strengthen  Hughes'  theory  of  magnetism.  (See 
Magnetism,  Hughes1  Theory  of.} 

Elongation  of  Needle. — (See  Needle,  Elon- 
gation of.) 

Embosser,  Telegraphic An  appa- 
ratus for  recording  a  telegraphic  message  in 
raised  or  embossed  characters. 

Emptied. — A  term  sometimes  applied  to  a 
completely  discharged  secondary  or  storage 
cell. 

It  is  difficult  to  determine  exactly  when  a  stor- 
age cell  is  completely  emptied  or  "discharged/' 
The  cell  is  generally  regarded  as  discharged 
when  its  voltage  falls  below  a  certain  point. 

Endosmose. — The  unequal  mixing  of  two 
liquids  or  gases  through  an  interposed  me- 
dium. 

The  presence  of  an  electric  current  affects  the 
endosmose.  (See  Currents,  Diaphragm.) 

Endosmose,  Electric. — Differences  in  the 
level  of  liquids  capable  of  mixing  through  the 
pores  of  a  diaphragm  separating  them,  pro- 
duced by  the  flow  of  an  electric  current 
through  the  liquid. 

Wiedemann,  who  investigated  these  phenom- 
ena, employed  a  porous  earthenware  vessel  closed 
at  the  bottom  and  terminated  at  its  upper  end  by 
a  glass  bell  provided  with  a  glass  tubulure,  to 


which  was  attached  a  horizontal  arm  for  the  es- 
cape of  the  liquid  raised  in  the  tubulure.  The 
battery  terminals  were  attached  to  platinum  elec- 
trodes placed  respectively  inside  the  porous  cell, 
and  in  a  vessel  of  water  outside  of  the  porous  cell, 
in  which  the  porous  cell  was  placed ;  on  the  passage 
of  the  current  from  the  outside  of  the  cell  to  the 
inside  the  liquid  rose  in  the  glass  tubulure  and  ran 
over  the  horizontal  tube  into  a  vessel  placed  ready 
to  receive  it. 

Energizing,  Electrically Causing 

electricity  to  produce  any  effect  in  an  electro- 
receptive  device. 

An  electro-magnet  is  energized  by  the  passage 
of  a  current  through  its  coils. 

Energy. — The  power  of  doing  work. 

The  amount  of  work  done  is  measured  by  the 
product  of  the  farce,  by  the  space  through  which 
the  force  moves.  Thus  one  pound  raised  verti- 
cally through  ten  feet,  ten  pounds  raised  through 
one  foot,  or  five  pounds  raised  through  two  feet,  all 
represent  the  same  amount  of  work ;  viz.,  ten  foot- 
pounds. 

If  a  weight  of  ten  pounds  be  raised  through,  a 
vertical  height  of  one  foot,  by  means  of  a  string 
passing  over  a  pulley,  there  will  have  been  ex- 
pended an  amount  of  energy  represented  by  the 
work  of  ten  foot-pounds.  If  the  weight  be  pre- 
vented in  any  way  from  falling,  as  by  securing 
the  string  to  a  fixed  support,  the  weight  will  have 
stored  in  it  an  amount  of  energy  equal  to  ten  foot- 
pounds, and  if  permitted  to  fall,  will  be  capable 
of  doing  an  amount  of  work  which,  leaving  out  air 
resistance  and  friction,  is  exactly  equal  to  that 
originally  expended  in  raising  it  to  the  position 
from  which  it  fell;  viz.,  ten  foot-pounds  of  work. 

Energy,  Actual Energy  actually 

employed  in  doing  work  as  distinguished 
from  energy  that  only  possesses  the  power  of 
doing  work,  but  not  actually  doing  such 
work. 

This  term  is  also  used  in  the  sense  of  kinetic 
energy  or  energy  due  to  motion,  but  kinetic  en- 
ergy is  no  more  actual  than  potential  energy. 

Energy,  Atomic Chemical-potentiai 

energy.    (See  Energy,  Chemical-Potential.} 
Energy,  Chemical-Potential The 

potential  energy  possessed  by  the  elementary 
chemical  atoms.     (See  Energy,  Potential} 
If  a  weight  of  one  pound  be  raised  vertically 


Ene.] 


214 


[Eue. 


against  the  earth's  attraction,  through  a  distance 
of  say  ten  feet,  and  placed  on  a  suitable  support, 
an  amount  of  energy,  equal  to  the  ten  foot-pounds 
of  work  done  on  the  weight,  becomes  potential. 

In  the  same  manner  if  the  elementary  atoms  of 
carbon  and  oxygen,  when  combined  so  as  to  form 
carbonic  acid,  are  raised  or  separated  from  one 
another  sufficiently  to  decompose  the  carbonic 
acid  and  separate  the  carbon  from  the  oxygen,  the 
amount  of  potential  energy  the  carbon  and  oxygen 
possess,  as  a  result  of  having  been  separated,  is 
equal  precisely  to  that  originally  required  to  sepa- 
rate them.  In  this  manner  each  chemical  element 
possesses  a  store  of  chemical -potential  energy 
peculiar  to  it,  and  any  element  with  which  it  may 
subsequently  enter  into  combination.  When  ele- 
ments combine  chemically  this  potential  energy  is 
expended  in  producing  heat. 

Energy,  Conser?ation  of The  in- 
destructibility of  energy. 

The  total  quantity  of  energy  in  the  universe  is 
unalterable. 

The  total  energy  of  the  universe  is  not,  how- 
ever, available  for  the  production  of  work  useful 
for  man. 

When  energy  disappears  in  one  form  it  reap- 
pears in  some  other  form.  This  is  called  the  con- 
servation or  indestructibility  of  energy.  The  com  - 
monest  form  in  which  energy  reappears  is  as  heat, 
and  in  this  case  some  of  the  heat  is  lost  to  the 
earth  by  radiation.  This  degradation  or  dissipa- 
tion of  energy  causes  some  of  the  energy  of  the 
earth  to  become  non-available  to  man. 

Energy  is  therefore  available  and  non-available. 
(See  Entropy.} 

Energy,  Correlation  of A  term 

sometimes  applied  to  the  different  phases  un- 
der which  energy  may  appear. 

Since  energy  is  indestructible,  when  it  disap- 
pears in  one  form  or  phase,  it  must  reappear  in 
another  form  or  phase.  The  correlation  of  the 
different  phases  of  energy,  therefore,  necessarily 
follows  from  the  fact  that  all  energy  is  indestruc- 
tible. 

Energy.  Degradation  of  —  — Such  a 
dissipation  of  energy  as  to  render  it  non- 
available  to  man.  (See  Energy,  Conserva- 
tion of.  Entropy?) 

Energy,  Dissipation  of The  ex- 
penditure or  loss  of  available  energy. 


Energy,      Electric 


— The    powei 


which  electricity  possesses  of  doing  work. 

In  the  case  of  a  liquid  mass  at  different  levels, 
the  liquid  at  the  higher  level  possesses  a  certain 
amount  of  potential  energy  measured  by  the 
quantity  of  the  liquid  at  the  higher  level,  and  the 
excess  of  its  height  over  that  of  the  lower  level; 
or,  by  the  difference  between  the  two  levels.  Any 
difference  of  level  will  produce  a  flow  of  the  liquid 
from  the  higher  to  the  lower  level,  and  during 
the  flow  of  this  current  of  liquid,  potential  energy 
will  be  lost,  and  a  certain  amount  of  work  will  be 
done. 

In  the  case  of  electricity,  the  difference  of  elec- 
tric level,  or  potential,  between  any  two  points  of 
a  conductor,  causes  an  electric  current  to  flo\r 
between  these  points  toward  the  lower  electric 
level,  during  which  electric  potential  energy  is 
lost,  and  work  is  accomplished  by  the  electric 
current.  (See  Potential,  Electric.') 

The  amount  of  this  ele^  trie  work  is  measured  by 
the  quantity  of  electricity  that  flows,  multiplied 
by  the  difference  of  potential  under  which  it 
flows.  (See  Joule.  Volt-Coulomb.) 

Electric  energy,  however,  is  generally  meas- 
ured in  electric  power,  or  rate  of  doing  electric 
work. 

Since  an  ampere  is  one  coulomb-per-second,  if 
we  measure  the  difference  of  potential  in  volts, 
the"  product  of  the  amperes  by  the  vo.ts  will  give 
the  electrical  power  in  volt -amperes,  or  watts,  or 
units  of  electric  power.  C  E  =  Watts.  (See 
Ampere.  Volt.  Watt.} 

One  horse  power  equals  550  foot-pounds  per 
second.  One  watt  or  volt-ampere  =  7J-ff  of  a 
horse-power,  or  one  horse-power  equals  746  volt 
amperes  or  watts,  therefore: 

The  cttrrent  in  amperes,  multiplied  by  the  dif- 
ference of  potential  in  volts,  divided  by  746, 
equals  the  rate  of  doing  work  in  horse-powers. 

Thus,  if  .7  ampere  is  required  to  operate  a 
1 6  candle,  no  volt,  incandescent  lamp,  it  requires 
4.8  watts  per  candle. 

One  Walt  =  44.2394  foot-pounds  per  minute,     i 

One  Watt  =  .737324  foot-pound  per  second. 

The  Heat  Activity,  or  the  heat-per- second 
produced  by  an  electric  current,  is  also  propor- 
tional to  -the  product  C  E,  or  the  watts,  for  the 
heat  is  proportional  to  the  square  of  the  current 
in  amperes  multiplied  by  the  resistance  in  ohms, 
or  C2  R  =  the  watts.  (See  Calorimeter,  Elec- 
tric.) 


Eiie.J 


215 


[Ene. 


By  Ohm's  Law  (See  Ohm's  Law) 

C  =  J-  (i),  or  C  R  =  E  (2), 
R 

But  the  electric  power,  or  the  watts,  =  C  E    (3). 
If,  now,  we  substitute  the  value  of  E,  taken 
from  equation  (2)  in  equation  (3)  we  have 
CE  =  C  X  CR  =  C8  R; 

therefore  C8  R  =  Watts. 

To  determine  the  heating  power  of  a  current 
in  small  calories,  calling  H,  the  amount  of  heat 
required  to  raise  I  gramme  of  water  through  i° 
Cent.,  and  C,  the  current  in  amperes — 

H  =  C*  R  X  .24. 
Or,  for  any  number  of  seconds,  /, 

H  =  C2  R/  X  .24. 
(See  Calorie.) 
But  from  Ohm's  Law, 


and  the  formula  for  electric  power  or  the  watts 
=  C  E.  (2)  By  substituting  in  equation  (2) 
and  the  value  of  C,  in  equation  (i), 


C  E  =  EX       =       = 


That  is  to  say,  the  electric  power  in  any  part  of 
a  circuit  varies  directly  as  the  square  of  the 
electromotive  force. 

We,  therefore,  have  three  expressions  for  the 
value  of  the  watt,  or  the  unit  of  electric  power, 

viz.  : 

C  E  =  Watts.         (i) 
C*R  =  Watts.       (2) 


=  Watts. 


(3) 


(i;)  C  E  =  Watts;  or  the  electric  power  is  pro- 
portional to  the  product  of  the  quantity  of  elec- 
tricity per-second,  that  passes,  in  amperes,  and 
the  difference  of  electric  potential  or  /eve/, 
through  which  it  passes,  in  volts. 

(2.)  Ca  R  =  Watts;  or  the  electric  power 
varies  directly  as  the  resistance  R,  when  the  cur- 
rent is  constant,  or  as  the  square  of  the  current, 
if  the  resistance  is  constant.  That  is  to  say,  if 
with  a  given  resistance  the  power  of  a  given 
current  has  a  certain  value,  and  the  current 
flowing  through  this  same  resistance  be  doubled, 
the  power  is  four  times  as  great,  or  is  as  the 
square  of  the  current. 

E» 
(3.)  =-  =  Watts,  or  the  electric  power  is  in- 


versely as  the  resistance  R,  when  the  electro- 
motive force  is  constant,  and  is  directly  propor- 
tional to  the  square  of  the  electromotive  force  if 
the  resistance  is  constant.  , 

A  circuit  of  one  ohm  resistance  will  have  a 
power  of  one  watt,  when  under  an  electromo- 
tive force  of  one  volt,  since  it  would  then  have 
a  current  of  one  ampere  flowing  through  it,  and 
C  E  =  i.  If,  however,  the  resistance  be  halved 
or  becomes  .5  ohm,  then  two  amperes  pass,  or 
the  power  equals  2  watts. 

The  power  varies  as  the  square  of  the  electro- 
motive force  in  any  part  of  a  circuit,  when  tht 
resistance  is  constant  in  that  part.  Thus  2  am- 
peres, and  2  volts,  in  a  circuit  of  one  ohm 
resistance,  give  a  power,  C  E  =  2  X  2  =4  watts. 
If  now,  R,  remaining  the  same,  the  electro- 
motive force  be  raised  to  4  volts,  then  since  E,  is 
doubled,  C,  or  the  amperes,  is  doubled,  and  C 

E8        16 

XE  =  4X4=i6  watts,  or  -TT-  =  —  =  10. 
K  I 

Energy,  Electric,  Transmission  of 

• — The  transmission  of  mechanical  energy  be- 
tween two  distant  points  connected  by  an 
electric  conductor,  by  converting  the  me- 
chanical energy  into  electrical  energy  at  one 
point,  sending  the  current  so  produced 
through  the  conductor,  and  reconverting  the 
electrical  into  mechanical  energy  at  the  other 
point. 

A  system  for  the  electric  transmission  of  energy 
embraces: 

(i.)  A  conducting  circuit  between  the  two 
stations. 

(2.)  An  electric  source  or  battery  of  electric 
sources  or  machines  at  one  of  the  stations,  gener- 
ally in  the  form  f  a  dynamo-electric  machine 
or  machines,  for  converting  mechanical  energy 
into  electric  energy. 

(3.)  Electro-receptive  devices,  generally  electric 
motors,  at  the  other  station  for  reconverting  the 
electric  into  mechanical  energy.  (See  Motor, 
Electric.) 

Energy,  Flow  of The  flow  or  trans- 
mission of  energy  from  the  medium  or  die- 
lectric surrounding  a  conductor  which  is 
directing  a  current  of  electricity  on  to  the 
conductor.  (See  Law,  Poynting's^ 

Energy,  Hysteresial,  Dissipation  of 

— The   dissipation   of  energy  by  means  of 


Ene.] 


213 


[Ent. 


hysteresis.     (See    Energy,    Dissipation   of. 
Hysteresis?) 

Energy,  Kinetic Energy  which  is 

due  to  motion  as  distinguished  from  potential 
energy.     (See  Energy,  Potential?) 

Energy-Meter.— (See  Meter,  Energy?) 
Energy  of  Position.— (See  Position,  En~ 

ergy  °f-} 

Energy  of  Stress.— (See  Stress,  Energy 
of.) 

Energy,  Potential Stored  energy. 

Potency,  or  capability  of  doing  work. 

Energy  possessing  the  power  or  potency  of 
doing  work,  but  not  actually  performing  such 
work. 

The  capacity  for  doing  work  possessed  by 
a  body  at  rest,  arising  from  its  position  as 
regards  the  earth,  or  from  the  position  of  its 
atoms  as  regards  other  atoms,  with  which  it 
is  capable  of  combining. 

A  pound  of  coal,  if  raised  vertically  one  foot, 
possesses,  as  a  mere  weight,  an  amount  of  energy 
capable  of  doing  an  amount  of  work  equal  to  oie 
foot-pound.  The  atoms  of  carbon,  however,  of 
which  it  is  composed,  have  been  raised  or  sepa- 
rated from  those  of  oxygen,  or  some  other  elemen- 
tary substance,  and  when  the  coal  is  burned,  or 
the  carbon  atoms  fall  towards  the  oxygen  atoms 
(*.  e.,  unite  with  them),  the  coal  gives  up  the 
potential  energy  of  its  atoms  in  the  form  of  heat. 

All  elementary  substances  possess  in  the  same 
way  atomic  or  chemical-potential  energy \  or  the 
energy  with  which  they  tend  to  fall  together, 
or  enter  into  combination.  This  energy  varies  in 
amount  in  different  elements  and  becomes  kinetic, 
as  heat,  on  combination  with  other  elements.  (See 
Energy,  Chemical-Potential.) 

Energy,  Radiant Energy  trans- 
ferred to  or  charged  on  the  universal  ether. 

Radiant  energy  is  of  three  forms,  viz.: 
(I.)  Obscure  radiation,  or  heat. 
(2.)  Luminous  radiation,  or  light. 
(3.)  Electro-magnetic  radiation. 

Energy,  Static —A  term  used  to  ex- 
press the  energy  possessed  by  a  body  at  rest, 
resulting  from  its  position  as  regards  other 
bodies,  in  contradistinction  to  kinetic  energy 
or  the  energy  possessed  by  a  body  whose 


atoms,  molecules  or  masses  are  in  actual 
motion. 

Potential  energy. 

The  general  term  for  static  energy  is  potential 
energy.  (See  Energy,  Potential.) 

Energy,  Storage  of—  —The  change 
from  any  form  of  kinetic  energy,  to  any  form 
of  potential  energy.  (See  Energy.  Kinetic. 
Energy,  Potential?) 

Engine,  Electro-Magnetic A  mo- 
tor whose  driving  power  is  electricity.  (See 
Motor.  Electric?) 

Engraving,    Acoustic Engraving 

by  the  human  voice. 

In  the  Phonograph,  Graphophone  and  Gramo 
phone,  a  diaphragm,  set  in  vibration  by  th_ 
speaker's  voice,  cuts  or  engraves  a  record  of  its 
to-and-fro  movements  on  a  sheet  of  tin  foil,  a 
cylinder  of  hardened  wax,  or  a  specially  coated 
plate  of  metal  or  glass.  This  record  is  employed 
in  order  to  reproduce  the  speech.  (See  Phonograph.) 

Engraving,  Electric  —  -  —A  method 
for  electrically  etching  or  engraving  a  me- 
tallic plate  by  covering  it  with  wax,  tracing 
the  design  on  the  wax  so  as  to  expose  the 
metal,  connecting  the  metal  with  the  positive 
terminal  of  a  battery,  and  placing  it  in  a 
bath  opposite  another  plate  of  metal. 

By  the  action  of  electrolysis  the  metal  is  dis- 
solvedfrom  the  exposed  portions  and  deposited 
on  the  plate  connected  with  the  other  terminal 
of  the  battery.  (See  Electrolysis.) 

In  this  manner  the  design  is  obtained  in  the 
form  of  an  etching  or  cutting  of  the  plate. 

By  connecting  the  waxed  plate  to  the  negative 
terminal  of  the  electric  source,  the  metal  will  be 
deposited  on  the  exposed  portions  of  the  plate, 
thus  producing  the  design  in  relief.  Unless 
great  care  is  taken,  this  latter  method  is  not, 
however,  apt  to  produce  a  sufficiently  uniform 
deposit  to  enable  the  plate  so  formed  to  be  used 
for  printing  from. 

Electric  engraving  is  sometimes  called  electro- 
etching. 

Entropy. — In  thermo-dynamics  the  non- 
available  energy  in  any  system. — (Clausius 
and  Mayer?) 

In  thermo-dynamics,  the  available  energy 
in  any  system. — (Tait,  Thomson  and  Max 
well?) 


Ent] 


217 


[Eqn. 


As  will  be  noticed,  this  term  is  used  in  entirely 
different  and  opposite  senses  by  different  scientific 
men.  The  latter  sense  is,  perhaps,  the  one  most 
generally  taken. 

Heat  energy  is  available  for  doing  useful  exter- 
nal work  only  when  the  source  ol  heat  utilized  is 
hotter  than  surrounding  bodies,  that  is,  when  the 
heat  is  transferred  from  a  hotter  to  a  colder  body. 
When  all  bodies  have  acquired  the  same  temper- 
ature, they  can  do  no  more  external  work.  In 
the  various  transformations  of  energy  some  of  the 
energy  is  converted  into  heat,  and  this  heat  is 
gradually  diffused  through  the  universe  and  thus 
becomes  non-available  to  man.  Therefore,  the 
entropy  of  our  earth  is  decreasing. 

"Entropy,  in  thermodynamics,"  says  Max- 
well, "id  a  quantity  relating  to  a  body  such  that 
its  increase  or  diminution  implies  that  heat  has 
entered  or  left  the  body.  The  amount  of  heat 
which  enters  or  leaves  the  body  is  measured  by  the 
product  of  the  increase  or  diminution  of  entropy 
into  the  temperature  at  which  it  takes  place." 

Entropy,  Electric — A  term  pro- 
posed by  Maxwell  for  use  in  thermo-elec- 
tric phenomena  to  include  the  doctrine  of 
entropy  in  electric  science. 

"When  an  electric  current,'5  says  Maxwell, 
"  passes  from  one  metal  to  another,  heat  is 
emitted  or  absorbed  at  the  junction  of  the  metals. 
We  should,  therefore,  suppose  that  the  electric 
entropy  has  diminished  or 'increased  when  the 
electricity  passes  from  one  metal  to  the  other,  the 
electric  entropy  being  different  according  to  the 
.  nature  of  the  medium  in  which  the  electricity  is, 
and  being  affected  by  its  temperature,  stress, 
strain,  etc." 

Equalizer,  Feeder An  adjustable 

resistance  placed  in  the  circuit  of  a  feeder  for 
the  purpose  of  regulating  the  difference  of 
potential  at  the  junction  box. 

Equalizer,  Magnetic A  device  for 

equalizing  the  otherwise  unequal  force  ex- 
erted between  a  magnet  pole  and  its  arma- 
ture at  varying  distances. 

Since  the  force  of  magnetic  attraction  increases 
rapidly  with  the  decrease  of  the  distance,  it  fol- 
lows that  any  force  sufficiency  great  to  cause  the 
motion  of  an  armature  towards  a  ]>ule,  against  the 
force  of  gravity,  will  result  in  t!ie  movement  of  the 
armature  to  the  pole,  and  tha-,  therefore,  no  dif- 
ferentiation as  to  the  final  result  will  be  produced 


by  a  powerful  current,  and  a  current  just  strong 
enough  to  start  the  action.  If,  however,  the 
armature  move  against  the  action  of  a  spring,  the 
latter  can  be  so  arranged  that  the  force  with 
which  it  opposes  the  motion  of  the  armature  in- 
creases, the  nearer  the  armature  is  to  the  pole, 
and  in  this  way  the  movement  of  the  armature 
can  be  made  proportional  to  the  strength  of  the 
current  energizing  the  electro-magnet. 

A  similar  method  consists  in  mechanical  devices 
that  cause  the  armature  to  work  with  lessened 
mechanical  advantage  as  it  approaches  the  po'e. 

Or,  thepolar  surfaces  may  be  so  shaped  by  cut- 
ting, or  by  the  addition  of  suitable  projections, 
as  to  cause  the  approach  of  the  armature  to  be 
attended  by  a  nearly  constant  force. 

Equator,  Geographical •  — An  imag- 
inary great  circle  passing  around  the  earth 
midway  between  its  poles. 

Equator,  Magnetic The  magnetic 

parallel  or  circle  on  the  earth's  surface  v/here 
a  magnetic  needle,  suspended  so  as  to  be  free 
to  move  in  a  vertical  as  well  asinahcrizontal 
plane,  remains  horizontal. 

An  irregular  line  passing  around  the  earth 
approximately  midway  between  the  earth's 
magnetic  poles.  (See  Dip  or  Inclination, 
Angle  of?) 

Equator  of  Magnet. — (See  Magnet,  Equa- 
tor of.) 

Equatorial. — Pertaining  to  the  equator. 

Equatorially. — In  the  direction  of  the 
equator. 

Equipotential  Surface  of  a  Conductor 
through  which  a  Current  is  Flowing. — 
(See  Surface,  Equipotential,  of  a  Conductor 
through  which  a  Current  is  Flowing?) 

Eqnipotential  Surface,  or  Level  Surface 
Of  Escaping  Fluid. — (See  Sttrface,  Equipo- 
tential, or  Level  Surface  of  Escaping  Fluid.) 

Equipotential  Surfaces,Electrostatic 

—  (See  Surfaces,  Equipotential,  Electro- 
static?) 

Eqnipotential    Surfaces,   Magnetic  - 
—(See  Surfaces,  Equipotential,  Magnetic?) 

Equivalence,   Electro-Chemical,  Law  of 

The  amount  of  chemical  action  pro- 
duced by  an  electric  current,  passed  through 
various  chemical  substances,  is  proportional 
to  the  chemical  equivalent  of  each  substance, 


Equ.] 

that  is,  to  its  atomic  weight,  divided  by  its 
valency.     (See  Valency.) 

Thus,  the  atomic  weight  of  oxygen  is  sixteen 
times  greater  than  the  atomic  weight  of  hydrogen. 
Oxygen  is  a  diad;  that  is,  has  twice  the  combin- 
ing power  of  hydrogen.  The  passage  of  a  given 
quantity  of  electricity  will  liberate  eight  times,  by 
weight,  as  much-  oxygen  as  hydrogen;  or,  to  put 
it  in  another  way,  the  passage  of  a  given  quan- 
tity of  electricity  will  liberate  two  atoms  of 
hydrogen  for  every  atom  of  oxygen. 

The  atomic  weight  of  chlorine  is  35.4.  The 
passage  of  a  given  amount  of  electricity  will 
liberate  a  weight  of  chlorine  35.4  greater  than  the 
weight  of  hydrogen;  or,  for  every  atom  of 
chlorine  it  will  liberate  one  atom  of  hydrogen. 
Here  the  passage  of  a  given  amount  of  electricity 
liberates  one  atom  of  the  monad  element  hydrogen 
for  every  atom  of  the  monad  element  chlorine. 

The  atomic  weight  of  gold  is  196.2,  and  its 
atomicity  or  valency  is  3.  The  passage  of  a 


given  amount  of  electricity  will  liberate 


10.6.2  _ 


65.4  in  ic  compounds  as  great  a  weight  of  the 
triad  element  gold  as  of  hydrogen;  or,  will  liberate 
them  in  the  proportion  of  one  atom  of  gold  for 
every  three  atoms  of  hydrogen. 

Generalizing,  it  appears,  therefore,  that  the 
passage  of  the  same  quantity  of  electricity  through 
an  electrolyte  liberates  the  same  number  of  atoms 
of  a  monad  element,  no  matter  what  their  nature 
may  be.  It  liberates  one-half  as  many  of  the  diad 
atoms  as  it  does  of  the  monads,  and  one-third  as 
many  of  the  triad  atoms  as  of  the  monads. 

Professor  Lodge  points  out,  that  assuming  the 
truth  of  the  theory  that  a  current  of  electricity 
flows  in  an  electrolyte  by  means  of  a  true  electric 
convection,  each  atom  carrying  an  electric 
charge,  then  it  would  seem  that  every  monad 
atom  carries  an  equal  charge  of  electricity, 
whether  it  be  an  atom  of  hydrogen,  chlorine, 
potassium,  silver,  or  mercury.  That  each  diad 
element  carries  twice  as  much,  and  that  each 
triad  element  carries  three  times  as  much. 

In  general,  the  number  of  atoms  liberated  by  a 
given  current  of  electricity  is  equal  to  the  num- 
ber of  atoms  of  hydrogen,  divided  by  the  valency 
of  the  atom.  ' '  The  electric  charge, ' '  says  Lodge, 
"belonging  to  each  atom  of  matter,  is  a  simple 
multiple  of  a  definite  quantity  of  electricity,  which 
quantity  is  an  absolute  constant,  quite  independent 
of  the  nature  of  the  particular  substance  to  which 
the  atom  belongs." 


218  [Equ- 

The  specific  charge  thus  hypothetically  given  to 
each  atom  of  matter  is  believed  never  to  be  lost. 

Atoms  capable  of  entering  into  combination  are 
supposed  to  be  oppositely  charged,  and  chemical 
affinity  is,  according  to  this  supposition,  believed 
to  be  the  result  of  the  mutual  attractions  of  opposite 
electric  charges  naturally  and  originally  pos- 
sessed by  the  atoms  of  matter. 

Lodge  points  out  the  following  results  which 
naturally  flow  from  the  hypothesis  that  the  atoms 
of  matter  possess  definite  positive  and  negative 
charges  of  electricity,  viz.: 

(i.)  That  the  amount  of  electricity  possessed 
by  each  monad  atom  is  exceedingly  small,  being 
about  the  hundred  thousand  millionth  part  of 
the  ordinary  electrostatic  unit,  or  less  than  the 
hundred  trillionth  of  a  coulomb. 

(2.)  The  charge  being  small,  the  potential  is 
necessarily  low. 

Probably  something  between  one  and  three 
volts  is  a  high  difference  of  potential  between  two 
oppositely  charged  atoms. 

(3.)  The  nearness  of  the  attracting  atoms,  how- 
ever, can  cause  a  very  strong  electrostatic  attrac- 
tion between  them. 

(4. )  That  chemical  affinity,  or  atomic  attraction, 
is  caused  by  the  presence  of  these  electric  charges. 
(5.)  That  the  electrical  force  between  two 
atoms  at  any  distance  is  ten  thousand  million 
billion  billion  times  greater  than  their  gravitation 
attraction  at  the  same  distance,  or,  the  force  has 
an  intensity  per  unit  of  mass  capable  of  producing 
an  acceleration,  nearly  one  trillion  times  greater 
than  that  of  gravity  at  the  earth's  surface. 

Equivalent,  Chemical The  quo- 
tient obtained  by  dividing1  the  atomic  weight 
of  any  elementary  substance  by  its  atomicity. 
(See  Weight,  Atomic.  Atomicity?) 

The  ratio  between  the  quantity  of  an  ele- 
ment and  the  quantity  of  hydrogen  it  is 
capable  of  replacing. 

That  quantity  of  an  elementary  substance 
that  is  capable  of  combining  with  or  replac- 
ing one  atom  of  hydrogen. 

The  chemical  equivalent  has  a  different  value 
from  the  atomic  weight  whenever  the  valency 
is  greater  than  unity.  Thus  the  atomic  weight 
of  gold  is  196.2,  but  since  in  ic  compounds  one 
atom  of  gold  is  capable  of  combining  with  three 
atoms  of  hydrogen,  the  weight  of  the  gold  equiva- 
lent to  that  of  one  atom  of  hydrogen  is  one-third 
of  196.2,  or  65  4. 


Eqn.j 


219 


[Esc. 


Equivalent  Conductivity.— (See  Conduc- 
tivity, Equivalent?) 
Equivalent,  Electro-Chemical A 

number  representing  the  weight  in  grammes 
of  an  elementary  substance  liberated  during 
electrolysis  by  the  passage  of  one  coulomb  of 
iiectricity.  (See  Electrolysis.  Coulomb?) 

The  chemical  equivalent  of  a  substance 
multiplied  by  the  electro-chemical  equivalent 
of  hydrogen. 

The  electro- chemical  equivalent  is,  therefore, 
found  by  multiplying  the  electro-chemical  equiva- 
lent of  hydrogen  by  the  chemical  equivalent  of 
the  element. 

It  may  be  determined  experimentally  that  one 
coulomb  of  electricity,  expended  electrolytically, 
will  liberate  .0000105  gramme  of  hydrogen. 
Therefore  a  current  of  one  ampere,  or  one  coulomb - 
fer-second,  will  liberate  .0000105  gramme  of  hy- 
drogen per  second.  The  number  .0000105  is  the 
electro-chemical  equivalent  of  hydrogen. 

In  the  same  manner  the  electro-chemical  equiva- 
lents of  the  other  elements  are  obtained  by  multi- 
plying the  electro-chemical  equivalent  of  hydrogen 
by  the  chemical  equivalent  of  the  substance. 

Thus,  the  chemical  equivalent  of  potassium  is 
39.1,  therefore  its  electro-chemical  equivalent  is 
39.1  X  .0000105  =.00041055.  By  multiplying 
the  strength  of  the  current  that  passes  by  the 
electro- chemical  equivalent  of  any  substance  we 
obtain  the  weight  of  that  substance  liberated  by 
electrolysis.  (See  Equivalence,  Electro -Chemical, 
Law  of.) 

To  determine  the  electro-chemical  equivalent 
of  the  other  elements  see  table  of  chemical  equiva- 
lents on  page  212. 

Equivalent,  Jonle's The  mechan- 
ical equivalent  of  heat.  (See  Heat,  Mechan- 
ical Equivalent  of.) 

Equivalent  of  Heat,  Mechanical 

(See  Heat,  Mechanical  Equivalent  of.) 

Equivalent  Besistance.— (See  Resistance, 
Equivalent.) 

Equivolt. — A  term  proposed  by  J.  T. 
Sprague  for  the  unit  of  electrical  energy,  ap- 
plied especially  to  chemical  decomposition. 

Sprague, defines  an  equivolt  as  follows  :    "The 
mechanical  energy  of  one  volt  electromotive  force 
exerted  under  unit  conditions  through  one  equiva- 
lent of  chemical  action  in  grains." 
8—  Vol    1 


This  term  has  not  been  generally  accepted. 
(See  Volt-Coulomb.  Joule.) 

Erb's  Standard  Size  of  Electrodes.— (See 

Electrodes,  Erb's  Standard  Size  of.) 

Erg1. — The  unit  of  work,  or  the  work  done 
when  unit  force  is  overcome  through  unit 
distance. 

The  work  accomplished  when  a  body  is 
moved  through  a  distance  of  one  centimetre 
with  the  force  of  one  dyne.  (See  Dyne.) 

A  dyne  centimetre. 

The  work  done  when  a  weight  of  one  gramme 
is  raised  against  gravity  through  a  vertical  height 
of  one  centimetre  is  equal  to  981  ergs,  because 
the  weight  of  one  gramme  is  i  X  981  dynes,  or 
981  ergs. 

The  following  values  for  the  erg,  the  unit  of 
work,  and  the  dyne,  the  unit  of  force,  are  taken 
from  Hering: 

I  erg   =  i  dyne  centimetre. 
I  erg   =  o.ooooooi  joule. 
981  ergs  =  i  gramme  centimetre. 
1,937.5  ergs  =  I  foot  grain. 

13,562,600  ergs  .=  I  foot-pound. 

i  dyne   =  i  .0194  milligrammes. 
I  dyne    =  0.015731  grain. 
i  dyne   =  0.0010194  grammes. 
I  dyne   =  0.00003596  ounce  avoirdupois. 
63.568  dynes  —  I  grain. 
981  dynes  =  i  gramme. 

Ergmeter. — An  apparatus  for  measuring 
the  work  of  an  electric  current  in  ergs. 

Erg-ten. —  A  term  proposed  for  ten  million 
ergs  or  i  X  10  10=  10,000,000,000. 

In  representing  large  numbers  containing  many 
ciphers  the  following  plan  is  generally  adopted  for 
representing  the  number  of  ciphers  that  are  to  be 
added  to  a  given  number.  Thus,  suppose  it  is 
desired  to  represent  the  number  3,800,000,000. 
When  written  38  X  io8  it  indicates  that  38  is  to 
be  multiplied  by  lo8  or  100,000,000,  or,  in  other 
words,  that  38  is  to  be  followed  by  8  ciphers, 
thus  3,800,000,000. 

A  negative  exponent,  as  3  X  io~8  represents 
the  corresponding  decimal  thus,  .00000003. 

i  erg  X  io10,  or  10,000,000,000  is  called  an 
erg  -ten.  I  X  J°6  =  an  erg  -six.  These  terms 
are  not  in  general  use.  Ten  meg-ergs  is  a  pref- 
erable phrase  to  an  erg-ten.  (See  Meg-erg. ) 

Escape,    Electric A    term    some- 


Esc.] 


220 


[Eva. 


times  employed  to  indicate  the  loss  of  charge 
on  an  insulated  conductor.  (See  Leakage, 
Electric?) 

Escaping   Fluid,  Flow-Lines  of  - 
(See  Flow-Lines  of  Escaping  Fluid?) 

Escaping  Fluid,  Stream-Lines  of  - 
(See  Stream-Lines  of  Escaping  Fluid.} 

Essential  Resistance.  —  (See  Resistance, 
Essential.} 

Etching,  Electro  --  A  term  some- 
times employed  instead  of  electro-engraving. 
(See  Engraving,  Electric?) 

Etching,  Galvanic  ---  Electro-En- 
graving. (See  Engraving,  Electric.} 

Ether.  —  The  tenuous,  highly  elastic  fluid 
that  is  assumed  to  fill  all  space,  and  by  vibra- 
tions or  waves  in  which  light  and  heat  are 
transmitted. 

Although  the  existence  of  the  ether  is  assumed 
in  order  to  explain  certain  phenomena,  its  actual 
existence  is  very  generally  credited  by  scientific 
men,  and,  in  reality,  proofs  are  not  wanting  to 
fairly  establish  such  existence. 

Light  and  heat  are  believed  to  be  due  to  trans- 
verse vibrations  in  the  ether.  Magnetism  appears 
to  be  due  to  whirls  or  whirlpools,  and  an  elec- 
tric current  is  believed  by  some  to  be  due  to 
pulses  of  waves  of  ether  set  in  motion  by  differ- 
ences in  the  ether  pressures. 

It  is  not  correct  to  regard  the  luminiferous 
ether  as  possessing  no  weight,  or  as  being  im- 
ponderable. Maxwell  estimates  its  density  as 


1,000,000,000,000,000,000,000 

is  very  readily  moved  or  set  into  vibration,  its 
rigidity  being  estimated  at  about     - 

1,000,000,000 

that  of  steel. 

According  to  the  speculations  of  some  physi- 
cists the  ether  is  not  discontinuous  or  granular, 
but  it  is  similar  to  what  might  be  regarded  as  an 
almost  impalpable  jelly. 

Ethereal.  —  Pertaining  to  the  universal 
ether. 

Eudiometer.  —  A  voltameter  in  which  sep- 
arate graduated  vessels  are  provided  for  the 
reception  and  measurement  of  the  gaseous 
products  evolved  during  electrolysis.  (See 
Voltameter.} 


In  all  cases  electrodes  for  eudiometers  must  be 
used  which  do  not  enter  into  combination  with  the 
evolved  gaseous  products.  In  the  case  of  oxygen 
and  hydrogen,  platinum  is  generally  used. 

A  form  of  eudiometer  is  shown  in  Fig.  241. 
Two  separate  glass  ves- 
sels, provided  at  the  top 
with  stop  cocks,  and 
open  at  their  lower 
ends,  rest  in  a  vessel  of 
water  A,  over  platinum 
electrodes,  connected 
electrically  with  binding 
posts  K,  K.  Both  ves- 
sels are  filled  with  water 
slightly  acidulated  with 
sulphuric  acid,  and, 
when  connected  with 
a  battery  of  sufficient 
electromotive  force  (not 
less  than  1.45  volts), 

electrolysis  takes  place,  Fig.  241.  Eudiometer. 
and  hydrogen  gas  collects  in  the  vessel  over 
the  platinum  electrode  connected  with  the  neg- 
ative battery  terminal,  and  oxygen  in  the  vessel 
over  the  electrode  connected  with  the  positive 
battery  terminal.  The  volume  of  the  hydrogen 
is  approximately  twice  as  great  as  that  of  the 
oxygen.  (See  Water,  Electrolysis  of.) 

The  proportion  is  not  exactly  2  to  i,  because, 

(i.)  Some  of  the  hydrogen  is  occluded  or  ab- 
sorbed by  the  platinum  electrode. 

(2.)  Some  of  the  oxygen  is  given  off  as  tri- 
atomic  oxygen,  or  ozone,  which  is  denser  and 
occupies  less  space  than  free  atomic  oxygen. 

Eudiometric.— Pertaining  to  the  eudiom- 
eter. (See  Eudiometer?) 

Endiometrically. — By  means  of  the  eudi- 
ometer. 

Evaporation.— The  change  from  the  liquid 
to  the  vaporous  state. 

Wet  clothes  exposed  to  the  air  are  dried  by  the 
evaporation  of  the  water. 

Evaporation  is  greater: 

(I.)  The  more  extended  the  surfaces  exposed. 

(2.)  The  higher  the  temperature  of  the  air. 

(3.)  The  dryer  the  air,  or  the  smaller  the 
quantity  of  vapor  it  contains  already. 

(4.)  The  stronger  the  wind. 

(5.)  The  smaller  the  barometric  pressure. 

Evaporation,  Electric The  forma- 


Eva.] 


221 


LExc. 


lion  of  vapors  at  the  surfaces  of  substances 
by  the  influence  of  negative  electrification. 

The  term  electric  evaporation  was  proposed  by 
Crookes  for  the  formation  of  metallic  vapors  of 
such  substances  as  metallic  platinum,  exposed  in 
high  vacua  to  the  effects  of  negative  electrifica- 
tion. He  shows  that  under  these  circumstances 
the  surface  molecules  of  the  platinum  lose  their 
power  of  cohering  and  fly  off  into  the  space 
around  them,  i.  e  ,  suffer  true  evaporation.  This 
action  takes  place  under  atmospheric  pressures, 
but,  like  ordinary  evaporation,  is  greatly  facili- 
tated by  the  presence  of  a  high  vacuum, 

True  electric  evaporation  takes  place  with 
liquids  as  well  as  with  solids.  In  an  experiment 
with  water,  the  influence  of  the  kind  of  the  elec- 
trification was  clearly  shown.  A  vessel  of  water 


Fig.  24.2.    Electrical  Evaporation. 

exposed  to  the  air  was  first  positively  electrified, 
but  after  an  exposure  of  i|  hours  only  a  trifling 
evaporation  was  noticeable.  The  water  was 
then  negatively  electrified,  and  at  the  end  of  i^ 
hours  had  lost  y^1^  part  of  its  weight  more  than 
did  the  positively  charged  water. 

Professor  Crookes  experimented  with  cadmium, 
and,  in  order  to  show  that  electric  evaporation  is 
different  from  evaporation  produced  by  the  agency 
«f  heat,  tried  the  following,  viz.:  A  high  vacuum 
U-tube,  shaped  as  shown  in  Fig  242,  was  pro- 


Fig   243.     Electrical  Evaporation. 

vided  with  platinum  poles  sealed  in  the  glass  at 
A  and  B.  Two  pieces  of  cadmium,  C  and  D, 
were  placed  in  the  tube  in  the  position  shown, 
and  the  "hb^  uniformly  heated  by  means  of  a  gas- 
burner  :jid  air  oath,  and  maintained  at  a  constant 
temperacure.  i'he  current  was  then  passed  for 
ibout  an  hour,  B,  being  made  the  negative  pole. 


No  metal  was  deposited  in  the  neighborhood  oi 
the  positive  pole,  the  portions  of  the  tube  sur- 
rounding the  positive  pole  being  quite  clean, 
while  the  corresponding  portions  of  the  other  limb 
of  the  tube  were  thickly  coated,  as  shown  by  the 
shading  in  the  drawing. 

In  another  experiment,  in  which  the  tempera- 
ture was  kept  lower  than  in  the  preceding,  viz., 
just  below  the  melting  point  of  the  cadmium,, 
after  the  current  had  passed  for  an  hour,  the  limb 
of  the  tube  through  which  the  current  had  passed 
had  received  a  thick  coating,  while  the  other  was 
nearly  free  from  coating,  as  shown  in  Fig.  243. 
Here  the  increase  in  the  amplitude  of  the  mole- 
cular oscillation  under  the  influence  of  the  elec- 
tricity is  manifest. 

Evaporation,  Electrification  by  — -  — 

An  increase  in  the  difference  of  potential  ex- 
isting in  a  mass  of  vapor  attending  its  sudden 
condensation. 

The  free  electricity  of  the  atmosphere  is  be- 
lieved by  some  to  be  due  to  the  condensation  of 
the  vapor  of  the  air  that  results  in  rain,  hail, 
clouds,  etc.  It  is  probable,  however,  that  the 
true  effect  of  condensation  is  mainly  limited  to 
the  increase  of  a  feeble  electrification  already 
possessed  by  the  air  or  its  contained  vapor.  The 
small  difference  of  potential  of  the  exceedingly 
small  drops  of  water  in  clouds  is  enormously  in- 
creased by  the  union  or  coalescing  of  many 
thousands  of  such  drops  into  a  single  rain  drop. 
(See  Electricity,  Atmospheric.] 

Exchange,  Telephonic,  System   of 

— A  combination  of  circuits,  switches  and 
other  devices,  by  means  of  which  any  one  of 
a  number  of  subscribers  connected  with  a 
telephonic  circuit,  or  a  neighboring  telephonic 
circuit  or  circuits,  may  be  placed  in  electrical 
communication  with  any  other  subscriber 
connected  with  such  circuit  or  circuits. 

A  telephone  exchange  consists  essentially  of  a 
multiple  switchboard,  or  a  number  of  multiple 
switchboards,  furnished  with  spring-jacks,  an- 
nunciator drops,  and  suitable  connecting  cords.  A 
call  bell,  or  bells,  is  also  provided.  The  annun- 
ciator drops  are  often  omitted.  (See  Board., 
Multiple  Switch.) 

Excitability.  Electric,  of  Nerve  or  Hi ns- 
cnlar  Fibre  —  —The  effect  produced  by  an 
electric  current  in  stimulating  the  nerve  of  » 


Exc.] 


222 


[Exh. 


living  animal,  or  in  producing  an  involuntary 
contraction  of  a  muscle. 

Du  Bois-Reymond  has  shown  that  these  effects 
depend  : 

(l.)  On  the  strength  of  the  current  employed. 
The  excitability  occurs  only  when  the  current 
begins  to  flow,  and  when  it  ceases  flowing;  or, 
when  the  electrodes  first  touch  the  nerves,  and 
when  they  are  separated  from  it.  Subsequent 
investigations  have  shown  that  this  is  true  only 
for  the  frog's  nerves,  and  is  true  for  the  human 
nerves  only  in  the  case  of  moderate  currents, 
strong  currents  producing  tetanus. 

(2.)  On  the  rapidity  with  which  the  current 
used  reaches  its  maximum  value,  that  is,  on  the 
rapidity  of  change  of  current  density.  (See 
Current  Density.') 

Excitability,    Electro-Nervous    — 

In  electro-therapeutics  the  electric  excitation 
of  a  nerve. 
Excitability,    Electrotonic — The 

actual  excitability  of  a  nerve  when  in  the 
electrotonic  condition.  (See  Electrotonus. 
Anelectrotonus.  Kathelectrotonus.) 

Excitability,  Faradic Muscular  or 

nervous  excitability  following  the  employment 
of  the  rapidly  intermittent  currents  produced 
by  induction  coils.  (See  Coil,  Induction.) 

Faradic  excitability  is  different  from  galvanic 
excitability,  or  that  produced  by  means  of  a  con- 
tinuous voltaic  current.  (See  Excitability,  Gal- 
vanic. ) 

Excitability,  Galvanic  — A  term 

sometimes  employed  for  electric  excitability 
of  nerve  or  muscular  fibre.  (See  Excitability, 
Electric,  of  Nerve  or  Muscular  Fibre?) 

Excitation,  Compensated,  of  Alternator. 
— (See  Alternator,  Compensated  Excitation 

*f) 

Excitation,  Direct The  excitement 

of  a  muscle  by  placing  an  electrode  on  the 
muscle  itself. 

Excitation,    Electro-Muscular    - 
In  electro-therapeutics  the  galvanic  or  faradic 
excitation  of  the  muscle,  or  its  excitation  by 
the  continuous  currents  of  a  voltaic  battery,  or 
the  alternating  currents  of  an  induction  coil. 

Excitation,  Faradic  -  —Excitation  of 
muscle  or  nerve  fibre  by  means  of  rapidly 


alternating  currents  of  electricity.  (See 
Excitability,  Faradic?) 

Excitation,  Indirect The  excite- 
ment of  a  muscle  from  its  nerve. 

Exciter  of  Field.— (See  Field,  Exciter  of.) 

Exciting  Liquid  of  Voltaic  Cell.— (See 
Cell,  Voltaic,  Pr -imary.  Exciting  Liquid  oj '.) 

Execution,  Electric Causing  the 

death  of  a  criminal,  in  cases  of  capital  pun- 
ishment, by  means  of  the  electric  current. 

Electric  execution  has  been  adopted  by  the 
State  of  New  York,  in  accordance  with  the 
following  law  : 

"The  Court  shall  sentence  the  prisoner  to 
death  within  a  certain  week,  naming  no  day  or 
hour,  and  not  more  than  eight  nor  Jess  than  five 
weeks  from  the  day  of  sentence.  The  execution 
must  take  place  in  the  State  prison  to  which  con- 
victed felons  are  sent  by  the  Court,  and  the  execu- 
tioner must  be  the  agent  and  warden  of  the  prison. 

"No  newspaper  may  print  any  details  of  the 
execution,  which  is  to  be  inflicted  by  electricity. 
A  current  of  electricity  is  to.  be  caused  to  pass 
through  the  body  of  the  condemned  of  sufficient 
intensity  to  kill  him,  and  the  application  is  to  be 
continued  until  he  is  dead." 

Exhaustion,  Electric  —  —Physiological 
effects  resembling  those  produced  by  sun- 
stroke, resulting  from  prolonged  exposure 
to  the  radiation  of  unsually  large  voltaic  arcs. 
(See  Sun-Stroke,  Electric) 

Exhaustion  of  Primary  Voltaic  Cell.— 
(See  Cell,  Voltaic,  Primary,  Exhaustion  of.) 

Exhaustion  of  Secondary  Voltaic  Cell.— 

(See  Cell,  Voltaic,  Secondary,  Exhaustion  of.) 

Exhaustion  of  Voltaic  Cell.— (See  Cell, 
Voltaic,  Exhaustion  of.) 

Exhaustion,  Reaction  of  -  —A  con- 
dition of  nervous  and  muscular  irritability  to 
electric  excitation  when  a  certain  reaction, 
produced  by  a  given  current  strength,  cannot 
be  reproduced  without  an  increase  of  current 
strength. 

The  reaction  of  exhaustion  may  be  regarded  as 
a  special  variety  of  the  reaction  of  degeneration. 
(See  Degeneration,  Reaction  of.) 

The  reaction  of  degeneration  embraces  the 
following  modifications  of  irritability,  viz. : 


Exp.J 


223 


[Eye. 


•  (i.)  Disappearance  or  diminution  of  nervous 
irritability  to  both  galvanic  and  faradic  currents. 

(2.)  Disappearance  of  far:.dic  and  increase  of 
galvanic  irritability  of  muscles,  generally  associ- 
ated with  an  increase  of  mechanical  irritability. 

(3  )  Disappearance  of  faradic  and  increase  of 
galvanic  muscular  irritability  associated  generally 
with  increased  mechanical  irritability. 

(4.)  Tardy,  delayed  contraction  of  muscles  in- 
stead of  quick  reaction  of  normal  muscle. 

(5.)  Marked  modifications  of  normal  sequence 
i.f  contraction. — Liebig  6°  Rohe. 

Expanding       Magnetic        Whirl.— (See 

Whirl,  Expanding  Magnetic?) 


Exploder,  Electric  Mine 


— A  small 


Expansion,    Co-efflcient    of 


—The 


fractional  increase  in  the  dimensions  of  a  bar 
or  rod  when  heated  from  32  degrees  to  33 
degrees  F.  or  from  o  degree  to  I  degree  C. 

The  fractional  increase  in  the  length  of  the  bar 
is  called  the  Co-efficient  of  Linear  Expansion. 

The  fractional  increase  in  the  surface  is  called 
the  Co-efficient  of  Surface  Expansion. 

The  fractional  increase  in  the  volume  is  called 
the  Co-efficient  of  Cubic  Expansion. 

Expansion,  Electric  -  — The  increase 
in  volume  produced  in  a  body  on  giving  such 
body  an  electric  charge. 

A  Leyden  jar  increases  in  volume  when  a 
charge  is  imparted  to  it.  This  result  is  due  to  an 
expansion  of  the  glass  due  to  the  electric  charge. 
According  to  Quincke,  some  substances,  such  as 
resinous  or  oily  bodies,  manifest  a  contraction  of 
volume  on  the  reception  of  an  electric  charge. 

Expansion  Joint.  —  (See  Joint,  Expan- 
sion?) 

Expansion,  Linear,  Co-efflcient  of  — 

A  number  expressing  the  fractional  increase  in 
length  of  a  bar  for  a  given  increment  of  heat. 
The   co-efficients  of  expansion  of  a  few  sub- 
stances are  given  in  the  following  table: 
Temp. 

Aluminium 16  to  100  degrees  C.  .0.0000235 

loo     "        •     ..0.0000188 
100 

100 

100 
100 

TOO 
100 

100 

100 


Brass     o 

Copper o 

German  silver. .  o 

Glass o 

Iron. ". .  13 

T  .ea<l    .    . ' o 

•Platinum o 

Silver o 

Zinc. . .               ,  o 


.  .0.0000167 
.  .0.0000184 
.  .0.0000071 
.  .0.0000123 
.  .0.0000280 
.  0.0000089 
.  .0.0000194 
.  .0.0000230 


— (Anthony  &>  Brackett.} 


magneto-electric  machine  used  to  produce  the 
currents  of  high  electromotive  force  employed 
in  the  direct  firing  of  blasts. 

Exploder,    Electro-Magnetic    — A 

small  magneto-electric  machine  used  to  pro- 
duce the  currents  of  high  electromotive  force 
employed  in  the  direct  firing  of  blasts. 

Explorer,   Electric An  apparatus 

operated  by  means  of  induced  currents,  and 
employed  for  the  purpose  of  locating  bullets 
or  other  foreign  metallic  substances  in  the 
human  body.  (See  Balance,  Induction, 
Hughes'.) 

Explorer,  Magnetic  -  —A  small,  flat 
coil  of  insulated  wire,  used,  in  connection  with 
the  circuit  of  a  telephone,  to  determine  the 
position  and  extent  of  the  magnetic  leakage 
of  a  dynamo-electric  machine  or  other  similar 
apparatus.  (See  Magnetophone.) 

Explosive  Distance. — (See  Distance,  Ex- 
plosive.) 

Extension  Call-Bell (See  Bell,  Exten- 
sion Call.) 

External  Circuit. — (See  Circuit,  Exter- 
nal.) 

External  Secondary  Resistance.  —  (See 
Resistance,  External  Secondary ) 

Extra  Currents.— (See  Currents,  Extra.} 

Extraordinary  Resistance. — (See  Resist- 
ance, Extraordinary?) 

Extra-Polar  Region. — (See  Region,  Ex- 
tra-Polar?) 

Eye,  Electro-Magnetic —  — A  term  pro- 
posed for  a  certain  form  of  spark-micrometer 
employed  by  Hertz  in  his  experiment  on  elec- 
tro-magnetic radiation. 

This  apparatus  has  received  the  above  name 
because  it  enables  the  observer  to  see  or  localize 
an  electromagnetic  disturbance. 

The  particular  spark-micrometer  that  has  re- 
ceived the  name  of  the  electro-magnetic  eye  had 
the  form  of  a  circle  35  centimetres  in  radius,  and 
was  formed  of  a  copper  wire  2  millimetres  in  di- 
ameter. Like  all  spark-micrometer  circuits,  it 
had  its  terminals  separated  by  a  small  air-space. 

Eye,  Selenium An  artificial  eye  in 


Fac.] 


224 


[Far. 


which  a  selenium  resistance  takes  the  place 
of  the  retina  and  two  slides  the  place  of  the 
eyelids. 

The  selenium  resistance  is  placed  in  the  circuit 
of  a  battery  and  a  galvanometer.  When  the 
slides  L,  L,  Fig.  244,  are  shut,  the  galvanometer 
deflection  is  less  than  when  they  are  open. 

The  opening  of  the  aperture  between  the  slides 
L,  L,  may  be  automatically  accomplished  by  the 
action  of  the  light  itself,  by  moving  them  by  an 
electro-magnet  placed  in  the  circuit  of  a  local  bat- 
tery, and  a  selenium  resistance  may  be  so  arranged 
that  when  light  falls  on  it  the  slides  L,  L,  are 
moved  together,  and  when  the  amount  of  such 
light  is  small  they  are  moved  apart,  by  the  action 


of  a  spring,     In  this  way  there  is  obtained   a 
device  roughly  resembling  the  dilatation  or  con- 


.B 


Fig.  244..     Selenium  Eye, 


traction  of  the  pupil  of  the  eye  from  the  action  of 
light  on  the  iris.     (See  Photometer,  Selenium.) 


Fac-Simile  Telegraphy,  or  Panteleg- 
raphy. — (See  Telegraphy,  Fac-Simile.} 

Fahrenheit's  Thermometer  Scale. — (See 
Scale,  Thermometer,  Fahrenheit's?) 

Fall  of  Potential.— (See  Potential,  Fall 
of.) 

False  Magnetic  Pole (See  Pole, 

Magnetic,  False.) 

False  Resistance. — (See  Resistance, 
False.) 

False  Zero. — (See  Zero,  False.) 

Fan  Guard.— (See  Guard,  Fan.) 

Farad. — The  practical  unit  of  electric 
capacity. 

Such  a  capacity  of  a  conductor  or  condenser 
that  one  coulomb  of  electricity  is  required  to 
produce  in  the  conductor  or  condenser  a 
difference  of  potential  of  one  volt. 

As  in  gases,  a  quart  vessel  will  hold  a  quart  of 
gas  under  unit  pressure  of  one  atmosphere,  so,  in 
electricity,  a  conductor  or  condenser,  whose  capa- 
city is  one  farad,  will  hold  a  quantity  of  electricity 
equal  to  one  coulomb  when  under  an  electromotive 
force  of  one  volt. 

It  may  cause  some  perplexity  to  the  student  to 
understand  why  there  should  be  in  electricity  one 
unit  of  capacity  to  represent  the  size  of  the  vessel 
or  conductor,  and  another  to  represent  the 
amount  or  quantity  of  electricity  required  to  fill 


such  vessel.  But,  like  a  gas,  electricity  acts,  in 
effect,  as  if  it  were  very  compressible,  so  that  the 
quantity  required  to  fill  any  condenser  will  de- 

N  "' 


Fig  24.  J.  Elevation  of  Standardized  Condenser. 

pend  on  the  electromotive  force  under  which  it  is 
put  into  the  conductor  or  condenser. 

For    purposes  of  measurement,  capacities  of 
conductors  are  compared  with  those  of  condensers 


Fig,  246.    Plan  of  Standardized  Condenser. 


whose  capacities  are  known   in  microfarads,  or 
fractions    thereof.      The     microfarad,     or    the 

of  a  farad,  is  used  because  of  the  very 

1,000,000 

great  size  of  a  farad. 


Far,] 


225 


[Fau. 


Fig.  245  shows  an  elevation,  and  Fig.  246  a 
plan  of  the  form  often  given  to  a  standardized 
condenser  or  microfarad.  The  condenser  is 
charged  by  connecting  the  terminals  of  the  elec- 
tric source  to  the  binding  posts  N  and  N.  It  is 
discharged  by  means  of  the  plug  key  P',  that 
connects  the  brass  pieces  A  and  B,  when  pushed 
firmly  into  the  conical  space  between  them. 

The  condenser  is  made  by  placing  sheets  of  tin 
foil  between  sheets  of  oiled  silk  or  mica  in  the 
box  and  connecting  the  alternate  sheets  to  one  of 
(he  brass  pieces  B,  and  the  other  set  to  the  brass 
piece  A,  as  will  be  better  understood  from  an 
inspection  of  Fig.  247. 


Fig.  247    Method  of  Construction  of  a  Condenser. 

Condensers  are  generally  made  of  the  capacity 
of  the  ^  of  a  microfarad.  Sometimes,  however, 
they  are  made  so  that  either  all  or  part  of  the 
condenser  may  be  employed,  by  the  insertion  of 
the  different  plug  keys. 

The  form  of  condenser  shown  in  Fig.  248  is 


Fig.  24.8.  Standard  Condenser 

capable  of  ready  division  into  five  separate  val- 
ues, viz.:   .05,  .05,  .2,  .2  and  .5  microfarad. 

Farad,  Micro The  millionth  part 

of  a  farad.     (See  Farad.} 

Faraday  Effect.— (See  Effect,  Faraday.} 
Faraday's  Cube. — 'See  Cube,  Faraday's) 


Faraday's  Dark  Space. — (See  Space, 
Dark,  Faraday's) 

Faraday's  Net. — (See  Net.  Faraday's) 

Faradic     Apparatus,    Magneto-Electric 

(See  Apparatus,  Faradic .  Mag- 
neto-Electric) 

Faradic  Brush. — (See    Brush,  Faradic) 

Faradic  Current. — (See  Current  Fara- 
dic) 

Faradic  Excitation. — (See  Excitation.. 
Faradic)  • 

Faradic  Induction  Apparatus. — (See 
Apparatus,  Faradic  Induction) 

Faradic  Irritability. — (See  Irritability, 
Faradic) 

Faradic  Machine. — (See  Machine,  Fara- 
dic) 

Faradization. — In  electro-therapeutics,  the 
effects  produced  on  the  nerves  or  muscles 
by  the  use  of  a  faradic  current,  in  order  to 
distinguish  such  effects  from  galvanization 
or  those  produced  by  a  voltaic  current.  (See 
Galvanization) 

Faradization,  General A  method 

of  applying  the  faradic  current  similar  to 
that  employed  in  general  galvanization. 
(See  Galvanization,  General) 

Faradization,  Local A  method  of 

applying  the  faradic  current  in  general  simi- 
lar to  that  employed  in  local  galvanization. 
(See  Galvanization,  Local) 

Fault.— Any  failure  in  the  proper  working 
of  a  circuit  due  to  ground  contacts,  cross- 
contacts  or  disconnections.  (See  Contacts. 
Cross) 

Faults  are  of  three  kinds,  viz. : 

(i.)  Disconnections.     (See  Disconnection) 

(2)  Earths.     (See  Earth) 

(3.)  Contacts.     (See  Contacts) 

Various  methods  are  employed  for  detecting 
and  localizing  faults,  for  the  explanation  of 
which  reference  should  be  had  to  standard  elec- 
trical works  on  testing  or  measurements. 

Fault,  Ironwork,  of  Dynamo A 

ground  or  connection  between  the  current  of 
a  dynamo  and  any  part  of  its  ironwork. 


Fau.l 


226 


[Fie. 


If  the  dynamo  is  in  good  connection  with  the 
ground,  as  is  frequently  the  case  in  marine  plants, 
this  fault  is  the  same  as  a  ground. 

Faults,  Localization  of Determin- 
ing the  position  of  a  fault  on  a  telegraph  line 
or  cable  by  calculations  based  on  the  fall  in 
the  potential  of  the  line  measured  at  different 
points,  or  by  loss  of  charge,  etc. 

For  details,  see  standard  works  on  electrical 
measurements. 

Feed,  Clockwork,  for  Arc  Lamps 

An  arrangement  of  clockwork  for  obtaining 
a  uniform  feed  motion  of  one  or  both  elec- 
trodes of  an  arc  lamp. 

The  clockwork  is  automatically  thrown  into  or 
out  of  action  by  an  electro-magnet,  usually  placed 
in  a  shunt  circuit  around  the  carbons. 

Feed,  To To  supply  with  an  electric 

current,  as  by  a  dynamo  or  other  source. 

Feeder. — One  of  the  conducting  wires  or 
channels  through  which  the  current  is  dis- 
tributed to  the  main  conductors. 

Feeder,  Standard  or  Main The 

main  feeder  to  which  the  standard  pressure 
indicator  is  connected,  and  whose  pressure 
controls  the  pressure  at  the  ends  of  all  the 
other  feeders. 

The  term  pressure  in  the  above  definition  is 
used  in  the  sense  of  electromotive  force  or  differ- 
ence  of  potential. 

Feeder-Wires. — (See  Wires,  Feeder) 
Feeders. — In  a  system  of  distribution  by 
constant  potential,  as  in  incandescent  elec- 
tric lighting,  the  conducting  wires  extend- 
ing between  the  bus-wires  or  bars,  and  the 
junction  boxes. 

A  feeder  differs  from  a  main  in  that  a  main 
consists  of  a  conductor  that  may  be  tapped  at  any 
point  to  supply  a  customer,  while  a  feeder  leads 
direct  from  the  dynamo  or  other  source  to  a  main 
and  is  not  tapped  at  any  point. 

Feeders,    Negative The    feeders 

that  are  connected  with  the  negative  terminal 
of  the  dynamo.  (See  Feeders.) 

Feeders,  Positive The  feeders  that 

are  connected  with  the  positive  terminal  of 
the  dynamo.  (See  Feeders.) 


Feeding  Device  of  Electric  Arc  Lamp.— 

(See  Device,  Feeding,  of   an    Arc   Lamp. 
Feed,  Clockwork,  for  Arc-Lamps^) 
Feeding-Wire. — (See  Wire,  Feeding^ 

Feet,  Ampe"re The  product  of  the 

current  in  amperes  by  the  distance  in  feet 
through  which  that  current  passes. 

It  has  been  suggested  that  the  term  ampere- 
feet  should  be  employed  in  expressing  the  strength 
of  electro-magnetism  in  the  field  magnets  of 
dynamo-electro  machines  or  other  similar  ap- 
paratus. 

Ferranti  Effect.— (See  Effect,  Ferranti^ 

Ferro-Magnetic  Substance. — (See  Sub- 
stance, Ferro-Magnetic?) 

Fibre,  Quartz A  fibre  suitable  for 

suspending  galvanometer  needles,  etc.,  made 
of  quartz. 

The  quartz  fibre  is  obtained  by  fusing  quartz  and 
drawing  out  the  fused  material  as  a  fine  thread, 
in  a  manner  similar  to  the  production  of  glass 
fibres.  Quartz  fibres  possess  marked  advantage 
over  silk  fibres,  in  that  they  are  5.4  times  stronger 
for  equal  diameters,  and  especially,  in  that  they 
return  to  the  zero  point,  after  very  considerable 
deflections. 

Quartz  fibres  are  readily  obtained  by  fusing 
quartz  pebbles  together  in  the  voltaic  arc,  and 
drawing  them  apart  with  a  rapid,  but  steady,  uni- 
form motion. 

Fibre  Suspension. — (See  Suspension, 
Fibre?) 

Fibre,  Vulcanized A  variety  of  in- 
sulating material  suitable  for  purposes  not 
requiring  the  highest  insulation. 

Vulcanized  fibre  is,  however,  seriously  affected 
by  long  exposure  to  moisture. 

Fibrone.— An  insulating  substance. 

Field,  Air That  portion  of  a  mag- 
netic field  in  which  the  lines  of  force  pass 
through  air  only. 

Field,  Alternating An  electrostatic 

or  magnetic  field  the  positive  direction  of  the 
lines  of  force  in  which  is  alternately  reversed 
or  changed  in  direction. 

Field,  Alternating  Electrostatic  — 
An  electrostatic  field,  the  potential  of  which 
is  rapidly  alternating. 


Fie.] 


227 


[Fie. 


An  alternating  electrostatic  field  is,  according 
to  Tesla's  experiments,  produced  in  the  neighbor- 
hood of  the  terminals  of  the  secondary  of  an  in- 
duction  coil,  through  whose  primary,  alternations 
of  high  frequency  are  passing. 

Field,  Alternating  Magnetic. — A  mag- 
netic field  the  direction  of  whose  lines  of 
force  is  alternately  reversed. 

Field,  Density  of The  number  of 

lines  of  force  that  pass  through  any  field,  per 
unit  of  area  of  cross-section. 

Field,  Electric A  term  sometimes 

used  in  place  of  an  electrostatic  field.  (See 
Field,  Electrostatic^) 

Field,  Electro-Magnetic The  space 


traversed  by  the  lines  of  magnetic  force  pro- 
duced by  an  electro-magnet.  (See  Field, 
Magnetic?) 

Field,  Electrostatic The  region  of 

electrostatic  influence  surrounding  a  charged 
body. 

Electrostatic  attractions  or  repulsions  take 
place  along  certain  lines  called  lines  of  electro- 
static force.  These  lines  of  force  produce  a  field 
called  an  electrostatic  field.  Electric  level  or 
potential  is  measured  along  these  lines,  just  as 
gravitation  levels  are  measured  with  a  plumb  line 
along  the  lines  of  gravitation  force.  (See  Poten- 
tial, Electric.') 

Work  is  done  when  a  body  is  moved  along  the 
lines  of  electrostatic  force  in  a  direction  from  an 
oppositely  charged  body,  or  towards  a  similarly 
charged  body,  just  as  work  is  done  against 
gravity  when  a  body  is  moved  along  the  lines  of 
gravitation  force,  away  from  the  earth's  centre, 
or  vertically  upwards. 

Field,  Exciter  of In  a  separately 

excited  dynamo-electric  machine,  the  dyna- 
mo-electric machine,  voltaic  battery,  or  other 
electric  source  employed  to  produce  the  field 
of  the  field  magnets.  (See  Machine,  Dyna- 
mo-Electric,} 

Field,  Intensity  of The  strength 

of  a  field  as  measured  by  the  number  of  lines 
of  force  that  pass  through  it  per  unit  of  area 
of  cross-section.  (See  Field,  Electrostatic. 
Field,  Magnetic^ 

Field,     Magnetic The    region    of 


magnetic  influence  surrounding  the  poles  of  a 
magnet. 

A  space  or  region  traversed  by  lines  of 
magnetic  force. 

A  place  where  a  magnetic  needle,  if  free 
to  move,  will  take  up  a  definite  position,  under 
the  influence  of  the  lines  of  magnetic  force. 

Unit  strength  of  magnetic  field  is  the  field 
which  would  be  produced  by  a  magnetic  pole  of 
unit  strength  at  unit  distance. 

Magnetic  attractions  and  repulsions  are  assumed 
to  take  place  along  certain  lines  called  lines  of 
magnetic  force.  The  directions  of  these  lines  in 
any  plane  of  a  magnetic  field  may  be  shown  by 
sprinkling  iron  filings  over  a  sheet  of  paper  held 
in  a  horizontal  position  to  a  magnet  pole  inclined 


Fig.  249.    Magnetic  Field. 

to  the  paper  in  the  desired  plane  and  then  gently 
tapping  the  paper. 

The  groupings  of  iron  filings  so  obtained  are 
sometimes  called  magnetic  figures . 

The  directions  of  the  lines  of  force  thus  shown 
will  appear  from  an  inspection  of  Fig.  249,  taken 
in  a  plane  joining  the  two  poles  of  a  straight  bar 
magnet,  and  Fig.  250,  taken  in  a  plane  at  right 
angles  to  the  north  pole  of  a  straight  bar  magnet. 

In  Fig.  249,  the  repulsion  of  the  lines  of  force 
at  either  pole  is  shown  by  the  radiation  of  the 
chains  ot  magnetized  iron  particles.  The  mutual 
attraction  of  unlike  polarities  is  shown  by  the 
curved  lines. 

In  Fig.  250,  the  repulsion  of  the  similarly  mag- 
netized chains  is  clearly  shown. 

Lines  of  magnetic  force  are  assumed  to  pass 
out  from  the  north,  pole  and  back  again  into  the 
magnet  at  its  south  pole.  This  assumed  direction 


Fie.] 


228 


[Fie. 


is  called  the  direction  of  the  lines  of  magnetic 
force. 

Faraday  expressed  his  conception  of  lines  of 
magnetic  force  as  follows: 

"Every  line  offeree  must  therefore  be  consid- 
ered as  a  closed  circuit,  passing,  in  some  part  of 
its  course,  through  a  magnet  and  having  an  equal 
amount  of  force  in  every  part  of  its  course.  There 


Fig,  230.     Magnetic  Field. 

exist  lines  of  force  within  the  magnet  of  the  same 
nature  as  those  without.  What  is  more,  they  are 
exactly  equal  in  amount  to  those  without.  They 
have  a  relation  in  direction  to  those  without  and 
are,  in  fact,  continuations  of  them." 

When  a  conductor,  such  as  a  wire  through 
which  a  powerful  current  of  electricity  is  flowing, 
is  dipped  in  a  mass  of  iron  filings,  a  chain  of  iron 
filings  is  formed,  the  north  end  of  which  is  urged 
around  the  conductor  in  one  direction  and  the 
south  end  in  the  opposite  direction,  so  that  the 
movable  chain  of  filings  surrounis  or  grips  the 
conductor  in  concentric  rings  or  circles. 

The  density  of  a  magnetic  field 'is  directly  pro- 
portional to  the  number  of  lines  of  force  per  unit 
of  area  of  cross-section. 

A  single  line  of  fo*ce,  or  a  unit  line  of  force,  is 
such  an  intensity  of  field  as  exists  in  each  square 
centimetre  of  cross-section  of  a  unit  magnetic 
field. 

A  magnetic  field  is  uniform,  or  possesses  ttni- 
form  intensity,  when  it  possesses  the  same  num- 
ber of  lines  of  force  per  squire  centimetre  of  area 
of  cross-secti  >n. 

Field,  Magnetic,  Alternating  -  —The 
magnetic  field  produced  by  means  of  an 
alternating  current. 


Field,  Magnetic,  Dissymmetrical 

A  field  whose  lines  of  force  are  not  symmet- 
rically distributed  in  adjacent  halves. 

Field,  Magnetic,  Expanding  of- 

An  increase  in  the  length  of  the  lines  of  mag- 
netic force  in  any  field,  or  an  increase  in  the 
length  of  their  magnetic  circuit. 

Field,  Magnetic,  of  an  Electric  Current 
The  magnetic  field  surrounding  a  cir- 


Fig.  231.     Field  of  Current. 

cuit  through  which  an  electric  current  is  flow- 
ing. 

An  electric  current  produces  a  magnetic  field. 
This  was  discovered  by  Oersted  -f 

in  1819,  and  may  be  shown  by 
sprinkling  iron  filings  on  a  sheet 
of  paper,  placed  on  the  wire 
conductor  conve)  ing  the  cur- 
rent, at  right  angles  to  the  direc- 
tion in  which  the  current  is  pass- 
ing. Here  the  lines  of  force 
appear  as  concentric  circles,  ex- 
tending around  the  conductor, 
as  shown  in  Fig.  251.  Their 
direction,  as  regards  the  length 
of  the  conductor,  is  shown  in 
Fig.  252.  The  electric  current 
sets  up  these  magnetic  whirls 
around  the  conductor  on  its 
passage  through  it. 

The  direction  of  the  lines  of  „ 

'  J    Fig.  2 5 2.    Direc- 

magnetic. force  produced   by  an      tion  of  Lines  of 

electric   current,  and   hence  its      force, 
magnetic  polarity^  depends  on  the  direction  in 
which  the  electric  current  flows.     This  direction 


Fie.] 


229 


[Fie, 


may  be  remembered  as  follows:  If  the  current 
flows  towards  the  observer,  the  directions  of  the 
lines  of  magnetic  force  is  opposite  to  that  of  the 
hands  of  a  watch,  as  shown  in  Fig.  253. 


Fig  233.    Direction  of  Lines  of  Force. 

It  is  from  the  direction  of  the  lines  of  magnetic 
force  that  the  polarity  of  a  helix  carrying  a  cur- 
rent is  deduced.  (See  Solenoid,  Magnetic.  Mag- 
net, Electro  ) 

A  magnetic  field  possesses  the  following  prop- 
erties, viz.: 

(i.)  All  magnetizable  bodies  are  magnetized 
when  brought  into  a  magnetic  field.  (See  Indue, 
tion,  Magnetic.") 

(2.)  Conductors  moved  through  a  magnetic 
field  so  as  to  cut  its  lines  of  force  have  differences 
of  potential  generated  in  them  at  different  points, 
and  if  these  points  be  connected  by  a  conductor, 
an  electric  current  is  produced.  (See  Induction, 
Electro-Magnetic. ) 

Field,  Magnetic,  Pulsatory A  field, 

the  strength  of  which  pulsates  in  such  manner 
as  to  produce  oscillatory  currents  by  induc- 
tion. 

Field,  Magnetic,  Reversing That 

portion  of  the  field  of  a  dynamo-electric  ma- 
chine, produced  by  the  field-magnet  coils,  in 
which  the  currents  flowing  in  the  armature 
coils  are  stopped  or  reversed  after  the  coil  has 
passed  its  theoretical  position  of  neutrality. 

Sparkless  commutation  is  obtained  by  placing 
the  brushes  on  the  commutator  so  as  to  corre- 
spond with  the  reversing  field. 

Field,  Magnetic,  Shifting A  term 

proposed  by  Professor  Elihu  Thomson  to  ex- 
press a  field  of  magnetic  lines  of  changing 
position  with  respect  to  the  axis  of  the  pole 
from  which  they  emanate. 

A  shifting  magnetic  field  is  especially  a  phe- 
nomenon of  a  rapidly  alternating  magnetic  field 


occurring  in  a  substance  like  hardened  steel  in 
which  the  coercive  force  is  lairly  nigh.  It,  for 
example,  a  single  magnet  pole  of  an  electro- 
magnet,  whose  coils  are  traversed  by  a  rapidly 
alternating  current  of  electricity ,  15  placed  near  one 
end  of  a  steel  file,  the  changing  polarity  developed 
thereby  moves  or  shifts  Irom  the  point  directly 
over  the  pole  towards  the  distant  end.  The 
presence  of  this  shifting  field  can  be  shown  by  the 
rotation  of  discs  of  copper  suitably  inclined  to  ihe 
end  of  the  file.  In  a  similar  manner  a  prismatic 
mass  of  steel,  placed  with  one  of  its  flat  sides 
on  the  pole  of  a  rapidly  alternating  magnetic 
field,  will  have  a  magnetic  field  developed  in  it, 
which  will  move  or  shift  from  the  flat  base 
towards  the  upper  edge.  Movable  masses  of  good 
conducting  metal,  such  as  copper,  will  be  set  in 
rotation  in  a  direction  such  as  would  be  caused 
by  an  escape  of  gas  therefrom. 
.  The  shifting  magnetic  field  travels  from  the 
upper  portions  of  the  prism  just  as  a  stream  of 
escaping  gaseous  substance  would. 

Field,  Magnetic,  Spreading-Out A 

term  sometimes  used  to  represent  an  expand- 
ing magnetic  field.  (See  Field,  Magnetic, 
Expanding  of.) 

Field,  Magnetic,  Stray That  por- 
tion of  the  field  of  a  dynamo-electric  machine 
which  is  not  utilized  for  the  development  of 
differences  of  potential  in  the  armature,  be- 
cause its  lines  of  force  do  not  pass  through 
the  armature. 

Field,  Magnetic,  Strength  of  —  —The 
dynamic  force  acting  on  a  free  magnetic  pole, 
placed  in  a  magnetic  field. 

If  a  free  magnetic  pole  could  be  placed  in  a 
magnetic  field,  it  would  begin  to  move  towards 
the  opposite  pole  of  the  field,  under  its  magnetic 
attraction,  just  as  an  unsupported  body,  free  to 
move,  would  begin  to  fall  towards  the  earth. 
The  strength  of  a  magnetic  field  corresponds  to 
the  acceleration  of  the  force  of  gravity  in  the 
case  of  a  falling  body.  The  strength  of  the  mag- 
netic pole  corresponds  to  the  mass  of  the  falling 
body.  The  force  impressed  in  the  case  of  the 
magnetic  field  is  equal  to  the  strength  of  the  pole 
multiplied  by  the  strength  of  the  field. 

Field,  Magnetic,  Symmetrical A 

field  whose  lines  of  force  are  symmetrically 
distributed  in  adjacent  halves. 


Fie.] 


230 


[Fil. 


Field,  Magnetic,  Uniform A  field 

traversed  by  the  same  number  of  lines  of 
magnetic  force  in  all  unit  portions  of  area  of 
cross-section.  (See  Field,  Magnetic?) 

Field,  Magnetic,  Waste A  term 

sometimes  employed  for  stray  field.  (See 
Field,  Magnetic,  Stray.) 

Field,  Rotating-Current A  mag- 
netic field  produced  by  means  of  a  rotating 
current.  (See  Current,  Rotating?) 

Field,  Uniform  Density  of  —  —A  uni- 
form density  in  all  equal  areas  of  cross- 
section  of  field. 

Field,  Yortex-Ring The  field  of 

influence  possessed  by  a  vortex-ring. 

Professor  Dolbear  points  out  the  fact  that  the 
direction  of  the  rotation  of  a  fluid  constituting  a 
vortex-ring  resembles  the  magnet  flux  in  a  mag. 
netic  field,  and  shows,  from  the  action  of  such  rings 
on  one  another,  that  they  possess  a  true  field,  or 
atmosphere  of  influence  outside  their  actual 
bodies.  He  infers  that  such  rings  possess  true 
polarity,  since  the  motions  producing  them  have 
different  directions  on  opposite  sides  or  ends. 

Figure  of  Merit  of  Galvanometer. — (See 
Galvanometer,  Figure  of  Merit  of.) 

Figures,   Breath Faint  figures  of 

condensed  vapor  produced  by  electrifying  a 
coin,  placing  it  momentarily  on  the  surface  of 
a  sheet  of  clean,  dry  glass,  and  then  breath- 
ing gently  on  the  spot  where  the  coin  was 
placed. 

The  moisture  collects  on  the  electrified  portions 
of  the  plate  and  torms  a  fairly  distinct  image  ol 
the  coin. 

Figures,  Electric Figures  of  various 

shapes  produced  on  electrified  surfaces  by  the 
arrangement  of  dust  particles  or  vapor 
vesicles  under  the  influence  of  electric  charges. 

Electric  figures  are  of  two  varieties,  viz. : 

(i.)  Dust  figures. 

(2.)  Breath  figures. 

Figures,    Lichtenberg's     Dust  — 

Figures  produced  by  writing  on  a  sheet  of  shel- 
lac with  the  knob  of  a  charged  Leyden  jar  and 
then  sprinkling  over  the  sheet  dried  and 
powdered  sulphur  and  red  lead,  which  have 


been  previously  mixed  together,  and  are  so 
rendered,  respectively  negative  and  positive. 

The  red  lead  collects  on  the  negative  parts  of 
the  shellac  surface,  and  the  sulphur  on  the  posi- 
tive parts,  in  curious  figures,  known  as  Lichten- 
berg's Dust  Figures,  one  of  which  is  shown  in 
Fig.  254. 


Fig*  254-    Lichtenberg's  Dust  Figures. 

These  figures  show  very  clearly  that  an  electric 
charge  tends  to  creep  irregularly  over  the  surface 
of  an  insulating  substance. 

Figures,  Magnetic A  name  some- 
times applied  to  the  groupings  of  iron  filings 
on  a  sheet  of  paper  so  held  in  a  magnetic  field 
as  to  be  grouped  or  arranged  under  the  in- 
fluence of  the  lines  of  force  of  the  same.  (See 
Field,  Magnetic?) 

Filament. — A  slender  thread  or  fibre. 
The  term  is  applied  generally  to  threads  or 
fibres  varying  considerably  in  diameter. 

Filament,  Current A  term  some- 
times employed  in  place  of  current  streamlet. 
(See  Streamlets.  Current?) 

Filament,  Magnetic A  polarized 

line  or  chain  of  ultimate  magnetic  particles. 

This  is  sometimes  called  a  uniform  magnetu 
filament. 

A  bar-magnet  possesses  but  two  free  poles. 
When  broken  ai  Us  neutral  point  or  equator,  the 
bar  will  develop  free  poles  at  the  broken  ends. 
This  is  explained  by  considering  the  magnet  to 
be  composed  of  a  number  of  separate  particles, 
separately  magnetized.  A  single  chain  or  fila- 
ment of  such  particles  is  called  a  magnetic 
filament.  (See  Magnet,  Neutral  Point  of.  Mag* 
nettsm,  Hughes'  Theory  of.  Magnetism^ 
E-wing's  Theory  of.) 

Filament  of  Incandescent  Electric  Lamp. 


F11.J 


231 


[Fir. 


— (See  Lamp,  Incandescent  Electric,  Fila- 
ment of.) 
Filament,  Uniform   Magnetic A 

term  sometimes  applied  to  a  magnetic  fila- 
ment. (See  Filament,  Magnetic.) 

Filaments,  Flashed Filaments  for 

an  incandescent  lamp,  that  have  been  sub- 
jected to  the  flashing  process.  (See  Carbons, 
Flashing  Process  for) 

Filamentous  Armature  Core. — (See  Core, 
Armature,  Filamentous.) 
;  Film  Cut-Out— (See  Cut-Out,  Film.) 

Finder,  Induction A  term  some- 
times employed  for  a  magnetic  explorer. 

Finder,  Position*,  Electric A  de- 
vice by  means  of  which  the  exact  position  of 
an  object  can  be  obtained. 

By  means  of  a  position -finder  a  gunner  can 
be  telephoned  or  otherwise  ordered  to  fire  at  ob- 
jects he  cannot  see,  and  yet  obtain  a  fair  degree 
of  accuracy. 

Finder,  Range,  Electric A  de- 
vice by  means  of  which  the  exact  distance  of 
an  enemy's  ship  or  other  target  can  be  readily 
determined. 

The  operation  of  an  electric  range-finder  is  based 
on  a  method  somewhat  similar  to  the  solving  of  a 
triangle  for  the  purpose  of  determining  distances. 
If  the  base  line  of  a  triangle  and  the  two  angles 
at  the  base  are  known,  the  other  two  sides  and 
the  included  angle  can  be  determined. 

In  the  range-finder,  the  resistance  of  a  German 
silver  wire  corresponds  to  the  graduated  arc  of 
the  theodolite  used  to  measure  the  angles,  and  a 
rheostat,  as  a  receiving  instrument,  measures  the 
values  of  the  angles.  The  base  line  is  a  constant, 
so  that  the  receiving  instrument  is  marked  in 
yards  instead  of  angles.  To  use  the  range-finder, 
two  observers  watch  the  target  object  continu- 
ously through  a  telescope.  They  do  this  and 
nothing  else,  while  a  third  observer  watches  a 
galvanometer  and  so  alters  a  resistance,  by  moving 
a  contact  or  slide  key  along  a  resistance  wire,  as 
to  keep  the  needle  of  the  galvanometer  constantly 
at  zero.  The  exact  distance  being  thus  ascer- 
tained, the  gunner  can  make  the  proper  allowance 
in  firing.' 

Finder,  Wire Any  form  of  galva- 
nometer used  to  locate  or  find  the  corre- 


sponding ends  of  different  wires  in  a  bunched- 
cable. 

The  different  wires  in  a  cable  are  usually  tagged 
and  numbered  at  the  end  of  the  cable  and  at  the 
joints.  The  telephone  has  been  successfully  em- 
ployed as  a  wire  finder. 

Fire  Alarm  Annunciator. — (See  Annun- 
ciator, Fire  Alarm.) 

Fire  Alarm,  Automatic (See 

Alarm,  Fire  Automatic.) 

Fire  Alarm  Contact— (See  Contact,  Fire 
Alarm.) 

Fire  Alarm  Signal  Box. — (See  Box,  Fire 
Alarm  Signal.) 

Fire  Alarm  Telegraph  Box. — (See  Box, 
Fire  Alarm  Telegraph.} 

Fire  Ball.— (See  Ball,  Fire.) 

Fire  Cleansing.— (See  Cleansing,  Fire.) 

Fire   Extinguisher,    Electric A 

thermostat  or  mercury  contact,  which  auto- 
matically completes  a  circuit  and  turns  on  a 
water  supply  for  extinguishing  a  fire,  on  a 
certain  predetermined  increase  of  tempera- 
ture. 

Fire,  Hot,  St.  Elmo's A  term  pro- 
posed by  Tesla  for  a  form  of  powerful  brush 
discharge  between  the  secondary  terminals  of 
a  high  frequency  induction  coil.  (See  Dis- 
charge, Brush-and- Spray?) 

This  form  of  St.  Elmo's  fire  differs  from  the 
ordinary  form  in  being  hot.  Its  general  appear- 
ance is  shown  in  Fig.  255,  taken  from  Tesla, 


Fig.  255.    St.  Elmo's  Hot  Fire. 

Describing  its  production  he  says  :  '-In  many  of 
these  experiments,  when  powerful  effects  are 
wanted  for  a  short  time,  it  is  advantageous  to  use 


Fir.] 


233 


[Flo. 


iron  cores  with  the  primaries.  In  such  case  a 
very  large  primary  coil  may  be  wound  and  placed 
side  by  side  with  the  secondary,  and,  the  nearest 
terminal  of  the  latter  being  connected  to  the 
primary,  a  laminated  iron  core  is  introduced 
through  the  primary  into  the  secondary  as  far  as 
the  streams  will  permit.  Under  these  conditions 
an  excessively  powerful  brush,  several  inches 
long,  which  may  be  appropriately  called  '  St. 
Elmo's  hot  fire, '  may  be  caused  to  appear  at  the 
other  terminal  of  the  secondary,  producing  strik- 
ing effects.  It  is  a  most  powerful  ozonizer  ;  so 
powerful  indeed,  that  only  a  few  minutes  are  suf- 
ficient to  fill  the  whole  room  with  the  smell  of 
ozone,  and  it  undoubtedly  possesses  the  quality  of 
exciting  chemical  affinities." 

Fire,  St.  Elmo's Tongues  of  faintly 

luminous  fire  which  sometimes  appear  on  the 
pointed  ends  of  bodies  in  connection  with  the 
earth,  such  as  the  tops  of  church  steeples  or 
the  masts  of  ships. 

The  appearance  of  the  St.  Elmo's  fire  is  due  to 
brush  discharges  of  electricity. 

Fishes,  Electric A  term  applied  to 

various  fishes,  such  as  the  eel  and  the  ray, 
which  possess  the  ability  of  protecting  them- 
selves by  giving  electric  shocks  to  objects 
touching  them.  (See  Eel,  Electric.} 

Fishing1  Box. — (See  Box,  Fishing?) 

Fittings  or  Fixtures,  Electric  Light  — 

—  The  sockets,  holders,  arms,  etc.,  required 
for  holding  or  supporting  incandescent  electric 
lamps. 

Fixed  Secondary.  —  (See  Secondary, 
Fixed.) 

Fixtures,  Telegraphic A  term  gen- 
erally limited  to  the  variously  shaped  supports 
provided  for  the  attachment  of  telegraphic 
wires. 

Fixtures,  Telegraphic  House-Top  — 
Telegraphic  fixtures  placed  on  the  roofs  of 
buildings  for  the  support  of  the  lines. 

Flaming  Discharge.  —  (See  Discharge, 
Flaming.) 

Flash,  Side A  sparking  or  lateral 

discharge  taking  place  from  the  sides  of  a 
conductor,  when  an  impulsive  rush  of  elec- 
tricity passes  through  it. 


The  phenomenon  of  siae  flashing  is  due  to  a 
lateral  discharge  which  takes  the  alternative  path, 
instead  of  a  path  of  much  smaller  ohmic  resist- 
ance. The  tendency  to  side  flash  results  from 
the  fact  that  the  metallic  circuit  possesses  induct- 
ance. (See  Path,  Alternative.  Discharge,  Lat- 
eral. Inductance. ) 

Flashed  Carbons.  —  (See  Carbons, 
Flashed.) 

Flashed  Filaments.  —  (  See  Filaments, 
Flashed.) 

Flashes,  Auroral Sudden  variations 

in  the  intensity  of  the  auroral  light. 

Intermittent  flashes  of  auroral  light  that 
occur  during  the  prevalence  of  an  aurora. 
(See  Aurora  Borealis.) 

Flashing  of  Carbons,  Process  for  the  — 

— (See  Carbons,  Flashing  Process  for.) 

Flashing  of  Dynamo-Electric  Machine. — 

(See  Machine,  Dynamo-Electric,  Flashing 
of.) 

Flat  Cable.— (See  Cable,  Flat.) 

Flat  Duplex  Cable.— (See  Cable,  Flat 
Duplex.) 

Flat  Ring  Armature. — (See  Armature, 
Flat  Ring.) 

Flats. — A  name  sometimes  applied  to  those 
parts  of  commutator  segments  the  surface  of 
which,  through  wear,  has  become  lower  than 
the  other  portions.  (See  Commutator.) 

Fleming's  Gauss. — (See  Gauss,  Flem- 
ing's.) 

Fleming's  Standard  Toltaic  Cell.— (See 
Cell,  Voltaic,  Standard,  Fleming's.) 

Flexible  Electric  Light  Pendant. — (See 
Pendant,  Flexible  Electric  JLight.) 

Flexible  Lead. — (See  Lead,  Flexible.) 

Floating  Battery,  De  la  Rive's. — (See 
Battery,  Floating,  De  la  Rive's.) 

Flow.— In  hydraulics,  the  quantity  of 
water  or  other  fluid  which  escapes  from  an 
orifice  in  a  containing  vessel,  or  through  a 
pipe,  in  a  given  time. 

Flow-Lines  of  Escaping  Fluid.  — Lines 
\vithin  the  mass  of  a  fluid  in  motion,  drawn  at 


Flo.]  2 

a  number  of  points,  so  that  the  flow  at  any 
instant  is  tangential  at  such  points  to  the 
curved  path. 

Flow,  Magnetic    •    — The    magnetic 

flux.     (See  Flux,  Magnetic!) 
Flow  of  Current,  Assumed  Direction  of 

—  — (See  Current,  Assumed  Direction 
of  Flow  of.) 

Flow  of  Energy.— (See  Energy,  Flow  of) 
Flow  of  Lines  of  Electrostatic  Force.— 

(See  Force,  Electrostatic,  Lines  of,  Assumed 
Flow  of.) 

Flow  of  Magnetic  Induction.— (See  In- 
duction, Magnetic,  Flux  or  Flow  of) 

Fluid,  Depolarizing An  electro- 
lytic fluid  in  a  voltaic  cell  that  prevents  polari- 
zation. (See  Cell,  Voltaic,  Polarization  of) 

Fluid  Insulator.— (See  Insulator.  Fluid) 

Fluoresce.  —  To  become  self-luminous 
when  exposed  to  light. 

A  body  is  said  to  fluoresce  when  it  shines,  by 
means  of  the  light  it  produces.  In  this  respect  it 
differs  from  an  illumined  body,  which  shines  by 
reflected  light. 

Fluorescence. — A  property  possessed  by 
certain  solid  or  liquid  substances  of  becoming 
self-luminous  while  exposed  to  light. 

In  fluorescence  the  refrangibility  of  rays  of 
light  is  changed.  The  invisible  rays  beyond  the 
violet,  the  ultra-violet,  become  visible,  so  that 
the  light  is  transformed,  the  particles  absorbing 
one  wave  length  and  emitting  another.  (See  Incan- 
descence.) 

Canary  glass,  or  glass  colored  yellow  by  oxide 
of  uranium,  or  a  solution  of  sulphate  of  quinine, 
possesses  fluorescent  properties.  The  path  of  a 
pencil  of  light  brought  to  a  focus  in  either  of  these 
substances,  or  a  beam  or  cone  of  light  passed 
through  them,  is  rendered  visible  by  the  particles 
lying  in  this  path  becoming  self-luminous.  The 
path  of  a  beam  of  light  entering  the  dusty  air  of 
a  darkened  chamber  is  visible  from  the  light  being 
diffused  or  scattered  in  all  directions  by  the  float- 
ing dust  particles. 

In  a  fluorescent  substance,  the  path  of  the  light 
is  also  rendered  visible  by  the  particles  which  lie 
in  its  path,  throwing  out  light  in  all  directions. 
There  is,  however,  this  difference,  that  in  the 


[Fly. 

case  of  the  dust  particles  the  Kght  which  comes 
directly  from  the  beam  is  reflected  ;  while  in  the 
case  of  the  fluorescent  body  the  light  comes  from 
the  particles  themselves,  which  are  set  into  vibra- 
tion by  the  light  that  is  passing  through,  and  has 
been  absorbed  by  their  mass. 

Fluorescence  is,  therefore,  a  variety  of  phos- 
phorescence. (See  Phosphorescence.) 

Fluorescent— Possessing  the  capability  of 
fluorescing. 

Fluorescing.— Exhibiting  the  property  of 
fluorescence. 

Flush  Box.— (See  Box,  Flush.) 

Flimograph.— An  apparatus  for  electri- 
cally registering  the  varying  height  of  water 
in  a  tidal  stream  or  in  the  ocean  ;  or,  in  general, 
differences  of  water  levels. 

Flux,  Magnetic •  —The  number  of 

lines  of  magnetic  force  that  pass  or  flow 
through  a  magnetic  circuit. 

The  total  number  of  lines  of  magnetic  force 
in  any  magnetic  field. 

The  magnetic  flux  is  also  called  the  magnetic 
flow. 

A  Committee  of  the  American  Institute  of 
Electrical  Engineers  on  "  Units  and  Standards  " 
proposed  the  following  as  the  definition  of  mag- 
netic flux. 

"  The  magnetic  flux  through  a  surface  bounded 
by  a  closed  curve  is  the  surface  integral  of  mag- 
netic induction  taken  over  the  bounded  surface, 
and  when  produced  by  a  current  is  also  equal  to 
the  line  integral  of  the  vector  potential  of  the  cur- 
rent taken  round  the  boundary." 

"  The  uniform  and  unit  time  rate  of  change  in 
flux  through  a  closed  electric  circuit  establishes 
unit  electromotive  force  in  the  circuit." 

Fluxes  range  in  present  practical  work  from 
loo  to  100, 000,000  C.  G.  S.  lines,  and  the  working 
units  would  perhaps  prefix  milli-  and  micro-. 

Flux  of  Magnetic  Induction. — (See  In- 
duction, Magnetic,  Flux  or  Flow  of) 

Flux  or  Flow  of  Magnetism. — (See  Mag- 
netism, Flux  or  Flow  of) 

Fly.  Electric  —  — A  wheel  or  other  de- 
vice driven  by  the  reaction  of  a  convective 
discharge.  (See  Flyer,  Electric.  Convec- 
tion, Electric) 


Fly.] 


234 


L  for. 


Flyer,  Electric 


— A  wheel  arranged 


so  as  to  be  set  into  rotation  by  the  escape  of 
convection  streams  from  its  points  when 
connected  with  a  charged  conductor. 

A  wheel  formed  of 
light  radial  armsP,  P,  P, 
etc.,  shaped  as  shown  in 
Fig.  256,  and  capable  of 
rotation  on  the  vertical 
axis  A,  is  set  into  rapid 
rotation  when  connected 
with  the  prime  conduc- 
tor of  a  frictional  or  in- 
fluence machine,  through 
the  convection  streams  of 
air  particles,  which  are  Fig.  236.  Electric  Flyer. 
shot  off  from  the  points  or  extremities  of  the 
radial  arms.  The  wheel  is  driven  by  the  reac- 
tion of  these  streams  in  a  direction  opposite  to 
that  of  their  escape.  (See  Discharge,  Convective. ) 

Focus. — A  point  in  front  or  back  of  a  lens 
or  mirror,  where  all  the  rays  of  light  meet  or 
seem  to  meet.  (See  Lens,  Achromatic) 

Fog,  Electric A  dense  fog  which 

occurs  on  rare  occasions  when  there  is  an 
unusual  quantity  of  free  electricity  in  the 
atmosphere. 

During  these  electric  fogs  the  free  electricity  of 
the  atmosphere  changes  its  polarity  at  frequent 
intervals. 

Following  Horn  of  Pole  Pieces  of 
Dynamo-Electric  Machine. — (See  Horns, 
Following,  of  Pole  Pieces  of  a  Dynamo- 
Electric  Machine?) 

Foot-Candle.— (See  Candle,  Foot.) 

Foot-Pound. — A  unit  of  work.  (See 
Work.) 

The  amount  of  work  required  to  raise  I 
pound  vertically  through  a  distance  of  i  foot. 

The  same  amount  of  work,  viz.,  3  foot-pounds, 
is  done  by  raising  I  pound  through  a  vertical 
distance  of  3  feet,  or  3  pounds  through  a  verti- 
cal distance  of  I  foot. 

Apart  from  air  friction,  the  amount  of  work 
done  in  raising  I  pound  through  I  foot,  viz.,  I 
foot-pound,  is  the  same  whether  this  work  be 
done  in  one  second  or  in  one  day.  The  power, 
or  the  rate  of  doing  work,  is,  however,  very  dif- 
ferent in  the  two  cases.  (See  Power.) 

Force. — Any  cause  which  changes  or  tends 


to  change  the  condition  of  rest  or  motion  of 
a  body. 


Force,  Centrifugal 


— The  force  that 


is  supposed  to  urge  a  rotating  body  directly 
away  from  the  centre  of  rotation. 

If  a  stone  be  tied  to  a  string  and  whirled  around, 
and  the  s'ring  break,  the  stone  will  not  fly  off  di- 
rectly away  from  the  centre,  but  will  move  along 
the  tangent  to  the  point  where  it  was  when  the 
string  broke. 

The  centrifugal  force  in  reality  is  the  force 
which  is  represented  by  the  tension  to  which  the 
string  is  subjected  during  this  rotation. 

Force,  Coercitive A  name  some- 
times applied  to  coercive  force.  (See  Force, 
Coercive?) 

Force,  Coercive The  power  of  re- 
sisting magnetization  or  demagnetization. 

Coercive  force,  in  the  sense  of  resisting  demag- 
netization, is  sometimes  called  magnetic  reten- 
tivity. 

Hardened  steel  possesses  great  coercive  force; 
that  is,  it  is  magnetized  or  demagnetized  with 
difficulty. 

Soft  iron  possesses  very  feeble  coercive  force. 

It  is  on  account  of  the  feeble  coercive  force  of 
the  soft  iron  -ore  of  an  electro-magnet  that  its 
main  value  depends,  since  it  is  thereby  enabled  to 
rapidly  acquire  its  magnetization,  on  the  comple- 
tion of  a  circuit  through  its  coils,  and  to  rapidly 
lose  its  magnetization  on  the  opening  of  such 
circuit. 

Force,  Contact A  difference  of  elec- 
trostatic potential,  produced  by  the  contact  of 
dissimilar  metals. 

That  a  difference  of  potential  is  produced  by 
the  mere  contact  of  dissimilar  mitals  is  now  gen- 
erally  recognize!.  Such  a  force  is  generally 
called  the  true  contact  force.  (See  Force,  True 
Contact. ) 

According  to  Lodge,  a  true  contact  force  has 
no  existence.  There  is  no  evidence,  he  thinks, 
of  a  peculiar  electromotive  force  at  the  point  of 
contact,  but  that  the  phenomena  are  due  simply 
to  the  fact  that  the  metals  are  immersed  in  air  or 
oxygen,  which  is  capable  of  combining  with  one 
of  them,  and  that,  therefore,  the  cause  of  the 
phenomena  is  the  greater  action,  for  instance,  of 
the  oxygen  of  the  air  on  the  zinc  than  on  the 
cupper. 


For.] 


235 


[For. 


According  to  this  view,  the  voltaic  effect  is 
due  not  to  the  difference  of  potential  between 
the  zinc  and  copper,  but  to  the  difference  of  the 
action  of  the  air  or  moisture. 

Force  de  Cheyal  or  Cheral   Vapeur. — 

The  French  term  for  horse-power. 

The  force  de  cheval  is  equal  to  75  kilogramme- 
metres  per  second,  or  32,549  foot-pounds  per 
minute. 

The  English  horse-power  is  equal  to  33,000 
foot-pounds  per  minute.  I  force  de  cheval  equals 
.98634 horse-power;  I  horse-power  equals  1.01385 
force  de  cheval. — (Hering.) 

Force,  Electric The  force  developed 

by  electricity. 

This  term  is  generally  limited  to  the  force  of 
attraction  or  repulsion  produced  by  an  electro- 
static  charge. 

Force,  Electromotive The  force 

starting  electricity  in  motion,  or  tending  to 
start  electricity  in  motion. 

The  force  which  moves  or  tends  to  move 
electricity. 

The  term  is  an  unfortunate  one.  Strictly  speak- 
ing, electromotive  force  is  not  a  force  at  all : 
at  least,  it  is  not  a  force  in  the  Newtonian  sense, 
where  force  is  only  that  which  acts  on  matter. 

The  term  electromotive  force  is  generally  writ- 
ten thus  :  E.  M.  F. 

The  unit  of  electromotive  force  is  the  volt. 

When  electric  induction  takes  place,  there 
results  a  change  in  the  distribution  of  the  thing 
called  electricity,  whereby  a  movement  occurs  that 
results  in  a  positive  and  a  negative  charge.  The 
cause  which  produces  this  movement  is  called  the 
electromotive  force. 

There  is  an  unfortunate  want  of  uniformity  at 
present  in  the  use  of  the  term  "electromotive 
force."  By  some,  the  electromotive  force  is  re- 
garded as  something  which  causes  the  difference 
of  potential ;  by  others  the  electromotive  force  is 
regarded  as  being  produced  by  the  difference  of 
potential;  and,  by  still  others,  electromotive  force 
is  regarded  as  the  entire  electric  moving  cause 
produced  i>y  any  source;  while  anything  less  than 
this  is  called  by  them  potential  difference. 

Those  who  regard  the  electromotive  force  as 
the  cause  which  produces  the  potenthl  difference 
look  on  the  electromotive  force  as  acting  within 


the  source  and  maintaining  a  potential  difference 
at  its  terminals. 

Silvanus  P.  Thompson  uses  the  term  electro- 
motive force  in  his  "Elementary  Lessons  in 
Electricity  and  Magnetism"  as  follows:  "The 
term  '  electromotive  force '  is  employed  to  denote 
that  which  moves  or  tends  to  move  electricity 
from  one  place  to  another.  For  brevity  we  some- 
times write  it  E.  M.  F.  In  this  particular  case  it 
is  obviously  the  result  of  difference  of  potential 
and  proportional  to  it  ;  just  as  in  water  pipes,  a 
difference  in  level  produces  a  pressure,  and  the 
pressure  produces  a  flow  as  soon  as  the  tap  is 
turned  on,  so  difference  of  potential  produces 
electromotive  force,  and  electromotive  force  sets 
up  a  current  as  soon  as  a  circuit  is  completed  for 
the  electricity  to  flow  through." 

Mascart  and  Joubert,  in  their  work  on  '  •  Elec- 
tricity and  Magnetism,"  Vol.  I.,  say:  "In  all 
cases  the  difference  of  potential  V1—  V2,  may  be 
considered  as  producing  the  motion  of  electrical 
masses  ;  it  is  often  called  the  electromotive  force." 

Maxwell,  in  his  "Elementary  Treatise  on  Elec- 
tricity," spe  iking  of  the  potential  differences 
which  may  be  shown  to  exist  at  the  terminals  of 
a  Daniell  voltaic  cell  when  on  opjn  circuit,  says  : 
"This  difference  of  potential  is  called  the  electro- 
motive force  of  a  Daniell  cell." 

Balfour  Stewart,  in  his  "  Electricity  and  Mag- 
netism, ' '  says :  ' '  This  difference  of  electric  level 
we  shall  call  E,  and,  indeed,  it  is  merely  a  manner 
of  expressing  the  cause  of  electromotive  force." 

Prof.  Fleming,  in  his  "Short  Lectures  to  Elec- 
trical Artisans,"  says:  "The  difference  of  elec- 
trical level  or  potential  must  be  caused  by  some 
electromotive  force  acting  in  the  conductor." 

Prof.  Anthony,  in  "A  Review  of  Modern 
Electrical  Theories,"  regards  the  potential  dif- 
ference as  due  to  electromotive  force.  He  says  : 
"  Difference  of  potential  results  from  a  changed 
electrical  distribution,  an  electrical  strain,  and 
represents  the  tendency  to  return  to  the  state  of 
equilibrium.  Electromotive  force  is  the  some- 
thing from  without  that  produced  the  electric 
strain." 

Hering,  in  his  "Principles  of  Dynamo-Electric 
Machines,"  says  :  "  Difference  of  potential  is,  as 
the  name  implies,  the  difference  of  electrical  po- 
tential between  any  two  points  of  a  circuit,  and 
may,  therefore,  be  applied  to  that  at  the  poles  of 
a  machine,  battery  or  lamp,  or  at  the  ends  of 
leads,  or,  in  general,  to  any  tw  >  points  in  a  cir- 
cuit. The  term  'electromotive  toice,'  however, 


For.] 


236 


[For. 


applies  only  to  the  maximum  difference  ot  potential 
which  exists  in  the  circuit,  or,  in  other  words,  the 
total  generated  difference  of  potential." 

This  last  paragraph  expresses  the  distinction 
between  the  two  terms  as  ordinarily  used  in  con- 
nection with  dynamos  and  batteries. 

Force,  Electromotive,  Absolute  Unit  of 

A  unit  of  electromotive  force  ex- 
pressed in  absolute  or  C.  G.  S.  units. 

The  one-hundred-  millionth  part  of  a  volt, 
since  i  volt  equals  ios  C.  G.  S.  units  of  elec- 
tromotive force.  (See  Units,  Practical?) 

Force,  Electromotive,  Average  or  Mean 

The  sum  of  the  values  of  a  number  of 

separate  electromotive  forces  divided  by  their 
number. 

The  square  root  of  the  mean  square  of  the 
electromotive  force  of  an  alternating  or  vari- 
able current. 

When  a  wire  in  the  armature  of  a  dynamo- 
electric  machine  cuts  the  lines  of  magnetic  force 
in  the  field  of  the  machine,  the  electromotive 
force  produced  depends  on  the  number  of  lines 
of  force  cut  per  second.  This  will  vary  for  dif- 
ferent positions  of  the  coil.  The  mean  value  of 
the  varying  electromotive  forces  between  the 
brushes  is  the  average  electromotive  force. 

Force,   Electromotive,    Back  —       — A 

term  sometimes  used  for  counter  electro- 
motive force. 

Counter  electromotive  force  is  the  preferable 
term.  (See  Force,  Electromotive,  Counter.] 

Force,    Electromotive,    Counter  — 

An  opposed  or  reverse  electromotive  force, 
which  tends  to  cause  a  current  in  the  oppo- 
site direction  to  that  actually  produced  by 
the  source. 

In  an  electric  motor,  an  electromotive  force 
contrary  to  that  produced  by  the  current 
which  drives  the  motor,  and  which  is  pro- 
portional to  the  velocity  attained  by  the 
motor. 

Counter  electromotive  force  acts  to  diminish 
the  current  in  the  same  manner  as  a  resistance 
would,  and  is  therefore  sometimes  called  spurious 
resistance  in  order  to  distinguish  it  from  an  ohmic 
or  true  resistance. 

Counter  electromotive  force  is  sometimes  ex- 
pressed in  ohms,  though  it  is  not  a  true  ohmic 
rests  ance.  (See  Resistance,  Spurious.) 


The  counter  electromotive  force  of  a  voltaic 
battery  is  due  to  the  polarization  of  the  cells. 
Since  this  force  is  due  to  the  current  in  the  cell,  it 
can  never  exceed  such  current  or  reverse  its  direc- 
tion. It  may,  however,  equal  it  and  thus  stop  its 
flow.  (See  Cell,  Voltaic,  Polarization  oj.) 

In  a  storage  cell,  the  charging  current  produces 
an  electromotive  force  counter  to  itself,  which,  as 
in  a  motor,  is  a  true  measure  of  the  energy  stored 
in  the  cell.  Economy  requires  that  the  electro- 
motive force  of  the  charging  current  should  be  as 
little  as  possible  greater  than  that  of  the  counter 
electromotive  force  of  the  cell  it  is  charging. 

In  a  voltaic  arc  a  counter  electromotive  force  is 
believed  to  be  set  up  by  polarization. 

Force,  Electromotive,  Counter,  of  Can- 

vective  Discharge Resistance  to  the 

passage  of  an  electric  discharge  through  a 
high  vacuum,  somewhat  of  the  nature  of  a 
counter  electromotive  force. 

The  resistance  to  the  passage  of  convective  dis- 
charges, therefore,  is  due  to  the  following  causes: 

(i.)  True  ohmic  resistance. 

(2.)  Counter  electromotive  force. 

Force,  Electromotive,  Counter,  of  Mutual 
Induction  —  —The  counter  electromotive 
force  produced  by  the  mutual  induction  of 
the  primary  and  secondary  circuits  on  each 
other. 

Force,  Electromotive,  Counter,  of  Self- 
induction  —  —That  part  of  the  impressed 
electromotive  force  which  is  producing,  or 
which  tends  to  produce,  at  any  instant  a 
change  in  the  current  strength. 

Force,  Electromotive,  Counter,  of  Self- 
induction  of  the  Primary  —  — A  counter 
electromotive  force  produced  in  the  primary 
circuit  of  an  induction  coil  by  the  action 
thereon  of  a  simple  periodic  electromotive 
force. 

The  counter  electromotive  force  produced 
in  the  primary  circuit  of  an  induction  coil  by 
the  application  of  a  simple  periodic  impressed 
electromotive  force  to  the  primary  circuit. 

Force,  Electromotive,  Counter,  of  Self- 
induction  of  the  Secondary  —  — A 
counter  electromotive  force  produced  in  the 
secondary  by  the  periodic  variations  in  the 
effective  electromotive  force  in  the  secondary. 


For.] 


237 


[For. 


Force,  Electromotive,  Direct  —      — An 

electromotive  force  acting  in  the  same  direc- 
tion as  another  electromotive  force  already 
existing. 

The  term  direct  electromotive  force  is  em- 
ployed in  contradistinction  to  counter  electromo- 
tive force.  (See  Force,  Electromotive,  Counter. ) 

Force,  Electromotive,  Effective  - 

The  difference  between  the  direct  and  the 
counter  electromotive  force. 

Force,  Electromotive,  Effective,  of  Sec- 
ondary —  —The  difference  between  the 
direct  and  the  counter  electromotive  force  in 
the  secondary  of  an  induction  coil. 

Force,  Electromotive,  Generated  by  Dy- 
namo-Electric Machine,  Method  of  Increas- 
ing   The  electromotive  force  of  a  dy- 
namo-electric machine  may  be  increased  in 
the  following  ways,  viz : 

(I.)  By  increasing  its  speed  of  rotation. 

(2.)  By  increasing  the  strength  of  the  magnetic 
field  in  which  the  armature  rotates. 

(3.)  By  increasing  the  size  of  the  field  through 
which  the  armature  passes  in  unit  time,  the  in- 
tensity remaining  the  same. 

(4.)  By  increasing  the  number  of  armature 
windings,  i.  e.,  by  making  successive  parts  of  the 
same  wire  pass  simultaneously  through  the  field. 

Force,  Electromotive,  Impressed 

The  electromotive  force  acting  on  any  cir- 
cuit to  produce  a  current  therein. 

The  impressed  electromotive  force  may  be  re- 
garded as  producing  two  parts,  viz. :  The  effective 
electromotive  force  and  the  counter  electromotive 
force. 

Force,  Electromotive,  Inductive  — 
A  term  sometimes  used  in  place  of  counter 
electromotive  force  of  self-induction. 

Force,  Electromotive,  Inverse An 

electromotive  force  which  acts  in  the  oppo- 
site direction  to  another  electromotive  force 
already  existing.  (See  Force,  Electromotive, 
Counter.) 

Force,  Electromotive,  Motor  -  —A 
term  proposed  by  F.  J.  Sprague  for  the  coun- 
ter electromotive  force  of  an  electric  motor. 
(See  Force,  Electromotive,  Counter?) 

This  term  was  propose  I  by  Sprajue  as  express- 


ing the  necessity  for  the  existence  of  a  counter 
electromotive  force  in  an  electric  motor,  in  order 
to  permit  it  to  utilize  the  energy  of  the  electric 
current  which  drives  it. 

Force,  Electromotive,  of  Induction  — 

— The  electromotive  force  developed  by  any 
inductive  action. 

In  a  coil  of  wire  undergoing  induction,  the 
value  of  the  induced  electromotive  force  does  not 
depend  in  any  manner  on  the  nature  of  the  ma- 
terial of  which  the  coil  is  composed. 

It  has  been  shown: 

(l.)  That  the  electromotive  force  of  induction  is 
independent  of  the  width,  thickness  or  material  of 
the  wire  windings.  —  {Faraday.} 

(2.)  That  it  is  dependent  on  the  form  of  the 
conductor,  and  the  character  of  the  change  it  ex- 
periences as  regards  the  magnetic  induction  which 
takes  place  through  it. 

Since  any  increase  in  the  strength  of  a  current 
flowing  through  a  coiled  circuit,  produces  a  coun- 
ter electromotive  force,  which  opposes  the  electro- 
motive force  producing  the  current,  it  is  clear 
that  the  impressed  electromotive  force  must  do 
work  against  this  counter  electromotive  force  all 
the  time  the  current  strength  is  increasing. 

The  movement  of  a  circuit  of  a  given  length 
through  a  given  field  with  a  given  velocity  pro- 
duces the  same  electromotive  force  whether  the 
circuit  be  formed  of  conducting  material  or  non- 
conducting material,  or  consists  of  an  electrolyte. 

Force,  Electromotive,  of  Secondary  or 
Storage  Cell,  Time-Jail  of —  — A  gradual 
decrease  in  the  potential  difference  of  a  stor- 
age battery  observed  during  the  discharge  of 
the  same. 

When  a  secondary  or  storage  battery  is  first 
discharged,  a  slight  decrease  of  its  potential  dif- 
ference takes  place  and  a  potential  difference  of  a 
slightly  decreased  value  is  maintained  nearly  con- 
stant during  a  protracted  period  of  discharge. 

Force,  Electromotive,  of  Secondary  or 
Storage  Cell,  Time-Rise  of—  —A  gradual 
increase  in  the  potential  difference  of  a 
secondary  or  storage  cell  observed  on  begin- 
ning the  discharge  after  a  prolonged  rest. 

When  a  secondary  or  storage  cell  is  discharged 
and  then  given  a  prolonged  rest  by  opening  its 
circuit,  a  gradual  but  decided  rise  in  its  potential 
difference  is  observed  on  again  beginning  its  dis- 
charge. 


For.) 


23S 


[For. 


Force,   Electromotive,  Photo An 

electromotive  force  produced  by  the  action  of 
light  on  selenium.  (See  Cell,  Selenium?) 

Force,  Electromotive,  Reacting  Induc- 
tive, of  the  Primary  Circuit The  back 

or  counter  electromotive  force  produced  in  the 
primary  circuit  by  the  current  set  up  by  in- 
duction in  the  secondary. 

Force,  Electromotive,  Secondary  Im- 
pressed   An  electromotive  force  pro- 
duced in  the  secondary  coil  or  circuit  by  a 
periodic  electromotive  force  impressed  on  the 
primary. 

Force,    Electromotive,    Simple-Periodic 

An  electromotive  force  which  varies 

in  such  manner  as  to  produce  a  simple 
periodic  current,  or  an  electromotive  force  the 
variations  of  which  can  be  correctly  repre- 
sented by  a  simple-periodic  curve. 

Force,  Electromotive,  Thermo An 

electromotive  force,  or  difference  of  potential, 
produced  by  differences  of  temperature 
acting  at  thermo-electric  junctions. 

Force,  Electromotive,  Transverse 

An  electromotive  force  excited  by  a  mag- 
netic field  in  a  substance  in  which  electric 
displacement  is  occurring. 

It  is  to  a  transverse  electromotive  force  that  the 
Hall  effect  is  due.  (See  Effect,  Hall.) 

Force,  Electromotive,  Zigzag An 

electromotive  force,  the  curve  of  which  would 
have  the  general  form  of  a  zigzag. 

Force,  Electrostatic The  force  pro- 
ducing the  attractions  or  repulsions  of  charged 
bodies. 

Force,    Electrostatic,    Lines    of  — 
Lines  of  force  produced  in  the  neighborhood 
of  a  charged  body  by  the   presence  of  the 
charge. 

Lines  extending  in  the  direction  in  which 
the  force  of  electrostatic  attraction  or  repul- 
sion acts. 

An  insulated  charged  conductor  produces 
around  it  an  electrostatic  field,  in  a  manner  some- 
what similar  to  the  magnetic  field  produced  by 
a  macnet  or  an  electric  rur-^nt.  (See  Field, 
Electrostat'u .  > 


Lines  of  electrostatic  force  pass  through  dielec- 
trics. Whether  the  force  acts  to  produce  electro- 
static induction,  by  means  of  a  polarization  of  the 
dielectric,  or  by  means  of  a  tension  set  up  in  the 
substance  of  the  dielectric,  is  not  known. 

Force,  Electrostatic,  Lines  of,  Assumed 

Flow  of A  mathematical  conception  in 

which  the  phenomena  of  electricity  are  com- 
pared with  the  similar  phenomena  of  heat. 

In  heat  no  flow  of  heat  occurs  over  isothermal 
surfaces,  or  surfaces  at  the  same  temperature. 
Between  different  isothermal  surfaces,  the  flow 
will  vary  with  the  power  of  heat  conduction.  In 
electricity,  no  flow  occurs  over  equipotential  sur- 
faces. Specific  inductive  capacity  corresponds  to 
heat  conductivity,  and  the  lines  of  force  to  the 
lines  of  heat  conduction.  (See  Capacity,  Specific 
Inductive. ) 

Force,  Lines  of,  Contraction  of 

A  decrease  that  occurs  in  the  length  of  the 
circular  lines  of  force  that  surround  a  circuit 
through  which  an  electric  current  is  passing, 
while  the  current  is  decreasing  in  intensity  or 
strength. 

The  contraction  or  decrease  in  the  average 
diameter  of  the  circular  lines  of  force  of  an  elec- 
tric circuit  is  similar  to  the  expansion  or  growth 
of  lines  of  force,  excepting  that  the  movement  is 
one  of  decrease  in  diameter,  and  takes  place  in 
the  opposite  direction,  i.  e.,  towards  the  circuit, 
instead  of  away  from  it.  (See  Force,  Lines  of, 
Growth  or  Expansion  of.} 

Force,  Lines  of,  Cutting Passing  a 

conductor  through  lines  of  magnetic  force,  so 
as  to  cut  or  intersect  them. 

The  cutting  of  lines  of  magnetic  force  produces 
differences  of  potential.  This  is  true  whether  the 
conductor  moves  through  a  stationary  field  or 
whether  the  field  itself  moves  through  the 
stationary  conductor,  so  that  the  lines  of  force  and 
the  conductor  cut  one  another.  This  cutting  is 
mutual.  Each  line  of  force  cuts  and  is  cut  by  the 
circuit  Since  all  lines  of  force  form  closed-cir- 
cuits or  paths,  the  cutting  of  the  circuit  by  the 
lines  of  force,  or  the  reverse,  forms  a  link  or  chain, 
and  the  cutting  takes  place  at  the  moment  of 
linking  or  unlinking,  i.  e.,  of  cutting. 

Force,  Lines  of,  Diffusion  of The 

deflection  of  the  lines  of  magnetic  force  from 


For.] 


239 


[For. 


their  ordinary   position,   between   the   poles 
that  produce  them. 

Force,  Lines  of,  Direction  of The 

direction  in  which  it  is  assumed  that  the  lines 
of  magnetic  force  pass. 

It  is  generally  agreed  to  consider  the  lines  of 
magnetic  force  as  coming  out  of  the  north  pole  of 
a  magnet  and  passing  into  its  south  pole,  as 
shown  in  Fig.  257. 


Fig.  2J7.    Direction  of  Lines  of  Force. 

This  is  sometimes  called  the  positive  direction 
of  the  lines  of  force  and  agrees  in  general  with  the 
direction  in  which  the  electric  current  is  assumed 
to  flow,  which  is  from  the  positive  to  the  nega- 
tive. That  is  to  say,  the  lines  of  magnetic  force 
are  assumed  to  flow  or  pass  out  of  the  north  pole 
and  into  the  south  pole  of  a  magnet.  Of  course 
there  is  no  direct  evidence  of  any  flow,  or  of  any 
particular  direction  characterizing  the  lines  of 
force.  (See  Field,  Magnetic.) 

The  lines  of  electrostatic  force  are  assumed  to 
pass  out  of  a  positively  charged  surface  and  into 
a  negatively  charged  surface. 

Force,  Lines  of,  Growth  or  Expansion  of 

The  increase  in  the  length  of  path 

through  which  lines  of  force  pass,  consequent 
on  an  increase  in  the  strength  of  the  mag- 
netization of  a  magnet,  or  on  an  increase  in 
the  strength  of  the  magnetizing  current. 

The  circular  lines  of  force  which  surround  a  con  - 
ductor  through  which  a  current  is  flowing,  may  be 
regarded  as  starting  from  the  surface  c  f  the  con- 
ductor and  growing  in  bizj  as  they  spread  out- 
wards, at  the  same  time  new  lines  of  force  being 
formed  in  their  places.  This  action  continues  while 
the  strength  of  the  current  is  increasing,  somewhat 
like  the  series  of  concentric  waves  which  are 
formed  on  the  surface  of  water,  when  a  stone  is 
dropped  into  it. 

In  their  growth  or  expansion  outwards  from 
the  conductor,  if  the  lines  of  force  cut  or  pass 
through  neighboring  conductors,  they  produce 


therein  differences  of  electric  ootential,  capable, 
on  being  connected  by  a  conductor,  of  produc« 
ing  electric  currents. 

Force,  Lines  of.  Radiation  of The 

passing  of  lines  of  force  out  of  the  north 
pole  of  a  magnet  or  solenoid. 

In  gross  matter  all  lines  of  magnetic  induction 
either  pass  through  magnetized  iron,  or  other 
paramagnetic  substance  which  surrounds  an 
electric  circuit.  Since  lines  of  force  pass  through 
a  vacuum,  the  ether  which  occupies  such  a  space 
must  also  be  regarded  as  permitting  the  passage 
of  lines  of  force. 

Force,  Loops  of A  term  sometimes 

employed  in  the  sense  of  lines  of  force.  (See 
Force,  Magnetic,  Lines  of.) 

The  term  "Lines  of  Force"  is  generally 
adopted  in  place  of  Faraday's  term  "Loops  of 
Force." 

Force,  Magnetic The  force  which 

causes  the  attractions  or  repulsions  of  mag- 
netic poles. 

Force,  Magnetic,  Line  of Arbitra- 
rily a  single  line  of  magnetic  force. 

Practically  the  lines  of  magnetic  force 
which  pass  through  a  unit  area  of  cross-sec- 
tion of  a  magnetic  field  of  unit  strength. 

Force,  Magnetic,  Lines  of Lines 

extending  in  the  direction  in  which  the  mag- 
netic force  acts. 

Lines  extending  in  the  direction  in  which 
the  force  of  magnetic  attraction  or  repulsion 
acts.  (See  Field,  Magnetic?) 

Faraday  regarded  the  lines  of  magnetic  force  as 
possessing  tension  along  one  direction.  Lines  of 
force  act  as  if  they  were  stretched  elastic  threads, 
possessed  of  the  property  of  lengthening  or  short- 
ening, and  of  repelling  one  another. 

Force,  Magnetic,  Lines  of,  Conducting 
Power  for A  term  employed  by  Fara- 
day for  magnetic  permeability.  (See  Perme- 
ability, Magnetic?) 

Force,    Magnetic,    Lines    of,    Positive 

Direction  of The  direction  in  which 

a  free  north-seeking  pole  would  move  along 
the  lines  of  force  when  placed  in  a  magnetic 
field. 


For.] 


240 


[For. 


Force,  Magnetic,  Telluric  -The 

earth's  magnetic  force. 

Force,  Magneto-Motive The  force 

that  moves  or  drives  the  lines  of  magnetic 
force  through  a  magnetic  circuit  against  the 
magnetic  resistance. 

A  Committee  of  the  American  Institute  of  Elec- 
trical Engineers  on  "Units  and  Standards"  pro- 
posed the  following  definition. 

1  he  magneto-motive  force  in  a  magnetic  cir- 
cuit is  47t  multiplied  by  the  flow  of  the  current 
linked  with  that  circuit.  The  magneto-motive 
iorce  between  two  points  connected  by  a  line  is 
the  line  integral  of  the  magnetic  force  along  that 
line.  Difference  of  magnetic  potential  constitutes 
magneto-motive  force." 

The  same  committee  gave  the  electro-magnetic 
dimensional  formula  Li  M^  T-1. 

The  flow  or  flux  of  lines  of  magnetic  force  in 
any  magnetic  circuit  is  proportional  to  the  mag- 
neto-motive force  divided  by  the  magnetic  resist- 
ance ;  or,  expressing  the  law  in  the  form  of  Ohm's 
law  for  current: 

..    „.  Magneto -Motive  Force 

Magnetic  I1  lux  =  — ^__~T 

Reluctance. 

In  this  formula  the  word  reluctance  is  used  in 
place  of  magnetic  resistance.  In  the  case  of  an 
electro-magnet,  the  magneto-motive  force  is  pro- 
portional to  the  strength  of  the  current  which  flows 
and  the  number  of  times  it  circulates;  or,  more 
simply,  is  proportional  to  the  number  of  ampere 
turns.  (See  Turns,  Ampere.) 

Force,  Magneto-Motive,  Absolute  Unit  of 

471  multiplied  by  unit  current  of  one 

turn. 

Force,  Magneto-Motive,  Practical  Unit 

of A  value  of  the  magneto-motive  force 

equal  to  4*  multiplied  by  the  amperes  of  one 
turn,  or  to  TO  of  the  absolute  unit. 

Force,  Motor  Electromotive  -     -  — A 

term  proposed  by  F.  J.  Sprague  for  the 
counter  electromotive  force  of  a  motor. 

During  the  rotation  of  the  armature  of  an 
electric  motor  in  its  field,  a  counter  electromotive 
force  is  produced  in  its  coils,  which  acts  as  a 
spurious  resistance  and  opposes  the  flow  or  pass- 
age of  the  driving  current  through  its  coils.  As 
the  speed  of  the  motor  increases,  this  counter 
electromotive  force  increases  and  the  strength  of 
the  driving  current  decreases  until  a  certain 


maximum  speed  is  reached,  when,  theoretically, 
no  current  passes. 

When  a  load  is  placed  on  the  electric  motor, 
the  speed,  and  consequently  the  counter  electro- 
motive force,  is  decreased  and  more  driving  cur- 
rent is  permitted  to  pass.  It  was  this  considera- 
tion, viz. :  that  the  load  automatically  regulates 
the  current  required  to  drive  the  motor,  that  kd 
to  the  name  motor  electromotive  force.  (See 
Force,  Electromotive,  Counter.) 

Force,  Resolution  of  —  —The  separa- 
tion of  a  single  force,  acting  with  a  given 
intensity  in  a  given  direction,  into  a  number 
of  separate  forces  -, 
acting  in  some  other 
direction. 

Thus  the  force  D  B, 
Fig.  258,  acting  with 
the  intensity  and  in  the 
direction  shown,  may  c 
be  resolved  into  two 
component  forces,  D 


Fig.  238.    Resolution  of 
Force. 


E  and  D  C,  acting  in  the  directions  and  having 
the  intensities  shown.  The  single  force  D  B,  has 
been  resolved  into  two  separate  forces  D  E  and 
CD. 

Force,  True  Contact A  force  or 

effect  entirely  distinct  from  the  voltaic  effect, 
which  exists  at  the  points  of  contact  be- 
tween two  dissimilar  metals. 

The  truth  of  the  existence  of  a  true  contact  force 
at  the  junction  of  dissimilar  metals  is  seen  by  the 
reversible  heat  effects  observed,  when  a  current 
of  electricity  is  passed  across  a  junction  of  two 
dissimilar  metals.  When  the  current  is  passed  in 
one  direction,  an  increase  of  temperature  is  pro- 
duced, but  when  passed  in  the  opposite  direction, 
a  decrease  of  temperature.  (See  Effect,  Peltier.) 

Hence  there  would  appear  to  be  a  force  existing 
at  the  junction,  helping  the  electricity  along  in 
one  direction,  but  opposing  it  in  the  opposite  di- 
rection. In  one  direction  the  electricity  does 
work  and  consumes  its  own  energy  in  so  doing. 
In  the  other  direction  it  opposes  the  passage  of 
the  current,  and  there  results  a  generation  of 
heat. 

Force,  Tubes  of Tubes  bounded  by 

lines  of  electrostatic  or  magnetic  force. 

Lines  of  force  never  intersect  one  another. 
Hence  a  tube  of  force  may  be  regarded  as  con- 


For.] 


241 


taining  the  same  number  of  lines  of  force  at  any 
and  every  cross-section. 

Tubes  of  electrostatic  force  always  terminate 
against  equal  quantities  of  positive  and  negative 
electricity  respectively.  They  terminate  when 
they  meet  a  conducting  surface. 

The  term  tubes  of  force  is  somewhat  mislead- 
ing, since  such  so-called  tubes  are  in  general 
cones  rather  than  tubes. 

Force,  Twisting A  term  sometimes 

used  for  torque.  (See  'Torque) 

Force,  Unit  of A  force  which,  act- 
ing for  one  second  on  a  mass  of  one 
gramme,  will  give  it  a  velocity  of  one  centi- 
metre per  second. 

Such  a  unit  of  force  is  called  a  dyne.  (See 
Dyne.) 

Forces,  Composition  of Finding 

th«  direction  and  intensity  of  a  single  force 
which  represents  the  total  effect  of  two  or 
more  forces  acting  simultaneously  on  a  body. 
(See  Component.) 

Forces,  Parallelogram  of  —  — A  paral- 
lelogram constructed  about  the  two  lines  that 
represent  the  direction  and  intensity  with 
which  two  forces  are  simultaneously  acting 
on  a  body,  in  order  to  determine  the  direction 
and  intensity  of  the  resultant  force  with 
which  it  moves. 

If  the  two  forces  A  C  and  A  B,  Fig.  259,  simul- 
taneously act  in  the  direc-  B  ID 
tion  of  the  arrows  on  a 
body  at  A,  the  direction 
and  intensity  of  the  re- 
sultant A  D,  is  deter-  pig.  239.  Farallelo- 
mined  by  drawing  C  D  eram  of  Forces. 
and  B  D,  parallel  respectively  to  A  B  and  A  C. 
The  diagonal  A  D,  of  the  parallelogram  AC  D  B, 
thus  produced,  gives  this  resultant.  (See  Com- 
ponent. ) 

Fork,  Trolley The  mechanism 

which  mechanically  connects  the  trolley  wheel 
to  the  trolley  pole.  (See  Trolley.) 

Forked  Circuits.— (See  Circuits,  Forked) 

Forked  Lightning.  —  (See  Lightning, 
Forked) 

Formal  Inductance  of  Circuit.— (See  In- 
ductance, Formal,  of  Circuit) 


Forming  Plates  of  Secondary  or  Stor- 
age  Cells. — (See  Plates  of  Secondary  or  Stor- 
age Cells,  Forming  of.) 

Formulae. — Mathematical  expressions  for 
some  general  rule,  law,  or  principle. 

Formulae  are  of  great  assistance  in  science  in 
expressing  the  relations  which  exist  between  cer- 
tain forces  or  values,  and  the  effects  that  result 
from  their  operations,  since  they  enable  us  to  ex 
press  these  relations  in  clear  and  concise  forms. 

Thus  in  the  formulation  of  Ohm's  law: 

C_E 
-R 

we  see  that  the  continuous  current  C,  in  any  cir- 
cuit, is  equal  to  the  electromotive  force  E,  divided 
by  the  resistance  R.  Again,  we  see  that  the  cur- 
rent is  directly  proportional  to  the  electromotive 
force,  and  inversely  proportional  to  the  resistance. 

Formulae  are  usually  written  in  the  form  of  an 
equation  and  therefore  contain  the  sign  oiequality 
or  =. 

Formulae,  Photometric (See  Pho- 
tometric Formula.) 

Foucault  Currents. — (See  Currents,  Fou- 
cault!) 

Four-Way  Splice  Box.— (See  Box,  Splice, 
Four-  Way.) 

Frames,  Sectional  Plating Frames 

employed  for  so  holding  the  objects  to  be 
plated  that  they  shall  receive  a  greater  depth 
of  deposit  on  certain  portions  of  their  surface 
than  elsewhere. 

Sectional  printing  frames  depend  for  their 
action  on  the  fact  that  the  portions  receiving  the 
greater  depth  of  deposit  are  nearer  one  of  the 
electrodes  than  the  rest  of  the  surface. 

Franklinic  Electricity.  —  (See  Elec- 
tricity, Franklinic.) 

Franklinization. — Electrization  by  means 
of  a  frictional  or  influence  machine  as  distin- 
guished from  faradization  or  electrization  by 
means  of  an  induction  coil. 

This  term  is  used  only  in  medical  electricity. 

Free  Charge. — (See  Charge,  Free.) 

Free  Magnetic  Pole. — (See  Pole,  Mag- 
netic, Free.) 

Frequency  of  Alternations. — (See  Alter- 
nations, Frequency  of) 


Fri.] 


242 


[Fun. 


Friction  Brake.—  (See  Brake,  Friction?) 
Frictional     Electrical     Machine. — (See 

Machine  Frictional  Electric?) 
Frictional  Electricity.— (See  Electricity , 

Frictional.} 

Frog1,  Galvanoscopic The  hind  legs 

cf  a  recently  killed  frog  employed  as  an  elec- 
troscope or  galvanoscope,  by  sending  an  elec- 
tric current  from  the  nerves  to  the  muscles. 
(See  Electroscope?) 

In  1786,  Luigi  Galvani  made  the  observation 
that  when  the  legs  of  a  recently  killed  frog  were 
touched  by  a  metallic  conductor  connecting  the 
nerves  with  the  muscles,  the  legs  were  convulsed 
as  though  alive.  He  repeated  this  experiment 
and  found  the  move- 
ments  were  more  pro- 
nounced when  two  dis- 
similar metals,  such  as 
iron  and  copper,  were 
employed  in  the  manner 
shown  in  Fig.  260. 

The  classic  experi- 
ment created  intense 
excitement  in  the  scien- 
tific world,  and  Galvani 
at  first  believed  that  he 
had  discovered  the  true  vital  fluid  of  the  animal, 
but  afterwards  recognized  it  as  electricity,  which 
he  believed  to  be  obtained  from  the  body  of  the 
animal.  Volta  claimed  that  the  movements  were 
due  to  electricity  caused  by  the  contact  of  dissimi- 
lar metals,  and  thus  produced  his  famous  voltaic 
pile.  (See /*'/,?,  Voltaic.} 

Frog,  Trolley The  name  given  to 

the  device  employed  in  fastening  or  holding 
together  the  trolley  wires  at  any  point  where 
the  trolley  wire  branches,  and  properly  guiding 
the  trolley  wheel  along  the  trolley  wire  on  the 
movement  of  the  car  over  the  track. 

Frog,  Trolley,  Right-Hand A  trol- 
ley frog  used  at  the  point  where  the  branch 
trolley  wire  leaves  the  main  line  on  the  right 
of  the  direction  in  which  the  car  is  moving. 

Frog  Trolley,  Standard The  trol- 
ley frog  used  at  the  point  where  two  branch 
lines  make  equally  converging  angles  to  the 
main  line. 

Frog,  Trolley,  Three-Way A  trol- 


Fig:  260.    Galvanoscopic 
Frog 


ley  frog  used  where  the  line  branches  in  three 
directions. 

Frying  of  Arc.— (See  Arc,  Frying  of.} 
Fulgurite.— A  tube  of  vitrified  sand,  be- 
lieved to  be  formed  by  a  bolt  of  lightning. 

The  fulgurite  consists  of  an  irregular  shaped 
tube  of  glass  formed  of  sand  which  has  been 
melted  by  the  electric  discharge. 

Fnll  Contact. -(See  Contact,  Metallic.} 

Fuller's    Mercury    Bichromate  Voltaic 

Cell.— (See  Cell,  Voltaic,  Fuller's  Mercury 
Bichromate?) 

Fulminate.— The  name  of  a  class  of  highly 
explosive  compounds. 

Fulminating  gold,  silver  and  mercury  are 
highly  explosive  substances.  Fulminates  are 
employed  in  percussion  caps. 

Function,  Trigonometrical Cer- 
tain quantities,  the  values  of  which  are  de- 
pendent on  the  length  of  the  arcs  subtended 
by  angles,  which  are  taken  for  the  measures 
of  the  arcs  or  angles  instead  of  the  arcs 
themselves. 

The  trigonometrical  functions  are  the  sine,  the 
co-sine,  the  tangent,  the  co-tangent,  the  secant 
and  the  co-secant. 

These  are  generally  abbreviated  thus,  viz. :  sin., 
.  cos.,  tan.,  cot.,  sec.  and  co-sec. 

The  sine  of  an  angle  or  arc  is  the  perpendic- 
ular distance  from  one    L  c 
extremity  of  the  arc  to 
the     diameter     passing 
through   the   other  ex- 
tremily. 

Thus  in  Fig.  261  B  D,  G 
is  the  sine  of  the  angle 
B  O  A,   or  of  the  arc, 
B  A. 

The  co-sine  of  an  an- 
gle or  arc  is  that  part  of  Fig.  zbr.    Trigonometri- 
the  diameter  which  lies  cal  Functions. 

between  the  foot  of  the  sine  and  the  centre.  Thus, 
D  O,  is  the  co-sine  of  the  angle  B  O  A,  or  of  the 
arc  B  A. 

The  co-sine  of  an  arc  is  equal  to  the  sine  of  its 
complement.  Thus  E  O  B,  or  B  E,  the  comple- 
ment of  B  A,  has  for  its  sine  I  B.  which  is  equal 
to  O  D.  (See  Ang*e,  Complement  of.} 

If  the  arc  is  greater  than  a  right  angle,  or  90 


F\ 


Fun.] 


243 


[Fus. 


degrees,  such,  for  instance,  as  the  angle  TOG, 
or  the  arc  B  E  F  G,  B  D,  is  its  sine.  This  is  also 
the  sine  of  B  O  A,  or  B  A,  which  is  the  supple- 
ment of  T  O  G,  or  B  E  F  G.  Hence  the  sine  of 
an  arc  is  equal,  to  the  sine  of  its  supplement. 

The  same  is  true  of  the  co-sine. 

The  tangent  of  an  angle  or  arc  is  a  straight 
line  touching  the  arc  at  one  extremity,  drawn 
perpendicular  to  the  diameter  at  that  end  of  the 
arc,  and  limited  by  a  straight  line  connecting  the 
centre  of  the  circle  and  the  other  end  of  the  arc. 
Thus  C  A,  is  the  tangent  of  the  angle  B  O  A,  or 
the  arc  B  A. 

The  co-tangent  of  an  angle  or  arc  is  equal  to 
the  tangent  of  its  complement.  Thus  E  T,  is  the 
co-tangent  of  the  angle  B  O  A,  or  the  arc  B  A. 

The  tangent  of  an  angle  or  arc  is  equal  to  the 
tangent  of  its  supplement.  Thus  A  C,  is  the  tan- 
gent of  the  angle  B  O  A,  or  the  arc  B  A.  It  is 
also  equal  to  the  tangent  of  the  angle  B  O  G,  or 
the  arc  B  E  F  G,  the  corresponding  supplement  of 
the  angle  B  O  A,  or  the  arc  B  A. 

The  secant  of  an  angle  or  arc  is  the  straight 
line  drawn  from  the  centre  of  the  circle  through 
one  extremity  of  the  arc  and  limited  by  the  tan- 
gent passing  through  the  other  extremity.  Thus 
O  C,  is  the  secant  of  the  angle  B  O  A,  or  of  the 
arc  B  A. 

The  secant  of  an  angle  or  arc  is  equal  to  the 
secant  of  its  supplement. 

The  co-secant  of  an  angle  or  arc  is  equal  to 
the  secant  of  its  complement. 

Thus  O  T,  is  the  co-secant  of  the  angle  BOA, 
or  of  the  arc  B  A. 

It  will  be  observed  that  the  co-sine,  the  co- 
tangent and  the  co-secant  are  respectively  the 
sine,  tangent  and  secant  of  the  complement  of 
the  arc,  or  in  other  words,  the  complement-sine, 
the  complement-tangent  and  tiie  comple.nent- 
secant. 

Fundamental  Units.  -  (See  Units,  Funda- 
mental.') 

Furnace,  Electric  —A  furnace  in 

which  heat  generated  electrically  is  employed 
for  the  purpose  of  effecting  difficult  fusions 
for  the  extraction  of  metals  from  their  ores, 
or  for  other  metallurgical  operations. 

In  electric  furnaces,  the  heat  is  derived  either 
from  electric  incandescence  or  from  the  voltaic  arc. 
The  latter  form  is  frequently  adopted. 

The  substance  to  be  treated  is.  exposed  directly 


to  the  voltaic  arc.  In  some  forms  of  furnace  the 
crushed  ore  is  permitted  to  fall  through  the  arc, 
and  the  melted  matter  received  in  a  suitable  ves- 
sel in  which  the  separation  of  the  substances  so 
formed  is  afterwards  completed.  In  other  forms 
of  furnace,  the  ore  is  placed  between  two  elec- 
trodes of  carbon  or  other  refractory  substance, 
between  which  a  powerful  current  is  passed.  In 
the  Cowles  furnace,  when  aluminium  is  reduced, 
molten  copper  forms  an  alloy  with  the  aluminium 
as  soon  as  separated. 

Very  numerous  applications  of  electricity  to 
furnace  operations  have  been  made. 

Fuse  Block.— (See  Block,  Fuse.) 

Fuse  Board.— (See  Board,  Fuse.) 

Fuse  Box.— (See  Box,  Fuse.) 

Fuse,  Branch —A  safety  fuse  or 

strip  placed  in  a  branch  circuit.  (See  Fuse, 
Safety.) 

Fuse,  Converter A  safety  fuse  con- 
nected with  the  circuit  o(  a  converter  or 
transformer. 

Fuse,  Electric A  device  for  elec- 
trically igniting  a  charge  of  powder. 

Electric  fuses  are  employed  both  in  blasting 
operations  and  for  firing  cannon. 

Electric  fuses  are  operated  either  by  means  of 
the  direct  spark,  or  by  the  incandescence  of  a 
thin  wire  placed  in  the  circuit.  They  are  there- 
fore either  high  tension,  or  low  tension  fuses. 

The  advantages  of  an  electric  fuse  consist  in 
the  fact  that  its  use  permits  the  simultaneous  fir- 
ing of  a  number  of  charges  in  a  mining  operation, 
thus  obtaining  a  greater  effect  from  the  explosion. 
A  fulminate  of  mercury  is  frequently  employed 
in  connection  with  some  forms  of  electric  fuses. 

Fuse,  Electric,   High-Tension A 

fuse  that  is  ignited  by  the  heating  power  of 
an  electric  spark. 

High  tension  fuses,  therefore,  require  a  high 
electromotive  force.  This  is  obtained  either  by 
means  of  induction  coils  or  Ly  some  form  of 
electrostatic  induction  machine. 

Fuse,  Electric,   Low-Tension A 

fuse  that  is  ignited  by  heating  a  wire  to  incan- 
descence by  the  passage  through  it  of  an 
electric  current. 
Fuse,  Electric,  Stratham's A  form 


Fas.] 


244 


[Gal, 


ot  fuse,  in  which  the  ignition  is  effected  by  the 
electric  spark,  is  shown  in  Fig.  262. 

The  spark  passes  through  a  break  A  B,  in  the  in- 
sulated leads  D.  Since  gunpow- 
der is  not  readily  ignited  by  an 
electric  spark,  a  peculiar  priming 
material  is  employed  at  A  B,  in  the 
place  of  ordinary  powder. 

Fuse  Links.  —  (See  Links, 
Fuse.) 
Fuse,    Magazine   — A 

safety  fuse  so  arranged  as  to 
readily  permit  the  replacement 
of  the  fuse  when,  burned  out. 

A  spool  contains  a  coil  of  fuse     ^y~  2fr2 
wire.      In    order    to   release    the    Stratham's 
burned-out  fuse,   a  wedge-shaped         Fuse. 
device  is  provided  to  open  the  clamps  that  hold 
the  fuse  strip  to  release  the  portions  of  burned- 
out  fuse  left,  and  connection  with  the  fuse  strip 
is  severed  while  the  attachment  of  the  new  strip 
is  being  made. 

Fuse,  Main A  safety  fuse  or  strip 

placed  in  a  main  circuit.     (See  Fuse,  Safety?) 

Fuse,  Platinum A  thin  platinum 

wire  rendered  incandescent  by  the  passage  of 
an  electric  current  and  employed  for  the  igni- 
tion of  a  charge  of  powder.  (See  Fuse, 
Electric?) 

Fuse,  Safety A  strip,  plate  or  bar 

of  lead,  or  some  readily  fusible  alloy,  that  au- 
tomatically breaks  the  circuit  in  which  it  is 
placed  on  the  passage  of  a  current  of  suf- 


ficient power  to  fuse  such  strip,  plate  or  bar, 
when  such  current  would  endanger  the  safety 
of  other  parts  of  the  circuit. 

Safety  fuses  are  often  called  safety  strips  or 
safety  plugs. 

Safety  fuses  are  made  of  alloys  of  lead,  and 
are  placed  in  boxes  lined  with  non-combustible 
material  in  order  to  prevent  fires  from  the  molten 
metal. 

Fig.  263  shows  a  fusible  strip  F,  connected  with 
leads  L,  L.  Safety  fuses  are  placed  on  all  branch 
circuits,  and  are  made  of  sizes  proportionate  to 
the  number  of  lamps  they  guard. 


Fig.  263.    Safety  Fuse. 

Since  incandescent  lamps  are  generally  placed 
in  the  circuit  in  multiple-arc,  or  in  multiple-series, 
one  or  more  of  the  circuits  can  be  opened  by  the 
fusion  of  the  plug  without  interfering  with  the 
continuity  of  the  rest  of  the  circuits.  In  series 
circuits,  however,  such  as  arc-light  circuits,  when 
a  lamp  is  cut  out,  a  short  circuit  or  path  around 
it  must  be  provided  in  order  to  avoid  the  extin- 
guishing of  the  rest  of  the  lights. 

Fuse  Wire.— (See  Wire,  Fuse.) 

Fusible  Plug. — A  term  commonly  applied 
to  a  safety  plug.  (See  Fuse,  Safety 


G 


Gains. — The  spaces  cut  m  the  faces  of 
telegraph  poles  for  the  support  or  placing  of 
the  cross  arms. 

Galvanic  Battery.— (See  Battery,  Gal- 
vanic?) 

Galvanic  Cell.— (See  Cell,  Voltaic?) 

Galvanic  Circle. — (See  Circle,  Galvanic.) 

Galvanic  Circuit. — (See  Circuit,  Gal- 
vanic?) 


Galvanic  Dosage. — (See  Dosage,  Gal- 
vanic?) 

Galvanic  Electricity.— (See  Electricity, 
Galvanic?) 

Galvanic  Excitability  of  Nerve  or  Mus- 
vjular  Fibre. — (See  Excitability,  Electric, 
of  Nerve  or  Muscular  Fibre?) 

Galvanic  Irritability. — (See  Irritability, 
Galvanic?^ 


245 


[Gal. 


Galvanic  Multiplier.— (See  Multiplier, 
Galvanic?) 

Galvanic  Polarization. — (See  Polariza- 
tion, Galvanic?) 

Galvanic  Taste. — (See  Taste,  Galvanic?) 

Galvanism. — A  term  sometimes  employed 
to  express  the  effects  produced  by  voltaic 
electricity. 

Galvanization,  Central A  variety 

of  general  galvanization  in  which  the  kathode 
is  placed  on  the  epigastrium  and  the  anode 
moved  over  the  body. 

Galvanization,  Electro-Metallurgical 
The  process  of  covering  any  conduc- 
tive surface  with  a  metallic  coating  by  elec- 
trolytic deposition,  such,  for  example,  as  the 
thin  copper  coating  deposited  on  the  carbon 
pencils  or  electrodes  used  in  systems  of  arc 
lighting. 

The  term  is  borrowed  from  the  French,  in 
which  it  has  the  above  signification.  It  is  prefer- 
ably replaced  by  the  term  electro-plating.  (See 
Plating,  Electro.) 

The  term  galvanization  is  never  correctly  ap- 
plied to  the  process  for  covering  iron  with  zinc  or 
other  metal  by  dipping  the  same  in  a  bath  of 
molten  metal. 

Galvanization,      Electro-Therapeutical 

—  In  electro-therapeutics,  the  effects 
produced  on  nervous  or  muscular  tissue  by 
the  passage  of  a  voltaic  current. 

Galvanization,  General  —  — A  method 
of  applying  a  current  therapeutically  by  the 
use  of  electrodes  of  sufficient  size  to  direct 
the  current  through  practically  the  entire 
body. 

Galvanization,  Labile  -  — A  term 
employed  in  electro-therapeutics,  in  contradis- 
tinction to  stabile  galvanization,  to  designate 
the  method  of  applying  the  current  by  keep- 
ing one  electrode  at  rest  in  firm  contact  with 
one  part  of  the  body,  and  connecting  the  other 
electrode  to  a  sponge  which  is  moved  over 
the  parts  of  the  body  that  are  to  be  treated. 

Galvanization,  Local  —  —The  applica- 
tion of  galvanization  to  parts  or  organs  of  the 
body  in  contradistinction  to  general  galvani- 
zation. 


Galvanization,  Stabile A  term 

employed  in  electro-therapeutics  in  which  the 
current  is  caused  to  pass  continuously  and 
steadily  through  the  portions  of  the  body  un- 
dergoing galvanization. 

In  stabile  galvanization,  the  current  is  applied 
to  and  removed  from  the  body  gradually,  in  order 
to  avoid  shocks  at  the  beginning  and  end  of  the 
application. 

Galvanized  Iron. — (See  Iron,  Galvan- 
ized?) 

Galvano. — A  word  sometimes  used  in 
France  in  place  of  the  word  electro,  to  signify 
an  article  reproduced  in  copper  by  electro- 
metallurgy, especially  an  electrotype  or  wood- 
cut. 

Galvano-Causty. — (See  Causty,  Galvano.) 

Galvano-Cautery. — (See     Cautery,    Gal- 
vano?) 
Galvano-Cautery,     Chemical    — A 

term  sometimes  applied  to  electro  puncture 
or  the  application  of  electrolysis  to  the  treat- 
ment of  diseased  growths.  (See  Cautery, 
Electric.  Puncture,  Electro?) 

The  term  chemical  galvano-cautery  would  ap- 
pear to  be  poorly  chosen,  as  it  would  imply  the 
existence  of  a  cautery  action,  which  in  point  of 
fact  does  not  exist 

Galvano-Faradization. — In  electro-thera- 
peutics, the  simultaneous  excitation  of  a  nerve 
or  muscle  by  both  a  voltaic  and  a  faradic  cur- 
rent. 

Galvano-Magnet. — A  term  sometimes  used 
for  electro-magnetic. 

Electro  magnetic  is  by  far  the  preferable  term, 
and  is  almost  universally  employed  in  the  United 
States. 

Galvanometer. — An  apparatus  for  meas- 
uring the  strength  of  an  electric  current  by 
the  deflection  of  a  magnetic  needle. 

The  galvanometer  depends  for  its  operation  on 
the  fact  that  a  conductor,  through  which  an  elec- 
tric current  is  flowing,  will  deflect  a  magnetic 
needle  placed  near  it.  This  deflection  is  due  to 
the  magnetic  field  caused  by  the  current.  (See 
Field,  Magnetic,  of  an  Electric  Current.) 

This  action  of  the  current  was  first  discovered 
by  Oersted.  A  wire  conveying  a  current  in  the 


Gal.] 


246 


[Gal. 


direction  shown  by  the  straight  arrow,  Fig.  264, 
or  from  +  to  — ,  will  deflect  a  magnetic  needle  in 
the  direction  shown  by  the  curved  arrows. 

The  following  rules  show  the  direction  of  the 


Fig.  264.     Oersted's  Experiment. 

deflection  of  a  magnetic  pole  by  an  electrical  cur- 
rent: 

(I.)  Place  the  right  hand  on  the  conductor 
through  which  the  current  is  flowing,  with  the 
palm  facing  the  north  pole,  and  with  the  fingers 
pointing  in  the  direction  of  the  current.  The 
thumb  will  indicate  the  direction  in  which  the 
north  pole  tends  to  move. 

(2.)  Suppose  an  ordinary  corkscrew  so  placed 
along  the  conductor,  through  which  a  current  of 
electricity  is  passing,  that  when  twisted,  it  will 
move  in  the  direction  of  the  current.  The  han- 
dle will  then  turn  in  the  direction  in  which  the 
north  pole  of  the  magnet  tends  to  move. 

(3.)  Imagine  one  swimming  along  the  con- 
ductor in  the  direction  of  the  current  and  facing 
the  magnet.  The  north  pole  wiil  tend  to  move 
towards  the  left  hand  of  the  swimmer. 

Prof.  Forbes  has  shown  that  the  direction  of 
the  deflection  of  a  magnet  by  a  current  is  such 
A  B  C 


Fig.  265.    Amptre's  Apparatus. 

that  if  the  magnet  were  flexible,  it  would  wrap 
itself  round  the  current. 

If  the  wire  be  bent  in  the  form  of  a  hollow  rec- 
tangle F,  D,  E,  G,  Fig.  265,  and  the  needle,  M, 


be  placed  inside  the  circuit,  the  upper  and  lower 
branches  of  the  current  will  deflect  the  needle  in 
the  same  direction,  and  the  effect  of  the  current 
will  thus  be  multiplied.  Mercury  cups  are  pro- 
vided at  A,  B  and  C,  for  a  ready  change  in  the 
direction  of  the  current.  (See  Needle,  Astatic.) 

This  principle  of  the  multiplication  of  the  de- 
flecting power  of  a  current  was  first  applied  to  gal- 
vanometers by  Schweigger,  who  used  a  number  of 
turns  of  insulated  wire  for  the  purpose  of  obtain- 
ing a  greater  deflection  of  the  needle.  He  called 
such  a  device  a  multiplier.  In  extremely  sensi- 
tive galvanometers,  very  many  turns  of  wire  are 
employed,  in  some  cases  amounting  to  many 
thousands.  Such  galvanometers  are  of  high  re- 
sistance. Others,  of  low  resistance,  often  con- 
sist of  a  single  turn  of  wire  and  are  used  in  the 
direct  measurement  of  large  currents. 

A  Schweigger's  multiplier  or  coil  C,  C,  oi 
many  turns  of  insulated  wire,  is  shown  in  Fig.  266. 
The  action  of  such  a  coil  on  the  needle  M,  is  com- 
paratively great,  even  when  the  current  is  small. 


Fig.  266-     Schweigger's  Multiplier. 


In  the  case  of  any  galvanometer,  when  no  cur- 
rent is  passing,  the  needle,  when  at  rest,  should  in 
general  occupy  a  position  parallel  to  the  plane  of 
the  coiL  On  the  passage  of  the  current,  the 
needle  tends  to  place  itself  in  a  position  at  right 
angles  to  the  direction  of  the  current,  or  to  the 
length  of  the  conducting  wire  in  the  coil.  The 
strength  of  the  current  passing  is  determined  by 
observing  the  amount  of  this  deflection  as  meas- 
ured in  degrees  on  a  graduated  circle  over  which 
the  needle  moves. 

The  needle  is  deflected  by  the  current  from  a 
position  of  rest,  either  in  the  earth's  magnetic 
field  or  in  a  field  obtained  from  a  permanent  or 
an  electro  magnet  In  the  first  case,  when  in  use 
to  meamre  a  current,  the  plane  of  the  galvanom- 
eter coils  must  coincide  with  the  planes  of  the 
magnetic  meridian.  In  the  other  case,  the  instru- 


Gal.] 


247 


[Gal. 


ment  may  be  used  in  any  position  in  which  the 
needle  is  free  to  move. 

Galvanometers  assume  a  variety  of  forms  ac- 
cording either  to  the  purposes  for  which  they  are 
employed,  or  to  the  manner  in  which  their  deflec- 
tions are  valued. 

Galvanometer,  Absolute A  galva- 
nometer whose  constant  can  be  calculated 
with  an  absolute  calibration.  (See  Calibra- 
tion, Absolute?) 

Such  a  galvanometer  is  called  absolute  because 
if  the  dimensions  of  its  coil  and  needle  are  known, 
the  current  can  be  determined  directly  from  the 
observed  deflection  of  the  needle. 

Galvanometer,  Aperiodic A  gal- 
vanometer the  needle  of  which  comes  to  its 
position  without  any  oscillation. 

A  dead-beat  galvanometer.  (See  Galva- 
nometer, Dead-Beat?) 

Galvanometer,  Astatic —  A  galva- 
nometer, the  needle  of  which  is  astatic.  (See 
Needle,  Astatic?] 

Nobili's  astatic  galvanometer  is  shown  in  Fig. 
267.  The  astatic  needle,  suspended  by  a  fibre  b, 
has  its  lower  needle  placed  inside  a  coil,  a,  con- 
sisting of  many  turns  of  insulated  wire,  its  upper 
needle  moving  over  the  graduated  dial.  The  cur- 
rent to  be  measured  is  led  into  and  from  the 
coil  at  the  binding  posts,  x  and  y. 


Fig.  267.    Astatic  Galvanometer. 

In  this  instrument,  if  small  deflections  only  are 
employed,  the  deflections  are  sensibly  propor- 
tional to  the  strength  cf  the  deflecting  currents. 

Galvanometer,  Ballistic A  galva- 
nometer designed  to  measure  the  strength  of 
currents  that  last  but  for  a  moment,  such,  for 
example,  as  the  current  caused  by  the  dis- 
charge of  a  condenser. 


The  quantity  of  electricity  passing  in  any  cir- 
cuit is  equal  to  the  current  multiplied  by  the  time. 
Since  the  current  caused  by  the  discharge  of  a 
condenser  lasts  but  for  a  small  time,  during  which 
it  passes  from  zero  to  a  maximum  and  back  again 
to  zero,  the  magnetic  needle  in  a  ballistic  galva- 
nometer takes  the  form  of  a  ballistic  pendulum, 
i.  e.,  it  is  given  such  a  mass,  and  acquires  such  a 
slow  motion,  that  its  change  of  position  does  not 


Fig.  268.    Ballistic  Galvanometer. 

practically  begin  until  the  impulses  have  ceased 
to  act. 

In  the  ballistic  galvanometer  of  Siemens  and 
Halske,  the  coils  R,  R,  Fig.  268,  have  a  bell- 
shaped  magnet,  M,  suspended  inside  them  by 
means  cf  an  aluminium  wire.  The  magnet  is  pro- 
vided with  a  mirror  S,  for  measuring  the  deflec- 
tions. The  bel'-shap-d  magnet  is  shown  in  ele- 
vation at  M,  and  i.i  p'ane  at  n,  s. 

In  using  the  ballistic  galvanometer,  it  is  neces- 
sary to  see  that  the  needle  is  absolutely  at  rest  be- 
fore the  charge  is  sent  through  the  coils. 

A  form  of  ballistic  galvanometer  by  Nalder  is 
shown  in  Fig.  269. 

The  ordinary  form  of  compensating  magnet 
is,  in  this  galvanometer,  replaced  by  the  small  mag- 
net A,  capable  of  rotation  in  a  horizontal  plane,  but 
incapable  of  being  raised  or  lowered,  as  is  usual 
in  such  magnets.  This  form  of  compensating  mag- 
net possesses  the  advantage  of  being  able  to  alter 
the  direction  of  the  field  on  the  needle  system, 


Gal.] 


248 


[Gal. 


without  considerably  altering  its  intensity.  When 
the  galvanometer  is  for  ready  use  the  magnet  A,  is 
turned  until  the  needle  is  brought  to  zero.  The 


Fig.  2bg.    Nalder's  Galvanometer. 

combined  field  of  earth  and  magnet  A,  are  then 
brought  to  the  degree  of  sensitiveness  required 


Fig.  270.  Nalder's  Galvanometer. 
by  rotating,  magnet  B,  on  its  shaft,  or  altering 
its  distance  from  the  needle.  In  order  to  insure 
ease  in  replacing  the  fibre,  the  front  coil  is  hinged 
as  shown.  The  fibre  D,  is  supported  on  E,  one 
end  of  which  it  is  free  to  turn,  so  as  to  permit  of 
the  removal  of  torsion;  D,  being  twisted  can  be 
raised  or  lowered  at  E.  The  needle  system  with 
heavy  bell-shaped  magnet  is  shown  in  Fig.  270. 

Galvanometer,  Combined  Tangent  and 

Sine A  galvanometer  furnished  with 

two  magnetic  needles  of  different  lengths. 
The  small  needle  is  used  for  tangent  measure- 
ments, and  the  long  needle  for  sine  measure- 
ments. 

Galvanometer  Constant. — (See  Constant, 
Galvanometer?) 

Galvanometer,  Dead-Beat A  gal- 
vanometer, the  needle  of  which  comes  quickly 
to  rest,  instead  of  swinging  repeatedly  to-and- 
fro.  (See  Damping?) 

Galvanometer,  Deprez-D'Arsonval  

— A  form  of  dead-beat  galvanometer. 

The  movable  part  of  the  Deprez-D'Arsonval 
galvanometer  consists  of  a  light  rectangular  coil 


C,   Fig.   271,  of  many  turns  of  wire,  supported 

by  two  silver  wires  H  J  and  D  E,  between  the 

poles  of  a  strong  permanent  horseshoe  magnet 

A  A.     The  position  of 

the  coil  may  be  altered 

as  to  height  by  screws 

at  H  and  E.     The  sup- 

porting  wires,  prevent 

by    their    torsion     the 

swinging  cf  the  coil,  as 

does  also  the  cylinder 

of  soft  iron   B,  placed 

inside  the  coil,  and  sup- 

ported    independently 

of  it.     The  movements  if 

of  the  coil  are  observed 

by  means  of  a  spot  of 

light  reflected  from    a 

mirror  J,    attached    to 

the  wire  H  J. 

Galvanometer,  Detector  --  A  form  of 
galvanometer  employed  for  rough  testing 
work. 

A  form  of  detector  galvanometer  is  shown  in 
Fig.  272. 


271.  Deprez-D"  Arson- 
val  Galvanometer. 


Fig.  2J  2.    Detector  Galvanometer. 


A  gal- 
vanometer containing  two  coils  so  wound  as 
to  tend  to  deflect  the  needle  in  opposite 
directions. 

The  needle  of  a  differential  galvanometer  shows 
no  deflection  when  two  equal  currents  are  sent 
through  the  coils  in  opposite  directions,  since, 
under  these  conditions,  each  coil  neutralizes  the 
other's  effects.  Such  instruments  may  be  used 
in  comparing  resistances.  The  Wheatstone 
Bridge,  however,  in  most  cases,  affords  a  prefer- 
able method  for  such  purposes.  (See  Bridge 
Electric. ) 


Gal.]  249 

A  form  of  differential  galvanometer  is  shown  in 

Fig-  273- 

Sometimes  the  current  is  so  sent  through  the 
two  coils,  that  each 
coil  deflects  the  nee- 
dle in  the  same  di- 
rection. In  this  case 
the  instrument  is  no 
longer  differential  in 
action. 

If  the  magnetic 
needle,  in  such  cases, 
is  suspended  at  the 
exact  centre  of  the 
line  which  joins  the 
centres  of  the  coils, 
the  advantage  is 
gained  by  obtaining 
a  field  of  more  nearly 

uniform  intensity  F'S-273-  Differential  Galva- 
around  the  needle.  nomtttr. 

Galvanometer,  Figure  of  Merit  of 

The  reciprocal  of  the  current  required  to  pro- 
duce a  deflection  of  the  galvanometer  needle 
through  one  degree  of  the  scale. 

The  smaller  the  current  required  to  produce  a 
deflection  of  one  degree,  the  greater  the  figure 
of  merit,  or  the  greater  the  sensitiveness  of  the 
galvanometer. 

Galvanometer,  Marine A  galva- 
nometer devised  by  Sir  William  Thomson  for 
use  on  steamships  where  the  motion  of  mag- 
netized masses  of  iron  would  seriously  disturb 
the  needles  of  ordinary  instruments. 

An  unscreened  needle  would  be  so  much  af- 
fected by  the  motion  of  the  engines,  the  shaft  and 
the  screw,  as  to  be  useless  for  galvanometric 
measurement. 

The  needle  of  the  marine  galvanometer  is 
shielded  or  cut  off  from  the  extraneous  fields  so 
produced,  by  the  use  of  a  magnetic  screen  or 
shield,  consisting  of  an  iron  box  with  thick  sides, 
inside  of  which  the  instrument  is  placed. 

The  needle  is  suspended  by  means  of  a  silk 
fibre  attached  both  above  and  below,  in  line  with 
the  centre  of  gravity  of  the  needle.  In  this  man- 
ner, the  oscillations  of  the  ship  do  not  affect  the 
needle. 

Galvanometer,  Mirror A  galva- 
nometer in  which,  instead  of  reading  the  de- 
flections of  the  needle  directly  by  its  move- 


[Gal, 


ments  over  a  graduated  circle,  they  are  read 
by  the  movements  of  a  spot  of  light  reflected 
from  a  mirror  attached  to  the  needle. 

This  spot  of  light  moves  over  a  graduated 
scale,  or  its  movements  are  observed  by  means  of 
a  telescope. 


Fig.  2-j 4.    Mirror  Galvanometer. 

A  form  of  mirror  galvanometer  designed  by  Sir 
William  Thomson  is  shown  in  Fig.  274.  Tht 
needle  is  attached  directly  to  the  back  of  a  light, 
silvered  glass  mirror,  and  consists  of  several  small 
magnets  made  of  pieces  of  a  watch  spring.  The 
needle  and  mirror  are  suspended  by  a  single  silk 
fibre  and  are  placed  inside  the  coil.  A  compen- 
sating magnet  N  S,  movable  on  a  vertical  axis,  is 
used  to  vary  the  sensitiveness  of  the  instrument. 
The  lamp  L,  placed  back  of  a  slot  in  a  wide 
screen,  throws  a  pencil  of  light  on  the  mirror  Q, 
from  which  it  is  reflected  to  the  scale  K. 

A  form  of  lamp  and  scale  with  slot  for  light  is 
shown  in  Fig.  275. 


Fig.  2JS.     Galvanometer  Lamp  and  Scale. 

Galvanometer,  Potential A  term 

sometimes    applied    to    a    voltmeter.    (See 
Voltmeter?) 

Galvanometer,  Reflecting A  term 

sometimes  applied  to  a  mirror  galvanometer, 
(See  Galvanometer,  Mirror) 


Gal.] 


250 


[Gal. 


Galvanometer,  Sensibility  of 


—The 

readiness  and  extent  to  which  the  needle  of  a 
galvanometer  responds  to  the  passage  of  an 
electric  current  through  its  coils.  (See  Gal- 
vanometer^) 

Galvanometer-Shunt. — (See  Shunt,  Gal- 
vanometer?) 

Galvanometer,  Sine  — A  galva- 
nometer in  which  a  vertical  coil  is  movable 
around  a  vertical  axis,  so  that  it  can  be  made  to 
follow  the  magnetic  needle  in  its  deflections. 

In  the  sine  galvanometer,  the  coil  is  moved  so 
as  to  follow  the  needle  until  it  is  parallel  with  the 
coil.  Under  these  circumstances,  the  strength 
of  the  deflecting  currents  in  any  two  different 
cases  is  proportional  to  the  sines  of  the  angles  of 
deflection. 

A  form  of  sine  galvanometer  is  shown  in  Fig. 
276.  The  vertical  wire  coil  is  seen  at  M.  A 
needle  of  any  length  less  than  the  diameter  of  the 
coil  M,  moves  over  the  graduated  circle  N.  The 
coil  M,  is  movable  over  the  graduated  horizontal 
circle  H,  by  which  the  amount  of  the  movement 


276.    Sine  Galvanometer. 


necessary  to  bring  the  needle  to  zero  is  measured. 
The  current  strength  is  proportional  to  the  sine 
of  the  angle  measured  on  this  circle,  through 
which  it  is  necessary  to  move  the  coil  M,  from  its 


position  when  the  needle  is  at  rest  in  the  plane  of 
the  earth's  magnetic  meridian,  until  the  needle 
is  not  further  deflected  by  the  current,  although 
parallel  to  the  coil  M. 

Galvanometer,  Tangent — An  instru- 
ment in  which  the  deflecting  coil  consists  of 
a  coil  of  wire  within  which  is  placed  a  needle 
very  short  in  proportion  to  the  diameter  of 
the  coil,  and  supported  at  the  centre  of  the 
coil. 


Fig.  277.     Tangent    Galvanometer. 

A  galvanometer  acts  as  a  tangent  galvanometer 
only  when  the  needle  is  very  small  as  compared 
with  the  diameter  of  the  coil.  The  length  of  the 
needle  should  be  less  than  one-twelfth  the  diameter 
of  the  coil. 

A  form  of  tangent  galvanometer  is  shown  in 
Fig-  277.  The  needle  is  supported  at  the  exact 
centre  of  the  coil  C. 

Under  these  circumstances,  the  strengths  of 
two  different  deflecting  currents  are  proportional 
to  the  tangents  of  the  angles  of  deflection.  Tan- 
gent galvanometers  are  sometimes  made  with 
coils  of  wire  containing  many  separate  turns. 

Galvanometer,  Tangent,  Obach's 

A  form  of  galvanometer  in  which  the  deflect- 
ing coil,  instead  of  being  in  a  fixed  vertical 
position,  is  movable  about  a  horizontal  axis, 
so  as  to  decrease  the  delicacy  of  the  instru- 
ment, and  thus  increase  its  range  of  work. 

Galvanometer,  Torsion  —  —A  galva- 
nometer in  which  the  strength  of  the  deflecting 
current  is  measured  by  the  torsion  exerted  on 
the  suspension  system. 

A  ball-shaped  magnet,  shown  at  the  right  of 
Fig.  278,  is  suspended  by  a  thread  and  spiral 


Gal.] 


251 


[Gal. 


spring  between  two  coils  of  high  resistance, 
placed  parallel  to  each  other  in  the  positions 
shown.  On  the  deflection  of  the  magnet,  by  the 
current  to  be  measured,  the  strength  of  the  current 
is  determined  by  the  amount  of  the  torsion  re- 
quired to  bring  the  magnet  back  to  its  zero  point. 


Pig.  278.     Torsion  Galvanometer, 

The  angle  of  torsion  is  measured  on  the  horizontal 
scale  at  the  top  of  the  instrument. 

In  the  torsion  galvanometer,  unlike  the  electro- 
dynamometer,  the  action  between  the  coils  and  the 
movable  magnet  is  as  the  current  strength  causing 
the  deflection.  In  the  electro-dynamometer, 
since  an  increase  of  current  in  the  deflecting  coils 
also  takes  place  in  the  deflected  coil,  the  mutual 
action  of  the  two  is  as  the  square  of  the  current 
strength  causing  the  deflection. 

Galvanometer,  Upright A  gal- 
vanometer, the  needle  of  which  moves  in  a 
vertical  plane.  (See  Galvanometer,  Ver- 
tical. 

Galvanometer,  Tertical A  gal- 
vanometer the  needle  of  which  is  capable  of 
motion  in  a  vertical  plane  only. 

In  the  vertical  galvanometer,  the  north  pole  of 
the  needle  is  weighted  so  that   the  needle  as- 
sumes a  vertical  position  when  no  current  is  pass- 
ing.    In  the  form  shown  in  Fig.  279,  two  needles 
9— Vol.  1 


are  sometimes  employed,  one  of  which  is  placed 
inside  the  coils  C,  C. 

The  vertical  galvanometer  is  not  as  sensitive  as 
the  ordinary  forms.  It  is  employed,  however, 
in  various  forms  for  an 
electric  current  indica- 
tor, or  even  for  a 
rough  current  meas- 


Galvanometer 
Voltmeter. — An  in- 
strument devised  by 
Sir  William  Thom- 
son, for  the  meas- 
urement of  differ- 
ences of  electric 
potential. 


Fig,  2TQ.     Vertical  Galva- 
nometer. 

This  instrument  is  so  arranged  that  by  a  single 
correction  for  the  varying  strength  of  the  earth's 
field  in  any  place,  the  results  are  read  at  once  in 
volts. 

A  coil  of  insulated  wire  shown  at  A,  Fig.  280, 
has  a  resistance  of  over  5,000  ohms.  A  magnetic 
needle,  formed  of  short  parallel  needles  placed 
above  one  another,  and  called  a  magnetometer 
needle,  is  attached  to  a  long  but  light  aluminium 
index,  moving  over  a  graduated  scale.  A  mova- 
ble, semi-circular  magnet  B,  called  the  restoring 
magnet,  is  placed  over  the  needle,  and  is  used 
for  varying  the  effect  of  the  earth's  field  at  any 
point.  The  sensitiveness  of  the  instrument  may 
be  varied  either  by  the  restoring  magnet  or  by 
sliding  the  magnetometer  box  nearer  to  or  further 
away  from  the  coil. 

The  voltmeter  galvanometer  depends  for  its 
operation  on  the  fact  that  when  a  galvanometer 
of  sufficiently  high  resistance  is  introduced  be- 


Fig.  280.     Galvanometer  Voltmeter. 

tween  any  two  points  in  a  circuit,  the  current  that 
passes  through  it,  and  hence  the  defiection  of  its 
needle,  is  directly  proportional  to  the  difference 
of  potential  between  such  two  points. 


Gal.] 


252 


[Gas. 


Galvanometers  for  the  commercial  measure- 
ments of  currents  assume  a  variety  of  forms. 
They  are  generally  so  constructed  as  to  read  off 
the  amperes,  volts,  ohms,  watts,  etc.,  directly. 
They  are  called  amperemeters  or  ammeters,  volt- 
meters, ohmmeters,  wattmeters,  etc.  For  their 
tiller  description  reference  should  be  had  to 
standard  works  on  electrical  measurement. 

Galranometric. — Of  or  pertaining  to  the 
galvanometer.  (See  Galvanometer?) 

Galvanometrical. — Of  or  pertaining  to  the 
galvanometer.  (See  Galvanometer.} 

Galvanometrically. —  In  a  galvanometric 
manner. 

Galvano-Plastics. — (See  Plastics,  Gal- 
•vano) 

Galvanoplasty. — The  art  of  galvano- 
plastics.  (See  Plastics,  Galvano) 

GalYano-Puncture. — (See  Puncture,  Gal- 
vano) 

Galvanoscope. — A  term  sometimes  im- 
properly employed  in  place  of  galvanometer. 

A  galvanoscope,  strictly  speaking,  is  an  instru- 
ment intended  rather  to  show  the  existence  of  an 
electric  current  than  to  measure  it  in  degrees. 
It  may,  however,  be  roughly  calibrated,  and  then 
it  differs  from  a  galvanometer  only  in  delicacy 
and  accuracy. 

Galvano-Therapeutics. — A  term  some- 
times used  for  electro-therapeutics. 

Electro  therapeutics  is  by  far  the  preferable 
term  and  is  almost  universally  employed  in  the 
United  States. 

Gap,  Air A  gap,  or  opening  in 

a  magnetic  circuit  containing  air  only.  (See 
Gap,  Air,  Magnetic?) 

The  air  gap  between  two  magnetic  poles  may 
be  regarded  as  the  space  in  which  an  armature 
acting  as  a  magneto  receptive  device  is  placed, 
which  by  the  action  upon  it  of  the  lines  of  mag- 
netic force  passing  through  the  gap  has  differ- 
ences of  potential  generated  in  its  coils  of  insulated 
wire. 

Gap,  Air,  Magnetic A  gap  filled 

with  air  which  exists  in  the  opening  at  any 
part  of  a  core  of  iron  or  other  medium  of  high 
permeability. 

The  space  between  the  pole  pieces  and  arma- 


ture core  is  called  the  air  gap  in  dynamos  or 
motors  even  though  partly  filled  with  copper  con- 
ductors. It  is  also  called  the  interference  space. 

The  gap  or  air  space  of  an  electro-magnet  de- 
creases the  strength  of  its  magnetization  be- 
cause— 

The  increased  reluctance  of  the  air  gap  causes 
a  decrease  in  the  number  of  lines  of  magnetic 
force  which  pass  through  the  magnetic  circuit. 

Gap,  Spark A  gap  forming  part  of 

a  circuit  between  two  opposing  conductors, 
separated  by  air,  or  other  similar  dielectric 
which  is  closed  by  the  formation  of  a  spark 
only  when  a  certain  difference  of  potential 
is  attained. 

Gap,  Wire-Gauge  — (See  Gauge, 

Wire,  Gap.) 

Gas-Battery.— (See  Battery,  Gas) 

Gas  Burner,  Argand,  Plain-Pendant, 

Electric  — (See  Burner,  Argand 

Electric,  Plain-Pendant) 

Gas  Burner,  Argand,  Ratchet-Pendant, 
Electric (See  Burner,  Argand  Elec- 
tric, Ratchet-Pendant) 

Gas  Burner,  Automatic  Electric — 

(See  Burner,  Automatic  Electric) 

Gas  Burner,  Plain-Pendant,  Electric 
--(See  Burner,  Plain-Pendant  Elec- 
tric) 

Gas  Burner,  Ratchet-Pendant,  Electric 
(See  Burner,  Ratchet-Pendant  Elec- 
tric) 

Gas-,  Carbonic  Acid A  gaseous  sub- 
stance formed  by  the  union  of  one  atom  of 
carbon  with  two  atoms  of  oxygen. 

Carbonic  acid  gas  is  formed  during  the  com- 
bustion of  carbon  by  a  sufficient  supply  of  air. 

Gas,  Dielectric  Density  of A  term 

sometimes  emploved  instead  of  dielectric 
strength  of  gas.  (See  Gas,  Dielectric 
Strength  of) 

Gas,  Dielectric  Strength  of The 

strain  a  gas  is  capable  of  bearing  without 
suffering  disruption,  or  without  permitting  a 
disruptive  discharge  to  nass  through  it. 

The  dielectric  strength  of  a  gas  depends — 

(I.)  On  the  nature  of  the  gas. 

(2.)  On  its  pressure. 


Gas.] 


253 


[Gau. 


It  has  been  calculated  roughly  that  it  requires 
40,000  volts  per  centimetre  to  pass  a  disruptive 
discharge  through  dry  air  at  ordinary  pressures. 

Gas-Jet,    Carcel    Standard  — (See 

Car  eel  Standard  Gas-  Jet.) 

Gas-Jet  Photometer.— (See  Photometer.) 

Gas-Lighting,  Electric The  electric 

ignition  of  a  gas-jet  from  a  distance. 

Gas-Lighting-,  Multiple  Electric 

A  system  of  electric  gas-lighting  in  which  a 
number  of  gas-jets  are  lighted  by  means  of 
a  discharge  of  high  electromotive  force, 
derived  from  a  Ruhmkorff  coil  or  a  static 
induction  machine. 

Such  devices  are  operated  by  means  of  minute 
electric  sparks  which  are 
caused  to    pass    through 
the  escaping  gas-jets. 

The  spark  for  this  pur- 
pose is  obtained  either  by 
means  of  the  extra  current 
from  a  spark  coil,  by  means 
of  an  induction  coil  or  by 
static  discharges.  (See 
Currents,  Extra.  Coil, 
Spark.  Coil,  Induction.) 

A  gas  tip  for  use  in  multiple  gas-lighting  ap- 
paratus is  shown  in  Fig.  281.  The  spark  is 
formed  immediately  over  the  slot  in  the  burner, 
and  therefore  ignites  the  escaping  gas. 

Gas,  Occlusion  of The  absorption 

or  shutting  up  of  a  gas  in  the  pores,  or  on  the 
surfaces  of  various  substances. 

Carbon  possesses  in  a  marked  degree  the  prop- 
erty of  occluding  or  absorbing  gases  in  its  pores. 
These  occluded  gases  must  be  driven  out  from  the 
carbon  conductor  employed  in  an  incandescent 
lamp,  since  otherwise  their  expulsion,  on  the  in- 
candesence  of  the  carbon,  consequent  on  the  light- 
ing of  the  lamp,  will  destroy  the  high  vacuum  of 
the  lamp  chamber  and  thus  lead  to  the  ultimate 
destruction  of  the  filament  (See  Lamp,  Electric, 
Incandescent. ) 

Gassing. — The  evolution  of  gas  from  the 
plates  of  a  storage  or  secondary  cell. 

Gastroscope. — An  electric  apparatus  for 
the  illumination  and  inspection  of  the  human 
stomach. 


Fig.  28  r.    Multifile  Gas- 
yet. 


The  light  is  obtained  by  means  of  a  platinum 
spiral  in  a  glass  tube  surrounded  by  a  layer  of 
water  to  prevent  undue  heating.  The  platinum 
spiral  is  placed  at  the  extremities  of  a  tube,  pro- 
vided with  prisms,  and  passed  into  the  stomach 
of  the  patient.  A  separate  tube  for  the  supply 
of  air  for  the  extension  of  the  stomach  is  also 
provided. 

Gastroscopy. — The  examination  of  the 
stomach  by  the  gastroscope.  (See  Gastro- 
scope.) 

Gange,  Battery.— A  form  of  portable  gal- 
vanometer, suitable  for  ordinary  testing  work. 
A  form  of  battery  gauge  is  shown  in  Fig.  282. 


Fig.  282.     Battery  Gauge. 

Gauge,  Electrometer A  device  em- 
ployed in  connection  with  some  of  Sir  Wil- 
liam Thomson's  electrometers  to  ascertain 
whether  the  needle,  connected  with  the  layer 
of  acid  that  acts  as  the  inner  coating  of  the 
Leyden  jar  used  in  connection  therewith,  is  at 
its  normal  potential. 


Gauge,  Wire,  American 


— A  name 


sometimes  applied  to  the  Brown  &  Sharpe 
Wire  Gauge.  (See  Gauges,  Wire,  Varieties 
of.) 

Gange,  Wire,  Birmingham A  term 

sometimes  applied  to  one  of  the  English  wire 
gauges. 

Gauge,  Wire,  Gap A  wire  gauge  in 

which  gaps  are  left  for  the  introduction  of  the 
wire  to  be  measured, 


Gau.] 


254 


[Gau. 


Gauge,  Wire,  Micrometer A  gauge 

employed  for  accurately  measuring  the  di- 
ameter of  a  wire  in  thousandths  of  an  inch, 
based  on  the  principle  of  the  vernier  or  mi- 
crometer. (See  Fig.  283.) 

The  wire  to  be  measured  is  placed  between  a 
fixed  support  B,  and  the  end  C,  of  a  long  mova- 
ble screw,  which  accurately  fits  a  threaded  tube  a. 
A  thimble  D,  provided  with  a  milled  head,  fits 
over  the  screw  C,  and  is  attached  to  the  upper 
part.  The  lower  circumference  of  D,  is  divided 
into  a  scale  of  twenty  equal  parts.  The  tube  A,is 
graduated  into  divisions  equal  to  the  pitch  of  the 
screw.  Every  fifth  of  these  divisions  is  marked 
as  a  larger  division. 

The  principle  of  the  operation  of  the  gauge  is 
as  follows:  Suppose  the  screw  has  fifty  threads  to 
the  inch,  the  pitch  of  the  screw,  or  the  distance 
between  two  contiguous  threads,  is  therefore  ^ 
or  .02  of  an  inch. 

One  complete  turn  of  the  screw  will,  therefore, 
advance  the  sleeve  D,  over  the  scale  a,  the  .02  of 
an  inch.  If  the  screw  is  only  moved  through 
one  of  the  twenty  parts  marked  on  the  end  of 
the  thimble  or  sleeve  parts,  or  the  ^  of  a  com- 


plete  turn,  the  end  C,  advances  towards  B,  the 

sV  of  ?V>  *'•  *•»  Tinnr  or  •°°I  mch- 

Suppose  now  a  wire  is  placed  between  B  and 
C,  and  the  screw  advanced  until  it  fairly  fills  the 


Fig.  283.     Vernier  Wire  Gauge. 
space  between  them,  and  the  reading  shows  two 
of  the  larger  divisions  on  the  scale  a,  three  of  the 
smaller  ones  and  three  on  the  end  of  the  sleeve 
D,  then 

Two  large  divisions  of  scale  a =     .2      inch 

Three  smaller  divisions  of  scale  a..  =     .06       " 
Three  divisions  on  circular  scale 

onD =     .003     " 

Diameter  of  wire .263 

Serious  inconvenience  has  arisen  in  practice 


NEW  LEGAL  STANDARD  WIRE  GAUGE  (ENGLISH). 
Tables  of  Sizes,  Weights,  Lengths  and  Breaking  Strains  of  Iron  Wire. 


Size  on 
Wire 

Gauge, 

Diameter. 

Sectional 
area  in 
sq.  inches. 

Weight  of 

Length  of 
Cwt. 

Breaking  Strains. 

Size  on 
Wire 
Gauge. 

Inch. 

Millimetres. 

ioo  yards. 

Mile. 

Annealed. 

Bright. 

500 
464 

432 
400 

37' 
348 
324 
300 
276 
252 
232 

212 
192 

55 

1  60 

144 

128 

116 
104 
092 
080 
072 
064 
056 
048 
040 
036 

12.7 

n.  8 
n. 

IO.2 

9-4 

8.8 

8.2 

7.6 

e:4 

5-9 
5-4 
4-9 
4-5 
4.1 
3-7 
3-3 

1.6 

2.3 

2. 

1.8 
1.6 
1.4 

1.2 
I. 

.9 

1963 
1691 
1466 
1257 
1087 
0951 
0824 
0707 
0598 
0499 
0423 

°353 
0290 
0243 

0201 
0163 
OI29 
010)6 
0085 
0066 
0050 
O04I 
0032 
OO2, 
00l8 
0013 

0010 

Lbs. 

'93  -4 
166.5 
144.4 
123.8 
107.1 
93-7 

69.9 
58.9 
49.1 
41.6 
34-8 
28.0 
24. 
19  8 
16. 
12.7 
10.4 

«'4 
6.5 

5- 
4- 
3-2 
2.4 
1.8 

1.2 
I. 

Lbs. 

34°4 
2930 
2541 
2179 
1885 
1649 
1429 
1225 
i°37 
864 
732 
612 
502 
422 
348 
282 
223 
'83 
148 
114 
88 

7° 
56 
42 
32 

21 

18 

Yards. 

58 
67 
78 

91 
105 

120 
138 
101 

190 

228 

269 

322 

393 
467 
566 
700 
882 
1077 

1333 
1723 
2240 
2800 
3soo 
4067 
6222 
9333 

11200 

Lbs. 
10470 
9017 
7814 
6702 
5796 
5072 
4397 
377° 

3'9° 
2660 

2254 
1883 

1544 
1298 
1072 
869 
687 
564 
454 
355 
268 
218 
172 
131 

97 
67 

55 

Lbs. 
15700 
13525 
11725 
10052 
8694 
7608 
6595 
5655 
4785 
399° 
338i 
2824 
2316 
1946 
1608 

1303 
1030 

845 
680 
532 
402 
326 
257 
197 
MS 

IOO 

82 

7/0 
6/0 
5/o 
4/0 
3/o 

2/0 

1/0 

I 

2 

3 
4 

I 

8 

9 
10 
ii 

12 
'3 

'4 
15 
16 
17 
18 
'9 

20 

6>o 

S/o 

**f  

3  

6  

I....... 

5 

I....... 

(Issued  by  the  Iron  and  Steel  Wire  Manufacturers'  Association.) 


tiau.] 


255 


[Gau. 


from  the  numerous  arbitrary  numbers  of  sizes  of 
wires  employed  by  different  manufacturers. 
These  differences  are  gradually  leading  to  the 
abandonment  of  arbitrary  sizes  for  wires  and  em- 
ploying in  place  thereof  the  diameters  directly  in 
inches  or  thousandths  of  an  inch. 

Gauge,  Wire,  Bound —A  device  for 

accurately  measuring  the  diameter  of  a  wire. 

The  round  wire  gauge  shown  in  Fig.  284  is 
very  generally  used  for  telegraph  lines.  Notches 


Fig.  284.    Round  Wire  Gauge. 

for  varying  widths,  cut  in  the  edges  of  a  circular 
plate  of  tempered  steel,  serve  to  approximately 
measure  the  diameter  of  a  wire,  the  sides  of  the 
wire  being  passed  through  the  slots.  Numbers, 
indicating  the  different  sizes  of  the  wire,  are 
affixed  to  each  of  the 
openings. 

Gauge,  Wire,  Self- 
Registering  A 

wire  gauge  arranged 
to  give  the  exact  di- 
ameter of  the  wire  to 
be  measured  directly 
without  calculation. 

A  form  of  self- register- 
ing wire  gauge  is  shown 
in  Fig.  285.  The  wire 
or  plate  is  inserted  in  the 
gap  between  a  fixed  and  Fig-.  283.  Wire  and 
a  movable  plate.  The  Ptate  Gauge. 

numbers  corresponding  to  the  diameter  of  the 
wire  or  plate  are  shown  on  one  side  of  the  gauge 
and  the  gauge  numbers  on  the  other  side. 


Gauge,  Wire,  Standard A  wire 

gauge  adopted  by  the  National  Telephone 
Exchange  Association  at  Providence,  R.  I., 
and  by  the  National  Electric  Light  As- 
sociation, at  Baltimore,  Md.,  in  February, 
1886. 

The  value  of  the  standard  as  compared  with 
the  other  gauges  will  be  seen  from  an  inspection 
of  the  table  in  this  column: 

Gauges,    Wire,  Varieties  of The 

following  table  gives  a  comparison  of  the 
principal  wire  gauges  in  use. 

COMPARISON   OF   THE    DIFFERENT   WIRE 
GAUGES. 


"3  bo 

!«- 

s  . 

rt  'f< 

*.**, 

*f 

41 

•o  y 

^S« 

h  tit 

.SO 

C   fl> 

Jse- 

t-  S  rt 
4)  °  *i3 

JJi 

•a-s 

Is 

Is 

jjjf 

1r? 

I** 

£<5 

^  3 

a  " 

•So 

«  o 

«£ 

m 

2  Is 
o,£s 

oooooo 

.46 

00000 

•V 

oooo 

.46 

454 

•393 

•4 

.400 

000 

.40964 

425 

.362 

•36 

.372 

00 

.3648 

38 

•  331 

•33 

.348 

o 

•32495 

34 

.307 

•305 

•324 

I 

.2893 

3 

•  283 

.285 

.300 

2 

•25763 

284 

.263 

.265 

.276 

3 

.  22942 

259 

.244 

.245 

.252 

4 

.20431 

238 

•  225 

•  225 

.232 

5 

-i8i94 

22 

.207 

.205 

.212 

6 

.  16202 

203 

.192 

.19 

.192 

7 

.14428 

18 

.177 

•'75 

.176 

8 

.12849 

165 

.162 

.16 

,160 

9 

•IT443 

148 

.148 

.145 

.144 

10 

.10189 

'34 

•'35 

.13 

.128 

n 

.090742 

12 

.12 

.1175 

.116 

12 

.080808 

109 

.105 

.105 

.104 

13 

.071961 

095 

.092 

.0925 

'4 

.064084 

083 

.oi 

•08 

.080 

.083 

IS 

-057068 

072 

.072 

.07 

.072 

.072 

16 

•05082 

06S 

.063 

.061 

.064 

-065 

17 

.045257 

OSB 

.052 

•0525 

.056 

.058 

18 

.040303 

049 

.047 

•  045 

.048 

•049 

'9 

•03S390 

042 

.041 

•039 

.040 

.04 

20 

.031961 

035 

.035 

.034 

.036 

•035 

21 

.028462 

032 

.032 

.032 

•0315 

22 

.025^47 

028 

.028 

•27 

.028 

.0295 

23 

.022571 

025 

.025 

.024 

.024 

.027 

24 

.0201 

022 

.023 

.0215 

.022 

.025 

2=; 

.0179 

02 

.02 

.019 

.020 

.023 

26 

.01594 

018 

.Ol8 

.018 

.018 

.0205 

27 

.014195 

016 

.017 

.017 

.0164 

.01875 

28 

.012641 

014 

.Ol6 

.016 

.0148 

.0165 

29 

.011257 

013 

.015 

•015 

.0136 

.0155 

3° 

.OIOO25 

012 

.014 

.014 

.OT24 

•CI375 

31 

.008928 

01 

.0135 

.013 

.OIl6 

.01225 

32 

.00795 

009 

•013 

.012 

.OI08 

.01125 

33 

.00708 

008 

.Oil 

.Oil 

.0100 

.01025 

34 

.006304 

007 

.OI 

.OI 

.0092 

.0095 

35 

.005614 

005 

.0095 

.OOg 

.0084 

.009 

36 

.005 

004 

.009 

.COO 

.0076 

•  0075 

37 

.004453 

.0085 

.00725 

.0068 

.0065 

38 

.003965 

.008 

.0065 

.006 

.00575 

39 

•003531 

.0075 

•00575 

.005^ 

.005 

40 

.003144 

.007 

.005 

.0048 

.0045 

1 

256 


[Gau. 


NUMBER,    DIAMETER,    WEIGHT,    LENGTH   AND   RESISTANCE    OF    PURE    COPPER 

WIRE. 

American  Gauge. 


No. 

Diameter. 
Inches. 

Weight,  sp.  gr.  =  8.889. 

Length. 

Resistance  of  Pure  Copper  at  70°  Fahrenheit. 

Grs.  per  !t. 

Lbs.  per  1,00-3 
feet. 

Ft.  per  Ib. 

Ohms  per  1,000  ft. 

Feet  per  ohm. 

Ohms  per  Ib. 

DOOO... 

.46000 

4475-33 

640.40 

1-56 

.051 

19605.69 

.0000798 

000.  .. 

.40964 

3549-07 

507.01 

1.97 

.064 

I5547-87 

.000127 

oo... 

.36480 

2814.62 

4^2.09 

2.49 

.o8t 

12330.36 

.000202 

o... 

.32486 

2*33.28 

319.04 

3-'3 

.102 

97a3-63 

.000320 

I... 

.  28930 

1770.13 

252.88 

3-95 

.129 

7754-66 

.00051 

2... 

•25763 

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36223.59 

Gauss. — The  unit  of  intensity  of  magnetic 
field. 

The  term  gauss  for  unit  of  intensity  of  mag- 
netic field  was  proposed  by  S.  P.  Thompson  as 
being  that  of  a  field  whose  intensity  is  equal  to 
lo9  C.  G.  S.  units,  that  is,  io8  lines  of  force  per 
square  centimetre. 

J.  A.  Fleming  proposes,  for  the  value  of  the 
gauss,  such  strength  of  field  as  would  develop  an 
electromotive  force  of  one  volt  in  a  wire  one 
million  centimetres  in  length,  moving  through 
such  a  field  with  unit  velocity. 

Fleming's  value  for  the  gauss  was  assumed  on 
account  of  the  small  value  of  the  gauss  proposed 


by  S.  P.  Thompson.  It  is  one  hundred  times 
greater  in  value  than  Thompson's  gauss. 

Sir  William  Thomson  proposes,  for  the  value  of 
the  gauss,  such  an  intensity  of  magnetic  field  as  is 
produced  by  a  current  of  one  weber  (ampere)  at 
the  distance  of  one  centimetre. 

Oanss,  Fleming's Such  a  strength 

of  magnetic  field  as  is  able  to  develop  an 
electromotive  force  of  one  volt  in  a  wire  one 
million  centimetres  in  length  moved  through 
the  field  with  unit  velocity.  (See  Gauss.) 

Gauss,  S.  P.  Thompson's  —  — Such  a 
strength  of  magnetic  field  that  its  intensity 
is  equal  to  ios  C.  G.  S.  units.  (See  Gauss.) 


Gaii.] 


257 


[Gen. 


Gauss,  Sir  William  Thomson's 

Such  an  intensity  of  magnetic  field  as  would  be 
produced  by  a  current  of  one  ampere  at  the 
distance  of  one  centimetre.  (See  Gauss.} 

Geissler  Mercurial  Pump. — (See  Pump, 
Air,  Geissler,  Mercurial.} 
Geissler  Tubes. — (See  Tubes,  Geissler.} 

General  Faradization. — (See  Faradiza- 
tion, General?) 

General  Galvanization. — (See  Galvaniza- 
tion, General.} 

Generation  of  Current  by  Dynamo-Elec- 
tric Machine. — (See  Current,  Generation  of, 
by  Dynamo-Electric  Machine?) 

Generator,  Dynamo-Electric An 

apparatus  in  which  electricity  is  produced  by 
the  mechanical  movement  of  conductors 
through  a  magnetic  field  so  as  to  cut  the 
lines  of  force. 

A  dynamo-electric  machine.  (See  Machine, 
Dynamo-Electric?) 

A  dynamo  electric  machine  operates  on  the 
general  principles  of  electro-dynamic  induction. 
Strictly  speaking,  however,  in  a  dynamo-electric 
generator  the  conductors  are  actually  moved 
through  the  lines  of  force.  In  this  respect,  there 
fore,  a  dynamo-electric  generator  differs  from  a 
transformer,  in  which  the  lines  of  force  are  moved 
through  the  conductor.  (See  Induction,  Electro- 
Dynamic.  Transformer.  Induction,  Mutual.} 

Generator,  Motor A  dynamo-elec- 
tric generator  in  which  the  power  required  to 
drive  the  dynamo  is  obtained  from  an  elec- 
tric current. 

Motor  generators  are  used  in  systems  of  elec- 
trical distribution  for  the  purpose  of  changing 
the  potential  of  the  current.  They  consi.-t  of 
dynamos,  the  armatures  of  which  are  furnished 
with  two  separate  windings,  of  fine  and  coarse 
wire  respectively.  One  of  these,  generally  the 
fine  wire,  receives  the  driving  or  motor  cur- 
rent, usually  of  high  potential,  and  the  other, 
the  coarse  wire,  furnishes  the  current  used,  usu- 
ally of  low  potential. 

The  advantage  of  having  the  windings,  which 
receive  the  driving  current,  of  fine  wire,  is  to 
enable  a  current  of  high  potential  to  be  dis- 
tributed over  the  line  from  distant  stations  to 


places  where  it  is  desired  to  use  the  energy  of  the 
current  at  a  much  lower  potential. 

Motor  generators  often  consist  simply  of  two 
distinct  machines  mechanically  connected,  one 
acting  as  a  motor  and  the  other  as  a  dynamo. 

Motor  generators  are  sometimes  called  dynamo- 
motors  or  dynamotors. 

Aldrich  draws  the  following  distinction  between 
a  dynamo-motor  and  a  dynamotor  : 

(I.)  A  dynamo-motor  is  an  energy  transformer 
with  the  dynamo  and  motor  in  the  same  electric 
circuit. 

(2.)  A  dynamotor  is  an  energy  transformer  with 
the  dynamo  and  motor  iu  the  same  magnetic  cir- 
cuit. 


Fig.  286.     Edison's  Pyro-Ma^netic  Generator. 

Generator,  Pyro-Magnetic  —      —  An  ap* 

paratus  for  producing  electricity  directly  from 
heat  derived  from  the.  burning  of  fuel. 


Gen.] 


258 


[Gil. 


The  operation  of  the  pyro-magnetic  generator 
is  dependent  upon  the  fa:t  that  any  variation  in 
the  number  of  lines  of  magnetic  force  that  pass 
through  a  conductor  will  develop  differences  of 
electric  potential  therein.  Such  variations  may 
be  effected  either  by  varying  the  position  of  the 
conductor  as  regards  the  magnetic  field,  or  by 
varying  the  magnetic  field  itself.  The  latter 
method  of  generating  differences  of  potential  is 
utilized  in  the  pyro-magnetic  generator,  and  is 
effected  in  it  by  varying  the  magnetization  of  rolls 
of  thin  iron  or  nickel  by  the  action  of  heat. 

A  form  of  pyro-magnetic  generator  devised  by 
Edison  is  shown  in  Figs.  286  and  287. 


Fig.  287.     Edison's  Pyro- Magnetic  Generator. 

This  apparatus  is  sometimes  called  a  pyro- 
magnetic  dynamo. 

Eight  electro  magnets  are  provided,  each  with 
an  armature  consisting  of  a  roll  of  corrugated 
iron.  Each  of  these  armatures  is  provided  with 
a  coil  of  insulated  wire  wound  on  it  and  pro- 
tected by  asbestos  paper.  The  armatures  pass 
through  two  iron  discs  as  shown.  The  armature 
coils  are  connected  in  series  in  a  closed-circuit, 
the  wires  from  the  coils  being  connected  with 
metallic  brushes  that  rest  on  a  commutator  sup- 
ported on  a  vertical  axis.  A  pair  of  metallic 
rings  is  provided  above  the  commutator  to  carry 
off  the  current  generated. 

The  vertical  axis  is  provided  below  with  a  semi- 
circular screen  called  a  guard  plate  which  rotates 
with  the  axis  and  cuts  off  or  screens  one-half  the 
iron  armatures  from  the  heated  air. 

When  the  axis  is  rotated,  the  difference  in  the 


magnetization  of  the  armatures,  when  hot  and 
cold,  develops  electromotive  forces  which  result 
in  the  production  of  an  electric  current. 

Generator,  Secondary A  term  fre- 
quently employed  for  a  converter  or  trans- 
former. 

The  word  transformer  is  now  almost  univer- 
sally employed.  (See  Transformer.) 

Generator,  Watt A  term  sometimes 

employed  for  stating  the  power  in  watts  that 
any  electric  source  is  capable  of  producing. 

Estimating  the  power  of  a  dynamo-electric 
machine  by  the  number  of  watts  it  is  capable  of 
producing  is  very  convenient  in  practice,  and  is 
now  very  generally  adopted.  A  dynamo  capable 
of  furnishing  a  difference  of  potential  of  1,000 
volts,  and  a  current  of  10  amperes,  would  be  said 
to  be  a  10,000  watt-generator. 

The  term  watt-generator,  though  applicable  to 
the  case  of  any  electric  source,  is  in  practice 
generally  limited  to  the  case  of  dynamo-electric 
machines  or  secondary  batteries. 

Generators,  Motor,  Distribution  of  Elec- 
tricity by (See  Electricity ;  Distribu- 
tion of,  by  Motor  Generators) 

Geographical  Distribution  of  Thunder 
Storms. — (See  Storms,  Thunder,  Geograph- 
ical Distribution  of.) 

Geographical  Equator. — (See  Equator, 
Geographical.) 

Geographical  Meridian.— (See  Meridian, 
Geographical.) 

German  Silver  Alloy. — (See  Alloy,  Ger- 
man Silver.) 

Gilding,  Electric The  electrolytic 

deposition  of  gold  on  any  object. 

Electro-plating  with  gold.  (See  Plating, 
Electro.) 

The  surfaces  of  the  object  to  be  gilded  are 
made  electrically  conducting,  if  not  already  so, 
and  are  then  connected  to  the  negative  terminal 
of  a  voltaic  cell  or  other  source,  and  immersed  in 
a  plating  bath  containing  a  solution  of  a  salt  of 
gold,  directly  opposite  a  plate  of  gold,  connected 
with  the  positive  terminal  of  the  source.  The 
objects  to  be  plated  thus  become  the  kathode,  and 
the  plate  of  gold  the  anode  of  the  plating  bath. 
On  the  passage  of  a  suitable  current,  the  gold  is 
dissolved  from  the  plate  at  the  anode  and  deposited 


Gil.] 


259 


[Gov. 


on  the  object  at  the  kathode.  (See  Bath,  Gold. 
Kathode.  Anode. ) 

Gilt  Plumbago.— (See  Plumbago,  Gilt.) 
Gimbals. — Concentric  rings  of  brass,  sus- 
pended on  pivots  in  a  compass  box,  and  on 
which  the  compass  card  is  supported  so  as  to 
enable  it  to  remain  horizontal  notwithstand- 
ing the  movements  of  the  ship.  (See  Com- 
pass, Azimuth.) 

Each  ring  is  suspended  on  two  pivots  placed 
directly  opposite  each  other,  that  is,  at  the  ends 
of  a  diameter,  which  in  one  ring  is  at  right  angles 
to  that  in  the  other. 

Girder  Armature. — (See  Armature,  Gir- 
der) 
Globe,   Vapor,   of  Incandescent   Lamp 

A  glass  globe  surrounding  the  cham- 
ber of  an  incandescent  electric  lamp,  for  the 
purpose  of  enabling  the  lamp  to  be  safely 
used  in  an  explosive  atmosphere,  or  to  permit 
the  lamp  to  be  exposed  in  places  where  water 
is  liable  to  fall  on  it. 

Such  a  vapor  globe  is  shown  in  Fig.  288.  In 
the  event  of  accidental  breakage  of  the  outside 
globe,  the  lamp  chamber 
proper  prevents  the  igni- 
tion of  the  explosive 
gases.  In  such  cases, 
however,  the  outer  pro- 
tecting chamber  should 
be  promptly  replaced. 

In  some  forms  of  vapor 
globes,  a  valve  is  pro- 
vided, opening  outwards, 
in  order  to  permit  the  ex- 
panded air  to  escape 
when  a  given  pressure  is 
reached,  and  yet,  at  the 
same  time,  to  prevent  the 
entrance  of  gas  or  vapor 
from  without. 

Glow    Discharge.— 

,0        T^  -     7  FlS  iS8      l/apor  Globe. 

(bee  Discharge,  Glow.) 
Glow  Lamp.— (See  Lamp ,  Electric  Glow) 
Gold  Bath.— (See  Bath,  Geld) 

Gold-Leaf  Electroscope.— (See  Electro- 
scope, Gold-Leaf) 

Gold-Plating.-(See  Plating,  Gold) 
Gong,  Electro-Mechanical A  gong 


struck  or  operated  by  mechanical  force  at 
times  which  are  dependent  on  the  passage  of 
an  electric  current. 

The  motive  power  is  the  mechanical  force  de- 
veloped by  a  bent  spring,  the  fall  of  a  weight, 
etc. ,  and,  by  suitable  mechanism,  is  permitted  to 
act  only  on  the  passage  of  an  electric  current. 


Gorernor,  Centrifugal 


— A  device  for 


maintaining  constant  the  speed  of  a  steam 
engine  or  other  prime  mover,  despite  sudden 
changes  in  the  load  or  work. 

In  a  ball  governor,  any  increase  in  speed 
causes  the  balls  to  fly  out  from  the  centre  of  rota- 
tion by  centrifugal  force.  This  motion  is  utilized 
to  control  a  valve  or  other  regulating  device.  If 
the  speed  of  the  engine  falls,  the  balls  move 
towards  the  centre,  shifting  the  valve  or  regulat- 
ing device  in  the  opposite  direction. 

Governor,  Current A  current  regu- 
lator. 

A  device  for  maintaining  constant  the  cur- 
rent strength  in  any  circuit. 

Current  governors  are  either  automatic  or  non- 
automatic.  (See  Regulation,  Automatic.) 

Governor,  Electric A  device  for 

electrically  controlling  the  speed  of  a  steam 
engine,  the  direction  of  current  in  a  plating 
bath,  the  speed  of  an  electric  motor,  the  re- 
sistance of  an  electric  circuit,  the  flow  of 
water  or  gas  into  or  from  a  containing  vessel, 
or  for  other  similar  purposes. 

The  particular  form  assumed  by  the  apparatus 
varies  with  the  character  of  the  work  it  is  intended 
to  accomplish.  In  some  cases  an  ordinary  ball 
or  centrifugal  governor  is  employed  to  open  or 
close  a  circuit;  or,  a  mass  of  mercury  in  a  rotat- 
ing vessel  is  caused,  at  a  certain  speed,  to  open  or 
close  a  circuit;  or,  the  resistance  of  a  bundle  of 
carbon  discs  is  caused  to  vary,  either  by  pressure 
produced  by  centrifugal  force,  or  by  the  move- 
ment of  an  armature. 

Governor,  Periodic A  name  ap- 
plied by  Ayrton  &  Perry  to  a  form  of  gover- 
nor for  an  electric  motor,  in  which  the  cur- 
rent is  automatically  cut  out  for  a  certain 
portion  of  each  revolution. 

Governor,  Spasmodic  — A  name 

given  by  Ayrton  &  Perry  to  a  form  of  gover- 
nor for  an  electric  motor,  in  which  the  cur- 


Gov.J 


260 


[Gra- 


rent  is  automatically  cut  off  in  proportion  as 
the  work  is  cut  off. 

The  spasmodic  governor  consists  essentially  of  a 
cone  dipping  into  the  surface  of  mercury  in  a  rotat- 
ing vessel.  As  the  speed  of  the  governor  increases 
on  a  lightening  of  the  load,  the  surface  of  the  mer- 
cury is  curved  by  the  increased  centrifugal  force, 
until  finally  the  mercury  leaves  the  contact  point 
and  thus  cuts  off  the  current. 

Governor,  Steam,  Electric A  de- 
vice used  in  connection  with  a  valve  to  so 
electrically  regulate  the  supply  of  steam  to  an 
engine,  that  the  engine  shall  be  driven  at 
such  a  speed  as  will  maintain  either  a  con- 
stant current  or  a  constant  potential. 

In  the  electric  governor,  the  steam  valve  is 
operated  by  an  electro-magnet,  whose  coils,  in 
the  case  of  a  constant  current  machine,  are  of 
thick  wire  placed  in  the  main  circuit,  and,  in 
that  of  a  constant  potential  machine,  are  of  thin 
wire  placed  in  a  shunt  around  the  mains. 

Gradnators. — Devices,  generally  electro- 
magnetic, employed  in  systems  of  simultane- 
ous telegraphic  and  telephonic  transmission 
over  the  same  wire,  so  inserted  in  the  line  cir- 
cuit as  to  obtain  the  makes  and  breaks  re- 
quired in  a  system  of  telegraphic  communi- 
cation so  gradually  that  they  fail  to  sensibly 
influence  the  diaphragm  of  a  telephone  placed 
in  the  same  circuit. 

Gramme. — A  unit  of  weight  equal  to 
I54323S  grains. 

The  gramme  is  equal  to  the  weight  of  one  cubic 
centimetre  of  pure  water  at  the  temperature  of  its 
maximum  density.  It  has  various  multiples  and 
decimal  divisions— of  the  former,  the  kilogramme 
or  one  thousand  grammes  is  the  most  frequently 
used ;  of  the  latter,  the  centigramme  or  the  one- 
hundredth  of  a  gramme,  and  the  milligramme  or 
the  one -thousandth  of  a  gramme.  (See  Weights 
and  Measures,  Metric  System  of.) 

Gramme  Atom. — (See  Atom,  Gramme) 

Gramme  Molecule. — (See  Molecule, 
Gramme!) 

Gramophone. — An  apparatus  for  record- 
ing and  reproducing  articulate  speech.  (See 
Phonograph.} 

Gramophone  Record. — (See  Record, 
Gramophone.) 


Graphite. — A  soft  variety  of  carbon  suit- 
able for  writing  on  paper  or  similar  surfaces. 

Graphite  is  the  material  that  is  employed  for 
the  so-called  black  lead  of  lead  pencils.  It  is 
sometimes  called  plumbago.  Strictly  speaking, 
the  term  graphite  is  only  applicable  to  the  variety 
of  plumbago  suitable  for  use  in  lead  pencils. 

Graphite  is  used  for  rendering  surfaces  to  be 
electro-plated,  electrically  conducting,  and  also  for 
the  brushes  of  dynamos  and  motors.  P'or  the 
latter  purpose  it  possesses  the  additional  advantage 
of  decreasing  the  friction  by  means  of  its  marked 
lubricating  properties. 

Graphophone,  Micro A  modifica- 
tion of  the  phonograph  in  which,  instead  of  a 
single  diaphragm,  a  number  of  separate  non- 
metallic  diaphragms  are  caused  to  act  on  a 
single  diaphragm  to  record  the  speech,  so  that 
the  separate  diaphragms  can  be  thrown  into 
strong  vibration  when  reproducing  the  speech. 

Graphophone,  Phonograph A  term 

sometimes  applied  to  the  graphophone.  (See 
Graphophone,  Micro.  Phonograph) 

Graphophone  Record. — (See  Record, 
Graphophone) 

Gray's  Harmonic  Telegraphic  Analyzer. 
— (See  Analyzer,  Gray's  Harmonic  Tele- 
graphic) 

Gray's  Harmonic  Telegraphy. — (See  Te- 
legraphy, Gray's  Harmonic  Multiple) 

Gravitation. — A  name  applied  to  the  force 
which  causes  masses  of  matter  to  tend  to 
move  towards  one  another. 

This  motion  is  assumed  to  be  that  of  attraction, 
that  is,  the  bodies  are  assumed  to  be  drawn  to- 
gather.  It  is  not  impossible,  however,  that  they 
may  be  pushed  together. 

Gravitation,  like  electricity,  is  well  known,  so 
far  as  its  effects  are  concerned ;  but,  as  to  the  true 
cause  of  either,  particularly  the  former,  we  are  in 
comparative  ignorance. 

The  general  facts  of  gravitation  may  be  suc- 
cinctly stated  by  the  following  law,  generally 
known  as  Newton's  law. 

Every  particle  of  matter  in  the  universe  is  at- 
tracted by  every  other  particle  of  matter,  and 
itself  attracts  every  other  particle  of  matter,  with 
a  force  which  is  directly  proportional  to  the  pro- 
duct of  the  masses  of  the  two  quantities  of  matter 


Ura.] 


261 


[Gua. 


and  inversely  proportional  to  the  square  of  the 
distance  between  them. 

Gravity  Ammeter. — (See  Ammeter,  Grav- 
ity.} 

Gravity,  Centre  of The  centre  of 

weight  of  a  body. 

Bodies  supported  at  their  centres  of  gravity  are 
in  equilibrium,  since  their  weight  is  then  evenly 
distributed  around  the  point  of  support. 

Gravity-Drop  Annunciator.— (See  An- 
nunciator, Gravity-Drop.) 

Gravity,  Voltaic  Cell (See  Cell, 

Voltaic,  Gravity.) 

Gravity  Voltmeter. — (See  Voltmeter, 
Gravity?) 

Great  Calorie. — (See  Calorie,  Great.) 

Grenet  Voltaic  Cell.— (See  Cell,  Voltaic, 
Grenet?) 

Grid. — A  lead  plate,  provided  with  perfor- 
ations, or  other  irregularities  of  surface,  and 
employed  in  storage  cells  for  the  support  of 
the  active  material. 

The  support  provided  for  the  active  material 
on  the  plate  of  a  secondary  or  storage  cell. 

The  grid  receives  its  name  from  its  resemblance 
to  a  gridiron.  The  active  material  is  generally 
maintained  on  the  grid  by  means  of  variously 
shaped  apertures  or  holes.  These  are  generally 
larger  near  the  centre,  so  as  to  prevent  the  falling 
out  of  the  material  after  it  has  been  hardened  by 
compression.  (See  Cell,  Secondary.  Cell,  Stor- 
age.) 

Various  forms  have  been  given  to  the  grid. 
The  object  of  these  forms,  in  general,  is  to  in- 
sure the  retention  of  the  active  material  by  the 
grid. 

The  grids  are  preferably  suspended  from  suit- 
able supports  fastened  to  the  top  of  the  battery 
jars,  instead  of  resting  on  the  bottom  of  the  bat- 
tery jars. 

Grip,  Cable A  grip  provided  for 

seizing  the  end  of  a  cable  when  it  is  to  be 
drawn  into  a  duct  or  conduit. 

Grove's  Voltaic  Cell.— (See  Cell,  Voltaic, 
Grove.) 

Grothuss'  Hypothesis. — (See  Hypothesis, 
Grothuss'.) 


Ground  Circuit.— (See  Circuit,  Ground.) 

Ground  Detector.— ( See  Detector, 
Ground.) 

Ground  or  Earth.— A  general  term  for 
the  earth  when  employed  as  a  conductor,  or 
as  a  large  reservoir  of  electricity. 

The  term  ground  is  also  applied  to  a  fault 
caused  by  an  accidental  and  undesired  connection 
between  an  electric  circuit,  line  or  apparatus  and 
the  ground.  (See  Fault.) 

'  Ground  Plate  of  Lightning  Protec- 
tor.— (See  Plate,  Ground,  of  Lightning 
Protector?) 

Ground-Return. — A  general  term  used 
to  indicate  the  use  of  the  ground  or  earth 
for  a  part  of  an  electric  circuit. 

The  earth  or  ground  which  forms  part  of 
the  return  path  of  an  electric  circuit. 

The  ground-return  is  generally  used  in  the 
Morse  system  of  telegraphy  as  practiced  in  the 
United  States. 

Ground-Wire. — The  wire  or  conductor 
leading  to  or  connecting  with  the  ground  or 
earth  in  a  grounded  circuit. 

This  is  sometimes  called  an  earth -grounded 
wire. 

A  circuit  is  grounded  when  it  is  completed  in 
part  by  the  ground  or  earth. 

Grounded  Circuit.— (See  Circuit, 
Grounded?) 

Growth  or  Expansion  of  Lines  of  Force. 

— (See  Force,  Lines  of.  Growth  or  Expan- 
sion of) 

Guard,  Fan — A  wire  netting  placed 

around  the  fan  of  an  electric  motor  for  the 
purpose  of  preventing  its  revolving  arms 
from  striking  external  objects. 

Guard,  Lightning — A  term  some- 
times used  for  lightning  rod.  (See  Rod, 
Lightning?) 

Guard,  Transformer,  Lightning 

A  transformer  lightning  arrester.  (See  Ar* 
rester,  Lightning,  Transformer.) 


Gua.] 


262 


[Hal. 


Guard,  Wire  Shade A  guard  of 

wire  netting  provided  for  the  protection  of  a 
shade. 

A  form  of  wire  shade  is  shown  in  Fig.  289. 


Fig.  289.     Wire  Shade  Guard. 

Gutta-Percha. — A  resinous  gum  obtained 
from  a  tropical  tree,  and  valuable  electrically 
for  its  high  insulating  powers. 

Gutta-percha  readily  softens  by  heat,  but  on 


cooling  becomes  hard  and  tough.  Un'ike  India- 
rubber,  it  possesses  bat  little  elasticity.  Its 
specific  inductive  capacity  is  4.2,  that  of  air  being 
I,  and  of  vulcanized  rubber,  2.94.  (See  Capacity \ 
Specific  Inductive ,) 

Gutta-percha  is  obtained  largely  from  the  East 
Indies,  from  a  tree  which  yields  a  brownish  gum. 
It  is  a  fibrous  and  tenacious  substance  with  but 
little  flexibility,  and  is  unaffected  by  acids.  Oils 
produce  less  effect  upon  it  than  on  India-rubber. 

Gutta-percha  is  one  of  the  best  insulating  mate- 
rials known  for  sub-aqueous  cables. 

Gymnotus  Electricus. — The  electric  eel. 
(See  &l,  Electric.} 

Gyrometer. — A  speed  indicator.  (See  In- 
dicator, Speed.} 


H. — A  contraction  for  the  horizontal  inten- 
sity of  the  earth's  magnetism. 

H. — A  contraction  proposed  for  one  unit 
of  self-induction. 

H. — A  contraction  used  in  mathematical 
writings  for  the  magnetizing  force  that  exists 
at  any  point,  or,  generally,  for  the  intensity  of 
the  magnetic  force. 

The  letter  H,  when  used  in  mathematical 
writings  or  formulae  for  the  intensity  of  the 
magnetic  force,  is  always  represented  in  bold  or 
heavy  faced  type,  thus  :  H . 

H-Armature    Core. — (See    Core,   Arma- 
ture, H.) 
Hail,  Assumed  Electric  Origin  of • 

A  hypothesis,  now  generally  rejected,  framed 
to  explain  the  origin  of  the  alternate  coatings 
of  ice  and  snow  in  a  hail  stone,  by  the  alter- 
nate electric  attractions  and  repulsions  of 
the  stones  between  neighboring,  oppositely 
charged,  snow  and  rain  clouds. 

It  is  now  generally  recognized  that  the  electric 
manifestations  attending  hail  storms  are  the 
effects  and  not  the  causes  of  the  hail.  (See  Para- 
greles.} 

Hair,  Electrolytic  Removal  of 

The  permanent  removal  of  hair  from  any  part 


of  the  body,  by  the  electrolytic  destruction  of 
the  hair  follicles. 

A  platinum  negative  electrode  is  inserted  in  the 
hair  follicle  arid  the  positive  electrode,  covered  with 
moist  sponge  or  cotton,  is  held  in  the  hand  of  the 
patient.  A  current  of  from  two  to  four  milli-am- 
peres  from  a  battery  of  from  eight  to  ten  Le- 
clanche  elements  is  then  passed  for  from  ten  to 
thirty  seconds.  A  few  bubbles  of  gas  appear, 
and  the  hairs  are  then  removed  from  the  follicles 
by  a  pair  of  forceps.  (See  Mini-Ampere.) 

When  the  work  is  properly  done  there  is  no 
destruction  of  the  skin  and  therefore  no  marks  or 


In  the  removal  of  hair  from  the  face,  it  is  pref- 
erable that  the  current  should  slowly  reach  its 
maximum  strength. 

Half-Shades    for   Incandescent    Lamps. 

— Shr/ies  for  incandescent  electric  lamps,  in 
which  one-half  of  the  lamp  chamber  proper 
is  covered  with  a  coating  of  silver,  or  other 
reflecting  surface  for  reflecting  the  light,  or  is 
ground  for  the  purpose  of  diffusing  the  light. 
The  half-shade  is  applicable  to  cases  where  it 
is  desired  to  throw  out  the  light,  not  in  all  direc- 
tions, but  on  one  side  only  of  any  plane.  Some- 
times the  dividing  plane  is  taken  parallel  to  the 
length  of  the  incandescing  filament  and  sometimes 
at  right  angles  to  it.  When  the  lamp  is  placed 


Hal.J 


263 


[Hea. 


within  a  surrounding  globe  the  reflecting  surface 
may  be  placed  on  this  globe  instead  of  on  the 
lamp  chamber. 

Hall  Effect.— (See  Effect,  Hall.} 
Hiilloyau  Lines. — (See  Lines,  Halleyan.) 
Halpine-Savage  Torpedo.— (See  Torpedo, 
H alpine-  Savage?) 

Handhole  of  Conduit. — A  box  or  opening 
communicating  with  an  underground  cable, 
provided  for  readily  tapping  the  cable,  and 
of  sufficient  size  to  permit  of  the  introduction 
of  the  hand. 

Hand-Lighting  Argand  Electric  Burner. 
— (See  Burner,  Argand  Electric,  Hand- 
Lighter^) 

Hand-Lighting  Electric  Burner. — (See 
Biirner,  Hand-Lighting  Electric?) 

H  a  n  d  •  R  e  gulation. — (  See  Regulation, 
Hand.) 

Hand-Regulator. — (See  Regulator, 
Hand.) 

Hanger-Board.— (See  Board,  Hanger.) 

Hanger,  Cable A  hanger  or  hook 

suitably  secured  to  the  cable  and  designed  to 
sustain  the  weight 
of  the  cable  by 
intermediately  sup- 
porting it  on  iron  or 
steel  wires  strung 
above  the  cable. 


29°'    Cable  Ha"Ser- 


A  cable  hanger  or 
cable  clip  is  shown  in 
Fig.  290.  The  mode 
of  supporting  the  cable 
C,  by  the  hanger  hook 
H,  will  be  readily  un- 
derstood from  an  in- 
spection of  the  figure. 

The  weight  per  foot  of  an  aerial  cable  is  gener- 
ally so  great  that  the  poles  or  supports  would  re- 
quire  to  be  very  near  together,  unless  the  device 
of  intermediate  supports,  by  means  of  cable  clips 
or  hangers,  were  adopted. 

Hanger,  Double-Curve  Trolley  --  A 

trolley  hanger  generally  employed  at  the  ends 
of  single  and  double  curves,  and  on  inter- 
mediate points  on  double  track  curves,  sup- 
ported by  lateral  strain  in  opposite  directions. 


Hanger,  Single-Curve  Trolley  —  —A 

trolley  hanger  supported  on  a  single  track 
curve,  except  at  the  ends  and  on  the  inside 
curve  of  a  double  track  line,  by  lateral  strain 
in  one  direction. 

Hanger,  Straight-Line  Trolley A 

trolley  hanger  on  a  straight  trolley  line  suit- 
ably supported  by  a  span  wire  so  as  to  have 
a  vertical  strain  only. 

Hanger,  Trolley .  —A  device  for  sup- 
porting and  properly  insulating  trolley  wires. 

Hard-Drawn  Copper  Wire. — (See  Wire, 
Copper,  Hard-Drawn.) 

Harmonic  Receiver. — (See  Receiver,  Har- 
monic.) 

Harmonic  Telegraphy.— (See  Telegraphy, 
Grays  Harmonic  Multiple.) 

Head  Bath,  Electric (See  Bath, 

Head,  Electric) 

Head  Breeze,  Electro-Therapeutic — 

(See  Breeze,  Head,  Electro-  Therapeutic.) 

Head  Light,  Locomotive,  Electric 

An  electric  light  placed  in  the  focus  of  a  par- 
abolic reflector  in  front  of  a  locomotive  engine. 

The  lamp  is  so  placed  that  its  voltaic  arc  is  a 
little  out  of  the  focus  of  the  reflector,  so  that,  by 
giving  a  slight  divergence  to  the  reflected  light, 
the  illumination  extends  a  short  distance  on  either 
side  of  the  tracks. 

Heat. — A  form  of  energy. 

The  phenomena  of  heat  are  due  to  a  vibratory 
motion  impressed  on  the  molecules  of  matter  by 
the  action  of  some  form  of  energy. 

Heat  in  a  body  is  due  to  the  vibrations  or 
oscillations  of  its  molecules.  Heat  is  transmitted 
through  space  by  means  of  a  wave  motion  in  the 
universal  ether.  This  wave  motion  is  the  same 
as  that  causing  light. 

A  hot  body  loses  its  heat  by  producing  a  wave 
motion  in  the  surrounding  ether.  This  process 
is  called  radiation.  ( See  Radiation. ) 

The  energy  given  off  by  a  heated  body  cooling 
is  called  radiant  energy 

Radiant  energy  is  transmitted  by  means  of 
ether  waves;  it  is  of  two  kinds,  viz. : 

(I.)  Obscure  Htat,  or  heat  which  does  not 
affect  the  eye,  although  it  can  impress  a  photo- 
graphic image  on  a  sufficiently  sensitive  photo- 
graphic plate. 


Hea.J 


264 


[Hea. 


(2.)  Luminous  I  feat,  or  heat  which  accompanies 
tight.  (See  Energy,  Radiant.] 

Heat  is  conducted,  or  transmitted  through 
bodies,  with  different  degrees  of  readiness. 

Some  bodies  are  good  conductors  of  heat, 
others  are  poor  conductors. 

Heat  is  transmitted  through  liquids  by  means 
of  currents  occasioned  by  differences  in  density 
caused  by  differences  of  temperature.  These 
currents  are  called  convection  currents. 

Heat  is  measured  as  to  its  relative  degree  of  in- 
tensity by  the  thermometer.  It  is  measured  as  to 
its  amount  or  quantity  by  the  calorimeter.  (See 
Thermometer,  Electric.  Calorimeter.) 

The  heat  unit  most  commonly  employed  is, 
perhaps,  the  calorie,  or  the  amount  of  heat  re- 
quired to  raise  one  gramme  of  water  one  degree 
centigrade. 

Another  heat  unit,  very  generally  employed  in 
the  United  States  and  England,  is  the  quantity  of 
heat  required  to  raise  one  pound  of  water  one  de- 
gree Fahrenheit.  This  is  called  the  English  heat 
unit.  (See  Calorie.  Units,  Heat.  Joule.  Volt- 
Coulomb.) 

Heat,  Absorption  and  Generation  of,  in 

Voltaic  Cell The  heat  effects  which 

attend  the  action  of  a  voltaic  cell. 

The  chemical  action  of  the  exciting  liquid  or 
electrolyte  on  the  positive  plate  or  element  of  a 
voltaic  cell,  like  all  cases  of  chemical  combination, 
is  attended  by  a  development  of  heat. 

When,  however,  the  circuit  of  the  cell  is  closed, 
the  energy  liberated  during  the  chemical  combi- 
nation appears  as  electricity,  which  develops  heat 
in  all  parts  of  the  circuit.  (See  Heat,  Electric. 
Cell,  Voltaic.) 


Hea*,  Atomic 


—  A  constant  product 


obtained  by  multiplying  the  specific  heat  of 
an  elementary  substance  by  its  atomiciveight. 
(See  Weight,  Atomic.} 

Dulong  and  Petit  have  discovered  the  remark- 
able fact  that  the  product  of  the  specific  heat  of 
all  elementary  substances  by  their  atomic  weights 
'3  nearly  the  same.  The  product  is  called  the 
atomic  heat,  and  is  about  equal  to  6.4. 

Dulong  and  Petit's  law  may  be  stated  as  fol- 
ows,  viz. :  All  elementary  atoms  require  the  same 
quantity  of  heat  to  heat  them  to  the  same  number 
of  degrees. 

The  atomic  heat  of  any  body  divided  by  its 
specific  heat  gives  its  atomic  weight. 


The  heat  imparted  to  any  body  performs  three 
kinds  of  work,  viz.: 

(i.)  That  expended  in  external  work,  such, 
for  example,  as  in  overcoming  the  atmospheric 
pressure. 

(2.)  That  expended  in  internal  work,  or  in 
overcoming  the  attractions  of  the  atoms  and  driv- 
ing them  apart. 

(3.)  That  expended  in  overcoming  the  temper- 
ature, or  the  true  specific  heat,  or  heat  expended 
in  increasing  the  molecular  vis-viva. 

The  expenditure  ot  energy  is  greatest  in  the 
third  head.  The  exact  value  of  the  three  factors 
is  as  yet  unknown,  and  in  the  opinion  of  Weber 
and  others  the  correctness  of  Dulong  and  Petit's 
law  cannot  be  regarded  as  being  satisfactorily 
established. 

Regnault  has  proved  that  Dulong  and  Petit's  law 
is  true  for  compound  bodies,  i.  e.,  in  all  compounds 
of  similar  composition  the  product  of  the  specific 
heat  by  the  total  chemical  equivalent  is  constant. 

The  following  table  from  Anthony  and  Bracket 
illustrates  the  law  of  Dulong  and  Petit: 


Elements. 

Specific  Heat 
ofEqual  Weight. 

Atomic 
Weight. 

Product  of 
Specific 
Heat  into 
Atomic 
Weight. 

f, 

Mercury  
Silver  

o  0314  (Solid) 

199.71 

6.128 

Gold  

Tin  

fi 

Lead  

5 

6     i§7 

"This  product— the  atomic  heat  of  elements, 
the  molecular  heat  of  compounds—  has  the  follow- 
ing physical  meaning:  Of  any  substance  whose 
atomic  or  molecular  weight  we  know,  we  may 
take  a  number  of  grammes  numerically  equal  to 
the  atomic  or  molecular  weight;  for  example, 
35-5  grammes  of  chlorine,  16  grammes  of  marsh 
gas;  we  may  call  such  quantity  the  gramme  atom 
or  the  gramme  molecule  of  the  substance.  The 
atomic  heat  or  the  molecular  heat  of  a  substance 
is  the  number  of  calories  of  heat  necessary  to 
raise  the  temperature  of  a  gramme  atom  or  a 
gramme  molecule  of  the  substance  through  i 
degree  C."—(Damett.) 

Heat,  Electric  -  —The  heat  developed 
by  the  passage  of  an  electric  current  through 
a  conductor. 


Hea.j 


265 


[Hea. 


Heat  is  developed  by  the  passage  of  a  current 
through  any  conductor,  no  matter  what  its  resist- 
ance may  be. 

If  the  conductor  is  of  considerable  length,  and 
of  good  conducting  power,  the  heat  developed  is 
not  very  sensible,  since  it  is  spread  over  a  consid- 
erable area,  and  is  rapidly  lost  by  radiation. 

H,  the  heat  generated  in  any  conductor  of  a 
resistance  R,  by  the  passage  through  it  of  an  elec 
trie  current  C,  is  equal  to 

H  =  C2  R,  in  watts. 

But  one  watt  =  .24  small  calorie  per  second. 
Therefore,  the  heat  which  is  generated, 

H  =  C2  R  X  -24  calories  per  second. 
For  the  case  of  a  uniform  wire  of  circular  cross- 
section  the  resistance  R,  in  ohms  is  directly  pro- 
portional to  the  length  1,  and  inversely  propor- 
tional to  the  area  of  cross-section  ;rr3,  or 


R  =:-..  that  is,  H  =  C., 


The  temperature  to  which  a  wire  of  a  given  re- 
sistance is  raised,  will  of  course  vary  with  the 
mass  of  the  wire,  its  radiating  surface,  and  its 
specific  heat  capacity.  If  the  same  number  of 
heat  calories  are  generated  in  a  small  weight  of  a 
conductor,  whose  radiating  surface  is  small,  the 
resulting  temperature  will  of  course  be  far  higher 
than  if  generated  in  a  larger  mass  provided  with 
a  much  greater  radiating  surface.  In  general, 
however,  its  temperature  increases  as  the  square 
of  the  current  strength  when  the  resistance  is  con- 
stant, and  increases  as  the  resistance  of  the  wire 
per  unit  of  length  is  greater. 

The  temperature  a  wire  acquires  by  the  passage 
of  a  current  through  it  varies  inversely  as  the 
third  power  of  the  radius.  If  two  wires  of  the 
same  material  have  the  same  lengths,  but  different 
radii,  the  temperature,  acquired  by  the  pas- 
sage of  an  electric  current,  will  depend  on  the 
heat  developed  per  second,  less  that  radiated  per 

second.     Since  the  former  varies  as  —  ,  and  the 

r2 

latter  as  r,  that  is,  as  1  X  2itr,  the  temperatures 

attained  vary  as  J-,  and  not  as  —,  as  frequently 
r8  r2 

stated.  —  (Larden.) 

The  current  required  to  raise  the  temperature 
of  a  bare  copper  wire  a  given  number  of  degrees 
above  the  temperature  of  the  air  is  given  in  the 
following  tab1*  • 


BARE  COPPER  WIRES. 


Current  required  to  increase  the  temperature  of  a  copper 
wire  t"  Centigrade  above  the  surrounding  air,  the 
copper  wire  being  bright  polished  or  blackened. 


Diameter  in 
Centimetres 

CURRENT  IN  AMPERES. 

and  Mils 

(thousandths  of 

an  inch). 

t  =  i°  C. 

t  =  9°  C. 

t  =  23°  C. 

Cm. 

Mils. 

Bright 

Black 

Bright 

Black 

Bright 

Black 

.1 

40 

I.O 

1.4 

3.0 

4.1 

4.8 

6.6 

.2 

80 

2.8 

3-9 

8-3 

11.5 

'3-5 

18.7 

•  3 
•4 

1  20 

1  60 

5-2 

8.0 

7.2 

II.  0 

15-3 
23.6 

31.2 

32.7 

24.9 
38-3 

34-4 

53  •« 

200 

n.  i 

15.4 

33-° 

45-7 

53-5 

74-1 

- 

240 

14-6 

20.3 

43-4 

60.0 

70.3 

97-4 

•I 

280 

'8.5 

25.6 

54-6 

75.6 

88.7 

123 

.8 

310 

22.6 

3I-3 

66.7 

92.4 

1  08 

'50 

•9 

350 

26.9 

37-3 

79.6 

no 

129 

179 

I.O 

39° 

3'-5 

43-6 

93-3 

129 

210 

2.O 

79° 

89.2 

123 

264 

365 

428 

593 

3-o 

I  ZOO 

164 

227 

485 

671 

787 

1090 

4.0 

1570 

252 

349 

746 

'035 

121  1 

1675 

s-° 

6.0 
7.0 

1970 

2360 
2760 

353 
463 
584 

488 
642 
808 

'043 
'37i 
1728 

1444 
1828 
2392 

1699 
2225 
2803 

2343 
3080 
3882 

8.0 

3150 

7J4 

988 

2110 

2922 

3422 

474' 

9.0 

3540 

851 

1178 

2519 

3486 

4088 

5659 

IO.O 

34-4 

394° 

997 

1380 

2950 

4084 

4788 

6626 

Diameter  in 
Cent  metres 

CURRENT  IN  AMPERES. 

and  Mils 

(thousandths  o 

an  inch). 

t  =  49°  C. 

t  =  81°  C. 

Cm. 

Mils. 

Bright. 

Black. 

Bright. 

Black. 

.1 

40 

^5 

8-9 

7-9 

II.  0 

.2 

80 

18.3 

=5-3 

22.4 

31.0 

•3 

170 

33-5 

46.4 

41.2 

57-o 

•4 

1  60 

51-7 

71-5 

63.4 

87.8 

•5 

aoo 

72.2 

99.9 

88.6 

123 

.6 

240 

94.9 

13* 

116 

161 

•7 

380 

119 

165 

M7 

203 

.8 

310 

146 

202 

179 

248 

•9 

350 

'74 

24I 

214 

296 

I.O 

390 

204 

283 

251 

347 

2.0 

790 

577 

799 

709 

981 

3-0 

1180 

1061 

1468 

'3°3 

1805 

4.0 

157° 

1633 

2260 

2006 

2776 

S-o 

1970 

2283 

3160 

2802 

3880 

6.0 

2360 

3000 

4'54 

3685 

5100 

7.0 

2760 

378i 

5233 

4642 

6426 

8.0 

3150 

4620 

6396 

5671 

7850 

9.0 

3540 

55" 

7630 

6769 

9370 

IO.O 

34.4 

3940 

6425 

8935 

7926 

10973 

7OOOO 

— (Forbes.) 

Heat,  Electric   Convection  of  —  — A 

term  employed  to  express  the  dissymmetrical 
distribution  of  temperature  that  occurs  when  a 


Hea.] 


26t> 


[Hea. 


current  of  electricity  is  sent  through  a 
metallic  wire,  the  middle  of  which  is  main- 
tained at  a  constant  temperature,  and  the 
ends  at  the  temperature  of  melting  ice. 

The  distribution  of  heat  during  the  pas- 
sage of  a  current  through  an  unequally 
heated  conductor. 

If  the  central  portions  of  a  metallic  bar  are 
heated  the  curve  of  heat  distribution  is  sym- 
metrical. On  sending  an  electric  current  through 
the  wire  it  is  heated  according  to  Joule's  law, 
and  the  curve  of  heat  distribution  is  still  sym- 
metrical. But  the  current  in  passing  from  the 
colder  to  the  hotter  parts  of  the  wire  produces 
an  additional  heating  effect  at  this  point,  and  in 
passing  from  the  warmer  to  the  colder  parts  o  f 
the  wire  produces  a  cooling  effect.  (See  Effect, 
Peltier.  Effect,  Thomson.)  The  curve  of  heat 
distribution  is  then  no  longer  symmetrical.  The 
term  Electrical  Convection  of  Heat,  has  been 
given  to  the  dissymmetrical  distribution  of  heat 
so  effected. 

Sir  William  Thomson,  who  studied  these 
effects,  found  that  the  electrical  convection  of 
heat  in  copper  takes  place  in  the  opposite 
direction  to  that  in  iron;  that  is  to  say,  the  elec- 
trical convection  of  heat  is  negative  in  iron,  (*'.  <?., 
the  direction  is  opposite  to  that  of  the  current), 
and  positive  in  copper. 

Heat,  Irreversible Heat  pro- 
duced in  a  homogeneous  conductor  by  the 
passage  of  electricity  through  it. 

This  heat,  according  to  Joule's  law,  is  propor- 
tional to  the  square  of  the  current,  and  is  produced 
no  matter  in  what  direction  the  current  is  pass- 
ing. In  this  respect  it  is  unlike  the  heat  pro- 
duced by  the  passage  of  electricity  through  a 
heterogeneous  conductor,  in  which  case  heat  is 
developed  or  liberated  only  by  the  passage  of  the 
current  in  a  given  direction  :  on  the  passage  of  the 
current  in  the  opposite  direction,  heat  being 
absorbed  and  the  temperature  lowered.  (See 
Heat,  Reversible.} 

Heat  Lightning. — (See  Lightning,  Heat.) 

Heat,  Luminons A  variety  of  radi- 
ant energy  which  affects  the  eye,  as  light. 

Radiant  heat  and  light  are,  in  reality,  different 
effects  produced  by  one  and  the  same  cause,  viz., 
by  vibrations  or  waves  in  the  universal  ether. 
In  general  the  waves  producing  heat  are  of 


greater  length  and  smaller  frequency  than  are 
those  producing  light. 

Heat,  Mechanical  Equivalent  of 

The  amount  of  mechanical  energy,  converted 
into  heat,  that  would  be  required  to  raise  the 
temperature  of  i  pound  of  water  i  degree 
Fahr. 

The  mechanical  equivalence  between  the 
amount  of  energy  expended  and  the  amount 
of  heat  produced,  as  measured  in  heat  units. 

Joule's  experiments,  the  results  of  which  are 
generally  accepted,  gave  772  foot-pounds  as  the 
energy  equivalent  to  that  expended  in  raising  the 
temperature  of  i  pound  of  water  i  degree  Fahr. 

Heat,  Molecular The  number  of 

calories  of  heat  required  to  raise  the  tempera- 
ture of  one  gramme-molecule  of  any  sub- 
stance i  degree  C.  (See  Molecule,  Gramme. 
Heat,  Atomic.) 

Heat,  Obscure A  variety  of  radiant 

energy  which  does  not  effect  the  eye. 

Radiant  heat  is  sometimes  divided  into  lumi- 
nous heat  and  obscure  heat.  (See  Heat,  Lumi- 
nous.) 

Heat,  Red The  temperature  at 

which  a  body,  whose  temperature  is  gradually 
increasing,  begins  to  glow  or  to  emit  red  rays 
of  light. 

When  a  refractory  solid  body  is  gradually 
heated  to  incandescence,  the  red  waves  of  light 
are  first  emitted,  then  the  orange,  and  successively 
afterwards  the  yellow,  green,  blue,  indigo  and 
violet,  when  the  body  emits  white  light  or  is 
white  hot. 

Heat,  Reversible The  heat  pro- 
duced in  a  heterogeneous  conductor  by  the 
passage  through  it  of  an  electric  current  in  a 
certain  direction. 

Reversible  heat  is  produced  at  the  junction  of 
two  metals,  where  a  difference  of  potential  exists 
between  them,  or  where  their  heterogeneity  is 
greatest.  It  is  called  reversible  because,  it  de- 
pends upon  the  direction  in  which  the  :urrent 
is  passing.  If  the  current  be  passed  in  a  certain 
direction  across  the  junction,  heat  is  liberated; 
while,  if  it  be  passed  in  the  opposite  direction, 
heat  is  absorbed,  or  cold  results. 

Reversible  heat  effects  are  seen  in  the  Peltier 
effect.  (See  Effect,  Peltier.) 


Hca.J 


267 


[Hel. 


Heat,  Specific — The  capacity  of  a 

substance  for  heat  as  compared  with  the 
capacity  of  an  equal  quantity  of  some  other 
substance  taken  as  unity. 

Water  is  generally  taken  as  the  standard  for 
comparison,  because  its  capacity  f  >r  heat  is  greater 
than  that  of  any  other  common  substance. 

Different  quantities  of  heat  are  required  to 
raise  the  temperature  of  a  given  weight  of  dif- 
ferent substances  through  i  degree.  The  spe- 
cific heats  of  substances  are  generally  compared 
with  water  or  with  hydrogen,  the  capacity  of 
these  substances  for  heat  being  very  great. 

According  to  Dulong  and  Pettit,  the  specific 
heat  of  all  elementary  atoms  is  the  same.  For 
example,  the  heat  energy  of  an  atom  of  hydrogen 
is  equal  to  that  of  an  atom  of  oxygen,  but  since 
a  given  mass  of  hydrogen,  under  similar  condi- 
tions of  temperature  and  pressure,  contains  sixteen 
times  as  many  atoms  as  an  equal  mass  of  oxygen, 
therefore,  when  compared  weight  for  weight, 
hydrogen  has  a  specific  heat  sixteen  times  greater 
than  that  of  oxygen. 

Or,  in  general,  co  nparing  equal  weights,  the 
specific  heat  of  an  elementary  substance  is  in- 
versely proportional  t  >  its  atomic  weight.  (See 
Heat,  Atomic.} 


Heat,  Specific,  of  Electricity 

Electricity,  Specific  Heat  of.) 


—(See 


Heat  Unit. — The  quantity  of  heat  required 
to  raise  a  given  weight  of  water  through 
a  single  degree. 

There  are  a  number  of  different  heat  units. 
The  most  important  are: 

(I.)  The  British  Heat  Unit,  or  Thermal  Unit,  or 
the  amount  of  heat  required  to  raise  I  pound 
of  water  I  degree  Fahr.  This  unit  represents  an 
amount  of  work  equal  to  772  foot  pounds. 

(2.)  The  Greater  Calorie,  or  the  amount  of  heat 
required  to  raise  the  temperature  of  i.oco 
grammes  of  water  I  degree  C.  (See  Calorie.) 

(3.)  The  Smaller  Calorie,  or  the  amount  of  heat 
required  to  raise  the  temperature  of  one  gramme 
of  water  I  degree  C. 

(4.)  The  Joule,  or  the  quantity  of  heat  developed 
in  one  second  by  the  passage  of  a  current  of  one 
ampere  through  a  resistance  of  one  ohm. 

I  joule  equals  .0002407  large  calories. 

I  joule  equals. 2407  small  calories. 

I  foot-pound  equals  1.356  joules. 


I  pound- Centigrade  equals  1884.66  joules. 

I     "  '•       1389.6  foot  pounds. 

I      "       Fahrenheit  1047.03  joules. 

Heat  Unit,  English  -  —(See  Units, 
Heat.) 

Heat  Unit  or  Calorie. —(See  Calorie.) 
Heat  Unit  or  Joule. — (See  Joule) 

Heat,  White  -  — The  temperature  at 
which  light  of  all  wave  lengths  from  the  red 
to  the  violet  is  emitted  from  a  heated  body, 
and  the  body,  therefore,  glows  with  a  white 
light. 

A  solid  substance  heated  to  white  incandescence 
emits  a  continuous  spectrum,  i.  e.,  a  spectrum  in 
which  all  the  wave  lengths  of  light  from  the  red 
to  the  violet  are  present. 

Heater,  Electric  —  — A  device  for  the 
conversion  of  electricity  into  heat  for  purposes 
of  artificial  heating. 

Electric  heaters  consist  essentially  of  coils  or 
circuits  of  some  refractory  metal  through  which 
the  current  is  passed.  These  coils  or  circuits  are 
surrounded  by  air  or  finely  divided  solids,  and  are 
placed  inside  metallic  boxes  or  radiators,  which 
throw  off  or  radiate  the  heat  produced. 

When  employed  for  the  heating  of  liquids  the 
coils  are  placed  directly  in  the  liquid  to  be 
heated,  or  are  surrounded  by  radiating  boxes 
placed  in  the  liquid. 

Heating  Effects  of  Currents. — (See  Cur- 
rents, Heating  Effects  of.) 

Hedgehog:  Transformer. —  (See  Transr 
former,  Hedgehog) 

Hecto-Ampdre One  hundred  am- 
peres. 

Heliograph.—  An  instrument  for  tele- 
graphic communication  that  operates  by  em- 
ploying flashes  of  light  to  represent  the  dots 
and  dashes  of  the  Morse  alphabet,  or  the 
movements  of  the  needles  of  a  needle  tele- 
graph to  the  right  or  the  left.  (See  Alphabet, 
Telegraphic) 

The  flishes  of  light  are  thrown  from  the  sur- 
face of  a  plane  mirror.  Motions  to  the  right  or 
left  may  be  employed  in  order  to  distinguish 
between  the  dots  and  dashes,  or  the  same  may  be 
effected  by  the  re  ativ:  durations  of  t'le  flas.'ic-.  of 


Ke!.] 


2G8 


[Hoi. 


light,   or  by   the  intervals    between    successive 
flashes. 

Telegraphic  communication  has  been  carried 
on  between  steamers  during  foggy  weather  by 
means  of  their  fog  horns;  or  between  locomotives 
by  their  steam  whistles. 

Helix,  Dextrorsal A  name  some- 
times applied  to  a  dextrorsal  solenoid.  (See 
Solenoid,  Dextrorsal?) 

The  magnetic  polarity  of  a  helix  or  solenoid 
depends  not  only  on  the  direction  in  which  the 
current  is  passed,  but  also  on  the  direction  in 
which  the  wire  is  coiled  or  wound .  (See  Magnet, 
Electro.} 

Helix,  Sinistrorsal A  name  some- 
times applied  to  a  sinistrorsal  solenoid.  (See 
Solenoid,  Sinistrorsal?) 

Hemihedral  Crystal.— (See  Crystal,  Hem- 
ihedral?) 

Henry,  A  —  —The  practical  unit  of  self- 
induction. 

It  has  been  generally  agreed  in  the  United 
States  to  ca^ll  the  practical  unit  of  self-induction 
a  henry,  in  place  of  a  secohm  or  quadrant. 
The  name  henry  should  be  adopted,  not  only  by 
American  electricians,  but  also  by  those  of  other 
countries,  since  the  terms  secohm  or  quadrant 
are  contrary  to  the  generally  adopted  usage  of 
employing  for  such  the  names  of  distinguished 
electricians,  who  have  passed  from  their  labors. 

The  fact  that  of  all  discoverers  in  the  field  of  self- 
induction,  none  possesses  so  great  a  claim  as  that  of 
Prof.  Henry,  must  be  generally  acknowledged. 
As  early  as  1832  he  published  in  Silliman's  Jour- 
nal a  paper  in  which  he  described  experiments, 
showing  clearly  that  the  spark  obtained  by  break- 
ing the  current  of  a  battery,  in  which  along  wire 
was  interposed,  was  greater  than  when  a  short 
wire  was  employed,  and  that  this  increased  length 
of  spark  was  further  increased  by  coiling  the  wire, 
and  that  the  phenomena  were  ascribed  to  the  ac- 
tion of  the  current  on  itself. 

A  committee  of  the  American  Institute  of 
Electrical  Engineers,  after  careful  consideration, 
recommended  to  the  Institute  that  the  value  of 
the  practical  unit  of  inductance  should  be  equal  to 
io9  C.  G.  S.  units  of  inductance,  usually  ex- 
pressed by  a  length  equal  to  one  earth  quadrant 
or  1,000,000,000  centimetres. 

The  value  of  the  practical  unit  of  inductance, 
or  the  "henry,"  may  in  some  cases  be  too  high  for 


convenience;  in  such  cases  it  may  be  expressed 
by  some  fractional  dimension,  such,  for  example, 
as  milli-henry. 

Hercules  Stone.— (See  Stone,  Hercules?) 
Hermetical    Seal. — (See   Seal,  Hermeti- 
cal.) 

Hertz's  Theory  of  Electricity.— (See  Elec- 
tricity, Hertz's  Theory  of.) 

Heterostatic. — A  term  applied  by  Sir 
William  Thomson  to  distinguish  a  form  of 
electrometer  in  which  the  electrification  is 
measured  by  determining  the  mutual  influ- 
ence of  the  attraction  exerted  by  the  charge 
to  be  measured  and  the  attraction  of  an  oppo- 
site charge  imparted  to  the  instrument  by  a 
source  independent  of  the  charge  to  be  meas- 
ured. 

The  term  heterostatic  distinguishes  this  form  of 
electrometer  from  an  idiostatic  instrument,  or  one 
in  which  the  measurement  is  effected  by  deter- 
mining the  repulsion  between  the  charge  to  be 
measured  and  the  repulsion  of  a  charge  of  the 
same  name,  *'.  e.,  positive  or  negative,  imparted 
to  the  instrument  from  an  independent  source. 
(See  Electrometer.') 

Hick's  Automatic    Button    Repeater. — 

(See  Repeaters,  Telegraphic?) 

High-Bars. — A  term  applied  to  those  com- 
mutator segments,  or  parts  of  commutator 
segments,  which,  through  less  wear,  faulty 
construction  or  looseness,  are  higher  than  ad- 
joining portions.  (See  Commutator?) 

High-Frequency  Currents,  Electric  Light- 
ing by (See  Lighting,  Electric,  by 

High-Frequency  Currents?) 

High  Resistance  Magnet— (See  Magnet, 
High  Resistance?) 

High  Speed  Electric  Motor. — (See  Mo- 
tor, Electric,  High  Speed?) 

High  Tension  Electric  Fuse. — (See  Fuse, 
Electric  High  Tension?) 

Hissing  of  Arc. — (See  Arc,  Hissing  of?) 

Holder  for  Safety  Fuse. — A  box  or  other 
receptacle  of  refractory  material  for  holding 
a  safety  fuse,  and  catching  the  molten  metal 
when  fused. 

The  holder  or  fuse  box  is  provided  to  prevent  the 


Hoi.] 


269 


molten  metal  of  the  fuse  from  setting  fire  to  any 
combustible  material  on  which  it  might  other- 
wise fall. 

Holders,  Carbon,  for  Arc  Lamps  — 

A  clutch  or  clamp  attached  to  the  end  of  the 
lamp  rod  or  other  support,  and  provided  to 
hold  the  carbon  pencils  used  on  arc  lamps. 
(See  Lamp,  Arc,  Electric?) 

Holders  for  Brushes  of  Dynamo-Electric 
Machine. — A  device  for  holding  the  collect- 
ing brushes  of  a  dynamo-electric  machine. — 
(See  Machine,  Dynamo-Electric?) 

Hole,  Armature A  term  sometimes 

applied  for  armature  bore  or  chamber.  (See 
Bore,  Armature?} 

Hole,  Armature  Bore,  Elliptical 

An  armature  bore  or  chamber  ellipsoidal  in 
shape. 

Holohedral  Crystal.— (See  Crystal,  Holo- 
hedral?) 

Holtz  Machine. — (See  Machine,  Holtz?) 

Home  Station. — (See  Station,  Home?) 

Homogeneous  Current  Distribution. — 
(See  Current,  Homogeneous  Distribution  of.} 

Hood  for  Electric  Lamp. — A  hood  pro- 
vided for  the  double  purpose  of  protecting  the 


Fig.  2Qi.     Arc  Lamp  Hood. 

body  of  an  electric  lamp  from  rain  or  sun, 
and  for' throwing  its  light  in  a  general  down- 
ward direction. 

Hoods  for  arc  lamps  are  generally  conical  in 
shape. 


A  form  of  hood  for  an  exposed  arc  lamp  is 
shown  in  Fig.  291. 

Horizontal  Component  of  Earth's  Mag- 
netism.—  (See  Component,  Horizontal,  of 
Earth's  Magnetism.) 

Horns,  Following,  of  Pole  Pieces  of 
a  Dynamo  -  Electric  Machine The 

edges  or  terminals  of  the  pole  pieces  of  a  dy- 
namo-electric machine  towards  which  the 
armature  is  carried  during  its  rotation. 


Fig    2Q2.     Horns   of  Dynamo, 

According  to  S.  P.  Thompson,  the  following 
horns,  b,  d,  Fig.  292,  are  those  towards  which 
the  armature  is  carried  ;  the  leading  horns,  a,  c, 
those  from  which  it  is  carried. 

As  the  change  in  the  magnetic  intensity  is  more 
sudden  when  the  armature  is  moved  from  the 
pole  pieces,  and  least  when  moved  towards  them, 
it  is  clear  that  the  leading  horns  in  a  dynamo  • 
electric  machine,  and  the  following  horns  in  an 
electric  motor,  become  heated  during  rotation  by 
the  production  of  Foucault  currents.  (See  Cur- 
rents, Foncault.  Machine,  Dynamo  Electric.) 

Horns,  Leading,  of  Pole  Pieces  of  a  Dy- 
namo-Electric Machine The  edges 

or  terminals  of  the  pole  pieces  of  a  dynamo- 
electrical  machine  from  which  the  armature 
is  carried  during  its  rotation. 

Thus,  in  Fig.  292,  a  and  c,  are  the  leading  horns 
of  the  pole  pieces. 

Horns  of  Pole  Pieces  of  Dynamo-Electric 
Machine. — The  edges  of  the  pole  pieces  of  a 
dynamo-electric  machine  towards  or  from 
which  the  armature  is  carried  during  its  rota- 
tion. 

These  are  called  the  following  and  the  leading 
horns. 


Horse-Power. — A   commercial     unit 
power  or  rate  of  doing  work. 


for 


Hor.] 


270 


[Hoa 


A  rate  of  doing  work  equal  to  33,000  pounds 
raised  i  foot  per  minute,  or  550  pounds  raised 
I  foot  per  second. 

A  rate  of  doing  work  equal  to  4,562.33 
kilogrammes  raised  I  metre  per  minute. 

A  careful  distinction  must  be  drawn  between 
work  and  power.     The  same  amount  of  work 
is  done  in  raising    I    pound    through   10  feet 
whether  it  be  done  in  one  minute  or  in  one  hour. 
The  power  expended  or  the  rate  of  doing  work 
is,  however,  quite  different,  being  in  the  former 
case  sixty  times  greater  than  in  the  latter. 
I  horse-power  =  550  foot-pounds  per  second. 
"  =  33,000  foot-pounds  per  min- 

ute. 
"  =  4,562.33   kilogramme-metres 

per  minute. 

"  =  745,941  watts. 

"  =  1.01385  metric  horse-power. 

Horse-Power,  Electric (See  Power, 

Horse,  Electric?) 

Horse-Power  Hour. — (See  Hour,  Horse- 
Power). 

Horse-Power,  Metric A  unit  of 

power  in  which  rate  of  doing  work  is  equal 
to  75  kilogramme-metres.  (See  Horse- 
Power.) 

Horseshoe  Electro-Magnet. — (See  Mag- 
net, Electro,  Horseshoed) 

Horseshoe  Magnet. — (See  Magnet,  Horse- 
shoe?) 

Hot,   Red Sufficiently   heated  to 

emit  red  light  only.     (See  Heat,  Red.) 

Hot  St.  Elmo's  Fire.— (See  Fire,  Hot,  St. 
Elmo's.) 

Hot,  White — Sufficiently  heated  to 

emit  all  the  colored  lights  of  the  spectrum. 
(SeeJfeat,  White.} 

Hotel  Annunciator. — (See  Annunciator, 
Hotel) 

Hour,  Ampdre A  unit  of  electrical 

quantity  equal  to  one  ampere  flowing  for  one 
hour. 

The  ampere-hour  is  in  reality  a  unit  of  quanti- 
ty like  the  coulomb.  It  is  used  in  the  service  of 
electric  currents,  and  is  equal  to  the  product  of 
the  current  delivered  by  the  time  in  hours.  The 
ampdre  hour  is  not  a  measure  of  energy,  but  when 


combined  with  the  volt,  and  expressed  in  watt 
hours,  it  is  a  measure  of  energy. 

The  capacity  of  any  service  for  maintaining  a 
flow  of  current  is  measured  in  ampere-hours. 
Thus,  if  any  service,  such  as  a  primary  or  sec- 
ondary battery,  has  a  capacity  of  80  ampere- 
hours,  it  will  supply  8  amperes  for  ten  hours,  01 
it  may  give  10  amperes  for  eight  hours. 

The  storing  capacity  of  accumulators  is  gener 
ally  given  in  ampere-hours.  The  same  is  true  ol 
primary  batteries. 

One  coulomb  equals  .0002778  ampSre-hours. 

One  ampere-hour  equals  3,600  coulombs. 

Hour,  Horse-Power A  unit  of  work 

An  amount  of  work  equal  to  one  horse- 
power for  an  hour. 

One  horse  power  is  equal  to  1,980,000  foot- 
pounds, or  745.941  watt  hours. 

Hour,  Kilo- Watt A  unit  of  electri- 
cal power  equal  to  a  kilo-watt  maintained  for 
one  hour. 

Hour,  Lamp Such  a  service  of  elec- 
tric current  as  will  maintain  one  electric  lamp 
during  one  hour. 

The  number  of  lamp-hours  is  obtained  by  mul- 
tiplying the  number  of  lamps  by  the  average 
number  of  hours  during  which  the  lamps  are 
burning. 

The  use  of  lamp-hours  is  for  the  purpose  of 
estimating  the  current  supplied  to  a  consumer  by 
counting  the  number  of  hours  each  lamp  is  in 
service. 

To  convert  lamp-hours  to  watt-hours,  multiply 
the  number  of  lamp-hours  by  the  number  oi 
watts  per  lamp.  The  watt  hours,  divided  by  746, 
will  then  give  the  electrical  horse-power  hours. 
(See  Hour,  Watt.) 

Hour,  Watt A  unit  of  electrical 

work. 

An  expenditure  of  an  electrical  work  of 
one  watt  for  one  hour. 

Lamp-hours  are  converted  to  watt-hours  by 
multiplying  the  number  of  lamp-hours  by  the 
number  of  watts  per  lamp.  (See  Hour,  Lamp.) 

House  Annunciator. — (See  Annunciator, 
House.} 

House  Main. — (See  Main,  House.} 

House-Service  Conductor.— (See  Conduc- 
tor, House-Service} 


Hon.] 


271 


[Hyp. 


House-Top  Fixtures,  Telegraphic 

(See  Fixtures,  Telegraphic  House-  Top.} 
House  Wire. — (See  Wire,  House?) 
Hughes'  Electro-Magnet.— (See  Magnet, 
Electro,  Hughes'.) 

Human  Body,  Electric  Resistance  of 

— (See  Body,  Human,  Resistance  of.) 

Hydro-Electric  Bath.— (See  Bath,  Hydro- 
Electric?) 

Hydro-Electric    Machine,    Armstrong's 

(See  Machine,  Armstrong's  Hydro- 
Electric?) 

Hydrogen,  Electrolytic Hydrogen 

produced  by  electrolytic  decomposition. 

It  is  the  electrolytic  hydrogen  liberated  in  a 
voltaic  cell  at  the  surface  of  the  negative  plate, 
which  causes  polarization  and  consequent  de- 
crease in  the  resulting  current  strength,  by  rea- 
son both  of  the  counter-electromotive  force  it 
produces  and  the  increased  resistance  it  produces 
in  the  cell. 

Electrolytic  hydrogen  is  atomic  hydrogen;  i.  e., 
hydrogen  with  its  bonds  open  or  free.  It  there- 
fore possesses  much  stronger  chemical  affinities 
than  does  molecular  hydrogen.  Electrolytic 
oxygen  which  is  evolved  at  the  same  time  as  the 
electrolytic  hydrogen  has  been  successfully  em- 
ployed in  electric  bleaching.  Hydrogen  per- 
oxide is  also  formed  and  acts  as  a  bleaching  agent. 

Hydrometer  or  Areometer. — An  appa- 
ratus for  determining  the  specific  gravity  of 
liquids.  (See  Areometer  or  Hydrometer?) 

Hydro-Plastics.— (See   Plastics,   Hydro?) 

Hydro-Plasty.— The  art  of  hydro-plastics. 
(See  Plastics,  Hydro?) 

Hydrotasimeter,  Electric An  elec- 
trically operated  apparatus  designed  to  show 
at  a  distance  the  exact  position  of  any  water 
level. 

In  most  forms  of  the  electric  hydrotasimeter  a 
float  placed  in  the  liquid  and  connected  with  an 
electric  circuit  breaks  this  circuit,  and,  at  intervals, 
sends  positive  impulses  into  the  line  when  rising 
and  negative  impulses  when  falling.  These  are 
registered- by  means  of  an  index  moved  by  a  step- 
by-step  motion,  positive  currents  moving  it  in 
one  direction  and  negative  currents  moving  it  in 
the  opposite  direction. 


Hygrometer. — An  apparatus  for  determin- 
ing the  amount  of  moisture  in  the  air. 

Hygrometrical. — Of  or  pertaining  to  the 
hygrometer. 

Hygrometrically. — In  the  manner  of  the 
hygrometer. 

Hypothesis. — A  provisional  assumption  of 
facts  or  causes  the  real  nature  of  which  is 
unknown,  made  for  the  purpose  of  studying 
the  effects  of  such  causes. 

When  the  facts  assumed  by  a  hypothesis  can 
be  shown  to  be  presumably  true  the  hypothesis 
becomes  a  theory.  A  theory,  therefore,  gives  a 
more  correct  expression  of  the  relations  between 
the  causes  and  effects  of  natural  phenomena  than 
does  a  hypothesis. 

Hypothesis,  Double-Fluid   Electric 

— (See  Electricity,  Double-Fluid  Hypothesis 
of.) 

Hypothesis,  Grothiiss' A  hypothe- 
sis proposed  by  Grothiiss  to  account  for  the 
electrolytic  phenomena  that  occur  on  closing 
the  circuit  of  a  voltaic  cell. 

Grothtiss'  hypothesis  assumes: 

(i.)  That  before  the  electric  circuit  is  closed 
the  molecules  of  the  electrolyte  are  arranged  in 
an  irregular  or  unpolarized  condition,  as  repre- 


Fig.  293.   GrotkOss'  hypothesis  of  Electrolytic  Polari- 
zation. 

sented  at  (i),  Fig.  293.  These  molecules  are 
shaded  as  shown  in  Fig.  294,  to  indicate  then-  com- 
position and  polarity. 

(2.)  When  the  circuit  is  closed  and  a  current 


Hyp.] 


272 


[Hys, 


begins  to  pass,  a  polarization  of  the  electrolyte,  as 
shown  at  (2),  ensues,  whereby  all  the  negative 
ends  of  the  molecules  of  hydrogen  sulphate,  o 
sulphuric  acid,  are  turned  towards  the  positive 
or  zinc  plate,  and  all  the  positive  ends  towards 
the  negative  or  copper  plate.  This,  as  will  be 
seen,  will  turn  the  SO4  ends  towards  the  zinc, 
and  the  Hz  ends  towards  the  copper. 

(3.)  A  decomposition  of  the  polarized  chain, 
whereby  the  SO4 
unites  with  the  zinc 
and  the  H2  liberated 
reunites  with  the  SO4 
of  the  molecule  next 
to  it  in  the  chain,  and 
its  liberated  Hs  with  Fig.  294.  Conventionalized 
the  one  next  to  it,  and  Molecule. 

so  on  until  the  last  liberated  H2  in  the  chain  is 
given  off  at  the  surface  of  the  copper  or  negative 
plate.  This  leaves  the  chain  of  molecules  as 
shown  at  (3). 

(4.)  A  semi-rotation  of  the  molecules  of  the 
chain,  as  at  (3),  until  they  assume  the  position 
shown  at  (4).  This  rotation  is  required,  since  all 
the  molecules  in  (3)  are  turned  with  their  similar 
poles  towards  similarly  charged  battery  plates. 

Hypothesis,   Single-Fluid  Electric  — 

— (See  Electricity,  Single-Fluid  Hypothe- 
sis of.) 

Hypothetical. — Of  or  pertaining  to  a  hy- 
pothesis. 

Hypsometer. — An  apparatus  for  determin- 
ing the  height  of  a  mountain  or  other  eleva- 
tion by  ascertaining  the  exact  temperature  at 
which  water  boils  at  such  elevation. 

The  use  of  a  thermometer  to  measure  the 
height  of  a  mountain  or  other  elevation  is  based 
on  the  fact  that  a  given  decrease  in  the  tempera- 
ture of  the  boiling  point  of  water  invariably  at- 
tends a  given  decrease  in  the  atmospheric  press- 
ure. Therefore,  as  the  observer  goes  further 
above  the  level  of  the  sea,  the  boiling  point  of 
water  becomes  lower,  and  from  this  decrease  the 
height  of  the  mountain  or  other  elevation  may  be 
calculated. 

Hypsometrical. — Of  or  pertaining  to  the 
hypsometer. 

Hypsometrically. — In  the  manner  of  the 
hypsometer. 


Hysteresial  Dissipation  of  Energy. — (See 
Energy,  Hysteresial  Dissipation  of.) 

Hysteresis,  —  Molecular  friction  to  mag- 
netic change  of  stress. 

A  retardation  of  the  magnetizing  or  de- 
magetizing  effects  as  regards  the  causes 
which  produce  them. 

The  quality  of  a  paramagnetic  substance 
by  virtue  of  which  energy  is  dissipated  on  the 
reversal  of  its  magnetization. 

The  ratio  of  magnetic  induction  to  the  mag- 
netizing force  producing  it,  or,  in  other  words, 
the  magnetic  permeability,  is  greater  when  the 
magnetizing  force  is  decreasing,  than  when  it  is 
increasing.  This  phenomenon  is  seen  in  the  well 
known  retention  of  magnetism  in  iron  after  the 
withdrawal  of  the  force  causing  the  magnetization, 
and  was  called  by  Ewing  hysteresis,  from 
'vtfrefitao,  to  lag  behind. 

If  a  curve  is  constructed  in  which  the  hori- 
zontal abscissas  represent  the  magnetizing  force, 
or  the  magnetizing  current  to  which  they  are 
proportional,  and  the  vertical  ordinates  the 
number  of  lines  of  induction  passing  through  the 
body  that  is  being  magnetized,  both  in  the  case 
of  gradually  increasing  and  gradually  decreasing 
currents,  the  curve  will  be  found  to  have  greater 
values  for  the  decreasing  than  for  the  increasing 
current  Constructing  a  curve  in  this  manner  for 
the  case  of  a  ring  of 
iron,  which  has  been 
first  suddenly  magnet- 
ized and-  then  demag- 
netized, taking  the 
magnetizing  force  along 
the  line  F  H,  Fig. 
295,  and  the  result- 
ing magnetization 
along  the  line  M  N,  a 
loop  is  formed  in  the 
curve,  as  shown  in  the 
figure.  The  arrows 
show  the  direction  of  Fig.  295.  Curves  of  Hys- 
the  magnetizing  force;  teresis  (Swing). 

the  shaded  area  the  work  done  due  to  hysteresis. 

The  area  of  this  loop  represents  the  amount  of 
energy  per  unit  of  volume  expended  in  perform- 
ing a  magnetic  cycle,  i.  e.,  in  carrying  the  iron 
ring  through  a  magnetization  and  subsequent 
demagnetiz  ation. 

The  physical  meaning  of  the  loop  is  that  a  lag- 


273 


[Hys. 


ging  of  magnetization  has  occurred.  This  lag- 
ging of  the  magnetization  is  due  to  hysteresis. 
Ewing  gives  the  value  for  the  energy  in  ergs 
dissipated  per  cubic  centimetre,  for  a  complete 
magnetic  cycle  for  a  number  of  substances,  as 
follows  : 

Energy  dissipated 
in  ergs  per  cubic 
centimetre,  during 
a  complete  cy  cle  of 
doubly  reversed 
strong  magnetiza- 
Sample  of  Iron  operated  upon.  tion. 

Very  soft  annealed  iron 9,300  ergs. 

Less  soft  annealed  iron 16,300  " 

Hard  drawn  steel  wire 60.000  " 

Annealed  steel  wire 70,500  " 

Same  steel,  glass  hard 76,000  " 

Piano-forte    steel     wire,   normal 

temper 116,000  " 

Same,  annealed 94,000  ' ' 

Same,  glass  hard 117,000  " 

Approximately  28  foot-pounds  of  energy  are 
required  to  make  a  double  reversal  of  strong 
magnetization  in  a  cubic  foot  of  iron.  Energy 
expended  in  this  way  takes  the  form  of  heat. 
This  heat,  however,  is  to  be  distinguished  from 
heat  produced  by  Foucault  currents. 

According  to  Ewing,  hysteresis  is  greatly  de- 
creased by  keeping  the  iron  in  a  state  of  mag- 
netic vibration.  In  this  way,  the  energy  dis- 
sipated in  a  complete  magnetic  cycle  is  corre- 
spondingly decreased.  This  observation  of  Ewing 
agrees  with  the  prior  observation  of  Hughes,  who 
noticed  that  tapping  or  twisting  a  bar  of  iron 
greatly  accelerates  the  removal  of  its  residual 
magnetism. 

The  phenomena  of  hysteresis,  according  to 
Fleming,  accounts  for  part  of  the  energy  which 
is  dissipated  in  a  dynamo-electric  machine: 

(i.)  In  the  field  magnets. 

In  an  ordinarily  constructed  continuous  current 
dynamo,  work  is  done  in  magnetizing  the  field 
mapnets.  not  only  to  give  the  iron  its  initial  mag- 
netism, but  also  to  constantly  reproduce  the  mag- 
netism which  the  machine  loses  by  reason  of  the 


continual  vibrations  to  which  it  ii  subjected  dur- 
ing its  run.  If  sufficient  residual  magnetism 
were  retained,  on  the  withdrawal  of  the  magneti- 
zing force  there  would  be  no  necessity  for  the 
current  in  the  field  magnets  ;  but,  since  this  is 
removed  by  even  a  small  vibration,  the  energy  of 
the  exciting  current  must  needs  be  expended. 

(2.)  In  the  armature  of  the  dynamo. 

The  soft  iron  of  the  core  is  subjected  to  succes- 
sive magnetizations  and  demagnetizations.  Ac- 
cording to  Fleming,  in  the  case  of  a  core  having 
a  volume  of  9,003  cubic  centimetres,  with  fifteen 
reversals  per  second,  the  loss  is  equal  to  about  i 
horse-power. 

Hysteresis,  Static That  quality  in 

iron,  or  other  paramagnetic  substance,  by 
virtue  of  which  energy  is  dissipated  during 
every  reversal  of  its  magnetization. 

Static  hysteresis  is  so  named  in  order  to  dis- 
tinguish it  from  viscous  hysteresis.  (See  Hystere- 
sis, Viscous.) 

Hysteresis,  Yiscous The  time-lag 

observed  in  magnetizing  a  bar  of  iront 
which  is  referable  neither  to  induction  in  the 
iron,  nor  to  self-induction  in  the  magnetizing 
current,  but  to  the  magnetic  viscosity  of  the 
substance. 

A  sluggishness  exhibited  by  iron  for  mag- 
netization or  demagnetization  due  to  magnetic 
viscosity. 

The  difference  between  static  and  viscous 
hysteresis  is  thus  stated  by  Fleming  in  consider- 
ing the  analogous  mechanical  case  of  lifting  a 
weight  in  a  viscous  fluid.  "Apart  from  fluid 
resistance,  the  work  done  in  lifting  the  weight 
against  gravity,  say  one  hundred  times,  is  a  hun- 
dred times  the  work  required  to  be  spent  to  lift 
it  once  ;  but  if  fluid  resistance  comes  into  play, 
and  if  this  varies  as  the  square  of  the  velocity  of 
the  moving  body, .  then  the  total  work  done  in 
lifting  t'.ie  weight  through  the  fluid  will  be  de- 
pendent also  upon  the  rate  at  which  the  cycle  is 
performed." 


274 


[111. 


I.  H.  P. — A  contraction  for  indicated  horse- 
power, or  the  horse-power  of  an  engine  as 
obtained  by  the  means  of  an  indicator  card. 

I.  W.  Cr. — A  contraction  for  Indian  wire 
gauge. 

Idio-ElectricSo — A  name  formerly  applied 
to  such  bodies  as  amber,  resin  or  glass,  which 
are  readily  electrified  by  friction,  and  which 
were  then  supposed  to  be  electric  in  them- 
selves. 

This  distinction  was  based  on  an  erroneous 
conception,  and  the  word  is  now  obsolete. 

Idiostatic. — A  term  employed  by  Sir  Wil- 
liam Thomson  to  designate  an  electrometer 
in  which  the  measurement  is  effected  by  de- 
termining the  repulsion  between  the  charge 
to  be  measured  and  that  of  a  charge  of  the 
same  sign  imparted  to  the  instrument  from 
an  independent  source.  (See  Heterostatic) 

Idle  Poles.— (See  Poles,  Idle.) 

Igniter,  Jablochkoff A  small  strip 

of  carbon,  or  some  carbonaceous  material 
that  is  readily  rendered  incandescent  by  the 
current,  placed  between  the  free  ends  of  the 
parallel  carbons  of  a  Jablochkoff  candle,  for 
the  establishment  of  the  arc  on  the  passage 
of  the  current. 

The  igniter  is  necessary  in  the  Jablochkoff  elec- 
tric candle,  since  the  parallel  carbons  are  rigidly 
kept  at  a  constant  distance  apart  by  the  insulat- 
ing material  placed  between  them,  and  cannot 
therefore  be  moved  together  as  in  the  case  of  the 
ordinary  lamp.  (See  Candle,  Jablochkoff.) 

Ignition,  Electric  —  —The  ignition  of 
a  combustible  material  by  heat  of  electric 
origin. 

The  electric  ignition  of  wires  is  generally  ac- 
complished by  electric  incandescence.  Ignition 
may  be  accomplished  by  the  heat  of  the  voltaic 
arc.  (See/fcotf,  Electric.  Furnace,  Electric.') 

The  ignition  of  combustible  gases  is  accom- 
plished by  the  heat  of  the  electric  spark.  (See 
Burner,  Automatic,  Electric.} 

Illumination,  Artificial  —  — The  em- 
ployment of  artificial  sources  of  light. 


A  good  artificial  illuminant  should  possess  the 
following  properties,  viz.: 

(i.)  It  should  give  a  general  or  uniform  illumi- 
nation as  distinguished  from  sharply  marked 
regions  of  light  and  shadow. 

To  this  end  a  number  of  small  lights  well  dis- 
tributed are  preferable  to  a  few  large  lights. 

(2.)  It  should  give  a  steady  light,  uniform  in 
brilliancy,  as  distinguished  from  a  flickering, 
unsteady  light.  Sudden  changes  in  the  intensity 
of  a  light  injure  the  eyes  and  prevent  distinct 
vision. 

(3.)  It  should  be  economical,  or  not  cost  too 
much  to  produce. 

(4.)  It  should  be  safe,  or  not  likely  to  cause 
loss  of  life  or  property.  To  this  intent  it  should, 
if  possible,  be  inclosed  in  or  surrounded  by  a 
lantern  or  chamber  of  some  incombustible  mate- 
rial, and  should  preferably  be  lighted  at  a  dis- 
tance. 

(5  )  It  should  not  give  off  noxious  fumes  or 
vapors  when  in  use,  nor  should  it  unduly  heat 
the  air  of  the  space  it  illumines. 

(6. )  It  should  be  reliable,  or  not  apt  to  be  un- 
expectedly extinguished  when  once  lighted. 

'  The  electric  incandescent  lamp  is  an  excellent 
artificial  illuminant. 

(l.)  It  is  cap  able  of  great  subdivision,  and  can, 
therefore,  produce  a  uniform  illumination. 

(2.)  It  is  steady  and  free  from  sudden  changes 
in  its  intensity. 

(3.)  It  compares  favorably  in  point  of  economy 
with  coal  oil  or  gas,  provided  its  extent  of  use  is 
sufficiently  great. 

(4.)  It  is  safer  than  any  known  illuminant, 
since  it  can  be  entirely  inclosed  and  can  be 
lighted  from  a  distance  or  at  the  burner  without 
the  dangerous  friction  match. 

The  leads,  however,  must  be  carefully  insu- 
lated and  protected  by  safety  fuses.  (See  Fuse, 
Safety.) 

(5.)  It  gives  off  no  gases,  and  produces  far  less 
heat  than  a  gas-burner  of  the  same  candle  power. 

It  perplexes  many  people  to  understand  why 
the  incandescent  electric  light  should  not  heat 
the  air  of  a  room  as  much  as  a  gas  light,  since  it 
is  quite  as  hot  as  the  gas  light.  It  must  be  re- 
membered, however,  that  a  gas-burner,  when 
lighted,  not  only  permits  the  same  quantity  of 


111.] 


275 


gas  to  enter  the  room  which  would  enter  it  if 
the  gas  were  simply  turned  on  and  not  lighted, 
but  that  this  bulk  of  gas  is  still  given  off,  and  is, 
indeed,  considerably  increased  by  the  combina- 
tion of  the  illuminating  gas  with  the  oxygen  of  the 
atmosphere ;  and,  moreover,  this  great  bulk  of 
gas  escapes  as  highly  heated  gases.  Such  gases 
are  entirely  absent  in  the  incandescent  electric 
light,  and  consequently  its  power  of  heating  the 
surrounding  air  is  much  less  than  that  of  gas 
lights. 

(6.)  It  is  quite  reliable,  and  will  continue  to 
burn  as  long  as  the  current  is  supplied  to  it. 

Illumination,  Lighthouse,  Electric 

— The  application  of  the  electric  arc  light 
to  lighthouses. 

A  powerful  arc  light  is  placed  in  the  focus  of 
the  dioptric  lens  now  commonly  employed  in 
lighthouses.  Since  the  consumption  of  the  carbon 
electrodes  would  alter  the  position  of  the  focus  of 
the  light,  electric  lamps  for  such  purposes  are 
constructed  to  feed  both  of  their  carbons,  instead 
of  the  upper  carbon  only,  as  in  the  case  of  the 
ordinary  arc  lamp.  Such  lamps  are  called  focus- 
ing lamps. 

Illumination,  Unit  of A  standard 

of  illumination  proposed  by  Preece,  equal  to 
the  illumination  given  by  a  standard  candle 
at  the  distance  of  12.7  inches. 

According  to  Preece,  the  illumination  of  the 
average  streets  of  London,  where  gas  is  employed, 
is  equal  to  about  one-tenth  of  this  standard  in  the 
neighborhood  of  a  gas  lamp,  and  about  one- 
fiftieth  in  the  middle  space  between  two  lamps. 

The  term  unit  of  illumination,  in  place  of  in- 
tensity of  light,  was  proposed  by  Preece  in  order 
to  avoid  the  very  great  difficulty  in  determining 
the  intensity  of  a  light  in  a  street  or  space  where 
there  were  a  number  of  luminous  sources,  and 
where  the  directions  of  incidence  of  the  different 
lights  vary  so  greatly. 

A  carcel  standard  at  the  distance  of  a  metre 
will  illumine  a  surlace  to  the  same  intensity  of 
illumination  as  a  standard  candle  at  the  distance 
of  12,7  inches.  (See  Candle,  Foot.) 

Illumined  Electrode.— (See  Electrode, 
Illumined?) 

Imbibition  Currents. — (See  Currents,  Im- 
bibition.] 

Images,  Electric A   term   some- 


times applied  to  the  charge  produced  on  a 
neighboring  surface  by  induction  from  a 
known  charge. 

A  positive  charge  produces,  by  induction,  on  a 
flat  metallic  surface  near  it,  a  negative  charge 
which  is  distributed  with  varying  density  over  the 
surface,  but  acts  electrically  as  would  an  equal 
quantity  of  negative  electricity  placed  back  of  the 
plate  at  the  same  distance  the  positive  charge  is 
in  front  of  it.  The  correspondence  of  this  charge 
with  the  image  of  an  object  seen  in  a  plane  mirror, 
has  led  to  the  term  electric  image. 

Maxwell  defines  electric  image  as  follows:  "  An 
electric  image  is  an  electrified  point,  or  system  of 
points,  on  one  side  of  a  surface,  which  would  pro- 
duce, on  the  other  side  of  that  surface,  the  same 
electrical  action  which  the  actual  electrification  of 
the  surface  really  does  produce." 

Impedance. — Generally  any  opposition  to 
current  flow. 

The  sum  of  the  ohmic  resistance  and  the 
spurious  resistance  of  a  circuit  measured  in 
ohms. 

A  quantity  which  is  related  to  the  strength 
of  the  impressed  electromotive  force  of  a  sim- 
ple periodic  or  alternating  current,  in  the  same 
manner  that  resistance  is  related  to  the  steady 
electromotive  force  of  a  continuous  current. 

In  the  case  of  steady  currents,  the  current 
strength  is  equal  to  the  electromotive  force  dl. 
vided  by  the  resistance ;  or, 

Electromotive  force 
Current  strength  =;  — 

Resistance. 

In  the  case  of  a  simple  period  ic  or  alternating  cur. 
rent,  the  average  current  strength  is  equal  to  the 
average  impressed  electromotive  force  divided  by 
the  impedance;  or, 
Average  current  strength  = 

Average  impressed  electromotive   force 
Impedance. 

Since  impedance,  like  true  resistance  of  the  cir- 
cuit,  can  be  measured  in  ohms,  it  is  sometimes 
called  the  virtual  resistance. 

Impedance  is  a  quantity  equal  to  the  square 
root  of  the  sum  of  the  squares  of  the  inductive 
resistance  of  the  circuit  and  the  ohmic  resistance. 

In  the  case  of  simple  periodic  or  alternating 
currents,  the  average  current  strength  is  equal  to 
the  average  impressed  electromotive  force,  divided 
by  the  impedance ;  the  maximum  current  strength 


lmp.J 


276 


[Inc. 


is  equal  to  the  maximum  impressed  electromotive 
force,  divided  by  the  impedance. 

The  impedance  of  a  circuit  can  be  repre- 
sented geometrically  as  fol 
lows:  Draw  a  right  angled 
triangle  (Fig.  296),  the  base 
of  which  represents  the 
ohmic  resistance  of  the  cir- 
cuit, and  the  perpendicular, 
the  inductive  resistance 


C         RESISTANCE 

Fig.  2<)b.     Geometrical 
'       Representation  of  Itn- 
then  the  hypothenuse  will     pedance. 
represent  the  impedance. 

Since  the  ohmic  resistance  equals  R,  and  the  in- 
ductive resistance  equals  the  inductance  L,  mul- 
tiplied by  2  it  n,  in  which  n,  is  the  frequency,  the 
value  of  the  impedance  is  equal  to 
•/Ra  +  4  it*  n»  L«. 

Impedance  Coil. — (See  Coil,  Impedance!) 

Impedance,    Impulsive    or    Oscillatory 

The  impedance  which    a  conductor 

offers    to   an   impulsive  or   oscillatory    dis- 
charge. 

The  impulsive  impedance  varies  in  simple  pro- 
portion to  the  frequency  of  the  periodic  current. 
It  depends  on  the  form  and  size  of  the  circuit,  but 
it  is  independent  of  its  resistance  or  permeability. 

Imponderable. — That  which  possesses  no 
weight. 

A  term  formerly  applied  to  the  luminiferous 
or  universal  ether,  but  now  generally  aban- 
doned. 

It  is  very  questionable  whether  it  is  possible  for 
any  form  of  matter  to  be  actually  imponderable 
or  to  possess  no  attraction  for  other  matter. 

An  imponderable  fluid,  as,  for  example,  the 
universal  ether,  as  the  term  is  now  generally  em- 
ployed, is  a  fluid  whose  weight  is  comparatively 
small  and  insignificant,  and  not  a  fluid  an  infinite 
quantity  of  which  would  be  entirely  devoid  of 
weight. 

Impressed  Electromotive  Force. — (See 
Force,  Electromotive,  Impressed!) 

Impulse,  Electro-Magnetic An  im- 
pulse produced  in  the  ether  surrounding  a 
conductor  by  the  action  of  an  impulsive  dis- 
charge, or  by  a  pulsating  field. 

Impulse,  Electromotive An  im- 
pulse producing  an  impulsive  rush  of  elec- 
tr'city. 


The  term  is  employed  to  distinguish  between 
the  ordinary  electromotive  force  which  produces  a 
steady  current  of  electricity  and  an  electromotive 
impulse  which  produces  an  impulsive  rush  of  elec- 
tricity or  impulsive  discharge. 

Impulsion  Cell. — (See  Cell,  Impulsion!) 

Impulsion  Effect.— (See  Effect,  Impul- 
sion!) 

Impulsive  Impedance. — (See  Impedance, 
Impulsive  or  Oscillatory!) 

Incandesce. — To  shine  or  glow  by  means 
of  heat. 

Incandescence. — The  shining  or  glowing  of 
a  substance,  generally  a  solid,  by  reason  of  a 
sufficiently  high  temperature. 

Incandescence,  Electric  —  —The  shin- 
ing or  glowing  of  a  substance,  generally  a 
solid,  by  means  of  heat  of  electric  origin. 

Electric  incandescence  of  solid  substances  differs 
from  ordinary  incandescence,  in  the  fact  that  un- 
less the  substance  is  electrically  homogeneous 
throughout,  the  temperature  is  not  uniform  in  all 
parts,  but  is  highest  in  those  portions  where  the 
resistance  is  highest  and  the  radiation  smallest. 

The  deposition  of  carbon  in  and  on  a  carbon 
conductor  by  the  flashing  process  is  quite  different 
as  performed  by  electrical  incandescence,  than  it 
would  be  if  the  carbons  were  heated  by  ordinary 
furnace  or  other  heat.  (See  Carbons,  Flashing 
Process  for.} 

Incandescence,  Thermal The  shin- 
ing or  glowing  of  a  substance,  generally  a 
solid,  by  means  of  heat  other  than  that  of 
electric  origin. 

Incandescent. — Shining  or  glowing  with 
heat. 

Incandescent  Ball  Electric  Lamp. — (See 
Lamp,  Electric,  Incandescent  Ball!) 

Incandescent  Electric  Lamp,  Life  Curve 

of (See  Curve,  Life,  of  Incandescent 

Lamp!) 

Incandescent  Electric  Lamp,  Life  of  — 

— (See  Lamp,  Electric,  Incandescent,  Life 
of!) 
Incandescent  Straight  Filament  Lamp. 

— (See  Lamp,  Incandescent,  Straight  Fila- 
ment.} 


Inc.] 


277 


[Ind 


Incandescing.— Glowing  or  shining  by 
means  of  heat. 

Inclination,  Angle  of The  angle 

which  a  magnetic  needle,  free  to  move  in  a 
vertical  and  horizontal  plane,  makes  with  a 
horizontal  line  passing  through  its  point  of 
support. 

The  angle  of  magnetic  dip. 

A  magnetic  needle,  supported  at  its  centre  of 
gravity,  and  capable  of  moving  freely  in  a  ver- 
tical as  well  as  in  a  horizontal  plane,  does  not 
retain  a  horizontal  position  at  all  parts  of  the 
earth's  surface. 

The  angle  which  marks  its  deviation  from  the 
horizontal  position  is  called  the  angle  of  dip  or 
inclination.  (See  Dip,  Magnetic.) 

Incandescent  Electric  Lamp.  —  (See 
Lamp,  Electric,  Incandescent.) 

Inclination  Chart. — (See  Chart,  Inclina- 
tion.) 

Inclination  Compass. — (See  Compass,  In- 
clination.) 

Inclination,  Magnetic The  an- 
gular deviation  from  a  horizontal  position  of 
a  freely  suspended  magnetic  needle.  (See 
Dip,  Magnetic.  Chart,  Inclination.) 

Inclination  Map. — (See  Map  or  Chart, 
Inclination!) 

Inclination  of  Magnetic  Needle. — (See 
Needle,  Magnetic,  Inclination  of) 

Inclinometer. — A  name  sometimes  given 
to  an  inclination  compass.  (See  Compass, 
Inclination.) 

Incomplete  Circuit. — (See  Circuit,  In- 
complete.) 

Increased  Electric  Irritability.—  (See 
Irritability,  Electric,  Increased.) 

Increment  Key. — (See  Key,  Increment.) 

Increment  Key  of  a  Quadrnplex  Tele- 
graphic System.— (See  Key,  Increment,  of 
Quadruple*  Telegraphic  System.) 

India  Rubber. — A  resinous  substance  ob- 
tained from  the  milky  juices  of  several  tropi- 
cal trees. 

India  rubber  or  caoutchouc  is  obtained  from 
the  Siphonia  elastica  of  South  America. 


India  rubber  is  quite  elastic  and  possesses  high 
powers  of  electric  insulation.  When  vulcanized 
or  combined  with  sulphur,  it  still  retains  its 
powers  of  electric  insulation  in  a  high  degree. 
In  this  state  it  is  highly  electrified  by  friction. 
(See  Caoutchouc.) 

Indicating  Bell. — (See  Bell,  Indicating!) 

Indicator,  Automatic Any  auto- 
matic device  for  electrically  indicating  the 
number  of  times  a  circuit  has  been  opened  or 
closed,  and  thus  the  number  of  times  a  given 
operation  has  occurred  which  has  caused  the 
opening  or  closing  of  such  circuit. 

An  annunciator  with  an  automatic  drop  is 
sometimes  called  an  automatic  indicator.  (See 
Annunciator,  Electro-Magnetic.  Annunciator 
Drop,  Automatic.) 

Indicator,  Electric A  name  ap- 
plied to  various  devices,  generally  operated 
by  the  deflection  of  a  magnetic  needle,  or  the 
ringing  of  a  bell,  or  both,  for  indicating,  at 
some  distant  point,  the  condition  of  an  electric 
circuit,  the  strength  of  current  that  is  passing 
through  it,  the  height  of  water  or  other  liquid, 
the  pressure  on  a  boiler,  the  temperature,  the 
speed  of  an  engine  or  line  of  shafting,  the 
working  of  a  machine  or  other  similar  events 
or  occurrences. 

A  term  sometimes  used  in  place  of  annun- 
ciator. (See  Annunciator, Electro-Magnetic.) 

Indicators  are  of  various  forms.  They  are 
generally  electro-magnetic  in  character.  They 
are  automatic  in  action. 

Indicator,  Electric  Circuit A  de- 
vice, generally  in  the  form  of  a  vertical  gal- 
vanometer, employed  to  indicate  the  presence 
and  direction  of  a  current  in  a  circuit,  and 
often  to  roughly  measure  its  strength.  (See 
Galvanometer,  Vertical.) 

Indicator,  Electric,  for  Steamships 

— An  electric  indicator  operated  by  circuits 
connected  with  the  throttle  valve  and  revers- 
ing gear  of  the  steam  engine. 

The  signal  "stop, "for  example,  sent  by  the 
navigating  officer  to  the  engineer,  causes  him  to 
close  the  throttle.  This  act  places  the  indicator 
needle  at  "=top,"  and  thus  informs  the  officer 
that  his  signal  has  been  obeyed.  In  the  same 


Ind.] 


278 


[Inch 


manner,  the  opening  of  the  throttle  sets  the  in- 
dicator needle  to  "ahead,"  etc. 

Indicator,  Electric    Throwback 

An  annunciator  with  a  drop  that  is  electrically 
replaced.  (See  Annunciator,  Electro-Mag- 
netic^) 

Indicator,    Lamp An    apparatus 

used  in  the  central  station  of  a  system  of  in- 
candescent lamp  distribution  to  indicate  the 
presence  of  the  proper  voltage  or  potential 
difference  on  the  mains. 


Fig.  297.    Edison-Htrwell  Lamp  Indicator. 

The  lamp  indicator  of  Edison  and  Howell  is 
shown  in  Fig.  297.  It  consists  essentially  of  a 
Wheatstone  bridge  with  the  resistances  arranged 
as  shown.  A  galvanometer  at  G,  serves,  by  the 
movements  of  its  magnetic  needle,  to  act  as  an 
indicator.  This  needle  remains  at  zero,  when 
the  potential  difference  is  the  exact  voltage  re- 
quired on  the  circuit  with  which  the  indicator  is 
connected.  The  incandescent  lamp  at  L,  being 
one  of  the  resistances,  and  being  constantly 
traversed  by  the  current,  will  have  a  fixed  resist- 
ance for  the  temperature  at  which  it  is  designed 
to  run.  The  other  resistances  are  so  proportioned 
as  to  insure  the  needle  at  G,  remaining  at  zero. 
If,  however,  the  potential  varies,  the  temperature 
of  the  lamp  L,  varies,  and,  being  carbon,  its  re- 
sistance also  varies,  a  rise  of  temperature  cor- 
responding to  a  fall  of  lamp  resistance,  which 
destroys  the  balance  of  the  bridge  and  deflects 
the  galvanometer  needle.  The  attendant  then 
regulates  the  potential  to  bring  the  needle  back  to 
zero. 

Indicator,  Mechanical  Throwback 

— An  annunciator  with  a  mechanical  drop. 
(See  Annunciator,  Electro-Magnetic.  An- 
nunciator, Drop.  Annunciator,  Gravity?) 

Indicator,  Pendnlnm An  annun- 
ciator, the  indicating  arm  of  which  is  operated 


by  means  of  a  pendulum.  (See  Annunciator, 
Pendulum?) 

Indicator,  Potential An  apparatus 

for  indicating  the  potential  difference  between 
any  points  of  a  circuit. 

A  voltmeter  is  a  potential  indicator.  It  is, 
however,  more  than  an  indicator,  since  it  gives 
the  value  of  the  potential  difference  in  volts.  (See 
Voltmeter.}  A  lamp  indicator  is  a  potential  in- 
dicator. (See  Indicator,  Lamp.) 

Indicator,  Semaphore An  annun- 
ciator in  which  a  gravity  drop  or  shutter  is 
caused  to  fall  by  the  action  of  the  electric 
current,  thus  exposing  a  number  of  other 
signals  back  of  the  drop  or  shutter. 

Indicator,  Speed — A  name  some- 
times applied  to  a  tachometer.  (See  Tachom- 
eter:) 

A  form  of  speed  indicator  is  shown  in  Fig. 
298.  The  endless  screw  drives  the  wheel  when 
the  triangular  point  is  held  firmly  against  the 
centre  of  the  revolving  shaft  or  pulley. 


Fig.  298.    Speed  Indicator. 

Indicator,  Voltaic  Battery A  de- 
vice for  indicating  the  condition  of  a  voltaic 
battery. 

Indifferent  Point.— (See  Point,  Indif- 
ferent?) 

Indirect  Excitation.— (See  Excitation, 
Indirect?) 

Induced  Atomic  Currents.— (See  Cur- 
rents, Induced,  Atomic  or  Molecular?) 

Induced  Current. — (See  Current,  In- 
duced?) 

Induced  Direct  Current. — (See  Current, 
Direct,  Induced?) 

Induced  Electrostatic  Charge.  —  (See 
Charge,  Induced  Electrostatic?) 

Induced  Molecular  Currents. — (See  Cur* 
rents.  Induced  Molecular?} 


Ind.] 

Induced  Reverse  Currents.  —  (See  Cur- 
rent, Reverse,  Induced?) 

Inductance  ---  The  induction  of  a 
circuit  on  itself,  or  on  other  circuits. 

Self-induction. 

A  term  now  generally  employed  instead  of 
self-induction. 

That  property  in  virtue  of  which  a  finite 
electromotive  force,  acting  on  a  circuit,  does 
not  immediately  generate  the  full  current  due 
to  its  resistance,  and  when  the  electromotive 
force  is  withdrawn,  time  is  required  for  the 
current  strength  to  fall  to  zero.  —  (Fleming.) 

A  quality  by  virtue  of  which  the  passage  of 
an  electric  current  is  necessarily  accompanied 
by  the  absorption  of  electric  energy  in  the 
formation  of  a  magnetic  field. 

The  inductance  of  a  circuit  depends: 

(i.  )  On  the  form  or  shape  of  the  circuit. 

(2.)  On  the  magnetic  permeability  of  the  space 
surrounding  the  circuit. 

(3.)  On  the  magnetic  permeability  of  the  circuit 
itself. 

For  the  variations  of  current  strength  in  elec- 
tric circuits,  inductance  is  not  unlike  mass,  or 
moment  of  inertia,  as  regards  variations  of  velo- 
city. Time  is  required  to  produce  velocity  in  a 
heavy  body  by  the  action  of  any  force;  so  also 
time  is  required  to  produce  a  current  by  the 
action  of  an  electromotive  force. 

The  electro-magnetic  energy  present  in  any 
given  current  is  equal  to  the  square  of  the  current 
multiplied  by  the  inductance.  Since  one  of  these 
factors  (the  current  strength)  represents  the 
force,  the  other,  the  inductance,  must  have  the 
dimension  of  a  distance  or  length.  Inductance, 
therefore,  is  measurable  in  units  of  length.  If 
the  circuits  are  formed  of  magnetizable  materials, 
the  inductance  of  a  circuit  is  the  ratio  between  the 
total  inductance  taking  place  through  the  circuit 
to  the  current  producing  it. 

If  the  circuit  is  formed  entirely  of  non-magnetic 
material,  surrounded  entirely  by  materials  of 
constant  magnetic  permeability  (such  as  air,  in- 
sulators and  diamagnetic  materials  generally),  the 
inductance  is  a  constant  quantity  and  depends 
only  on  the  form  or  shape  of  the  circuit.  In  this 
case,  the  total  inductance  through  the  circuit  is  pro- 
portional to  the  magnetizing  force,  and  the  mag- 
netic resistance,  or  the  magnetic  conductance  of 
the  magnetic  circuit,  is  equal  to  the  total  indue- 


279 


[Ind. 


tion  through  the  circuit,  divided  by  the  magnetiz- 
ing force. 

In  cases  where  the  magnetic  circuit  is  partly  or 
wholly  of  paramagnetic  substances,  where  the 
induction  bears  no  constant  ratio  to  the  magnetiz- 
ing force,  and  where  the  induction  takes  place 
partly  or  wholly  in  media  of  variable  permeability, 
the  co-efficient  of  self- induction,  or  the  inductance, 
must  be  denned  in  three  ways: 

(i.)  As  the  ratio  between  the  counter  electro- 
motive force  in  any  circuit  and  the  time  rate  or 
variation  of  the  current  producing  it. 

(2.)  As  the  ratio  between  the  total  induction 
through  the  circuit  and  the  current  producing  it. 

(3.)  As  the  energy  associated  with  the  circuit 
in  the  form  of  magnetic  field,  due  to  unit  current 
in  that  circuit,  or  as  the  co-efficient  by  which  half 
the  square  of  the  current  must  be  multiplied  to 
obtain  the  electro-kinetic  energy  of  the  circuit  at 
that  instant.  -  (Fleming.) 

A  flat  sheet  or  strip  of  metal  possesses  less  in- 
ductance  than  a  round  conductor  of  equal  cross- 
section. 

This  may  be  explained  by  conceiving  that  a 
flat  conductor  presents  a  greater  absorption  sur- 
face to  the  dielectric. 

Therefore,  the  perfect  form  for  a  conductor 
transmitting  rapidly  alternating  currents  is  that 
of  a  flat  sheet  or  strip  of  copper,  or  preferably  a 
copper  tube. 

The  experiments  of  Hughes  show  that  the  in- 
ductance of  a  conductor  may  be  regarded  as  an 
effect  due  to  the  time  required  for  the  rapidly 
periodic  current  to  penetrate  the  conductor,  and 
that  the  decrease  in  the  inductance,  produced  by 
forming  the  conductor  of  a  strip  or  bar,  is  due 
to  the  decreased  distance  the  current  has  to  pass 
to  the  inner  parts. 

Inductance,  Absolute  Unit  of A 

unit  of  length  equal  to  one  centimetre. 

A  length  equal  to  an  earth  quadrant  or  IO» 
centimetres  is  called  the  practical  unit  of  induct- 
ance. The  practical  unit  of  inductance  was  form- 
erly called  a  secohm  or  quadrant  It  is  now  gen- 
erally called  a  henry.  (See  Henry,  A.) 

Inductance  Bridge.— (See  Bridge,  In- 
ductance) 

Inductance,  Co-efficient  of A  con- 
stant quantity,  such  that  when  multiplied  by 
the  current  strength  passing  in  any  coil  or  cir- 
cuit, will  represent  numerically  the  induction 
through  the  coil  or  circuit  due  to  that  curren*. 


Iiid. 


280 


rind. 


A  term  sometimes  used  for  co-efficient  of 
self-induction.  (See  Induction,  Co-efficient 
of-} 

Inductance,  Constant The  induct- 
ance which  occurs  in  circuits  formed  wholly 
of  non-magnetic  materials,  immersed  in  or 
surrounded  by  media  of  constant  magnetic 
permeability  or  magnetic  conductance  for 
lines  of  magnetic  force.  (See  Permeability, 
Magnetic?) 

When  the  lines  of  magnetic  force  pass  through 
such  materials  as  ordinary  insulators,  or  diamag- 
netic  materials,  such  as  copper,  the  inductance  is 
constant,  provided  the  geometric  form  of  the  cir- 
cuit remains  the  same. 

Inductance,   Formal,  of  Circuit 

That  part  of  the  counter  electromotive  force 
of  a  circuit  which  depends  on  the  form  of  the 
circuit. 

Inductance,  or  Self-Induction,  Practical 

Unit  of —A  length  equal  to  the  earth 

quadrant  or  10°  centimetres. 

The  absolute  unit  of  inductance  is  equal  to  i 
centimetre. 

Inductance,  Oscillatory,  Electric 

Inductance  produced  by  electric  oscillations. 

Inductance,  Unit  of—  — A  term  now 
generally  used  for  unit  of  self-induction. 

The  value  of  the  inductance  may  be  given 
either  in  absolute  or  in  practical  units  of  induct- 
ance. The  absolute  unit  of  inductance  is  equal 
to  a  length  of  one  centimetre.  The  practical  unit 
of  inductance  is  equal  to  1,000,000,000  centi- 
metres or  jo1  centimetres. 

The  praciical  unit  of  inductance  was  formerly 
called  a  secohm.  The  term  henry  is  generally 
used  for  this  unit.  (See  Henry,  A.) 

Inductance,  Variable The  induc- 
tance which  occurs  in  circuits  formed  partly 
or  wholly  of  substances  like  iron  or  other 
paramagnetic  substances,  the  magnetic 
permeability  of  which  varies  with  the  inten- 
sity of  the  magnetic  induction,  and  where  the 
lines  of  force  have  their  circuit  partly  or 
wholly  in  such  material  of  variable  magnetic 
permeability. 

Induction. — An    influence   exerted  by  a 


charged  body  or  by  a  magnetic  field  on.  neigh- 
boring bodies  without  apparent  communica- 
tion. 

A  medium  is  necessary  to  connect  the  body 
producing  the  induction  and  that  in  which  the 
induction  is  produced.  (See  Induction,  Electro- 
static. Induction,  Magnetic.  Induction,  Electro- 
Dynamic. ) 

Induction,  Apparent  Co-efficient  of 

— A  term  sometimes  used  for  co-efficient  of 
apparent  magnetic  induction.  (See  Induc- 
tion, Magnetic,  Apparent  Co-efficient  of.} 

It  is  called  the  apparent  co-efficient  of  induction 
because  its  value  is  different  from  what  it  would 
be  if  the  eddy  currents  were  entirely  suppressed. 
The  eddy  currents  increase  the  resistance  of  the 
primary  and  decrease  its  inductance. 

Induction-Balance,  Hughes' (See 

Balance,  Induction,  Hughes'?) 

Induction,  Balance  of,  in  Cable 

The  removal  of  induction  in  a  cable  by 
neutralization  by  the  presence  of  equal  and 
opposite  effects. 

A  balance  is  obtained  of  the  inductive  effects  of 
the  neighboring  conductors,  whether  in  the 
bunched  cable  or  outside  of  it. 

Induction-Bridge.— (See  Bridge,  Induc- 
tance?) 

Induction,  Co-efficient  of A  term 

sometimes  used  for  co-efficient  of  magnetic 
induction.  (See  Induction,  Magnetic,  Co- 
efficient of} 

Induction  Coil.— (See  Coil,  Induction} 

Induction  Coil,  Inverted (See 

Coil,  Induction,  Inverted.  Transformer} 

Induction,  Current A  term  some- 
times used  for  voltaic  induction.  (See  Induc- 
tion, Voltaic.  Induction,  Electro-Dynamic} 

Induction,  Dissymmetrical,  of  Armature 

An  induction  produced  by  the  passage 

of  a  different  number  of  lines  of  magnetic 
force  through  adjoining  halves  of  the  arma- 
ture. 

Induction,  Electro-Dynamic  — = Elec- 
tromotive forces  set  up  by  induction  in  con- 
ductors which  are  either  actually  or  practically 
moved  so  as  to  cut  the  lines  of  magnetic 
force. 


Ind.J 

I 

These  electromotive  forces,  when  permitted  to 
act  through  a  circuit,  produce  an  electric  current. 
Electro-dynamic  induction  may  be  produced  in 
any  circuit  in  two  ways: 

(I.)  By  causing  expanding  or  contracting  lines 
of  magnetic  force  to  pass  through  that  circuit. 

(2.)  By  causing  the  circuit  or  conductor  to  pass 
through  the  lines  of  magnetic  force. 

In  all  cases  the  lines  of  force  are  made  to  pass 
through  the  conductor  or  wire. 

There  are  four  cases  of  electro- magnetic  induc- 
tion: 

(i.)  That  in  which  expanding  or  contracting 
lines  of  magnetic  force,  produced  by  rapidly  vary- 
ing the  current  in  any  circuit,  are  caused  to  pass 
through  or  cut  that  circuit  and  consequently  to 
produce  differences  of  potential  therein. 

(2.)  That  in  which  expanding  or  contracting 
lines  of  magnetic  force  produced  by  any  circuit  by 
the  rapidly  varying  strength  of  the  electric 
current  passing  through  that  circuit,  are  caused 
to  pass  through  another  neighboring  circuit  and 
thus  produce  differences  of  potential  therein. 

(3.)  That  produced  by  moving  a  conductor 
through  a  magnetic  field  so  as  to  cut  its  lines  of 
magnetic  force.  In  this  way  the  strength  of  the 
magnetic  field  may  remain  practically  constant, 
but  this  strength  as  regards  the  field  of  the  fixed 
conductor  is  varying,  as  the  magnet  producing 
such  a  field  is  moved  toward  or  from  such  cir- 
cuit, and  m  this  way  differences  of  potential  are 
produced  in  the  circuit. 

(4. )  That  produced  by  moving  an  inducing  field 
past  a  fixed  conductor.  This  may  le  accom- 
plished by  moving  an  electro-magnet,  an  electric 
circuit,  or  a  permanent  magnet  past  the  conductor 
in  which  the  difference  of  potential  is  to  be  in- 
duced. 

There  are  therefore  four  distinct  varieties  of 
electro-dynamic  induction: 

(i.)  Self-induction  or  inductance.  (See  Induct- 
ance.) 

(2.)  Mutual  induction,  or,  as  it  is  sometimes 
called,  voltaic  current  induction.  (See  Induction, 
Mutual.} 

(3.)  Electro-magnetic    induction,   or,   as  it   is 
sometimes  calleJ,  dynamo-electric  induction. 
(4.)  Magneto-electric  induction. 
If  the  terminals  of  a  voltaic  cell  be  connected 
with  the  ends  of  a  comparatively  long  coil  of  in- 
sulated wire,  no  appreciable  spark  will  be  observed 
on  closing  the  cell,  because  the  current  induced 
by  self-induction  is  in  the  opposite  direction  to  the 


281 


[Ind. 


current  of  the  cell  and  weakens  it.  On  breaking 
contact,  however,  a  spark  is  readily  observed. 
This  is  due  to  the  induced  current  on  breaking, 
which,  flowing  in  the  same  direction  as  the  cur- 
rent of  the  cell,  strengthens  it. 


Fig.  299.     Mutual  Induction 

The  coil  B,  Fig.  299,  consists  of  two  parallel 
coils  of  insulated  wire,  the  terminals  of  one  of 
which,  called  the  primary  coil,  are  connected 
with  the  battery  cell  P  N,  and  those  of  the 
other,  called  the  secondary  coil,  with  the  galva- 
nometer G. 

Under  these  circumstances  it  is  found : 
(i.)  That  at  the  moment  of  closing  the  circuit 
through  the  primary  coil,  a  momentary  current 
is  produced  in  the  secondary  coil  in  a  direction 
opposite  to  that  of  the  current  through  the  primary, 
as  is  shown  by  the  direction  of  the  deflection  of 
the  needle  of  the  galvanometer. 

(2.)  At  the  moment  of  breaking  the  circuit 
through  the  primary  coil,  an  induced  current  is 
produced  in  the  secondary  coil  in  the  same  direc- 
tion as  that  flowing  through  the  primary  coil. 

(3.)  These  induced  currents  are  momentary, 
and  continue  in  the  secondary  only  while  the  in- 
tensity of  the  current  in  the  primary  is  varying, 
*.  <?.,  while  variations  are  occurring  in  the  strength 
of  the  magnetic  field  in  which  the  secondary  coil 
is  placed,  therefore  while  the  expanding  or  con- 
tracting lines  of  force  are  passing  through  the  sec- 
ondary coil. 

If,  for  instance,  when  the  current  is  established 
in  the  primary  coil,  and  no  current  exists  in  the 


Fig.  300.    Mutual  Induction. 

secondary,  the  intensity  of  the  current  in  the 
primary  be  varied  by  establishing  a  shunt  circuit 
across  the  battery  terminals,  as  by  placing  a  short 
wire  d,  Fig.  300,  in  the  mercury  cups  g,  2,  thus 


Ind.] 


282 


[Ind. 


decreasing  the  intensity  of  the  current  in  the 
primary,  an  induced  current  will  be  set  up  in  the 
secondary  circuit  in  the  same  direction  as  the 
primary  current. 

From  all  of  these  phenomena,  we  see  that  any 
increase  of  current  in  a  conductor  produces  in  a 
neighboring  conductor  an  induced  inverse  current, 
or  one  in  the  opposite  direction  to  the  inducing 
current,  while  a  decrease  of  such  current  produces 
a  direct  induced  current,  or  one  in  the  same 
direction  as  the  inducing  current. 

If  the  induction  coil  be  made,  as  in  Fig.  301, 
with  its  primary  coil  movable  into  and  out  of  the 
secondary  coil,  then  the  following  phenomena  will 
occur: 

(i.)  When  the  primary  coil  is  moved  toward 
the  secondary  coil  an  inverse  current  is  induced 
in  the  secondary ;  and, 

(2  )  When  the  primary  coil  is  moved  away  from 
the  secondary  coil  a  direct  current  is  induced  in 
the  secondary. 

The  movements  of  permanent  magnets  towards 
or  from  a  coil  will  also  produce  an  induced  cur- 
rent. 

If,  for  example,  the  apparatus  be  arranged  as 
in  Fig.  302,  then: 


These  facts  may  be  expressed  by  the  following 
laws  : 
(i.)  Any  increase  in  thenumber  of  lines  of  force 


Fig,  301.    Electro- Dynamic  Induction. 

(i.)  A  motion  of  the  magnet  towards  the  coil 
produces  an  induced  current  in  the  coil  in  one 
direction,  and 

(2.)  Its  motion  away  from  the  magnet  produces 
an  induced  current  in  the  coil  in  the  opposite 
direction. 

The  directions  of  these  induced  currents  are 
respectively  inverse  and  direct  as  compared  with 
the  direction  of  the  amperian  currents  which  are 
assumed  to  produce  the  magnetic  poles  of  perma- 
nent magnets,  or  of  the  currents  that  actually 
produce  electro-magnets.  (See  Magnetism,  Am- 
p$re's  Theory  of.} 


Fig.  302.    Magneto-Electric  Induction. 

which  pass  through  a  circuit  produces  an  inverse 
current  in  that  circuit,  while  any  decrease  in  the 
number  of  such  lines  of  force  which  pass  through 
any  circuit  produces  a  direct  current  in  that 
circuit. 


Fleming's  Rule. 


(2.)  The  intensity  of  the  induced  current,  or, 
more  correctly,  the  difference  of  potential  pro- 
duced, is  proportional  to  the  rate  of  increase  or 
decrease  of  the  lines  of  force  passing  through  the 
circuit. 

A  conductor,  therefore,  when  moved  through 


283 


[ind. 


a  magnetic  field  so  as  to  cut  the  lines  of  magnetic 
force,  will  have  a  difference  of  potential  generated, 
and  if  its  circuit  is  closed  so  that  the  difference  of 
potential  can  neutralize  itself,  it  will  have  a  cur- 
rent produced  in  it  by  induction. 

A  simple  but  effective  manner  of  remembering 
the  direction  of  such  currents  is  that  proposed  by 
Fleming. 

If  the  hand  be  held  with  the  fingers  extended, 
as  in  Fig.  303,  and  the  direction  of  the  forefinger 
represent  the  positive  direction  of  the  lines  of 
force,  i.  e.,  those  coming  out  of  the  N.  pole  of  a 
magnet,  then,  if  a  wire  or  other  conductor  be 
moved  in  the  direction  in  which  the  thumb  points, 
so  as  to  cut  these  lines  of  force  at  right  angles, 
that  is,  if  the  conductor  have  its  length  moved 
directly  across  these  lines,  it  will  have  an  induced 
current  developed  in  it  in  the  direction  in  which 
the  middle  finger  points.  (See  Force,  Lines  of, 
Direction  of.) 

Or,  the  same  thing  can,  perhaps,  be  even  more 
readily    remembered  by 
cutting  a  piece  of  paper 
In  the   shape  shown  in  v.  § 
Fig.  304,  marking  it  as  a  | 
shown,  and  then  bending  +3  "g 
the  arm  P,  upward  at  the  Jj  $ 
dotted  line,  so  as  to  form  Q  p 
three  axes  at  right  angles 
to  one  another.  ,_ 

As  has  been  already  c  -g 
remarked,  a  difference  of  g  £ 
potential,  and  not  a  cur-  8  § 
rent,  is  produced  by  mov- 
ing  a  conductor  through 
a  magnetic  field  so  as  to 
cut  its  lines  of  force. 


Direction  of 
Motion. 


c 
304- 


.  . 

Fleming's  Rule. 


It  can  be  shown  that  in  order  to  generate  a  dif- 
ference of  potential  of  one  volt,  100,000,000  C.  G. 
S.  lines  of  force  must  be  cut  per  second. 

In  electro-dynamic  induction,  the  induced  cur- 
rent is  produced  by  the  energy  absorbed  in  moving 
the  conductor  through  the  magnetic  field.  Lenz 
has  shown  that  in  all  cases  of  electro-dynamic 
induction,  produced  by  the  movement  either  of 
the  circuit  or  of  the  magnet,  the  current  induced 
in  the  circuit  is  in  such  a  direction  as  to  produce 
a  magnet  pole  which  would  tend  to  oppose  the 
motion. 

Induction,    Electro-Magnetic  --  A 

variety  of  electro-dynamic  induction  in  which 
electric  currents  are  produced  by  the  motion 
10—  Vol.  1 


of  electro-magnets  or  electro-magnetic  sole- 
noids. (See  Induction,  Electro-Dynamic^} 

Induction,  Electrostatic The  pro- 
duction of  an  electric  charge  in  a  conductor 
brought  into  an  electrostatic  field. 

If  the  insulated  conductor  A  B,  Fig.  305,  be 
brought  into  the  positive  electrostatic  field  of  the 
insulated  conductor  C,  then, 

(I.)  A  charge  will  be  produced  on  A  and  B,  as 
will  be  indicated  by  the  divergence  of  the  pith 
balls. 

(2.)  This  charge  is  negative  at  the  end  A, 
nearest  C,  and  positive  at  the  end  B,  furthest 
from  C,  as  canbesho\\n  by  sen  electroscope.  (See. 
Electroscope. ) 


B 


Fig.  3  OS      Electrostatic  Induction. 


(3.)  The  charges  at  A  and  B,  are  equal  to  each 
other  ;  for,  if  the  conductor  A  B,  be  removed  from 
the  field  of  C,  without  touching  it,  the  opposite 
charges  completely  neutralize  each  other. 

(4.)  If,  however,  the  conductor  A  B,  be  touched 
at  any  place  by  a  conductor  connected  with  the 
earth,  it  will  lose  its  positive  charge,  and  will 
remain  negatively  charged  when  removed  fron? 
the  field  of  C.  It  is  in  this  manner  that  an  electro- 
phorus  is  charged.  (See  Electrophonis. ) 

(5.)  The  amount  of  the  charges  produced  in  the 
conductor,  A  B,  can  never  be  greater  than  that 
in  the  inducing  body  C.  That  is  to  say,  »be 


Fig.  $06.    Induction  Precedes  Attraction. 

negative  electricity  at  A,  may  be  sufficient  in 
amount  to  neutralize  the  positive  charge  on  C,  if 
allowed  to  do  so.  la  point  of  fact  the  charge  in- 


Ind.] 


284 


[Ind. 


duced  is  less  in  amount  than  the  inducing  charge, 
according  to  the  distance  between  C  and  A,  and 
the  nature  and  condition  of  the  medium  which 
separates  them. 

The  attraction?  of  light  bodies  by  charged  sur- 
faces are  due  to  the  opposite  charge  produced  on 
those  parts  of  th;  light  bodies  that  are  nearest  the 
charged  body 

The  pith  ball  B,  Fig.  306,  suspended  by  a  silk 
thread  between  an  insulated  positively  charged 
conductor  A,  and  the  uninsulated  conductor  C, 
will  receive  by  induction  a  negative  charge  on 
the  side  nearest  A,  and  a  positive  charge  on  the 
side  nearest  C.  It  is  therefore  attracted  to  A, 
where,  receiving  a  positive  cnarge,  it  is  repelled  to 
C,  where  it  is  discharged  and  again  assumes  a 
vertical  position.  Induction  again  occurs,  and 
consequent  attraction  and  repulsion.  These 
movements  follow  one  another  so  long  as  a  suffi- 
cient charge  remains  in  A. 

Induction,    Faradic,    Apparatus 

(See  Apparatus,  Faradic  Induction?) 

Induction-Finder. — (See  Finder,  Induc- 
tion^ 

Induction,  Lateral An  induction 

observed  between  closely  approached  portions 
of  a  circuit  through  which  an  impulsive  dis- 
charge, such  as  the  disruptive  discharge  of  a 
Leyden  jar,  is  passed  as  a  long  spark,  thereby 
making  the  resistance  of  the  circuit  high. 

A  long  copper  wire,  bent  in  the  form  of  a  rec- 
tangle, has  its  free  ends  near  their  extremities 
bent  so  as  to  approach  within  half  an  inch  of  each 
other.  One  of  the  ends  of  the  wire  is  provided 
with  a  metallic  ball  and  the  other  end  connected 
with  the  earth.  If,  now,  a  Leyden  jar  charge  is 
passed  through  the  wire  by  connecting  the  outer 
coating  with  the  end  of  the  earth-connected  wire 
and  holding  the  inside  coating  near  the  knob,  a 
spark  will  pass  through  the  half  inch  of  space  be- 
tween the  approached  portions  of  the  circuit. 

This  discharge  is  due  to  what  was  formerly 
called  lateral  induction.  The  discharge  of  a 
Leyden  jar  is  an  oscillatory  discharge,  and  it 
passes  through  the  intervening  air  space  instead 
of  through  the  conductor  because  the  resistance 
of  the  latter  to  the  rapid  alternations  produces  a 
counter  electromotive  force  which  acts  as  a  re- 
sistance whose  value  is  greater  than  that  of  the 
airspace  itself.  (See  Path,  Alternative.) 


Induction,  Magnetic The  produc- 
tion of  magnetism  in  a  magnetizable  substance 
by  bringing  it  into  a  magnetic  field. 

Suppose  a  small  portion  of  a  magnetizable  body 
is  placed  in  a  magnetic  field  produced  in  a  gap 
separating  two  closely  approximated  poles.  To 
simplify  matters,  suppose  this  small  portion  to  be 
a  free  unit  pole.  It  will  be  acted  on  by  two 
forces: 

(i.)  The  force  due  to  the  magnetic  field. 

(2.)  The  force  dae  to  the  free  magnetism, 
which  appears  at  the  surface  of  the  gap  or  cut. 

The  force  on  the  unit  pole  is  compounded  of 
these  two  separate  forces,  and  is  called  the  magnetic 
induction  of  the  space.  Magnetic  induction  is, 
therefore,  strictly  speaking,  a  quantity. 

The  direction  of  magnetic  force  and  the  mag- 
netic induction  are  the  same  in  an  air  space  out- 
side a  magnet.  Within  a  bar  of  iron  or  other 
paramagnetic  material,  under  induction  in  a  mag- 
netic field,  the  magnetic  force  at  any  point  is  due 
not  only  to  the  external  or  original  field,  but  also 
to  the  field  produced  by  the  polarity  induced, 
which  acts  opposed  to  the  magnetic  force  at 
points.  Magnetic  force  and  magnetic  induction 
are  identical  only  where  there  is  no  magnetism.— 
{Fleming.) 

When  a  magnetizable  body  is  brought  into  a 
magnetic  field  the  following  phenomena  occur, 
viz.: 

(i.)  The  lines  of  magnetic  force  pass  through 
the  body  and  are  condensed  upon  it.  (See  Field, 
Magnetic.  Paramagnetic. ) 

(2.)  If  the  body  is  free  to  move  around  an  axis, 
but  is  not  free  to  move  bodily  towards  the  magnet 
pole,  it  will  come  to  rest  with  its  greatest  extent 
or  length  in  the  direction  ol  the  lines  of  force; 
*'.  e.,  in  the  direction  in  which  it  will  offer  the 
least  resistance  to  the  lines  oJ  force  that  thread 
through  it. 

(3. )  The  body  will  therefore  become  a  magnet, 
its  south  pole  being  situated  where  the  lines  of 
force  enter  it  and  its  north  pole  where  they  pass 
out  from  it.  Since  the  lines  of  magnetic  force 
are  assumed  to  come  out  of  the  north  pole  of  a 
magnet  and  to  enter  its  south  pole,  if  a  magnet- 
izable substance  is  brought  near  a  north  pole, 
the  lines  of  force  from  that  north  pole  will  enter 
it  at  those  parts  nearest  such  north  pole,  thereby 
rendering  such  points  south,  and  will  pass  out  of 
its  further  end,  which  will  thereby  become  north. 

(4.)  The  Intensity  of  the  induced  magnetisrrt 


End.] 

/ 

jyill  depend  on  the  number  of  lines  of  force  that 
pass  through  it. 

(5.)  The  direction  of  the  axis  of  magnetization 
will  depend  on  the  directions  in  which  the  lines 
of  force  thread  through  the  body.  (See  Axis, 
Magnetic.] 


285 


[Iiirt. 


N  S         N' 

Fig.  307,    Magnetic  Induction. 

If  a  bar  of  iron,  N'  S  ,Fij.  307,  be  brought  near 
the  magnetized  bar,  N  S,  poles  will  be  produced 
in  it  by  induction,  as  may  be  shown  by  throwing 
iron  filings  on  it. 

The  nearer  the  body  to  Demagnetized  is  brought 
to  the  magnetizing  pole  the  greater  will  bo  the 
number  of  lines  of  torce  that  thread  through  it. 
Consequently,  the  intensity  of  the  induced  mag- 
netism will  be  greater  ;  this  will  be  greatest  when 
the  bodies  actually  touch  each  other. 

The  production  of  magnetism,  therefore,  by 
contact  or  touch  is  only  a  special  case  of  the  pro- 
duction of  magnetization  by  induction. 

The  attraction  of  a  magnetizable  body  by  a 
magnet  pole  is  caused  by  the  mutual  attraction 
which  exists  between  the  pole  produced  by  induc- 
tion and  the  pole  producing  the  induction.  This, 
it  will  be  seen,  is  similar  to  the  attraction  caused 
by  an  electric  charge. 

The  following  terms  are  given  by  Fleming  as 
employed  in  the  same  sense  as  magnetic  induc- 
tion of  an  area: 

(i.)  The  number  of  unit  tubes  of  induction 
passing  through  the  area. 

(2.)  The  number  of  lines  of  force  (induction) 
passing  through  the  area..— (Faraday.) 

(3.)  The  total  magnetic  induction  through  the 
area. —  {Maxwell. ) 

(4.)  The  flux  or  flow  of  magnetic  induction 
through  an  area. — (Mascart  &*  Joubert.} 

(5.)  The  surface-integral  of  magnetic  induction 
over  an  area.  —  {Fleming. ) 

Induction,  Magnetic,  Apparent  Co-effi- 
cient of The  co-efficient  of  induction 

as  influenced  by  the  presence  of  eddy  cur- 
rents. 

This  is-  called  the  co-efficient  of  apparent  in- 
duction, because  its  value  is  not  the  same  as  it 
would  be  if  the  eddy  currents  were  entirely  sup- 
Dressed 


The  value  of  the  co-efficient  of  apparent  induc- 
tion depends  on  the  amount  of  the  retardation  of 
the  magnetism;  or,  what  is  the  same  thing,  on 
the  strength  of  the  eddy  currents. 

Induction,  Magnetic,  Co-efficient  of 

— A  term  sometimes  used  instead  of  magnetic 
permeability.  (See  Permeability,  Magnetic.} 

The  ratio  existing  between  the  number  of 
lines  of  magnetic  induction  that  pass  through 
any  area  of  cross-section  of  a  magnetic  cir- 
cuit and  the  magnetizing  force  producing 
such  induction. 

If  B,  equals  the  magnetic  induction,  or  the  num- 
ber of  lines  of  force  that  pass  through  any  area  of 
cross-section,  and  H,  equals  the  magnetizing  force, 
and  n,  equals  the  permeability,  or  the  co-efficient 
of  magnetic  induction ;  then, 
_B 
^~H° 

Induction,    Magnetic,    Dynamic • 

The  induction  which  takes  place  in  the  field 
of  a  magnet  whose  field  is  moving  as  regards 
the  body  in  which  induction  is  occurring. 

This  movement  of  the  field  may  be  attained, 

(i.)  By  the  movement  of  the  magnet. 

(2.)  By  the  movement  of  the  body  in  which 
induction  is  taking  place. 

(3.)  By  the  expansion  or  contraction  of  the  lines 
of  magnetic  force  produced  by  variations  of  the 
strength  of  the  magnetic  field;  or,  in  other  words, 
by  the  movement  of  the  field.  (See  Induction, 
Electro-Dynamic. ) 

Induction,   Magnetic,   Flux  or  Flow  of 

A  term  employed  in  the  same  sense 

as  the  magnetic  induction  which  takes  place 
through  any  given  area. 

The  flux  or  flow  of  magnetic  induction  is  equal 
to  the  magnitude  of  the  area  multiplied  by  the 
normal  induction  which  takes  place  in  one  unit 
of  that  area. 

Induction,   Magnetic,    Lines    of  — 

Lines  which  show  not  only  the  direction  in 
which  magnetic  induction  takes  place,  bul 
also  the  magnitude  of  the  induction. 

A  line  of  induction  may  be  regarded  as  a  line 
along  which  induction  takes  place,  or  as  the  axis 
of  a  tube  of  induction. 

This  term  is  often  loosely  used  for  lines  of  force. 

Induction.  Magnetic,  Static T>«? 


Ind.j 


286 


[Ind. 


induction  which  takes  place  in  the  field  of  a 
magnet  whose  field  is  stationary  as  regards 
the  body  in  which  induction  is  occurring. 

The  term  static  magnetic  induction  is  used  in 
contradistinction  to  dynamic  magnetic  induction 
which  occurs  in  a  moving  field.  (See  Induction^ 
Electro-Dynamic. } 

Induction,    Magnetic,    Surface-Integral 

of A  term  employed  in  the  same  sense 

as  the  magnetic  induction  which  takes  place 
over  a  given  area. 

Induction,  Magneto  -  Electric A 

variety  of  electro-dynamic  induction  in  which 
electric  currents  are  produced  by  the  motion 
of  permanent  magnets,  or  of  conductors  past 
permanent  magnets.  (See  Induction,  Elec- 
tro-Dynamic.} 

Induction,  Mutual Induction  pro- 
duced by  two  neighboring  circuits  on  each 
other  by  the  mutual  interaction  of  their  mag- 
netic fields.  (See  Induction,  Electro-Dy- 
namic. Currents,  Extra) 

Induction  produced  in  neighboring  charged 
conductors  by  the  mutual  interaction  of  their 
electrostatic  fields.  (See  Field,  Electro- 
static.} 

The  mutual  induction  of  two  conductors  or  cir- 
cuits, is  equal  to  the  ratio  of  the  induction  which 
takes  place  through  one  of  the  circuits,  to  the 
strength  of  current  in  the  other  circuit,  which  is 
producing  the  induction 

Induction,  Mutual,  Co-efflcient  of 

The  quantity  which  represents  the  number 
of  lines  of  force  which  are  common  to  or 
linked  in  with  two  circuits,  which  are  pro- 
ducing mutual  induction  on  each  other. 

The  maximum  value  the  co-efficient  of  mutual 
induction  can  have,  is  equal  to  the  square  root  of 
the  product  of  the  inductance  of  the  two  circuits, 
or  "1/L  X  N,  in  which  L  and  N,  are  the  constant 
co- efficients  of  self-induction  of  the  two  circuits. 

Induction,  Mutual,  Loops  of Loops 

or  lines  of  induction  produced  in  any  circuit 
by  variations  in  the  intensity  of  the  current 
flowing  in  a  neighboring  circuit. 

The  lines  of  induction  produced  by  a  circuit,  in 
which  a  current  of  electricity  is  flowing,  are 
closed  loops  or  circles  surrounding  the  circuit 
once  or  more.  The  wire  or  circuit  is  formed  by 


coiling  a  conductor  a  number  of  times  in  a  cir- 
cular coil,  and  this  circular  coil  is  placed  near 
another  coil  in  which  a  varying  current  is  flowing. 
As  the  lines  of  induction  grow  or  increase, 
ihey  cut  the  circular  coil,  forming  lines  of  induc- 
tion in  the  shape  of  loops,  a  number  of  whfch  pass 
around  it.  They  are  called  loops  of  mutual  in- 
duction. 

Induction,   Open-Circuit The  in 

duction  produced  in  an  open  circuit  by  means 
of  electric  pulses  in  neighboring  circuits. 

The  researches  of  Hertz  have  shown  that  when 
an  impulsive  discharge,  or  an  oscillatory  dis- 
charge, occurs,  an  induction  occurs  even  in  open 
circuited  conductors.  He  shows  that  these  induc- 
tive- effects  are  due  to  electro-magnetic  waves  or 
oscillations  set  up  in  the  surrounding  ether, 
which  are  propagated  through  free  ether  with  the 
velocity  of  light.  When  these  electro-magnetic 
waves  or  radiations  impinge  on  any  circuit,  if  it? 
dimensions  be  such  that  sympathetic  vibrations 
can  be  excited  therein,  such  vibrations  are  set  up 
and  cause  similar  phenomena  to  those  of  the  ex- 
citing cause,  viz.,  oscillatory  discharges  or  elec- 
tro-magnetic vibrations.  Hertz  calls  these  sym- 
pathetic circuits,  resonators,  from  their  resem- 
blance to  acoustic  resonators.  (See  Resonators, 
Electric.) 

Induction,  Oscillatory A  name 

sometimes  applied  to  open-circuit  induction. 
(See  Induction,  Open-Circuit) 

Induction,  Reflection  of A  term 

proposed  by  Fleming  to  express  an  action 
which  resembles  a  reflection  of  inductive 
power. 

The  coils  A  and  B,  Fig.  308,  are  arranged  as 


Fig.  308.     Reflaction  of  Induction* 

shown,  so  as  to  act  as  the  primary  and  secondary 
respectively  of  an  induction  coil,   and  are  placed 


Ind.] 


287 


[Inu 


conjugate  or  perpendicular  to  each  other.  (See 
Coils,  Conjugate.)  Therefore,  no  sounds  are 
heard  in  the  telephone  T,  when  the  current  is 
rapidly  reversed.  If,  however,  a  plate  of  copper, 
C,  is  placed  in  the  position  shown,  then  sounds 
are  heard  in  the  telephone.  The  action  here 
resembles  a  reflection  of  the  inductive  action  from 
A  to  B,  by  means  of  the  plate  C.  The  explana- 
tion is,  of  course,  simple.  Though  A,  can  exert 
no  action  on  B,  because  the  two  coils  are  conju- 
gate to  each  other,  yet  A,  can  produce  secondary 
currents  in  C ;  and  these  reacting  on  B,  produce 
tertiary  currents  in  C,  and,  therefore,  sounds  in 
the  telephone. 

Induction,  Self Induction  produced 

in  a  circuit  at  the  moment  of  starting  or  stop- 
ping the  currents  therein  by  the  induction  of 
the  current  on  itself.  (See  Currents,  Extra.) 

A  coil  having  unit  self-induction,  is  sometimes 
said  to  have  one  tube  of  induction,  or  line  of  force 
added  to  its  field  for  each  increase  of  one  unit  of 
current. 

Induction,  Self,  Absolute  Unit  of 

A  term  sometimes  employed  for  absolute  unit 
of  inductance.  (See  Inductance,  Absolute 
Unit  of.) 

Induction,  Self,  Ayrton  &  Perry's 
Standard  of A  standard  for  the  com- 
parison of  values  of  self-induction. 

The  standard  of  self-induction  of  Ayrton  & 
Perry  consists  of  three  bobbins  of  wire,  two  fixed 
and  one  movable.  The  movable  bobbin  is  so  ar- 
ranged as  to  be  capable  of  motion  through  1 80 
degrees  within  the  fixed  bobbins.  The  coils  are 
wound  on  the  surface  of  the  zone  of  a  sphere. 

This  apparatus  permits  of  the  ready  compari- 
son of  the  self-induction  in  different  circuits,  or  in 
the  same  circuit  under  different  conditions. 

Induction,  Self,  Co-efflcient  of — 

The  number  of  lines  of  force  the  current  would 
induce  or  enclose  in  itself  when  the  current 
flowing  through  it  is  equal  to  one  absolute 
unit. 

A  term  sometimes  employed  in  the  sense 
of  inductance  of  a  circuit. 

The  co-efficient  of  self-induction  is  defined  by 
Fleming  as  follows  :  "In  the  case  of  circuits  con- 
veying electric  currents,  which  are  wholly  made 
of  non-magnetic  material,  and  wholly  immersed 


in  a  medium  of  constant  magnetic  permeability, 
the  total  induction  through  the  circuit  per  unit  of 
current  flowing  in  that  circuit,  when  removed 
from  the  neighborhood  of  all  other  magnets  and 
circuits,  is  called  the  co-efficient  of  self-induction; 
otherwise  the  ratio  of  the  numerical  values  of  the 
electro -magnetic  momentum  of  such  circuit,  and 
the  current  flowing  in  it,  when  totally  removed 
from  all  other  currents  and  magnets,  is  the  nu- 
merical value  of  the  inductance  of  the  circuit. ' ' 

Since  the  magnetic  lines  due  to  a  current  in  a 
circuit  thread  through  the  convolutions  of  the  cir- 
cuit itself,  any  variation  in  the  current  induces 
a  difference  of  potential  in  the  circuit  itself,  since 
the  lines  of  force  produced  by  the  current  in  the 
circuit  pass  through  or  cut  the  circuit. 

The  ratio  between  this  self-induced  electromo- 
tive force,  and  the  rate  of  change  in  the  current 
which  causes  it,  is  called  the  co-efficient  of  self- 
induction.-  (S.  P.  Thompson.) 

For  a  given  coil  the  co-efficient  of  self-induction 
is,  according  to  S.  P.  Thompson  : 

(i.)  Proportional  to  the  square  of  the  number 
of  convolutions. 

(2.)  Is  increased  by  the  use  of  an  iron  core. 
•  (3.)  If  the  magnetic  permeability  is  assumed  as 
constant,  the  co-efficient  of  self-induction  is  nu- 
merically equal  to  the  product  of  the  number  of 
lines  of  magnetic  force  due  to  the  current,  and 
the  number  of  times  they  are  enclosed  by  the 
circuit. 

Induction,  Self,  Magnetic A  re- 
tardation in  the  appearance  of  magnetization, 
after  the  application  of  the  magnetizing  force, 
due  to  the  influence  of  the  magnetic  lag. 

Magnetic  retardation. 

This  retardation  in  the  magnetization  has  re- 
ceived the  name  of  magnetic  self-induction  or  re- 
tardation because  it  corresponds  to  the  retarda- 
tion in  the  starting  or  stopping  of  a  current,  in  a 
conducting  circuit,  due  to  the  self-induction  of  thfe 
current. 

Induction,  Self,  Unit  of The  unit 

of  inductance.  (See  Inductance,  Unit  of.) 

The  unit  of  self-induction  is  now  generally 
called  the  unit  of  inductance. 

Induction,    Symmetrical,  of  Armature 

An  induction  produced  by  the  simul- 
taneous passage  of  the  same  number  of  lines 
of  magnetic  force  through  adjoining  halves  of 
the  armature. 


Ind.] 


288 


find. 


Induction  Telegraphy,  Current  Induc- 
tion System  of —(See  Telegraphy,  In- 
duction, Current  Induction  System  of.) 

Induction  Telegraphy,  Static  Induction 
System  of —(See  Telegraphy,  Induc- 
tion, Static  Induction  System  of.) 

Induction  Top. — (See  Top,  Induction.) 

Induction,  Total  Magnetic  —The 

total  magnetic  induction  of  any  space  is  the 
number  of  lines  of  magnetic  induction  which 
pass  through  that  space,  where  the  magnetiz- 
able material  is  placed,  together  with  the  lines 
added  by  the  magnetization  of  the  magnetic 
material. 

Induction,  Tubes  of —A  portion  of 

a  magnetic  field  containing  a  number  of 
closely  contiguous  lines  of  induction  termi- 
nated by  equipotential  surfaces^  or  surfaces 
perpendicular  to  the  lines  of  induction. 

Tubes  of  induction  possess  the  following  char- 
acteristics : 

(I.)  The  product  of  a  normal  cross-section  of  a 
tube  and  the  mean  magnetic  induction  which 
takes  place  over  that  section  is  the  same  for  all 
tross-sections  of  the  tube.  In  other  words,  the 
flux  or  flow  of  induction  is  constant  throughout 
the  entire  length  of  the  tube. 

(2.)  The  normal  cross-section  of  any  equipoten- 
tial surface  at  any  point  of  a  tube  of  induction  is 
inversely  proportional  to  the  magnetic  induction 
at  that  point. 

(3.)  All  tubes  of  induction  form  endless  tubes. 
This  is  necessary,  since  all  lines  of  induction  form 
closed  circuits. 

(4.)  All  tubes  of  induction  may  be  expressed 
by  a  single  line  of  induction,  which,  in  the  case  of 
a  uniform  field,  occupies  the  centre  of  the  tube. 
(See  Force^  Tubes  of.) 

Induction,  Toltaic A  variety  of 

flectro-dynamic  induction  produced  by  cir- 
cuits on  themselves  or  on  neighboring  circuits. 

Mutual  induction.  (See  Induction,  Elec- 
tro-Dynamic.) 

This  kind  of  induction  is  usually  called  current 
induction. 

Induction,  Unipolar A  term  some- 
times applied  to  the  induction  that  occurs 
when  a  conductor  is  so  moved  through  a 


magnetic  field  as  to  continuously  cut  its  lines 
of  force. 

If  the  conducting  wire,  ABC,  Fig.  309,  be  n> 


3°9'  Unipolar  Induction. 
tated  (in  a  direction  toward  the  observer)  around 
the  pole  N,  of  a  magnet,  it  will  continuously  cut 
its  lines  of  magnetic  force  in  practically  the  same 
direction,  and  will  therefore  produce  a  difference 
of  potential  that  will  result  in  a  continuous  cur- 
rent in  the  direction  of  the  arrows.  The  end  A, 
is  supported  in  a  recess  in  N,  while  the  end  near 
C,  slides  on  a  projection  on  the  middle  of  the 
magnet. 

Unipolar  induction  occurs  in  the  case  of  Stur- 
geon's wheel,  in  which  a  metallic  disc  mounted 
on  an  axis  is  rotated  between  the  poles  of  a  mag- 
net so  as  to  cut  the  lines  of  magnetic  force.  In 
this  case  a  difference  of  potential  is  generated 
which  will  produce  a  current  that  flows  from  the 
axis  to  the  periphery,  provided  contact  points  are 
placed  on  the  axis  of  rotation  and  the  periphery 
of  the  disc  connecting  these  parts  of  the  disc  in  a 
closed  circuit. 

Unipolar  dynamos  operate  by  the  continuous 
cutting  of  lines  of  magnetic  force. 

Strictly  speaking,  there  is  no  such-  thing  as  a 
unipolar  dynamo  or  unipolar  induction,  since  a 
single  magnetic  pole  cannot  exist  by  itself.  Con- 
tinuous cutting  of  lines  of  magnetic  force,  how- 
over,  can  exist,  and  produces,  unuke  the  ordinary 
bipolar  induction,  a  continuous  current  without 
the  use  of  a  commutator. 

Inductionless  Resistance.  — (See  Resist- 
ance, Inductionless.) 

Inductive  Capacity,  Specific (See 

Capacity,  Specific  Inductive!) 

Inductive  Circuit.— (See  Circuit,  Indue* 
five.) 


289 


Inducwre  Electromotive  Force. — (See 
Force,  Electromotive.  Inductive.) 

Inductive  Retardation.— (See  Retarda- 
tion, Inductive.} 

Inductive  Resistance.— (See  Resistance, 

Inductive.) 

Inductinty,  Specific  Magnetic 

A  term  sometimes  employed  for  specific  mag- 
netic conductivity.  (See  Conductivity,  Spe- 
cific Magnetic?) 

Inductometer,    Differential An 

apparatus  for  measuring,  by  means  of  a  gal- 
vanometer, the  momentary  currents  produced 
by  the  discharge  of  a  cable. 

Currents  produced  by  the  discharge  of  a  cable 
are  of  so  short  a  duration  that  they  do  not  pro- 
duce  much  more  than  a  momentary  effect  on  a 
galvanometer  needle. 

The  inductive  charge  in  a  cable,  or  the  quan- 
tity of  electricity  produced  in  it  by  induction,  is: 

(i.)  Directly  as  the  electromotive  force  of  the 
charging  battery; 

(2.)  Inversely  as  the  square  root  of  the  thick- 
ness of  the  coating  of  gutta-percha  or  other  insu- 
lating material  between  the  conducting  wires  and, 
the  metallic  sheathing; 

(3.)  Directly  as  the  square  root  of  the  diameter 
of  the  copper  wire  of  the  conductor;  and 

(4. )  Dependent  on  the  specific  inductive  capa- 
city of  the  insulating  material  employed  in  the 
cable. 

In  order  to  cause  the  cable  discharge  to  more 
thoroughly  affect  the  galvanometer  needle,  Mr. 
Latimer  Clark  employed  a  differential  instrument 
with  a  large  battery  and  three  reversing  keys,  by 
means  of  which  he  gave  a  rapid  succession  of 
charges  to  the  cable.  He  called  the  instrument  a 
Differential  Inductometer. 

Indnctophone  — A  device,  suggested  by 
Mr.  Willoughby  Smith,  for  obtaining  electric 
communication  between  moving  trains  and 
fixed  stations  by  means  of  the  currents  devel- 
oped by  induction  in  a  spiral  of  wire  fixed  on 
the  moving  engine,  by  its  motion  past  spirals 
on  the  line,  into  which  intermittent  currents 
are  passed. 

Tne  spiral  on  the  engine  is  placed  in  the  circuit 
of  a  telephone.  (See  Teletrrat>}'  .  /  ductive.\ 


Inductor  Dynamo. — (See  Dynamo,  Indue* 
tor.) 

Indnctorium. — A  name  sometimes  applied 
trt  a  Ruhmkorff  induction  coil.  (See  Coil, 
Induction.) 

Inequality,  Annual,  of  Earth's  Magnetic 

Variation    or  Inclination Annual 

variations  in  the  value  of  the  magnetic  varia- 
tion or  inclination  at  any  place.  (See  Varia- 
tion, Magnetic.  Inclination,  Magnetic.) 

Inequality,  Annual,  of  Earth's  Magnet- 
ism   Variations  in  the  value  of  the 

earth's  magnetism  during  the  earth's  revolu- 
tion depending  on  the  position  of  the  sun. 

Annual  variations  in  the  earth's  magnetism. 
(See  Variations,  Magnetic,  Annual.) 

Inequality,  Diurnal,  of  Earth's  Magnetic 

Variation  or  Inclination Diurnal 

variations  in  the  value  of  the  earth's  magnetic 
variation  or  inclination.  (See  Variation, 
Magnetic.  Inclination,  Magnetic.) 

Inequality,  Diurnal,  of  Earth's  Magnet- 
ism   Inequalities  or  variations  in  the 

value  of  the  earth's  magnetism,  dependent  on 
the  position  of  the  sun  during  Jhe  earth's 
rotation. 

Inequality,  Lunar,  of  Earth's  Magnetic 
Variation  or  Inclination  -  —Small  va- 
riations in  the  value  of  the  magnetic  variation 
or  inclination,  dependent  on  the  position  of 
the  moon  as  regards  the  magnetic  meridian. 

Inequality,  Lunar,  of  Earth's  Magnet- 
ism   Small  variations  in  the  value  of 

the  earth's  magnetism  dependent  on  the  po- 
sition of  the  moon  as  regards  the  magnetic 
meridian. 

Inertia. — The  inability  of  a  body  to  change 
its  condition  of  rest  or  motion,  unless  some 
force  acts  on  it. 

The  inertia  of  matter  is  expressed  in  Newton's 
first  law  of  motion,  as  follows  •• 

"Every  body  tends  to  preserve  its  state  of  rest 
or  of  uniform  motion  in  a  straight  line,  except  in 
so  far  as  it  is  acted  on  by  an  impressed  force." 

All  matter  possesses  inertia. 

Inertia,  Electric  —  —A  term  some- 
times employed  instead  of  electro-magnetic 
inertia.  (See  Inertia,  Electro-Magnetic.) 


Ine.J 


290 


[Ins. 


A  term  employed  to  indrate  the  tendency 
of  a  current  to  resist  its  stopping  or  starting. 

By  self-induction  an  electromotive  force  is  pro- 
duced in  a  wire  or  other  conductor  at  the  moment 
of  starting  the  current  in  it  that  tends  to  oppose 
the  starting  of  such  current,  and  also  an  electro- 
motive force  at  the  moment  of  stopping  the  cur- 
rent, in  such  a  direction  as  to  prolong  or  continue 
the  current.  In  other  words,  self-induction  tends 
to  retard  the  rise  or  fall  of  the  current. 

Fleming  traces  the  following  comparison  be- 
tween the  moment  of  inertia  of  a  rotating  wheel 
and  the  energy  of  its  rotation  on  the  one  side,  and 
the  inductance  of  a  circuit  and  the  electro-mag- 
netic energy  of  the  circuit  on  the  other. 

(i.)  The  angular  momentum  of  a  fly-wheel  is 
equal  to  the  numerical  product  of  its  moment  of 
inertia  and  the  angular  velocity  of  the  wheel. 
Similarly  the  electro-magnetic  momentum  is  equal 
to  the  product  of  the  inductance  of  the  circuit  by 
the  current  flowing  through  it  at  any  instant. 

(2.)  The  rate  of  change  of  the  angular  mo- 
mentum of  the  wheel,  at  any  instant,  is  a  measure 
of  the  rotational  force  of  the  couple  acting  at  that 
instant. 

Similarly  the  rate  of  change  of  the  electro-mag- 
netic momentum  of  the  circuit  is  the  measure  of 
the  electromotive  force  acting  on  it  so  far  as 
mere  change  of  current  is  concerned,  and  irre- 
spective of  that  part  of  the  electromotive  force  re- 
quired to  overcome  the  ohmic  resistance. 

An  electric  current  does  not  start  or  stop  in- 
stantaneously. It  requires  time  to  do  either,  just 
as  a  stream  of  water  or  other  fluid  does,  and  it  is 
this  property  which  is  referred  to  by  the  term 
electric  inertia.  Inertia  does  not  appear  to  be 
possessed  by  electricity  apart  from  matter.  « '  It 
is  doubtful,"  says  Lodge,  "whether  electricity 
of  itself,  and  disconnected  from  matter,  has  any 
inertia." 

Inertia,  Electro-Magnetic A  term 

sometimes  employed  instead  of  inductance, 
or  the  self-induction  of  a  current.  (See  In- 
ductance. Inertia,  Electric?) 

Inertia,  Electro-Magnetic,  Co-efflcient  of 

A  term  sometimes  employed  in  place 

of  the  co-efficient  of  inductance  or  self-induct- 
ance of  a  circuit. 

Inertia,  Magnetic The  inability  of 

a  magnetic  core  to  instantly  lose  or  acquire 
magnetism. 


A  magnet  core  tends  to  continue  in  the  mag. 
netic  state  in  which  it  was  placed. 

The  magnetic  inertia  is  sometimes  called  the 
magnetic  lag. 

To  decrease  the  magnetic  inertia,  the  strength 
of  the  magnetizing  current  is  increased  and  the 
length  of  the  iron  core  decreased.  The  iron 
should  also  be  quite  soft.  (See  Lag,  Magnetic. 
Force,  Coercive.') 

Inferred  Zero.— (See  Zero,  Inferred) 

Infinity  Plug.— (See  Plug,  Infinity.) 

Influence. — A  term  sometimes  used  instead 
of  electrostatic  induction.  (See  Induction, 
Electrostatic) 

.The  word  influence  is  used  by  some  to  apply 
to  the  case  of  electrostatic  induction,  as  distin- 
guished from  electro-magnetic  or  magnetic  induc- 
tion. 

Influence  Charge. — (See  Charge,  Influ- 
ence) 

Influence  Machine. — (See  Machine,  In- 
fluence) 

Inker,  Morse A  form  of  tele- 
graphic ink-writer.  (See  Ink-  Writer,  Tele- 
graphic) 

Ink- Writer,  Telegraphic —A  device 

employed  for  recording  the  dots  and  dashes 
of  a  telegraphic  message  in  ink  on  a  fillet  or 
strip  of  paper. 

A  telegraphic  ink-writer  is  a  form  of  telegraphic 
recorder.  (See  Recorder,  Morse.) 

Inside  Wiring.— (See  Wiring,  Inside) 

Insolation,  Electric A  term  some- 
times employed  for  electric  sunstroke,  or 
electric  prostration.  (See  Sunstroke,  Elec- 
tric. Prostration,  Electric) 

Installation. — A  term  embracing  the 
entire  plant  and  its  accessories  required  to 
perform  any  specified  work. 

The  act  of  placing,  arranging  or  erecting 
a  plant  or  apparatus. 

Installation,  Electric The  estab- 
lishment of  any  electric  plant. 

An  electric  light  installation,  for  example,  in- 
cludes the  steam  engine  and  boilers,  or  other 
prime  movers,  the  dynamo-electric  machines,  the 
line  wires  or  leads,  and  the  lamps. 

Insulated  Body.— (See  Body,  Insulated^ 


ins.] 


291 


fins. 


Insulating-  Cements. — (See  Cements,  In- 
sulating^ 

Insulating  Sleere. — (See  Sleeve,  Insula- 
ting) 

Insulating  Stool. — (See  Stool,  Insula- 
ting) 

Insulating  Tape. — (See  Tape,  Insula- 
ting) 

Insulating  Tube. — (See  Tube,  Insula- 
ting) 

Insulating  Varnish. — (See  Varnish,  Elec- 
tric) 

Insulation,  Electric •  — Non-conduct- 
ing material  so  placed  with  respect  to  a  cori- 
ductor  as  to  prevent  the  loss  of  a  charge,  or 
the  leakage  of  a  current. 

In  the  case  of  coils  the  character  of  the  insula- 
tion of  the  coil  of  wires  through  which  the  cur- 
rent is  to  pass  must  be  considered  from  the  stand- 
point of  the  cooling  of  the  coil  by  radiation. 

In  considering  the  safest  and  most  economical 
current  density  to  employ  in  any  dynamo  or 
motor,  the  depth  of  the  coil,  i.  e.,  the  thickness  of 
its  coils,  must  be  considered,  as  well  as  the  char- 
acter of  the  materials  employed  for  the  insulation. 
Such  substances  as  silk  or  wool,  which  are  char- 
acterized by  low  heat  conduction,  retain  the  heat 
longer  than  cotton.  Hence  the  depth  of  a  silk 
covered  coil  should  necessarily  bele^s  than  that  of 
one  covered  with  cotton. 

Insulation  Joint. — (See  Joint,  Insula- 
tion.} 

Insulatian,  Porons  — —  — An  insulating 
material  containing  air  or  gas  placed  between 
the  conductor  and  the  insulating  covering. 

A  strip  of  perforated  paper  is  used  for  cover- 
ing the  bare  conductor,  and  the  insulating  ma- 
terial is  placed  on  the  outside  of  this  ;  or,  a  cord 
is  wrapped  separately  around  Ae  conductor,  and 
the  insulating  material  is  placed  on  the  outside  of 
this.  By  these  means,  as  will  be  seen,  a  layer  of 
air  exists  between  the  conductor  and  its  insulating 
covering. 

Insulation  Resistance. — (See  Resistance, 
Insulation) 

Insulation,  Static A  term  em- 
ployed in  electro-therapeutics  for  a  method 
of  treatment  by  convection  stream0  or  dis- 


charges, in  which  the  patient  is  seated  on  an 
insulated  stool  connected  to  one  pole  or 
electrode  of  an  influence  marline,  while  the 
other  pole  or  electrode  is  connected  to  the 
ground. 
Insulator  Cap. — (See  Cap,  Insulator) 

Insulator,  Dice-Box A  name  some- 
times applied  to  a  double-cone  insulator.  (See 
Insulator,  Double-Cone) 

Insulator,  Double-Cone An  insu- 
lator in  which  the  line  wire  passes  through  and 
is  supported  by  means  of  a  tube  consisting  of 
two  inverted  cones  joined  at  their  smaller 
bases. 

Insulator,  Double-Cup — An  insula- 
tor consisting  of  two  funnel-shaped  cups, 
placed  in  an  inverted  position  on  the  sup- 
porting pin  and  insulated  from  one  another 
by  a  free  air  space,  except  near  the  ends, 
which  are  cemented. 

The  wire  is  wrapped  in  a  groove  on  the  outside 
of  the  outer  cup.  This  possesses  the  advantage 
of  exposing  it  to  the  rain,  which  thus  cleanses  the 
insulator  and  improves  its  power  of  insulation. 
The  inner  cup  is  supported  on  a  pin  and  the  outer 
cup  cemented  to  it.  Any  leakage  must,  there- 
fore,  pass  over  the  entire  surface  of  both  cups. 

Insulator,  Double-Shackle A  form 

of  insulator  used  in  shackling  a  wire,  consist- 
ing of  two  single-shackle  insulators. 

Insulator,  Double-Shed A  double- 
cup  insulator.  (See  Insulator,  Double-Cup) 

Insulator,  Fluid An  insulator  pro- 
vided with  a  small,  internally  placed,  annular, 
cup-shaped  space,  filled  with  an  insulating 
oil,  thus  increasing  the  insulating  power  of  the 
support. 

The  line  wire  is  wrapped  in  a  groove  on  the 
outside  of  the  insulator.  Any  surface  leakage 
between  the  wire  and  ground  in  wet  weather 
must  occur  between  the  outer  surface  of  the  insu- 
lator, which  is  kept  cleansed  by  the  rain,  and  the 
inner  surface,  where  it  is  supported  by  the  pin. 
But  to  do  this,  the  current  must  cross  the  oil  in 
the  cup,  which,  from  its  high  power  of  insulation, 
effectually  prevents  leakage. 

Insulator,  Inrert   — An   insulator 


Ins.] 


292 


[Int 


placed  on  the  top  of  the  wire  instead  of  under- 
neath it,  as  was  formerly  done. 

Insulator,  Oil A  fluid  insulator 

filled  with  oil.  (See  Insulator,  Fluid.) 

Insulator  Pins.— (See  Pins,  Insulator.} 

Insulator,  Single-Shackle  —  —A  form 
of  insulator  used  for  shackling  a  wire.  (See 
Shackling  a  Wire.) 

Insulator,  Single-Shed  —  — An  insula- 
tor with  a  single  inverted  cup. 

The  wire  is  wrapped  around  a  groove  on  the 
outside  of  the  cup,  where  it  is  exposed  to  the 
cleansing  action  of  the  rain.  The  cup  is  inverted 
and  supported  on  a  pin,  to  which  it  is  screwed  and 
cemented. 

Insulator,  Telegraphic  or  Telephonic 
A  non-conducting  support  of  tele- 
graphic, telephonic,  electric  light  or  other 
wires. 

Insulators  are  generally  made  of  glass,  earthen- 


Fig,  3  to.     Glass 
Insulator. 


Fig.  311      Porcelain 

Insulator. 


ware,  porcelain  or  hard  rubber,  and  assume  a 
variety  of  forms,  some  of  which  are  shown  in  Figs. 
310,  31 1  and  312.  Of  whatever  material  they  are 
made,  it  is  necessary  that  the 
surface  on  which  the  wire  rests, 
or  around  which  it  is  wrapped, 
should  be  smooth,  so  as  to  avoid 
fbrasion,  either  of  its  insulat 
ing  covering  or  of  the  wire  it- 
self. 

Two  things  are  to  be  con 
sidered  in  the  selection  of  an 
insulator,  viz.; 

(i.)  The  insulating  power  of 
the  material  of  which  the  in- 
sulator is  composed,  so  as  to  Fig.  3x2.  Hard 
reduce  the  leakage  as  much  as  Rub!>er  Insulator. 
P0«sible.  (See  Leakage ;  Electric. \ 

(2.)  The   tensile  strength  of  the  material  so 


that  in  case  of  heavy  wires  no  breaks  may  result 
from  the  fracture  of  the  insulator. 

Some  forms  of  insulators  are  shown  in  Figs. 
310,311  and  312.  They  are  screwed  to  the  pins 
by  the  threads  shown.  The  insulating  materials 
of  which  they  are  tormed  are  of  glass,  porcelain 
and  hard  rubber  respectively. 

Insulator,  Window-Tube A  tube 

of  vulcanite  or  other  insulating  material  pro- 
vided for  the  insulation  of  a  wire  entering  a 
room. 

The  wire  conductor  passes  through  the  middle 
of  the  tube,  which  is  firmly  fixed  in  an  opening 
passing  through  the  window  frame. 

Insulator,  Z A  form  of  double- cup 

insulator  in  which  the  insulating  material, 
earthenware  or  porcelain,  is  made  in  a  single 
piece,  instead  of  in  two  separate  pieces. 

The  body  of  the  insulator  is  conical  in  form, 
and  the  interior  air  space  presents  a  shape  ap- 
proximately that  of  the  letter  Z. 

The  double  form  is  used  in  order  to  diminish 
the  leakage. 

Intensity  Armature.— (See  Armature, 
Intensity?) 

Intensity,  Connection  of  Toltaic  Cells  for 

A  term  formerly  employed  for  series- 
connected  voltaic  battery  cells.  (Obsolete.) 

Intensity,  Magnetic  — Density  of 

magnetic  induction. 

Magnetic  flux  per  square  centimetre. 

A  committee  of  the  American  Institute  of  Elec- 
trical Engineers  on  "Units  and  Standards,"  pro- 
poses the  following  definition  for  magnetic  inten- 
sity: 

The  induction  density  at  a  point  within  an  ele- 
ment of  surface  is  the  surface  differential  at  that 
point. 

The  practical  unit  of  magnetic  intensity  is 
to9  or  100,000,000  C.  G.  S.  lines  per  square  cen- 
timetre. 

In  practice,  excluding  the  earth's  field,  intensi- 
ties range  from  100  to  20,000  C.  G.  S.  lines  per 
square  centimetre,  and  the  working  unit  should, 
perhaps,  have  the  prefix  milli  or  micro. 

Intensity,  Magnetic,  Pole  of The 

earth's  magnetic  poles  as  determined  by 
means  of  the  osculations  of  a  magnetic 

need  e. 


lot,] 


293 


[loii. 


The  points  ot  the  earth's  greatest  magnetic 
intensity. 

Intensity  of  Current— (See  Current,  In- 
tensity of.} 

Intensity  of  Field.— (See  Field,  Inten- 
sity of.) 

Intensity  of  Light.— (See  Light,  Inten- 
sity of.} 

Intensity  of  Magnetization.— (Sec  Mag- 
netization, Intensity  of.} 

Intensity,  Photometric,  Unit  of - 

The  amount  of  light  produced  by  a  candle 
that  consumes  two  grains  of  spermaceti  wax 
per  minute.  (See  Candle.) 

Inter  Air  Space.— (See  Space.  Inter  Air.) 

Intercrossing. — In  a  system  of  telephonic 
communication,  a  device  for  avoiding  the  dis- 
turbing effects  of  induction  by  alternately 
crossing  equal  sections  of  the  line.  (See 
Connection,  Telephonic  Cross.) 

Interference  of  Electro-Magnetic 
Wares. — (See  Waves,  Electro-Magnetic, 
Interference  of.) 

Interlocking  Apparatus.— (See  Appa- 
ratus Interlocking.) 

Intermittent  Contact. — (See  Contact,  In- 
termittent.) 

Intermittent  Cross.— A  form  of  electnc 
cross.  (See  Cross.  Electric.) 

Intermittent  Current. — (See  Currant.  In- 
termittent.) 

Intermittent  Disconnection. — (S-*  Dis- 
connection, Intermittent ) 

Intermittent  Earth.— (See  Earth,  Inter- 
mittent.) 

Internal  Circuit.— (See  Circuit,  In- 
ternal.) 

internal  Polarization  of  Moist  Bodies.— 

'See  Polarization,  Internal,  of  Moist 
Bodies.) 

Interrupter. — Any  device  for  interrupting 
or  breaking  a  circuit. 

Interrupter,  Automatic An  auto- 
matic contact  breaker  (See  Make~and- 
Break.  Automatic.) 


Interrupter,  Reed A  term  some« 

times  applied  to  a  tuning-fork  interrupter. 
(See  Interrupter,  Tuning-Far k.) 

Interrupter,  Tuning-Fork An  in- 
terrupter in  which  the  successive  makes  and 
breaks  are  produced  by  the  vibrations  of  a 
tuning-fork  or  reed. 

The  tuning-fork  or  reed  is  maintained  in  vibra- 
tion by  any  suitable  means.  Such  interrupters 
are  applied  to  various  uses.  Synchronous  mul- 
tiplex telegraphy  affords  an  example  of  such  uses. 

Invariable  Calibration  of  Galvanometer 

— (See  Calibration,  Invariable,  of  Galva- 
nometer.) 

Inverse  Electromotive  Force.— (See  Force. 
Electromotive,  Inverse.) 

Inverse  or  Make-Induced  Current.— (See 

Current,  Make-Induced) 
Inverse  Secondary  Current— (See  Cur. 

rent,  Inverse  Secondarv^ 

Inversion,    Thermo-Electric —An 

inversion  of  the  thermo-electric  electromotive 
force  of  a  couple  at  certain  temperatures. 
(See  Diagram,  Thermo-Electric.) 

Invert  Insulator. — (See  insulator,  In- 
vert.) 

Inverted  Induction  Coil. —(See  Coil, 
Induction.  Inverted.) 

Inverted  Type  of  Dynamo.— (See  Dy- 
namo, Inverted) 

Invisible  Electric  Floor  Matting. — (See 

Matting,  Invisible  Electric  Floor.') 

Ions.— Groups  of  atoms  or  radicals  which 
result  frcra  the  electrolytic  decomposition  of 
a  molecule. 

The  iont  are  respectively  electro-positive  and 
electro-negative.  The  electro-positive  ion  ap- 
pears  at  the  plate  connected  with  the  tlectro- 
negative  terminal^  or  at  the  kathode,  and  is  called 
the  kaihion. 

The  electro-negative  ion  appears  at  the  plate 
connected  with  the  clearo-positive  teYminal^  01 
at  the  anodet  and  is  called  the  anion.  (See 
Electrolysis,  Kathion.  Anion.) 

Ions,  Electro-Negative The  neg«- 

ative  atoms,  or  groups  of  atoms,  called  rad- 
icals, into  which  the  molecule?  of  an  electro- 


lon.J 


[Iso. 


lyte  are  decomposed  by  electrolysis.    (See 
Electrolysis) 

The  electro-negative  ions  are  called  the  anions, 
because  they  appear  at  the  anode  of  a  decompo- 
sition cell.  (See  Anions.  Anode.) 


Ions,  Electro-Positive 


— The  pos- 


itive atoms,  or  groups  of  atoms,  called  rad- 
icals, into  which  the  molecules  of  an  electro- 
lyte are  decomposed  by  electrolysis.  (See 
Electrolysis.) 

The  electro-positive  ions  are  called  the  kathions, 
because  they  appear  at  the  kathode  of  a  decom- 
position cell.  (See  Kathion.  Kathode.) 

Iron-Clad  Electro-Magnet. — (See  Mag- 
net, Electro,  Iron-Clad?) 

Iron-Clad  Magnet.— (See  Magnet,  Iron- 
Clad) 

Iron  Core,  Effect  of,  on  the  Magnetic 
Strength  of  a  Hollow  Coil  of  Wire  - 

An  increase  in  the  number  of  lines  of  mag- 
netic force,  beyond  those  produced  by  the 
current  itself,  due  to  the  opening  out  of  the 
closed  magnetic  circuits  in  the  atoms  or 
molecules  of  the  iron. 

The  atoms  or  molecules  of  the  iron  possess 
naturally  closed  magnetic  circuits,  or  closed  lines 
of  magnetic  force,  lying  entirely  within  the  mass 
of  the  iron.  When  the  iron  is  placed  in  a  magnetic 
field,  these  minute  closed  circuits  open  out  and 
are  added  to  the  lines  of  force  produced  by  the 
circuit  itself.  The  opening  out  of  these  closed 
atomic  or  molecular  lines  of  magnetic  force  is  at- 
tended by  the  formation  of  lines  of  polarized 
molecules  or  atoms. 

Roughly  speaking,  according  to  Lodge,  for 
each  single  line  of  magnetic  force  produced  by  the 
electric  current,  there  are  some  3,000  lines  of 
magnetic  force  added  to  it  from  the  iron,  the  ex- 
act number  varying  with  the  kind  of  iron,  the 
physical  condition  of  the  iron  and  the  degree  of 
magnetization. 

Iron,  Galvanized Iron  covered  by 

a  layer  of  zinc  by  dipping  it  in  a  bath  of 
molten  zinc. 

The  process  of  galvanizing  iron  is  designed  to 
prevent  the  corrosion  or  rusting  of  the  iron  on 
exposure  to  the  air.  (See  Metals,  Electrical  Pro- 
tection of.) 

The  word  galvanized  probably  had  its  origin  in 


an  assumed  galvanic  or  voltaic  action,  in  causing 
the  zinc  to  adhere  to  the  iron.  The  true  galvanic 
or  voltaic  action,  viz.,  the  galvanic  protection, 
comes  after  the  galvanizing  process  is  completed. 

Iron-Work    Fault     of     Dynamo.— (See 

Fault,  Iron-  Work,  of  Dynamo) 

Irreversible  Heat. — (See  Heat,  Irreversi- 
ble) 

Irritability,  Electric Irritability 

of  nervous  or  muscular  tissue  by  an  electric 
discharge. 

Irritability,  Electric,  Diminished 

A  decreased  irritability  of  nervous  or  muscu- 
lar tissue,  produced  by  an  electric  current  of 
given  strength. 

Diminished  electric  irritability  is  often  present 
in  certain  diseases  of  the  motor  apparatus. 

Irritability,  Electric,  Increased  — 

An  irritability  of  nervous  or  muscular  tissue 
produced  by  a  much  weaker  electric  current 
than  that  required  to  produce  it  in  normal 
tissue. 

Irritability,  Faradic  —Muscular 

contractions  produced  by  the  action  of  a 
faradic  current  on  a  nerve. 

The  action  of  the  faradic  current  is  to  cause  a 
prolonged  tonic  contraction,  which  continues 
while  the  current  continues.  Though  the  natural 
action  is  to  produce  a  contraction,  followed  by  a 
relaxation  on  each  make  and  break,  yet  the  makes 
and  breaks  follow  one  another  so  rapidly  that  the 
relaxation  has  not  time  to  occur  before  the  next 
contraction  follows. 

Irritability,  Galvanic Muscular 

contractions  produced  by  the  action  of  a  gal- 
vanic current. 

The  action  of  a  galvanic  current  is  to  cause  a 
single,  quick,  momentary  contraction  of  a  muscle 
on  each  starting  or  completion  of  the  circuit. 

The  contractions  are  stronger  in  the  case  of 
galvanic  currents  when  the  direction  of  the  cur  - 
rent  is  reversed  with  a  commutator  instead  of  by 
an  actual  break  at  the  poles.  Such  a  break  is 
called  a  voltaic  alternative,  and  the  currents  so  pro- 
duced voltaic  alternatives.  (See  Alternative.-, 
Vo'.taic.) 

Isobaric  Lines. — (See  Lines,  Isobaric) 

Isobars. — Lines  connecting  places  on  the 


ISO.] 


295 


[Jar. 


earth's  surface  which  have  the  same  barome- 
tric pressure. 

The  isobaric  lines  are  generally  corrected  for 
iiSerences  of  elevation  of  the  surface. 

Isobars  are  often  called  isobaric  lines. 

A  study  of  the  isobaric  lines,  or  isobars,  is  of 
great  assistance  in  making  forecasts  or  predictions 
of  coming  changes  in  the  weather. 

Isocuasmen  Curves.— (See  Curves,  Iso- 
ckasmen?) 

ISOChronism. — Equality  of  time  of  vibra- 
tion or  motion. 

Isochronize. — To  produce  equality  of 
time  of  vibration  or  motion. — (See  Jsochron- 
zsm?) 

Isochronizing. — Producing  equality  of 
time  of  vibration  or  motion.  (See  Isochron- 
tsm.) 

Isochronous  Yibrations  or  Oscillations. 
—  (See  Vibrations  or  Oscillations,  Isochron- 
ous^ 

Isoclinic  Chart. — (See  Chart,  Inclina- 
tion^) 

Isoclinic  Lines. — (See  Lines,  Isoclinic?) 

Isodynamic  Chart. — (See  Chart,  Isody- 
namic?) 


Isodynamic    Lines. — (See  Lines,   Isody- 
namic?) 

Isodynamic    Map. — (See     Chart,    Isody- 
namic?) 

Iso-Electric    Points. — (See   Points,  Iso- 
Electric?) 

Isogonal. — Pertaining  to  the  isogonic  lines. 
Isogonal  lanes. — (See  Lines,  Isogonal.) 
Isogonal  Map  or  Chart— (See   Map  or 
Chart,  Isogonal?) 

Isogonic. — Pertaining  to  the  isogonal  lines. 
Isogonic  Chart — (See  Chart,  Isogonic?) 
Isogonic  Lines, — (See  Lines,  Isogonic?) 
Isogonic  Map.— (See  Map,  Isogonic?) 

Isolated  Electric  Lighting.— (See  Light- 
ing, Electric,  Isolated?) 

Isolatine. — A  kind  of  insulating  material. 
Isothermal  Surfaces. — (See  Surfaces,  Iso- 
thermal?) 

Isotropic    Conductor. — (See    Conductor, 
Isotropic?) 

Isotropic  Medium. — (See  Medium, 
tropic?) 


J.— A  contraction  proposed  for  Joule. 

Jablochkoff  Candle.— (See  Candle,  Jab- 
tochkoff.) 

Jacketed  Magnet. — (See  Magnet,  Jack- 
eted?) 

Jacobi's  Law. — (See  Law,Jacobi's?) 

Jar,  Electric  — A  name  formerly 

given  to  the  Leyden  jar. 

Jar,  Leyden A  condenser  in  the 

form  of  a  jar,  in  which  the  metallic  coatings 
are  placed  opposite  each  other  on  the  outside 
and  the  inside  of  the  jar  respectively. 

The  metal  coatings  should  not  extend  to  more 
than  two-thirds  of  the  height  of  the  jar,  the  rest 
of  the  glass  being  varnished  to  avoid  the  creeping 
of  the  charges  over  the  glass  in  damp  weather, 
i'hc  inside  coating  is  connected  by  means  of  a 


metallic  chain  to  a  knob  on  the  top  of  the  jar,  as 
shown  in  Fig.  313.  The  conductor  supporting 
the  knob  passes  through  a  dry  cork  or  plug  of 
some  insulating  material. 

To  charge  the  jar,  the  outside  coating  is  con- 
nected with  the  earth,  as 
by  holding  it  in  the  hand, 
and  the  outside  coating 
is  connected  with  the 
conductor  of  a  machine. 
(See  Condenser.  Accu- 
mu/jfor. ) 

The  inner  coating  of 
the  jar  is  usually  con- 
nected with  the  knob  by 
means  of  a  chain  or  wire  ***3*3. 
as  shown  above.  This  necessitates  a  support  for 
the  ball  and  stem,  which  is  generally  obtained  by 
a  cork  or  wooden  plug  inserted  in  the  mouth  of 


Jar.T 


296 


[Jet. 


the  jar.  Such  a  form,  however,  is  extremely  ob- 
jectionable, since,  although  the  top  of  the  jar  be 
Covered  with  shellac  varnish  to  avoid  leakage,  it 
affords  but  a  poor  insulation  in  damp  weather,  be- 
sause  both  the  metallic  rod  supporting  the  ball  and 


'fig,  3 1 4.0    Sir  William  Thomson's  Leyden  Jar. 

the  damp  wood  or  cork  are  in  connection  with  the 
glass  and  thus  facilitate  leakage. 

To  overcome  these  objections  a  form  of  jar  has 
been  devised  by  Sir  William  Thomson,  in  which  the 
knob  is  supported  on  three  feet,  which  rest  on  the 
inner  coating.  In  this  form  the  uncoated  glass 
can  be  readily  kept  dry  and  clean.  This  form  is 
shown  in  Fig.  314. 

A  layer  of  sulphuric  acid  is  sometimes  employed 
for  the  inner  coating  of  the  Leyden  jar.  This 
serves  the  double  purpose  of  acting  as  a  coating 
and  an  absorber  of  moisture  during  damp 
weather. 

Jar,    Leyden,    Capacity  of — The 

quantity  of  electricity  a  Leyden  jar  will  hold 
at  a  given  difference  of  potential. 

The  capacity  of  a  jar  is  equal  to  the  quantity 
of  electricity  divided  by  the  difference  of  potential 
such  quantity  produces  in  the  jar;  or  the  capacity 

=  y,  where  Q  =  the  quantity,  and  V,  the  differ- 
ence of  potential. 

Jar,  Leyden,  Coatings  of — (See 

Coatings  of  Leyden  Jar.) 

Jar,  Lightning A  Leyden  jar,  the 

coatings  of  which  consist  of  metallic  filings. 

As  the  discharge  passes,  an  irregular  series  of 
sparks  appear,  which  somewhat  resemble  in  their 
shape  a  lightning  flash.  Hence  the  origin  of  the 
term. 

Jar  of  Secondary  Cell.— The  containing 


vessel  in  which  the  plates  of  a  single  secondary 
cell  are  placed. 

Jar,  Porons A  porous  cell.     (See 

Cell,  Porous.) 

Jar,  Scintillating A  Leyden  jar, 

the  coatings 'of  which,  instead  of  being  formed 
of  continuous  sheets  of  tin-foil  or  other  con- 
ducting substances,  are  formed  of  small  pieces 
of  such  substances,  placed  at  regular  intervals 
on  the  glass  or  dielectric  so  as  to  leave  a  small 
space  between  them. 

Such  a  jar  has  received  the  name  of  scintillat- 
ing jar,  because  when  discharged  by  connecting 
its  two  opposite  coatings  the  discharge  appears  as 
minute  sparks,  which  jump  across  the  space 
between  the  metallic  pieces. 

Jar,  Unit A  small  Leyden  jar  some- 
times employed  to  measure  approximately  the 
quantity  of  electricity  passed  into  a  Leyden 
battery  or  condenser. 

As  shown  in  Fig.  315,  the  unit  jar  consists  of  a 
small  Leyden  jar  j,  whose  outer  coating  is  con- 
nected with  a  sliding  metallic 
rod  b,  provided  at  each  end 
with  a  rounded  knob,  and  the 
inner  coating  of  which  is  con- 
nected with  a  metallic  knob  c, 
placed  as  shown,  inside  a 
glass  jar  d,  opposite  a  ball  on 
the  lower  end  of  b. 

When,  now,  the  inside  of 
the  unit  jar,  or  the  end  con- 
nected with  c,  is  connected 
with  the  charging  source,  such 
as  a  machine,  and  the  outside 
at  a,  is  connected  with  the  jar 

or  jars    to    be  charged,   for 

i     ,,     .  ,       Fig- 3 ' 5-    Unit  Jar. 

every  spark  that  passes  be- 
tween d  and  c,  a  definite  quantity  has  passed  a. 

The  value  of  this  unit  charge  may  be  varied  by 
varying  the  distance  between  d  and  c. 

The  smaller  the  unit  jar  is  in  proportion  to  the 
jar  to  be  charged,  and  the  shorter  the  distance 
between  c  and  d,  the  more  reliable  are  the  com- 
parative results  obtained. 

Jars,  Leyden,  Charging,  by  Cascade  — 

— (See  Cascade,  Charging  Leyden  Jars  by.) 
Jet,    Gas,    Carcel    Standard — A 

lighted  gas  jet  employed  for  determining  the 
candle-power  of  gas  by  measuring  the  height 


Jet.] 


297 


[Joi. 


of  a  jet  of  gas  burning  under  a  given  press- 
ure, and  used  in  connection  with  the  light  of 
a  larger  gas  burner,  burning  under  similar 
conditions,  for  the  photometric  measurement 
of  electric  lights. 


Fig  316.     Seven-Carcel 
Standard  G.^s  Jet. 


Fig-.  317.     Carcel  Candle 
Burner. 


In  Fig.  316  is  shown  a  section  of  a  seven-carcel 
standard  gas  jet,  and  in  Fig.  317,  a  section  of  a 
candle  burner,  connected  within  the  same  service 
pipe.  The  gas  for  both  burners  is  received  in  a 
chamber,  from  whence  it  passes  by  an  opening  to 
the  burner,  under  the  constant  pressure  obtained 
by  the  weight  of  the  bell  C,  ar.d  the  tube  A.  The 
burner  shown  in  Fig.  317,  which  is  used  as  the 
standard  of  comparison,  will  give  a  candle-£>ower 
determined  from  the  height  of  the  jet  of  the 
burning  gas.  This  height  is  measured  in  milli- 
metres by  the  motion  of  a  circular  screen. 

The  determination  of  the  candle-power  of  gas  by 
means  of  a  jet  photometer  is  only  approximately 
correct,  unless  many  precautions  are  taken. 

Jet  Photometer.— (See  Photometer,  Jet^ 
Jewelry,  Electric Minute  incan- 
descent   electric  lamps  substituted   for  the 
rarer  gems  in  articles  of  jewelry. 

The  lamps  are  lighted  by  means  of  small  pri- 
mary or  storage  batteries,  carried  in  the  pocket  or 
elsewhere  on  the  person. 

Joint,  .  American  Twist —A  tele- 
graphic or  telephonic  joint  in  which  each  of 
the  two  wires  is  twisted  around  the  other. 
(See /(?/«/,  Telegraphic  or  Telephonic^ 


The  twisted  joint  is  sometimes  subsequently 
soldered. 


Fig  318.    American  Twist  Joint. 

The  American  twist  joint  is  shown  in  Fig.  318. 
This  joint  is  easily  made  and  is  very  serviceable. 


Joint,  Bell-Hanger's 


— A  joint  for 


telegraphic  or  telephonic  wires  in  which  the 
ends  are  merely  looped  together.  (See  Joint, 
Telegraphic  or  Telephonic?) 

Joint,  Britannia A  telegraphic  or 

telephonic  joint  in  which  the  wires  are  laid 
side  by  side,  bound  together  and  subsequently 
soldered.  (See  Joint,  Telegraphic  or  Tele- 
phonic^) 


Fig.  311).    Britannia  Joint. 

The  Britannia  joint  is  shown  in  Fig.  319.  No, 
16  wire,  B.  W.  G.,  is  used  as  the  binding  wire. 

Joint,  Butt An  end-to-end  joint. 

A  joint  effected  in  wires  by  placing  the 
wires  end  on  and  subsequently  soldering. 

Butt  joints  are  formed  by  bringing  the  ends  to 
be  joined  together  and  securing  them  while  in 
such  position. 

Joint,  Butt  and  Lap,  of  Belts —The 

joint  in  a  leather  belt,  employed  for  transmit- 
ting power  from  a  line  of  shafting  where  the 
ends  are  simply  brought  together  and  laced, 
is  called  a  butt  joint,  in  contradistinction  to  a 
lap  joint,  or  a  joint  formed  by  placing  one  end 
of  the  belt  over  the  other  and  lacing  or  rivet- 
ing the  two. 

In  using  delicate  galvanometers,  the  slightest 
change  in  the  speed  of  the  engine  driving  the 
dynamo-electric  machine  producing  the  current, 
causes  an  annoying  fluctuation  of  the  needle  that 
prevents  accurate  reading,  when  lap  joints  are  usect 
in  the  belt  instead  of  butt  joints,  unless  the  former 
are  very  carefully  made.  Lap  joints  may  also  cause 
a  flickering  in  the  lights.  When,  however,  lap 
joints  are  made  by  cutting  the  belt  by  an  oblique 
section  and  properly  securing  them  so  that  their 


Joi.] 


298 


[Joi. 


elevation  at  the  joint  is  no  greater  than  elsewhere, 
the  lap  joint  is  preferable  to  the  butt  joint. 

Joint,  Expansion A  joint  for  under- 
ground conductors,  tubes  or  pipes,  exposed 
to  considerable  changes  of  temperature,  in 
which  a  sliding  joint  is  provided  to  safely 
permit  a  change  of  length  on  expansion  or 
contraction. 

Joint,  Insulation A  joint  in  an  insu- 
lating material  or  covering  in  which  a  conti- 
nuity is  insured  in  the  conducting  as  well  as 
the  insulating  substance. 

Joint,  Lap A  joint  effected  by  over- 
lapping short  portions  near  the  ends  of  the 
things  to  be  joined,  and  securing  them  while 
in  such  position. 

Joint,  Lap,  for  Wires A  joint 

effected  between  two  wires  by  overlapping 
their  ends  and  subsequently  soldering. 

Joint,  Magnetic The  line  of  junc- 
tion between  two  separate  parts  of  magnetiza- 
ble materal. 

Magnetic  joints  should  be  of  such  a  nature  as 
to  permit  the  passage  of  the  lines  of  magnetic 
force  with  the  least  increase  in  the  resistance  of 
the  magnetic  circuit 

Magnetic  joints  in  the  field  magnets  of  a  dynamo- 
electric  machine  should  be  as  few  as  possible,  since 
the  resistance  of  the  best  magnetic  joint  to  the 
passage  of  the  lines  of  force  is  necessarily  greater 
than  that  of  the  same  material  without  such 
joints. 

Joint,  Metallic  Conducting A  joint 

in  a  conductor  in  which  a  continuity  of  con- 
ducting power  is  secured. 

Joint  Resistance  of  Parallel  Circuits. — 

(See  Resistance,  Joint,  of  Parallel  Circuits?) 

Joint,  Sleeve A  junction    of    the 

ends  of  conducting  wires  obtained  by  passing 
them  through  tubes  and  then  twisting  and 
soldering. 

All  joints  should  be  soldered,  but  in  so  doing 
care  must  ba  taken  that  the  soldering  liquid  or 
solid  employed  is  free  from  acids  or  other  corro- 
sive materials,  and  that  all  traces  of  the  soldering 
liquid  or  solid  are  removed  from  the  wire  before 
the  joint  is  covered  with  insulating  material. 

Kerite,  okonite  or  other  insulating  tape,  should 


preferably  be  wrapped  around  the  joint  after 
it  is  soldered. 

in  making  a  joint  in  a  giitta-percha  covered 
wire,  such  as  a  submarine  cable,  the  following 
method  may  be  employed:  The  bared  and 
cleansed  wires  are  twisted  together  and  soldered. 
The  soldered  joint  is  then  covered  with  a  layer 
of  plastic  insulating  material  made  of  a  mixture 
of  gutta-percha,  tar  and  rosin.  (See  Chatterton's 
Compound.'}  In  order  to  insure  a  good  junction 
between  this  and  the  gutta-percha  covering  on  the 
rest  of  the  -wire,  the  outer  surface  of  the  gutta- 
percha  is  removed  for  about  two  inches  from  each 
side  of  the  joint,  so  as  to  remove  its  oxidized  sur- 
face. After  the  coating  is  put  on,  it  is  warmed 
gently  by  a  warm  joining  tool,  not  by  the  flame 
of  a  lamp.  A  sheet  of  -warmed  gutta-percha  is 
then  wrapped  around  the  joint,  and  while  it  and 
the  joint  are  still  hot,  another  coating  of  the 
plastic  insulating  material  is  applied.  Successive 
layers  of  gutta-percha  and  some  other  insulating 
material  are  generally  applied  in  the  case  of  sub- 
marine cables. — (Culley.) 

Joint,  Telegraphic,  Mclntire's  Parallel 

Sleeve A  joint  for  telegraphic  or  other 

wires,  in  which  the  ends  to  be  joined  are 
slipped  into  parallel  sleeves  or  tubes,  which 
are  afterward  twisted  around  each  other. 

A  general  view  of  the  parallel  sleeve  joint,  both 
before  and  after  twisting,  is  shown  in  Fig.  320. 


Fig.  330.    Mclntire's  Parallel  Sleeve  Joint. 

The  twisting  is  done  by  means  of  the  specially 
devised  twisting  clamp  shown  in  Fig.  321. 


Fig.  321.  Twisting  Clamp  for  Mclntire's  Para 

Joint,  Telegraphic  or  Telephonic 

A  juncture  of  the  ends  of  two  electric  con- 
ductors so  as  to  insure  a  permanent  junc- 
tion whose  resistance  shall  not  be  appreci- 
ably greater  per  unit  of  length  than  that  of 
the  rest  cf  the  wire. 


Joi.]  299 

In  making  a  joint,  care  should  always  be  taken 
to  scrape  the  insulating  material  from  the  wires 
and  clean  their  surfaces  before  twisting  them  to- 
gether. 

Telegraph  wires  were  formerly  joined  by  the 
ordinary  bell-hangers' joint;  that  is,  the  wires  were 
simply  looped  together.  The  constant  vibrations 
to  which  the  wires  are  subjected  caused  such  a 
joint  to  be  abandoned  and  an  improvement  intro- 
duced by  bolting  the  ends  together,  as  shown  in 
Fig.  322. 


[Kao. 


Fig.  322.     Telegraphic  Joint. 

Joint,  Testing  of Ascertaining  the 

resistance  of  the  insulating  material  around 
a  joint  in  a  cable. 

The  resistance  of  the  insulating  material  of  a 
cable  at  a  joint  is  necessarily  high,  since  the 
joint  forms  but  a  small  part  of  length  of  the  cable. 
It  should  not,  however,  be  large  as  compared  with 
an  equal  length  of  another  part  of  the  cable  with 
a  perfect  core. 

Two  methods  for  testing  cable  joints  are  gener- 
ally employed,  viz. : 

(I.)  A  conductor  is  charged  through  the  joints 
for  a  given  time,  and  the  deflection  obtained  by 
its  discharge  compared  with  the  discharge  of  the 
same  condenser  charged  for  an  equal  length  of 
time  through  a  few  feet  of  perfect  cable. 

(2.)  A  charged  conductor  is  permitted  to  dis- 
charge itself  through  the  joint,  and  the  amount 
lost  in  a  given  time  noted. 

For  description  of  different  methods,  see 
Kempe's  "  Handbook  of  Electrical  Testing." 

Joulad. — A  term  proposed  for  the  Joule. 


This  term  is  not  generally  adopted.  (See 
Joule.} 

Joule.  —  The  unit  of  electric  energy  or 
work. 

The  volt-coulomb. 

The  amount  of  electric  work  required  to 
raise  the  potential  of  one  coulomb  of  elec- 
tricity one  volt. 

The  joule  may  be  regarded  as  a  unit  of  energy 
or  work  in  general,  apart  from  electrical  work  or 
energy. 

I  joule  ..........  =  10,000,000  ergs. 

I  joule  ..........  =  .  73732  foot-pounds. 

I  joule  ..........  =  i  volt-coulomb. 

I  joule  ..........  =  .24  calorie. 

4.2  joules  .........  =  i  small  calorie. 

I  joule  per  second  =  i  watt. 

The  British  Association  proposed  to  call  one 
joule  the  work  done  by  one  watt  in  one  second. 

Joule,  as  a  Heat  Unit.  —  The  quantity  of 
heat  developed  by  the  passage  of  a  current 
of  one  ampere  through  a  resistance  of  one 
ohm. 


Joule  Effect.—  (See  Effect,  Joule) 

Joule's    Cylindrical    Electro-Magnet— 

(See  Magnet,  Electro,  Joule's  Cylindrical.) 

Joule's  Law.  —  (See  Laws  of  Joule?) 
Junction  Box.  —  (See  Box,  Junction^ 
.Tump-Spark    Burner.  —  (See     Burner, 
fump-Spark^ 

Junction,  Thermo-Electric.  —  A  junction 
between  any  thermo-electric  couple.  (See 
Cell,  Thermo-Electrzc) 


K. — A  contraction  for  electrostatic  capa- 
city. (See  Capacity,  Electrostatic^ 

K.  C.  C. — In  electro-therapeutics,  a  brief 
method  of  writing  kathodic  closure  contrac- 
tion, or  the  effects  of  muscular  contraction 
abserved  at  the  kathode  on  the  closure  of  a 
circuit. 

K.  I).  C. — In  electro-therapeutics,  a  brief 
method  of  writing  kathodic  duration  con- 


traction, or  the  effects  of  muscular  contrac- 
tion observed  at  the  kathode  after  the  current 
has  been  passing  for  some  time. 

K.  W. — A  contraction  for  kilo-watt.  (See 
Watt,  Kilo.) 

Kaolin. — A  variety  of  white  clay  some- 
times employed  for  insulating  purposes. 

Jablochkoff  sometimes  employed  kaolin  be- 
tween  the  parallel  carbons  of  his  electric  candle 


Kap.] 


300 


[Key. 


for  the  purpose  of  insulating  them  from  each 
other.  He  also  devised  an  electric  lamp  in  which 
a  spark  of  considerable  difference  of  potential, 
obtained  from  an  ordinary  induction  coil,  was 
caused  to  raise  a  surface  of  kaolin  to  incan- 
descence by  passage  over  it. 

Eapp  Lines. — (See  Lines,  Kapp) 

Kartarert. — A  kind  of  insulating  material. 

Katelectrotonus. — A  word  sometimes  used 
instead  of  kathelectrotonus.  (See  Kathe- 
lectrotonus) 

Kathelectrotonic  State.  —  (See  State, 
Kathelectrotonic) 

Katheleetrotonic  Zone.  —  (See  Zone, 
Kathelectrotonic^ 

Kathelectrotonns. —  In  electro-therapeu- 
tics, the  condition  of  increased  functional  ac- 
tivity that  occurs  in  a  nerve  in  the  neighbor- 
hood of  the  kathode  or  negative  electrode. 
(See  Electrotonus.) 

Kathion. — The  electro-positive  ion,  atom 
or  radical  into  which  the  molecule  of  an 
electrolyte  is  decomposed  by  electrolysis. 
(See  Electrolysis.  Ions.) 

Kathion  is  sometimes  written  cathion. 

In  electrolysis  the  kathion,  or  the  electro-posi- 
tive ion  or  radical,  appears  at  the  kathode  or 
electro-negative  electrode.  Similarly,  the  anion, 
or  the  electro-negative  ion  or  radical,  appears  at 
the  anode  or  the  electro-positive  electrode. 

Kathodal. — Pertaining  to  the  kathode. 
(See  Kathode.) 

Kathode. — The  conductor  or  plate  of  an 
electro-decomposition  cell  connected  with  the 
negative  terminal  or  electrode  of  a  battery  or 
other  source. 

The  word  kathode  is  sometimes  applied  to  the 
negative  terminal  of  a  battery  or  source,  whether 
connected  with  a  decomposition  cell  or  not.  It 
is  preferable,  however,  to  restrict  its  use  to  de- 
composition cells.  (See  Anode.) 

The  word  kathode  is  sometimes  written  cathode. 

Kathodic. — Pertaining  to  the  kathode. 
(See  Kathode.) 

Kathodic  Electro-Diagnostic  Reactions. 

— (See  Reactions,  Electro-Diagnostic) 
Keeper  of  Magnet. — (See  Magnet,  Keeper 


Kerite. — An  insulating  material. 
Kerr  Effect— (Se&  Effect,  Kerr.) 
Key  Board.— (See  Board,  Key.) 

Key,  Capillary  Contact •  —  A  form  of 

fluid  contact  in  which  the  circuit  is  closed  or 
broken  by  means  of  a  wire  which  is  dipped 
into  or  removed  from  the  surface  of  a  mass 
of  mercury. 

In  order  to  avoid  an  increase  in  the  resistance 
of  the  circuit,  due  to  the  formation  of  oxide  ot 
mercury,  the  contact  surface  of  the  mercury  is 
kept  covered  with  a  layer  of  dilute  alcohol. 

Key,  Discharge A  key  employed  to 

enable  the  discharge  from  a  condenser  or 
cable  to  be  readily  passed  through  a  galva- 
nometer for  purposes  of  measurement. 

Key,  Discharge,  Kempe's A  dis- 
charge key  constructed  as  shown  in  Fig.  323. 


Fig.  323.     Kempe's  Discharge  Key. 

The  solid  lever,  hinged  at  one  extremity,  plays 
between  two  contacts  connected  to  two  terminals, 
and  has  two  finger  triggers  at  its  free  end  marked 
•'Discharge"  and  "Insulate,"  connected  respec- 
tively to  two  ebonite  hooks.  The  hook  attached 
to  that  marked  "  Discharge  "  is  a  little  higher  than 
the  other,  so  that  when  the  lever  is  caught  against 
it,  the  key  rests  in  an  intermediate  position  be- 
tween the  contacts,  and,  when  caught  against  the 
lower  trigger,  it  rests  against  the  bottom  contact. 
When  in  the  last  position,  a  depression  of  the 
"  Insulate  "  trigger  causes  the  lever  to  spring  up 
against  the  second  hook,  thus  insulating  it  from 
either  contact,  and  on  the  depression  of  the  "Dis- 
charge "  trigger,  the  lever  springs  up  against  the 
top  contact. 

Key,  Discharge,  Webb's A  dis- 
charge key  constructed  as  shown  in  Fig.  324. 

A  horizontal  lever  L,  Fig.  324,  passing  between 
two  contacts  and  hinged  at  J,  is  pressed  upward 
by  a  spring.  The  free  end  of  this  lever  termi- 
nates in  two  steps,  I  and  2.  A  vertical  lever,  pro- 


Key.] 


301 


[Key. 


vided  with  an  insulating  handle,  is  jointed  at  J', 
and  has  at  C,  a  projecting  metallic  tongue  that 
engages  in  the  upper  step  when  the  lever  H,  is 
vertical,  and  on  the  lower  step  when  it  is  slightly 
mored  from  the  free  end. 

When  the  projection  C,  rests  on  the  lower  step 
2,  the  lever  L,  is  intermediate  between  the  top 
and  bottom  contacts,  and  is,  therefore,  discon- 


If 


Fig.  324.      Webb's  Discharge  Key. 

nected  from  either  of  them;  but,  when  it  rests  on 
the  upper  step,  it  is  in  contact  with  the  lower 
contact. 

When  the  lever  H,  is  so  moved  as  to  have  the 
projection  C,  away  from  both  steps,  the  lever  L, 
is  pressed  by  its  spring  against  the  upper  contact. 

The  battery  terminals  axe  connected  with  the 
condenser  terminals  when  the  lever  L,  is  touching 
the  lower  contact,  but  when  the  lever  L,  touches 
the  top  contact,  the  condenser  is  connected  with 
the  galvanometer  terminals. 

Key,  Double-Contact  Form  of  Bridge, 
Sprague's A  key  designed  to  succes- 
sively close  two  separate  circuits. 

K 


123  4 

Fig.  325.     Spr ague's  Double-Contact  Key. 

Sprague's  double-contact  key  is  shown  in  Fig. 
325.  On  depressing  K,  the  contacts  c,  c,  are  first 
closed  and  afterwards  contacts  at  c',  c'.  Metallic 


pieces,  I,  2,  3  and  4,  serve  to  make  contacts  with 
apparatus  used  in  connection  with  the  key. 

The  battery  circuit  is  connected  to  I  and  2, 
and  the  galvanometer  to  3  and  4,  so  that  the  bat- 
tery circuit  is  closed  first,  and  the  galvanometer 
afterwards.  This  form  of  key  is  used  in  connec- 
tion with  the  Wheatstone  Bridge. 

Key,  Double-Contact,  Lambert's 

A  key  used  in  cable-work,  and  constructed 
as  shown  in  Fig.  326. 


fff  326.     Lambert's  Double- Contact  Key. 

In  Thomson's  method  for  the  determination  of 
electrostatic  capacity,  the  capacity  of  the  cable 
is  compared  with  that  of  a  condenser  containing 
a  known  charge.  These  two  charges  are  so  con- 
nected electrically  as  to  discharge  into  and 
neutralize  each  other  if  equal,  but  if  not,  t>  pro- 
duce a  galvanometer  deflection  by  a  charge 
equal  to  their  difference. 

A  Lambert  double  contact  key  is  shown  in  Fig. 
326.  The  connections  are  such  that  the  pushing 
forward  of  K,  depresses  keys  that  permit  a  bat- 
tery to  simultaneously  charge  the  condenser  and 
the  cable.  On  drawing  K,  back,  the  two  charges 
are  allowed  to  mix.  Then  on  depressing  K,  the 
difference  of  the  charges,  if  any,  is  discharged 
through  the  galvanometer.  . 

Key,  Double-Tapper The  key  used 

in  a  system  of  needle  telegraphy  to  send 
electric  impulses  through  the  lines  in  alter- 
nately opposite  directions.  (See  Telegraphy, 
Single-Needle?) 

Key,  Increment A  telegraphic  key 

so  connected  that  an  increase  cr  increment 
in  the  line  current  occurs  whenever  the  key  is 
depressed. 

The  increment  key  is  used  in  duplex  and  quad- 
ruplex  systems  of  telegraphic  transmission. 

Key,  Increment,  of  Quadruples  Tele- 
graphic System A  key  employed  to 

increase  the  strength  of  the  current  and  so 
operate  one  of  the  distant  instruments  in  a 


Key.] 


302 


[Key. 


quadruplex  system  by  an  increase  in  the 
strength  of  the  current.  (See  Telegraphy, 
Quadruplex^) 

Key,  Magneto-Electric A  tele- 
graph key  for  sending  an  electric  impulse 
into  a  line,  so  arranged  that  a  coil  of  wire  on 
an  armature  connected  with  the  key  lever  is, 
<  by  the  movements  of  the  key,  moved  toward 
or  from  the  poles  of  a  permanent  magnet,  the 
movements  of  the  key  thus  producing  the 
currents  sent  into  the  line. 

Key,  Plug A  simple  torm  of  key  in 

which  a  connection  is  readily  made  or  broken 
by  the  insertion  of  a  plug  of  metal  between 
two  metallic  plates  that  are  thus  introduced 
into  a  circuit. 

A  form  of  plug  key  is  shown  in  Fig.  327. 


Fig.  327.    Plug  Key. 

Key,  Reversing  — -  —A  key  inserted  in 
the  circuit  of  a  galvanometer  for  obtaining 
deflections  of  the  needle  on  either  side  of  the 
galvanometer  scale. 

A  form  of  reversing  key  is  shown  in  Fig.  328. 

The  galvanometer  terminals  are  connected-to  the 

binding  posts  2  and  3,  and  the  circuit  terminals 

to  the  other  two  posts.    On  depressing  K,  the 

3 


Fig.  328.    Reversing  Key. 

Current  flows  in  one  direction  and  on  depressing 
K',  it  flows  in  the  opposite  direction.  Clamps, 
operated  by  handles,  are  provided  so  as  to  close 
either  of  the  keys  permanently,  if  so  desired. 


Key,  Reversing,    of  Quadruplex   Tele- 
graphic System •  —A  key  employed  to 

reverse  the  direction  of  the  current  and  so 
operate  one  of  the  distant  instruments,  in  a 
quadruplex  system,  by  a  change  in  the 
direction  of  the  current.  (See  Telegraphy, 
Quadruplex.) 

Key,  Short-Circuit A  key  which 

in  its  normal  condition  short  circuits  the  gal- 
vanometer. 


Fig.  329.    Short-Circuit  Key. 


Such  a  short-circuit  key  is  provided  for  the 
purpose  of  protecting  the  galvanometer  from  in- 
jury by  large  currents  being  accidentally  passed 
through  its  coils.  In  the  form  shown  in  Fig.  329, 
the  spring  S,  rests  against  a  platinum  contact ; 
but  when  depressed  by  the  insulated  head  at  K, 
it  rests  against  an  ebonite  contact,  and  throws 
the  galvanometer  into  the  desired  circuit. 

The  key  is  provided  with  double  binding  posts 
at  P  and  N,  for  convenience  of  attachment  to  re- 
sistance coils,  batteries,  etc. 

In  the  form  of  a  short-circuit  key  shown  in  Fig. 
330,  a  catch  is  provided  for  the  purpose  of  keep- 
ing the  key  down  when  once  depressed.  Its 
arrangement  will  be  readily  understood  from  an 
inspection  of  the  figure. 


JC 


Fig.  330.     ShoH-Circuit  Key. 

Key,  Sliding-Contact The  key  em- 
ployed in  the  slide  form  of  Wheatstone 
bridge,  to  make  contact  with  the  wire  over 
which  the  sliding  contact  passes.  (See 
Bridge,  Electric,  Slide  Form  of.) 


303 


[Kit. 


Key,  Stationary  Floor An  electric 

key  or  push  button  placed  on  the  floor  so  as 
to  be  readily  closed  by  the  foot. 

This  form  of  key  is  especially  suitable  for  use 
in  connection  with  an  electric  bell  and  annuncia- 
tor for  readily  calling  an  attendant.  (See  Annun- 
ciator, Electro-Magnetic.} 

Key,  Telegraphic The  key  em- 
ployed for  sending  over  the  line  the  successive 
makes  and  breaks  that  produce  the  dots  and 
dashes  of  the  Morse  alphabet,  or  the  deflec- 
tions of  the  needle  of  the  needle  telegraph. 
(See  Telegraphy,  American  System  of.) 

Kick. — A  recoil. 

Kicking  Coil.— (See  Coil,  Kicking.) 

Kilo  (as  a  prefix). — One  thousand  times. 

Kiloampere. — One  thousand  amperes. 

Kiloampere  Balance. — (See  Balance, 
Kiloampere^) 

Kilodyne. — One  thousand  dynes.  (See 
Dyne.) 

Kilogramme. — One  thousand  grammes, 
or  2.2046  pounds  avoirdupois.  (See  Weights, 
French  System  of) 

Kilojoule. — One  thousand  joules. 

Kilometre. — One  thousand  metres. 

Kilowatt. — One  thousand  watts. 

Kilowatt  Hour. — (See  Hour,  Kilowatt!) 

Kine. — A  unit  of  velocity  proposed  by  the 
British  Association. 

A  kine  equals  I  centimetre  per  second. 

Kinetic  Energy. — (See  Energy,  Kinetic.) 

Kinetic  Theory  of  Matter. — (See  Matter, 
Kinetic  Theory  of.) 

Kinetics,  Electro A  term  some- 
times applied  to  the  phenomena  of  electric 
currents,  or  electricity  in  motion,  as  distin- 
guished from  electrostatics,  or  the  phenom- 
ena of  electric  charges,  or  electricity  at  rest. 

Kinetograph. — A  device  for  the  simultane- 
ous reproduction  of  a  distant  stage  and  its 
actors  under  circumstances  such  that  the 
actors  can  be  heard  at  any  distance  from  the 
theatre. 

The  sounds  heard  by  the  distant  audience  are 
actual  reproductions  of  those  uttered  during  the 


performance,  though  not  at  the  time  of  their 
utterance.  The  appearance  of  the  stage  and  its 
actors  represents  the  appearance  of  a  previous 
reproduction  of  the  play  or  opera  or  other  per- 
formance, as  taken  by  means  of  a  Kodak  camera 
with  a  film  cylinder  and  drop  shutter,  operated 
by  an  electric  motor,  exposing,  say,  forty  plates 
a  second.  By  means  of  a  projecting  lantern  these 
photographic  pictures  are  thrown  on  a  curtain  on 
a  stage  at  the  distant  theatre  in  regular  order  of 
sequence,  while  a  loud-speaking  phonograph 
puts  song  and  speech  into  the  mouths  of  the 
mimic  actors  and  thus  gives  the  phantom  stage 
the  semblance  of  life  and  reality. 

Kite,  Franklin's A  kite  raised  in 

Philadelphia,  Pa.,  in  June,  1752,  by  means  of 
which  Franklin  experimentally  demonstrated 
the  identity  between  lightning  and  electricity, 
and  which,  therefore,  led  to  the  invention  of 
the  lightning  rod. 

It  is  true  that  Dalibard,  on  the  loth  of  May, 
1752,  prior  to  Franklin's  experiment,  succeeded 
in  drawing  sparks  from  a  tall  iron  pole  he  had 
erected  in  France.  This  experiment  was,  how  • 
ever,  tried  at  the  suggestion  of  Franklin,  to  whom 
it  must  properly  be  ascribed. 

A  description  of  this  kite  is  given  by  Franklin 
in  the  following  letter: 

Letter  XI,  from  BENJ.  FRANKLIN,  Esq.,  of  Phil- 
adelphia, to  PETER  COLLINSON,  Esq., 
F.  R.  S.,  London. 

"OCT.  19,  1752. 

"As  frequent  mention  is  made  in  public  papers, 
from  Europe,  of  the  success  of  the  Philadelphia 
experiment  for  drawing  the  electric  fire  from 
clouds  by  means  of  pointed  rods  of  iron  erected 
on  high  buildings,  etc.,  it  may  be  agreeable  to 
the  curious  to  be  informed  that  the  same  experi- 
ment has  succeeded  in  Philadelphia,  though 
made  in  a  different  and  more  easy  manner,  which 
is  as  follows: 

"  Make  a  small  cross  of  two  light  strips  of  cedar, 
the  arms  so  long  as  to  reach  to  the  four  corners  of  a 
large  thin  handkerchief  when  extended ;  tie  the 
corners  of  the  handkerchief  to  the  extremities  of 
the  cross,  so  you  have  the  body  of  a  kite,  which, 
being  properly  accommodated  with  a  tail,  loop 
and  string,  will  rise  in  the  air  like  those  made  of 
paper,  but  this,  being  of  silk,  is  fitter  to  bear  the 
wet  and  wind  of  a  thunder  gust  without  tearing. 
To  the  top  of  the  upright  stick  of  the  cross  is  to 


304 


[Lag. 


foe  fixed  a  very  sharp  pointed  wire  rising  a  foot 
or  more  above  the  wood.  To  the  end  of  the 
twine,  next  the  hand,  is  to  be  tied  a  silk  ribbon, 
and  where  the  silk  and  twine  join,  a  key  may  be 
fastened.  This  kite  is  to  be  raised  when  a  thun- 
der gust  appears  to  be  coming  on,  and  the  per- 
son who  holds  the  string  must  stand  within  a 
door  or  window,  or  under  some  cover,  so  that 
the  silk  ribbon  may  not  be  wet,  and  care  must  be 
taken  that  the  twine  does  not  touch  the  frame  of 
the  door  or  window.  As  soon  as  any  of  the 
thunder  clouds  come  over  the  kite  the  pointed 
wire  will  draw  the  electric  fire  from  them,  and 
the  kite,  with  all  the  twine,  will  be  electrified, 
and  the  loose  filaments  of  the  twine  will  stand 
out  every  way,  and  be  attracted  by  an  approach- 
ing finger.  And  when  the  rain  has  wet  the  kite 
and  twine  so  that  it  can  conduct  the  electric  fire 
freely,  you  will  find  it  stream  out  plentifully  from 
the  key  on  the  approach  of  your  knuckle.  At 
this  key  the  phial  may  be  charged,  and  from 
electric  fire  thus  obtained  spirits  may  be  kindled, 
and  all  the  other  electric  experiments  be  per- 
formed,  which  are  usually  done  by  the  help  of  a 


rubbed  glass  globe  or  tube,  and  thereby  the 
sameness  of  the  electric  matter  with  that  of  light- 
ning completely  demonstrated. 

"B.  FRANKLIN." 

Knife  Break  Switch.— (See  Switch,  Knife 
Break) 

Knot  or  Nautical  Mile. — A  length  equal 
to  6,087  feet. 

The  English  statute  mile  is  equal  to  5,280  feet. 
The  value  of  the  nautical  mile  is  therefore  in  excess 
of  that  of  the  statute  mile. 

Kohlrausch's  Law.  —  (See  Law  of  Kohl- 
rausch.) 

Krizik's  Bars.— (See  Bars,  KriziPs.) 
Kyanized. — Subjected    to    the    kyanizing 
process.     (See  Kyanizing) 

Kyanizing. — A  process  employed  for  the 
preservation  of  wooden  telegraphic  poles  by 
injecting  a  solution  of  corrosive  sublimate 
into  the  pores  of  the  wood.  (See  Pole,  Tele- 
graphic?) 


L. — A  contraction  for  co-efficient  of  in- 
ductance. (See  Inductance,  Co-efficient  of.) 

L. — A  contraction  for  length. 

Labile  Galvanization. — (See  Galvaniza- 
tion, Labile.) 

Lag,  Angle  of The  angle  through 

which  the  axis  of  magnetism  of  the  armature 
of  a  dynamo-electric  machine  is  shifted  by 
reason  of  the  resistance  its  core  offers  to  sud- 
den reversals  of  magnetization. 

An  armature  of  a  bi  polar  dynamo  electric  ma- 
chine has  its  magnetism  reversed  twice  in  every 
rotation.  The  iron  of  the  core  resists  these  mag- 
netic reversals.  The  result  of  this  resistance  is  to 
Bhift  the  axis  of  magnetism  in  the  direction  of  ro- 
tation.  The  angle  through  which  the  axis  has 
thereby  been  shifted  is  called  the  angle  of  lag. 

The  term,  angle  of  lag,  is  sometimes  incorrectly 
applied  so  as  to  include  a  similar  result  produced 
ly  the  magnetization  due  to  thi  armature  current 
itself.  It  is  this  latter  action  which,  in  armatures 
With  soft  iron  cores,  is  the  mam  cause  of  the  angle 


of  lead.  (See  Brushes,  Lead  of.  Lead^  Angle 
of.)  • 

Lag,  Angle  of,  of  Cnrrent An 

angle  whose  tangent  is  equal  to  the  ratio  of 
the  inductive  to  the  ohmic  resistance. 

An  angle,  the  tangent  of  which  is  equal  to 
the  inductive  resistance  of  the  circuit,  divided 
by  the  ohmic  resistance  of  the  circuit. 

An  angle,  the  co-sine  of  which  is  equal  to 
the  ohmic  resistance  of  the  circuit,  divided 
by  the  impedance  of  the  circuit. 

Lag,  Magnetic A  magnetic  viscos- 
ity as  manifested  by  the  sluggishness  with 
which  a  magnetizing  force  produces  its  mag- 
netizing effects  in  iron. 

The  tendency  of  the  iron  core  of  a  magnet, 
or  of  the  armature  of  a  dynamo-electric  ma- 
chine, to  resist,  and,  therefore,  retard  mag- 
netization. 

This  retardation,  or  lag,  is  called  the  magnetic 
lag. 

The  lead  necessary  to  give  the  brushes  of  a  dy- 
namo-electric machine  to  insure  quiet  action  has  by 


Lam.J 


305 


[Lam. 


some  been  erroneously  ascribed  to  the  magnetic 
lag.  The  lead,  though  due  to  lag  in  part,  in  reality 
is  mainly  due  to  the  resultant  magnetization  of 
the  armature  both  by  the  field  magnets  and  by  its 
own  current.  (See  Lead,  Angle  of.)  This  dis- 
placement of  the  brushes  is  measured  by  an  angle 
sometimes,  though  erroneously,  called  the  angle 
of  lag.  (See  Lag,  Angle  of.) 

Lamellar  Distri- 
bution of  Magnet- 
ism.— (See  Magnet- 
ism, Lamellar  Dis- 
tribution of.) 

Laminated  Core. 
— (See  Core,  Lami- 
nated) 

Laminating  Core. 
— (See  Core,  Lami- 
nation of.) 

Lamination  of 
Armature  Core.  — 
(See  Core,  Armature, 
Lamination  of) 

Lamination  of 
Cores.  —  (See  Core, 
Lamination  of) 

Lamp,     All-Night 

A  term  some- 
times applied  to  a 
double  -  carbon  arc 
lamp.  (See  Lamp, 
Electric  Arc,  Double* 
Carbon) 

A  form  of  all-night 
arc  lamp  is  shown  in 
Fig.  351.  When  the 
consumption  of  the  first 
pair  of  carbons  has  Fig.  331.  All-Night  Arc 
reached  a  certain  limit  Lamp. 

the  current  is  automatically  switched  over  to  the 
other  pair. 

Lamp,  All-Night  Electric A  lamp 

provided  with  carbon  electrodes  so  as  to  burn 
all  night  without  recarboning. 

A    double-carbon     electric     lamp.       (See 
Lamp;  All-Night) 

Lamp,  A~e An   electric  lamp,  the 

source  of  whose  light  is  a  voltaic  arc. 


Lamp,   Arc,   Electric An  electric 

lamp  in  which  the  light  is  produced  by  a  vol- 
taic arc  formed  between  two  or  more  carbon 
electrodes. 

The  carbon  electrodes  are  placed  in  various 
positions,  either  parallel,  horizontal,  inclined 
to  one  another  or  vertically  one  above  the  other. 
The  latter  is  the  form  most  generally  adopted, 
since  it  permits  the  ready  feeding  of  the  upper 
carbon. 

The  carbons  are  maintained  during  their  con- 
sumption at  a  constant  distance  apart,  by  the  aid 
of  various  feeding  devices.  Such  devices  are  op- 
erated generally  by  trains  of  wheel-work,  by  me- 
chanical or  electrical  motors,  or  by  the  simple 
action  of  a  spring,  by  gravity  or  by  the  attraction 
of  a  solenoid. 

The  carbon  pencils  or  electrodes  are  held  in 
carbon  holders,  consisting  of  chitches  or  clamps, 
attached  to  the  end  of  the  lamp  rods. 

When  the  lamp  is  not  in  operation  the  carbons 
are  usually  in  contact  with  one  another;  but,  on 
the  passage  of  the  current,  they  are  separated 
the  required  distance  by  the  action 
of  an  electro-magnet  whose  coils 
are  traversed  by  the  direct  or  main 
current. 

In  order  to  maintain  the  elec- 
trodes a  constant  distance  apart, 
the  up  per  carbon  in  some  lamps  is 
held  in  position  by  the  operation  of 
a  clutch,  or,  in  others,  by  a  detent, 
that  engages  in  a  toothed  wheel. 
The  position  of  this  clutch  or  de- 
tent is  controlled  by  the  action  of 
an  electro-magnet  whose  coils  are 
usually  situated  in  a  shunt  or  de- 
rived circuit,  of  high  resistance, 
around  the  electrodes.  When  the 
carbons  are  at  their  normal  dis- 
tance apart,  the  shunt  current  is 
not  of  sufficient  strength  to  move 
the  clutch  or  detent  from  the  position  in  which 
it  prevents  the  downward  motion  of  the  upper 
carbon  rod.  When,  however,  by  the  burning 
or  consumption  of  the  carbons,  the  resistance 
of  the  arc  has  increased  to  an  extent  which  can 
be  predetermined,  the  increased  current  that  is 
thereby  passed  through  the  shunt  circuit  is  now 
sufficiently  strong  to  release  the  clutch  or  de- 
tent, thus  permitting  the  fall  or  feed  of  the  upper 
carbon.  In  a  well  designed  lamp  this  occurs 


Fig.  332. 
Arc  Lamp. 


Lam.J 


306 


[Lam. 


so  gradually  as  to  produce  no  perceptible  effect 
on  the  steadiness  of  the  light. 

Arc  lamps  are  generally  placed  in  series  circuits, 
that  is,  in  circuits  in  which  the  current  passes  suc- 
cessively through  all  the  lamps  in  the  circuit,  and 
returns  to  the  source.  In  ortler  to  avoid  the  break- 
ing of  the  entire  circuit  through  the  extinguish- 
-ng  of  a  single  arc,  on  the  breaking  of  its  cir- 
-uit,  an  automatic  safety  device  is  provided  for 
each  lamp.  This  safety  device  consists  essentially 
of  an  electro-magnet  so  placed  in  a  shunt  circuit, 
that,  as  the  resistance  of  the  arc  becomes  too 
great,  the  increased  current,  which  will  then  flow 
through  the  coils  of  the  electro-magnet,  at  last 
produces  a  movement  of  its  armature  which  closes 
a  short  circuit  around  the  lamp,  and  thus  cuts  it 
out  of  the  circuit. 

Arc  lamps  assume  a  great  variety  of  forms.  A 
well  known  form  is  shown  in  Fig.  332. 

Lamp,  Arc,  Triple  Carbon  --  An  arc 

lamp  in  which  three  carbon  electrodes  are 
used. 

The  positive  carbons  consist  of  two  ordinary 
cylindrical  carbons,  placed  parallel  to  each  other. 
The  negative  carbon  is  shaped  like  the  figure  8. 
The  arc  is  established  between  one  of  the  positive 
carbons  and  the  corresponding  side  of  the  nega- 
tive carbon.  The  feeding  of  the  lamp  is  attended 
by  a  shifting  back  and  forth  of  the  arc  between 
the  positive  carbons  and  from  side  to  side  of  the 
negative  carbons. 

The  design  of  the  triple  carbon  arc  lamp  is  to 
produce  a  lamp  of  long  life. 

Lamp    Bracket,    Electric 

•  -  •  —  (See  Bracket,  Lamp, 
Electric) 

Lamp    Bulb.  —  (See    Bulb, 


Lamp,  Carcel 


An 


oil  lamp  employed  in  France 
as  a  photometric  standard. 

Fig.  333  shows  a  formofcar- 
cel  lamp.  Like  the  standard 
candle,  the  carcel  is  a  standard 
only  when  it  consumes  a  given 
weight  of  the  light-producing 
substance  in  a  given  time. 

Lamp,  Chamber  of  -- 

The  glass  bulb  or  chamber  of 
an  incandescing  electric  lamp 
in  which  the  incandescing 


333- 
Carcel  Lamp. 

conductor     is 


placed,  and  in  which  is  maintained  a  high 
vacuum. 

The  transparency  of  the  lamp  chamber  and 
consequently  the  efficiency  of  the  lamp  may  de- 
crease— 

( I . )  From  the  settling  of  dust  or  dirt  on  its  outer 
walls. 

(2.)  From  the  deposit  of  carbon  or  metal  on  its 
inner  walls. 

To  obviate  the  first  cause  of  diminished  trans- 
parency the  outside  of  the  lamp  chamber  should 
be  frequently  cleansed.  The  diminished  trans- 
parency, due  to  the  second  cause,  cannot  be 
removed.  When  it  has  reached  a  certain  point,  it 
is  more  economical  to  replace  the  old  lamp  by  a 
new  lamp. 

In  a  properly  made  lamp  the  dimming  of  tne 
lamp  chamber  is  not  apt  to  occur  unless  a  stronger 
current  than  the  normal  current  is  passed  through 
the  lamp. 

Lamp  Clamp.  — (See  Clamp  for  Arc 
Lamps) 

Lamp,  Contact A  form  of  semi- 
incandescent  electric  lamp  in  which  a  carbon 
pencil  is  pressed  against  a  slab  of  carbon  or 
other  refractory  material. 

The  source  of  light  in  an  electric  contact  lamp 
is  twofold,  viz.: 

(l.)  A  minute  arc  formed  at  the  points  of  im- 
perfect contact. 

(2.)  The  incandescence  of  the  carbon  pencil, 
and  the  points  of  the  slab  of  carbon  against  which 
it  is  pressed. 

Lamp  Contacts.— (See  Contacts,  Lamp) 
Lamp,    Electric,    Arc,    Carbon    Elec- 
trodes for (See  Electrodes,   Carbon, 

for  Arc  Lamps) 

Lamp,  Electric,  Arc,  Differential . 

An  arc  lamp  in  which  the  movements  of 
the  carbons  are  controlled  by  the  differential 
action  of  two  magnets  opposed  to  each  other, 
one  of  whose  coils  is  in  the  direct  and  the 
other  in  a  shunt  circuit  around  the  carbons. 

Sometimes  the  differential  coils  are  placed  op 
the  same  magnet  core. 

Lamp,  Electric,  Arc,  Double  Carbon 

— An  electric  arc  lamp  provided  with  two 
pairs  of  carbon  electrodes,  sa  arranged  that 
when  one  pair  is  consumed,  the  circuit  is  auto- 
matically completed  through  the  other  pair 


LUIU.J 


307 


[I.uu. 


Lamp,  Electric  Glow A  *erm  em- 
ployed mainly  in  Europe  for  an  incandescent 
electric  lamp.  (See  Lamp,  Electric,  Incan- 
descent^) 

Lamp,  Electric,  Incandescent An 

electric  lamp  in  which  the  light  is  produced 
by  the  electric  incandescence  of  a  strip  or 
filament  of  some  refractory  substance,  gener- 
ally carbon. 

The  carbon  strip  or  filament  is  usually  bent  into 
the  form  of  a  horseshoe  or  loop,  and  placed  inside 
a  glass  vessel  called  the  lamp  chamber.  The 
lamp  chamber  is  exhausted  by  means  of  a  mercury 
pump,  generally  to  a  fairly  high  vacuum. 

In  order  to  insure  the  complete  removal  from 
the  lamp  chamber  of  all  the  air  it  originally  con- 
tained, the  carbon  strips  that  are  placed  within  it 
are  maintained  at  a  high  temperature  during  the 
process  of  exhaustion.  This  temperature,  in 
practice,  is  obtained  by  sending  the  current 
through  the  carbon  strip  as  soon  as  nearly  all 
the  air  is  removed.  Towards  the  end  of  the 
pumping  operation  the  current  is  increased  so 
as  to  raise  the  carbons  to  their  full  bril- 
liancy. 

The  lamp  chamber  is  also  maintained  at  a 
fairly  high  temperature. 

To  insure  this  heating  of  the  walls  of  the  lamp 
chamber  by  the  incandescent  carbons  during 
pumping,  for  the  purpose  of  driving  off  all  the 
air  adhering  to  the  walls  of  the  chamber,  they  are 
sometimes  covered  with  some  readily  removable 
preparation  of  lamp  black. 

The  operation  of  driving  off  the  gases  absorbed 
by  the  carbons  is  termed  the  occluded  gas  process, 
and  is  essential  to  the  successful  sealing  of  an 
incandescent  lamp.  By  its  means,  a  considerable 
quantity  of  air  or  other  gaseous  substances  shut 
up  or  occluded  by  the  carbon  is  driven  out  of  the 
far i.on,  which  it  \vould  be  impossible  to  get  rid  of 
by  the  mere  operation  of  pumping.  In  order  to 
insure  the  success  of  the  operation,  it  is  necessary 
that  tlie  heating  mu«t  take  place  while  the  lamp 
is  being  exhausted,  since  otherwise  the  expelled 
gases  would  b?  re-absorbed.  (See  Gas,  Occlu- 
sion of } 

Both  t!ie  exhaustion  and  the  incandescence  con- 
thiue.  up  to  the  moment  the  lamp  chamber  is 
hermetically  sealed;  otherwise,  some  of  the  air 
mi'/ht  remain  in  the  lamp  chamber. 

The  lamp  chamber  is  herme€Lally  sealed, 
usually  by  the  iusion  of  the  glass  ia  the  manner 


adopted  in    the    sealing    of   Geissler    tubes    or 
Crookes'  radiometers. 

For  the  preparation  of  the  carbon  strip,  its 
carbonization  and  the  flashing  of  the  strip,  see 
Carbonization,  Processes  of.  Carbons,  Flashing 
Process  for. 

The  ends  of  the  carbon  strip, 
or  filament,  are  attached  to  lead- 
ing-in  wires  of  platinum  that  pass 
through  the  glass  walls  of  the 
lamp  chamber,  and  are  fused 
therein  by  melting  the  glass 
around  them  in  the  same  manner 
as  are  the  leading-in  wires  of  the 
Geissler  tubes  and  other  similar 
apparatus. 

Incandescent  lamps  are  gener- 
ally connected  to  the  leads  or  cir-  fig-.  334.  Incan- 
cuits  in  multiple-arc  or  in  multi-   Ascent  Electric 
pie-series.     They  are,  however, 
sometimes  connected  to  the  line  in  series.     (See 
Circuits,  Varieties  of.) 

In  the  case  of  multiple-arc  or  multiple-series 
connection,  the  resistance  of  the  filament  is  com- 
paratively high.  In  the  case  of  series-connec- 
tion the  resistance  is  comparatively  low. 

Incandescent  electric  lamps  assume  a  variety  of 
different  forms.  In  all  cases,  however,  the  shape 
of  the  filament  is  such 
that  the  leading-in 
wires  that  carry  the 
current  to  and  from 
the  filament  shall  en- 
ter and  leave  the  lamp 
chamber  at  points  that 
are  comparatively 
near  together.  This 
is  for  the  purpose  of 
avoiding  the  unneces 
sary  production  of 
shadows. 

Commercial  incan- 
descent electric  lamps 
are  generally  marked 
with  the  potential  dif- 
ference in  volts  that 
must  be  applie.l  at  the 
terminals  in  order  to 
furnish  the  current 
necessary  to  properly 
operate  teem.  If  this 
potential  difference  is 
made  greater,  the  can- 


Fig.  33S'    Swan  fncanJescent 


Lam.] 


308 


[Lam. 


Tie-power  of  the  lamp  is  greatly  increased,  but  its 
life  greatly  decreased. 

The  lamp  chamber  is  more  liable  in  such  cases 
to  become  less  transparent  from  the  deposit  of  a 
'.bin  layer  of  carbon  or  metal  on  its  inner  surfaces. 

In  the  Swan  lamp  the  filament  is  made  of  cot- 
ton thread.  These  threads  are  immersed  in  a 
mixture  of  two  parts  of  sulphuric  acid  and  one  of 
water,  which  converts  the  cellulose  of  the  thread 
into  artificial  parchment.  The  filaments  are  rap- 
idly washed  as  soon  as  they  are  removed  from  the 
sulphuric  acid  until  all  traces  of  the  acid  are  re- 
moved.  They  are  then  passed  through  discs  so 
as  to  insure  a  uniform  area  of  cross-section,  and 
are  then  wrapped  on  rods  of  carbon  or  earthen- 
ware of  the  required  outline,  packed  in  a  crucible 
filled  with  powdered  charcoal,  and  carbonized. 

The  form  generally  given  to  the  Swan  filament 
is  that  shown  in  Fig.  335. 

Lamp,  Electric,  Incandescent  Ball 

— An  incandescent  electric  lamp  in  which 
the  light  is  produced  by  a  sphere  or  ball  of 
carbon  placed  in  an  exhausted  receiver  of 
glass. 

When  subjected  to  the  effects  of  electrostatic 
waves  of  high  frequency  of  alternation,  such  a 
lamp  becomes  luminous 
from  the  incandescence  of 
the  carbon  ball  or  sphere. 
Tesla's  incandescent  ball 
electric  lamp  is  a  modifica- 
tion of  his  straight  filament 
lamp.  (See  Lamp,  Incan- 
descent, Straight  Filament .) 

The  construction  of  Tes- 
la's ball  incandescent  elec- 
tric lamp  will  be  readily 
understood  from  an  inspec- 
tion of  Fig.  336. 

Lamp,  Electric,  In- 
candescent,  Half-Shades 

for (See    Half- 
Shades  for  Incandescent  Lamps.) 

Lamp,   Electric,  Incandescent,  Life  of 

The  number  of  hours  that  an  incan- 
descent electric  lamp,  when  traversed  by  the 
normal  current,  will  continue  to  afford  a  good 
commercial  light. 

The  failure  of  an  electric  incandescent  lamp 
results  either  from  the  volatilization  or  rupture 
of  the  carbon  conductor,  or  from  the  failure  of  the 


vacuum  of  the  lamp  chamber.  Since  the  em- 
ployment of  the  flashing  process,  and  the  process 
for  removing  the  occluded  gases,  it  is  not  unusual 
for  incandescent  lamps  to  have  a  life  cf  several 
thousand  hours.  (See  Carbons^  Flashing  Pro- 
cess for.') 

The  life  of  an  incandescent  electric  lamp  should 
not  be  considered  as  continuing  until  the  filament 
actually  breaks.  As  soon  as  the  lamp  chamber 
has  become  covered  with  such  a  deposit  of  car- 
bon or  coating  of  metal  as  to  considerably  de- 
crease the  amount  of  light  which  passes  through 
the  chamber,  the  lamp  should  be  considered  as 
useless. 

Lamp,  Electric,  Incandescent,  Three- 
Filament,  for  Multi-Phase  Circuits 

— An  incandescent  lamp  for  use  on  multi- 
phase circuits,  provided  with  three  leading-in 
wires,  connected  to  the  free  ends  of  three 
filaments,  the  other  ends  of  which  are  con- 
nected in  a  common  joint. 

When  properly  acting,  the  current  passing 
through  each  filament  should,  at  any  instant, 
equal  the  sum  of  the  currents  ia  the  other  two 
filaments,  which,  as  is  well  known,  is  the  property 
of  any  three-phase  circuit. 

Lamp,  Electric,  Outrigger  for 

(See  Outrigger  for  Electric  Lamp) 

Lamp,  Electric,  Pendant An  in- 
candescent electric  lamp  suspended  by  flexible 
twin-wire. 

Lamp,  Electric,  Safety An  in- 
candescent electric  lamp,  with  thoroughly 
insulated  leads,  employed  in  mines,  or  other 
similar  places,  where  the  explosive  effects  of 
readily  igmtable  substances  are  to  be  feared. 

Such  lamps  are  often  directly  attached  to  a 
portable  batter)',  in  which  case  they  can  be  read- 
ily carried  about  from  place  to  place. 

Lamp,  Electric,  Semi-Incandescent 

— An  electric  lamp  in  which  the  light  is  due 
to  the  combined  effects  of  a  voltaic  arc  and 
electric  incandescence. 

In  the  Reynier  semi-incandescent  lamp,  shown 
in  Fig.  337,  a  thin  pencil  of  carbon  C,  is  gentlj 
pressed  against  a  block  of  graphite  B.  A  lateral 
contact  is  provided  at  L,  through  a  block  o< 
graphite  I,  by  means  of  which  the  curn-nt  \«  re  • 


Lam.] 


309 


[Lam. 


to  the  lower  part  only  of  the  movable  rod 
C,  which  part  alone  is  rendered  incandescent. 
In  this  lamp,  the  light  is  due  both  to  the  incan- 

•C 


Fig.  337*    Semi- Incandescent  Lamp, 

aescence  of  the  rod  C,  and  to  the  small  arc  formed 
at  J,  between  its  lower  end  and  the  contact  block 
B,  though  mainly  from  the  latter.  The  semi- 
incandescent  electric  lamp  has  not  as  yet  been  in- 
produced  to  any  considerable  extent. 

Lamp,  Electric,  Series-Connected  Incan- 
descent   An  incandescent  electric  lamp 

adapted  for  use  in  series  circuits. 


Fig,  338.    Serbs  Incandescent  Electric  lamp. 

A  form  of  series  incandescent  lamp,  attached 
to  pendant  and  shade,  is  shown  hi  Fig.  338. 

In  thQ  series  connected  incandescent  lamp,  un- 
Hlce  the  multiple-connected  incandescent  electric 
lamp,  the  resistance  of  the  filament  is  low.  This 
Is  done  in.  order  to  prevent  the  total  resistance  of 


the  circuit  from  requiring  too  high  an  electro- 
motive force  for  operation.  In  order  to  preserve 
the  continuity  of  the  circuit  on  the  failure  of  any 
lamp  to  operate,  some  form  of  automatic  cut-out 
is  employed.  This  is  generally  some  form  of 
film  cut-out.  (See  Cut-Out,  Film.) 

Lamp  Hour. — (See  Hour,  Lamp.) 

Lamp,  Incandescent,  Electric  Filament 

Of A  term  now  generally  applied  to  the 

incandescing  conductor  of  an  incandescent 
electric  lamp,  whether  the  same  be  of  very 
small  cross-section  or  of  comparatively  large 
cross-section. 

The  term  filament  is  properly  applied  to  a  con- 
ductor containing  fibres  or  filaments  extending  in 
the  general  direction  of  the  length  of  the  incan- 
descing conductor.  Such  a  conductor  is  made  of 
carbonizable  fibrous  material,  cut  or  shaped  prior 
to  carbonization  so  as  to  have  its  fibres  extend- 
ing with  their  greatest  length  in  the  direction  of 
length  of  the  filament. 

Lamp,  Incandescent,  Straight  Filament 

An    incandescent    electric    lamp    in 

which  a  straight  filament,  placed  in  an  ex- 
hausted glass  chamber,  is  rendered  luminous 
by  the  effects  of  electro- 
static waves  or  thrusts  of 
high  frequency. 

The  straight  filament  in 
candescent  lamp  is  the  in- 
vention of  Tesla.  One 
form  of  such  a  lamp  is 
shown  in  Fig.  339. 

The  glass  globe  b,  of  the 
lamp  is  provided  with  a 
cylindrical  neck,  inside  of 
which  is  placed  a  tube  m, 
of  conducting  material,  on 
the  side  and  over  the  end 
of  the  insulating  plug  n. 

The  light-giving  fila- 
ment e,  is  a  straight  car- 
bon stem,  connected  to  the 
plate  by  a  conductor  cov- 
ered with  a  refractory  in- 
sulating material  k.  An 
insulated  tube-socket  p, 
provided  with  a  metallic  lining  s,  serves  to  sup  • 
port  the  lamp  and  connect  it  with  one  pole  of  the 
source  of  current.  It  will  be  noticed  that  the  coat- 


33Q.      Tesla's 
Straight  Filament  In- 
candescent Lamp. 


Lam.] 


310 


[Law. 


ings  s  and  m,  form  the  plates  of  a  condenser. 
The  other  terminal  of  the  machine  may  be  con- 
nected to  the  metal  coated  walls  of  the    room, 
or  to  metallic  plates  suspended  from  the  ceiling. 
Lamp  Indicator. — (See  Indicator,  Lamp.) 


Lamp,  Pilot 


— In  systems   for  the 


operation  of  electric  lamps,  an  incandescent 
lamp  employed  in  a  station  to  indicate  the 
difference  of  potential  at  the  dynamo  ter- 
minals, by  means  of  the  intensity  of  its  emitted 
light. 

Lamp  Rod. — (See  Rod,  Lamp?) 

Lamp  Socket  Switch. — (See  Switch, 
Lamp  Socket?) 

Lamps,  Bank  of — A  term  applied 

to  a  number  of  lamps,  equal  to  about  half  the 
load,  that  were  formerly  placed  in  view  of  the 
attendant  in  circuit  with  a  dynamo  that  is  to 
be  placed  in  a  parallel  circuit  with  another 
dynamo,  one  of  the  lamps  of  which  is  also 
in  view. 

When  the  lamps  "in  bank  "  were  judged  to  be 
of  the  same  brilliancy  as  the  one  fed  by  the  other 
dynamo,  the  attendant  switched  the  dynamo  par- 
allel with  the  other,  and  at  the  same  time  cut  off 
the  bank  of  lamps  from  the  switched  in  dynamo. 

The  method  is,  however,  wrong.  The  proper 
way  is  to  make  the  voltage  of  the  dynamo  equal 
to  that  of  the  circuit.  Then  connect  it  and 
finally  raise  its  electromotive  force  until  it  takes 
its  share  of  the  load. 

Lamps,  Cartoning Placing  carbons 

in  electric  arc  lamps. 

When  the  carbons  are  consumed,  the  lamp 
requires  recarboning.  The  old  carbon  ends  are 
replaced  by  new  carbons,  and  the  lamp  rods 
cleansed. 

Large  Calorie. — (See  Calorie,  Great.) 
Latent    Electricity. — (See     Electricity, 
Latent) 

Lateral  Discharge. — (See  Discharge, 
Lateral.) 

Lateral  Induction. — (See  Induction,  Lat- 
eral.) 

Lateral  Leakage  of  Lines  of  Magnetic 
Force. — (See  Leakage,  Lateral,  of  Lines  of 
Magnetic  Force?) 


Lateral  Magnetic  Leakage.— (See  Leak- 
age, Lateral,  of  Lines  of  Magnetic  Force?) 

Latitude,  Magnetic The  distance 

a  place  is  situated  north  or  south  of  the  mag- 
netic equator 

All  places  that  have  the  same  magnetic  latitude 
have  the  same  value  for  the  magnetic  inclination 
and  magnetic  intensity,  or  are  on  the  same  isocli- 
nal and  isodynamic  lines.  The  magnetic  latitude 
is  the  same  at  all  points  of  a  magnetic  parallel. 

Launch,  Electric A  boat,  the  mo- 
tive power  for  which  is  electricity,  suitable  for 
launching  from  a  ship. 

Up  to  the  present  time  electric  launches  have 
been  propelled  by  means  of  electric  motors,  driven 
by  means  of  powerful  storage  batteries. 

A  form  of  electric  launch  constructed  for  the 
English  Government  is  shown  in  Fig.  340.  It  is 


-  340,    Electric  Launch. 

48^  feet  in  length  over  all,  by  8  feet  9  inches 
beam,  with  an  average  draft  of  2  feet  3  inches. 
Its  speed  is  8  knots  per  hour.  It  will  carry  forty 
fully  equipped  soldiers. 

Law,  Jacobi's  --  The  maximum  work 
done  by  a  motor  is  reached  when  the  counter- 
electromotive  force  is  equal  to  one-half  of  the 
impressed  electromotive  force,  or, 


Law,  Joule's  ----  The  heating  power  of 
a  current  is  proportional  to  the  product  of 
the  resistance  and  the  square  of  the  current 
strength.  (See  Heat,  Electric?) 

Law,  Natural  --  A  correct  expression 
of  the  order  in  which  the  causes  and  effects 
of  natural  phenomena  follow  one  another. 

The  law  of  gravitation,  for  example,  correctly 
expresses  the  order  of  sequence  of  the  phenomena 
which  result  when  unsupported  bodies  fall  to  the 
earth.  It  should  be  carefully  borne  in  mind,  how- 
ever, that  natural  laws  cannot  be  regarded  as 
explaining  the  ultimate  causes  of  natural  phenc- 


Law.] 


311 


[Law. 


mena,  but  merely  express  their  order  of  occur- 
rence or  sequence. 

We  are  ignorant,  for  example,  of  the  true  cause 
of  gravitation  and  are  only  acquainted  with  its 
effects.  This  is  true  of  all  ultimate  physical 
causes,  save  for  our  belief  in  their  origin  in  a 
Divine  will. 

Law  of  Electro-Chemical  Equivalence. 
— (See  Equivalence,  Electro-Chemical,  Law 
of) 

Law  of  Kohlrausch. — In  electrolytic  con- 
duction, each  atom  has  a  rate  of  motion  for 
a  given  liquid,  which  is  independent  of  the 
element  with  which  it  may  have  been  com- 
bined. 

In  the  following  table,  the  rate  of  motion  of 
various  kinds  of  atoms  through  nearly  pure  water 
for  a  difference  of  potential  of  one  volt  per  linear 
centimetre,  is  given: 

H I.o8    centimetres  per  hour. 

K 0.205  centimetre  " 

Na 0.126  "  " 

Li 0.094  "  " 

Ag 0.166  "  " 

C 0.213  "  " 

1 0.216  "  " 

NO8 0.174          "  " 

Law  of  Ohm,  or  Law  of  Current 
Strength. — The  strength  of  a  continuous 
current  is  directly  proportional  to  the  differ- 
ence of  potential  or  electromotive  force  in  the 
circuit,  and  inversely  proportional  to  the  re- 
sistance of  the  circuit,  /.  e.,  is  equal  to  the 
quotient  arising  from  dividing  the  electromo- 
tive force  by  the  resistance. 


Fig.  341.     Current  Strength  in  Circuit. 
Ohm's  law  is  expressed  algebraically  thus: 
C  =  5;  or,  E  =  C  R. 

If  the  electromotive  force  is  given  in  volts,  and 
the  resistance  in  ohms,  the  formula  will  give  the 
current  strength  directly  in  amperes. 


The  resistance  of  any  electric  circuit,  as,  for 
example,  that  shown  in  Fig.  341,  consists  of  three 
parts,  viz.: 

(i.)  The  internal  resistance  of  the  source,  r. 

(2.)  That  of  the  conducting  wires  or  leads,  r'; 
and 

(3.)  That  of  the  electro-receptive,  r",  energized 
by  the  current.  Ohm's  law  applied  to  this  case 
would  be: 


_ 

= 


That  is,  the  resistance  of  the  entire  circuit  is 
equal  to  the  sum  of  the  separate  resistances  of  its 
different  parts. 

Since  C=  H,  (i);  then  E  =  C  R,  (2); 
and  R  =  ?,  (3). 

But,  since  a  current  of  one  ampere  is  equal  to 
one  coulomb  per  second,  then,  in  order  to  deter- 
mine in  coulombs  the  quantity  of  electricity  pass- 
ing in  a  given  number  of  seconds,  it  is  only  neces- 
sary to  multiply  the  current  by  the  time  in  seconds, 
or  Q  =  C  T  (4). 

Hence,  referring  to  the  above  equations  (i), 
(2),  (3)  and  (4);  according  to  Ohm's  law: 

(i.)  The  current  in  amperes  is  equal  to  the 
electromotive  force  in  volts  divided  by  the  resist- 
ance in  ohms. 

(2.)  The  electromotive  force  in  volts  is  equal  to 
the  product  of  the  current  in  amperes  and  the 
resistance  in  ohms. 

(3.)  The  resistance  in  ohms  is  equal  to  the  elec- 
tromotive force  in  volts  divided  by  the  current  in 
amperes. 

(4.)  The  quantity  of  electricity  in  coulombs  is 
equal  to  the  current  in  amperes  multiplied  by  the 
time  in  seconds. 

Law  of  Yolta,  or  Law  for  Contact-Series. 

—  A  law  for  the  differences  of  electric  potential 
produced  by  the  contact  of  dissimilar  metals 
or  other  substances. 

"  The  difference  of  potential  between  any  two 
metals  is  equal  to  the  sum  of  the  differences  of 
potential  between  the  intervening  substances  in 
the  contact  series"  (See  Electricity,  Contact. 
Series,  Contact.) 


Law,  Pfluger's 


— A  given  tract  of 


nerve  is  stimulated  by  the  appearance  of 
kathelectrotonus  and  the  disappearance  of  an- 
electrotonus ;  not,  however,  by  the  disap- 


Law.J 


312 


Law, 


pearance  of  kathelectrotonus  nor  by  ihe  ap- 
pearance of  anelectrotonus. — (Landois  and 
Stirling?} 

Law,  Poynting's At  any  point  in 

a  magnetic  field,  or  a  conductor  conveying 
current,  the  energy  moves  perpendicularly  to 
the  plane  containing  the  lines  of  electric  force 
or  the  lines  of  magnetic  force,  and  the  amount 
of  energy  crossing  the  unit  of  area  of  this 
plane  per  second  is  equal  to  the  product  of 
the  intensities  of  the  two  forces  multiplied  by 
the  sine  of  the  angle  between  them,  divided 
by  4?t. 

If  E,  represents  the  electric  force  of  a  small  body 
charged  with  positive  electricity,  and  H,  the 
magnetic  force  or  forces  of  a  smaller  free  unit 
north  pole,  and,  if  these  forces  at  any  point  in 
the  magnetic  field  are  inclined  at  an  angle,  9, 
then  e,  the  flow  of  energy  per  second  at  this  point, 
in  a  direction  oerpendicular  to  the  planes  of  E  and 
His, 

E  H  sin.  9 

C  — :  

\it 

There  is,  therefore,  a  difference  in  the  direction 
of  the  flow  of  electricity  and  the  flow  of  electric 
energy.  Electricity  may  be  conceived  as  passing 
through  the  conductor  something  like  water 
through  a  pipe,  but  electrical  energy  does  not 
travel  in  this  way.  Electrical  energy  travels 
through  the  surrounding  dielectric,  which  is 
thereby  strained,  and  it  propagates  this  strain 
from  point  to  point  until  it  reaches  the  conductor 
and  is  there  dissipated. 

Law,  Toltametric The    chemical 

action  produced  by  electrolysis  in  any  elec- 
trolyte is  proportional  to  the  amount  of  elec- 
tricity which  passes  through  the  electrolyte. 

This  is  called  the  Voltametric  law,  because  any 
vessel  containing  an  electrolyte,  and  furnished 
with  electrodes,  so  that  electrolysis  may  take  place 
on  the  passage  of  the  current,  and  is  provided 
with  means  for  measuring  the  amount  of  the 
electrolysis  which  occurs,  is  called  a  Voltameter. 
(See  Voltameter.  Electrolysis.'] 

Laws,  Amptfre's,  or  Laws  of  Electro- 
Dynamic  Attraction  and  Repulsion  — 

Laws  expressing  the  attractions  and  repul- 
sions cf  electric  circuits  en  one  another  or 
on  magnets. 


Laws,  DuVs  •  — "  The  magnetism  ex- 
cited at  any  transverse  section  of  a  magnet  is 
proportional  to  the  square  root  of  the  distance 
between  the  given  section  and  the  near  end 
of  the  magnet." 

"  The  free  magnetism  at  any  given  trans- 
verse section  of  a  magnet  is  proportional  to 
the  difference  between  the  square  root  of  half 
the  length  of  the  magnet  and  the  square  root 
of  the  distance  between  the  given  section  and 
the  nearest  end." 


Laws,  KirchhoiTs 


—  The  laws  for 


branched  or  shunted  circuits. 

These  laws  may  be  expressed  as  follows: 

(I.)  In  any  number  of  conductors  meeting  at  a 
point,  if  currents  flowing  to  the  point  be  considered 
as  -[-,  and  those  flowing  away  from  it  as  — ,  the 
algebraic  sum  of  the  meeting  currents  will  be 
zero. 

This  is  the  same  thing  as  saying  as  much  elec- 
tricity must  flow  away  from  the  point  as  flows  to- 
ward it. 

(2.)  In  any  system  of  closed  circuits  the  alge- 
braic sum  of  the  products  of  the  currents  into  the 
resistances  is  equal  to  the  electromotive  force  in 
the  circuit. 

In  this  case  all  currents  flowing  in  a  certain 
direction  are  taken  as  positive,  and  those  flowing 
in  the  opposite  direction  as  negative.  All  elec- 
tromotive forces  tending  to  produce  currents  in 
the  direction  of  the  positive  current  are  taken  as 
positive,  and  those  tending  to  produce  currents  iu 
the  opposite  direction,  as  negative. 

E 
This  follows  from  Ohm's  law;  for,  since  C  =  — , 

R 

the  electromotive  force  E  =  CR,  and  this  is  true, 
no  matter  how  often  the  circuit  is  branched. 

Laws,  Lenz's Laws  for  determining 

the  directions  of  currents  produced  by  electro- 
dynamic  induction. 

The  direction  of  the  currents  set  up  by  electro- 
dynamic  induction  is  always  such  as  to  oppose 
the  -notions  by  which  such  currents  were  pro- 
duced. 

Laws  of  Becquerel,  or  Laws  of  Mag- 
neto-Optic Rotation. — Laws  for  the  mag- 
neto-optic rotation  of  the  plane  of  polarization 
of  light.  (See  Rotation,  Magneto-Optic^ 

Laws  of  Con^omfo,  o»«  Laws  of  Electro- 


Law.  I  3 

static  and  Magnetic  Attractions  and  Re- 
pulsions. —  Laws  for  the  force  of  attraction 
and  repulsion  between  charged  bodies  or  be- 
tween magnet  poles. 

The  fact  that  the  force  of  electrostatic  attrac- 
tion or  repulsion  between  two  charges,  is  directly 
proportional  to  the  product  of  the  quantities  of 
electricity  of  the  two  charges  and  inversely  propor- 
tional to  the  square  of  the  distance  between  them, 
is  known  as  Coulomb''  s  Law.  Coulomb  also  as- 
certained that  the  attractions  and  repulsions  be- 
tween magnet  poles  are  directly  proportional  to  the 
product  of  the  strength  of  the  two  poles,  and  in- 
Tersely  proportional  to  the  square  of  the  distance 
between  them.  This  is  also  called  Coulomb's 
Law. 

Coulomb's  law,  in  order  to  be  accurate,  must 
take  into  account  the  specific  inductive  capacity 
of  the  intervening  medium.  The  correct  expres- 
sion for  the  force  between  two  quantities  q  and  q', 
of  electricity  would  be,  therefore, 


where  K,  is  equal  to  the  specific  inductive  capacity 
of  the  medium  separating  the  two  charges. 

In  a  similar  manner  when  the  force  is  exerted 
between  two  magnet  poles,  to  be  accurate,  we  must 
take  into  account  the  magnetic  permeability  of 
the  medium  between  the  two  magnets.  The  cor- 
rect  expression  for  the  force  between  two  magnet 
poles  is,  therefore, 

•p.  _ 
" 


when  ju,  is  the  magnetic  permeability. 
Laws  of  Faraday,  or  Laws  of  Electrolysis 

--  Laws  for  the   effects  of  electrolytic 
decomposition.     (See  Electrolysis!) 

These  laws  are  as  follows: 

(i.;  The  amount  of  an  electrolyte  decomposed 
is  directly  proportional  to  the  quantity  of  elec- 
tricity which  passes  through  it  ;  or,  the  rate  at 
which  a  body  is  electrolyzed  is  proportional  to 
the  current  strength  producing  such  electrolysis. 

(2.)  If  the  same  current  be  passed  through  dif- 
ferent electrolytes,  the  quantity  of  each  ion 
evolved  is  proportional  to  its  chemical  equivalent. 

Laws  of  Jonle.  —  Laws  expressing  the  de- 
velopment of  heat  produced  in  a  circuit  by  an 
electric  current. 

These  laws  may  be  expressed  as  follows  : 

(l.)  The  amount  of  heat  developed  in  any  cir- 


[Lea. 

cuit  is  proportional  to  its  resistance,  providing 
the  current  strength  is  constant. 

(2. )  The  amount  of  heat  developed  in  any  cir- 
cuit is  proportional  to  the  square  of  the  current 
passing,  providing  the  resistance  is  constant. 

(3.)  The  amount  of  heat  developed  in  any  cir- 
cuit is  proportional  to  the  time  the  current  con- 
tinues. 

Or,  H  =  C*  RtX0.24. 

Where  H,  equals  the  heat  in  small  calories,  C, 
equals  the  current  in  amperes,  R  equals  the  re- 
sistance in  ohms,  t,  equals  the  time  in  seconds, 
and  0.24,  the  heat-units  per  second  developed  in 
a  resistance  of  i  ohm  by  the  passage  of  i  am- 
pere. 

Lay  Torpedo.— (See  Torpedo,  Lay.) 


Layer,   Crookes' 


— A      layer,     or 


stratum,  of  the  residual  atmosphere  of  a 
vacuous  space,  in  which  the  molecules,  recoil- 
ing from  a  heated  or  electrified  surface,  do 
not  meet  other  molecules,  but  impinge  on  the 
walls  of  the  vessel  directly  opposite  such 
heated  or  electrified  surface. 

A  Crookes  layer  may  result  as  the  effect  of 
two  different  causes,  viz. : 

(i.)  The  rarefaction  of  the  gas  is  such  that  the 
distance  between  the  walls  of  the  vessel  and  the 
heated  surface  is  less  than  the  mean-free-path  of 
the  molecules. 

(2.)  The  wall  is  so  near  the  heated  surface  that 
the  distance  between  the  two  is  less  than  the  ac- 
tual mean-free-path  of  the  molecules.  Under 
these  last-named  circumstances  Crookes'  layers 
may  result,  whatever  be  the  density  of  the  gas. 

Laying-Up  Cables. — (See  Cables,  Lay- 
ing-Up.) 

Lead,  Angle  of  —  — The  angular  devia- 
tion from  the  normal  position,  which  must  be 
given  to  the  collecting  brushes  on  the  com- 
mutator cylinder  of  a  dynamo-electric  ma- 
chine, in  order  to  avoid  destructive  burning. 
(See  Commutator,  Burning  <z/.) 

The  necessity  for  giving  the  collecting  brushes 
a  lead,  arises  both  from  the  magnetic  lag  and  from 
the  distortion  of  the  field  of  the  machine  by  the 
magnetization  of  the  armature  current.  The 
angle  of  lead  is,  therefore,  equal  to  the  sum  of  the 
angle  of  lag,  and  the  angular  distortion  due  to  the 
magnetization  produced  by  the  armature  current . 


Lca.J 


314 


[La. 


Lead,  Cable A  lead  containing  a 

conductor  formed  of  several  stranded  con- 
ductors, as  distinguished  from  a  wire  lead  or 
a  lead  containing  a  single  conductor. 

Lead,  Flexible A  conductor  formed 

of  a  number  of  small  stranded  conductors  for 
the  purpose  of  obtaining  flexibility. 

Lead,  Flexible  Twin A  flexible 

conductor  in  which  two  parallel  and  sepa- 
rately insulated  wires  are  placed. 

Lead  of  Brushes  of  Dynamo-Electric 
Machine. — The  angular  deviation  from  the 
normal  position,  which  it  is  necessary  to  give 
the  brushes  on  the  commutator  of  a  dynamo- 
electric  machine,  in  order  to  obtain  efficient 
action.  (See  Lead,  Angle  of.) 

Lead  Scoring  Tool. — (See  Tool,  Scoring, 
Lead?) 

Lead  Sleeve. — (See  Sleeve,  Lead.) 

Lead,  Tee.— (See  Tee,  Lead.) 

Lead,  Wire A  lead  consisting  of  a 

single  conductor,  as  distinguished  from  a 
cable  lead,  or  a  lead  containing  a  number  of 
stranded  conductors. 

Lead  Wire.— (See  Wire,  Lead) 

Leading  Horn  of  Pole  Pieces  of  Dynamo- 
Electric  Machine. — (See  Horns,  Leading,  of 
Pole  Pieces  of  a  Dynamo-Electric  Machine.) 

Loading-Ill  Wires. — (See  Wires,  Lead- 
ing-In.) 

Leading-Up  Wires.— (See  Wires,  Lead- 
ing-Up.) 

Leads. — The  conductors  in  any  system  of 
electric  distribution. 

In  distribution  by  parallel,  the  conductors 
through  which  the  current  flows  from  the  source 
are  sometimes  called  the  leads  in  contradis- 
tinction to  those  through  which  it  returns  to 
the  source. 

The  leads,  or  main  conductors,  in  a  multiple 
system  of  electric  lighting,  must  maintain  a  con- 
stant  potential  at  the  lamp  terminals.  The  dimen- 
sions of  the  leads  are,  therefore,  so  proportioned  as 
to  absorb  as  small  an  amount  of  potential  as  pos- 
sible. Since,  in  incandescent  lighting,  where  the 
connected  to  the  leads  in  multiple-arc, 

total  resistance  of  the  lamps  is  comparatively 


small,  the  resistance  of  the  leads  must  be  quite 
small  in  order  to  avoid  a  marked  drop  of  poten- 
tial. Comparatively  large  conductors  must, 
therefore,  be  used. 

The  main  conductor  for  series  circuits,  such  as 
for  arc-lights,  has  in  all  parts  the  same  current 
strength.  Since  the  sum  of  the  resistances  of  the 
lamps  in  such  a  circuit  is  quite  high,  a  compara- 
tively high  resistance  in  the  conductor  may  be 
employed  without  a  proportionally  large  absorp- 
tion of  potential.  Comparatively  small  conduc- 
tors can  therefore  be  used.  (See  Electricity,  Dis- 
tribution  of,  by  Constant  Currents.  Electricity, 
Distribution  of,  by  Alternating  Currents.) 

Leads,  Armature,  Twist  in  -  —A  dis- 
placement of  the  ends  of  the  wires  connected 
to  the  commutator  segment,  with  respect  to 
the  position  of  the  coils  on  the  armature,  for 
the  purpose  of  obtaining  a  more  convenient 
position  for  the  diameter  of  commutation, 
that  is,  for  the  collecting  brushes. 

Leak,  Oscillatory A  leak  or  grad- 
ual loss  of  electricity  which  takes  place  in 
alternately  opposite  directions. 

Leak,  Unidirectional A  gradual 

loss  or  leakage  of  electricity  which  takes  place 
in  one  and  the  same  direction. 

The  term  has  been  employed  to  distinguish 
such  a  leak  from  an  oscillatory  leak. 

Leakage  Conductor. — (See  Conau<-fo>; 
Leakage) 

Leakage,  Electric  — The  gradual 

dissipation  of  a  current  due  to  insufficient  in- 
sulation. 

Some  leakage  occurs  under  nearly  all  circum- 
stanres.  On  telegraphic  lines,  during  wet 
weather,  the  leakage  is  often  so  great  as  to  inter- 
fere with  the  proper  working  of  the  lines. 

Leakage,  Electrostatic The  grad- 
ual dissipation  of  a  charge  due  to  insufficient 
insulation. 

The  leakage  of  a  well  insulated  conductor, 
placed  in  a  high  vacuum,  is  almost  inappreciable. 
Crookes  has  maintained  electric  charges  in  high 
vacua  for  years  without  appreciable  loss. 

Leakage,  Lateral,  of  Lines  of  Magnetic 
Force The  failure  of  lines  of  magnetic 


Lea.] 


315 


[Len. 


force  to  pass  approximately  parallel  to  one 
another  through  a  bar  of  iron  or  other  mag- 
netizable material,  when  it  has  come  to  rest 
in  a  magnetic  field  in  which  it  is  free  to 
move. 

The  escape  of  the  lines  of  magnetic  force 
from  the  sides  of  a  bar  or  other  similar 
magnet,  instead  of  from  the  poles  at  the 
end. 

When  a  bar  of  magnetizable  material,  sus- 
pended so  as  to  be  free  to  move,  comes  to  rest  in 
a  magnetic  field  in  which  it  is  undergoing  mag- 
netization, it  has  its  greatest  length  parallel  to 
the  direction  of  the  lines  of  force.  If  the  bar  is  a 
long,  thin,  straight  bar,  the  lines  of  force  do  not 
all  pass  in  or  come  out  at  its  ends.  On  the  con- 
trary, many  of  these  lines  of  force  or  induction 
pass  in  or  come  out  at  other  points.  The  mag- 
netic induction  is,  therefore,  unequal  at  different 
sections  of  the  bar.  In  other  words,  the  mag- 
netic flux  or  intensity  is  not  constant  per  unit  of 
all  cross-sections  of  such  bar. 

Leakage,  Magnetic A  useless  dis- 
sipation of  the  lines  of  magnetic  force  of  a 
dynamo-electric  machine,  or  other  similar 
device,  by  their  failure  to  pass  through  the 
armature  where  they  are  needed. 

Useless  dissipation  of  lines  of  magnetic 
force  outside  that  portion  of  the  field  of  a 
dynamo-electric  machine  through  which  the 
armature  moves. 

Such  a  leakage  can  be  detected  by  an  instru- 
ment called  a  magnetophone.  (See  Magneto- 
phone.} 

Magnetic  leakage  results  in  lowering  the  effi- 
ciency of  the  dynamo.  (See  Co-efficient,  Econo- 
mic, of  a  Dynamo-Electric  Machine. ) 

Leclanche~'s  Voltaic  Cell.— (See  Cell, 
Voltaic,  Lcdanch^ 

Leg". — In  a  system  of  telephonic  exchange, 
where  a  ground  return  is  used,  a  single  wire, 
or,  where  a  metallic  circuit  is  employed,  two 
wires,  for  connecting  a  subscriber  with  the 
main  switchboard,  by  means  of  which  any 
subscriber  may  be  legged  or  placed  directly 
in  circuit  with  two  or  more  other  parties. 
Leg  of  Circuit. — (See  Circuit,  Leg  of.) 
Legal  Earth  Quadrant.— (See  Quadrant, 
Legal  Earth) 
11— Vol.  1 


Legal  Ohm.— (See  Ohm,  Legal.) 

Legging-Key  Board.— (See  Board,  Leg- 
gtng-Key.) 

Length  of  Spark.— (See  Spark,  Length 
of) 

Lens,  Achromatic A  lens  the 

images  formed  by  which  are  free  from  the 
false  coloration  produced  in  other  lenses  by 
dispersion. 

An  ordinary  lens  can  be  rendered  approxi- 
mately achromatic  by  the  use  of  a  diaphragm. 
Achromatic  lenses  generally  consist  of  the  com 


•^%"«  342-    Equal  and  Opposite  Refracting  Angles. 

bination  of  a  double  convex  lens  of  flint  glass  arx? 
a  concave  lens  of  crown  glass. 

The  ray  of  light  entering  the  prism  A  B  Cj 
Fig.  342,  suffers  dispersion  (separation  into  pris 
made  colors).  This  dispersion  in  the  sam' 


Principle  of  Achromatitm. 


medium  is  proportional  to  the  angle  g,  between 
the  incident  and  emergent  faces,  called  the  re- 
fracting angle. 

If,  now,  another  prism  B  C  D,  of  the  same  ma- 
terial, with  a  refracting  angle  g',  equal  to  g,  is 
combined  with  the  first  prism  in  the  manner 
shown  in  Fig.  342,  it  will  produce  an  equal  but 
opposite  dispersion,  so  that  the  ray  of  light  will 
emerge  at  R',  free  from  rainbow  tints,  but  par- 
allel to  its  original  direction. 

The  variety  of  glass  called  crown  glass  pro- 
duces only  half  as  great  dispersion  of  light  as  the 
variety  called  flint  glass,  under  the  same  refract* 


t-en.] 


316 


ing  angle  g.  If  the  prism  A  B  C,  of  crown  glass, 
Fig-  343,  whose  angle  g,  is  twice  as  great  as  the 
refracting  angle  g  ,  of  the  prism  B  C  D,  of  flint 
glass,  be  placed  together  in  the  manner  shown, 
then  the  ray  R,  will  be  transmitted  at  R' ,  free  from 
color,  but  will  not  eiixrge  par  ailed  to  its  original 
direction  ;  in  other  words,  it  suffers  refraction  or 
bending.  Consequently  such  a  combination  can 
be  used  to  free  a  pencil  of  light  from  false  colora- 
tion and  yet  permit  it  to  undergo  refraction, 
and  thus  act  as  a  lens.  (See  Refraction.') 

The  construction  ot  achromatic  lenses  is  based 
on  this  principle. 

The  crown  glass  is  generally  made  with  two 


Fig.  344.    Piano-Convex        Fig.  343.    Achromatic 
Achromatic  Lens.  Lens. 

convex  surfaces  ;  the  flint  glass,  with  one  con- 
cave and  one  plane  surface,  as  shown  in  Fig. 
344- 

Sometimes  both  surfaces  of  the  flint  glass  are 
made  curved,  as  in  Fig.  345. 

Lenz's  Law. — (See  Law,  Lens's.) 

Letter  Box,  Electric  —  — A  device 
that  announces  the  deposit  of  a  letter  in  a 
box  by  the  ringing  of  a  bell,  or  by  the  move- 
ment of  a  needle  or  index. 

These  devices  generally  act  by  the  closing  or 
opening  of  an  electric  circuit  on  the  fall  of  the 
letter  into  the  box. 


Leyden  Jar. — (See  far,  Leyden) 
Leyden  Jar  Pattery. — (See  Battery,  Ley 
den  Jar.} 

Lichtenberg's  Dust  Figures. — (See  Fig- 
ures, Lichtenberg's  Dust) 

Life  Curve  of  Incandescent  Electric 
Lamp. — (See  Curve,  Life,  cf  Incandescent 
Electric  Lamp?) 

Life  of  Electric  Incandescent  Lamp. — 

(See  Lamp,  Incandescent,  Life  of.) 

Light,  Auroral  -  —The  light  given  off 
during  the  prevalence  of  an  aurora.  (See 
Aurora  Bore  alts) 

Light,  Electric  —  —Light  produced  by 
the  action  of  electric  energy. 

Electric  light  is  produced  by  electric  energy  in 
various  ways,  the  most  important  of  which  are  as 
follows,  viz.: 

(I.)  By  the  passage  of  an  electric  discharge 
through  a  gas  or  vapor,  either  in  a  rarefied  condi- 
tion, at  ordinary  atmospheric  pressure,  or  at  pres- 
sures higher  than  that  of  the  ordinary  pressure. 
In  any  of  these  cases  the  gas  or  vapor  is  heated  to 
incandescence  by  the  passage  of  the  discharge. 

(2.)  By  the  incandescence  of  a  solid  by  the 
heating  power  of  the  current,  as  in  the  incandes- 
cent lamp. 

(3.)  By  the  incandescence  of  a  solid  by  the  ac- 
tion of  a  rapidly  alternating  electrostatic  field,  as 
in  Tesla's  incandescent  lamp. 

\4. )  By  the  volatilization  of  a  solid  and  the  form- 
ation thereby  of  a  voltaic  arc. 

(5.)  By  the  combination  of  the  effects  of  incan- 
descence and  the  voltaic  arc. 

The  amount  of  light  produced  in  proportion  to 
the  amount  of  energy  expended  to  produce  it 
is  probably  least  in  the  case  of  light  produced 
by  the  sparks  of  a  Wimshurst  or  Holtz  machine, 
or  as  in  ( I ),  than  in  any  other  case  in  which  electric 
energy  acts  to  produce  luminous  energy. 

Light,  Electric,  Pumping  of  —  — (See 
Pumping  of  Electric  Light) 

Light,  Intensity  of  —  —The  brilliancy 
or  illuminating  power  of  a  light  as  measured 
by  a  photometer  in  standard  candles  or  other 
standard  units.  (See  Photometer.  Candle, 
Standard) 

Light,  Maxwell's  Electro  -  Magnetic 
Theory  of — A  hypothesis  for  the 


317 


cause  or  light  proposed  by  Maxwell,  based 
on  the  relations  existing  between  the  phe- 
nomena of  light  and  those  of  electro-magnet- 
ism. 

Maxwell's  electro-magnetic  theory  of  light  as- 
sumes that  the  phenomena  of  light  and  magnet- 
ism are  each  due  to  certain  motions  of  the  ether, 
electricity  and  magnetism  being  due  to  its  r«Ma- 
tions,  and  light  to  oscillations,  or  its  to-and-fro 
motions. 

Maxwell  proposed  this  theory  to  show  that  the 
phenomena  of  light,  heat,  electricity  and  magnet- 
ism could  all  be  explained  by  one  and  the  same 
cause,  viz.,  a  vibratory  or  oscillatory  motion  of 
the  particles  of  the  hypothetical  ether.  Maxwell 
died  before  completing  his  hypothesis,  and  it  has 
never  since  been  sufficiently  developed  to  thor- 
oughly entitle  it  to  the  name  of  a  theory.  This 
theory  has  more  recently  been  elaborated  by 
Hertz.  (See  Electricity,  Hertz's  Theory  of  Elec- 
tro-Magnetic Radiations  or  Waves .) 

There  are,  however,  numerous  considerations 
which  render  it  probable  that  electric  and  mag- 
netic phonomena,  like  those  of  light  and  heat, 
have  their  origin  in  a  vibratory  or  oscillatory  mo- 
tion  of  the  luminiferous  ether.  A  few  of  these, 
as  pointed  out  by  Maxwell,  S.  P.  Thompson, 
Lodge,  Larden  and  others,  are  as  follows: 

(I.)  It  is  possible  that  the  thing  called  elec- 
tricity is  the  ether  itself,  negative  electrification 
consisting  in  an  excess  of  the  ether,  and  positive 
electrification  in  a  d-ficit.  (See  Electricity,  Sin- 
gle-Fltdd  Hypothesis  of.) 

(2.)  It  is  possible  that  electrostatic  phenomena 
consist  in  a  strain  or  deformation  of  the  ether. 
A  dielectric  may'differ  from  a  conductor  in  that 
the  former  may  have  such  an  attraction  for  the 
ether  as  to  give  it  the  properties  of  an  elastic 
solid,  while  in  the  latter  the  ether  is  so  free  to 
move  that  no  strain  can  possibly  be  retained  by 
it.  (See  Dielectric.  Conductor.) 

(3.)  Dielectrics  are  transparent  and  conductors 
are  opaque. 

There  are  exceptions  to  this  in  the  case  of  vul- 
canite and  many  other  excellent  dielectrics.  Nor 
should  this  similarity  be  expected  to  be  general  in 
view  of  the  well  known  differences  that  exist  be- 
tween diathermancy  and  transparency. 

(4.)  It  Is  possible  that  an  electric  current  con- 
sists of  a  real  motion  ot  translation  of  the  ether 
through  a  conductor. 

(5.)  It  is  possible  that  electromotive  force  re- 


sults from  differences  of  ether  pressures.     This 
would  of  course  follow  from  (4). 

(6.)  The  vibrations  of  light  are  propagated  in 
a  direction  at  right  angles  to  the  direction  in 
which  the  light  is  moving.  The  magnetic  field 
of  a  current  is  propagated  in  planes  at  right 
angles  to  the  direction  in  which  the  current  is 
flowing. 

(7.)  It  is  possible  that  lines  of  electrostatic  and 
magnetic  force  consist  of  chains  of  polarized  ether 
particles. 

(8.)  The  velocity  of  propagation  of  light  agrees 
very  nearly  with  the  velocity  of  propagaiion  of 
electro-magnetic  induction.  (See  Ratio  Velocity.) 
(9. )  In  certain  axial  crystals  the  difference  of 
transparency  in  the  direction  of  certain  axes, 
corresponds  with  the  direction  in  which  such 
crystals  conduct  electricity. 

Recent  investigations  render  it  almost  certain 
that  light  and  electro-magnetic  waves  or  radia- 
tions are  one  and  the  same,  and,  therefore,  have 
the  same  velocity  of  propagation  through  free 
ether.  Through  fixed  ether,  that  is,  through  the 
ether  that  exists  between  the  molecules  of  differ- 
ent kinds  of  matter,  as  is  well  known,  the  velocity 
of  propagation  differs  with  different  substances. 
(See  Electricity,  Hertz's  Theory  of  Electro-Mag- 
netic Radiations  or  Waves. ) 

Light,    Northern (See    Aurora 

Borealis^) 

Light,  Platinum-Standard  — The 

light  emitted  by  a  surface  of  platinum  one 
square  centimetre  in  area,  at  its  temperature 
of  fusion. 

This  is  called  the  Violle  Standard  and  is  ex- 
tensively used  in  France. 

Light,  Search,  Automatic — A  search 

light  in  which  a  parallel  or  slightly  diverging 
beam  of  light  is  automatically  caused  to 
sweep  the  horizon,  and  thus  disclose  the  ap- 
proach of  a  torpedo  boat  or  other  similar 
danger. 

This  is  called  an  automatic  search  light  because 
it  may  be  caused  to  automatically  sweep  the  hori- 
zon, instead  of  being  manipulated  by  hand,  as 
usual. 

Light,  Search,  Electric An  electric 

arc  light  placed  in  a  focusing  lamp  before  a 
lens  or  mirror,  so  as  to  obtain  either  a  parallel 
beam  or  a  slightly  divergent  pencil  of  light 


318 


for  lighting  the  surrounding  space  for  pur- 
poses of  exploration. 

Light,    Southern    — (See   Aurora 

Australis?) 

Light,  Tail A  light  displayed  at  the 

rear  end  of  trains  in  order  to  avoid  rear  colli- 
sions. (See  Railroads,  Block  System  for.} 

Lighter,  Cigar,  Electric An  ap- 
paratus for  electrically  lighting  a  cigar. 
•  A  cigar  lighter  consists  essentially  of  a  wire  or 
rod  of  refractory  substance,  rendered  incandes- 
cent by  the  passage  of  a  current  obtained  from  a 
voltaic  battery,  secondary  generator,  or  other 
electric  source. 

Lighter,  Electric,  Argand A  name 

sometimes  given  to  an  argand  electric  plain- 
pendant  burner.  (See  Burner,  Argand- 
Electric,  Plain-Pendant?) 

Lighter,  Electric,  Argand  Valve 

A  name  sometimes  given  to  an  argand  elec- 
tric ratchet-pendant  burner.  (See  Burner, 
Argand- Electric,  Ratchet-Pendant?) 

Lighthouse  Illumination,  Electric 

—(See  Illumination,  Lighthouse,  Electric?) 

Lighting,  Arc Artificial  illumina- 
tion obtained  by  means  of  an  arc  light. 

The  term  arc  lighting  is  used  in  contradistinc- 
tion to  incandescent  lighting.  In  the  United 
States,  and,  indeed,  generally,  a  number  of  arc 
lights  are  placed  in  series  on  the  line  circuit,  con- 
nected generally  with  a  series  dynamo.  Each 
of  the  lamps  is  provided  with  a  safety  cut-out, 
which  cuts  out  or  removes  a  defective  lamp  from 
the  circuit  by  automatically  turning  or  switching 
the  current  through  a  shunt  of  low  resistance. 

Lighting,  Electric,  by  High  Frequency 

Currents A  system  of  electric  lighting, 

in  which  rods,  bars  or  filaments  of  carbon  or 
other  refractory  substances  are  raised  to  in- 
candescence when  placed  in  a  rapidly  alternat- 
ing electrostatic  field. 

This  system  of  electric  lighting  was  invented 
by  Nikola  Tesla.  Its  general  principles  will  be 
understood  from  an  inspection  of  Fig.  346. 

G,  is  a  dynamo  producing  alternating  currents 
of  comparatively  low  potential.  A  portion  of  its 
current  P,  acting  as  the  primary  of  an  induction 
coil,  induces  alternating  currents  of  high 


potential  in  the  secondary  circuit  S,  which, 
charging  the  condenser  C,  is  disruptively  dis- 
charged into  the  circuit  A,  provided  with  an  air 
gap  at  A'  through  P'.  The  inductive  action 
of  P',  on  S',  products  oscillatory  currents  of 


Fig.  346. 


Tesla.' s  High  Frequency  Currents 
System  of  Lighting:. 


enormous  frequency  and  potential  in  the  second- 
ary circuits  connected  therewith.  In  the  ap- 
paratus shown  in  Fig.  346,  two  incandescent 
electric  lamps  are  connected  with  the  secondary 
circuit,  one  with  a  single  straight  filament,  and 
the  other  with  a  ball  conductor.  The  other 
terminal  of  S  ,  is  connected  to  the  walls  of  the 
room  to  be  lighted.  (See  Lamp,  Incandescent, 
Straight  Filament.  Lamp,  Electric,  Incandes- 
cent Ball.} 

Lighting,  Electric,  Central  Station  - 

— The  lighting  of  a  number  of  houses  or  other 
buildings  from  a  single  station,  centrally  lo- 
cated. 

Central  station  lighting  is  distinguished  from  iso- 
lated lighting  by  the  fact  that  a  number  of  sepa- 
rate buildings,  houses  or  areas,  are  lighted  by  the 
current  produced  at  a  single  station,  centrally 
located,  instead  of  from  a  number  of  separate 
electric  sources  located  in  each  of  the  houses,  etc., 
to  be  lighted.  (See  Electricity,  Distribution  of. ) 


Lighting,  Electric    Gas 


—Igniting 


gas  jets  by  means  of  electric  discharges. 

Electric  sparks  are  caused  to  pass  through  a 
jet  of  escaping  gas,  and  thus  to  light  it.  These 
sparks  are  obtained  from  a  spark-coil,  i.  e.,  a 
coil  of  insulated  wire  connected  in  series  with 
the  circuit  so  as  to  produce  an  extra  current  on 
the  sudden  breaking  of  the  circuit,  the  discharge 
of  which  produces  a  spark  capable  of  igniting  the 
gas.  In  cases  where  a  number  of  burners  are  to 
be  simultaneously  lighted  the  sparks  required  for 


319 


lighting  the  gas  are  obtained  from  the  secondary 
of  an  induction  coil.  (See  Burner,  Automatic 
Electric.) 

Lighting,    Electric,    Isolated A 

system  of  electric  lighting  where  a  separate 
electric  source  is  placed  in  each  house  or 
area  to  be  lighted,  as  distinguished  from  the 
central  station  lighting,  where  electric  sources 
are  provided  for  the  production  of  the  current 
required  for  an  entire  neighborhood. 

Lighting,  Electric,  Long-Arc  System  of 

— A  system  of  electric  lighting  in  which 


long  arcs  are  maintained  between  the  carbon 
electrodes. 

Lighting,    Electric,    Short-Arc    System 

A  system  of  electric  lighting  in  which 

short  voltaic  arcs  are  maintained  between  the 
carbon  electrodes. 

Systems  of  short  arcs  require  an  electromotive 
force  of  about  25  volts,  which  is  about  one-half 
that  employed  in  long  arcs.  To  develop  an 
equal  amount  of  heat  energy  in  a  short  arc  as  in 
a  long  arc,  therefore,  requires  that  the  current  be 
of  double  strength. 

The  greater  part  of  the  light  of  a  voltaic  arc 
is  given  off  from  a  tiny  crater,  which  is  formed  in 
the  end  of  the  positive  carbon.  In  the  short-arc 
system  the  crater  lies  so  near  the  negative  carbon 
that  much  of  its.  light  is  necessarily  obscured,  and 
troublesome  shadows  are  sometimes  produced. 
The  long-arc  system  avoids  these  difficulties. 

Lightning. — The  spark  or  bolt  that  results 
from  the  disruptive  discharge  of  a  cloud  to 
the  earth,  or  to  a  neighboring  cloud.  (See 
Electricity,  Atmospheric.  Kite,  Franklin's?) 

Lightning  Arrester. — (See  Arrester, 
Lightning?) 

Lightning,    Back-Stroke    of An 

electric  discharge,  caused  by  an  induced 
charge,  which  occurs  after  the  direct  dis- 
charge of  a  lightning  flash. 

The  shock  is  not  caused  by  the  lightning  flash 
itself,  but  most  probably  by  a  charge  which  is  in- 
duced in  neighboring  conductors  by  the  discharge. 
A  similar  effect  may  be  noticed  by  standing  near 
the  conductor  of  a  powerful  electric  machine, 
when  shocks  are  felt  at  every  discharge. 

The  back-stroke  has  been  ascribed  by  many  to 


the  oscillations  by  which  a  disruptive  discharge 
is  effected.  (See  Discharge,  Oscillating.) 

The  effects  of  the  return  shock  are  sometimes 
quite  severe.  They  are  often  experienced  by 
sensitive  people,  on  the  occurrence  ot  a  lightning 
discharge,  at  a  considerable  distance  from  the 
place  where  the  discharge  occurred. 

In  some  instances,  the  return  stroke  has  been 
sufficiently  intense  to  cause  death.  In  general, 
however,  its  effects  are  much  less  severe  than 
those  of  the  direct  lightning  discharge. 

Lightning,  Ball A  name  some- 
times given  to  globular  lightning,  (See 
Lightning,  Globular?) 

Lightning,  Chain A  variety  of 

lightning  flash  in  which  the  discharge  takes 
a  rippling  path,  somewhat  resembling  a 
chain. 

Lightning  Conductor. — (See  Rod,  Light- 
ning?) 

Lightning,  Forked A  variety  of 

lightning  flash,  in  which  the  discharge,  on 
nearing  the  earth  or  other  object,  divides  into 
two  or  more  branches. 

Lightning,  Globular A  rare  form 

of  lightning,  in  which  a  globe  of  fire  appears, 
which  quietly  floats  for  a  while  in  the  air  and 
then  explodes  with  great  violence. 

The  exact  cause  of  globular  lightning  is  un- 
known. Phenomena  allied  to  it,  however,  have 
been  observed  by  Plant6  during  the  series  dis- 
charge of  his  rheostatic  machine.  Similar  pheno- 
mena are  sometimes,  though  rarely,  observed 
during  the  discharge  of  a  powerful  Leyden  battery. 
Sir  Wm.  Thomson  ascribes  the  effect  to  an  optical 
illusion  due  to  the  persistence  of  the  visual  impres- 
sion of  a  bright  flash.  This,  however,  would  not 
account  for  the  explosion  which  almost  invariably 
attends  globular  lightning. 

Lightning  Guard. — (See  Guard,  Light- 
ning?) 


Lightning,     Heat 


— A  variety  of 
lightning  flash  in  which  the  discharge  lights 
up  the  surfaces  of  the  neighboring  clouds. 

Sheet  lightning  is  unaccompanied  by  thunder. 
It  may  be  regarded  as  a  brush  discharge  from  one 
cloud  to  another. 

Heat  lightning  is  a  variety  of  sheet  lightning. 
(See  Lightning,  Sheet.) 


L'g.3 


320 


[Liu. 


Lightning  Jar. — (See  Jar,  Lightning!) 
Lightning,    Return-Stroke    of A 

term  sometimes  applied  to  the  back-stroke  of 
lightning.  (See  Lightning,  Back-Stroke  of.) 

Lightning  Rod. — (See  Rod,  Lightning!) 

Lightning  Rod  for  Ships.— (See  Rod, 
Lightning,  for  Ships.) 

Lightning,  Sheet A  variety  of 

lightning  flash  unaccompanied  by  any  thunder 
audible  to  the  observer,  in  which  the  entire 
surfaces  of  the  clouds  are  illumined. 

The  cause  of  sheet  lightning  has  been  ascribed 
to  reflection  from  clouds  of  lightning  flashes 
that  occur  too  far  below  the  horizon  either  to 
permit  them  to  be  directly  seen,  or  the  thunder 
to  be  heard. 

If  a  Geissler  tube,  which  contains  several  con- 
centric tubes,  be  charged  by  a  Holtz  machine, 
and  then  touched  at  different  parts  by  the  hands, 
a  succession  of  luminous  discharges  will  be  seen 
in  the  dark,  that  bear  a  remarkable  resemblance 
to  the  flashes  of  heat  or  sheet  lightning. 

Lightning  Stroke. — (See  Stroke,  Light- 
ning.) 
Lightning  Stroke,  Back  or  Return  — — 

— (See  Stroke,  Lightning,  Back  or  Return.) 

Lightning,  Summer A  name  some- 
times given  to  heat  lightning.  (See  Light- 
ning, Heat!) 

Lightning,  Volcanic The  lightning 

discharges  that  attend  most  volcanic  erup- 
tions. 

Volcanic  lightning  is  possibly  sometimes  due  to 
the  friction  of  volcanic  dust  particles  against  one 
another,  or  against  the  air,  but  is  more  probably 
caused  by  the  sudden  condensation  of  the  water 
vapor  that  is  generally  disengaged  during  volcanic 
eruptions. 

Lightning,  Zigzag The  common- 
est variety  of  lightning  flashes,  in  which  the 
discharge  apparently  assumes  a  forked  zig- 
zag, or  even  a  chain-shaped  path. 

This  form  is  seen  in  the  discharge  of  a  Holtz 
machine,  or  of  a  Ruhmkorff  Induction  Coil. 

Photographic  pictures  of  such  lightning  dis- 
charges appear  to  show  that  these  discharges  are 
in  reality  zigzag  curves,  rather  than  sharp  angu- 
lar zigzags. 


Limiting  Stop. — (See  Stop,  Limiting!) 

Limb,  Rheoscopic A  term  some- 
times applied  to  a  sensitive  nerve  muscle  prep- 
aration, employed  to  detect  the  presence  of 
an  electric  current.  (See  Frog,  Galvano- 
scope.) 

Line. — A  wire  or  other  conductor  connect- 
ing any  two  points  or  stations. 

Line,  Aclinic A  line  connecting 

places  on  the  earth's  surface  which  have  no 
magnetic  inclination. 

The  magnetic  equator  of  the  earth.  (See 
Equator,  Magnetic.) 

Line  Adjuster. — An  instrument  invented 
by  Delany  for  overcoming  the  effects  of  leak- 
age on  the  adjustment  of  the  relays  in  a  way 
line. 

When  any  key  is  opened,  the  line  circuit  is 
simultaneously  broken  at  both  ends  so  that  there 
is  a  moment  of  no  current,  which  causes  all  the 
relays  to  respond. 

Line,  Aerial An  air  line  as  dis- 
tinguished from  an  underground  conductor. 

Line,  Agonic A  line  connecting 

places  on  the  earth's  surface  where  the  mag- 
netic needle  has  no  declination,  or  where  it 
points  to  the  true  geographical  north.  (See 
Agonic.) 

Line,  Artificial A  line  so  made  up 

by  condensers  and  resistance  coils  as  to  have 
the  same  inductive  effects  on  charging  or  dis- 
charging as  an  actual  telegraph  line. 

In  duplex  telegraphy  by  the  differential  method, 
the  artificial  line  used  must  have  its  capacity 
balanced  against  that  of  the  line,  so  as  to  avoid 
the  effects  of  self-induction,  and  other  effects  pro- 
duced by  charging  and  discharging. 

Line,  Capacity  of  —  —The  ability  of  a 
line  or  cable  to  act  like  a  condenser-  and 
therefore  like  it  to  possess  a  capacity.  (See 
Cable,  Capacity  cf.) 

Line  Circuit. — (See  Circuit,  Line!) 

Line  Circuit,  Telegraphic (See 

Circuit,  Line,  Telegraphic!) 

Line,  Neutral,  of  a  Magnet A  line 

joining  the  neutral  points  of  a  magne-t  of 


Liii.j 


321 


[Liu. 


points  approximately  midway  between  the 
poles. 

This  is  sometimes  called  the  equator  of  the 
magnet. 

The  neutral  point  is  the  point  where  the  lines 
of  force  outside  the  magnet  extend  parallel  to  the 
surface  of  the  magnet. — (Hering.) 

Line,  Neutral,  of  Commutator  Cylinder 

A  line  on  the  commutator  cylinder  of 

a  dynamo-electric  machine  connecting  the 
neutral  points,  or  the  points  of  maximum 
positive  and  negative  difference  of  potential. 
(See  Machine,  Dynamo-Electric,} 

Line  of  Least  Sparking. — (See  Sparking, 
Least  Line  of.) 

Line,  Single-Wire  — . A  term  some- 
times used  for  a  solid-wire  conductor.  (See 
Line,  Solid.) 

Line,  Solid  — A  line  formed  of  a 

single  conductor,  as  distinguished  from  a  line 
formed  of  several  conductors  or  by  a  stranded 
cable. 

Line,  Stranded A  line  formed  of 

several  strands  or  separate  conductors  twisted 
into  one. 

Line,  Telegraphic,  Telephonic,  etc. 

— The  conducting  circuit  provided  for  the 
transmission  of  the  electric  impulses  or  cur- 
rents employed  in  any  system  of  electric 
transmission. 

Line,  Telpher The  conducting  line 

used  in  a  system  of  "".elpherage.  (See  Tel- 
phe>  age.) 

Line,  Through A  line  extending 

between  two  terminal  points,  as  distinguished 
from  a  line  containing  way  stations. 

Line,  Trunk  —  — In  a  system  of  tele- 
phonic communication  any  line  connecting 
distant  stations  and  used  by  a  number  of 
subscribers  at  each  end  for  purposes  of  inter- 
communication. 

Line,  Way A  line  communicating 

with  way  stations. 

Line  Wire.— (See  Wire,  Line.) 

Lineman. — On?  who  puts  up  and  repairs 
line  circuits  and  attends  to  the  devices  con- 
nected therewith. 


In  a  system  of  electric  lighting  the  lineman 
attends  to  carboning  the  lamps,  cleaning  the 
lamp  rods,  and,  generally,  to  the  minor  details  of 
the  lines,  insulators  and  the  electro-receptive  de- 
vices placed  on  the  line. 

Lines,  Halleyan A  term  sometimes 

applied  to  the  isogonal  lines. 

The  isogonal  lines  are  sometimes  called  the 
Halleyan  lines,  from  Halley,  who  published  the 
first  chart  of  such  lines  in  the  year  1701. 

Lines,  Isobaric Lines  connecting 

places  on  the  earth's  surface  which  simulta- 
neously have  the  same  barometric  pressure. 

The  isobaric  lines  are  sometimes  called  isobars. 

Lines,  Isoclinic Lines  connecting 

places  that  have  the  same  angle  of  magnetic 
dip  or  inclination.  (See  Dip,  Magnetic.) 

Lines,  Isodynamic Lines  connect- 
ing places  which  have  the  same  total  mag- 
netic intensity. 

The  magnetic  intensity  of  a  place  is  determined 
by  the  number  of  oscillations  that  a  small  mag- 
netic needle,  moved  from  its  position  of  rest  in 
the  magnetic  meridian  of  any  place,  makes  in  a 
given  time.  This  method  is  similar  to  that  em- 
ployed for  determining  the  intensity  of  gravity  at 
any  place  by  observing  the  number  of  oscillations 
that  a  pendulum  of  a  given  length  makes  in  a 
given  time  at  that  place.  If,  for  example,  a  mag- 
netic  needle  at  one  place  makes  21 1  oscillations  IP 
ten  minutes,  and  245  in  the  same  time  at  another 
place,  then  the  relative  intensities  of  magnetism 
at  these  places  are  as  the  squares  of  those  num- 
bers, or  as  44,521  : 60,025,  or  as  I  :  1.348. 

Lines,  Isogonal  -  — Lines  connecting 
places  that  have  the  same  magnetic  declina- 
tion. (See  Declination.) 

Lines,  Isogonic  -  — A  term  sometimes 
used  for  isogonal  lines.  (See  Lines,  Isogcnal.) 

Lines,  Isothermal  —  — Lines  connect- 
ing points  or  places  which  have  the  same 
mean  temperature. 

Lines,  Kapp  —  — A  term  proposed  by 
Mr.  Gisbert  Kapp  for  a  unit  of  lines  of  mag- 
netic force. 

One  Kapp  line  =  6,000  C.  G.  S.  magnetic  lines. 

Since  there  are  6.4514  square  centimetres  in -a 

square    inch,    I     Kapp    line    per    square    inch 

6,oco 


64514 


—  930  C.  G.  S.  lines  per  square  cm 


Llii.j 


322 


[Loc. 


The  totll  number  of  Kapp  lines  passing  through 
a  magnet  and  air  space  is  equal  to  the  ampere 
turns  divided  by  the  total  magnetic  reluctance  in 
the  magnetic  circuit. — (Urquharl.) 

Lines  of  Electric  Displacement. — (See 
Displacement,  Electric,  Lines  of.} 

Lines  of  Electrostatic  Force. — (See  Force, 
Electrostatic,  Lines  of.) 

Lines  of  Force,  Cutting (See  Force, 

Lines  cf,  Cutting} 

Lines  of  Force,  Direction  of (See 

Force,  Lines  of,  Direction  of} 

Lines  of  Inductive  Action. —  (See  Action, 
Inductive,  Lines  of} 

Lines  of  Magnetic  Force. — (See  Force, 
Magnetic,  Lines  of} 

Lines  of  Magnetic  Force,  Conducting 
Power  for  -  — (See  Force,  Magnetic, 
Lines  of.  Conducting  Power  for} 

Lines  of  Magnetic  Induction. — (See  In- 
duction. Magnetic,  Lines  of} 

Lines,  Overhead  —  — A  term  applied 
to  telegraph,  telephone  and  electric  light  or 
power  lines  that  run  overhead,  in  contradis- 
tinction to  similar  lines  placed  underground. 

Lines,  Vortex-Stream Lines  ex- 

ttnding  in  the  direction  in  which  the  particles 
cf  a  fluid  are  moving. 

A  vortex  stream  is  supposed  to  be  composed  of 
a  number  of  vortex -stream  lines. 

Linked  Magnetic  and  Electric  Chain. — 

(See  Chain,  Linked  Magnetic  and  Electric.} 

Links,  Fuse  -  — Strips  or  plates  of 
fusible  metal  in  the  form  of  links,  employed 
for  safety  fuses  for  incandescent  or  other 
circuits. 

Liquid,  Bright  Dipping A  liquid 

*used  in  electro-plating  for  dipping  articles 
preparatory  to  electro-plating,  so  as  to  insure 
a  bright  plating  deposit  on  them  when  after- 
wards subjected  to  the  plating  process. 

A  bright  dipping  liquid  is  prepared  by  the  ad- 
dition of  I  volume  of  common  table  salt  to  a 
mixture  of  loo  volumes  each  of  sulphuric  and 
nitric  acids.  For  small  objects  or  articles  of 
copper,  cr  other  readily  corroded  metals,  the 


above  solution  is  diluted  by  the  addition  of  one. 
eighth  its  volume  of  water. 

Liquid,  Electropoion A  battery 

liquid  consisting  of  i  pound  of  bichromate 
of  potash  dissolved  in  10  p'ounds  of  water,  to 
which  2&  pounds  of  commercial  sulphuric 
acid  has  been  gradually  added. 

This  liquid  is  employed  with  the  carbon-zinc 
cell  or  the  bichromate  of  potash  cell. 

Liquid,  Exciting,  of  Voltaic  Cell- 

The  electrolyte  or  liquid  in  a  voltaic  cell, 
which  acts  on  the  positive  plate. 

Liquid  Level  Alarm. — (See  Alarm,  Watet 
or  Liquid  Level} 

Liquid  Resistance  Load. — (See  Load 
Liquid  Resistance} 

Liquid,  Stripping A  liquid  em- 
ployed to  remove  a  coating  of  one  metal 
from  the  surface  of  another,  without  affecting 
the  other  metal. 

The  character  of  the  stripping  liquid  used  will 
depend  on  the  kind  of  metal  to  be  removed,  and 
whether  the  stripping  is  to  be  accomplished  by 
solution  effected  by  chemical  action,  or  by  electro- 
lytic action. 

Liquid,  Specific  Resistance    of 

(See  Resistance,  Specific,  of  Liquid} 


Liquor,  Spent 


— Any  liquor,  such  as 


that  in  the  acid  or  other  baths  used  in  electro- 
plating, that  has  become  weakened  by  use. 
Listening  Cam. — (See  Cam,  Listening} 

Load,  Liquid  Resistance An  arti- 
ficial load  for  a  dynamo-electric  machine, 
consisting  of  a  mass  of  liquid  interposed  be- 
tween electrodes. 

A  liquid  is  generally  rendered  better  conduct- 
ing by  the  addition  of  a  small  quantity  of  soluble 
salt,  such,  for  example,  as  sulphate  of  soda. 

Local  Action  of  Dynamo-Electric  Ma- 
chine.— (See  Action,  Local,  of  Dynamo- 
Electric  Machine} 

Local  Action  of  Voltaic  Cell. — (See  Ac* 
tion,  Local,  of  Voltaic  Cell.) 

Local  Battery. — (See  Battery,  Local.) 

Local  Battery  Circuit.— (See  Circuit 
Local-Battery} 


Loc.J 


323 


[Loo. 


Local  Currents. — (See  Currents,  Local.} 

Local  Faradization. — (See  Faradization, 
Local.} 

Local  Galvanization.— (See  Galvaniza- 
tion, Local) 

Localization  of  Faults.— (See  Faults, 
Localization  of.} 

Lock,  Electric A  lock  that  is  au- 
tomatically unlocked  by  the  aid  of  electricity. 

The  electric  lock  is  so  arranged  that  the  action 
of  a  push  button  at  a  distance  unlocks  the  door. 
A  speaking  tube  communicates  with  the  house, 
and  the  pressing  of  a  push  button  on  any  floor  of 
the  house  unlocks  the  door.  The  mere  shutting 
of  the  door  locks  it. 

A  form  of  electric  lock  is  shown  in  Fig.  347. 


347-     Electric  Lock. 


Locomotive,  Electric  --  A  railway 
engine  whose  motive  power  is  electricity. 
(See  Railroads,  Electric) 

Locomotive  Head  Light,  Electric  -- 

(See  Head  Light,  Locomotive) 

Lodestone.  —  A  name  formerly  applied  to 
an  ore  of  iron  (magnetic  iron  ore),  that  natu- 
rally possesses  the  power  of  attracting  pieces 
of  iron  to  it. 

Lodestone,  or  magnetic  iron  ore,  must  be  re- 
garded as  a  magnetizable  substance  that  has  be- 
come permanently  magnetic  from  its  situation  in 
the  earth's  magnetic  field.  Such  beds  of  ore 
concentrate  the  lines  of  the  earth's  magnetic  field 
on  them,  and  thus  become  magnetic. 


Lodge's  Standard  Voltaic  Cell.  — (See 
Cell,  Voltaic,  Standard,  Lodge's) 

Log,  Electric An  electric  device 

for  measuring  the  speed  of  a  vessel. 

A  log,  operated  by  the  rotation  of  a  wheel,  is 
caused  to  register  the  number  of  its  rotations  by  a 
step-by-step  recording  apparatus  operated  by 
breaks  in  the  circuit,  made  during  the  rotation 
of  the  wheel,  at  any  given  number  of  turns,  say 
ico,  or  some  other  convenient  multiple.  Such  a 
log  may  be  kept  constantly  in  the  water,  and  ob- 
served when  required,  or  it  can  be  caused  to 
make  a  permanent  record  ot  its  actual  speed  at 
any  time  during  the  entire  run. 

Logarithm. — The  exponent  of  the  power 
to  which  it  is  necessary  to  raise  a  fixed  num- 
ber, in  order  to  produce  a  given  number. 

A  table  of  logarithms  enables  the  operations  oi 
multiplication,  division,  the  raising  of  powers, 
and  the  extraction  of  roots,  to  be  readily  per- 
formed by  simple  addition,  subtraction,  multi- 
plication or  division,  respectively.  When  thor- 
oughly understood,  logarithms  greatly  reduce  the 
labor  of  mathematical  calculations.  For  the  man- 
ner in  which  they  are  used,  the  student  is  referred 
to  any  standard  work  on  mathematics. 

Logarithmic  Curve. — (See  Curve,  Loga- 
rithmic) 

Long-Coil  Magnet. — (See  Magnet,  Lcttg- 
Coil) 

Long-Core  Electro-Magnet. — (See  Mag- 
net, Electro,  Long-Core) 

Long-Shunt  Compound- Wound  Dynamo- 
Electric  Machine. — (See  Machine,  Dyna- 
mo-Electric, Compound-  Wound,  L  o  ng- 
Shunt) 

Longitude,   Electric   Determination    ol 

The  determination  of  the  longitude  of 

a  place,  by  differences  in  time  between  it  and 
a  place  on  the  prime  meridian,  as  simultane- 
ously determined  telegraphically. 

In  determinations  of  this  character  allowance 
must  be  made  for  the  retarding  effects  of  long 
telegraphic  lines,  or  cables. 

Loom,  Electric  —      — A  device  by  means 
of  which  Jacquard  cards  in  the  ordinary  loo' 
are  replaced  by   a  simple   perforated    metal 
plate,  the  perforations  in  which  correspond 
to  those  in  the  Jaccuard  card. 


Loo.] 


324 


[Lur. 


The  necessary  movements  are  effected  by 
means  of  electro-magnets. 

Loop  Break. — A  device  for  introducing  a 
loop  in  a  break  made  at  any  part  of  a  circuit. 

The  rigidity  of  the  line  wire,  between  the  points 
of  attachment  of  the  loop  introduced,  is  main- 
tained by  means  of  some  inflexible  non-conducting 
material  inserted  in  the  break. 

Loop  Circuit.— (See  Circuit,  Loop.} 

Loop,  Drip An  inclined  loop  placed 

where  the  outside  conductors  enter  a  build- 
ing. 

The  inclination  is  upwards  towards  the  point 
of  entrance  to  the  building.  This  device  of 
a  drip  loop  is  adopted  for  the  purpose  of  prevent- 
ing  the  rain  water  from  flowing  along  the  inclined 
wire  into  the  building.  This  is  effected  by  making 
the  wire  incline  from  the  building,  thus  throwing 
the  drainage  from  the  building. 

Loop,  Electric A  portion  of  a  main 

circuit  consisting  of  a  wire  going  out  from 
one  side  of  a  break  in  the  main  circuit  and 
returning  to  the  other  side  of  the  break. 

Loops  are  employed  for  the  purpose  of  con- 
necting a  branch  telegraph  office  with  the  main 
line;  for  placing  one  or  more  electric  arc  lamps 
on  the  main  line  circuit;  for  connecting  a  mes- 
senger call  or  telephone  circuit  with  a  mainline; 
and  for  numerous  similar  purposes. 

Loops  of  Force. — (See  Force,  Loops  of,} 

Loops  of  Mutual  Induction. — (See  Induc- 
tion, Mutual,  Loops  of.} 

Low-Resistance  Magnet. — (See  Magnet, 
Low-Resistance.} 

Low-Tension  Electric  Fuse. — (See  Fuse, 
Electric,  Low-  Tension.} 

Loxodrograph. — An  apparatus  for  electri- 
cally recording  on  paper  the  actual  course  o' 
a  ship  by  the  combined  action  of  magnetism 
and  photography. 

Luces. — Plural  of  lux.    (See  Lux^ 

Luminescence. — A  limited  power  of  emit- 
ting light,  possessed  by  certain  bodies  which 
have  previously  acquired  potential  energy  by 
exposure  to  light  or  radiant  energy. 

The  term  luminescence  was  proposed  by  E. 
Wiedemann  to  cover  the  case  of  the  emission  of 


light  under  circumstances  differing  from  the  emis- 
sion or  radiation  of  light  by  incandescence.  Lu- 
minescence applies  to  the  case  of  a  radiation, 
generally  selective  in  character,  that  is  apparently 
due  to  effects  allied  to,  or  the  same  as,  those  of 
fluorescence  and  phosphorescence.  For  example, 
magnesium  oxide  or  zinc  oxide,  when  heated 
above  a  certain  critical  temperature,  radiates  far 
more  light  than  equally  hot  carbon. 

The  spectrum  of  such  luminescent  light  is  espe- 
cially rich  in  certain  wave  lengths.  The  ability 
of  the  substance  to  continue  to  furnish  this  extra 
light  is,  however,  limited.  After  a  comparatively 
short  time,  the  additional  light,  or  selective  radia- 
tion, disappears.  The  luminescent  light  is  appa- 
rently due  to  molecular  potential  energy  stored  in 
the  substance  during  its  exposure  to  light.  Lumi- 
nescence may  be  developed  in  bodies  in  the  fol- 
lowing manner,  viz. : 

(I.)  By  heat. 

(2.)  By  chemical  action. 

(3.)  By  friction. 

(4.)  By  exposure  to  the  sun,  or  by  actual  impact 
of  light  waves. 

(5.)  By  electricity. 

(6.)  By  vital  forces,  as  in  the  fire  fly,  or  the 
glow  worm. 

Luminescence,  Rejuvenation  of 

Reimparting  by  exposure  to  light,  or  any  other 
suitable  means,  the  power  of  luminescence  to 
a  substance  after  it  has  lost  this  power. 

Luminous  Absorption. — (See  Absorption, 
Luminous!) 

Lunar  Inequality  of  Earth's  Magnetic 
Variation  or  Inclination. — (See  Inequality, 
Lunar,  of  Earth's  Magnetic  Variation  or 
Inclination!) 

Lunar  Inequality  of  Earth's  Magnetism. 

— (See  Inequality,  Lunar,  of  Earth's  Mag- 
netism?) 

Lux.— A  name  proposed  by  Preece  for  the 
unit  of  intensity  of  illumination. 

The  illumination  given  by  a  standard 
candle  at  the  distance  of  12.7  inches. 

The  illumination  given  by  I  carcel  at  the 
distance  of  i  metre. 

The  illumination  given  by  a  lamp  of  io,ooc 
candles  at  105.8  feet.  (See  Illumination 
Unit  of.} 


325 


M 


M. — A  contraction  sometimes  used  to  ex- 
press a  gaseous  pressure  of  the  .oooooi  of 
an  atmosphere. 

1,000,000  M.  equals  760  mm.  of  mercury  or  I 
atmosphere  of  pressure. 

A  vessel  containing  air,  which  has  been  ex- 
hausted to  the  .oooooi  of  its  pressure  at  760 
mm.,  or  one  atmosphere,  has  a  pressure  or  ten- 
sion of  I  M. 

This  contraction  is  used  by  Crookes  in  his  re- 
searches on  the  properties  of  radiant  matter.  (See 
Matter ;  Radiant,  or  Ultra  Gaseous. ) 

>u. — A  contraction  used  in  mathematical 
writings  for  magnetic  permeability,  or  the 
specific  conductibility  of  any  substance  for 
lines  of  magnetic  force. 

mm. — A  contraction  for  millimetre.  (See 
Weights,  French  System  of.} 

M.  P.  H.— A  contraction  sometimes  used  in 
railroad  work  to  indicate  miles  per  hour. 
Machine,    Armstrong's    Hydro-Electric 

A  machine  for  the  development  of 

electricity   by  the  friction  of  a  jet  of  steam 
passing  over  a  water  surface. 
Steam  generated  in  a  suitably  insulated  boiler, 


Fig.  348.     Armstrong's  Hydro-Electric  Machine. 

Fig.  34?,  is  allowed  to  escape  through  a  tortuous 
nozzle,  from  a  series  of  apertures  opposite  a 
pointed  comb,  attached  to  an  insulated  conductor. 


The  cooling  of  the  steam  during  its  passage 
through  a  flat  box,  termed  the  coolino  box,  con- 
nected with  the  nozzles,  causes  a  partial  condensa- 
tion, so  that  the  box  always  contains  a  small 
quantity  of  water. 

The  friction  of  the  drops  of  water  against  the 
orifice,  and,  possibly,  their  friction  against  the 
water  surface  itself,  are  the  cause  of  the  electricity 
produced. 

A  conductor  connected  with  the  pointed  comb 
furnishes  positive  electricity.  The  boiler  fur- 
nishes negative  electricity.  The  hydro-electric 
machine  is  not  a  very  economical  source  of  elec- 
tricity, and  is  only  employed  for  experimental 
purposes.  It  was  discovered  accidentally  through 
a  shock  given  to  an  engineer,  who  placed  his 
hand  in  a  jet  of  steam  escaping  from  a  leaking 
boiler  he  was  endeavoring  to  mend.  The  causes 
were  first  studied  by  Sir  Wm.  Armstrong,  who, 
in  1840,  devised  the  apparatus  just  described. 

Machine,    Dynamo-Electric    — A 

machine  for  the  conversion  of  mechanical 
energy  into  electrical  energy,  by  means  of 
magneto-electric  induction. 

The  term  is  also  applied  to  a  machine  by 
means  of  which  electrical  energy  is  converted 
into  mechanical  energy  by  means  of  magneto- 
electric  induction.  Machines  of  the  latter  class  are 
generally  called  motors,  those  of  the  former, 
generators. 

Prof.  S.  P.  Thompson  defines  a  dynamo-elec- 
tric machine  as  follows,  viz. :  "  A  machine  for 
converting  energy  in  the  form  of  mechanical 
power  into  energy  in  the  form  of  electric  currents, 
or  vice  versa,  by  the  operation  of  setting  con- 
ductors (usually  in  ihe  form  of  coils  of  copper 
wire)  to  rotate  in  a  magnetic  field,  or  by  vary- 
ing a  magnetic  field  in  the  presence  of  conduc- 
tors." 

The  tejm  dynamo  was  first  applied  to  such 
machines,  because  in  the  form  in  which  this 
machine  first  appeared,  viz.:  the  series- wound 
machine,  it  was  self-exciting,  or  required  no  ex- 
citement other  than  what  it  received  by  the  rota- 
tion of  its  armature  in  the  field  of  its  magnets, 
or,  indeed,  in  the  field  of  the  earth.  (See Machine, 
Dynamo-Electric,  Reaction  Principle  of.) 

A  dynamo-electric  generator,  or  a  dynamo-elec- 


Mac.] 


326 


[Mac. 


fric  machine  proper,  consists  of  the  following 
parts,  viz.: 

(i.)  The  revolving  portion,  usually  the  arma- 
ture, in  which  the  electromotive  force  is  developed, 
which  produces  the  current. 

It  must  be  borne  in  mind  that  it  is  not  current, 
but  difference  of  electric  potential,  or  electromotive 
force,  that  is  developed  by  any  electric  source 
front  which  a  current  is  obtained.  For  ease  of 
reference,  however,  we  will  speak  of  an  electric 
current  as  being  generated  by  the  armature,  or  by 
the  source.  No  ambiguity  will  be  introduced  if 
the  student  bears  the  above  in  mind. 

(2.)  Thejie/d  magnets,  which  produce  the  field 
in  which  the  armature  revolves. 

(3. )  hi  pole  pieces,  or  free  terminals  of  the  field 
magnets. 

(4. )  The  commutator,  by  which  the  currents  de- 
veloped in  the  armature  are  caused  to  flow  in 
one  and  the  same  direction.  In  alternating 
machines,  and  in  some  continuous  current  dynamos 
Zhis  part  is  called  the  collector,  and  does  not  rec- 
tify the  currents. 

(5.)  The  collecting  brushes,  that  rest  on  the 
commutator  cylinder  and  take  off  the  current 
generated  in  the  armature. 

Machine,  Dynamo-Electric,  Alternating- 
Current  A  dynamo-electric  machine 

ia  which  alternating  currents  are  produced. 

The  field  magnets  may  be  either  permanent 
jnagnets  or  electro-magnets.  When  electro-mag- 
aets  are  used,  their  coils  may  be  separately  ex- 
cited by  another  machine  whose  current  is  con- 
tinuous; or,  they  may  be  excited  by  the  commuted 

:rrent  of  a  separate  coil  on  the  armature;  or,  they 
may  be  partly  excited  by  commuted  currents  and 
partly  by  commuted  currents  from  a  transformer, 
placed  in  the  main  circuit  of  the  dynamo. 

Machine,  Dynamo-Electric,  Armature  of 

(See    Armature,    Dynamo- Electric 

Machine?) 

Machine,  Dynamo-Electric,  Bed-Piece  of 

The  frame  or  base  on  which  a  dynamo 

is  supported. 

The  bed-piece  is  sometimes  called  the  dynamo 
frame  or  base. 

Machine,  Dynamo-Electric,  Bi-Polar 

— A  dynamo-electric  machine,  the  armature 
of  which  rotates  in  a  field  formed  by  two 
magnet  poles,  as  distinguished  from  a  ma- 


chine the  armature  of  which  rotates  in  a  field 
formed  by  more  than  two  magnet  poles. 

A  dynamo-electric  machine  whose  armature 
rotates  in  the  field  formed  by  more  than  two 
poles  is  called  a  multi-polar  machine.  (See  Ma- 
chine, Dynamo-Electric,  Multi-Polar.) 

Machine,    Dynamo-Electric,   Carca*s  of 

— ; A  term  sometimes  used  in  place  of 

the  field  magnet  frame  of  a  dynamo-electric 
machine.  (See  Machine,  Dynamo-Electric, 
Frame  of.) 

The  term,  field  magnet  frame,  would  appear 
to  be  the  preferable  term.  The  term,  however, 
is  used  in  France,  and  is  derived  from  the 
French  word  for  skeleton. 

Machine,  Dynamo-Electric,   Closed-Coil 

A     dynamo-electric     machine,     the 


armature  coils  of  which  are  grouped  in  sec- 
tions, communicating  with  successive  bars  of 
a  collector,  so  as  to  be  connected  continu- 
ously together  in  a  closed  circuit. 

The  Gramme  dynamo  and  most  continuous- 
current  dynamos  are  closed-coil  dynamos. 

Machine,  Dynamo-Electric,  Closed-Coil 

Disc A   closed-coil  dynamo-electric 

machine,  ihe  armature  core  of  which  is  disc- 
shaped. 

Machine,   Dynamo-Electric,  Closed-Coil 

Drum A  closed-coil  dynamo-electric 

machine,  the  armature  core  of  which  is 
drum-shaped. 

Machine,   Dynamo-Electric,    Closed-Coil 

Ring A  closed-coil  dynamo-electric 

machine,  the  armature  core  of  which  is  ring- 
shaped. 

Machine,    Dynamo-Electric,    Collectors 

—(See  Collectors  of  Dynamo-Electric 

Machines.} 

Machine,  Dynamo-Electric,  Compound 
Winding  of (See  Winding,  Com- 
pound, of  Dynamo-Electric  Machine.)  * 

Machine,  Dynamo-Electric,  Compound- 
Wound  Machines  whose  field  mag- 
nets are  excited  by  more  than  one  circuit  of 
coils,  or  by  more  than  a  single  electric 
source. 

The  object  of  compound  winding  is  to  make 


Mac.] 


327 


[Mae. 


the  dynamo  self-regulating  under  changes  in  its 
working  load.  A  shunt- wound  dynamo  renders 
both  series  and  multiple  circuits  approximately 
constant  as  regards  their  working.  Multiple  cir- 
cuits, however,  require  great  constancy  of  poten- 
tial, and  for  this  purpose  the  compounding  of  the 
dynamos  is  necessary . 

In  the  compound  dynamo,  the  shunt  coils  are 
superposed  on  the  series  coils,  or  are  used  in  con- 
nection with  them.  The  shunt  coils  consist  of  a 
much  greater  number  of  convolutions  of  fine  wire 
than  the  series  coils,  which  are  of  coarse  wire. 

Separate  excitation  is  sometimes  compounded 
either  with  series  or  with  shunt  field  magnet 
coils. 

Compound  dynamos  are  of  two  classes,  viz.: 

(l.)  Those  designed  to  produce  a  constant 
potential,  and 

(2. )  Those  designed  to  produce  a  constant  cur- 
rent. 

For  Constant  Potential : 

In  the  long-shunt  compound-wound  dynamo, 
the  terminals  of  the  shunt  coil  are  connected  with 
the  binding  posts  of  the  machine.  As  the  cur- 
rent leaves  the  armature  it  has  two  paths  to  take  : 
one,  the  thick  series  coils,  to  the  external  circuit, 
and  the  other  the  finer  and  longer  shunt  coils. 
The  resistance  of  the  shunt  coils  is  greater  than 
that  of  the  armature.  Current  variations  in  the 
armature  will,  therefore,  produce  no  appreciable 
effect  on  the  magnetizing  power  of  the  shunt, 
which  acts  as  a  nearly  uniform  exciter  of  the  field. 

In  a  shunt-wound  dynamo  connected  to  a 
multiple  circuit,  the  introduction  of  an  additional 
number  of  receptive  devices  into  the  circuit  re- 
quires more  current,  and  this  would  tend  to  cause 
a  slight  drop  in  the  potential.  The  object  of  the 
series  coils  is  to  prevent  this  drop.  The  series 
coils,  therefore,  act  as  compensators.  If  the 
coils  are  too  powerful  the  compensation  will 
have  the  effect  of  increasing  the  potential. 

The  combination  of  a  series  and  separately  ex- 
cited machine  is  shown  in  Fig.  351.  The  field  is 
in  series  with  the  armature,  but  has  also  an  ad- 
ditional and  separate  excitation. 

The  combination  of  a  series  and  shunt  machine 
insures  the  excitation  of  the  field  both  by  the 
main  and  by  the  shunted  current.  Such  a  com- 
bination is  shown  in  Fig.  353. 

For  Constant  Current  : 

The  combination  of  shunt  and  separately  ex- 
cited  machines  is  shown  in  Fig.  356.  In  this 
machine  the  field  is  excited  by  means  of  a  shunt 


to  the  external  circuit,  and  by  a  current  produced 
by  a  separate  source. 

The  combination  of  a  series  and  magneto  ma- 
chine is  shown  in  Fig.  352.  This,  also,  is 
designed  to  give  a  constant  current. 

Machine,  Dynamo-Electric,  Compound- 
Wound,  Long-Shunt A  compound- 
wound  dynamo- electric  machine,  in  which 
the  shunt-field  magnet  coils  form  a  shunt  to 
the  binding  posts  of  the  machine. 

In  the  short-shunt  compound-wound  dynamo - 
electric  machine,  the  ends  of  the  shunt  coil  are 
connected  to  the  brushes  of  the  machine. 

Machine,  Dynamo-Electric,  Compound- 
Wound,  Short-Shunt A  compound- 
wound  dynamo-electric  machine  in  which  the 
shunt-field  magnet  coils  form  a  shunt  to  the 
armature  only,  as  distinguished  from  the 
armature  and  series  coils  combined. 

In  the  short-shunt  dynamo-electric  machine, 
the  ends  of  the  shunt  coil  are  connected  to  the 
brushes  of  the  machine,  and  not  to  the  binding 
posts  of  the  machine,  or  to  the  external  circuit,  as 
in  the  long-shunt  machine. 

Machine,  Dynamo-Electric,  Continuous- 
Current  A  dynamo-electric  machine, 

the  current  of  which  is  commuted  so  as  to 
flow  in  one  and  the  same  direction,  as  dis- 
tinguished from  an  alternating  dynamo. 

Machine,  Dynamo-Electric,  Double-Mag- 
net   A  term  sometimes  applied  to  a 

dynamo-electric  machine,  the  field  magnets 
of  which  have  two  consequent  poles. 

Machine,  Dynamo-Electric,  Economic 
Co-efficient  of A  name  formerly  ap- 
plied to  the  efficiency  of  a  dynamo-electric 
machine.  (See  Machine,  Dynamo-Electric, 
Efficiency  of.) 

Machine,  Dynamo-Electric,  Efficiency 

of The  ratio  between  the  electric 

energy  or  the  electrical  horse-power  produced 
by  a  dynamo,  and  the  mechanical  energy  or 
horse-power  expended  in  driving  the  dynamo. 

The  Efficiency  may  be  the  Commercial  Effi- 
ciency, which  is  the  useful  or  available  energy  in 
the  external  circuit  divided  by  the  total  median- 
ical  energy  ;  or  it  may  be  the  Electrical  Efficiency, 
which  is  the  available  electric  energy  divided  by 
the  total  electric  energy. 


Mac.] 


328 


[M:C. 


The  Efficiency  of  Conversion  is  the  total  elec- 
trical energy  developed,  divided  by  the  total 
mechanical  energy  applied. 

If  M,  equals  the  mechanical  energy, 

W,  the  useful  or  available  electrical  energy, 

and 
w,  the  electrical  energy  absorbed  by  the  ma- 

chine, and 

m,   the  Straf  Power,  or  the  power  lost  in 
friction,   eddy  currents,   air   friction,  etc. 
Then,  since 
M  =  W  -f  w  +  m, 

o  •  lira  • 

Commercial  Efficiency  .  .  =  -  = 


- 
M 


W 

-  . 
W  +  w  -4-m 


Electrical  Efficiency  ____  = 


W 


_         . 

W  -f-  w 


Efficiency  of  Conversion  =     +  w—    W  +  w 


M        W-(-  w  -f-  m 
Machine,  Dynamo-Electric,  Flashing  of 

A  name  given  to  long  flashing  sparks 

at  the  commutator,  due  to  the  short  cir- 
cuiting, of  the  external  circuit  at  the  com- 
mutator, by  arcing  over  the  successive  com- 
mutator insulating  strips. 

Machine,  Dynamo-Electric,  Frame  of 
The  bed-piece  that  supports  a  dyna- 
mo-electric machine. 

The  frame  is  sometimes  called  the  dynamo  bed- 
piece. 

The  word  frame  is  sometimes  applied  to  the 
field  magnet  cores  and  yokes. 

Machine,  Dynamo-Electric,  Local  Action 

Ot (See  Action,  Local,  of  Dynamo- 
Electric  Machine?) 

Machine,  Dynamo-Electric,  Mouse-Mill, 
Sir  Wm.  Thomson's  -  — A  dynamo- 
electric  machine  designed  by  Sir  Wm. 
Thomson,  named  from  the  resemblance  of 
its  armature  to  a  mouse  mill. 

The  armature  conductor  of  this  dynamo  con- 
sists of  parallel  bars  of  copper,  arranged  on  a 
hollow  cylinder,  like  the  bars  on  a  mouse  mill. 

Machine,  Dynamo-Electric,    Multipolar 

— A  dynamo-electric  machine,  the 

armature  of  which  revolves  in  a  field  formed 
by  more  than  a  single  pair  of  poles. 

This  form  is  usually  adopted  for  large  machines 
as  being  more  economical. 

Fig.  349  shows  a  multipolar  dynamo  with  four 
poles. 


Machine,    Dynamo-Electric,    Open-Coil 

— A    dynamo-electric     machine,     the 

armature  coils  of  which,  though  connected  to 


Fig.  34Q.    Multipolar  Dynamo  with  Four  Poles. 

the  successive  bars  of  the  commutator,  are  not 
connected  continuously  in  a  closed  circuit. 

The  Brush  and  the  Thomson-Houston  arc  dy- 
namos are  open-coil  machines. 

Machine,    Dynamo-Electric,     Open-Coil 

Disc An   open-coil    dynamo-electric 

machine,   the    armature   of    which   is   disc- 
shaped. 

Machine,    Dynamo-Electric,    Open-Coil 

Drum An  open-coil  dynamo-electric 

machine,  the  armature  core  of  which  is  drum- 
shaped. 

Machine,    Dynamo-Electric,    Open-Coil 

Ring — An   open-coil   dynamo-electric 

machine,  the  armature  core  of  which  is  ring- 
shaped. 

Machine,    Dynamo-Electric,   Output    of 

The  electric  power  of  the  current  gen- 
erated by  a  dynamo-electric  machine  ex- 
pressed in  volt-amperes,  watts  or  kilo-watts. 
S.  P.  Thompson  suggests  that  dynamo- electric 
machines  be  rated  as  to  their  practical  safe  ca- 
pacity in  units  of  output  of  1,000  -watts,  or  one 
kilo-watt.  According  to  this,  an  8-unit  machine 
might  give,  say,  100  amperes  at  a  difference  of 
potential  of  80  volts,  or  2,000  amperes  at  a  differ- 
ence of  potential  of  4  volts.  Such  a  unit  would  be 
far  more  expressive  than  the  usual  method  ot  rat- 
ing a  machine  as  having  a  capacity  of  such  and 
such  a  number  of  lights. 

Machine,      Dynamo-Electric,    Reaction 
Principle  of The  mutual  interaction 


329 


[Mae. 


between  the  current  generated  in  the  armature 
coils  of  a  dynamo-electric  machine  and  the 
field  of  the  machine,  each  strengthening  the 
other  until  the  full  working  current,  which 
the  machine  is  capable  of  developing,  is 
produced. 

When  the  armature  of  a  series  or  shunt  dynamo 
commences  to  rotate,  the  differences  of  potential 
generated  in  its  coils  are  very  small,  since  the 
field  of  the  magnet  is  weak,  being  merely  the 
residual  magnetism.  The  current  so  produced 
in  the  armature,  circulating  through  the  field 
magnet  coils,  increases  the  intensity  of  the  mag- 
netic field  of  the  machine,  and  this,  reacting  on 
the  armature,  results  in  a  more  powerful  current 
through  it.  This  current  again  increases  the 
strength  of  the  magnetic  field  of  the  machine, 
which  again  reacts  to  increase  the  current 
strength  in  the  armature  coils,  and  this  continues 
until  the  machine  is  producing  its  full  output. 

A  dynamo-electric  machine  very  rapidly 
"builds  «/,"  or  reaches  its  maximum  current 
after  starting.  The  reaction  principle  was  dis- 
£overed  by  Soren  Hjorth,  of  Copenhagen. 

Machine,  Dynamo-Electric,  Reversibility 

of The  ability  of  a  dynamo  to  act  as 


-  35°.    Separately  Excited  Dynamo 


a  motor  when  traversed   by  an  electric  cur- 
rent.    (See  Motor,  Electric.) 

Machine,  Dynamo-Electric,  Separate 
Coil  -  —  A  dynamo-  electric  machine  in 
which  the  field  magnets  are  excited  by  means 


of  coils  on  the  armature,  separate  and  dis- 
tinct from  those  which  furnish  current  to  the 
external  circuit. 

Machine,  Dynamo-Electric,  Separately 

Excited A  dynamo-electric  machine 

in  which  the  field  magnet  coils  have  no  con- 
nection with  the  armature  coils,  but  receive 
their  current  from  a  separate  machine  or 
source. 

A  separately  excited  dynamo-electric  machine 
is  shown  in  Fig.  350. 

Separate  excitation  for  constant  current  ma- 
chines has  not  come  into  any  extended  use  in  the 
United  States. 

Machine,  Dynamo-Electric,  Series  and 
Magneto  — A  compound-wound  dy- 
namo-electric machine  in  which  the  arma- 
ture circuit  of  a  magneto-electric  machine  is 
connected  in  series  with  the  armature  and 
field  magnet  circuits  of  a  series  dynamo. 

The  circuit  connections  of  a  series  and  magneto 
dynamo  are  shown  in  Fig.  351. 


Fig  3 ST.     Series  and  Magneto  Dynamo. 

Machine,  Dynamo-Electric,  Series  and 
Separately  Excited  -  — A  compound- 
wound  dynamo-electric  machine  in  which 
there  are  two  separate  circuits  on  the  field 
magnet  cores,  one  of  which  is  connected  in 
series  with  the  field  magnets  and  the  exter- 
nal circuit,  and  the  other  with  some  source 
by  which  it  is  separately  excited. 


Mac.] 


330 


[Mac. 


A  series  and  separately  excited  compound- 
Wound  dynamo-electric  machine  is  shown  in 
Fig-  352. 


Fig.  352.     Series  and  Separately  Excited  Dynamo. 

This  machine  is  employed  for  maintaining  a 
constant  potential  at  its  terminals. 

Machine,  Dynamo-Electric,  Series   and 
Shunt  Wound  — A  compound-wound 


Fig.  353.    Series  and  Shunt-  Wound  Dynamo. 

dynamo-electric  machine  in  which  the  field 
magnets  are  wound  with  two  separate  coils, 
one  of  which  is  in  series  with  the  armature 
and  the  external  circuit,  and  the  other  in 
shunt  with  the  armature. 


This  is  usually  called  a  compound-wound  ma 
chine.  (See  Machine,  Dynamo  Electric,  Com- 
pound- Wound.) 

A  compound-wound  series  and  shunt  dynamo- 
electric  machine  is  shown  in  Fig.  353.  This  ma- 
chine is  designed  to  maintain  constant  potential 
at  its  terminals. 

There  are  two  varieties  of  series  and  shunt  - 
wound  dynamos,  viz. : 

(I.)  Long-shunt  compound-wound  dynamo. 

(2.)  Short-shunt  compound-wound    dynarno. 

(See  Machine,  Dynamo-Electric,  Compound- 
Wound,  Long- Shunt.  Machine,  Dynamo-Electric, 
Compound- Wound,  Short -Shunt.) 

Machine,  Dynamo-Electric,  Series- Wound 

• — A  dynamo-electric  machine,  in  which 

the  field  circuit  and  the  external  circuit  are 


D    D    D   D 

Fig.  354..     Series  Dynamo. 

connected  in  series  with  the  armature  circuit, 
so  that  the  entire  armature  current  must  pass 
through  the  field  coils. 

A  series  dynamo -electric  machine  is  shown  in 
Fig.  354.  Here  the  armature  circuit,  the  field 
circuit  and  the  external  circuit  are  all  connected 
in  series. 

Since  in  a  series-wound  dynamo  the  armature 
coils,  the  field  and  the  external  series  circuit  are  in 
series,  any  increase  in  the  resistance  of  the  external 
circuit  will  decrease  the  electromotive  force  from 
the  decrease  in  the  magnetizing  currents.  A  de- 
crease in  the  resistance  of  the  external  circuit  will, 
in  a  like  manner,  increase  the  electromotive  force 
from  the  increase  in  the  magnetizing  current 


Mac.] 


331 


[Mac. 


The  use  of  a  regulator  avoids   these  changes  in 
the  electromotive  force. 


355-     Series  Dynamo, 

The  dynamo  shown  in  Fig.  355  is  series  con- 
nected. The  armature  is  ring  shaped.  The 
armature  core  cons;sts  of  a  ring  made  of  soft  iron 
wire.  The  field  is  bi-polar,  and  is  obtained  by 
the  use  of  four  magnet  coils  and  two  consequent 
poles. 

Machine,  Dynamo-Electric,  Shunt  and 
Separately  Excited A  compound- 
wound  dynamo-electric  machine,  in  which 


ig-  5f6.     Shunt  and  Separately  Excited  Dynamo. 

the  field  is  excited  both  by  means  of  a 
shunt  fo  the  armature  circuit,  and  by  a 
current  produced  by  a  separate  source. 
A   bhunt  a  id    separately  excited    compound- 


wound  dynamo  electric  machine  is  shown  in  Fig. 
356.  This  machine  maintains  a  constant  current 
in  its  circuit,  notwithstanding  changes  in  its  ex- 
ternal circuit. 

Machine,  Dynamo-Elect  ic,  Shnnt-  Wound 

-Adynamo-electricmachinein  which 

the  field  magnet  coils  are  placed  in  a  shunt 
to  the  armature  circuit,  so  that  on  y  a 
portion  of  the  current  generated  passes 
through  the  field  magnet  coils,  but  all  the 
difference  of  potential  of  the  armature  acts 
at  the  terminals  of  the  field  circuit. 

A  shunt  dynamo-electric  machine  is  shown  in 
Fig-  357- 


•O— « 

D      D     D     D 

Fig.  357.    Shunt  Dynamo. 

In  a  shunt  dynamo-electric  machine,  an  in- 
crease in  the  resistance  of  the  external  circuit  in- 
creases the  electromotive  force,  and  a  decrease  in 
the  resistance  of  the  external  circuit  decreases  the 
electromotive  force.  This  is  just  the  reverse  of 
the  series -wound  dynamo. 

In  a  shunt-wound  dynamo  a  continuous  balanc  • 
ing  of  the  current  occurs.  The  current  dividing 
at  the  brushes  between  the  field  and  the  e.vtiTiial 
circuit  in  the  inverse  proportion  to  the  resistance 
of  these  circuits,  if  the  resistance  of  the  rxfrrml 
circuit  becomes  greater,  a  proportionately  yre.itrr 
current  passes  through  the  field  magnets,  and  5-0 
causes  the  electromotive  force  to  become  greater. 

If,  on  the  contrary.the  resistance  of  the  external 
circuit  decreases,  less  current  passes  through  the 
field,  and  the  electromotive  force  is  proportion- 
ately decreased. 


Mac.] 


332 


[Mac. 


In  a  shunt-wound  dynamo  the  resistance  of  the 
shunt  should  be  at  least  four  hundred  times  that 
of  the  armature.  It  is  sometimes  as  much  as  one 
thousand  times  as  great. — (Urguhart.) 

To  obtain  complete  regulation  of  the  machine 
some  form  of  compounding  is  necessary.  (See 
Machine,  Dynamo-Electric,  Compound-  Wound. ) 

Machine*  Dynamo-Electric,  Single  Mag- 
net   A  dynamo-electric  machine,  in 

which  the  field  magnet  poles  are  obtained 
by  means  of  a  single  coil  of  insulated  wire, 
instead  of  by  more  than  a  single  coil. 

Machine,  Dynamo- Electric,  Sparking  of 
An  irregular  and  injurious  oper- 
ation of  a  dynamo-electric  machine,  at- 
tended with  sparks  at  the  collecting 
brushes. 

Sparking  consists  in  the  formation  of  small 
arcs  under  the  collecting  brushes.  One  cause-of 
sparking  is  to  be  found  in  the  brushes  leaving 
one  commutator  strip  before  making  connection 
with  the  next  strip. 

Sparking  from  this  cause  may  be  avoided  by  so 
placing  the  brushes  as  to  cause  them  to  bridge 
over  the  space  between  two  consecutive  bars, 
thus  permitting  them  to  touch  one  bar  before 
leaving  the  other.  Two  brushes,  electrically  con- 
nected, are  sometimes  employed  for  this  purpose, 
or  the  slots  between  contiguous  bars  are  slightly 
inclined  to  the  axis  of  rotation. 

Sparking  causes  a  burning  of  the  commutator 
strips,    and    an    irregular    consumption  of  the 
brushes,  both  of  which   produce  further  irregu 
larities  by  the  wear   of  the  brushes   against  the 
commutator  bars. 

At  the  moment  the  brush  touches  two  contigu- 
ous commutator  bars,  it  short  circuits  the  coil 
terminating  at  those  bars.  On  the  breaking  of 
this  closed  circuit,  a  spark  appears  under  the 
brushes.  This  spark  is  often  considerable,  since 
from  the  comparatively  small  resistance  of  the 
coil,  it  is  apt,  when  short-circuited,  to  produce  a 
heavy  current  if  not  exactly  at  the  neutral  point. 

Another  cause  of  sparking  is  to  be  found  in  the 
self-induction  of  the  armature  coils.  The  extra 
current  on  breaking  forms  an  injurious  spark 
under  the  brushes.  This  spark  may  be  consid- 
erable, since  the  current  produced  in  the  coil  on 
momentarily  short  circuiting  it  by  the  brushes 
simultaneously  touching  the  adjoining  commu 
tator  currents  may  be  large. 

Sparking  occurs  when  the  brushes  are  not  set 


close  to  the  neutral  line.  Since  the  principal 
cause  for  the  change  in  the  lead  of  the  brushes  is 
the  magnetizing  effect  of  the  armature  coils,  it  is 
preferable  to  make  the  number  of  windings  of 
these  as  few  as  possible,  and  to  obtain  the  neces- 
sary differences  of  potential  by  increasing  the 
speed  of  rotation  and  the  strength  of  the  mag- 
netic field  of  the  machine.  Short  armature  coils 
also  lessen  the  sparking  due  to  self-induction. 

Sparking  at  the  brushes  is  also  caused  by  the 
jumping  of  improperly  supported  or  constructed 
brushes. 

When  the  brushes  are  not  set  close  to  the  neu- 
tral point,  long  flashing  sparks  are  apt  to  occur. 

Alack  of  symmetry  of  winding  of  the  arma 
ture  coils  will  necessarily  be  attended  by  injurious 
flashing,  from  the  impossibility  of  properly  ad- 
justing the  brushes. 

Machine,  Dynamo-Electric,  Synchroniz- 
ing   Adjusting  the  phases  of  two 

alternating  current  dynamos  so  as  to  per- 
mit their  being  coupled  or  joined  in  par- 
allel. 

Machine*  Dynamo-Electric,  to  Short  Cir- 
cuit a To  put  a  dynamo-electric  ma- 
chine on  a  circuit  of  comparatively  small 
electric  resistance. 

Machine,  Dynamo-Electric,  Unit  of  Out- 
put of A  unit  for  the  electric  power 

furnished  by  the  current  of  a  dynamo- 
electric  machine. 

A  unit  of  output  equal  to  1,000  watts 
or  i  kilowatt. 

A  machine  furnishing  a  current  of  100  amperes 
at  a  difference  of  potential  of  So  volts,  would 
have  an  output  of  S,ooo  watts,  and  would, 
therefore,  be  rated  as  an  8-unit  machine. 

Machine,  Electric,  Rubber  of  —  —A 
cushion  of  leather  covered  with  an  electric 
amalgam,  and  employed  to  produce  elec- 
tricity by  its  friction  against  the  plate  or 
cylinder  of  a  frictional  electric  machine. 
(See  Machine,  Frictional  Electric. ) 

Machine,  Electrostatic  Induction  of 

A  machine  in  which  a  small  initial  charge 
produces  a  greatly  increased  charge  by  its 
inductive  action  on  a  rapidly  rotated  disc 
of  glass  or  other  dielectric. 

An  excellent  type  and  example  of  such  a  ma- 
chine is  found  in  the  Holtz  machine,  which  con- 


Mac.] 


333 


[JLic. 


sists  of  the  following  parts,  as  shown  in  Fig.  358, 
viz  ; 

(i.)  A  stationary  glass  plate  A,  fixed  at  its 
edges  to  insulated  supports- 

(2.)  A  movable  plate  B,  capable  of  rapid  rota- 
tation  on  a  horizontal  axis,  by  a  driving  pulley. 


Fig.  358.     Holtz  Electric  Machine. 

(3.)  Armatures  of  varnished  paper  f,  f',  placed 
on  opposite  sides  of  the  fixed  plate  at  holes  or 
windows  P,  P',  cut  in  the  plate.  The  armatures 
are  placed  on  the  side  of  the  fixed  plate  away  from 
the  moving  plate,  or  on  the  back  of  the  plate,  so  that 
the  plate,  on  its  rotation,  moves  towards  tongties  of 
paper  attached  to  the  middle  of  the  arma  ure. 

(4.)  Metal  combsp'.aced  in  front  of  the  movable 
disc  opposite  the  armatures,  and  connected  with 
the  brass  balls  m,  n,  one  of  which  is  movable 
towards  and  from  the  other  by  means  of  a  suitably 
supported  insulating  handle  connected  with  it. 

A  small  initial  charge  is  given  to  one  of  the 
armatures  by  holding  a  plate  of  electrified  vul- 
canite against  it,  and  rotating  the  machine  while 
the  balls  m,  n,  are  in  contact.  As  soon  as  the  ma- 
chine is  charged  the  balls  zrzgradttally  separated, 
when  a  torrent  of  sparks  will  pass  between  them 
so  long  as  the  plate  is  rotated. 

When  the  balls  are  separated  too  far  the  sparks 
cease  to  pass.  The  balls  must  then  be  again 
brought  into  contact  and  gradually  separated  as 
before. 

The  Holtz  machine  can  be  regarded  as  a  re- 
volving electrophorus  provided  with  means  for 
constantly  discharging  and  recharging  the  upper 
metallic  plate.  (See  Electrophorus.} 

The  action  of  the  machine  is  well  described  by 
S.  P. Thompson  in  his  "Elementary  Lessons  on 
Electricity  and  Magnetism,  "  as  follows: 

"Suppose  a  small  -f-  charge  to  be  imparted  at 
the  outset  to  the  right  armature  f ' ;  this  charge  acts 


inductively  across  the  discs  upon  the  metallic 
comb,  repels  electricity  through  it,  and  leaves  the 
points  negatively  electrified.  They  discharge 
negatively  electrified  air  upon  the  front  surface  of 
the  movable  disc ;  the  repelled  charge  passes 
through  the  brass  rods  and  balls,  and  is  dis- 
charged through  the  left  comb  upon  the  front  side 
of  the  movable  disc.  Here  it  acts  inductively 
upon  the  paper  armature,  causing  that  part  of  it 
which  is  opposite  itself  to  be  negatively  charged 
and  repelling  a  -|-  charge  into  its  farthest  part, 
viz.,  into  the  tongue,  which  being  bluntly  pointed, 
slowly  discharges  a  4.  charge  upon  the  back  of  the 
movable  disc.  If  now  the  disc  be  turned  round, 
this  +  charge  on  the  back  comes  over  from  the 
left  to  the  right  side,  in  the  direction  indicated  by 
the  arrow,  and,  when  it  gets  opposite  the  comb, 
increases  the  inductive  effect  of  the  already  exist- 
ing _f-  charge  on  the  armature,  and  therefore 
repels  more  electricity  through  the  brass  rods  and 
knob  into  the  left  comb.  Meantime  the  —  charge, 
which  we  saw  had  been  induced  in  the  left  arma- 
ture, has  in  turu  acted  on  the  left  comb,  causing 
a  -f-  charge  to  be  discharged  by  the  points  upon 
the  front  of  the  di:C ;  and  drawing  electricity 
through  the  brass  rods  and  knobs,  has  made  the 
right  comb  still  more  highly  — ,  increasing  the 
discharge  of  — ly  electrified  air  upon  the  front 
of  the  disc,  neutralizing  the-f-  charge  which  is  be- 
ing conveyed  over  from  the  left.  These  acti.  us  re- 
sult in  causing  the  top  half  of  the  moving  disc  to 
be  — ly  electrified.  The  charges  on  the  front 
serve,  as  they  are  carried  round,  to  neutralize  the 
electricities  let  off  by  the  points  of  the  combs, 
while  the  charges  on  the  back,  induced  respect- 
ively m  the  neighborhood  of  each  ot  the  arma- 
tures, serve,  when  the  rotation  of  the  disc  con- 
veys them  round,  to  increase  the  inductive  influ- 
ence of  the  charge  on  the  other  armature." 

The  student  will  be  aided  in  following  Prof, 
Thompson's  explanation  by  the  diagrammatic 
sketch,  shown  in  Fig.  359.  Here  the  rotating  plate 
is  shown  for  convenience  in  the  form  of  a  cylinder. 
The  armatures  are  shown  on  the  back  of  the  plate 
at  f  and  f,  opposite  the  brass  collecting  combs  P' 
and  P,  with  their  discharging  rods  and  balls  a,  a. 

The  effect  of  the  positive  charge  given  to  the 
right  hand  armature  f',  directly  through  the 
comb  P',  rods  a,  a,  comb  P,  to  left  hand  arma- 
ture f,  is  readily  seen.  The  rotation  of  the  plate 
being  in  the  direction  of  the  curved  arrow;  the 
charging  of  the  front  of  the  plate  by  convection 
streams  from  the  combs,  and  the  back  of  the  plate 


Mac.  ] 


334 


from  the  points  of  the  paper  armatures,  as  well  as 
the  character  of  the  charge,  will  be  understood. 
There  thus  results,  as  is  shown,  a  positive  charge 
on  both  the  front  and  back  of  the  upper  half  of 


f'f-  35Q-  PM*  offfoltz  Machine. 
the  rotating  plate,  and  a  negative  charge  on  both 
sides  of  its  lower  half.  A  reversal  of  polarity  of 
the  plate  occurs  at  the  line  P  a  a  P'.  Sometimes 
the  reversal  does  not  occur,  and  the  machine  either 
loses  its  charge  entirely,  or  in  part.  A  conductor 
S  S,  furnished  with  points,  is  sometimes  provided 
to  lessen  the  chances  of  lack  of  reversal. 

Machine,  Faradic A  machine   for 

producing  faradic  currents. 

There  are  two  varieties  of  faradic  machines, 
viz.:  magnet o-faradic  apparatus  and  simple  in. 
duction  apparatus. 

Machine,    Frictional     Electric A 

machine  for  the  development  of  electricity 
by  friction. 

A  frictional  electric  machine  consists  of  a  plate 
or  cylinder  of  glass  A,  Fig.  360,  capable  of  rota- 
tion on  a  horizontal  axis. 

A  rubber  formed  of  a  chamois  skin,  covered 
with  an  amalgam  of  tin  and  mercury,  is 
placed  at  B.  By  the  rotation  of  the  plate  the 


Fig,  360.  Frictional  Electric  Machine. 
rubber  becomes  negatively  and  the  glass  posi- 
tively excited.  An  insulated  conductor  D,  called 
the  prime  or  positive  conductor,  provided  with  a 
comb  of  points,  becomes  positively  charged  by  in- 
duction. The  machine  will  develop  electricity 


best  if  a  conductor  attached  to  the  rubber  is  con- 
nected with  the  ground,  as  by  a  chain. 

Machine,  Holtz A  particular  form 

of  electrostatic  induction  machine.  (See 
Machine,  Electrostatic  Induction.} 

Machine,  Influence An  electrical 

machine  depending  for  its  action  on 
electrostatic  induction. 

The  Wimshurst  and  Holtz  machines  are  influ- 
ence machines.  (See  Machine,  Electrostatic  In- 
duction. Machine,  Wimshurst  Electrical.  Ma- 
thine,  Holtz.} 

Machine,  Influence,  Wimshnrst's  Alter- 
nating   An  electrostatic  induction 

machine  by  means  of  which  a  series  of 
rapidly  alternating  charges  are  produced. 

Although  such  a  machine  furnishes  a  torrent  of 
sparks  between  its  terminals,  yet  it  is  unable  to 
furnish  a  permanent  charge  to  a  Leyden  jar 
or  condenser,  since  its 
oscillatory  discharges, 
continually  undo  at  any 
small  interval  of  time 
what  was  done  at  the 
preceding  interval,  and 
thus  leave  the  jar  un- 
charged. 

Machine,    Magneto 
Blasting  —A 

magneto-e  1  e  c  t  r  i  c 
machine  employed 
for  generating  the 

,  .        .        Fig  ibi.    Magneto  El,'cttic 

current  used  in  elec-  MaMftt. 

trie  blasting. 

Machine,  Magneto-Electric A  ma- 
chine in  which  there  are  no  field  magnet 
coils,  the  magnetic  field  of  the  machine 
being  due  to  the  action  of  permanent 
steel  magnets. 

A  dynamo  in  which  currents  are  produced  by 
the  motion  of  armature  coils  past  permanent  mag- 
nets. (See  Machine,  Dynamo-Electric. ) 

A  magneto- electric  machine  is  shown  in  Fig. 
361. 

Another  form  of  magneto-electric  machine  is 
shown  in  Fig.  362. 

This  latter  form  of  machine  is  known  as  a  hand 
generator,  in  contradistinction  to  one  driven  by 
power  and  called  a  power  generator. 


Mac.] 


335 


[Mac. 


The  field  is  obtained  by  means  of  a  number  of 
separate  permanent  magnets  so  combined  as  to 


Fig.  362.    Magneto- Electric  Machine. 
act  as  a  single  magnet.     The  armature  is  rotated 
by  hand. 

Machine,  Mouse-Mill A   form    of 

convection  induction  machine,  invented 
by  Sir  William  Thomson  to  act  as  the  re- 
plenisher  of  his  electrometer.  (See  Ma- 
chine, Electrostatic  Induction.} 

Machine,  Rheostatic  —  —A  machine 
devised  by  Plante  in  which  continuous 
static  effects  of  considerable  intensity  are 
obtained  by  charging  a  number  of  con- 
densers in  multiple-arc  and  discharging 
them  in  series. 

The  condensers  are  charged  by  connecting 
them  with  a  number  of  secondary  or  storage  bat- 
teries. 

Machine  Telegraphy. — (See  Telegraphy, 
Machine. ) 

Machine,  Tiippler  Holtz  -  —A  modified 
form  of  Holtz  machine  in  which  the  initial 
charge  of  the  armatures  is  obtained  by  the 
friction  of  metallic  brushes  against  the 
armatures. 

Machine,    Wimshurst  Electrical — 

A  form  of  convection  electric  machine 
invented  by  Wimshurst. 

Like  the  Holtz  machine,  the  Wimshurst  ma- 
chine is  a  convection  induction  machine.  It  is, 
however,  more  efficient  in  action,  and  will  prob- 
ably soon  supersede  the  former  machine.  The 
Wunshurst  machine  consists  of  two  shellac-var- 
nished glass  plates  that  are  rapidly  rotated  in  op- 
posite directions.  Thin  metallic  strips  are  placed 
on  the  outside  of  each  of  the  plates,  in  the  radial 
positions  shown  in  Fig.  363.  These  strips  act 


both  as  inductors  and   carriers ;  the  carriers  of 
one  plate  acting  as  inductors  to  the  other  plate. 

Two  curved  bra<=s  rods,  terminating  in  fine  wire 
brushes  that  touch  the  plates,  are  placed  as  shown, 
one  at  the  front  of  the  plate,  and  one  at  the  back, 
at  right  angles  to  each  other.  Pairs  of  conduct- 


Fig.  363.     The  Wimshurst  Electrical  Machine. 

ors,  connected  together,  provided  with  collecting 
points,  are  placed  diametrically  opposite  each 
other,  as  shown.  Sliding;  conductors,  terminated 
with  metallic  balls,  are  provided  for  discharging 
the  conductors.  Leyden  jars,  the  inner  coatings 
of  which  are  connected  with  two  discharging 
rods,  and  the  outer  coatings  together,  may  be  em- 
ployed in  this  as  in  the  Holtz  machine. 

The  exact  action  of  this  machine  is  not  thor- 
oughly understood. 

Machines,  Dynamo-Electric,  Varieties  of 

Dynamo-electric  machines  may  be 

divided  into  classes  according  to — 

(i  )  The  manner  in  which  the  magnetism  of 
the  field  magnets  is  obtained. 

(2.)  The  character  of  their  armatures. 

(3.)  The  nature  of  the  current  obtained, 
whether  continuous  or  alternating. 

(4.)  The  form  of  their  field  magnets. 

(5.)  The  nature  of  their  magnetic  fields. 

(6.)  The  manner  in  which  the  current  of  the 
field  magnets,  the  armature  and  the  external 
circuits  are  connected. 

Mack —  — A  term  proposed  by  Mr. 
Oliver  Heaviside  for  a  unit  of  self-induc- 
tion. 

The  term  Mack  is  derived  from  Maxwell.  The 
unit  of  self  induction  has  also  been  a  secohm  and 
a  quadrant. 


Mad.] 


336 


[Mag. 


The  term  Max  would  seem  to  be  indicated. 
In  the  United  States  the  unit  of  sell -induction  is 
called  a  Henry,  after  Prof.  Joseph  Henry.  (See 
Henry,  A.) 

Made  Circuit.— (See  Circuit,  Made  ) 
Magazine  Fuse.— (See  Fuse,  Magazine. ) 
Magne-Crystallic   Action.— (See    Action, 
Magne-Crystallic. ) 

Magnet.— A  body  possessing  the  power 
of  attracting  the  unlike  pole  of  another 
magnet  or  of  repelling  the  like  pole ;  or 
of  attracting  readily  magnetizable  bodies 
like  iron  filings  to  either  pole. 

A  body  possessing  a  magnetic  field. 
(See  Field,  Magnetic.} 

The  lines  of  force  are  assumed  in  passing 
through  the  magnetic  field  to  come  out  at  the  north 
pole  of  the  magnet  and  to  go  in  at  the  south  pole. 
All  lines  of  force  form  closed  magnetic  circuits.  If 
a  magnetizable  body  is  brought  into  a  magnetic 
field,  the  lines  of  magnetic  force  are  concentrated 
on  it  and  pass  through  it.  The  body  therefore  be- 
comes magnetic  The  intensity  of  the  resulting 
magnetism  depends  on  the  number  of  lines  of 
force  that  pass  through  the  body,  and  the  polar- 
ity on  the  direction  in  which  they  pass  through  it. 

A  magnetized  bar  cannot  be  regarded  as  a 
source  of  energy  in  itself.  Energy  must  be  ex- 
pended to  magnetize  the  iron,  and  must  also  be 
expended  to  demagnetize  it. 

Magnet,  Anomalous —A  magnet  pos- 
sessing more  than  two  free  poles. 

There  is  no  such  thing  as  a  unipolar   magnet. 


Fig.  364.    Anomalous  Magnet. 

All  magnets  have  two  poles.  Sometimes,  how- 
ever, several  magnets  are  so  grouped  that  there 
appear  to  be  more  than  two  poles  in  the  same 
magnet. 

A..  JB>  C  D 


Fig.  36  J.    Anomalous  Magnet. 

Thus,  in  Fig.  364,  the  magnet  ABC  appears 
to  possess  three  poles,  two  positive  poles  at  A 
and  C,  and  a  central  negative  pole  at  B. 


It  is  clear,  however,  that  the  central  pole  is  in 
reality  formed  of  two  juxtaposed  negative  poles, 
and  that  ABC  actually  consists  of  two  magnets 
with  two  poles  to  each. 

The  magnet  A  B  C  D  Fig.  365,  which  in  like 
manner  appears  to  possess  four  separate  poles,  in 
reality  is  formed  of  three  magnets  with  two  poles 
to  each. 

Since  unlike  magnetic  poles  neutralize  each 
other,  it  is  clear  that  only  similar  poles  can  thus 
be  placed  together  in  order  to  produce  addition- 
al magnet  poles. 


Fig.  366.    Anomalous  Magnet. 

The  six-pointed  star  shown  in  Fig.  366,  is  an 
anomalous  magnet  with  apparently  seven  poles. 
The  formation  of  the  central  N-pole,  as  is  evi- 
dent from  an  inspection  of  the  drawing,  is  due  to 
the  six  separate  north  poles,  n,  n,  n,  n,  n,  n,  of 
the  six  separate  magnets  Sn,  Sn,  etc.  Such  a 
magnet  would  be  formed  by  touching  the  star  at 
the  point  N,  with  the  S-pole  of  a  sufficiently 
powerful  magnet. 

The  extra  poles  are  sometimes  called  con- 
sequent poles.  Their  presence  may  be  shown  by 
means  of  a  compass  needle,  or  by  rolling  the 
magnet  in  iron  filings,  which  collect  on  the  poles. 

Magnet,  Artificial  -  -A  magnet  pro- 
duced by  induction  from  another  magnet, 
or  from  an  electric  current. 

Any  magnet  not  found  in  nature  is  called  an 
artificial  magnet. 

Magnet,  Axial  —  —A  name  sometimes 
given  to  a  solenoid  with  an  axial  or 
straight  core. 

Magnet,  Bell-Shaped A  modifica- 
tion of  a  horseshoe  magnet  in  which  the 
approached  poles  are  semi-annular  in 
shape,  and  form  a  split  tube. 

Bell -shaped  magnets  are  used  in  many   galra- 


Mag.]  337 

nometers,  because  they  can  be  readily  dampened 
by  surrounding  them  by  a  mass  of  copper.  The 
needle  in  its  motion  produces  currents  that  tend 
to  oppose,  and,  therefore,  to  stop  its  motion. 
(See  Laws,  Lfnz's.) 

Magnet,  Club-Footed An  electro- 
magnet whose  core  is  in  the  Jorm  of  a 
horse-shoe  and  is  provided  with  a  mag- 
netizing coil  on  one  pole  only. 
Magnet  Coil.— (See  Coil,  Magnet ) 
Magnet,  Compensating  —  — A  magnet 
placed  over  a  magnetic  needle,  generally 
over  the  magnetic  needle  of  a  galvanome- 
ter, for  the  purpose  of  varying  the  direc- 
tion and  intensity  of  the  magnetic  force  of 
the  earth  on  such  needle.  (See  Galvanom- 
eter, Reflecting.} 

A  magnet,  called  a  compensating  magnet,  is 
sometimes  placed  on  a  ship,  near  the  compass 
needle,  for  the  purpose  of  neutralizing  the  local 
variations  produced  on  the  compass  needle  by 
the  magnetism  of  the  ship. 

Magnet,  Compound — A  number  of 

single  magnetsplaced  par- 
allel  and  with  their  similar 
poles  facing  one  another, 
as  shown  in  Fig.  367. 

Compound  magnets  are 
stronger  in  proportion  to  their 
weight  than  single  magnets. 

Magnet,  Compound 
Horseshoe A  horse- 
shoe magnet  composed 
of  several  separate  horse- 
shoe magneto  placed  with  S 
their  similar  poles  to- 
gether. Fig.  367.  Compound 

Magnet. 

A  compound  horseshoe  magnet  is  shown  in 
Fig.  368. 

A  horseshoe  magnet  possesses  greater  portative 
power  than  a  straight  bar  magnet  of  the  same 
weight.  (See  Power,  Portative. ) 

(i.)  Because  its  opposite  poles  are  nearer  to- 
gether; and 

(2  )  Because  the  magnetic  resistance  of  its 
circuit  is  less,  the  lines  of  magnetic  force  closing 
through  the  armature,  and  thus  concentrating 
the  magnetic  attraction  on  the  armature. 

Electro-magnets  are  generally  made  of  the 
horseshoe  shap-i. 


[Mag. 


Magnet,   Controlling    — A    name 

sometimes  applied  to  the  controller  in  the 
Thomson-Houston  automatic  system  of 
current  regulation.  (See  Controller  ) 

Generally  any  mag- 
net which  controls 
some  particular  ac- 
tion. 

Magnet,  Cylindri- 
cal   A  magnet 

in   the  shape    of  a 
cylinder. 

A  helix  or  solenoid 
through  which  a  cur- 
rent of  electricity  is 
passing  is,  so  far  as  ex- 
ternal space  is  con- 
cerned, the  exact  magr 
netic  equivalent  of  a 
cylindrical  magnet. 

Magnet,  Damping 

Any  magnet 

employed    for    the 

...        .  .          Fig  368.     Compound  Horst- 

purpose  of  checking  shot  Magnet. 

the  velocity  of  motion  of  a  moving  body 

or  magnet. 

Dampening  magnets  generally  act  by  the  resist- 
ance which  they  offer  to  the  passage  of  a 
metallic  disc,  so  moved  as  to  cut  the  lines  offeree 
of  their  field. 

Magnet,  Electro A  magnet  pro- 
duced by  the  passage  of  an  electric  current 
through  a  coil  of  insulated  wire  surround- 
ing a  core  of  magnetizable  material. 

The  magnetizing  coil  is  called  a  helix  or  sole- 
noid. (See  Magnetism,  Ampere's  Theory  of.) 

Strictly  speaking,  the  term  electro- magnet  is 
limited  to  the  case  of  a  magnet  provided  with  a 
solt  iron  core,  which  enables  it  to  rapidly  acquire 
its  magnetism  on  the  passage  of  the  magnetizing 
current,  a-id  as  rapidly  to  lose  its  magnetism  on 
the  cessation  of  such  current. 

An  elect!  ic  current  passed  around  a  bar  of 
magnetizable  material,  in  the  manner  and  direc- 
tion shown  in  Fig.  369,  will  produce  the  polarity 
N  and  S,  at  its  ends  or  extremities  as  marked. 

The  directions  of  the  currents  required  to  pro- 
duce N  and  S,  poles  respectively  are  shown  in 
Fig.  37°- 

The  cause  of  this  difference  of  polarity  will  be 
readily  understood  from  a  study  of  the  direction 


Mag.] 


338 


[Mug. 


of  lines  of  magnetic  force  in  the  field  produced 
by  an  electric  current. 


Fig,  3tx).    Polarity  of  Current. 

The  direction  of  this  polarity  may  be  predicted 
by  the  following  modification  of  a  rule  by  Ampere: 

Imagine  yourself  swimming  in  the  wire  in  the 
direction  of  the  current ;  if,  then,  your  face  is 


Fig.  370.    North  and  South  Magnet  Poles. 

turned  toward  the  bar  that  is  being  magnetized, 
its  North  seeking  pole  will  be  on  your  left. 

A 


Fig.  371.    Deflection  of  Fig.  372.     Drfl  ction  of 

Magnetic  Needle.  Magnetic  Needle. 

If,  for  example,  the  conductor  A  B,  be  traversed 
by  a  current  in  the  direction  from  B,  to  A,  as 
shown  in  Fig.  371,  the  north  pole  N,  of  the 
needle  N  S,  placed  under  the  conductor,  is  de- 
flected, as  shown,  to  the  left  of  the  observer,  who 
is  supposed  to  be  swimming  in  the  current,  facing 
the  needle.  It  the  current  flow  in  the  opposite 


direction,  as  from  A,  to  B,  as  shown  in  Fig.  372, 
the  N,  pole  of  the  needle  is  deflected  as  shown, 
but  still  to  the  left  of  the  observer  supposed  to  be 
swimming  as  before. 

In  any  electric  circuit,  the  lines,  of  magnetic 
force,  produced  by  the  passage  of  the  current,  form 
circles  around  the  circuit  in  planes  at  right  angles 
to  the  direction  of  the  current,  as  shown  in  Fig. 
373.  The  direction  of  these  lines  of  force  is  the 
same  as  that  of  the  hands  of  a  watch,  if  the  cur- 
rent be  supposed  to  flow  away  from  the  observer. 
(See  Field,  Magnetic,  of  an  Electric  Current.} 


Fig.  373.    Direction  of  Lines  of  Force. 

Remembering  now  that  the  lines  of  force  are 
supposed  to  come  out  at  the  north  pole  cf  a  magnet, 
and  to  pass  in  at  the  south  pole,  it  is  evident  that 
if  the  current  flows  in  the  direction  shown  in  Fig. 


Fig.  374.    Direction  of  Lines  of  Forct, 

374,  the  lines  of  force  will  come  out  at  the  north 
pole  and  pass  in  at  the  south  pole. 

Since  in  a  right-handed  helix  the  wire  passes 
around  the  axis  in  the  opposite  direction  to  that 
in  which  it  passes  in  a  left-handed  helix,  it  is 
evident  that  the  helices  shown  in  Fig.  375  at  I, 
and  2,  will  produce  opposite  polarities  at  the 
points  of  entrance  and  exit  by  a  current  flowing 
in  the  direction  of  the  arrows. 

If  the  current  be  sent  through  the  right-handed 
helix,  shown  at  I,  from  b,  to  a,  that  is,  from  the 
left  to  the  right  in  the  figure,  a  south  pole  will  be 
produced  at  b,  and  a  north  pole  at  a.  If,  how- 
ever, it  be  sent  from  a,  to  b,  the  polarity  will  be 
reversed. 

If  the  current  be  sent  through  the  left-handed 


Mag.] 


339 


[Mag. 


helix,  shown  at  2,  from  a,  to  b,  that  is,  trom  the  left 
to  the  right  in  the  figure,  a  north  pole  will  be  pro- 
duced at  a,  and  a  south  pole  at  b.  If,  however,  it 
be  sent  in  the  opposite  direction,  the  polarity  will 
be  reversed. 

Therefore,  in  an  electro-magnet,  on  the  core 
of  which  several  layers  or  thicknesses  of  wire  are 
wound,  in  which  the  current  flows  through  one 
layer,  in,  say  a  direction  from  right  to  left,  the  cur- 
rent must  return  through  the  next  layer  in  the 
opposite  direction,  or  from  left  to  right.  The 
polarities  of  the  same  extremities  of  the  helices 
are,  however,  the  same  in  all  cases,  since  the 
layers  are  successively  right  and  left  handed 
to  the  current.  The  winding  shown  at  3,  pro- 
duces consequent  poles. 

The  following  laws  express  the  more  important 
principles  concerning  electro-magnets : 

(l.)  The  magnetic  intensity  (strength)  of  an 
electro-magnet  is  nearly  proportional  to  the 
strength  of  the  magnetizing  current,  provided  the 
core  is  not  saturated. 

(2.)  The  magnetic  strength  is  proportional  to 
the  number  of  turns  of  wire  in  the  magnetizing 
coil ;  that  is,  to  the  number  of  ampere  turns.  (See 
Turns,  Ampere.) 

(3  )  The  magnetic  strength  is  independent  of 
the  thickness  or  material  of  the  conducting  wires. 

These  laws  may  be  embraced  in  the  more  gen- 
eral statement  that  the  strength  of  an  electro- 


-  37  f-    Right-Handed,  Left-  Handed  and  Anomalous 
Helices. 


magnet,  the  size  of  the  magnet  being  the  same, 
is  proportional  to  the  number  of  its  ampere  turns. 
(See  Turns,  Ampere.) 

A  short  interval  of  time  is  required  for  a  cur- 
rent to  thoroughly  magnetize  a  powerful  electro- 
magnet. 

A  few  moments  are  also  required  for  a  power- 
ful magnet  to  thoroughly  lose  its  magnetism.  At 
the  same  time  electro-magnets  are  capable  of 
acquiring  or  losing  their  magnetism  with  very 
great  rapidity.  It  is,  in  fact,  on  this  ability  pos- 
sessed to  so  remarkable  a  degree  by  soft  iron,  that 


he  value  of  an  electro-magnet  for  many  purposes 
depends.  (See  Lag,  Magnetic.) 

A  difference  exists  between  the  action  of  a  mag- 
netized disc  and  a  hollow  coil  of  wire  through 
which  a  current  of  electricity  is  passing.  So 
far  as  the  space  outside  either  is  concerned,  the 
action  is  the  same,  but  the  coil  is  penetrable  on 
the  inside  and  the  disc  is  not,  and  for  the  inside  of 
the  space,  therefore,  there  is  a  difference  in  the  ac- 
tion. 

Magnet,  Electro,  Bar An  electro- 
magnet, the  core  of  which  is  in  the  form  of 
a  straight  bar  or  rod. 

Magnet,  Electro,  Cylindrical An 

electro-magnet,  the  core  of  which  consists 
of  a  hollow  cylinder  provided  with  a  slot 
extending  parallel  to  its  axis. 

The  gap  in  the  cylinder  suffices  for  the  placing 
of  the  magnetizing  coils,  and  forms  the  pules. 
This  form  of  electro-magnet  was  devised  by 
Joule.  Its  construction  will  be  understood  from 
an  inspection  of  Fig.  376. 


Fig.  yjb.     Cylindrical  Electro- Magnet. 

Magnet,  Electro,  Horseshoe — An 

electro-magnet,   the  core  of  which   is  in 
the  shape  of  a  horseshoe  or  U. 
Magnet,    Electro,   Hughes' An 

electro-magnet  in  which  a  U-shaped  per- 
manent magnet  is  provided  with  pole 
pieces  of  soft  iron,  on  which  only  are 
placed  the  magnetizing  coils. 

A  quick  acting  electro-magnet,  in 
which  the  magnetizing  coils  are  placed  on 
soft  iron  pole  pieces  that  are  connected 
with  and  form  the  prolongations  of  the 
poles  of  a  permanent  horseshoe  magnet. 

Hughes  devised  this  form  of  electro  magnet  in 
order  to  obtain  the  best  effects  from  currents  of 
but  short  duration. 

He  thus  obtained  a  quick  acting  magnet,  neces- 
sary to  insure  the  success  of  his  system  of  printing 
telegraph,  where  the  magnetizing  currents  at 
times  have  a  dura. ion  cf  but  the  .20  of  a  second. 


Mag.] 


340 


[Mag. 


-  377-     Iron- dad 
Electro- Magnet. 


Magnet,    Electro,    Joule's     Cylindrical 

An  electro- magnet  provided  with 

a  hollow  cylindrical  core.  (See  Magnet, 
Electro,  Cylindrical. ) 

Magnet,    Electro,   Iron  Clad  —An 

electro-magnet  whose  magnetizing  coil  is 
almost  entirely  surrounded  by  iron. 

The  effect  of  the  iron  casing  is  to  greatly  re- 
duce the  magnetic  re- 
sistance of  the  circuit. 
A  form  of  iron-clad  elec- 
tro-magnet is  shown  in 
Fig-  377-  Here  one  of 
the  poles  is  connected 
with  a  casing  of  iron, 
external  to  the  coils,  and 
is  thus  brought  nearer  to 
the  other  pole. 

Magnet,     Electro, 
Long-Core  —      — An  electro-magnet  with 
a  long  core  of  iron. 

A  long-core  electro-magnet  magnetizes  and 
demagnetizes  much  more  slowly  than  a  short- 
core  electro-magnet. 

Magnet,  Electro,  Short-Core An 

electro-magnet  with  a  short  core  of  iron. 

A  short-core  electro-magnet  possesses  the 
power  of  being  magnetized  and  demagnetized 
much  more  rapidly  than  a  long-core  magnet. 

Magnet,  Electro,  Yoked-Horseshoe 

A  horseshoe  electro-magnet,  in  which  the 
two  straight  limbs  are  formed  of  two 
straight  rods  or  bars,  yoked  together  atone 
pair  of  ends  by  a  yoke  or  bar  of  iron. 

In  some  cases  the  magnetizing  coils  are  placed 
on  each  of  the  limbs.  Sometimes,  however,  a 
single  coil  is  placed  at  the  middle  of  the  yoke 
and  the  limbs  are  left  bare. 

Even  with  the  closest  possible  fitting  the  re- 
sistance ot  the  magnetic  circuit  is  much  greater 
in  this  form  of  electro-magnet,  owing  to  the 
smaller  permeability  of  the  air  gap  at  the  joints, 
than  it  would  be  if  the  entire  core  were  made  of 
a  single  piece  of  iron.  A  yoked  electro- magnet 
is,  however,  more  convenient  to  make  and  use. 

Magnet,  Electro,  Zigzag  -  -A  multi- 
polor  electro-magnet,  the  magnetizing 
coils  of  which  are  separately  wound  in 
grooves  cut  in  the  face  of  straight  or 
curved  bars. 


A  form  ot  zigzag  electro-magnet  devised  by 
Joule  is  shown  in  Fig.  378.  The  spiral  char- 
acter of  the  wind.ng 
produces  the  alternate 
North  and  South  polari- 
ties shown  in  the  figure. 

Magnet,  Equator  of 
— A  point  ap- 
proximately midway 
between  the  poles  ofa 
straight  bar  magnet, 

i  •  j  Fig.  378.     Zigzag  Electro- 

or     nearly     midway  Magnet: 

from  the  poles  of  a  horseshoe  magnet  if 
measured  along  the  bar  from  each  pole. 

.This  term  was  proposed  by  Dr.  Gilbert.  It  is 
now  almost  entirely  displaced  by  the  term  neutral 
point, 

Magnet^  High-Resistance  -  —A  term 
sometimes  used  in  place  of  long-coil  mag- 
net whose  coils  have  a  high  electric  resist- 
ance. (See  Magnet,  Long-  Coil. ) 

The  term  long-coil  magnet  is,  perhaps,  the 
preferable  one,  because  the  resistance  of  a  coil, 
per  se,  has  nothing  to  do  with  its  magnetizing 
power,  which  is  determined  by  its  ampere  turns. 
(See  Turns,  Ampere,  Magnet,  Long-Coil.} 

Magnet,  Horseshoe magnetized 

bar  of  steel  or  iron  bent  in  the  form  ofa 
horseshoe  or  letter  U. 

Magnet,  Iron  Clad A  magnet  whose 

magnetic  resistance  is  lowered  by  a  casing 
of  iron  connected  with  the  core  and  pro- 
vided for  the  passage  of  the  lines  of  mag- 
netic force.  (See  Magnet,  Tubular.") 

Magnet,  Jacketed A  term  some- 
times applied  to  a  form  of  iron-clad  mag- 
net. (See  Magnet,  Iron-Clad. ) 

Magnet,  Keeper  of A  mass  of  soft 

iron  applied  to  the  poles  of  a  magnet 
through  which  its  lines  of  magnetic  force 
pass.  (See  Field,  Magnetic. ) 

The  keeper  of  a  magnet  differs  from  its  arma- 
ture in  that  the  keeper  while  acting  as  such  is 
always  kept  on  the  poles  to  prevent  loss  of  mag- 
netization, while  the  armature,  besides  acting  as 
a  keeper,  may  be  attracted  towards,  or,  if  an 
electro- magnet,  be  repelled  from  the  magnet 
poles.  While  performing  its  functions  the  keeper 
is  always  fixed,  the  armatuie  generally,  though 


Mag.l 


341 


[Mag. 


not  always,  is  in  motion.  A  keeper  is,  of  course, 
only  used  with  permanent  magnets. 

Opinion  is  divided  as  to  the  efficacy  of  the 
keeper  in  preventing  loss  of  magnetization  in 
certain  cases. 

Magnet,    Long  Coil  -An   electro- 

magnet whose  magnetizing  coil  consists 
of  many  turns  of  thin  wire. 

Magnet,  Low-Resistance —  —A  term 
sometimes  used  in  place  of  short-coil 
magnet.  (See  Magnet,  Short-Coil.) 

This  term,  short-coil  magnet,  is  the  preferable 
one. 

Magnet,  Marked  Pole  of A  name 

formerly  applied  to  that  pole  of  a  magnet 
which  points  approximately  to  the  geo- 
graphical north. 

If  the  pole  of  the  magnet  that  points  to  the 
geographical  north  be  in  reality  the  north  pole 
of  the  magnet,  then  the  earth's  magnetic  pole  in 
the  Northern  Hemisphere  is  of  south  magnetic 
polarity.  In  the  United  States,  and  Europe 
generally,  this  is  regarded  as  the  fact. 

The  French,  however,  formerly  called  the 
pole  ot  the  needle  that  points  to  the  earth's  geo- 
graphical north,  the  south  or  austral  pole.  In 
America  and  England  it  is  called  the  north  fole, 
the  marked  pole,  or  the  north  seeking  pole,  and 
the  Northern  Hemisphere  is  assumed  to  possess 
south  magnetic  polarity.  (See  Pole,  Magnetic, 
Austral.  Pole,  Magnetic,  Boreal.) 

Magnet,  Moment  of  -  -The  effective 
force  of  a  magnetic  couple  as  obtained  by 
multiplying  one  of  the  forces  of  the  couple 
by  the  perpendicular  distance  between 
the  directions  of  the  forces. 

The  moment  of  a  magnet  is  equal  to  the  prod- 
uct of  the  volume  of  the  magnet  and  the  in- 
tensity or  magnetization,  or  simply  its  magnetiza- 
tion. 

Magnet.  Natural  —  —A  name  some- 
times given  to  a  lodestone.  (See  Lode- 
stone.  ) 

Magnet,  Neutral  Line  of  —  —(See  Line, 
Neutral,  of  a  Magnet.) 

Magnet,  Permanent  —  -A  magnet  of 
hardened  steel  or  other  paramagnetic  sub- 
stance which  retains  its  magnetism  for  a 
long  time  after  being  magnetized. 


A  permanent  magnet  is  distinguished,  in  this 
respect,  from  a  temporary  magnet  of  soft  iron, 
which  loses  its  magnetization  very  shortly  alter 
being  taken  from  the  magnetizing  field. 

Magnet,  Portatiye  Power  of  —  —The 
lifting  power  of  a  magnet. 

The  portative  or  lifting  power  of  a  magnet, 
depends  on  the  form  of  the  magnet,  as  well  as  on 
its  strength.  A  horseshoe  magnet,  for  example, 
will  lift  a  much  greater  weight  than  the  same 
magnet  if  in  the  form  of  a  straight  bar. 

This  is  due  not  only  to  the  mutual  action  of  the 
approached  poles,  but  also  to  the  decreased  re- 
sistance of  the  magnetic  circuit,  and  to  the  greater 
number  of  lines  of  magnetic  force  that  pass 
through  the  armature.  The  portative  power  is 
proportional  to  the  area  of  contact  and  the  square 
of  the  magnetic  intensity,  the  formula  being 

p  _      A  X  B» 

"   87TX98i, 

in  which  P,  is  the  lifting  power  in  grammes,  A, 
the  area  of  contact  in  square  centimetres,  and  B, 
is  the  number  of  lines  of  force  per  square  centi- 
metre. 

Magnet  Operation (See  Operation, 

Magnet. ) 

Magnet,  Receiving A  name  some- 

times  given  to  the  relay  of  a  telegraphic 
system.  (See  Relay.) 

In  general,  any  magnet,  used  directly  in 
the  receiving  apparatus,  at  the  receiving 
end  of  a  line  connecting  a  system  of  elec- 
tric communication  between  transmitting 
and  receiving  instruments. 

Magnet,  Regulator A  magnet,  the 

operation  of  which  is  to  automatically 
effect  any  desired  regulation. 

The  magnet  in  the  Thomson-Houston 
system  of  automatic  regulation,  by  means 
of  which  the  commutator  collecting 
brushes  are  automatically  shifted  to  such 
positions  on  the  commutator  as  will  main- 
tain the  current  practically  constant,  de- 
spite the  changes  in  the  resistance  of  the 
circuit  external  to  the  machine.  (See 
Regulation,  Automatic.} 

Magnet,  Relay  -  -An  electro-magnet, 
whose  coils  are  connected  to  the  main  line 
of  a  telegraphic  circuit,  and  the  movements 


Mag.] 


342 


[Mag. 


of  whose  armature  is  employed  to  bring  a 
local  battery  into  action  at  the  receiving 
station,  the  current  of  which  operates  the 
register  or  sounder. 

Magnet,  Short-Coil An  electro- 
magnet whose  magnetizing  coil  consists 
of  a  few  turns  of  short,  thick  wire. 

Magnet,  Simple A  simple  mag- 
netized bar. 

The  term  simple  magnet  is  used  in  contradis- 
tinction to  compound  magnet.  (See  Magnet, 
Compound. ) 

Magnet,  Sluggisn A  magnet  that 

magnetizes  or  demagnetizes  sluggishly. 

An  electro-magnet  becomes  sluggish  when  sur- 
rounded by  a  sheathing  of  copper,  on  account  of 
the  currents  induced  in  the  sheathing  in  a  direc- 
tion opposite  to  those  passing  through  the  mag- 
netizing coil. 

Magnet,  Solenoidal A  thin,  uni- 
formly magnetized  straight  bar  of  steel,  of 
such  a  length  that  its  poles,  situated  at 
extremities  or  ends  of  its  longer  axis,  act 
on  external  objects  as  if  equal  and  oppo- 
site quantities  of  magnetism  were  con- 
centrated at  such  extremities. 

It  derives  its  name  solenoidal  from  the  simi- 
larity between  its  action  and  that  of  a  solenoid. 
Unless  very  carefully  magnetized,  a  magnet  will 
not  act  as  a  solenoid  magnet.  (See  Magnet, 
Electro.  Magnetism,  Solenoidal  Distribution  of.) 

Magnet,  Tubular A  form  of  horse- 
shoe magnet,  in  which  one  pole  is  brought 
near  the  opposite  pole  by  a  hollow  cylin- 
der or  tube  of  iron,  which  is  placed  in  con- 
tact with  one  of  the  magnetic  poles,  so  as 
to  completely  surround  the  other,  except 
in  the  plane  of  cross-section  of  that  pole. 

A  form  of  iron-clad  magnet.  (See 
Magnet,  Iron-Clad.} 

There  is  thus  obtained  a  magnet,  with  two  con- 
centric poles,  one  solid  and  the  other  annular, 
the  portative  power  of  which  is  much  greater  than 
that  of  a  horseshoe  magnet  of  equal  dimensions. 

Magnet,  Field,  of  Dynamo-Electric  Ma- 
chine   One  of  the  electro-magnets 

employed  to  produce  the  magnetic  field 
of  a  dynamo-electric  machine. 


The  field  magnets  consist  of  a  suitable  frame, 
or  core,  on  which  the  field  magnet  coils  are 
wound. 

Thejif/d  magnet  cores  are  made  of  thick  and 
solid  iron,  as  soft  as  possible.  They  should  con- 
tain plenty  of  iron  in  order  to  avoid  too  ready 
magnetic  saturation. 

All  edges  and  corners  are  to  be  avoided,  since 
they  tend  to  cause  an  irregular  distribution  of  the 
field. 

The  field  magnets  should  in  general  have  suffi- 
cient magnetic  strength  to  prevent  the  magnet- 
izing effect  of  the  armature  from  unduly  influ- 
encing the  field,  and  thus,  by  causing  too  great  a 
lead,  produce  injurious  sparking. 

Magnetic  or  Magnetical.— Pertaining  to 
magnetism. 

Magnetic  Adherence.— (See  Adherence, 
Magnetic. } 

Magnetic  Air  Circuit.— (See  Circuit,  Air, 
Magnetic. } 

Magnetic  Air  (Jap— (See  Gap,  Air,  Mag- 
netic. } 

Magnetic  Attraction.— (See  Attraction, 
Magnetic. } 

Magnetic  Axis.— (See  Axis,  Magnetic. } 

Magnetic  Axis  of  a   Straight   Needle.— 

(See  Axis,  Magnetic,  of  a  Straight  Needle.} 

Magnetic  Azimuth.— (See  Azimuth,  Mag- 
netic } 

Magnetic  Battery.— (See  Battery,  Mag- 
netic.} 

Magnetic  Bridge.— (See  Bridge,  Mag- 
netic.} 

Magnetic  Circuit.— (See  Circuit,  Mag- 
netic.} 

Magnetic  Closed-Circuit.— (See  Circuit, 
Closed  Magnetic. } 

Magnetic  Conductance.— (See  Conduct- 
ance, Magnetic.} 

Magnetic  Core,  Closed (See  Core, 

Closed- Magnetic. 

Magnetic  Core,  Open (See  Core, 

Open- Magnetic. ) 

Magnetic  Couple.— (See  Coupe,  Mag- 
netic} 


Mag.] 


343 


[Mag. 


Magnetic  Curves. — (See  Curves,  Mag- 
netic. } 

Magnetic  Day  of  Disturbance.— (See  Day 
of  Disturbance,  Magnetic. } 

Magnetic  Declination.  —  (See  Declina- 
tion } 

Magnetic  Density.— (See  Density,  Mag- 
•-•efic. ) 

Magnetic  Dip.— (See  Dip,  Magnetic.) 

Magnetic  Elements  of  a  Place.— (See 
Elements,  Magnetic,  of  a  Place. } 

.Magnetic  Equalizer.  —  (See  Equalizer, 
Magm  tic. } 

Magnetic  Explorer. —(See  Explorer,  Mag- 
netic } 

Magnetic,  Ferro Magnetic  after 

the  manner  of  iron  or  other  paramagnetic 
body.  (See  Paramagnetic. } 

Magnetic  Field.— (See  Field,   Magnetic.} 

Magnetic  Field,  Reversing. (See 

Field,  Magnetic,  Reversing.} 

Magnetic  Field,  Shifting. (See 

Field  Magnetic,  Shifting.} 

Magnetic  Figures.— See  Figures,  Mag- 
netic. Field,  Magnetic.} 

MiirnHic  Filament.  —  (See  Flameni 
Magnetic} 

Magne'.ic  Flow.— (See  Flow,  Magnetic.} 
Magnetic  Flux.— (See  Flux,  Magnetic.} 
Magnetic  Force.— (See  Force,  Magnetic.} 
Magnetic  Inclination.— (See  Inclination, 
Magnetic  } 

Magm  tic   Induction.  —  (See    Induction, 
Magnetic  } 
Magnetic    Induction,  Dynamic. 

(See  Induction,   Magnetic,  Dynamic. } 

Magnetic  Induction,  Static- (See 

Induction,   Magnetic,    Static} 

Magnetic  Inertia.— (See  Inertia,  Mag- 
netic } 

Magnetic  Intensity.  —  (See  Intensity, 
Magnetic.} 

Magnetic  Joint.  — (See  Joint,    Magnetic.} 


Magnetic  Lag. — (See  Lag,  Magnetic.} 

Magnetic  Latitude. — (See  Latitude,  Mag- 
netic. } 

Magnetic  Leakage. — (See  Leakage,  Mag- 
netic.} 

Magnetic  Lines  of  Force.— (See  Force* 
Magnetic,  Lines  of. } 

Magnetic  Mass. — (See  Mass,  Magnetic. } 

Magnetic  Memory. — (See  Memory,  Mag- 
netic. } 

Magnetic  Meridian.  —  (See  Meridian, 
Magnetic} 

Magnetic  Moment. — (See  Moment,  Mag- 
netic} 

Magnetic  Normal  Day.— (See  Day,  Nor- 
mal, Magnetic.} 

Magnetic  Observatory.  —  (See  Observa- 
tory, Magnetic. 

Magnetic  Output. — (See  Output,  Mag- 
netic. } 

Magnetic  Parallel.— (See  Parallels,  Mag- 
netic } 

Magnetic  Permeability.  —  (See  Permea- 
bility, Magnetic.} 

Magnetic  Permeance. — (See  Permeance, 
Magnetic. } 

Magnetic  Permeation. — (See  Permeation, 
Magnetic. } 

Magnetic  Poles.— (See  Poles,  Magnetic. } 

Magnetic  Poles,  False. —(See  Pole, 

Magnetic,  False.} 

Magnetic  Proof  Piece.— (See  Piece,  Mag- 
netic Proof.} 

Magnetic  Proof  Plane.— (See  Plane, 
Proof,  Magnetic.} 

Magnetic  Reluctance.— (See  Reluctance, 
Magnetic.} 

Magnetic  Repulsion.  —  (See  Repulsion, 
Magnetic} 

Magnetic  Resistance.  —(See  Resistance, 
Magnetic.} 

Magnetic  Retardation.  —  (See  Retarda- 
tion Magnetic} 


Mag.] 


344 


[Mag. 


Magnetic  Retentiyity.— (See  Retentivity, 
Magnetic.') 

Magnetic  Saturation. — (See  Saturation, 
Magnetic. ) 

Magnetic  Screen  or  Shield.— (See  Screen 
or  Shield,  Magnetic. ) 

'      Magnetic    Screening.  —  (See    Screening, 
Magnetic.) 

Magnetic,  Self  Induction. — (See  Induc- 
tion, Self,  Magnetic.) 

Magnetic  Shells.— (See  Shells,  Magnetic.) 
Magnetic  Shunt.— (See  Shunt,  Magnetic  ) 

Magnetic  Sidero A  term  proposed 

by  S.  P.  Thompson  to  replace  the  term 
ferro-magnetic.     (See  Magnetic,  Ferro.) 

Magnetic  Solenoid.— (See  Solenoid,  Mag- 
netic. ) 

Magnetic  Sounds.— (See  Sounds,  Mag- 
netic. ) 

Magnetic  Spin.— (See  Spin,  Magnetic.) 
Magnetic    Storm.— (See     Storm,     Mag- 
netic.) 

M  gnetic  Strain.  —  (See  Strain,  Mag- 
netic.} 

Magnetic  Stress.— (See  Stress,  Magnetic. ) 
Magnetic   Susceptibility.— (See    Suscepti- 
bility, Magnetic.) 

Magnetic  Theodolite.  —  (See  Theodolite, 
Magnetic  ) 

Magnetic  Unit  Pole.— (See  Pole,  Unit, 
Magnetic. ) 

Magnetic  Units.— (See    Units,  Magnetic) 

Magnetic- Vane  Ammeter.— (See  Ammeter, 
Magnetic-  Vane. ) 

Magnetic  Vane  Voltmeter.  —  (See  Volt- 
'  meter,  Magnetic-Vane.) 

Magnetic  Variations.  —  (See  Variations, 
Magnetic. ) 

Magnetic  Variation  Transit.— (See  Tran- 
sit, Magnetic  Variation.) 

Magnetic  Variometer.— (See  Variometer, 
Magnetic. ) 


Magnetic  Viscosity.-  (See  Viscosity,  Mag- 
netic) 
Magnetic  Whirl.— (See  Whirls,  Magnetic.) 

Magnetic  Whirl,  Expanding  —(See 

Whirl,  Magnetic,  Expanding.) 

Magnetics,  Electro That  branch  of 

electric  science  which  treats  of  the  rela- 
tions that  exist  between  electric  circuits 
and  magnets. 

Magnetism.  —  That    branch  of  science  I 
which  treats  of  the  nature  and  properties 
of  magnets  and  the  magnetic  field.    (See 
Field,  Magnetic.) 

A  property  or  condition  of  matter  at- 
tended by  the  existence,  of  a  magnetic 
field. 

Magnetism,  Ampere's  Theory  of A 

theory  or  hypothesis  proposed  by  Ampere, 
to  account  for  the  cause  of  magnetism,  by 
the  presence  of  electric  currents  in  the 
ultimate  particles  of  matter. 


Fig.  37<J.     Unmagnetized 
Bar  {after  Ampkre}. 


Fig.  380.      Magnetized 
Bar  (after  Ampere) . 


This  theory  assumes  : 

(I.)  That  the  ultimate  particles  of  all  magneti- 
zable  bodies  have  closed  electric  circuits  in  which 
electric  currents  are  continually  flowing. 

(2.)  That  in  an  unmagnetized  body  these  cii  - 
cuits  neutralize  one  another  because  they  have 
different  directions. 

(3.)  That  the  act  of  magnetization  consists  in 
such  a  polarization  of  the  particles  as  will  cause 
these  currents  to  flow  in  one  and  the  same  direc- 
tion,  magnetic  saturation  being  reached  when  all 
the  separate  circuits  are  parallel  to  one  another. 

(4.)  That  coercive  force  is  due  to  the  resistance 
these  circuits  offer  to  a  change  in  the  direction 
of  their  planes. 

Figs.  379  and  380  show  the  circular  paths  of 
some  of  these  circuits.  Fig.  379  shows  the  as- 


Mag.] 


345 


[Mag. 


sumed  condition  of  an  unmagnetized  bar.  Fig. 
380  the  assumed  condition  of  a  magnetized 
bar. 

A  careful  inspection  of  the  figures  will  show  that 
in  a  magnetized  bar  all  the  separate  currents  flow 
in  the  same  direction.  All  the  circuits  except 
those  on  the  extreme  edge  of  the  bar  will,  there- 
fore, have  the  currents  flowing  in  them  in  opposite 
directions  to  that  in  their  neighboring  circuits, 
and,  therefore,  will  neutralize  one  another .  There 
•will  remain,  however,  a  current  in  a  circuit  on  the 
outside  of  the  bar,  which  must  therefore  be  re- 
garded as  the  magnetizing  current. 

Guided  by  these  considerations,  Ampere  pro- 
duced a  coil  of  wire,  called  a  solenoid,  which  is 
the  equivalent  of  the  magnetizing  circuit  assumed 
by  his  theory. 

It  therefore  follows  that  an  electric  current  sent 
through  a  coil  of  insulated  wire  surrounding  a 
rod  or  bar  of  soft  iron,  or  other  readily  magnet- 
izable material,  will  make  the  same  a  magnet.  A 
magnet  so  produced  is  called  an  electro-magnet. 
(See  Magnet,  Electro.} 

The  magnetizing  coil  is  called  a  helix  or  sole- 
noid. See  Solenoid,  Electro -Magnetic.) 

The  polarity  of  the  magne'  depends  on  the 
direction  of  the  current,  or  on  the  direction  of 
winding  of  the  helix  or  solenoid.  (See  Solenoid, 
Sinistrorsal.  Solenoid,  Dextrorsal.) 

The  improbability  of  an  electric  current  con- 
tinually flowing  in  a  circuit  without  the  expendi- 
ture of  energy,  has  led,  perhaps,  the  majority  of 
scientific  men  to  reject  Ampere's  theory  of  mag- 
netism. 

Lodge,  however,  does  not  agree  with  the  ma- 
jority of  physicists  in  regarding  a  constant  flow 
of  electricity  through  the  molecules  of  magnetiza- 
ble substances  as  an  impossibility.  On  the  sup- 
position that  the  atoms  or  molecules  possess 
no  resistance,  the  current  would  flow  through 
them  lorever.  He  says:  ."To  all  intents  and  pur- 
poses certainly  atoms  are  infinitely  elastic,  and 
why  should  they  not  also  be  infinitely  conducting  ? 
%  Why  should  the  dissipation  of  energy  occur,  in 
respect  to  an  electric  current  circulating  wholly 
inside  an  atom?  There  is  no  reason  why  it 
should.  " 

Magnetism,  Animal A  term  some- 
times applied  to  hypnotism  or  artificial 
somnambulism. 

Magnetism,  Earth's,  Theories  as  to  Cause 

of The  various  theories  or  hypotheses 


respecting  the  cause  of  the  earth's  magnet- 
ism. 

Any  theory  or  hypothesis  which  shall  satisfac- 
torily explain  the  cause  of  the  earth's  magnetism 
must  account  for  the  following  phenomena,  viz.  ; 

(i.)  Variations  in  the  intensity  of  the  earth's 
magnetic  field. 

(2.)  Variations  in  the  earth's  magnetic  inclina- 
tion, declination  and  intensity. 

The  following  hypotheses  have  been  proposed'. 

1st.  That  the  earth's  magnetism  is  due  to  the 
circulation  round  the  earth  of  electric  currents 
produced  by  differences  of  temperature  which  the 
earth's  surface  acquires  from  exposure  to  the  sun 
during  its  rotation. 

As  the  earth  rotates  from  west  to  east,  the  area 
of  greatest  heat  would  move  round  the  earth  in 
the  opposite  direction,  or  from  east  to  west.  K 
now  those  differences  of  temperature  could  pro. 
duce,  in  a  manner  not  as  yet  explained,  thermo- 
electric currents  circulating  round  the  earth  from 
east  to  west,  such  currents  would  produce,  in  the 
Northern  Hemisphere  of  the  earth,  south  mag- 
netic polarity,  and  in  the  Southern  Hemisphere 
north  magnetic  polarity,  which  would  account  for 
the  magnetic  polarity  of  the  earth. 

Differences  in  the  intensity  of  the  earth's  mag- 
netic field,  and  in  the  inclination  and  direction  of 
its  lines  ot  magnetic  force,  would  be  explained, 
according  to  this  hypothesis,  by  the  differences  in 
the  amount  of  the  solar  radiation  at  different 
times. 

The  objection  to  this  theory  is  to  be  found  in 
the  fact  that  by  far  the  larger  part  of  the  earth's 
surface  at  the  Equator  is  composed  of  water,  so 
that  the  differences  of  potential  at  such  parts, 
produced  by  the  differences  of  temperature,  are 
not  readily  set  up  in  the  earth's  crust,  if,  indeed, 
they  are  set  up  at  all. 

2d.  That  the  earth's  magnetism  is  due  to  in- 
duction from  an  already  magnetized  sun.  This 
theory  was  brought  forward  by  Secci  and  others. 
It  is  not  generally  credited. 

3d.  A  theory  proposed  by  Biglow,  which  ac- 
counts for  the  earth's  magnetism  by  rotation  in 
the  magnetic  field  of  the  sun's  light  and  radia- 
tion. 

Biglow  believes  that  the  earth's  magnetism  is 
due  to  its  rotation  in  the  magnetic  field  of  the 
sun's  light.  As  the  sun's  light  illumines  one-half 
of  the  earth's  surface,  the  earth's  rotation  causing 
different  portions  of  the  surface  to  pass  through 


346 


this  illumim  d  area,  produces,  in  Prof.  Biglow's 
opinion,  th  ft  differences  in  the  direction  and  in- 
tensity of  'Jie  magnetic  lines  of  the  earth's  field 
that  correspond  to  differences  in  the  earth's  mag- 
netic intensity,  declination  and  inclination. 

It  will  be  observed  that  in  all  these  theories  the 
sun  is  the  prime  factor  in  the  production  ot  the 
earth's  magnetism. 

The  evident  connection  between  the  earth's 
magnetism  and  the  solar  radiation  is  established 
from  the  well  known  connection  between  the  so- 
called  magnetic  storms  and  variations  in  the  in- 
tensity of  the  earth's  magnetism. 

Magnetic  storms  are  always  attended  by  out- 
bursts of  solar  energy,  known  technically  as 
sun  spots.  A  series  of  observations  on  the  num- 
bers and  frequency  of  sun-spots,  plotted  in  the 
form  of  a  curve,  the  ordinates  of  which  represent 
the  times  of  occurrence  of  the  spots  and  the 
abscissas,  the  number  of  such  spots,  prove  that 
such  curve  agrees,  in  a  remarkable  manner,  with 
a  similar  curve  representing  the  variations  of  the 
earth's  magnetic  field. 

An  evident  connection,  too,  exists  between  the 
earth's  magnetism  and  the  pr6valence  of  the 
aurora  borealis. 

Magnetism,  Electro Magnetism 

produced  by  means  of  electric  currents. 

The  discovery  by  Oersted,  in  1820,  of  the  ac- 
tion of  an  electric  current  on  a  magnetic  needle, 
was  almost  immediately  followed  by  the  simul- 
taneous and  independent  discoveries  by  Arago 
and  Davy,  ot  the  method  of  magnetizing  iron 
by  the  passage  of  an  electric  current  around  it. 

These  observations  were  first  reduced  to  a 
theory  by  Ampere  (See  Magnetism^  Ampere's 
Theory  of .  Magnet,  Electro.) 

Magnetism,  Ewing's  Theory  of  -  —A 
theory  of  magnetism  proposed  by  Prof. 
Ewing,  based  on  the  assumption  of  orig- 
inally magnetized  particles. 

Ewing's  theory  of  magnetism  assumes  that  the 
ultimate  particles  ot  matter  are  naturally  mag- 
netic and  possess  polarity.  In  this  respect  Ewing's 
theory  agrees  with  the  theories  of  Hughes  and 
Weber.  Ewing  does  not  believe,  however,  in  the 
necessity  for  the  assumption  of  any  arbitrary  re- 
straining or  constraining  force  to  the  movements 
of  these  ultimate  magnetic  particles  other  than 
those  due  to  their  own  mutual  magnetic  attractions 
and  repulsions.  He  assumes  that  in  a  magnet, 


the  centres  about  which  the  molecular  magnets 
rotate  are  maintained  at  constant  distances  from 
one  another,  save  only  as  they  are  affected  by  the 
action  of  strain. 

He  has  experimentally  demonstrated  the  prin- 
ciples of  his  theory  by  means  of  a  model  in  which 
a  number  of  small  magnetic  needles  are  so  sup- 
ported as  to  be  capable  of  free  motion  in  a  hori- 
zontal plane,  when  under  varying  magnetic 
forces. 

According  to  Ewing,  "magnetic  hysteresis" 
is  not  the  result  of  any  quasi  frictional  resistance 
to  molecular  rotation,  but  arises  from  a  molecule 
moving  from  one  position  of  stable  equilibrium  co 
another  position  of  stable  equilibrium  through  a 
position  of  unstable  equilibrium.  "  This  pro- 
cess "  says  Ewing,  "considered  mechanically,  is 
not  reversible.  The  forces  are  different  for  the 
same  displacement,  going  and  coming,  and  there 
is  dissipation  of  energy.  In  the  model,  the  energy 
thus  expended  sets  the  little  bars  swinging,  and 
their  swings  take  some  time  to  subside.  In  the 
actual  solid,  the  energy  which  the  molecular 
magnet  loses  as  it  swings  through  unstable  posi- 
tions, generates  eddy  currents  in  surrounding 
matter.  Let  the  magnets  of  the  model  be 
furnished  with  air  vanes  to  damp  their  swings 
and  the  correspondence  is  complete." 

In  Hughes'  modification  of  Weber's  theory  of 
magnetism,  it  was  held,  that  when  magnetized 
iron  was  suddenly  demagnetized  by  torsion  or 
flexure,  it  lost  its  magnetization  because  the  mo- 
lecular magnets  came  to  rest  in  closed  chains,  which 
produced  no  external  effects.  Experimentation 
with  Ewing's  model  of  a  magnet  shows  that  when 
the  separate  magnets  after  having  been  placed  in 
any  particular  grouping  are  permitted  to  come  to 
rest  free  from  any  external  magnetic  force,  they  do 
not  arrange  themselves  in  closed  chains,  but  in 
general  the  tendency  appears  to  be  the  formation 
of  lines  consisting  of  two,  three  or  more  magnets, 
each  member  of  a  line  being  strongly  controlled 
by  its  next  member  in  that  line,  but  influenced 
by  the  neighbors  which  lie  off  the  line  on  either 
side. 

The  fact  that  a  given  force,  suddenly  applied, 
produces  more  magnetic  induction  than  when 
gradually  applied,  and  leaves  less  residual  mag- 
netism when  suddenly  than  when  gradually  re- 
moved,  is  presumably  due  to  the  inertia  of  the 
molecules. 

The  influence  of  mechanical  vibration  in  in- 
creasing the  magnetic  susceptibility  and  decreas. 


347 


[Mag. 


ing  the  magnetic  retentiveness,  is  ascribed  by 
Ewing  to  the  fact  that  the  vibrations  cause 
periodic  variations  in  the  distances  between  the 
centres  of  rotation  of  the  magnetic  molecules; 
thus  making  the  molecular  magnets  respond  more 
readily  to  changes  of  magnetic  force  during  the 
time  they  are  moving  away  from  one  another, 
when  their  magnetic  stability  is  less,  but  also  in- 
creasing the  ease  with  which  they  respond  to 
changes  of  magnetic  force,  by  causing  them  to 
swing. 

Ewing  discusses  the  theoretical  effects  of  tem- 
perature on  magnetism  as  follows,  viz. :  Suppose 
a  moderate  magnetizing  force  to  be  applied  so 
that  nothing  like  saturation  is  obtained,  if  now 
the  temperature  be  raised;  then 

(i.)  The  magnetic  permeability  increases  until 
the  temperature  reaches  a  certain  (high)  critical 
value. 

(2.)  At  this  temperature  there  is  suddenly  an 
almost  complete  disappearance  of  magnetic 
quality. 

He  explains  these  facts  as  follows,  viz.:  An 
increase  of  temperature  by  increasing  the  distance 
between  the  molecular  centres  causes  a  decrease 
In  their  stability. 

The  loss  of  magnetic  qualities,  when  a  certain 
temperature  is  reached,  is,  he  believes,  due  to  the 
fact  that  at  such  temperatures  the  magnetic 
molecules  are  set  into  actual  rotation,  when, 
naturally,  all  traces  of  polarity  would  disappear. 

Ewing's  theory  of  magnetism  also  accounts  to 
a  considerable  extent  for  the  effects  of  stress  and 
consequent  elastic  strain  on  the  magnetic  qualities 
of  iron,  nickel  and  cobalt. 

The  following  general  summary  of  his  theory 
is  taken  mainly  from  Prof.  Ewing's  original 
articles  as  published  in  the  Journal  of  the  Society 
of  Arts: 

(i.)  That  in  considering  the  magnetization  of 
iron  and  othtr  magnetic  metals  to  be  caused  by 
the  turning  of  permanent  molecular  magnets,  we 
may  look  simply  to  the  magnetic  forces  which 
the  molecular  magnets  exert  upon  one  another  as 
the  cause  of  their  directional  stability.  There  is 
no  need  to  suppose  the  existence  of  any  quasi- 
elastic  directing  force,  or  any  quasi-frictional  re- 
sistance to  rotation. 

(2. )  That  the  intermolecular  magnetic  forces  are 
sufficient  to  account  for  all  the  general  character- 
istics of  the  process  of  magnetization,  including 
the  variations  of  susceptibility  which  occur  as 
the  magnetizing  force  is  increased. 

12_Vol.  1 


(3.)  That  the  intermolecular  magnetic  forces 
are  equally  competent  to  account  for  the  known 
facts  of  retentiveness  and  coercive  force,  and  the 
characteristics  of  cyclic  magnetic  processes. 

(4.)  The  magnetic  hysteresis  and  the  dissipation 
of  energy  which  hysteresis  involves  are  due  to 
molecular  instability,  resulting  from  intermolec- 
ular magnetic  actions,  and  are  not  due  to  any- 
thing in  the  nature  of  frictional  resistance  to  the 
rotation  of  the  molecular  magnets. 

(5.)  That  this  theory  is  wide  enough  to  admit  an 
explanation  of  the  differences  in  magnetic  quality 
which  are  shown  by  different  substances,  or  by 
the  same  substance  in  different  states. 

(6.)  That  it  accounts  in  a  general  way  for  the 
known  effects  of  vibration,  of  temperature,  and 
of  stress,  upon  magnetic  quality. 

(7  )  That,  in  particular,  it  accounts  for  the 
known  fact  that  there  is  hysteresis  in  the  relation 
of  magnetism  to  stress. 

(8.)  That  it  further  explains  why  there  is  in 
magnetic  metals  hysteresis  in  physical  quality 
generally  with  respect  to  stress. 

(9.)  That,  in  consequence,  any  (not  very  small) 
cycle  of  stress  occurring  in  a  magnetic  metal  in- 
volves dissipation  of  energy. 

It  can  be  demonstrated  by  means  of  experi- 
ments with  a  model  constructed  according  to 
Ewing's  hypothesis,  that  this  hypothesis  comes 
nearer  than  any  which  had  been  proposed  tefore 
in  explaining  the  following  effects: 

(i.)  The  behavior  of  a  piece  of  iron  when 
placed  in  a  magnetic  field  whose  strength  is  made 
to  pass  through  a  cycle  of  changes. 

(2.)  That  nearly  all  reversals  of  sign  on  the 
change  of  the  magnetizing  force  are  accompanied 
by  small  changes  in  the  magnetization. 

(3.)  That  a  piece  of  iron  submitted  to  vibra- 
tions or  mechanical  shocks,  is  magnetized  and 
demagnetized  more  readily  and  with  a  smaller 
hysteresial  area  than  if  it  had  remained  undis- 
turbed by  vibrations. 

(4.)  The  phenomenon  of  "time  lag  "in mag-1 
netization. 

(5.)  The  phenomena  of  stress,  both  those  which 
occur  when  a  body  has  first  been  placed  in  a 
magnetic  field  and  the  stress  made  to  vary,  and 
those  which  occur  when  a  body  is  first  placed  in 
a  constant  stress  and  the  magnetizing  force  is 
made  to  vary. 

(6.)  The  effects  of  heat  on  magnetization,  both 
as  regards  the  effect  of  comparatively  low  heating 
on  increase  of  magnetic  susceptibility,  and  ;he 


348 


[Mag. 


effect  of  excessive  heating  to  decrease  the  sus- 
ceptibility. 

The  author  is  indebted  for  the  above  summary 
of  demonstrable  facts  to  a  paper  recently  read  be- 
fore the  Electrical  Section  of  the  Franklin  Insti- 
tute, by  Prof.  Henry  Crew. 

Magnetism,  Flux  or  Flow  of The 

quantity  of  magnetism,  or  the  number  of 
lines  of  force  which  pass  in  any  magnetic 
circuit  under  a  given  magneto-motive  force, 
against  a  given  magnetic  reluctance. 


Magnetism,  Galvano 


A  term  some- 


times used  for  electro-magnetism. 

Electro-magnetism  is  by  far  the  preferable 
term,  and  is  almost  universally  used  in  the  United 
States. 

Magnetism,  Horizontal  Component  of 
Earth's  --  (See  Component,  Horizontal, 
of  Earth's  Magnetism.) 

Magnetism,  Hughes'  Theory  of  -      —A 

theory  propounded  by  Hughes  to  account  for 
the  phenomena  of  magnetism  apart  from  the 
presence  of  electric  currents. 

Hughes'  theory,  or,  more  strictly  speaking, 
hypothesis  of  magnetism,  though  very  similar  to 
that  of  Ampere,  does  not  assume  the  improbable 
condition  of  a  constantly  flowing  electric  current. 

Hughes'  hypothesis  assumes: 

(i.)  That  the  molecules  of  matter,  and,  per- 
haps, more  probably,  the  atoms,  possess  naturally 
opposite  magnetic  polarities,  which  are  respect- 
ively +  and  —  ,  or  N  and  S. 

(2.)  That  these  molecules,  when  arranged  in 
closed  chains  or  circuits,  are  capable  of  neutral- 
izing one  another  so  far  as  external  action  is  con- 
cerned. 


i: 


8\ 


Fig.  38 z.     Closed  Molecular  Chain. 

Two  such  arrangements  or  groupings  are 
shown  in  Figs.  381  and  382.  It  will  be  observed 
that  the  magnetic  chain  or  circuit  is  complete, 


and  that,  therefore,  the  substance  can  possess  no 
magnetic  properties  so  far  as  external  action  is 
concerned. 


4- 


Fig.  382.     Closed  Groupings. 

(3.)  That  the  act  of  magnetization  consists  in 
such  a  rotation  of  the  molecules  that  a  polariza- 
tion of  the  substance  is  effected  —  that  is,  the 
molecules  are  rotated  on  their  axes  so  that  one  set 
of  poles  tend  to  point  in  one  direction  and  the 
other  set  of  poles  in  the  opposite  direction. 

Partial  magnetization  consists  in  partial  polari- 
zation. Magnetic  saturation  is  reached  when  the 
polarization  is  complete.  (See  Saturation,  Mag- 
netic.) 

Coercive  force  is  the  resistance  the  body  offers 
to  the  polarization  or  rotation  of  its  molecules. 
(See  Force,  Coercive.) 

Hughes'  hypothesis  of  magnetism  would  ap- 
pear to  be  strengthened  by  the  following  facts: 

(I.)  A  bar  of  steel  or  iron  is  sensibly  elongated 
on  being  magnetized.  This  would  naturally  re- 
sult if  the  molecules  be  supposed  to  be  longer  in 
one  direction  than  in  any  other. 

(2.)  A  tube,  furnished  at  its  ends  with  plates  of 
flat  glass  and  filled  with  water  containing  finely 
divided  magnetic  oxide  of  iron,  is  nearly  opaque 
to  light  when  unmagnetized,  but  will  permit  some 
light  to  pass  through  it  when  magnetized. 

(3.)  A  magnet,  if  cut  at  its  neutral  point,  will 
possess  opposite  polarities  at  the  cut  ends;  and, 
no  matter  to  what  extent  this  subdivision  is  car- 
ried, the  particles  will  still  possess  opposite  polar- 
ities. 

These  facts  are,  however,  also  explained  by 
Ampere's  hypothesis  of  magnetism,  with,  how- 
ever, the  improbable  assumption  of  a  constantly 
flowing  current  in  each  molecule. 

The  following  experiment  by  Von  Betz  tends 
somewhat  to  confirm  Hughes'  hypothesis: 

He  placed  a  powerful  horseshoe  magnet  in  a 
solution  of  iron  and  deposited  a  bar  or  plate  of 
metallic  iron  between  the  poles  by  electrolysis. 
Here  the  molecules,  at  the  time  of  their  deposi- 
tion, were  subjected  to  a  polarizing  force  which 
tended  to  place  them  all  in  the  same  direction, 
and,  as  the  solution  from  which  they  were  ob- 
tained permitted  great  freedom  of  motion,  they 
were  all  presumably  deposited  in  lines  parallel  to 
one  another.  When  this  bar  of  iron  was  subse 


Mag.] 


[Mag. 


quently  magnetized  it  was  found  to  be  much  more 
powerful  in  comparison  to  its  size  than  any  other 
magnet. 

Mr.  Shelford  Bidwell  has  shown  that  the  act  of 
magnetization  produces  a  shortening  rather  than 
a  lengthening  of  the  magnetizable  material. 
When  the  magnetization  is  moderate  there  is  a 
true  lengthening  of  the  material,  but  when  a 
more  powerful  magnetizing  force  is  exerted  a 
true  contraction  or  shortening  is  observed. 

M 

L 


of 

in 


•  3$  3'    Bidwell  Apparatus. 


The  Bidwell  apparatus  is  shown  in  Fig.  383. 
The  bar  of  iron  to  be  magnetized  is  shown  at 
R  R.  The  magnetization  is  obtained  by  means  of 
the  coil  of  wire  C.  The  upper  end  of  the  bar 
presses  against  the  rod  L,  fulcrumed  at  F.  The 
other  end  of  the  bar  bears  against  a  pivoted 
mirror  M,  from  which  a  «pot  of  light  is  reflected. 

In  the  case  of  the  magnetization  of  nickel,  the 
experiments  of  Bidwell  showed  the  existence  of 
contraction  far  both  weak  and  strong  currents. 
This  contraction  is  much  greater  than  in  the  case 
of  iron. 

Magnetism,  Lamellar   Distribution 

-  —  The  distribution  of    magnetism 
magnetic  shells. 

A  term  sometimes  applied  to  such  a  dis- 
tribution of  magnetism  in  a  plate,  that  the 
magnetized  particles  are  arranged  with  their 
greatest  length  in  the  direction  of  the  thick- 
ness of  the  plate,  so  that  the  poles  are  situ- 
ated at  the  faces  of  the  plate,  and  conse- 
quently the  extent  of  such  polar  surfaces  is 
great  when  compared  with  the  thickness  of 
the  plate. 

The  term  lamellar  distribution  of  magnetism  is 
used  in  contradistinction  to  solenoidal  distribution. 
(See  Magnetism,  Solenoidal  Distribution  of.  ) 

A  thin  sheet  or  disc  of  magnetize!  material 
whose  opposed  extended  faces  are  of  opposite 


magnetic  polarities,  an  i  the  extent  of  whose  sur- 
fa;e  is  vc?ry  great  as  co  nparei  with  its  thickness, 
is  sometimes  called  a  magnetic  shell. 

The  field  produced  by  a  magnetic  shell  is  ex- 
actly similar  to  that  produced  by  a  closed  voltaic 
circuit,  the  edges  of  the  space  inclosed  by  which 
correspond  t )  the  edges  of  the  magnetic  shell. 

The  magnetic  intensity,  or  the  number  of  lines 
of  force  per  unit  arei  of  cross-section,  is  equal 
over  all  parts  of  the  surface  of  a  si.nple  magnetic 
shell. 

A  magnetic  shell  may  be  conceived  as  consist- 
ing of  a  very  great  number  of  short,  straight 
magnetic  needles,  placeJ  side  by  side,  with  their 
north  poles  terminating  at  one  of  the  faces  of  the 
sheet  and  their  south  poles  at  the  opposite  face, 
the  breadth  of  the  sheet  being  very  great  as  com- 
pared with  its  thickness.  Such  a  distribution  of 
magnetism  is  known  as  a  lamellar  distribution. 

Magnetism,  Residual The  magnet- 
ism remaining  in  the  core  of  an  electro-mag- 
net on  the  opening  of  the  magnetizing  cir- 
cuit. 

The  small  amount  of  magnetism  retained 
by  soft  iron  when  removed  from  any  mag- 
netizing field. 

When  hard  iron  or  steel  is  removed  from  a  mag- 
netizing field  it  retains  nearly  all  its  magnetism. 
Such  magnetism  is  also,  in  reality,  residual  mag- 
netism, but  the  term  is  generally  limited  to  the 
case  of  soft  iron. 

Magnetism,  Solenoidal  Distribution  of 

- — —  — A  term  sometimes  applied  to  such 
a  distribution  of  magnetism  in  P.  bar  that 
the  magnetized  particles  are  arranged  with 
their  poles  in  the  direction  of  the  length  of  the 
bar,  the  ends  of  which  are  of  opposite  mag- 
netic polarities,  and  the  extent  of  whose  sur- 
faces is  small  as  compa  -ed  wt)  the  length 
of  the  bar. 

The  term  solenoidal  distribution  - ;  used  in  con- 
tradistinction to  lamellar  distribution,  (.see  Mag- 
netism, Lamellar  Distribution  of. ) 

Magnetism,  Strength  of A  term 

sometimes  used  in  the  sense  of  intensity  of 
magnetization.  (See  Magnetization,  Inten- 
sity of.} 

The  term,  strength  of  magnetism,  is  sometimes 
u  ed  for  flux  or  quantity  of  magnetism. 

Intensity  of  magnetization,  is  the  preferable 
term. 


350 


[Mag. 


Magnetism,  Terrestrial A  name 

applied  to  the  magnetism  of  the  earth. 

Terrestrial  magnetism  has  been  ascribed  to  a 
variety  of  causes.  (See  Magnetism,  Earth's, 
Theories  as  to  Cause  of. ) 

Magnetism,    Vertical     Component     of 

Earth's (See    Component,     Vertical^ 

of  Earth's  Magnetism) 

Magnetite. — Magnetic  oxide  of  iron,  or 
Fe3  O4,  found  in  nature,  as  an  ore  or  mineral. 

Lode-stone  consists  of  .pieces  of  magnetized 
magnetite. 

Magnetizable. — Capable  of  being  magnet- 
ized after  the  manner  of  a  paramagnetic  sub- 
stance like  iron. 

The  most  magnetizable  metals  are  iron,  nickel, 
cobalt  and  manganese.  (See  Paramagnetism.) 

Magnetization. — The  act  of  calling  out  or 
of  endowing  with  magnetic  properties. 

Magnetizable  substances  are  magnetized  by 
being  placed  in  magnetic  fields.  (See  Field,  Mag- 
netic. Magnetization,  Methods  of.) 

The  act  of  initial  magnetization  is  not  exactly 
the  same  as  the  act  of  subsequent  magnetization. 

A  piece  of  steel,  which  has  once  been  magnet- 
ized and  subsequently  demagnetized,  is  a  thing  en- 
tirely distinct,  as  regards  its  magnetization,  from 
a  piece  of  steel  which  has  never  before  been  mag- 
netized, and  such  a  piece  can  never  be  placed  ex- 
actly in  the  same  position  as  regards  a  magnet- 
izing force,  unless  it  is  actually  melted  and  recast, 
or,  perhaps,  maintained  for  a  comparatively  long 
time  at  a  white  heat. 

Magnetization,    Anomalous The 

magnetization  obtained  from  an  oscillatory 
discharge,  such  as  that  of  a  Leyden  jar. 

In  1842,  Henry  described  the  real  character  of 
anomalous  magnetization,  and  showed  that  there 
was  nothing  anomalous  in  such  magnetization,  but 
rather  in  the  fact  that  the  magnetizing  currents 
possessed  no  simple  direction.  He  remarks  on 
this  subject  as  follows: 

'•This  anomaly,  which  has  remained  so  long 
unexplained,  and  which,  at  first  sight,  appears  at 
variance  with  all  our  theoretical  ideas  of  the  con- 
nection of  electricity  and  magnetism,  was,  after 
considerable  study,  satisfactorily  referred  to  an 
action  ot  the  discharge  of  a  Leyden  jar  which  had 
never  before  been  recognized.  The  discharge, 


whatever  may  be  its  nature,  is  not  correctly  rep- 
resented (employing  the  simplicity  of  Franklin) 
by  the  single  transfer  of  an  imponderable  fluid 
from  one  side  of  the  jar  to  the  other  ;  the  phe- 
nomena require  us  to  admit  the  existence  of  a 
principal  discharge  in  one  direction  and  then 
several  reflex  actions  backward  and  forward,  each 
more  feeble  than  the  preceding,  until  the  equi- 
librium is  obtained.  All  the  facts  are  shown  to 
be  in  accordance  with  the  hypothesis,  and  a  ready 
explanation  is  afforded  by  it  of  a  number  of  phe- 
nomena which  are  to  be  found  in  the  older  works 
on  electricity,  but  whi  h  have  until  this  time  re- 
mained unexplained." 

Magnetization  by  Touch. — The  produc- 
tion of  magnetism  in  a  magnetizable  sub- 
stance by  touching  it  with  a  magnet. 

There  are  three  methods  of  magnetization  by 
touch,  viz.: 

(i.)  Single  touch. 

(2.)  Separate  touch. 

(3.)  Double  touch. 

In  single  touch,  the  magnetization  of  a  bar  of 
iron  or  other  magnetizable  material  is  effected  by 
the  touch  of  a  single  magnet. 

In  Single  Touch,  the  magnetizing  magnet  is 
drawn  over  the  bar  to  be  magnetized  from  end  to 
end  and  returned  through  air,  the  stroke  being 
repeated  a  number  of  times.  The  end  of  the 
bar  the  magnet  leaves  is  magnetized  oppositely 
to  the  magnetizing  pole. 

By  some  writers  the  method  of  single  touch  is 
described  as  that  effected 
by  placing  the  magnet- 
izing magnet  N  S  (Fig. 
384)  on  the  middle  of 
the  bar  to  be  magnetized, 
and  drawing  it  to  the 
end  and  returning 
through  the  air  as  be-  [-J-N  s^I| 

fore,  and  then  reversing  •* — 

the  pole,  placing   it    on  FiS-  384.    Magnetization 
the   middle  of  the  bar          *  Sin^e  Touck- 
and  drawing   it  towards  the    other  end.     The 


Fig.  38 5.    Magnetization  by  Separate  Touch. 

former  would,  however,  appear  to  be  the  better 
Use  of  the  term  single  touch. 

In  Separate  Touch,  two  magnetizing  bars  are 
placed  with  their  opposite  poles  at  the   middle 


Mag.] 


351 


of  the  bar  to  be  magnetized  and  drawn  away  from 
each  other  towards  its  ends,  as  shown  in  Fig. 
385.  This  motion  is  repeated  a  number  of  times, 
the  poles  being  each  time  returned  through  the 
air. 

In  the  above,  as  in  all  cases  of  magnetization 
by  touch,  better  effects  are  produced,  if  the  bar 


^SyTMSfS^-^"^ 


a 


Fig.  386.    Magnetization  by  Double  Touch. 

to  be  magnetized  is  rested  on  the  opposite  poles 
of  another  magnet,  or,  as  shown  in  Fig.  386, 
placed  near  them. 

In  Double  Touch  the  two  magnets  are  placed 
with  their  opposite  poles  together  on  the  middle 
of  the  bar  to  be  magnetized,  as  shown  in  Fig. 
386.  They  are  then  moved  to  one  end  of  the  bar, 
•when,  instead  of  removing  them  and  passing  them 
back  through  the  air  to  the  other  end,  they  are 
moved  over  the  surface  of  the  bar  to  be  magnet- 
ized to  the  other  end,  and  these  to  and-fro  mo- 
tions are  repeated  a  number  of  times.  The  mo- 
tion is  stopped  at  the  middle  of  the  bar,  when  the 
magnetizing  magnets  are  moving  in  the  opposite 
direction  to  that  at  which  they  began  to  move. 
This  insures  an  equal  number  of  strokes  to  the 
two  halves  of  the  bar.  The  method  of  double 
touch  produces  stronger  magnetization  than 
either  of  the  other  methods,  but  does  not  effect 
such  an  even  distribution  of  the  magnetism,  and 
therefore  is  not  applicable  to  the  magnetization 
of  needles. 

A  variety  of  double  touch  is  shown  in  Fig.  387, 
where  four  bars,  to  be  magnetized,  are  placed  in 
the  form  of  a  hollow  rectangle,  with  only  their 
ends  touching  at  their  edges,  the  angular  spaces 


Fig.  387.    Magnetization  by  Double  Touch. 

at  the  corners  being  filled  with  pieces  of  soft  iron. 
The  horseshoe  magnet  N  S,  is  then  moved  around 
the  circuit  several  times  in  the  same  direction. 
This  is  believed  t3  produce  a  more  uniform  mag- 


netization than  the  ordinary  method  of  double 
touch. 

Magnetization,    Co-efficient  of A 

number  representing  the  intensity  of  magnet- 
ization produced  in  a  magnetizable  body, 
divided  by  the  magnetizing  force  H. 

Calling  k,  the  co-efficient  of  magnetization  ;  I, 
the  intensity  of  the  resulting  magnetization,  and 
H,  the  magnetizing  force  producing  it,  then 
I 


k  = 


II 


The  co-efficient  of  magnetization  is  sometimes 
called  the  magnetic  susceptibility. 

A  paramagnetic  body  when  placed  in  a  mag- 
netic field  concentrates  the  lines  of  magnetic  force 
on  it,  or  causes  them  to  pass  through  it.  The 
intensity  of  the  magnetization  so  produced  de- 
pend*, therefore, 

(i.)  On  the  intensity  of  the  magnetizing  field. 

(2.)  On  the  ability  of  the  metal  to  concentrate 
the  lines  of  force  on  it;  that  is,  on  the  nature  of 
the  metal,  or  on  its  magnetic  permeability.  (See 
Permeability,  Magnetic.  Paramagnetism.  Dia- 
magnetism. ) 

The  intensity  of  magnetization  will,  therefore, 
be  equal  to  the  product  of  the  co- efficient  of  mag- 
netization and  the  intensity  of  the  magnetizing 
field.  It  will,  also,  of  course,  depend  on  the  area 
of  cross-section  of  the  magnetized  body. 

The  co-efficient  of  magnetization  of  paramag- 
netic bodies  is  said  to  be  positive,  and  that  of  dia- 
magnetic  bodies  to  be  negative,  because  paramag- 
netic bodies  concentrate  the  lines  of  magnetic 
force  on  them,  while  diamagnetic  bodies  appear 
to  repel  the  lines  of  force.  (See  Paramagnetic. 
Diamagnetic. ) 

Magnetization,  Critical  Current  of — 

• — The  current  at  which  any  certain  or  definite 
effect  of  magnetization  is  produced. 

Magnetization,    Intensity  of  — A 

quantity  showing  the  intensity  of  the  magnet- 
ization produced  in  a  substance. 

A  quantity  showing  the  intensity  with 
which  a  magnetizable  substance  is  mag- 
netized. 

The  intensity  of  magnetization  depends: 

(i.)  On  the  intensity  of  the  magnetizing  field. 

(2.)  On  the  magnetic  permeability,  or  on  the 
conducting  power  of  the  substance  for  lines  of 
magnetic  force. 


352 


[Hag. 


The  greater  the  strength  of  the  magnetizing 
field,  and  the  greater  the  magnetic  permeability, 
the  greater  is  the  intensity  of  the  magnetization 
produced. 

When,  therefore,  a  magnetizable  substance  is 
placed  in  a  magnetizing  field,  the  intensity  of  the 
magnetization  will  depend  on  the  magnetic  sus- 
ceptibility of  the  substance ;  that  is,  on  the  ratio  of 
the  induced  magnetization  to  the  magnetizing  force 
producing  it. 

Soft  iron  has  a  high  co-efficient  of  magnetization, 
or  its  magnetic  susceptibility  is  high.  (See  Sus- 
ceptibility,  Magnetic.  Magnetization,  Co-ejficient 
of-} 

The  intensity  of  magnetization  through  a  sub- 
stance is  measured  by  dividing  the  magnetic 
moment  by  the  magnetic  volume. 

If  a  bar  of  soft  iron  is  placed  with  its  greatest 
length  extending  in  the  direction  of  the  lines  of 
force  in  a  magnetic  field,  it  will  have  induced  in 
it  a  certain  intensity  of  magnetization  which  may 
be  expressed  as  follows: 

Intensity  of  Magnetization  =  ^r-p  —  =  k  H, 

where  m,  equals  the  strength  of  the  magnet ;  1,  its 
length  ;  k,  the  co-efficient  of  magnetization,  and 
H,  the  intensity  of  the  magnetizing  field. — (S.  P. 
Thompson.) 

"  The  moment  of  a  magnet,  or  of  any  element 
of  a  magnet,  may  be  considered  numerically  to  be 
made  up  of  two  factors,  one,  its  volume,  and  the 
other  its  intensity  of  magnetization,  or  simply 
its  magnetization,  and  hence,  for  a  uniformly  mag- 
netized small  linear  needle,  we  may  define  the 
intensity  of  its  magnetization  by  saying  that  it  has 
magnetic  moment  of  unit  volume."— (Fleming.) 

Magnetization,  Maximum A  term 

sometimes  used  for  magnetic  saturation. 

Urquhart  states,  as  the  result  of  numerous  ex- 
periments, that  the  number  of  lines  of  magnetic 
force  that  usually  pass  through  a  bar  of  soft  iron 
I  square  centimetre  in  area  of  cross- section,  when 
magnetized  to  a  maximum,  is  equal  to  32,000. 
Ewing  gives  the  number  in  the  particular  case  of 
a  very  extraordinary  magnetization  as  being  equal 
to  45,350  per  square  centimetre  area  of  cross- 
section. 


Magnetization,  Methods  of 


— Mag- 


netization effected  either  by  induction  from 
another  magnet,  or  by  means  of  induction  by 
an  electric  current. 


The  substance  to  be  magnetized  is  brought  into 
a  magnetic  field,  so  that  the  lines  of  magnetic 
force  pass  through  it.  All  methods  of  magnet- 
ization may  be  divided  into  methods  of  magnetiza- 
tion by  touch,  and  magnetization  by  the  electric 
current.  (See  Magnetization  by  Touch.) 

Magnetization,  Permanent,  Intensity  of 

A  term  employed  for  the  intensity  of 

a  permanent  magnetization  produced  in  hard 
steel,  as  distinguished  from  the  magnetization 
temporarily  produced  in  soft  iron.  (See  Mag- 
netization, Intensity  of) 

Magnetization,  Temporary,  Intensity  of 

The  intensity  of  the  magnetization 

temporarily  induced  in  a  bar  of  soft  iron,  as 
distinguished  from  permanent  magnetization 
induced  in  hard  steel.  (See  Magnetization, 
Intensity  of.) 

Magnetization,  Time-Lag  of  —      —A  lag 

which  appears  to  exist  between  the  time  of 
action  of  the  magnetizing  force  and  the  ap- 
pearance of  the  magnetism. 

The  time  which  must  elapse  in  the  case  of 
a  given  paramagnetic  substance  before  a  mag- 
netizing force  can  produce  magnetization. 

In  the  opinion  of  some  physicists  there  is  no 
such  thing  as  a  true  magnetic  time-lag,  the  ap- 
parent time-lag  being  due  entirely  either  to  hys- 
teresis or  to  eddy  currents.  According  to  them, 
while  the  magnetizing  force  is  increasing,  it  pro- 
duces, in  the  iron,  reversely-directed  surface- 
eddy-currents,  which  produce  a  reversed  or 
opposed  magnetizing  force  in  the  more  deeply 
seated  layers  of  the  iron,  the  time-lag  being  due 
to  the  interval  which  is  required  for  these  eddy 
currents  to  die  away  and  thus  permit  the  mag- 
netizing force  to  produce  its  full  magnetization. 

According  to  others,  however,  a  true  time- 
lag  does  exist  entirely  apart  from  the  existence  of 
surface-eddy-currents. 

Magnetize. — To  endow  with  magnetic 
properties. 

Magnetized. — Endowed  or  impressed  with 
magnetic  properties. 

Magnetizing. — Causing  or  producing  mag- 
netism. 

Magneto-Blasting  Machine. — (See  Ma- 
chine, Magneto-Blasting?) 


Mag/  353 

Magneto-Electric  Bell.— (See  Bell,  Mag- 
neto-Electric.) 

Magneto-Electric  Brake. — (See  Brake, 
Magneto-Electric.) 

Magneto-Electric  Call-Bell.— (See  Call- 
fell,  Magneto-Electric.) 

Magneto-Electric  Faradic  Apparatus. — 

(See  Apparatus,  Faradic,  Magneto-Elec- 
tric.) 

Magneto-Electric  Induction. —  (See  In- 
duction, Magneto-Electric.) 

Magneto-Electric  Machine. — (See  Ma- 
chine, Magneto-Electric) 

Magneto-Electric  Medical  Apparatus.— 
(See  Apparatus,  Magneto-Electric  Medi- 
cal) 

Magneto-Electricity,—  (See  Electricity, 
Magneto) 

Magnetograph.— The  permanent  record 
obtained  from  the  action  of  a  self-recording 
magnetometer.  (See.  Magnetometer,  Self- 
Jtecording.) 

Magnetometer. — An  apparatus  for  the 
measurement  of  magnetic  force. 


[Mag. 


The  magnetometer  shown  in  Fig.  388,  consists 
of  a  magnetized  bar  suspended  by  two  wires  pass- 
ing over  a  pulley,  as  shown.  The  magnet  is  held 
by  the  frame  S  S,  provided  with  a  graduated  scale 
K.  The  mirror  S,  is  supported  by  a  vertical  post 
attached  to  the  frame,  and  serves  to  reflect  a  scale 
placed  below  a  distant  reading  telescope.  This 
form  of  magnetometer,  is  called  the  bitilar  mag- 
netometer, and  was  the  one  used  by  Gauss  in  his 
study  of  the  earth's  magnetism. 

A  variety  of  forms  have  been  given  to  delicate 
magnetometers.  Some  are  self-recording.  (See 
Magnetometer,  Self-Recording.) 

Magnetometer,  Differential A  form 

of  magnetometer  in  which  the  principles  of  the 
differential  galvanometer,  as  applied  to  the 
electric  circuit,  are  applied  to  the  magnetic 
circuit. 

The  differential  magnetometer  of  Eickemeyer  is 
shown  in  Figs.  389  and  390.  Its  principles  of 
operation  will  be  understood  from  the  following 
considerations. 

Referring  to  Fig.  389.  Suppose  Fj  and  F2  are 
two  electromotive  forces  connected  in  series,  and 
x  and  y,  two  resistances  to  be  compared.  Each  of 
the  resistances  x  and  y,  is  shunted  respectively  by 
two  conductors  a  and  b,  whose  resistance  we 
wish  to  compare.  Since  the  action  of  each  of 
them  on  the  galvanometer  G,  is  opposite,  its  nee- 
dle remains  at  zero,  when  the  current  in  a,  is 
equal  to  the  current  in  b. 

If,  instead  of  electric  circuit,  we  take  the  idea 
of  magnetic  circuit  or  the  number  of  lines  of 
magnetic  force,  and  instead  of  potential  difference, 


Fig  388.    Magnetometer. 

In  some  magnetometers  the  magnetic  force  is 
measured  by  the  torsion  of  a  wire,  as  in  the  tcr- 
•ion  balance.  (See Balance,  Coulomb'1  s  Torsion.) 


Fig.  389.    Eickemeyer' s  Differential  Magnetometer. 

magneto-motive  force,  and  instead  of  electric  re« 
sistance,  magnetic  resistance,  we  have  the  princi- 
ples on  which  the  Eickemeyer  differential  magnet- 
ometer is  founded. 

The  magnetic  circuit  of  the  differential  magnet- 
ometer consists  of  two  pieces  ot  soft  iron,  shaped 


Mag.J 


354 


[Mag. 


as  shown  at  Fj  and  F8,  Fig.  390.  A  magnetic 
coil  C,  surrounds  the  middle  portion  of  each  cir- 
cuit as  shown.  The  operation  as  described  by 
Mr.  Chas.  Steinmetz,  from  whom  the  above  de- 
scription is  mainly  taken,  is  as  follows,  viz. :  ' '  The 
front  part  Sj  of  the  left  iron  piece  becomes  south, 
and  the  back  part  n1  north  polarity;  the  front 
part  of  the  right  iron  piece  ng  becomes  north,  and 
the  back  part  south;  and  the  lines  of  magnetic 
force  travel  in  the  frant  from  the  right  to  the  left, 
from  ns  to  B!  ;  in  the  back  the  opposite  way,  from 
the  left  to  the  right,  or  from  HJ  to  S;,  either 
through  the  air,  or,  when  n2  and  sx,  or  nl  and  s2, 
are  connected  by  a  piece  of  magnetizable  metal, 
through  this  and  through  the  air. 

In  the  middle  of  the  coil  C,  stands  a  small  soft 
iron  needle  with  an  aluminum  indicator,  which 
plays  over  a  scale  K,  and  is  held  in  a  vertical 
position  by  the  lines  of  magnetic  force  of  the  coil 
C,  itself,  deflected  to  the  left  by  the  lines  of  mag- 
netic force  traversing  the  front  part  of  the  instru- 
ment from  na  to  Sj,  deflected  to  the  right  by  the 
lines  traversing  the  back  from  na  to  s2.  This 
needle  shows  by  its  zero  position  that  the  mag- 
netic flow  through  the  air  in  front  from  n3  to  Sj 
has  the  same  strength  as  the  magnetic  flow  in  the 
back  from  n^  to  sa  through  the  air. 

Now  we  put  a  piece  of  soft  iron  x  on  the  front 
of  the  instrument.  A  large  number  of  lines  go 
through  x,  less  through  the  air  from  n3  to  Sj ;  but 
all  these  lines  go  from  n ,  to  s2  through  the  air 
at  the  back  part  of  the  magnetometer,  the  front 
part  and  back  part  of  the  instrument  being  con- 
nected in  series  in  the  magnetic  circuit.  There- 
fore the  needle  is  deflected  to  the  right  by  the 
magnetic  flow  in  the  back  of  the  instrument. 

Now,  we  put  another  piece  of  iron,  y,  on  the 
back  part  of  the  instrument,  then  equilibrium 
would  be  restored  as  soon  as  the  same  number  of 
lines  of  magnetic  force  go  through  x,  as  through 
y,  because  then  also  the  same  number  of  lines  go 
through  air  in  the  front  as  in  the  back.  As  will 
be  noted,  the  air  here  takes  the  place  of  the  resist- 
ances a  and  b,  influencing  the  galvanometer 
needle  G,  as  in  the  diagram  Fig.  389. 

The  operation  of  the  instrument  is  exceedingly 
simple  and  is  as  follows  :  Into  the  coil  C,  an  elec- 
tric current  is  sent  which  is  measured  by  the  am- 
meter A,  and  regulated  by  the  resistance-switch 
R.  Then  the  needle,  which  before  had  no  fixed 
position,  points  to  zero. 

Now,  we  lay  the  piece  of  iron,  the  magnetic 
properties  of  which  we  want  to  determine,  on  the 


back  part  of  the  instrument.  The  needle  is  de- 
flected to  the  left.  On  the  front  of  the  instrument 
we  put  Norway  iron  rods  of  known  cross-section 
and  known  conductivity,  until  equilibrium  is 
again  restored.  Then  the  iron  in  the  front  has 
the  same  magnetic  resistance  as  the  iron  in  the 
back,  and  the  ratio  of  the  cross- sections  gives 
directly  the  ratio  of  the  conductivities  ;  so  that 
by  a  single  reading  the  magnetic  conductivity  of 
any  piece  of  iron  can  be  compared  with  that  of 
the  Norway  iron  standard. 

For  absolute  determinations,  the  iron  is  turned 
off  into  pieces  of  exactly  4  square  centimetres 
cross-section  and  20  centimetres  in  length,  both 
ends  fitting  into  holes  in  large  blocks  of  Norway 
iron,  which  are  laid  against  the  pole  pieces  of  the 
magnetometer,  so  that  the  transient  resistance 
from  pole  face  to  iron  is  eliminated. 


Fig.  3  go.    Eickemeyer"  s  Differential  Magnetometer, 

Magnetometer,  Self-Recording  —      — A 

self-recording  apparatus,  by  means  of  which 
the  daily  and  hourly  variations  of  magnetic 
needles  in  the  earth's  field,  at  any  locality,  are 
continuously  registered. 

The  self  recording  magnetometer  employed  in 
the  observatory  at  Kew,  consists  essentially  of 
means  of  obtaining  a  photographic  record  of  a 
spot  of  light  reflected  from  a  mirror,  attached  to 
the  needle  whose  variations  are  to  be  recorded. 
The  photographic  record  is  received  on  a  strip  of 
sensitized  paper,  maintained  in  uniform  and  con- 
tinuous motion  by  means  of  suitable  clock-work. 
The  record  so  obtained  is  called  a  magneto- 
graph. 

Magneto-Motive  Force.  —  (See  Force, 
Magneto-Motive?) 


355 


[M.ak. 


Magneto-Motive  Force,  Absolute  Unit  of 

(See  Force,  Magneto-Motive,  Abso- 
lute Unit  oft 

Magneto-Motive  Force,  Practical  Unit  of 
(See  Force,  Magneto-Motive,  Prac- 
tical Unit  of.) 

Magneto-Optic  Rotation.— (See  Rotation, 
Magneto-Optic) 

Magnetophone. — A  species  of  magnetic 
siren  in  which  sounds  are  produced  in  an 
electro-magnetic  telephone  by  the  periodic 
currents  produced  in  its  coils  by  the  rotation 
ef  a  perforated  metallic  disc  in  a  magnetic 
field. 

As  the  speed  of  the  disc  increases,  the  pitch  of 
the  note  increases.  The  apparatus  was  invented 
by  Prof.  Carhart,  in  1883.  A  similar  apparatus 
is  useful  in  studying  the  distribution  of  the  mag- 
netic field  of  a  dynamo-electric  machine.  In  this 
case,  a  small,  thin  coil  of  insulated  wire  is  held  in 
the  different  regions  around  the  machine,  while 
the  telephone  is  held  to  the  ear  of  the  observer. 
Magnetic  leakage,  or  useless  dissipation  of  lines 
of  magnetic  force  outside  the  field  proper  of  the 
machine,  is  at  once  rendered  manifest  by  the 
musical  note  caused  by  variations  in  the  intensity 
of  the  field. 

Since  the  intensity  of  the  note  heard  will  vary 
according  to  the  intensity  of  the  field,  and  also 
according  to  the  position  in  which  the  coil  is  held, 
such  a  coil  becomes  a  magnetic  explorer,  and  by 
its  use  the  distribution  and  varying  intensity  of  an 
irregular  field  can  be  ascertained.  Its  use  is 
especially  advantageous  in  proportioning  dynamo- 
electric  machines  and  electric  motors.  (See  Ex- 
plorer, Magnetic. ) 

Magneto-Receptive  Device. — (See  Device, 
Magneto-Receptive?) 

Magneto-Static  Current  "Meter.  —  (See 
Meter,  Current,  Magneto-Static?) 

Magneto-Static  Screening.— (See  Screen- 
ing, Magneto-Static?) 
Magneto-Statics. — (See  Statics.  Magneto?) 

Magneto-Therapy. — (See  Therapy,  Mag- 
neto?) 

Main  Battery. — (See  Battery,  Main.) 
Main-Battery     Circuit.  —  (See    Circuit, 
Ma  in-Battery?) 


Main,  Electric The  principal  con- 
ductor in  any  system  of  electric  distribution. 

Main  Feeder. — (See  Feeder,  Standard  or 
Main?) 

Main  Fuse. — (See  Fuse,  Main?) 

Main,  House A  term  employed  in 

a  system  of  multiple  incandescent  lamp  dis- 
tribution for  the  conductor  connecting  the 
house  service  conductors  with  a  centre  of 
distribution,  or  with  a  street  main. 

Main-Line  Cut-Out.— (See  Cut-Out,  Main- 
Line?) 

Main,  Street In  a  system  of  incan- 
descent lamp  distribution  the  conductors  ex- 
tending in  a  system  of  networks  through  the 
streets  from  junction  box  to  junction  box, 
through  which  the  current  is  distributed 
from  the  feeder  ends,  through  cut-outs,  to 
the  district  to  be  lighted,  and  from  which 
service  wires  are  taken. 

Main,  Sub A  name  sometimes 

given  to  the  distributing  conductor  that  is 
connected  directly  to  a  main. 

The  branch  nearest  the  main.  (See 
Branch?) 

Main  Wire.— (See  Wire,  Main?) 

Mains  of  Electric  Railroads. — The  wires 
or  conductors  used  for  carrying  the  current 
from  the  feeders  through  the  tap  wires  to  the 
trolley  wires. 

Make. — A  completion  of  a  circuit. 

Make-and-Break. — The  periodic  alternate 
completion  and  opening  of  a  circuit. 

Make-and-Break,  Automatic A 

term  sometimes  employed  for  such  a  combi- 
nation of  contact  points  with  the  armature  of 
any  electro-magnet,  that  the  circuit  is  auto- 
matically made  and  broken  with  great  rapidity. 

An  automatic  make-and-break  is  used  in  most 
forms  of  electric  alarms  in  connection  with  some 
form  of  electric  bell.  (See  Alarm,  Electric.) 

It  is  also  used  in  the  Ruhmkorff  ind  action  coil 
in  order  to  produce  the  variations  in  the  primary 
circuit.  (See  Coil,  Induction.) 

Make-Induced  Current.  —  (See  Current, 
Make-Induced?\ 


Mak,] 


356 


[Mar. 


Making-    the    Primary.— (See    Primary, 
Making  the.) 
Mallet,    Electro-Magnetic    Dental  

—(See  Dental-Mallet,  Electro-Magnetic.) 
Mangin  Projector. — (See  Projector,  Man- 

&*•} 

Man-Hole,  Compartment,  of  Conduit 

— A  man-hole  provided  with  suitably  sup- 
ported shelves  or  compartments,  guarded  by 
locked  doors  that  protect  different  cable  sec- 
tions. 

Man-Hole  of  Conduit. — An  opening  of 
sufficient  size  to  admit  a  man,  communi- 
cating from  the  surface  of  the  roadbed  with 
an  underground  conduit. 

Manipulator,  Breguet's The  send- 
ing instrument  employed  by  Breguet  in  his 
system  of  step-by-step  or  dial  telegraphy. 
(See  Telegraphy,  Step-by-Step.) 

Manometei. — An  apparatus  for  measuring 
the  tension  or  pressure  of  gases. 

Manometers  are  either  mercurial  or  metallic. 
Mercurial  manometers  are  of  two  classes,  viz., 
manometers  with  free  air  and  manometers  with 
compressed  air. 

Manometers  measure  the  pressure  of  gases 
either  in  atmospheres,  i.  e.,  in  multiples  or  deci- 
mals of  15  pounds  to  the  square  inch,  or  in  inches 
of  mercury. 

Map  or  Chart,  Inclination A  chart 

or  map  on  which  lines  are  drawn,  showing 
the  lines  of  equal  dip  or  inclination,  or  the 
isoclinic  lines. 

An  inclination  chart  is  shown  in  Fig.  391. 

It  will  be  seen  that  the  magnetic  equator,  or 
line  of  no  dip,  does  not  correspond  with  the  geo- 
graphical equator,  being  generally  north  of  the 
equator  in  the  Eastern  Hemisphere,  and  south  of 
it  in  the  Western.  The  figures  attached  to  the 
lines  indicate  the  value  of  the  angle  of  dip. 

Map  or  Chart,  Isodynamic A  map 

of  the  earth  on  a  mercator's  projection,  on 
which  isodynamic  lines  are  drawn. 

An  isodynamic  chart  is  shown  in  Fig.  392.  It 
will  be  observed  that  the  isodynamic  lines  do  not 
exactly  coincide  with  the  isoclinic  lines,  since  the 
line  of  least  magnetic  intensity  does  not  correspond 
with  the  line  of  the  magnetic  equator. 

The  point  of  least  magnetic  intensity  is  found  at 


about  lat.  20  degrees  S.,  and  Ion.  35  degrees  W. 
The  point  of  greatest  magnetic  intensity  is  found 
at  about  lat.  52  degrees  N.  and  Ion.  92  degrees 
VV. 

Another,  though  weaker  point  of  magnetic  in- 
tensity, is  found  in  Siberia.  These  are  distin- 
guished from  the  true  magnetic  poles  by  the  term 
Poles  of  Intensity. 

The  Poles  of  Vertuity,  as  determined  by  the 
dipping  needle,  and  the  Poles  of  Intensity,  as  de- 
termined by  the  needle  of  oscillation,  therefore  do 
not  coincide  in  the  Northern  Hemisphere. 

Map  or    Chart,  Isogonal A  term 

sometimes  used  for  an  isogonic  map  or  chart. 

Map  or  Chart,  Isogonic A  chart 

on  which  the  isogonal  lines  are  marked. 

An  isogonic  map  or  chart  is  sometimes  called 
a  declination  map  or  chart . 

In  the  declination  or  variation  chart,  shown  in 
Fig.  393,  the  region  of  western  declination  is  in- 
dicated by  the  shading.  There  is  a  remarkable 
oval  patch  in  the  northeastern  part  of  Asia,  in 
which  the  declination  is  west  A  similar  oval  of 
decreased  inclination  is  seen  in  the  Southern 
Pacific. 

The  entire  earth  acts  like  a  huge  magnet  with 
south  magnetic  polarity  in  the  Northern  Hemi- 
sphere. 

It  is  not  known  whether  the  earth  possesses 
but  a  single  pair  of  magnetic  poles  or  more 
than  a  single  pair.  The  variations  in  the  dec- 
lination, and  in  the  intensity  of  its  magnetism, 
due  to  the  position  of  the  sun,  ss  well  as  the 
marked  magnetic  disturbances  that  accompany 
the  occurrence  of  sun  spots,  would  appear  to  con- 
nect the  earth's  magnetism  in  some  manner  with 
the  solar  radiation.  (See  Magnetism,  Earth's, 
Theories  as  to  Cause  of.) 

Marine  Galvanometer. — (See  Galvanom- 
eter, Marine.) 

Mariner's  Compass. — (See  Compass,  Azi- 
muth.) 

Marked  Pole  of  Magnet. — (See  Magnet, 
Marked  Pole  of.) 

Markers. — Colored  flags,  or  signal  lights, 
generally  green,  displayed  in  systems  of 
block  railway  signaling  at  the  ends  of 
trains,  in  order  to  avoid  accidents  from  trains 
breaking  in  two.  (See  Railroads,  Block 
System  for.) 


Mar.] 


357 


[Mar. 


Mar.] 


358 


[Mar. 


Mar.] 


359 


[Mar. 


Mas.] 


360 


[Mat. 


Mass. — The  quantity  of  matter  contained 
in  a  body. 

Mass  must  be  carefully  distinguished  from 
•weight.  The  weight  of  a  given  quantity  of 
matter  depends  on  the  attraction  which  the  earth 
possesses  for  it,  and  this,  on  the  earth's  surface, 
varies  with  the  latitude,  being  greatest  at  the 
poles  and  least  at  the  equator.  It  also  varies 
with  different  elevations  above  the  level  of  the  sea. 
The  mass,  however,  is  the  same  under  all  circum- 
stances, whether  for  different  latitudes  or  alti- 
tudes, on  the  earth's  surface. 

Mass  Attraction.— (See  Attraction,  Mass.] 

Mass,  Magnetic  —  — A  quantity  of  mag- 
netism which  at  unit  distance  produces  an 
action  equal  to  unit  force. 

Mass,  Unit  of  —  —The  quantity  of  mat- 
ter which  under  certain  conditions  will  balance 
the  weight  of  a  standard  gramme  or  pound. 

The  gramme  is  equal  to  the  one-thousandth 
part  of  a  piece  of  platinum  called  the  kilogramme, 
deposited  as  a  standard  in  the  archives  of  the 
French  Government,  and  intended  to  be  equal  to 
the  mass  of  I  cubic  centimetre  of  water  at  the  tem- 
perature of  its  maximum  density. 

Massage. — A  treatment  for  the  purpose 
of  effecting  changes  in  general  nutrition  or 
action  of  particular  parts  of  the  body,  by 
kneading,  rubbing,  friction,  etc. 


Electro The  application 

of  electricity  to  the  body  during  its  massage. 
Connections  are  established  between  the  patient 
and  a  battery  by  connecting  one  electrode  of  a 
source  to  the  kneading  instrument,  and  the  other 
electrode  to  the  body  of  the  patient. 

Masses,  Electric  —  — A  mathematical 
conception  for  such  quantities  of  electricity 
as  at  unit  distance  will  produce  an  attrac- 
tion or  repulsion  equal  to  unit  force. 

Electrical  masses  are  assumed  to  be  equal  when 
they  produce  on  two  identical  bodies  of  small 
dimensions  charges  of  the  same  electric  force. 

Master  Clock. — (See  Clock,  Master.) 
Materials,   Insulating — Non-con- 
ducting substances  which  are  placed  around  a 
conductor,  in  order  that  it  may  either  retain 
an  electric  charge,  or  permit  the  passage  of 


an  electric  current  through  the  conductor 
without  sensible  leakage. 

Various  gases,  liquids  or  solids  may  be  em- 
ployed as  insulators.  A  very  high  vacuum  affords 
the  best  known  insulation. 

Matter. — Anything  which  occupies  space  in 
three  directions  and  prevents  other  matter  from 
simultaneously  occupying  the  same  space. 

Matter  is  composed  of  atoms,  which  unite  to 
form  molecules.  (See  Atom.  Molecule. ) 

Matter,  Elementary Matter  which 

cannot  be  decomposed  into  simpler  matter. 

Varieties  of  elementary  matter  are  called 
elements.  (See  Element. ) 

Matter,     Kinetic     Theory    of -.—A 

theory  which  assumes  that  the  molecules  of 
matter  are  in  a  constant  state  of  motion  or 
vibration  towards  or  from  one  another  in 
paths  that  lie  within  the  spheres  of  their 
mutual  attractions  or  repulsions. 

The  molecules  of  gases  have  great  freedom 
of  motion,  and  are  so  far  removed  from  one 
another  as  to  be  but  little,  if  any,  influenced  by 
their  mutual  attractions.  They  are  therefore 
assumed  to  move  in  s-traight  lines  with  very  great 
velocity  until  they  collide  against  one  another,  or 
against  the  sides  of  the  containing  vessel,  when 
they  are  reflected  and  again  move  in  straight  lines 
in  a  new  path. 

Matter,  Radiant,  or  Ultra-Gaseous  — 

— A  term  proposed  by  Crookes  for  the 
peculiar  condition  of  the  gaseous  matter  which 
constitutes  the  residual  atmospheres  of  high 
vacua. 

This  is  now  generally  recognized  as  a  fourth 
state  of  matter,  these  four  states  being: 

(i.)  Solid. 

(2.)  Liquid. 

(3.)  Gaseous. 

(4. )  Ultra-gaseous  or  radiant. 

The  peculiar  properties  of  radiant  matter  are 
seen  in  the  mechanical  effects  of  the  localized 
pressures  produced  when  such  residual  atmos- 
pheres are  locally  heated  or  electrified. 

In  Crookes*  radiometer,  vanes  of  mica,  silvered 
on  one  face  and  covered  with  lampblack  on  the 
opposite  face,  are  supported  on  a  vertical  axis  so 
as  to  be  capable  of  rotation  and  placed  in  a  glass 
vessel  in  which  a  high  vacuum  is  maintained.  On 


MatJ 


361 


[Mat. 


exposing  the  instrument  to  the  radiation  from  a 
candle  or  gas  flame,  a  rapid  rotation  takes  place. 
(See  Radiometer,  Crookes' .) 

The  explanation  is  as  follows :  The  lampblack 
covered  surfaces  absorb  the  radiant  heat,  and  be- 
coming heated,  the  molecules  of  gas  in  the  residual 
atmosphere  are  shot  violently  from  them,  and  by 
their  reaction  drive  the  vanes  around  in  the 
opposite  direction  to  that  from  which  they  are 
thrown  off.  The  molecules  are  also  shot  off  from 
the  silvered  surfaces,  but,  as  these  are  cooler,  the 
effect  is  not  as  great  as  at  the  blackened  surfaces. 

In  a  gas,  at  ordinary  pressure,  the  heated  sur- 
faces are  also  bombarded  by  other  molecules  of 
the  gas,  but  in  high  vacua  the  mean  free  path  of 
the  molecules  is  so  great  that  there  is  no  interfer- 
ence, a  Crookes1  layer  existing  between  the  vanes 
and  the  walls  of  the  glass  vessel.  (See  Layer^ 
Crookes\) 

When  a  Crookes'  tube  is  furnished  with  suit- 
able electrodes,  and  electric  discharges  are  sent 
through  it  between  these  electrodes,  a  stream  of 
molecules  is  thrown  off  in  straight  lines  from  the 
surface  of  the  negative  electrode, 

Some  of  the  effects  of  this  molecular  bombard- 
ment are  seen  by  the  use  of  the  apparatus  shown 
in  Fig.  394.  When  the  positive  and  negative 


Fig.  394*    Effects  of  Molecular  Bombardment. 

terminals  are  arranged  as  shown,  the  paths  of  the 
molecular  streams  are  seen  as  luminous  streams 
whose  directions  are  those  shown  in  the  figures. 

The  figure  on  the  left  shows  the  path  taken  in 
a  low  "vacuum.  Streams  pass  from  the  negative 
electrode  to  each  of  the  positive  electrodes. 

The  figure  on  the  right  shows  the  discharge  in 
a  high  vacuum.  Here  the  streams  pass  off  at 
right  angles  to  the  face  of  the  negative  electrode, 


and  proceed  therefrom  in  straight  lines,  inde- 
pendently of  the  position  of  the  positive  electrode. 
Since,  therefore,  the  negative  electrode  at  a,  is  in 
the  shape  of  a  concave  mirror,  the  luminous 
particles  converge  to  a  focus  near  the  centre  of 
the  glass  vessel,  and  then  diverge  to  the  opposite 
wall. 

Refractory  substances  placed  at  such  a  focus  of 
molecular  bombardment,  as  shown  in  Fig.  395,  are 
rendered  incandescent. 

In  a  similar  manner,  phosphorescent  substances 
exposed  to  such  molecular  streams  emit  a  beauti- 


Forces  cf  Molecular  Bombardment. 


ful  phosphorescent  light.  (Sea  Phosphorescence, 
Electric.) 

Matter,  Thomson's  Hypothesis  of 

A  hypothesis  as  to  the  structure  of  matter 
suggested  by  Sir  William  Thomson,  in  order 
to  show  how  the  extremely  tenuous  ether 
might  possess  rigidity. 

The  fact  that  the  ether,  although  a  fluid  sub- 
stance, possesses  the  properties  of  a  rigid  solid, 
has  given  no  little  trouble  to  physicists.  Thomson 
explains  this  rigidity  of  the  ether  as  being  due  to 
a  rapid  motion  in  its  fluid  particles. 

A  perfectly  flexible  rubber  tube  filled  with 
water  or  other  fluid,  possesses,  when  at  rest,  a 
very  great  degree  of  flexibility.  When  in  mo- 
tion, however,  the  tube  becomes  more  and  more 
rigid,  as  the  flow  increases  in  rapidity.  Thorn- 


Mat. 


362 


[Ked. 


son  imagines  the  ether  to  be  set  in  motion  in 
minute  vortex  rings,  and  shows  that  a  readily 
movable  fluid  body,  like  ether,  once  set  in  such 
motion  should  possess  the  properties  of  a  solid. 
In  a  perfect  fluid,  such  as  ether,  these  vortex 
rings  once  formed,  would  be  practically  imperish- 
able or  indestructible. 

Thomson  regards  the  atoms  of  matter  as  con- 
sisting  of  such  vortex  rings.  Vortex  rings  can  be 
formed  in  the  air  by  cutting  a  circular  aperture 
in  the  end  of  a  pasteboard  box,  and  tapping 
sharply  against  the  end  of  the  box.  In  order  to 
render  the  rings  visible,  the  box  may  be  previously 
filled  with  smoke. 

Vortex  rings  formed  in  smoky  air  differ  from 
vortex  rings  in  the  ether,  in  the  fact  that  air  is 
not  a  perfect  fluid,  while  ether  is.  Air  vortex 
rings  increase  in  size  and  decrease  in  energy. 
Vortex  rings  of  the  ether  would  not  vary  in  size. 

According  to  Thomson's  vortex  theory  of 
matter,  the  atoms  of  matter  are  the  same  as  the 
ether  which  surrounds  them.  They  cannot  be 
produced  in  ether  by  any  known  way ;  therefore, 
they  cannot  be  manufactured,  or,  as  it  were, 
created.  Nor,  on  the  other  hand,  can  they  be 
destroyed;  in  other  words,  they  are  indestruct- 
ible. They  are  elastic,  capable  of  definite  vibra- 
tions, possess  all  the  properties  of  matter  save,  in 
the  opinion  of  some,  the  very  important  prop- 
erty of  gravitation.  As  Prof.  Lodge  points  out, 
the  fact  that  this  property  is  not  present  should 
cause  Sir  William  Thomson's  theory  of  matter  to 
be  accepted  with  considerable  hesitation. 

Matthiessen's  Metre-Gramme  Standard. 

— (See  Metre-Gramme  Standard,  Matthies- 
sen's.) 

Matthiessen's  Mile  Standard. — (See  Mile 
Standard,  Matthiessen's.) 

Matting,  Invisible  Electric  Floor  • 

— A  matting  or  other  floor  covering,  provided 
with  a  series  of  electric  contacts,  which  are 
closed  by  the  passage  of  a  person  walking 
over  them. 

This  matting  is  provided  as  an  adjunct  to  a 
system  of  burglar  alarms.  The  electric  bell  or 
annunciator,  connected  with  the  different  con- 
tacts, is  disconnected  during  the  day-time,  or  while 
the  rooms  are  occupied.  (See  Alarm,  Burglar. ) 

Maximum  Magnetization. — (See  Mag- 
netization, Maximum^ 


Mclntire's  Parallel  Sleeve  Telegraphic 
Joint. — (See  Joint,  Telegraphic,  Mclntire's 
Parallel  Sleeved) 

Measurements,  Electric  —Deter- 
minations of  the  values  oi  the  electromotive 
force,  resistance,  current,  capacity,  energy, 
etc.,  in  any  electric  circuit. 

Electric  m  easurements  may  be  either  qualitative 
or  quantitative. 

In  qualitative  electric  measurements  the  rela- 
tive values  only  are  obtained;  in  quantitative 
measurements  the  actual  values  are  obtained. 

Mechanical  Alarm,  Electric  —  — (See 
Alarm,  Electro-Mechanical.} 

Mechanical  Electric  Bell.— (See  Bell, 
Electro-Mechanical.) 

Mechanical  Equivalent  of  Heat. — (See 
Heat,  Mechanical  Equivalent  of.) 

Mechanical  Mine. — (See  Mine,  Mechani- 
cal.) 

Mechanical    Throwback     Indicator.  — 

(See  Indicator,  Mechanical  Throwback.) 

Medical  Induction  Coil.— (See  Coil,  In- 
duction Medical.) 

Medical  Magneto-Electric  Apparatus. — 

(See  Apparatus,  Magneto-Electric  Medi- 
cal.) 

Medium,  Anisotropic A  medium 

in  which  equal  stresses  do  not  produce  equal 
strains  when  applied  in  different  directions. 

A  medium,  homogeneous  in  structure  like 
crystalline  bodies,  but  possessing  different 
powers  of  specific  inductive  capacity  in  differ- 
ent directions. 

An  eolotropic  medium.  (See  Medium, 
Eolotropic.) 

The  latter  term  is  used  to  distinguish  it  from 
an  isotropic  medium.  (See  Medium,  Isotropic.) 

Medium,  Eolotropic A  medium 

in  which  equal  stresses  do  not  produce  the 
same  strains  when  applied  in  different  direc- 
tions. (See  Medium,  Isotropic.) 

Medium,  Electro-Magnetic  — Any 

medium  in  which  electro-magnetic  phenom- 
ena occur. 

The  medium  through  which  electro-magnetic 
waves  are  propagated  is  now  universally  re- 


Med.J 


363 


[Viet. 


garded  as  the  luminiferous  or  universal  ether. 
(See  Electricity,  Hertz's  Theory  of  Electro-Mag- 
netic Radiations  or  Waves,} 

Medium,  Iso tropic A  medium  in 

which  equal  stresses  applied  in  any  direction 
produce  equal  strains. 

A  transparent  medium  which  possesses  the 
same  optical  or  electric  properties  in  all  di- 
rections. 

An  optically  homogeneous,  transparent 
medium. 

Such  media  are  called  isotropic  to  distinguish 
them  from  anisotropic  or  eolotropic,  or  those  in 
which  equal  stresses  produce  unequal  strains  in 
different  directions.  (See  Medium,  Anisotropic. 
Medium,  Eolotropic.) 

Meg  or  Mega  (as  a  prefix).— 1,000,000 
times  ;  as,  megohm,  1,000,000  ohms  ;  mega- 
volt,  1,000,000  volts. 

Megaloscope,  Electric An  appara- 
tus for  the  medical  exploration  of  the  cavities 
of  the  body. 

The  light  necessary  for  exploration  is  obtained 
from  a  small  incandescent  lamp  placed  at  the 
extremity  of  a  tube,  suitably  shaped  for  introduc- 
tion into  the  special  organ  for  which  it  is  devised. 
The  organ  so  illumined  throws  its  light  on  a 
prism,  by  means  of  which  the  light  is  caused  to 
pass  through  a  series  of  lenses  by  which  it  is 
viewed . 

Megavolt. — 1,000,000  volts. 
Megohm. — 1,000,000  ohms. 

Meidinger  Yoltaic  Cell.— (See  Cell,  Vol- 
taic, Meidinger?) 

Memory,  Magnetic A  term  pro- 
posed by  J.  A.  Fleming  for  coercive  force. 

Soft  iron  has  but  a  feeble  memory  of  its  past 
magnetization. 

Mercurial  Connection.— (See  Connection, 
Mercurial?) 

Mercurial  Contact.  —  (See  Connection, 
Mercurial?) 

Mercurial    Temperature    Alarm.— (See 

Alarm,  Mercurial  Temperature?) 
Mercury  Break.— (See  Break,  Mercury?} 
Mercury  Cup.— (See  Cup,  Mercury?) 


Meridian,  Astronomical  - 

circle    passing    through    any 


A  great 

point    in    the 


heavens,  and  the  North  and  South  poles  of 
the  heavens. 

The  astronomical  meridian  corresponds  to  the 
geographical  meridian.  The  former  is  considered 
as  passing  around  the  dome  of  the  heavens;  the 
latter,  around  the  surface  of  the  earth.  In  order 
to  locate  any  point  in  the  heavens,  a  great  circle 
of  the  heavens  is  caused  to  pass  through  that  point 
and  through  the  astronomical  North  and  South 
poles. 

Meridian,  Geographical The  geo- 
graphical meridian  of  a  place  is  a  great  circle 
passing  through  that  place  and  the  North  and 
South  geographical  poles  of  the  earth. 

Meridian,  Magnetic The  magnetic 

meridian  of  any  place  is  the  meridian  which 
passes  through  the  poles  of  a  magnetic  needle 
at  that  place  when  in  a  position  of  rest  under 
the  free  influence  of  the  earth's  magnetism. 

The  plane  of  the  magnetic  meridian  at  any  place 
is  a  vertical  plane  pa-sing  through  the  poles  of  a 
magnetic  needle  in  a  position  of  rest  under  the 
free  influence  of  the  earth's  magnetism  at  that 
place. 

The  magnetic  meridian  may  be  regarded  as  the 
vertical  plane  in  which  a  freely  suspended  mag- 
netic needle  comes  to  rest  in  the  earth's  magnetic 
field. 

Meridional. — Pertaining  to  the  meridian. 
Message  Wire.— (See  Wire,  Message?) 
Messenger  Call.— (See  Call,  Messenger.) 
Metallic  Arc.— (See  Arc,  Metallic.) 

Metallic  Circuit.— (See  Circuit,  Metal- 
lic?) 

Metallic  Coating.— (See  Coating,  Metal- 
lic?] 

Metallic  Conducting  Joint. — (See/0/«/, 
Metallic  Conducting?) 

Metallic  Contact.— (See  Contact,  Metal- 
lic?) 

Metallic  Electric  Conduction.  —  (See 
Conduction,  Electric,  Metallic.) 

Metallization. — The  rendering  of  a  non~ 
conducting  surface  electrically  conducting  by 
covering  it  with  a  metallic  coating,  so  u.i  to 


Mol.J 


364 


[Met. 


enable  it  to  readily  receive  a  metallic  coating 
by  electro-plating.  (See  Plating,  Electro?) 

Metallochromes.  —  A  name  sometimes 
given  to  Nobili's  rings.  (See  Rings,  No- 
bili's.) 

Metalloid. — A  name  formerly  applied  to  a 
non-metallic  body,  or  to  a  body  having  only 
some  of  the  properties  of  a  metal,  as  carbon, 
boron,  oxygen,  etc. 

The  term  is  now  but  little  used. 

Metallurgy,  Electro That  branch 

of  applied  science  which  relates  to  the  elec- 
trical reduction  or  treatment  of  metals. 

Metallurgical  processes  effected  by  the 
agency  of  electricity. 

Electro-Metallurgy  embraces : 

(i.)  The  reduction  of  metals  from  their  ores, 
either  directly  during  fusion  by  the  heat  of  the 
voltaic  arc,  or  the  heat  of  incandescence,  or  by 
the  electrolysis  of  solutions  of  their  ores,  or  ores 
in  the  fused  state.  (See  Electrolysis.  Furnace, 
Electric.) 

(2.)  Electroplating. 

(3.)  Electrotyping. 

The  application  of  electricity  to  the  reduction 
of  metals  is  carried  on  in  the  electric  furnace  for 
the  reduction  of  the  aluminium  ores,  for  example. 

Metals,  Electric  Deflagration  of  — 

The  volatilization  of  metals  by  electric  in- 
candescence. 

Metals,    Electric    Refining    of  - 
Purifying  metals  by  means  of  electricity. 

Different  methods  are  employed  for  the  electric 
refining  of  metals.  They  are  generally  electro- 
lytic in  character. 

Metals,  Electrical  Protection  of 

The  protection  of  a  metal  from  corrosion  by 
placing  it  in  connection  with  another  metal, 
which,  when  exposed  to  the  corroding  liquid, 
vapor  or  gas,  will  form  with  the  metal  to  be 
protected  the  positive  element  of  a  voltaic 
couple. 

The  negative  element  of  a  voltaic  couple  is 
protected  by  the  presence  of  the  positive  element, 
which  is  alone  corroded.  This  method  has  been 
adopted  with  considerable  success  to  electrically 
protect  metals  from  corrosion. 

The  following  are  examples  of  this  protection  : 

(I.)  Davy    proposed    to    protect    the    copper 


sheathing  of  ships  from  corrosion  by  attaching 
pieces  of  zinc  to  the  copper  sheathing.  This 
succeeded  too  well,  since  the  copper  salts  which 
were  formerly  produced,  and  acted  as  a  poison 
to  the  marine  plants  and  animals,  being  now 
absent,  permitted  these  organisms  to  thrive  to 
such  an  extent  as  to  seriously  foul  the  ship's 
bottom. 

(2.)  A  ring  of  zinc  attached  to  a  lightning  rod, 
near  its  points,  has,  it  is  claimed,  the  power  of 
protecting  the  points  from  corrosion. 

(3.)  Iron  bars  of  railings,  if  sunk  or  embedded 
in  zinc,  are  preserved  from  corrosion  near  the 
junction  of  the  two  metals,  but  if  sunk  in  lead  are 
rapidly  corroded,  because  iron  is  electro-positive 
to  lead,  but  electro-negative  to  zinc. 

(4.)  Tinned  iron  rapidly  corrodes  or  rusts 
when  the  iron  is  exposed  to  the  atmosphere  by  a 
scratch  or  abrasion,  because  the  iron  is  electro- 
positive to  tin.  Nickel-plated  iron,  for  the  same 
reason,  rusts  rapidly  on  the  exposure  of  an 
abraded  surface. 

(5.)  Zinced  or  galvanized  iron,  or  iron  covered 
with  a  deposit  of  zinc,  is  protected  from  corro- 
sion because  the  zinc,  being  positive  to  iron,  can 
alone  be  corroded,  and  the  zinc  is  also  protected 
in  part  by  the  coating  of  insoluble  oxide  that  is 
formed. 

Meteorites. — Aerolites.     (See  Aerolites.) 

Meter,  Ampdre  -  — (See  Ampere- 
Meter.  Ammeter?) 

Meter,  Current A  term  now  ap- 
plied to  an  electric  meter  or  galvanometer 
which  measures  the  current  in  amperes,  as 
distinguished  from  one  which  measures  the 
energy  in  watts. 

This  term  is  sometimes  loosely  applied  to  a 
galvanometer. 

The  term  galvanometer  is  preferable.  (See 
Galvanometer.) 

Meter,  Current,  Magneto-Static  —      — A 

current  meter  in  which  a  small  steel  magnet, 
or  system  of  magnets,  is  suspended  at  tht 
centre  of  the  uniform  magnetic  field  produced 
by  the  combined  influence  of  two  coils  and 
two  systems  of  powerful  permanent  magnets. 

Meter,  Electric Any  apparatus  for 

measuring  commercially  the  quantity  of  elec- 
tricity that  passes  in  a  given  time  through 
any  consumption  circuit. 


Mcl«j 


365 


Electric  meters  are  constructed  in  a  great 
variety  of  forms;  they  may,  however,  be  ar- 
ranged under  the  following  heads  : 

(l.)  Electro-Magnetic  Meters,  or  those  in  which 
the  current  passing  is  measured  by  the  electro- 
magnetic effects  it  produces. 

In  such  meters  the  entire  current  may  pass 
through  the  meter. 

(2.)  Electro-Chemical  Meters,  or  those  in  which 
the  current  passing  is  measured  by  the  electroly- 
tic decomposition  it  effects. 

In  these  meters,  a  shunted  portion  only  of  the 
current  is  usually  passed  through  a  solution  of  a 
metallic  salt,  and  the  current  strength  calculated 
from  the  amount  of  electrolytic  decomposition 
thus  effected. 

(3.)  Electro-  Thermal  Meters,  or  those  in  which 
the  current  passing  is  measured  by  a  movement 
effected  by  the  increase  in  temperature  of  a  resist- 
ance through  which  the  current  is  passed,  or  by 
the  amount  of  a  liquid  evaporated  by  the  heat 
generated  by  the  current. 

(4.)  Electric-Time  Meters,  or  those  in  which 
no  attempt  is  made  to  measure  the  current  that 
passes,  but  in  which  a  record  is  kept  of  the  num- 
ber of  hours  that  an  electric  lamp,  motor  or 
other  electro-receptive  device  is  supplied  with 
current. 

Edison's  electric  meter  is  of  the  second  class. 
It  consists  of  two  voltameters,  or  electrolytic  cells, 
containing  zinc  sulphate,  in  which  two  plates  of 
chemically  pure  zinc  are  dipped.  The  current 
that  passes  is  determined  by  the  amount  of  the 
variation  in  weight  of  the  zinc  plates.  To  deter- 
mine this,  the  plates  are  weighed  at  stated  in- 
tervals :  one  plate  every  month,  the  other  plate, 
which  is  intended  to  act  as  a  check  on  the  first, 
only  once  in  three  months.  Some  difficulty  has 
been  experienced  in  the  employment  of  meters  of 
this  class,  from  the  variations  in  the  value  of  the 
shunt  resistance,  due  to  variations  in  the  condi- 
tion and  temperature  of  the  electrolytic  cell. 
The  use  of  a  compensating  resistance,  however, 
has,  it  is  claimed,  removed  this  objection.  (See 
Voltameter. ) 

Meter,    Electric-Time An  electric 

meter  in  which  the  current  passing  is  esti- 
mated by  recording  the  number  of  hours  that 
an  electric  lamp  or  other  electro-receptive 
device  is  supplied  with  a  known  current. 
(See  Meter,  Electric?] 


Meter,  Electro-Chemical An  elec- 
tric meter  in  which  the  current  passing  is 
measured  by  the  electrolytic  decomposition  it 
effects.  (See  Meter,  Electric?) 

Meter,  Electro-Magnetic An  elec- 
tric meter  in  which  the  current  passing  is 
measured  by  the  electro-magnetic  effects  it 
produces.  (See  Meter,  Electric?) 

Meter,  Electro-Thermal  • — An  elec- 
tric meter  in  which  the  current  passing  is 
measured  by  means  of  the  heat  generated  by 
the  passage  of  the  current  through  a  resist- 
ance. (See  Meter,  Electric?] 

Meter,  Energy A  term  sometimes 

applied  to  a  watt  meter.  (See  Meter, 
Watt?] 

Meter,  Milli-Ampere An  ampere 

meter  graduated  to  read  milli-amperes. 

Meter,  Watt An  instrument  gener- 
ally consisting  of  a  galvanometer  constructed 
so  as  to  measure  directly  the  product  of  the 
current,  and  the  difference  of  potential. 

Since  the  watt  is  equal  to  the  product  of  the 


Fig.  3Q6.     Watt  Meter. 

current  by  the  electromotive  force,  if  the  current 
and  electromotive  force  are  simultaneously  meas- 
ured, their  product  gives  directly  the  watts. 
The  scale  reading  of  a  watt  meter  may  be  grad- 
uated so  as  to  give  the  watts  directly. 

A  watt  meter  consists  essentially  of  a  thick  wire 
coil,  placed  in  series  in  the  circuit  whose  electric 
power  is  to  be  measured,  and  a  thin  wire  coil 


Met.] 


366 


LMic. 


placed  in  a  shunt  around  the  circuit  to  be  meas- 
ured. These  two  coils,  instead  of  acting  on  a 
needle,  act  on  each  other,  and  the  amount  of  this 
deflection  will,  therefore,  be  proportional  to  the 
watts  present. 
A  form  of  watt  meter  is  shown  in  Fig.  396. 

Method,  Deflection A  method  em- 
ployed in  electrical  measurements,  as  distin- 
guished from  the  zero  method,  in  which  a 
deflection,  produced  on  any  instrument  by  a 
given  current,  or  by  a  given  charge,  is  utilized 
for  determining  the  value  of  that  current  or 
charge. 

The  conditions  remaining  the  same,  the  same 
Current  or  charge  will  produce  the  same  deflection 
at  any  time.  Different  deflections  produced  by 
currents  or  charges,  the  values  of  which  are  un- 
known, are  determined  by  certain  ratios  existing 
between  the  deflections  and  the  currents  or 
charges.  These  ratios  are  determined  experi- 
mentally by  the  calibration  of  the  instrument. 
(See  Calibrate.} 

Deflection  methods  are  opposed  to  zero  or  null 
methods,  in  which  latter  a  balance  of  opposite 
electromotive  forces,  or  a  proportionally  equal 
fall  of  electric  potential,  is  ascertained  by  the 
failure  of  a  delicately  poised  needle  to  be  moved 
by  a  current  or  a  charge. 

Method,  Null  or  Zero Any  method 

employed  in  electrical  measurements,  in  which 
the  values  of  the  electromotive  force  in  volts, 
the  resistance  in  ohms,  or  the  current  in  am- 
peres, or  other  similar  units,  are  determined 
by  balancing  them  against  equal  values  of  the 
same  units,  and  ascertaining  such  equality,  not 
by  the  deflections  of  the  needle  of  a  galvano- 
meter, or  of  an  electrometer,  but  by  the  ab- 
sence of  such  deflections. 

The  advantage  of  zero  methods  is  iound  in  the 
fact  that  the  galvanometer  or  electrometer  may 
then  be  made  as  sensitive  as  possible,  which  is  not 
otherwise  the  case,  since  great  deflections  are 
generally  to  be  avoided,  especially  in  tangent 
galvanometers.  (See  Galvanometer.  Electrom- 
eter.) 

Method  of   Magnetization  by  Touch. — 

(See  Magnetization  by  Touch.) 

Methven's  Screen. — (See  Screen,  Meth- 
-ven  's.) 


Metre  Bridge. — (See  Bridge,  Metre?) 
Metre  Candle. — (See  Candle,  Metre.) 
Metre-Gramme  Standard,  Matthiessen's 

— A  unit  of  resistance. 

The  resistance  of  a  wire  one  metre  in 
length,  and  of  such  a  diameter  as  would  cause 
the  wire  to  weigh  one  gramme. 

One  metre-gramme  of  pure  hard  drawn  cop  per 
has  a  resistance  of  .1469  B.  A.  units  at  zero  de- 
grees C.  as  determined  by  Matthiessen  {Phil. 
Mag.,  May,  1865). 

Metre-Millimetre A  resistance  unit 

of  length  of  a  wire  or  other  conductor  of  the 
length  of  one  metre  and  of  the  area  of  cross- 
section  of  one  square  millimetre. 

According  to  the  report  of  the  Committee  of  the 
American  Institute  of  Electrical  Engineers  cf  1890, 
on  a  Standard  Wiring  Table,  a  metre  millimetre 
of  pure  soft  copper  wire  has  a  resistance  of  .02057 
B.  A.  units  at  zero  degrees  C.  From  the  corre- 
sponding term,  milfoot,  millimetre-metre  would 
appear  to  be  the  preferable  term. 

Metric  Horse-Power. — (See  Horse- Pm.  ?•*-, 
Metric?) 

Metric  System  of  Weights  and  Meas- 
ures.— (See  Weights  and  Measures,  Metric 
System  of.) 

Mho. — A  term  proposed  by  Sir  Wm. 
Thomson  for  the  practical  unit  of  conductiv- 
ity. 

Such  a  unit  of  conductivity  as  is  equal  to 
the  reciprocal  of  I  ohm. 

The    conducting   power  is  equal  to  _  or  the 

R 

,  eciprocal  of  the  resistance. 

The  word  mho,  as  is  evident,  is  obtained  by  in- 
verting the  order  of  sequence  of  the  letters  in  the 
word  ohm. 

Mica. — A  mineral  substance  employed  as 
an  insulator. 

Mica  is  a  silicious  mineral.  It  occurs  of  vary- 
ing degrees  of  transparency,  and  splits  or  cleaves 
readily  into  transparent  laminae.  It  is  a  good 
non  conductor,  is  fairly  fire  proof,  and  is  not 
hydroscopic. 

Mica  is  used  extensively  in  insulating  the  me- 
tallic segment  of  commutators  of  motors  and 
dynamo-electric  machines  and  in  various  other 
electric  work. 


Mic.] 


36? 


Mica,  Moulded  — • — An  insulating  sub- 
stance consisting  of  finely  divided  mica  made 
into  a  paste,  with  some  fused  insulating 
substance,  and  moulded  into  any  desired 
shape. 

Finely  divided  mica  mixed  with  gum-shellac 
rendered  plastic  by  means  of  heat,  forms  a  good 
insulating  substance. 

Micro  (as  a  prefix). — The  one-millionth; 
as,  a  microfarad,  the  millionth  of  a  farad ;  a 
microvolt,  the  one-millionth  of  a  volt. 

Micro-Farad. — (See  Farad, Micro') 

Micro-Gfraphophone. — A  modified  form  of 
phonograph  in  which  several  independent 
non-metallic  diaphragms  are  used  instead  of 
the  single  diaphragm  of  the  phonograph.  (See 
Graphophone,  Micro.) 

Micrometer,  Arc An  apparatus  for 

the  accurate  measurement  of  the  length  of  a 
voltaic  arc  by  means  of  a  micrometer. 

The  distance  between  two  carbon  electrodes — 
one  movable  and  the  other  fixed — placed  inside  a 
glass  vessel,  is  accurately  determined  by  means  of 
a  micrometer  placed  on  the  movable  electrode. 
The  operation  is  similar  to  that  of  the  vernier 
•wire  gauge. 

Micrometer,  Spark A  term  some- 
times applied  to  Hertz's  electric  resonator. 
(See  Resonator,  Electric) 

Micron. — A  measure  of  length. 

The  one-millionth  part  of  a  metre. 

The  micron  is  equal  to  .00004  °f  an  inch,  very 
nearly. 

Microphone. — An  apparatus  invented  by 
Prof.  Hughes  for  rendering  faint  or  distant 
sounds  distinctly  audible. 

The  microphone  depends  for  its  operation  on 
variations  produced  in  the  resistance  of  the  circuit 
of  a  battery,  or  other  electric  source,  by  means  of 
a  loose  contact.  These  variations  in  the  resist- 
ance are  caused  to  produce  corresponding  move- 
ments in  the  diaphragm  of  a  receiving  telephone. 

The  loose  contact  may  take  a  variety  of  forms. 
Originally  it  was  made  in  the  form  shown  in  Fig. 
397,  in  which  a  small  piece  of  carbon  E,  pointed 
at  both  ends,  is  inserted  in  holes  near  the  ends  of 
cross-pieces  of  carbon  B  and  C.  The  thin  upright 
board  A,  on  which  these  are  supported,  acts  as  a 


sounding  board  or  diaphragm,  and  its  movements 
by  sound  waves  are  at  once  audible  to  a  person 
listening  at  the  receiving  telephone.  The  walk- 
ing of  a  fly  over  the  sounding  board  is  heard  as  a 
loud  sound. 

The  forms  of  transmitting  telephones  invented 
by  Reis,  Edison,  Blake,  Berliner  and  others,  are 
in  reality  varieties  of  microphones. 


Fig.  3Q7.    Microphone. 

Microphone  Relay. — (See  Relay,  Micro- 
phone) 

Micro-Seismograph. — (See  Seismograph 
Micro) 

Microtasimeter. — An  apparatus  invented 
by  Edison  to  measure  minute  differences  of 
temperature,  or  of  moisture,  by  the  resulting 
differences  of  pressure. 

A  change  of  temperature,  or  moisture,  is  caused 
to  produce  variations  in  the  resistance  of  a  button 
of  compressed  lampblack,  placed  in  the  circuit  of 
a  delicate  galvanometer.  The  apparatus,  though 
of  surprising  delicacy,  is  scarcely  capable  of  prac- 
tical application,  from  the  fact  that  the  resistance 
of  the  carbon  does  not  resume  its  normal  value  011 
the  removal  of  the  pressure. 

Micro- Yolt— (See  Volt,  Micro) 

Mil.— A  unit  of  length  equal  to  the  -nnnr  of 
an  inch,  or  .001  inch,  used  in  measuring  the 
diameter  of  wires. 

Mil,  Circular  —  — A  unit  of  area  em- 
ployed in  measuring  the  areas  of  cross-sec- 
tions of  wires,  equal  to  .78540  square  mil. 

The  area  of  a  circle  one  mil  in  diameter. 


Mil.] 


368 


[Min. 


One  circular  mil  equals  .000000785  square  inch. 

The  area  of  cross-section  of  a  circular  wire  in 
circular  mils  is  equal  to  the  square  of  its  diameter 
expressed  in  mils.  (See  Units,  Circular.) 

Mil-Foot— A  resistance  unit  of  length  of 
one  foot  of  wire  or  other  conductor  of  one 
mil  diameter. 

The  resistance  of  a  mil-foot  of  soft  copper  wire 
or  wire  I  foot  long  and  .001  of  an  inch  in  diam- 
eter is  equal  to  9.720  B.  A.  units  at  O  degrees  C. 

Mil,  Square A  unit  of  area  em- 
ployed in  measuring  the  areas  of  cross-sec- 
tions of  wires,  equal  to  .00000 1  square  inch. 

One  square  mil  equals  1.2732  circular  mil. 

Mile,  Nautical A  knot,  or  a  dis- 
tance of  6,087  feet,  or  very  nearly  1.15  statute 
miles. 

The  --rTFtnr  of  the  earth's  equatorial  cir- 
cumference, or  the  cV  of  a  degree  of  longi- 
tude at  the  equator,  or  about  2,029  yards. 

A  nautical  or  geographical  mile  being  the 
5T|5Tj  of  24,899  miles,  has  a  value  somewhat 
greater  than  that  of  the  statute  mile. 

Mile  Standard,  Matthiessen's A 

standard  of  resistance  equal  to  the  resistance 
of  one  mile  of  pure  copper  wire  fV  inch  in 
diameter  at  15.5  degrees  C. 

Matthiessen's  mile  standard  has  a  resistance  of 
13.59  B.  A.  units  at  15.5  degrees  C. 

Mile,  Statute  —  —The  ordinary  unit  of 
distance  on  land,  equal  to  5,280  feet. 

Mill!  (as  a  prefix). — The  one-thousandth 
part. 

Milli-Ainpere. — The  thousandth  of  an  am- 
pere. 

Milli-Calorie. — The  smaller  calorie.  (See 
Calorie,  Small.} 

Milli-Oerstedt. — The  one-thousandth  of 
an  Oerstedt. 

Mimosa  Sensitira. — A  sensitive  plant 
whose  leaves  fold  or  shut  up  when  touched. 

The  fibres  of  all  the  sensitive  plants,  such,  for 
example,  as  the  above,  the  Venus'  Fly-trap,  etc., 
like  all  muscular  fibre,  and  indeed  all  protoplasm, 
suffer  contraction  when  traversed  by  electric  cur- 
rents. 

Mine,  Electro-Contact  -  — A  sub- 
marine mine  that  is  fired  automatically  on 
the  completion  of  the  current  of  a  battery 


placed  on  the  shore  through  the  closing  of 
floating  contact  points  by  passing  vessels. 
(See  Mine,  Submarine.} 

Mine  Exploder,  Electro-Magnetic 

A  form  of  electro-magnetic  exploder.  (See 
Exploder,  Electro-Magnetic.) 

Mine,    Mechanical A  submarine 

mine  that  is  fired  when  struck  by  a  passing 
ship  by  the  action  of  some  contrivance  con- 
tained within  the  torpedo  itself,  and  having 
no  connection  whatever  with  the  shore. 

Mine,  Observation A  variety  of 

submarine  mine  that  is  fired  when  the 
enemy's  vessels  are  observed  to  be  within  the 
destructive  area  of  the  mine.  (See  Mine, 
Submarine.} 

Various  means  are  adopted  for  obtaining  the 
current  required  for  firing  such  mines.  A  suffi- 
ciently powerful  battery  is  generally  used.  An 
electro-magnetic  mine  exploder  may,  under  cer- 
tain circumstances,  be  employed.  (See  Mine 
Exploder,  Electro -Magnetic.} 

Mine,  Submarine A  mass  of  gun- 
cotton  or  other  explosive  contained  in  a 
water-tight  vessel  and  placed  under  water  so 
as  to  be  exploded  on  the  passage  over  it  of 
an  enemy's  vessel. 

A  submarine  mine  is  a  stationary  torpedo  ar- 
ranged for  the  defense  of  a  harbor.  A  harbor 
is  protected  by  a  number  of  mines  which  are  so 
arranged  as  to  be  readily  exploded  by  the  passage 
of  an  enemy's  ship,  but  safely  crossed  by  other 
vessels. 

Submarine  mines  consist  essentially  of  gun- 
cotton  or  other  explosives  contained  in  water-tight 
vessels  anchored  in  very  carefully  located  posi- 
tions, and  connected  with  the  shore  by  means  of 
cables. 

An  operating-room  at  the  shore  end  of  the 
cable  is  furnished  with  batteries,  measuring  in- 
struments, contact  keys,  etc.,  etc.,  by  means  of 
which  the  mines  can  be  exploded  by  the  trans- 
mission of  an  electric  current  through  the  cables; 
or,  the  mines  are  furnished  with  automatic  cir- 
cuit closers  in  which  two  central  points  are  closed 
by  the  passage  of  the  vessel.  In  ordinary  times 
this  current  is  too  weak  to  ignite  the  fuse,  and 
merely  closes  a  relay  in  the  operating-room, 
which  in  turn  directs  a  current  through  a  bell  or 
indicator,  but,  ot  course,  too  weak  to  fire  the  fuse. 


JLin.] 


369 


[Mom. 


In  times  of  war,  however,  the  relay  sends  a 
current  through  the  cable  sufficiently  strong  to 
heat  a  platinum  indium  fuse,  ignite  a  fulminate  of 
mercury  cap,  and  thus,  by  the  detonation  of  the 
primer  of  dry  gun-cotton,  explode  the  full  charge 
of  damp  gun-cotton  in  the  torpedo  or  mine. 

Mine,  Subterranean A   mass   of 

gun  powder,  gun-cotton  or  other  explosive, 
placed  under  ground  in  vessels  suitable  for 
protection  against  moisture,  and  fitted  with 
electrically  connected  electric  fuses,  which  are 
either  exploded  automatically  by  the  move- 
ment of  an  enemy  over  them,  or  by  an  oper- 
ator placed  at  a  safe  distance  within  an  en- 
trenchment. 


Molecular     Currents.— (See     Currents, 
Molecular  or  Atomic?) 
Molecular  Currents,  Induced (See 


One  ampere  flow- 

(See  Hour,  Ampere) 

A  unit  of  electrical 


Minute,  Ampere 

ing  for  one  minute. 

Minute,  Watt  — 

work. 

The  expenditure  of  an  electrical  power  of 
one  watt  for  one  minute. 

The  watt-minute  is  equal  to  60  joules.  This 
unit  of  electrical  work  is  seldom  used. 

Miophone. — An  apparatus  invented  by 
Boudet  based  on  the  use  of  the  microphone, 
and  designed  for  the  medical  examination  of 
the  muscles. 

Mirror  Galvanometer. — (See  Galvanom- 
eter, Mirror) 

Moist  Electrode.— (See  Electrode,  Moist) 

Moisture,  Eifect  of,  on  Electrical  Phe- 
nomena    — The  influence  of  moisture 

on  the  surfaces  of  insulators  in  causing  the 
loss  or  dissipation  of  an  electric  charge. 

This  luss  is  more  rapid  with  negatively  charged 
bodies  than  with  those  positively  charged. 

Molar  Attraction.  —  (See  Attraction, 
Molar.) 

Molecular. — Pertaining  to  the  molecule. 
(See  Molecule) 

Molecular  Attraction.— (See  Attraction, 

Molecular.) 

Molecular  Bombardment. — (See  Bom- 
bardment, Molecular) 

Molecular  Chain.— (See  C'lain,  Molecu- 
lar) 


Currents,  Induced  Molecular  or  Atomic) 

Molecular  Range. — (See  Range,  Molecu' 
lar) 

Molecular  Repulsion. — (See  Repulsion 
Molecular) 

Molecular  Rigidity.  —  (See  Rigidity, 
Molecular) 

Molecular  Theory  of  Muscle  and  Nerve 
Currents. — (See  Theory,  Alolecular,  of  Mus- 
cle and  Nerve  Currents) 

Molecule. — A  group  of  atoms  whose 
chemical  bonds  or  affinities  are  mutually 
satisfied. 

The  smallest  quantity  of  a  compound  sub- 
stance that  can  exist  as  such. 

Water  is  a  compound  substance  formed  of  two 
atoms  of  hydrogen  combined  with  one  atom  of 
oxygen.  The  molecule  of  water,  therefore,  or 
the  smallest  quantity  of  water  that  can  exist,  must 
contain  two  atoms  of  hydrogen  and  one  of  oxygen. 

The  molecule  of  hydrogen  consists  of  two  atoms 
of  hydrogen.  Since  hydrogen  is  a  monad,  or  an 
element  whose  atomicity  is  one,  it  can  combine 
with  one  atom  of  hydrogen  and  form  a  molecule, 
since  then  its  bonds  will  be  fully  satisfied.  (See 
Atomicity.) 

Molecule,    Closed-Magnetic    Circuit    of 

— (See    Circuit,    Closed-Magnetic,  of 

Molecule.) 

Molecule,  Gramme The  weight  of 

any  substance  taken  in  grammes  numerically 
equal  to  the  molecular  weight. 

Moment,  Magnetic  —  — The  sum  of  the 
two  forces  of  the  directive  couple  multiplied 
by  half  the  perpendicular  distance  between  the 
directions  of  these  forces  ;  or,  in  other  words, 
the  moment  of  a  magnet  is  equal  to  its  length 
multiplied  by  the  intensity  of  the  magnetism 
of  one  of  its  poles.  (See  Couple,  Magnetic) 

Moment  of  Couples. — (See  Couple,  Mo- 
ment of) 

Momentary  Current. — (See  Current,  Mo- 
mentary) 

Momentum,  Electro-Magnetic,  of  Sec- 
ondary Circuit A  quantity  equal  to 


Moii.J 


370 


[Mot. 


the  co-efficient  of  mutual  induction,  multi- 
plied by  the  current  strength  in  the  primary, 
when  the  primary  current  is  fully  established. 
When  the  primary  current  is  fully  established, 
the  number  of  lines  of  force  which  pass  through 
the  secondary  circuit  is  equal  to  the  co-efficient  of 
mutual  induction,  multiplied  by  the  strength  of 
the  primary  current. 

Monophotal  Arc-Light  Regulator. — (See 
Regulator,  Monophotal  Arc-Light?) 
Mordey  Effect.— (See  Effect,  Mordey?) 
Morse  Alphabet.— (See  Alphabet,    Tele- 
graphic: Morses?) 

Morse  Inker. — (See  Inker,  Morsel) 
Morse  Recorder. — (See  Recorder,  Morsel) 
Morse  Register.— (See  Register,  Morse?) 
Morse     System    of    Telegraphy. — (See 
Telegraphy,  Morse  System  of.) 

Morse's  Telegraphic  Alphabet. — (See  Al- 
phabet, Telegraphic  :  Morse's.) 

Morse's  Telegraphic  Sounder. — (See 
Sounder,  Morse's  Telegraphic?) 

Motion,  Energy  of A  term  some- 
times applied  to  actual  or  kinetic  energy  in 
contradistinction  to  potential  energy.  (See 
Energy,  Actual?) 

Motion,  Simple-Harmonic Motion 

which  repeats  itself  at  regular  intervals,  taking 
place  backwards  or  forwards,  and  which  may- 
be studied  by  comparison  with  uniform  mo- 
tion round  a  circle  of  reference. — (Dam'ell.) 


Fig.  398.    Simple-Harmonic  Motion. 

Motion  which  is  a  simple  periodic  function 
of  the  time. 

Suppose  a  pendulum  be  set  swinging  in  a  cer- 
tain path.  If  the  path  of  such  a  pendulum,  or, 
as  it  is  generally  called,  a  conical  pendulum,  be 


looked  at  from  above  or  from  below,  it  will  appear 
to  be  circular;  if  observed  from  one  side  it  will 
appear  elliptical,  and  this  elliptical  path  will  ap- 
pear longer  and  narrower  as  the  eye  of  the  ob- 
server approaches  the  level  of  the  plane  in  which 
the  bob  moves,  when  the  bob  will  appear  to 
travel  backwards  and  forwards  in  a  straight  line. 
The  bob  will  appear  to  be  moving  faster,  when  it 
is  moving  right  across  the  field  of  view. 

Let  the  circle  Q  C  R  (Fig.  398)  be  the  path  in 
which  the  bob  moves,  and  let  Q  A,  A  B,  B  C,  C  o, 
etc.,  be  equal  distances  in  such  path.  Let  the 
lines  A  a,  B  b,  C  c,  o  O,  etc.,  be  drawn  perpendicu- 
lar to  the  line  Q  R.  Then  when  looked  at,  with 
the  eye  on  the  level  of  the  plane  in  which  the  bob 
travels,  the  line  Q  R,  will  be  the  path  in  which 
the  bob  appears  to  move  backwards  and  for- 
wards, and  the  lines,  Q  a,  a  b,  b  c,  c  O,  etc.,  will 
represent  the  spaces  apparently  traversed  in 
equal  intervals  of  time. 

The  circle  Q  o  R,  is  called  the  circle  of  refer- 
ence. 

Motion,  Simple-Harmonic,  Amplitude  of 

— The  length  of   the  swing  from   the 


median  position  to  its  extreme  position,  in 
either  direction. 

The  line  O  Q,  or  O  R,  in  the  circle  of  reference 
Q  O  R  (Fig.  398). 

Motion,  Simple-Harmonic,  Negative  Di- 
rection of The  motion  which  a  body, 

with  a  simple-harmonic  motion,  has  when  it 
appears  to  move  from  left  to  right. 

Motion,  Simple-Harmonic,  Period  of 

— The  interval  of  time  which  elapses  between 
two  successive  passages  of  a  moving  particle, 
over  the  same  point,  in  the  same  direction. 

The  period  of  simple-harmonic  motion  repre- 
sents the  time  of  one  complete  motion  around  a 
circle  called  the  circle  of  reference.  (See  Motion, 
Simple -Harmonic. ) 

Motion,  Simple-Harmonic,  Phase  of  — 

— The  position  of  a  point  executing  a  simple 
harmonic  motion,  expressed  in  terms  of  the 
interval  of  time  which  has  elapsed  since 
such  point  last  passed  through  the  middle 
of  its  path  in  the  positive  direction. — (An- 
thony <$-»  Brackett?) 

The  exact  position  of  a  particle  executing  a 
simple-harmonic  motion  for  any  instant  of  time 
can  be  readily  expressed  in  terms  of  the  phase. 


Mot. 


371 


[Mot. 


Motion,  Simple-Harmonic,  Positive 

Direction  of The  motion  which  a. 

body  moving  in  simple-harmonic  motion  has, 
when  it  appears  to  move  from  right  to  left. 

Motion,  Simple-Periodic A  term 

sometimes  employed  in  the  sense  of  simple- 
harmonic  motion.  (See  Motion,  Simple- 
Harmonic.') 

Motion,  Simple-Sine —A  term  some- 
times employed  in  the  sense  of  simple-har- 
monic motion.  (See  Motion,  Simple-Har- 
monic^) 

Motograph,  Electro An  apparatus 

invented  by  Edison  whereby  the  friction  of  a 
platinum  point  against  a  rotating  cylinder  of 
moist  chalk,  is  reduced  by  the  passage  of 
an  electric  current. 

This  result  is  due  to  electrolytic  action  at  the 
points  of  contact,  varying  the  friction. 

The  electro-motograph,  though  less  certain  in 
its  action  than  an  electro-magnet,  may  replace  it 
in  certain  electric  apparatus. 

The  detailed  construction  of  the  electro-moto- 
graph will  be  understood  from  an  inspection  of 

Fig-  399- 

The  lever  A,  pivoted  with  a  universal  joint  at 
C,  has  a  metallic  point  at  its  free  extremity  F, 
resting  on  a  strip  of  moistened  paper  N,  and  held 
against  it  with  some  pressure  by  the  action  of  the 
spring  S.  The  paper  N,  rests  on  the  metallic 
drum  G,  over  which  it  is  moved  on  the  rotation 
of  the  drum  by  clockwork.  A  spring  R,  acts  to 
move  the  lever  A,  in  a  direction  opposite  to  that 
in  which  it  tends  to  move  by  the  rotation  of  the 
drum  G. 

The  main  battery  L,  is  connected  at  its  negative 
pole  to  the  point  F,  and  at  its  positive  pole,  through 
the  key  K,  to  the  metallic  drum  G.  The  local  bat- 
tery L  B,  is  connected  through  the  sounder  X,  to 
the  contacts  D  and  X. 

When  the  key  K,  is  open,  the  friction  of  F,  on 
the  paper  N,  is  sufficient  to  move  the  lever  A,  to 
the  right  so  as  to  close  the  circuit  of  the  local 
battery,  but  when  the  key  K,  is  depressed,  the 
current  of  L,  passing  through  the  paper,  decom- 
poses the  chemicals  with  which  ic  is  moistened, 
lessens  the  friction  of  the  point  F,  and  permits  the 
spring  B,  to  draw  the  lever  A,  to  the  left,  thus 
opening  the  circuit  of  the  local  battery  L  B. 

The  movements  of  the  key  are  therefore  repro« 
duced  by  the  armature  of  the  electro-magnet  X. 


An  excellent  loud  speaking  telephone  has  been 
devised  by  Edison  on  the  principle  of  the  electro- 
motograph. 


Fig.  3QQ.    Electro-Motograph. 

Motor,  Compound-Wound An  elec- 
tric motor  whose  field  magnets  are  excited  by 
a  series  and  a  shunt  wire.  (See  Machine, 
Dynamo-Electric,  Compound-  Wound.) 

Motor,  Differentially  Wound A 

compound-wound  motor,  in  which  the  cur- 
rent in  the  shunt  coils  opposes  in  its  magnet- 
izing effects  the  current  in  a  series  coil,  so 
that  the  efficient  magnetizing  effect  produced 
is  the  difference  in  the  magnetizing  effect  of 
the  two  coils. 

Motor,  Electric A  device  for  trans- 
forming electric  power  mto  mechanical 
power. 

All  practical  electric  motors  depend  for  their 
operation  on  the  tendency  to  motion  in  a  mag- 
netic field  of  a  conductor  carrying  a  current  01 
on  magnetic  attraction  or  repulsion.  The  entire 
magnetism  may  be  produced  by  u,  e  current,  or 
part  may  be  obtained  from  permanent  magnets, 
and  the  rest  from  electro-magnets. 

A  dynamo-electric  machine  will  act  as  a  motor 
if  a  current  is  sent  through  it.  Such  a  motor  is 
sometimes  called  an  electro-motor.  The  term 
electric  motor  would,  however,  appear  to  be  the 
preferable  one. 

In  all  cases  the  rotation  is  in  such  a  direction  as 
to  induce  in  the  armature  an  electromotive  force 
opposed  to  that  of  the  driving  current  ;  this  is 
therefore  called  the  counter  electromotive  force. 

A  magneto-dynamo,  or  a  dynamo  the  field  of 
which  is  obtained  from  permanent  magnets,  or  a 
separately  excited  dynamo,  will  operate  as  a 
motor  when  a  current  is  sent  through  its  arma- 
ture, and  will  turn  it  in  the  opposite  direction  to 
that  required  to  drive  it  in  order  to  produce  a 
current  in  the  same  direction. 

A  series  dynamo  will  operate  as  a  motor  when 


Mot.] 


372 


[Mot. 


a  current  is  sent  through  it.  If  the  current  is 
sent  through  it  in  the  opposite  direction  to  that 
which  it  produces  when  in  operation  as  a  gener- 
ator, the  polarity  of  the  field  is  reversed  and  the 
dynamo  will  turn  as  a  motor  in  the  opposite  direc- 
tion to  that  required  to  produce  the  current.  If 
the  current  is  reversed,  the  polarity  of  both  the 
field  and  the  armature  is  again  reversed,  and  the 
dynamo  still  rotates  as  a  motor  in  the  opposite 
direction  to  that  in  which  it  is  rotated  as  a 
generator. 

A  series  dynamo,  therefore,  always  rotates  as  a 
motor  in  a  direction  opposite  to  that  of  its  rotation 
as  a  generator. 

When,  however,  the  polarity  of  the  field  only 
is  reversed  by  changing  the  connection  between 
the  armature  and  the  field,  the  rotation  is  in  the 
same  direction. 

A  shunt  dynamo  operated  as  a  motor  will  also 
turn  in  but  one  direction,  but  this  direction  is  the 
same  as  that  in  which  it  turns  when  operating 
as  a  generator;  for  if  the  direction  of  the  current 
in  the  armature  is  the  same  as  in  a  generator, 
that  in  the  shunt  is  reversed. 

A  compound  wound  dynamo  will  move  in  a 
direction  opposite  to  that  of  its  motion  as  a  gene- 
rator if  the  series  part  is  more  powerful  than  the 
shunt,  and  in  the  same  direction  if  the  shunt  part 
is  more  powerful  than  the  series.  To  use  a  com- 
pound-wound dynamo  as  a  differential  motor  the 
connections  need  not  be  changed.  For  a  cumu- 
lative motor  it  is  necessary  to  reverse  the  connec- 
tions of  the  series  coils. 

Alternating-Current  Dynamo. — The  current 
from  an  alternating-current  dynamo,  if  sent 
through  another  similar  alternating-current  dy- 
namo running  at  the  same  speed,  will  drive  it  as  a 
motor.  Such  a  machine  possesses  the  disadvan- 
tage of  requiring  to  be  maintained  at  a  speed  de- 
pending on  that  of  the  driving  dynamo,  and  also 
that  it  requires  to  be  brought  to  nearly  this  speed 
before  the  driving  current  is  supplied  to  it.  As  a 
result  of  this  last  requirement,  variations  in  the 
load  are  apt  to  stop  the  motor.  Considerable 
improvements,  however,  are  being  introduced 
into  alternate-current  motors,  by  which  these 
difficulties  are  almost  entirely  removed. 

An  alternating  current  sent  through  any  self- 
exciting  dynamo -electric  machine,  such  as  a 
shunt  or  series  machine,  will  drive  it  continu- 
ously as  a  motor.  The  sudden  reversals  in  the 
magnetization  of  its  cores  will,  however,  unless 
Ihe  cores  are  thoroughly  laminated,  set  up  power- 


ful eddy  currents  that  will  injuriously  heat  the 
machine,  and  there  is  also  excessive  sparking  at 
the  brushes. 

The  reversibility  of  any  dynamo -electric  ma- 
chine, or  its  ability  to  operate  as  a  motor  if  sup- 
plied with  a  current,  leads  to  a  fact  of  great 
importance  in  the  efficiency  of  electric  motors, 
viz.:  that  during  rotation  there  is  induced  in  the 
armature  during  its  passage  through  the  field  of 
the  machine,  an  electromotive  force  opposed  co 
that  produced  in  the  armature  by  the  driving 
current,  or  a  counter  electromotive  force.  (See 
Resistance,  Spurious.  Force,  Counter  Electro- 
motive.'] This  counter  electromotive  force  acts 
as  a  spurious  resistance,  and  opposes  the  passage 
of  the  driving  current,  so  that,  as  the  speed  of  the 
electric  motor  increases,  the  strength  of  the  dr'v- 
ing  current  becomes  less,  until,  when  a  certain 
maximum  speed  is  reached,  very  little  current 
passes.  In  actual  practice,  this  maximum  speed 
is  not  attained,  or  is  only  momentarily  attained, 
and  a  small,  nearly  constant,  current  is  expended 
in  overcoming  friction  at  the  bearings,  air  fac- 
tion, etc. 

When,  however,  the  load  is  placed  on  the 
motor,  that  is,  when  it  is  caused  to  do  work,  the 
speed  is  reduced  and  the  counter  electromotive 
force  is  decreased,  thus  permitting  a  greater  cur- 
rent to  pass.  The  fact  that  the  load  thus  auto- 
matically regulates  the  current  required  t  >  drive 
the  mo;or,  renders  electric  mo  ors  very  economi- 
cal in  operation. 

The  relations  between  the  power  required  to 
drive  the  generating  dynamo,  and  that  produced 
by  the  electric  motor,  are  such  that  the  maximum 
work  per  second  is  done  by  the  motor  when  it 
runs  at  such  a  rate  that  the  counter  electro- 
motive force  it  produces  is  half  that  of  the  current 
supplied  to  it.  The  maximum  work  or  activity  of 
an  electric  motor  is  therefore  done  when  its  theo- 
retical efficiency  is  only  50  per  cent.  This, 
however,  must  be  carefully  distinguished  from 
the  maximum  efficiency  of  an  electric  motor.  A 
maximum  efficiency  of  100  per  cent,  can  be  at 
tained  theoretically  ;  and,  in  actual  practice,  con- 
siderably over  90  per  cent,  is  obtained.  In  such 
cases,  however,  the  motor  is  doing  work  at  less 
than  its  maximum  power. 

This  is  Jacobi's  law  of  maximum  effect,  but 
does  not  apply  to  actual  motors  on  account  of  the 
Jimitations  of  current  carrying  capacity.  For 
example,  a  motor  of  9  horse  power  and  90  per 
cent,  efficiency  loses  I  horse-power  in  heat  within 


Mot.] 


373 


[Mot. 


itself.  Hence,  if  run  according  to  Jacobi's  law, 
it  would  only  produce  the  same  amount,  *'.  e.,  I 
horse-power  in  useful  work  instead  of  9.  More 
than  this  would  overheat  it. 

An  efficiency  of  100  per  cent,  is  reached  when 
the  counter  electromotive  force  of  the  motor  is 
equal  to  that  of  the  source  supplying  the  driving 
current.  Supposing  now  the  driving  machine  to 
be  of  the  same  type  as  the  motor,  and  the  two 
machines  are  running  at  the  same  speed.  If 
now  a  load  is  put  on  the  motor  so  as  to  reduce  its 
speed,  and  thus  permit  it  to  produce  a  counter 
electromotive  force  of  but  90  per  cent.,  its 
efficiency  will  be  but  90  per  cent.  In  such  a 
case,  therefore,  the  efficiency  is  represented  by 
the  relative  speeds  of  the  generator  and  the 
motor. 

Motor,    Electric,     Alternating-Current 

— An  electric  motor  driven  or  operated 


by  means  of  alternating  currents.  (See 
Motor,  Electric?) 

Dr.  Louis  Duncan  divides  alternating  motors 
into  two  classes,  viz. : 

(i.)  Those  in  which  there  is  but  one  trans- 
formation in  the  machine,  viz.,  that  of  the  electric 
energy  of  the  armature  current  into  the  mechani- 
cal energy  of  the  armature's  rotation. 

(2.)  Those  in  which  there  are  two  transforma- 
tions, viz.: 

(a.)  The  transformation  of  electrical  energy 
from  the  main  current  to  electrical  energy  in  the 
armature  current. 

(b.)  The  transformation  of  the  electric  energy 
of  the  armature  current  into  mechanical  energy. 

Alternating  motors  of  the  first  type  are  iound 
in  the  ordinary  alternating-current  dynamo  re- 
versed. Those  of  the  second  type  in  Tesla's  or 
Thomson's  motors. 

Motor,  Electric,  Direct-Current  — 

An  electric  motor  driven  or  operated  by 
means  of  direct  or  continuous  electric  cur- 
rents, as  distinguished  from  a  motor  driven 
or  operated  by  alternating  currents.  (See 
Motor,  Electric?) 

Motor,  Electric,  High-Speed The 

ordinary  electric  motor. 

The  term  high-speed  electric  motor  is  used  in 
contradistinction  to  low -speed  electric  motor. 
(See  Motor,  Electric,  Low-Speed.} 

Motor,    Electric,    Low-Speed A 


slow-speed  motor.  (See  Motor,  Electric, 
Slow-Speed?) 

Motor,    Electric,  Overload  of — A 

load  greater  than  that  which  an  electric  motor 
can  carry  while  at  its  greatest  efficiency  of 
operation,  or  a  load  which  causes  injurious 
heating  of  a  motor. 

Motor,  Electric,  Reversing  Gear  of  - 

— Apparatus  for  so  reversing  the  direction  of 
the  current  through  an  electric  motor  as  to  re- 
verse the  direction  of  its  rotation.  (See  Rail- 
road, Electric?) 

Motor,  Electric,   Slow-Speed  -       —An 

electric  motor  so  constructed  as  to  run  with 
fair  efficiency  at  slow  speed. 

The  electric  motor  develops  a  counter  electro- 
motive for»;e  when  in  motion,  which,  of  course, 
increases  with  the  increase  of  motion.  The  elec- 
tric motor  has,  as  generally  constructed,  its  great- 
est efficiency  at  high  speed.  When  used  on  street 
railroads,  the  high  speed  requires  to  be  decreased 
by  various  forms  of  reduction  gear.  The  loss  of 
power  which  all  such  gear  involve,  together  with 
the  noise  attending  their  use,  render  any  decrease 
in  speed  that  can  be  obtained  on  the  part  of  the 
motor,  without  serious  loss  of  efficiency,  desir- 
able. 

Motor-Electromotive  Force. — (See  Force, 
Motor  Electromotive.} 

Motor,  Pyromagnetic  -  -  A  motor 
driven  by  the  attraction  of  magnet  poles  on 
a  movable  core  of  iron  or  nickel  unequally 
heated. 

The  intensity  of  magnetization  of  iron  decreases 
with  an  increase  of  temperature,  iron  losing  most 
of  its  magnetization  at  a  red  heat.  A  disc  of  iron 
placed  between  the  poles  of  a  magnet,  so  as  to 
be  capable  of  rotation,  will  rotate,  if  heated  at  a 
part  nearer  one  pole  than  the  other,  since  it  be- 
comes less  powerfully  magnetized  at  the  heated 
part. 

In  the  form  of  pyromagnetic  motor  devised  by 
Edison,  and  shown  in  Fig.  400,  in  elevation,  and 
in  Fig.  401,  in  vertical  section,  the  disc  of  iron  is 
replaced  by  a  series  of  small  iron  tubes,  or  di- 
vided annular  spaces,  heated  by  the  products  of 
combustion  from  a  fire  placed  beneath  them.  In 
order  to  render  this  heating  local,  a  flat  screen  is 
placed  dissymmetrically  across  the  top  to  prevent 


Mot.] 


374 


[Mov. 


the  passage  of  air  through  the  portion  of  the  iron 
tubes  so  screened.  The  air  is  supplied  to  the 
furnace  by  passing  down  from  above  through  the 


Fig.  400.    Pyromagnetic  Motor. 

tubes  so  screened.  This  is  shown  in  the  draw- 
ings, the  direction  of  the  heating  and  the  cooling 
air  currents  being  indicated  by  the  arrows.  The 


Fig.  40 1.     Pyromagnetic  Motor. 

supply  of  air  from  above  thus  insures  the  more 
rapid  cooling  of  the  screened  portion  of  the 
tubes. 


Motor,      Rotating-Current 


—  An 


electric  motor  designed  for  use  with  a  rotat- 
ing electric  current. 


Unlike  alternating  current  motors,  rotary-cur- 
rent motors  will,  like  continuous-current  motors, 
readily  start  with  a  load.  (See  Current,  Rotating, ) 

Motor,  Series-Wound An  electric 

motor  in  which  the  field  and  armature  are 
connected  in  series  with  the  external  circuit  as 
in  a  series  dynamo.  (See  Machine,  Dynamo- 
Electric,  Series-  Wound?) 

Motor,  Shunt-Wound An  electric 

motor  in  which  the  field  magnet  coils  are 
placed  in  a  shunt  to  the  armature  circuit. 
(See  Machine,  Dynamo-Electric,  Shunt- 
Wound?) 

Motor  Standards.  —  (See  Standards, 
Motor?) 

Moulded  Mica. — (See  Mica,  Moulded?) 

Moulding,  Electric  Wood  —  —  Mould- 
ing of  dried,  non-conducting  wood,  provided 
with  longitudinal  grooves  for  the  reception 
and  support  of  electric  wires  or  conductors. 

Wood  mouldings  are  employed  for  the  protec- 
tion and  concealment  of  electric  conductors. 

Moulding  Wiring.  —  (See  Wiring, 
Moulding?) 

Mouse-Mill  Dynamo.  —  (See  Dynamo, 
Mouse-Mill?) 

Mouse-Mill  Machine.  —  (See  Machine, 
Mouse-Mill?) 

Mouth  Pieces. — (See  Pieces,  Mouth?) 

Movable  Secondary.  —  (See  Secondary, 
Movable?) 

Mover,  Prime In  a  system  of  dis- 
tribution of  power  the  motor  by  which  sec- 
ondary motors  or  movers  are  driven. 

In  a  steam  plant,  the  steam  engine  is  the  prime 
mover;  the  shafts  or  machines  driven  by  the  main 
shaft  are  sometimes  called  the  secondary  m  vers. 
The  main  shaft  is  called  the  drivhg  shaf  .  Its 
motion  is  carried  by  means  of  belts  to  other 
shafts,  called  driven  shafts.  The  pulleys  on  the 
driving  or  driven  shafts  aie  called  respectively 
the  driving  and  driven  pulleys. 

Movers,  Secondary The  shafts  or 

machines  driven  by  the  main  shafts  in  order 
to  distinguish  them  from  the  steam  engine  or 
other  mover  which  drives  it.  (See  Mover, 
Prime?) 


Mai.] 


375 


[Mul. 


Multi-Cellular  Electrostatic  Voltmeter. 

— (See  Voltmeter,  Multi-Cellular  Electro- 
static^) 

Multiphase  Current.— (See  Current,  Mul- 
tiphase.) 

Multiphase  Dynamo.  —  (See  Dynamo, 
Multiphase) 

Multiphase  System. — (See  System,  Multi- 
phased) 

Multiple-Arc  Circuit.  —  (See  Circuit, 
Multiple-Arc?) 

Multiple- Arc-Connected  Electro-Recep- 
tive Devices. — (See  Devices,  Electro-Recep- 
tive, Multiple-Arc-Connected?) 

Multiple-Arc-Connected  Sources. — (See 
Sources,  Multiple-Arc-Connected.) 

Multiple-Arc-Connected  Translating  De- 
vices.—(See  Devices,  Translating,  Mul- 
tiple-A  re-  Connected?) 

Multiple-Brush  Rocker. — (See  Rocker, 
Multiple-Brush ) 

Multiple-Brush  Yoke.— (See  Yoke,  Mul- 
tiple-Pair Brush?) 

Multiple  Cable  Core.— (See  Cable,  Mul- 
tiple-Core?) 

Multiple  Circuit— (See  Circuit,  Mul- 
tiple?) 

Multiple  Conduit — (See  Conduit,  Mul- 
tiple.) 

Multiple-Connected  Battery.— (See  Bat- 
tery, Multiple-Connected) 

MuMiple-Connected  Electro-Receptive 
Devices. — (See  Devices,  Electro-Receptive, 

Multiple-  Connected) 

Multiple-Connected  Electro-Receptive 

Devices,  Automatic  Cut-Out  for (See 

Cut-Out,  Automatic, for  Multiple-Connected 
Electro-Receptive  Devices?) 

Multiple-Connected  Translating  Devices. 
— (See  Devices,  Translating,  Multiple-Con- 
nected?) - 

Multiple  Connection.  -  (See  Connection, 
Multiple?) 


Multiple  Distribution  of  Electricity  by 
Constant  Potential  Circuits. — (See  Elec- 
tricity, Multiple  Distribution  of,  by  Constant 
Potential  Circuits?) 

Multiple        Electric-Gaslighting.— (See 

Gaslighting,  Multiple  Electric?) 

Multiple-Series.— A  multiple  connection 
of  series  groups.  (See  Connection,  Series 
Multiple) 

Usage  in  regard  to  this  term  is  divided.  By 
some  the  term  multiple-series  is  applied  to  a  series 
connection  of  parallel  groups.  This  is  done  on 
account  of  the  order  of  the  words,  multiple-series 
indicating,  it  is  claimed,  a  series  connection  of 
multiple  groups. 

Multiple-Series  Circuit. — (See  Circuit, 
Multiple-  Series.) 

Multiple-Series-Connected  Electro-Re- 
ceptive Devices. — (See  Devices,  Electro- 
Receptive,  Multiple-  Series-  Connected.) 

Multiple  -  Series  Connected     Sources. — 

(See  Sources,  Multiple-Series-Connected.) 

Multiple-Series-Connected  Translati  ng 
Devices. — (See  Devices,  Translating,  Mul- 
tiple-Series-Connected) 

Multiple-Series  Connection. — (See  Con- 
nection, Multiple-Series. ) 

Multiple-Switch  Board.  —  (See  Board, 
Multiple-Switc  I.) 

Multiple  Transformer.  —  (See  Trans- 
former, Multiple?) 

Multiple  Transmission. — (See  Trans- 
mission, Multiple?) 

Multiple  Working  of  Dynamo-Electric 
Machines. — (See  Working,  Multiple,  of 
Dynamo-Electric  Machines) 

Multiplex  Telegraphy.  —  (See  Teleg- 
raphy, Multiplex) 

Mnltiplicafor. — A  word  sometimes  used 
for  multiplier. 

Multiplier,  Galvanic A  term  for- 
merly applied  to  a  galvanometer.  (See  Gal- 
vanometer?) 

Multiplier,  Schweigger's The 

name  first  given  to  a  coil  consisting  of  a 


Mul.] 


376 


[Nee, 


number  of  turns  of  insulated  wire,  provided 
for  the  purpose  of  increasing  the  strength  of 
the  magnetic  field  produced  by  an  electric 
current,  and  consequently  the  amount  of  its 
deflecting  power  on  a  magnetic  needle. 

Schweigger's  multiplier  was  in  fact  an  early 
form  of  galvanometer.  (See  Galvanometer.) 

Multiplying1  Power  of  Shunt.  —  (See 
Shunt,  Multiplying  Power  of.) 

Multipolar  Armature.  —  (See  Armature, 
Multipolar) 

Multipolar  Dynamo-Electric  Machine.  — 
(See  Machine,  Dynamo-Electric,  Multipo- 


Muscular,   Electro 


-Pertaining    to 


Multipolar-Electric    Bath.—  (See    Bath, 

Multipolar  Electric.) 

Muscle  Current.  —  (See  Current,  Muscle) 
Muscles,  Electrical  Excitation  of  -- 

(See  Excitation,  Electro-Muscular) 


the  influence  of  electricity  on  the  muscles. 

Muscular  or  Nerve  Fibre,  Excitability 

of (See    Excitability,     Electric,    oj 

Nerve  or  Muscular  Fibre) 

Muscular   Pile,    Matteucci's (See 

Pile,  Muscular,  Matteucci's) 

Musket,  Electric A  gun  in  which 

the  charge  is  ignited  by  a  platinum  wire  ren- 
dered incandescent  by  the  action  of  a  bat- 
tery placed  in  the  stock  of  the  gun. 

Mutual  Inductance. — (See  Inductance) 

Mutual      Induction.  —  (See     Induction, 
Mutual.) 

Mutual  Induction,  Co-efficient   of 

— (See  Induction,  Mutual,  Co-efficient  of.) 

Myria  (as  a  prefix). — A  million  times. 


N. — A  contraction  employed  in  mathe- 
matical writings  for  the  whole  number  of 
lines  of  magnetic  force  in  any  magnetic  cir- 
cuit. 

N. — A  contraction  for  North  Pole. 

This  N,  may  be  distinguished  from  the  N,  used 
for  expressing  the  whole  number  of  lines  of  mag- 
netic force,  by  making  the  former  light  and  the 
latter  heavy. 

N.  H.  P. — A  contraction  for  Nominal 
Horse-Power. 

Nominal  horse-power  is  a  somewhat  indefi- 
nite term  for  a  quantity  dependent  on  the  length 
of  stroke  and  the  dimensions  of  the  cylin- 
der. This  quantity  is  a  dependent  one,  be- 
cause  it  varies  necessarily  with  the  type  of  en- 
gine. 

Nascent  State. — (See  State,  Nascent.) 

Natural  Currents. — (See  Currents,  Nat- 
ural) 
Natural  Law. — (See  Law,  Natural?) 

Natural  Magnet. — (See  Magnet,  Nat- 
ural^ 


Natural  Unit  of  Electricity.— (See  Elec- 
tricity, Natural  Unit  of) 
Natural  Unit  of  Quantity  of  Electricity, 

— (See  Electricity,  Unit  Quantity  of,  Natu- 
ral) 

Nautical  Mile. — (See  Mile,  Nautical) 

Needle  Annunciator. — (See  Annunciator, 
Needle) 

Needle,  Astatic A  compound  mag- 
netic needle  of  great  sensibility,  possessing 
little  or  no  directive  power. 

An  astatic  needle  consisting  of  two  separate 
magnetic  needles,  rigidly  connected  together 
and  placed  parallel  and  directly  over  each 
other,  with  opposite  poles  opposed. 

An  astatic  needle  is  shown  in  Fig.  402.  The 
two  magnets  N  S,  and  S'  N',  are  directly  opposed 
in  their  polarities,  and  are  rigidly  connected  to- 
gether by  means  of  the  axis  a,  a.  So  disposed, 
the  two  magnets  act  as  a  very  weak  single  needle 
when  placed  in  a  magnetic  field. 

Were  the  two  magnets  N  S,  and  S'  N',  of  ex- 
actly equal  strength,  with  their  poles  placed  in 
exactly  the  same  vertical  plane,  they  would  com- 
pletely neutralize  each  other,  and  the  needle 


flee.] 


377 


[Xee. 


would  have  no  directive  tendency.     Such  a  sys- 
tem would  form  an  Astatic  Pair  or  Couple. 

In  practice  it  is  impossible  to  do  this,  so  that  the 


Fig.  402.     Astat  c  Needle. 

needle  has  a  directive  tendency,  which  is  often 
east  and  west. 

The  cause  of  the  east  and  west  directive  ten- 
dency of  an  unequally  bal- 
anced astatic  system  will 
be  understood  from  an  in- 
spection of  Fig.  403.  Un- 
less  the  two  needles,  N  S, 
and  S'  N',  are  exactly  op-  ;a 

posed,  they  will  form  a  Fi.'.4<>3-  Astatic  Pair. 
single  short  magnet,  N  N  NN,  S  S  S  S,  the  poles 
of  which  are  on  the  sides  of  the  needle.  The 
system  pointing  with  its  sides  due  n-rth  and 
south  will  appear  to  have  an  east  and  we.-t  direc- 
tion. 

The  principal  use  of  the  astatic  needle  is  in  the 
astatic  galvanometer,  in  which  the  needle  is  de- 
flected by  the  passage  of  an  electric  current 
through  a  conductor  placed  near  the  needle. 
Therefore  it  is  evident  that  one  of  the  needles 
must  be  outside  and  the  other  inside  the  coil.  In 
the  most  sensitive 
form  of  galvanome- 
ter there  is  also  a 
coil  surrounding  the 
upper  needle,  the 
two  coils  being  op- 
positely connected, 
so  that  the  deflection 
on  both  needles  is  in 
the  same  direction, 
and  the  deflecting  Fig  404.  Astatic  System. 
power  is  equal  to  the  sum  of  the  two  coils,  while 
the  direc  ive  power  of  the  needles  is  the  differ- 
ence of  their  magnetic  intensities. 

In  the  astatic  system,  as  shown  in  Fig.  404,  the 
current,  which  flows  above  one  needle,  flows  be- 
low the  other,  and  therefore  deflects  both  needles 


in  the  same  direction,  since  their  poles  point  in 
opposite  directions. 

In  some  galvanometers  a  varying;  degree  of 
sensitiveness  is  obtained  by  means  of  a  magnet, 
called  a  compensating  magnet,  placed  on  an  axis 
ab  .ve  the  magne  ic  needle.  As  the  compensat 
ing  magnet  is  moved  towards  or  away  from  the 
needle  the  effect  of  the  earth's  field  is  varied,  and 
with  it  the  sensitiveness  of  the  galvanometer. 
Such  a  magnet  may  form  with  the  needle  an 
astatic  system.  (See  Magnet,  Compensating. 
Galvanometer,  Astatic.  Galvanometer,  Mirror. 
Multiplier,  Schweigger' s). 

Needle  Electrode. — (See  Electrode,  Nee- 
dle) 

Needle,  Elongation  of  •  — A  phrase 

sometimes  used  for  the  angular  deflection  of 
a  needle. 

Needle,  Magnetic A  straight  bar- 
shaped  needle  of  magnetized  steel,  poised 
near  or  above  its  centre  of  gravity,  and  free 
to  move  either  in  a  horizontal  plane  only,  or 
in  a  vertical  plane  only,  or  in  both. 

A  magnetic  needle  free  to  move  in  a  vertical 
plane  only  is  called  a  dipping  needle.  A  mag- 
netic needle  free  to  move  in  a  horizontal  plane 
only,  as  shown  in  Fig.  405,  is  the  form  employed 


Fi*.  40  j      Magnetic  Needle. 

in  the  mariner's  compass.     This  form  of  magnetic 
needle  is  the  one  most  commonly  employed. 

For  use  as  a  mariner's  compass  the  needle  is 
supported  on  gimbals  and  placed  in  a  box  pro- 
vided with  a  card  on  which  are  marked  the 
points  of  the  compass.  (See  Compass,  Azimuth. 
Compass,  Points  of.) 

Needle,  Magnetic,  Annual  Variations  of 

Variations  in  the  value  of  the  mag- 


N-er.J 


378 


[Nee. 


netic  declination  that  take  piace  at  regular 
penods  of  the  year. 

The  annual  variations  of  the  magnetic  field  were 
discovered  by  Cassini  in  1786. 

Needle,   Magnetic,    Daily    Tariation   of 

Variations  in  the  value  of  the  magnetic 

declination  that  take  place  at  different  periods 
of  the  day. 

It  was  noticed,  for  example,  in  London  that  the 
north  pole  of  the  magnetic  needle  begins  to  move 
westward  between  7  and  8  A.  M.  and  continues 
this  movement  until  I  P.  M.,  when  it  begins  to 
move  towards  the  east  until  near  10  p.  M.,  when 
it  again  begins  its  westward  course. 

Needle,    Magnetic,    Damped    — A 

magnetic  needle  so  placed  as  to  quickly  come 
to  rest  after  it  has  been  set  in  motion.  (See 
Damping?) 

Magnetic  damping  is  readily  effected  by  caus- 
ing the  needle  to  move  near  a  metallic  plate.  On 
the  motion  of  the  needle  the  currents  set  up  in  the 
plate  by  dynamo  electric  induction  tend,  accord- 
ing to  Lenz's  law,  to  oppose  the  motions  pro- 
ducing them.  (See  Induction,  Electro-Dynamic. 
Laws,  Lenz's.) 

Needle,  Magnetic,  Declination  of  — 

The  angular  deviation  of  the  magnetic  needle 
from  the  true  geographical  north. 

The  variation  of  the  magnetic  needle. 

The  declination  of  the  magnetic  needle  is  either 
E.  or  W.,  (See  Declination,  Angle  of.) 

Declination,  or  variation,  is  different  at  dif- 
ferent parts  of  the  earth's  surface. 

Lines  connecting  places  which  have  the  same 
value  and  direction  for  the  declination  are  called 
isogonal  lines.  A  chart  on  which  the  isogonal 
lines  are  marked  is  called  a  variation  chart. 

The  value  of  the  declination  varies  at  dif- 
ferent times.  These  variations  of  the  declination 
are: 

(l.)  Secular,  or  those  occurring  during  great 
intervals  of  time.  Thus,  in  London,  in  1580  the 
magnetic  needle  had  a  variation  of  about  n 
degrees  east.  This  eastern  declination  decreased 
in  1622  to  6  degrees  E.,  and  in  1680  the  needle 
pointed  to  the  true  north.  In  1692  the  declina- 
tion was  6  degrees  W.;  in  1730,  13  degrees  W. ; 
in  1765,  20  degrees  W. ;  and  in  1818  the  needle 
reached  its  greatest  western  declination  and  is 


now  moving  eastwards.  The  declination,  how- 
ever, is  still  west. 

(2.)  Annual,  the  needle  varying  slightly  in  its 
declination  during  different  seasons  of  the  year. 

(3.)  Diurnal,  the  needle  varying  slightly  in  its 
declination  during  different  hours  of  the  day. 

(4.)  Irregular,  or  those  which  occur  during 
the  prevalence  of  a  magnetic  storm. 

It  has  been  discovered  that  the  occurrence  of  a 
magnetic  storm  is  simultaneous  with  the  occur- 
rence of  an  unusual  number  of  sun  spots.  (See 
Spots,  Sun.) 

Needle,  Magnetic,  Deflection  of  — 

The  movement  of  a  needle  out  of  a  position  of 
rest  in  the  earth's  magnetic  field  or  in  the 
field  of  another  magnet,  by  the  action  of  an 
electric  current  or  another  magnet. 

The  deflection  of  the  needle  is  sometimes  called 
its  elongation.  This  latter  term  is,  however,  but 
little  used,  and  is  unnecessary. 

Needle,    Magnetic,     Dipping   — A 

magnetic  needle  suspended  so  as  to  be  tree 
to  move  in  a  vertical  plane,  employed  to  de- 
termine the  angle  of  dip  or  the  magnetic  in- 
clination. (See  Dip,  Magnetic,  Inclination, 
Magnetic.  Inclinometer.  Chart,  Inclina- 
tion^] 

A  dipping  needle  is  shown  in  Fig.  406.    The 


angle  B  O  C,  which  marks  the  deviation  of  the 
needle  from  the  horizontal  position,  is  called  the 
angle  of  dip. 


Nee.] 


379 


[Neg. 


Needle,  Magnetic,  Directive  Tendency  of 

— The  tendency  of  a  magnetic  needle  to 


move  so  as  to  come  to  rest  in  the  direction  of 
the  lines  of  the  earth's  magnetic  field. 

The  directive  power  of  the  magnetic  needle  is 
due  to  the  attraction  of  the  earth's  magnetic  poles 
for  the  poles  of  the  needle,  or  to  the  action  of  the 
earth's  magnetic  field.  Since  the  force  of  the 
earth's  magnetism  forms  a  couple,  there  is  no 
tendency  for  the  needle  to  move  bodily  forward 
towards  either  of  the  earth's  poles.  Its  tendency 
is  merely  to  rotate  until  it  comes  to  rest  within 
the  lines  of  the  earth's  magnetic  field,  entering  at 
its  south  pole,  passing  through  its  mass  and 
coming  out  at  its  north  pole. 

Of  course  this  would  be  true  in  the  case  of  a 
directing  magnet  only  when  it  is  at  a  great  dis- 
tance from  the  needle.  Otherwise,  there  would 
be  motion  towards  the  poles  as  well  as  rotation. 

Needle,  Magnetic,  Inclination  or  Dip  of 

The  deviation  of  a  mechanically  bal- 
anced magnetic  needle  from  a  horizontal  po- 
sition. 

The  direction  of  a  magnetic  needle  in  all  parts 
of  the  earth,  except  at  the  magnetic  equator, 
differs  from  a  level  or  horizontal  position.  One 
of  its  ends  inclines  or  dips  towards  the  ground. 
(See  Dip,  Magnetic.  Needle,  Magnetic,  Dipping.) 

Needle,  Magnetic,  Orientation  of  — 

The  coming  to  rest  of  a  magnetic  needle  in 
the  earth's  magnetic  field. 

Needle,  Magnetic,  Variation  of 

The  angular  deviation  of  a  magnetic  needle 
from  the  true  geographic  north. 

The  declination  of  the  magnetic  needle. 
(See  Declination.} 

Needle  of  Oscillation. — A  small  magnetic 
needle  employed  for  measuring  the  intensity 
of  a  magnetic  field  by  counting  the  number  of 
oscillations  the  needle  makes  in  a  given  time, 
when  disturbed  from  its  position  of  rest  in 
such  field.  (See  Magnetization,  Intensity  of. 
Lines,  Isodynamic.) 

This  use  of  a  magnetic  needle  in  determining 
the  magnetic  intensity  of  any  place  is  analogous 
to  the  use  of  the  pendulum  in  determining  the  in- 
tensity of  gravity  at  any  place. 

Suppose,  for  example,  that  at  a  certain  place  the 
needle  made  245  oscillations  in  ten  minutes,  and 
13— Vol.  1 


that  at  another  place  it  made  211  in  the  same 
time.  Then  the  relative  intensities  at  these  two 
places  would  be  as  the  square  of  these  two  num- 
bers, or  as  I  :  1.3482. 

Needle,  Telegraphic A  needle  em- 
ployed in  telegraphy  to  represent  by  its  move- 
ments to  the  left  or  right  respectively  the  dots 
and  dashes  of  the  Morse  alphabet.  (See 
Telegraphy,  Needle  System  of.) 

Needle,  Throw  of A  phrase  some- 
times used  for  the  angular  deflection  of  a 
needle,  particularly  when  the  needle  is  swing- 
ing. 

The  displacement  of  the  magnetic  needle  is 
called  the  deflection,  the  elongation,  or  the  throw. 
The  first  will  appear  to  be  the  preferable  term 
when  the  needle  conies  to  rest  in  a  displaced  posi- 
tion. 

Negative  Charge. — (See  Charge,  Nega- 
tive^ 

Negative  Direction  of  Electrical  Con- 
vection of  Heat. — (See  Direction,  Negative, 
of  Electrical  Convection  of  Heat.) 

Negative  Direction  of  Simple-Harm  on  ic 
Motion. — (See  Motion,  Simple-Harmonic, 
Negative  Direction  of.) 

Negative  Electricity.— (See  Electricity, 
Negative.) 

Negative      Electrode.— (See      Electrode, 
Negatived) 
Negative  Element  of  a  Voltaic  Cell.— 

(See  Element,  Negative,  of  a  Voltaic  Cell.) 
Negative  Feeders.— (See  Feeders,  Nega- 
tive^ 

Negative  Omnibus  Bars.— (See  Bars, 
Negative  Omnibus?) 

Negative  Phase  of  Electrotonus. — (See 
Electrotonus,  Negative  Phase  of.} 

Negative    Plate  of  Storage  Battery. — 

(See  Plate,  Negative,  of  Storage  Cell.} 

Negative  Plate  of  Voltaic  Cell.— (See 
Plate,  Negative,  of  Voltaic  Cell.} 

Negative  Pole. — (See  Pole,  Negative.} 
Negative  Potential. — (See  Potential,  Neg- 
ative^ 

Negative  Side  of  Circuit.— (See  Circuit, 
Negative  Side  of.} 


380 


[Nig. 


Negative  Wire.— (See  Wire,  Negative!) 

Negatively. — In  a  negative  manner. 

Negatively  Excited. — Charged  with  nega- 
tive electricity.  (See  Electricity,  Negative?) 

Nerve  or  Muscular  Fibre,  -  Excitability 

of  —(See  Excitability,  Electric,  of 

Nerve  or  Muscular  Fibre.} 

Nerves,  Action  of  Electricity  on  — 

Stimulating  and  other  actions  produced  in 
nerves  by  the  passage  of  electricity  through 
them,  dependent  on  the  direction  and  char- 
acter of  the  current.  (See  Electrotonus. 
Galvanization.  Faradization.  Galvano- 
Faradization?) 


Net,    Faraday's 


— An  insulated  net 


of  cotton  gauze,  or  other  similar  material, 
capable  of  being  turned  inside  out  without 
being  thereby  discharged,  employed  for  de- 
monstrating that  in  a  charged,  insulated  con- 
ductor the  entire  charge  is  accumulated  oh 
the  outer  surface  of  the  conductor. 


Fig.  407.    Faraday's  Net. 

Faraday's  net,  as  shown  in  Fig.  407,  consists 
of  a  bag  N,  of  cotton  gauze,  or  mosquito  netting, 
supported  on  an  insulating  stand  I.  When  tested 
by  a  proof  plane,  no  free  electric  charge  is  found 
on  the  inside,  though  such  a  charge  is  readily 
v  detected  by  the  same  means  on  the  outside.  By 
I  the  aid  of  the  silk  strings  S,  S,  the  bag  can  be 
turned  inside  out,  when  the  charge  will  then  all 
be  found  on  the  then  inside,  or  the  now  outside. 
Faraday  was  in  the  habit  of  protecting  his 
delicate  electroscopes  against  outside  electrifica- 
tion by  covering  them  with  gauze.  To  properly 
act  as  an  electric  screen,  the  gauze  should  be  con- 
nected with  the  earth. 

Faraday  constructed  a  small  insulated  room, 


twelve  feet  in  height,  breadth  and  depth,  covered 
on  the  inside  with  tin-foil,  and,  on  charging  this 
room  from  the  outside,  he  was  unable  to  detect 
the  presence  of  any  charge  on  the  inside,  even  by 
the  aid  of  his  most  delicate  instruments.  This 
room  is  often  referred  to  as  Faraday's  Cube. 


Nets,  Torpedo 


— Steel  wire  netting 
suspended  from  or  attached  to  a  ship's  side 
for  the  purpose  of  ensuring  protection  against 
moving  torpedoes. 

Network  of  Currents. — (See  Currents, 
Network  of.  Laws,  Kirchhoff's?) 

Neutral  Armature. — (See  Armature, 
Neutral?) 

Neutral  Feeder.  —  The  feeder  that  is 
connected  with  the  neutral  or  intermediate 
terminal  of  the  dynamos  in  a  three-wire  sys- 
tem of  distribution.  (See  Feeders?) 

Neutral  Line  of  Commutator  Cylinder. 

— (See  Line,  Neutral,  of  Commutator 
Cylinder?) 

Neutral  -  Omnibus  Bars.  —  (See  Bars, 
Neutral-Omnibus.) 

Neutral  Point.— (See  Point,  Neutral.) 

Neutral  Points  of  a  Dynamo-Electric 
Machine. — (See  Points,  Neutral,  of  Dynamo- 
Electric  Machine?) 

Neutral  Points  of  Magnet. — (See  Points, 
Neutral,  of  Magnet?) 

Neutral  Points  of  Thermo-Electric  Dia- 
gram.— (See  Points,  Neutral,  of  Thermo- 
Electric  Diagram?) 

Neutral-Relay  Armature.  -  (See  Arma- 
ture, Neutral-Relay?) 

Neutral  Section  of  Magnet. — (See  Sec- 
tion, Neutral,  of  Magnet?) 

Neutral  Wire.— (See  Wire,  Neutral.) 
Neutral  Wire  Ampere-Meter.— (See  Am- 
pere-Meter, Balance  or  Neutral  Wire?) 
New  Ohm. — (See  Ohm,  New.) 
Nickel  Bath. -(See  Bath,  Nickel?) 

Nickeling,  Electro Electroplating 

with  nickel.     (See  Plating,  Electro?) 

Nickel-Plating.- (See  Plating,  Nickel?) 
Night  Bell.- (See  Bell,  Night* 


Nod.] 


381 


[Noi. 


Nodal  Point.— (See  Point,  Nodal.} 

Nodes,  Electrical  —  —  Points  in  an  open 
circuited  conductor,  through  which  electrical 
oscillations  are  passing,  which  possess  a  con- 
stant mean  value  of  potential,  while  the  poten- 
tial at  its  ends  alternates  between  two  fixed 
limits. 

Points  on  a  conductor  where  the  strength 
of  the  induced  oscillatory  current  is  equal  to 
zero. 

The  nodal  points  on  a  conductor  through  which 
electrical  oscillations  are  passing  therefore  cor- 
.  respond  closely  to  the  nodes  on  a  vibrating  wire 
or  cord. 

Dr.  Hertz  employed  the  following  appara- 
tus in  order  to  show  the  position  of  two  nodes 
in  a  conductor:  An  induction  coil,  A.  had  its  sec- 
ondary terminals  connected  as  shown  in  Fig.  408, 


Fig.  408.      Nodes  in  Conductor. 

to  two  metallic  spheres,  C  and  C'.  The  spark  mi- 
crometer circuit,  a  c  d  b,  was  placed  near  it,  as 
shown,  and  the  sparking  distance  of  the  secondary 
urcuit  of  the  induction  eoil  adjusted,  ho  that  the 
spark  micrometer  circuit  was  in  unison  wiih  it. 
When  sparks  were  passed  between  the  terminals 
of  the  induction  coil  A,  sparks  pas=e<!  between  the 
terminals  I  and  2,  at  M,  under  the  influe  ce  of 
resonant  action. 

If,  now,  a  second  micrometer  circuit,  e  g  h  f, 
exactly  similar  to  a  c  d  b,  was  added,  as  shown  in 
the  figure,  and  the  two  joined  near  the  term.nals  I 
2  3  4,  by  conducting  wires,  as  shown,  the  entire 
system  of  the  micrometer  circuit  formed  a  closed 
metallic  circuit,  the  fundamental  vibration  of 
which  would  have  two  nodes,  one  at  the  middle 
point  of  c  d,  and  the  other  at  g  h.  The  inter- 
nodes  would  be  at  the  junctions  i  3,  and  2  4,  and 
under .  these  circumstances  a  true  resonant  ac- 
tion existed  between  the  secondary  circuit  and  the 
micrometer  circuit,  as  was  shown  by  the  fact  that 
any  alteration  in  the  circuit  e  g  h  f ,  whether  by 


increasing  or  decreasing  its  length,  diminished 
the  sparking  distance.  Since  the  conductor  con- 
necting points  2,  and  4,  was  in  the  position  of 
the  node,  where  the  strength  of  the  excited  oscil- 
latory current  was  zero,  its  removal  from  between 
these  points  should  have  no  influence  on  the 
intensity  of  the  vibration.  This  was  found  on 
trial  to  be  the  case.  Electrical  vibrations  may 
therefore  be  excited  by  electrical  resonance  in 
conductors  corresponding  not  only  to  the  simple 
fundamental  note  or  vibration,  but  also  to  the 
higher  electrical  overtones. 

The  apparatus  shown  in  Fi  *.  409,  from  Tesla, 
illustrates  the  phenomena  of  alternative  path,  as 
well  as  electric  nodes.  The  terminals  of  an  in- 
duction coil  are  connecter),  as  shown,  to  a  con- 
denser and  to  a  thick  copper  conductor.  Though 
the  two  incandescent  lamps  are  placed  as  shown, 
yet  they  are  raised  to  luminosity  by  a  species  of 
brush  discharge  that  passes  through  them,  al- 
though they  would  be  short  circuited  to  any  cur- 
rent but  an  oscillatory  discharge. 


Fig.  4O<).    Nodes  in  a  Conductor. 

Nodular  Deposit,  Electro-Metallurgical 

— (See  Deposit,  Electro-Metallurgical 


Nodular^) 
Noisy  Arc. — (See  Arc,  Noisy.) 


Nom.J 


382 


[Num. 


Nominal   Candle-Power.  —  (See   Power, 
Candle,  Nominal?) 
Non- Automatic    Variable    Resistance.— 

(See  Resistance,  Variable,  Non- Automatic.} 

Non-Conductors.  —  Substances  that  offer 
so  great  resistance  to  the  passage  of  an  elec- 
tric current  through  their  mass  as  to  practi- 
cally exclude  a  discharge  passing  through 
them. 

Njn  conductors  are  called  insulators,  because 
they  electrically  insulate  substances  placed  on  or 
surrounded  by  them. 

The  terms  non-conductors  or  insulators  are 
ordinarily  used  in  a  relative  sense  to  mean  bodies 
which  allow  no  practical  or  appreciable  current 
to  pass  through  them,  since  there  are  no  sub- 
stances known,  apart,  perhaps,  from  the  universal 
ether,  that  absolutely  prevent  the  flow  of  an  elec- 
tric current,  the  difference  of  potential  of  which 
is  sufficiently  great 

The  entire  absence  of  ordinary  matter,  as  in  the 
case  of  a  high  vacuum,  appears  to  render  a  high 
vacuum  very  nearly,  if  not  entirely,  an  absolute 
insulator. 

Non-Electrics.— A  term  formerly  applied 
to  substances  like  metals  or  other  conductors 
which  appeared  not  to  become  electrified  by 
friction. 

The  term  non-electric,  was  used  in  contradis- 
tinction to  electrics,  or  substances  readily  elec- 
trified by  friction.  The  distinction  no  longer 
holds,  since  non-electrics,  ifinsulated,  are  readily 
electrified  by  friction. 

Non-Homogeneous  Current-Distribu- 
tion.— (See  Current,  Non-Homogeneous, 
Distribution  of.) 

Non-Illumined  Electrode. — (See  Elec- 
trode, Non-Illumined) 

Non-Inductive  Resistance.— (See  Resist- 
ance, Non-Inductive.) 

Non-Oscillatory  Discharge. — (See  Dis- 
charge, Non-Oscillatory) 

Non- Polarized  Armature.—  (See  Arma- 
ture, Non-Polarized?] 

Non-Polarizable  Electrodes. — (See  Elec- 
trodes, Non-Polar  izable?) 

Non-Wasting  Electrode.—  (See  Electrode, 
Non-  Wasting?) 


Normal  Day,  Magnetic (See  Day, 

Normal  Magnetic.) 

Northern  Light.— The  Aurora  Borealis. 
(See  Aurora  Borealis?) 

Notation,  Algebraic A  system  of 

arbitrary  symbols  employed  in  algebra. 

The  following  brief  description  of  the  notation 
employed  in  algebra  is  for  the  use  of  the  non- 
mathematical  reader. 

Quantities  are  represented  in  algebra  by  let 
ters,  such  as  a,  and  b,  x,  and  y,  etc. 

Addition  is  represented  thus:  a  +  b. 

Subtraction  is  represented  thus:  a — b. 

Multiplication  is  represented  thus:  a  X  b,  or 
simply  by  writing  the  letters  next  to  each  other  ab. 

Division  is  represented  thus:  a  -j-  b,  or  3 

An  Exponent,  or  figure  placed  to  the  right  of  a 
letter,  above  it  as  a3,  indicates  that  the  quantity 
represented  by  a,  is  to  be  multiplied  by  itself  three 
times,  as  a  X  a  X  a,  or  a  a  a. 

A  Co-efficient,  or  figure  placed  to  the  left  of  a 
quantity,  indicates  the  number  of  times  that  quan- 
tity is  to  be  taken;  thus,  3  a,  indicates  that  a  is  to 
be  added  three  times,  thus:  a-f-a-|-a,or3Xa. 

A  Radical  Sign  or  Root,  thus  \/a,  or  2v/a, 
indicates  that  the  square  root  of  the  quantity  at 
is  to  be  taken.  In  the  same  manner  s\/~a,  indi- 
cates that  the  cube  root  of  a  is  to  be  taken. 


»*. 


These  expressions  are  sometimes  written  a*,  or 
Equality  is  indicated  thus:  as=a  XaXa,  or 


A  negative  exponent  a~*  indicates  _,  or  is  the 

a2 

exponent  of  the  reciprocal  of  the  quantity  indi- 
cated. 

Null  or  Zero  Method. — (See  Method, 
Null  or  Zero?) 

Null  Point.— (See  Point,  Null.) 

Number,  Diacritical Such  a  num- 
ber of  ampere-turns  at  which  a  given  core 
would  receive  a  magnetization  equal  to  half 
saturation. 


Obs.] 


383 


[Ohm. 


£1. — A  contraction  for  megohm.  (See 
Okm,  Meg.) 

&. — A  contraction  for  ohm.     (See  Ohm?) 
Obscure  Heat. — (See  Heat,  Obscure?) 
Observation  Mine.— (See  Mine,  Observa- 
tion?) 

Observatory,  Magnetic An  obser- 
vatory in  which  observations  of  the  variations 
in  the  direction  and  intensity  of  the  earth's 
magnetic  field  are  made. 

Magnetic  observatories  are  generally  furnished 
with  self-registering  magnetic  apparatus,  such  as 
magnetographs,  magnetometers,  inclinometers. 
(See  Magnetometer.  Magnetograph.  fnclinome- 
ter.) 

Magnetic  observatories  are  generally  con- 
structed entirely  of  non-magnetic  materials;  that 
is,  of  such  materials  as  are  destitute  of  paramag- 
netic properties. 

Obtuse  Angle.— (See  Angle,  Obtuse?) 
Occlusion  of  Gas.— (See   Gas,  Occlusion 

Odorscope. — An  apparatus  in  which  the 
determination  of  an  odor  was  attempted  by 
the  measurement  of  the  effect  the  odorous 
vapor,  or  effluvia,  produced  on  a  variable 
contact  resistance. 

The  microtasimeter  was  used  in  connection 
with  the  odorscope.  (See  Diagometer,  Rous- 
seau's. Microtasimeter.'] 

Oerstedt,  An A  proposed  term  for 

the  unit  of  electric  current,  in  place  of  an 
ampere. 

The  term  has  not  been  adopted. 

Ohm. — The  unit  of  electric  resistance. 

Such  a  resistance  as  would  limit  the  flow 
of  electricity  under  an  electromotive  force  of 
one  volt  to  a  current  of  one  ampere,  or  to  one 
coulomb  per  second.  (See  Unit,  B.  A.  Ohm, 
Legal.  Ohm,  Standard?) 

A  value  equal  to  10°  absolute  electro-mag- 
netic units. 

A  value  which  is  represented  by  a  velocity 
of  10°,  or  1, 000,000,000  centimetres  per  second. 


It  may  be  difficult  at  first  to  see  how  resistance 
can  be  correctly  represented  by  a  velocity.  The 
following  consideration  may  render  this  clear : 
The  formula  for  calculating  the  velocity  is 

D 

V  =  -,p  or  the  velocity  equals  the  distance  passed 

through  in  unit  time.  Now,  by  examining  the 
formula  for  the  value  of  the  resistance,  expressed 
in  terms  of  the  electro-magnetic  units  (see 
Units,  Electro-Magnetic,  Dimensions  of),  it  may 
be  seen  to  be  that  resistance  = 


Electromotive  force 
Curi  ent. 


But  this  value  is  of  the  nature  of  a  velocity, 
being  equal  to  the  length,  divided  by  the  time. 
Resistance,  therefore,  has  the  dimensions  of  a 
velocity. 

This  is  clearly  expressed  by  Silvanus  P.  Thomp- 
son in  his  ' '  Elementary  Lessons  in  Electricity 
and  Magnetism,"  as  follows,  viz.:  "  Suppose  we 
have  a  circuit  composed  of  two  horizontal  coils, 
C  S,  and  D  T  (Fig.  410),  i  centimetre  apart, 
joined  at  C  D,  and  completed  by  means  of  a 
sliding  piece,  A  B.  Let  this  variable  circuit  be 
placed  in  a  uniform  magnetic  field  of  unit  inten- 
sity, the  lines  of  force  being  directed  vertically 
downwards  through  the  circuit. 

"If,  now,  the  slider  be  moved  along  towards 
S  T,  with  a  velocity  of  n,  centimetres  per  second, 
the  number  of  additional  lines  of  force  embraced 
by  the  circuit  will  increase  at  the  rate  of  n,  per 
second  ;  or,  in  other  words,  there  will  be  an  in- 


g.  410.     Resistance  as  a  Velocity. 


duced  electromotive  force  impressed  upon  the  cir- 
cuit, which  will  cause  a  current  to  flow  through 
the  slider  from  A  to  B.  Let  the  rails  have  no 
resistance,  then  the  strength  of  the  current  will 
depend  on  the  resistance  of  A  B.  Now,  let  A  B, 
move  at  such  a  rate  that  the  current  shall  be  of 
unit  strength.  If  its  resistance  be  one  absolute 
(electro-magnetic)  unit,  it  need  only  move  at  the 
rate  of  I  centimetre  per  second.  If  its  resistance 
be  greater,  it  must  move  with  a  proportionately 


Ohm.J 


384 


[Ohm. 


greater  velocity  ;  the  velocity  at  which  it  must 
move  to  keep  up  a  current  of  unit  strength  being 
numerically  equal  to  its  resistance.  The  resist- 
ance  known  as  "  i  ohm  "  is  intended  to  be  so9  ab- 
solute electro-magnetic  units,  and,  therefore,  is 
represented  by  a  velocity  of  io9  centimetres,  or 
10,000,000  metres  (/  earth-quadrant)  per 
second."' 

Ohm,  B.  A. A  contraction  for 

British  Association  ohm. 

Ohm,  Board  of  Trade A  unit  of  re- 
sistance as  determined  by  a  committee  of  the 
English  Board  of  Trade. 

A  committee  consisting  of  Sir  W.  Thomson, 
Lord  Rayleigh,  Dr.  J.  Hopkinson  and  other 
authorities  appointed  by  the  Board  of  Trade 
(England)  has  recently  recommended  that  the 
ohm  be  taken  as  the  resistance  of  a  column  of 
mercury  106.3  centimetres  in  length  and  one 
square  millimetre  area  of  cross-section  at  o  de- 
grees C.  and  since  this  value  agrees  with  the  best 
experimental  results,  it  will  probably  be  generally 
and  finally  adopted. 

Ohm,    British    Association  — The 

British  Association  unit  of  resistance, 
adopted  prior  to  1884. 

The  value  of  the  unit  of  electric  resistance,  or 
the  ohm,  was  determined  by  a  Committee  of  the 
British  Association  as  being  equal  to  the  resistance 
at  o  degree  C.  of  a  column  of  mercury  I  square 
millimetre  in  area  of  cross-section  and  104.9 
centimetres  in  length.  This  length  was  taken  as 
coming  nearest  the  value  of  the  true  ohm  de- 
auced  experimentally  from  certain  theoretical 
considerations.  Subsequent  re-determinations 
showed  the  value  so  obtained  to  be  erroneous. 

The  value  of  the  ohm  is  now  taken  internation- 
ally, as  adopted  by  the  International  Electric 
Congress  in  1884,  as  the  resistance  of  a  column 
of  mercury  106  centimetres  in  length,  and  I 
square  millimetre  in  area  of  cross-section.  This 
last  value  is  called  the  legal  ohm,  to  distinguish  it 
from  the  B.  A.  ohm,  which,  as  above  stated,  is 
equal  to  a  mercury  column  104.9  centimetres  in 
length.  Usage  now  sanctions  the  use  of  the 
word  ohm  to  mean  the  legal  ohm. 

This  value  of  the  legal  ohm  is  provisional  until 
the  exact  length  of  the  mercury  column  can  be 
finally  determined.  (See  Ohm,  Board  of  Trade. ) 

The  following  are  the  relative  values  of  these 
units,  viz.: 


i  legal  ohm =  1.0112  B.  A.  ohm. 

"       "     =  1 .0600  Siemens  unit. 

I  B.  A.  ohm =    .9889  legal  ohm. 

i      "       " =  i  .0483  Siemens  unit. 

i  Siemens  unit =    .9540  B.  A.  ohm. 

"  "    =    .9434  legal  ohm. 

Ohm,  Legal The    resistance  of  a 

column  of  mercury  i  square  millimetre  in 
area  of  cross-section,  and  106  centimetres  in 
length,  at  the  temperature  of  o  degree  C.  or 
32  degrees  F.  (See  Unit.B.  A.) 

i  ohm  =  1.00112  B.  A.  units.  This  va!ue  of 
the  ohm  was  adopted  by  the  International  Elec- 
tric Congress,  in  1884,  as  a  value  that  should  be 
accepted  internationally  as  the  true  value  of  the 
ohm.  This  value,  however,  was  provisional,  and 
was  never  actually  legalized.  It  will  probably  be 
replaced  by  the  new  (106.3  cm-)  °hm.  (See 
Ohm,  Board  of  Trade.} 

Ohm,  Meg1 One  million  ohms. 

Ohm,  New A  term  sometimes  used 

for  the  Board  of  Trade  ohm.  (See  Ohm, 
Board  of  Trade.) 

Ohm,  Standard A  length  of  wire 

having  a  resistance  of  the  value  of  the  true 
or  legal  ohm,  employed  in  standardizing  re- 
sistance coils. 

The  standard  ohm,  as  issued  by  the  Electric 
Standards  Committee  of  England,  has  the  form 


J'tf.  411.     Standard  Ohm. 

shown  in  Fig.  411.  The  coil  of  wire  is  formed 
of  an  alloy  of  platinum  and  silver,  insulated  by 
silk  covering  and  melted  paraffine.  Its  ends  are 
soldered  to  thick  copper  rods  r,  r',  for  ready 
connection  with  mercury  cups.  The  coil  is  at 
B.  The  space  above  it  at  A,  is  filled  with  paraffine, 
except  at  the  opening  t,  which  is  provided  for 
the  insertion  of  a  thermometer. 


Ohm.J 


335 


[Ope. 


Ohm,   True An  ohm    having    the 

true  theoretical  value  of  the  ohm.    (See  Ohm.} 

Ohmage.— The  value  of  the  resistance  of 
a  circuit  expressed  in  ohms. 

Ohmic  Resistance.  —  (See  Resistance, 
Ohmic  or  True.) 

Ohmmeter. — A  commercial  galvanometer, 
devised  by  Ayrton,  for  directly  measuring  by 
the  deflection  of  a  magnetic  needle,  the  re- 
sistance of  any  part  of  a  circuit  through 
which  a  strong  current  of  electricity  is 
flowing. 

Ayrton's  ohmmeter  is  represented  diagram- 
matically  in  Fig.  412.  Two  coils  C  C,  and  c  c, 


f. 

Fig.  412,    Ayrton's  Ohmmeter. 

consisting  of  a  short  thick  wire,  and  a  long  thin 
wire,  respectively,  are  placed  at  right  angles  to 
each  other,  and  act  on  a  soft  iron  needle  situated 
as  shown.  The  short,  thick  wire  coil  C  C,  is  con- 
nected in  series  with  the  resistance  O,  to  be 
measured.  The  long,  fine  wire  coil,  of  kn<nun 
high  resistance,  is  placed  as  a  shunt  to  the  un- 
known resistance. 

Under  these  circumstances,  it  can  be  shown 
that  the  action  on  the  needle  is  that  due  to  the  ratio 
of  the  difference  of  potential  at  the  terminals  of 
the  unknown  resistance  and  the  current  strength 

in  the  thick  wire  coil,  or  R  =  — ,   as  may  be 

deduced  from  Ohm's  law. 

The  coils  are  so  proportioned  that  the  current 
when  flowing  through  1he  short  thick  wire  moves 
the  needle  to  the  zero  of  the  scale,  while  the  long 
thin  wire  produces  a  deflection  directly  propor- 
tional to  the  resistance. 

Ohm's  Law. — (See  Law  of  Ohm) 

Oil,  Colza An  oil  obtained  from  the 

seed  of  the  Brassica  oleracea,  a  species  of 
cabbage. 

Colza  oil  is  extensively  used  for  purposes  of  il- 
lumination and  in  the  carcel  standard  lamp.  (See 
Lamp)  Carcel.) 


Oil  Cup. — A  cup  containing  oil  for  lubri 
eating  machinery. 

Oil  Insulator. — (See  Insulator,  Oil.) 

Oil  Transformer.— (See  Transformer, 
Oil.) 

Oiler,  Automatic —An  oil  cup  or  res- 
ervoir that  automatically  spreads  oil  over  the 
bearings  of  r_i.  chinery  in  motion. 

Okonite. — A  variety  of  insulating  material. 

Omnibus  Bars. — (See  Bars,  Omnibus) 

Omnibus  Wires. — (See  Wires,  Omnibus^ 

Opacity,  Selective Opaque  in  a  cer- 
tain direction  or  directions  only. 

Certain  substances  are  opaque  to  polarized  lighl 
in  certain  planes  only.  Thus,  a  plate  of  tourma- 
line permits  light  polarized  in  a  certain  plane 
freely  to  pass  through  it,  but  is  entirely  opaque 
in  a  plane  at  right  angles  thereto. 

S.  P.  Thompson  and  Lodge  have  shown  that 
such  crystals  of  tourmaline  possess  curious  prop- 
erties in  regard  to  the  conduction  of  heat.  While 
warming,  the  crystal  conducts  heat  better  in  a  cer- 
tain direction  than  in  the  opposite  direction.  While 
cooling,  exactly  the  opposite  effects  are  observed. 
In  the  same  manner,  while  the  crystal  is  rising  in 
temperature,  there  is  an  accumulation  of  positive 
electricity  at  one  end,  an  1  negative  at  the  other. 
While  the  crystal  is  cooling,  the  reversa  i  s  true- 

Open-Box  Conduit.— (See  Conduit,  Open- 
Box) 

Open  Circuit. — (See  Circuit,  Open) 
Open-Circuit     Electric     Oscillations. — 

(See  Oscillations,  Open-Circuit,  Electric) 
Open-Circuit  Induction. — (See  Induction, 

Open-Circuit) 
Open-Circuit  Oscillation,  Period  of  — 

— The  time  in  which  the  oscillations  set  up  in 
a  circuit  by  electrical  resonance  require  to 
make  a  complete  one  to-and-fro  motion. 

The  period  of  an  open-circuit  electric  oscillation 
is  determined  by  the  product  of  the  co-efficients 
of  self-induction  of  the  conductor,  and  does  not 
dt-pend  on  the  composition  of  the  terminals.  It  is 
practically  independent  of  their  resistances. 

Open-Circuit  Single-Current  Signaling. — 

(See  Signaling,  Single-Current,  Open- 
Circuit) 


Ope.] 


386 


[Ore. 


Open-Circuit  Yoltaic  Cell— (See  Cell, 
Voltaic,  Open-Circuit} 

Open-Circuit  Voltmeter. — (See  Volt- 
meter, Open-Circuit,} 

Open-Circuited. — Put  on  an  open  circuit. 

Open-Circuited  Conductor. — (See  Con- 
ductor, Open-Circuited} 

Open-Circuited  Thermostat. — (See  Ther- 
mostat, Open-Circuit.} 

Open-Coil  Drum  Dynamo-Electric  Ma- 
chine.— (See  Machine,  Dynamo-Electric, 
Open-Coil  Drum} 

Open-Coil    Dynamo-Electric  Machine. — 

(See  Machine,  Dynamo-Electric,  Open-Coil} 

Open-Coil  Ring  Dynamo-Electric  Ma- 
chine.— (See  Machine,  Dynamo- Electric, 
Open-Coil  Ring} 

Open-Iron-Circuit  Transformer. — (See 
Transformer,  Open-Iron-Circuit} 

Open-Iron  Magnetic  Circuit. — (See  Cir- 
cuit, Open-Iron  Magnetic} 

Open  Magnetic  Core. — (See  Core,  Open- 
Magnetic} 

Opening  Shock. — (See  Shock,  Opening} 

Operation,  Magnet  -  — The  use  of  a 
magnet  for  the  purpose  of  removing  particles 
of  iron  from  the  human  eye. 

Optical  Strain.— (See  Strain,  Optical} 

Optical  Strain,  Electro-Magnetic  — 

(See  Strain,  Optical  Electro-Magnetic} 

Optical  Strain,  Electrostatic  —  — (See 
Strain,  Electrostatic,  Optical} 

Optics,  Electro That  branch  of 

electricity  which  treats  of  the  general  relations 
that  exist  between  light  and  electricity. 

The  phenomena  of  electro-optics  may  be  ar- 
ranged under  the  following  heads,  viz. : 

(i.)  Electrostatic  stress,  produced  by  an 
electrostatic  field  causing  an  optical  strain  in  a 
transparent  medium,  whereby  such  medium 
acquires  the  property  of  either  rotating  the  plane 
of  polarization  of  a  beam  of  plane  polarized  light, 
or  of  doubly  refracting  light. 

(2.)    Electro  magnetic    stress    produced  by  a 


magnetic  field  causing  an  optical  strain  in  a  trans- 
parent medium,  whereby  such  medium  acquires 
the  property  of  either  rotating  the  plane  of  polar- 
ization, or  of  doubly  refracting  light.  (See  Re- 
fraction, Double,  Electric} 

(3.)  Changes  in  the  electric  resistance  of  bodies 
caused  by  the  action  of  light.  (See  Cell,  Sele- 
nium. ) 

(4.)  The  relation  existing  between  the  values  oi 
the  index  of  refraction  of  a  transparent  medium 
and  its  specific  inductive  capacity.  (See  Refrac- 
tion. Capacity,  Specific  Inductive} 

This  relation  has  been  shown  to  be  as  follows  : 

The  specific  inductive  capacity  is  approxi- 
mately equal  to  the  square  of  the  index  ot  re- 
fraction. 

•(5.)  The  relation  existing  between  the  velocity 
of  light  and  the  value  of  the  ratio  of  electrostatic 
and  the  electro-magnetic  units,  thus  giving  a 
basis  for  an  electro-magnetic  theory  of  light. 
(See  Light,  Maxwell's  Electro-Magnetic  Theory 
of} 

Polarized  light  reflected  from  the  surface  of  a 
magnet,  although  it  penetrates  the  substance  to 
but  a  trifling  extent,  yet  has  its  plane  of  polariza- 
tion distinctly  rotated  by  the  magnetic  whirls  in 
the  iron. 

Oral  or  Speak  ing-Tube  Annunciator.— 

(See  Annunciator,  Oral  or  Speaking-  Tube} 
Ordinate. — A  distance  taken  on  a  per- 
pendicular line  called  the  axis  of  ordinates,  in 
contradistinction  to  the  axis  of  abscissas. 
(See  Ordinates,  Axis  of} 

Thus  in  Fig.  413,  D  i,  is  the  ordinate  of  the 
point  D,  in  the  curve  O  D  R. 

Ordinates,  Axis  of One  of  the  axes 

of  co-ordinates  used 
for  determining  the 
position  of  the  points 
in  a  curved  line. 

Thus  in  Fig.  413  the 
line  A  B,  is  called  the  axis 
of  ordinates  because  it  is 
the  line  on  which  the  or- 

n 

dinate  2  D,  is  measured.    „. 

rig- 

Ores,      Electric 
Treatment  of—       — Processes  for  the   ex- 
traction of  metals  from  their  ores. 

These  processes  are*  referable  to  three  dis- 
tinct classes,  viz. : 


AxisofOrdi. 


387 


[Osin- 


(I.)  Those  in  which  the  reduction  is  effected  by 
means  of  heat  of  electric  origin. 

(2.)  Those  in  which  the  reduction  is  effected  by 
the  combined  action  of  heat  and  electrolysis. 

(3.)  Those  in  which  the  reduction  is  effected  by 
means  of  electrolysis  only. 

Organ,  Electric A  wind  organ,  in 

which  the  escape  of  air  into  the  different 
pipes  is  electrically  controlled. 

In  an  electric  organ,  the  keys,  instead  of  oper- 
ating levers,  as  usual,  to  admit  the  passage  of  air 
into  the  pipes,  merely  complete  the  circuit  of  a 
battery  through  a  series  of  controlling  electro-mag- 
nets. With  such  an  arrangement,  the  keyboard 
can  be  placed  at  any  desired  distance. 

Electric  organs  have  been  constructed,  in  which 
a  chemical  or  mechanical  record  is  made  of  the 
notes  struck  by  the  performer,  as  well  as  the 
musical  value  of  such  notes.  By  such  a  device 
the  musical  creations  of  a  composer  are  perma- 
nently recorded  in  characters  that  are  capable  of 
interpretation  by  a  compositor  skilled  in  musical 
notation. 

Orientation  of  Magnetic  Needle. — (See 
Needle,  Magnetic,  Orientation  of.) 

Origin,  Point  of  —  — The  point  where 
the  axes  of  co-ordinates  start  or  originate. 
(See  Co-ordinates,  Axes  of.) 

Orthogonal. — Rectangular,  or  right-an- 
gled. 

Oscillating  Discharge. — (See  Disoharge, 
Oscillating^) 

Oscillating  Needle.— (See  Needle  of  'Oscil- 
lation.) 

Oscillation,  Centre  of A  point  in 

a  body  swinging  like  a  pendulum,  which  is 
neither  accelerated  nor  retarded,  during  its 
oscillations,  by  the  portions  of  the  pendulum 
that  are  situated  respectively  above  or  below  it. 

If  all  the  mass  were  concentrated  at  the  centre 
of  oscillation  the  time  of  oscillation  would  be  the 
same. 

The  centre  of  oscillation  is  always  below  the 
centre  of  gravity.  The  vertical  distance  between 
the  centre  of  oscillation  and  the  point  of  support 
of  a  pendulum,  determines  the  virtual  length  of 
the  pendulum,  and  hence  its  number  of  vibra- 
tions per  second.  (See  Pendulum,  Laws  oj. ) 


Oscillations,   Electric 


— The   series 


of  partial,  intermittent  discharges  of  which 
the  apparent  instantaneous  discharge  of  a 
Leyden  jar  through  a  small  resistance  actu- 
ally consists. 

These  partial  discharges  produce  a  series  of 
electric  oscillations  of  the  current  in  the  circuit  of 
the  discharge,  which  consist  of  true  to-and-fro 
or  backward -and-forward  motions  of  the  elec- 
tricity. This  phenomenon  was  discovered  by 
Joseph  Henry. 

Oscillations,  Open-Circuit,  Electric 

— Electric  oscillations  produced  in  open  cir- 
cuits by  the  presence  of  electric  pulses  in 
neighboring  circuits. 

Oscillatory  Discharge. — (See  Discharge, 
Oscillatory^) 

Oscillatory  Electric  Displacement. — (See 
Displacement,  Electric,  Oscillatory^) 

Oscillatory  Electromotive     Force. — An 

electromotive  force  which  is  rapidly  periodic. 

Oscillatory  Inductance. — (See  Induc- 
tance, Oscillatory,  Electric?) 

Oscillatory  Induction. — (See  Induction, 
Oscillatory^ 

Osmose. — The  unequal  mixing  of  liquids  of 
different  densities  through  the  pores  of  a 
separating  medium. 

If  a  solution  of  sugar  and  water  be  placed  in  a 
bladder,  the  neck  of  which  is  tied  to  a  straight 
glass  tube,  and  the  bladder  is  then  immersed  in  a 
vessel  of  pure  water  with  the  tube  in  a  vertical 
position,  the  two  liquids  will  begin  to  mix,  the 
sugar  and  the  water  passing  through  the  bladder 
into  the  pure  water,  and  the  pure  water  passing 
into  the  sugar  and  water  in  the  bladder.  This 
latter  current  is  the  stronger  of  the  two,  as  will  be 
shown  by  the  water  rising  in  the  vertical  glass 
tube. 

The  stronger  of  the  two  currents,  that  is,  the 
one  directed  towards  the  higher  level,  or  the  one 
which  produces  the  higher  level,  is  called  the  en- 
dosmotic  current,  and  the  weaker  current  the 
exosmotic  current. 

Osmose,  Electric A  difference  of 

liquid  level  between  two  liquids  placed  on 
opposite  sides  oE  a  diaphragm  produced  by 
the  passage  of  a  strong  electric  current 


Osm.J 


388 


[Ozo. 


through  the  liquids  between  two  electrodes 
placed  therein. 

The  higher  level  is  on  the  side  towards  which  the 
current  flows  through  the  diaphragm,  thus  appa- 
rently indicating  an  onward  motion  of  the  liquid 
with  the  current,  or,  in  other  words,  the  liquid  is 
higher  around  the  kathode  than  around  the  anode. 
The  difference  of  level  is  most  marked  when 
poorly  conducting  liquids  are  employed. 

As  a  converse  of  this,  Quincke  has  shown  that 
electric  currents  are  set  up  when  a  liquid  is  forced 
by  pressure  through  a  porous  diaphragm.  The 
term  diaphragm  currents  has  been  proposed  for 
these  currents.  Their  electromotive  force  depends 
on  the  nature  of  the  liquid,  on  the  material  of  the 
diaphragm,  and  on  the  pressure  that  forces  the 
liquid  through  the  diaphragm.  (See  Phenomena, 
Electro-Capillary.  Currents,  Diaphragm.} 

Osmotic.— Of  or  pertaining  to  osmose. 
(See  Osmose.} 

Osteotome,    Electric A   revolving 

electrically  propelled   saw,   employed  in  the 
surgical  cutting  of  bones. 

An  electric  osteotome  consists  essentially  of  a 
form  of  revolving  engine  known  as  a  dental  en- 
gine, furnished  with  a  circular  saw,  or  other  ro- 
tary cutter,  driven  or  propelled  by  electricity. 

Outgoing  Current.— (See  Current,  Out- 
going) 

Outlet. — In  a  system  of  incandescent  lamp 
distribution  the  places  in  a  building  where 
the  fixtures  or  lamps  are  attached. 

The  outlets  are  left  in  a  building  by  the  wire- 
man  for  the  electric  fixtureman  to  attach  the  de- 
vice intended  to  be  used  on  the  circuits  so  pro- 
vided. 

Output,  Magnetic The  product  of 

the   magnetic   flux  by  the  magneto-motive 
force. 

Output  of  Dynamo-Electric  Machine. — 

(See  Machine,  Dynamo-Electric,  Output  of) 

Outrigger  for  Electric  Lamp.— A  device 
for  suspending  an  electric  arc  lamp  so  as  to 
cause  it  to  stand  out  from  the  wall  of  a 
building. 

An  outrigger  and  hood  with  lamp  attached  are 
shown  in  Fig.  414. 


Outrigger  Torpedo.  -  (See  Torpedo,  Out- 
rigger) 

Orer-Compounded1. — The  compounding  @f 
a  dynamo-electric  machine  so  as  to  produce 


Fig -414.     Outrigger  and  Hood. 

an  increase  of  voltage  under  increase  of  load. 
Over-compounding  is  generally  employed  for 
compensating  for  drop  or  loss  of  potential  in  the 
line  or  conductor,  and  is  adjusted  to  a  definite 
percentage  of  increase  from  light  to  full  load  in 
accordance  with  the  amount  of  drop,  or  loss,  for 
which  such  compensation  was  designed. 

Overhead  Lines. — (See  Lines,  Overhead.} 

Overhead  System,  Continuous,  of  Motive 

Power  for  Electric  Railroads (See 

Railroads,  Electric,    Continuous    Overhead 
System  of  Motive  Power  for.) 

Overload  of  Electric  Motor.— (See  Motor, 
Electric,  Overload  of.} 

Overtones.— Additional,  faint  tones,  ac- 
companying nearly  every  distinct  musical 
tone,  by  the  presence  of  which  the  peculiarity 
or  quality  of  such  tone  is  produced.  (See 
Sound,  Characteristics  of.} 

Overtones,  Electric Electric  vibra- 
tions produced  in  open-circuited  conductors 
by  electric  resonance,  of  higher  rates  than  the 
fundamental  vibrations. 

The  existence  of  electrical  overtones  necessitates 
the  existence  of  electric  nodes.  (See  Nodes,  Elec- 
trical.) 

Overtype  Dynamo.— (See  Dynamo,  Over- 
type) 

Ozite. — An  insulating  substance. 

Ozokerite. — An  insulating  substance. 


Ozo.J 


389 


[Par. 


Ozone. — A  peculiar  modification  of  oxygen 
which  possesses  more  powerful  oxidizing 
properties  than  ordinary  oxygen. 

Ozone  is  now  generally  believed  to  be  tri- 
atomic  oxygen,  or  oxygen  in  which  the  bonds  are 
closed,  thus: 


O- 


-O 


The  peculiar  smell  observed  when  a  torrent  of 
electric  sparks  passes  between  the  terminals  of 
a  Holtz  machine,  or  a  Ruhmkorff  coil,  is  caused 
by  the  ozone  thus  formed. 

In  a  similar  manner  ozone  is  formed  in  the  at- 


mosphere during  the  passage  through  the  air  of  a 
flash  of  lightning. 

During  the  so-called  electrolysis  of  water,  a  com- 
pound formed  by  the  union  of  two  volumes  of 
hydrogen  with  one  volume  of  oxygen,  some  of  the 
oxygen  is  given  off  in  the  form  of  ozone.  Since 
ozone  has  a  somewhat  smaller  volume  than  that 
of  the  oxygen  forming  it,  the  volume  of  the 
oxygen  liberated  is  somewhat  less  than  half  the 
volume  of  the  hydrogen. 

There  are  a  number  of  different  forms  of  ap- 
paratus designed  for  the  production  of  ozone. 
They  consist  essentially  either  of  means  for  pass- 
ing  a  torrent  of  electric  sparks  through  air  or  for 
producing  a  species  of  polarization  in  the  air. 


P.  D.  or  p.  d. — A  contraction  frequently  em- 
ployed for  difference  of  potential.  (See  Poten- 
tial, Difference  of.) 

Pacinotti  Projections.— (See  Projections, 
Pacinotti.) 

Pacinotti  Ring.— (See  Ring,  Pacinotti.) 

Pair,  Astatic A  term  sometimes 

applied  to  an  astatic  couple.  (See  Couple, 
Astatic.') 

Palladium. — A  metal  of  the  platinum 
group. 

Metallic  palladium  has  a  tin-white  color,  and, 
when  polished,  a  high  metallic  lustre.  It  is 
tenacious  and  ductile,  and,  like  iron,  can  be 
welded  at  a  white  heat.  It  is  very  refractory  and 
possesses  in  a  marked  degree  the  power  of  ab- 
sorbing or  occluding  hydrogen  and  other  gases. 
It  is  not  affected  by  oxygen  at  any  temperature, 
nor  readily  affected  by  ordinary  corrosive  agents. 

Palladium  Alloy.— (See  All«y,  Pal- 
ladium!) 

Pane,  Magic A  condenser  formed 

of  a  sheet  of  glass  covered  on  one  side  with 
pieces  of  tin-foil  with  small  spaces  between 
them  pasted  in  some  design  on  the  glass. 

On  the  discharge  of  a  Leyden  jar  through  these 
metallic  pieces,  the  design  is  seen  as  a  series  of 
minute  sparks,  which  bridge  the  spaces  between 
the  adjacent  pieces  of  foil. 


Pantelegraphy. — A  system  for  the  tele- 
graphic transmission  of  charts,  diagrams, 
sketches  or  written  characters. 

Pantelegraphy  is  more  frequently  called  fac- 
simile telegraphy.  (See  Telegraphy,  Fac- Simile.) 

Paper  Carbons. — (See  Carbons,  Paper.) 

Paper  Cut-Out— (See  Cut-Out,  Paper) 

Paper  Perforator. — (See  Perforator, 
Paper.) 

Paper  Winder,  Automatic A  de- 
vice, driven  by  clockwork,  for  automatically 
delivering  the  paper  fillet  on  which  a  tele- 
graphic message  is  received. 

Parabolic  Reflector.— (See  Reflector, 
Parabolic.) 

Paraffin e.  —  A  name  given  to  various 
solid  hydrocarbons  of  the  marsh  gas  series, 
that  are  derived  from  coal  oil  or  petroleum  by 
the  action  of  nitric  acid. 

Paraffine  possesses  excellent  powers  of  insula- 
tion, and  forms  a  good  dielectric  medium.  Dried 
wood,  boiled  in  melted  paraffine,  forms  a  fair  in- 
sulating material. 

Paraffiue  Wire. — (See  Wire,  Paraffined) 

Paraffining. — Covering  or  coating  with 
paraffine. 

The  paraffine  is  applied,  while  melted  by  heat, 
either  by  means  of  a  brush,  or  by  dipping  the 
article  in  the  fused  mas«. 


Par.] 


390 


[Par. 


Care  must  be  taken  in  paraffining  wooden  or 
other  absorbent  articles,  to  dry  them  before  im- 
mersing in  the  melted  paraffine,  since,  if  water  be 
present,  steam  is  formed  explosively,  and  the 
melted  paraffine  scattered  in  all  directions. 

Paragreles. — Lightning  rods,  intended  to 
protect  fields  against  the  destructive  action  of 
hail.  (See  Hail,  Assumed  Electrical  Ori- 
gin of] 

It  was  formerly  believed  that  hail  is  caused  by 
electricity.  It  is  now  generally  believed  that  the 
electricity  in  hail  storms  is-  caused  by  the  hail. 
It  will,  therefore,  readily  be  understood  that  para- 
greles  can  afford  no  real  protection. 

Parallax. — The  apparent  angular  displace- 
ment of  an  object  when  seen  from  two  dif- 
ferent points  of  view. 

In  reading  the  exact  division  on  a  scale  to  which 
a  needle  points,  care  must  be  taken  to  look  di- 
rectly down  on  the  needle,  and  not  sideways,  so 
as  to  avoid  the  error  of  displacement  due  to 
parallax. 

Parallel  Circuit.— (See  Circuit,  Parallel.} 
Parallel  Series. — (See  Series,  Parallel?) 

Parallelogram  of  Forces. — (See  Forces, 
Parallelogram  of.} 

Parallels,  Magnetic  —  —Lines  connect- 
ing places  on  the  earth's  surface  at  right 
angles  to  the  isogonal  lines,  or  lines  of  equal 
declination  or  variation. 

The  magnetic  parallels  are  at  right  angles  to 
the  magnetic  meridians.  The  magnetic  parallels 
lie  in  planes  parallel  to  the  magnetic  equator. 
(SeelVeedte,  Magnetic,  Declination  of  .  Meridian, 
Magnetic. ) 

Paramagnetic. — Possessing  properties  or- 
dinarily recognized  as  magnetic. 

Possessing  the  power  of  concentrating  the 
lines  of  magnetic  force. 

Paramagnetic  is  a  term  employed  in  contra- 
distinction to  diamagnetic.  (See  Diamagnetic.} 
A  paramagnetic  substance,  cut  in  the  form  of  a 
bar  whose  length  is  much  greater  than  its  breadth 
and  thickness,  will,  when  suspended  in  a  magnetic 
field  in  the  manner  shown  in  Fig.  415,  take  up  a 
position  of  rest  with  its  greatest  length  in  the  direc- 
tion of  the  lines  of  force,  i.  e.,  will  point  axially. 


Fig  413.     Diamagnetic 
Polarity 


In  other  words,  the  lines  of  force  will  so  pass 
through  the  paramagnetic  substance  as  to  reduce 
the  magnetic  resistance  of  the  circuit  as  much  as 
possible. 

Paramagnetic  substances,  therefore,  concen- 
trate the  lines  of  force  on  them.  (See  Resistance, 
Magnetic.} 

Diamagnetic  substances,  on  the  contrary,  when 
placed  as  shown  in  Fig.  415,  assume  a  position  of 
rest  with  their  least  dimensions  in  the  direction  of 
the  lines  of  force,  i.  e. 
they  point  equatorially. 
This  is  the  position  in 
which  they  are  placed 
by  the  lines  of  force,  in 
order  to  insure  the  least 
magnetic  resistance  in 
the  circuit  of  these  lines. 
The  magnetic  resistance 
of  diamagnetic  sub- 
stances is  great  as  com- 
pared with  that  of  par- 
amagnetic substances. 

The  term  ferro  -mag. 
netic  has  been  proposed 
for  paramagnetic.  If 
another  term  be  required,  which  is  doubtful, 
sidero-magnetic,  proposed  by  S.  P.  Thompson, 
would  appear  to  be  preferable.  (See  Magnetic, 
Ferro.  Magnetic,  Sidero.} 

Tyndall  believes  that  the  magnetic  polarity 
possessed  by  diamagnetic  substances  is  the  result 
of  a  distinct  polar  force,  different  in  its  nature 
from  ordinary  magnetism.  His  views,  in  this  re- 
spect, are  not  generally  accepted.  (See  Polarity < 
Diamagnetic.}' 

Paramagneticallr. — In  a  paramagnetic 
manner.  (See  Paramagnetism.} 

Paramagnetism. — The  magnetism  of  a 
paramagnetic  substance. 

Parasitical  Currents. — (See  Currents, 
Parasitical.} 

ParatonnSre. — A  French    term  for  light- 
ning rod,   sometimes   employed    in   English  \ 
technical  works. 

Lightning  rod  would  appear  to  be  the  prefer- 
able term. 

Partial  Contact — (See  Contact,  Partial.} 
Parti.il  Disconnection. — (See  Disconnec- 
tion, Partial?) 


Par.] 


391 


[Ten. 


Partial  Earth.— (See  Earth,  Partial) 

Partial  Reaction  of  Degeneration. — (See 
Degeneration,  Partial  Reaction  of.) 

Passive  State.— (See  State,  Passive) 

Path,  Alternative-  —The  path  or 
circuit  taken  by  an  impulsive  discharge,  in 
preference  to  another  path  or  circuit,  open  to 
the  discharge,  although  of  enormously  smaller 
ohmic  resistance. 

The  alternative  path  is  the  path  taken  by  the 
discharge  produced  by  what  was  formerly  called 
lateral  induction. 

The  explanation  of  the  reason  the  discharge 
takes  the  alternative  path  is  that  the  counter-elec- 
tromotive force  of  self-induction  of  the  circuit, 
produced  by  the  impulsive  discharge,  is  so  great 
as  to  make  the  path  of  the  circuit  itself,  although 
formed  of  conducting  materials,  practically  non- 
conducting. 

If  a  Leyden  jar  is  provided  with  discharge  wires 
or  conductors,  as  shown  is  Fig.  416,  a  discharge 


would  pass  across  an  air  space  in  preference  to 
a  metallic  circuit,  was  greater  for  a  thick  copper 


Fig.  416.     Phenomena  of  Alternative  Path. 

taking  place  at  A,  is  accompanied  simultaneously 
by  an  even  longer  spark  at  B,  between  the  ends 
of  two  long  open-circuit  leads. 

To  explain  in  a  general  manner  the  phenomena 
of  the  alternative  path,  we  may  say  that  the  dis- 
charge at  A,  gives  rise  to  electric  oscillations  in  the 
leads  connected  with  B,  and  that  there  are  sent  out 
into  the  surrounding  medium  radiations  of  pre- 
cisely the  same  nature  as  those  which  produce 
light,  only  of  a  wave  length  so  long  as  to  be  un- 
able to  produce  on  the  eye  the  effects  ot  light. 

If  the  space  between  the  balls  at  B,  is  too  great 
for  the  discharge  to  take  place,  the  wires  glow 
and  throw  out  minute  sparks  or  brushes  of  light. 

The  action  of  the  ordinary  lightning  arrester 
depends  on  the  principle  of  the  alternative  path. 
The  resistance  of  the  metallic  circuit,  composed 
of  the  line  and  the  instruments,  is  so  great  in  the 
case  of  the  impulsive  discharge  of  a  lightning 
flash,  that  the  discharge  takes  place  between  a 
series  of  points  connected  with  the  line  plate  and 
another  series  of  points  connected  with  the  ground 
plate.  -  (See  Arrester,  Lightning  ) 

Dr.  Lodge,  who  has  studied  the  principle  of 
alternative  path  in  the  case  cf  lightning  rods, 
finds  that  the  distance  at  which  the  discharge 


Fig.  4 17.     Edison  Electric  Pen. 

rod,  40  feet  long,  than  for  an  iron  rod  of  No.  27 
B.  W.  G.  of  33.03  ohmic  resistance. 

Patrol  Alarm  Box. 

— (See  Box,  Patrol 
Alarm) 

Peltier    Effect  - 

(See  Effect,  Peltier) 

Pen    Carriage.  — 

(See  Carriage,  Pen) 

Pen,  Electric  — 

— A  device  for  mani- 
fold copying,  in  which 
a  sheet  of  paper  is 
made  into  a  stencil  by 
minute  perforations 
obtained  by  a  needle 
driven  by  a  small 
electric  motor  and  the 
stencil  afterwards  em- 
ployed in  connection 
with  an  inked  roller 
for  the  production  of 
any  required  number 
of  copies. 

Mechanical  pens  are 
constructed  on  the  same 
principle,  the  perfora- 
tions being  obtained  by 
mecnamcal  instead  of 
by  electric  power. 

In  the  Edison  electric 
pen,  Fig.  417,  the  yvc-Fig-4z8.  Electric  Pendant. 
forations  are  made  by  an  electric  motor  driven 
by  a  voltaic  battery.  The  manifold  press  with 
its  inked  pad  is  shown  to  the  left  of  the  figure. 

Pendant  Cord.— (See  Cord,  Pendant) 
Pendant,  Electric A  hanging  fix- 


Pen.] 


392 


[Per. 


ture  provided  with  a  socket  for  the  support  of 
an  incandescent  lamp. 

A  form  of  electric  pendant  is  shown  in  Fig. 
418. 

Pendant,  Flexible  Electric  Light  - 
— A  pendant  for  an  incandescent  lamp  formed 
by  the  flexible  conductors  which  support  the 
lamp. 

The  ad  vantages  procured  by  a  flexible  pendant 
are  evident  in  that  both  the  length  of  the  flexible 
conductor  from  which  the  lamp  is  hanging  and 
position  of  the  lamp  can  be  changed  considerably. 

Pendulum  Annunciator. — (See  Annun- 
ciator, Pendulum  or  Swinging?) 

Pendulum,  Electric A  pendulum 

so  arranged  that  its  to-and-fro  motions  send 
electric  impulses  over  a  line,  either  by  making 
or  breaking  contacts. 

An  electrical  tuning  fork  whose  to-and-fro 
movements  are  maintained  by  electric  im- 
pulses. 

Electric  pendulums  are  employed  in  systems 
for  the  electrical  disti  ibution  of  time. 

Sometimes  instead  of  using  true  pendulums  for 
such  purposes,  coils,  mounted  on  tuning  forks,  or 
on  the  ends  of  flexible  bars  of  steel,  called  reeds, 
are  used  for  the  purpose  of  e^ablishing  cur- 
icnts,  or  modifying  the  currents  that  are  already 
passing  in  a  circuit.  The  movement  of  a  mag- 
netic diaphragm,  as  in  the  case  of  a  telephone 
diaphragm,  towards  and  from  a  coil  of  wire,  is 
another  illustration  of  an  electric  pendulum. 

Electric  tuning-fork  pendulums  are  employed 
in  Delany's  system  of  synchronous-  multiplex  teleg- 
raphy, and  in  Gray's  harm  >nic-multiple  teleg- 
raphy. (See  Telegraphy,  Synchronous-Multi- 
plex, Delany's  System.  Telegraphy,  Gray's  Har- 
monic-Multiple. ) 

Pendulum,  Laws  of  — The  laws 

which  express  the  peculiarities  of  the  motion 
of  a  simple  pendulum. 

A  simple  pendulum  is  one  in  which  the  entire 
weight  is  considered  as  concentrated  at  a  single 
point,  suspended  at  the  end  of  a  weightless,  in- 
flexible and  inextensible  line. 

The  following  are  the  laws  of  the  simple  pen- 
dulum : 

(I.)  Oscillations  of  small  amplitude  are  approx- 
imately isochronous;  that  is,  are  made  in  times 
that  are  sensibly  eqinl.  (See  Vibration  or  Wave, 
Amplitude  of.  Jsochronism.) 


(2.)  In  pendulums  of  different  lengths,  the 
duration  of  the  oscillations  is  proportional  to  the 
square  root  of  the  length  of  the  pendulum. 

(3.)  In  the  same  pendulum,  the  length  being 
preserved  invariable,  the  duration  of  the  oscilla- 
tion is  inversely  proportional  to  the  square  root 
of  the  intensity  of  gravity. 

The  intensity  of  gravity,  at  any  latitude,  may 
be  determined  by  the  number  of  oscillations  of  a 
pendulum  of  a  given  length.  In  the  same  man- 
ner the  intensity  of  a  magnetic  field,  or  the  in- 
tensity of  magnetization  of  a  magnet,  may  be  de- 
termined by  the  needle  of  oscillation,  by  observing 
the  number  of  oscillations  a  needle  makes  in  a 
given  time  when  disturbed  from  its  position  of 
rest.  (See  Needle  of  Oscillation.) 

Since  a  simple  physical  pendulum  is  a  physical 
impossibility,  the  virtual  length  of  a  pendulum, 
that  is,  the  vertical  distance  between  its  point  of 
support  and  the  centre  of  oscillation,  is  taken  as 
the  true  length  of  the  pendulum. 

If  the  irregularly  shaped  body,  shown  in  Fig. 
419,  whose  centre  of  gravity  is  at  G,  is  made  to 
swing  like  a  pendulum,  either  on 
S,  or  O,  its  oscillations  will  be 
performed  in  equal  times,  and 
the  body  will  act  as  a  simple 
pendulum,  whose  virtual  length 
is  SO. 

If,  while  suspended  at  S,  it  be 
struck  at  O,  it  will  oscillate 
around  S,  without  producing  p!g  4T9  centr- 
any  pressure  on  the  supporting  of  OscMati  ». 
axis  at  S,  on  which  it  turns.  If  fl  mating  entirely 
submerged  in  a  liquid,  a  blow  at  O,  would  c  ause 
it  to  move  in  a  straight  line  in  the  direction  of 
the  blow,  without  rotation. 

The  point  O,  is  caUed  the  centre  of  percussion, 
or  the  centre  of  oscillation.  The  centre  of  oscil- 
lation is  always  below  the  centre  of  gravity. 

Pentane  Standard. — (See  Standard,  Pen- 
tane.} 

Percussion,  Centre  of That  point  in 

a  body  suspended  so  as  to  move  as  a  pendu- 
lum at  which  a  blow  would  produce  rotation, 
but  no  forward  motion,  or  motion  of  transla- 
tion. 


Perforator,  Paper 


— An   apparatus 


employed  in  systems  of  automatic  telegraphy 
for  punching  in  a  fillet  of  paper  the  circular  or 
elongated  spaces  that  produce  the  dots  and 


Per.] 


393 


[Per. 


dashes  of  the  Morse  alphabet,  when  the  fillet  is 
drawn  between  metal  terminals  that  form  the 
electrodes  of  a  battery.  (See  Telegraphy, 
Automatic.) 

Perforator,  Pneumatic  -  — A  paper 
perforator  operated  by  means  of  compressed 
air.  (See  Perforator,  Paper.) 

Period  of  Open-Circuit  Oscillation. — (See 
Open-Circuit  Oscillation,  Period  of.) 

Period  of  Simple-Harmonic  Motion. — 
(See  Motion,  Simple-Harmonic,  Period  of) 

Period  of  Vibration. — (See  Vibration, 
Period  of.) 

Period,  Vibration  —  —The  period  of  a 
single  or  a  whole  vibration  in  a  conductor,  in 
which  an  oscillatory  vibration  is  being  pro- 
duced by  electrical  resonance  when  respond- 
ing to  its  fundamental  vibration. 

Hertz  gives  the  following  value  for  the  vibration 
period:  Calling  T,  the  single  or  half  vibration 
period;  L,  the  co-efficient  of  self-induction  in  abso- 
lute magnetic  measure,  and  therefore  expressed  in 
centimetres;  C,  the  capacity  of  the  terminals,  in 
electrostatic  measure,  and  therefore  also  expressed 
in  centimetres;  v,  the  velocity  of  light  in  centi- 
metre second?,  then,  when  the  resistance  of  the  con- 
ductor is  small,  T  =  it  L  C. 
v 

Periodic  and  Alternate  Discharge. — (See 
Discharge,  Periodic.  Discharge,  Alternat- 
ing^ 

Periodic  Current,  Power  of —    — The 

rate  of  transformation  of  the  energy  of  a  cir- 
cuit traversed  by  a  simple  periodic  current. 


Fig.  420.    Power  of  Periodic  Current. — (Fleming.) 

If  the  thin  line  in  the  curve,  Fig.  420,  repre- 
sents the  impressed  electromotive  force  in  an  in- 
ductive circuit,  and  the  thick  line  the  correspond- 
ing current,  then,  at  any  instant,  say  at  the  point 
M,  the  rate  at  which  energy  is  being  expended  on 
the  circuit,  is  equal  to  the  ordinate  P  M,  multi- 
plied by  the  ordinate  Q  M.  The  mean  power  is 


the  mean  of  all  such  products  taken  at  points  of 
time  very  near  together. 

The  power  of  a  periodic  current,  or  the  work 
expended  per  second  on  such  a  circuit,  is  equal 
to  half  the  product  of  the  maximum  values  of  the 
current,  at  any  instant,  and  the  maximum  value 
of  the  impressed  electromotive  force,  multiplied 
by  the  cosine  of  the  angle  of  lag. 

Periodic  Governor. — (See  Governor, 
Periodic) 

Periodically    Decreasing    Discharge. — 

(See  Discharge,  Periodically  Decreasing) 

Periodicity.— The  rate  of  change  in  the 
alternations  or  pulsations  of  an  electric  cur- 
rent. 

Periodicity  of  Auroras  and  Magnetic 
Storms.  —  (See  Auroras  and  Magnetic 
Storms,  Periodicity  of.) 

Permanency,  Electric The  prop- 
erty possessed  by  most  metallic  substances, 
while  in  the  solid  state,  of  retaining  a  constant 
electric  conducting  power  at  the  same  tem- 
perature. 

The  electric  permanency  of  hard  drawn  wire  is 
small,  since  such  wire  becomes  gradually  an- 
nealed, and  thus  changed  in  its  electric  resist- 
ance. 

Matthiessen  showed  that  some  specimens  of 
annealed  German  silver  wire  increased  in  their 
conducting  power  at  the  rate  of  about  .02  per 
cent,  yearly. 

Permanent  Intensity  of  Magnetization. 

— (See  Magnetization,  Permanent,  Intensity 
of.) 

Permanent  Magnet  Voltmeter. —  (See 
Voltmeter,  Permanent  Magnet.) 

Permanent  State  of  Charge  on  Telegraph 
Line. — (See  State,  Permanent,  of  Charge  on 
Telegraph  Line) 

Permeability  Curve. — (See  Curve,  Per- 
meability) 

Permeability,  Magnetic Conducti- 

bility  for  lines  of  magnetic  forces. 

The  ratio  existing  between  the  magnetiza- 
tion produced,  and  the  magnetizing  force  pro- 
ducing such  magnetization. 

If  jit  equals  the  permeability,  B,  the  magnetiza- 


Per. 


394 


[Phe. 


tion  produced,  or  the  intensity  of  magnetic  induc- 
tion, and  H,  the  magnetizing  force;  then, 


The  permeability  of  non-magnetic  materials, 
such  as  insulators,  or  non-magnetic  metals,  such  as 
copper,  etc.,  is  assumed  to  be  practically  equal  to 
that  of  air,  or  to  unity. 

The  magnetic  permeability  decreases  as  the 
magnetization  increases.  When  a  piece  of  iron 
has  been  magnetized  up  to  a  certain  intensity,  its 
permeability  becomes  less  for  any  further  magnet- 
ization; or,  the  substance  shows  a  tendency  to 
reach  magnetic  saturation.  In  good  iron,  this 
limit  is  reached  at  about  125,000  lines  of  force  to 
the  square  inch  of  rea  of  cross  section. 

The  magnetic  permeability  varies  greatly,  not 
only  with  different  specimens  of  iron,  but  also  with 
the  previous  history  of  the  iron,  as  to  whether  or 
not  it  has  before  been  subjected  to  magnetization  or 
demagnetization,  and  also  as  to  whether  the  value 
of  the  permeability  is  taken  while  the  magnetiza- 
tion is  increasing  or  decreasing. 

Permeameter.  —  An  apparatus  devised  by 
S.  P.  Thompson,  for  roughly  measuring  the 
magnetic  permeability. 

Thompson's  permeameter  consists  essentially  of 
a  rectangular  piece  of  soft  iron,  provided  with  a 
slot,  for  the  reception  of  the  magnetizing  coil.  A 
hole  bored  in  one  end  of  the  block  serves  to  receive 
the  bar  or  rod  of  iron  whose  permeability  is  to  be 
determined.  On  the  magnetization  of  the  bar  to 
be  tested,  the  square  root  of  the  force  required  to 
detach  the  rod  from  the  lower  surface  of  the  iron 
block,  is  a  measure  of  the  permeation  of  the  lines 
of  magnetic  forces  through  its  end  faces. 

Permeance,  Magnetic  -  —Magnetic 
permeability.  (See  Permeability,  Magnetic!) 

Permeating,  as    of  Lines   of  Force.— 

The  passing  of  lines  of  force  through  a  mag- 
netic substance.  (See  Permeability,  Mag- 
netic^ 

Permeation,  Magnetic  --  The  pass- 
age of  lines  of  magnetic  force  through  any 
permeable  substance. 

Permissive  Block  System  for  Railroads. 

—  (See  Railroads,  Permissive  Block  System 
for.} 


Pfluger's  Law.— (See  Law,  PJluger's^] 
Phantom  Wires.— (See  Wires,  Phantom^ 

Phase,  Angle  of  Difference  of,  between 
Alternating    Currents   of    Same    Period 

The  angle  which  measures  the  shift- 
ing of  phase  of  a  simple  periodic  current  with 
respect  to  another  due  to  lag  or  other  cause. 

Phase,  Shifting  of,  of  Alternating  Cur- 
rent  — A  change  in  phase  of  current 

due  to  magnetic  lag  or  other  causes. 

Phase    of   Vibration.— (See    Vibration, 
Phase  of.) 

Phelps'  Stock    Printer.— (See  Printer, 
Stock,  Phelps .} 

Phenomena,  Electro-Capillary  — 

Phenomena  observed  in  capillary  tubes  at 
the  contact  surfaces  of  two  liquids. 

Where  acidulated  water  is  in  contact  with 
mercury,  each  liquid  possesses  a  definite  sur- 
face tension,  and  each  a  definite  shape  of  sur- 
face. The  two  liquids,  however,  do  not  actually 
touch,  there  being  a  small  interval  or  space  be- 
tween them.  This  space  acts  as  a  minute  accu- 
mulator. But  the  liquid  and  water,  being  different 
substances  in  contact,  possess  different  potentials. 
Any  cause  which  alters  the  shape  of  these  con- 
tact surfaces,  and  consequently  the  extent  of  the 
spaces  between  them,  necessarily  alters  the  capa- 
city of  the  condenser,  and  consequently  the  dif- 
ference of  potential.  Therefore  the  mere  shaking 
•f  the  tube,  or  heating  it,  will  produce  electric 
currents  from  the  resulting  differences  of  po- 
tential. Conversely,  an  electric  current  sent 
across  the  contact-surfaces  will  produce  motion  as 
a  result  of  a  change  in  the  value  of  the  surface 
tension.  An  electro-capillary  telephone  has  been 
constructed  on  the  former  principle,  and  an 
electrometer  on  the  latter.  (See  Electrometer, 
Capillary.) 


Phenomena,  Porret 


-An  increase 


in  the  diameter  of  a  nerve  fibre  in  the  neigh- 
borhood of  the  positive  pole  when  traversed 
by  a  voltaic  current. 

When  a  voltaic  current  passes  through  fresh 
living  substance  the  contents  of  the  muscular  fibre 
exhibit  a  streaming  movement  in  the  direction  the 
current  is  flowing,  viz.,  from  the  positive  to  the 


Phe.J 


395 


[Pho. 


negative.     This  causes  the  fibre  to  swell  up  or 
increase  in  diameter  at  the  negative  electrode. 

Pherope. — A  name  sometimes  applied  to 
a  telephote.  (See  Telephote.) 

Phial,  Leyden A  name  sometimes 

applied  to  a  Leyden  jar.     (See  Jar,  Leyden.) 

Philosopher's  Egg. — (See  Egg,  Philoso- 
pher 's.~) 

Phonautograph. — An  apparatus  for  the 
automatic  production  of  a  visible  tracing  of 
the  vibrations  produced  by  any  sound. 

Phonautographic  apparatus  consists  essentially 
of  devices  by  which  the  sound  waves  are  caused 
to  impart  their  to-and  fro  movements  to  a  dia- 
phragm, at  the  centre  of  which  a  pencil  or  tracing 
point  is  attached.  The  record,  is  received  on  a 
sheet  of  paper,  or  wax,  or  on  a  smoked  glass  or 
other  suitable  surface. 

Leon  Scott's  Phonautograph,  which  is  among 
the  forms  best  known,  consists  of  a  hollow  conical 


Fig.  421.    Scott's  Phonautograph. 

vessel  A,  Fig.  421,  with  a  diaphragm  of  parch- 
ment stretched  tightly  like  a  drumhead  over  its 
smaller  aperture  B.  A  tracing  point  attached  to 
the  centre  of  the  diaphragm,  traces  a  sinuous 
line  on  the  surface  of  a  soot-covered  cylinder  C, 
that  is  uniformly  rotated  under  the  tracing  point. 
As  the  cylinder  is  advanced  a  short  distance  with 
every  rotation,  a  sinuous  spiral  line  is  .traced  on 
the  surtace. 

Phone. — A  term  frequently  used  for  tele- 
phone. 
Phonic  Wheel.— (See  Wheel,  Phonic.) 

Phonogram. — A  record  produced  by  the 
phonograph.     (See  Phonograph) 

Phonograph.— An  apparatus    for  the  re- 
production of  articulate  speech,  or  of  sounds 


of  any  character,  at  any  indefinite  time  after 
their  occurrence,  and  for  any  number  of  times. 
In  Edison's  phonograph  the  voice  of  the 
speaker,  received  by  an  elastic  diaphragm  of  thin 
sheet  iron  or  other  similai  material,  is  caused  to 
indent  a  sheet  of  tin-foil  placed  on  the  surface  of 
a  cylinder  C,  Fig.  422,  that  is  maintained  at  a 
uniform  rate  of  rotation  by  the  crank  at  W.  In 


Fig.  422. 

the  form  shown  in  Fig.  422,  the  motion  is  by  hand. 
In  a  later  improved  form  the  cylinder  is  driven  by 
means  of  an  electric  motor  or  by  clockwork. 

In  order  to  reproduce  the  speech  or  other 
sounds  the  phonogram  record  is  placed  on  the 
surface  of  a  cylinder  similar  to  that  on  which  it 
was  received  (or  is  kept  on  the  same  surface), 
and  the  tracing  point,  placed  at  the  beginning  of 
the  record  and  being  maintained  against  it  by 
gentle  pressure,  is  caused,  by  the  rotation  of 
cylinder,  to  follow  the  indentations  of  the  phono- 
gram record.  As  the  point  is  thus  moved  up  and 
down  the  hills  and  hollows  of  the  record  surface, 


Fig.  423.    Edison's  Improved  Phonograph. 

the  diaphragm,  to  which  it  is  attached,  is  given  to- 
and-fro  motions  that  exactly  correspond  to  the 
to-and  fro  motions  it  had  when  impressed  origin- 
ally by  the  sounds  it  recorded  on  the  phono- 
gram record.  A  per  on  listening  at  this  did- 


Pho.] 


[Pho. 


phragm  will  therefore  hear  an  exact  reproduction 
of  the  sounds  originally  uttered. 

In  this  manner  the  voices  of  relatives,  'dis- 
tinguished singers  or  statesmen  can  be  preserved 
for  future  generations. 

In  Edison's  improved  phonograph  the  record 
surface  consists  of  a  cylindt  r  of  hardened  wax.  The 
rotary  motion  of  the  cylinder  is  obtained  by  means 
of  an  electric  motor.  Two  diaphragms  are  used, 
one  for  recording,  and  one  for  reproducing  the 
sound  waves.  As  shown  in  Fig.  423,  the  record- 
ing  diaphragm  is  in  position  against  the  cylinder. 
The  recording  diaphragm  is  made  of  malleable 
glass.  The  reproducing  diaphragm  is  formed  of 
bolting  silk  covered  with  a  thin  layer  of  shellac. 

In  the  Graphophone  of  Bell  and  Tainter  the 
point  attached  to  the  diaphragm  is  caused  to  cut 


Fig.  424..    Bell  and  Tainter's  Graphophoiu. 
or  engrave  a  cylinder  of  hardened  wax.    Two 
separate  diaphragms  are  employed,  one  for  speak- 
ing, and  the  other  for  hearing. 

The  recording  surface  is  made  of  a  mixture  of 
beeswax  and  paraffine.  A  uniformity  of  rotation  of 
the  cylinder  is  obtained  by  means  of  a  motor  pro- 
vided with  a  suitable  governor.  An  ordinary  con- 
versation of  some  five  minutes,  it  is  claimed,  can 
be  recorded  on  the  surface  of  a  cylinder  6  inches 
long  and  I \  inch  in  diameter. 

In  the  Gramophone  of  Berliner,  a  circular  plate 
of  metal,  covered  with  a  film  of  finely  divided  oil 


or  grease,  receives  the  record  in  a  sinuous,  spiral 
line.  This  record  is  subsequently  etched  into  the 
metal  by  any  suitable  means,  or  is  photographic- 
ally reproduced  on  another  sheet  of  metal. 

Glass  covered  with  a  deposit  of  soot  is  some- 
times employed  for  the  latter  process.  The  ap- 
paratus is  shown  in  Fig.  425,  as  arranged  for  the 
reproduction  of  speech. 

In  Mr.  Berliner's  apparatus,  the  record  surface 
is  impressed  by  a  point  attached  to  the  trans- 
mitting diaphragm,  in  a  direction  parallel  to  tke 
record  surface,  and  not,  as  in  the  instrument  of 
Mr.  Edison,  in  a  direction  at  right  angles  to  the 
same.  This  method  would  appear  to  be  the  best 
calculated  for  a  more  exact  reproduction  of  ar- 
ticulate speech,  since  it  permits  comparatively 
loud  speaking  or  singing,  without  interfering 


Fig,  425.     Berliner's  Gramophone. 

with  the  quality  of  the  reproduced  sounds.  Since 
the  resistance  to  indentation,  or  vertical  cutting, 
increases  more  rapidly  than  the  increase  in  the 
amplitude  of  vibration  of  the  cutting  point,  it 
follows  that  the  louder  the  sounds  recorded  by  the 
phonograph  or  graphophone,  the  less  complete 
would  be  the  quality  of  the  reproduced  sounds, 
or  the  less  the  probability  of  the  peculiarities  of 
the  speaker's  voice  being  recognized.  In  order 
to  avoid  this,  the  speaker  in  the  phonograph  and 
the  graphophone  speaks  in  an  ordinary  conversa- 
tional tone  only.  (S^e  Vibration  or  Wave,,  Am- 
plitude of ) 

For  purposes  of  dictation,  and,  indeed,  most 
commercial  purposes,  this  is  rather  an  advantage 
than  otherwise. 

Phonograph  Record.  —  (See  Record 
Phonograph.} 

Phonoplex. — Literally  sound  folds. 

A  system  of  telegraphy.  (See  Telegraphy, 
Phonoplex.} 


Pho.] 


397 


[Pho. 


Phonoplex  Telegraphy.  —  (See  Telegra- 
phy, Phonoplex^) 

Pkonopore. — A  modified  form  of  har- 
monic telegraph. 

Phonozenograph. — An  instrument  devised 
by  De  Feltre  to  indicate  the  direction  of  a 
distant  sound. 

A  Deprez-D'Arsonval  galvanometer,  a  Wheat- 
stone's  bridge,  and  a  microphone  of  peculiar  con- 
struction, are  placed  in  the  circuit  of  a  voltaic 
battery  and  a  receiving  telephone.  The  observer 
determines  the  direction  of  the  distant  sound  by 
means  of  the  sounds  heard  under  different  condi- 
tions in  the  telephone. 

Phosphoresce. — To  emit  phosphorescent 
light. 

Phosphorescence. — The  power  of  emitting 
light,  or  becoming  luminous  by  simple  ex- 
posure to  light. 

Bodies  that  possess  the  property  of  phosphor- 
escence, when  exposed  to  a  bright  light  acquire 
the  power,  when  subsequently  carried  into  the 
dark,  of  continuing  to  emit  light,  for  periods 
varying  from  a  few  seconds  to  several  hours. 
The  diamond,  barium  and  calcium  sulphides, 
dry  paper,  silk,  sugar,  and  compounds  of  ura- 
nium, are  examples  of  phosphorescent  substances. 

The  effects  of  phosphorescence  appear  to  be 
due,  in  some  cases,  to  sympathetic  vibrations  set 
up  in  the  molecules  of  the  phosphorescent  body 
by  the  exciting  light.  (See  Vibrations,  Sympa- 
thetic.') 

In  other  cases,  however,  that  are  not  exactly 
understood,  the  wave  length  of  the  emitted  light 
is  more  rapid  than  that  of  the  exciting  light. 

The  fire-fly,  the  glow-worm,  and  decaying 
animal  or  vegetable  matter,  exhibit  a  species  of 
phosphorescence  that  appears  to  be  due  to  the  ac- 
tual oxidation  or  gradual  burning  of  a  peculiar, 
specific,  chemical  substance. 

Phosphorescence  may  therefore  be  divided  into 
two  classes,  viz. : 

(i.)  Physical  phosphorescence,  or  that  produced 
by  the  actual  impact  of  light, .and, 

(2.)  Chemical  phosphorescence,  or  that  caused 
by  actual  chemical  combination  or  combustion  of 
a  specific  substance.  Tin's  is  sometimes  called 
spontaneous  phosphorescence. 

Physical  phosphorescence  may  be  produced  in 
a  variety  of  ways,  viz. : 


(I.)  By  an  Elevation  of  Temperature: 
A  variety  of  fluorspar,  called  chlorophane, 
shines  with  a  beautiful  greenish  blue  light  when 
heated  tj  less  than  a  red  heat.  Here  the  non- 
luminous  rays  are  apparently  transformed  into 
luminous  rays. 

A  phosphorescent  substance  like  fluorspar 
eventually  loses  its  ability  to  phosphoresce.  It 
regains  it,  however,  on  exposure  to  the  light,  i.  t., 
if  such  an  exhausted  body  be  exposed  to  sunlight  it 
again  phosphoresces  on  exposure  t;>  non-luminous 
heat.  The  light  emitted,  during  phosphorescence 
by  heat,  is,  probably,  wholly  due  to  potential 
energy  acquired  during  exposure  to  the  light. 
(See  Luminescence.)  The  phosphorescence  by 
heat  exhibited  by  fluorspar  is  sometimes  called 
fluorescence.  It  is  preferable,  however,  to  call 
the  phenomena  phosphorescence.  (See  Fluores- 
eence. ) 

(2.)  By  Mechanical  Effects: 

The  flashes  of  light  emitted  during  the  attri- 
tion or  friction  of  some  bodies,  when  not  traceable 
directly  to  electricity,  are,  most  probably,  to  be 
ascribed  to  phosphorescence. 

(3.)  By  M  jlecular  Bombardment. 

The  molecular  bombardment  due  to  the  mole- 
cules of  residual  gas  shot  off  from  the  negative 
electrode  of  an  exhausted  receiver  through  wnch 
an  electric  discharge  is  passing,  produces  many 
brilliant  effects  of  phosphorescence. 

(4.)  By  Electricity. 

An  electric  spark  produces  phosphorescence  in 
such  substances  as  canary  glass,  solution  of  sul- 
phate of  quinine,  etc.,  etc. 

(5.)  Exposure  to  Sunlight,  or,  in  fact,  to  any 
light. 

The  different  rays  of  the  sun  are  not  equally 
able  to  excite  phosphorescence.  As  a  rule  the 
violet  or  ultra  violet  rays  excite  the  greatest  phos- 
phorescence. The  light  excited  is  often,  though 
not  always,  of  a  greater  wave  length  than  the 
exciting  light. 

Phosphorescent  paints  for  rendeiing  the  posi- 
tion of  a  push  button,  electric  call,  match  safe, 
gas  pendant  or  some  other  similar  object  visible 
at  night,  consist  essentially  of  sulphides  of  cal- 
cium or  barium,  or  of  mixtures  of  the  same. 

Phosphorescence,    Chemical A 

variety  of  phosphorescence,  in  which  the  errit- 
ted  light  is  produced  by  the  actual  combustion 


398 


[i'ho. 


of  a  specific  chemical  substance  by  the  oxygen 
of  the  air. 

Chemical  phosphorescence  is  seen  in  the  fire 
fly  and  the  glow-worm.     (See  Phosphorescence.} 

Phosphorescence,  Electric Phos- 
phorescence caused  in  a  substance  by  the 
passage  of  an  electric  discharge. 
"  The  phosphorescent  material  is  placed  in  an 
exhausted  glass  tube,  as  shown  in  Fig.  426,  and 
submitted  to  the  action  of  a  series  of  discharges, 
as  from  a  Ruhmkorff  coil,  or  Holtz  machine. 
The  violet-blue  light  of  such  discharge  is  very 
efficient  in  producing  phosphorescence.  Phosphor- 
escence is  thus  effected  by  subjecting  the  phos- 
phorescent material  to  the  molecular  bombard- 
ment which  is  produced  by  such  discharges  in  a 
high  vacuum.  (See  Bombardment,  Molecular.) 


Phosphorus.  Electric    Smelting  of 


Fig.  426.    Electric  Phosphorescence. 

Phosphorescence,  Physical  —       — Phos- 


phorescence produced  in  matter  by  the  actual 
impact  of  light  waves  resulting  in  a  vibratory 
motion  of  the  molecules  of  sufficient  rapidity 
to  cause  them  to  emit  light. 

Physical  phosphorescence  is  distinguished  from 
chemical  phosphorescence  in  that  in  the  former 
the  energy  required  to  produce  molecular  vibra- 
tions is  imparted  by  the  light  to  which  the  phos- 
phorescent body  is  exposed,  while  in  chemical 
phosphorescence  the  energy  producing  the  light 
is  derived  from  the  chemical  potential  energy 
of  the  specific  substance  burned.  (See  Phosphor, 
escence. ) 

Phosphorescent, — Possessing  the  proper- 
ties or  qualities  of  phosphorescence. 

Phosphorescing1. — Emitting  phosphores- 
cent light.  (See  Phosphorescence?) 

Phosphorescope. — An  apparatus  for  meas- 
uring the  phosphorescent  power  of  any  sub- 
stance. (See  Phosphorescence?) 


-  An  electric  process  for  the  direct  production 
of  phosphorus. 

In  the  electric  smelting  of  phosphorus,  the 
crude  material,  consisting  of  a  mixture  of  bones  or 
animal  phosphates  and  carbon,  is  fed  into  a  space 
between  two  electrodes  connected  to  the  poles  of 
a  source  of  powerful  alternating  currents.  The 
apparatus  is  similar  in  general  to  the  Cowles  fur- 
nace for  the  reduction  of  aluminium.  The  heat 
produced  by  the  alternating  currents  decomposes 
the  phosphates,  and  the  volatilized  phosphorus 
is  condensed  in  suitable  chambers. 

Photochronograph. — An  electric  instru- 
ment for  automatically  recording  the  transit 
of  a  star  across  the  meridian. 

In  a  small  camera  connected  with  the  eye -piece 
of  the  transit  instrument  is  placed  a  sensitized 
plate. 

A  sidereal  clock  has  an  electric  attachment  to 
its  pendulum,  so  made  that  a  shutter  alternately 
exposes  and  conceals  the  photographic  plate,  and 
thus  permits  the  image  of  a  star  to  be  formed  on 
the  plate  at  intervals  during  its  passage  across 
the  field  of  the  telescope.  An  image  of  the  spider 
lines  is  afterwards  fixed  on  the  plate  by  the  light 
of  a  lamp,  held  for  a  few  moments  before  the  ob- 
ject glass  of  a  telescope.  A  shutter  is  provided, 
by  means  of  which  this  light  is  prevented  from 
falling  on  the  trail  of  the  star  across  the  field  of 
the  glass.  In  this  manner  the  time  of  passage  of 
the  star  across  the  meridian  is  automatically  re- 
corded on  the  photographic  plate. 

The  photochronograph  is  also  adapted  for 
similarly  automatically  recording  the  transit  or 
passage  of  any  heavenly  body  across  any  imagin- 
ary line  in  the  heavens. 

Photo-Electric  Cell.— (See  Cell,  Photo- 
Electric?) 

Phot  o-Electricity.  —  (  See  Electricity, 
Photo?) 

Photo-Electromotive  Force. — (See  Force, 
Electromotive,  Photo?) 

Photometer. — An  apparatus  for  measuring 
the  intensity  of  the  light  emitted  by  any 
luminous  source. 

There  are  various  methods  for  measuring  the 
intensity  of  a  beam  of  light  passing  through  any 
given  space,  or  emitted  from  any  luminous 


Pho. 


399 


[Pho. 


source;  these  methods  are  embraced  in  the  use 
of  the  following  apparatus: 

(l.)  Calorimetric Photometer,  in  which  the  light 
to  be  measured  is  absorbed  by  the  face  of  a 
thermo-electric  pile,  and  the  electric  current 
thereby  produced  is  carefully  measured.  Since 
obscure  radiation  or  heat  will  also  thus  produce 
an  electric  current,  it  is  necessary  first  to  absorb 
all  the  heat  by  passing  the  beam  of  light  through 
an  alum  cell. 

(2.)  Actinic,  or  Chemical  Photometers,  in  which 
the  intensity  of  the  light  is  estimated  by  a  com- 
parison of  the  depth  of  coloration  produced  on  a 
fillet  of  photographic  paper  under  similar  con- 
ditions of  exposure  to  a  standard  light,  and  the 
light  to  be  measured. 

The  combination  of  pure  hydrogen  and  chlorine, 
or  the  decomposition  of  pure  mercurous  chloride, 
have  been  employed  for  the  purpose  of  determin- 
ing the  intensities  of  two  lights  by  measuring  the 
amount  of  chemical  action  effected. 

(3.)  Shadow  Photometers,  in  which  a  shadow 
produced  by  the  light  to  be  measured  is  compared 
with  a  shadow  produced  by  a  standard  candle. 
(See  Candle,  Standard.) 


Fig.  427.     The  Shadow  Photometer. 

Rumford's  photometer,  shown  in  Fig.  427,  is 
an  example  of  this  form  of  instrument.  The 
standard  candle,  shown  at  L,  casts  a  shadow  C", 
of  an  opaque  rod  C,  on  the  screen  at  B. 

The  light  to  be  measured  L',  is  moved  away 
from  the  screen  until  its  shadow  C',  on  the  screen 
at  A,  is  judged  by  the  eye  to  be  of  the  same 
depth.  The  distance  between  the  screen  and  the 
lights  is  then  measured  in  straight  lines.  The 
relative  intensities  of  the  two  lights  are  then  pro- 
portional to  the  squares  of  their  distances.  If,  for 
example,  the  candle  be  at  10  inches  from  the 
screen,  and  the  lamp  at  40  inches,  then  the 
intensities  are  as  ios :  40'  or  as  100  :  1,600,  or  the 
lamp  is  a  16  candle-power  lamp. 


This  photometer  is  based  on  the  fact  that  the 
shadow  of  each  source  is  illumined  by  the  light 
of  the  other  source. 

These  results  are  more  accurate  if  the  two 
shadows  are  adjoining  or  nearly  adjoining. 

(4. )  Translucent-Disc  Photometers.  — The  light 
to  be  measured  and  a  standard  candle  are  placed 
on  opposite  sides  of  a  sheet  of  paper  the  centre  of 
which  contains  a  grease  spot.  The  standard 
candle  is  kept  at  a  fixed  distance  from  the  paper 
and  both  it  and  the  paper  are  moved  towards  or 
from  the  light  to  be  measured  until  both  sides  of 
the  paper  are  adjudged  to  be  equally  illumined. 

In  Bunsen's  photometer  a  vertical  sheet  of 
paper' with  a  grease  spot  at  its  centre,  is  exposed 
to  the  illumination  of  a  standard  candle  on  one 
side,  and  the  light  to  be  measured  on  the  other. 

The  sheet  of  paper  is  placed  inside  a  dark  box 
provided  with  two  plane  mirrors  placed  at  such 
an  angle  to  the  paper  that  an  observer  can  readily 
see  both  sides  of  the  paper  at  the  same  time. 

This  box  can  be  slid  along  a  graduated,  hori- 
zontal scale  towards,  or  from,  the  light  to  be 
measured,  and  carries  with  it  the  standard  candle 
mounted  on  it  at  a  constant  distance  of  10  inches. 
If  the  box  is  too  near  the  light  to  be  measured, 
the  grease  spot  appears  brighter  on  the  side  of  the 
sheet  of  paper  nearest  the  candle.  If  too  near 
the  candle,  it  appears  brighter  on  the  side  of  the 
sheet  of  paper  nearest  the  light  to  be  measured. 
The  position  in  which  the  spot  appears  equally 
bright  on  both  sides,  is  the  position  in  which  both 
sides  of  the  paper  are  equally  illumined,  and  the 
relative  intensities  of  the  two  lights  are  then 
directly  as  the  squares  of  their  distances  from  the 
sheet  of  paper. 

Shadow,  and  translucent-disc  photometers 
being  dependent  on  equal  illumination,  are  re- 
liable only  when  the  color  of  the  lights  compared 
is  the  same.  For  the  determination  of  the  photo- 
metric intensity  of  very  bright  lights,  the  standard 
candle  is  replaced  by  a  carcel  lamp,  a  standard 
gas  jet,  or  by  the  light  emitted  by  a  given  mass 
of  platinum,  heated  to  incandescence  by  a  given 
current  of  electricity.  (See  Lamp,  Carcel.  Gas- 
jet,  Carcel  Standard.  Light,  Platinum  Stand- 
ard.} 

Preece's  photometer  belongs  to  the  class  of 
translucent  disc  photometers.  A  tiny  incandes- 
cent lamp  is  placed  in  a  box,  the  top  of  which  has 
a  white  paper  screen  on  which  is  a  grease  spot. 
The  box  is  placed  in  the  street  where  the  intensity 
of  illumination  is  to  be  measured,  and  the  inten- 


Pho.] 


400 


[rko. 


sity  of  the  light  of  the  incandescent  lamp  is 
varied  until  the  grease  spot  disappears.  The 
current  of  electricity  then  passing  through  the 
incandescent  lamp  acts  as  the  measure  of  the 
iliumination. 

In  the  case  of  the  shadow  photometer,  or  of 
Bunsen's  photometer,  if  the  intensity  of  illumina- 
tion is  the  same,  the  relative  intensities  of  the  two 
lights  may  be  determined  as  follows: 

Calling  I,  and  i,  respectively  the  relative  inten- 
sities of  the  standard  light,  and  the  light  to  be 
measured,  and  D,  and  d,  their  respective  dis- 
tances from  the  screen,  then 

I  :  i  :   :  D8   :  d2,  or  I  X  d2  =  i  X  D2; 

/  d2 
that  is,  i  =  I  ^— 

Or,  the  intensity  of  the  light  to  be  measured  is 

(d8  \ 
=—  j  times  the  intensity  of  the  standard  light. 

If,  for  example,  D  and  d,  represent  10  and  100 
inches,  respectively,  the  intensity  of  i,  is  100  times 
the  intensity  I,  the  standard  1'ght. 

(5.)  Dispersion  Photometers.  A  class  of  pho- 
tometers in  which,  in  order  to  more  readily  com- 
pare or  measure  a  very  bright  or  intense  light, 
like  that  of  an  arc  lamp,  the  intensity  of  the  light 
is  decreased  by  dispersion  a  readily  measurable 
amount. 

Ayr  ton  &*  Perry's  Dispersion  Photometer. — A 
photometer  in  which,  in  order  to  bring  an  in- 
tensely bright  light,  like  an  electric  arc  light,  to 


Fig.  428.    Ayrton  &*  Perry's  Dispersion  Photometer. 

such  an  intensity  as  will  permit  it  to  be  readily 
compared  with  a  standard  candle,  its  intensity  is 
weakened  by  its  passage  through  a  diverging 
(concave)  lens. 

Ayrton  &  Perry's  dispersion  photometer  is 
shown  in  two  different  positions,  Figs.  428  and 
429.  The  apparatus  is  supported  on  a  tripod 
stand  E,  arranged  so  as  to  obtain  exact  leveling. 


A  plane  mirror  H,  movable  around  a  pin  placed 
directly  under  its  centre,  can  be  rotated  and  thus 
reflect  the  light  after  its  passage  through  the 
diverging  lens,  while  still  maintaining  its  distance 
from  the  electric  light. 

The  horizontal  axis  of  this  mirror  is  inclined 
45  degrees  to  its  reflecting  surface  in  order  to 
avoid  errors  arising  from  varying  absorption  at 
different  angles  of  reflection. 

The  inclination  of  the  beam  to  the  horizontal 
is  indicated  by  means  of  an  index  attached  to  the 
mirror  and  moving  over  the  graduated  circle  G. 

A  black  rod  A,  casts  its  shadow  on  a  screen  of 
white  blotting  paper  B.  A  standard  candle, 
placed  in  the  holder  D,  casts  its  shadow  alongside 
the  shadow  cast  by  the  electric  light.  The  lens 
is  now  displaced  until  the  shadow  of  the  electric 
light  is  of  the  same  intensity  as  that  of  the  candle, 
when  viewed  successively  through  sheets  of  red 
and  green  glass. 

A  graduated  scale  serves  to  mark  the  distances 
of  the  candle  and  the  lens,  respectively,  from  the 
screen,  from  which  data  the  intensity  ot  the 
electric  light  may  be  calculated. 


Fig.  429.    Ayrton  and  Perry's  Dispersion  Photometer. 


(6.)  Selenium  Photometers.  —  Instruments  in 
which  the  relative  intensities  of  two  lights  are  de- 
termined by  the  variations  produced  in  a  selenium 
resistance. 

In  Siemens'  Selenium  photometer  a  selenium 
cell  is  employed  in  connection  with  an  electric 
circuit  for  determining  the  intensity  of  light. 

The  tube  A  B,  Fig.  430,  is  furnished  at  A,  with 
a  diaphragm,  and  at  B,  with  a  selenium  plate, 
connected  by  wires  G  G,  with  the  circuit  of  a 
battery  and  a  galvanometer. 

A  graduated  scale  L  M,  bears  the  standard 
candle  N.  The  tube  A  B,  is  capable  of  rotation 
on  the  vertical  axis  F.  A  reflecting  mirror  gal- 
vanometer is  used  in  connection  with  the  selenium 
photometer.  The  light  to  be  measured  is  placed 


PaO.] 


401 


[Pho. 


at  right  angles  to  the  scale  L  M,  and  the  tube  A 
B,  directed  towards  it,  and  the  ga.vanometer  de 
flection  compared  with  the  deflection    obtained 
when  turned  towards  the  standard  candle. 

(7.)  Gas-jet  Photometers. — Instruments  in 
which  the  candle-power  of  a  gas-jet  is  determined 
by  measuring  the  height  at  which  the  jet  burns 
when  under  unit  conditions  of  volume  and  press- 
ure of  gas  consumed . 


Fig.  430.     Siemens'  Selenium  Photometer. 

In  determining  the  candle-power  of  an  intense 
light  like  the  electric  arc  light,  a  large  gaslight 
is  used  instead  of  a  standard  candle,  and  the 
photometric  power  of  this  gaslight  is  carefully 
determined  by  comparison  with  a  gas- jet  photom- 
eter. (See  Jet,  Gas,  Car  eel Standard.} 


Photometer,  Actinic 


— A  photom- 


eter in  which  the  intensity  of  any  light  is  meas- 
ured by  the  amount  of  chemical  decomposi- 
tion it  effects.  (See  Photometer.) 

In  some  actinic  photometers  the  intensity  of  the 
light  to  be  measured  is  determined  by  the  com- 
parison of  the  depth  of  coloration  of  a  sensi- 
tized film  under  similar  conditions  of  exposure 
to  a  standard  light  and  the  light  to  be  measured. 

Photometer,  Calorimetric A  pho- 
tometer in  which,  the  light  to  be  measured  is 
absorbed  by  the  face  of  a  thermo-electric  pile, 
and  the  intensity  of  the  light  estimated  from 
the  strength  of  the  electric  current  thereby 
produced. 

In  order  to  avoid  the  error  arising  from  the 
current  produced  from  the  absorption  of  the  ob- 
scure radiation  from  the  light,  all  tlie  hear,  is  first 
absorbed  by  passing  the  light  through  an  alum 
cell.  (See  Photometer. ) 

Photometer,  Chemical  —  — A  photom- 
eter in  which  the  intensity  of  the  light  to  be 


measured  is  determined  from  the  amount  of 
chemical  action  effected  m  a  given  time. 

Photometer,  Dispersion A  photom- 
eter in  which  the  light  to  be  measured  is  de- 
creased in  intensity  a  known  amount  so  as  to 
more  readily  permit  it  to  be  compared  with  a 
standard  light  of  much  smaller  intensity. 
(See  Photometer?)  ~~ 

Photometer,  Electric An  electrical 

instrument  for  measuring  the  intensity  of 
illumination. 

A  form  of  electric  photometer  invented  by  C. 
R.  Richards  depends  for  its  indications  on  the 
variations  that  occur  in  the  resistance  of  a  wire  on 
change  of  temperature.  An  iron  wire,  whose 
change  of  temperature  is  utilized  for  measuring 
the  intensity  of  any  light  to  whose  radiations  it  is 
opposed,  is  covered  by  a  deposit  of  lampblack. 
On  exposure  to  the  light  whose  intensity  is  to 
be  measured,  the  light  is  absorbed  l<y  the  lamp- 
black and  an  increase  in  temperature  occurs. 

In  order  to  get  rid  of  the  heat  rays  that  are 
associated  with  the  light  rays,  the  rays  before 
falling  on  the  soot-covered  wire  are  caused  to  pass 
through  a  solution  of  alum  ;  the  intensity  of  the 
light  is  then  calculated  by  reference  to  the  change 
in  the  resistance  of  the  soot-covered  wire,  which 
is  made  one  of  the  arms  of  a  Wheatstone  bridge. 

Photometer,  Gas-Jet — A  photom- 
eter in  which  the  candle-power  of  a  gas-jet  is 
estimated  from  a  measurement  of  the  height 
at  which  the  jet  burns  under  unit  conditions 
of  volume  and  pressure.  (See  Photometer?) 

Photometer,  Jet An  apparatus  for 

determining  the  candle  power  of  a  luminous 
source  by  means  of  the  height  of  a  jet  of  the 
gas,  whose  candle-power  is  being  determined, 
when  burning  under  constant  conditions  as 
to  pressure,  etc.  (See  Jet,  Gas,  Carcel 
Standard?) 

Photometer,  Selenium A  photom- 
eter in  which  the  intensity  of  a  light  is  esti- 
mated by  the  comparison  of  the  changes  in 
the  resistance  of  a  selenium  resistance  suc- 
cessively exposed  under  similar  conditions  to 
this  light  and  to  a  standard  light.  (See 
Photometer?) 

Photometer,  Shadow A  photom- 
eter in  which  the  intensity  of  the  light  to  be 


Pho.] 


402 


[Pho. 


measured  is  estimated  by  a  comparison  of 
the  distances  at  which  it  and  a  standard  light 
produce  a  shadow  of  the  same  intensity. 
(See  Photometer?) 

Photometer,  Translucent  Disc A 

photometer  in  which  the  light  to  be  measured 
is  placed  on  one  side  of  a  partly  translucent 
and  partly  opaque  disc,  and  a  standard  can- 
dle is  placed  on  the  opposite  side,  and  the  in- 
tensity of  the  light  estimated  by  the  distances 
of  the  light  from  the  disc  when  an  equal  illu- 
mination of  all  parts  of  the  disc  is  obtained. 
(See  Photometer?) 

When  the  illumination  of  the  opposite  sides  of 
such  a  disc  is  equal,  the  relative  positions  of  the 
transparent  and  opaque  portions  of  the  disc  are 
indistinguishable. 

Photometer,  Yarley's  •  — A  form  of 

photometer  in  which  the  intensity  of  the  light 
to  be  measured  is  determined  from  the  rel- 
ative openings  of  two  concentric  circular 
diaphragms  placed  in  two  rotating  discs,  and 
through  which  the  standard  light  and  the 
light  to  be  measured  respectively  pass. 

The  general  arrangement  of  Varley's  photo- 
meter  is  shown  in  Fig.  431.  The  concentric  cir- 


ring  is  fully  open,  the  other  is  completely  closed , 
or,  if  one  ring,  say  the  outer,  is  opened  160  de- 
grees, the  inner  is  opened  20  degrees.  The 
quantity  of  light  then  which  passes  through  the 
outer  ring  from  the  light  to  be  measured  is  eight 
times  that  passed  through  the  inner  ring.  The 
circle  is  divided  into  2,000  parts,  instead  of  int9 
360  degrees,  and,  by  means  of  a  vernier,  these 
parts  are  further  divided  into  10  parts,  permitting 
a  reading  of  the  20,000  divisions. 

Two  collimeters  placed  in  front  of  the  disc, 
project  a  disc  with  a  black  centre,  and  a  luminous 
spot  respectively.  The  discs  are  regulated  until 
the  light  projected  on  the  screen  produces  a  uni- 
form disc.  This  is  readily  ascertained,  since  if 
one  or  the  other  predominate,  a  disc  with  gray 
spot,  or  a  gray  marginal  ring  with  a  bright  spot, 
will  appear. 

The  general  appearance  of  the  circular  dia- 
phragm, corresponding  to  different  relative  posi- 
tions of  the  two  discs,  is  shown  in  Fig.  432. 


43  1.    Varlev's  Photometer. 


cular  apertures  extend  circumferentially  180  de- 
grees,  and  are  reversed  so  that  when  one  half 


Fig.  4.32.    Circular  Diaphragm  of  Varley's  Photometer. 

Photometric. — Of  or  pertaining  to  the 
photometer.  (See  Photometer?) 

Photometrically. — In  a  photometric  man- 
ner. 

Photophone. — An  instrument  invented  by 
Bell  for  the  telephonic  transmission  of  artic- 
ulate speech  along  a  ray  of  light  instead  of 
along  a  conducting  wire. 

A  beam  of  light,  reflected  from  a  diaphragm 
against  which  the  speaker's  voice  is  directed,  is 
caused  to  fall  on  a  selenium  resistance  inserted  in 
the  circuit  of  a  voltaic  battery,  and  a  telephone. 
The  changes  thus  effected  in  the  resistance  of  the 
circuit  by  the  varying  amounts  of  light  reflected  on 
the  selenium  resistance  from  the  diaphragm,  while 
moving  to-and-fro  under  the  influence  of  the  speak- 
er's voice,  produce  in  the  receiving  telephone  a 
series  of  to-and  fro  movements  similar  to  those  im- 
pressed on  the  transmitting  diaphragm.  One  lis- 
tening at  the  telephone  can  hear  whatever  has  been 
spoken  in  the  neighborhood  of  the  transmitting 
diaphragm.  Telephonic  communication  can, 
therefore,  by  such  means  be  carried  on  afong  ? 


Pho.] 


403 


[fie. 


ray  or  beam  of  light,  theoretically  through  any 
distance.  (See  Resistance,  Selenium.') 

A  block  of  vulcanite  or  of  certain  other  sub- 
stances  may  be  used  as  the  receiver,  since  it  has 
been  discovered  that  a  rapid  succession  of  flashes 
of  light  produces  an  audible  sound  in  small  masses 
of  these  substances. 

The  term  sonorescence  has  been  proposed  for 
the  property  possessed  by  such  substances  of 
emitting  sounds  when  subjected  to  such  inter- 
mittent, flashes  of  light.  (See  Sonorescence. .) 


Photophore,  Troure's 


— An  appa- 


ratus in  which  the  light  of  a  small  incandescent 
electric  lamp  is  employed  for  purposes  of 
medical  exploration. 

A  small  incandescent  lamp  is  placed  in  a  tube 
containing  a  concave  mirror  and  a  converging 
lens. 

Photo-Telegraphy. — The  electric  produc- 
tion of  pictures,  writing,  charts  or  diagrams 
at  a  distance. 

Photo-Telegraphy  is  sometimes  called  telepho- 
tography; it  is  a  species  of  fac-simiie  telegraphy. 
(See  Telegraphy,  Fac-Simile.  Telepho(ographv-) 

Photo- Voltaic  Effect.— (See  Effect,  Photo- 
Voltaic) 

Physical  Change. — (See  Change,  Phy- 
sical?) 

Physical  Phosphorescence. — (See  Phos- 
phorescence, Physical?) 

Physiological. — Pertaining  to  physiology. 

Physiological  Rheoscope. — (See  Rheo- 
scope,  Physiological.} 

Physiologically. — In  a  physiological  man- 
ner. 

Physiology,  Electro The  study  of 

electric  phenomena  of  living  animals  and 
plants. 

Living  animals  and  plants  present  electric 
phenomena,  due  to  the  electricity  naturally  pro- 
duced by  them.  It  is  the  province  of  electro- 
physiology  to  ascertain  the  causes  and  effects  of 
these  phenomena. 


Piano,  Electric 


— A  piano  in  which 


the  strings  are  strucK  by  hammers  actuated 
by  means  of  electro-magnets,  instead  of  by 
the  usual  mechanical  action  of  levers. 


An  electric  piano-action  is  mainly  useful  in  per- 
mitting the  instrument  to  be  played  at  any  dis- 
tance from  the  key-board,  it  is  also  of  value 
from  the  ease  it  affords  in  recording  the  pieces 
played. 

It  fails,  however,  to  properly  preserve  the  vari- 
ous modulations  of  force  so  requisite  for  brilliant 
instrumentation. 

Pickle. — An  acid  solution  in  which  me- 
tallic objects  are  dipped  before  being  gal- 
vanized, or  electroplated,  in  order  to 
thoroughly  cleanse  their  surfaces. 

The  pickle  used  for  the  preparation  of  iron  for 
galvanization  is  a  weak  solution  of  sulphuric  acid 
in  water.  Various  acids,  or  acid  liquids,  are  em 
ployed  for  insuring  the  thorough  cleansing  of 
metallic  surfaces  so  necessary  in  order  to  ensure 
an  even,  uniform,  adherent  coating  of  metal  by 
the  process  ot  electroplating.  (See  Plating, 
Electro. ) 

Piece,  Magnetic  Proof A  para- 
magnetic rod,  ellipsoid  or  sphere  employed 
for  ascertaining  the  distribution  of  magnetism 
over  a  magnet  by  the  force  required  to  de- 
tach the  same.  (See  Paramagnetic?) 

Prof.  S.  P.  Thompson  points  out  the  fact 
that  the  presence  of  the  proof-piece  so  alters  the 
distribution  of  magnetism  on  the  magnet  to  be 
measured  as  to  render  this  method  unreliable. 
He  also  shows  that  the  force  required  for  detach- 
ment depends  on  the  magnetic  permeability  of 
the  proof-piece,  as  well  as  on  its  shape  and  its 
position  in  the  magnetic  circuit. 

•   Pieces,  Month Openings  into  air 

chambers,  generally  circular  in  shape,  placed 
over  the  diaphragms  of  telephones,  phono- 
graphs, gramophones  or  graphophones  to 
permit  the  ready  application  of  the  mouth  in 
speaking,  so  as  to  set  the  diaphragm  into 
vibration. 

The  mouth  piece  miy  be  also  utilized  by  the 
ear  of  an  observer  listening  so  as  to  be  affected 
by  its  vibrations. 

Pieces,  Pole,  of  Dynamo-Electric  Ma- 
chine   Masses  of  iron  connected  with 

the  poles  of  the  field  magnet  frames  of 
dynamo-electric  machines,  and  shaped  to 
conform  to  the  outline  or  contour  of  the 
armature. 


Pi  I.'] 

The  pole  pieces  are  made  in  a  variety  of  forms, 
but  in  all  cases  are  so  shaped  as  to  conform  to  the 
outline  of  the  space  in  which  the  armature  rotates. 

The  pole  pieces  are  brought  as  near  as  possible 
to  the  armature,  so  as  to  increase  the  intensity  of 
the  magnetic  induction.  The  intervening  air 
space  should  be  as  thin  as  possible,  but  of  as  large 
an  area  as  convenient. 

The  opposite  pole  pieces  should  not  have  their 
ext.  nsions  brought  too  near  together,  as  this  will 
pjrmit  o'f  serious  loss  through  magnetic  leakage. 
The  distance  between  them  should  be  as  many 
times  the  depth  of  the  armature  windings  as 
possible.  (See  Leakage,  Magnetic. ) 

Rounded  edges  are  preferable  to  sharp  edges 
for  the  same  reason. 

Pile,  Dry A  voltaic  pile  or  battery 

consisting  of  numerous  cells,  the  voltaic 
couple  in  each  of  which  consists  of  sheets  of 
paper  covered  with  zinc-foil  on  one  side  and 
black  oxide  of  manganese  on  the  other. 

Various  modifications  of  the  above  form  have 
been  made. 

The  term  dry-pile  is  a  misnomer,  since  all  such 
piles  contain  substances  moistened  by  liquid 
electrolytes. 

Pile,  Muscular,  Matteucci's A  vol- 
taic battery  or  pile,  the  elements  of  which  are 
formed  of  longitudinal  and  transverse  sections 
of  muscle  alternately  connected. 

Matteucci's  experiments  appear  to  show  that 
the  lower  the  animal  is  in  tne  scale  of  creation, 
the  stronger  is  the  current  produced,  and  the 
longer  its  duration.  Du  Bois-Reymond  has 
shown  that  the  muscular  current  is  not  due  to 
contact,  but  to  the  differences  of  electric  poten- 
tial naturally  possessed  by  the  muscles  the.ii- 
selves. 

The  nerves  also  possess  the  power  of  producing 
differences  of  electromotive  force,  and  hence  cur- 
rents. (See.  Electrotonus. ) 

Pile,  Thermo,  Differential A  ther- 
mopile in  which  the  two  opposite  faces  are 
exposed  to  the  action  of  two  nearly  equal 
sources  of  heat  in  order  to  determine  accu- 
rately the  differences  in  the  thermal  intensities 
of  such  sources  of  heat. 


fPil. 

series,  so  as  to  form  a  single  thermo-electric 
source.  (See  Couple,  Ther mo-Electric?) 

A  thermo  electric  pile  is  sometimes  called  a 
thermo-electric  battery. 

Fig  433  shows  Nobili's  thermopile,  in  which 
a  number  of  bismuth- 
antimony  thermo-elec- 
tric couples  connected 
in  a  continuous  se- 
ries, as  shown  panly 
in  Fig.  434,  are  insu- 
lated from  one  another, 
except  at  their  June 
tions,  and  packed  in  a 
metallic  box,  supported 
as  shown  in  Fig  433. 
The  free  terminals  of  Fig.  433.  Thf? 'mo- Electric 
the  series  are  con-  Pile. 

nected  to  binding  posts.  Differences  of  tem- 
perature between  ihe  two  faces  of  the  pile,  where 
the  junctions  are  exposed,  result  in  a  difference 
of  potential  equal  to  the  sum  of  the  differences  of 
potential  of  all  the  thermo-electric  couples. 

A  careful   inspec-  ^>  i 

tion  will  show    that  ('  ==~===^ 

the  junctions  are 
formed  successively 
at  opposite  faces  of 
the  pile,  so  that  if 
the  junctions  be 
numbered  succes- 
sively, the  even  junc- 
tions will  come  at 
one  face,  and  the 


Ft'f.  434.     Series-Connected 
Thermo- Electric  Couples. 

odd  junctions  at  the  other.  This  is  necessary 
in  order  to  permit  all  the  thermo-electric  couples 
to  add  their  differences  of  potential ;  for,  if,  as 
in  fig.  43S>  a  thermo-electric  chain  be  formed, 


Pile,  Tjenno-Electric 


-A  number 


of  separate  thermo-electric  couples,  united  in 


Fig.  435.     Thermo-Llectnc  Circuit. 


no  currents  will  result  from  equally  heating  any 
two  consecutive  junctions  ],  J,  of  the  metals  A 
and  B,  since  the  electromotive  forces  so  produced 
oppose  each  other. 

Thermopiles  have  been  constructed  by 
Clamond,  of  couples  of  iron  and  an  atioy  of  zinc 
and  antimony,  of  sufficient  power  to  produce  a 
voltaic  arc  whose  illuminating  power  equaled  40 


pr.i 


405 


ffcla. 


carcel  b-irr?er^.  Many  practical  difficulties  exist 
which  will  have  to  be  surmounted,  however,  before 
such  piles  can  be  employed  as  commercial  electric 
sources. 

Pile,  Voltaic A  battery  consisting 

of  a  number  of  voltaic  couples  connected  so 
as  to  form  a  single  electric  source. 

A  form  simi  ar  to  Volta's  original  pile,  consist- 
ing ot  alternate  discs  of  copper  and  zinc,  separated 
from  each  other  by  discs  of  wet  cloth,  and  piled 
on  one  another,  so  as  to  form  a  numher  of  separate 
voltaic  couj-les  connected  in  series,  is  shown  in 
Fig.  436.  The  thick  plates  marked  Zn,  are  of 
zinc  ;  the  «opper  plates,  marked  Cu,  are  much 


Pin,  Insulator 


— A   bolt   by  means 


Fig-  43(>.     Voltaic  Pile. 

thinner.  The  discs  of  moistened  cloth  are  shown 
at  d  d.  One  end  of  such  a  pile  would  then  be 
terminated  by  a  plate  of  copper,  and  the  other 
by  a  plate  of  zinc.  The  copper  end  forms  the 
positive  electrode,  and  the  zinc  end  the  negative 
electrode.  (See  Cell,  Voltaic  ) 

Pilot  Lamp.— (See  Lamp,  Pilot.) 

Pilot  Transformer.— (See  Transformer, 
Pilot.) 

Pilot  Wires.— (See  Wires,  Pilot.) 


of  which  an  insulator  is  attached  to  the  tele- 
graphic support  or  arm. 

The  insulator  pins  or  bolts  are  generally  fixed  to 
the  insulator  by  means  of 
screw  threads  turned  on 
their  ends.  They  are  then 
cemented  to  the  insulators  by 
any  suitable  moisture-proof 
cement. 

The  pin  and  insulator  con- 
nected  to  one  another  by 
means  of  a  screw  thread  are 
shown  in  Fig.  437. 

Pin,  Switch  -       —A 

metallic  pin  or  plug  pro- 
vided for  insertion  in  a 
telegraphic  switch  board. 
A  form  of  switch  pin  is 
shown  in  Fig.  438.  The 
metallic  end  is  conical  in 
form,  and  is  provided  with 
two  longitudinal  slots  at  Fig.  437.  Insulator 
right  angles  to  each  other  in  1'in. 

order  to  insure  a  light  spring  connection  with 
the  metallic  contact  plate  in  which  the  pin  is  in- 
serted. 

Pith. — A  light,  cellular  material,  forming  the 
central  portions  of  most  exogenous  plants. 

An  excel'ent  pith,  suitable  for 
electrical  purposes,  is  furnished  by 
the  dried  interior  of  the  elder- berry 
stick. 

Pith  Ball.— (See  Balls,  Pith.) 

Pith  -  Ball    Electroscope.  — 

(See  Electroscope,  Pith-Ball.) 

Pivot  Suspension.— (See  Sus- 
pension, Pivot) 

Plain-Pendant  Argand  Elec- 
tric Burner.  —  (See  Burner, 
Plain-Pendant  Electric) 

Plain-Pendant  Electric  Burner.  —  (See 
Burner,  Plain-Pendant  Electric.) 

Plane  Angle. — (See  Angle,  Plane) 

Plane,   Proof A   small   insulated 

conductor  employed  to  take  test  charges  from 
the  surfaces  of  insulated,  charged  conductors. 


40G 


[Pla. 


The  proof-plane  is  used  in  connection  with 
some  form  of  electrometer.  (See  Balance,  Cou- 
lomb''! Torsion.') 

Plane,  Proof,  Magnetic  —  —A  small 
coil  of  wire  placed  in  the  circuit  of  a  delicate 
galvanometer,  and  used  for  the  purpose  of 
exploring  a  magnetic  field. 

When  the  coil  is  suddenly  inverted  in  a  mag- 
netic field,  if  a  long-coil  galvanometer  provided 
with  a  heavy  needle  is  used,  the  number  of  lines 
of  force  which  pass  through  the  area  of  cross-sec- 
tion of  the  coil  will  be  proportional  to  the  sine  of 
half  the  angle  of  the  first  swing  of  the  needle. 

Plant. — A  word  sometimes  used  for  in- 
stallation, or  for  the  apparatus  required  to 
carry  on  any  manufacturing  operation. 

An  electric  plant  includes  the  steam  engines 
or  other  prime  motors,  the  generating  dynamo  or 
dvnamos,  the  lamps  and  other  electro-receptive 
devices,  and  the  circuits  connected  therewith. 

Plant  Electricity.  —  (See  Electricity, 
Plant.  Plants,  Electricity  of.) 

Plants,   Electricity   of — Electricity 

produced  naturally  by  plants  during  their  vig- 
orous growth. 

DuBois-Reymond  and  others  have  shown  that 
plants  while  in  a  vigorous  vital  state  are  active 
sources  of  electricity. 

If  one  of  the  terminals  of  a  galvanometer  be 
inserted  into  a  fruit  near  its  stem,  and  the  other 
terminal  into  the  opposite  part  of  the  fruit,  the 
galvanometer  at  once  shows  the  presence  of  an 
electric  current. 

Buff  has  shown  that  the  roots  and  interior  por- 
tions of  plants  are  always  negatively  charged, 
while  the  flowers,  fruits  and  green  twigs  are  posi- 
tively charged. 

Plant  tissue  or  fibre,  like  the  muscular  fibre  of 
animals,  exhibits  in  many  cases  a  true  contraction 
on  the  passage  through  it  of  an  electric  current. 
This  is  seen  in  the  Mimosa  sensitiva,  or  Sensitive 
Fern,  in  the  Venus'  Fly-Trap,  and  in  several  other 
species  of  plants. 

Fouillet  concludes  from  numerous  observations 
that  the  free  positive  electricity  of  the  atmosphere 
is  partly  due  to  the  vapors  disengaged  by  grow- 
ing plants. 

The  peculiar  geographical  distribution  of  thun- 
der storms,  however,  does  not  favor  this  assump- 


tion. (See  Storm,  Thunder,  Geographical  Dis- 
tribution of.) 

Plastics,  Galvano  —  — A  term  some- 
times employed  for  electrotyping,  that  is 
where  the  deposits  are  sufficiently  thick  to 
permit  of  ready  separation  from  the  object 
which  forms  the  mould. 

Literally,  the  cold  moulding  or  shaping  of 
metals  by  electrotyping.  (See  Plating,  Elec- 
tro. Metallurgy,  Electro?) 

The  word  galvano-plastics  is  sometimes  used 
as  synonymous  with  electrotyping,  electro-plat- 
ing, or  electro-metallurgy  generally. 

Plastics,  Hydro The  art  of  elec- 
trically shaping  or  depositing  metals  in  the 
wet  by  electrotyping.  (See  Plastics,  Gal- 
vano.) 

Plate,  Arrester,  of  Lightning  Protector 

That   plate  of  a  lightning  protector 

which  is-  directly  connected  with  the  circuit 
to  be  protected,  as  distinguished  from  the  plate 
that  is  connected  with  the  ground.  (See 
Arrester,  Lightning?) 

Plate  Condenser.— (See  Condenser,  Plate?) 
Plate,  Ground,  of  Lightning  Arrester — 

— That  plate  of  a  comb  lightning  arrester 
which  is  connected  to  the  earth  or  ground. 
(See  Arrester,  Lightning,  Comb?) 

Plate,  Negative,  of  Storage  Cell 

That  plate  of  a  storage  cell  which,  by  the 
action  of  the  charging  current,  is  converted 
into  or  partly  covered  with  a  coating  of  spongy 
lead. 

That  plate  of  a  storage  battery  which  is 
connected  with  the  negative  terminal  of  the 
charging  source,  and  which  is  therefore  the 
negative  pole  of  the  battery  on  discharging. 

The  usage  is  the  reverse  of  that  in  the  case  of 
the  primary  battery. 

Plate,  Negative,  of  Yoltaic  Cell  - 

The  electro-negative  element  of  a  voltaic 
couple.  (See  Couple,  Voltaic?) 

That  element  of  a  voltaic  couple  which  is 
negative  in  the  electrolyte  of  the  cell.  (See 
Electrolyte?) 

The  negative  plate  of  a  voltaic  rell  is  the  plate 
not  acted  on  by  the  electrolyte.  In  a  zinc  carbon 


Pla.] 


407 


[Pla. 


couple  in  dilute  sulphuric  acid,  the  carbon  plate 
is  the  negative  plate.  (See  Cell,  Voltaic.) 

The  negative  plate  is  to  be  carefully  distin- 
guished from  the  negative  pole,  which  is  the  ter- 
minal connected  to  the  positive  plate.  The 
terminal  connected  to  the  negative  plate  is  the 
positive  pole.  (See  Cell,  Voltaic.) 

Plate,  Positive,  of  Storage  Battery  - 

— That  plate  of  a  storage  battery  which  is 
converted  into,  or  covered  by,  a  layer  of  lead 
peroxide,  by  the  action  of  the  charging  current. 
That  plate  of  a  storage  battery  which  is 
connected  with  the  positive  terminal  of  the 
charging  source  and  which  is,  therefore,  the 
positive  pole  of  the  battery  on  discharging. 

'It  will  be  noticed  that  the  usage  in  this  respect 
is  the  reverse  of  that  in  the  case  of  primary  bat- 
teries, in  which  the  positive  plate  is  positive  in 
the  liquid  only;  the  end  which  projects  from  the 
liquid,  or  the  terminal  connected  with  it  being 
negative. 

In  storage  batteries,  the  positive  plate  is  con- 
nected with  the  positive  pole.  (See  Battery, 
Storage.  Cell,  Voltaic.) 

Plate,  Positive,  of  Voltaic  Cell  - 

The  electro-positive  element  of  a  voltaic 
couple.  (See  Couple,  Voltaic.} 

That  element  of  a  voltaic  couple  which  is 
positive  in  the  electrolyte  of  the  cell.  (See 
Electrolysis.) 

The  positive  plate  of  a  voltaic  cell  is  the  plate 
out  from  which  the  current  flows  through  the 
electrolyte. 

The  zinc  plate  of  a  zinc-carbon  couple  is  the 
positive  plate.  (See  Cell,  Voltaic. ) 

The  current  leaves  the  cell,  however,  to  flow  or 
pass  through  the  external  circuit  at  the  wire  or 
terminal  connected  with  the  negative  plate.  (See 
Cell,  Voltaic.) 

Plate,    Primary,   of   Condenser 

That  plate  of  a  condensing  transformer  in 
which  the  inducing  charge  is  placed  in  order 
to  induce  a  charge  of  different  potential  in  the 
secondary  plate. 

Plate,   Secondary,  of  Condenser  — 

That  plate  of  a  condensing  transformer  in 
which  'the  induced  charge  is  produced  by  the 
induction  of  a  charge  on  the  primary  plate. 

Plate,  Zinc,  of  Voltaic  Cell,  Amalgama- 


tion of Covering  the  surface  of  the 

zinc  plate  of  a  voltaic  cell  with  a  thin  layer  of 
amalgam  in  order  to  avoid  local  action.  (See 
Action,  Local,  of  Voltaic  Cell.  Zinc,  Amal- 
gamation of.) 

Plates,  Arrester A  term  sometimes 

applied  to  the  two  plates  of  an  ordinary  cflmb 
lightning  arrester.  (See  Arrester,  Lightning, 
Comb.) 

The  plate  that  is  connected  to  the  line  to  be 
protected,  is  more  correctly  called  the  arrester 
plate,  and  that  connected  to  the  ground  the  ground 
plate. 

Plates  of  Secondary  or  Storage  Cell, 

Forming  of Obtaining  a  thick  coating 

of  lead  peroxide  on  the  lead  plates  of  a  storage 
battery,  by  repeatedly  sending  the  charging 
current  through  the  cell  alternately  in  opposite 
directions. 

The  effect  of  sending  a  current  between  two 
lead  plates  immersed  in  dilute  sulphuric  acid,  is  to 
coat  one  of  the  plates  with  lead  peroxide.  On  the 
sending  of  the  current  in  the  opposite  direction, 
the  other  plate  is  coated  with  lead  peroxide.  If 
now  the  current  is  sent  in  the  opposite  direction, 
more  peroxide  is  deposited  on  one  of  the  plates, 
and  the  peroxide  at  the  other  plate  is  converted 
into  spongy  lead. 

At  the  end  of  charging,  the  battery  will  form 
an  independent  source  of  current.  (See  Cell, 
Storage. ) 

Platform,  Pole A  platform,  capable 

of  supporting  several  men,  placed  on  a  termi- 
nal pole  provided  with  a  cable  box,  for  the 
purpose  of  affording  a  ready  means  of  inspect- 
ing and  arranging  the  conductors  in  the  box. 

Plating  Balance. — (Se&Balance,  Plating.) 

Plating  Bath,  Electro  -  -  (See  Bath, 
Electro-Plating?) 

Plating,  Copper — Electro-plating 

with  copper.  (See  Plating,  Electro.  Bath, 
Copper^ 

Plating,  Electro — The  process  of 

covering  any  electrically  conducting  surface 
with  a  metal  by  the  aid  of  the  electric 
current. 

By  the  aid  of  electro-plating,  the  baser  metals 
are  covered  w  th  silver,  gold  or  platinum,  or  with 
any  other  metal,  such  as  nickel  or  copper. 


Pla.J 


408 


[Pla. 


The  process  of  electro-plating  is  carried  on  as 
follows: 

The  object  to  be  plated  is  connected  with  the 
negative  terminal  of  a  battery  and  placed  in  a  so- 
lution of  the  metal  with  which  it  is  to  be  plated, 
opposite  a  plate  of  that  metal  connected  to  the 
positive  terminal  of  the  bat  ery.  If,  for  example, 
the  object  is  to  be  plated  with  copper,  it  is  pi  »ced 
in  a  solution  of  copper  sulphate  or  blue  vitriol, 
opposite  a  plate  of  copper.  By  this  arrangement 
the  object  to  be  plated  forms  the  kathode  of  the 
plating  bath,  and  the  plate  of  copper  forms  the 
anode. 

On  the  passage  of  the  current  the  copper  sul- 
phate (Cu  SO4)  is  decomposed,  metallic  copper 
being  deposited  in  an  adherent  layer  on  the  arti- 
cles attached  to  the  kathode,  and  the  acid  radical 
(SO4)  appearing  at  the  anode,  where  it  combines 
with  one  of  the  atoms  of  the  copper  plate.  Since 
for  every  molecule  of  copper  sulphate  decomposed 
in  theelecirolyte,anewmoleculeol  copper  sulphate 
is  thus  formed,  by  the  gradual  solution  of  the  copper 
anode,  the  strength  of  the  solution  in  the  bath  is 
maintained  as  long  as  any  of  the  copper  plate  re- 
mains at  the  anode,  and  the  ordinary  activity  of 
the  cell  is  not  otherwise  interfered  with. 

When  any  other  metals,  such  as  gold,  silver  or 
nickel,  for  example,  are  to  be  deposited,  suitable 
solutions  of  their  salts  are  placed  in  the  bath,  and 
plates  of  the  same  metal  hung  at  the  anode. 

The  character  and  coherence  of  the  metallic 
coatings  thus  obtained  depend  on  the  nature  and 
strength  of  the  plating  bath,  and  on  the  density 
of  the  current  employed.  The  size  and  position 
of  the  anode,  as  compared  with  the  size  and  posi- 
tion of  the  objects  to  be  plated,  must  therefore  be 
carefully  attended  to,  as  well  as  the  strength  of 


Fig.   43Q.    Electro- Plating 

the  metallic  solution  and  the  current  strength 
passing.  (See  Current  Density.} 

Fig.  439,  shows  a  bath  arranged  for  silver- 
plating. 

The  anode  consists  of  a  plate  of  i-ilver.     The 


spoons,  forks,  etc.,  to  be  plated  are  immersed  in 
a  suitable  silver  solution  and  connected  with  the 
kathode. 

The  electro-plating  process  when  employed  for 
the  production  of  electrotype  plates  is  called 
electrotyping.  Here  the  object  is  to  obtain  a  re- 
production in  metal  of  any  particular  form,  such 
as  of  type  or  of  some  natural  object.  It  was 
called  by  Jacobi  the  galvanofilastic  process.  The 
term  electrotyping  is,  however,  more  generally 
adopted.  (See  Electrotyping,  or  the  Electrotype 
Process.') 

Plating,  Gold Electro-plating  with 

gold.     (See  Plating,  Electro.    Bath,  Gold.} 

Plating,     Nickel Electro  -  plating 

with  nickel.  (See  Plating,  Electro.  Bath, 
Nickel} 

Plating,  Sectional Plating  an  article 

with  a  greater  thickness  of  metal  at  certain 
points  than  at  the  rest  of  the  surface. 

Sectional  plating  is  employed  for  such  objects 
as  spoons,  etc.,  which  are,  by  this  method,  given 
a  greater  thickness  of  deposit  at  the  under  portions 
of  the  bowl  and  handle,  where  the  spoon  usually 
rests,  and  is,  therefore,  exposed  to  the  greatest 
wear. 

Sectional  plating  is  effected  by  means  of  sec- 
tional plating  frames.  (See  Plating,  Electro. 
Frames,  Sectional  Plating. ) 

Plating,  Silver — Electro-plating 

with  silver.  (See  Plating,  Electro.  Bath, 
Silver?) 

Platinoid. — An  alloy  consisting  of  German 
silver  containing  I  or  2  per  cent,  of  metallic 
tungsten. 

Platinoid  is  suitable  for  use  in  resistance  coils  on 
account  of  the  comparatively  small  influence  pro- 
duced on  its  electric  resistance  by  changes  t  f 
temperature. 

Its  resistance  is  60  per  cent,  higher  than  that 
of  German  silver. 

Platinum. — A  refractory  and  not  readily 
oxidizable  metal,  of  a  tin-white  color. 

The  co-efficient  of  expansion  of  platinum  by 
heat  is  very  nearly  that  of  ordinary  giass.  Pla- 
tinum is,  therefore,  generally  employed  ior  the 
leading-in  conductors  of  an  incandescent  lamp. 
These  conductors  are  fused  into  the  glass  of  t>e 
lamp  chamber.  On  the  heating  of  the  wires  by 


Pla.] 


409 


[Plu. 


the  current,  the  glass  expands  t  qually  with  the 
wires,  and  the  vacuum  in  the  lamp  chamber  is 
not,  therefore,  injured. 

Platinum  Alloy. — (See  Alloy,  Platinum- 
Silver^) 

Platinum  Black. — Finely  divided  platinum 
that  possesses,  in  a  marked  degree,  the  power 
of  absorbing  or  occluding  gases. 

Platinum  black  is  obtained  by  the  action  of 
potassium  hydrate  on  platinum  chloride.  Unlike 
metallic  platinum  it  is  of  a  black  color. 

Platinum  Fuse. — (See  Fuse,  Platinum?) 

Platinum-Silver  Alloy.— (See  Alloy,  Plat- 
inum-Silver^ 

Platinum  Standard  Light.— (See  Light, 
Platinum  Standard^) 

Platymeter. — An  instrument  invented  by 
Sir  William  Thomson  for  comparing  the 
capacities  of  two  condensers. 

Plow. — The  sliding  contacts  connected  to 
the  motor  of  an  electric  street  car,  and  placed 
within  the  slotted  underground  conduit,  and 
provided  for  the  purpose  of  taking  off  the 
current  from  the  electric  mains  placed  therein, 
as  the  contacts  are  pushed  forward  over  them 
by  the  motion  of  the  car. 

Similar  contacts,  placed  in  the  rear  of  the  motor 
car  and  drawn  after  the  train,  form  what  is  techni- 
cally known  as  the  sled,  or  when  rolling  on  over- 
head wires  as  trolleys.  (See  Railroad,  Electric.) 

Plow,  Electric A  plow  driven  by 

an  electric  motor  placed  either  on  a  wagon  to 
which  the  plow  is  attached,  or  by  a  stationary 
electro-motor,  by  the  aid  of  cords  or  other 
flexible  belts. 

One  of  the  first  practical  applications  of  the  elec- 
tric transmission  of  energy  was  for  the  operation 
of  a  plow,  driven  electrically,  by  an  electric  current 
generated  at  some  distance,  and  transmitted  to 
the  electric  motor  by  suitable  conductors. 

Pliicker  Tube.— (See  Tube,  Pliicker.) 

Plug. — A  piece  of  metal  in  the  shape  of  a 
plug,  provided  for  making  or  breaking  a  cir- 
cuit by  placing  in,  or  removing  from,  a  con- 
ical opening  formed  in  the  ends  of  two 
closely  approached  pieces  of  metal  which  are 


connected  with  the  circuits  to  be  made  or 
broken. 

As  the  plug  is  inserted  in  the  opening  it  bridges 
over  the  opening  and  thus  closes  the  circuit  con- 
nected with  the  separate  pieces  of  metals.  On 
removing  the  plug  the  circuit  is  opened  or  broken. 

Plug. — In  telegraphy,  an  inexpert  operator. 

Plug,  Double — A  plug  so  constructed 

that  when  inserted  in  a  spring-jack  it  makes 
two  connections,  one  at  its  point  and  one  at 
its  shank.  (See  Spring-Jack.) 

Plug,  Fusible A  term  sometimes 

applied  to  a  safety  fuse.  (See  Plug,  Safety.) 

Plug,  Infinity A  plug  hole  in  a  box 

of  resistance  coils,  in  which  the  two  pieces  of 
brass  it  connects  are  not  connected  by  any 
resistance  coil,  and  which,  therefore,  leaves, 
when  withdrawn,  an  open  circuit  of  an  in- 
finite resistance. 

Plug,  Safety A  wire,  bar,  plate  or 

strip  of  readily  fusible  metal,  capable  of  con- 
ducting, without  fusing,  the  current  ordinarily 
employed  on  the  circuit,  but  which  fuses,  and 
thus  breaks  the  circuit,  on  the  passage  of  an 
abnormal  current.  (See  Fuse,  Safety.) 

A  safety  plug  is  only  used  on  circuits  in  which 
the  electro-receptive  devices  are  connected  with 
the  leads  in  multiple.  In  this  case  the  fusing  of 
the  safety  plug,  and  the  consequent  opening  of  the 
circuit  with  which  it  is  connected,  does  not  affect 
the  rest  of  the  circuit.  On  series-connected  circuits 
a  different  form  of  safety  device  is  used.  (See 
Cut -Out,  Automatic,  for  Series-Connected  Elec- 
tro-Receptive Devices. ) 

Plug,  Short-Circuiting A  plug  by 

means  of  which  one  part  of  a  circuit  is  cut 
out  by  being  short-circuited. 

Plug  Switch.— (See  Switch,  Plug.) 

Plug,  Wall — A  plug  provided  for 

the  insertion  of  a  lamp  or  other  electro-re- 
ceptive device  in  a  wall  socket,  and  thus  con- 
necting it  with  a  lead. 

Plugging. — Completing  a  circuit  by  means 
of  plugs. 

Plugs,  Grid Plugs  of  active  ma- 
terial that  fill  the  spaces  or  apertures  in  the 
lead  grid  or  plate  of  a  storage  battery. 


Plu.] 


410 


[Poi. 


The  active  material  forming  the  plugs  is  placed 
in  the  spaces  in  the  grid  while  in  the  plastic  con- 
dition. On  the  subsequent  hardening  of  this  ma- 
terial, these  grid  plugs  cannot  readily  fall  out, 
since  the  spaces  are  so  shaped  that  their  interior 
portions  are  01  greater  diameter  than  at  the  sur- 
face of  the  plates. 

Plumbago. — An  allotropic  modification  of 
carbon. 

Plumbago,  the  material  commonly  known  as 
black  lead,  is  the  same  as  graphite.  Powdered 
plumbago  is  employed  in  electrotyping  processes 
for  rendering  non-conducting  surfaces  electrically 
conducting.  For  this  purpose  powdered  plum- 
bago is  dusted  on  the  surfaces,  which  thus  acquire 
the  power  of  receiving  a  metallic  lustre  by  fric- 
tion. Stove  polishes  are  formed  of  mixtures  of 
plumbago  and  other  cheap  materials.  (See 
Graphite.} 

Strictly  speaking,  the  term  graphite  is  properly 
applied  to  such  varieties  of  plumbago  as  are  suit- 
able for  direct  use  for  writing  purposes,  as  in  lead 
pencils. 

Plumbago,  Coppered  -  -  Powdered 
plumbago  coated  with  copper,  for  use  in  the 
metallization  of  objects  to  be  electro-plated. 
(See  Metallization?) 

Plumbago,  Gilt Powdered  plum- 
bago whose  conducting  power  for  electricity 
has  been  increased  by  coating  it  with  metallic 
gold. 

Gilt  plumbago  is  used  for  rendering  non-con- 
ducting surfaces  electrically  conducting  and  thus 
preparing  them  for  electro-plating. 

To  prepare  gilt  plumbago,  dissolve  in  ico  parts 
of  sulphuric  ether  I  part  of  chloride  of  gold,  mix 
in  this  60  parts  of  powdered  plumbago,  and  ex- 
pose to  air  and  light  until  all  ether  has  volatilized. 
Then  dry  in  an  oven. 

Plumbago,  Silvered  —  — Powdered 
plumbago  coated  with  metallic  silver  for  use 
in  the  metallization  of  objects  to  be  electro- 
plated. 

Plunge  Battery. — (See  Battery,  Plunged) 

Pneumatic  Perforator. — (See  Perforator, 
Pneumatic?) 

Pneumatic  Signals,  Electro  -  —(See 
Signals,  Electro-Pneumatic?) 

Pockets,  Armature  -  — Spaces  pro- 
vided in  an  armature  for  the  reception  of  the 


armature  coils.  (See  Coils,  Armature,  of 
Dynamo-Electric  Machine?) 

Poggendorff's  Voltaic  Cell.— (See  Cell, 
Voltaic,  Poggendorff's.} 

Point,  Carbon  — : A  term  formerly 

applied  to  the  carbon  electrodes  used  in  the 
production  of  the  voltaic  arc. 

Point,  Indifferent A  point  in  the 

intra-polar  regions  of  a  nerve  where  the  ane- 
lectrotonic  and  kathelectrotonic  regions  meet, 
and  where  the  excitability  is  therefore  un- 
changed. 

This  is  sometimes  called  the  neutral  point. 

Point  of  Lightning  Rod.  — (See  Rod, 
Lightning,  Points  on.) 

Point  of  Origin.— (See  Origin,  Point  of.) 

Point,  Neutral In  electro-thera- 
peutics, a  term  sometimes  used  instead  of  in- 
different point.  (See  Point,  Indifferent.) 

Point,  Nodal — The  null  point  in  a 

circuit  traversed  by  electric  oscillations.  (See 
Point,  Null.) 

Point,   Null Such  a  point   on    a 

micrometer  circuit,  that  when  joined  or  con-, 
nected  with  the  second- 
ary circuit  of  an  in- 
duction coil,  the  sparks 
in  the  micrometer  cir- 
cuit are  either  very 
greatly  decreased  or 
are  entirely  absent. 

The  null  point  on  the 
micrometer  circuit  is  situ- 
ated symmetrically  with 
respect  to  the  micrometer 
knobs. 

If  the  induction  coil  A, 
Fig.  440,  has  its  second- 
ary circuit  connected  as 
shown  with  the  microm-  Fig.  440.  Null  Point. 
eter  circuit  at  the  point  e,  situated  at  the  centre 
of  the  micrometer  circuit,  the  point  will  be  a  null 
point,  and  the  effects  of  sparks  at  the  micrometer 
knobs,  at  M,  will  be  greatly  decreased.  Under 
the  conditions  shown  in  the  figure,  the  electrical 
oscillations  in  the  micrometer  circuit  must  be  re- 
garded as  in  the  condition  of  stationary  waves  or 
vibrations.  It  would  seem,  therefore,  that  defi- 
nite waves  or  vibrations  are  setup  in  the  microm- 


Poi.] 


411 


[Pol. 


eter  circuit,  in  the  same  way  as  are  the  vibra- 
tions produced  in  an  elastic  bar  set  in  vibration 
by  a  violin  bow,  or  by  a  blow  from  a  hammer. 

Points,  Consequent  —  —The  points  or 
places  in  an  anomalous  magnet  where  the 
consequent  poles  are  situated.  (See  Magnet, 
Anomalous.  Pole,  Anomalous?) 

Points,  Corresponding  -  —  — Points 
where  the  lines  of  electrostatic  force  sur- 
rounding an  insulated  charged  conductor 
enter  the  surfaces  of  neighboring  conductors. 

Points  on  the  surface  of  a  body  placed  in 
an  electrostatic  field  where  the  lines  of  elec- 
trostatic force  enter  its  surface,  and  thus  pro- 
duce a  charge  equal  and  opposite  to  that 
of  the  surface  of  the  body  at  the  points  from 
which  they  came. 

Corresponding  points  receive,  in  accordance 
with  the  laws  of  electrostatic  induction,  charges 
equal  and  opposite  to  those  of  the  surfaces  from 
which  the  lines  of  electrostatic  force  originate. 

Points,  Electric    Action    of The 

effect  of  points  placed  on  an  insulated, 
charged  conductor,  in  slowly  discharging  the 
conductor  by  electric  convection.  (See  Con- 
fection, Electric.} 

The  cause  of  this  action  of  points  is  to  be  at- 
tributed to  the  increased  density  of  a  charge  on 
the  surface  of  a  conductor  at  the  points  and  the 
consequent  production  of  convection  streams  of 
air,  which  thus  gradually  carry  off  the  charge. 
(See  Charge,  Distribution  of.) 

Points,  Iso-Electric  —  — A  term  some- 
times used  in  electro-therapeutics  for  points 
of  equal  potential. 

Points,  Neutral,  of  Dynamo-Electric  Ma- 
chine  Two  points  of  greatest  differ- 
ence of  potential,  situated  on  the  commutator 
cylinder,  at  the  opposite  ends  of  a  diameter 
thereof,  at  which  the  collecting-  brushes  must 
rest  in  order  to  catry  off  the  current  quietly. 

These  are  called  the  neutral  points  because  the 
coils  that  are  short-circuited  by  the  brushes  lie  in 
the  magnetically  neutral  points  of  the  armature. 
(See  Line,  Neutral,  of  Commutator  Cylinder.) 

Points,  Neutral,  of  Magnet  —       — Points 
approximately  midway  between  the  poles  of 
14— Vol.  1 


a  magnet.  (See  Line,  Neutral,  of  a  Magnet. 
Magnet,  Equator  of.) 

Points,  Neutral,  of  Therino-Electric  Dia- 
gram   —The  points  on  alhermo-electric 

diagram  where  the  lines  representing  the 
thermo-electric  powers  of  any  two  metals 
cross  one  another. 

A  mean  temperature  for  any  two  metals  irr 
a  thermo-electric  series,  at  which,  if  their  two 
junctions  are  slightly  over  and  slightly  undep 
the  mean  temperature  (the  one  as  much 
above  as  the  other  is  below),  no  effective 
electromotive  force  is  developed.  (See  Dia- 
gram, Ther  mo-Electric.  Couple,  Thermo- 
Electric^) 

Points  or  Rhumbs  of  Compass.— (See 
Compass,  Points  of.) 

Polar  Region. — (See  Region,  Polar.) 

Polar  Tips.— (See  Tips,  Polar.) 

Polarity,  Diamagnetic A  polar- 
ity the  reverse  of  ordinary  magnetic  polarity, 
the  existence  of  which  was  assumed  by  Fara- 
day to  explain  the  phenomena  of  diamag- 
netism.  (See  Diamagnetism.) 

Faraday  assumed  that  diamagnetic  substances, 
when  brought  into  a  magnetic  field,  acquired 
north  magnetism  in  those  parts  that  were  nearest 
the  north  pole,  instead  of  south  magnetism,  as 
with  ordinary  magnetic  substances.  The  north 
pole  thus  obtained  would,  he  thought,  explain 
the  apparent  repulsion  of  a  slender  rod  of  a-iy  di- 
amagnetic material  delicately  suspended  lu  a 
strong  magnetic  field,  and  cause  it  to  point  equa- 
torially,  or  with  the  lines  of  force  passing  through 
its  least  dimensions.  This  supposition  was  sub^e- 
quently  abandoned  by  Faraday.  It  has  recently 
been  r.vived  by  Tyndall.  (S_-e  Diamagnetism.) 

The  action  of  a  diamagnetic  body,  when  placed 
in  a  magnetic  field,  is  now  generally  ascribed  to 
the  fact  that  the  atmosphere,  by  which  such  body 
is  surrounded,  is  more  powerfully  paramagnetic 
than  the  diamagnetic  substance.  The  diamag 
netic  substance  comes  to  rest  in  an  equatorial  posi- 
tion, because  in  that  position  there  is  the  greatest 
length  of  air  in  the  path  of  the  magnetic  lines, 
which  has  a  smaller  magnetic  resistance  than  the 
diamagnetic  substance. 

Polarity,  Magnetic The    polarity 

acquired  by  a  magnetizable  substance  when 
brought  into  a  magnetic  field. 


Pol.] 


412 


[Pol. 


The  direction  of  magnetic  polarity,  acquired  by 
a  substance  when  brought  into  a  magnetic  field, 
depends  on  the  direction  in  which  the  lines  of 
magnetic  force  pass  through  it.  Where  these 
lines  enter  the  substance  a  sou:h  pole  is  pro- 
duced, and  where  they  pass  out,  a  north  pole  is 
produced.  The  axis  of  magnetization  lies  in  the 
direction  of  the  lines  of  force  as  they  pass 
through  the  body,  and  the  intensity  of  magnetiza- 
tion depends  on  the  number  of  these  lines  of 
force  which  pass  through  the  body. 

The  cause  of  magnetic  polarity  is  not  definitely 
known.  Hughes'  hypothesis  attributes  it  to  a 
property  inherent  in  all  matter.  Ampere  at- 
tributes it  to  closed  electric  circuits  in  the  ultimate 
particles.  Whatever  its  cause,  it  is  invariably 
manifested  by  a  magnetic  field,  the  lines  of  force  of 
which  are  assumed  to  have  the  direction  already 
mentioned.  (See  Magnetism,  Hughes'"  Theory 
of.  Magnetism,  Ampere's  Theory  of.  Magnet- 
ism, Swing's  Theory  of.) 

Polarization,  Galvanic A  term 

sometimes  applied  to  the  polarization  of  a 
voltaic  cell.  (See  Cell,  Voltaic,  Polariza- 
tion of.) 

Polarization,  Internal,  of  Moist  Bodies 

A  polarization  exhibited  by  such 

moist  bodies  as  the  nerves,  muscular  fibres, 
the  juicy  parts  of  vegetables  and  animals,  or 
in  general  by  all  bodies  possessing  a  firm  struc- 
ture filled  with  a  liquid,  on  the  passage 
through  them  of  a  strong  electric  current. 

Polarization,  Magnetic  Rotary 

The  rotation  of  the  plane  of  polarization  of  a 
beam  of  plane-polarized  light  consequent  on 
its  passage  through  a  plate  of  glass  subjected 
to  the  stress  of  a  magnetic  field.  (See  Rota- 
tion, Magneto-Optic?) 

Polarization  of  Dielectric. — (See  Dielec- 
tric, Polarization  of.) 

Polarization  of  Electrolyte. — (See  Elec- 
^  trolyte,  Polarization  of.) 

Polarization  of  Yoltaic  Cell.— (See  Cell, 
Voltaic,  Polarization  of.) 

Polarized    Armature. — (See    Armature, 

Polarized.) 

Polarized  Relay.— (See  Relay,  Polarized.) 
Polarizing      Current.  —  (See      Currf,it , 

Polarization.) 


Polarizing  Electro-Therapeutic  Current. 

— (See  Current,  Electro-  Therapeutic  Polar- 
izing?) 


Pole,  Analogous 


— That  pole  of  a 


pyro-electric  substance,  like  tourmaline,  which 
acquires  a  positive  electrification  while  the 
temperature  of  the  crystal  is  rising.  (See 
Electricity,  Pyro?) 

Pole,  Anomalous A  name  some- 
times given  to  those  parts  or  poles  in  an 
anomalous  magnet  which  consist  of  two  simi- 
lar free  poles  placed  together.  (See  Magnet, 
Anomalous.) 

Pole,  Antilogous That  pole  of  a 

pyro-electric  substance,  like  tourmaline,  which 
acquires  a  negative  electrification  when  the 
temperature  of  the  crystal  is  rising,  and  a 
positive  electrification  when  it  is  falling.  (See 
Electricity,  Pyro.) 

Pole,  Armature (See  Armature, 

Pole?) 

Pole  Changer. — A  switch  or  key  for  chang- 
ing or  reversing  the  direction  of  current  pro- 
duced by  any  electric  source,  such  as  a  bat- 
tery 

The  commutator  of  a  Ruhmkorff  coil  is  a  sim- 
ple form  of  pole  changer.  It  is,  however,  usu- 
ally called  a  commutator.  (See  Coil,  Induction. ) 

Pole-Changing  and  Interrupting  Elec- 
trode Handle. — (See  Electrode-Handle, 
Pole-Changing  and  Interrupting?) 

Pole-Changing  Switch. — (See  Switch, 
Pole-Changing?) 

Pole  Climbers. — (See  Climbers,  Pole?) 

Pole,  Consequent A  magnet  pole 

formed  by  two  free  north  or  two  free  south 
poles  placed  together.  (See  Magnet,  Anom- 
alous?) 


Pole,  Magnetic,  Austral 


—  A  name 


formerly  employed  in  France  for  the  north- 
seeking  pole  of  a  magnet. 

That  pole  of  a  magnet  which  points  to  the 
earth's  geographical  north. 

It  will  be  observed  that  the  French  regarded  the 
magnetism  of  the  earth's  Northern  Hemisphere 


Pol.] 


413 


[Pol. 


as  north,  and  so  named  the  north-seeking  pole  of 
the  needle  the  austral  or  south  pole. 

The  north-seeking  pole  of  the  magnet  is  some- 
times called  the  boreal  or  north  pole.  (See  Pole, 
Magnetic,  Boreal,) 

Pole,  Magnetic,  Boreal A  name 

formerly  employed  in  France  for  the  south- 
seeking  pole  of  a  magnet,  as  distinguished 
from  the  austral  or  north-seeking  pole. 

That  pole  of  a  magnet  which  points  to- 
ward the  geographical  south. 

If  the  earth's  magnetic  pole  in  the  Northern 
Hemisphere  be  of  north  magnetism,  then  the  pole 
of  a  needle  that  points  to  it  must  be  of  the  oppo- 
site polarity,  or  of  south  magnetism.  In  this 
country  we  call  the  end  which  points  to  the  nonh. 
the  north-seeking  pole  or  marked  pole.  In 
France  the  end  which  points  to  the  north  was 
formerly  called  the  austral  pole.  Austral  means 
sjuth  pole.  (See  Pole,  Magnetic,  Austral.) 

Pole,  Magnetic,  False A  term  pro- 
posed by  Mascart  and  Joubert  to  designate 
the  place  or  places  on  the  earth  which  appar- 
ently act  as  magnetic  poles,  in  addition  to 
the  two  true  magnetic  poles,  near  the  earth's 
geographical  poles. 

According  to  these  authorities,  the  earth  pos- 
sesses two  magnetic  poles  only,  viz.,  a  negative 
pole  in  the  Northern  Hemisphere  and  a  positive 
pole  in  the  Southern  Hemisphere.  The  addi- 
tional poles  are  called  by  them  the  false  magnetic 
poles. 

Pole,  Magnetic,  Free A  pole  in  a 

piece  of  iron,  or  other  paramagnetic  sub- 
stance, which  acts  as  if  it  existed  as  one  mag- 
netic pole  only. 

A  free  magnetic  pole  has  in  reality  no  physical 
existence.  The  conception,  however,  is  of  use  in 
describing  certain  magnetic  phenomena.  If  the 
bar  of  iron  be  so  long  as  to  practically  place  one 
pole  beyond  the  sensible  action  of  the  other,  either 
pole  may  be  regarded  as  a  free  pole. 

Pole,  Magnetic,  Marked That  pole 

of  a  magnetic  needle  which  points  approxi- 
mately to  the  earth's  geographical  north. 
(Obsolete.) 

The  north-seeking  pole  of  a  magnetic  needle. 

Pole,  Magnetic,  North  -  —That  pole 
of  a  magnetic  needle  which  points  approxi- 
mately to  the  earth's  geographical  north. 


The    north-seeking    pole    of    a   magnetic 
needle. 
Pole,  Magnetic,  North-Seeking  

That  pole  of  a  magnetic  needle  which  points 
approximately  towards  the  earth's  geographi- 
cal north. 

Pole,  Magnetic,  Salient  -  — A  term 
sometimes  applied  to  the  single  poles  at  the  ex- 
tremities of  an  anomalous  magnet,  in  order  to 
distinguish  them  from  the  double  or  consequent 
pole  formed  by  the  juxtaposition  of  two  simi- 
lar magnetic  poles.  (See  Magnet,  Anoma- 
lous^) 

Pole,  Magnetic,  South  -  —That  pole 
of  a  magnetic  needle  which  points  approxi- 
mately towards  the  earth's  geographical  south. 

The  south-seeking  pole  of  a  magnetic 
needle. 

Pole,  Magnetic,  South-Seeking 

That  pole  of  a  magnetic  needle  which  points 
approximately  toward  the  geographical  south. 

Pole,  Negative That   pole  of   an 

electric  source  through  which  the  current  is 
assumed  to  enter  or  flow  back  into  the  source 
after  having  passed  through  the  circuit  ex- 
ternal to  the  source. 

Pole-Pieces  of  Dynamo-Electric  Machine. 

— (See  Pieces,  Pole,  of  Dynamo-Electric 
Machined) 

Pole  Platform.— (See  Platform,  Pole) 

Pole,    Positive That    pole    of   an 

electric  source  out  of  which  the  electric  cur- 
rent is  assumed  to  flow. 

Pole  Steps. — Short  rods  or  bars  shaped  so 
as  to  be  readily  inserted  in  holes  near  the 
base  of  telegraph  or  electric  light  'poles,  so  as 
to  serve  as  steps  to  enable  a  lineman  to  reach 
the  permanently  placed  steps. 

Permanent  steps  are  placed  only  at  some  dis- 
tance from  the  ground,  in  order  to  prevent  the 
ready  climbing  of  the  poles  by  unauthorized 
persons. 

Pole,  Telegraphic A  wooden  or  iron 

upright  on  which  telegraphic  or  other  wires 
are  hung. 

Wooden  poles  are  generally  round. 


Pol.J 


414 


[Pol. 


The  terminal  pole,  or  the  last  pole  at  each  end 
•of  the  line,  or  where  the  wires  bend  at  an  angle 
of  nearly  90  degrees,  is  made  larger  than  usual 
and  is  often  cut  square. 

The  holes  for  the  poles  must  be  dug  in  the  true 
line  of  the  wires,  and  not  at  an  angle  to  such  line. 
As  little  ground  should  be  disturbed  in  the  dig- 
ging as  possible.  Earth  borers,  or  modifications 
of  the  ordinary  ship  auger,  are  generally  em- 
ployed for  this  purpose.  When  the  pole  is  placed 
in  position  the  ground  should  be  rammed  or 
punned  around  the  pole. 

In  setting  the  pole,  it  is  generally  buried  at  least 
5  feet  in  the  ground.  In  England  the  poles  are 
planted  to  a  depth  of  about  one-fifth  of  their 
length.  In  embankments  and  loose  ground,  they 
are  planted  deeper  than  in  more  solid  earth.  On 
curves,  the  poles  should  be  inclined  a  little  so  as 
to  lean  back  against  the  lateral  strain  of  the  wire, 
since  by  the  time  the  ground  has  completely  set, 
the  strain  of  the  wire  will  have  pulled  them  into 
an  erect  position. 

Care  must  be  taken  to  so  plant  the  poles  on 
that  side  of  a  road  or  railway  that  the  prevailing 
winds  will  blow  them  off  the  roadbed,  should  it 
overturn  them.  As  to  location,  the  top  of  steep 
cuttings  is  preferable  to  the  slope.  In  all  exposed 
positions,  it  is  preferable  to  strengthen  the  poles 
by  stays  attached  to  both  sides. 

Where  the  number  of  wires  is  unusually  large, 
heavy  timber,  or  in  case  of  its  absence,  double 


Fig.  441.     Telegraphic 
Brackets. 


Fig.  442.     Telegraphic 
Anns. 


poles  suitably  braced  together,  must  be  employed. 
In  long  lines  the  poles  should  all  be  numbered  in 
order  to  afford  ease  of  reference  in  case  of  repair. 

When,  even  with  the  best  punning,  and  other 
precautions,  the  pole  is  judged  to  be  unable  to 
resist  the  strain  on  it,  stays  and  struts  are  em- 
ployed. A  stay  is  used  when  it  is  desired  to  re- 
move the/w//or  tension  from  the  pole  ;  a  strut, 
when  it  is  desired  to  remove  the  thrust  or  pressure. 

The  arms  or  brackets,  or  the  cross-pieces  that 


support  the  insulators,  should  all  be  placed  on 
the  same  side  of  the  poles.  Some  common  forms 
of  brackets  are  shown  in  Fig.  441,  and  of  tele- 
graphic arms  in  Fig.  442. 

Saddle  brackets  should  be  placed  on  alternate 
sides  of  the  poles.  When  the  strain  on  an  insula- 
tor is  too  great,  on  account  of  the  wire  going  off 
at  a  sharp  angle,  a  shackle  is  used.  This  is  a 
special  form  of  insulator  which  confines  the  strain 
to  one  spot. 


Fig.  443.    Double  Shackles. 

A  form  of  double  shackle  is  shown  in  Fig. 
443.  The  wire  passes  around  the  recess  at  B, 
between  the  two  insulators. 

On  curves,  or  in  any  situation  where  there  is  a 
probability,  in  case  of  the  breaking  of  an  insula- 


Fig.  444.    Hook  Guard, 


tor,  of  a  wire  getting  into  a  dangerous  position, 
guards  should  be  employed. 

Guards  are  of  two  kinds,  viz.:  hoop  guards 
and  hook  guards.  A  form  of  hook  guard  is 
shown  in  Fig.  -*|/|/|- 

When  wooden  poles  are  employed  various  pre- 
servative methods  are  adopted  to  protect  the 
wood  from  decay,  which  is  very  apt  to  occur, 
especially  where  the  pole  enters  the  ground. 
Some  of  these  forms  are  as  follows,  viz.  : 

( I . )  Charring  and  tarring  the  butt  end  of  the 
pole  where  it  enters  the  ground,  so  as  to  expel 
the  sap  and  destroy  injurious  plant  or  animal 
germs. 


Pol.] 


415 


[For. 


The  charred  end  is  then  cleansed  and  dipped 
in  a  mixture  of  tar  and  slaked  lime. 

(2.)  Bumetizing,  or  the  introduction  of 
chloride  of  zinc  into  the  pores  of  the  wood,  by 
placing  the  poles  in  an  open  tank  tilled  with  a 
solution  of  this  salt. 

(3  )  Ayanizing,  or  the  similar  introduction  of 
corrosive  sublimate,  or  mercuric  chloride. 

(4.)  Boucherizing,  or  the  injection  of  a  solution 
of  copper  sulphate  into  the  pores  of  the  wood. 

(5.)  Creosoting,  or  the  application  of  creosote 
to  well  seasoned  poles. 

Pole,  Telegraphic,  Punning  of  — 

Ramming  or  packing  the  earth  around  the 
base  of  a  telegraph  pole  for  the  purpose  of 
more  securely  fixing  it  in  the  ground. 

Pole,  Telegraphic,  Terminal  —  —The 
pole  at  either  end  of  a  telegraphic  line. 

As  the  first  or  last  pole  in  a  telegraphic  line  is 
not  supported  on  opposite  sides  by  the  line  wires, 
it  is  generally  made  stouter  than  the  intermediate 
poles,  and  greater  care  is  taken  to  fix  it  securely 
in  the  ground. 

Pole,  Testing A  term  sometimes 

employed  in  electro-therapeutics  for  the  in- 
different pole  or  electrode.  (See  Electrode, 
Indifferent?) 

Pole,  Trolley The  pole  which  sup- 
ports the  trolley  bearing  and  rests  on  the 
socket  in  the  trolley  base  frame  in  an  over- 
head wire  electric  railway  system. 

Pole,  Unit,  Magnetic  —  — A  magnetic 
pole  of  such  a  strength  that  it  would  act  with 
a  unit  or  dyne  of  force  on  another  unit  pole  at 
a  distance  of  one  centimetre. 

Poles,  Consequent  —  —The  name  given 
to  single  magnetic  poles  formed  by  two  free 
N.  poles  or  two  free  S.  poles  placed  together. 
(See  Magnet,  Anomalous?) 

Poles,  Idle  —  — Poles  or  electrodes  in 
Crookes'  tubes,  between  which  discharges  are 
not  taking  place. 

The  idle  poles  have  no  connection  with  the  in- 
duction coils  or  other  sources  from  which  the  elec- 
tric discharges  are  obtain*  d.  These  poles  are  pro- 
vided for  attaching  galva.nometer  wires,  etc.,  in  the 
study  of  the  Edison  effect,  or  for  the  study  of  the 


electrical  condition  of  the  dark  space  and  other 
regions  of  the  atmosphere  of  the  tube. 

Poles,  Magnetic The  two  points 

where  the  lines  of  magnetic  force  pass  from 
the  iron  into  the  air,  and  from  the  air  into 
the  iron. 

The  two  points  in  a  magnet  where  the 
magnetic  force  appears  to  be  concentrated. 

In  reality  the  magnetic  force  is  most  concen- 
trated at  the  neutral  points  of  a  magnet,  through 
which  all  the  lines  of  force  pass. 

All  magnets  possess  at  least  two  poles,  one 
positive  or  north,  and  the  other  negative  or  south. 

The  lines  of  magnetic  force  are  assumed  to 
come  out  of  a  magnet  at  its  north  pole,  and  to 
enter  it  at  its  south  pole. 

Poles,  Magnetic,  of  Verticity  —  — (See 
Verticity,  Poles  of,  Magnetic?) 

Poles  of  Condenser. — The  terminals  of  a 
condenser.  (See  Condenser.} 

Poles  of  Magnetic  Intensity. — (See  In- 
tensity, Magnetic,  Pole  of.) 

Polyphase  Current. — (See  Current, 
Multi-Phase:) 

Polyphotal  Arc  Light  Regulators. — (See 
Regulator,  Polyphotal  Arc-Light?) 

Popgun,  Electro-Magnetic  —  — A  mag- 
netizing coil,  provided  with  a  tubular  space 
for  the  insertion  of  a  core,  much  shorter  than 
the  length  of  the  coil,  which,  when  the  ener- 
gizing current  is  passed  through  the  coil, 
is  thrown  violently  out  from  the  coil. 

The  movement  and  consequent  expuUion  of  the 
core  is  due  to  the  action  of  the  lines  of  magnetic 
force  which  complete  their  circuit  through  the 
core. 

Porcelain. — A  variety  of  insulating  ma- 
terial. 

A  translucent  variety  of  earthenware. 
Porous  Cell.— (See  Cell,  Porous?) 
Porous  Cup. — (See  Cup,  Porous?) 
Porous      Insulation. — (See     Insulation, 
Porous?) 

Porous  Jar. — (See  far,  Porous.) 
Porret's  Phenomena. — (See  Phenomena, 
Porret?) 


Por.J 


416 


TPos. 


Portative  Power.  —  (See  Power,  Porta- 


placed  on  the  top  of  the  carrier  and  connected  the 
several  helices    successively    with    the    electric 


Portelectric.  —  An  electric  carrier. 

A  system  of  electric  transportation  by 
means  of  the  successive  attractions  of  a  num- 
ber of  hollow  helices  of  insulated  wire  on  a 
hollow  solenoidal  iron  car. 

The  solenoidal  car  forms  the  movable  core  of  the 
helical  coils.  As  it  moves  through  these  coils  it 
automatically  closes  the  circuit  of  an  electric  cur- 
rent through  the  coils  in  advance  of  it  and  opens 
the  circuit  of  the  coils  in  its  rear.  In  this  way  the 
solenoidal  car  advances  in  a  line  coincident  with 
the  axis  of  the  helical  coils,  being  virtually  sucked 
through  them  by  their  magnetic  attractions.  This 
system  of  electric  propulsion  is  unique  in  systems 
of  electric  traction.  The  motor  becomes  a  mere 
mass  of  iron  or  other  paramagnetic  material. 
The  system  is  suitable  for  the  carriage  of  mail  or 
other  comparatively  light  articles  at  a  high  speed. 

In  an  experimental  plant  at  Dorchester,  Mass., 
a  track  of  2,784  feet  in  length  was  laid  in  the  ap- 
proximate form  of  an  oval.  The  track  was 
formed  by  an  upper  and  lower  rail  of  steel,  suit- 
ably supported  by  stringers. 

The  car,  which  forms  the  movable  core  of  the 
solenoidal  coils,  was  of  wrought  iron,  and  was 
cylindrical  in  shape,  with  conical  ends.  It  was 


Fig.  4^5.    Portelectric  Track. 

12  feet  in  length  and  10  inches  in  diametei,  and 
weighed  about  500  pounds.  It  would  carry  about 
10,000  letters.  It  had  two  flanged  wheels  above 
and  two  below. 

The  solenoidal  coils,  by  the  attractive  power  of 
which  the  core  was  moved,  embraced  the  track 
and  the  movable  core  or  carrier.  They  were 
fixed  along  the  track  at  intervals  of  6  feet  from 
centre  to  centre.  Each  coil  was  formed  of  630 
turns  of  No.  14  copper  wire.  The  upper  track 
rail  is  divided  into  sections  which  form  conductors 
for  the  driving  current.  A  central  wheel  was 


Fig.  446.    Portelectric  Car. 

source  as  the  carrier  was  drawn  forward.  A 
speed  of  about  34  miles  an  hour  was  reached. 

A  section  of  the  track  is  shown  in  Fig.  445,  and 
the  shape  and  general  structure  of  the  carrier  in 
Fig.  446. 

Portrait,  Electric A  portrait 

formed  on  paper  by  the  electric  volatilizatio? 
of  gold  or  other  metal. 

An  electric  portrait  is  obtained  by  cutting  OH 
a  thin  card  a  portrait  in  the  form  of  a  stencil.  A 
sheet  of  gold  leaf  is  then  placed  on  one  side  of  the 


Fig.  447,     Electric  Portrait. 

paper  stencil,  and  a  sheet  of  paper  on  the  othei 
side  ;  sheets  of  tin-foil  are  then  placed  on  the  out. 
side,  as  shown  in  Fig.  447,  and  the  whole  firmly 
pressed  together.  If,  now,  a  disruptive  discharge 
is  passed  through  from  one  sheet  of  tin-foil  to  the 
other,  the  gold  leaf  is  volatilized,  and  a  purplish 
stain  is  left  on  the  paper  of  the  outlines  of  the 
stenciled  card,  thus  forming  an  electric  portrait. 

Position,  Energy  of A  term  used 

for  stored  energy,  or  potential  energy.  (See 
Energy,  Potential.) 

Positive  Direction  of  a  Simple-Harmonic 
Motion. — (See  Motion,  Simple-Harmonic, 
Positive  Direction  of.) 


Pos.] 


417 


[Pot. 


Positive  Direction  of  Lines  of  Magnetic 
Force. — (See  Force,  Magnetic,  Lines  of, 
Positive  Direction  of.) 

Positive  Direction  of  the  Electrical  Con- 
Tection  of  Heat. — (See  Direction,  Positive, 
ef  Electrical  Convection  of  Heat?) 

Positive  Direction  Round  a  Circuit. 
—(See  Direction,  Positive,  Round  a  Cir- 
cuit^ 

Positive  Direction  Through  a  Circuit. 
— (See  Direction,  Positive,  Through  a  Cir- 
cuit?) 

Positive  Electricity. — (See  Electricity, 
Positive?] 

Positive  Electrode.  —  (See  Electrode, 
Positive?) 

Positive  Feeders. — (See  Feeders,  Posi- 
tive?) 

Positive-Omnibus  Bars. — (See  Bars,  Posi- 
tive Omnibus?) 

Positive  Phase  of  Electrotonus. — (See 
Electrotonus,  Positive  Phase  of?) 

Positive  Plate  of  Storage  Battery. — (See 
Plate,  Positive,  of  Storage  Battery?) 

Positive  Plate  of  Yoltaic  Cell.— (See 
Plate,  Positive,  of  Voltaic  Cell?) 

Positive  Pole.— (See  Pole,  Positive?) 

Positive  Potential.— (See  Potential,  Posi- 
tive?) 

Positive  Side  of  Circuit— (See  Circuit, 
Positive  Side  of?) 

Positively.— In  a  positive  manner. 

Positively  Excited. — Excited  or  charged 
with  positive  electricity.  (See  Electricity, 
Positive?) 

Post,  Binding A  device  for  con- 
necting the  terminal  of  an  electric  source 
with  the  terminal  of  an  electro-receptive  de- 
vice, or  for  connecting  different  parts  of  an 
electric  apparatus  with  one  another. 

The  conducting  or  circuit  wire  is  either  intro- 
duced in  the  opening  a,  or  c',  Fig.  448,  and 
clamped  by  the  screw  b,  or  b',  or  is  placed  in 
the  space  d,  d,  and  kept  in  place  by  means  of  a 
thumbscrew.  Sometimes  two  openings  are 
provided  at  c,  and  c',  for  the  purpose  of  connect- 
ing two  wires  together. 


A  device  for  coupling  or  connecting  the  ends 
of  two  wires  to  each  other.  It  is  then  called  a 
coupler.  (See  Couple,  Voltaic.') 

I' 


Fig.  448.     Binding  Posts. 

Pot,  Porous The  porous  jar  or  cell 

of  a  voltaic  cell.  (See  Cell,  Porous?) 

Potential,  Alternating A  poten- 
tial, the  sign  or  direction  of  which  is  alter- 
nately changing  from  positive  to  negative. 

An  alternating  potential  may  be  obtained  either 
in  the  case  of  an  electrostatic  field,  or  in  that 
of  a  magnetic  field. 

Potential,  Alternating  Electrostatic 

— The  potential  of  a  charge  that  is  under- 
going rapid  alternations. 
Potential,  Alternating,  Magnetic  — 

The    difference   of  magnetic  potential   pro- 
duced by  alternating  electric  currents. 

Potential,  Constant  —  — A  potential 
which  remains  constant  under  all  conditions. 

A  machine  or  other  electric  source  is  said  to 
have  a  constant  potential  when  it  is  capable, 
while  in  operation,  of  maintaining  a  constant 
difference  of  electric  pressure  between  its  two 
terminals  on  changes  of  load.  (See  Circuit, 
Constant -Potential. ) 

Potential,  Difference  of—  —A  term 
employed  to  denote  that  portion  of  the 
electromotive  force  which  exists  between 
any  two  points  in  a  circuit. 

The  difference  of  potential  at  the  poles  of  any 
electric  source,  such  as  a  battery  or,  dynamo,  is 
that  portion  of  the  total  electromotive  force 
which  is  available,  and  is  equal  to  the  total 
electromotive  force,  less  what  is  lost  in  the 
source. 

Some  difference  of  opinion  exists  as  to  the  exact 
meaning  that  is  attached  to  the  phrase  difference 
of  potential. 

A  positively  electrified  body  is  said  to  have  a 
higher  electric  potential  than  the  earth,  whose 
potential  is  taken  as  zero. 


Pot.] 


418 


[Pot 


Potential,    Difference    of,    Methods    of 

Measuring  —  — Methods  employed  for  de- 
termining differences  of  potential. 

These  methods  are  as  follows: 

(i.)  By  the  Method  of  Weighing,  that  is,  by 
obtaining  the  -weight  required  to  overcome  the 
attraction  between  two  oppositely  charged  plates, 
or  oppositely  energized  coils;  or  by  measuring 
the  repulsion  between  similarly  charged  surfaces, 
or  similarly  energized  coils. 

(2.)  By  the  Use  of  Electrometers,  or  apparatus 
designed  for  measuring  differences  of  potential. 
(See  Electrometers. ) 

(3-)  -By  the  Use  of  Galvanometers. 

Differences  of  potential,  in  the  case  of  currents, 
may  be  determined  from  the  quantity  of  electri- 
city which  flows  per  second  through  a  given 
circuit,  that  is,  by  the  number  of  amperes,  just 
as  the  pressure  of  water  at  any  point  in  the  side 
of  a  containing  vessel  can  be  determined  by  the 
quantity  of  water  that  flows  per  second.  Differ- 
ence of  potential  in  the  case  of  currents,  there- 
fore, may  be  measured  by  any  galvanometer 
which  measures  the  current  directly  in  amperes, 
provided  the  resistance  of  the  circuit  is  known. 

Potential,  Drop  of  —  — A  term  some- 
times used  instead  of  fall  of  potential.  (See 
Potential,  Fall  of.) 

Potential,  Electric  —  —The  power  of 
doing  electric  work. 

Electric  level. 

Electric  potential  can  be  best  understood  by 
comparison  with  the  case  of  a  liquid  such  as 
water. 

The  ability  of  a  water  supply  or  source  to  do 
work  depends: 

(I.)  On  the  quantity  of  water. 

(2. )  On  the  level  of  the  water,  as  compared  with 
some  other  level;  or,  in  other  words,  on  the  dif- 
ference between  the  two  levels. 

In  i  like  manner  the  ability  of  electricity  to  do 
work  depends: 

(i.)  On  the  quantity  of  electricity. 

(2.)  On  the  electric  potential  at  the  place  where 
the  electricity  is  produced,  as  compared  with  that 
at  some  other  place;  or,  in  other  words,  on  the 
difference  of  potential. 

In  the  case  of  water  flowing  through  a  pipe, 
when  its  flow  has  been  fully  established,  the  quan- 
tity which  passes  in  a  given  time  is  the  same  at 
any  cross-section  of  the  pipe. 


In  the  case  of  electricity,  the  quantity  of  elec- 
tricity flowing  through  any  conductor,  or  part  of 
a  circuit,  is  the  same  at  any  cross-section.  A  gal- 
vanometer introduced  into  a  break  in  any  part  of 
the  conductor  would  show  the  same  strength  of 
current. 

But,  though  the  quantity  of  water  which  passes 
is  the  same  at  any  cross-section  of  a  pipe,  the 
pressure  per  square  inch  is  not  the  same,  even  in 
the  case  of  a  horizontal  pipe  of  the  same  diameter 
throughout,  but  becomes  less,  or  suffers  a  loss  of 
head,  or  difference  of  pressure,  at  any  two  points 
along  the  pipe.  This  difference  of  pressure  causes 
the  flow  of  water  between  these  two  points  against 
the  resistance  of  the  pipe. 

So,  too,  in  the  case  of  a  conductor  carrying  an 
electric  current,  when  the  full  current  strength 
has  been  established,  the  quantity  of  electricity 
that  passes  is  the  same  at  all  cross-sections. 


Fig.  449.     Hydraulic  Gradient. 

The  electric  pressure  or  potential,  however, 
is  by  no  means  the  same  at  all  points  in  the 
conductor,  but  suffers  a  loss  of  electric  head  or 
level,  in  the  direction  in  which  the  electricity  is 
flowing.  It  is  this  electric  head  or  level,  or  dif- 
ference of  electric  potential,  that  causes  the  elec- 
tricity to  flow  against  the  resistance  of  the  con- 
ductor. 

These  analogies  can  be  best  shown  by  the  fol- 
lowing illustration: 

In  Fig.  449,  a  reservoir,  or  source  of  water,  at 
C,  communicates  with  the  horizontal  pipe  A  B, 
furnished  with  open  vertical  tubes  at  a,  b,  c,  d,  e, 
f,  g,  and  B.  If  the  outlet  at  B,  is  closed,  the  level 
of  the  water  in  the  communicating  vessels  is  the 
same  as  at  the  source;  but  if  the  liquid  escape 
freely  from  B,  the  level  of  the  water  in  the  branch 
pipes  will  be  found  on  the  inclined  dotted  line,  or 
at  a',  b',  c',  d',  e',  f,  g',  which  may  be  called 
the  hydraulic  gradient. 

The  pressure  per  square  inch,  at  any  cross  sec 
tion  of  the  horizontal  pipe,  which  is  measured  by 
the  height  of  the  liquid  in  the  vertical  pipe  at  that 
point,  decreases  in  the  direction  in  which  the  liquid 
is  flowing.  The  force  that  urges  the  liquid 


Pot.] 


419 


Pot 


through  the  pipe  between  any  two  points,  may 
be  called  the  liquid-motive  force  (Fleming)  and  is 
measured  by  the  difference  of  pressure  between 
these  points. 

In  Fig.  450,  the  dynamo-electric  machine  at  D, 
has  its  negative  pole  grounded,  and  its  positive 
pole  connected  to  a  long  lead,  A  B,  the  positive 
pole  of  which  is  also  grounded.  A  fall  of  poten- 
tial, represented  by  the  inclined  dotted  line, 
occurs  between  A  and  B,  in  the  direction  in  -which 
the  electricity  is  flowing. 


Fig.  450.     Fall  of  Electric  Potential 

The  dynamo-electric  machine  may  be  regarded 
as  a  pump  that  is  raising  the  electricity  from  a 
lower  to  a  higher  level,  and  passing  it  through 
the  lead  A  B.  The  electric  pressure  or  potential 
producing  the  flow  is  greatest  near  the  dynamo  and 
least  at  the  further  end,  the  differences  at  the 
points  a,  b,  c,  d,  e,  f,  and  g,  being  represented  by 
the  vertical  lines  aa',  bb',  c  c',  d  d',  e  e',  f  f,  and 

gg' 

The  electricity  flows  between  any  two  points  as 
a  and  b,  in  the  conductor  A  B,  in  virtue  of  the 
difference  of  electric  pressure  or  potential  be- 
tween these  two  parts,  or  the  difference  between 
a  a'  and  b  b' . 

Differences  of  potential  must  be  distinguished 
from  differences  in  electric  charge,  or  electrostatic 
density.  If  two  conductors  at  different  potentials 
are  connected  by  a  conductor,  a  current  will  flow 
through  this  conductor.  When  their  potential  is 
the  same,  no  current  flows.  The  density  of  a 
charge  is  the  quantity  of  electricity  per  unit  of 
area. 

The  electric  potential  is  the  same  at  all  points 
of  an  insulated  charged  conductor;  the  density  is 
different  at  different  points,  except  in  the  case  of 
a  sphere.  The  potential,  however,  is  the  same, 
since  no  current  flows,  or  the  charge  does  not  re- 
distribute itself.  The  density  on  an  insulated, 
isolated  sphere,  is  uniform  over  all  parts  of  the 
surface,  and  its  potential  is  the  same  at  all  points. 
If  now  the  sphere  be  approached  to  another  body, 
its  density  will  vary  at  different  parts  of  its  sur- 


face,  and  while  the  charge  ic  redistributing  itself 
so  as  to  produce  these  differences  in  density  the 
potential  will  vary.  As  soon,  however,  as  this 
redistribution  is  effected  and  no  further  current 
exists,  the  potential  is  the  same  over  all'  points, 
though  the  density  differs  at  different  points. 

An  electric  source  not  only  produces  but  also 
maintains  a  difference  of  potential.  In  the  case 
of  the  flow  of  liquid  in  a  pipe,  ii  a  continuous 
current  of  the  liquid  be  maintained  from  the 
higher  level  in  the  reservoir  to  a  lower  level,  as, 
for  example,  by  means  of  a  pump,  it  must  flow 
through  the  pump  to  the  reservoir,  from  the  lower 
level  towards  the  higher  level.  In  case  of  an 
electric  source,  since  the  thing  called  electricity 
flows  through  a  closed  circuit,  if  its  direction  of 
flow  in  that  part  of  the  circuit  external  to  the 
source — i.  e.t  in  the  external  or  useful  current — - 
be  from  a  higher  to  a  lower  level,  then  its  flow 
through  the  remainder  of  the  circuit — i.  e., 
through  the  source — must  be  from  the  lower  to  the 
higher  level.  Since,  however,  the  electrical  po- 
tential of  a  body  represents  the  work  the  elec- 
tricity is  capable  of  doing,  the  work  done  by  the 
electricity  may  be  regarded  as  being  that  done 
when  it  passes  from  the  higher  to  the  lower  level. 

Potential,      Electrostatic  —The 

power  of  doing  work  possessed  by  a  unit 
quantity  of  positive  electricity  charged  or  re- 
siding on  an  insulated  body. 

Potential,    Electrostatic,    Difference  of 

Difference  of  potential  of  an  electric 

charge.  (See  Potential,  Difference  of. 
Electrostatics?) 

Potential  Energy. — (See  Energy,  Poten- 
tial) 

Potential,  Fall  of A  decrease  of 

potential  in  the  direction  in  which  an  elec- 
tric current  is  flowing,  proportional  to  the  re- 
sistance when  the  current  is  constant.  (See 
Potential,  Electric) 

Potential  Galvanometer. — (See  Galva- 
nometer, Potential) 

Potential  Indicator. — (See  Indicator, 
Potential) 

Potential,  Magnetic The  amount 

of  work  required  to  bring  up  a  unit  north- 
seeking  magnetic  pole  from  an  infinite  dis- 
tance to  a  given  point  in  a  magnetic  field. 


Pot.] 


420 


[Pun. 


Potential    of    Conductor,    Methods    of 

Varying (See  Conductor,  Potential 

of,  Methods  of  Varying?) 

Potential  of  Conductors. — (See  Conduc- 
tor, Potential  of.) 

Potential,  Negative That  potential 

in  the  circuit  external  to  the  source  towards 
which  the  electric  current  flows. 

Generally  the  lower  potential,  or  lower 
level. 

Potential,  Positive That  potential 

in  the  circuit  external  to  the  source,  from 
which  the  electric  current  flows. 

The  higher  potential  or  higher  level. 

Potential,  Uniform — A  potential 

that  does  not  vary. 

A  constant  potential.  (See  Potential,  Con- 
stant.) 

An  electric  source  is  said  to  generate  a  uniform 
potential  when  it  maintains  a  constant  difference 
of  potential  at  its  terminals. 

Potential,  Unit  Difference  of  — 

Such  a  difference  of  potential  between  two 
points  that  requires  the  expenditure  of  one 
erg  of  work  to  bring  a  unit  of  positive  elec- 
tricity from  one  of  these  points  to  the  other, 
against  the  electric  force.  (See  Erg) 

The  practical  unit  of  difference  of  potential  is 
the  volt.  (See  Volt.) 

Potential,  Zero An  arbitrary  level 

from  which  electric  potentials  are  measured. 

As  we  measure  the  heights  of  mountains  from 
the  arbitrary  mean  level  of  the  sea,  so  we  measure 
electric  levels  from  the  arbitrary  level  of  the  po- 
tential of  the  earth. 

Potentiometer. — An  apparatus  for  the 
galvanometric  measurement  of  electromotive 
forces,  or  differences  of  potential,  by  a  zero 
method.  (See  Method,  Null  or  Zero) 

In  the  potentiometer  the  difference  of  potential 
to  be  measured  is  balanced  or  opposed  by  a 
known  difference  of  potential,  and  the  equality 
of  the  balance  is  determined  by  the  failure  of  one 
or  more  galvanometers,  placed  in  shunt  circuits, 
to  show  any  movement  of  their  needles. 

The  principle  of  operation  of  the  potentiometer 
will  be  understood  from  an  inspection  of  Fig.  451. 
A  secondary  battery  S,  has  its  terminals  con- 


nected to  the  ends  of  a  uniform  wire  A  B,  of  high 
resistance  called  the  potentiometer  wire.  There 
will,  therefore,  occur  a  regular  drop  or  fall  of  po- 
tential along  this  wire,  which,  since  the  wire  is 
uniform,  will  be  equal  per  unit  of  length.  This 
drop  of  potential  can  be  shown  by  connecting  the 
terminals  of  a  delicate  galvanometer,  generally  of 
high  resistance,  to  different  parts  of  the  wire, 
when  the  deflection  of  the  needle  will  be  propor- 

S 


Fig.  451.     Potentiometer. 


tional  to  the  drop  of  potential  between  the  two 
points  of  the  wire  touched.  If,  now,  the  terminals 
of  a  standard  cell  be  inserted  in  tne  circuit  of 
the  galvanometer,  so  as  to  oppose  the  current 
taken  from  the  potentiometer  wire,  and  the  con- 
tacts of  the  potentiometer  wire  be  slid  along  the 
wire  until  no  deflection  of  the  galvanometer  needle 
is  produced,  the  drop  of  potential  between  these 
two  points  on  the  wire  will  be  equal  to  the  differ- 
ence of  potential  of  the  standard  cell.  (See  Cell, 
Voltaic,  Standard.) 

Suppose,  now,  it  be  desired  to  measure  the  dif- 
ference of  potential  between  two  points  a  and  b, 
on  the  wire  C,  through  which  a  current  is  flow- 
ing. Connect  the  points  b  and  d,  and  a  and  c, 
as  shown,  with  the  delicate  high  resistance  gal- 
vanometer G,  in  either  of  them.  Now  slide  c, 
towards  d,  until  the  needle  of  G,  shows  no  deflec- 
tion. The  potential  between  a  and  b,  is  then 
equal  to  that  between  c  and  d. 

Potentiometer  Wire. — (See  Wire,  Po- 
tentiometer) 

Power. — Rate  of  doing  work. 

Mechanical  power  is  generally  measured  in 
horse  power,  which  is  equal  to  work  done  at  the 
rate  of  550  foot-pounds  per  second. 

The  C.  G.  S.  unit  of  power  is  one  erg  per 
second. 

The  practical  unit  of  power  is  the  watt,  or 
10,000.000  ergs  per  second.  The  kilowatt  is 
even  more  frequently  used  as  the  unit  of  power 
than  the  watt.  (See  Power,  Unit  of.) 

Power,  Absorptive The  property 


Pow.] 


42  L 


[Po>v. 


possessed  by  many  solid  bodies  of  taking  in 
and  condensing  gases  within  their  pores. 

Carbon  possesses  marked  absorptive  powers. 
The  absorption  of  gases  in  this  manner  by  solid 
bodies  is  known  technically  as  the  occltision  of 
gasts.  '(See  Gas,  Occlusion  of.) 

One  volume  of  charcoal,  at  ordinary  tempera- 
tures and  pressures,  absorbs  of 

Ammonia 90    volumes 

Hydrochloric  acid 85 

Sulphur  dioxide 65 

Hydrogen  sulphide 55 

Nitrogen  monoxide 40          " 

Carbonic  acid  gas 35  " 

Ethylene       35  " 

Carbon  monoxide 9.42      " 

Oxygen 9.25      " 

Nitrogen 6.50      " 

Hydrogen 1.25      " 

— (Saussure.) 

Power,  Candle An  intensity  of 

light  emitted  from  a  luminous  body  equal  to 
the  light  produced  by  a  standard  candle. 
(See  Candle,  Standard.) 

The  light-giving  power  of  one  standard 
candle. 

Power,  Candle,  Nominal A  term 

sometimes  applied  to  the  candle-power  taken 
in  a  certain  favorable  direction. 

This  term  is  generally  used  in  arc  lighting. 
In  the  ordinary  arc  lamp  the  greatest  amount  of 
light  is  emitted  at  a  particular  point,  viz.,  from 
the  crater  in  the  upper  or  positive  carbon.  (See 
Arc,  Voltaic.) 

Power,    Candle,    Bated A  term 

sometimes  used  for  nominal  candle-power. 

Power,    Candle,    Spherical The 

average  or  mean  value  of  candle  power 
taken  at  a  number  of  points  around  the  source 
of  light. 

Power,  Conducting The  ability  of 

a  given  length  and  area  of  cross-section  of  a 
substance  for  conducting  light,  heat,  elec- 
tricity or  magnetism,  as  compared  with  an 
equal  length  and  area  of  cross-section  of 
some  other  substance  taken  as  a  standard. 

Power,  Conducting,  for  Electricity 

— The  ability  of  a  given  length  and  area  of 


cross-section  of  a  substance  to  conduct  elec- 
tricity, as  compared  with  an  equal  length  and 
area  of  cross-section  of  some  other  substance, 
such  as  pure  silver  or  copper. 

No  substance  is  known  that  does  not  offer  some 
resistance  to  the  passage  of  an  electric  current. 

The  following  table  is  taken  from  Sylvanus  P. 
Thompson's  ' '  Elementary  Lessons  in  Electricity 
and  Magnetism' ' : 

GOOD  CONDUCTORS. 


Silver, 
Copper, 


Other  metals, 
Charcoal. 


PARTIAL  CONDUCTORS. 


Water, 

The  human  body, 

Cotton, 


Wood, 

Marble, 

Paper. 


NON-CONDUCTORS. 


Oils, 

Porcelain, 
Dry  wood, 
Silk, 
Resins, 


Gutta-percha, 

Shellac, 

Ebonite, 

Paraffine, 

Glass, 


Dry  air. 


Heat  decreases  the  conducting  power  of  ele- 
mentary substances.  This  decrease  in  the  con- 
ducting power  is  approximately  proportional  to 
the  increase  of  temperature.  Carbon  is  an  ex  - 
ception  to  the  law,  being  a  better  conductor  at  a 
red  or  white  heat  than  when  cold. 

The  resistance  of  some  alloys,  such  as  German 
silver  and  platinoid,  is  but  little  affected  by  mod- 
erate changes  of  temperature.  These  alloys  are, 
therefore,  employed  in  the  construction  of  resist- 
ance coils. 

At  a  red  heat  insulators  become  fairly  good 
conductors  of  electricity. 

At  very  low  temperatures  the  conducting 
powers  of  the  metals  increase. 

Wroblewski  has  shown  that  at  extremely  low 
temperatures  copper  increases  in  its  conducting 
power  for  electricity.  He  cooled  copper  to  — 200 
degrees  C.,  the  temperature  of  the  solidification 
of  nitrogen,  and  found  that  at  this  temperature 
its  conducting  power  increased  to  about  nine  times 
its  conducting  power  at  O  degrees  C. 

It  may  be  remarked  here  that  at  exceedingly 
low  temperatures  a  metal  would  take  in  or  absorb 
heat  from  the  surrounding  medium  with  very 
great  rapidity.  In  this  sense  it  might  be  said  that 


Pow.J 


422 


[Pow. 


its  conducting  power  for  heat  was  greatly  in- 
creased. 

Kohlrausch  estimates  the  conducting  power  of 
distilled  water  at  .000000000025,  that  of  mer- 
cury being  taken  as  unity. 

The  best  conductors  of  electricity  are  the  best 
conductors  of  heat. 

This  fact  is  well  illustrated  by  the  following 
table  from  Ayrton : 

RELATIVE  CONDUCTIVITIES  PER  CUBIC  UNIT. 

Name  of  Metal.               Electricity.  Heat. 

Silver,  annealed ico  100 

Copper,       "        94.1  74.8 

Gold,           "        73  54.8 

Platinum 16.6  9.4 

Iron 15.5  IO.I 

Tin 11.4  15.4 

Lead 7.6  7.9 

Bismuth i.i  1.8 

The  electric  conductivity  of  porous  conductors 
decreases  much  more  rapidly  than  the  heat  con- 
ductivity. 

Practically  perfect  insulators  for  electricity  can 
be  obtained,  but  are  unknown  for  heat. 

Edlund  believes  the  universal  ether  to  be  al- 
most a  perfect  conductor.  He  bases  this  belief 
on  the  phenomena  of  sun  spots,  the  occurrence  of 
which  is  almost  immediately  followed  by  the 
occurrence  of  magnetic  disturbances  on  the 
earth. 

Lodge  regards  the  luminiferous  ether  as  being 
almost  a  perfect  non-conductor,  because  he  thinks 
that  conductors  must  be  opaque.  It  may  be  sug- 
gested in  this  connection  that  Edlund's  hypothesis 
as  to  the  conductibility  of  magnetic  effects  through 
the  ether  is  also  capable  of  an  explanation  by  the 
effects  of  magnetic  induction. 

The  conducting  power  for  alternating  currents 
is  not  the  same  as  for  steady  currents.  When 
the  alternations  become  very  high,  the  difference 
between  these  conducting  powers  of  the  metals 
becomes  almost  inappreciable. 

Iron  is  an  enormously  worse  conductor  of 
electricity  than  copper  for  rapidly  alternating 
currents,  at  least  when  the  alternations  are  not 
too  great.  When,  however,  the  alternations  are 
extremely  high,  such  as  those  which  are  produced 
by  the  discharge  of  a  Leyden  jar  or  lightning 
flash,  the  iron  is  as  good  a  conductor  as  the  cop- 
per. The  reason  for  this  is  evident.  The  dis- 
charge in  such  cases  keeps  to  the  extreme  outer 


layer  of  the  conductor,  so  that  the  composition  of 
the  substance  is  practically  of  no  effect. 

Hughes  has  shown  that  the  resistance  of  an  iron 
telephone  line  of  the  usual  diameter,  to  periodic 
currents  of  about  loo  per  second,  is  somewhat 
more  than  three  times  its  resistance  for  steady 
currents. 

There  is  no  such  thing  as  conduction  of  elec- 
tricity in  gases.  Electricity  makes  its  way  through 
a  gas  by  a  sudden  piercing  of  the  dielectric,  or,  in 
other  words,  by  a  disruptive  discharge.  (See 
Discharge,  Disruptive.')  In  such  a  disruptive 
discharge  it  may  be  assumed  that  the  gas  be- 
comes a  conductor  of  electricity  while  the  dis- 
charge is  passing.  It  would  then  partake  of  the 
nature  of  an  electrolytic  conductor,  since  the  dis- 
charge takes  place  by  means  of  a  true  locomotion 
of  atoms.  (See  Conduction,  Electrolytic.) 

Power,  Conducting,  for  Heat The 

ability  of  a  substance  to  transmit  heat  through 
its  mass. 

The  metals  are  good  conductors  of  heat.  They 
are  also  good  conductors  of  electricity.  The 
conducting  powers  for  heat  and  electricity  are 
nearly  identical.  As  the  temperature  of  a  body 
increases,  its  conducting  power  for  heat  is  de- 
creased. Carbon  forms  an  exception  to  this 
statement. 

The  flow  of  heat  across  a  wall  formed  of  a 
homogeneous  material,  the  exposed  faces  of  which 
are  of  equal  extent  and  are  maintained  at  a  con- 
stant difference  of  temperature,  takes  place  in 
accordance  with  the  following  laws: 

(l.)  The  rate  of  flow  across  all  perpendicular 
sections  is  the  same. 

(2.)  A  uniform  drop  of  temperature  occurs 
from  one  side  of  the  wall  to  the  other  in  the  direc- 
tion in  which  the  flow  is  taking  place. 

(3. )  The  rate  of  flow  is  proportional  to  the  dif- 
ference in  temperature. 

The  similarity  between  the  laws  of  the  flow  of 
heat  under  the  circumstances  just  named  and  the 
flow  of  electricity  through  a  conductor  is  evident; 
the  electrical  current  being  the  same  in  all  parts 
of  the  circuit,  a  drop  of  potential  occurring  in 
the  direction  in  which  the  current  is  moving, 
and  the  flow  being  proportional  to  the  difference 
of  potential. 

Power,    Conducting,  Tables    of  — 

Tables    in    which    the    relative    conducting 


Pow.] 


423 


[Povv. 


powers  of  different  substances  are  given.  (See 
Resistance,  Tables  of.) 

Power,  Electric Power  developed 

by  means  of  electricity. 

Power,  Electric,  Distribution  of 

The  distribution  of  electric  power  by  means 
of  any  suitable  system  of  generators,  connect- 
ing circuits  and  electric  motors. 

Power,  Electric  Transmission  of 

The  transmission  of  mechanical  energy  by 
converting  it  into  electric  energy  at  one  point 
or  end  of  a  line,  and  reconverting  it  into 
mechanical  energy  at  some  other  point  on  the 
line.  (See  Energy,  Electric,  Transmission 
of.) 

Power,  Horse A  rate  ot  doing  work 

equal  to  550  foot-pounds  per  second,  or  33,- 
ooo  foot-pounds  per  minute. 

I  horse- power=745- 94  X  io7  ergs  per  second. 


"  =745.941  watts.      (See  Watt.) 

"  =42.746  Ib.    Fahr.    heat    units 

per     min.      (See     Units, 

Heat.} 
"  =23.748  Ib.  Cent,  heat  units  per 

min.     (See  Units,   Heat.) 

Power,  Horse,  Electric Such  a 

rate  of  doing  electric  work  as  is  equal  to 
746  watts  or  746  volt-coulombs  per  second. 

This  rate  is  equivalent  to  33,000  foot-pounds 
per  minute,  or  550  foot-pounds  per  second. 

Just  as  I  pound  of  water  raised  through  the 
vertical  distance  of  I  foot  requires  the  expendi- 
ture of  a  foot-pound  of  energy,  so  I  coulomb  of 
electricity  acting  through  the  difference  of  poten- 
tial of  I  volt  requires  a  certain  amount  of  work 
to  be  done  on  it.  (See  Coulomb.  Volt.  Po- 
tential, Electric.) 

This  amount  is  called  a  volt-coulomb  or  joule, 
and  measured  in  foot-pounds  is  equal  to  .737324 
foot-pounds.  The  volt -coulomb,  or  joule,  isthere- 
fore  the  unit  of  electric  work,  just  as  the  foot- 
pound is  the  unit  of  mechanical  work. 

The  electric  work  of  any  circuit  in  joules  is 
equal  to  the  product  of  the  volts  by  the  coulombs. 

If  we  determine  the  rate  per  second  at  which 
the  coulombs  pass,  and  multiply  this  product  by 
the  volts,  we  have  a  quantity  which  represents  the 
electrical  power,  or  rate  of  doing  electrical  work. 


But  I  ampdre  is  equal  to  I  coulomb  per  second; 
therefore,  if  we  multiply  the  current  in  am- 
peres by  the  difference  of  potential  in  volts,  the 
product  is  equal  to  the  electrical  power  or  rate  of 
doing  electrical  work. 

The  product  of  an  ampere  by  a  volt  is  called 
a  volt-amp&re,  or  a  watt. 

One  watt  =  .0013406  horse-power,  or 

Ons  horse-power  =  745.941  watts. 

C  E 

Therefore  the  electrical  horse-power  =  — z1 

746 

where  C  =  the  current  in  amperes  and  E  =  the 
difference  of  potential  in  volts. 

Power,    Multiplying,     of  Shunt 

(See  Shunt,  Multiplying  Power  of.) 

Power  of  Periodic  Current. — (See  Cur- 
rent, Periodic,  Power  of.) 


Power,  Portative 


-The   carrying 


power  of  a  magnet.  (See  Magnet,  Porta- 
tive Power  of.) 

Power,  Projecting,  of  Magnet  —      — The 

power  a  magnet  possesses  of  throwing  or  pro- 
jecting its  lines  of  magnetic  force  across  an 
intervening  air  space  or  gap. 

The  greater  the  air  space  the  greater  the  mag- 
netic reluctance,  and  consequently  the  greater  the 
magnetizing  force  required  to  overcome  it.  Mag- 
nets of  great  projecting  power  are  generally  of 
great  length,  to  accommodate  the  long  coils  of 
wire  required. 

Power,  Resuscitating,  of  Secondary  Bat- 
tery Cell The  power  possessed  by  an 

apparently  completely  discharged  secondary 
or  storage  cell  of  furnishing  additional  current 
after  a  protracted  rest. 

This  resuscitating  power  is  probably  due  to 
depolarization.  It  is  therefore  present  in  primary 
as  well  as  in  secondary  batteries. 

Power,  Stray  —  — That  part  of  the 
power  employed  in  driving  a  dynamo,  which 
is  lost  through  friction,  air  churning  or  air 
currents,  eddy  currents,  hysteresis,  etc. 

Power,  Tliermo-Electric A  num- 
ber which,  when  multiplied  by  the  difference 
of  temperature  of  a  thermo-electric  couple, 
will  give  the  difference  of  potential  thereby 
generated  in  micro-volts.  (See  Diagram, 
Thermo-Electric) 


Pow.] 


424 


LPri. 


Power,  Units  of Various  units  em- 
ployed in  the  measurement  of  power. 

The  following  table  of  units  of  power  is  taken 
from  Hering's  work  on  dynamo-electric  machines. 

Unit  of  Power. 

i  erg  per  second. .  =  .0000001  watt. 
I  watt,  or   I   volt- 
ampere,     or      i 
joule  per  second, 
or  I  volt-coulomb 

per  second =  looooooo  ergs  per  second. 

"  =  44.2394    foot-pounds    per 

min. 
"  =  6. 1 1622    kilogram  -  metres 

per  min. 
«  =. 0573048  Ib.-Fah.,  heat  unit 

per  min. 
"  =  .318360  Ib.-Cent.,  heatunit 

per  min. 
"  =  .0144402  klgr.-Cent.   heat 

unit  per  min. 

"  =  .0013592     metric    horse- 

power. 

«'  =  .0013406  horse  power. 

I   foot-pound    per 

Klin =  226043  ergs  per  second. 

"  =  .0226043  watt. 

"  =  .13825  kilogram-metre  per 

min. 

"  =  .00003072     metric    horse- 

power. 

"  =  .000030303  horse-power. 

I   kilogram  -  metre 

per  min =  1635000  ergs  per  second. 

"  =  .163500  watt. 

"  =7.23314     foot-pounds    per 

min. 

««  =  .0002222     metric     horse- 

power. 

"  =  .0002192  horse-power. 

I  metric  horse- 
power, or  i 
French  horse- 
power, or  I  che- 
val-vapeur,  or  I 
force  de  cheval, 
or  i  Pferdekraft.  =  735.75  X  io7  ergs  per 

second. 

"  =  735.750  watts. 

"  =  32549.0    foot-pounds    per 

min. 

"  =  4500  kilogram-metres  per 

min. 


I  metric  h.-p.,  etc.  =42.162  Ib.-Fah.,  heat  units 

per  min. 
"  =  23.423  Ib.-Cent.,  heat  units 

per  min* 
"  =  10.625     klg.-Cent.,     heat 

units  per  min. 

"  =  .98634    horse-power    heat 

units  per  min. 

I  horse-power =745.94    x     io7    ergs    per 

second. 

"          =  745-941  watts. 

"  . . . .  =  33000  foot  pounds  per  min. 

"          =  4562.33    kilogram  -  metres 

per  min. 

"         =42.746  Ib.  -Fah.,  heat  units 

per  min. 

"         =  23.748  Ib.-Cent.,  heat  units 

per  min. 

"         =  10.772     klg.-Cent.,    heat 

units  per  min. 

"          =  1.01385      metric       horse- 
power. 

I    Ib.-Fah.,    heat 

unit  per  min. . . .  =  17.45  X  io7  ergs  per  sec. 
"  =  17.4505  watts. 

"  =  .23718  metric  horse-power. 

"  =  .023394  horse-power. 

I  Ib.  Cent.,    heat 

unit  per  min =  31.41  x  io7  ergs  per  sec. 

"  =31.4109  watts. 

"  =  .04269  metric  horse-power. 

"  =  .042109  horse-power, 

i  klgr.-Cent.,  heat 

unit  per  min =  69.25  x  io7  ergs  per  sec. 

"  =  69.249  watts. 

"  =  .0941 2  metric  horse-power. 

=  .092835  horse-power. 

Poynting's  Law.— (See  Law,  Poyntmg's.) 

Practical  Unit  of  Inductance,  or  Self- 
induction. — (See  Inductance,  or  Self-Induc- 
tion^ Practical  Un  it  of.) 

Practical  Unit  of  Magneto-Motive  Force. 

— (See  Force,  Magneto-Motive,  Practical 
Unit  of.) 

Practical  Units.— (See  Units,  Practical?) 

Pressel. — A  press  switch  or  push  connected 
to  the  end  of  a  flexible,  pendant  conductor. 
Pressure  Wires.— (See  Wires,  Pressure!) 

Primary  Battery.— (See  Battery,  Print' 

ary.) 


Pri.] 


425 


[Pro. 


Primary,  Breaking  the Breaking 

or  opening  the  circuit  of  the  primary  of  an 
induction  coil.  (See  Primary,  The.) 

Primary  Coil. — (See  Coil,  Primary.} 

Primary,  Making  the Closing  or 

completing  the  circuit  of  the  primary  of  an 
induction  coil.  (See  Primary,  The.} 

Primary  Plate  Condenser. — (See  Plate, 
Primary,  of  Condenser?) 

Primary  Spiral.— (See  Spiral,  Primary) 

Primary,  The That  conductor  in 

an  induction  coil,  or  transformer,  which  re- 
ceives the  impressed  electromotive  force,  or 
which  carries  the  inducing  current. 

On  changes  in  the  jurrent  intensity  in  the 
primary,  currents  are  induced  in  the  secondary. 
(See  Induction,  Electro-Dynamic.  Coil,  Induc- 
tion. Transformer.') 

Prime  Conductor.  —  (See  Conductor, 
Prime) 

Prime  Motor.— (See  Mover,  Prime) 
Prime  Mover.— (See  Mover,  Prime) 

Printer,  Stock,  Callahan's A  form 

of  printing  telegraph  used  in  sending  stock 
quotations  telegraphically.  (See  Telegraphy, 
Printing.  Ticker,  Stock) 

Printer,  Stock,  Phelps' A  form  of 

printing  telegraph  used  in  sending  stock  quo- 
tations telegraphically.  (See  Ticker,  Stock. 
Telegraphy,  Printing) 

Probe,  Electric A  metallic  con- 
ductor inserted  in  the  body  of  a  patient  in 
order  to  ascertain  the  exact  position  of  a 
bullet,  or  other  foreign  metallic  substance. 

Two  conductors  are  placed  parallel  to  each 
other,  and  are  separated  at  the  extremity  of  the 
probe  by  any  suitable  insulating  material.  On 
contact  with  the  metallic  substance,  an  electric 
bell  is  rung  by  the  closing  of  the  circuit,  or  the 
same  thing  is  more  readily  detected  by  the  de- 
flection of  the  needle  of  a  galvanometer,  or  by  a 
telephone  placed  in  the  circuit. 

Process,  Electrotyping (See  Elec- 

trotyping,  or  the  Electrotype  Process) 

Processes  of  Carbonization.— (See  Car- 
bonization, Processes  of) 


Production  of  Electricity  by  Light.—' 

(See  Electricity,  Production  of,  by  Light) 

Prognosis,  Electric In  electro- 
therapeutics, a  prognosis,  or  prediction  of  the 
fatal  or  non-fatal  termination  of  a  disease, 
from  an  electro-diagnosis  based  on  the  exag- 
gerated or  diminished  reactions  of  the  excit- 
able tissues  of  the  body  when  subjected  to 
the  varying  influences  of  electric  currents. 
(See  Diagnosis,  Electro) 

Projections,  Pacinotti  —Radial 

projections  or  teeth  in  an  armature  core  ex- 
tending from  the  central  shaft,  so  as  to  form 
slots,  pockets,  or  armature  chambers,  for  the 
reception  of  the  armature  coils. 

The  term  Pacinotti  projections  was  given  to 
these  teeth  because  they  were  first  introduced  by 
Pacinotti  in  his  dynamo-electric  machine. 

Projector,  Mangin A  special  form 

of  search  light. 

The  Mangin  reflector  consists  of  a  concavo- 
convex  mirror,  the  convex  surface  of  which  is 
silvered  and  acts  as  a  reflector.  The  radii  ot 
curvature  of  the  two  surfaces  are  such  that  the 
light  undergoes  the  two  refractions,  i.  e.,  on  en- 
tering and  on  passing  out  of  the  mirror,  in  such  a 
manner  as  to  pass  out  of  the  mirror  in  absolute 
parallelism,  and  thus  destroy  all  aberration. 


Fig.  452.    Mangin  Projector. 

The  Mangin  projector  is  shown  in  longitudinal 
and  in  cross-section  in  Fig.  452,  and  the  projector 
B,  is  placed  in  one  end  of  the  cylinder  A,  furnished 
with  the  openings  for  the  ventilation  of  the  cham- 
ber. 

The  cylinder  is  supported  on  trunnions,  and  by 
means  of  screws  can  be  given  any  desired  inclina- 
tion, in  a  manner  which  will  be  readily  under- 
stood from  an  inspection  of  the  drawing. 

The  source  of  light  is  an  arc  lamp  of  the  focus- 
ing type.  A  smill  disc  is  placed  in  front  of  the 


Pro.] 


426 


[Pul. 


arc  in  order  to  stop  the  direct  light  from  the  arc 
which  would  have  divergent  rays.  The  door  C, 
is  formed  of  a  number  of  cylindrical  lenses,  placed 
parallel  to  one  another,  which  cause  the  rays  to 
diverge  horizontally,  when  so  desired. 

Prony  Brake. — (See  Brake,  Prony) 

Proportional  Coils.— (See  Coils,  Propor- 
tional^) 

Proportionate  Arms.— (See  Arms,  Pro- 
portionate^ 

Proportionate  Arms  of  Electric  Bridge. 

— (See  Arms,  Proportionated) 

Prostration,  Electric  —  — Physiological 
exhaustion  or  prostration,  resembling  that 
produced  by  sunstroke,  resulting  from  pro- 
longed exposure  to  the  radiation  of  an  unusu- 
ally large  voltaic  arc.  (See  Sunstroke, 
Electric?) 

Protection,  Electric,  of  Houses,  Ships 
and  Buildings  Generally  —  — Means  for 
protection  against  the  destructive  effects  of  a 
lightning  discharge,  consisting  essentially  in 
the  use  of  lightning  rods.  (See  Rod,  Light- 
ning^ 

Protection,  Electric,   of  Metals 

(See  Metals,  Electrical  Protection  of.) 

Protectiye  Sheath.— (See  Sheath,  Pro- 
tective) 

Protector,  Cable A  device  for  the 

safe  discharge  of  the  static  charge  produced 
on  the  metallic  sheathing  of  a  cable,  or  on 
conductors  surrounding  or  adjacent  to  the 
cable,  consequent  on  changes  in  the  electro- 
motive force  applied  to  the  conducting  core  of 
such  cable. 

The  cable  protector  is  provided  for  the  purpose 
of  preventing  the  discharge  of  the  charge  from 
piercing  and  thus  injuring  the  insulation  of  the 
cable  itself. 

Protector,  Comb A  term  some- 
times applied  to  a  lightning  protector  or  ar- 
rester, in  which  both  the  line  and  ground 
plates  are  furnished  with  a  series  of  teeth, 
like  those  on  a  comb.  (See  Arrester,  Light- 
ning) 


Protector,  Toltaic  Battery A  de- 
vice for  automatically  disconnecting  a  voltaic 
battery,  whenever  the  circuit  in  which  it  is 
placed  becomes  grounded. 

The  battery  protector  is  used  in  systems  of  elec- 
tric gaslighting,  where,  unless  great  care  is  exer- 
cised in  insulating  the  circuits, considerable  annoy- 
ance is  often  experienced  from  the  readiness  with 
which  grounds  are  established.  This  arises  from 
the  high  electromotive  force  of  the  spark  ob- 
tained from  the  spark  coil,  piercing  the  insula- 
tion and  establishing  a  ground  through  the  gas 
pipes. 

Protoplasm,  Effects  of  Electric  Currents 

on Contractions  observed  in  all  pro- 
toplasm on  the  passage  of  an  electric  current 
through  it. 

Protoplasm,  the  basis  of  plant  and  animal  life, 
or  the  jelly-like  matter  that  fills  all  organic  cells, 
whatever  may  be  the  origin  of  such  cells,  suffers 
contraction  when  traversed  by  an  electric  cur- 
rent. 

An  increased  activity  in  the  movements  of  a 
form  of  microscopic  life  called  the  anuzba  is  occa- 
sioned by  slight  shocks  from  an  induction  coil  ; 
stronger  discharges  produce  tetanic  contractions, 
with,  in  some  cases,  expulsion  of  food  or  even  of 
the  nucleus.  A  uniform  strength  of  current  pro- 
duces contraction  and  imperfect  tetanus. 

Pull. — A  contact  maker,  similar  in  general 
construction  to  a  push  button,  but  operated 
by  means  of  a  pulling  rather  than  a  pushing 
force. 

The  pull  is  preferable  to  the  push  in  exposed 
positions,  such  as  outer  doors,  where  moisture  is 
apt  to  injure  pushes. 

Pull,  Chain A  chain  pendant  at- 
tached to  a  pendant  burner  for  the  move- 
ment of  the  wipe-spark  spring  and  the 
ratchet  in  an  electrically  lighted  gas  burner. 

Pull,  Door  Bell,  Electric A  cir- 
cuit-closing device  attached  to  a  bell  pull  and 
operated  by  the  ordinary  motion  of  the  pull 

Pull,  Electric  Bell  —  — A  circuit-clos- 
ing device  operated  by  a  pull. 

Fig.  453  shows  a  form  of  electric  bell  pull.  On 
pulling  the  bell  handle,  contact  springs,  that 
rest  on  a  ring  of  insulating  material  when  the 


Pul.] 


427 


IPum, 


pull  is  in  its  normal  position,  are  brought  into  con- 
tact with  a  metal  ring,  thus  completing  the  cir- 


'?•  453  •    Electric  Bell  Pull. 


euit.     The  bell  pull  is  often  used  to  replace  the 
ordinary  push  button. 

Pulley,  Driven  --  A  pulley  attached 
to  the  driven  shaft.  (See  Mover,  Prime?) 

Pulley,  Driving  ---  A  pulley  attached 
to  the  driving  shaft.  (See  Mover,  Primed) 

Pulsating  Current.—  (See  Current,  Pul- 
sating?) 

Pulsation.  —  A  quantity  of  the  nature  of 
an  angular  velocity,  equal  to  i  it  multiplied 
by  the  frequency  of  the  oscillation,  or,  equal 
to  2  it  divided  by  the  duration  of  a  single 
period. 

Pulsatory  Current.  —  (See  Current,  Pul- 
satory?) 

Pulsatory  Magnetic  Field.—  (See  Field, 
Magnetic,  Pulsatory?) 

Pulse,  Electrical  --  An  electric  oscil- 
lation. 

A  momentary  flow  of  electricity  from  a 
conductor,  which  gradually  varies  from  the 
zero  value  to  the  maximum,  and  then  to  the 
zero  value  again,  like  a  pulse  or  vibration  in 
an  elastic  medium. 

Electric  pulses  are  set  up  in  conductors  con- 
rected  with  the  coatings  of  a  Leyden  jar,  on  the 
discharge  of  the  same.  Such  pulses  produce  a 
series  of  electrical  oscillations,  which  move  alter- 
nately backwards  and  forwards,  until  the  dis- 
charge is  gradually  dissipated.  (See  Oscillations, 
Electric.)  ' 

The  circumstances  influencing  the  rate  of 
propagation  of  an  electric  pulse  through  different 
parts  of  a  closed  circuit,  according  to  Lodge,  are  —  • 


(i.)  The  extra  inertia,  or  the  so-called  magnetic 
susceptibility  in  the  conducting  substance,  es- 
pecially at  its  outer  parts. 

(2. )  An  undue  constriction  or  throttling  of  the 
medium  through  which  the  disturbance  is  pass- 
ing. 

(3.)  The  nature  of  the  insulating  medium. 

Pump,  Air,  Geissler  Mercurial  - 
A  mercurial  air  pump,  in  which  the  vacuum 
is  attained  by  the  aid  of  a  Torricellian  vacuum. 

In  the  Geissler  Mercury  Pump,  Fig.  454,  a 
vacuum  is  obtained  by  means  of  the  Torricellian 
vacuum  produced  in 
a  large  glass  bulb  that 
forms  the  upper  ex- 
tremity of  a  barome- 
tric column.  The 
lower  end  of  this  tube 
or  column  is  con- 
nected with  a  reser- 
voir of  mercury  by 
means  of  a  flexible 
rubber  tube.  To  fill 
the  bulb  with  mer- 
cury the  reservoir  is 
raised  above  its  level, 
*.  <?.,  above  thirty 
inches,  the  air  it  con- 
tains being  allowed  to 
escape  through  an 
opening  governed  by 
a  stopcock.  The  ves- 
sel to  be  exhausted  is 
connected  with  the 
bulb,  and  by  means 
of  a  two-way  exhaus- 
tion cock,  communi-  Fig.  434.  Geissler"*  Mer- 
cation  can  be  made  curial  Air  Pump, 

with  the  bulb,  when  it  contains  a  Torricellian 
vacuum,  and  shut  off  from  it  while  its  air  is  being 
expelled. 

In  actual  practice  the  mercury  is  mechanically 
pumped  into  the  barometric  column,  and  the 
valves  are  opened  either  by  hand,  or  automati- 
cally by  electrical  means. 

Pump,  Air,  Mechanical A  mechan- 
ical device  for  exhausting  or  removing  the  air 
from  any  vessel. 

An  excellent  form  of  air  pump  is  shown  in  Fig. 
455'  which  is  a  drawing  of  Bianchi's  pump. 

Three  valves,  all  opening  upwards,  are  placed 


Pum.] 


428 


IP.VT. 


455>     Barrel  of 
Bianchi's  Air  Pump. 


at  the  top  and  bottom  of  the  cylinder,  and  in  the 
piston,  resp«ctively.  These  valves  are  mechan- 
ically opened  and  closed  at  the  proper  moment 
by  the  movements  of  the  piston,  i.  e.,  their  action 
is  automatic.  This  enables  a  much  higher  vacuum 
to  be  obtained  than  when  the  valves  open  and 
close  by  the  tension  of  the  air. 

Mechanical  pumps  are  unable  to  readily  pro- 
duce the  high  vacua  employed  in  most  electric 
lamps.  Mercury  pumps 
are  employed  for  this 
purpose.  (See  Pump, 
Air,  Mercurial.) 

Pump,  Air,  Mer- 
curial   A  de- 
vice for  obtaining  a 
high  vacuum  by  the 
use  of  mercury. 

Mercury  pumps  are 
in  general  of  two  types 
of  construction,  viz. : 

(i.)  The  Geissler 
pump. 

(z.)  The  Sprengel  pump.  (See  Pump,  Air, 
Geissler  Mercurial.  Pump,  Air,  SprengeFs 
Mercurial.) 

Punip,  Air,  Sprengel's  Mercurial 

A  mercurial  air  pump  in  which  the  vacuum 
is       obtained       by 
means   of  the  fall 
of  a  stream  of  mer- 
cury. 

In  the  Sprengel 
mercury  pump,  Fig. 
456,  the  fall  of  a  mer- 
cury stream  causes 
the  exhaustion  of  a 
reservoir  connected 
with  the  vertical 
tube,  by  the  mechan- 
ical action  of  the 
mercury  in  entang- 
ling bubbles  of  air. 
These  bubbles  are 
largest  at  the  begin- 
ning of  the  txhaus- 
tion,  but  become 
smaller  and  smaller  Fig.  456.  SprengeFs  Mer- 
near  the  end,  until,  curial  Air  Pump. 

at  last,  the  characteristic  metallic  click  of  mer- 
cury or  other  liquid  falling  in  a  good  vacuum 


is  heard.  The  exhaustion  may  be  considered  as 
completed  when  the  bubbles  entirely  disappear 
from  the  column. 

The  Sprengel  pump  produces  a  better  vacuum 
than  the  Geissler  pump,  but  is  slower  in  its 
action. 

In  actual  practice,  the  mercury  that  has  fallen 
through  the  tube  is  again  raised  to  the  reservoir 
connected  to  the  drop  tube  by  the  action  of  a 
mechanical  pump. 

Pumping  of  Electric  Lights.— A  term 
sometimes  applied  to  a  pulsating  or  period- 
ical increase  and  decrease  in  the  brilliancy  of 
the  light. 

This  action  is  generally  due  to  the  periodic  slip- 
ping of  the  belt  or  other  driving  mechanism.  In 
the  case  of  arc  lamps  it  may  also  be  caused  by  the 
improper  action  of  the  feeding  device  of  the 
lamp. 

Puncture,  Electro The  application 

of  electrolysis  to  the  treatment  of  aneurisms 
or  diseased  growths. 

The  blood  is  decomposed  by  the  introduction 
of  a  fine  platinum  needle  connected  with  the 
anode  of  a  battery,  and  insulated,  except  near  its 
point,  by  a  covering  of  vulcanite. 

The  kathode  is  a  sponge-covered  metallic  plate. 

Puncture,  Galrano A  term  some- 
times applied  to  electro-puncture.  (See 
Puncture,  Electro?) 

Punning  of  Telegraph  Pole.— (See  Pole, 
Telegraphic,  Punning  of.) 

Push, — A  name  sometimes  applied  to  a 
push  button,  or  to  a  floor  push.  (See  Push, 
Floor.  Button,  Push.) 

Push  Button.— (See  Button,  Push.) 

Push-Button  Rattler.  —  (See  Rattler, 
Push-Button.} 

Push,  Floor A  push  button  placed 

on  the  floor  of  a  room  so  as  to  be  readily 
operated  by  means  of  the  foot.  (See  But- 
ton, Push.) 

Pyknometer, — A  term  sometimes  used 
for  the  specific  gravity  bottle  employed  in 
determining  the  specific  gravity  of  a  liquid. 

Pyrheliometer. — An  apparatus  for  mea- 
suring the  energy  of  the  solar  radiation. 


429 


[Qua, 


The  pyrheliometer  consists  essentially  of  a 
short  cylinder,  the  area  of  whose  base  is  accu- 
rately determined.  The  cylinder  being  filled  with 
a  known  weight  of  water,  the  water  surface  is  ex- 
posed for  a  definite  time  to  the  sun's  radiation, 
and  the  increase  in  temperature  carefully  deter- 
mined. The  product  of  the  weight  of  the  water 
thus  heated  by  the  increase  in  degrees,  gives 
the  number  of  heat  units,  from  which  the  total 
energy  absorbed  is  readily  calculable.  In  order 
to  avoid  loss  by  reflection  or  diffusion  from  the 
water  surface,  it  is  covered  by  a  layer  of  lamp- 
black. (See  Units,  Heat.  Calorimeter.) 

Pyro  -  Electricity.  —  (See      Electricity, 
Pyro) 
Pyro-Magnetic  Generator  or  Dynamo.— 

(See  Generator,  Pyro-Magnetic^) 

Pyro-Magnetic  Motor. — (See  Motor,  Pyro- 
Magnetic^ 

Pyrometer. — An  instrument  for  deter- 
mining temperatures  higher  than  those  that 
can  be  readily  measured  by  thermometers. 

Pyrometers  are  operated  in  a  variety  of  ways. 
A  common  method  is  by  the  expansion  of  a  metal 
rod. 

Pyrometer,  Siemens'  Electric An 

apparatus  for  the  determination  of  tempera- 


ture by  the  measurement  of  the  electric  resist- 
ance of  a  platinum  wire  exposed  to  the  heat 
whose  temperature  is  to  be  measured. 

The  platinum  wire  is  coiled  on  a  cylinder  of 
fire-clay,  so  that  its  separate  convolutions  do  not 
touch  one  another.  It  is  protected  by  a  platinum 
shield,  and  is  exposed  to  the  temperature  to  be 
measured  while  inside  a  platinum  tube. 

The  resistance  of  the  platinum  coil  at  O  degree 
C.  having  been  accurately  ascertained,  the  temper- 
ature to  which  it  has  been  exposed  can  be  calcu- 
lated from  the  change  in  its  resistance  when  ex- 
posed to  the  unknown  temperature. 

Pyrometer,    Siemens'    Water  —      — A 

pyrometer  employed  for  determining  the  tem- 
perature of  a  furnace,  or  other  intense  source 
of  heat,  by  calorimetric  methods,  /.  e.,  by  the 
increase  in  the  temperature  of  a  known 
weight  of  water,  into  which  a  metal  cylinder 
of  a  given  weight  has  been  put,  after  being 
exposed  for  a  given  time  to  the  source  of 
heat  to  be  measured. 

When  copper  cylinders  are  employed,  the  in- 
strument possesses  a  range  of  temperatu  e  of 
1, 800  degrees  F. ;  when  a  platinum  cylinder  is 
used,  it  has  a  range  of  2,700  degrees  F. 


Q 


Q. — A  contraction  for  electric  quantity. 

Quad. — A  contraction  sometimes  em- 
ployed in  place  of  quadruplex  telegraphy. 
(See  Telegraphy,  Quadruplex^ 

Quadrant. — A  term  proposed  for  the  unit 
of  self-induction. 

An  earth  quadrant  is  equal  to  io9  centi- 
metres. 

In  the  United  States  the  word  henry  is  used 
for  the  unit  of  self-induction.  (See  Henry,  A.} 

Quadrant  Electrometer.— (See  Electro- 
meter, Quadrant.) 

Quadrant  Electroscope,  Henley's.— (See 
Electroscope,  Quadrant,  Henley's.) 

Quadrant,  Legal A  length  equal  to 

9,978  kilometres,  instead  of  the  assumed 
10,000  kilometres. 


Quadrant,  Standard A  length  equal 

to  10,000  kilometres. 

Quadrature,  In A  term  employed 

to  express  the  fact  that  one  simple  periodic 
quantity  lags  90  degrees  behind  another. 

The  electromotive  force  of  s-elf-induction  is  said 
to  be  in  quadrature  with  the  effective  electro- 
motive force  or  current. 

Quadrnplex  Telegraphy,  Bridge  Method 

of — (See  Telegraphy,  Quadruplex, 

Bridge  Method  of.) 

Qualitative  Analysis.  —  (See  Analysis, 
Qualitative.) 

Quality  or  Timbre  of  Sound.— (See  Sound,. 
Quality  or  Timbre  of.) 

Quantitative  Analysis. — (See  Analysis,, 
Quantitative.) 


Qua.] 


430 


[Rad. 


Quantity    Armature.  —  (See  Armature, 
Quantity?) 
Quantity,     Connection    of    Battery  for 

(See   Battery,    Connection    of,  for 

Quantity.} 
Quantity  Efficiency  of  Storage  Battery. 

— (See  Efficiency,  Quantity,  of  Storage  Bat- 
tery) 

Quantity,  Unit    of    Electric A 

definite    amount    or    quantity  of  electricity 
called  the  coulomb.     (See  Coulomb?) 

Although  the  exact  nature  of  electricity  is  un- 
known, yet,  like  a  fluid  (a  liquid  or  gas),  electricity 
can  be  accurately  measured  as  to  quantity. 


A  current  of  I  ampdre,  for  example,  is  a 
current  in  which  one  coulomb  of  electricity  passes 
in  every  second. 

A  condenser  of  the  capacity  of  I  farad,  is 
large  enough  to  hold  I  coulomb  of  electricity 
if  forced  into  the  condenser  under  an  electro- 
motive force  of  i  volt.  (See  Capacity,  Electro- 
static. Farad.  Volt.  Ampere.} 

Quiet  Arc. — (See  Arc,  Quiet?) 

Quiet  Discharge. — (See  Discharge,  Si- 
lent?) 

Qnicking  Solution.  —  (See  Solution, 
Quicking?) 


R. — A  contraction  used  for  ohmic  resist- 
ance. 

p.— A  contraction  used  for  specific  resist- 
ance. 

Radial  Armature. —  (See  Armature, 
Radial?) 

Radially  Laminated  Armature  Core. — 
(See  Core,  Armature,  Radially-Laminated?) 

Radiant  Energy. — (See  Energy,  Radiant) 

Radiant  Matter. — (See  Matter,  Radiant, 
or  Ultra-Gaseous?) 

Radiate. — To  transfer  energy  by  means  of 
waves. 

Radiating.— Transferring  energy  by  means 
of  waves. 

Radiation.— Transference  of  energy  by 
means  of  waves. 

When  an  elastic  body  is  set  into  vibration, 
whether  it  be  the  vibrations  that  produce  light, 
heat  or  electricity,  energy  is  charged  on  the 
body,  and  the  body  will  then  continue  to  vibrate 
until  it  imparts  to  some  medium  surrounding  it 
an  amount  of  energy  exactly  equal  to  that  orig- 
inally imparted  to  itself. 

In  the  case  of  a  sonorous  body  the  energy  is 
transferred  from  the  vibrating  body  to  the  air 
around  it.  For  example,  in  the  case  of  an  elastic 
metallic  wire  set  into  vibration,  the  wire  will  con- 
tinue to  vibrate  until  it  does  as  much  work  on 
the  surrounding  air  as  was  originally  done  on  it, 
in  order  to  set  it  into  vibration. 


In  the  case  of  a  heated  body  the  energy  is 
transferred  from  the  body  to  the  luminiferous 
ether  around  it.  For  example,  in  the  case  of  the 
same  wire  heated  above  the  temperature  of  the 
air,  the  energy  imparted  to  the  molecules  of  the 
metal  by  the  source  of  heat  causes  them  to 
move  towards  and  from  one  another.  These 
to  and -fro  motions  of  the  molecules  cause  the 
surrounding  ether  to  be  set  into  waves,  and  as 
much  energy  is  imparted  to  the  ether,  as  was 
originally  imparted  to  the  wire  in  order  to  heat  it. 

In  the  case  of  a  luminous  body  the  energy  is 
transferred  from  the  body  to  the  luminiferous 
ether.  For  example,  if  the  wire  is  heated  to 
luminosity  by  a  certain  amount  of  energy  im- 
parted to  it,  the  surrounding  ether  is  now  set 
into  waves  of  both  light  and  heat,  which  differ 
from  one  another  only  in  their  wave  length,  and 
the  luminous  body  will  continue  to  radiate  light 
and  heat  until  it  imparts  to  the  surrounding 
ether  an  amount  of  energy  exactly  equal  to  that 
originally  imparted  to  it. 

So,  too,  in  the  case  of  a  body  charged  with 
electricity.  If  disruptively  discharged,  the  im- 
pulsive rush  of  electricity,  so  produced,  causes  the 
energy  charged  on  it  to  be  radiated  as  electro- 
magnetic waves  into  the  surrounding  ether.  The 
discharging  body  is,  to  all  intents  and  purposes,  in 
the  same  condition  as  the  vibrating  elastic  wire, 
and  dissipates  or  radiates  its  energy  in  much  the 
same  manner. 

Radiation,    Electro-Magnetic 
The  sending  out  in  all  directions  from  a  con- 


Had.] 


431 


[Rad. 


ductor,  through  which  an  oscillating  discharge 
is  passing,  of  electro-magnetic  waves  in  all 
respects  similar  to  those  of  light  except  that 
they  are  of  much  greater  length.  (See  Elec- 
tricity, Hertz's  Theory  of  Electro-Magnetic 
Radiations  or  Waves.) 

Radiation  of  Electricity. — (See  Electri- 
city, Radiation  of.) 

Radiation  of  Lines  of  Force.— (See  Force, 
Lines  of,  Radiation  of.) 

Radical,  Compound  — A  group  of 

unsaturated  atoms. 

A  group  of  elementary  atoms,  some  of  the 
bonds  of  which  are  open,  or  not  connected 
or  joined  with  the  bonds  of  other  atoms. 
(See  Atomicity?) 

For  example,  hydroxyl,  HO,  is  a  compound 
radical,  with  one  of  the  two  bonds  of  the  diad 
oxygen  atom,  open  or  unsaturated. 

Radical,  Simple  •  — An  unsaturated 

atom  with  its  bond  or  bonds  free. 

A  single  unsaturated  atom  as  distinguished 
from  an  unsaturated  group  of  atoms. 

Radicals. — Unsaturated  atoms  or  groups  of 
atoms,  in  which  one  or  more  of  the  bonds  are 
left  open  or  free. 

Radicals  are  either  Simple  or  Compound. 

The  radical  may  be  regarded  as  the  basis  to 
which  other  elements  may  be  added,  or  as  the 
nucleus  around  which  they  may  be  grouped. 

Thus  HaO,  forms  a  complete  chemical  molecule, 
because  the  bonds  of  all  its  constituent  atoms  are 
saturated,  thus  H  —  O  —  H.  But  H  —  O  — ,  or 
hydroxyl,  is  a  radical,  because  its  oxygen  atom 
possesses  one  unsaturated  or  free  bond.  By 
combining  with  the  radical  (NO8),  it  forms  nitric 
acid,  thus  H  —  O  —  (NO2)  or  H  NO8. 

During  electrolysis,  the  molecules  of  the  elec- 
trolyte are  decomposed  into  two  groups  of  simple 
or  compound  radicals,  called  ions.  These  ions  are 
respectively  electro-positive  and  electro-negative, 
and  are  called  kathions  and  onions.  (See  Ions. 
Electrolysis.) 

Radiometer,  Crookes' An  appara- 
tus for  showing  the  action  of  radiant  matter 
in  producing  motion  from  the  effects  of  the 
reaction  of  a  stream  of  molecules  escaping 
from  a  number  of  easily  moved  heated  sur- 
faces. (See  Matter,  Radiant,  or  Ultra- 
Gaseous^) 


Radiometer,    Electric,  Crookes • 

A  radiometer  in  which  the  repulsion  of  the 
molecules  of  the  residual  atmosphere  takes 
place  from  electrified  instead  of  from  heated 
surfaces.  (See  Radiometer,  Crookes'!) 

Radio-Micrometer,  Boys' An  elec- 
trical apparatus  for  measuring  the  intensity 
of  radiant  heat. 

The  action  of  the  radio-micrometer  depends  on 
the  deflection,  by  a  magnetic  field,  of  a  suspended 
thermo-electric  circuit  composed  of  three  metals, 
viz.:  two  bars  of  antimony  and  bismuth,  or  of 
their  alloys,  which  are  soldered  side  by  side  to 
the  end  of  a  minute  disc  or  strip  of  copper  foil,  as 
shown  in  Fig.  457.  This  disc  or  foil  of  copper  is 


Fig.  457.    Boys'  Radio-Micrometer. 

provided  for  the  purpose  of  receiving  the  radia- 
tion that  is  to  be  measured.  The  upper  ends  of 
the  thermo-couple  are  soldered  to  the  ends  of  a 
long,  narrow,  inverted  U-shaped  piece  of  copper 
wire,  which  completes  the  thermo-electric  circuit. 

The  absorption  of  radiant  energy  by  the  cop- 
per disc  connected  to  the  thermo-electric  couple 
produces  an  electric  current,  and  the  circuit, 
being  suspended  in  a  magnetic  field,  is  at  once 
deflected  to  a  degree  dependent  on  the  intensity 
of  the  radiation,  or  of  the  current  generated  at 
the  thermo-electric  junction. 

The  means  adopted  for  the  suspension  of  the 
system  are  shown  in  Figs.  457  and  458.  A 
small  piece  of  straight  wire  is  soldered  to  the  up- 


Had.j 


432 


[Rai. 


QUARTZ 
FIBRE 


GLASS 
TUBE 


per  end  of  the  copper  stirrup,  which  completes 
the  thermo-electric  circuit.  This  wire  is  cemented 
to  the  lower  end  of  a  glass  tube,  the  upper  end 
of  which  is  provided  with  a  mirror,  and  the  whole 
suspended,  as  shown,  by  a 
quartz  fibre  in  the  field  of  a 
powerful  magnet. 

In  a  radio-micrometer  made 
by  Prof.  Boys,  the  minuteness  of 
the  suspended  circuit  may  be 
judged  from  the  following  ac- 
tual dimensions,  viz. :  Thermo- 
electric bars,  £  x  ^  x  ^fa  inch  ; 
copper  circuit  of  number  36 
copper  wire,  I  inch  long  and 
about  ^j  inch  wide ;  copper 
heat-receiving  surface,  black- 
ened on  the  face  exposed  to  the 
radiation,  -fa  inch  in  diameter, 
or  i  x  &  inch;  receiver,  ^  inch 
square,  yfa  inch  thick  ;  quartz 
fibre  4  inches  long,  ^fo^  inch  in 
diameter. 

This  instrument,  when  pro- 
perly adjusted  for  extreme  sen- 
sitiveness, should  give  clear  in- 
dications when  the  blackened 
surface  is  warmed  but  the  Fig.  458.  Boys' 
Tillf&ffffiT  degree  Centigrade.  It  Radio-Micrometer. 
will  respond  to  the  heat  radiated  on  the  surface 
of  a  half  penny  from  a  candle  flame  at  a  dis- 
tance of  1,530  feet. 

In  order  to  avoid  the  disturbance  due  to  the 
magnetic  qualities  of  the  antimony  and  bismuth 
bars,  the  central  portions  of  the  metallic  block, 
inside  which  the  system  is  suspended,  is  made 
of  iron,  as  shown  by  the  heavier  shading  in 
Fig-  457- 

This  mass  of  iron  serves  as  a  magnetic  screen 
to  the  thermo-electric  bars,  but  permits  the  action 
of  the  field  on  the  circuit. 

Radiophone. — A  name  sometimes  given  to 
the  photophone.  (See  Photophone^ 

Radiophony. — The  production  of  sound  by 
a  body  capable  of  absorbing  radiant  energy 
when  an  intermittent  beam  of  light  or  heat 
falls  on  it. 

The  action  of  radiant  energy,  when  absorbed 
by  matter,  is  to  cause  its  expansion  by  the  conse- 
quent increase  of  temperature.  This  occurs  even 
when  the  body  is  but  momentarily  exposed  to  a 


COPPER 
WIRE 


Bt. 


flash  of  light,  but  the  instantaneous  expansion 
thus  produced  immediately  dies  away,  and  by 
itself  is  indistinguishable.  If,  however,  a  suffi- 
ciently rapid  succession  of  such  flashes  fall  on  the 
body,  the  instantaneous  expansions  and  contrac- 
tions produce  an  appreciable  musical  note. 

The  sounds  so  produced  have  been  utilized  by 
Bell  and  Tainter  in  the  construction  of  the  Phtto- 
phone.  (See  Photophone.'] 

Railroad,  Electric A  railroad,  or 

railway,  the  cars  on  which  are  driven  or  pro- 
pelled by  means  of  electric  motors  connected 
with  the  cars. 

The  electric  current  that  drives  the  motor  is 
derived  either  from  storage  batteries  placed  on 
the  cars,  or  from  a  dynamo-electric  machine,  or 
battery  of  dynamo-electric  machines,  conveniently 
situated  at  some  point  on  the  road.  The  current 
from  the  dynamo  is  led  along  the  line  by  suitable 
electric  conductors  and  is  passed  into  the  electric 
motor  as  the  car  runs  along  the  tracks  in  various 
ways,  viz. : 

Systems  for  the  electric  propulsion  of  cars  may, 
therefore,  be  divided  into  the  dependent  system,  in 
which  the  driving  current  is  obtained  from  conduc- 
tors placed  somewhere  outside  the  cars,  and  the 
independent  system,  where  the  current  is  derived 
from  primary  or  secondary  batteries  placed  on 
the  cars.  (See  Railroads,  Electric,  Dependent 
System  of  Motive  Power  for.  Railroads,  Electric, 
Independent  System  of  Motive  Power  for.} 

In  the  dependent  system,  the  conductors  which 
supply  the  car  with  current  are  placed  either 
overhead,  on  the  surface  of  the  road-bed  or  un- 
derground. Thus  arise  three  divisions  of  the 
dependent  system: 

(I.)  The  Surface  System. 

(2. )  The  Underground  System. 

(3.)  The  Overhead  System. 

(I.)  The  Surface  System. — By  placing  one  or 
both  rails  in  the  circuit  of  the  dynamo  and  taking 
the  current  from  the  tracks  by  means  of  sliding 
or  rolling  contacts  connected  with  the  motor. 

(2.)  The  Underground  System. — By  placing  the 
conducting  wires  parallel  to  each  other  in  a  longi- 
tudinally slotted  underground  conduit  in  the  road- 
bed, and  provided  with  two  central  plates,  insu- 
lated  from  one  another  and  connected  respectively 
to  the  motor  terminals,  and  taking  the  current 
by  means  of  a  traveling  brush  or  roller,  called  a 
plow,  sled  or  shoe.  On  the  movement  ot  the  car 
over  the  track,  these  traveling  contacts  touch  the 


ilai.j 


433 


[Rai. 


two  parallel  line  conductors  in  the  conduit  and 
<ake  the  electric  current  therefrom.  (See  Plow. 
Sled.) 

(3.)  The  Overhead  System.—  By  placing  the 
(ine  conductors  on  poles  along  the  road,  and 
taking  the  current  therefrom  by  means  of  suitable 
traveling  contacts  called  trolleys,  or  by  sliders. 

Where  a  single  conductor  is  employed,  the  re- 
turn  conductor  generally  consists  of  the  track 
itself,  or  of  the  track  and  ground.  (See  Trolley.} 

The  first  method,  viz.,  that  of  using  the  tracks 
alone  as  conductors,  is  not  much  employed. 

The  use  of  the  track  and  ground  as  a  return  for 
the  current  is  now  very  generally  employed. 

In  some  systems  the  track  is  divided  into  sec- 
tions which  are  successively  brought  into  connec- 
tion with  the  main  conductors  by  contacts  effected 
by  the  attraction  between  magnets  carried  on  the 
car  and  contact  pieces  of  magnetic  material  placed 
below  the  surface.  The  rail  section  thus  tempo- 
rarily energized  is  placed  in  connection  with  the 
motor. 

In  order  to  regulate  the  speed,  various  devices 
are  employed  to  vary  the  current  strength  in  the 
motor  circuit.  These  devices  consist  essentially 
of  rheostats  or  resistances  introduced  into,  or  re- 
moved  from,  the  motor  circuit  on  the  movement 
by  hand  of  a  lever  that  forms  part  of  the  circuit, 
over  contact  plates  connected  to  the  resistance 
coils. 

In  order  to  change  the  direction  of  the  car,  the 
direction  of  rotation  of  the  electric  motor  is 
changed.  This  is  effected  by  some  form  of  re- 
versing gear  or  mechanism  that  changes  the  di- 
rection of  rotation  of  the  motor,  either  by  shifting 
the  brushes,  by  changing  the  field,  or  by  any 
other  means.  (See  Telpherage.  Motor,  Elec- 
tric. Rheostat.) 

Railroads,  Absolute  Block   System  for 

A  block  system   in  which  one  train 

only  is  permitted  to  occupy  a  given  block  at 
any  time.  (See  Railroads,  Block  System  for.*) 

Railroads,  Automatic  Electric  Safety  Sys- 
tem for A  system  for  automatically 

preventing  the  approach  of  two  trains  at  any 
speed  beyond  a  predetermined  distance  of 
each  other. 

The  system  consists  essentially  in  the  automatic 
closing  of  the  circuit  of  an  electric  motor  placed 
on  the  locomotive  between  the  steam  dome  and 
the  sand  box.  This  motor  is  in  circuit  with  a 
local  battery  placed  on  the  cow-catcher,  and  in- 


troduced in  the  circuit  of  the  motor  by  a  magaet 
placed  on  the  cow-catcher,  as  shown  in  Fig.  459, 


Fig.  459.    Locomotive  tuith  Safety  System. 
which  represents  a  locomotive  provided  with  tkis 
system. 

The  magnet  is  on  open  circuit  with  generators 
placed  on  the  rear  car  of  a  second  train,  or  with 
generators  at  a  bridge  or  crossing. 

By  means  of  double  sectional-conductors  placed 
along  the  track,  the  generators  are  automatically 
closed  through  the  magnet,  one  conductor  being 
in  permanent  connection  with  the  magnet,  while 
the  other  is  connected  to  the  generator  in  the  rear 
car  of  a  second  train,  at  a  switch  or  crossing.  The 
other  terminals  of  the  magnet  and  generators  are  in 
permanent  electricial  connection  with  the  rails, 
which  are  employed  as  return  ground  conductors. 

Fig.  460  shows  the  application  of  the  safety 
electric  system  to  a  bridge. 


Fig.  460.     Safety  System  for  Bridge. 

Fig.  461  shows  the  application  of  the  safety 
system  at  grade  crossing. 


Fig.  461.    Safety  System  for  Grade  Crossing. 

The  author  is  indebted  to  Mr.  E.  P.  Thompson 
for  cuts  and  general  description. 

Railroads,  Block  System  for A  sys- 
tem for  securing  safety  from  collisions  of  mov- 
ing railroad  trains  by  dividing  the  road  into  a 
number  of  blocks  or  sections  of  a  given 
length,  and  so  maintaining  telegraphic  com- 
munication between  towers  located  at  the 
ends  of  each  of  such  blocks  as  to  prevent, 


Rai.J 


434 


[Rai. 


by  the  display  of  suitable  signals,  more  than 
one  train  or  engine  from  being  on  the  same 
block  at  the  same  time. 

There  are  two  kinds  of  railway  block  systems 
in  common  use,  viz.: 

(I.)  1\\&  Absolute  Block  System. 

(2.)  The  Permissive  Block  System. 

In  the  absolute  system,  which  is  the  safer,  one 
train  only  is  permitted  on  any  particular  block  at 
a  given  time. 

In  the  permissive  block  system  more  than  one 
train  is  permitted,  under  certain  circumstances 
and  conditions,  to  occupy  the  same  block  simul- 
taneously, each  train  then  being  notified  of  the 
fact  that  it  is  not  alone  on  the  block. 

The  absolute  block  system,  though  expensive 
to  construct  and  maintain,  is  the  only  one  that 
should  be  permitted  by  law  to  exist  on  roads  whose 
traffic  exceeds  a  certain  amount. 

An  absolute  block  system  is  employed  on  the 
London  Underground  Railroad,  and  on  the  Penn- 
sylvania Railroad  Systems. 

The  system  in  use  on  the  New  York  Division 
of  the  Pennsylvania  Railroad  is  as  follows  : 

The  road  between  Philadelphia  and  Jersey  City 
is  divided  into  some  seventy  sections,  the  length 
of  each  section  being  dependent  on  the  amount  of 


Fig.  462.    Slock  Tower. 

daily  traffic  ,  thus,  between  Jersey  City  and  New- 
ark, where  the  traffic  is  great,  there  are  some 
fifteen  sections,  although  the  distance  is  only  7.9 
miles. 

In  each  block-tower  there  are  connections  with 
three  separate  and  distinct  telegraph  lines  or  cir- 
cuits, viz. : 

(i.)  A  line  or  wire  called  the  train  wire,  con- 
necting the  block-tower  with  the  General  Dis- 
patcher's office  at  Jersey  City.  This  line  is  used 
for  sending  train  orders  only. 

(2.)  A  line  or  wire  called  the  block  wirt,  con- 


necting each  block-tower  with  the  next  tower  on 
each  side  of  it. 

(3.)  A  line  or  wire  called  the  message  wire,  and 
used  for  local  traffic  or  business. 

The  general  arrangement  of  the  block-tower  is 
shown  in  Fig.  462. 

Each  of  the  block-towers  is  sufficiently  elevated 
above  the  road-bed  to  afford  the  operator  an  un- 
obstructed view  of  the  tracks. 

The  operator,  having  ascertained  the  actual 
condition  <}f  the  track,  either  by  observation  or  by 
telegraphic  communication  with  the  stations  on 
either  side  of  him,  gives  notice  of  this  condition  to 
all  trains  passing  his  station  by  the  display  of 
certain  semaphore  signals. 

The  semaphore  signals  as  used  on  the  Penn- 
sylvania Railroad  are  shown  in  Figs.  463  and  464. 

The  form  shown  in  Fig.  463  is  used  in  the  abso- 


*g-  4(>3-  Semaphore  Signal— Absolute  System. 
lute  system,  and  that  shown  in  Fig.  464 in  the  per- 
missive system.  These  signals  consist  essentially 
of  an  upright  support  provided  with  a  movable 
arm  A  B,  called  the  semaphore  arm,  capable  of 
being  set  in  any  of  two  or  three  positions.  The 
semaphore  signal  is  placed  outside  the  signal 
tower,  often  several  hundred  feet  away,  but  is 
readily  set  from  the  tower  in  any  of  the  desired 
positions  by  the  operator,  by  the  movement  of 
rods  connected  with  levers. 

In  the  permissive  system,  the  semaphore  arm 
can  be  set  in  three  positions,  viz. : 

(i.)  In  a  horizontal  position,  or  where  the 
semaphore  arm  makes  an  angle  of  90  degrees  with 
the  upright. 

(2.)  Or  it  may  be  dropped  down  from  the 
horizontal  position  through  an  angle  of  75 
degrees,  as  shown  in  Fig.  463. 

(3.)  Or  it  may  occupy  a  position  exactly  inter < 


Rai.] 


435 


[Rid. 


mediate  between  the  first  and  second,  or  37°  30' 
below  the  horizontal,  as  shown  in  Fig.  464. 

Position  No.  I  is  the  danger  signal,  and  when 
it  is  displayed  the  train  may  not  enter  the  block 
it  governs. 

Position  No.  2  shows  that  the  track  is  clear, 
and  that  the  train  may  safely  enter  the  block  it 
governs. 

Position  No.  3,  which  is  used  in  the  permissive 
block  system,  only  signifies  caution,  and  permits 
the  train  to  cautiously  enter  the  block  and  look 
out  for  further  signals. 

The  semaphore  arm  consists  of  a  light  wooden 
arm,  1 1  inches  wide  by  5^  feet  in  length,  painted 
red  or  other  suitable  color  that  can  be  easily  dis- 
tinguished by  daylight. 

By  night  the  positions  of  the  semaphore  arm 
are  indicated  by  colored  lights.  These  lights  are 


Fig.  464.    Semaphore  Signal — Permissive  System. 

operated  as  follows,  viz. :  in  the  absolute  system, 
the  semaphore  arm  A  B,  pivoted  at  A,  bears  at 
its  shorter  end  a  disc  or  lens  of  red  glass  R,  and, 
in  the  permissive  system,  below  this  another  disc 
or  lens  of  green  glass  G.  An  oil  lantern,  pro- 
vided with  an  uncolored  glass  lens,  is  so  sup- 
ported on  a  bracket  fastened  to  the  upright  that 
when  the  semaphore  arm  points  to  danger  the 
red  glass  is  immediately  in  front  of  the  lantern  ; 
when  it  points  to  caution,  the  green  glass  is  in 
front  of  the  lantern;  but  when  it  points  to  safety, 
the  lantern  is  left  uncovered  save  by  its  uncolored 
glass. 

At  night,  therefore,  when  the  semaphore  arm 
is  set  to  danger,  a  red  light  is  displayed;  when  it 
points  to  caution,  a  green  light  is  displayed ;  and 
when  it  points  to  safety,  a  white  light  is  displayed. 

In  some  systems  the  position  of  the  semaphore 


arm  is  shown  at  night  by  means  of  light  reflected 
from  a  parabolic  mirror;  at  the  focus  of  which  the 
signal  lantern  is  placed.  This  method  possesses 
the  advantage  over  other  systems  of  rendering  it 
very  improbable  that  the  engineer  would  mistake 
an  ordinary  light  for  a  signal  light. 

The  green  light  is  only  used  in  the  permissive 
block  system.  In  the  absolute  block  system,  the 
semaphore  arm  has  two  positions  only  ;  viz.,  dan- 
ger, or  horizontal,  and  safety,  or  75  degrees  below 
the  horizontal. 

A  single  arm  is  used  when  it  is  intended  to 
govern  a  single  track  only.  Where  the  condition 
of  a  number  of  tracks  is  to  be  indicated,  several 
arms  are  employed,  one  above  the  other. 

When  seman  r.ore  signals  are  placed  on  each  side 
of  a  double-track  road,  the  semaphore  arm  point- 
ing to  the  right  of  the  vertical  support  governs 
the  line  running  to  the  right. 

When  the  semaphore  signals  are  placed  at 
junctions  or  switch-crossings,  the  operator  in  the 
signal-tower  opens  or.  closes  the  switches  from 
the  tower  by  the  movements  of  levers  that  set  the 
switches,  and  then  displays  the  proper  semaphore 
signal  for  that  crossing  or  route  ;  red,  or  danger, 
if  the  route  is  blocked,  and  white,  or  safety,  if  it 
is  clear.  Here  the  interlocking  apparatus  is  em- 
ployed, which  consists  in  devices  by  means  of 
which,  when  a  route  has  once  been  set  up  and  a 
signal  given  for  that  route,  the  switches  and  sig- 
nals are  so  interlocked  that  no  signal  can  pos- 
sibly be  given  for  a  conflicting  route. 

The  signals  or  switches  are  operated  by  means 
of  iron  rods  passing  over  rollers  or  pulleys. 
These  rods  are  attached  by  suitable  connections 
to  the  switch  or  semaphore  signals,  and  are 
operated  by  means  of  levers  from  the  signal- 
tower.  Switches  can  be  operated  as  far  as  1,000 
feet  from  the  tower;  signals  as  far  as  2,500  feet. 

Colored  switch-signals  are  placed  opposite  the 
end  of  the  switches  to  indicate  the  positions  of 
the  switch.  These  signals  consist  of  red  and 
white  discs  for  day,  and  a  lantern  provided  with 
red  and  white  glasses  for  night.  When  the 
switch  on  any  line  is  open,  the  switch-signal  shows 
red;  when  shut,  it  shows  white.  These  switch- 
signals  are  only  used  in  the  yards. 

No  passenger  train  is  permitted  on  a  block, 
after  another  train  has  passed  the  signal  station, 
until  a  dispatch  has  been  received  from  the 
station  ahead  that  the  train  has  passed  and  the 
block  is  thus  cleared. 

As  an  additional  precaution  against  rear  col- 


Rai.] 


436 


[Rai. 


lisions,  tail-lights  are  displayed  at  the  ends  of  the 
trains.  These  consist  of  lanterns  placed  on  each 
side  of  the  rear  end  of  the  last  car.  These 
lanterns  are  furnished  with  three  glass  slides. 
The  side  of  the  lantern  towards  the  rear  of  the 
car  shows  a  red  light;  that  to  the  front  and  side 
of  the  car  shows  a  green  light.  The  engineer, 
looking  out  of  the  cab,  can  thus  see  a  green  light, 
which  serves  as  a  "marker**  and  indicates  to 
him  that  his  train  is  intact  By  day  a  green  flag, 
placed  in  the  same  position  as  the  lantern,  serves 
the  same  purpose  as  a  marker.  An  observer  on 
the  track,  or  in  the  tower,  sees  the  red  lights  on 
the  rear  of  the  train  when  it  has  passed. 

Freight  trains  are  now  run  on  separate  tracks, 
except  in  places  where  the  extra  tracks  are  not 
yet  completed.  Here  they  do  not  run  on  schedule 
time,  but  are  permitted  to  follow  one  another  at 
intervals  that  depend  on  the  condition  of  the 
tracks  as  shown  by  the  signals  displayed. 

Railroads,  Electric,  Continuous  Over- 
head System  of  Motive  Power  for 

A  variety  of  the  dependent  system  of  motive 
power  for  electric  railroads  in  which  a  con- 
tinuous bare  conductor  is  connected  with  the 
terminals  of  a  generating  dynamo,  and  sup- 
ported overhead  by  suitable  means,  and  a 
traveling  wheel  or  trolley  is  moved  over  the 
same  by  the  motion  of  the  car,  in  order  to 
carry  off  the  current  from  the  line  to  the  car 
motor.  (See  Railroads,  Electric,  Depend- 
ent System  of  Motive  Power for .) 
Railroads,  Electric,  Continuous  Surface 

System  of  Motive    Power  for A 

variety  of  the  dependent  system  of  motive 
power  for  electric  railroads,  in  which  the  ter- 
minals of  the  generating  dynamo  are  con- 
nected to  the  continuous  bare  metallic  con- 
ductor that  extends  along  the  entire  track  on 
the  surface  of  the  roadway  or  street,  and  from 
which  the  current  is  taken  off  by  means  of  a 
traveling  conductor  connected  with  the  mov- 
ing car.  (See  Railroads,  Electric,  Continu- 
ous Underground  System  of  Motive  Power 
for.) 

Railroads,  Electric,  Continuous  Under- 
ground System  of  Motive  Power  for  — 

A  variety  of  the  dependent  system  of  motive 
power  for  electric  railways,  in  which  a  con- 
tinuous bare  conductor  is  placed  under- 


ground in  an  open  slotted  conduit,  and  the 
current  taken  off  from  the  same  by  means  of 
sliding  or  rolling  contacts  carried  on  the  mov- 
ing car.  (See  Railroads,  Electric,  Depend- 
ent System  of  Motive  Power  for) 

Railroads,  Electric,  Dependent  System 
of  Motive  Power  for  —  —A  term  now 
generally  used  for  a  system  of  motive  power 
for  the  propulsion  of  electric  railway  cars,  in 
which  the  electric  current  is  taken  from  wires 
or  conductors  connected  with  electric  sources 
external  to  the  cars. 

A  dependent  system  of  motive  power  for  elec- 
tric railways  includes  three  distinct  varieties, 
namely : 

(i.)  The  Underground  System. 

(2.)  The  Surface  System. 

(3.)  The  Overhead  System. 

In  all  of  these  systems  the  bare  conductor  con- 
nected with  the  terminals  of  a  generating  dynamo 
may  form  either  one  continuous  wire  or  it  can 
be  divided  into  separate  portions  or  sections. 

The  underground  system  embraces  two  distinct 
varieties : 

ist.  A  continuous  bare  conductor  placed  in  an 
open  slotted  conduit. 

2d.  A  sectional  bare  conductor  placed  in  an 
open  slotted  conduit. 

In  the  first  variety  of  the  underground  system, 
bare  conductors  are  placed  in  an  open  slotted 
conduit,  and  connected  with  the  terminals  of  a 
dynamo-electric  machine  which  generates  the 
current  that  is  to  be  employed  for  the  propulsion 
of  the  cars.  Traveling  contacts  placed  on  the 
car  and  connected  with  an  electric  motor,  carry 
off  the  current  from  the  bare  conductor  by  rolling 
or  sliding  over  it. 

In  the  second  variety  of  the  underground  sys- 
tem, a  section  of  a  bare  conductor,  or  bare  metal- 
lic points  that,  on  the  passage  of  the  car  over 
them  are  automatically  connected  with  the  gen- 
erating dynamo,  replace  the  continuous  metallic 
conductors  of  the  first  system. 

In  the  surface  system,  the  wires  or  conductors 
that  are  connected  with  the  generating  dynamo, 
instead  of  being  placed  in  the  underground  open 
slotted  conduit,  are  placed  directly  on  the  surface 
of  the  street  or  roadbed  and  the  current  carried 
off  from  the  same  by  suitable  contacts  placed  on 
the  car. 

In  most  cases,  however,  in  which  the  surface 
system  is  adopted,  the  conductors  that  are  con- 


Eai.] 


437 


[Rai. 


nected  with  the  generating  dynamo  do  not  ex- 
tend throughout  the  entire  length  of  the  track, 
but  are  limited  to  sections  of  the  track  that  are 
suitably  connected  with  the  generating  dynamo. 
In  some  of  these  systems  arrangements  are 
devised,  by  which  the  car,  as  it  passes  over  the 
track,  automatically  connects  these  sections  with 
the  generating  dynamo  while  passing  over  the 
same,  and  disconnects  them  after  such  sections 
have  been  passed. 

The  overhead  system  embraces  two  varieties: 

(i.)  A  continuous  trolley  wire. 

(2.)  A  divided  or  sectional  trolley  wire. 

In  the  continuous  trolley  wire  system,  the  cur- 
rent is  taken  off  from  the  continuous  wire  by 
means  of  a  trolley  wheel  that  moves  over  the 
trolley  wire. 

Such  a  system  is  especially  suitable  for  suburban 
Districts  or  small  towns.  In  such  a  system  the 
trolley  wire  is  connected  with  a  number  of  feeder 
wires  that  either  extend  from  the  generating  sta- 
tion the  entire  length  of  the  line,  and  are  con- 
nected with  such  line  at  suitable  points;  or,  sepa- 
rate feeders  extend  from  the  station  to  points  on 
the  line  where  they  are  tapped  into  the  trolley 
wire. 

In  the  divided  or  sectional  trolley  wire  system 
the  wire  is  divided  into  suitable  sections,  and 
feeders  extend  the  entire  length  of  the  line  and 
are  connected  to  the  central  points  of  each  section; 
or,  the  feeders  extend  the  entire  length  of  the 
line  and  tap  into  both  ends  of  the  section. 

The  author  is  indebted  to  G.  W.  Mansfield  for 
the  principal  facts  contained  in  the  above  descrip- 
tive matter. 

Rail  roads.  Electric,  Diyided  Overhead 
System  of  Motive  Power  for A  sec- 
tional overhead  system  of  motive  power  for 
electric  railroads.  (See  Railroads,  Electric, 
Sectional  Overhead  System  of  Motive  Power 
for,} 

Railroads,  Electric,  Divided  Surface 
System  of  Motive  Power  for A  sec- 
tional system  of  motive  power  for  electric 
railroads.  (See  Railroads,  Electric,  Sec- 
tional Surface  System  of  Motive  Power 
for.) 

Railroads,  Electric,  Divided  Under- 
ground System  of  Motive  Power  for • 

— A  sectional  system  of  motive  power  for 
electric  railroads.  (See  Railroads,  Electric, 


Sectional  Underground  System  of  Motive 
Power  for.} 

Railroads,  Electric,  Double-Trolley  Sys- 
tem for A  system  of  electric  railroad 

propulsion,  in  which  a  double  trolley  is  em- 
ployed to  take  the  driving  current  from  two 
overhead  trolley  wires. 

The  double-trolley  system  differs  from  the 
single-trolley  system  in  that  it  employs  no  earth 
return.  The  parallel  wires  also  avoid  the  effects 
of  injurious  induction  in  neighboring  telegraph 
or  telephone  wires.  (See  Railroads,  Electric, 
Dependent  System  of  Motive  Power  for.") 

Railroads,  Electric,  Independent  System 

of  Motive  Power  for A  term  for  the 

electric  propulsion  of  railway  cars  by  means 
of  primary  or  storage  batteries  placed  on  the 
car  and  directly  connected  with  the  motor. 

This  is  called  the  independent  system,  because, 
unlike  the  dependent  system,  the  energy  required 
for  the  propulsion  of  the  car  is  obtained  directly 
from  the  energy  of  the  electric  source  placed  on 
the  car,  instead  of,  as  in  the  dependent  system, 
outside  of  the  car. 

Railroads,  Electric,  Sectional  Overhead 

System  of  Motive  Power  for A  variety 

of  the  dependent  system  of  motive  power  for 
electric  railroads,  in  which  sections  of  bare 
conductors  are  supported  overhead  on  poles 
placed  along  the  railroad  track,  and  the  cur- 
rent taken  off  from  the  same  by  means  of 
traveling  conductors  such  as  the  trolley 
wheel,  which  is  moved  over  the  trolley  wire 
by  the  motion  of  the  car. 

Various  systems  are  employed  for  connecting 
the  different  sections  of  the  trolley  wire  by  means 
of  feeder  wires  with  the  generating  dynamo. 
(See  Railroads,  Electric,  Dependent  System  of 
Motive  Power  for.} 

Railroads,  Electric,  Sectional  Surface 
System  of  Motive  Power  for A 

variety  of  the  dependent  system  of  motive 
power  for  electric  railroads  in  which  conduc- 
tors are  placed  on  the  roadbed  or  along  the 
track,  and  the  current  taken  off  from  the  same 
by  means  of  contacts  connected  with  the  mov- 
ing car,  and  so  arranged  as  to  automatically 
switch  in  such  bare  sections  on  the  passage 


Rai.] 


438 


[Ray. 


of  the  car  over  them,  and  to  switch  them  out 
as  the  car  leaves  them.  (See  Railroads, 
Electric,  Dependent  System  of  Motive  Power 
for) 

Railroads,  Electric,  Sectional  Under- 
ground System  of  Motive  Power  for 

— A  variety  of  the  dependent  system  of 
motive  power  for  electric  railroads  in  which  a 
sectional  conductor  is  placed  underground  in 
a  slotted  conduit,  and  the  current  taken  from 
the  same  by  means  of  sliding  or  rolling  con- 
tacts connected  with  the  moving  car.  (See 
Railroads,  Electric,  Dependent  System  of 
Mot i-ve  Power  for.) 

Railroads,  Electric,  Section  Line  of 

— Any  part  of  the  overhead  electric  conduc- 
tors insulated  from  other  parts  so  as  to  permit 
its  supply  of  electric  power  to  be  separately 
controlled. 

Railroads,  Electric,  Signal  Service  Sys- 
tem for The  system  of  electric  signals 

used  on  railways  for  ascertaining  the  condition 
of  the  roads,  sending  instructions  to  engineers, 
and  conveying  intelligence  generally  from 
stations  along  the  road  to  the  running  trains. 

Railroads,  Electric,  Single-Trolley  Sys- 
tem   A  system  of  electric  railroad 

propulsion  in  which  a  single  trolley  is  em- 
ployed to  take  the  driving  current  from  a 
single  overhead  trolley  wire. 

The  earth,  or  a  conductor  placed  along  the 
track  on  the  roadbed,  acts  as  the  return.  (See 
Railroads,  Electric,  Dependent  System  of  Mo- 
tive Power  for.) 

Railroads,  Permissive  Block  System  for 

A  block  system  in  which  more  than 

one  train  is  permitted  under  given  conditions 
to  occupy  the  same  block  simultaneously. 
(See  Railroads,  Block  System  for.) 

Railway,  Electric An  electric  rail- 
road. (See  Railroad,  Electric) 

Range,  Molecular — The  distance  at 

which  the  molecules  of  matter  exert  a  sensi- 
ble attraction  for  one  another. 

This  distance  has  been  estimated  in  the  case  of 
zinc  and  oxygen  as  equal  to  about  the  ten-mil- 
lionth of  a  millimetre. 


Ratchet-Pendant  Argand-Electric  Burner. 

— (See  Burner,  Argand-Electric,  Ratchet- 
Pendant^ 

Ratchet-Pendant  Electric  Burner. — (See 
Burner,  Ratchet-Pendant,  Electric) 

Ratchet-Pendant  Electric  Candle  Burner. 

— (See  Burner,  Ratchet-Pendant  Candle 
Electric) 

Ratio,    Velocity A   ratio,    in   the 

nature  of  a  velocity,  that  exists  between  the 
dimensions  of  the  electrostatic  and  the  elec- 
tro-magnetic units. 

This  ratio  will  be  understood  from  the  com- 
parison of  the  following  units.  In  each  case  the 
numerator  gives  the  dimensions  in  the  electro- 
static and  the  denominator  the  dimensions  in  the 
electro-magnetic  system  : 


Quantity, 


Here  the  value  of  the  ratio,  viz.,  the  length 
divided  by  the  time,  is  clearly  in  the  nature  of  a 

velocity,   for  V  =  —    . 


Potential, 


Capacity, 


L-i  T* 


L-i  T 
Resistance,  j — ^zj 


_ 

V3 


A  remarkable  similarity  exists  between  the 
value  of  the  -velocity  expressed  in  C.  G.  S.  units, 
and  the  velocity  of  light,  which  is  of  great  signifi- 
cance in  the  electro-magnetic  theory  of  light.  (See 
Light,  Maxwell's  Electro-Magnetic  Theory  of.) 

The  velocity  of  light  is  2.9992  X  io10  cen- 
timetres per  second. 

The  velocity  ratio,  v,  is  2.9800  X  io10  centi- 
metres per  second. 

Rattler,  Push-Button A  device 

connected  with  a  push  button  to  show  that 
the  bell  connected  at  a  distant  point,  in  the 
circuit  of  a  push  button,  rings  when  the  button 
is  pressed. 

Ray,  Actinic  —  — A  ray  of  light  or  other 
form  of  radiant  energy  that  possesses  the 


Ray.] 


439 


[Rec. 


power  of  effecting  chemical  action.      (See 
Decomposition ) 

All  rays  of  light,  and  even  some  of  those  in- 
visible to  the  human  eye,  are  actinic  to  some 
particular  chemical  substance  or  another. 
Whether  the  ether  waves  produce  the  effects  of 
heat,  of  light  or  of  chemical  decomposition  de- 
pends on  the  nature  of  the  material  on  which 
they  fall,  as  well  as  on  the  character  of  the  waves 
themselves. 

Ray,  Electric   (Raia   torpedo) A 

species  of  fish  named  the  ray,  which,  like  the 
electric   eel,    pos- 
sesses the  power 
of  producing  elec- 
tricity. 

The  electric  or- 
gan is  situated  at 
the  back  of  the 
head,  and  consists 
of  hundreds  of  poly- 
gonal, cellular 
laminae,  supplied 
with  numerous 
nerve  fibres,  as 
shown  in  Fig.  465. 
(See  Fishes.  Elec- 
tric.') 

Rayleigh's 
Form  of  Clark's 
Standard  Yoltaic 
Cell.— (See  Cell, 

Voltaic,     Stand- 
ard,     Rayleigh's 

Form  of  Clark's)     Fig.  463.     The  Raia  Torpedo. 

Reaction. — In  electro -therapeutics  mus- 
cular contractions  following  the  closing  or 
opening  of  an  electric  circuit. 

Reaction  Coil. — (See  Coil,  Reaction!) 

Reaction  of  Degeneration. — (See  Degen- 
eration, Reaction  of.) 

Reaction  of  Exhaustion.— (See  Exhaus- 
tion, Reaction  of.) 

Reaction  Principle  of  Dynamo-Electric 
Machines. — (See  Machine,  Dynamo-Elec- 
tric, Reaction  Principle  of) 

Reaction  Telephone.— (See  Telephone, 
Reaction) 


Reaction  Time.— (See  Time,  Reaction) 

Reaction     Wheel,    Electric (See 

Wheel,  Reaction,  Electric) 

Reactions,  Kathodic  and  Anodic  Electro- 
Diagnostic  The  reactions  which  oc- 
cur at  the  kathode  or  anode  of  an  electric 
source  placed  on  or  over  any  part  of  a  living 
body. 


Fig.  466.    Kathodic  and  Anodic  Reactions. 

Fig.  466,  from  De  Watteville's  "  Medical  Elec- 
tricity" represents  what  he  assumes  takes  place  at 
the  points  of  entrance  and  exit  of  the  current  in  a 
nerve  submitted  to  the  action  of  the  anode  of  an 
electric  source.  Two  zones  are  formed,  an  anodic 
and  a  kathodic  zone;  the  virtual  anode  is  formed 
by  the  portion  of  the  skin  nearer  the  nerve,  and 
the  virtual  kathode  by  the  adjoining  muscles. 
There  are  thus  formed  two  zones  of  influence — 
one  immediately  around  the  anode,  called  the 
polar  or  anodic  electrotonic  zone,  and  one  sur- 
rounding this  and  including  the  virtual  kathode, 
and  called  the  peripolar,  or  kathelectrotonic  zone. 

Reading*     Telescope.  —  (See     Telescope, 
Reading) 
Real  Efficiency  of   Storage   Battery. — 

(See  Efficiency,  Real,  of  Storage  Battery) 

Real  Hall  Effect— (See  Effect,  Hall, 
Real) 

Recalescence. — The  property,  possessed 
by  incandescent  steel  when  cooling,  of 
again  becoming  incandescent  after  a  certain 
degree  of  cooling  has  been  reached. 

The  property  of  recalescence  was  first  pointed 
out  by  Barrett. 

A  steel  wire  heated  at  the  middle  or  near  one 
end  to  a  bright  red,  and  allowed  to  cool  in 
a  dim  light,  will  cool  until  a  low  red  heat  is 
reached,  when  it  will  be  observed  to  reheat  at 
some  point  in  the  originally  heated  portion.  This 
reheating  is  manifested  by  a  brighter  red  spot 


Roc. 


440 


[Rec. 


which  moves  along  the  portion  originally  heated. 
This  reheating  is  called  recalescence,  and  is  due 
to  latent  heat  (potential  energy),  which,  disap- 
pearing when  the  bar  was  heated,  again  becomes 
sensible  (kinetic  energy)  on  cooling. 

The  temperature  at  which  recalescence  takes 
place  is  sensibly  the  temperature  at  which  heated 
steel  regains  its  magnetizability. 

Received  Current. — (See  Current,  Re- 
ceived.} 

Receiver,  Gramophone The  re- 
ceiver employed  in  the  gramophone.  (See 
Gramophone.} 

Receiver,  Graphophone The  re- 
ceiver employed  in  the  graphophone.  (See 
Phonograph.} 

Receiver,    Harmonic A    receiver, 

employed  in  systems  of  harmonic  telegraphy, 
consisting  of  an  electro-magnetic  reed,  tuned 
to  vibrate  to  one  note  or  rate  only.  (See  Te- 
legraphy, Grays  Harmonic  Multiple?) 

Receiver  Magnet. — (See  Magnet,  Receiv- 
ing) 

Receiver,  Phonographic —The  ap- 
paratus employed  in  a  telephone,  phono- 
graph, graphophone  or  gramophone  for  the 
reproduction  of  articulate  speech.  (See 
Phonograph?] 

Receiver,  Telephonic The  receiver 

employed  in  the  telephone.  (See  Tele- 
phone^ 

Receptive    Device,    Electro (See 

Device,  Electro-Receptive?) 

Receptive  Device,  Magneto  -  —(See 
Device,  Magneto-Receptive?) 

Reciprocal The  reciprocal  of  any 

number  is  the  quotient  arising  from  dividing 
unity  by  that  number. 

Thus,  for  example,  the  reciprocal  of  4,  is  \  or 
.250. 

The  conducting  power  of  any  circuit  is  equal 
to  the  reciprocal  of  its  resistance  ;  or,  in  other 
words,  the  conducting  power  is  inversely  propor- 
tional to  the  resistance. 


The  following  table  contains   the  reciprocals 
of  the  numerals  up  to  100  : 

TABLE  OF  RECIPROCALS. 


Re- 

Re- 

Re- 

Re- 

Re- 

cipro- 

No. 

cipro- 

No. 

cipro^ 

No. 

cipro- 

No. 

cipro- 

cal. 

cal. 

cal. 

cal. 

cal. 

0.5000 

22 

o  0455 

42 

o  0338 

62 

o  0:61 

82 

O   O    22 

0-3333 

23 

o  °435 

43 

o  0233 

63 

o  0159 

83 

O   O    2O 

o  2500 

24 

o  0417 

44 

o  0227 

64 

o  0156 

84 

009 

O    2OOO 

25 

o  0400 

45 

O   O222 

65 

o  0154 

85 

008 

o  1667 

26 

o  0385 

46 

o  0217 

66 

o  0152 

86 

006 

o  1429 

27 

o  0370 

47 

o  0213 

67 

o  0149 

87 

005 

o  1250 

28 

o  0357 

48 

o  0208 

68 

o  0147 

88 

O04 

0    IIII 

29 

o  0345 

49 

o  0204 

69 

o  0145 

89 

O   O       2 

o  1000 

3° 

o  0333 

5° 

O  O2OO 

70 

o  0143 

90 

O    O       I 

o  0909 

3i 

o  0323 

5i 

o  0106 

7' 

o  0141 

91 

O    O      O 

o  0833 

32 

o  0313 

52 

o  0192 

72 

o  0139 

92 

o  o  09 

o  0769 

33 

o  0303 

53 

o  0189 

73 

o  0137 

93 

o  o  c8 

o  0714 

34 

o  0294 

54 

o  0185 

74 

o  0135 

94 

0   0   06 

o  0667 

35 

o  0286 

55 

o  0182 

75 

o  0133 

95 

o  o  05 

o  o6as 

36 

o  0278 

56 

o  0179 

76 

o  0132 

96 

o  o  04 

o  0588 

37 

o  0270 

57 

o  0175 

77 

o  0130 

97 

o  o  03 

o  0556 

38 

o  0263 

58 

o  0172 

78 

o  0128 

98 

o  o  02 

o  0526 

39 

o  0256 

59 

o  0169 

79 

o  0127 

)<) 

O   O   OI 

o  0500 

4° 

o  0250 

60 

o  0167 

80 

o  0125 

IOO 

o  o  oo 

o  0476 

4» 

o  0244 

61 

o  0164 

81 

o  0123 

— ( Clark  or*  Sabine. ) 

Recoil  Circuit. — (See  Circuit,  Recoil.} 

Record,    Chronograph A    record 

made  by  means  of  a  chronograph  for  the  pur- 
pose of  measuring  and  recording  small  inter- 
vals of  time.  (See  Chronograph,  Electric?) 

Record,  Gramophone  —  —The  irregular 
indentations,  cuttings  or  tracings  made  by  a 
point  attached  to  the  diaphragm  spoken 
against,  and  employed  in  connection  with  the 
receiving  diaphragm  for  the  reproduction  of 
articulate  speech. 

Record,  Graphophone The  record 

made  by  the  movement  of  the  diaphragm  of 
the  graphophone.  (See  Phonograph.} 

Record,  Phonographic The  record 

produced  in  a  phonograph,  for  the  subse- 
quent reproduction  of  audible  articulate 
speech. 

Record,  Telephonic The  record 

produced  by  the  diaphragm  of  a  receiving 
telephone. 

Various  methods  have  been  proposed  for  ob- 
taining telephonic  records,  but  none  of  them 
have  yet  been  introduced  into  actual  commercial 
use. 

Recorder,  Chemical,  Bain's A  n  ap- 
paratus for  recording  the  dots  and  dashes  of 


Rec.] 


441 


[Rcc. 


a  Morse  telegraphic  dispatch,  on  a  sheet  of 
chemically  prepared  paper. 

A  fillet  of  paper  soaked  in  some  chemical  sub- 
stance, such  as  ferro-cyanide  of  potassium,  is 
moved  at  a  uniform  rate  between  the  two  ter- 
minals of  the  line,  one  of  which  is  iron  tipped,  so 
that  on  the  passage  of  the  current,  a  blue  dot,  or  a 
dash,  will  be  made  on  the  paper  according  to  the 
length  of  time  the  current  is  passing. 

In  order  to  insure  a  moist  condition  of  the  paper 
fillet,  some  deliquescent  salt,  like  ammonium 
nitrate,  is  generally  mixed  with  the  ferro-cyanide 
of  potassium. 


Fig.  467.     Bain  Recorder. 

A  Bain  recorder  is  shown  in  Fig.  467.  A,  is 
a  drum  of  brass,  tinned  on  the  outside.  The 
paper  fillet  is  drawn  from  the  roll  and  kept 
pressed  against  the  cylinder  A,  by  a  small  wooden 
roller  B.  The  needle,  which  is  a  metallic  point, 
is  placed  in  connection  with  one  end  of  the  line 
wire,  and  the  brass  drum  is  connected  with  the 
other  end  through  the  earths  Care  must  be  ob- 
served to  connect  the  needle  point  with  the  posi- 
tive electrode,  as  otherwise  the  paper  will  not  be 
marked.  (See  Electrolysis.') 

The  Bain  recorder  is  now  almost  entirely  re- 
placed by  the  Morse  sounder.  (See  Sounder, 
Morse  Telegraphic.} 

Recorder,  Morse  —  — An  apparatus  for 
automatically  recording  the  dots  and  dashes 
of  a  Morse  telegraphic  dispatch,  on  a  fillet  of 
paper  drawn  under  an  indenting  or  marking 
point  on  a  striking  lever,  connected  with  the 
armature  of  an  electro-magnet. 

This  apparatus  is  sometimes  called  a  Morse 
register. 

The  Morse  recording  or  registering  apparatus 
is  shown  in  Fig.  468. 

The  paper  fillet  passes  between  a  pair  of  rollers 
r,  driven  by  the  clockwork  W.  The  upper  roller 
is  provided  with  a  groove,  so  that  the  movement 
of  the  stylus  at  the  bent  end  of  the  lever  L,  by  the 


electro-magnet  M,  moving  its  armature  attached 
to  the  lever  L,  may  indent  or  emboss  the  paper 
fillet.  When  no  current  is  passing,  the  armature 
of  the  magnet  and  the  lever  L,  are  drawn  back  by 
the  action  of  an  adjustable  spring  at  n. 


Fig.  468.     Morse  Recorder. 

In  the  drawing,  the  ordinary  Morse  sounder  is 
shown  on  the  right.  The  sounder  has  almost 
entirely  replaced  the  recording  apparatus. 

Recorder,  Siphon An  apparatus 

for  recording  in  ink  on  a  sheet  of  paper,  by 
means  of  a  fine  glass  siphon  supported  on  a 
fine  wire,  the  message  received  over  a  cable. 

One  end  of  the  siphon  dips  in  a  vessel  of  ink. 
The  record  is  received  on  a  fillet  of  paper  moved 
mechanically  under  the  siphon.  The  ink  is  dis- 
charged from  the  siphon  by  electric  charges  im- 
parted to  the  ink  by  a  static  electric  machine. 


Fig.  46 >p.      The  Siphon  Recorder. 

In  the  annexed  sketch  of  the  siphon  recorder, 
Fig.  469,  a  light  rectangular  coil  b  b,  of  very  fine 
wire,  is  suspended  by  a  thin  wire  f  f,  between  the 
poles  N,  S,  of  a  powerful  compound  permanent 
magnet,  and  moving  on  the  vertical  axis  of  the 
supporting  wire  f  f,  and  adjustable  as  to  tension, 
at  h.  A  stationary  soft  iron  core  a,  is  magnetized 


SIPHON     RECORDER 

Fig.  470.    Record  of  Siphon  Recorder. 

by  induction  and  strengthens  the  magnetic  field 
of  N,  S.     The  cable  current  is  received  by  the 


Rec.] 


442 


coil  b  b,  through  the  suspending  wire  f  f ,  and  is 
moved  by  it  to  the  right  or  the  left,  according  to 
its  direction,  to  an  extent  that  depends  on  the 
current  strength. 

The  fine  glass  siphon  n,  which  dips  into  a 
reservoir  of  ink  at  m,  is  capable  of  movement  on 
a  vertical  axis  1,  and  is  moved  backwards  or  for- 
wards, in  one  direction  by  a  thread  k,  attached 


S     E     T   T    L     ED 
Fig.  471.    Record  of  Siphon  Recorder. 
to  b,  and  in  the  opposite  direction  by  a  retractile 
spring  attached  to  an  arm  of  the  axis  1. 

As  the  paper  is  moved  under  the  point  of  the 
siphon,  an  irregular  curved  line  is  marked  thereon. 

Two  records  as  actually  received  by  a  siphon 
recorder  are  shown  in  the  Figs.  470  and  471. 
Movements  upwards  correspond  to  the  dots,  and 
downwards  to  dashes. 

Rectification  of  Alcohol,   Electric  - 
— (See  Alcohol,  Electric  Rectification  of.} 

Rectified. — Turned  in  one  and  the  same 
direction. 

The  alternate  currents  in  a  dynamo-electric 
machine  are  rectified  or  caused  to  flow  in  one  ajid 
the  same  direction  by  means  of  a  commutator. 

The  word  commuted,  generally  used  in  this 
connection,  would  appear  to  be  preferable  to  the 
word  rectified.  (See  Commutator.) 

Rectilinear  Co-ordinates,  Abscissa  of • 

— (Set  Abscissa  of  Rectilinear  Co-ordinates) 

Rectilinear  Current— (See  Current,  Rec- 
tilinear^) 

Red  Heat— (See  Heat,  Red) 

Red  Hot— (See  Hot,  Red) 

Reducteur  or  Resistance  for  Yoltmeter. 
— A  coil  of  known  resistance  as  compared 
with  the  resistance  of  the  coils  of  a  voltmeter, 
and  connected  with  them  in  series  for  the 
purpose  of  increasing  the  range  of  the  instru- 
ment. (See  Voltmeter) 

Reducteur  or  Shunt  for  Ammeter.— A 
shunt  coil  connected  in  multiple  with  the  coils 
of  an  ammeter  for  the  purpose  of  changing 
the  value  of  the  readings. 

The  ratio  of  the  resistance  of  the  reducteur  and 
the  ammeter  coils  is  known.  A  reducteur  in- 
creases the  range  of  current  measured  by  the  am- 
meter 


Refining  of  Metals,  Electric 


— the 

refining  of  metals  by  the  application  of  elec- 
trolysis. 

When  certain  precautions  are  taken,  metals 
thrown  down  from  their  solutions,  are  obtained  in 
a  chemically  pure  condition.  This  fact  is  utilized 
in  the  electrical  refining  of  metals.  If,  for  exam- 
ple, a  plate  of  impure  copper  is  to  be  refined 
electroly  tically,  it  is  used  as  the  anode  of  a  copper 
bath,  and  placed  opposite  a  thin  plate  of  pure  cop- 
per forming  the  kathode.  The  passage  of  the 
current  gradually  dissolves  the  copper  from  the 
plate  at  the  anode,  and  deposits  it  in  a  chemically 
pure  condition  on  the  plate  at  the  kathode. 

Somewhat  similar  principle*  are  employed  for 
electrically  refining  other  metals. 

Reflect. — To  throw  off  from  a  surface,  ac- 
cording to  the  laws  of  reflection,  as  of  waves 
in  an  elastic  medium.  (See  Reflection,  Laws 
of) 

Reflecting. — Throwing  off  from  a  surface, 
according  to  the  laws  of  reflection.  (See 
Reflection,  Laws  of) 

Reflecting  Galvanometer.— (See  Gal- 
vanometer, Reflecting) 

Reflection. — The  throwing  back  of  a  body 
or  wave  from  a  surface  at  an  angle  equal  to 
that  at  which  it  strikes  such  surface.  (See 
Reflection,  Laws  of) 

Reflection,  Laws  of The  laws  gov-r 

erning  the  reflection  of  light 

(I.)  The  angle  of  reflection,  or  the  angle  in- 
cluded between  the  reflected  ray  and  the  perpen- 
dicular to  the  reflecting  surface  at  the  point  of 
incidence,  is  equal  to  the  angle  of  incidence,  or 
the  angle  included  between  the  striking  ray  and 
the  perpendicular  to  the  reflecting  surface  at  the 
point  of  incidence. 

(2.)  The  plane  of  the  angle  of  incidence  co- 
incides with  the  plane  of  the  angle  of  reflection. 

Reflection  of  Electro-Magnetic  Wares. 

— (See  Waves,  Electro-Magnetic,  Reflection 
of) 

Reflection  of  Induction.— (See  Induc- 
tion, Reflection  of) 

Reflector. — A  plane  or  curved  surface, 
capable  of  regularly  reflecting  light. 

Reflector,  Parabolic  —  —A  reflector, 


Ref.j 


413 


[Keg. 


or  mirror,  the  reflecting  surface  of  which  is 
a  paraboloid,  or  such  a  surface  as  would  be 
obtained  by  the  revolution  of  a  parabola 
about  its  axis. 

A  parabolic  curve,  which  may  be  regarded  as 
a  section  of  a  parabola,  is  shown  in  Fig.  472. 
A  parabola  has  the  following  properties:  If  lines 
F  P,  F  P,  etc.,  be  drawn  from  the  point  F, 
called  the  focus,  to  any  point,  P,  P,  etc.,  in  the 
curve,  and  the  lines  Pp,  Pp,  Pp,  etc.,  be  then 
drawn  severally  parallel  to  the  axis,  V  M,  then 
all  such  angles,  F  P  p,  F  P  p,  will  be  bisected  by 
verticals  to  tangents  at  the  point  P,  P,  and  P. 

Therefore,  if  a  light  be  placed  at  the  focus  of  a 
parabolic  reflector,  all  the  light  reflected  from  the 
surface  of  the  parabola  will  pass  off  sensibly  par- 
allel to  the  axis  V  M. 

In  Locomotive  Head 'lights ;  a 
lamp  is  placed  at  the  focus  of 
a  parabolic  reflector,  and  the 
parallel  beam  so  obtained  is 
utilized  for  the  illumination  of 
the  track.   In  a  search  light  an  v! 
electric  arc  lamp  is  placed  at      p\ 
the  focus  of  a  parabolic  reflec- 
tor,  or  at  the  focus  of  a  lens. 

A    parabolic    reflector     is 
used  for  search  lights,   some-  Fig.  472.    Parabolic 
times  in  connection  with  an  Reflector. 

arc  lamp.  A  focusing  arc  lamp  must  be  used  for 
this  purpose,  so  as  to  maintain  the  voltaic  arc  at 
the  focus  of  the  parabolic  reflector,  notwithstand- 
ing the  unequal  consumption  of  the  positive  and 
negative  carbons.  (See  Arc,  Voltaic.') 

Refract. — To  change  the  direction  of  waves 
in  any  elastic  medium  in  accordance  with 
the  laws  of  refraction.  (See  Refraction) 

Refracting. — Changing  the  direction  of 
waves  in  an  elastic  medium  in  accordance 
with  the  laws  of  refraction. 

Refraction.— The  bending  of  a  ray  of 
sound,  light,  heat,  or  electro-magnetism  at 
the  surface  of  any  medium  whose  density 
differs  from  that  through  which  such  ray 
was  previously  passing. 

Rays  of  sound,  light,  heat  or  electro-mag- 
netism are  transmitted  or  propagated  in  straight 
lines  as  long  as  the  density  of  the  homogeneous 
medium  through  which  they  are  pissing  under- 
goes no  change.  That  is,  as  long  as  the  medium 
15— Vol.  1 


is  homogeneous  or  isotropic.  (See  Medium,  Iso- 
tropic.)  As  the  rays  enter  the  surface  of  a 
medium  which  differs  in  density  from  that  through 
which  they  have  been  passing,  they  are  bent  or 
refracted  at  the  surface  of  such  a  medium. 

This  bending  takes  place  towards  a  perpen- 
dicular to  the  refracting  surface  at  the  point  of  in- 
cidence, when  the  medium  in  to  which  the  rays  are 
entering  is  of  greater  density  than  that  they  are » 
leaving,  and  from  the  perpendicular  when  the 
medium  they  are  entering  is  of  less  density  than 
that  they  are  leaving. 

The  refraction  or  bending  of  the  ray  is  caused 
by  the  difference  in  the  velocity  with  which  the 
waves  are  propagated  through  the  two  media. 

There  is  no  refraction  or  deviation  when  the 
two  rays  enter  the  new  medium  at  right  angle, 
to  its  surface,  or  when  there  is  no  angle  of  inci- 
dence. 

Refraction,  Double — The  property 

possessed  by  certain  substances  of  splitting 
up  a  ray  of  light  passed  through  them  into 
two  separate  rays,  and  thus  doubly  refracting 
the  ray. 

Certain  specimens  of  calc  spar  possess  the  prop- 
erty of  double  retraction.  Each  of  the  two  rays 
into  which  the  original  ray  is  separated  is  polar- 
ized. Such  calc  spar  is  called  doubly  refracting 
calc  spar. 

Refraction,  Double,  Electric The 

property  of  doubly  refracting  light  acquired 
by  some  transparent  substances  while  in  an 
electrostatic  or  electro-magnetic  field. 

Transient  or  momentary  powers  of  double 
refraction,  acquired  by  a  transparent  sub- 
stance while  placed  in  an  electric  field. 

The  intensity  of  double  refraction  is  propor- 
tioned to  the  square  of  the  electric  force. 

The  action  of  an  electric  field  in  endowing  a 
substance  with  the  power  of  double  refraction 
while  kept  in  such  field,  is  due  to  the  strain  pro- 
duced by  the  electrostatic  stress  of  the  field. 

A  similar  transient  power  of  double  refraction 
is  acquired  by  many  bodies  when  subjected  to 
the  strain  produced  by  a  simple  mechanical 
stress. 

Refreshing  Action  of  Current — (See  Ac- 
tion, Refreshing,  of  Current?) 

Region,  Extra-Polar •  —A  term  ap- 
plied in  electro-therapeutics  to  the  region. 


Reg.] 

which  lies  outside  or  beyond  the  therapeutic 
electrode. 

The  term  extra-polar  region  is  used  in  contra- 
distinction to  polar  region.  (See  Region,  Polar.) 

Region,  Polar A  term  applied  in 

electro-therapeutics  to  that  region  or  part  of 
the  body  which  lies  directly  below  the  thera- 
peutic electrode. 

Register,  Double-Pen  Telegraphic 

— A  telegraphic  register  provided  with  two 
separate  styluses  or  pens  for  recording  the 
telegraphic  message  on  a  fillet  of  paper.  (See 
Register,  Telegraphic!) 

Register,  Morse A  name  sometimes 

given  to  a  Morse  recorder.  (See  Recorder, 
Morse?) 

Register,  Telegraphic An  appa- 
ratus employed  at  the  receiving  end  of  a  tele- 
graphic line  for  the  purpose  of  obtaining  a 
permanent  record  of  the  telegraphic  dispatch. 

The  telegraphic  register  consists  essentially  of 
means  whereby  a  fillet  or  tape  of  paper  is  drawn 
mechanically  under  a  pen  or  stylus  attached  to 
the  armature  of  an  electro-magnet  and  moving 
therewith. 

The  pen  or  stylus  presses  against  the  paper 
whenever  the  armature  is  attracted  to  the  elec- 
tro-magnet, and  is  held  there  while  the  cur- 


444 


[Reg. 


Fig.  t73  t*k-  Writing  Register. 
•cent  is  passing  through  the  coils  of  the  electro- 
magnet. By  these  means  the  dots  and  dashes  of 
the  telegraphic  alphabet  are  recorded  on  the 
paper  fillet  as  embossed  or  printed  dots  and 
dashes.  The  Morse  register  is  an  apparatus  of 
this  description.  (See  Recorder,  Morse.) 

A  form  of  ink-writing  telegraphic  register  is 
shown  in  Fig.  473.    It  is  self-starting. 


Register,  Time,  for  Railroads A 

telegraphic  recording  apparatus  or  register 
designed  to  record  all  telegraphic  messages 
transmitted  over  a  line. 

The  record  is  received  on  an  endless  band  or 
fillet  of  paper.  It  is  useful  in  case  of  disputes  as 
to  the  time  certain  messages  were  sent  over  the 
line. 

Register,  Watchman's  Electric 

A  device  for  permanently  recording  the  time 
of  a  watchman's  visit  to  each  of  the  dif- 
ferent localities  he  is  required  to  visit  at  stated 
intervals. 

These  registers  are  of  a  variety  of  forms.  They 
consist,  however,  in  general,  of  a  drum  or  disc  of 
paper  driven  by  clockwork,  on  which  a  maik  is 
made  by  a  stylus  or  pencil,  operated  on  the  clos- 
ing of  a  circuit  by  the  pressing  of  a  push  button 
or  the  pressing  of  a  key  by  the  watchman  at  each 
station. 

Registering  Apparatus,  Electric 

(See  Apparatus,  Registering,  Electric!) 

Registering  Electrometer.— (See  Elec- 
trometer, Registering!) 

Regulable,  Automatically Capa- 
ble of  being  automatically  regulated.  (See 
Regulation,  Automatic!) 

Regulate,  Automatically To  regu- 
late in  an  automatic  manner.  (See  Regula- 
tion, Automatic!) 

Regulation,  Automatic Regulation 

automatically  effected. 

Regulation,  Automatic,  of  Dynamo-Elec- 
tric Machine Such  a  regulation  of  a 

dynamo-electric  machine  as  will  automati- 
cally preserve  constant  either  the  current  or 
the  potential  difference. 

The  automatic  regulation  of  dynamo-electric 
machines  may  be  accomplished  in  the  following 
ways,  viz.: 

(I.)  By  a  Compound  Winding  of  the  Machine. 

This  method  is  particularly  applicable  to  con- 
stant-potential machines.  By  this  winding,  the 
magnetizing  effect  of  the  shunt  coils  is  maintained 
approximately  constant,  while  that  of  the  series 
coils  varies  proportionally  to  the  load  on  the  ma- 
chine. 

The  series  coils  are  sometimes  wound  close  to 


-Keg.] 


445 


[Beg. 


the  poles  of  the  machine,  and  the  shunt  coils 
nearer  the  yoke  of  the  magnets.  Custom,  how- 
ever, varies  in  this  respect,  and  very  generally 
the  shunt  coils  are  placed  nearer  the  poles  than 
the  series  coils.  (See  Machine,  Dynamo -Electric, 
Compound-  Wound.") 

(2.)  By  Shifting  the  Position  of  the  Collecting 
Brushes. 

In  the  Thomson-Houston  system  of  current 
regulation,  the  current  is  kept  practically  con- 
stant by  the  following  devices:  The  collecting 
brushes  are  fixed  to  levers  moved  by  the  regula- 
tor magnet  R,  as  shown  in  Fig.  474,  the  arma- 
ture of  which  is  provided  with  an  opening  for  the 
entrance  of  the  paraboloidal  pole  piece  A.  A 
dash-pot  is  provided  to  prevent  too  sudden  move- 
ment. 

When  the  current  is  normal,  the  coil  of  the 
regulator  magnet  is  short-circuited  by  contact 
points  at  S  T,  which  act  as  a  shunt  of  very  low  re- 
sistance. These  contact  points  are  operated  by 
the  solenoid  coils  of  the  controller,  traversed  by 
the  main  current.  The  cores  of  this  solenoid  are 
suspended  by  a  spring.  When  the  current  be- 
comes too  strong,  the  contact  point  is  opened, 
and  the  current,  traversing  the  coil  of  the  regu- 
lar magnet  A,  attracts  its  armature,  which  shifts 
the  collecting  brushes  into  a  position  in  which  a 
smaller  current  is  taken  off. 

A  carbon  shunt,  r,  of  high  resistance,  is  pro- 
vided  to  lessen  the  spark  at  the  contact  points  S 
T,  which  occurs  on  opening  the  circuit. 


Fig.  474-     Thomson- Houston  Regulator* 

In  operation  the  contact  points  are  continually 
opening  and  closing,  thus  maintaining  a  practi- 
cally constant  current  in  the  external  circuit. 

(3.)  By  the  Automatic  Variation  of  a  Resist, 
ance  shun  ting  the  field  magnets  of  the  machine, 
as  in  the  Brush  system. 

In  Fig.  475  the  variable  resistance  C,  forms  a 
part  of  the  shunt  circuit  around  the  field  mag- 
nets F  M..  This  resistance  is  formed  of  a  pile  of 
carbon  plates.  On  an  increase  of  the  current, 
such,  for  example,  as  would  result  from  turning 
out  some  of  the  lames,  the  electro  magnet  B, 


placed  in  the  main  circuit,  attracts  its  armature 
A,  and,  compressing  the  pile  of  carbon  plates  C, 
lowers  their  resistance,  thus  diverting  a  propor- 
tionally larger  portion  of  the  current  from  the 
field  magnet  coils  F  M,  and  maintaining  the  cur- 
rent practically  constant. 

In  some  machines  the  same  thing  is  done  by 
hand,  but  this  is  objectionable,  since  it  requires 
the  presence  of  an  attendant. 

(4.)  By  the  Introduction  of  a  Variable  Resist- 
ance into  the  shunt  circuit  of  the  machine,  as  in 
the  Edison  and  other  systems. 


Fig.  47 S-     The  Brush  Regulator. 

This  resistance  may  be  adjusted  either  auto- 
matically by  an  electro-magnet  whose  coils  are 
in  an  independent  shunt  across  the  mains,  or  may 
be  operated  by  hand. 

In  Fig.  476,  the  variable  resistance  is  shown 
at  R,  the  lever  switch  being  in  this  case  operated 
by  hand  whenever  the  potential  rises  or  falls  be- 
low the  proper  value. 


Fig.  476.     The  Edison  Regulator. 

The  machine  shown  is  thus  enabled  to  main- 
tain a  constant  potential  on  the  leads  to  which  the 
lamps  L,  L,  L,  etc.,  are  connected  in  multiple  arc. 

(5.)  Dynamometric  Governing,  in  which  a 
series  dynamo  is  made  to  yield  a  constant  cur- 
rent by  governing  the  steam  engine  that  drives 
it,  by  means  of  a  dynamometric  governor.  This 
governor  operates  by  maintaining  a  constant 
torque  or  turning  moment,  instead  of  by  means  of 


Beg.] 


446 


[Rel. 


the  usual  centrifugal  governor  which  maintains  a 
constant  speed. 

(6.)  Electric  Governing  of  the  Driving  Engine, 
in  which  the  governor  is  regulated  by  the  cur- 
rent itself  instead  of  by  the  speed  of  rotation,  as 
usual. 

Regulation,  Hand Such  a  regula- 
tion of  a  dynamo-electric  machine  as  will  pre- 
serve constant,  either  the  current  or  the 
potential,  said  regulation  being  effected  by 
hand  as  distinguished  from  automatic  regu- 
lation. 


Regulator,  Automatic 


— A  device 


for  securing  automatic  regulation  as  dis- 
tinguished from  hand  regulation.  (See 
Regulation,  Hand.  Regulation,  Automatic?) 

Regulator,  Hand  -  —  A  resistance 
box,  the  separate  coils  or  resistances  of  which 
can  be  readily  placed  in  or  removed  from  a 
circuit  by  means  of  a  hand-moved  switch. 

The  term  hand  regulator  is  used  as  distin- 
guished from  automatic  regulator.  (See  Regu- 
lator, Automatic.  Regulation,  Automatic.} 

Regulator  Magnet.  —  (See  Magnet,  Regu- 
lator^ 

Regulator,  Monophotal  Arc-Light  - 

—  A  term  sometimes  employed  for  an  electric 
arc  lamp  in  which  the  whole  current  passes 
through  the  arc-regulating  mechanism,  and 
which    is  usually  operated  singly   in   circuit 
with  a  dynamo. 

Regulator,  Polyphotal  Arc-Lamp  — 
A   regulator  for  an  arc  lamp   suitable  for 
maintaining  a  number  of  lamps  m  series  cir- 
cuit with  the  dynamo. 

Polyphotal  regulators  differ  from  monophotal 
regulators  in  that  their  regulating  electro  mag- 
nets are  energized  by  a  shunt  circuit  around  the 
electrodes  of  the  lamp,  while  in  monophotal  regu- 
lators such  electro-magnets  are  placed  in  the  di- 
rect circuit  The  terms  monophotal  and  poly- 
photal  are  not  generally  used  in  America. 

Reguline  Electro-Metallurgical  Deposit. 

—  (See  Deposit,  Electro-Metallurgical,  Reg- 


Relative  Calibration. — (See  Calibration^ 
Relative?) 

Relay. — An  electro-magnet,  employed  in 
systems  of  telegraphy,  provided  with  contact 
points  placed  on  a  delicately  supported  arma- 
ture, the  movements  of  which  throw  a  battery, 
called  the  local  battery,  into  or  out  of  the 
circuit  of  the  receiving  apparatus. 

A  relay  is  sometimes  called  a  receiving  magnet. 


Rejuvenation    of    Luminescence.  —(See 
Luminescence,  Rejuvenation  of.) 


Fig.  477 •     Telegraphic  Relay. 

The  use  of  a  relay  permits  much  smaller  cur- 
rents to  be  used  than  could  otherwise  be  done, 
since  the  electric  impulses,  on  reaching  a  distant 
station,  are  required  to  do  no  other  work  than 
attracting  a  delicately  poised  movable  contact, 
and  thus,  by  throwing  a  local  battery  into  the 
circuit  of  the  receiving  apparatus,  to  cause  such 
local  battery  to  perform  the  work  of  register- 
ing. Its  use  is  especially  required  in  the  Morse 
system  of  telegraphy  in  order  to  cause  the  sounder 
to  be  distinctly  heard. 

A  form  of  relay  that  is  much  used  is  shown  in 

Fig-  477- 

The  electro- magnet  M,  is  wound  with  many 
turns  of  very  fine  wire.  In  the  form  used  by  the 
Western  Union  Telegraph  Company,  there  are 
about  8, 500  turns,  having  resistance  of  150  ohms. 
A  screw  m,  is  provided  for  moving  the  electro- 
magnet M,  a  slight  distance  in  or  out,  for  the  pur- 
poses of  adjustment.  A  semi-cylindrical  arma- 
ture A,  of  soft  iron,  is  attached  to  the  insulated 
armature  lever  a,  the  lower  end  of  which  is  sup- 
ported by  a  steel  arbor,  which  is  pivoted  between 
two  set  screws. 

A  retractile  spring  S',  regulable  at  S,  is  pro- 
vided for  moving  the  armature  away  from  the 
electro-magnet.  There  are  four  binding  posts, 
two  of  which  are  placed  in  the  circuit  of  the 
electro-magnet,  and  two  in  that  of  the  local  bat- 
tery. The  ends  of  the  line  wire  are  connected 
with  the  former,  and  the  receiving  instrument 
placed  ii.  the  circuit  of  the  latter.  A  platinum 


Rel.] 


447 


[Rel. 


contact  is  placed  on  the  end  of  a  screw  supported 
at  F,  opposite  a  similar  contact,  near  the  end  a, 
of  the  armature  iever.  The  contact  is  regulable 
by  means  of  a  screw  c. 

On  the  energizing  of  the  electro -magnet,  the 
attraction  of  its  armature  closes  the  platinum 
contact,  and,  by  thus  completing  the  circuit  of  the 
local  battery,  causes  an  attraction  of  the  armature 
of  the  receiving  apparatus.  On  the  cessation  of 
the  current  in  the  main  line,  the  spring  S  ,  pulls 
the  armature  away  from  the  magnet,  breaks  the 
circuit  of  the  local  battery,  and  thus  permits  a 
similar  spring  on  the  receiving  instrument  to  pull 
its  armature  away.  Thus  all  the  movements  of 
the  armature  of  the  relay  are  reproduced  with  in- 
creased intensity  by  the  armature  of  the  receiving 
instrument. 

The  connections  of  the  relay  to  the  local  bat- 
tery and  the  registering  apparatus,  will  be  better 
understood  from  an  inspection  of  Fig.  478,  which 
represents  a  form  of  relay  much  used  in  Germany. 


Relay,  Differential A  telegraphic 


Fig.  478.     Telegraphic  Relay,  German  Pattern. 

The  retractile  spring  f,  is  regulated  by  the  up- 
and-down  movements  of  its  lower  support,  which 
slides  in  the  vertical  pillar  S.  The  line  wire  is 
shown  at  m  m,  connected  at  one  end  to  earth  by 
a  ground  wire. 

The  registering  apparatus  R,  is  connected  in 
the  circuit  of  the  local  battery  L,  as  shown. 
The  contacts  are  made  by  the  end  B,  of  the  lever 
B  B',  attached  to  the  armature  A,  of  the  electro- 
magnet M  M. 

Relay  Bell.— (See  Bell,  Relay,  Electric) 

Relay,  Box-Sounding  Telegraphic  

—A  relay  the  magnet  of  which  is  surrounded 
by  a  resonant  case  of  wood  for  the  purpose 
of  increasing  the  intensity  of  the  sound  made 
by  the  armature  of  the  magnet. 

A  form  of  box-sounding  relay  is  shown  m  Fig. 
479- 


Fig.  479     Box- Sounding  Relay 

relay  containing  two  differentially  wound  coils 
of  wire  on  its  magnet  cores. 

When  the  currents  which  pass  through  these 
two  coils  are  of  the  same  strength,  there  is  no 
movement  of  the  armature,  since  the  fields  of  the 
two  coils  neutralize  each  other. 

The  differential  relay  is  used  in  the  differential 
method  of  duplex  and  quadruplex  telegraphy. 
(See  Telegraphy,  Duplex  Differential  Method  of. 
Telegraphy,  Quadruplex  Differential  Method  of  .} 

Relay  Magnet — A  name  sometimes  given 
to  a  relay.  (See  Relay) 

Relay,  Microphone A  device  for 

automatically  repeating  a  telephonic  message 
over  another  wire. 


Fig.  480.    Microphone  Relay. 
A  form  of  microphone  relay  is  shown  in  Figs. 
480  a'nd  481. 

Several  minute  microphones  mounted  on  the 


Fig.  481.    Microphone  Relay. 

diaphragm  of  the  telephone  whose  message  is  to 
be  repeated,  so  vary  the  resistance  of  a  local  bat- 
tery included  in  their  circuit  as  to  automatically 
repeat  the  articulate  speech  received. 

The  microphones  may  oe  connected  either  in 


Rel.] 


448 


[Bel. 


multiple  arc  or  in  series,  as  shown  respectively  to 
the  left  and  right  in  Fig.  480. 

Relay,  Pocket  Telegraphic A  form 

of  telegraphic  relay  of  such  small  dimensions 
as  to  permit  it  to  be  readily  carried  in  the 
pocket. 

Relay,  Polarized A  telegraphic  re- 
lay provided  with  a  permanently  magnetized 
armature  in  place  of  the  soft  iron  armature  of 
the  ordinary  instrument. 

In  the  form  of  polarized  relay  shown  in  Fig. 
482,  N  S,  is  a  steel  magnet,  whose  magnetism  is 
consequently  permanent,  with  its  north  and  south 
poles  at  N,  and  S,  respectively.  The  cores  of 
the  electro-magnet  m,  m',  are  of  soft  iron,  and, 
since  they  rest  on  the  north  pole  of  the  permanent 
steel  magnet,  the  poles,  brought  very  near  to- 
gether by  the  armatures  at  n,  n',  will  be  of  the 
same  polarity  as  N,  when  no  current  is  passing 
through  the  coils  m,  m' ;  but  when  such  current 
does  pass,  one  of  these  poles  becomes  of  stronger 
north  polarity,  while  the  other  changes  its  polar- 
ity to  south. 

By  these  means  to-and  fro  movements  of  the 
armature  lever,  with  its  contact  point,  are  effected 
without  the  use  of  a  retractile  spring  ;  movement 
in  one  direction  occurring  on  the  closing  of  the 
circuit  due  to  the  electro-magnetism  developed 


Fig.  482.    Polarized  Relay. 

by  the  coils  m,  m',  and  movement  in  the  opposite 
direction,  on  the  losing  of  this  magnetism  on 
breaking  the  circuit,  by  the  permanent  magnet- 
ism of  the  steel  magnet  N  S. 

These  movements  are  imparted  to  the  soft  iron 
lever  c,  c',  pivoted  at  B,  and  passing  between  the 
closely  approached  soft  iron  poles  at  n,  n'.  This 
lever  rests  at  the  end  c',  against  a  contact  point 


when  moved  in  one  direction,  and  against  an  in- 
sulated point  when  moved  in  the  opposite  direc- 
tion. It  rests  against  the  insulated  point  when 
no  current  is  passing  through  the  coils  m,  m'. 

If  the  armature  lever  were  placed  in  a  position 
exactly  midway  between  the  poles  n,  and  n',  it 
would  not  move  at  all,  being  equally  attracted  by 
each;  but  if  moved  a  little  nearer  one  pole  than 
the  other,  it  would  be  attracted  to,  and  rest 
against,  the  nearer  pole. 

When  alternating  currents  are  employed  on 
the  line,  the  lever  c,  c',  must  be  adjusted  as  nearly 
as  possible  in  the  middle  of  the  space  between  n 
and  n',  in  which  case  it  will  remain  on  the  side  to 
which  it  was  last  attracted,  until  a  current  in  the 
opposite  direction  moves  it  to  the  other  side. 

LB 


SOB 


Fig.  483.     A  Detail  of  the  Polarized  Relay. 

The  space  between  the  magnet  poles  n,  n', 
and  the  contacts  of  the  armature  lever  at  D,  and 
D',  are  shown  in  detail  in  Fig.  483,  which  is  a 
plan  of  Fig.  482.  The  binding  posts  for  the  line 
battery  are  shown  at  L  B,  i,  and  2,  and  those 
for  the  local  battery  at  A  and  B.  The  dotted 
lines  show  the  connections. 

Since  the  polarized  relay  dispenses  with  the  re- 
tractile spring,  it  is  far  more  sensitive  than  the 
ordinary  instrument.  Once  adjusted,  no  further 
regulation  is  required,  in  which  respect  it  differs 
very  decidedly  from  non-polarized  relays. 

There  are  other  forms  of  polarized  relays,  but 
the  above  will  suffice  to  illustrate  the  general 
principle  of  their  operation. 

Relay  Shunt,  Steam's (See  Shunt, 

Relay,  Steam's.) 

Reluctance,  Magnetic A  term  re- 
cently proposed  in  place  of  magnetic  resist- 
ance to  express  the  resistance  offered  by  a 


Rel.] 


449 


[Rep. 


medium  to  the  passage  through  its  mass  of 
lines  of  magnetic  force. 

The  term  reluctance,  in  the  sense  of  resistance 
to  passage  of  lines  of  magnetic  force,  has  been 
proposed  in  place  of  resistance,  for  the  purpose 
of  carrying  out  the  conception  of  regarding  the 
flow  of  lines  of  force  in  a  magnetic  circuit  as 
being  due  to  a  magneto-motive  force,  and  being 
opposed  by  a  reluctance  of  the  substances  form- 
ing such  circuit  to  the  passage  of  such  lines. 

According  to  this  conception, 

The  magnetic  flux  = 

The  magneto-motive  force 
The  reluctance. 

Reluctance,    Magnetic,  Unit  of 

Such  a  magnetic  reluctance  in  a  closed  cir- 
cuit that  permits  unit  magnetic  flux  to 
traverse  it  under  the  action  of  unit  magneto- 
motive force. 

In  present  practical  work  reluctances  vary 
from  100,000  to  100,000,000  of  the  practical 
units. 

Reluctivity. — A  term  proposed  for  mag- 
netic reluctance.  (See  Reluctance,  Mag- 
netic^) 

This  term  is  not  generally  adopted. 

Removable  Key  Switch. — (See  Switch, 
Removable  Key?) 

Renovation  of  Secondary  Cell. — (See 
Cell,  Secondary  or  Storage,  Renovation  of.) 

Renovation  of  Secondary  or  Storage 
Cell. — (See  Cell,  Secondary  or  Storage, 
Renovation  of.) 

Reofore. — A  rheophore.    (See  Rheophore.) 

Repeaters,  Telegraphic Tele- 
graphic devices,  whereby  the  relay,  sounder 
or  registering  apparatus,  on  the  opening  and 
closing  of  another  circuit,  with  which  it  is 
suitably  connected,  is  caused  to  repeat  the 
signals  received. 

Repeaters  are  employed  to  establish  direct 
communication  between  very  distant  stations,  or 
to  connect  branch  lines  to  the  main  line. 

Fig.  484,  shows  Wood's  Button  Repeater.  This 
repeater 'consists  simply  of  a  three-point  switch 
L,  capable  of  being  placed  on  the  points  i,  2  and 
3  ;  and  a  ground  switch  at  4.  The  circuits  are 
arranged  between  the  sounders  S,  S',  relays 


M,  M',  main  batteries  B,  B',  and  the  two  main 
lines  E,  and  W,  in  the  manner  shown. 


Fig.  484.     Woofs  Button  Repeater. 

If  the  lever  L,  is  in  the  position  shown  in  the 
drawing,  the  lines  E  and  W,  form  independent 
circuits. 

If  the  ground  switch  4  is  closed,  and  the  lever 
L,  is  placed  on  2,  2,  the  eastern  line  repeats  into 
the  western.  If  the  lever  L,  is  placed  on  the 
plates  3,  3,  the  western  line  repeats  into  the 
eastern. 

This  repeater  is  non- automatic  and  can  be 
worked  in  but  one  direction  at  a  time  ;  moreover, 
it  requires  the  services  of  an  attendant. 

The  automatic  repeater  can  be  operated  in  both 
directions,  and  dispenses  with  the  constant  ser- 
vices of  an  attendant  at  the  repeating  station. 

In  sending  a  dispatch  through  a  repeater,  the 
dots  and  dashes  are  prolonged  so  as  to  give  the 
lever  of  the  repeating  instrument  time  in  which 
to  move  backwards  and  forwards. 


Fig.  483-    HicVs  Automatic  Button  Repeater. 

In  Hick's  Automatic  Repeater,  shown  in  Fig. 
485,  the  switch  or  circuit-changer  is  automatic  in 
its  action. 

The  relay  magnets  are  shown  at  M,  M',  the 
sounders  at  R  and  R'  ;  f,  f,  are  platinum  con- 
tacts  operated  by  levers  1  and  1',  and  L  and  L', 
are  extra  local  magnets,  that  act  on  armatures 


Rep.] 


450 


[Rep. 


placed  directly  opposite  the  armatures  of  the  relay 
magnets. 

The  extra  local  magnet  L,  is  cut  out  of  the 
circuit  of  B',  the  extra  local  battery,  when  the 
main  circuit  is  broken,  and  the  armature  is  in 
contact  with  c.  As  soon  as  this  happens,  how- 
ever, the  spring  s,  drawing  away  the  armature, 
and  thus  opening  the  short-circuit  of  no  rcsist- 
»  ance  between  c  and  a,  establishes  a  circuit 
through  L.  On  a,  coming  in  contact  with  c,  the 
circuit  is  again  broken. 

The  tension  of  the  spring  s,  is  so  regulated  that 
a  very  rapid  vibration  of  a,  is  maintained  so  con- 
stantly, that  it  is  impossible  to  close  the  main  cir- 
cuit when  L,  is  not  cut  out.  The  armature  a, 
will  therefore  respond  to  very  weak  impulses  of 
the  relay  magnet 

On  breaking  the  western  main  circuit  N,  the 
lever  a,  vibrates  very  rapidly.  The  lever  1,  of  the 
sounder  R,  first  breaks  the  circuit  of  L,  and  after- 
wards that  of  the  eastern  main  circuit  E,  which 
passes  through  M.  Both  L'  and  M',  being 
broken,  a  slight  tension  of  s',  will  hold  a,  in 
place,  thus  avoiding  the  breaking  of  the  western 
main  circuit  through  the  closing  of  the  local  cir- 
cuit through  R.  On  the  closing  of  the  western 
circuit,  the  reverse  of  these  operations  occurs. 

The  author  has  taken  the  above  explanation 
mainly  from  Pope's  work  on  "  Modern  Practice 
of  the  Electric  Telegraph." 

Repeating  Sounder. — (See  Sounder,  Re- 
peating.} 

Replenisher. — A  static  influence  machine 
devised   by  Sir  William 
Thomson    for  charging 
the    quadrants    of    his 
quadrant  electrometer. 

Two  brass  carriers  C 
and  D,  shown  in  Fig.  486, 
are  electrically  fixed  to  the 
end  of  the  vulcanite  rod 
E,  which  is  capable  of  ro- 
.,  tation  by  the  thumb  screw 
at  M,  in  the  direction 
shown  by  the  arrow.  Hol- 
low metal  half-cylinders, 
A  and  B,  act  as  inductors, 
a  strip  of  brass  fixed  around  Fig.  486.  The  Reflen- 
the  edges  of  a  piece  of  vul- 
canite P,  connecting  the  metallic  springs  S,  and 
S',  as  shown. 

The  action  of  the  replenisher  is  readily  under- 


stood from  the  following  considerations,  as  sug- 
gested by  Ayrton  in  his  "Practical  Electricity  "  : 

A  and  B,  Fig.  487,  are  two  insulated  hollow 
metallic  vessels  having  a  small  difference  of  po- 
tential between  them,  A,  being  the  higher.  C, 
and  D,  are  two  small  uncharged  conductors  held 
by  insulating  strings.  If  C  and  D,  be  held  near 
A  and  B,  as  shown,  the  potential  of  C,  will,  by 
induction,  be  raised  somewhat  above  that  of  D, 
so  that  when  connected  by  a  conductor,  such  as 
the  metallic  wire  W,  a  small  quantity  of  positive 
electricity  will  flow  from  C,  to  D,  thus  leaving  D, 
positively,  and  C,  negatively  charged. 

If,  now,  C  and  D,  are  removed  from  W,  and 
placed  in  the  bottom  of  B  and  A,  as  shown  in 
Fig.  488,  the  difference  of  potential  between  A, 
and  B,  will  be  thereby  increased,  and  if  they  are 
then  withdrawn,  and  totally  discharged,  and 


Fig.  487.    Action  of  Replenisher. 

again  placed  in  the  first  position  shown,  an  ad- 
ditional charge  can  be  given  to  A  and  B,  and  this 
can  be  repeated  as  often  as  desired. 

In  the  replenisher,  A  and  B,  correspond  to  the 
vessels  A  and  B  ;  the  brass  carriers  C  and  D, 
to  the  balls  C  and  D,  and  the  spring  S  S,  and  M, 


Fig.  488.    Action  of  Replenisher. 

to  the  wire  W.     No  initial  charge  need  be  given 
to  A  and  B,  since  they  are  invariably  found  to 


Rep.] 


451 


[Res. 


be  at  a  sufficient  difference  of  potential  to  build 
up  the  charge. 

Replenisher,  Carriers  of The 

moving  conductors  of  a  replenisher  which 
carry  the  charges  and  thus  permit  of  an  ac- 
cumulation of  such  charges.  (See  Re- 
plenisher.) 

Repulsion,  Electric  -  —The  mutual 
driving  apart  or  tendency  to  mutually  drive 
apart  existing  between  two  similarly  charged 
bodies,  or  the  mutual  driving  apart  of  similar 
electric  charges. 

Repulsion,  Electro-Dynamic The 

mutual  repulsion  between  two  electric  circuits 
whose  currents  are  flowing  in  opposite  direc- 
tions. 

Parallel  currents  flowing  in  opposite  directions 
repel  one  another,  because  their  lines  of  magnetic 
force  have  the  same  direction  in  adjoining  parts  of 
the  circuit.  (See  Dynamics,  Electro.) 

Repulsion,  Electro-Magnetic  —  —The 
mutual  repulsion  produced  by  two  similar 
electro-magnetic  poles. 

Repulsion,  Electrostatic  — The 

mutual  repulsion  produced  by  two  similar 
electric  charges. 

Repulsion,  Magnetic  —  —The  mutual 
repulsion  exerted  between  two  similar  mag- 
netic poles. 

Repulsion,  Molecular The  mutual 

repulsion  existing  between  molecules  arising 
from  their  kinetic  energy.  (See  Matter,  Ki- 
netic Theory  of.) 

Residual  Atmosphere — (See  Atmosphere, 
Residual.) 

Residual  Charge. — (See  Charge,  Resid- 
ual.) 

Residual  Magnetism. — (See  Magnetism, 
Residual.) 

Resin. — A  general  term  applied  to  a  variety 
of  dried  juices  of  vegetable  origin. 

Resins  are,  in  general,  transparent,  inflamma- 
ble solids,  soluble  in  alcohol,  and,  in  general, 
excellent  non-conductors  of  electricity.  Rosin  is 
one  of  the  varieties  of  resin. 

Resinous  Electricity. — (See  Electricity, 
Resinous.) 

Resistance. — Something  placed  in  a  circuit 
for  the  purpose  of  opposing  the  passage  or 

* 


flow  of  the  current  in  the  circuit  or  branches 
of  the  circuit  in  which  it  is  placed. 

The  electrical  resistance  of  a  conductor  is 
that  quality  of  the  conductor  in  virtue  of 
which  there  is  a  fixed  numerical  ratio  be- 
tween the  potential  difference  of  the  two 
opposing  faces  of  a  cubic  unit  of  such  con- 
ductor, and  the  quantity  of  electricity  which 
traverses  either  face  per  second,  assuming  a 
steady  flow  to  take  place  normal  to  these 
faces,  and  to  be  uniformly  distributed  over 
them,  such  flow  taking  place  solely  by  an  elec- 
tromotive force  outside  the  volume  considered. 

The  term  is  used  in  the  first  definition  in  the 
concrete  sense  of  something  intended  for  or  used 
as  a  resistance.  For  the  physical  definitions  and 
facts  see  Resistance,  Electric. 

Gases  offer  very  high  resistance  to  the  flow  of 
an  electric  current.  Their  non-conducting  power 
causes  the  increase  of  resistance  which  attends 
the  polarization  of  a  voltaic  cell.  (See  Cell, 
Voltaic,  Polarization  of.) 

Resistances  consist  of  coils,  strips,  bars  or 
spirals  of  metal,  or  plates  of  carbon,  or  metallic 
powders,  powdered  or  granulated  carbon,  or 
liquids. 

Resistance,  Absolute  Unit  of  —  —The 
one  thousand  millionth  of  an  ohm.  (See 
Ohm.  Units,  Practical.) 

Resistance,  Assymmetrical  -  — Con- 
ductors or  parts  of  conductors,  which  offer  a 
greater  resistance  to  the  flow  of  an  electric 
current  in  one  direction  than  in  another. 

Assymmetrical  conductors  are  unknown,  so  far 
as  structural  peculiarities  are  concerned,  but  can 
be  obtained  by  the  use  of  counter  electromotive 
forces,  acting  as  resistance.  This  term  was  pro- 
posed by  Wilke  in  discussing  the  obtaining  of 
continuous  currents  by  commutatorless  dynamo- 
electric  machines. 

The  resistance  of  the  human  body  is  possibly  an 
assymmetrical  resistance. 

An  evident  application  of  an  assymmetrical  re- 
sistance is  to  direct  alternating  currents  so  as  to 
cause  the  current  that  passes  to  flow  in  and  to  the 
same  direction. 

Resistance,  Balanced A  resistance 

so  placed  in  a  circuit  as  to  be  balanced  or 
made  equal  to  another  resistance  connected 
therewith. 


Kes.] 


452 


[Res. 


Resistance,  Balanced,  for  Dynamos 

— A  resistance  that  possesses  a  range  suf- 
ficient to  balance  one  dynamo  against  another 
with  which  it  is  desired  to  run  in  parallel. 
— (  Urquhart) 

Resistance  Box. — (See  Box.  Resistance^ 

Resistance  Bridge.— (See  Bridge,  Resist- 
ance) 

Resistance  Coil. — (See  Coi2.  Resistance^ 

Resistance  Coil,  Standard —(See 

Coil,  Resistance,  Standard) 

Resistance,  Conductivity The  re- 
sistance offered  by  a  substance  to  electric 
conduction,  or  to  the  passage  of  electricity 
through  its  mass. 

Resistance,    Dielectric    — A  term 

sometimes  employed  for  the  resistance  of  a 
dielectric  to  mechanical  strains  produced  by 
electrification. 

The  dielectric  resistance  of  the  glass,  or  other 
dielectric  of  a  Leyden  jar  or  condenser,  is  fre- 
quently overcome  by  the  passage  of  the  charges 
on  the  conducting  surfaces,  and  the  glass  is  thus 
pierced. 

The  term  dielectric    resistance  would  appear 
to  be  badly  chosen;  for.  like  all  substances,  dielec- 
trics possess  a  true  ohmic  resistance,  which  in 
creases  with  the  increase  of  length,  and  decreases 
with  the  increase  of  area  of  cross-section. 

The  resistance  of  the  dielectric,  however,  differs 
from  the  ordinary  ohmic  resistance  of  conductors, 
in  that  the  resistance  of  the  dielectric  is  suddenly 
overcome,  and  the  discharge  passes  disruptively 
as  a  spark. 

Resistance,  Effect  of  Heat  on  Electric 

Nearly  all  metallic   conductors  have 

their  electric  resistance  increased  by  an  in- 
crease of  temperature. 

The  carbon  conductor  of  an  incandescent  elec- 
tric lamp,  on  the  contrary,  has  its  resistance 
decreased  when  raised  to  electric  incandescence. 
The  decrease  amounts  to  about  three-eighths  of  its 
resistance  when  cold. 

The  effects  of  heat  on  electric  resistance  may  be 
summarized  as  follows: 

(i.)  The  electric  resistance  of  metallic  conduc- 
tors  increases  as  the  temperature  rises.  In  some 
alloys  this  increase  is  small. 

(2.)  The  electric  resistance  of  electrolytes  de- 
creases as  the  temperature  nses. 


(3.)  The  electric  resistance  of  dielectrics  and 
non-conductors  decreases  as  the  temperature  rises. 

RESISTANCE  AND   CONDUCTIVITY   OF    PURE 
COPPER  AT  DIFFERENT  TEMPERATURES. 


v  £ 

to 

w  JJ 

£ 

V 

o 

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"°  2 

V 

o 

B 

t*  ^ 

•a 

S  rt 

11 

•I 

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B  ^ 

I 

o 

3 
"O 

« 

V  B 

gj 

8 
M 

§ 
o 

0° 

00000 

I.OOOOO 

16° 

.06168 

.94190 

I 

00381 

.99624 

17 

.06563 

.93841 

a 

00756 

.99250 

18 

.06959 

•93494 

3 

01135 

.98878 

'9 

•07356 

.93148 

4 

S 

01515 
01896 

.98508 
.98139 

20 
21 

.07742 
.08164 

.928x4 
.62452 

6 

02280 

•97771 

22 

•08553 

.92121 

I 

02663 

03048 

97406 
.97042 

23 
24 

.08954 
•09365 

.91782 
•9'445 

9 

03435 

.96679 

25 

.09763 

.91110 

10 

03822 

.96319 

26 

•  0161 

.90776 

ii 

04199 

•9597° 

27 

•  0567 

.90443 

12 

04599 

•95603 

28 

•  1972 

.90113 

>3 

04990 

•95247 

29 

•  1382 

.89784 

»4 

05406 

.94893 

30 

.  1782 

.89457 

15 

05774 

•94541 

— (Latimer  Clark.) 

Resistance,  Electric The  ratio  be- 
tween the  electromotive  force  of  a  circuit 
and  the  current  that  passes  therein. 

The  reciprocal  of  electrical  conductivity. 
Resistance  can  be  defined  as  the  reciprocal  of 
electrical    conductivity    because    even   the   best 
electrical  conductors  possess  appreciable  resist- 
ance. 

Ordinarily  the  resistance  of  a  circuit  may  be 
conveniently  regarded  as  that  which  opposes  or 
resists  the  passage  of  the  current.  Strictly  speak- 
ing, however,  this  is  not  true,  since  from  O&m's 
law  (See  Law  of  Ohm,  or  Law  of  Current 
Strength} 

E 

C  =  — ,  from  which  we  obtain 
R 
E 
R  =  — ,  which  shows  that  resistance  is  a 

C 

ratio  between  the  electromotive  force  that  causes 
the  current  and  the  current  so  produced. 

Resistance  may  be  expressed  as    a  velocity. 
The   dimensions   of  resistance  in  terms  of  the 
electro-magnetic  units  are 
L 


(See  Units,  Electro- Magnetic.)  But  these  are  the 
dimensions  of  a  velocity,  which  is  the  ratio  of  the 
distance  passed  over  in  unit  time.  Resistance  may 
therefore  be  expressed  as  a  velocity. 


Res.] 


453 


[Res. 


"The  resistance  known  as  'one  ohm'  is  in. 
tended  to  be  io9  absolute  electro-magnetic  units, 
and,  therefore,  is  represented  by  a  velocity  of  icP 
centimetres  or  10,000,000  metres  (one  earth  quad- 
rant) per  second." — (Sylvanus  Thompson.) 

Resistance  may  be  represented  by  a  velocity, 
one  ohm  being  the  resistance  of  a  wire,  which, 
if  moved  through  a  unit  field  of  force  at  the  rate 
of  1,000,000,000  (lo9)  centimetres  per  second  will 
have  a  current  of  one  ampere  generated  in  it. 
(See  Resistance,  Ohmic.  Resistance,  Spurious.) 

The  true  value  of  the  ohm  is  exactly  to9  centi- 
metres. The  material  standards  employed,  *.  e., 
the  B.  A.  and  "legal  "  ohms,  are  not  absolutely 
of  this  value. 

One  mil-foot  of  soft  copper  at  10.22  degrees  C. 
or  50.4  degrees  F.  has  the  standard  resistance  of 
exactly  10  legal  ohms ;  at  15.56  or  59.9  degrees 
F.,  it  has  a  resistance  of  10.20  legal  ohms,  and 
at  23.9  degrees  C.  or  75  degrees  F.,  10.53  legal 
ohms. 

RESISTANCE. 

Resistance  of  Wires  of  Pure  Annealed  Copper  at  o"  C. 
(Density  =  <?.?.) 


C   „; 

Resistance  of  Wire    of  Pure  An- 

t t 

&>     QJ 

v  a  « 
a  «  P 

s  Mi 

nealed  Copper  at  O  degree  C. 

|j  §§! 

c?£  bboj 

01    qj    O   Jz 

Ohms 

Metres 

Ohms 

.2  M 

b*.     CD 

••3  5  ***  fi§ 

per 

per 

per 

° 

*~ 

Kilometre. 

Ohm. 

Kilogramme. 

5 

'75 

5-7 

.8 

1230.5 

.00456 

4-4 

135.28 

7-4 

i.  06 

944.38 

.00784 

3-9 

106.35 

9-5 

1.35 

722 

.0128 

3-4 

80.8 

12.5 

i.  80 

563-92 

.0222 

3 

62.93 

16 

2-3 

439-0? 

.0365 

•7 

51 

19.8 

2.8 

355.65 

•°557 

•4 

40.23 

25 

3-6 

281 

.088 

.2 

33.82 

29 

4.2 

236.08 

•»a3 

27-95 

36 

I95-I5 

.185 

.8 

22.7 

44 

6-3 

158.08 

.278 

.6 

17.89 

56 

8 

124.9 

•448 

•5 

15.75 

63 

9.1 

109.75 

•574 

•4 

13-7 

73 

10.5 

95-651 

-763 

•3 

11.84 

85 

12 

82.42 

1-03 

.2 

10.06 

100 

'4 

70.247 

1.42 

.1 

8-47 

119 

17 

59.024 

2.02 

6-99 

144 

20 

48.782 

*-95 

.O 

5.66 

178 

25 

39-5I5 

4.19 

.8 

4-47 

225 

S2 

31.225 

7.21 

•7 

2.83 

'  294 

42 

23.9 

12.3 

.6 

2.52 

400 

57 

17-56 

'  22.78 

•5 

1.74 

576 

81 

12.305 

46.  8  1 

•4 

I-I75 

902 

122.4 

8.173 

110.41 

•34 

.808 

1251 

177.9 

5.622 

222.55 

•3 

.7181 

1607 

228.5 

4-377 

367-2 

.24 

.4026 

2508 

357 

2.801 

895.36 

.a 

.2797 

3614 

»-945 

1.857.6 

.16 

.179 

559° 

803.1 

1-245 

4,489 

.12 

.1007 

9929 

1428 

•7 

I4.I79 

.1 

.0699 

14369 

2056 

.486 

29.549 

.08 

.0447 

24570 

3213 

•3" 

78,943 

.06 

•  0252 

5713 

•>73 

227,515 

.04 

•  OII2 

88878 

12848 

.078 

1142,405 

The  following  table,  based  on  Matthiessen's 
measurements,  gives  the  relative  resistances  of 
equal  lengths  and  cross-sections  of  a  number  of 
different  substances  used  in  electricity  as  com. 
pared  with  silver. 

LEGAL  MICROHMS. 


Resistance  in  Microhms 

at  o  degree  C. 

NAMES  OF  METAL. 

Relative 
Resistance. 

Cubic 
Centimetre. 

Cubic  Inch. 

Silver,  annealed... 

1.504 

0.5921 

Copper,  annealed. 
Silver,  hard  drawn 

1.598 
1.634 

0.6292 
0.6433 

'063 

Copper,  h'rd  dr"wn 

* 
1.634 

0.6433 

!o86 

Gold,  annealed.  .  .  . 

2.058 

0.8102 

•369 

Gold,  hard  drawn. 
Aluminium,  ann'ld 

2.094 
2.912 

0.8247 
1.147 

•393 
•935 

Zinc,  pressed  

5.626 

2.215 

3-741 

Platinum,  annealed 

9.057 

3-565 

6.  022 

Iron,  annealed..    . 

9.716 

3-825 

6.460 

Nickel,  annealed  . 

12.47 

4.907 

8.285 

Tin,  pressed  

13.21 

5-202 

8.784 

Lead,  pressed...   . 
German  silver...   . 

19.63 
20.93 

7.728 
8.240 

13-05 
13.92 

Antimony,  pressed 

35-5° 

13.98 

23.60 

77     1C 

Bismuth,  pressed.  . 

94-32 

67  •  *5 

87-23 

—  (Ayrton.) 

The  above  resistances  are  for  chemically  pure 
substances  only.  Slight  impurities  produce  a  very 
considerable  increase  in  the  resistance. 

Resistance,  Electric,  of  Liquids  -- 

The  resistance  offered  by  a  liquid  mass  to 
the  passage  of  an  elec- 
trie  current 

As  a  rule  the  electric  re- 
sistances of  liquids,  with 
the  single  exception  of  mer- 
cury, are  enormously  high- 
er than  those  of  metallic 
bodies. 

To  roughly  determine 
the  resistance  of  a  liquid, 
a  section  is  taken  between 
two  parallel  metallic  plates 
A  and  B,  Fig.  489,  placed 
as  shown  in  the  figure,  and 
an  electric  current  is  pass- 
ed between  them. 

In  order  to  accurately 
vary  the  size  of  the  plates 
immersed  in  the  liquid,  and 


4$<).    Resistance  oj 
Liquid. 


— (Hospitalier. ) 


hence  the  area  of  cross-section  of  the  liquid  con- 
ductor,  as  well  as  the  distance  between  the  plates, 
the  apparatus  shown  in  Fig.  490  may  be  used,  in 


K*S.J  454  [Res. 

TABLE  OF  CONDUCTING  POWERS  AND  RESISTANCES  IN  OHMS— B.  A.  UNITS. 


NAMES  OF  METALS. 

Conducting 
power  at  o  de- 
gree C. 

Resistance  of  a 
wire  one   foot 
long  weighing 
one  grain. 

Resistance  of  a 
wire  one  metr«- 
long  weighing 
one  gramme. 

Resistance  of  a 
wire    one  foot 
!°ng  nftro  '"eh 
in  diameter. 

Resistance  of  a 
wire  one  metre 
long,  one  milli- 
metre in  diam- 
eter. 

Approximate 
percentage  of 
variation   in   re- 
sistance for  i  de- 
gree of  tempera- 
ture at  2odeg. 

0.2214 
0.2421 
0.2064 
0.2106 
0.5849 
0-5950 
0.06822 
0.5710 
3-536 
1.2425 
1.0785 
1.317 
3-a36 
3-324 
5-°54 
18.740 

4.243 

3.652 
8.391 

0.1544 
o.  1689 
o.  1440 
0.1469 
0.4080 
0.4150 
0.05759 
0.3983 
2.464 
0.7522 
0.8666 
0.9184 
2.257 
2.3295 

3-525 
13.071 

2.959 
1.850 
1.668 

9.936 
9-J5i 
9.718 
9.940 
12.52 
12.74 
17.72 
32.22 
55-°9 
59-4° 
75-78 
80.36 

U9-39 
2:6.0 
798.0 
600.0 

»43-35 
127.32 
66.10 

o  01957 
o  02103 
o  02057 
o  02104 
o  02650 
o  02697 
o  03751 
o  07244 
o  1166 
o  1251 
o  1604 
o  1701 
o  2527 
o  457' 

1  689 

I  270 

0.3140 

0.2695 

0.1399 

o-377 

100.00 

0.388 

Copper,  hard  drawn  ..... 

99-55 

o-355 

77.96 

Zinc,  pressed  ............ 

29.02 

0.365 

16.81 
13.11 
12.36 
8.32 
4.62 
1.24 

0.365 
0.387 
0.389 
o-354 

O.O72 
O.O3I 
0.044 

0.065 

Antimony,  pressed  ...... 
Bismuth,  pressed..  .  ...... 

Platinum  -  silver,      alloy, 

German    silver,  hard  or 

Gold,   silver,  alloy,  hard 

which  these  distances  are  readily  adjustable,  as 
shown. 

Resistance,  Equivalent A  single 

resistance  which  may  replace  a  number  of 
separate  resistances  in  a  circuit  without  alter- 
ing the  value  of  the  current  traversing  it. 

Resistance,  Essential  — A  term 

sometimes  used  instead  of  internal  resist- 
ance. 


f*f-   49O.    Apparatus  for   Measuring  Resistance   <tf 
Liquid. 

Resistance,  External  Secondary A 

term  proposed  by  Du  Bois  Reymond  for  the 
change  in  the  resistance  of  a  circuit  external  to 
the  electric  source  when  cataphoric  action 
takes  place.  (See  Action,  Cataphoric^) 

"  If  the  copper  electrodes  of  a  constant  battery 
be  placed  in  a  vessel  filled  with  a  solution  of 
cupric  sulphate  and  from  each  electrode  there 
projects  a  cushion  saturated  with  this  fluid,  then, 


— (Jenkin.) 

on  placing  a  piece  of  muscle,  cartilage,  vegetable 
tissue,  or  even  a  prismatic  strip  of  coagulated 
albumen  across  these  cushions,  we  observe,  that 
very  soon  after  the  circuit  is  closed,  there  is  a 
considerable  variation  of  the  current.  *  *  * 
This  phenomenon  is  called  '  external  secondary 
resistance.'  " — (Landois  and  Sterling.) 

Resistance,  Extraordinary A  term 

sometimes  employed  instead  of  external  re- 
sistance. (See  Resistance,  External  Secon- 
dary^) 

Resistance,  False A  resistance  aris- 
ing from  a  counter  electromotive  force  and 
not  directly  from  the  dimensions  of  the  circuit, 
or  from  its  specific  resistance. 

The  false  resistance  of  any  circuit  is  sometimes 
called  its  spurious  resistance.  (See  Force,  Electro- 
motive, Counter.  Resistance \  Spurious.) 

Resistance,  Inductionless A  term 

sometimes  used  instead  of  non-inductive  re- 
sistance. (See  Resistance,  Non-Inductive.) 

Resistance,  Inductive A  resistance 

which  possesses  self-induction. 

Resistance,  Insulation The  re- 
sistance of  a  line  or  conductor  existing  be- 
tween the  line  or  conductor  and  the  earth 
through  the  insulators,  or  between  the  two 


Bes.j 

wires  of  a  cable  through  the  insulating 
material  separating  them. 

The  insulation  resistance  of  a  telegraph  line  is 
the  resistance  that  exists  between  the  line  and  the 
earth,  through  its  insulators.  The  insulation  re- 
sistance will  decrease  as  the  length  of  line  in- 
creases, since  for  any  increase  in  the  number  of 
poles  and  insulators  there  is  a  proportional  in- 
crease in  the  area  of  cross-section  of  the  insula- 
ting supports. 

If  the  insulation  resistance  is  1,000,000  ohms 
per  mile,  in  a  line  200  miles  m  length,  the  insula- 
tion resistance  is  only  5,000  ohms,  that  is, 

1,000,000 

—  =  5,000  ohms. 
200 

Resistance,  Joint,  of  Parallel  Circuits 

The  joint  resistance  of  two  parallel 

circuits  is  determined  by  means  of  the  follow- 
ing formula  ; 

R=FTT- 

Where  R  =  the  joint  resistance  of  any  two  cir- 
cuits whose  separate  resistances  are  respectively 
r  and  r  . 

When  there  are  three  resistances  r,  r'  and  r*, 
in  parallel,  the  joint  resistance, 


.  ,   .. 

rr   -|-rr   -j-rr 

(See  Circuits,  Varieties  of. ) 

Resistance,  Magnetic The  recipro- 
cal of  magnetic  permeability  or  conducti- 
bility  for  lines  of  magnetic  force. 

Resistance  offered  by  a  medium  to  the 
passage  of  the  lines  of  magnetic  force  through 
it. 

The  magnetic  resistance  of  the  circuit  of  the 
lines  of  force  is  reduced  by  forming  the  circuit  of 
a  medium  having  a  high  magnetic  permeability, 
such  as  soft  iron.  This  is  accomplished  by  the 
armature  or  keeper  of  a  magnet,  or  by  the  iron  in 
an  iron-clad  magnet.  (See  Magnet,  Iron- Clad.) 

Resistance,     Measurement    of  — 

Methods  employed  for  determining  the  re- 
sistance of  any  circuit  or  part  of  a  circuit. 

Numerous  methods  are  employed  for  this  pur- 
pose. Amon^  these  are  : 

(l .)  TJie  use  of  a  resistance  box  with  a  Wheat- 
stone  bridge,  by  opposing  or  balancing  the  un- 
known resistance  against  a  known  resistance. 
(See  Balance,  Wheatstone'1  s  Electric.) 


[Res. 

(2.)  The  differential  galvanometer.  (See  Gal- 
vanometer, Differential^) 

(3 . )  The  method  of  substitution. 

(4.)  Comparison  of  the  deflections  of  a  gal- 
vanometer. 

Method  of  Substitution.  —  A  resistance-box  R, 
Fig.  491,  galvanometer  G,  and  the  resistance  x, 
that  is  to  be  measured,  are  placed  in  the  direct 
circuit  of  the  battery  B,  by  means  of  conductors 
of  such  thick  wire  that  their  resistance  can  be 
neglected. 

The  deflection  of  the  ga'vanometer  is  first 
measured  with  x,  in  circuit,  and  no  resistance  in 
tne  box  R.  The  resistance  x,  is  then  cut  out  of 
the  circuit  by  placing  a  thick  copper  wire  across 
the  terminals  of  the  mercury  cups  at  mm',  and 
resistances  unplugged  in  R,  until  the  same  deflec- 
tion is  obtained.  Then,  if  the  electromotive  force 
of  the  battery  has  remained  constant,  the  resist- 
ances unplugged  equal  the  unknown  resistance. 

For  full  description  of  the  various  methods  of 
determining  resistance  the  reader  is  referred  to 
'•'•Ayrton's  Practical  Electricity,''  '•'•Kempe's 
Handbook  of  Testing,"  or  other  standard  books 
on  electrical  measurements. 


in' 


Fig.  49  z     S^stitution  Method. 

When  several  resistances  are  placed  in  series  ill 
any  circuit,  by  measuring  the  difference  of  poten- 
tial at  their  terminals,  their  values  can  be  deter, 
mined  by  simple  calculation,  being  directly  pro- 
portional  to  these  differences  of  potential. 

This  method  is  especially  applicable  to  the 
measurement  of  such  low  resistances  as  the  arma- 
tures of  dynamo-electric  machines. 

Resistance,  Non-inductive A  re- 
sistance m  which  self-induction  is  practically 
absent. 

An  incandescent  lamp  filament  is  practically  a 
non-inductive  resistance  when  compared  with  a 
coil  on  the  helix  of  an  electro-magnet. 

Resistance  of  Human  Body.— (See  Body, 
Human,  Resistance  of.) 


Res.] 


456 


[Res. 


Resistance  of  Toltaic  Arc. — (See  Arc, 
Voltaic,  Resistance  of.) 

Resistance,  Ohmic The  true  resist- 
ance of  a  conductor  due  to  its  dimensions 
and  specific  conducting  power,  as  distin- 
guished from  the  spurious  resistance  produced 
by  a  counter  electromotive  force.  (See  Force, 
Electromotive,  Counter.  Resistance,  Spuri- 
ous.) 

The  term  ohmic  resistance  must  be  regarded  as 
a  pleonasm.  Its  use  can  only  be  permitted  in 
contradistinction  to  counter  electromotive  force 
resistance.  True  and  spurious  resistance  would 
seem  preferable. 

Resistance  or  Cell,  Selenium A 

mass  of  crystalline  selenium,  the  resistance  of 
which  is  reduced  by  placing  it  in  the  form  of 
narrow  strips  between  the  edges  of  broad 
conducting  plates  of  brass. 

The  selenium  employed  for  this  purpose  is  the 
vitreous  variety  which  has  been  fused  and  main* 
tained  for  several  hours  at  about  220  degrees  C., 
by  means  of  which  its  resistance  is  reduced. 

By  exposure  to  sunlight,  the  resistance  of  a 
selenium  cell  is  decreased  fully  one-half  its  re- 
sistance  in  the  dark.  The  selenium  cell  is  used 
in  the  photophone.  (See  Photophone.) 

Resistance  or  Reducteur  for  Voltmeter. 

— (See  Reducteur  or  Resistance  for  Volt- 
meter.) 

Resistance,   Secondary   — A  term 

sometimes  used  in  place  of  external  secon- 
dary resistance.  (See  Resistance,  External 
Secondary) 

Resistance  Slide. — (See  Slide,  Resist- 
ance^ 

Resistance,  Specific The  particular 

resistance  which  a  substance  offers  to  the 
passage  of  electricity  through  it. 

In  absolute  measure,  the  resistance  in  ab- 
solute units  between  the  opposite  faces  of  a 
centimetre  cube  of  the  given  substance. 

In  the  practical  system  the  resistance  given 
in  ohms. 

Resistance,  Specific  Conduction 

A  term  sometimes  used  instead  of  specific 
resistance.  (See  Resistance,  Specific!) 


Resistance,  Specific,  of  Liquids - 

The  resistance  of  a  given  length  (one  centi- 
metre) and  area  of  cross-section  (one  square 
centimetre)  of  any  liquid  as  compared  with 
the  resistance  of  an  equal  length  and  cross- 
section  of  pure  silver. 

The  resistance  of  a  few  common  liquids  and  so. 
lutions  is  here  given  from  Lupton: 

Water,  pure,  at  75  degrees  C. .  I.l88  X  IO»  ohms, 
i.  e.,  118,800,000. 

Water  at  4  degrees  C 9-IQo X  IO*     •• 

Water  at  n  degrees  C 3-4OO  X  IO*    *• 

Dilute  hydrogen  sulphate  (sul- 
phuric acid)  at  18  degrees 
C.,  5  per  cent,  acid 4.88 

Dilute  hydrogen  sulphate  at 
1 8  degrees  C.,  3  per  cent, 
acid 1.38 ohms. 

Nitric  acid  at  18  degrees  C., 

density  1.32 i.6l      •« 

Saturated  solution  of  copper 
sulphate  (blue  vitriol)  at  10 
degrees  C 29.30  «« 

Saturated  solution  of  zinc  sul- 
phate at  14  degrees  C 21.50  •' 

Hydrochloric  acid,  20  per  cent, 
acid,  at  18  degrees  C 1.34  " 

Sal  ammoniac,  25  percent,  salt  2.53      «* 

Common  salt,  saturated,  at  13 
degreesC ...5.30  «« 

It  will  be  observed  that  the  resistance  varies 
considerably  with  differences  of  temperature. 

Resistance,  Spurious A  false  re- 
sistance arising  from  the  development  of  a 
counter  electromotive  force.  (See  Resist- 
ance, False.  Force,  Electromotive,  Coun- 
ter.) 

The  spurious  resistance  is  also  called  the  false 
resistance,  in  order  to  distinguish  it  from  the  true 
or  ohmic  resistance.  (See  Resistance,  Electric.) 

Resistance,  Standard A  resistance 

used  for  comparison  with  or  the  determina^ 
tion  of  unknown  resistances. 

A  committee  appointed  by  the  American  Insti- 
tute of  Electrical  Engineers  in  1890  reported  the 
following  values  for  the  standard  resistance  of 
copper  wire;  at  O  degree  C.  in  B.  A.  U.  and  legal 
ohms,  viz.: 


Res.] 


457 


[Res. 


STANDARD  RESISTANCE  AT  o*  C. 

B.  A.  U.  Legal  Ohms. 
•  Meter-mfllimetre," 

" soft  copper "...       .02057  .02034 

Cubic  centimetre...      .000001616  .000001598 

«« Mil-foot" 9.720  9.612 

Resistance,  Tables  of Tables  in 

which  the  resistance  of  equal  lengths  and 
cross-sections  of  different  substances  is 
given  in  ohms,  or  other  units  of  resistance. 

Resistance  Thermometer. — (See  Ther- 
mometer, Electric  Resistance?) 

Resistance,  Transition  — A  term 

sometimes  used  in  electro-therapeutics  for  a 
change  in  the  value  of  the  resistance  caused 
by  polarization. 

Whenever  an  electric  current  passes  through 
a  fluid  substance  and  decomposes  the  fluid,  the 
decomposition  products  collect  on  the  electrodes 
and  produce  an  increase  in  the  resistance  of  the 
circuit. 

Resistance,  True The  resistance 

which  a  conductor  offers  to  the  passage  of  a 
current  by  reason  of  its  dimensions  and  spe- 
cific conducting  power,  as  distinguished  from 
a  spurious  resistance  produced  by  a  counter 
electromotive  force. 

The  true  resistance  is  sometimes  called  the 
ohmic  resistance.— (See  Resistance,  Spurious. 
Resistance,  Ohmic.} 

Resistance,  Unit  of Such  a  resist- 
ance that  unit  difference  of  potential  is  re- 
quired to  cause  a  current  of  unit  strength 
to  pass.  (See  Ohm.  Potential,  Electric. 
Potential,  Difference  of.) 

Resistance,  Unit  of,  Absolute The 

one  thousand  millionth  of  an  ohm.  (See 
Ohm.  Units,  Practical?} 

Resistance,  Unit  of,  Jacobi's The 

electric  resistance  of  25  feet  of  a  certain 
copper  wire  weighing  345  grains. 

Another  unit  of  electric  resistance  proposed 
by  Jacobi  was  the  resistance  of  a  copper  wire 
one  metre  in  length  and  one  millimetre  in  diame- 
ter. 

Resistance,  Unit  of,  Matthiessen's 

. — The  resistance  of  one  statute  mile  of  pure 
annealed  copper  wire  -iV  inch  in  diameter  at 


15.5  degrees  C,  and  determined  by  him  to  be 
13.59  B.  A.  ohms. 
Resistance,  Unit  of,  Varley's The 

resistance  of  one  statute  mile  of  a  special 
copper  wire  ^  inch  in  diameter. 

Varley's  unit  was  afterwards  adjusted  by  him 
to  equal  25  Siemens  Mercury  Units. 

Resistance,  Variable A  resistance 

the  value  of  which  can  be  readily  varied. 
Variable  resistances  are  either  : 
(I.)  Automatically  variable  resistances;  or 
(2.)  Non- automatically  variable  resistances. 

Resistance,  Variable,  Automatic 

A  resistance  the  value  of  which  can  be  auto- 
matically varied. 

A  pile  of  carbon  plates  resting  on  one  another, 
in  loose  contact,  offers  a  high  resistance,  but  when 
compressed  as  by  an  electro-magnet  their  resist- 
ance is  lowered.  Brush  employs  such  an  auto- 
matic resistance  in  the  regulation  of  his  dynamo- 
electric  machine.  (See  Regulation,  Automatic.) 

Resistance,  Variable  Non-Antomatic 

— A  resistance  the  value  of  which  is  regulated 
by  hand.  (See  Rheostat?) 

Resistance,  Virtual A  term  some- 
times employed  instead  of  impedance.  (See 
Impedance?) 

Resonance,  Electric The  setting 

up  of  electric  pulses  in  open-circuited  con- 
ductors, by  the  action  of  pulses  in  neighboring 
conductors. 

Electric  resonance,  like  acoustic  resonance, 
takes  place  when  a  correspondence  exists  between 
the  time-rate  of  vibration  of  the  body  producing 
the  resonance,  and  the  body  in  which  the  reso- 
nance is  produced.  In  other  words,  when  the 
wave  lengths  are  the  same  in  the  two  bodies,  or 
when  the  wave  length  in  one  is  equal  to  a  half 
wave  length,  or  some  definite  multiple  of  a  half 
wave  length  of  the  other. 

Partial  resonance  may  occur,  when  there  is  a 
small  difference  between  the  wave  lengths  of  the 
two  bodies.  Beyond  certain  limits,  however,  this 
is  so  small  as  to  be  practically  absent. 

When  an  electrical  pulse  is  started  in  a  con- 
ductor  by  the  discharge  of  a  Leyden  jar,  a  side  flash 
spark  is  obtained  in  the  alternative  path,  between 
the  discharge  points.  The  length  of  this  spark  has 
its  greatest  value,  when  the  time  required  for  the 


Res.] 


458 


O 


pulse  to  travel  backwards  and  forwards  along  the 
conducting  wires,  is  exactly  equal  to  the  time  of 
a  complete  oscillation  in  the  circuit,  or  when  the 
length  of  the  open-circuit  wires  is  equal  to  half  a 
wave  length,  or  some  multiple  oi  half  a  wave 
length. 

The  fact  that  the  length  of  the  spark  is  greatest 
when  certain  relations  exist  between  the  dimen- 
sions of  the  two  circuits,  shows  that  the  time-rate 
of  an  electrical  pulse  in  any  circuit  depends  on 
the  dimensions  of  that  circuit. 

In  the  case  of  acoustic  resonance,  in  order  that 
one  tuning  fork  may  be  able  to  excite  vibrations  in 
another,  the  fork  producing  or  exciting  the  vibra- 
tion must  be  strictly  in  unison  with  the  fork  in 
which  the  vibrations  are  excited,  and  any  varia- 
tions produced  in  the  rate  of  vibration  of  the 
sounding  fork,  by  overloading  it,  or,  in  other 
words,  by  altering  its  dimensions,  checks  the 
effects  of  its  resonance. 

In  a  similar  manner,  any  alterations  in  the  di- 
mensions of  the  circuit,  checks  or  diminishes  the 
effects  of  electric  reson- 
ance in  a  neighboring  cir- 
cuit, which  was  previously 
in  unison  with  it.  This 
has  been  experimentally 
shown  by  Hertz  as  fol- 
lows: 

An  induction  coil  A, 
Fig.  492,  has  the  terminals 
of  its  secondary  connected 
to  an  open  rectangular  cir- 
cuit provided  with  spark- 
ing terminals,  I,  and  2, 
called  a  spark  micrometer. 
Under  certain  conditions, 
when  the  discharge  oc- 
curs at  the  terminals  B, 
of  the  ordinary  discharger,  sparks  are  produced 
by  electric  resonance  in  the  electric  resonator 
formed  by  the  spark  micrometer  at  M. 

Supposing,  now,  that  a  certain  character  of  spark 
is  obtained  at  the  terminals  B,  that  is,  a  cei, 
tain  velocity  of  electrical  pulsations  is  obtained 
which  depends  on  the  nature  of  the  spark;  sup- 
pose, moreover,  that  the  dimensions  of  the  spark 
micrometer  or  electric  resonator  are  such  that  the 
greatest  length  of  spark  is  obtained.  Then,  any 
alteration  in  the  character  of  these  sparks,  be- 
tween the  terminals  at  B,  varies  the  intensity  of 
C'he  sparks  in  the  spark  micrometer. 

3£  for  example,   the  apparatus  be  arranged 


B 


O 


1  t 

Fig.  49  a.    Electrical 
Resonance. 

as  shown  in  Fig.  493,  in  which  one  of  the  sec- 
ondary terminals  of  the  induction  coil  has  con- 
nected with  it  a  copper  wire  i  g  h.  The  sparks  at 
M,  decrease  considerably.  When,  however,  the 
conductor  C,  is  connected  with  the  free  end  H, 
of  this  additional  conductor,  then  this  effect  is 
not  observed,  as  is  shown  by  the  fact  that  when 
the  conductor  C,  is  attached  at  the  point  G,  it 
produces  no  effect  on  it. 


Fig.  493.    Electric  Resonance. 

In  another  experiment  with  the  same  apparatus, 
matters  may  be  arranged  that  the  sparks  in  the 
micrometer  circuit  pass  singly.  When,  now,  an- 
other conductor  C',  is  attached  to  K,  a  stream  of 
sparks  immediately  passes. 

It  would  appear,  therefore,  from  the  above  ex- 
periments, that  when  two  circuits  are  taken, 
having  as  nearly  as  possible  the  same  vibration 
periods,  any  alteration  in  the  dimensions  of  either 
will  prevent  one  from  producing  electrical  reso- 
nance in  the  other. 

In  the  above  experiments  Hertz  demonstrated 
the  following  facts,  viz., 

(I.)  The  sparks  in  the  micrometer  circuit  are 
smaller  when  the  discharges  take  place  between 
points,  or  a  point  and  a  plate,  instead  of  between 
knobs. 

(2.)  The  micrometer  sparks  are  feebler  in  rare- 
fied gas  than  in  air  at  ordinary  pressures. 

(3.)  Extremely  slight  differences  in  the  nature 
of  secondary  sparks  produce  considerable  differ- 
ence in  the  length  of  the  micrometer  sparks. 

Hertz  found  the  above  results  were  obtained 
when  the  secondary  sparks  were  of  a  brilliant 
color,  and  were  attended  by  a  sharp  crack. 

(4.)  The  length  of  the  spark  in  the  micrometer 


Res.] 


459 


circuit  varies  with  the  length  of  the  micrometer 
circuit. 

This,  of  course,  follows  from  the  fact  that  any 
alteration  of  the  length  in  the  micrometer  circuit, 
produces,  by  electrical  retardation,  a  correspond- 
ing alteration  in  the  time  of  the  electrical  pulses. 

(5.)  No  effect  is  produced  in  the  length  ot  the 
micrometer  spark  by  variations  in  the  material, 
the  resistance,  or  the  diameter  of  the  wire  forming 
the  micrometer  circuit. 

This  is  probably  because  the  rate  of  propaga- 
tion of  electrical  pulses  along  a  conductor,  de- 
pends mainly  on  the  capacity  of  the  conductor, 
and  on  its  co-efficient  of  self-induction,  and  only 
to  a  slight  extent  on  its  resistance. 

(6.)  The  length  of  wire  connecting  the  microm- 
eter circuit  with  the  secondary  circuit  has  but 
little  effect,  provided  such  length  does  not  exceed 
a  few  metres. 

Local  disturbances,  therefore,  must  traverse 
conductors  without  undergoing  any  appreciable 
change. 

(7. )  The  position  of  the  point  on  the  micrometer 
circuit  connected  with  the  secondary  circuit,  is  of 
the  greatest  importance. 

When  the  point  on  the  micrometer  circuit  is 
situated  symmetrically  with  respect  to  the  two  mi- 
crometer knobs,  variations  of  potential  will  reach 
the  terminals  in  the  same  phase,  and  there  will  be 
but  little  effect,  as  seen  by  the  sparks  between  the 
micrometer  knobs.  Such  a  point  on  the  microm  j 
eter  knobs  is  called  the  null  point,  or  it  is  called  as 
in  a  corresponding  case  in  acoustics,  a  nodal  point. 
(See  Point,  Null.  Point,  Nodal.} 

(8.)  When  the  conductors  are  of  sufficient 
length,  their  approach  produces  disturbances  in 
a  previously  adjusted  and  quiet  spark  microm- 
eter, just  as  the  approach  of  a  conductor  would. 

Probably  one  of  the  most  curious  effects  con- 
nected with  the  phenomena  of  electrical  resonance 
is  that  pointed  out  by  Lodge,  viz. :  that  when  the 
spark  from  a  secondary  circuit  is  so  placed  that 
the  light  is  visible  from  a  micrometer  circuit,  the 
effects  of  the  discharge  are  greatly  increased. 
Lodge  also  found  that  the  light  from  burning 
magnesium  wire,  or,  in  general,  light  rich  in  the 
ultra-violet  rays,  produces  the  same  effect. 

Resonator,  Electric An  apparatus 

employed  by  Hertz  in  his  investigations  on 
electric  resonance.  (See  Resonance,  Elec- 
tric^ 

An  «J£rfric  resonator  consists  essentially  of  an 


open-circuited  conductor,  or  circuit  of  such  dimen- 
sions that  electro-magnetic  waves  or  pulses  are 
propagated  through  it  at  the  same  rate  as  those 
which  are  occurring  in  a  neighboring  circuit 
from  which  electro-magnetic  radiation  is  tak- 
ing place.  Under  these  circumstances  electro- 
magnetic  pulses  are  set  up  sympathet  cally  by 
resonance  in  the  open  circuit  of  the  resonator,  like 
the  sympathetic  vibrations  in  a  tuning  fork,  when 
placed  near  another  vibrating  tuning  fork,  which 
is  giving  off  sound  waves  of  exactly  the  same 
period  of  vibration  as  its  own. 

Resonator,  Electro-Magnetic A 

term  applied  to  the  Hertz  spark  micrometer, 
in  which  electro-magnetic  waves  are  produced 
by  electric  resonance.  (See  Resonance,  Elec- 
tric.) 

Resultant. — In  mechanics,  a  single  force 
that  represents  in  direction  and  intensity  the 
effects  of  two  or  more  separate  forces. 

The  separate  forces  are  called  the  components. 
(See  Components.) 

Retardation.— A  decrease  in  the  speed  of 
telegraphic  signaling  caused  either  by  the 
induction  of  the  line  conductor  on  itself,  or 
by  mutual  induction  between  it  and  neighbor- 
ing conductors,  or  by  condenser  action,  or  by 
all. 

The  line  must  receive  a  certain  charge  before 
a  current  sent  into  it  at  one  end  can  produce  a 
signal  at  the  other  end.  This  charge  will  de- 
pend on  the  length  and  surface  of  the  wire,  on  the 
neighborhood  of  the  wire  to  the  earth  or  other 
wires,  and  on  the  nature  of  the  insulating  mate 
rial  between  the  wire  and  neighboring  conductors. 
This  results  in  a  charge  given  to  the  wire  which 
is  lost  as  a  current  for  signaling.  The  greater  the 
electrostatic  capacity  of  the  line  wire,  the  greater 
will  be  the  retardation  in  signaling.  (See  Capa- 
city, Specific  Inductive.  Dielectric.  Capacity, 
Electrostatic.  Induction,  Electro-Dynamic.) 

Retardation  in  signaling  is  produced  by  the 
following  causes : 

(i.)  Self-Induction  which  produces  extra  cur- 
rents. (See  Induction,  Self.  Currents,  Extra.) 

The  extra  current  on  making,  retards  the  be- 
ginning of  the  signal ;  the  extra  current  on  break- 
ing, retards  its  stopping. 

(2.)  Mutual  Induction  between  the  line  con 
ductor  and  neighboring  conductors. 


Ret.] 


460 


[Rhe. 


(3.)  The  Magnetic  Inertia  or  Lag,  or  the  time 
required  to  magnetize  or  demagnetize  the  core  of 
the  electro -magnetic  receptive  devices  used  on 
the  line. 

(4.)  By  Condenser  Action,  the  cable  acting  as  a 
condenser. 

Retardation,  Electric A  retarda- 
tion in  the  starting  or  stopping  of  an  electric 
current,  arising  from  self-induction.  (See  In- 
duction, Self.  Retardation?) 

Retardation,  Inductive—  — A  retarda- 
tion in  the  appearance  of  a  signal  at  the  dis- 
tant end  of  a  cable,  produced  by  the  action  of 
induction.  (See  Retardation?) 

Retardation,  Magnetic  -  — A  retarda- 
tion in  the  magnetization  or  demagnetization 
of  a  substance  due  to  magnetic  lag.  (See 
Retardation.  Lag,  Magnetic?) 


Retarding,  Electrically 


— Decreas- 


ing the  speed   of  telegraphic   signaling,   by 
means  of  induction.     (See  Retardation?) 

Retentivity,  Magnetic  —  — A  term  pro- 
posed by  Lament  in  place  of  coercive  force, 
or  the  power  possessed  by  a  magnetizable 
substance  of  resisting  magnetization  or  de- 
magnetization. (See  Force,  Coercive?) 

Return  Circuit. — (See  Circuit,  Return?) 

Return,    Earth (See    Earth    Re- 

tiirn?) 
Return  Ground. — (See  Ground-Return?) 

Return  Wire  or  Conductor. — (See  Wire, 
Return?) 

Returns. — In  a  system  of  distribution,  those 
conductors  through  which  the  current  flows 
back  from  the  electro-receptive  devices  to 
the  source.  (See  Leads?) 

The  word  returns  is  sometimes  used  in  a  sys- 
tem of  distribution  by  parallel  circuits,  to  distin 
guish  between  the  conductor  by  which  the  cur- 
rent  goes  back  or  returns  from  the  receptive  de- 
vices to  the  dynamo,  and  the  conductor  that  leads 
it  to  the  receptive  devices.  The  term  leads  is, 
however,  often  applied  to  both  conductors. 

Reverse-Induced  Current— (See  Current, 
Reverse-Induced?) 


Reversed  Currents. — (See  Currents.  Re- 
versed?) 

Reverser,  Current A  switch,  or 

other  apparatus,  designed  to  reverse  the  di- 
rection of  a  current. 

Reversible  Bridge. — (See  Bridge,  Rever- 
sible?) 

Reversible  Heat.— (See  Heat,  Reversible?) 

Reversibility  of  Dynamo. — The  ability 
of  a  dynamo  to  operate  as  a  motor  when  tra- 
versed by  an  electric  current.  (See  Motor, 
Electric?) 

Reversing  Gear  of  Electric  Motor. — (See 
Motor,  Electric,  Reversing  Gear  of?) 

Reversing  Key. — (See  Key,  Reversing?) 

Reversing  Key  of  Quadruplex  Tele- 
graphic System. — (See  Key,  Reversing,  of 
Quadruple x  Telegraphic  System?) 

Reversing  Magnetic  Field. — (See  Field, 
Magnetic,  Reversing?) 

Rheochord. — A  word  formerly  employed 
instead  of  rheostat.  (See  Rheostat?) 

Rheometer. — A  word  formerly  employed 
for  any  device  for  measuring  the  strength  of 
a  current. 

This  word  is  now  obsolete  and  is  replaced  by 
the  word  galvanometer.  (See  Galvanometer.'] 

Rheomotor. — A  word  formerly  employed 
to  designate  any  electric  source. 

This  word  is  now  obsolete,  and  replaced  by 
the  various  names  of  the  different  electric  sources. 
(See  Source,  Electric.") 

Rheophore. — A  word  formerly  employed  to 
indicate  a  portion  of  a  circuit  conveying  a  cur- 
rent and  capable  of  deflecting  a  magnetic 
needle  placed  near  it.  (Obsolete.) 

Rheoscope. — A  word  formerly  employed  in 
place  of  the  present  word  galvanoscope,  foi 
an  instrument  intended  to  show  the  presence 
of  a  current,  or  its  direction,  but  not  to 
measure  its  strength.  (Obsolete.) 

Rheoscope,  Physiological  —  — A  sensi- 
tive nerve-muscle  preparation  employed  to 
determine  the  presence  of  an  electric  current. 
(See  Frog,  Galvanoscope?] 


Rhe.] 


461 


[Kin. 


A  term  sometimes  applied  in  electro-thera- 
peutics to  the  frog's  legs  preparation  adapted 
to  show  the  presence  of  any  electric  current. 

The  physiological  rheoscope  is  adapted  to 
show  the  presence  of  an  electric  current  without 
the  use  of  a  galvanometer.  On  the  passage  of 
the  electric  current  the  frog's  legs  twitch  con- 
vulsively. 

Rheostat. — An  adjustable  resistance. 

A  rheostat  enables  the  current  to  be  brought 
to  a  standard,  i.  e.,  to  a  fixed  value,  by  adjusting 
the  resistance;  hence  the  name. 

The  term  rheostat  is  applied  generally  to  a 
readily  variable  resistance,  the  varying  values  of 
which  are  known. 

Rheostat,  Dynamo-Balancing An 

adjustable  resistance  whose  range  is  sufficient 
to  balance  the  current  of  one  dynamo  against 
another  with  which  it  is  required  to  run  in 
parallel. 

Rheostat,  Water A  rheostat    the 

resistance  of  which  is  obtained  by  means  of  a 
mass  of  water  of  fixed  dimensions.  (See 
Rheostat?) 

Rheostat,  Wheatstone's A  form  of 

apparatus  sometimes  employed  for  an  adjust- 
able resistance. 

This  apparatus  is  very  seldom  employed  in 
accurate  work. 

The  parallel  cylinders  A  and  B,  Fig.  494,  are 
formed  respectively  of  conducting  and  non-con- 
ducting materials,  the  bare  wire  on  which  can  be 
wound  from  either 
cylinder  to  the  other. 
When  introduced  into 
a  circuit,  only  the  re- 
sistance of  that  part 
of  the  wire  that  is  on 
B,  is  introduced  into 
the  circuit,  since  the 
bare  wire  on  A,  is 
short-circuited  by  the 
metallic  cylinder. 
This  rheostat  is  not 


Fig.  494. 

Rheostat. 


very  suitable  for  accurate  measurements,  owing 
to  the  difficulty  of  invariably  obtaining  reliable 
contacts. 

Rheostatic      Machine. — (See     Machine, 
Rheostatic.) 


Rheotorae. — A  word  formerly  employed 
for  any  device  by  means  of  which  a  circuit 
could  be  periodically  interrupted. 

This  word  is  now  obsolete,  and  is  replaced  by 
interrupter.  (See  Interrupter.) 

Rheotrope. — A  word  formerly  employed 
for  any  device  by  which  the  current  could 
be  reversed. 

This  word  is  now  obsolete  and  replaced  by 
commutator  or  current  reverser.  (See  Reverser^ 
Current.) 

Rhigolene. — A  highly  volatile  hydro-car- 
bon obtained  during  the  distillation  of  coal 
oil,  and  employed  in  the  flashing  treatment  of 
carbons  for  incandescent  lamps.  (See  Car- 
bons, Flashing  Process  for.) 

Rhumbs  of  Compass. — (See  Compass, 
Rhumbs  of.) 

Ribbed  Armature  Core.— (See  Core, 
Armature,  Ribbed.) 

Ribbon  Copper. — (See  Copper,  Ribbon) 

Right  Handed  Solenoid. — (See  Solenoid, 
Right-Handed.) 

Right-Hand  Trolley  Frog.— (See  Frog, 
Trolley,  Right-Hand.) 

Rigidity,    Molecular   — Resistance 

offered  by  the  molecules  of  a  substance  to 
rotation  or  displacement. 

The  molecular  rigidity  of  a  magnetizable  sub- 
stance was  until  recently  considered  to  be  the 
cause  of  fhe'tlifferences  of  coercive  force  or  mag- 
netic retentivity  possessed  by  different  substances. 
The  general  acceptance  of  Ewing's  theory  of 
magnetism  has,  of  course,  caused  the  above  view 
to  be  considerably  modified.  (See  Magnetism, 
Ewings  Theory  of.  Force,  Coercive.  Retentiv- 
ity, Magnetic.} 

Ring,  Ampdre The  turn  or  turns 

of  wire  used  in  electric  balances  for  the  meas- 
urement of  electric  current. 

Ring  Armature. — (See  Armature,  Ring.) 

Ring  Armature  Core.-  (See  Core,  Arma- 
ture, of  Dynamo-Electric  Machine?) 

Rings,  Electric A  term  sometimes 

used  instead  of  Nobili's  rings.  (See  Metal- 
lochromes.) 


Bin.] 


462 


[Rod. 


Rings,  Electro-Chromic A  term 

sometimes  applied  to  metallochromes.  (See 
Metallochromes^ 

Rings,  Nobili's A  term  sometimes 

used  for  metallochromes.  (See  Metallo- 
thromes.} 

Roaring  of  Arc. — (See  Arc,'  Roaring  of.} 

Rocker  Arm. — (See  Arm,  Rocker.} 

Rocker,  Brush  —  — In  a  dynamo-elec- 
tric machine  or  electric  motor,  any  device  for 
shifting  the  position  of  the  brushes  on  the 
cummutator  cylinder. 

Rocker,  Multiple-Pair  Brush  —  —A 
term  sometimes  used  for  multiple-pair  brush 
yoke.  (See  Yoke,  Multiple-Pair  Brttsh.} 

Rocker,  Single-Brush  -  — A  device 
by  means  of  which  a  single  pair  of  brushes 
are  so  supported  on  a  dynamo-electric  ma- 
chine or  electric  motor,  as  to  be  capable 
of  being  readily  shifted  into  the  desired 
position  on  the  commutator  cylinder. 

Rocker,  Single-Pair  Brush — A 

term  sometimes  used  for  single-pair  brush 
yoke.  (See  Yoke,  Single-Pair  Brush.) 

Rod  Clamp.— (See  Clamp,  Rod^ 

Rod,  Clutch  —  — A  clutch  or  clamp  pro- 
vided in  an  arc  lamp  to  seize  the  lamp  rod  and 
thus  arrest  its  fall,  during  feeding,  beyond  a 
certain  predetermined  point. 

The  clutch  or  clamp  is  caused  to  release  or  hold 
the  lamp  rod  by  the  action  of  an  electro-magnet 
placed  in  a  shunt  circuit  around  the  electrodes. 
(See  Lamp,  Arc,  Electric.') 

Rod,  Discharging  —  — A  jointed  rod 
provided  at  both  ends 
with  balls  and  con- 
nected at  the  middle  by 
a  swinging  joint  which 
permits  the  balls  to 
move  towards  or  from 
one  another,  employed 
for  the  disruptive  dis- 
charge of  Leyden  bat- 
teries or  condensers. 
(See  Discharge,  Dis- 
ruptive. Jar,  Leyden.) 

The  insulated  handles  H,  H,  Fig.  495,  permit 


the  balls  at  M,  M,  to  be  readily  applied  to  the 
opposite  coatings  of  the  jar  or  condenser. 

The  name  discharging  tongs  is  sometimes  ap- 
plied to  this  apparatus. 


Rod,  Lanip 


— A  metallic   rod   pro- 


Fig.  4Q5-    Discharging 
Rod. 


vided  in  electric  arc   lamps  for  holding  the 
carbon  electrodes. 

When  the  upper  carbon  only  is  fed,  as  is  the 
case  in  most  arc  lamps,  there  is  usually  but  one 
lamp  rod  provided.  The  clutch  or  clamp  of  the 
feeding  device  acts  against  this  rod,  which  must 
of  necessity  be  at  least  as  long  as  the  upper  carbon. 
(See  Lamp,  Arc,  £  lee  trie.) 

Rod,  Lightning  -  — A  rod,  or  wire 
cable  of  good  conducting  material,  placed  on 
the  outside  of  a  house  or  other  structure,  in 
order  to  protect  it  from  the  effects  of  a  light- 
ning discharge. 

Lightning  rods  were  invented  by  Franklin. 
The  results  of  a  very  extended  inquiry  on  the 
subject,  leave  no  room  for  doubt  that  a  lightning 
rod,  properly  placed  and  constructed,  affords  an 
efficient  protection  to  the  buildings  on  which 
it  is  placed. 

To  insure  this  protection,  however,  the  fol- 
lowing conditions  were,  until  very  recently,  gen- 
erally insisted  on  in  order  to  permit  the  rod  tj 
properly  act,  viz. : 

(i.)  The  rod,  generally  of  iron  or  copper, 
should  have  such  an  area  of  cross-  section  as  to 
enable  it  to  carry  without  fusion  the  heaviest  bolt 
it  is  liable  to  receive  in  the  latitude  in  which  it  is 
located. 

When  of  iron,  the  area  of  cross-section  should 
be  about  seven  times  greater  than  when  of 
copper. 

(2. )  The  rod  should  be  continuous  throughout, 
all  joints  being  carefully  avoided. 

When  joints  are  used,  they  should  be  made  of  as 
low  resistance  as  possible,  and  should  be  pro- 
tected against  corrosion. 

(3.)  The  upper  extremity  of  the  rod  should 
terminate  in  one  or  more  points  formed  of  some 
metal  that  is  not  readily  corroded,  such  as  pla- 
tinum or  nickel. 

(4.)  The  lower  end  of  the  rod  should  be  car- 
ried down  into  the  earth  until  it  meets  perma- 
nently damp  or  moist  ground,  where  it  should 
be  attached  to  a  fairly  extended  metallic  surface 
buried  in  the  ground. 

Metallic  plates  will  answer  for  grounding  the 


Rod.] 


463 


[Rod. 


rod,  but,  if  gas  or  water  pipes  are  available,  the 
rod  should  be  placed  in  good  electrical  connec- 
tion therewith,  by  wrapping  it  around  and 
solder  ing  it  to  such  pipes. 

This  fourth  requirement  is  of  great  importance 
to  the  proper  action  of  a  lightning  rod,  and  un- 
less thoroughly  fulfilled,  may  render  the  rod 
worthless,  no  matter  how  carefully  the  other  re- 
quirements are  attended  to.  When  a  bolt  strikes 
a  lightning  rod  which  is  not  properly  grounded, 
the  discharge  is  almost  certain  to  destroy  the 
building  to  which  the  rod  is  connected. 

(5. )  The  rod  should  not  be  insulated  from  the 
building,  unless  to  prevent  stains  from  the  oxi- 
dation of  the  metal.  On  the  contrary,  the  rod 
should  be  directly  connected  with  all  masses  of 
metal  in  its  path,  such  as  tin  roofs,  gutter  spouts, 
metallic  cornices,  etc.  In  this  way  only  can  dan- 
gerous disruptive  lateral  discharges  from  the  rod 
to  such  masses  of  metal  be  avoided. 

(6.)  The  rod  should  project  above  the  roof  or 
highest  part  of  the  building,  or,  in  other  words, 
the  height  of  the  rod  should  bear  a  certain  pro- 
portion to  the  size  of  the  building  to  be  pro- 
tected. 

A  rod  will  protect  a  conical  space  around  it, 
the  radius  of  whose  base  is  equal  to  the  vertical 
height  of  the  rod  above  the  ground,  but  whose 
sides  are  curved  inwards  instead  of  being  straight. 
Where  the  building  is  very  high,  a  number  of 
separate  rods  all  connected  to  one  another  should 
be  employed. 

A  lightning  rod  sometimes  fails  to  protect  a 
house  or  barn,  from  the  fact  that  a  heated,  ascend- 
ing current  of  air  from  a  fire  in  the  house,  or 
from  the  gradual  heating  of  green  hay  or  grain  in 
the  barn,  acting  as  a  conductor,  increases  the  vir- 
tual height  of  the  house  beyond  the  ability  of  its 
rods  to  protect  it. 

(7.)  A  stranded  conductor  is  much  better  than 
an  equal  cross-section  of  a  solid  rod  of  the  same 
metal. 

A  copper  tape  is  better  than  a  copper  rod  for 
lightning  rods,  because  a  rapidly  periodic  current, 
whose  periodicity  is  sufficiently  great,  passes 
practically  over  the  surface  of  the  conductor  only. 
Considering  an  electric  current  as  taking  its 
energy  from  the  surrounding  dielectric,  a  tape  is 
better,  because  the  surface  which  absorbs  the 
energy  is  greater  in  the  case  of  a  tape  than  of  a 
solid  rod.  (See  Law,  Poynting's.) 

A  lightning  rod  more  frequently  acts  to  quietly 
discharge  an  impending  cloud  by  connective  dis- 


charge than  by  an  actual  disruptive  discharge  of 
the  same.  (See  Discharge,  Convective,  Dis- 
charge, Disruptive.') 

Lightning  rods  should  be  frequently  tested  to 
see  that  no  breaks  or  oxidation  of  their  joints 
have  occurred. 

Professor  Lodge  takes  exception  to  some  of  the 
heretofore  generally  received  notions  concerning 
the  action  of  lightning  rods.  He  distinguishes 
between  two  distinct  kinds  of  discharge  that  may 
occur  between  a  charged  cloud  and  the  earth, 
viz.: 

(I.)-  A  steady  strain  or  current. 

(2.)  An  impulsive  rush  or  oscillatory  discharge. 

A  discharge  by  a  steady  strain  or  current  oc- 
curs when  the  cloud  gradually  approaches  a  point 
on  the  earth;  or,  in  the  case  of  the  cloud  being 
stationary,  when  it  receives  its  charge  gradually 
by  the  approach  of  another  cloud. 

In  steady  discharge,  the  lightning  rod,  with  its 
pointed  end,  either  quietly  discharges  the  cloud 
by  a  convective  discharge,  or  by  a  harmless  con- 
ductive discharge  through  the  rod,  after  a  spark 
has  passed  disruptively  between  the  cloud  and 
the  rod.  (See  Discharge,  Convective.  Dis- 
charge, Conductive.  Discharge,  Disruptive.') 

The  impulsive  discharge  or  rush  occurs  when- 
ever the  cloud  that  discharges  to  the  earth  re- 
ceives its  charge  suddenly,  as  by  the  discharge 
into  it  of  a  neighboring  cloud,  or  when  a  bound 
charge,  produced  by  the  presence  of  a  neighbor- 
ing charged  cloud,  is  suddenly  liberated  by  dis- 
harge,  and,  thus  becoming  free,  impulsively  dis- 
charges to  the  earth. 

In  all  cases  of  an  impulsive  discharge  or  rush,  a 
counter  electromotive  force  is  set  up  in  the  rod, 
which  resists  the  discharge  through  the  rod  and 
causes  the  electricity  to  rush  back  and  spit  off  in 
lateral  discharges.  In  this  case  the  conducting 
power  of  the  rod  has  no  effect  in  facilitating  the 
discharge.  Indeed,  the  smaller  its  resistance,  and 
the  longer  the  oscillations  last,  the  greater  the 
danger  from  lateral  discharges.  (See  Discharge, 
Lateral.  Path,  Alternative.) 

The  following  principles  advanced  by  Lodge 
differ  from  the  views  heretofore  generally  re- 
ceived, viz.: 

•  (l.)  Iron  is  a  better  substance  for  a  lightning 
rod  than  copper,  because  it  is  equally  as  good  a 
conductor  as  copper  for  very  rapidly  alternating 
currents,  and  is  more  difficult  to  fuse. 

(2.)  All  neighboring  metallic  conductoisaiUould 
be  connected  to  earth.  These  connections  should 


Rod  ' 


464 


[Rot. 


preferably  be  by  separate  conductors  rather  than 
by  the  rod  itself. 

(3.)  The  lightning  conductors  should  have  a 
good  separate  earth,  but  should  be  connected  to 
water  pipes,  gas  pipes,  etc.,  if  near  them,  by  an 
underground  connection. 

(4.)  The  lightning  conductor  should  be  de- 
tached from  the  building  and  not  close  against  it. 

(5.)  The  rod  should  be  of  flat  section,  or  a 
stranded  conductor. 

Rod,    Lightning,    for    Ships A 

system  of  rods  designed  to  afford  electric 
protection  for  vessels  at  sea. 

Since  the  lightning  discharge  takes  place  be- 
tween the  points  of  greatest  difference  of  poten- 
tial, and  these  points  are  generally  the  cloud 
and  the  nearest  point  of  the  earth,  tall  objects  are 
especially  liable  to  be  struck. 

Ships  at  sea  should,  therefore,  be  thoroughly 
protected  from  lightning. 

In  Harris'  system  of  lightning  protection  for 
ships,  the  rods  are  connected  with  a  series  of 
copper  plates  and  rods  so  placed  on  the  masts  as 
to  readily  yield  to  strains.  These  plates  or  rods 
are  electrically  connected  with  the  copper  sheath- 
ing of  the  vessel  and  -with  all  large  masses  of 
metal  in  the  vessel.  This  latter  precaution  is 
especially  necessary  in  the  case  of  men-of-war, 
in  order  to  protect  the  powder  magazine. 

Harris'  method  for  the  lightning  protection  of 
ships  was  adopted  only  after  very  considerable 
opposition.  It  proved,  however,  so  efficacious  in 
practice  that  serious  effects  of  lightning  on  vessels 
so  protected  are  now  almost  unknown.  In  1845, 
Harris  received  the  honor  of  knighthood  from 
the  English  Government  for  his  services  in  this 
respect 

Hod,  Lightning,  Points  on Points 

of  inoxidizable  material,  placed  on  lightning 
rods,  to  effect  the  quiet  discharge  of  a  cloud  by 
convection  streams.  (See  Rod,  Lightning. 
Convection,  Electric?) 

Rod,  Thnnder A  term   formerly 

used  for  lightning  rod.  (See  Rod,  Light- 
ning^ 

Rods,  Bus Heavy  copper  rods  em- 
ployed in  a  central  or  distributing  station,  to 
which  all  the  terminals  of  the  generating  dy- 
namos are  connected,  and  from  which  the  cur- 
rent passes  to  the  different  points  of  the  dis- 
tribution system  over  the  feeders. 


Bus  rods  are  often  called  bus  bars  or  bus  wires. 
(See  Wires,  Bus.) 

Rodding  a  Conduit. — (See  Conduit,  Rod- 
ding  a.} 

Rolling  Contact. — (See  Contact,  Rolling.} 

Rose,  Ceiling An  ornamental  ceil- 
ing plate  through  which  an  electric  conductor 
passes. 

Rosette. — An  ornamental  plate  provided 
with  contacts  connected  to  the  terminals  of 
the  service  wires,  and  placed  in  a  wall  for  the 
ready  attachment  of  the  incandescent  lamp. 

A  word  sometimes  used  in  place  of  rose. 

Rosette  Cut-Out.— (See  Cut-Out,  Rosette.) 

Rotary  Magnetic  Polarization. — (See 
Polarization,  Magnetic  Rotary?) 

Rotary-Phase  Current. — (See  Current, 
Rotating?) 

Rotary-Phase  Dynamo. — (See  Dynamo, 
Rotary-Phase?) 

Rotary-Phase  Motor. — (See  Motor,  Ro- 
tating Current?) 

Rotary-Phase  Transformer. — (See  Trans- 
former, Rotary-Phase?) 

Rotating  Brushes  of  Dynamo-Electric 
Machine. — (See  Brushes,  Rotating,  of 
Dynamo-Electric  Machines?) 

Rotating  Current. — (See  Current,  Rota- 
ting?) 

Rotating  Current  Field. — (See  Field, 
Rotating  Current?) 

Rotating  Current  Motor. — (See  Motor, 
Rotating  Current?) 

Rotating  Current  Transformer.— (See 
Transformer,  Rotatory  Current?) 

Rotation,  Electro-Magnetic  — A 

rotation  obtained  by  electro-magnetic  attrac- 
tions and  repulsions.  (See  Disc,  Arago's. 
Disc,  Faraday's.  Motor,  Electric?) 

Rotation,  Magneto-Optic A  rota- 
tion of  the  plane  of  polarization  of  a  beam 
of  polarized  light  on  its  passage  through  a 
transparent  medium  when  placed  in  a  strong 
magnetic  field. 

The  medium  only  possesses  such  properties 
while  in  the  field. 


Rub.] 


465 


[Sai. 


In  a  ray  of  ordinary  light  the  vibrations  of  the 
ether  particles  are  at  right  angles  to  the  direction 
of  the  ray,  or  to  the  direction  in  which  the  light 
is  moving.  But  the  vibrations  occur  indiscrimi- 
nately in  all  planes  passing  through  the  line  of 
direction.  Under  certain  circumstances,  all  the 
ether  particles  may  be  caused  to  move  in  planes 
that  are  parallel  to  one  another.  Such  a  beam  of 
jight  is  called  a  plane  polarized  beam. 

A  plane  polarized  beam  of  light,  when  passed 
through  many  transparent  substances,  will  have 
its  ether  particles  vibrating  in  the  same  plane 
when  it  emerges  from  the  medium,  as  it  had  before 
it  entered.  Some  transparent  substances,  how- 
ever, possess  the  property  of  rotating  or  turning 
the  plane  of  polarization  of  the  light  to  the  right 


Fig.  496.    Magneto- Optic  Rotation. 

or  to  the  left.  This  property  is  called  respec- 
tively right-handed  rotary  polarization,  and  left' 
handed  rotary  polarization. 

Many  substances  that  ordinarily  possess  no 
power  of  rotary  polarization  acquire  this  power 
when  placed  in  a  magnetic  field.  This  property 
of  a  magnetic  field  was  discovered  by  Faraday. 


The  effect  is  to  be  ascribed  to  the  strain  produced 
in  the  transparent  medium  by  the  stress  of  the 
magnetic  field.  It  may  be  caused  in  solid  bodies 
by  mechanical  force. 

The  apparatus  for  demonstrating  the  rotation 
of  the  plane  of  polarization  by  a  magnetic  field  is 
shown  in  Fig.  496. 

A  powerful  electro-magnet,  M,  M,  is  provided 
with  a  hollow  core.  The  substance  c,  is  placed 
in  the  field  produced  by  the  approached  poles, 
and  its  action  on  the  light  of  a  lamp,  placed  at 
the  end  1,  is  observed  by  suitable  apparatus  at  a. 

Rubber    of    Electrical    Machine. — A 

cushion  of  leather,  covered  with  an  electric 
amalgam,  and  employed  to  produce  electricity 
by  its  friction  against  the  plate  or  cylinder  of 
a  frictional  electric  machine.  (See  Machine, 
Frictional  Electric?) 

Rubbing  Contact.— (See  Contact,  Rub- 
bing.) 

Ruhmkorff  Coil.— (See  Coil,  Ruhmkorff) 

RuhmkorlTs  Commutator.— (See  Com- 
mutator,  Ruhmkorjf ~'s.) 

Rule,  Ampere's,  for  Effect  of  Current  on 

Needle A  magnetic  needle,  when 

placed  near  a  conductor  through  which  a 
current  is  flowing,  has  its  north  pole  deflected 
to  the  left  of  the  observer,  who  is  supposed 
to  be  swimming  with  the  current  and  facing 
the  needle. 


s 


S. — A  contraction  employed  for  second. 

S.  H.  M. — A  contraction  employed  for 
simple  harmonic  motion. 

S.  N.  Code. — A  contraction  for  single  needle 
code. 

S.  W.  G. — A  contraction  for  Standard  Wire 
Gauge. 

Saddles,  Telegraphic B  rackets 

placed  on  the  top  of  telegraphic  poles  for 
the  support  of  the  insulators. 

Saddle  brackets  are  usually  employed  for  the 
wire  attached  to  the  top  of  a  telegraph  pole.  (See 
Pole,  Telegraphic.) 


Safe  Carrying  Capacity  of  a  Conductor. 

-  (See  Capacity,  Safe  Carrying,  of  a  Con- 
ductor.) 

Safety  Catch.— (See  Catch,  Safety) 
Safety  Device  for  Multiple  Circuits. — (See 
Device,  Safety,  for  Multiple  Circuits.) 
Safety  Fuse.— (See  Fuse,  Safety.) 

Safety  Lamp,  Electric (See  Lamp, 

Electric  Safety?) 

Safety  Plug.— (See  Plug,  Safety.) 
Safety  Strip.— (See  Strip,  Safety) 
Saint  Elmo's  Fire.— (See  Fire,  St.  El- 
mo's?) 


1.J 


4G6 


[Scli. 


Salient  Magnetic  Pole.— (See  Pole,  Mag- 
netic, Salient?) 
Saline  Creeping. — (See  Creeping,  Saline.} 

Salts,  Electrolysis  of The  decom- 
position of  a  salt  into  its  electro-positive  and 
negative  radicals  or  ions.  (See  Electrolysis.) 

Sandy    Deposit,    Electro-Metallurgical 

(See  Deposit,  Electro-Metallurgical, 

Sandy.) 

Saturated  Solution. — (See  Solution,  Sat- 
urated.) 

Saturation,  Magnetic The  max- 
imum magnetization  which  can  be  imparted 
to  a  magnetic  substance. 

The  condition  of  iron,  or  other  paramag- 
netic substance,  when  its  intensity  of  mag- 
netization is  so  great  that  it  fails  to  be  further 
sensibly  magnetized  by  any  magnetic  force, 
however  great. 

When  the  core  of  an  electro-magnet  is  saturated 
by  the  passage  of  an  electric  current,  the  only 
further  increase  of  its  magnetization  that  is  possi- 
ble, is  that  due  to  the  magnetic  field  of  the  in- 
creased current  which  may  be  sent  through  its 
coils.  This  is  comparatively  insignificant. 

A  permanent  magnet  is  sometimes  said  to  be 
super-saturated,  that  is,  to  have  received  more 
magnetism  than  it  can  retain  for  any  considerable 
time  after  its  magnetization. 

In  the  saturated  field  magnets  of  a  dynamo-elec- 
tric machine  the  magnetic  density  is  seldom  taken 
at  a  larger  value  than  16,000  lines  per  square  cen- 
timetre of  area  of  cross- sect  ion.  But  this  is  only 
practical  saturation,  since  Ewing  has  forced 
45,300  lines  per  square  centimetre  by  using  an 
enormously  high  magnetizing  force  (H  =  24,500). 

Saturation,  Magnetic,  Diacritical  Point 

of A  term  proposed  by  S.  P.  Thomp- 
son for  such  a  value  of  the  co-efficient  of 
magnetic  saturation,  that  the  core  is  mag- 
netized to  exactly  one-half  its  possible  max- 
imum of  magnetization. 

Saw,  Electric A  platinized  steel 

wire,  employed  while  incandescent  for  cut- 
ting hard  substance. 

Scale,  Tangent  —  — A  scale  designed 
for  use  with  a  galvanometer,  on  which  the 
values  of  the  tangents  are  marked,  instead  of 


equal  degrees  as  ordinarily,  thus  avoiding  the 
necessity  of  finding  from  tables  the  tangents 
corresponding  to  the  degrees. 

Such  a  scale  may  be  constructed  as  follows: 
Draw  the  tangent  B  T,  to  the  circle,  Fig.  497, 
and  lay  off  on  it  any  number  of  equal  divisions 
or  parts,  as,  for  example,  the  thirty  shown  in  the 
annexed  figure.  Connect  these  parts  with  the 
centre  C,  of  the  circle.  The  arc  of  the  circle  will 


Pig-  4Q7-     Tangent  Scale. 

thus  be  divided  into  parts  proportional  to  the 
value  of  the  tangents  of  the  angles. 

These  parts  are  more  nearly  equal  the  nearer 
they  are  to  B,  and  grow  smaller  and  smaller  the 
further  they  are  from  B.  In  tangent  galva- 
nometers it  is  therefore  very  difficult  to  accurately 
determine  the  current  strength  when  the  deflec- 
tions of  the  needle  are  very  large. 

Scale,  Thermometer,  Centigrade  —  — A 
thermometer  scale,  in  which  the  length  of  the 
thermometric  tube  between  the  melting  point 
of  ice  and  the  boiling  point  of  water  is  divided 
into  one  hundred  equal  parts  or  degrees. 

Centigrade  degrees  are  indicated  by  a  C.,  thus 
O  degree  C.  or  100  degrees  C.,  to  distinguish  them 
from  Fahrenheit  degrees  that  are  marked  F. 
In  the  Fahrenheit  scale  the  freezing  point  of 
water  is  taken  at  32  degrees,  and  the  boiling  point 
at  212  degrees. 

Scale,  Thermometer,    Fahrenheit's 

— A  thermometer  scale  in  which  the  length 
of  the  thermometer  tube  between  the  melting 
point  of  ice  and  the  boiling  point  of  water  is 
divided  into  180  equal  parts  called  degrees. 

Fahrenheit  degrees  are  indicated  by  an  F., 
thus,  32  degrees  F. 

The  freezing  point  of  water  in  Fahrenheit's 
scale  is  marked  32  degrees  F.,  and  the  boiling 
point  of  water  is  marked  212  degrees  F. 

Schiseophone.— An  electro-mechanical  ap- 
pliance for  detecting  flaws  and  internal  de- 
fects in  rails  or  other  metallic  masses. 

The  schi>eophone  consists  essentially  in  the 
combination  of  a  microphone  and  telephone  with 
a  mechanical  hammer  and  induction  balance. 


Sch. 


467 


[Scr. 


Schweigger's  Multiplier. — (See  Multi- 
plier, Schweigger 's.) 

Scintillating  Jar. — (See  Jar,  Scintillat- 
ing^ 

Scratch  Brush. — (See  Brush,  Scratch?) 

Scratch  Brush,  Circular  — (See 

Brush,  Scratch,  Circular?) 

Scratch  Brush,  Hand (See  Brush, 

Scratch,  Hand?) 

Scratch  Brushing. — (See  Brushing, 
Scratch?) 

Screen,  Electric A  closed  conduc- 
tor placed  over  a  body  to  screen  or  protect  it 
from  the  effects  of  external  electrostatic  fields. 

An  electric  screen  is  sometimes  called  an  elec- 
tric shield. 

The  ability  of  a  closed,  hollow  conductor  to  act 
as  a  screen,  arises  from  the  fact  that  all  points  on 
its  inner  surface  are  at  the  same  potential,  and 
therefore  are  not  affected  by  an  increase  or  de- 
crease in  the  potential  of  the  outside  of  the  con- 
ductor as  compared  with  that  of  the  earth.  (See 
Net,  Faraday1  s.) 

No  considerable  thickness  is  required  for  the 
efficient  operation  of  an  electric  screen. 

Screen,  Magnetic A  hollow  box 

whose  sides  are  made  of  thick  iron,  placed 
around  a  magnet  or  other  body  so  as  to  cut 
it  off  or  screen  it  from  any  magnetic  field  ex- 
ternal to  the  box. 

Magnetic  screens  are  placed  around  delicate 
galvanometers  to  avoid  any  variations  in  their 
field  due  to  extraneous  masses  of  iron  or  neigh- 
boring magnets.  They  are  also  sometimes  placed 
around  watches  to  shield  or  screen  the  works 
from  the  effects  of  magnetism. 

To  act  effectively,  when  the  external  fields  are 
at  all  powerful,  magnetic  screens  must  be  made 
of  thick  iron.  They  differ  in  this  respect  from 
electrostatic  shields,  which  will  afford  protection 
against  electrostatic  charges  although  they  may 
be  but  mere  films. 

Screen,  Methven's  —  — A  vertical  rec- 
tangular metallic  screen  used  in  connection 
with  a  standard  argand  burner,  for  furnish- 
ing a  standard  amount  of  light  for  photo- 
metric purposes. 

In  a  rectangular  screen  a  small  vertical  slot  is 
made  of  such  dimensions  as  to  permit  an  amount 


of  light  to  pass  just  equal  to  two  standard  candles. 
The  proper  burning  of  the  argand  lamp  is  de- 
termined by  supplying  sufficient  gas  to  produce 
a  flame  exactly  3  inches  high.  The  glass 
chimney  used  in  the  burner  is  6  inches  high, 
and  is  provided  with  two  horizontal  wires  placed 
on  each  side  of  the  burner  at  the  required  height. 

Methven's  screen  possesses  the  advantage  of 
being  easily  used  and  of  furnishing  a  reliable 
standard  of  light.  Extended  experiments  made 
with  it  appear  to  show  that  the  amount  of  light 
produced  depends  rather  on  the  height  of  the 
gas  flame  than  on  the  quality  of  the  gas  itself. 
In  using  Methven's  screen  care  should  be  taken 

( i . )  To  see  that  the  gas  flame  is  of  exactly  the 
required  height. 

(2.)  That  the  chimney  on  the  lamp  is  quite 
clean. 

(3.)  That  the  top  of  the  flame  is  as  regular  as 
possible. 

As  this  last  point  is  almost  impossible  to  obtain  in 
actual  practice,  the  flame  is 
ad  justed  so  that  the  highest 
point  extends  about  one- 
eighth  of  an  inch  above  the 
height  of  the  horizontal 
wires. 

(4.)  That  the  lamp  and 
apparatus  be  permitted  to 
acquire  its  normal  temper- 
ature before  the  readings 
are  taken. 

Fig.  498  shows  the  con- 
struction of    the   ordinary 
Methven  standard   screen. 
The   vertical    slot  in    the 
screen  is  placed  as  shown 
before  the  standard  argand    Ft'&-  49&- 
burner.     Horizontal  wires       Standar 
for  the  adjustment  of  the  height  of  the  flame  are 
placed  one  on  each  side  of  the  gas  chimney. 

Screening,  Electrostatic  —  —Screening 
or  shielding  from  the  inductive  effects  of  a 
charge. 

A  continuous  metallic  surface  surrounding  an 
air  space  to  be  shielded,  completely  protects  any 
body  placed  within  such  air  space  from  electro- 
static influence.  (See  Cube,  Faraday's.) 

Screening,  Magnetic Preventing 

magnetic  induction  from  taking  place  by  in- 
terposing a  metallic  plate,  or  a  closed  circuit 
of  insulated  wire,  between  the  body  producing 


Scr.] 


468 


[Scr. 


the  magnetic  field  and  the  body  to  be  mag- 
netically screened. 

A  magnetic  needle  is  screened  from  the  action 
of  the  earth's  field  by  placing  it  inside  a  hollow 
iron  box,  which  prevents  the  lines  of  force  of  the 
earth's  field  from  passing  through  it  by  concen- 
trating them  on  itself.  This  action  is  dependent 
on  the  fact  that  iron  is  paramagnetic  and  there- 
fore offers  the  lines  of  force  less  resistance 
through  its  mass  than  elsewhere.  A  plate  of 
copper  would  not  effect  any  such  magnetic 
shielding  or  screening. 

In  any  magnetic  field,  however,  in  which  the 
strength  of  the  field  is  undergoing  rapid,  periodic 
variations,  a  plate  of  copper  or  other  electric 
conductor  may  act  as  a  screen  to  protect  neigh- 
boring conductors  from  the  effects  of  magnetic 
induction,  and  its  ability  to  thoroughly  effect 
such  a  screening  will  depend  directly  on  its 
conducting  power. 

If,  for  example,  the  copper  plate  c  (Fig.  499), 
be  interposed  between  a  coil  of  copper  ribbon  a, 
and  the  fine  wire  coil  b,  it  will  greatly  reduce  the 
intensity  of  the  induced  currents,  produced  when 
rapidly  alternating  currents  are  sent  through  a. 
If,  however,  the  copper  plate  be  slit,  as  shown  to 
the  right  at  a,  the  screening  effect  is  lost,  but  is 
regained  if  the  slit  be  connected  by  a  conductor. 
Similarly  a  flat  coil  of  insulated  wire  effects  no 
screening  action  when  open,  but  when  closed  acts 
as  the  uncut  copper  plate. 

Here  the  screening  action  is  due  to  thp  fact 
that  the  energy  of  the  field  is  spent  in  producing 
eddy  currents  in  the  interposed  metal  screen  or 
coils.  If  the  metal  screen  is  discontinuous  in  the 
direction  in  which  the  eddy  currents  tend  to  flow, 
the  inability  of  the  screen  to  absorb  the  energy  as 
eddy  currents  prevents  its  action  as  a  screen. 


Fig. 
The  word  magnetic  screening  is  generally  em- 


induction  from  occurring  in  a  neighboring  con- 
ductor, by  interposing  some  conducting  substance 
in  which  eddy  currents  can  be  freely  established. 

As  to  the  efficiency  of  the  screening  action,  if  the 
makes-and -breaks  do  not  follow  one  another  very 
rapidly,  the  following  principles  can  be  proved  : 

(i.)  If  the  screening  material  have  absolutely 
no  electrical  resistance  it  will  effect  a  perfect  mag- 
netic screening  when  placed  between  the  primary 
and  secondary,  no  matter  what  its  thickness 
may  be. 

(2.)  If  the  screen  have  a  finite  conductivity, 
the  screening  will  be  imperfect,  unless  the  thick- 
ness of  the  material  employed  is  considerable. 

If,  however,  the  makes-and-breaks  follow  one 
another  very  rapidly,  then 

The  screening  effect  of  even  imperfect  conduc- 
tors will  become  manifest  with  comparatively 
thin  screens  of  metal. 

As  to  magnetic  screening,  therefore,  it  follows 
that  the  less  the  conductivity,  the  greater  must 
be  the  speed  of  reversal,  in  order  that  the  screen- 
ing action  may  be  effective. 

Where  a  screen  of  iron  is  employed,  an  ad- 
ditional effect  is  produced  by  the  fact  that  the 
small  magnetic  resistance  of  the  metal,  or  its  con- 
ductivity for  lines  of  magnetic  force,  causes  the 
lines  of  induction  to  pass  through  its  mass,  and 
thus  effect  a  screening  action  for  the  space  on  the 
other  side.  This  action  is,  by  some,  called  mag- 
netic screening. 

In  the  case  of  iron  screens,  considerable  thick- 
ness  is  required  in  the  metal  plate,  in  order  to 
obtain  efficient  screening  action  of  this  latter 
character.  On  account  of  this  action  of  iron,  in 
conducting  away  lines  of  force,  a  much  smaller 
speed  of  reversal  is  required,  in  order  to  obtain 
effective  screening  action,  where  plates  of  iron 
are  used,  than  in  the  case  of  plates  of  other 
metal. 

The  apparatus  shown  in  Fig.  500  was  employed 


SOO.     Willoughby  Smith's  Apparatus. 

by  Mr.  Willoughby  Smith,  in  studying  the  effects 
of  magnetic  screening. 

The  flat  coils  A,  and  B,  were  employed  for  the 
primary  and  secondary   coils  respectively,  and 


ployed  in  the  latter  sense  of  preventing  magnetic      were  connected  to  the  battery  C,  and  the  galva- 


Sen] 


469 


[Sec. 


nometer  F,  as  shown.  Current  reversers,  D  and 
E,  were  so  arranged  as  to  reverse  galvanometer 
and  battery  alternately,  and  so  cause  the  oppo- 
site induced  currents  to  affect  the  galvanometer  in 
the  same  direction.  If  the  commutators  were 
caused  to  reverse  the  current  slowly,  a  plate  of 
copper  interposed  between  A  and  B,  produced 
but  little  effect  on  the  galvanometer,  but  if  the  re- 
versers were  driven  at  a  very  rapid  rate,  a  marked 
decrease  of  deflection  occurred. 

The  screening  action  of  the  metals,  or  their 
ability  to  diminish  the  galvanometer  deflection, 
is  in  the  order  of  their  electrical  conductivity,  ex- 
cept in  the  case  of  iron,  which,  as  we  have  seen 
already,  has  an  additional  screening  power,  due 
to  its  conducting  away  the  lines  of  magnetic  force. 

It  follows  from  the  preceding  principles  that 
the  use  of  lead  covered  cables,  for  the  conveyance 
of  periodic  currents,  of  the  frequency  of,  say,  sixty 
to  one  hundred  alternations  per  second,  is  of  but 
little  or  no  advantage  for  protecting  neighboring 
telephones  from  inductive  action,  because 

(i.)  Lead  is  a  poor  conductor. 

(2.)  The  rapidity  of  alternation  is  too  slow. 

J.  J.  Thomson  made  some  experiments  with 
electrical  oscillations  produced  by  resonance,  of 
about  ios  in  frequency.  He  obtained  this  fre- 
quency of  oscillation  from  oscillations  set  up  in 
the  primary  of  an  induction  coil,  in  a  secondary 
circuit  of  suitable  dimensions.  The  presence  of 
these  secondary  vibrations  or  waves  was  shown 
by  means  of  the  sparks  seen  at  the  terminals  of  a 
spark-micrometer  circuit.  Under  these  circum- 
stances he  found  that  the  interposition  of  a  thin 
sheet  of  tin  foil  or  gold  leaf  at  once  completely 
stopped  the  secondary  sparks  by  the  shielding 
action  it  exerted. 

Screening,  Magnetostatic  —  — Screen- 
ing from  the  inductive  effect  of  a  stationary 
magnetic  field. 

Magnetostatic  screening  differs  from  electrostatic 
screening  in  that  the  plate  of  iron  or  other  para- 
magnetic material  surrounding  the  space  to  be 
screened  must  have  a  fairly  considerable  thick- 
ness. This  arises  from  the  fact  that  the  magnetic 
susceptibility  of  the  substance  is  not  infinitely 
great. 

Screw,  Binding A  name  some- 
times applied  to  a  binding  post.  (See  Post, 
Binding.} 

Seal,  Hennetical Such  a  sealing  of 


a  vessel,  designed  to  hold  a  vacuum,  or  gas- 
eous atmosphere  under  pressures  greater  or 
less  than  that  of  the  atmosphere,  as  will  pre- 
vent either  the  entrance  of  the  external  at- 
mosphere into  the  vessel,  or  the  escape  of  the 
contained  gas  into  the  atmosphere. 

Hermetical  sealing  may  be  accomplished  either 
by  the  use  of  suitable  cements,  or  by  the  direct 
fusion  of  the  walls  of  the  containing  vessel.  The 
latter  method  is  generally  employed. 

Search  Light,  Automatic  —(See 

Light,  Search,  Automatic?) 

Search  Light,  Electric (See  Light, 

Search,  Electric?) 

Secohm. — The  practical  unit  of  self-induc- 
tion, or  the  practical  unit  of  inductance. 

The  secohm  is  equivalent  to  a  length  equal  to 
that  of  an  earth  quadrant,  or  10''  centimetres. 

The  word  secohm  is  a  contraction  for  second, 
ohm,  and  implies  the  fact  that  the  product  of  the 
ohm  and  the  second  are  taken. 

The  word  henry  is  now  generally  used  in  the 
United  States  for  secohm.  (See  Henry.} 

Secohmmeter. — An  apparatus  for  measur- 
ing the  co-efficient  of  self-induction,  mutual 
induction  and  capacity  of  conductors.  (See 
Secohm.  Induction,  Mutual.  Induction, 
Self.) 

The  principle  of  the  secohmmeter  depends 
upon  successively  performing  the  cycle  of  magnetic 
operations,  by  making  and  breaking  the  circuit 
of  a  galvanometer  by  means  of  a  commutator 
capable  of  working  at  a  definite  speed. 

Second,  Ampere One  ampere  flow- 
ing for  one  second.  (See  Hour,  Ampere.} 

Second,  Watt A  unit  of  electrical 

work. 

A  watt -second  equals  the  work  due  to  the  ex- 
penditu  re  of  an  electrical  power  of  one  watt  for 
one  second.  It  is  the  same  as  a  volt-coulomb. 

The  watt-second  and  the  H.  P.  hour,  etc., 

are  units  of  work,  since  Power  =  — ?E_, 

Time 
therefore,  power  X  time  =  work. 

Secondary  Battery. — (See  Battery,  Sec- 
ondary.} 

Secondary  Battery,  Cell  of — (See 

Cell,  Secondary.) 


Sec.] 


[Sec. 


Secondary  Cell.— (See  Cell,  Secondary?) 

Secondary  Cell,  Jar  of (See  Jar  of 

Secondary  Cell.) 

Secondary    Clock.— (See  Clock.  Second- 
ary.) 
Secondary  Coil.— (See  Coil,  Secondary) 

Secondary  Currents. — (See  Currents, 
Secondary) 

Secondary,  Fixed  -  —The  secondary 
of  an  induction  coil,  that,  as  is  common  in 
such  coils,  is  fixed,  as  contradistinguished 
from  a  movable  secondary.  (See  Secondary, 
Movable.) 

Secondary  Generator. — (See  Generator, 
Secondary.) 

Secondary  Impressed  Electromotive 
Force. — (See  Force,  Electromotive,  Second- 
ary Impressed) 

Secondary,  Movable The  second- 
ary conductor  of  an  induction  coil,  which,  in- 
stead of  being  fixed  as  in  most  coils,  is  mova- 
ble. 

The  peculiar  movements  observed  in  the 
secondary  of  an  induction  coil  when  the  second- 
ary is  free  to  move,  have  been  carefully  studied 
by  Prof.  Elihu  Thomson.  The  secondaries 
employed  for  this  purpose  are  in  the  shape  of 
rings,  discs,  spheres,  wedges,  bars,  wheels,  etc., 
etc. 

The  primary  is  in  the  form  of  a  straight  cylin- 
drical coil  surrounding  a  straight  core.  The  coils 
are  traversed  by  rapidly  alternating  currents  and 
possess  considerable  impedance. 

Among  the  many  phenomena  concerning  the 
behavior  of  movable  secondaries  in  such  a  rapidly 
alternating  field  are  the  following,  viz.: 

(A.)  A  metallic  ring,  resting  on  lugs  attached 
to  the  coils  of  the  primary,  is  thrown  violently  off 
the  magnet  on  the  passage  of  alternating  currents 
through  the  primary. 

(2.)  Two  metallic  rings  of  the  same  diamete, 
brought  into  the  field  are  mutually  attracted  to 
each  other,  with  sufficient  force  to  sustain  the 
weight  of  one  of  the  rings  when  the  other  ring  is 
held  in  the  field. 

(3.)  Metallic  spheres  are  set  into  rotation  when 
so  held  near  the  primary  pole  as  to  be  shielded 


from  the  action  of  part  of  the  rapidly  alternating 
field.  Wken  held  on  one  side  of  the  pole,  this 
rotation  occurs  in  the  opposite  direction  to  that 
when  held  on  the  opposite  side. 

(4.)  Metallic  discs  similarly  placed  are  simi- 
larly set  into  rotation. 

(5.)  The  speed  ot  rotation  of  spheres  or  discs 
varies  in  different  positions. 

(6.)  Spheres  or  discs  of  diamagnetic  substances 
attain  their  maximum  rotation  when  held  in  posi- 
tion  at  right  angles  to  those  of  paramagnetic  sub- 
stances. 

(7.)  Bars  of  steel  or  substances  possessing  high 
coercive  power,  placed  dissymmetrically  on  the 
primary  as  regards  their  centres  of  gravity,  ex- 
hibit the  phenomena  of  a  shifting  magnetic  field. 
(See  field,  Magnetic,  Shifting.) 

(8.)  A  wedge-shaped  piece  of  steel  placed  with 
a  flat  face  on  the  primary,  exhibits  a  shifting 
magnetic  field,  and  acts  on  movable  metallic 
masses  near  it,  just  as  though  a  fluid  substance 
was  escaping  with  great  velocity  from  its  edges. 

Secondary  Movers. — (See  Movers,  Second- 
ary.) 

Secondary  Plate  of  Condenser. — (See 
Plate,  Secondary,  of  Condenser) 

Secondary  Spiral. — (See  Spiral,  Second- 
ary.) 

Secretion  Current. — (See  Current,  Secre- 
tion.) 

Section  Line  of  Electric  Railway. — (See 
Railroads,  Electric,  Section  Line  of) 

Section,  Neutral,  of  Magnet — A 

section  passing  through  the  neutral  line  or 
equator  of  a  magnet.  (See  Line,  Neutral, 
of  a  Magnet.  Magnet,  Equator  of) 

Section,  Trolley  -  —A  single  contin- 
uous length  of  trolley  wire,  with  or  without 
its  branches. 

Sectional  or  Divided  Overhead  System 
of  Motive  Power  for  Electric  Railroads.— 

(See  Railroads,  Electric,  Sectional  Over- 
head System  of  Motive  Power  for.) 

Sectional  or  Divided  Surface  System  of 
Motive  Power  for  Electric  Railroads.— 

(See  Railroads,  Electric,  Sectional  Surf  ace 
System  of  Motive  Power  for) 


Sec.] 


471 


[Sep. 


Sectional  or  Divided  Underground 
System  of  Motive  Power  for  Electric  Bail- 
roads. — (See  Railroads,  Electric,  Sectional 
Underground  System  of  Motive  Power  for.} 

Sectional  Plating. — (See  Plating,  Sec- 
tional.) 

Sectional  Plating  Frame. — (See  Frames, 
fictional  Plating.) 

Seebeck  Effect.— (See  Effect,  Seebeck?) 

Seismograph,  Electric An  appa- 
ratus for  electrically  recording  the  direction 
and  intensity  of  earthquake  shocks. 

Seismograph,  Micro  — An  electric 

apparatus  for  photographically  registering 
the  vibrations  of  the  earth  produced  by  earth- 
quakes or  other  causes. 

The  micro-seismograph  consists  essentially  of  a 
microphone  placed  on  the  ground  and  connected 
with  a  telephone.  A  small  concave  mirror  mova- 
ble about  a  horizontal  axis  is  supported  on  a 
plate  of  aluminium  supported  on  a  platinum  wire 
connected  with  the  diaphragm  of  the  telephone. 
The  movements  of  the  diaphragm  of  the  telephone 
are  permanently  recorded  on  a  strip  of  sensitized 
paper  that  is  moved  before  the  mirror. 

Selective  Absorption. — (See  Absorption, 
Selective?) 

Selenium. — A  comparatively  rare  element 
generally  found  associated  with  sulphur. 

Selenium  Battery.— (See  Battery,  Selen- 
ium?) 

Selenium  Cell. — (See  Cell,  Selenium?) 

Selenium  Eye. — (See  Eye,  Selenium?) 

Selenium  Photometer.— (See  Photometer, 
Selenium?) 

Self-Induced  Current.—  (See  Currents, 
Self-Induced?) 

Self-Induction. — (See  Induction,  Self.} 

Self-Induction,  Co-efficient  of (See 

Induction,  Self  Co-efficient  of.) 

Self-Becording  Magnetometer.— (S  e  e 
Magnetometer,  Self -Recording?) 

Self-Begistering  Wire  Gauge.  —  (See 
Gauge,  Wire,  Self -Registering?) 

Self-Winding  Clock.— (See  Clock,  Self- 
Winding?) 


Semaphore. — A  variety  of  signal  apparatus 
employed  in  railroad  block  systems. 

The  semaphore  used  on  the  Pennsylvania  Rail- 
road consists  of  a  wooden  post,  in  the  neighbor- 
hood of  twenty  feet  in  height,  on  which  a  wooden 
arm  or  blade  six  feet  in  length  and  a  foot  in 
width,  is  displayed. 

When  the  block  is  clear,  during  the  day  the 
arm  is  placed  pointing  downwards  at  an  angle  of 
75  degrees  with  the  horizontal ;  during  night 
semaphore  displays  a  white  light.  When  the 
block  is  not  clear,  the  arm  or  blade  is  placed  in  a 
horizontal  position  by  day,  or  displays  a  red  light 
at  night.  (See  Railroads,  Block  System  for.) 

Semaphore  Arm. — (See  Arm,  Semaphore?) 

Semaphore  Indicator.— (See  Indicator, 
Semaphore?) 

Sender,  Zinc A  device  employed 

in  telegraphic  circuits,  by  means  of  which,  in 
order  to  counteract  the  retardation  produced 
by  the  charge  given  to  the  line,  a  momen- 
tary reverse  current  is  sent  into  the  line  after 
each  signal. 

A  zinc  sender  generally  consists  of  a  low  resist- 
ance Siemens  relay  introduced  between  the  line 
and  the  front  contact  of  the  signaling  key. 

Sensibility,  Electro An  effect  pro- 
duced on  a  sensory  nerve  by  its  electrization. 

Sensibility  of  Galvanometer. — (See  Gal- 
vanometer, Sensibility  of.) 

Sensitive  Thread  Discharge.— (See  Dis- 
charge, Sensitive  Thread?) 

Separate  Coil  Dynamo-Electro  Machine. 
— (See  Machine,  Dynamo-Electric,  Separate 
Coil.) 

Separate  Touch,  Magnetization  by 

— (See  Touch,  Separate?) 

Separately  Excited  Dynamo.— (See  Dy- 
namo, Separately  Excited) 

Separately  Excited  Dynamo-Electric 
Machine. — (See  Machine,  Dynamo-Electric, 
Separately  Excited.) 

Separator.— An  insulating  sheet  of  ebonite, 
or  other  similar  substance,  corrugated  and 
perforated  so  as  to  conform  to  the  outline  of 
the  plates  of  a  storage  battery,  and  placed 
between  them  at  suitable  intervals,  in  such  a 


Sen] 


472 


[Ser. 


manner  as  to  avoid  short-circuiting,  without 
impeding  the  free  circulation  of  the  liquid. 

Series  and  Magneto  Dynamo-Electric 
Machine. — (See  Machine,  Dynamo- Electric, 
Series  and  Magneto?) 

Series  and  Separately  Excited  Dynamo- 
Electric  Machine.— (See  Machine,  Dynamo- 
Electric,  Series  and  Separately  Excited?) 

Series  and  Shunt-Wound  Dynamo-Elec- 
tric Machine. — (See  Machine,  Dynamo- 
Electric,  Series  and  Shunt-  Wound?) 

Series  Circuit. — (See  Circuit,  Series?) 

Series-Connected  Battery. — (See  Battery, 
Series-  Connected?) 

Series-Connected  Electro-Receptive  De- 
vices.— (See  Devices,  Electro-Receptive,  Se- 
ries-Connected. ) 

Series-Connected  Electro-Receptive  De- 
vices, Automatic  Cut-out  for  —  — (See 
Cut-out,  Atttomatic,  for  Series-Connected 
Electro-Receptive  Devices?) 

Series-Connected  Sources. — (See  Sources, 
Series-Connected?) 

Series-Connected  Translating  Devices. 
— (See  Devices,  Translating,  Series-Con- 
nected?) 

Series-Connected  Yoltaic  Cells. — (See 
Cells,  Voltaic,  Series-Connected?) 

Series  Connection. — (See  Connection, 
Series?) 

Series,  Contact A  series  of  metals 

arranged  in  such  an  order  that  each  becomes 
positively  electrified  by  contact  with  the  one 
that  follows  it. 

The  contact  values  of  some  metals,  according 
to  Ayrton  and  Perry,  are  as  follows: 

CONTACT  SERIES. 


Difference  of  Potential  in  Volts. 

Zinc 

Lead 

Lead 

Tin 

Tin 

Iron 

Iron 

Copper 

Copper  

Platinum 

Platinum | 

Carbon f "3 


.210 
.069 

.146 
.238 


The  difference  in  potential  between  zinc  and 
carbon  is  equal  to  1.089,  and  is  obtained  by  add- 
ing the  successive  differences  of  potential  between 
the  intermediate  couples,  thus: 
. 210 -f  .069 +.313  +  .14  6-|- .238 +.113  =1.089. 

This  fact  is  known  technically  as  Volta' 's  Law, 
which  may  be  formulated  as  follows: 

The  difference  of  potential,  produced  by  the  con- 
tact of  any  two  metals,  is  equal  to  the  sum  of  the 
differences  of  potentials  between  the  intervening 
metals  in  the  contact  series. 

Series  Distribution  of  Electricity  by 
Constant  Currents. — (See  Electricity,  Se- 
ries Distribution  of,  by  Constant  Current 
Circuit?) 

Series-Multiple. — A  series  of  multiple 
connections.  (See  Circuit,  Series-Multiple?) 

Series-Multiple  Circuit. — (See  Circuit, 
Series-Multiple?) 

Series  -  Multiple-Connected  Electro-Re- 
ceptive Devices. — (See  Devices,  Electro-Re- 
ceptive, Series-Multiple-Connected?) 

Series-Multiple-Connected  Sources.  — 
(See  Sources,  Series-Multiple-Connected?) 

Series-Multiple-Connected  Translating 
Devices. — (See  Devices,  Translating,  Series- 
Multiple-Connected?) 

Series-Multiple  Connection. — (See  Con- 
nection, Series-Multiple?) 

Series,  Parallel  —  — A  term  some- 
times applied  to  a  multiple-series  connection. 
(See  Connection,  Multiple-Series?) 

Series,  Thermo-Electric A  list  of 

metals  so  arranged  according  to  their  ther- 
mo-electric powers,  that  each  metal  in  tke 
series  is  electro-positive  to  any  metal  lower  in 
the  list. 

Series-Transformer. — (See  Transformer, 
Series?) 

Series  Turns  of  Dynamo-Electric  Ma- 
chine.—(See  Turn-s,  Series,  of  Dynamo- 
Electric  Machine?) 

Series  Winding. — (See  Winding,  Series,} 

Series-Wound  Dynamo. — (See  Dynamo, 
Series?) 

Series-Wound  Dynamo-Electric  Machine. 
—  (See  Machine,  Dynamo-Electric,  Series^ 
Wound?) 


Ser.J 


473 


[She. 


Series-Wound  Motor. — (See  Motor,  Se- 
ries- Wound.} 

Service  Conductors. — (See  Conductors, 
Service.) 

Service,  Street In  a  system  of  in- 
candescent lamp  distribution  that  portion  of 
the  circuit  which  is  included  between  the 
main  and  the  service  cut-out. 

Serving,    Cable The   covering   of 

hemp  or  jute  spun  around  the  insulated  core 
of  a  cable  to  act  as  a  protection  against  the 
pressure  of  the  iron  wire  which  forms  the 
armor  of  the  cable. 

Shackling  a  Wire. — Inserting  an  insula- 
tion between  the  two  ends  of  a  cut  wire. 

Shaded  or  Screened. — Cut  off  or  screened 
from  the  effects  of  an  electrostatic  or  mag- 
netic field.  (See  Screening,  Magnetic.  Screen, 
Magnetic.  Screen,  Electric.) 

Shadow,  Electric  -  — A  term  some- 
times used  for  molecular  shadow.  (See 
Shadow,  Molecular.) 

Shadow,  Molecular — The  compara- 
tively dark  space  on  those  parts  of  the  walls 
of  Crookes'  tubes,  which  have  been  protected 
from  molecular  bombardment  by  suitably 
placed  screens. 


Fig  jo i.     Molecular  Shadow. 

If  a,  in  the  Crookes  tube,  shown  in  Fig.  501, 
be  connected  with  the  negative  pole  of  an  elec- 
tric source,  and  the  cross-shaped  mass  of  alu- 
minium at  b,  be  connected  with  the  positive  elec- 
trode, on  the  passage  of  a  series  of  rapid 
discharges,  phosphorescence  is  produced  by  the 
molecular  bombardment  from  a,  in  all  parts  of 
the  vessel  opposite  a,  except  those  lying  in  the 


projection  of  its  geometrical  shadow.  (See  Phos- 
phorescence, Electric. ) 

Shadow  Photometer.— (See  Photometer, 
Shadow?) 

Shaft,  Driven A  shaft  which  re- 
ceives its  power  from  the  driving  shaft.  (See 
Mover,  Prime?) 

Shaft,  Driving- The  main  line  of 

shafting  which  takes  its  power  directly  from 
the  prime  mover. 

Shallow-Water  Submarine  Cable.— (See 

Cable,  Submarine,  Shallow-  Water.) 

Sheath,  Protective A  device  at- 
tached to  a  transformer  or  converter,  to  pre- 
vent any  connection  from  taking  place  between 
the  high-potential  primary  circuit  and  the 
low-potential  secondary  circuit. 

The  protective  sheath  devised  by  Prof.  Elihu 
Thomson  consists  essentially  in  an  earth -con- 
nected copper  strip  or  divided  plate  interposed 
between  the  windings  for  the  secondary  and  pri- 
mary circuit.  Should  the  primary  circuit  lose  its 
high  insulation  it  becomes  grounded. 

Sheet,  Current  — The  sheet  into 

which  a  current  spreads  when  the  wires  of 
any  source  are  connected  at  any  two  points 
near  the  middle  of  a  very  large  and  thin  con- 
ductor. 

A  continuous  electric  current  does  not  flow 
through  the  entire  mass  of  a  conductor  in  any 
single  line  of  direction.  If  the  terminals  of  any 
source  are  connected  to  neighboring  parts  of  a, 
greatly  extended  thin  conductor,  the  current 
spreads  out  in  a  thin  sheet  known  as  a  cur- 
rent sheet,  and  instead  of  flowing  in  a  straight 
line  between  the  points,  spreads  over  the  plate 
in  curved  lines  of  flow,  which,  so  far  as  shape  is 
concerned,  are  not  unlike  the  lines  of  magnetic 
force. 

Sheet  Lightning.  —  (See  Lightning, 
Sheet) 

Shellac. — A  resinous  substance  possessing 
valuable  insulating  properties,  which  is  ex- 
uded from  the  roots  and  branches  of  certain 
tropical  plants. 

The  specific  inductive  capacity  of  shellac  as 
compared  with  air  is  2.74. 


She.] 


474 


[Shn. 


Shell,  Magnetic A  sheet  or  layer 

consisting  of  magnetic  particles,  all  of  whose 
north  poles  are  situated  in  one  of  the  flat 
surfaces  of  the  layer,  and  the  south  poles  in 
the  opposite  surface.  (See  Magnetism,  La- 
mellar Distribution  of.) 

Shell  Transformer. — (See  Transformer, 
Shell) 

Shield,  Magnetic,  for  Watches A 

hollow  case  of  iron,  in  which  a  watch  is  per- 
manently kept,  in  order  to  shield  it  from  the 
influence  of  external  magnetic  fields.  (See 
Screen,  Magnetic.) 

Shifting  Magnetic  Field.— (See  Field, 
Magnetic,  Shifting.) 

Shifting  Zero.— (See  Zero,  Shifting) 

Ships,  Lightning  Rods  for (See 

Rod,  Lightning,  for  Ships.) 

Ship's  Sheathing,  Electric  Protection  of 

Attaching  pieces  of  zinc  to  the  copper 

sheathing  of  a  ship  for  the  purpose  of  prevent- 
ing the  corrosion  of  the  copper  by  the  water. 
(See  Metals,  Electrical  Protection  of.) 

Shock,  Break A  term  sometimes 

employed  in  electro-therapeutics  for  the 
physiological  shock  produced  on  the  opening 
or  breaking  of  an  electric  circuit. 

Shock,  Electric The  physiological 

shock  produced  in  an  animal  by  an  electric 
discharge. 

Shock,  Opening The  physiological 

shock  produced  on  the  opening  or  breaking 
of  an  electric  circuit. 

Shock,  Static A  term  employed  in 

electro-therapeutics  for  a  mode  of  applying 
Franklinic  currents  or  discharges,  by  placing 
the  patient  on  an  insulating  stool  and  apply- 
ing one  pole  of  a  static  machine  provided 
with  small  condensers  or  Leyden  jars,  to  an 
insulated  platform  on  which  the  patient  is 
placed,  while  the  other  pole  is  applied  to  the 
body  of  the  patient  by  the  operator. 

* 

The  electrode  applied  to  the  body  of  the  pa- 
tient is  provided  with  a  ball  electrode.  Shocks 
are  given  to  the  patient  on  the  approach  of 
this  electrode  by  the  discharge  of  the  Leyden 
jars. 


Short-Arc  System  of  Electric  Lighting. 

— (See  Lighting,  Electric,  Short-Arc  Sys- 
tem^) 

Short-Circuit. — To  establish  a  short  cir- 
cuit. (See  Circuit,  Short.) 

Short-Circuit  Key.— (See  Key,  Short- 
Circuit.) 

Short-Circuiting. — Establishing  a  short 
circuit.  (See  Circuit,  Short.) 

Short-Circuiting  Plug.— (See  Plug, 
Short-Circuiting  ) 

Short-Coil  Magnet. — (See  Magnet,  Short- 
Coil) 

Short-Core  Electro-Magnet. — (See  Mag- 
net, Electro,  Short-Core) 

Short-Shunt  Compound-Wound  Dyna- 
mo-Electric Machine. — (See  Machine,  Dy- 
namo-Electric, Compound-  Wound,  Short- 
Shunt) 

Shunt. — An  additional  path  established 
for  the  passage  of  an  electric  current  or  dis- 
charge. 

Shunt. — To  establish  an  additional  path 
for  the  passage  of  an  electric  current  or  dis- 
charge. 

Shunt  and  Separately  Excited  Dynamo- 
Electric  Machine. — (See  Machine,  Dynamo- 
Electric,  Shunt  and  Separately  Excited) 

Shunt  Circuit.— (See  Circuit,  Shunt.) 

Shunt  Dynamo-Electric  Machine. — (See 
Machine.  Dynamo-Electric,  Shunt-  Wound) 


Shunt,    Electric 

Shunt,  Electric) 


Bell 


—(See    Bell. 


Shunt,  Electro-Magnetic In  a  sys- 
tem of  telegraphic  communication  an  electro- 
magnet whose  coils  are  placed  in  a  shunt 
circuit  around  the  terminals  of  the  receiving 
relay. 

The  electro-magnetic  shunt  operates  by  its 
self-induction.  Its  poles  are  permanently  closed 
by  a  soft  iron  armature  so  as  to  reduce  the  resist- 
ance of  the  magnetic  circuit.  (See  Induction, 
Self.) 


Shu.] 


475 


[Shu. 


On  making  the  circuit  in  the  coils  of  a  receiv- 
ing relay,  a  current  is  produced  in  the  coils  of  the 
electro  magnetic  shunt  in  the  opposite  direction 
to  the  relay  current;  and,  on  breaking  the  circuit 
in  the  relay,  a  current  is  produced  in  the  coils  of 
the  electro-magnetic  shunt  in  the  same  direction 
as  the  current  in  the  relay. 

The  connection  of  the  coils  of  the  electro-mag- 
netic shunt  with  those  of  the  receiving  relay,  how- 
ever, is  such  that  on  making  the  circuit  in  the 
relay  the  current  in  the  shunt  coils  flows  through 
the  relay  in  the  same  direction,  and  on  breaking 
the  circuit  it  flows  in  the  opposite  direction. 
Therefore  this  shunt  produces  the  following  effects: 

(i.)  At  the  commencement  of  each  signal  in 
the  receiving  relay,  it  produces  an  induced  cur- 
rent in  the  same  direction  which  strengthens  the 
current  in  the  relay. 

(2.)  At  the  ending  of  each  signal  in  the  receiv- 
ing relay,  it  produces  a  current  in  the  opposite 
direction,  which  hastens  the  motion  of  the  tongue 
of  the  polarized  relay.  (See  Relay,  Polarized.) 

Shnnt,    Galvanometer A   shunt 

placed  around  a  sensitive  galvanometer  for 
the  purpose  of  protecting  it  from  the  effects 
of  a  strong  current,  or  for  altering  its  sensi- 
bility. (See  Ihunt} 

The  current  which  will  flow  through  the  shunt 
wire  depends  on  the  relative  resistance  of  the  gal- 
vanometer and  of  the  shunt.  In  order  that  only 

total  curtent  shall  pass 
through  the  galvanome- 
ter, it  is  necessary  that 
the  resistances  of  the 
shunt  shall  be  the  \,  fa 
or  5^,  of  the  galvanom- 
eter resistance. 

Fig.  302  shows  a 
shunt,  in  which  the  re- 
sistances, as  compared 
with  that  of  the  galva- 
nometer, are  those  above 
referred  to.  The  galva- 
nometer terminals  are 


connected  at  N,  N.  Plug 


Fig.  JO2.     Galvanometer 

Shunt. 

keys  are  used  to  connect  one  or  another  of  the 
shunts  with  the  circuit.  (See  Shunt,  Multiplying 
Power  of.) 

Shunt,     Magnetic An    additional 

path  of  magnetic  material  provided  in  a  mag- 
16— Vol.  1 


netic  circuit  for  the  passage  of  the  lines  of 
force. 
Shunt,  Multiplying  Power  of  -  _  A 

quantity,  by  which  the  current  flowing  through 
a  galvanometer  provided  with  a  shunt,  must 
be  multiplied,  in  order  to  give  the  total  cur- 
rent. 

The  multiplying  power  of  a  shunt  may  be  de- 
termined from  the  following  formula,  viz.: 


/ 


X  C,  in  which 


=  the  mul- 


tiplying  power  of  a  shunt  whose  resistance  is  s; 
g,  is  the  galvanometer  resistance;  C,  the  current 
through  the  galvanometer,  and  A,  the  total  cur- 
rent passing;  s  and  g,  are  taken  in  ohms,  and  C 
and  A,  in  amperes. 

Suppose,  for  example,  that  but  ^  the  entire 
current  is  to  flow  through  the  galvanometer;  then 
the  resistance  of  the  shunt  must  evidently  be  £  g, 
for, 

s  i  i 


or,  ios  = 


10  s  —  s  = 


9  s=g;  or, 


Shunt  or  Reducteur  for  Ammeter.  —  (See 
Reducteur  or  Shunt  for  Ammeter) 

Shunt  Ratio.—  The  ratio  existing  between 
the  shunt  and  the  circuit  which  it  shunts 
(See  Shunt,  Multiplying  Power  of.} 

Shunt,  Relay,  Stearns'  ----  A  shunt 
employed  in  the  differential  method  of  duplex 
telegraphy  to  short-circuit  the  relay  and  then 
permit  the  line  current  to  be  cut  off  directly 
after  it  has  completed  its  work  in  closing  the 
local  circuit. 

The  use  of  the  relay  shunt  permits  the  slacken- 
ing of  the  armature  spring  of  the  relay,  because 
the  decreased  duration  of  the  line  current  does 
not  produce  so  strong  a  magnetization  of  the 
iron. 

Shunt-Turns  of  Dynamo-Electric  Ma- 
chine. —  (See  Turns,  Shunt,  of  Dynamo- 
Electric  Machine?) 

Shunt->Vouu<l  Dynamo-Electric  Ma- 
chine. —  (See  Machine,  Dynamo-Electric, 
Shunt-  Wound?) 

Shunt-  Wound  Motor.  —  (See  Motor, 
Shunt-  Wound} 


Shu.] 


476 


[Sig. 


Shunting.— Establishing  a  shunt  circuit. 

Shuttle  Armature.— (See  Armature, 
Shuttle?) 

Side  A,  of  Quadruples  Table.— (See  Table, 

Quadruple*,  A,  Side  of.) 

Side  B,  of  Quadruples  Table.— (See  Table, 
Quadruplex,  B,  Side  of.) 

Side  Flash.— (See  Flash,  Side.) 

Sidero-Magnetic.— (See  Magnetic,  Side- 
ro.) 

Siemens'  -  Armature  Electro-Magnetic 
Bell. — (See  Bell, Electro-Magnetic,  Siemens' 
Armature  Form.) 

Siemens'  Differeutial  Voltameter.— (See 
Voltameter  Siemens'  Differential.) 

Siemens'  Electric  Pyrometer.— (See  Py- 
rometer, Siemens  Electric?) 

Siemens-Halske  Voltaic  Cell. -(See  Cell, 
Voltaic,  Siemens-Halske?} 

Siemens'  Water  Pyrometer.— (See  Py- 
rometer, Siemens'  Water.) 

Signal  Arm.— (See  Arm,  Signal.} 

Signal,  Electric  Tell-Tale  -  —An 
electrically  operated  signal,  generally  silent, 
whereby  the  appearance  of  a  white  or  colored 
disc,  on  a  black  or  otherwise  uniformly 
colored  surface,  indicates  the  occurrence  of 
a  certain  predetermined  event 

Signal  Service  for  Electric  Railways. — 
(See  Railroads,  Electric,  Signal  Service 
System  for.} 

Signals,  Electro-Pneumatic  -  —Sig- 
nals operated  by  the  movements  of  dia- 
phragms or  pistons  moved  by  compressed 
air,  the  escape  of  which  is  controlled  electri- 
cally. 

Signaling,  Balloon,  for  Military  Pur- 
poses —  —Transmitting  intelligence  of  the 
movements  of  an  enemy's  army  obtained  from 
observations  made  in  balloons  by  means  of  tel- 
ephone circuits  connected  with  the  balloon. 

Signaling,  Curb  —  —In  cable  teleg- 
raphy a  system  for  avoiding  the  effects  of 
retardation  by  rapidly  discharging  the  cable 
before  another  electric  impulse,  is  sent  into 


it,  by  reversing  the  battery,  before  connecting 
it  to  earth,  and  then  connecting  to  earth  be- 
fore beginning  the  next  signal. 

Signaling,  Double-Curb In  curb 

signaling,  a  method  by  which  the  cable,  after 
being  connected  with  the  battery  for  sending 
a  signal,  is  subjected  to  a  reverse  battery,  bat 
instead  of  being  put  to  earth  after  this  con- 
nection, as  in  single-curb  signaling,  the  bat- 
tery is  again  reversed  and  connected  to  earth. 

The  time  during  which  the  cable  is  connected 
to  the  reversed  battery  before  being  put  to  earth, 
that  is,  the  time  during  wh'ch  it  receives  the 
positive  and  negative  currents,  may  be  made  of 
any  suitable  duration. 

Signaling,  Double-Current—  —Signal- 
ing by  means  of  currents  that  alternately 
change  their  direction. 

Double-current  signaling  was  devised  by  Var- 
ley  in  order  to  avoid  the  effects  of  the  induction 
of  underground  conductors  on  Morse  tele- 
graphic apparatus.  The  idea  of  reversing  the 
direction  of  the  current  was  to  hasten  the  dis- 
charge of  the  wire,  which  was  prolonged  by  in- 
duction. Double  current  working,  however, 
possesses  other  advantage.-,  and  is  u«ed  in  duplex 
and  quadruplex  transmission. 

Signaling,  Single-Curb  -  —In  curb 
signaling,  a  method  by  which  the  cable,  after 
connection  with  the  battery  for  sending  a 
signal,  is  subjected  to  a  reverse  battery  cur- 
rent, and  then  put  to  earth  before  again  being 
connected  to  the  battery  for  sending  the  next 
signal. 

Signaling,  Single-Current  —  —Signal- 
ing by  making  or  breaking  the  circuit  of  a 
single  current. 

Single-current  signaling  is  of  two  kinds,  viz. : 

(l.)  Open-Circuit  Signaling,  in  which  the  bat- 
teries are  fixed  at  each  station,  and  are  in  circuit 
only  when  signaling. 

(2.)  Closed -Circuit  Signaling,  where  the  bat- 
teries are  divided,  one  half  generally  being  at  each 
end  of  the  line,  and  so  connected  that  both  sets 
flow  in  the  same  direction. 

Signaling,  Single-Current,  Closed-Circuit 

A  system  of  single-circuit  signaling  in 

which   the  sending  batteries  are  placed  at 
each  end  of  the  line  and  are  so  connected  as 


477 


[Sin. 


to  remain  always  in  circuit.     (See  Signaling, 
Single-  Current?) 
Signaling,  Single-Current,  Open-Circuit 

A  system  of  single-current  signaling 

in  which  the  sending  batteries,  fixed  at  each 
station,  are  in  circuit  during  signaling  only. 
(See  Signaling,  Single-Current.) 

Signaling,  Velocity  of  Transmission  of 

The  speed  or  rate  at  which  successive 

signals  can  be  sent  on  any  line  without  the 
retardation  producing  serious  interference. 
(See  Retardation?) 

Silent  Discharge.— (See  Discharge,  Si- 
lent?, 

Silver  Bath.— (See  Bath,  Silver.) 

Silver  Chloride  Voltaic  Cell.— (See  Cell, 

Voltaic,  Silver  Chloride?) 

Silver  Plating.— (See  Plating,  Silver?) 

Silver  Voltameter. — (See  Voltameter, 
Silver?) 

Silvered  Plumbago. — (See  Plumbago,  Sil- 
vered?) 

Silvering,  Electro Covering  a  sur- 
face with  a  coating  of  silver  by  electro-plat- 
ing. (See  Plating,  Electro?) 

Electro-plating  with  silver. 

Silurus  Electricus. — The  electric  eel. 
(See  Eel,  Electric?) 

Simple  Arc. — (See  Arc,  Simple?) 
•   Simple  Circuit.— (See  Circuit,  Simple?) 

Simple  Electric  Candle-Burner.— (See 
Burner,  Simple  Candle  Electric?) 

Simple-Harmonic  Current. — (See  Cur- 
rent, Simple-Harmonic?) 

Simple-Harmonic  Curve. — (See  Curve, 
Simple-Harmonic?) 

Simple-Harmonic  Motion. — (See  Motion, 
Simple-Harmonic?) 

Simple  Magnet.— (See  Magnet,  Simple?) 

Simple-Periodic  Current. — (See  Cur- 
rents, Simple-Periodic?) 

Simple-Periodic  Electromotive  Force. 
— (See  Force,  Electromotive,  Simple- 
Periodic?) 


Simple-Periodic  Motion.— (See  Motion, 
Simple-Periodic?) 

Simple  Radical.— (See  Radical,  Simple.) 

Simple-Sine  Motion. — (See  Motion, 
Simple- Sine?) 

Simple  Voltaic  Cell.— (See  Cell,  Voltaic, 
Simple?) 

Simplex  Telegraphy. — (See  Telegraphy, 
Simplex?) 

Sims-Edison  Torpedo. — (See  Torpedo, 
Sims-Edison-) 

Sine  Galvanometer. — (See  Galvanometer, 

Sine.) 

Single-Brush  Rocker. — (See  Rocker, 
Single-Brush .) 

Single-Cup    Insulator.— (See   Insulator, 
Single-Shed) 
Single  Curb.— (See  Curb,  Single.) 

Single-Current  Signaling. — (See  Signal 
ing,  Single-Current.) 

Single-Curve  Trolley  Hanger. — (See 
Hanger,  Single-Curve  Trolley.) 

Single-Fluid  Hypothesis  of  Electricity. 

— (See  Electricity,  Single-Fluid  Hypothesis 
of.} 

Single-Fluid  Voltaic  Cell.— (See  Cell, 
Voltaic,  Single-Fluid.) 

Single-Loop  Armature. — (See  Armature, 
Single-Loop.) 

Single-Magnet  Dynamo-Electric  Ma- 
chine. —  (See  Machine,  Dynamo-Electric, 
.  Single-Magnet.) 

Single-Pair  Yoke.— (See  Yoke,  Single- 
Pair.} 

Single-Shackle  Insulator. — (See  Insula- 
tor, Single- Shackle} 

Single-Shed  Insulator. — (See  Insulator, 
Single-Shed?) 

Single-Stroke  Electric  Bell.— (See  Bell, 
Single-Stroke  Electric} 

Single  Touch.— (See  Touch,  Single.) 

Single-Wire   Cable.— (See  Cable.  Single- 

\Vire.) 


Sin.] 


478 


[Sine. 


Single-Wire  Circuit.— (See  Circuit, 
Single-  Wire?) 

Sinistrorsal  Solenoid  or  Helix.— (See  So- 
lenoid, Sinistrorsal?) 

Sinuous  Currents. — (See  Current,  Sinu- 
ous?) 

Siphon,    Electric  — A    siphon  in 

which  the  stoppage  of  flow,  due  to  the 
gradual  accumulation  of  air,  is  prevented  by 
electrical  means. 

In  the  electric  siphon,  an  opening  is  provided 
at  the  highest  part  of  the  bend  of  the  siphon  tube, 
and  a  chamber  is  attached  thereto,  provided  with 
a  float.  Contact  points  are  so  connected  with  the 
float  that  when  it  falls,  contact  is  made,  and  when 
it  rises,  contact  is  broken. 

The  closing  of  the  circuit,  on  the  fall  of  the 
float,  operates  an  electric  motor  which  drives  an 
air  pump  which  exhausts  the  air  from  the  siphon. 
Or  the  float  being  raised  in  the  siphon,  the  con- 
tact is  broken  and  the  operation  of  the  pump  is 
stopped. 

Siphon  Recorder. — (See  Recorder,  Si- 
phon?) 

Sir  William  Thomson's  Standard  Cell.— 
(See  Cell,  Voltaic,  Standard,  Sir  William 
Thomson's?) 

Skin  Effect.— (See  Effect,  Skin.} 

Skin,  Faradization  of The  thera- 
peutic treatment  of  the  skin  by  a  faradic  cur- 
rent. 

For  efficient  faradization  the  skin  should  be 
thoroughly  dried  and  a  metallic  brush  or  elec- 
trode employed.  For  very  sensitive  parts,  as, 
for  example,  the  face,  the  hand  of  the  operator, 
first  thoroughly  dried,  is  to  be  preferred  as  an 
electrode. 

Skin,  Human,  Electric  Resistance  of 

— The  electric  resistance  offered  by  the 
skin  of  the  human  body. 

The  electric  resistance  of  the  skin  is  subject  to 
marked  differences  in  different  parts  of  the  body, 
where  its  thickness  or  continuity  varies.  It 
varies  still  more  with  variations  in  its  condition  of 
moisture.  Even  in  the  same  individual  the  re- 
sistance varies  materially  under  apparently 
similar  conditions. 

Sleeve,  Insulating A  tube  of  treated 

paper  or  other  insulating  material,  provided 


for  covering  a  splice  in  an  insulated  con- 
ductor. 

Sleeve  Joint — (See/0/#/,  Sleeve.) 

Sleeve,  Lead A  lead  tube  provided 

for  making  a  joint  in  a  lead-covered  cable. 

Sled. — The  sliding  contacts  drawn  after  a 
moving  electric  railway  car  through  the  slotted 
underground  conduit  containing  the  wires  or 
conductors  from  which  the  driving  current  is 
taken. 

Slide  Bridge.— (See  Bridge,  Electric, 
Slide  Form  of.) 

Slide,  Resistance A  rheostat,  in 

which  the  separate  resistances  or  coils  are 
placed  in  or  removed  from  a  circuit  by  means 
of  a  sliding  contact  or  key. 

Apparatus  employed  in  telegraphy  for 
charging  a  conductor  to  a  given  fraction  of 
the  maximum  potential  of  the  battery  so  as 
to  adjust  its  charge  in  order  to  balance  the 
varying  charge  of  a  cable. 

The  resistance  slide  consists  essentially  of  a  set 
of  resistance  coils  of  high  insulation  and  of  equal 
resistance.  Suppose,  for  example,  ten  such  equal 
coils  to  be  connected  in  series,  then  if  connected 
to  the  charging  battery  the  potential  will  vary  by 
one-tenth  at  the  junction  between  each  pair.  A 
condenser,  therefore,  will  be  charged  to  any 
number  of  tenths  of  the  potential  of  the  charging 
battery  by  connecting  it  at  suitable  points. 

A  second  set  of  coils  of  equal  resistance  is  ar- 
ranged so  as  to  subdivide  any  of  the  lower  coils, 
thus  permitting  an  adjustment  to  within  a  hun- 
dredth of  the  potential  of  the  battery. 

Slide  Wire.— (See  Wire,  Slide) 
Sliding  Contact. — (See  Contact,  Sliding.) 

Slow-Speed  Electric  Motor. — (See  Motor, 
Electric,  Slow-Speed!) 

Sluggish  Magnet.— (See  Magnet,  Slug- 
gish^ 

Small  Calorie. — (See  Calorie,  Small?) 

Smee  Yoltaic  Cell.— (See  Cell,  Voltaic, 
Smee?) 

Smelting,  Electro The  separation 

or  reduction  of  metallic  substances  from  their 
ores  by  means  of  electric  currents. 


Sna.] 


479 


[Sol. 


Snap  Switch. — (See  Switch,  Snap.) 
Soaking-In. — A  term  sometimes  employed 
by   telegraphers    to    represent   the  gradual 
penetration  of  an  electric  charge  by  a  neigh- 
boring dielectric. 

An  electric  displacement  occurs  in  the  neigh- 
boring dielectric,  and  produces  thereby  what  is 
generally  called  the  residual  charge. 

Soakiug-Ont. — A  term  sometimes  em- 
ployed by  telegraphers  to  represent  a  gradual 
discharge  which  occurs  in  the  case  of  a 
charged  conductor  in  a  neighboring  dielec- 
tric. 

When  a  condenser,  or  other  similar  conductor, 
is  discharged,  the  discharge  is  not  instantaneous. 
The  charge  which  soaked  in,  gradually  recovers, 
or  soaks- out. 

Socket,  Electric  Lamp A  support 


-  S°3-    Lamp  Socket. 

for  the  reception  of  an  incandescent  electric 
lamp. 

Incandescent  lamp  sockets  are  generally  made 
so  that  the  mere  insertion  of  the  base  of  the  lamp 


.  304.    Lamf  Socket. 

in  the  socket  completes  the  connection  of  the  lamp 
terminals  with  the  terminals  of  the  socket.     The 


socket  terminals  are  connected  with  the  leads  that 
supply  current  to  the  lamp;  the  removal  of  the 
lamp  from  the  socket  automatically  breaks  its  cir- 
cuit. The  socket  is  generally  provided  with  a  key 
for  turning  the  lamp  on  or  off  without  removing 
it  from  the  socket. 

Figs.  503  and  504  show  forms  of  lamp  sockets 
for  incandescent  lamps  and  the  details  of  the  key 
for  connecting  or  disconnecting  the  lamp  with  the 
leads. 

Socket,  Wall  —  —A  socket  placed  in  a 
wall  and  provided  with  openings  for  the  inser- 
tion of  a  wall  plug  with  which  the  ends  of  a 
flexible  twin-lead  are  connected. 

A  wall-socket  permits  the  temporary  connec- 
tion of  a  portable  electric  lamp,  a  push  button  or 
other  device  with  the  conductor  or  lead. 

Soft-Drawn  Copper  Wire. — (See  Wire, 
Copper,  Soft-Drawn?) 

Soldering,  Electric A  process  for 

obtaining  metallic  joints,  in  which  heat  gen- 
erated by  the  electric  current  is  used  to  melt 
the  solder  in  the  place  of  ordinary  heat. 

Solenoid. — A  cylindrical  coil  of  wire  the 
convolutions  of  which  are  circular. 

An  electro-magnetic  helix.  (See  Solenoid, 
Electro-Magnetic,  or  Electro-Magnetic 
Helix.) 

A  solenoid  is  termed  dextrorsal  or  sinistrorsal 
according  to  the  direction  in  which  its  wire  is 
wound.  (See  Solenoid,  Dextrorsal.  Solenoid, 
Sinistrorsal.) 

Solenoid  Core. — The  core,  usually  of  soft 
iron,  placed  within  a  solenoid  and  magnetized 
by  the  magnetic  field  of  the  current  passing 
through  the  solenoid. 

The  soft  iron  core  of  a  solenoid  differs  from 
that  of  an  electro-magnet  in  the  fact  that  the  core 
of  the  solenoid  is  movable,  while  that  of  the  elec- 
tro-magnet is  fixed.  (See  Magnet,  Electro.) 

In  order  to  obtain  a  nearly  uniform  pull  in  its 
various  positions  in  the  solenoid,  the  soft  iron  cores 
are  made  of  a  shape  which  insures  a  greater  mass 
of  metal  towards  the  middle  of  the  core.  (See 
Bars,  KriziVs.) 

Solenoid,  Dextrorsal A  solenoid 

in  which  the  winding  is  right-handed.  (See 
Solenoid,  Practical.) 

Solenoid,  Electro-Magnetic,  or  Electro- 
Magnetic  Helix The  name  given  to 


Sol.] 


480 


[Sol. 


a  cylindrical  coil  of  wire,  each  of  the  convo- 
lutions of  which  is  circular. 

A  circuit  bent  in  the  form  of  a  helix,  supported 
at  its  two  extremities,  as  shown  in  Fig.  505,  and 
traversed  by  an  electric  current,  will  move  into 
the  magnetic  meridian  of  the  place,  and,  if  free  to 
move  in  a  vertical  plane,  will  come  to  rest  in  the 
line  of  the  magnetic  inclination  or  dip  of  the  place. 

A  solenoid  traversed  by  an  electric  current  ac- 
quires thereby  all  the  properties  of  a  magnet,  and 
is  attracted  and  repelled  by  other  magnets.  Its 
poles  are  situated  at  the  ends  of  the  cylinder  on 
which  the  solenoid  may  be  supposed  to  be  wound. 

Solenoid,  Ideal A  solenoid  con- 
sisting of  a  cylinder  built  up  of  a  number  of 
true  circular  currents,  with  all  faces  of  like 
polarity  turned  in  the  same  direction  and 
entirely  independent  of  one  another. 

The  practical  solenoid  differs  from  the  ideal 
solenoid  in  that  the  successive  circular  circuits  or 
currents  are  all  connected  with  one  another  in 
series. 

The  polarity  of  a  solenoid  depends  on  the  direc- 
tion of  the  current  as  regards  the  direction  in 
which  the  solenoid  is  wound. 

This  solenoid  is  sometimes  called  an  electro- 
magnetic solenoid  or  helix,  in  order  to  distinguish 


Fig.  S°S-    Practical  Solenoid. 
it  from  a  solenoidal  magnet.     (See  Magnet,  Sole- 
noidal.) 
A  solenoid,   if  suspended  so  as  to  be  free  to 


move,  will  come  to  rest  in  the  plane  of  the  mag- 
netic meridian  when  traversed  by  an  electric 
current. 

It  will  also  be  attracted  or  repelled  by  the  ap- 
proach of  a  dissimilar  or  similar  magnet  pole 
respectively,  as  shown  in  Fig.  505. 

Solenoid,  Left-Handed  —  — A  sinistror- 
sal  solenoid  or  one  in  which  the  winding  is 
left-handed.  (See  Solenoid,  Practical.} 

Solenoid,  Magnetic A  spiral  coil 

of  wire  which  acts  like  a  magnet  when  an 
electric  current  passes  through  it. 

The  magnetic  solenoid  must  be  distinguished 
from  a  solenoidal  magnet.  (See  Magnet,  Sole- 
noidal. Solenoid,  Electro-Magnetic,  or  Electro- 
Magnetic  Helix.} 

Solenoid,  Practical The  name  ap- 
plied to  the  ordinary  solenoid  in  order  to  dis- 
tinguish it  from  the  ideal  solenoid.  (See 
Solenoid,  Ideal.} 

A  Practical  Solenoid  consists,  as  shown  in  Figs. 


Fig.  job.    Practical  Solenoid. 

505  and  506,  of  a  spiral  coil  of  wire  in  which  the 
successive  circular  circuits  are  connected  to  one 
another  in  series. 


F*g>  SO?.  Right-Handed  Helix.  Fig.  508.  Left-Handed 
Helix.  Fig.  S°9-  Helix,  -with  Consequent  Poles. 

The  polarity  of  the  solenoid  depends  on  the 
direction  of  the  current,  and  therefore  on  the 
direction  of  winding.  In  any  solenoid,  however, 
the  polarity  may  be  reversed  by  reversing  the 
direction  of  the  current.  (See  Magnet,  Electro. } 

A  Right. Handed,  or  Dextrorsal  Solenoid,  is  one 
wound  in  the  direction  shown  in  Fig.  507  at  I. 


Sol.] 


481 


[Sou. 


A  Left-Handed,  or  Sinistrorsal  Solenoid,  is  one 
wound  in  the  direction  shown  in  Fig.  508  at  2. 

The  solenoid  shown  in  Fig.  509  at  3,  is  wound 
so  as  to  produce  consequent  poles.  (See  Poles , 
Consequent. ) 

Solenoid,  Right- if anded A  dex- 

trorsal  solenoid,  the  winding  in  which  is  right- 
handed.  (See  Solenoid,  Practical?) 

Solenoid,  Sinistrorsal  —  — A  solenoid 
in  which  the  winding  is  left-handed.  (See 
Solenoid,  Practical?) 

Solenoidal. — Pertaining  to  a  solenoid. 

Solid  Angle.— (See  Angle,  Solid.) 

Solid  Line.— (See  Line,  Solid.) 

Solution. — A  liquid  in  which  another  sub- 
stance, generally  a  solid,  is  dissolved. 

The  liquid  may  contain  either  a  solid,  another 
liquid,  or  a  gas. 

Solution,  Bain's  Printing  — The 

solution  used  in  Bain's  chemical  telegraph. 

Bain's  solution  is  made  by  mixing  together  one 
part  of  a  saturated  solution  of  potassium  ferro- 
cyanide,  with  two  parts  of  water. 

Solution,  Battery The  exciting 

liquid  for  voltaic  cells.  (See  Cell,  Voltaic.) 

Solution,  Chemical,  Bain's A  solu- 
tion employed  in  connection  with  Bain's  re- 
cording telegraph.  (See  Recorder,  Chemical, 
Bain's) 

Solution,  Quicking A  solution  of 

a  salt  of  mercury,  in  which  objects  to  be  elec- 
tro-plated are  dipped  after  cleansing,  just 
before  being  placed  in  the  plating  bath. 

If  the  articles  have  been  properly  cleansed,  im- 
mersion in  the  quicking  solution  will  cover  them 
with  a  uniform,  silver-like  coating,  which  will  in- 
sure an  adherent,  uniform  coating  in  the  plating 
bath. 

Solution,  Saturated A  solution  in 

which  as  much  of  the  solid  or  other  substance 
has  been  dissolved  in  the  liquid  as  it  will  take 
at  a  given  temperature. 

Solution,  Super-Saturation  of 

The  condition  assumed  by  a  warmed  satu- 
rated solution  of  a.  salt,  when  placed  in  a 
closed  vessel  out  of  contact  with  the  air,  and 
allowed  to  cool  without  being  shaken. 

Under  the  above  circumstances  the  solution 
may  be  cooled  without  depositing  any  crystals. 


Such  a  solution  is  said  to  be  super-saturated.  It 
will  immediately  deposit  crystals  if  a  crystal  of  the 
salt  dissolved  or  a  crystal  of  an.  isomorphous  salt 
be  dropped  in  the  solution,  or  often  if  merely 
shaken. 

It  is  important  in  standard  voltaic  cells  in 
which  zinc  sulphate  is  used,  that  the  solution  be 
saturated  but  not  super  saturated. 

Sonometer,  Hughes'  —  — An  apparatus 
for  determining  Lhe  amount  of  inductive  dis- 
turbance in  an  induction  balance,  by  compar- 
ing the  sounds  heard  in  a  telephone,  as 
a  result  of  such  induction,  with  the  sounds 
heard  in  the  same  telephone  under  circum- 
stances in  which  the  amount  of  disturbance 
is  directly  measurable. 

An  apparatus  devised  by  Professor  Hughes  to 
be  used  in  connection  with  the  induction  balance, 
in  order  to  measure  the  amount  of  disturbance  of 
balance  produced  therein  in  any  particular  case. 

Sonorescence. — A  term  proposed  for  the 
sounds  produced  when  a  piece  of  vulcanite  or 
any  other  solid  substance  is  exposed  to  a 
rapid  succession  of  flashes  of  light.  (See 
Photopkone.) 

Sound. — The  sensation  produced  on  the 
brain,  through  the  ear,  by  the  vibrations  of  a 
sonorous  body. 

The  sound  waves  that  are  capable  of  pro- 
ducing the  sensation  of  sound  on  the  brain 
through  the  ear. 

The  word  sound  is  therefore  used  in  science  in 
two  distinct  senses,  viz.: 

(i.)  Subjectively,  as  the  sensation  produced  by 
the  vibrations  of  a  sonorous  body. 

(2.)  Objectively,  as  the  waves  or  vibrations  that 
are  capable  of  producing  the  sensation  of  sound. 

Sound  is  transmitted  from  the  vibrating  body 
to  the  ear  of  the  hearer  by  means  of  alternate  to- 
and-fro  motions  in  the  air,  occurring  in  every 
direction  around  the  vibrating  body  and  firming 
spherical  waves  called  waves  of  condensation  and 
rarefaction.  Unlike  light  and  heat,  these  waves 
require  a  tangible  medium  such  as  air  to  trans- 
mit them. 

Sound,  therefore,  is  not  propagated  in  a 
vacuum.  The  vibrations  of  sound  are  longi- 
tudinal, that  is,  the  to-and-fro  motions  occur  in 
i  he  same  direction  as  that  in  which  the  sound  is 
traveling.  The  vibrations  of  light  are  iransversf, 


SOU.]  482 

that  is,  the  to-and-fro  motions  are  at  right  angles 
to  the  direction  in  which  the  light  is  traveling. 

Sound.— (Objectively.)  The  waves  in  the 
air  or  other  medium  which  produce  the  sen- 
sation of  sound. 

Sound.— (Subjectively.)  The  effect  pro- 
duced on  the  ear  by  a  vibrating  body. 

Sound,  Absorption  of Acoustic  ab- 
sorption.    (See  Absorption,  Acoustic?) 
Sound,    Characteristics    of The 

peculiarities  that  enable  different  musical 
sounds  to  be  distinguished  from  one  another. 

The  characteristics  of  musical  sounds  are: 

(i.)  The  Tone  or  Pitch,  according  to  which  a 
sound  is  either  grave  or  shrill. 

(2.)  The  Intensity  or  Loudness,  according  to 
which  a  sound  is  either  loud  or  feeble. 

(3.)  The  Quality  or  Timbre,  the  peculiarity 
which  enables  us  to  distinguish  between  two 
sounds  of  the  same  pitch  and  intensity,  but 
sounded  on  different  instruments,  as  for  example, 
on  a  flute  and  on  a  piano. 

Sound,  Quality  or  Timbre  of That 

peculiarity  of  a  musical  note  which  enables 
us  to  distinguish  it  from  another  musical  note 
of  the  same  tone  or  pitch,  and  of  the  same 
intensity  or  loudness,  but  sounded  on  another 
instrument. 

The  middle  C,  for  example,  of  a  pianoforte,  is 
readily  distinguishable  from  the  same  note  on  a 
flute,  or  on  a  violin ;  that  is  to  say,  its  quality  is 
different.  The  differences  in  the  quality  of  musi- 
cal sounds  are  caused  by  the  admixture  of  addi- 
tional sounds  called  overtones  which  are  always 
associated  with  any  musical  sound. 

Briefly,  nearly  all  so-called  simple  musical 
sounds  are  in  reality  chords  or  assemblages  of  a 
number  of  different  musical  sounds. 

In  the  case  of  the  many  different  notes  that  are 
present  in  an  apparently  simple  note  or  tone,  one 
of  the  notes  is  far  louder  than  all  the  others  and  is 
called  the  fundamental  tone  or  note,  and  is  what 
is  recognized  by  the  ear  as  the  note  proper.  The 
others  are  called  the  overtones.  The  overtones 
are  too  feeble  to  be  heard  very  distinctly,  but 
their  presence  gives  to  the  fundamental  note  its 
own  peculiar  quality.  In  the  case  of  a  note 
sounded  on  the  flute,  these  overtones  are  dif- 
ferent either  in  number  or  in  their  relative  intensi- 
ties from  the  same  note  sounded  on  another  instru- 


[Son. 


ment  Their  fundamental  tones,  however,  are 
the  same. 

The  peculiarities  which  enable  us  to  distinguish 
the  voice  of  one  speaker  or  singer  from  another 
are  due  to  the  presence  of  these  overtones.  The 
overtones  must  be  correctly  reproduced  by  the 
diaphragm  of  the  telephone,  or  phonograph, 
graphophone,  or  gramophone,  if  the  articulate 
speech  is  to  be  correctly  reproduced  wit'n  all  its 
characteristic  peculiarities. 

Sounder,  Morse  Telegraphic An 

electro-magnet  which  produces  audible 
sounds  by  the  movements  of  a  lever  attached 
to  the  armature  of  the  magnet. 

The  Morse  sounder  has  nrw  almost  entirely 
supplanted  the  paper  recorder  or  register.  On 
short  lines  it  is  placed  directly  in  the  telegraphic 
circuit.  On  long  lines  it  is  operated  by  a  local 
battery,  thrown  into  or  out  of  the  action  by  the 
relay.  (See  Relay.) 


Fig.  310.    Morse  Sounder. 

The  Morse  sounder,  shown  in  Fig.  510,  con- 
sists of  an  upright  electro-magnet  M,  whose  soft 
iron  armature  A,  is  rigidly  attached  to  the  striking 
lever  B,  working  in  adjustable  screw  pivots  as 
shown.  The  free  end  of  the  lever  is  limited  in  its 
strokes  by  two  set  screws  N,  N.  The  lower  of 
these  screws  is  set  so  as  to  limit  the  approach  of 
the  armature  A,  to  the  poles  of  the  electro-magnet; 
the  upper  screw  is  set  so  as  to  give  the  end  B, 
sufficient  play  to  produce  a  loud  sound.  A  re- 
tractile spring,  attached  to  the  striking  lever  near 
its  pivoted  end,  and  provided  with  regulating 
screw  S  S,  pulls  the  lever  back  when  the  current 
ceases  to  flow  through  M. 

The  dots  and  dashes  of  the  Morse  alphabet  are 
reproduced  by  the  sounder,  as  audible  signals, 
that  are  distinguished  by  the  operator  by  means 
of  the  different  sounds  produced  by  the  up  and 
down  stroke  of  the  lever  as  well  as  by  the  differ 


Sou.] 


483 


[Son. 


ence  in  the  intervals  of  time  between  the  succes- 
sive signals. 

Another  form  of  telegraphic  sounder,  similar 
in  its  general  construction  to  that  already  de- 
scribed, is  shown  in  Fig.  511. 


Fig.  511.    Telegraphic  Sounder. 

Sounder,  Repeating  --  A  telegraphic 
sounder  which  repeats  the  telegraphic  dis- 
patch into  another  circuit. 

Sounds,  Magnetic  --  Faint  clicks 
heard  on  the  magnetization  of  a  readily  mag- 
netizable substance. 

One  of  the  earlier  forms  of  Reis'  telephone, 
operated  by  means  of  a  rapid  succession  of  these 
faint  magnetic  sounds. 

Source,  Electric  --  Any  arrangement 
capable  of  maintaining  a  difference  of  poten- 
tial or  an  electromotive  force. 

The  following  are  the  more  important  electric 
sources,  arranged  according  to  the  character  of 
the  energy  which  is  converted  into  electric 
energy. 

ELECTRIC  SOURCES. 

1.  Voltaic  Cell  or  Primary 

Battery. 

2.  Charged  Storage  Cell  or 

Secondary  Battery. 

3.  Thermo  Cell  or  Thermo 

Battery. 

4.  Selenium  Cell   or   Sele- 

nium Battery. 

5.  Magneto  -  Electric    Ma-  ~| 

chine. 

6.  Dynamo-Electric       Ma- 

chine. 

7.  Frictional    Electric    Ma- 

chine. 

8.  Electrostatic      Induction 

Machine. 

9.  Magneto-Electric     Tele- 

phone Transmitter. 


Chemical  Poten- 
tial Energy. 


Radiant  Energy. 


Mechanical 
Energy. 


10.  Pyromagnetic  Generator. 

11.  Animal  or  Plant  ..........  Vital  Energy. 


Sources,  Multiple-Arc-Connected 

A  term  sometimes  applied  to  sources  connect- 
ed in  multiple.  (See  Sources,  Multiple-Con- 
nected?) 

Sources,  Multiple-Connected The 

connection  of  a  number  of  separate  sources 
so  as  to  form  a  single  source  by  joining  the 
positive  poles  of  all  the  separate  sources  to  a 
single  positive  lead  or  conductor,  and  all  the 
negative  poles  to  a  single  negative  lead  or 
conductor. 

The  multiple  connection  of  sources  results  in 
each  of  the  sources  discharging  its  current  into 
the  main  conductor  in  a  direction  parallel  to 
that  of  the  other  sources. 

The  electromotive  force  in  the  same  is  that  of 
any  single  source,  but  the  resistance  of  the  com- 
bined source  decreases  with  each  source  added. 
Supposing  the  resistance  of  each  source  be  the 
same,  then  if  ten  such  sources  are  connected  in 
multiple -arc,  the  resistance  of  the  combined  source 
is  but  one-tenth  the  resistance  of  a  single  source. 
(See  Circuit,  Multiple.') 

Sources  are  combined  in  multiple-arc  whenever 
the  current  furnished  by  the  separate  sources  is 
insufficient  to  properly  operate  the  electro-recep- 
tive or  translating  device  with  which  it  is  con- 
nected. 

Sources,  Multiple-Series-Connected 

— The  conection  of  a  number  of  separate 
sources  so  as  to  form  a  single  source  by  con- 
necting a  number  of  the  sources  in  groups 
in  series,  and  joining  these  groups  together 
in  multiple-arc. 

The  battery  of  sources  obtained  by  connecting 
a  number  of  separate  sources  in  multiple-series 
will  have  an  electromotive  force  equal  to  the 
sum  of  the  separate  electromotive  forces  of  the 
sources  connected  in  any  of  the  separate  series- 
connected  groups. 

The  current  produced  will  be  greater  in  propor- 
tion to  the  number  of  separate  groups  in  parallel. 
The  internal  resistance  will  be  increased  in  pro- 
portion  to  the  number  of  coils  in  series,  and  de- 
creased in  proportion  to  the  number  of  groups  in 
multiple-arc  or  parallel. 

Sources  are  connected  in  multiple-series  when 
both  the  electromotive  force  and  the  current  of 
any  single  source  are  insufficient  to  operate  the 
electro-receptive  or  translating  device.  (See 
Circuit^  Multiple- Series.} 


Sou.] 


484 


[Spa. 


Sources,  Parallel  •  Connected A 

term  sometimes  applied  to  multiple-connected 
sources.  (See  Sources,  Multiple-Connected^) 

Sources,  Series-Connected The 

connection  of  a  number  of  separate  electric 
sources  so  as  to  form  a  single  source,  in 
which  the  separate  sources  are  placed  in  a 
single  line  or  circuit  by  so  connecting  their  op- 
posite poles  that  the  current  produced  in  each 
passes  successively  through  each  of  the 
sources. 

The  series-connection  of  sources  results  in  an 
electromotive  force  equal  to  the  sum  of  the  sepa- 
rate electromotive  forces  produced  by  each 
source — that  is,  a  rise  of  potential  occurs  with  each 
source  added.  This  connection  increases  the  re- 
sistance of  the  circuit  by  the  amount  of  the  resist- 
ance of  each  source  introduced  into  the  circuit. 
The  value  of  the  resulting  current  depends  on  the 
total  electromotive  force  and  resistance  of  the 
series-connected  sources. 

Sources  are  connected  in  series  when  the 
electromotive  force  furnished  by  a  single  source 
is  insufficient  for  the  character  of  work  required 
to  be  done.  (See  Circuit ',  Series.) 

Sources,  Series-Multiple-Connected 

— The  connection  of  a  number  of  separate 
electric  sources,  so  as  to  form  a  single  source, 
in  which  the  separate  sources  are  connected 
in  a  number  of  separate  multiple  groups  or 
circuits,  and  these  groups  or  circuits  separ- 
ately connected  together  in  series.  (See  Cir- 
cuit, Series-Multiple.) 

Southern  Light. — A  name  sometimes  given 
to  the  Aurora  Australis.  (See  Aurora  Aus- 
tralis.) 

Space,  Clearance The  space  be- 
tween the  revolving  armature  of  a  dynamo- 
electric  machine,  or  electric  motor,  and  the 
polar  faces  of  the  pole  pieces, 

Space,  Dark,  Crookes' A  dark 

space  surrounding  the  negative  electrode  in  a 
rarefied  space  through  which  electric  dis- 
charges are  passing. 

Crookes'  dark  space  lies  immediately  between 
the  negative  electrode  and  its  glow  or  luminous 
discharge.  It  differs,  therefore,  from  Faraday's 
dark  space,  which  lies  between  the  luminous  dis- 
charges of  the  negative  and  positive  electrodes. 


The  radius  of  Crookes'  dark  space  increases 
with  the  degree  of  exhaustion.  It  varies  also 
with  the  character  of  the  residual  gas,  with  the 
temperature  of  the  negative  electrode,  and  some- 
what with  the  intensity  of  the  spark.  When  the 
vacuum  becomes  sufficiently  high,  the  dark  space 
fills  the  entire  tube  through  which  the  discharges 
are  passing. 

Crookes  has  found  that  in  the  case  of  substances 
that  become  phosphorescent  under  the  electric 
discharge,  phosphorescence  best  takes  place  when 
the  body  is  placed  on  the  boundary  of  the  dark 
space. 

Space,  Dark,  Faraday's The  gap 

in  the  continuity  of  the  luminous  discharges 
that  occurs  between  the  glow  of  the  positive 
and  negative  electrodes. 

Faraday's  dark  space  is  seen  in  a  partially  ex- 
hausted tube  through  which  the  discharges  of 
an  induction  coil  are  passing.  It  occurs  in  as 
low  a  vacuum  as  6  millimetres  of  mercury. 
As  the  vacuum  becomes  higher,  the  length  of  the 
dark  space  increases. 

Space,  Inter-Air A  term  some- 
times employed  for  the  air  space  between  the 
outer  surface  of  the  revolving  armature  of  a 
dynamo-electric  machine  and  the  adjacent 
faces  of  the  pole  pieces.  (See  Space,  Clear- 
ance.) 

Space,  Interferric A  term  some- 
times used  for  air  gap.  (See  Gap.  Air.) 

Span  Wire. — (See  Wire  Span.) 

Spark  Coil. — (See  Coil.  Spark) 

Spark  Gap. — (See  Gap,  Spark.) 

Spark,  Length  of The  length  of 

spark  that  passes  between  two  charged  con- 
ductors depends  : 

(I.)  On  the  difference  of  potential  between 
them. 

(2.)  On  the  character  of  the  gaseous  medium 
that  separates  the  two  conductors. 

(3.)  On  the  density  or  pressure  of  the  gaseous 
medium  between  the  conductors. 

Up  to  a  certain  pressure,  a  decrease  in  the 
density  causes  an  increase  in  the  length  of  the 
distance  the  spark  will  pass.  When  this  limit  is 
reached,  a  further  decrease  of  density  decreases 
the  length  of  spark.  A  high  vacuum  prevents 
the  passage  of  a  spark  even  under  great  differ- 
ences of  potential. 


Spa.] 


485 


[Spa. 


(4.)  On  the  kind  of  material  that  forms  the 
electrodes  between  which  the  charges  pass. 

(5.)  On  the  shape  of  the  charged  conductor. 

(6.)  On  the  direction  of  the  current. 

Sparks  from  the  prime  conductor  are  denser 
and  more  powerful  than  those  from  the  negative 
conductor. 

It  will  be  observed  that  the  length  of  the  spark 
practically  depends  mainly  on  two  circumstances, 
Ariz.,  on  the  differences  of  potential  of  the  oppo- 
site charges,  and  the  conducting  power  of  the 
medium  that  separates  the  two  bodies. 

Spark,  f -Shaped  — A  variety  of 

three-branched  spark  obtained  by  the  dis- 
charge of  a  Leyden  jar  through  a  peculiar 
form  of  induction  coil.  (See  Spark,  Three- 
Branched.} 

Spark,  Three-Branched A  pecu- 
liar form  of  branched  spark  obtained  by  the 
discharge  of  a  Leyden  jar  through  a  peculiar 
form  of  induction  coil. 

The  three- branched  spark  was  obtained  by 
Elihu  Thomson  by  the  use  of  the  following  appa- 
ratus: The  discharges  of  a  Leyden  jar,  charged  by 
a  Topler-Holtz  machine,  were  sent  through  an  in- 
duction coil,  the  primary  and  secondary  of  which 
L 


charged  from  a  Topler-Holtz  machine.  The 
discharge,  in  passing  from  the  knob  of  the  jar  to 
the  wire  L,  representing  the  line,  passed  by  the 


Fig.  312.    Apparatus  for  Three-Branched  Sparks. 
were  of  few  turns.     The  circuit  connections  were 
as  shown  in  Figs.  512  and  513,  and  the  apparatus- 
is  described  by  Thomson  as  follows: 

"A  double  coil  was  made,  Fig.  512,  in  which 
the  inner  turns  were  about  twelve  and  the  outer 
turns  twenty.  These  were  kept  separate  from  each 
other  and  a  branch  wire  taken  from  the  line  and 
slid  from  point  to  point  on  the  outer  wire  enabled 
the  effective  length  of  the  same  to  be  adjusted. 
The  inner  coil  was  connected  through  a  small 
spark  gap,  as  at  A,  to  the  outer  coating  of  a  Ley- 
den jar,  while  the  wire  L,  was  brought  near  the 
pole  of  the  jar,  which  was  continually  being 


Fig.  313.    Apparatus/or  Tand  Y  Shaped  Sparks. 

inner  coil.  When  a  certain  length  of  the  outer 
coil  was  employed,  only  a  very  short,  almost  im- 
perceptible spark  was  obtainable  at  a.  If  the 
balance  of  the  turns  were  disturbed  by  including 
more  or  less  than  the  proper  number  of  the  outer 
turns,  not  only  did  a  vigorous  spark  occur,  but 
the  gap  at  a,  could  be  quite  considerably  extended, 
in  accordance  with  the  amount  of  departure  taken 
from  the  proper  number  of  turns  required  to  pro- 
duce the  balance.  This  ex- 
periment indicates  that  it  is 
possible  to  make  a  selective 
path  for  the  Leyden  jar  dis- 
charge,  and  to  have  a  struc- 
ture  so  proportioned  that 
the  discharges  reaching  line 
will  pass  to  earth  without  F*£- 
tending  to  go  through  the  cir- 
cuit of  the  dynamo.  The  action  is  apparently 
due  to  a  balance  of  electromotive  forces  such 
that  the  discharge  which  tends  to  pass  from  the 
line  in  going  to  earth  induces  in  the  coil  con- 
nected to  the  dynamo  a  counter  electromotive 
force  which  nearly  wipes  out  the  potential  of  the 
discharge  before  it  reaches  the  dynamo.  This 
balance  of  inductive  effects  is  certainly  very  strik- 
ing, and  once  obtained,  it  is  disturbed,  as,  in  the 
experiments,  by  changing  the  relative  lengths  of 
the  coils  in  inductive  relation  through  so  small 
an  amount  as  an  inch  or  two. 

"  It  may  be  mentioned  here  that  some  curious 


Three- 
Branched  Sparks. 


Spa.] 


486 


[Spe. 


effects  of  spark  were  obtained  in  these  experi- 
ments. When  a  disturbance  of  the  balance  ex- 
ists and  a  spark  is  obtained  at  a,  the  character  of 
the  spark  is  different  from  that  of  the  Leyden  jar 
discharge.  It  appears  to  be  less  luminous,  the 
noise  less  sharp,  and  its  color  would  indicate  a 
greater  power  of  volatilizing  metal  and  perhaps  a 
greater  duration.  It  is  in  part,  no  doubt,  due  to 
a  current  local  to  the  coils  in  series  with  one  an- 
other. 

'•Another  curious  effect  was  the  production  of 
T-shaped  and  Y-s^aPe<^  sparks,  or  three- 
branched  sparks  (such  as  are  shown  in  Figs.  513 
and  5 14.)" 

"These  were  obtained  by  separating  the  elec- 
trodes at  A,  an  inch  and  a  half  or  thereabouts, 
and  bringing  the  third  eJectrode  from  the  outer 
coil  to  the  position  shown  in  Fig.  513.  The  dis- 
charges were  now  obtained  as  before  from  the 
charged  jar.  In  this  case  the  discharge  appears 
to  split  and  unite  in  air,  producing  the  curious 
shaped  sparks  shown.  It  would  seem  that  to  ob- 
tain these  effects— particularly  the  sparks  which 
were  three- branched  from  a  common  point  in  the 
centre  between  the  discharge  electrodes— the 
dielectric  air  must  break  down  simultaneously  be- 
tween the  three  electrodes.  It  would  easily  ex- 
plain the  T-shapes  to  assume  the  straight  part 
above  to  form  first,  and  the  cross  or  transverse 
spark  to  strike  from  the  side  of  this  spark  to  the 
third  electrode." 

Spark  Tube.— (See  Tube,  Spark,} 

Spark,  Wipe In  an  electric  gas- 
lighting  pendant  burner,  a  spark  obtained 
from  a  spark  coil  by  the  wiping  contact  of  a 
spring,  moved  by  the  pulling  of  the  pendant. 
(See  Burner,  Ratchet-Pendant,  Electric?) 

Spark,  Y-Shaped A  variety  of  three- 
branched  spark  obtained  by  the  discharge  of 
a  Leyden  jar  through  a  peculiar  form  of  induc- 
tion coil.  (See  Spark,  Three-Branched!) 

Sparking  Discharge. — (See  Discharge, 
Disruptive) 

Sparking  Distance.—  (See  Distance, 
Sparking!) 

Sparking,  Line  of  Least The  line 

on  a  commutator  cylinder  of  a  dynamo  con- 
necting the  points  of  contact  of  the  collecting 
brushes  where  the  sparking  is  a  minimum. 

In  some  forms  of  dynamos  the  line  of  least 


sparking  lies  parallel  to  the  lines  of  magnetic 
force  of  the  field. 

In  most  forms,  however,  it  is  at  right  angles  to 
such  lines.  The  exact  position  of  all  these  lines 
is  changed  by  the  angular  lead  of  the  brushes. 
(See  Lead,  Angle  of.) 

Sparking  of  Dynamo-Electric  Machine.— 

(See  Machine,  Dynamo-Electric,  Sparking 
of.) 

Spar  Torpedo.— (See  Torpedo,  Spar.) 

Spasmodic  Governor.— (See  Governor, 
Spasmodic) 

Speaking-Tube  Annunciator.— (See  An- 
nunciator, Oral  or  Speaking-  Tube) 

Speaking-Tube  Mouth  Piece,  Electric 

Alarm A  mouth  piece  for  a  speaking 

tube,  so  arranged,  that  the  movement  of  a 
pivoted  plate  covering  the  mouth  piece  au- 
tomatically rings  a  bell  at  the  other  end  of 
the  tube. 

Specific  Conduction  Resistance. — (See 
Resistance,  Specific  Conduction) 

Specific  Conductivity. (See  Conduc- 
tivity, Specific) 

Specific  Heat— (See  Heat,  Specific) 

Specific  Heat  of  Electricity.— (See  Elec- 
tricity, Specific  Heat  of) 

Specific  Hysteresial  Dissipation. — (See 
Dissipation,  Specific  Hysteresial.) 

Specific  Inductive  Capacity. — (See  Ca- 
pacity, Specific  Inductive) 

Specific  Magnetic  Capacity. — (See  Ca- 
pacity, Specific  Magnetic) 

Specific  Magnetic  Conductivity.— (See 
Conductivity,  Specific  Magnetic) 

Specific  Magnetic  Inductivitv.— (See  In- 
ductivity,  Specific  Magnetic) 

Specific  Resistance. — (See  Resistance, 
Specific) 

Specific  Resistance  of  Liquids.— (See 
Resistance,  Specific,  of  Liquids) 

Speech,  Articulate The  successive 

tones  of  the  human  voice  that  are  necessary 
to  produce  intelligible  words. 

The  phrase  articulate  speech  refers  to  the  join- 
ing or  articulation  of  the  successive  sounds  in- 
volved in  speech.  The  receiving  diaphragm  of  a 


Spe.J 


487 


[Spo. 


telephone  is  caused  to  reproduce  the  articulate 
speech  uttered  near  the  transmitting  diaphragm. 

Speed,  Critical,  of  Compound- Wound 

Dynamo The  speed  at  which  bath  the 

series  and  shunt  coils  of  the  machine  give  the 
same  difference  of  potential  when  the  full  load 
is  on  the  machine,  as  the  shunt  coil  would  if 
used  alone  on  open-circuit. 

Speed  Indicator. — (See  Indicator,  Speedy 

Speeding. — Varying  the  number  of  revolu- 
tions per  minute. 

The  speeding  of  a  dynamo  is  for  the  purpose 
of  obtaining  the  current  requisite  to  properly 
operate  the  electro  receptive  device  placed  in  its 
circuit. 

Spent  Acid.— (See  Acid,  Spent '.) 

Spent  Liquor. — (See  Liquor,  Spent.) 

Spherical  Armature. — (See  Armature, 
Spherical!) 

Sphygmogram. — A  record  made  by  a 
sphygmograph.  (See  Sphygmograph!) 

Sphygmograph. — An  instrument  for  re- 
cording the  peculiarities  of  the  normal  or 
abnormal  pulse. 

Sphygmograph,  Electrical An  in- 
strument for  electrically  recording  the  peculi- 
arities of  the  pulse. 

Sphygmophone. — An  apparatus  in  which 
a  microphone  is  employed  for  the  medical 
examination  of  the  pulse.  (See  Microphone.) 

Spider,  Armature A  light  frame- 
work or  skeleton  consisting  of  a  central  sleeve 
or  hub  keyed  to  the  armature  shaft,  and  pro- 
vided with  a  number  of  radial  spokes  or  arms 
for  fixing  or  holding  the  armature  core  to 
the  dynamo-electric  machine. 

Spider,  Driving Radial  arms  or 

spokes  connected  to  the  armature  of  a  dynamo- 
electric  machine  and  keyed  to  the  shaft  ,so  as 
to  act  as  a  driving  wheel  for  the  armature. 

Spin,  Magnetic A  term  sometimes 

employed  instead  of  magnetic  field. 

The  term  magnetic  spin  is  sometimes  used  in- 
stead of  magnetic  field  because  the  magnetism  is 
now  generally  believed  to  be  due  to  the  effects  of 
a  rotary  motion  or  spin  in  the  surrounding  uni- 
versal ether. 


Spiral,  Primary The  primary  of  an 

induction  coil  or  transformer.  (See  Trans- 
former. Coil,  Induction!) 

Spiral,  Boget's A  suspended  wire 

spiral  conveying  a  strong  electric  current  and 
devised  to  show  the  attractions  produced  by 
parallel  currents  flowing  in  the  same  direc- 
tion. 

The  lower  end  of  the  wire  spiral  dips  into  a 
mercury  cup.  On  the  passage  of  the  current,  the 
attraction  of  the  neighboring  turns  of  the  spiral 
for  each  other  shortens  the  length  of  the  spiral 
sufficiently  to  draw  it  out  of  the  mercury  and  thus 
break  the  circuit.  When  this  occurs  the  weight 
of  the  spiral  causes  it  to  fall  and  again  re-estab- 
lish the  circuit.  A  rapid  automatic-make-and- 
break  is  thus  established,  accompanied  by  a  brill- 
iant spark  at  the  mercury  surface  due  to  the  ex. 
tra  spark  on  breaking. 

Spiral,  Secondary The  secondary 

coil  of  an  induction  coil  or  transformer.  (See 
Transformer.  Coil,  Induction.) 

Splice  Box.— (See  Box,  Splice?) 
Split  Battery.— (See  Battery,  Split.) 
Split  Lead  Tee.— (See   Tee,  Split  Lead.) 
Spluttering  of  Arc. — (See  Arc ,  Splutter- 
ing of.) 

Spots,  Sun Dark  spots,  varying  in 

number  and  position,  which  appear  on  the 
face  of  the  sun  and  are  believed  by  some  to  be 
caused  by  huge  vortex  motions  in  the  masses 
of  glowing  gas  that  surround  the  sun's  body. 

Sun  spots  occur  in  greater  number  at  intervals 
of  about  every  eleven  years. 

Their  occurrence  is  generally  attended  with 
unusual  terrestrial  magnetic  variations.  (See 
Storm,  Magnetic.) 

In  the  opinion  of  most  astronomers  the  sun 
spots  mark  depressions  in  the  atmosphere  of  the 
sun.  Their  exact  causes  are  unknown,  though 
they  appear  to  be  dependent  on  a  local  cooling 
or  condensation  of  the  sun's  atmosphere. 

When  observed  through  a  telescope  the  sun 
spot  appears  as  a  dark  region  surrounded  by  a 
less  dark  region.  Though  darker  by  contrast 
with  thi  rest  of  the  sun's  face,  yet  such  spots  are 
in  reality  much  brighter  than  the  most  brilliant 
arc  light.  The  outline  of  the  sun  spot  is  quite 
irregular. 


Spr.J 


488 


[Sla. 


Spreading-Out  Magnetic  Field. — (See 
Field,  Magnetic,  Spreading-Out?) 

Sprengel  Mercury  Pump. — (See  Pump, 
Air,  SprengeFs  Mercurial?) 

Spring  Ammeter.  —  (See  Ammeter, 
Spring?) 

Spring  Contact. — (See  Contact,  Spring?) 

Spring,  Hold-Off A  spring  which 

acts  to  keep  one  thing  away  from  another  in 
opposition  to  some  force  tending  to  keep  it  in 
contact  with  such  a  thing. 

Spring,  Hold-On A  spring  which 

acts  to  keep  one  thing  against  another  in  op- 
position to  some  force  tending  to  pull  it 
away. 

A  hold  on  spring  is  sometimes  employed  in  a 
dynamo-electric  machine  for  the  purpose  of  keep- 
ing the  collecting  brushes  in  proper  pressure 
against  the  segments  of  the  commutator. 

Spring-Jack. — A  device  for  readily  insert- 
ing a  loop  in  a  main  electric  circuit.  The 
spring-jack  is  generally  used  in  connection 
with  a  multiple  switch  board.  (See  Board, 
Multiple  Switch.) 

Spring-Jack  Cut-Out — (See  Cut-Out, 
Spring-Jack.) 

Spurious  Hall  Effect.— (See  Effect,  Hall, 

Spurious?) 

Spurious  Resistance. — (See  Resistance, 
Spurious?) 

Stabile  Galvanization. — (See  Galvaniza- 
tion, Stabile?) 

Staggering. — A  term  sometimes  applied  to 
the  position  of  the  brushes  on  a  commutator 
cylinder,  in  which  one  brush  is  placed  slightly 
in  advance  of  the  other  brush  so  as  to  bridge 
over  a  break. 

When  a  break  occurs  in  the  circuit  ot  the  arma- 
ture wires,  the  device  of  staggering  the  brushes  is 
adopted  for  temporarily  bridging  over  the  break. 
When  a  break  occurs,  the  rewinding  of  the  arma- 
ture is  the  only  radical  cure. 

Standard  Candle. — (See  Candle,  Stand- 
ard?) 


Standard  Carcel  Gas  Jet— (See  Jet,  Gas, 
Carcel  Standard?) 

Standard,  Dynamo The  supports 

for  tha  bearings  of  a  dynamo-electric  ma- 
chine. .  . 

Standard  Earth  Quadrant — (See  Quad- 
rant, Standard?) 

Standard  of   Self-Induction,  Ayrton  & 

Perry's (See  Induction,  Self,  Ayrton 

&*>  Perry's  Standard  of.) 

Standard  Ohm.— (See  Okm,  Standard?) 

Standard,  Pentane A  standard 

source  of  light  used  in  photometric  measure- 
ments, in  place  of  a  Methven  screen. 

The  pentane  standard  is  constructed  in  general 
in  the  same  manner  as  the  Methven  standard. 
In  place,  however,  of  ordinary  coal  gas,  a  mixture 
of  pentane  and  air  is  used.  Pentane  is  a  variety 
of  coal  oil  left  after  several  distillations  of  ordinary 
crude  oil.  It  distills  at  a  temperature  not  greater 
than  50  degrees  centigrade. 

The  mixture  for  burning  consists  of  about 
twenty  volumes  of  air  to  seven  volumes  of  pen- 
tane. A  burner  of  the  pentane  standard  is  some- 
what similar  to  the  Methven  standard,  but  differs 
in  a  number  of  minor  details. 

Standard    Resistance    Coil.— (See    Coil, 
Resistance,  Standard?) 
Standard  Size  of  Electrodes,  Erb's 

— (See  Electrodes,  ErVs  Standard  Size  of.) 

Standard  Voltaic  Cell.— (See  Cell,  Voltaic, 
Standard.} 
Standard  Voltaic  Cell,  Clark's 

(See  Cell,  Voltaic,  Standard,  Clark's.) 

Standard  Voltaic  Cell,  Clark's,  Raj  leigh's 
Form  of (See  Cell,  Voltaic.  Stand- 
ard, Ray  leigh's  Form  of  Clark's?) 

Standard  Voltaic  Cell,  Fleming's  — 
(See  Cell,  Voltaic,  Standard,  Fleming's.) 

Standard   Voltaic   Cell,  Lodge's 

(See  Cell,  Voltaic,  Standard,  Lodges.) 

Standard  Voltaic  Cell,  Sir  William 
Thomson's (See  Cell,  Voltaic,  Stand- 
ard, Sir  William  Thomson's.) 

Standard  Wire  Gauge.— (See  Gauge, 
Wire,  Standard.) 


Sta.] 


489 


[Sta. 


Standardizing  a  Yoltaic  Cell.— (See  Cell, 
Voltaic,  Standardizing  a.) 

Standards,  Motor  —  —A  name  applied 
to  the  supports  for  the  bearings  of  an  electric 
motor. 

State,  Allotropic A  modification 

of  a  substance,  in  which,  without  changing 
its  chemical  composition,  it  assumes  a  condi- 
tion in  which  many  of  its  physical  and  chem- 
ical properties  are  different  from  those  it  or- 
dinarily possesses. 

Thus  the  element  carbon  occurs  in  three  widely 
different  allotropic  states,  viz. : 

(i.)  As  charcoal,  or  ordinary  carbon; 

(2.)  As  graphite,  or  plumbago;  and 

(3.)  As  the  diamond. 

State,  Anelectrotonic The  condi- 
tion of  decreased  functional  activity  which 
occurs  in  a  nerve  in  the  neighborhood  of  the 
anode  or  positive  terminal  of  a  source  to 
whose  influence  it  is  subjected.  (See  Anelec- 
trotonus^} 

State,  Electrotonic  — A  peculiar 

state  supposed  by  Faraday  to  exist  in  a  wire  or 
other  conductor,  whereby  differences  of  po- 
tential are  produced  by  means  of  its  move- 
ment through  a  magnetic  field. 

In  his  early  researches  Faraday  regarded  this 
state  as  a  necessary  condition  in  which  a  wire  or 
conductor  must  exist,  prior  to  its  movement 
through  a  magnetic  field,  in  orde  to  have  a  dif- 
ference of  potential  produced;  but  at  a  later  day 
he  abandoned  this  idea,  and  explained  the  true 
causes  of  electrodynamic  induction.  (See  In- 
duction, Electro- Dynamic.) 

The  term  electrotonic  state  is  to  be  carefully  dis- 
tinguished from  electrotonus,  or  the  change  pro- 
duced in  the  functional  activity  of  a  nerve  by  an 
electric  current.  (See  Electrotonus. ) 

State,  Kathelectrotonic The  con- 
dition of  increased  functional  activity  of  a 
nerve  in  the  neighborhood  of  the  kathode  or 
negative  terminal  of  a  source  to  whose  in- 
fluence it  is  subjected.  (See  Kathelectro- 
tonus.} 

The  kathelectrotonic  state  is  one  of  the  states 
or  conditions  of  electrotonus  or  altered  functional 
activity  produced  in  a  nerve  by  an  electric  cur- 
rent. (See  Electrotonus, } 


State,    Nascent  —A  term  used  in 

chemistry  to  express  the  state  or  condition  of 
an  elementary  atom  or  radical  just  liberated 
from  chemical  combination,  when  it  possesses 
chemical  affinities  or  attractions  more  ener- 
getic than  afterwards. 

According  to  Grothiiss'  hypothesis,  during  the 
decomposition  of  a  chain  of  polarized  molecules, 
such  for  example  as  in  the  case  of  hydrogen  sul- 
phate, Hs  SO4,  in  a  zinc-copper  voltaic  cell,  the 
two  atoms  of  hydrogen  Hg,  liberated  by  the  com- 
bination of  the  SO4,  with  an  atom  of  zinc,  Zn,  pos- 
sess a  stronger  affinity  for  the  SO4  of  the  molecule 
next  to  it,  than  does  its  own  H2,  and  thus  liber- 
ates its  two  atoms  of  hydrogen,  which  in  turn 
unite  with  the  SO4,  of  the  next  molecule  in  the 
polarized  chain,  and  this  continues  until  the  two 
atoms  of  hydrogen  liberated  from  the  last  mole- 
cule in  the  chain  are  given  off  at  the  copper  plate. 
(See  Hypothesis,  Grothitss'.) 

The  peculiar  properties  characteristic  of  the 
nascent  state  of  elements  is  doubtless  due  to 
the  fact  that  the  elements  are  then  in  a.  free 
state,  with  their  bonds  open  or  unsatisfied,  and 
therefore  possess  greater  affinities  than  when  they 
are  united  in  molecules.  Thus  H — ,  H — ,  or 
atomic  hydrogen,  should  possess  different  affinities 
than  H— H,  or  molecular  hydrogen. 


State,  Passive 


— The  condition  of  a 


metallic  substance  in  which  it  may  be  placed 
in  liquids  that  would  ordinarily  chemically 
combine  with  it,  without  being  attacked  or 
corroded. 

It  is  very  doubtful  whether  metallic  bodies  can 
be  properly  regarded  as  possessing  an  actual 
passive  state.  Iron,  for  example,  which  is  one  of 
the  metals  that  is  said  to  be  capable  of  assuming 
this  so-called  passive  state,  can  be  placed  in  this 
condition  by  immersing  it  for  a  few  moments  in 
concentrated  nitric  acid,  and  subsequently  wash- 
ing it.  It  will  then,  unlike  ordinary  iron,  neither 
be  attacked  by  concentrated  nitric  acid,  nor  will 
it  precipitate  copper  from  its  solutions.  This 
condition  is  now  generally  believed  to  be  due  to 
the  formation  of  a  thin  coating  of  magnetic  oxide 
on  its  surface. 

Many  of  the  instances  of  the  so-called  passive 
state  are  simply  cases  of  the  well  known  electrical 
preservation  of  metals  that  form  the  negative 
element  of  a  voltaic  combination,  under  which 
circumstances  the  positive  element  only  of  the 


Sta.J 


490 


[Ste 


voltaic  couple  is  chemically  attacked  by  the  elec- 
trolyte. (See  Cell,  Voltaic.  Metals,  Electrical 
Protection  of. ) 

State,  Permanent,  of  Charge  on  Tele- 
graph Line The  condition  of  the 

charge  on  a  telegraph  wire  when  the  current 
reaching  the  distant  end  has  the  same 
strength  as  at  the  sending  end. 

State,  Variable,  of  Charge  of  Telegraph 

Line The  condition  of  the  charge  on 

a  telegraph  wire  while  the  strength  of  the 
current  is  increasing  up  to  the  full  strength 
in  all  parts. 

The  duration  of  the  variable  state  is  directly  as 
the  length  of  the  line,  the  electrostatic  capacity 
and  the  total  resistance.  It  is  increased  by  leak- 
age, by  static  capacity  and  by  the  effects  of  the 
extra  current.  (See  Currents,  Extra.} 

Static  Breeze. — (See  Breeze,  Static.) 

Static  Electricity.  —  (See  Electricity, 
Static) 

Static  Energy. — (See  Energy,  Static) 

Static  Hysteresis.  —  (See  Hysteresis, 
Static) 

Static  Insulation.  —  (See  Insulation, 
Static) 

Static  Magnetic  Induction. — (See  Induc- 
tion, Magnetic,  Static) 

Static  Shock.— (See  Shock,  Static) 

Statics. — The  science  which  treats  of  the 
relations  that  must  exist  between  the  points 
of  application  of  forces  and  their  direction 
and  intensity,  in  order  that  equilibrium  may 
result. 

Statics,   Electro That  branch    of 

electric  science  which  treats  of  the  phenome- 
na and  measurement  of  electric  charges. 

Some  of  the  more  important  principles  ot  elec- 
trostatics are  embraced  in  the  following  laws: 

(l.)  Charges  of  like  name,  i.  e.,  either  positive 
T  negative,  repel  each  other.     Charges  ot  unlike 
aame  attract  each  other. 

(2.)  The  forces  of  attraction  or  repulsion  be 
tween  two  charged  bodies  are  directly  propor- 
tional to  the  product  of  the  quantities  of  electricity 
possessed  by  the  bodies  and  inversely  proportional 
to  the  square  of  the  distance  between  them. 


These  laws  can  be  demonstrated  by  the  use  of 
Coulomb's  torsion  balance.  (See  Balance,  Cou- 
lomb'1 s  Torsion.) 

Statics,   Magneto That  branch  of 

magnetism  which  treats  of  magnetic  attrac- 
tions and  repulsions,  the  distribution  of  lines 
of  magnetic  force  and  other  facts  regarding 
fixed  magnets. 

Station,  Central A  station,  cen- 
trally located,  from  which  electricity  for  light 
or  power  is  distributed  by  a  series  of  con- 
ductors radiating  therefrom. 

Station,  Distant A  term  applied  by 

an  operator  to  the  distant  end  ot  the  line  in 
order  to  distinguish  it  from  his  own  end. 

Station,   Distributing A   station 

from  which  electricity  is  distributed. 
A  central  station. 

Station,  Home A  term  applied  by 

an  operator  to  his  end  of  the  line,  in  order  to 
distinguish  it  from  the  other  or  distant  sta- 
tion. 

Station,  Transforming In  a  system 

of  distribution  by  transformers  or  converters 
a  station  where  a  number  of  transformers  are 
placed,  in  order  to  supply  a  group  of  houses 
in  the  neighborhood.  (See  Transformer. 
Electricity,  Distribution  of,  by  Alternating 
Currents.) 

Stationary  Floor  Key. — (See  Key,  Sta- 
tionary Floor) 

Stationary  Torpedo. — (See  Torpedo,  Sta- 
tionary) 

Stay  Rods,  Telegraphic Metal  rods 

attached  to  a  telegraph  pole,  and  securely 
fastened  in  the  ground  in  order  to  counteract 
the  effects  of  a  pull  or  tension  on  the  poles. 
(See  Pole,  Telegraphic.} 

Stay  rods  should  be  used  in  all  exposed  situa 
tions,  or  where  the  poles  are  exposed  to  severe 
strains. 

Steady  Current. -^-(See  Current,  Steady.) 

Stearns'  Relay  Shunt. — (See  Shunt,  Re- 
lay, Stearns  ) 

Steel,  Qualities  of.  Requisite  for  Mag- 
netization   Qualities  which  must  be 


SteJ 


491 


[Sto. 


possessed  by  steel  in  order  to  permit  it  to  per- 
manently retain  a  considerable  magnetization. 

For  the  purposes  of  permanent  magnetization 
steel  should  possess  the  following  qualities: 

It  should  be  hard  and  fine  grained.  Hard  cast 
steel  answers  the  purpose  very  well.  Scoresby 
showed  that  an  intimate  relation  exists  between 
the  quality  of  the  iron  from  which  the  steel  is 
made,  and  the  ability  of  the  steel  to  take  and  re- 
tain considerable  magnetism. 

The  steel  should  be  hardened  as  high  as  possi- 
ble and  the  temper  afterwards  drawn  by  heat  to 
a  violet-straw  color.  Practice  is  not  uniform  in 
this  respect,  the  exact  color  varying  with  the 
quality  of  the  steel. 

An  admixture  with  the  steel  of  about  y^  of  one 
per  cent  of  tungsten  is  said  to  increase  its  mag- 
netic powers. 

Cast  steel  is  not  generally  employed  for  mag- 
nets, wrought  steel  being  generally  preferred. 

Step-by-Step,  or  Dial  Telegraphy.— (See 

Telegraphy,  Step-by- Step?) 

Step-Down  Transformer. — (See  Trans- 
former, Step-Down?) 

Step-Up  Transformer. — (See  Transform- 
er, Step-Up) 

Sterilization,  Electric Sterilizing 

a  solution  by  depriving  it  of  whatever  germs 
it  may  contain  by  means  of  electrical  cur- 
rents. 

The  following  experiments  were  recently  made 
on  sterilization  by  means  of  electric  currents: 
The  fluid,  with  the  culture,  was  placed  in  a  glass 
test  tube,  wound  about  with  a  wire  coil  connected 
either  with  a  dynamo  or  accumulator  or  other 
electric  source.  Some  increase  in  temperature 
ras  made,  but  never  over  98°  Fahr.  When  a 
Current  1.25  volts,  2.5  amperes  passed,  a  com- 
plete sterilization  of  Micrococus  Prodigiosus  oc- 
curred at  the  end  of  twenty-four  hours. 

Blood  and  water  containing  pathogenic  germs 
was  sterilized  in  five  to  thirty  minutes.  The 
above  described  effects  would  appear  to  be  mag- 
netic rather  than  electric. 

Sticking. — A  word  applied  by  telegraphers 
to  the  failure  of  the  positive  pole  relay  arma- 
ture to  leave  the  magnet  pole  on  the  cessation 
of  the  current. 

In  telegraphy,  when  from  any  cause  a  circuit 
is  imperfectly  broken  by  an  operator's  key,  or  at 


the  points  of  contact  of  a  relay  or  other  instru- 
ment, such  failure  is  called  sticking.  When  an  arc 
is  formed  at  the  points  of  a  relay  where  the  local 
circuit  is  made  and  broken,  the  relay  "sticks." 
The  arc  is  caused  by  burning  of  the  platinum 
points.  Sticking  may  be  a  result  of  a  too  weak 
retractile  spring. 

Stone,  Hercnles A  name  given  by 

the  ancients  to  the  lodestone.  (See  Lode- 
stone?) 

Stool,  Insulating A  stool  provided 

with  insulating  supports  of  vulcanite  or  other 
insulator,  employed  to  afford  a  ready  insulat- 
ing stand  or  support. 

Stop,  Limiting A  stop  set  so  as  to 

limit  the  motion  of  an  electrically  vibrating  or 
oscillating  bar  to  any  predetermined  extent. 

Such  limiting  stops  are  common  on  telegraphic 
and  various  other  electrical  apparatus. 

Stopping-Off. — A  process  employed  in 
electro-plating,  in  which  a  metallic  article,  al- 
ready electro-plated  over  its  entire  surface,  is 
electro-plated  with  another  metal  over  certain 
parts  only. 

The  process  of  stopping-off  consists  of  covering 
the  parts  which  are  to  receive  the  metallic  coat- 
ing, with  various  stopping-off  varnishes.  By  this 
means  articles  can  be  electro-plated  on  \  arts  of 
their  surfaces  with  gold  and  on  the  remainder 
with  silver.  The  whole  surface  is  first  silvered 
and  the  portions  intended  to  be  afterwards  gilded 
are  then  stopped  off  and  the  object  placed  in  the 
gilding  bath. 

Stopping-Off    Varnish. — (See     Varnish, 

Stopping-Off.} 

Storage  Battery. — (See  Battery,  Storage?) 
Storage  Capacity  of  Secondary  Cell. — 

(See  Cell,  Secondary  or  Storage,  Capacity 

of?) 

Storage  Cell.— (See  Cell,  Storage?) 
Storage  of  Electricity. — (See  Electricity, 

Storage  of?) 

Storm,  Auroral A  term  sometimes 

employed  to  express  an  unusual  prevalence 
of  auroras. 

Storm,  Electric An  unusual  con- 
dition of  the  atmosphere  as  regards  the  quan- 
tity of  its  free  electricity. 


Sto.j 


492 


[Str. 


A  thunder  storm  is  a  variety  of  electric  storm. 
(See  Storm.  Thunder.} 

Storm,  Magnetic  —Irregularities  oc- 
curring in  the  distribution  of  the  earth's 
magnetism,  affecting  the  magnetic  declina- 
tion, dip,  and  intensity. 

Magnetic  storms  have  been  observed  to  accom- 
pany auroral  displays,  and  to  be  coincident  with 
the  occurrence  of  sun  spots,  or  unusual  outbursts 
of  solar  activity. 

The  coincidence  of  magnetic  storms  and  out- 
bursts of  solar  activity  is  unquestioned.  Wolf, 
of  Zurich,  has  shown  by  a  comparison  of  nu- 
merous observations  of  sun  spots,  the  unques- 
tioned correspondence,  in  the  times  of  their 
greatest  activity,  which  occur  every  n.i  years, 
with  the  time  of  occurrence  of  an  unusual  number 
of  sun  spots.  He  has  placed  these  results  in  the 
form  of  curves.  Those  shown  in  Fig.  515  are 
taken  from  observations  at  Paris  and  Prague. 
The  full  lines  represent  the  periods  of  sun  spots. 
The  dotted  lines  the  periods  of  magnetic  storms. 


Fig.  SfS-     Wolfs  Sun  Spot  Numbers. 

Storm,  Thunder A  storm  during 

which  electrical  discharges  accompanied  by 
thunder  take  place  between  two  clouds  or  be- 
tween a  cloud  and  the  earth.  (See  Elec- 
tricity. Atmospheric.  Storms,  Thunder, 
Geographical  Distribution  of.) 

Storms,  Thunder,  Geographical  Dis- 
tribution of The  following  general 

facts  as  to  the  geographical  distribution  of 
thunder  storms,  show  the  intimate  relation 
between  the  trequency  of  thunder  storms  and 
the  time  and  place  of  the  condensation  of 
vapor. 

(i.)  Thunder  storms  seldom,  if  ever,  occur  in 
the  polar  regions. 

This  is  probably  because  the   rainfall   in  the 


polar  regions  results  from  the  condensation  of  the 
vapor  that  was  formed  in  the  equatorial  or  tem- 
perate regions,  so  that  a  considerable  time 
elapses  between  the  evaporation  and  condensa- 
tion. 

(2.)  Thunder  storms  seldom,  if  ever,  occur  in 
rainless  districts,  owing  probably  to  the  absence 
of  the  condensation  of  vapor. 

(3.)  Thunder  storms  are  most  frequent  and 
violent  in  the  equatorial  regions,  where  the  rain- 
fall results  from  the  condensation  of  the  vapor  by 
the  action  of  ascending  currents,  conveying  the 
vapor  almost  immediately  after  its  formation  into 
the  upper  and  colder  regions  of  the  atmosphere. 

(4.)  Thunder  storms  occur  in  regions  beyond 
the  tropics,  at  those  seasons  of  the  year  when  the 
rainfall  results  from  the  condensation  of  the  vapor 
shortly  after  the  time  of  its  formation,  viz.,  in  the 
temperate  zones  in  the  hotter  parts  of  the  year. 

Straight-Line  Trolley  Hanger. — (See 
Hanger,  Straight-Line  Trolley?) 

Straightaway  Bunched  Cable. — (See 
Cable,  Bunched,  Straightaway?) 

Strain,  Dielectric The  strained 

condition  in  which  the  glass,  or  other  dielec- 
tric of  a  condenser,  is  placed  by  the  charging 
of  the  condenser. 

The  deformation  of  a  body  under  the  in- 
fluence of  a  stress.  (See  Stress.) 

The  stress  in  this  case,  *'.  e.,  the  force  produc- 
ing the  deformation  or  strain,  is  the  attraction  of 
the  opposite  charges.  This  stress,  in  the  case  of 
a  Ley  den  jar,  is  often  sufficiently  great  to  cause 
a  rupture  of  the  glass. 

Strain,  Electro-Magnetic —  The  de- 
formation produced  by  an  electro-magnetic 
stress.  (See  Stress^  Electro-Magnetic.) 

Strain,  Electrostatic,  Optical A 

strain  or  deformation  produced  in  a  plate  of 
glass,  or  other  transparent  solid,  by  subject- 
ing it  to  the  stress  of  an  electrostatic  field. 
(See  Stress,  Electrostatic.) 

To  obtain  the  electrostatic  stress,  holes  are 
drilled  in  the  plate  of  glass,  and  wires  from  a 
Holtz  machine  or  induction  coil  placed  therein, 
the  wires  being  separated  by  a  thin  layer  of  glass. 

The  glass,  on  being  traversed  by  a  beam  of 
plane  polarized  light,  rotates  the  plane  of  polar- 
ization of  the  light  in  the  same  direction  as  the 
glass  would  if  subjected  to  a  strain  in  the  direc 


Str.] 


493 


[Str. 


tion  of  the  lines  of  electric  force.  (See  Rotation, 
Magneto-  Optic. ) 

Strain,  Magnetic The  deformation 

produced  in  the  air-gap  between  two  dissimi- 
lar magnetic  poles,  or  in  any  substance  placed 
therein,  by  the  stress  of  the  lines  of  magnetic 
force  bridging  such  gap. 

Strain,  Optical A  deformation  or 

alteration  of  volume  produced  in  a  plate  of 
glass,  or  other  transparent  medium,  by  the 
action  of  any  stress.  (See  Strain,  Electro- 
Magnetic.  Strain,  Electrostatic,  Optical?) 

Strain,  Optical  Electro-Magnetic 

A  strain  produced  in  a  plate  of  glass  or  other 
transparent  medium  by  placing  it  in  a  mag- 
netic field.  (See  Stress,  Electro-Magnetic. 
Rotation,  Magneto-Optic?] 

Optical  strain,  whether  electrostatic  or  mag- 
netic, or  even  mechanical,  often  causes  a  medium 
to  acquire  the  power  of  double  refraction  or  ro- 
tary polarization.  (See  Refraction,  Double, 
Electric.  Rotation,  Magneto-Optic.) 

Stranded    Core    of    Cable.— (See    Core, 

Stranded,  of  Cable?) 

Stranded  Line.— (See  Line,  Stranded?) 
Strap  Copper.— (See  Copper,  Strap?) 
Straps  and  Climbers. — Devices  employed 

by  linemen  for  climbing  wooden   telegraph 

poles. 

Stratham's  Electric  Fuse.— (See  Fuse, 
Electric,  Stratham's?) 

Stratification  Tube.— (See  Tube,  Stratifi- 
cation?) 

Stratified  Discharge. — (See  Discharge, 
Stratified.) 

Stray  Field.— (See  Field,  Magnetic, 
Stray.) 

Stray  Power. — (See  Power,  Stray?) 
Stream-Lines  of  au  Escaping  Fluid. — 

Lines  which  show  the  actual  path  of  the 
particles  of  an  escaping  fluid. 

When  the  escape  has  reached  a  steady  condi- 
tion, the  stream-lines  correspond  to  the  flow  lines. 

Streamers.— Pillars  or  parallel  flashing 
columns  of  light  frequently  seen  during  the 
prevalence  of  an  aurora.  (See  Aurora  Bo- 
realis.) 


Streamers,  Auroral A  term  some- 
times applied  to  the  flashing  columns  or  pillars 
of  light  that  are  thrown  out  in  the  shape  of 
streams,  from  portions  of  the  sky  during  the 
prevalence  of  an  aurora.  (See  Aurora  Bo- 
realis.) 

Streaming  Discharge. — (See  Discharge, 
Streaming?) 

Streamlets,  Current A  theoretical 

conception  of  a  series  of  parallel  current 
streams  or  current  filaments,  flowing  through 
a  solid  conductor. 

In  the  case  of  uniform  distribution  of  an  elec- 
tric current  where  the  current  density  is  the  same 
for  all  areas  of  cross- section,  these  current  stream- 
lets are  all  of  the  same  strength. 

In  the  case  of  rapidly  alternating  currents, 
however,  the  current  streamlets  are  of  greater 
strength  near  the  surface.  When  the  rate  of  al- 
ternation is  sufficiently  great,  they  are  almost 
entirely  absent  at  the  central  parts. 

The  conception  of  current  streamlets  is  made 
in  order  to  account  for  the  increase  in  the  resist- 
ance of  a  solid  conductor  through  which  rapidly 
alternating  currents  of  electricity  are  passing. 
(See  Currents,  Simple-Periodic.) 

Streams,  Convection  —  — Streams  of 
electrified  air  or  other  gaseous  or  vaporous 
particles  given  off  from  the  pointed  ends  of 
charged,  insulated  conductors.  (See  Con- 
vection, Electric?) 

Street  Mains.— (See  Main,  Street.) 
Street  Service.— (See  Service,  Street?) 

Strength,  Field The  intensity  or 

total  flux  of  magnetism  of  a  dynamo. 

This  term  is  also  sometimes  roughly  used  for 
the  current  strength  in  the  field  magnet  circuit  of 
a  dynamo-electric  machine. 

Strength  of  Current.— (See  Current 
Strength?) 

Strength  of  Magnetic  Field.— (See  Field, 
Magnetic,  Strength  of.) 

Strength  of  Magnetism. — (See  Magnetism, 
Strength  of.) 

Stress.— The  pressure,  pull,  or  other  force 
producing  a  deformation  or  strain. 


Str. 


494 


[Sub. 


Stress,  Dielectric The  force  pro- 
ducing the  deformation  or  strain  in  a  dielec- 
tric. 

A  dielectric  strain,  in  the  case  of  a  Leyden  jar 
or  condenser,  is  sometimes  sufficiently  great  to 
pierce  the  dielectric. 

Stress,  Electro-Magnetic The  force 

or  pressure  in  a  magnetic  field,  which  produces 
a  strain  or  deformation  in  a  piece  of  glass .  or 
other  similar  substance  placed  therein.  (See 
Strain,  Optical  Electro-Magnetic) 

Stress,  Electrostatic The  force  or 

pressure  in  an  electrostatic  field,  which  pro- 
duces strain  or  deformation  in  a  piece  of  glass 
or  other  substance  placed  therein.  (See 
Strain,  Electrostatic,  Optical.) 

Stress,  Energy  of — A  term  some- 
times used  in  place  of  potential  energy.  (See 
Energy,  Potential.) 

Stress,  Magnetic The  force  acting 

to  produce  a  strain  in  the  air-gap  between 
two  dissimilar  magnet  poles  by  the  action  of 
the  lines  of  magnetic  force,  bridging  such  air 

gap- 

Striae,  Electric Parallel  streaked 

bands,  consisting  of  alternate  light  and  dark 
spaces,  produced  in  tubes  containing  low 
vacua,  by  the  passage  of  rapidly  alternating 
currents  through  them.  (See  Tube,  Strati- 
fication.) 

Strip,  Safety A  strip  or  bar  used  as 

a  safety  fuse.     (See  Fuse,  Safety.) 

Stripping. — Dissolving  the  metal  coating 
from  a  silver-plated  or  othe'r  metal-plated  ar- 
ticle. 

The  object  of  the  "stripping  "  process  is  tore- 
cover  silver  from  imperfectly  plated  ware,  or 
from  old  ware  which  is  to  be  replated. 

Stripping  of  silver  is  accomplished  either  in  the 
cold  or  by  aid  of  heat,  by  the  use  of  the  following 
solutions,  viz.: 
Concentrated  sulphuric  acid, 

(Baume',   66  degrees) ico  parts. 

Concentrated  nitric  acid, 

(Baume,  40  degrees). IO      " 

The  objects  are  suspended  in  this  liquid,  which, 
provided  it  be  not  diluted  with  water,  possesses 
the  property  of  dissolving  the  silver  without 
touching  the  metal  underneath. 


Stripping  Baths.— (See  Bath,  Strip- 
ping^ 

Stripping  Liquid. — (See  Liquid,  Strip- 
ping^ 

Stroke,  Lightning  — A  disruptive 

discharge  between  two  oppositely  charged 
clouds,  or  between  a  cloud  and  the  earth. 
(See  Discharge,  Disruptive!) 

Stroke,  Lightning,  Back  or  Return 

— An  electric  shock,  caused  by  an  induced 
charge,  produced  by  the  discharge  of  a  light- 
ning flash. 

The  shock  is  not  caused  by  the  lightning  flash 
itself,  but  by  a  charge  which  is  induced  in  neigh- 
boring conductors  by  the  discharge.  These  in- 
duced effects  are,  in  fact,  effects  of  electro-dy- 
namic induction.  (See  Induction,  Electro-Dy- 
namic.) A  similar  effect  may  be  noticed  by 
standing  near  the  conductor  of  a  powerful  electric 
machine,  when  shocks  are  felt  at  every  discharge. 

The  effects  of  the  return  shock  are  sometimes 
quite  severe.  These  effects  are  often  experienced 
by  sensitive  people  on  the  occurrence  of  a  light- 
ning discharge  at  a  considerable  distance. 

In  some  instances  the  return  stroke  has  been 
sufficiently  intense  to  cause  death.  In  general, 
however,  the  effects  are  much  less  severe  than 
those  of  the  direct  lightning  discharge. 

Struts  for  Telegraphic  Poles. — Inclined 
wooden  or  iron  poles,  applied  to  telegraph 
poles  in  order  to  support  the  thrust  or  press- 
ure acting  on  them.  (See  Pole,  Tele- 
graphic) 

Sturgeon's  or  Barlow's  Wheel. — A  wheel 
capable  of  rotation  on  a  horizontal  axis,  which, 
when  placed  between  the  poles  of  a  magnet, 
rotates  when  a  current  is  passed  through  it 
between  the  axis  and  the  circumference. 

Sub-Aqueous  Cable.— (See  Cable,  Sub- 
Ayueous.) 

Sub-Branch. — (See  Branch,  Sub.) 

Sub-Main.— (See  Main,  Sub) 

Submarine  Boat. — (See  Boat,  Sub- 
marine, Electric) 

Submarine  Cable. — (See  Cable,  Sub- 
marine.) 

Submarine  Mine. — (See  Mine,  Sub- 
marine.) 


Sab.] 


[Sur. 


Submarine     Telegraphy. — (See      Teleg- 
raphy, Submarined) 

Substance,    Ferro-Magnetic    — A 

term  proposed  in  place  of  paramagnetic,  for 
substances  that  are  magnetic  after  the  man- 
ner of  iron.  (See  Paramagnetic?) 

Subterranean    Mine.     (See  Mine,    Sub- 
terranean.} 


Subway,    Electric 


— An     accessible 


underground  way  or  passage  provided  for  the 
reception  of  electric  wires  or  cables. 

Underground  electric  conductors,  like  all  elec- 
tric conductors,  are  liable  to  faults,  crosses,  etc. 
Unless  they  are  readily  accessible,  very  serious 
loss  and  damage  may  occur  before  the  fault  is 
located  and  corrected. 

Sulphating. — A  name  applied  to  one  of  the 
sources  of  loss  in  the  operation  of  a  storage 
battery,  by  means  of  the  formation  of  a  coating 
of  inert  sulphate  of  lead  on  the  battery  plates. 

The  addition  of  a  solution  of  sulphate  of  soda 
to  the  sulphuric  acid  liquid  is  claimed  to  have  the 
effect  of  decreasing  the  extent  of  the  sulphating. 

Summer  Lightning. — (See  Lightning, 
Summer?) 

Sun  Spots.— (See  Spots,  Sun.} 

Sunstroke,  Electric,  or  Electric  Prostra- 
tion or  Insolation Physiological 

effects,  similar  to  those  produced  by  exposure 
to  the  sun,  experienced  by  those  exposed  for 
a  long  while  to  the  intense  light  and  heat  of 
the  voltaic  arc. 

Electric  sunstroke  is  sometimes  called  electric 
insolation,  or  electric  prostration. 

The  effects  of  electric  sunstroke  were  first 
noticed  by  Desprez  in  his  classic  experiments  on 
the  fusion  or  volatilization  of  carbon. 

On  undue  exposure  to  an  intense  electric  light 
the  eyes  are  irritated  and  the  skin  burned  as 
by  the  sun.  In  some  cases  it  is  claimed  that  the 
effects  of  sunstroke,  or  excessive  production  of 
heat,  as  in  true  insolation,  are  produced.  In  the 
applications  of  electricity  to  electric  furnaces, 
these  same  effects  have  been  noticed  in  an  inten- 
sified degree. 

From  some  recent  investigations  it  would  ap- 
pear that  these  effects  are  to  be  ascribed  to  the 
light  rather  than  to  the  heat. 


The  symptoms  are  as  follows:  Pain  in  the 
throat,  face  and  temples,  followed  by  a  coppery 
red  color  of  the  skin,  irritation  and  watering  of 
the  eyes,  when  the  symptoms  disappear.  The 
skin  peels  off  in  about  five  days. 

Superficial  Eddy  Currents.— (See  Cur- 
rents, Eddy,  Superficial.} 

Super-Saturation  of  Solution. — (See 
Solution,  Super-Saturation  of.} 

Supplement  of  Angle. — (See  Angle,  Sup- 
plement of.} 

Supply,  Unit  of,  Electrical A  unit, 

provisionally  adopted  in  England  by  the 
Board  of  Trade,  equal  to  1,000  amperes  flow- 
ing for  one  hour  under  an  electromotive  force 
of  one  volt. 

This  would,  of  course,  equal  1,000  watt-hours, 
and  would  be  the  same  as  100  amperes  flowing 
for  ten  hours  under  one  volt. 

One  unit  of  electrical  supply  is  equal  to  1.34 
actual  horse-power  expended  for  one  hour,  and 
will  feed  13. 4  Swan  lamps  of  21  candle-power  for 
one  hour.  It  is  equal  in  illuminating  power  in 
Swan  lamps  to  the  light  produced  by  loo  cubic 
feet  of  gas  consumed  in  twenty  14-candle  burners 
in  one  hour. 

The  unit  of  electrical  supply  is  called  a  "Board 
of  Trade  unit,"  a  B.  O.  T.  unit,  or  simply  a  bot. 
It  is  equal  to  one  kilo-watt  hour. 

Support,  Tripod  Roof  —  — A  support 
for  a  housetop  telegraphic  line. 

The  tripod  roof  support,  as  its  name  indicates, 
consists  of  a  three-legged  support  for  any  suitable 
insulator.  • 

A  common  form  is  shown  in  Fig.  516. 

Support,  Underground    Cable A 

support  provided  for  holding  a  cable  where 
it  passes  around  the  side  of  a  man-hole,  un- 
derground conduit,  or  other  similar  location. 


Surface,  Demarcation 


— The  surface 


at  which  a  demarcation  current  is  generated. 

The  surface  which  marks  the  point  of  in- 
jury in  a  muscle  or  nerve. 

Demarcation  currents  in  electro-therapeutics, 
are  currents  produced  in  injured  nerves  or 
muscles.  They  are  probably  due  to  the  chemical 
changes  that  take  place  between  the  injured  and 
the  uninjured  tissues.  The  demarcation  surface  is 


Sur.] 


496 


[Sur. 


the  surface  separating  parts  in  a  normal  condi- 
tion from  those  in  an  abnormal  condition. 

An  injury  to  a  muscle  or  nerve  causes  or  pro- 
duces at  such  surface  a  dying  substance  which  is 


Fig.  Jf6.     Tripod  Roof  Support. 

negative  to  the  uninjured,  normal  or  positive  sub- 
stance. Such  a  surface  results  in  a  demarcation 
current. 

Surface  Density. — (See  Density,  Surfaced) 

Surface,  Equipotential,  of  a  Conductor 
Through  Which  a  Current  is  Flowing  — 

— A  surface  described  within  the  mass  of  a 
conductor,  conveying  an  electric  current,  at 
points  perpendicular  to  the  direction  of  the 
flow,  all  possessing  the  same  potential. 

Surface,  Equipotential,  or  Level  Surface 
of  Escaping  Fluid A  surface  de- 
scribed within  the  mass  of  a  fluid  in  motion 
at  all  places  perpendicular  to  the  stream  lines 
passing  such  surface. 

Surface  Integral  of  Magnetic  Induction. 
— (See  Induction,  Magnetic,  Surface-Inte- 
gral of.) 

Surfaces,  Eqnipotential,  Electrostatic 

Surfaces,  all  the  points  of  which  are 

at  the  same  electric  potential.  (See  Poten- 
tial, Electric?) 


Electric  surfaces  perpendicular  to  the  lines 
of  electric  force  over  which  a  quantity  of 
electricity,  considered  as  being  concentrated 
at  a  point,  may  be  moved  without  doing 
work.  (See  Field,  Electrostatic.} 

Equipotential  surfaces  correspond  with  a  water 
level,  over  which  a  body  may  be  moved  horizon- 
tally without  doing  any  work  against  the  force  of 
gravity. 

In  the  case  of  the  charged  insulated  sphere, 
shown  in  Fig.  517,  the  equipotential  surfaces, 
represented  by  the  circles,  are  concentric. 


Fig.  317.    Equipotential  Surfaces. 

Surfaces,   Equipotential,  Magnetic  

— Surfaces  surrounding  the  poles  of  a  mag- 
net, or  system  of  magnets,  where  the  mag- 
netic potential  is  the  same.  (See  Potential, 
Magnetic?) 

Magnetic  equipotential  surfaces  extend  in  a 
direction  perpendicular  to  the  lines  of  magnetic 
force.  (See  Field,  Magnetic.) 

No  work  is  required  in  order  to  move  a  unit 
pole  over  equipotential  magnetic  surfaces,  be- 
cause in  so  doing  it  cuts  no  lines  of  magnetic 
force.  Work,  however,  is  done  when  the  motion 
is  from  one  equal  potential  surface  to  another. 

Equipotential  surfaces,  whether  electric  or  mag- 
netic, cannot  intersect  one  another,  since  their 
potential  is  the  same  at  all  points. 

Surfaces,  Isothermal Surfaces  con- 
necting points  in  a  body  which  have  the  same 
temperature. 

Surging  Discharge.— (See  Discharge, 
Surging.) 

Snrgings,  Electric Electric  oscilla- 
tions set  up  in  a  charged  conductor  that  is 
undergoing  rapid  discharge. 

These  surgings  produce  waves  in  the  surround- 
ing ether  that  travel  outwards  with  the  velocity  of 


Sns.] 


497 


[Sus. 


light.     (See  Electricity,  Hertz's   Theory  of  Elec- 
tro-Magnetic Radiations  or  Waves.} 

Susceptibility,  Magnetic  ---  The  ratio 
existing  between  the  induced  magnetization 
and  the  magnetic  force  producing  such  mag- 
netism, or  the  intensity  of  magnetism  divided 
by  the  magnetic  force. 

Susceptibility  relates  to  the  poles  produced  in  a 
body  by  a  magnetizing  force,  whereas  permea- 
bility refers  its  power  to  conduct  lines  of  force. 
When  the  inducing  field  has  unit  strength  oi 
magnetization,  the  magnetic  susceptibility  will 
measure  directly  the  strength  of  the  magnetiza- 
tion. 

When  a  bar  of  iron  is  placed  in  a  magnetic 
field,  it  is  threaded  by  the  lines  of  magnetic  force, 
and  thus  becomes  magnetized  by  induction.  This 
induction  will  necessarily  depend  both  on  the 
number  of  lines  of  force  in  the  magnetizing  field 
and  on  the  magnetic  permeability  of  the  magnet- 
ized body;  or,  in  other  words,  the  induction  is 
equal  to  the  product  of  the  intensity  of  the  mag- 
netizing field  and  the  magnetic  permeability  of 
the  body  in  which  the  induction  occurs. 

The  magnetic  susceptibility  is  sometimes  called 
the  Co-efficient  of  Magnetization;  calling  K,  the 
susceptibility,  H,  the  magnetizing  force,  and  I,  the 
intensity  of  the  resulting  magnetization;  then 

K=I. 
H 

The  magnetic  permeability  is  sometimes  called 
the  Co-efficient  of  Magnetic  Induction,  calling  #, 
the  permeability,  B,  the  magnetic  induction  and 
H,  the  magnetic  force  producing  the  induction  ; 
then 


Suspending  Wire  of  Aerial  Cable.—  (See 

Wire,  Suspending,  of  Atrz'al  Cable.) 

Suspension,  Bifllar  --  The  suspen- 
sion of  a  needle  by  two 
parallel  wires  or  fibres, 
as  distinguished  from 
a  suspension  by  a  sin- 
gle wire  or  fibre. 

A  bifilar  suspension  is 
shown  in  Fig  .518.     The 
two  threads,  a  b  and  a' 
b',  are  connected  to  the  Fif.jiS.    Bifilar 
needle  M  N,  so  as  to  per-  sitm- 

mit  it  to  hang  in  a  true  horizontal  position.     Any 


M            b 

\ 

j 

.    ffe 

&'          N 

twisting,  around  the  imaginary  axis  c  c',  causes 
the  lines  of  suspension,  ab  and  a'  b',  to  tend  to 
cross  one  another  and  so  shorten  the  axis  c  c' . 

Harris,  who  was  the  first  to  employ  the  bifilar 
suspension,  showed  that  the  reactive  force  im- 
parted to  the  suspension  threads  by  turning  the 
needle,  was: 

(i.)  Directly  proportional  to  the  distance  be- 
tween the  threads. 

(2.)  Inversely  as  their  lengths. 

(3.)  -Directly  proportional  to  the  weight  of  the 
suspended  body. 

(4.)  Proportional  to  the  angle  of  twist  or  torsion 
of  the  threads  on  each  other. 

Any  deflection  of  the  needle  shortens  the  verti- 
cal distance  between  the  points  of  support  and 
the  needle,  and  so  tends  to  lift  the  needle.  The 
motions  are  therefore  balanced  against  the  force 
of  gravity  instead  of  against  the  torsion  of  the 
fibre. 

Suspension,  Combined  Fibre  and  Spring 

The  suspension  of  a  needle  by  the 

combined  use  of  a  spiral  spring  and  a  single 
fibre. 

In  this  form  of  suspension  the  spring  is  intro- 
duced between  the  fibre  and  the  needle.  It  is 
valuable  for  marine  galvanometers  and  other  ap- 
paratus exposed  to  tilting  or  rolling  motions,  be- 
cause it  permits  the  instrument  to  be  tilted 
through  several  degrees  without  causing  any  con- 
siderable variation  in  the  deflections  produced  by 
the  current  or  the  charge. 

Suspension,  Fibre Suspension  of  a 

needle  by  means  of  a  fibre  of  unspun  silk  or 
other  material. 

A  fibre  suspension  generally  means  a  single 
fibre  or  thread.  It  may,  however,  be  applied  to 
a  bifilar  suspension.  (See  Suspension,  Bifilar.} 

A  fibre  suspension  is  to  be  preferred  to  a  pivot 
suspension,  since  it  eliminates  all  friction .  It  has, 
however,  the  disadvantage  of  necessitating  level- 
ing screws. 

Suspension,  Knife-Edge  —  —The  sus- 
pension of  a  needle  on  knife  edges  that  are 
supported  on  steel  or  agate  planes. 

A  suspension  of  this  kind  is  used  in  the  dip- 
ping needle,  since  it  permits  of  freedom  of  mo- 
tion in  a  single  vertical  plane  only. 

Suspension,  Pivot Suspension  of  a 

needle  by  means  of  a  jeweled  cup  and  a  me- 
tallic pivot. 


Swa.J 


498 


[Swi. 


The  jeweled  cup  is  placed  above  the  centre  of 
gravity  of  the  needle,  and  is  supported  on  a  steel 
point.  As  a  rule,  compass  needles  have  this 
variety  of  support. 

Swage. — A  particular  form  of  anvil  on 
which  highly  heated  metallic  plates  are  shaped 
by  hammering  them  into  forms  the  same  as 
that  of  the  anvil  on  which  they  are  placed. 

Swage. — To  fashion  heated  metallic  plates 
by  hammering  them  into  the  form  of  an,  anvil 
on  which  they  are  supported. 

Swaging. — Fashioning  highly  heated  me- 
tallic plates  into  any  desired  form  by  ham- 
mering while  on  suitable  dies.  • 

Swaging,  Electric The  forming  or 

shaping  of  metallic  plates  by  hammering 
them  against  suitable  anvils  or  dies  while 
softened  by  electrical  heating. 

The  electro-swaging  apparatus  consists  of  a 
welding  transformer  provided  with  a  movable 
clamp.  The  pressure  required  for  the  swaging 
is  attained  by  the  use  of  steam  admitted  into  a 
cylinder  by  a  lever  which  operates  a  four-way 
valve. 

The  rod,  bar,  or  plate  of  metal  to  be  shaped  or 
swaged,  is  first  heated  by  the  passage  of  a  pow- 
erful heating  current,  obtained  preferably  from  a 
welding  transformer,  one  of  the  clamps  of  which 
is  movable.  When  the  metal  is.suitably  softened 
by  the  passage  of  the  current,  it  is  then  subjected 
to  swaging. 

Swelling  Current.—  (See  Currents,  Swell- 
ing^ 

Swelling  Faradic  Current. — (See  Cur- 
rents, Swelling  JFaradtc.) 

Swinging  Annunciator. — (See  Annuncia- 
tor, Pendulum  or  Swinging.) 

Swinging  Cross. — (See  Cross,  Swinging 
or  Intermittent!) 

Switch,  Automatic,  for  Incandescent 

Electric  Lamps A  device  by  which 

incandescent  electric  lamps  can  be  lighted  or 
extinguished  at  a  distance  by  means  of  push 
buttons. 

The  automatic  switch  for  incandescent  lamps 
corresponds  in  electric  lighting  to  the  automatic 
gaslighting  device  in  systems  ot' electric  gaslight- 
ing.  It  consists  essentially  of  two  electro- 
magnets, one  for  turning  the  switch  which  lights 


the  lamp  by  cutting  them  into  the  circuit  of  the 
lighting  mains  or  conductors,  and  the  other  for 
extinguishing  them,  by  cutting  them  out.  These 
electro-magnets  are  operated  by  two  push  buttons, 
a  black  one  to  extinguish  the  lamp  and  a  white 
button  to  light  it. 

The  details  of  the  automatic  switch  are  shown  in 
Fig.  520.  The  mains  M1  andM2,  areconnected  to 
one  set  of  contacts,  and  the  branches  containing 


Fig,  519.    Automatic  Switch. 

the  lamps  to  be  lighted,  to  the  contacts  between 
them.  The  push  buttons,  P1  and  P2,  are  con- 
nected by  their  wires  to  the  main  M1  and  the 
branch  B*. 

These  buttons  are  made  respectively  positive 
and  negative,  and  are  marked  -f-  and  — .  The 
third  wire  of  the  push  button  is  connected  as 
shown  to  the  lamp  L,  and  the  switch  magnet, 
SM. 

When  the  contact  is  closed  atP1,  the  arma- 
ture of  S  M,  closes  the  contact  through  C. 
When  the  button  is  released,  connection  is  estab- 


Fig.  J2O.     Automatic  Switch. 

lished  between  the  magnet  and  the  lamp  L,  in 
series.  This  is  for  the  purpose  of  cutting  down 
the  circuit  to  the  ^  of  an  ampere,  and  thus  per- 
mitting a  thin  wire  to  serve  between  the  button 
and  the  switch  magnet. 

When  the  button,  P2,  is  closed  the  lamps  are 
turned  out. 

Switch  Board.— (See  Board,  Switch?) 

Switch  Board,     Multiple    — (See 

Board,  Multiple  Switch?) 


Swi.] 


499 


[Swi. 


Switch  Board,  Telegraphic  —(See 

Board,  Switch,  Telegraphic!) 

Switch  Board,    Trunking (See 

Board,  Switch,  Trunking?) 

Switch,    Break-Down A    special 

switch,  employed  in  small  three-wire  systems, 
for  connecting  the  positive  and  negative  bus- 
wires  in  such  a  manner  as  to  practically 
convert  it  into  a  two-wire  system  and  permit 
the  system  to  be  supplied  with  current  from 
a  single  dynamo.  (See  Wires,  Bus.} 

Switch,  Changing A  switch  de- 
signed to  throw  a  circuit  from  one  electric 
source  to  another. 

A  changing  switch,  for  example,  is  of  use  in 
disconnecting  a  circuit  from  one  dynamo  and 
connecting  it  to  another;  or,  in  other  words,  to 
suddenly  transfer  the  load  from  one  dynamo  to 
another. 

Switch,   Changing-Over A  term 

sometimes  applied  to  a  changing  switch. 
(See  Switch,  Changing!) 

Switch,  Distributing A   multiple 

switch  board.  (See  Board,  Multiple  Switch!) 

Switch,     Distributing,    for      Electric 

Lights A     switch    employed     in  a 

system  of  arc  lighting  by  series-distribu- 
tion, by  means  of  which  any  particular 
dynamo-electric  machine  or  a  number  of 


Fig.  J2T.    Double- Break  Knife  Switch. 

separate  dynamo-electric  machines  can 
be  connected  with  the  same  circuit  without 
interfering  with  the  lights.  (See  Board,  Mul- 
tiple Switch!) 

Switch,    Double-Break  — A  term 

sometimes  used  for  double-pole  switch.  (See 
Switch,  Double-Pole.) 


Switch,  Double-Break  Knife •  —A 

knife  switch  provided  with  double-break  con- 
tacts. 

A  double-break  knife  switch  is  shown  in  Fig. 
521- 

Switch,    Double-Pole A    switch 

that  makes  or  breaks  contact  with  both  poles 
of  the  circuit  in  which  it  is  placed. 

A  switch  consisting  of  a  combination  of 
two  separate  switches,  one  connected  to  the 
positive  lead  and  the  other  to  the  negative 
lead. 

Double-pole  switches  are  used  in  most  systems 
of  incandescent  lighting  in  order  to  insure  the 
thorough  separation  of  the  circuit  from  the  main 
conductor  or  leads  when  cut  out  and  to  diminish 
the  spark. 

Switch,  Feeder The  switch  em- 
ployed for  connecting  or  disconnecting  each 
conductor  of  a  feeder  from  the  bus-bars  in  a 
central  station. 

Switch,  Four-Point A  switch  by 

which  a  circuit  can  be  completed  through 
four  central  points. 

Switch,  Knife A  switch  which  is 

opened  or  closed  by  the  motion  of  a  knife 


-  532.    Lamp-Socket  Switch. 


contact  which  moves  between  parallel  contact 
plates. 

A  knife-edge  switch.  (See  Switch,  Knife- 
Edge} 

Switch,  Knife-Break  -  —A  knife 
switch.  (See  Switch,  Knife.} 

Switch,  Knife-Edge  --  A  term  some- 
times used  in  place  of  knife  switch.  (See 
Switch,  Knife.) 


Swi.] 


500 


[Swi. 


Switch,  Lamp-Socket  — A  switch 

placed  in  the  socket  of  an  incandescent  lamp 
and  provided  for  throwing  the  lamp  in  and 
out  of  the  circuit. 

A  form  of  lamp  socket  switch  is  shown  in  Fig. 
522.  Its  operation  will  be  understood  from  an 
inspection  of  the  drawing. 

Switch  Pin.— (See  Pin,  Switch^ 

Switch,  Plug  —  — A  switch  in  which  a 
metal  plug  is  withdrawn  to  throw  into  a  cir- 
cuit a  coil  or  other  device,  the  ends  of  which 
are  connected  to  metallic  blocks  that  are  suf- 
ficiently near  together  to  be  joined  and  short- 
circuited  by  the  insertion  of  the  plug. 

Switch,  Pole-Changing A  switch 

employed  for  changing  the  direction  of  the 
current  in  any  circuit. 

A  form  of  pole-changing  switch  is  shown  in  Fig. 
S23- 


Fig.  323.    Pole-Changing  Switch. 

If  the  two  outer  contacts  are  connected  to  the 
same  pole  as  the  source,  as,  for  example,  the 
positive,  and  the  two  intermediate  contacts  are 
connected  to  the  other  pole,  or  to  the  negative, 
then  in  the  position  shown  in  the  cut,  the  current 
will  flow  through  any  receptive  device  connected 
with  the  switch,  in  one  direction,  but  if  the 
switch  is  moved  to  the  left,  it  will  flow  in  the  op- 
posite direction. 

Switch,  Removable  Key A  plug 

switch.  (See  Switch,  Plug.) 

Switch,  Reversing A  switch  for 

reversing  the  direction  of  the  battery  current 
through  a  galvanometer. 

A  simple  reversing  switch  consists  of  four  in- 
sulated brass  segments  mounted  on  a  plate  of 
ebonite  and  furnished  with  openings  between 
them  for  plug  connections. 

The  battery  terminals  are  connected  to  two  di- 
agonally opposite  segments,  as  B,  and  D,  Fig. 
524,  and  the  leading  wires  of  the  galvanometer, 


or  other  instrument,  to  the  other  segments,  as  C 
and  A,  If,  now,  the  plugs  are  placed  between  B 
and  C*,  and  A  and  D,  the  battery  current  flows 
in  one  direction.  If,  however,  the  plugs  are 


Fig.  524"    Reversing  Switch. 

placed  between  A  and  B,  and  C  and  D,  the  bat- 
tery current  will  flow  in  the  opposite  direction. 

The  battery  current  is  cut  off  if  one  plug  is  re- 
moved. In  practice,  however,  it  is  preferable  to 
remove  both  plugs,  so  as  to  avoid  any  current 
from  want  of  sufficient  insulation. 

Switch,  Snap A  switch  in  which 

the  transfer  of  the  contact  points  from  one 
position  to  another  is  accomplished  by  means 
of  a  quick  motion  obtained  by  the  operation 
of  a  spring. 

The  object  of  the  snap  switch  is  to  prevent  the 
switch  resting  in  any  half  way  position,  and  thus 
preventing  the  establishing  of  an  arc. 

Switch,  Telephone,  Automatic A 

device' for  automatically  transferring  the  con- 
nection of  the  main  line  from  the  call  bell  to 
the  telephone  circuit. 

In  most  telephone  circuits,  as  now  arranged, 
the  automatic  switch,  besides  transferring  the  main 
line  from  the  call  bell  to  the  telephone  circuit, 


Fig:  323.     Automatic   Telephone  Switch. 

closes  the  local  battery  circuit  of  the  transmitter 
on  the  removal  of  the  telephone  from  its  support- 
ing hook. 


Swi.] 


501 


[Sym. 


The  means  whereby  this  is  accomplished  are 
shown  in  Fig.  525.  On  the  removal  of  the  tele- 
phone from  the  hook  L,  the  lever  is  pulled  up- 
wards by  the  spring  Z,  thus  closing  the  contacts  I, 
2  and  3,  by  which  the  local  battery  S,  is  closed 
through  the  circuit  of  the  transmitter,  the  tele- 
phone disconnected  from  the  circuit  of  the  call  bell 
M,  B,  and  connected  with  the  circuit  of  the  trans- 
mitter. On  replacing  the  telephone  on  the  hook 
L,  its  weight  depresses  the  lever,  breaking  con- 
nection with  I,  2  and  3,  and  establishing  connec- 
tion with  the  call  circuit. 

Switch,  Three-Point A  switch  by 

means  of  which  a  circuit  can  be  completed 
through  three  different  contact  points. 

Switch,  Time An  automatic  switch 

hi   which   a  predetermined  time  is  required 


either  to  insert  a  resistance  in  or  remove  it 
from  a  circuit. 
Switch,  Two-Point A  switch  by 

SYMBOLS   COMMONLY   USED  IN  ELECTRICAL  WORK. 


means  of  which  a  circuit  can  be  completed 
through  two  different  contact  points. 

Switch,  Two- Way A  switch  pro- 
vided with  two  contacts  connected  with  two 
separate  and  distinct  circuits. 

Switch,  Yale-Lock,  for  Burglar  Alarm 

(See  Alarm,  Yale-Lock  Switch 

Burglar?) 

Switched-In. — Placed  in  a  circuit  by  means 
of  a  switch.  (See  Closed-Circuited^) 

Switched-Out. — Cut  out  of  a  circuit  by 
means  of  a  switch.  (See  Open-Circuited^) 

Symbols  and  Diagrams,  Standard  Elec- 
tric   Standard  symbols  and  diagrams 

used  in  electro-technics. 

The  standard  electric  diagrams  and  symbols 
shown  on  pages  501,  and  502,  were  arranged  by 
Prof.  F.  B.  Crocker,  and  are  reproduced  from 
the  Electrical  Engineer. 


MECHANICAL. 


ELECTRICAL. 


MAGNETIC. 


Lori.  Length 

D.  Diameter 

E.orE.jf.F.  Electromotive 

T.    Volt 

N.  North  pole 

Morni.  Mass 

r.  Radius 

force 

amp.  Ampere 

S. 

South  pole 

fort.   Time 

H.P.      Horsepower 

P.D.  Potential  difference 

co.   Ohm 

m 

.  Strength  of  pole 

T.  Velocity 

I.H.P.  Indicated  " 

C.   Current 

O.  Megohm. 

H.  Magnetizing  force 

fort.  Force 

B.H.P.  Brake       " 

B.  Resistance 

B.A.U.  Brit.  Ass'n  Unit 

(C.G.S.) 

g.  Acceleration 
due  to  gravity. 

W<TTW.  Work. 

r.p.m.  Revolutions 
per  min. 
C.Q.S.   Centimetre 

p.  Specific  resistance 
Q.  Quantity 
K.  Electrostatic  capacity. 

mfd.  Microfarad 
h.  or  hy.     Henry 
z.  Electrochemical 

B.  Magnetic  induction 
(C.G.S.  lines) 
\.  Intensity  of  mag- 

P.  Power. 
rt.lb.  Footpound. 

gramme  second 
(System) 
A.YF.G.  American 

L.  Inductance  (  Coeffic.  of) 
A.M.  Amperemeter. 

equivalent 
i.   Joule 

fj.. 

Magnetic  per- 
meability 

Wire  Gauge 

Y.M.   Voltmeter 

K.W.  Kilowatt 

K. 

Magnetic  sus- 

B.W. Q.Birmingham 
Wire  Gauge 

F.M.  Field  Magnet 
-\-  Positive  pole  or  terminal 
—  Negative  '  '    ' 

...Complete  period 

(Alt.  cur.) 
~CL  Dynamo 

H 

ceptibility 
.  Horizontal 
intensity  of  Earth's 

-llll-  Battery 

magnetism 

Siemens  I  Jlrmatitrt 


Jlmmetef  ortbUmettr 


Alternating  Current 
Transformer  Diagram 
|     mmary  SM.f 
0     Pnmttry  Current 
B   Secondary  E  JHf 


Incandescent  Lighting 


Sym.J 


502 


[Sym. 


Morse  Telerrrafili  System 


RJutatol        RetutnnetCM  ? -print  SwUf* 

,£=,—    \Q>ndNlitr 


Alternating  Current  Transformer  System 


Crocker's  Chart  of  Standard  Electric  Symbols  and  Diagrams. 


Sym.J 


503 


[Sys. 


Symmetrical  Induction  of  Armature. — 

(See  Induction,  Symmetrical,  of  Armature, ,) 
Symmetrical     Magnetic      Field. — (See 
Field,  Magnetic,  Symmetrical!) 

Sympathetic  Electrical  Vibrations. — 
(See  Vibrations,  Sympathetic  Electrical!) 

Sympathetic  Vibrations.  —  (See  Vibra- 
tions, Sympathetic!) 

Synchronism. — The  simultaneous  occur- 
rence of  any  two  events. 

A  rotating  cylinder,  or  the  movement  of  an 
index  or  trailing  arm,  is  brought  into  synchronism 
with  another  rotating  cylinder  or  another  index 
or  trailing  arm,  not  only  when  the  two  are  mov- 
ing with  exactly  the  same  speed,  but  when  in  ad- 
dition they  are  simultaneously  moving  over  simi- 
lar portions  of  their  respective  paths. 

In  the  Breguet  Step-by-Step  or  Dial  Telegraph 
(See  Telegraphy,  Step-by-Step),  the  movements  of 
the  needle  on  the  indicator  are  synchronized  with 
the  movements  of  the  needle  on  the  manipulator. 
In  systems  of  Fac- Simile  Telegraphy  the  move- 
ments of  the  transmitting  apparatus  are  syn- 
chronized with  those  of  the  receiving  apparatus. 

In  Delany's  Synchronous  Multiplex  Telegraph 
System,  the  trailing  arm  that  moves  over  a  cir- 
cular table  of  contacts  at  the  transmitting  end, 
is  accurately  synchronized  with  a  similar  trailing 
arm  moving  over  a  similar  table  at  the  receiving 
end. 

Delany,  who  was  the  first  to  obtain  rigorous 
synchronism  at  the  two  ends  of  a  telegraphic 
line  hundreds  of  miles  in  length,  accomplishes 
this  by  the  use  of  La  Cour's  phonic  wheel, 
through  the  agency  of  correcting  electric  im- 
pulses, automatically  sent  in  either  direction  over 
the  main  line,  when  one  trailing  arm  get:  a  short 
distance  in  advance  or  back  of  the  other. 

With  alternating  current  dynamos,  where  one 
dynamo  is  feeding  incandescent  lamps  connected 
to  the  leads  in  multiple,  and  it  is  desired  to 
couple  another  alternating  current  dynamo  in 
parallel  with  the  first,  it  is  necessary  to  obtain  a 
complete  synchronism  of  the  two  dynamos  before 
coupling  them,  since  otherwise  the  lamps  will 
show  variations  in  their  light,  and  the  machine 
may  suffer. 

Synchronizable. — Capable  of  being  syn- 
chronized. (See  Synchronism!) 

Synchronize. — To  cause  to  occur  or  act 
simultaneously.  (See  Synchronism.) 


Synchronized. — Caused  to  occur  or  act 
simultaneously.  (See  Synchronism!) 

Synchronizing  Dynamo-Electric  Ma- 
chine.— (See  Machine,  Dynamo-Electric, 
Synchronizing!) 

Synchronous    Multiplex    Telegraphy. — 

(See  Telegraphy,  Synchronous  Multiplex, 
Delany's  System!) 

System,  Astatic An  astatic  com- 
bination of  magnets. 

An  astatic  needle  consists  of  an  astatic  system 
of  two  magnetic  needles.  The  needles  are 
rigidly  fixed  together  with  their  opposite  poles 
facing  each  other.  The  two  needles  form  an  as- 
tatic pair  or  couple.  (See  Needle,  Astatic.) 

System,  Block,  for  Railways (See 

Railroads,  Block  System  for!) 

System,    Centimetre  -  Gramme  -  Second 

(See  Units,  Centimetre  -  Gramme  - 

Second!) 

System,    Continuous    Underground,    of 

Motive  Power  for  Electric  Railroads 

— (See  Railroads,  Electric,  Continuous  Un- 
derground System  of  Motive  Power  for!) 

System,  Dependent,  of  Motive  Power  for 

Electric  Railroads (See  Railroads, 

Electric,  Dependent  System  of  Motive 
Power  for.) 

System,  Independent,  of  Motive  Powei 
for  Railroads (See  Railroads,  Elec- 
tric, Independent  System  of  Motive  Power 
for.) 

System,  Multiphase A  term  fre- 
quently applied  to  a  system  of  rotating  elec- 
tric currents.  (See  Current,  Rotating!) 

System  of  Distribution  of  Electricity  by 
Commntating  Transformers. — (See  Elec- 
tricity, Distribution  of,  by  Commutating 
Transformers!) 

System  of  Distribution  of  Electricity  by 
Condensers. — (See  Electricity,  Distribution 
of,  by  Alternating  Currents  by  Means  of 
Condensers.  Electricity,  Distribution  of,  by 
Continuous  Current  by  Means  of  Condens- 
ers!) 

System  of  Distribution  of  Electricity  bf 
Means  of  Alternating  Currents. — (See  Elec* 


504 


[Tai. 


tricity,  Distribution  of,  by  Alternating  Cur- 
rents.} 

System  of  Distribution  of  Electricity  by 
Motor  Generators. — (See  Electricity,  Dis- 
tribution of,  by  Motor  Generators^) 

System,  Three-Wire A  system  of 

electric  distribution  for  lamps  or  other  trans- 
lating devices  connected  in  multiple,  in  which 
three  wires  are  used  instead  of  the  two  usually 
employed. 

In  the  three-wire  system  two  dynamos  are  gen- 
erally employed,  which  are  connected  with  one 
another  in  series. 

The  three  conductors  are  connected  as  shown 
in  Fig.  527,  the  central  conductor  to  the  junction 
of  the  two  dynamos  and  the  two  others  to  their 
free  terminals,  and  the  difference  of  potential  be- 
tween the  central  and  the  two  outer  conductors 
is  maintained  the  same.  The  lamps,  or  other 
electro-receptive  devices,  are  placed  in  multiple- 
arc  between  either  branch,  and  so  distributed 
that  the  current  in  each  branch  is  the  same. 
When  such  balance  is  established  no  current 
flows  through  the  central  or  neutral  conductor. 
But  when  that  balance  is  disturbed,  the  surplus 
current  in  one  branch  is  taken  up  by  the  central 
conductor. 

The    three-wire    system    effects   considerable 


economy  in  the  weight  of  wire  required.  Since  in 
the  multiple- series-connection  of  electro -receptive 
devices  whatever  difference  of  potential  is  im- 
pressed on  the  mains  is  fed  to  each  device,  no 
higher  difference  of  potential  can  be  employed  on 
the  mains  than  that  which  the  devices  are  capa- 
ble of  taking.  In  the  case  of  an  incandescent 
lamp,  if  such  difference  be  exceeded,  too  strong 
a  current  is  passed  through  the  lamps  with  a 
consequent  decrease  in  their  life. 

In  the  three- wire  system  of  distribution  a  higher 
difference  of  potential  can  be  maintained  on  the 
mains  than  is  required  for  any  lamp  placed  in 


Fig.  327-     Three-Wire  System. 

connection  therewith,  and  in  this  manner  a  con- 
siderable saying  is  effected  in  the  cot  of  the  leads. 


A    DICTIONARY 


OF 


ELECTRICAL     WORDS 


VOLUME      TWO 


T. — A  symbol  used  for  time. 

T-shaped  Spark.— (See  Spark,  T-Shaped) 

Table,  Quadruplex,  A-Side  of  — 

That  side  of  a  quadruplex  system  which  is 
worked  by  means  of  reverse  currents.  (See 
Telegraphy,  Quadruple*) 

Table,  Quadruplex,  B-Side  of  - 

That  side  of  a  quadruplex  system  which  is 
worked  by  means  of  strengthened  currents. 
(See  Telegraphy,  Quadruplex.) 

Tables  of  Conducting  Powers.— (See 
Powers,  Conducting,  for  Electricity.  Re- 
sistance, Electric) 

Tachograph. — An  apparatus  for  recording 
the  number  of  revolutions  per  minute  of  a 
shaft  or  machine. 


Tachometer. — An  apparatus  for  indicating 
at  any  moment  on  a  revolving  dial  the  exact 
number  of  revolutions  per  minute  of  a  shaft 
or  machine. 

A  tachometer  is  sometimes  called  a  speed  in- 
dicator. 

Tachyphore. — A  term  proposed  by  Wurtz 
for  a  system  of  electric  transportation,  in 
which  a  carriage,  formed  of  magnetic  ma- 
terial, is  propelled  by  the  sucking  action  of 
solenoids  placed  along  the  track  and  ener- 
gized in  succession  during  the  passage  of  the 
car. 

This  is  generally  called  the  portelectric  sys- 
tem. (See  Portelectric.) 

Tail  Light.— (See  Light,  Tail) 
1 — Vol.  2 


Tai.J 


505 


[Tag. 


Tailings. — False  markings  received  in  sys- 
tems of  automatic  telegraphy,  due  to  retard- 
ation. (See  Retardation?) 

Tailings. — A  term  applied  to  the  current 
that  runs  out  of  a  line  at  the  receiving  end. 

The  current  that  continues  to  run  out  at 
the  receiving  end  of  the  circuit  after  the  send- 
ing current  is  broken. 

The  tailings  in  a  telegraphic  line  are  due  to  the 
effects  of  self-induction  and  static  capacity  follow- 
ing the  breaking  of  the  circuit  which  produce  a 
current  in  the  same  direction  as  that  sent  into  the 
line.  Consequently,  on  the  breaking  of  the  cir- 
cuit, the  current  continues  to  flow  out  of  the  line  at 
the  distant  or  receiving  end.  This  prolongation 
of  the  original  current  is  known  technically  as 
the  tailing  or  the  tailing  current. 

Talk,  Cross In  telephony  an  indis- 
tinctness in  the  speech  transmitted  over  any 
circuit,  due  to  this  circuit  receiving,  either  by 
accidental  contacts  or  by  induction,  the  speech 
transmitted  over  neighboring  circuits. 

Tangent. — One  of  the  trigonometrical 
functions.  (See  Function,  Trigonometrical?) 

Tangent  and  Sine  Galvanometer,  Com- 
bined   (See  Galvanometer,  Combined 

Tangent  and  Sine.) 

Tangent  Galvanometer.— (See  Galva- 
nometer, Tangent?) 

Tangent  Scale.— (See  Scale,  Tangent?) 

Tangentially  Laminated  Armature  Core. 

— (See  Core,  Armature,  Tangentially  Lam- 
inated^) 

Tank,  Cable A  water-tight  tank  in 

which  a  section  of  a  cable  is  placed  for  pur- 
poses of  testing. 

The  cable  is  tested  either  when  merely  covered 
by  water,  or  when  subjected  to  a  pressure  ap- 
proximately equal  to  or  in  excess  of  that  to  which 
it  will  be  subjected  when  laid  in  the  water. 

Reid  has  constructed  cable  tanks  for  testing 
under  pressures  as  great  as  4,500  pounds  per 
square  inch.  The  pressure  is  obtained  by  means 
of  force  pumps. 

When  a  cable  section  is  subjected  to  these 
pressures  any  flaws  or  defects  would  be  at  once 
detected  by  the  entrance  of  the  water. 


Tanning,  Electric An  application 

of  electric  currents  to  tanning  leather. 

The  dressed  hides  are  steeped  in  a  solution  of 
tannin  through  which  an  electric  current  is 
passed. 

It  is  claimed,  that  by  this  process,  the  hides 
are  thoroughly  tanned  in  from  one  to  four  days, 
in  place  of  from  four  to  twelve  months,  as  re- 
quired by  the  ordinary  process. 

The  tanning  solution  is  placed  in  a  vat  fur- 
nished with  suitable  electrodes  and  filled  with  the 
tanning  liquid,  and  the  articles  to  be  tanned  are 
placed  between  the  electrodes  and  a  motion  erf 
revolution  given  to  the  vat.  By  these  means 
the  time  required  for  the  completion  of  the  pro- 
cess is  considerably  shorter  than  that  required  by 
the  ordinary  process. 

Tap. — A  conductor  attached  to  a  larger 
conductor  in  a  shunted  circuit. 

Tap,  AmpSre  — A  tap  provided  for 

carrying  off  a  current  of  one  ampere. 

Tap  Wires.— (See  Wires,  Tap) 


Tape,    Insulating 


-A    ribbon    of 


flexible  material  impregnated  with  kerite, 
okonite,  rubber  or  other  suitable  insulating 
material,  employed  for  insulating  wires  or 
electric  conductors  at  joints,  or  other  exposed 
places. 

Sometimes  the  tape  is  formed  entirely  of  some 
or  another  the  above  named  insulating  materials. 

Taped  Wire.— (See  Wire,  Taped.} 

Tapper,     Double-Key (See      Key, 

Double  Tapper.) 

Target,  Electric A  target  in  which 

the  point  struck  by  the  ball  is  automatically 
registered  by  means  of  electric  devices. 

A  variety  of  targets  have  been  devised.  Gen- 
erally, however,  the  target  is  divided  into  a  num- 
ber of  separate  sections  provided  with  circuits  of 
wires,  on  the  making  or  breaking  of  any  of  which, 
by  the  impact  of  the  ball,  the  section  struck  is  au- 
tomatically indicated  on  an  electric  annunciator. 
(See  Annunciator,  Electro-Magnetic.) 

Taste,  Galvanic A  sensation  of  taste 

produced  when  a  voltaic  current  is  passed 
through  the  tongue  or  in  the  neighborhood  o£ 
the  gustatory  nerves,  or  nerves  of  taste. 


TeaJ  506 


[Tel. 


Teaser. — An  electric  current  teaser.  (See 
Teaser,  Electric  Current.} 

Teaser,  Electric  Current A  coil 

of  fine  wire  placed  on  the  field  magnets  of  a 
dynamo-electric  machine,  underneath  the  se- 
ries coil  wound  thereon,  and  connected  as  a 
shunt  across  the  main  circuit. 

The  name'  teaser  was  applied  by  Brush  to  the 
coil  of  fine  wire  used  as  above  described  to  main- 
lain  constant  electromotive  force  under  variations 
of  load. 

Technics,  Electro  -  —The  science 
which  treats  of  the  physical  applications  of 
electricity  and  the  general  principles  applying 
thereto. 

Tee,  Lead A  tee-shaped  lead  tube 

provided  for  the  purpose  of  taking  a  branch 
joint  from  a  main  cable  to  a  service  line. 

Tee,  Split-Lead  -  — A  tee-shaped  lead 
tube  that  is  split  for  readily  covering  a  joint 
at  a  loop  in  a  cable. 

Tel-Autogrram. — The  recorded  message 
obtained  by  means  of  a  tel-autograph.  (See 
Tel-Autograph^ 

Tel-Autograph. — A  telegraphic  system  for 
the  fac-simile  reproduction  of  handwriting. 

Teleautograph. — An  orthography  some- 
times employed  for  tel-autograph.  (See  Tel- 
Autograph!) 

Tele- Barometer,  Electric An  elec- 
tric recording  barometer  for  indicating  and 
recording  barometric  or  other  pressures  at  a 
distance. 

Telegrapher's  Cramp. — (See  Cramp, 
Telegrapher's?) 

Telegraphic.— Pertaining  to  telegraphy. 

Telegraphic  Alarm. — (See  Alarm,  Tele- 
graphic) 

Telegraphic  Alphabet. — (See  Alphabet, 
Telegraphic) 

Telegraphic  Alphabet,  Continental  Code 
(See  Alphabet,  Telegraphic :  Inter- 
national Code.} 

Telegraphic  Alphabet,  Morse's 

(See  Alphabet,  Telegraphic :'  Morse's) 


Telegraphic  Arm. — (See  Arm,  Tele* 
graphic) 

Telegraphic  Bracket. — (See  Bracket. 
Telegraphic) 

Telegraphic  Cable.— (See  Cable,  Tele- 
graphic) 

Telegraphic  Code. — (See  Code,  Tele- 
graphic) 

Telegraphic  Earth-Circuit. — (See  Cir- 
cuit, Earth,  Telegraphic) 

Telegraphic  Embosser. — (See  Embosser, 
Telegraphic) 

Telegraphic  Fixtures. — (See  Fixtures, 
Telegraphic) 

Telegraphic  Fixtures,  House-Top  — 

(See  Fixtures,  Telegraphic  House-  Top) 

Telegraphic  Ground  Circuit. — (See  Cir- 
cuit, Ground,  Telegraphic) 

Telegraphic  Joints.— (See  Joint,  Tele- 
graphic or  Telephonic) 

Telegraphic  Key.— (See  Key,  Telegraph- 
ic) 

Telegraphic  Line  Circuit. — (See  Circuit, 
Line,  Telegraphic) 

Telegraphic  Needle. — (See  Needle,  Tele- 
graphic) 

Telegraphic  Paper  Winder.— (See  Wind- 
ers, Telegraphic  Paper) 

Telegraphic  Pocket  Belay. — (See  Relay, 
Pocket  Telegraphic) 

Telegraphic  Register. — (See  Register, 
Telegraphic) 

Telegraphic  Switch  Board. — (See  Board, 
Switch,  Telegraphic) 

Telegraphic  Translator. — (See  Trans- 
later,  Telegraphic) 

Telegraphically.  —  In  a  telegraphic 
manner. 

Telegraphing. — Sending  a  communication 
by  i.ieans  of  telegraphy. 

Telegraphy,  Acoustic A  non-re- 
cording system  of  telegraphic  communica- 
tion, in  which  the  dots  and  dashes  of  the 
Morse  system,  or  the  deflections  of  the  needle 
in  the  needle  system,  ate  replaced  by  sounds 


Tel.] 


507 


[TeL 


that  follow  one  another  at  intervals,  that 
represent  the  dots  and  .  dashes,  or  the  de- 
flections of  the  needle,  and  thereby  the  letters 
of  the  alphabet. 

Morse  invented  a  sounder,  for  this  purpose, 
which  is  used  very  generally.  (See  Sounder, 
Morse  Telegraphic.} 

Steinheil  and  Bright  each  invented  acoustic 
systems  of  telegraphy  in  which  electro-magnetic 
btlls  are  used. 

For  details  of  the  apparatus  and  system  see 
Telegraphy,  Morse  System  of. 

Telegraphy,  American  System  of 

A  term  sometimes  applied  to  the  Morse  sys- 
tem of  telegraphy.  (See  Telegraphy,  Morse 
System  of.) 

Telegraphy  and  Telephony,  Simultane- 
ous, Over  a  Single  Wire Any  system 

for  simultaneous  transmission  of  telegraphic 
and  telephonic  messages  over  a  single  wire. 

These  systems  are  based,  in  general,  on  the 
fact  that  a  gradual  make-and-break  in  a  tele- 
phone circuit  fails  to  appreciably  affect  a  tele- 
phone diaphragm.  By  the  use  of  graduators  the 
makes  and  breaks  required  for  the  transmission 
of  the  telegraphic  dispatch  are  effected  so  grad- 
ually that  they  fail  to  appreciably  influence  the 
telephone  diaphragm,  and  thus  permit  simultane- 
ous telegraphic  and  telephonic  transmission  over 
a  single  wire.  (See  Graduators.) 

Telegraphy,  Autographic A  name 

sometimes  applied  to  fac-simile  telegraphy. 
(See  Telegraphy,  Fac-Szmzle.) 

Telegraphy,  Automatic A  system 

by  means  of  which  a  telegraphic  message  is 
automatically  transmitted  by  the  motion  of  a 
previously  perforated  fillet  of  paper  contain- 
ing perforations  of  the  shape  and  order  re- 
quired to  form  the  message  to  be  transmitted. 

The  paper  passes  between  two  terminals  of  the 
main  line,  the  circuit  of  which  is  completed  when 
the  terminals  come  into  contact  at  the  perforated 
parts,  and  is  broken  when  separated  by  the 
un perforated  parts  of  the  paper. 

In  the  automatic  telegraph  some  form  of  regis- 
tering apparatus  is  employed. 

In  the  Wheatstone  system,  the  perforations 
me  hanically  control  the  movements  ot  the  levers 
which  make  contacts  between  the  line  and  the 
battery. 


The  advantage  of  automatic  telegraphy  arises 
from  the  fact  that  the  rate  of  transmission  or  re- 
ception of  signals  does  not  depend  on  the  expert- 
ness  of  the  operators,  and  the  messages  may  be 
perforated  on  the  slips  preparatory  to  transmis- 
sion. 

Type  printing  telegraphs  are  often  used  for 
registering  apparatus,  in  which  case  the  im- 
pulses required  for  the  transmission  of  the  dif- 
ferent letters  are  automatically  sent  into  the  line 
by  the  depression  of  corresponding  keys  on  a 
suitably  arranged  key -board. 

Telegraphy,    Chemical A   system 

by  means  of  which  the  closings  of  the  main- 
line-circuit, corresponding  to  the  dots  and 
dashes  of  the  Morse  alphabet,  are  recorded 
on  a  fillet  of  paper  by  the  electrolytic  action 
of  the  current  on  a  chemical  substance  with 
which  the  paper  fillet  is  impregnated.  (See 
Recorder,  Chemical,  Bain's?) 


Telegraphy,    Contraplex 


— Duplex 


telegraphy  in  which  transmissions  are  simul- 
taneously made  from  opposite  ends  of  the 
line. 

When  the  transmissions  are  simultaneously 
made  from  the  same  end  of  the  line,  the  system  is 
called  diplex  telegraphy.  (See  Telegraphy,  Di- 


Telegraphy,   Dial 


— A    system    of 


telegraphy  in  which  the  messages  are  received 
by  the  motions  of  a  needle  over  a  dial  plate. 
(See  Telegraphy,  Step-by-Step^) 

Telegraphy,  Diplex  —  — A  method  of 
simultaneously  sending  two  messages  in  the 
same  direction  over  a  single  wire. 

Diplex  telegraphy  is  to  be  distinguished  from 
duplex  telegraphy,  where  two  messages  are  simul- 
taneously transmitted  over  a  single  wire  in  oppo- 
site directions. 

Telegraphy,  Double-Needle A  sys- 
tem of  needle  telegraphy  in  which  two  sepa- 
rate and  independently  operated  needles  are 
employed. 

This  system  differs  from  the  single-needle  sys- 
tem only  in  the  (act  that  two  needles,  entirely  in- 
dependent of  each  oi hi  r,  are  mounted  side  by  side, 
on  the  same  dial,  so  as  to  permit  their  simultane- 
ous operation  by  the  right  and  left  hand  of  th^ 


Tel.] 


508 


I'el. 


operator.     Each  needle  has  then-fore  a  separate 
wire. 

The  increase  in  speed  of  signaling  thus  obtained 
is  not,  however,  sufficiently  great  to  balance  the 
increased  expense  of  construction.  Single -needle 
instruments,  therefore,  are  preferred  to  those 
with  two  needles. 

/      Telegraphy,  Duplex,  Bridge  Method   of 

— A  system  whereby  two  telegraphic 
messages  can  be  simultaneously  transmitted 
over  a  single  wire  in  opposite  directions. 

Various  duplex  telegraphs  have  been  devised. 

The  Bridge  Duplex  is  shown  in  Fig.  528.  The 
receiving  relay  is  placed  in  the  cross  wire  of  a 
Wheatslone  bridge.  (See  Bridge,  Electric.} 


F;g.  328.     Duplex  Telegraphy,  Bridge,  Method. 

When  the  ends  of  this  cross  wire  are  at  the 
same  potential,  whicn  will  occur  when  the  resist- 
ances in  the  four  arms  are  proportionately  equal, 
no  current  passes. 

The  battery  is  connected  through  the  trans- 
mitter K,  which  is  arranged  so  that  the  battery 
contact  is  made  before  the  connection  of  the  line 
to  earth  is  broken,  to  H,  where  the  circuits 
branch  to  form  the  arms  of  the  bridge.  Adjust- 
able resistances  A,  B,  are  placed  in  the  two  arms 
•of  the  bridge. 

The  line  wire  L,  connected  as  shown,  forms 
the  third  arm,  and  a  rheostat  or  other  adjustable 
resistance  R,  connected  to  a  condenser  C,  as 
shown,  forms  the  fourth  arm.  (See  Rheostat.) 
The  relay  M,  is  placed  in  the  cross  wire  of  the 
bridge  thus  formed.  Small  resistances  V,  and 
W,  are  placed  in  the  circuit  of  the  battery  to  pre- 
vent injurious  short  circuiting. 

A  similar  disposition  of  apparatus  is  provided 
at  the  other  end  of  the  line.  If,  now,  the  four  re- 
sistances at  one  end  are  sui'ably  adjus  eH,  the 
relay  will  not  respond  to  the  outgoing  cu;rent; 
but,  since  an  earth  circuit  ii  emp'oyed,  it  \\ill 


respond  tc  the  incoming  current.  The  relay  at 
either  end,  therefore,  will  only  respond  to  signals 
from  the  other  end.  •  The  operator  may  thus 
signal  the  distant  station  w  hile,  at  the  same  time, 
his  relay,  not  being  affected  by  his  sending,  is  in 
readiness  to  receive  signals  from  the  other  end. 

Telegraphy,  Duplex,  Differential  Method 

of A  system  of  duplex  telegraphy  in 

which  the  coils  of  the  receiving  and  transmit- 
ting instruments  are  differentially  wound. 

A  differential  system  of  duplex  telegraphy  is 
shown  in  Fig.  529.  The  coils  of  the  receiving 
and  transmitting  galvanometers  at  A  and  B,  are 
differentially  wound.  One  of  the  coils  of  A,  is 
connected  to  that  of  B,  through  the  line,  as 
shown;  and  the  other,  in  each  to  the  rheostat; 
at  R,  and  R'.  As  thrse  coils  are  differentially 
wound,  when  equal  currents  flow  in  opposite 
directions  through  either  of  the  instruments  at  A 
B,  no  deflection  of  the  galvanometer  occurs. 

The  battery  at  A,  has  its  copper  terminal,  and 
that  at  B,  its  zinc  terminal,  connected  to  earth. 
When  the  keys  at  A  and  B,  are  depressed  simul- 
taneously, the  currents  sent  into  the  li;ie  flow  in 
the  same  direction  and  strengthen  each  other. 

Suppose  now  that  only  the  key  at  A,  be  de- 
pressed. The  current  divides  equally  between 
rheostat  and  line,  the  resistance  e  a  b  b  a'  e',  r', 
being  made  equal  to  th^  resistance  e  c  d  R. 

This  current  passes  through  both  coils  of  the 
instrument  at  A,  and  produces  no  deflection  of 
the  needle;  but  since  it  only  passes  through  one 
coil  at  B,  it  deflects  the  galvanometer  needle,  and 
produces  a  s-ijnal. 

b  b' 


Earth 


Fig.szq.      Duplex  Telegraphy,  Differential  Method. 

If  the  keys  at  A,  and  B,  are  simultaneously 
closed,  the  effect  on  the  line  is  to  add  the  current 
of  the  two  batteries,  but  each  rheostat  circuit  is 
traversed  by  its  own  battery  current  only. 

The  line-connec:ed  coils  of  the  ga  vanometer 
have,  the  -el  re,  the  stronger  currents  flowing 
through  them,  and  the  needles  of  both  are  moved, 
just  as  if,  with  a  single  battery  discharging  into 
the  line,  its  resistance  had  been  decreased.  Each 


Tel.J 


509 


[Tel. 


sender's  instrument  is  unaffected  by  the  currents 
he  sends  into  the  line,  and  is,  therefore,  ready  to 
be  operated  by  the  currents  sent  into  the  line  by 
the  sender  at  the  other  end  of  the  line. 

The  two  currents  in  duplex  telegraphy,  there- 
fore, do  not  pass  each  other  on  the  line;  on  the 
contrary,  they  are  sent  into  the  line  in  the  same 
direction. 

Since,  when  either  key  is  moving  there  is  a 
small  interval  of  time  when  the  circuit  is  broken 
for  incoming  currents,  the  keys  are  generally 
made  so  as  to  close  the  second  contact  before 
breaking  the  first. 

In  order  to  avoid  disturbing  the  balance  on  the 
introduction  of  the  resistance  of  the  batteries  at  A 
or  B,  on  closing  the  circuits,  an  equal  resistance 
is  added  at  r  and  r',  between  the  back  stop  and 
the  earth. 

Since  the  proper  operation  of  duplex  telegraphy 
requires  a  balance  in  the  resistance  of  the  circuits 
of  the  differentially  wound  coils,  a  rheostat  at  R, 
and  R',  is  necessary. 

Besides  balancing  the  line  for  resistance,  it  is 
necessary  to  balance  it  for  capacity.  A  condenser 
is,  therefore,  necessary  when  the  circuit  exceeds 
in  length  about  100  miles,  or  has  much  cable  or 
underground  wire. 

Telegraphy,  Fac-Simile  -  — A  system 
whereby  a  fac-simile  or  copy  of  a  chart, 
diagram,  picture  or  signature  is  telegraphically 
transmitted  from  one  station  to  another. 

Fac-simile  telegraphy  is  sometimes  called  auto- 
graphic telegraphy,  or  pantelegraphy. 

Bakewell's  fac-simile  telegraph,  which  was  one 
of  the  first  devised,  consists  of  two  similar  metal 
cylinders  c,  c',  arranged  at  the  two  ends  of  a 
telegraph  line  L,  at  M  and  M',  as  shown  in  Fig. 
53°-  These  cylinders  are  synchronously  rotated 


530.     Bakewell's  Fac-Simile   Telegraphy. 

and  provided  with  metallic  arms  or  tracers  r,  r', 
placed  on  a  horizontal  screw  in  the  line  circuit 
and  moved  laterally  over  the  surface  of  the 
cylinder  on  its  rotation. 

At  the  transmitting  station  the  chart,  writing, 


or  other  design  is  traced  with  varnish,  or  other 
non-conducting  liquid,  on  the  surface  of  the 
metallic  cylinder,  as  at  M,  and  a  sheet  of  chemi- 
cally prepared  paper,  similar  to  that  employed  in 
the  Bain  chemical  system  is  placed  on  the  surface 
of  the  receiving  cylinder  at  M'.  (See  Recorder, 
Chemical,  Bain's.) 

The  two  cylinders  being  synchronously  rotated, 
the  metallic  tracer  breaks  the  circuit  in  whick  it 
is  placed  when  it  moves  over  the  non-conducting 
lines  on  the  cylinder,  and  thus  causes  correspond- 
ing breaks  in  the  otherwise  continuous  blue  spiral 
line  traced  on  the  paper-covered  surface  of  M'. 

The  telegraph  keys  at  R,  R',  are  used  for  the 
purposes  of  ordinary  telegraphic  communication 
before  or  after  the  record  is  transmitted. 

Caselli's  Pan-Telegraph  is  an  improvement  on 
Bakewell's  Copying  Telegraph.  Better  methods 
are  employed  for  maintaining  the  synchronism 
between  the  transmitting  and  receiving  instru- 
ments, for  which  purpose  a  pendulum,  vibrating 
between  two  electro-magnets,  is  employed. 

Telegraphy,  Fire  Alarm  —  —A  systeu. 
of  telegraphy  by  means  of  which  alarms  can 
be  sent  to  a  central  station,  or  to  the  fire 
engine  houses  in  the  district,  from  call  boxes 
placed  on  the  line. 

The  alarms  are  generally  sounded  by  an  ap- 
paratus similar  to  a  district  call,  so  that  the  pall- 
ing back  of  a  lever  rotates  a  wheel,  by  means  et 
which  successive  makes  and  breaks  are  produced, 
the  number  and  sequence  of  which  enable  the 
receiving  stations  to  locate  the  particular  box 
from  which  the  signal  is  sent. 

In  the  case  of  some  buildings,  the  alarms  are 
automatic,  and  either  call  for  help  from  tke 
central  office,  or  for  the  watchman  in  the  build- 
ing, or  else  turn  on  a  series  of  water  faucets  er 
jets,  in  order  to  extinguish  the  fire.  In  tbese 
cases  thermostats  are  used.  (See  Thermostat. ) 

Telegraphy,  Gray's  Harmonic  Multiple 

A  system  for  the  simultaneous  trans- 
mission of  a  number  of  separate  and  distinct 
musical  notes  over  a  single  wire,  which 
separate  tones  are  utilized  for  the  simultane- 
ous transmission  of  an  equal  number  of  tele- 
graphic messages. 

The  separate  to  ies  are  thrown  into  the  lines 
by  means  of  tuning  forks  automatically  vibrated 
by  electro-magnets.  Th.se  forks  inierrupt  the 


Tel.] 


510 


circuit  of  batteries  connected  with  the  main  line 
at  the  sending  end  of  the  line. 

The  composite  tone  thus  formed,  is  separated 
into  its  component  tones  by  receiving  electro- 
magnets called  harmonic  receivers,  the  armature 
of  each  of  which  consists  of  a  steel  ribbon  or 
plate  tuned  to  one  of  the  separate  notes  sent  into 
the  line.  As  the  complex  or  undulatory  current 
passes  through  the  coils  of  each  harmonic  re- 
ceiver, that  note  only  affects  the  particular  arma- 
ture that  vibrates  in  unison  with  its  ribbon  or 
rued.  The  operator,  therefore,  at  this  receiver 
is  in  communication  only  with  the  operator  at 
i  he  key  of  the  circuit  that  is  sending  this  par- 
ticular note  into  the  line.  The  same  is  true  of  the 
other  receivers. 

The  Morse  alphabet  is  used  in  this  system,  the 
dots  and  dashes  being  received  as  musical  tones. 
In  practice  it  was  found  that  there  was  no  diffi- 
culty in  each  operator  recognizing  the  particular 
sound  of  his  own  instrument  in  receiving,  although 
many  instruments  were  in  the  same  room. 

By  a  subsequent  invention  the  signals  received 
are  converted  into  the  regular  Morse  characters 
by  means  of  an  ingenious  device. 

Telegraphy,  Induction  -  — A  system 
for  telegraphing  by  induction  between  moving 
trains  and  fixed  stations  on  a  railroad,  by 
means  of  impulses  transmitted  by  induction 
between  the  car  and  a  wire  parallel  with  the 
track. 

Two  systems  of  inductive  telegraphy  are  in 
actual  use,  viz., 

(i.)  The  Static  Induction  system  of  W.  W. 
Smith  and  Edison,  and 

(2. )  The  Current  or  Dynamic  Induction  system 
of  Willoughby  Smith  and  Lucius  J.  Phelps. 

In  the  System  of  Static  Induction,  one  of  the 
condensing  surfaces  which  receives  or  produces 
the  charge,  consists  of  a  wire  placed  on  the  road 
so  as  to  come  as  near  the  top  of  the  cars  of  the 
moving  train  as  possible.  The  other  condensing 
surface  is  composed  of  the  metal  roofs  of  the  mov- 
ing cars. 

Each  condensing  surface  is  connected  to  suit- 
able  instruments  and  batteries,  and  to  the  earth  ; 
the  line  wire  at  the  fixed  station  being  connected 
to  earth  through  a  ground  plate,  and  the  metal 
roof  of  the  cars  to  earth  through  the  wheels  and 
track. 

Under  these  circumstances  variations  in  the 
charge  of  either  of  the  condensing  surfaces  pro- 


duce inductive  impulses  that  are  received  by  the- 
other  surface  as  telegraphic  signals. 

The  Morse  alphabet  is  employed,  but  in  place 
of  the  ordinary  receiver  or  sounder,  a  telephone 
is  used. 

In  the  System  of  Current  Induction,  the  line 
wire  is  placed  near  the  track,  so  as  to  be  parallel 
with  a  coil  of  insulated  wire  placed  on  the  side  of 
the  car,  and  which  receives  the  inductive  impulses. 
The  coil  of  wire  on  the  train  is  connected  with 
instruments  and  batteries,  and  forms  a  metallic 
circuit.  The  line  wire  is  also  connected  with 
suitable  batteries  and  receiving  and  transmitting 
instruments. 

An  induction  coil  is  generally  employed,  since 
the  greater  and  more  rapidly  varying  difference 
of  potential  of  its  secondary  wire  renders  it  better 
suited  for  producing  effects  of  induction.  A  tele- 
phone is  employed  as  a  receiver,  as  in  the  system 
of  static  induction.  The  metallic  car  roof  and 
the  lower  truss  rods  have  been  successfully  used  as 
the  secondary  conductor  of  the  induction  coil. 

The  automatic  make-and-break  used  for  operat- 
ing the  induction  coil,  causes  the  Morse  characters 
employed  in  this  system  to  be  received  in  the 
receiving  telephone  as  shrill  buzzing  sounds. 

The  receiving  telephones  used  on  the  trains 
have  a  resistance  of  about  1,000  ohms. 

Telegraphy,  Induction,  Current  System 

of A  system  of  induction  telegraphy 

depending  on  current  induction  between  a 
fixed  circuit  along  the  road,  and  a  parallel 
circuit  on  the  moving  train. 

The  circuit  on  the  train  generally  consists  of  a 
coil  of  wire.  (See  Telegraphy,  Induction. ) 

Telegraphy,  Induction,  Dynamic  System 

of A  term  sometimes  used  in  place  of 

a  system  of  telegraphic  current  induction. 
(See  Telegraphy,  Induction?) 

Telegraphy,  Induction,  Static  System  of 

— A  system  of  inductive  telegraphy  de- 
pending on  the  static  induction  between  the 
sending  and  receiving  instrument. 

A  fixed  wire  placed  along  the  road  so  as  to  come 
near  another  wire  or  metallic  surface  on  the  mov- 
ing train,  imparts  to  the  latter  a  static  charge, 
which  is  utilized  for  the  transmission  of  dispatches. 
The  metal  roof  of  the  car  is  generally  used  for  the 
condensing  surface  receiving  the  charge.  (See 
Telegraphy,  Induction.) 


Tel.] 


oil 


[Tel. 


Telegraphy,  Machine A  term  some- 
times applied  instead  of  automatic  telegraphy. 
(See  Telegraphy,  Automatic?) 

A  system  of  telegraphy  is  properly  called  ma- 
chine telegraphy  when  both  the  transmission  and 
the  receiving  of  the  telegraphic  messages  are  ac- 
complished by  machine,  instead  of  by  the  hand,  as 
usual. 

Telegraphy,  Morse  System  of A 

system  of  telegraphy  in  which  makes  and 
breaks  occurring  at  intervals  corresponding 
to  the  dots  and  dashes  of  the  Morse  alphabet 
ace  received  by  an  electro-magnetic  sounder 
or  receiver. 

A  metallic  lever  A,  Fig.  531,  is  supported  on  a 
pivot  at  G,  between  two  set  screws  D,  D,  so  as  to 
have  a  slight  movement  in  a  vertical  plane.  This 
motion  is  limited  in  one  direction  by  a  stop  at  C, 
called  the  anvil  or  front  contact,  and  in  the  other 
direction  by  a  set  screw  F,  which  constitutes  its 
back  stop. 

The  front  stop  C,  is  provided  with  a  platinum 
contact  or  stud,  which  may  be  brought  into 
contact  with,  or  separated  from,  a  similar  stud 
placed  directly  opposite  it.  These  contacts  are 
connected  to  the  ends  of  the  circuit  so  that  on 


ig-  531-     Telegraphic    Key. 


the  movements  of  the  key,  by  the  hand  of  the 
operator  placed  on  the  insulated  head  B,  the  line 
is  closed  and  broken  in  accordance  with  the  dots 
and  dashes  of  the  Morse  alphabet.  A  spring,  the 
pressure  of  which  is  regulated  by  the  screw  F',  is 
provided  for  the  upward  movement  of  the  key. 
A  switch  H,  is  provided  for  closing  the  line  when 
the  key  is  not  in  use. 

The  system  generally  used  in  the  United  States 
is  known  as  the  "  Closed-  Circuit  System,"  the  bat- 
tery being  connected  to  line  whether  the  line  is  in 
use  or  not.  This  battery  is  generally  placed  at 
both  ends  of  the  line. 

In  Europe,  the  "  Open-Circuit  System  "  is  gen- 


erally used.  Alternating  currents  and  polarized 
relays  are  employed.  One  pole  is  connected  to 
the  line  at  the  front  of  the  key,  and  the  other 
pole  to  the  back  of  the  key.  When  the  line  is 
not  in  use,  it  is  connected  to  earth  at  both  ends 
by  switches  conveniently  placed  for  the  operators. 
With  this  system,  intermediate  stations  must  each 
have  a  main  battery,  while  in  the  closed-circuit 
system,  the  terminal  batteries  answer  for  all  inter- 
mediate offices,  which  in  some  cases  amount  to  as 
many  as  fifty. 

In  the  Morse  system,  eacji  station  is  provided 
with  a  key,  relay,  sounder  or  register,  and  local 
battery.  The  closed-circuit,  connecting  one 
station  with  another,  being  broken  by  the  open- 
ing of  the  switch  H,  or  the  working  of  the  key, 
so  as  to  open  and  close  its  contacts,  the  armature 
of  the  relay  opens  or  closes  the  circuit  of  the 
local  battery  and  operates  the  sounder  or  register- 
ing apparatus  connected  therewith.  (See  Sounder, 
Morse  Telegraphic.  Apparatus,  Registering, 
Telegraphic. ) 

Telegraphy,  Multiplex A  system 

of  telegraphy  for  the  simultaneous  transmis- 
sion of  more  than  four  separate  messages 
over  a  single  wire.  (See  Telegraphy,  Syn- 
chronous-Multiplex, Delany's  System.} 

Telegraphy,  Needle  System  of  -        — A 

system  of  telegraphy  in  which  signals  are 
transmitted  by  means  of  the  movements  of 
needles  under  the  influence  of  the  electric 
current.  (See  Telegraphy,  Single-Needle?) 


Telegraphy,  Phonoplex 


— A  system 


of  telegraphic  transmission  in  which  pulsatory 
currents,  superposed  on  the  ordinary  Morse 
currents,  actuate  a  modified  telephonic  re- 
ceiver, and  thus  permit  the  simultaneous 
transmission  of  several  separate  messages 
over  a  single  wire  without  interference. 

Telegraphy,  Printing  —  — A  system  of 
telegraphy  in  which  the  messages  received 
are  printed  on  a  paper  fillet. 

In  Callahan's  Printing  Telegraph,  two  type 
wheels  are  employed,  one  of  which  carries  letter 
type  and  the  other  numerals  on  its  circumference. 
These  printing  wheels  are  placed  alongside  of 
each  other,  as  shown  in  Fig.  532,  but  on  separ- 
ate and  independent  axes. 

The  type  wheels  are  moved  by  a  step -by -step 
device.  The  impulses  necessary  to  bring  the 


T.I.] 


512 


|TeL 


desired  letters  in  positi  -n  for  printing  are  auto- 
matically sent  by  a  circuit  maker  and  breaker. 
These  impulses  are  sent  into  the  line  by  the  de- 
pression of  keys  on  a  suitably  arranged  key- 
board. 

When  the  proper  letter  or  numeral  is  reached 
at  the  receiving  end,  the  printing  wheel  is 
stopped,  and  a  paper  fillet  is  pressed  against  its 
surface.  The  printing  wheel  is  kept  covered 
with  ink  by  means  of  an  inked  roller. 

The  transmitting  instrument  is  similar  in  its 
operation  to  the  Breguet  manipulator.  Separate 
transmitters  are  used  for  each  of  the  wires.  (See 
Telegraphy,  Step-  by  -  Step . ) 


Fig.  S32-     Callahan's  Printing  Telegraph. 

Telegraphy,  Quadruplex  —  — A  system 
for  the  simultaneous  transmission  of  four  mes- 
sages over  a  single  wire,  two  in  one  direction 
and  the  remaining  two  in  the  opposite  direc- 
tion. 

Quadruplex  telegraphy  consists  in  fact  of  du- 
plex telegraphy  duplexed. 

There  are  various  systems  of  quadruplex  teleg- 
raphy. The  most  important  are  the  bridge 
method  and  the  differential  method.  (See  Teleg- 
raphy, Quadruplex,  Bridge  Method  of.  Telegra- 
phy, Quadruplex,  Differential  Method  of.} 

Telegraphy,  Quadruplex,  Bridge  Method 

of  —  — A  system  of  quadruplex  telegraphy 
by  means  of  a  double  bridge  duplex  system. 
(See  Telegraphy,  Quadruplex.) 

In  the  bridge  method  of  quaHruplex  telegraphy, 
as  in  the  differential  metho-l,  changes  in  the  po'ar- 
ity  and  strength  of  the  current  are  utilized  to 
e-tablish  a  double  duplex  -ystcm  of  transmission. 
Fig.  533  from  Prescott's  "  EU-ctncity  an  I  Electric 
Telegraphy, "from  which  the  following  desciiption 


is  taken,  shows  the  method  first  employed  by  the 
Western  Union  Telegraph  Company  in  1874. 

A  double  current  transmitter,  or  pole  changer, 
is  shown  at  T',  with  its  operating  key  K'  and 
local  battery  e'.  This  instrument  interchanges 
the  poles  of  the  main  battery  E',  wnen  K,  is  de- 
pressed, and  thus  reverses  the  polarity  of  current 
on  the  line. 

The  increment  transmitter  T2,  is  connected  to 
the  battery  wire  12  of  T',  in  such  a  way  that 
when  K',  is  depressed,  the  main  battery  E',  is 
placed  in  series  with  battery  E,  of  say  twice  the 
strength  of  E',  thus  permitting  a  current  of  three- 
fold the  original  strength  to  be  sent  into  the  line. 


Fig.  533.     Quadruplex  Telegraphy,  Bridge  Method. 

Two  receiving  instruments  R'  and  R2,  a  e 
placed  at  the  distant  end  of  the  line.  R',  is  a 
polarized  relay  whose  armature  is  deflected  in 
one  direction  by  positive  currents,  and  in  the 
opposite  direction  by  negative  currents,  independ- 
ently of  their  strength.  That  is  to  say,  R',  re- 
sponds to  changes  in  the  direction  of  the  currents 
that  pass  through  its  coils,  but  not  to  changes  in 
their  strength.  (See  Relay,  Polarized.} 

Relay  R2,  is  non-polarized  and  the  movements 
of  its  soft  iron  armature  depend  on  a  change  in 
the  strength  of  the  current  only.  That  is  to  say, 
Ra,  responds  to  changes  in  the  strength  of  the 
current  passing  through  its  coils,  but  not  to 
changes  in  their  direction. 

These  two  relays  R  and  R8,  are  placed  in  the 
bridge  wire  of  a  \Vheatstone  bridge.  Ti.e  entire 
apparatus  of  transmitting  keys  and  relays  is 
duplicated  at  each  end  of  the  line.  Under  these 
conditions,  signals  transmitted  from  either  end  of 
the  line  affect  the  instruments  at  the  other  end  of 
the  line,  but  not  th«.ir  own  instruments,  in  the 
sime  manner  as  in  the  case  of  the  bridge  du 
plex.  (See  Telegraphy,  Duplex,  Bridge  Method 
of.} 

Telegraphy,    Quadruplex,     Differential 


Tel.] 


513 


[Tel, 


Method  of A   system  of  quadruplex 

telegraphy  by  means  of  a  double  differential 
duplex  system. 

Quadruplex  telegraphy  depends  for  its  opera- 
tio.i  on  the  use  of  two  differentially  wound  relays 
it  each  sta'ion.  One  of  these  relays  A,  as  shown 
in  Fi^.  534,  which  shows  the  general  arrangement 
of  the  system,  gives  signals  on  a  change  in  the 
i.irection  <  I  the  current,  but  none  on  a  change  in 
the  current  strength.  The  other  B,  gives  signals 
on  changes  in  current  strength,  but  none  on 
changes  in  direction.  They  are,  therefore,  in- 
dependent of  each  other,  and  operate  sounders 
that  are  under  the  independent  control  of  two 
distinct  receiving  operators. 

A  table,  divided  into  four  sections,  is  provided 
with  places  for  two  sending  and  two  receiving 
clerks.  The  name  "  A  side  "  is  given  to  the  side 
worked  by  the  reversed  currents,  and  the  "B_ 
side  "to  that  worked  by  the  strengthened  cur- 
nnts. 


CORRECTING 


BATTERY    1.    BATTERY    2. 

Fig.  3 3 4.    Quadruple*  Telegraphy,  Differential  Method. 

Referring  to  Fig.  534  the  reversing  key  on  the 
"  A  side  "  is  merely  indicated  so  as  to  avoid  con- 
fusion by  too  great  detail  ;  as  is  also  the  case  with 
the  increment  key  or  the  strengthening  key  at  B. 
From  the  connections  it  will  be  seen  that  when 
the  increment  key  is  at  rest,  the  reversing  key 
sends  currents  from  battery  I.  When  the  incre- 
ment key  is  depressed,  the  reversing  key  is  shifted 
from  battery  I,  and  connected  by  its  copper  con- 
necti  n  C,  with  the  battery  2,  of  double  the 
strength  of  I.  Since,  however,  I,  is  thus  connect- 
ed in  series  with  C,  the  current  strength  is  in- 
creased threefold. 

From  the  reversing  key  the  current  passes 
to  the  junction  of  the  two  coils  with  which  the 
relay  B,  is  differentially  w»und.  It  divides  here 
between  these  coils,  which  are  connected  to  simi- 


lar coils  on  relay  A,  as  shown.  The  current 
from  one  coil  on  A,  is  sent  to  line,  while  that  trom 
the  other  coil  goes  to  earth  through  the  compen- 
sating rheostat.  This  arrangement  forms  a  du- 
plex system,  the  outgoing  currents  of  which  have 
no  effect  on  the  home  relays. 

Resistances  R2  and  R;i,  are  connected  to  the 
batteries  I  and  2,  and  the  stops  in  the  increment 
key  in  the  manner  shown,  to  the  resistance  of  R3 
and  R3.  The  former  is  used  in  order  to  main- 
tain the  resistance  of  the  circuit,  whether  the  bat- 
tery is  in  or  out  of  circuit.  The  latter  is  called 
the  spark  coil,  and  is  intended  to  decrease  the 
sparking  on  closing  circuit. 

When  both  are  at  rest,  battery  I,  has  its  zinc 
connected  to  line  through  A,  and  its  copper  to 
earth  through  R2,  C  I,  the  lever  of  key  B  and 
key  A,  which  last  two  are  permanently  connect- 
ed. A  reversed  or  spacing  current  goes  to  line, 
without  affecting  the  home  relays,  since  it  passes 
in  opposite  directions  and  with  equal  strength 
through  differentially  wound  coils. 

When,  however,,  the  key  A,  is  worked  alone, 
it  reverses  the  current  and  the  signal  is  recorded 
by  tlje  distant  relay  A. 

If  key  B,  is  worked  alone,  it  breaks  connection 
with  copper  at  the  junction  of  the  two  batteries, 
and  makes  contact  with  terminal  copper  of  battery 
2,  so  as  to  send  a  zinc  current  of  threefold  strength. 
The  distant  relay  B,  records  a  signal  because  the 
current  is  now  strong  enough  to  move  it.  Relay 
A,  however,  is  not  affected,  since  the  current  has 
not  been  reversed. 

When  both  keys  are  simultaneously  in  action, 
then  whenever  B,  is  pressed,  although  the  strength 
of  A,  may  be  increased,  since  its  direction  is  not 
changed,  the  polarized  tongue  of  its  relay  is  un- 
affected by  the  movement  of  B,  but  any  increase 
of  current  causes  the  armature  of  the  distant  re- 
lay of  B,  to  move. 

This  armature  is  held  in  position  by  springs  of 
such  a  strength  as  to  prevent  its  motion  by  a 
weak  current,  and  being  unpolarized,  responds  to 
either  positive  or  negative  currents.  It,  there- 
fore, re-ponds  to  B,  and  records  a  signal.  When 
A,  is  pressed,  it  reverses  the  current,  and  conse- 
quently moves  the  distant  relay  A,  but  has  no 
effect  on  B,  since  it  causes  no  alternation  in  the 
strength  of  the  current. 

The  author  has  taken  the  above  almost  liter- 
ally fromCulley's  "  Handbook  ot  Practical  Teleg- 
raphy,"  to  which  the  reader  is  referred  for  a  fuller 
description  and  details  of  apparatus. 


Tel.] 


514 


[Tel. 


Telegraphy,  Simplex A  system  of 

telegraphy  in  which  a  single  message  only 
can  be  sent  over  the  line. 

Telegraphy,  Single-Needle A  sys- 
tem of  telegraphy  by  means  of  which  the 


F'£-  S3S-    Single-Needle  Telegraphic  Apparatus. 

signals  transmitted  are  received  by  observing 
the  movements  of  a  vertical  needle  over  a 
dial. 


Fif.  S3  6.      Wheat  stone  and  Cooke's  Single- Needle  Appa- 
ratus, Internal  Arrangement. 

Movements  of  the  top  of  the  needle  to  the  right 


of  the  observer  represent  the  dashes,  and  move- 
ments  to  the  left,  the  'dots  of  the  Morse  alpha- 
bet. 

The  single-needle  apparatus  of  Wheatstone  and 
Cooke's  system  is  shown  in  Figs.  535,  and  536. 
Fig.  535,  shows  the  external  appearance,  and  Fig. 


Fig.  S3  ?•     Wheatstone  and  Cooke's  Single-Needle  Ap- 
paratus. External  View. 

536,  the  internal  arrangements  as  seen  from  the 
back.     An  astatic  needle  is  placed  inside  two  coi) 
of  insulated  wire  C  C.     Only 
one  of  these  needles  N,  is  vis- 
ible on  the  face  of  the  receiving 
instrument.    The  current  from 
the  line   enters   at  L,   passes 
through    the    coil    C   C,    and 
leaves  at  N. 

The  movements  of  the  needle 
to  the  right  or  the  left  are  ob- 
tained by  changing  the  direc- 
tion of  the  current  in  the  coils 
C  C.  This  is  effected  by  work- 
ing the  handle  when  sending, 
and  thus  moving  the  commuta- 
tor at  S,  S,  and  bringing  the 
contact  springs  resting  thereon 
into  different  contacts. 

In  the  more  modern  form  of  single-needle  in- 
strument, shown  in  Fig.  537,  a  single  magnetic 
needle  N  S,  Fig.  538,  only  is  placed  in  the 
coil. 

This  needle  is  rigidly  attached  to  a  light  needle 
a,  b,  used  only  as  a  pointer,  and  is  alone  visible 
in  the  front  of  the  instrument.  The  relative  dis- 
position of  these  needles  is  shown  in  Fig.  538. 

The  reversals  of  the  current,  required  to  deflect 
the  needle  to  the  right  or  left,  are  obtained  by 


Fig.  338.    Needle 
and  Pointer. 


Tel.] 


515 


[Tel. 


means  of  a  double  key  or  tapper,  shown  in  Fig. 

539- 

The  levfrs  L  and  E,  are  connected  respectively 
to  line  and  earth,  and,  when  not  in  use,  rest  against 
C,  connected  with  the  po.-iiive 
side  of  the  battery;  but  when  de- 
pre<?ed  connect  with  Z,  attached 
to  the  negative  side  of  the  bat- 
tery. 

The  depression  of  L,  therefore, 
sends  a  negative  current  into  the 
line  and  deflects  the  needle,  say, 
to  the  left,  while  the  depression 
of  E,  sends  a  positive  current  into 
the  line  and  deflects  the  needle  Fig.  SS9-    Double 
to  the  right.     The  terms  positive    Key  or  Tapper. 
and  negative  currents  are  usL'd  in  telegraphy  to 
indicate  currents   whose   direction  is  positive  or 
negative. 

Telegraphy,    Speaking A    system 

for  the  telegraphic  transmission  of  articulate 
speech.     (See  Telephone.] 

Telegraphy,  Step-by-Step A  sys- 
tem of  telegraphy  in  which  the  signals  are 
registered  by  the  movements  of  a  needle  over 
a  dial  on  which  the  letters  of  the  alphabet, 
etc.,  are  marked. 

Dial  telegraphs  are  especially  employed  for 
communication  by  those  who  are  unable  to  readily 
read  the  Morse  characters. 

The  annexed  instrument,  devised  by  Breguet, 
"was  formerly  used  on  some  of  the  railway  sys- 
tems of  France. 

A  needle  advances  over  a  dial  by  a  step-by-step 


Fig.  340.     Step-by-Step  Wheel. 

movement  in  one  direction  only.  The  alternate 
to-and-fro  motions  of  the  armature  of  an  electro- 
magnet are  employed  to  i  npart  a  step-by-step 
mot  on  to  a  peculiarly  shaped  toothed  wheel 


T,  T,  Fig.  540,  through  the  action  of  a  horizontal 
arm  c,  attached  thereto  and  moving  between  the 
two  prongs  of  a  fork  d.  vibrating  on  a  horizontal 
axis  to  which  is  attached  a  vertical  pallet  i. 

The  receiving  instrument  is  called  the  indicator, 
and  consists  of  a  needle  attached  to  the  axis  of 
this  wheel.  The  needle  moves  over  the  fiace  of 


Fig.  341.    Breguet' s  Indicator. 

the  dial,  shown  in  Fig.  541,  on  which  are  marked 
the  letters  of  the  alphabet  and  the  numerals. 

The  sending  instrument  is  called  the  manipu- 
lator. It  consists  of  a  device  for  readily  sending 
over  the  line  the  number  of  successive  impulses 
required  to  move  the  needle  step-by-step  from 
any  letter  on  the  indicator  to  which  it  may  be 
pointing,  to  the  next  it  is  desired  to  send. 

The  dial,  shown  in  Fig.  542,  is  marked  on  its 
face  with  the  same  characters  as  the  indicator. 
The  edge  of  the  wheel  is  provided  with  twenty-six 
notches  in  which  a  pin  attached  to  a  movable  arm 
engages.  The  arm  is  jointed  so  that  it  can  be 
placed  in  any  of  the  notches  on  the  face  of  the 
wheel. 


Fig.  542.    Breguet' s  Manipulator. 

Below  the  dial  face,  and  attached  to  the  same 
axis  as  the  movab'e  aim,  is  a  wheel  provided 
with  undulations  consisting  of  thirteen  eleva'ions 
and  thirteen  depressions. 


Tel.] 


516 


[Tel. 


A  lever  T,  pivoted  at  a,  rests  in  these  undu- 
lations at  its  upper  end,  and  plays  between  two 
contact  points  at  P  and  Q. 

If,  now,  the  dials  of  the  indicator  and  the  man- 
ipulator both  being  at  O,  a  movement  is  given  to 
the  arm  by  the  handle  M,  to  any  point  on  the 
manipulator,  there  are  thus  produced  the  required 
number  of  makes  and  breaks  to  move  the  needle 
of  the  indicator  to  the  corresponding  letter  or 
character. 

Telegraphy,  Submarine A  system 

of  telegraphy  in  which  the  line  wire  consists 
of  a  submarine  cable. 

In  long  submarine  cables,  in  order  to  avoid 
retardation  from  the  self-induction  of  the  cur- 
rent, and  the  static  charge  arising  from  the  cable 
acting  as  a  condenser,  very  small  currents  are 
used.  To  detect  these  a  very  sensitive  receiving 
instrument,  such  as  the  mirror  galvanometer,  or 
the  siphon  recorder,  is  employed.  (See  Galva- 
nometer, Mirror.  Recorder,  Siphon.} 

According  to  Culley,  the  retardation  in  the 
case  of  one  of  the  submarine  cables  between 
Newfoundland  and  Ireland,  amounts  to  two- 
tenths  of  a  second  before  a  signal  sent  from  one  end 
produces  any  appreciable  effect  at  the  other  end, 
while  three-tenths  of  a  second  are  required  for  the 
current  through  the  cable  to  gain  its  full  strength. 

Telegraphy,  Synchronous- M  u  1 1  i  p  1  e  x, 

Delany's  System A  system  devised 

by  Delany  for  the  simultaneous  telegraphic 
transmission  of  a  number  of  messages  either 
all  in  the  same  direction,  or  part  in  one  direc- 
tion and  the  remainder  in  the  opposite  direc- 
tion. 

The  Delany  system  embraces  the  following 
parts  : 

(i.)  A  circular  table  of  alternate1  y  insulated 
and  grounded  contacts  at  either  end  of  a  tele- 
graphic line. 

(2.)  A  synchronized  rotating  arm  or  trailing 
contact,  at  each  end  ot  the  line,  driven  by  a 
phonic  -wheel,  and  maintained  in  synchronous 
rotation  by  means  of  electric  impulses  automatic- 
ally sent  out  over  the  main  line  in  either  direc- 
tion, on  the  failure  of  the  wheel  at  either  end  to 
rotate  synchronously  with  that  at  the  other  end. 

(3.)  Transmitting  and  receiving  instruments 
connecting  similar  conta  ts  at  each  end  of  the 
main  line,  and  forming  practically  separate  aid 
independent  lines  for  the  simultaneous  transmis- 


sion of  dispatches  over  the  main  line  in  either 
direction. 

The  main  line  is  simultaneously  connected  at 
both  of  its  ends  to  corresponding  operating  in- 
struments, and  transferred  from  one  set  of  instru- 
ments to  another  so  rapidly  that  the  operators, 
either  sending  or  receiving,  cannot  realize  that 
the  line  has  been  disconnected  from  their  instru- 
ments and  given  to  others,  because  each  of  them 
will  always  have  the  line  ready  for  use,  even  at 
the  highest  rate  of  manipulation,  and  will,  there- 
fore, to  all  practical  intents  and  purposes,  have 
at  his  disposal  a  private  wire  between  himself 
and  the  operator  with  whom  he  is  in  communica- 
tion. 

Therefore,  although  more  than  one  operator 
may  be  spoken  of  as  simultaneously  using  the 
line  at  any  given  time,  yet  in  reality  no  two  ope- 
rators are  absolutely  using  it  at  the  same  time;, 
but  they  follow  one  another  at  such  short  in- 
tervals, and  the  line  is  taken  from  one  operator 
and  transferred  to  another  so  rapidly,  that  none 
of  them  can  at  any  time  tell  but  that  he  has  the 
line  alone,  and  that  therefore  it  is  practically 
open  for  the  use  of  every  operator  just  as  if  he 
alone  had  control  of  it. 

There  will,  therefore,  be  established,  by  the 
use  of  a  single  line,  as  many  private  and  separate 
lines  as  there  are  transferences  of  the  line  from 
the  time  it  is  taken  from  the  first  operator,  and 
again  given  back  to  him. 

This  system  has  been  extended  to  as  many  as 
seventy-two  distinct  and  separate  priming  cir- 
cuits, maintained  and  operated  on  a  single  con- 
necting line  wire. 

The  speed  at  which  the  circuits  may  be  operated 
is  in  the  inverse  order  of  the  number  of  circuits 
organized.  The  best  results,  practically,  are 
obtained  from  six  divisions  of  the  contacts  in  the 
circle,  which  gives  each  operator  about  36  con- 
tacts with  the  line  per  second,  a  speed  which  ad- 
mits of  the  highest  rate  of  transmission  on  each  of 
the  six  circuits. 

Fig.  543  shows  the  apparatus  at  each  end  of 
the  line,  at  the  stations  X  and  Y.  The  apparatus 
at  each  end  is  substantially  identical.  A  steel 
fork  a,  at  each  station,  is  automatically  and  con- 
tinuously vibrated  by  the  action  of  the  local  bat- 
tery L  B,  and  the  electro-magnet  A,  called  the 
vibrator  magnet. 

Platinum  contacts  x,  x1,  placed  on  the  inm-r 
face>  of  the  tines  of  the  fork,  make  and  bnak 
contact  with  delicate  contact  springs  y,  y1. 


Tel.] 


51? 


|Te<, 


The  fork  being  mechanically  started  into  a 
vibratory  motion,  will  automatically  make  and 
break  its  local  circuit,  and  thus  send  impulses 
into  the  fork  magnet  A,  that  will  continuously 
maintain  the  vibrations  of  the  fork,  in  a  well 
known  manner. 

The  making  and  breaking  of  the  contacts  x 
and  y,  consequent  on  the  fork's  vibration,  open 
and  close  another  local  battery  placed  in  a  circuit 
called  the  motor  circuit,  in  which  is  also  placed  an 
electro-magnet  D,  the  function  of  which  is  to 
maintain  the  continuous  rotation  of  the  trans- 
mission apparatus  C. 


disc  C,  is  rotated   by  the  electro-magnet  D,  the 
trailing   contact   f,  sweeps  around  the  circular 


Fig.  343.     Delany's  Synchronous  Mutiplex  Telegraph. 

The  continuous  vibration  of  the  fork  makes  and 
breaks  the  contacts  at  x  and  y,  and  thereby 
makes  and  breaks  the  motor  circuit.  The  alter- 
nate  magnetizations  and  demagnetizations  of  the 
cores  of  the  motor-magnet  D,  cause  the  rotation 
of  the  transmission  apparatus  C. 

The  motor  magnet  and  transmission  wheel  or 
disc  C,  provided  with  projections  c,  c,  is  the  in- 
vention of  Paul  La  Cour,  and  is  styled  by  him  a 
"phonic  wheel." 

The  transmission  apparatus  is  illustrated  in  de- 
tail in  Figs.  544  and  545,  and  is  an  exact  coun- 
terpart of  the  receiving  apparatus  at  the  other 
end  of  the  line.  A  base  plate  E,  provided  with 


•f'f-  544-     'I he  I'honic  II  heel. 

binding  posts,  carries  a  vertical  rotary  shaft  F. 
A  circular  table  F1,  is  provided  with  a  series  of 
insulated  contacts  arranged  symmetrically  around 
the  axis  of  rotation  of  the  shaft.  A  radial  arm  Fz, 
connected  with  the  shaft  F,  carries  at  its  outer 
extremity  a  trailing  contact  finger  f.  As  the 


Fig*  545-     Th*  Phonic  Wheel. 

table  F1,  and  is  brought  successively  into  contact 
with  the  insulated  contact  pieces  placed  on  the 
upper  face  of  the  table  F1. 

The  main  line  Q,  Q,  has  one  of  its  ends  con- 
nected with  the  trailing  finger  f.  As  the  shaft 
F,  rotates,  the  line  is  therefore  brought  into  suc- 
cessive electrical  connection  with  the  series  of  in- 
sulated contacts  in  the  upper  face  of  the  table 
FI. 

Any  suitable  number  of  insulated  contacts  may 
be  placed  on  the  circular  table  F1;  sixty  are 
shown  in  Fig.  546.  In  practice  these  contacts 
are  connected  in  accordance  with  the  number  of 
circuits  which  it  is  desired  to  simultaneously 
maintain  on  the  same  wire.  In  the  special  case 
shown  in  the  figure  above  referred  to,  it  is  ar- 
ranged so  that  four  separate  circuits  shill  be 
established  on  the  same  line  wire. 

The  sixty  contacts  are  placed  in  six  indepen- 
dent series,  numbered  from  I  to  10,  consecu- 
tively. In  the  arrangement  here  shown  two  of 
the  contact  pieces  in  each  series  of  ten  are  con- 
nected in  the  same  circuit,  and,  as  there  are  six 
series,  each  of  the  circuits  so  connected  will  have 
twelve  contacts  for  each  rotation  of  the  disc,  and 
twelve  electrical  impulses,  as  will  be  afterwards 
described. 

The  detailed  mechanism,  by  means  of  which 
the  separate  and  independent  circuits  so  obtained 
are  utilized  for  the  transmission  and  reception  of 
messages,  is  shown  in  Fig.  546.  R,  R1,  Rs  and 
R3,  are  polarized  relays;  S,  S1,  S*  and  S;J  are 
ordinary  Morse  sounders,  although  in  the  practice 
of  this  invention  some  improvement  has  been  in- 
troduced in  connection  with  the  receiving  instru- 
ments. The  connections  with  the  main  and  the 
local  batteries  M  B  and  L  B,  are  clearly  shown 
in  the  figure. 

It  will  be  noticed  that  the  relay  R,  is  connected 


Tel.] 


518 


[Tel. 


-with  the  wire  r,  and  with  the  contacts  I  and  5  ; 
R1  is  connected  by  r1,  with  the  contacts  2  and  6, 
Re,  by  the  wire  r',  with  the  contacts  3  and  7, 
and  R8,  by  the  wire  r3,  with  the  contacts  4  and 
8.  Similar  instruments  and  circuits  are  placed 
at  each  end  of  the  line. 

Without  further  describing  the  operation  of  the 
instruments  shown  in  the  figure,  it  need  only  now 
be  borne  in  mind  that  the  corresponding  relays  at 
the  distant  stations  are  connected  with  the  corre- 
spondingly numbered  contacts.  When,  therefore, 
the  trailing  contact  finger  at  each  station  simul- 
taneously touches  the  contacts  bearing  the  same 
number,  the  corresponding  instruments  connected 


Pig,  34.6,     Working  and  Receiving  Currents. 

•with  these  contacts  at  each  station  will  be  placed 
in  communication  over  the  main  line,  the  trailing 
contact  finger  f,  completing  the  connection  of 
the  main  line  with  the  contact  arm  in  the  man- 
ner already  described. 

Telegraphy,  Time A  system  for 

the  telegraphic  transmission  of  time. 

A  system  of  time  telegraphy  includes  a  master 
clock,  the  movements  of  whose  pendulum  automati- 
cally transmit  a  number  of  electric  impulses  to  a 
number  of  secondary  docks  and  thus  moves  them ; 
or  self-winding  clocks  are  employed,  which  are 
corrected  daily  by  an  impulse  sent  over  the  line 
from  a  master  clock.  (See  Clock,  Electric.') 

Telegraphy,  Writing A  species  of 

:ac-simile  telegraphy,  by  means  of  which 
the  motions  of  a  pen  attached  to  a  transmit- 
ting instrument  so  vary  the  resistance  on 
two  lines  connected  with  a  receiving  instru- 
ment as  to  cause  the  current  received  thereby 
to  reproduce  the  motions,  on  a  pen  or  stylus, 
which  transfers  them  to  a  sheet  of  paper. 


A  system  of  writing  telegraphy  consists 
essentially  of  transmitting  and  receiving  in- 
struments connected  by  a  double  line  wire. 

The  transmitting  instrument  is  shown  in  Fig. 
547- 


Fig.  547.     Transmitter  of  Writing  Telegraphy. 

A  stylus  or  pen  resting  on  a  top  plate,  is  con- 
nected by  the  rod  C,  with  a  series  of  steel  contact 
springs  S,  S,  secured  to  the  base  and  placed  at 
right  angles  to  one  another.  A  series  of  resist- 
ances R,  R,  are  connected  with  the  lower  ends 
of  these  contact  springs.  Two  contact  bars, 
B,  B,  are  provided  on  the  side  facing  the  springs 
with  platinum  contacts  opposite  the  contacts  on 
the  springs.  The  stylus  rod  C,  is  securely  fixed 
to  the  base,  but  a  spring  at  the  lower  end  per- 
mits of  its  free  movement.  A  pressure  block  at 
P,  is  fastened  to  the  stylus  rod,  as  shown,  and  in 
its  normal  position  the  pressures  are  adjusted  so 
that  contact  is  secured  with  the  first  spring. 

A  movement  of  the  stylus,  as  in  writing, 
presses  the  contact  bar  against  the  spring,  vary- 
ing the  position  and  number  of  contacts,  and 
thereby  cutting  in  or  out  the  resistance  necessary 
to  effect  the  proper  movement  of  the  receiving 
pen. 

The  receiving  instrument  is  shown  in  Fig.  548. 
It  consists  of  two  electro-magnets  placed  at  right 
angles  to  each  other.  A  double  armature  sup- 


Tel. 


519 


[Tel. 


ports  the  receiving  stylus  or  pen  in  the  manner 
shown.  The  variations  in  the  current  sent  over 
the  line  by  the  varying  resistances  introduced 
into  the  circuit,  or  cut  out  or  in  by  the  action  of 
the  transmitting  stylus,  causes  variations  in  the 
position  of  the  double  armature,  under  the  vary- 
ing magnetic  attraction  of  the  receiving  electro- 
magnet, and  thus  causes  the  receiving  pen  to 
correctly  reproduce  the  motions  of  the  trans- 
mitting pen. 


Fig.  548,     Receiver  of  Writing  Telegraph. 

This  system  has  been  operated  over  a  line 
nearly  500  miles  in  length,  when  it  successfully 
reproduced  written  characters. 

The  author  is  indebted  for  the  drawings  and 
the  general  facts  to  the  Electrical  Engineer  of 
New  York. 

Tele-Hydro-Barometer,  Electric 

An  apparatus  for  electrically  transmitting  to, 
and  recording  at  a  distant  station  the  height 
of  water  or  other  liquid. 

Tele-Manometer,     Electric     — A 

gauge  for  electrically  indicating  and  record- 
ing pressure  at  a  distance. 

The  tele-manometer  includes  a  pressure  gauge 
furnished  with  electric  contacts  operated  by  the 
movements  of  the  needle  of  the  steam  gauge,  for 
instance,  and  indicating  and  recording  apparatus. 
An  alarm  bell  is  provided  to  call  attention  to  any 


rise  of  the  pressure  above  or  its  fall  below  the 
given  or  predetermined  limits  for  which  the 
hands  have  been  set. 

Telemeter. — An  apparatus  for  electrically 
indicating  and  recording  at  a  distance  the 
pressure  on  a  gauge,  the  reading  of  a  ther- 
mometer, or  the  indications  of  similar  in- 
struments. (See  Tele-Hydro-Barometer, 
Electric.  Tele-Manometer,  Electric.  Tele- 
Thermometer,  Electric?) 

Telephone. —To  communicate  by  means 
of  a  telephone. 

Telephone. — An  apparatus  for  the  electric 
transmission  of  articulate  speech. 

The  articulating  telephone,  though  first 
brought  into  public  use  by  Bell,  was  invented  by 
Reis,  in  Germany,  in  1861.  In  America,  after 
very  protracted  litigation,  Bell  has  been  decided 
legally  to  be  the  first  inventor,  but  scientific  men 
very  generally  recognize  the  principles  of  the  in- 
vention to  be  fully  anticipated  by  the  earlier  in- 
struments of  Reis.  Bell,  however,  is  ittstly  en- 
titled to  the  credit  of  inventing  the  first  really 
successful  telephone. 

In  Bell's  magneto-electric  telephone,  the 
transmitting  and  receiving  instruments  are  iden- 
tical. A  coil  C,  of  insulated  wire  connected  with 
the  line,  is  placed  on  a  core  of  magnetized  steel, 
mounted  opposite  the  centre  of  a  circular  dia- 
phragm of  thin  sheet  iron,  rigidly  supported  at 
its  edges. 

In  transmitting,  the  message  is  spoken  into  the 
mouth-piece  at  one  end,  as  at  D,  in  Fig.  549,  and 
the  to-and-fro  motions  thus 
imparted  to  the  metallic 
diaphragm  attached  to  the 
mouth-piece  P,  produce  in- 
duction currents  in  the  coil 
C,  on  the  magnet  M.  (See  In- 
duction, Electro-Dynamic.} 
These  impulses,  passing  over 
the  main  line  E  L,  Fig.  550, 
produce  similar  movements 
in  the  diaphragm  P',  of  the 
receiving  instrument,  at  D', 
and  thus  cause  it  to  repro- 
duce the  message,  in  articu- 
late  sounds,  to  one  listening  at  the  receiving  in- 
strument. A  ground  circuit  is  shown  in  the 
figure,  as  usually  employed  in  practice,  except 
for  long  distance  and  in  large  cities. 


Tel.] 


520 


[Tel. 


A  magneto-telephone  constitutes  in  reality  a 
magneto-electric  machine,  driven  or  propelled  by 
the  voice  of  the  speaker,  in  which  the  currents 
so  produced  instead  of  being  commuted  are  em- 
ployed uncommuted  to  reproduce  the  uttered 
speech. 

In  actual  practice  the  instrument  above  de- 
scribed is  replaced  by  the  electro-magnetic  tele- 

E  a  L 

D' 


B 

Fig.  SS°-     Telephone  Circuit. 

phone,  in  which  the  to-and-fro  motions  of  the 
transmitting  diaphragm  are  caused  to  vary  the 
resistance  of  a  button  of  carbon,  or  a  variable  con- 
tact transmitter  similar  to 
that  employed  by  Reis  in 
some  of  his  instruments. 
The  variable  resistance 
is  placed  in  the  circuit  of 
a  battery,  so  that  on 
speaking  into  the  trans- 
mitter, electric  impulses 
are  sent  over  the  line  and 
are  received  by  a  tele- 
phone with  a  magnet  core 
provided  with  a  coil  in  the 
main-line  circuit. 

The    telephone    is    ar- 
ranged for    actual    com- 
mercial use  in  the  United 
States    in     the     manner/7/^.  55 '•    Telephone  Ap- 
shown  in  Fig.  551.  paratus. 

Telephone.  Bi A  term  sometimes 

applied  to  a  double  telephone  receiver  so  ar- 
ranged as  to  permit  of  easy  application  to 
both  ears  of  the  listener  at  the  receiving  in- 
strument. 

Telephone  Cords.— (See  Cords,  Tele- 
phoned) 

Telephone,  Electro-Capillary  -  —A 
telephone  in  which  the  movements  of  the 
transmitting  diaphragm  produce  currents  by 
means  of  variations  in  the  electromotive 
forces  of  the  contact  surfaces  of  liquids  in 
capillary  tubes.  (See  Phenomena,  Electro- 
Capillary^) 

In  Breguet's  telephone  both  the  transmitting 
and  the  receiving  instruments  are  similar  in  con- 


struction and  operate  by  means  of  electro-capil- 
lary phenomena.  A  vertical  capillary  tube  com- 
municates at  its  upper  end  with  an  air  space 
below  a  diaphragm,  and  at  its  lower  end  with  a 
mercury  surface  on  which  rests  a  layer  of  acidu- 
lated water. 

A  line  wire  connects  the  mercury  reservoirs  of 
the  transmitting  and  receiving  instruments,  the 
remainder  of  the  circuit  being  formed  by  another 
wire  connecting  the  mercury  near  the  upper  parts 
of  the  two  vertical  tubes. 

The  alterations  in  the  contact  surfaces  at  the 
transmitting  end  produced  by  the  movements  of 
the  diaphragm,  cause  electric  impulses  that  pro- 
duce similar  movements  of  the  diaphragm  at  the 
receiving  end. 

Telephone,  Electro-Chemical A 

name  sometimes  given  to  the  Edison  electro- 
motographic  telephone.  (See  Telephone, 
Electro-Motographic?) 

Telephone,  Electro-Motographic 

A  telephone  in  which  the  receiver  consists  of 
a  diaphragm  of  mica  or  other  elastic  material 
operated  on  the  principle  of  the  electro- 
motograph. 

A  straight  lever,  which  forms  part  of  the  line 
circuit,  is  rigidly  attached  at  one  end  to  the  centre 
of  the  receiving  diaphragm,  and  rests  near  its 
other  end  on  the  surface  of  a  chalk  cylinder 
moistened  with  a  solution  of  caustic  potash  or 
potassium  iodide,  maintained  in  rotation  by  suit- 
able mechanical  means. 

Electric  impulses  being  sent  into  the  line  by  the 
voice  of  a  speaker  talking  at  a  transmitter  of  ordi- 
nary construction  reduce  the  friction  between  the 
lever  and  the  cylinder,  and  produce  slipping 
movements  of  the  lever  that  reproduce  articulate 
speech  in  the  receiving  diaphragm. 

Telephone,  Reaction An  electro- 
magnetic telephone  in  which  the  currents  in- 
duced in  a  coil  of  wire  attached  to  the  dia- 
phragm are  passed  through  the  coils  of  the 
electro-magnet,  and  thus  react  on  and 
strengthen  it. 

Telephone  Switch,  Automatic  —  — (See 
Switch,  Telephone,  Automatic?) 

Telephonic. — Pertaining  to  the  telephone. 

Telephonic  Alarm.— (See  Alarm,  Tele" 
phonic?) 


Tel.] 


521 


[Tel, 


Telephonic  Cable.  —  (See  Cable,  Tele- 
phonic^) 

Telephonic  Exchange. — (See  Exchange, 
Telephonic,  System  of.) 

Telephonic  Exchange,  System  of  — 
(See  Exchange,  Telephonic,  System  of.) 

Telephonic  Joints. — (See  Joint,  Tele- 
graphic or  Telephonic?) 

Telephonically. —  In  the  manner  of  the 
telephone.  (See  Telephoned) 

Telephoning. — Communicating  by  means 
of  the  telephone. 

Telephote. — An  apparatus  for  the  tele- 
graphic transmission  of  pictures  by  means  of 
the  action  of  light  on  selenium1.  (See  Tele- 
photography^) 

The  telephote  is  sometimes  called  the  pherope. 

Telephotography. — A  system  for  fac- 
simile transmission  by  means  of  dots  and 
lines  transmitted  by  means  of  a  continuous 
current  whose  intensity  is  varied  by  a  trans- 
mitting instrument  containing  a  selenium  re- 
sistance. (See  Telegraphy,  Fac-Simile. 
Resistance  or  Cell,  Selenium?) 

The  transmitter  consists  of  a  dark  box  mounted 
on  an  axis,  so  as  to  be  capable  of  a  sidewise 
motion.  The  picture  to  be  transmitted  is 
thrown  continuously  on  the  face  of  the  box  by 
any  lantern  projection  apparatus,  and  a  small 
opening  containing  a  selenium  resistance  receives 


wise  continuous  current  in  the  circuit  of  which  the 
selenium  resistance  is  placed. 

The  picture  is  received  at  the  other  end  on  a 
sheet  of  chemically  prepared  paper  moved  syn- 
chronously with  the  transmitting  box. 

Telescope,  Reading A  telescope 

employed  in  electric  measurements  for  read- 
ing the  deflections  of  the  galvanometer. 

The  image  of  numbers  on  an  illumined  scale  is 
seen  in  the  mirror  through  the  telescope,  shown 
in  Fig.  552. 

Teleseme. — A  self-registering  hotel  an- 
nunciator, by  means  of  which  a  dial  operated 
in  a  room  indicates  on  the  annunciator  the 
article  or  service  required. 

Tele-Thermometer,  Electric  -  — An 
electric  recording  thermometer  for  indicating 
and  recording  temperature  at  a  distance. 

The  tele- thermometer  consists  essentially  of  a 
transmitter  and  a  receiver.  The  transmitter 
consists  of  a  delicate  thermometer  provided  with 
suitable  contacts.  The  receiver,  which  is  in 
circuit  with  the  transmitter,  has,  in  some  forms, 
a  recording  dial  on  which  a  continuous  record, 
for  a  day  or  week,  is  made.  In  cases  where  it  is 
desired  that  a  given  maximum  temperature  shall 
not  be  exceeded,  an  alarm  bell,  connected  with 
contacts  on  the  dial  face,  is  rung. 

Telluric    Magnetic  Force. — (See  Forct, 
Magnetic,  Telluric?) 
Telpher  Line.— (See  Line,  Telpher^ 
Telpherage.— A  system  for  the  convey- 
ance  of  carriages  suspended  from  electric 


ffg.  352.    Reading  Telescope. 

the  alternations  of  light  and  shade,  and  transmits 
the  same  a-;  variatio  .sin  the  strength  of  the  other- 


fif-SSS-     C.rcuitfor  Telphtrage  System 

conductors,  and  driven  by  means  of  electric 
motors,  that  take  directly  from  the  conductors 
the  current  required  to  energize  them. 


Tern.] 


522 


[The. 


Two  lines  are  provided,  an  up  and  a  down  line, 
that  cross  each  other  at  regular  intervals.  Each 
line  is  in  segments,  and  the  alternate  segments 
are  insulated  from  each  other,  but  are  connected 
electrically  by  cross-pieces  on  the  supporting 
posts.  In  this  way  the  line  shown  in  Fig.  553  is 
obtained. 

The  two  lines  are  maintained  at  a  difference  of 
potential  by  a  dynamo-electric  machine  at  D, 
Fig.  554.  As  the  train  at  L  T,  or  L'  T',  is  of 
such  a  length  as  to  come  into  contact  with  two 
different  segments  at  the  same  time,  it  receives  a 
current  sufficient  to  run  the  motor  connected  with 
it,  the  current  being  received  through  a  conduc- 
tor joining  a  pair  of  wheels  that  are  insulated 
from  the  truck. 

The  general  arrangement  of  the  line  is  shown 
in  the  annexed  Fig.  554 


Fig.  SS4-     Circuit  for  Telpherage  System. 

Temperature  Alarm. — (See  Alarm,  Tem- 
perature.} 

Temperature,  Effects  of,  on  Electric  Re- 
sistance   (See  Resistance,  Effect  of 

Heat  on  Electric?) 

Tempering,  Electric  — A   process 

for  temperaing  metals  in  which  heat  of  elec- 
tric origin  is  employed  instead  of  ordinary 
furnace  heat. 

Temporary  Intensity  of  Magnetization. — 

(See  Magnetization,  Temporary  Intensity 
of.) 

Tension,  Electric A  term  often 

loosely  applied  to  signify  indifferently  surface 
density,  electromotive  force,  dielectric  stress, 
or  difference  of  potential. 

This  term  is  now  very  generally  abandoned. 

Terminal,  Cable  — —  — A  water-tight 
covering  provided  at  the  end  of  a  cable  to 
prevent  injury  to  the  cable  insulation  by  the 
moisture  of  the  air. 

Terminal,  Negative The  negative 

pole  of  a  battery  or  other  electric  source,  or 
the  end  of  the  conductor  or  wire  connected 
with  the  positive  plate. 


Terminal,  Positive The  positive 

pole  of  a  battery  or  other  electric  source,  or 
the  end  of  the  conductor  or  wire  connected 
to  the  negative  plate. 

Terminals. — A  name  sometimes    applied 
to  the  poles  of  a  battery  or   other  electric 
source,  or  to  the  ends  of  the  conductors  or. 
wires  connected  thereto. 

The  two  terminals  are  distinguished  as  the 
positive  and  the  negative.  Their  names  are  un- 
like those  of  the  battery  plates  to  which  they 
are  connected,  the  positive  terminal  being  con- 
nected with  the  negative  plate  and  the  negative 
terminal  with  the  positive  plate. 

Terrestrial  Magnetism. — (See  Magnet- 
ism, Terrestrial) 

Testing,  Methods  of  —Various 

methods  for  determining  the  values  of  the 
current  strength  in  any  circuit,  the  difference 
of  potential,  the  resistance,  the  coulombs, 
the  farads,  the  joules,  the  watts,  etc.  (See 
Measurements,  Electric) 

The  investigation  of  an  apparatus  or  cir« 
cuit  for  the  purpose  of  determining  whether 
it  is  in  standard  or  working  condition. 

Testing  of  Joints.— (See  Joint,  Test- 
ing of.) 

Testing  Pole.— (See  Pole,  Testing) 

Testing  Transformer. — (See  Trans- 
former, Testing.) 

Tetanus. — Continuous,  spasmodic  contrac- 
tion of  the  muscles. 

Tetanus,  Acoustic  •  — Tetanus  pro- 
duced in  a  muscle  by  means  of  alternate 
currents  induced  in  a  coil  of  wire  by  a  mag- 
netized steel  spring  vibrating  near  the  coil 
with  sufficient  rapidity  to  give  a  musical  note. 

The  rapidity  of  the  inductive  shock  can  be  de- 
termined from  the  pitch  of  the  musical  note;  hence 
the  use  of  the  term  acoustic. 

Theatrophone. — A  system  of  telephonic 
communication  between  theatres  or  operas 
and  subscribers,  by  means  of  slot  machines. 

Any  person  at  a  cafe,  club,  restaurant  or  other 
public  place,  by  the  theatrophone,  is  automati- 
cally placed  in  communication  with  the  theatre 
by  means  of  a  Deceiving  telephone  so  as  to  hear 


The.] 


523 


[The. 


the  performance  by  dropping  a  given  piece  of 
money  in  the  slot  of  the  machine. 


Theodolite,  Magnetic 


— An    appa- 


ratus for  measuring  the  declination  or  varia- 
tion of  the  magnetic  needle  at  any  place. 

A  divided  circle,  like  that  on  a  theodolite,  is 
supported  horizontally.  The  needle  is  formed  of 
a  tubular  magnet,  having  an  achromatic  lens  at 
one  end  and  a  scale  at  the  focus  of  the  lens  at  the 
other  end. 

Theory,  Alternation,  of  Muscular  Nerve 

Current  — A  theory  proposed  by  L. 

Hermann,  in  which  the  currents  of  nerves  or 
muscular  fibres  are  regarded  as  a  result  of 
their  alteration  from  an  original  condition. 

Hermann  states: 

(i.)  That  protoplasm  undergoing  partial  death 
at  any  part,  either  while  dying  or  by  metamor- 
phosis, becomes  negative  to  the  uninjured  part 

(2.)  Protoplasm,  when  excited  at  any  part,  be- 
comes negative  to  the  unexcited  part. 

(3.)  Protoplasm,  when  partially  heated  at  any 
part,  becomes  positive,  and,  on  cooling,  negative 
to  the  unchanged  part. 

(4. )  Protoplasm  is  strongly  polarizable  on  its 
surface,  the  polarization  constantly  diminishing 
with  excitement  and  while  dying. 

According  to  this  theory,  passive,  uninjured 
and  absolutely  fresh  tissues  are  devoid  of  elec- 
tric currents.  This  matter  must  still  be  regarded 
as  unsettled.  (See  Theory,  Molecular,  of  Mus- 
cles or  Nerve  Current. ) 

Theory,  Contact,  of  Toltaic  Cell 

(See  Cell,  Voltaic,  Contact  Theory  of.) 

Theory,  Difference •  —A  theory  as  to 

the  cause  of  the  electric  currents  excited  be- 
tween injured  and  uninjured  protoplasm. 

Theory,  Molecular,  of  Muscles  or  Nerve 

Current A   theory  proposed  by  Du 

Bois  Reymond,  in  which  every  nerve  or  mus- 
cular fibre  is  regarded  as  composed  of  a 
series  of  electromotive  molecules  arranged 
in  series  and  surrounded  by  a  neutral  con- 
ducting fluid. 

"  The  molecules  are  supposed  to  have  a  posi- 
tive equatorial  zone  directed  towards  the  surface 
and  two  negative  polar  surfaces  directed  toward 
the  transverse  section.  Every  fresh  transverse 
section  exposes  new  negative  surfaces,  and  every 


artificial  longitudinal  section  new  positive  area." 
— (Landois  and  Sterling.) 

Theory  of  Electric  Displacement. — (See 
Displacement,  Electric,  Theory  of.) 

Therapeutical  Electrization. — (See  Elec- 
trization, Therapeutical?) 
Therapeutic  Bath,  Electro  —(See 

Bath,  Electro-  Therapeutic?) 

Therapeutics,  Electro,  or  Electro- 
Therapy  The  application  of  electricity 

to  the  curing  of  disease.  (See  Biology,  Elec- 
tro^ 

Therapeutist,  Electric One  skilled 

in  electro-therapy. 

An  electro-medical  practitioner. 

Therapy,  Electro — A  term  some- 
times used  instead  of  electro-therapeutics. 
(See  Therapeutics,  Electro,  or  Electro- 
Therapy^) 

Therapy,  Magneto Alleged  electro- 
therapeutic  effects  produced  by  the  move- 
ments of  magnets  over  the  body  of  the 
patient. 

It  is  asserted  by  eminent  authorities  that  such 
effects  have  an  actual  existence.  They  should, 
however,  until  more  carefully  investigated,  be 
accepted  with  extreme  caution. 

Therm.— A  heat  unit  propose  1  by  the 
British  Association. 

A  therm  is  the  amount  of  heat  required  to 
raise  the  temperature  of  one  gramme  of  pure 
water  at  the  temperature  of  its  maximum  density 
one  degree  centigrade.  (See  Calorie.} 

Thermaesthesiometer. — An  instrument 
employed  in  electro-therapeutics  for  testing 
the  temperature  sense  in  nervous  diseases. 

The  thermaesthesiometer  consists  of  two  ther- 
mometers movable  on  a  standard,  with  flat  ves- 
sels of  mercury  in  order  to  readily  apply  them  to 
the  skin.  The  mercury  vessel  of  one  of  the  two 
thermometers  is  surrounded  by  an  insulated 
platinum  wire  and  may  be  warmed  at  pleasure  by 
passing  a  galvanic  current  through  the  wire. 

The  two  vessels,  brought  to  different  tempera- 
tures, are  set  on  the  same  part  of  the  skin,  one 
after  the  other,  so  as  to  test  the  sensibility  of  the 
skin  for  the  differences  in  temperature. 

Thermal  Absorption. — (See  Absorption, 
Thermal?) 


The.] 


524 


[The. 


Thermal  Cautery. — (See  Cautery,  Ther- 
mal^ 

Thermal  Incandescence. — (See  Incan- 
descence, Thermal?) 

Thermic  Balance. — (See  Balance,  Ther- 
mic, or  Bolometer?) 

Thermo-Battery.— (See  Battery,  Thermo?) 

Thermo  Call. — A  call  operated  by  means 
of  thermo  currents. 

Thermo-Cell.— (See  Cell,  Thermo-Elec- 
tric?) 

Thermo-Electric  Battery. — (See  Battery  t 
Ther  mo-Electric?) 

Thermo-Electric  Cell. — (See  Celt, 
Thermo-Electric?) 

Thermo-Electric  Couple. — (See  Couple, 
Thermo-Electric?) 

Thermo-Electric  Diagram. — (See  Dia- 
gram, Thermo-Electric?) 

Thermo-Electric  Effect.— (See  Effect, 
Thermo-Electric?) 

Thermo-Electric  Inversion. — (See  In- 
version, Thermo-Electric?) 

Thermo-Electric  Pile,  Differential 

— (See  Pile,  Thermo,  Differential?) 

Thermo-Electric  Pile  or  Battery. (See 

Pile,  Thermo-Electric?) 

Thermo-Electric  Power. — (See  Power, 
Thermo-Electric?) 

Thermo-Electric  Series. — (See  Series, 
Thermo-Electric?) 

Thermo-Electricity.—  (See  Electricity, 
Thermo^ 

Thermo-Electrometer. — A  name  some- 
times, but  not  happily,  applied  to  an  electric 
thermometer.  (See  Thermometer,  Electric?) 

Thermo-Electromotive  Force.  —  (See 
Force,  Electromotive,  Thermo?) 

Thermolysis. — A  term  applied  to  the 
chemical  decomposition  of  a  substance  by 

heat. 

Thermolysis,  or  dissociation,  is  an  effect  pro- 
duced by  an  action  of  heat  somewhat  similar  to 
the  effect  of  electrolysis,  or  chemical  decomposi- 
tion produced  by  the  passage  of  an  electric  cur- 
rent. When  a  chemical  substance  is  heated,  the 


vibration  of  its  molecules  is  attended  by  an  inter- 
atomic vibration  of  its  constituent  atoms  so  that  a 
decomposition  ensues.  If  the  temperature  is  not 
excessive,  these  liberated  atoms  recombine  with 
others  which  they  meet.  At  higher  temperatures, 
however,  such  recombination  is  impossible,  and  a 
permanent  decomposition  ensues,  called  ther- 
molysis or  dissociation. 

Thermometer,  Electric  —  — A  device 
for  determining  the  effects  of  an  electric  dis- 
charge by  the  movements  of  a  liquid  column 
on  the  expansion  of  a  confined  mass  of  air 
through  which  the  discharge  is  passed. 

Thermometer,  Electric  Resistance 

— A  thermometer  the  action  of  which  is 
based  on  the  change  in  the  electric  resistance 
of  metallic  substances  with  changes  in  tem- 
perature. 

The  electric  resistance  thermometer  is  used, 
among  other  purposes,  for  determining  the  temper- 
ature of  the  sea  at  different  depths.  Its  operation 
is  based  on  the  electric  resistance  of  two  perfectly 
similar  coils  of  insulated  wire,  enclosed  in  separate 
water- tight  copper  cases.  One  coil  is  placed  where 
the  temperature  is  to  be  determined,  and  the  other 
in  a  vessel  of  water,  the  temperature  of  which  is 
altered  until  the  two  coils  show  the  same  resist- 
ance, when,  of  course,  the  temperature  of  the 
distant  coil  is  the  same  as  that  of  the  water  sur- 
rounding the  other  coil. 

Thermometer  Scale,  Centigrade 

(See  Scale,  Thermometer,  Centigrade?) 

Thermometer  Scale,  Fahrenheit 

(See  Scale,  Thermometer,  Fahrenheit?) 

Thermophone. — Any  instrument  by  means 
of  which  sounds  are  produced  by  the  absorp- 
tion of  radiant  energy.  (See  Photophone?) 

A  telephone  has  been  constructed  in  which  the 
motions  of  the  receiving  diaphragm  are  effected 
by  the  expansions  and  contractions  of  a  thin  me- 
tallic wire  connected  to  the  diaphragm  and  placed 
in  the  circuit  of  the  main  line. 

Thermostat. — An  instrument  for  automati- 
cally maintaining  a  given  temperature  by  the 
closing  of  an  electric  circuit  through  the  ex- 
pansion of  a  solid  or  liquid. 

Thermostats  are  often  used  in  systems  of  auto- 
matic fire  telegraphy  and  in  systems  of  automatic 
temperature  regulation  in  connection  with  indi- 


The.] 


525 


[Tic. 


eating  instruments  for  sounding  an  alarm  or  giv- 
ing notice  when  the  temperature  changes. 

They  are  operated  either  on  open  or  closed  cir- 
cuits. 

Thermostat  Alarm. — (See  Alarm,  Ther- 
mostat?) 

Thermostat,      Closed-Circuit — A 

thermostat  maintained  normally  on  a  closed 
circuit. 

In  closed-circuit  thermostats,  the  adjustment 
for  any  degree  of  temperature  within  a  given 
range  is  effected  by  means  of  a  screw. 

Thermostat,  Electro-Pneumatic 

An  instrument  for  automatically  indicating 
the  existence  of  a  given  temperature  by  the 
closing  of  an  electric  circuit  on  the  expansion 
of  a  gas. 

Thermostat,  Mercurial A  thermo- 
stat operating  by  the  ex- 
pansion   of    a    mercury 
column. 

A  mercurial  thermostat 
is  shown  in  Fig.  555.  One 
terminal  is  connected  di- 
rectly with  the  mercury; 
the  other  is  placed  in  the 
arm  to  the  left.  On  a  cer- 
tain predetermined  tem- 
perature being  reached,  the 
rise  of  the  mercury  column 
completes  the  circuit  and 
rings  an  alarm  bell.  By 
connecting  the  thermostat 
with  an  annunciator,  the 
particular  locality  where  an 
excessive  temperature  has 
been  reached  is  indicated. 
Such  a  system  is  in  use  in  a  well  known  system  of 
fire  alarm. 


.  5SS-    Mercurial 
Thermostat. 


Thermostat,  Open-Circuit 


—A  ther- 


mostat maintained  normally  on  an  open  cir- 
cuit. 

In  open -circuit  thermostats  the  adjustment  for 
temperature  within  a  given  range  is  effected  by 
varying  the  distance  of  the  fixed  and  movable 
contact  points. 

Thermostatic.— Of  or  pertaining  to  a  ther- 
mostat. (See  Thermostat!) 

Thompson's  Gauss.— (See  Gauss,  S.  P. 
Thompson's!) 


Thomson's  Gauss.— (See  Gauss,  Sir  Wil- 
liam Thomson's!) 

Three-Branched  Sparks. — (See  Spark, 
Three-Branched!) 

Three-Filament  Incandescent  Electric 
Lamp  for  Multiphase  Circuits. — (See  Lamp, 
Electric,  Incandescent,  Three-Filament, 
for  Multiphase  Circuits?) 

Three-Way  Trolley  Frog.— (See  Frog, 
Trolley,  Three- Way?) 

Three- Wire  System.— (See  System,  Three- 
Wire.} 

Throttling1.— Choking,  or  stopping  off. 

Through  Circuit.— (See  Circuit, 
Through!) 

Through  Line.— (See  Line,  Through!) 

Throwback  Indicator,  Electrical . 

(See  Indicator,  Electric  Throwback!) 

Throwback  Indicator,  Mechanical 

— (See  Indicator,  Mechanical  Throwback!) 

Throw  of  Needle.— (See  Needle,  Throw 
of!) 

Thumb-Cock      Electric      Burner.— (See 

Burner,  Thumb-Cock  Electric!) 

Thunder. — A  loud  noise  accompanying  a 
lightning  discharge. 

Thunder  is  due  to  the  sudden  rush  of  the  sur- 
rounding air  to  fill  the  partially  vacuous  space 
accompanying  the  disruptive  discharge  of  a  cloud. 
This  space  is  caused  mainly  by  the  condensation  of 
the  vapor  formed  on  the  passage  of  the  discharge 
through  drops  of  rain  or  moisture  in  the  air,  as 
well  as  by  the  expansion  of  the  air  itself. 

Thunder  Rod.— (See  Rod,  Thunder?) 
Thunder  Storms,  Geographical  Distribu. 
tion  of  —       — (See  Storms,  Thunder,  Geo- 
graphical Distribution  of!) 

Tick,  Magnetic A  faint  metallic 

click  heard  on  the  magnetization  and  demag- 
netization of  a  magnetizable  substance. 

Ticker  Service,  Stock The  simul- 
taneous transmission  of  stock  quotations  or 
other  desired  information  to  a  number  of 
subscribers. 

The  stock  ticker-service  includes  a  central 
transmitting  station  connected  with  a  given  num- 


Tic.] 


526 


[Tis. 


her  of  subscribers,  each  of  whom  is  furnished 
with  a  stock  ticker.  The  transmitter  at  the  cen- 
tral station  consists  of  a  keyboard  and  a  cylinder 
furnished  with  spiral  pins.  The  spiral  pins  are 
connected  through  a  series  of  pole-changers  to 
separate  line  wires  radiating  in  all  directions  from 
the  central  office. 

The  connections  are  such  that,  a  rapid  rota- 
tion being  given  by  means  of  an  electric  mo- 
tor to  the  cylinder,  the  impulses  sent  out  by  the 
keyboard  are  transmitted  to  each  of  the  separate 
circuits.  Since  each  of  these  circuits  has  a  num- 
ber of  ticker  printers  connected  with  it,  reports  of 
fluctuations  in  prices  are  simultaneously  printed 
in  hundreds  of  different  offices. 

Ticker,  Stock A  form  of  step-by- 
step  telegraphic  instrument  employed  for  au- 
tomatically sending  and  recording  stock  quo- 
tations to  any  desired  number  of  subscribers. 
(See  Telegraphy,  Step-by-Step.) 

A  form  of  printing  telegraph. 

Callahan's  Printing  Telegraph  is  used  as  a 
stock  ticker.  (See  Telegraphy,  Printing.) 

Phelps'  Stock  Printer  is  employed  extensively 
as  a  stock  ticker.  This  form  of  printing  telegraph 
requires  but  a  single  wire,  and  has  a  working 
speed  of  almost  thirty  words  a  minute, 

A.  double  type-wheel,  maintained  in  motion  by 
clockwork,  is  stopped  at  the  desired  characters 
by  the  motion  of  a  polarized  relay,  working  be- 
tween the  poles  of  two  electro  magnets,  furnished 
with  a  soft  iron  or  non-polarized  armature.  The 
release  of  the  armature  of  the  printing  mag- 
net  releases  a  train,  and  thus  insures  the  impres- 
sion of  the  character  it  is  desired  to  print. 

The  type-wheel  is  driven  by  a  step-by-step 
movement  obtained  by  means  of  rapidly  alter- 
nating pulsations.  Although  these  pass  through 
the  coils  of  the  printing  magnet,  they  follow  one 
another  too  rapidly  to  charge  its  coils,  so  that  the 
armature  is  unaffected  until  a  pause  is  made, 
when,  its  armature  being  attracted,  it  releases 
the  printing  mechanism.  The  message  is  received 
on  a  fillet  of  paper,  fed  by  a  suitable  mechanism. 

Time-Ball,    Electric (See    Ball, 

Electric  Tinted) 

Time-Constant  of  Circuit— (See  Circuit, 
Time-Constant  of.) 

Time-Constant  of  Condenser.— (See  Con- 
dtnser,  Time-Constant  of.) 


Time-Constant  of  Electro-Magnet.— (See 

Constant,  Time,  of  Electro-Magnet?) 

Time  Cut-Out,  Automatic An  au- 

omatic  cut-out  arranged  on  a  storage  bat- 
tery so  as  to  cut  it  in  or  out  of  the  circuit  of 
the  charging  source  at  predetermined  times. 

Time-Fall  of  Electromotive  Force  of 
Secondary  or  Storage  Cell  During  Dis- 
charge.— (See  Force,  Electromotive,  of  Sec- 
ondary or  Storage  Cell,  Time-Fall  of.) 

Time-Lag  of  Magnetization. — (See  Mag- 
netization, Time-Lag  of.) 

Time,  Reaction The  time  required 

for  the  effects  of  an  electric  current  to  pass 
from  a  nerve  to  a  muscle. 

Time-Rise  of  Electromotive  Force  of 
Secondary  or  Storage  Cells  During  Dis- 
charge.— (See  Force,  Electromotive,  of  Sec- 
ondary or  Storage  Cell,  Time-Rise  of.) 

Time-Switch.— (See  Switch,  Time.) 

Time,  Telegraphic,  Register  for  Rail- 
roads   (See  Register,  Time,  for  Rail- 
roads?) 

Time  Telegraphy. — (See  Telegraphy, 
Time?) 

Tinned  Wire.— (See  Wire,  Tinned?) 

Tinning,  Electro Covering  a  sur- 
face with  a  coating  of  tin  by  electro-plating. 
(See  Plating,  Electro?) 

Stannic  chloride,  or  the  perchloride  of  tin,  dis. 
solved  in  water  in  the  proportion  of  30  parts  of  the 
salt  to  1,250  of  water,  makes  a  good  tinning 
bath. 

Tinnitus,  Telephone A  professional 

neurosis,  or  abnormal  nervous  condition  of  the 
auditory  apparatus,  believed  to  be  caused  by 
the  continual  use  of  the  telephone. 

Tips,  Polar The  free  ends  of  the 

field  magnet  pole  pieces  of  a  dynamo-electric 
machine. 

Tissue,  Nerve  or  Muscular  Excitability 
of-  —Electric  stimulation  of  nervous  or 
muscular  tissue. 


Ton.] 


527 


[Tor. 


The  general  effects  of  electric  stimulation  of 
nervous  or  muscular  tissue  may  be  summarized 
as  follows: 

(l.)  Electric  stimulation  of  a  motor  nerve,  pro- 
duces a  contraction  of  the  muscles  to  which  such 
nerve  is  distributed. 

(2.)  Electric  stimulation  of  a  sensory  nerve, 
produces  pain  in  the  parts  to  which  the  nerve  is 
distributed. 

(3.)  Electric  stimulation  of  mixed  motor  and 
sensory  nerves  produces  both  of  the  effects  men- 
tioned under  (i)  and  (2.) 

Tongs,  Cable  Hanger Tongs  pro- 
vided with  long  handles  for  the  purpose  of 
attaching  the  hangers  of  an  aerial  cable  to 
the  suspending  wire  or  rope. 

Tongs,  Discharging A  term  some- 
times used  for  a  discharging  rod.  (See  Rod, 
Discharging?) 

Tongue,  Relay,  Bias  of A  term 

employed  to  signify  such  an  adjustment  of  a 
polarized  relay,  that  on  the  cessation  of  the 
working  current,  the  relay  tongue  shall 
always  rest  against  the  insulated  contact,  and 
not  against  the  other  contact,  or  vice  versa. 

Sometimes,  as  in  the  split-battery  duplex,  the 
bias  is  toward  the  uninsulated  contact.  (See 
Relay ;  Polarized,} 

Tool,  Lead  Scoring A  tool  for 

readily  scoring  the  surface  of  the  lead  of  a 
lead-covered  cable,  when  the  same  is  to  be 
removed  preparatory  to  making  joints. 

Toothed-Ring  Armature.— (See  Arma- 
ture, Toothed-Ring?) 

Top,  Induction A  top  consisting 

of  an  iron  disc  supported  on  a  vertical  axis, 
which,  when  spun  before  the  poles  of  a  steel 
magnet,  assumes  an  inclined  position,  through 
the  influence  of  the  currents  induced  in  the 
disc. 

The  top  maintains  the  inclined  position  so  long 
only  as  the  strength  of  the  induced  currents  is 
sufficiently  great ;  that  is,  while  speed  of  rotation 
is  sufficiently  great. 

Toppler-Holtz  Machine. — (See  Machine, 
Toppler-Holtz?) 
Torch,    Electric   Gaslighting A 

gaslighting  appliance  consisting  of  the  com- 


bination of  a  portable  voltaic  battery  and  a 
spark  or  induction  coil. 

The  torch  is  mounted  on  the  end  of  a  rod  pro- 
vided with  means  for  turning  on  the  gas.  A  key 
is  then  touched  and  the  gas  lighted  by  the  spark 
produced  by  an  induction  coil  or  a  small  electro- 
static induction  machine. 

Torpedo,  Automobile A  torpedo 

which  contains  in  itself  the  power  for  its  own 
motion. 

The  moving  power  may  be  that  derived  from 
compressed  air  or  gas,  or  from  a  storage  bat- 
tery contained  within  the  torpedo.  An  auto- 
mobile torpedo  provided  with  a  storage  battery 
and  electric  motor  would  then  be  distinguished 
from  an  electrically  propelled  torpedo,  connected 
by  means  of  cables  with  a  driving  dynamo 
located  outside  the  torpedo  on  a  ship,  or  on  the 
shore. 

Torpedo  Boat. — (See  Boat,  Torpedo?) 

Torpedo  Cable.— (See  Cable,  Torpedo?) 

Torpedo,  Drifting A  torpedo  sus- 
pended from  a  float,  and  connected  by  means 
of  rope  with  similar  torpedoes,  allowed  to 
drift  with  the  current,  so  as  to  catch  against 
a  vessel. 

Torpedo,  Electric A  name  some- 
times given  to  the  electric  ray.  (See  Ray, 
Electric?) 

Torpedo,  Electric An  electrically 

operated  torpedo. 

This  latter  usage  of  the  term  is  the  commoner. 

Torpedo,  Halpine-Savage A  special 

form  of  torpedo,  in  which  electricity  is  both 
the  propelling  and  directing  power,  and  in 
which  the  electric  source  furnishing  the  pro- 
pelling current  is  contained  within  the 
torpedo. 

In  the  Halpine  Savage  torpedo,  the  propelling 
power  is  obtained  from  a  storage  battery  placed 
within  the  torpedo. 

Torpedo,  Lay A  moving  torpedo, 

in  which  the  moving  power  is  carbonic  acid 
gas,  or  compressed  air,  or  other  similar  power 
not  electric,  and  the  guiding  power  is  electric. 

The  Lay  torpedo  has  the  form  of  a  cylindrical 
boat  furnished  with  conical  ends.  The  explosive  is 
placed  in  the  fore  part  of  the  torpedo.  Flags  are 


Tor.] 


528 


[Ton. 


attached  to  the  torpedo,  showing  the  operator  the 
exact  course  taken  by  it. 

The  torpedo  is  started,  stopped  and  steered  by  • 
means  of  electric   currents   sent  to  the  torpedo 
through  an  insulated  cable  connected  with  the 
torpedo. 

Torpedo  Nets.— (See  Nets,  Torpedo^ 

Torpedo,  Outrigger A  pole  or 

spar  torpedo. 

The  torpedo  is  placed  in  a  metallic  case  and 
supported  on  the  end  of  a  spar  or  outrigger.  The 
spar  is  depressed  until  the  torpedo  is  sunk  below 
the  water  line.  The  torpedo  is  fired  when  its  end 
conies  in  contact  with  the  side  of  the  enemy's 
vessel. 

Torpedo,  Sims-Edison A  special 

form  of  torpedo  in  which  electricity  is  both 
the  propelling  and  the  directing  power,  but  the 
electric  source  is  situated  outside  of  the 
torpedo. 

The  torpedo  is  propelled  by  means  of  an  electric 
motor  placed  in  the  torpedo,  and  driven  by  means 
of  an  electric  current  transmitted  through  a  cable 
connected  with  the  sending  station. 

Torpedo,  Spar A  torpedo,  attached 

io  the  end  of  a  spar,  and  designed  to  be 
exploded  by  percussion  against  the  side  of  an 
enemy's  vessel,  when  thrust  against  the  side 
below  the  water-line. 

The  spar  torpedo  is  but  little  used,  having 
been  replaced  by  more  efficient  forms. 

Torpedo,  Stationary A  term  some- 
times employed  instead  of  a  submarine 
mine.  (See  Mine,  Submarined) 

A  stationary  torpedo  is  so  named  in  order  to 
distinguish  it  from  a  torpedo  which  is  moved 
through  the  water  by  any  means.  (See  Torpedo, 
Towing.) 

Torpedo,  Towing  •  — A  torpedo  ar- 
ranged to  be  towed  on  the  surface  after  a  ves- 
sel and  explode  when  it  strikes  the  side  of 
an  enemy's  vessel. 

The  torpedo  is  shaped  so  that  it  maintains  dur- 
ing its  motion  a  certain  distance  from  the  sides  of 
the  towing  boat  or  vessel. 

Torque. — That  moment  of  the  force  ap- 
plied to  a  dynamo  or  other  machine  which 
turns  it  or  causes  its  rotation. 


The  mechanical  rotary  or  turning  force 
which  acts  on  the  armature  of  a  dynamo^ 
electric  machine  or  motor  and  causes  it  to 
rotate. 

In  the  case  of  the  armature  of  a  dynamo- 
electric  machine  the  torque  is  equal  to  the  radius 
of  the  armature,  multiplied  by  the  pull  at  the 
circumference,  or  the  radius  of  its  pulley  multiplied 
by  the  pull  at  the  circumference  of  the  pulley. 

A  torque  is  exerted  on  the  shaft  of  a  motor  from 
the  electro-magnetic  action,  or  pull  at  the 
periphery  of  the  armature. 

The  torque  is  usually  measured  in  pounds  of 
pull  at  the  end  of  a  radius  or  arm  I  foot  in 
length. 

Torricellian  Yacuum.— (See  Vacuum, 
Torricellian?) 

Torsion  Balance,  Coulomb's (See 

Balance,  Coulomb's  Torsion?) 

Torsion  Galvanometer.— (See  Galvanom- 
eter, Torsion?) 

Total  Disconnection. — (See  Disconnec- 
tion, Total?) 

Total  Earth.— (See  Earth,  Total?) 

Total  Magnetic  Induction. — (See  Induc- 
tion, Total  Magnetic?) 

Touch,  Double A  method  of  mag- 
netization in  which  two  closely  approximated 
magnet  poles  are  simultaneously  drawn  from 
one  end  of  the  bar  to  be  magnetized  to  the 
other  and  back  again,  and  this  repeated  a 
number  of  times. 

Touch,    Separate A    method    of 

magnetization  in  which  two  magnetizing  poles 
are  simultaneously  applied  to  the  bar  to  be 
magnetized  and  drawn  over  it  in  opposite  di 
rections.     (See  Magnetization  by  Touch?) 

Touch,  Single A  method  of  mag- 
netization in  which  a  single  magnetizing  bar 
is  drawn  from  one  end  to  the  other  of  the  bzr 
to  be  magnetized,  and  returned  through  the 
air  for  the  next  stroke.  (See  Magnetization, 
Methods  of?) 

Tourmaline. — A  mineral  consisting  of 
natural  silicates  and  borates  of  alumina,  lime, 
iron,  etc.,  possessing  pyro-electric  properties, 
(See  Electricity,  Pyro.) 


Tow.] 


529 


[Tra. 


Tower,  Conning A  shot-proof 

tower  from  which  the  commander  of  a  turret 
ship  directs  the  movements  of  a  vessel  during 
action. 

Tower,  Electric A  high  tower  pro- 
vided for  the  support  of  a  number  of  electric 
arc  lamps,  employed  in  systems  of  general 
illumination. 

Tower  System  of  Electric  Lighting. — 
The  lighting  of  extended  areas  by  means  of 
arc  lights  placed  on  the  tops  of  tall  towers. 

The  tower  system  of  electric  illumination  is  only 
applicable  to  wide  open  spaces,  since  otherwise 
objectionable  shadows  are  apt  to  be  formed. 

Towing  Torpedo.— (See  Torpedo,  Taw- 
ing) 

Traction,  Magnetic The  force  with 

which  a  magnet  holds  on  to  or  retains  its 
armature,  when  once  attached  thereto. 

Magnetic  traction  is  to  be  distinguished  from 
magnetic  attraction,  or  the  ability  of  a  magnet 
pole  to  draw  an  armature  or  other  magnets  to- 
wards it  from  a  distance. 

Train  Wire.— (See  Wire,  Train) 

Tramway,  Electric A  railway  over 

which  cars  are  driven  by  means  of  elec- 
tricity. 

An  electric  railroad. 

The  term  tramway  is  sometimes  applied  to 
roads  in  cities,  as  distinguished  from  inter-urban 
roads. 

Transformer. — An  inverted  Ruhmkorff 
induction  coil  employed  in  systems  of  dis- 
tribution by  means  of  alternating  currents. 

A  transformer  is  sometimes  called  a  converter. 
The  word  transformer  is,  however,  the  one  most 
employed. 

A  transformer  consists  essentially  of  an  induc- 
tion coil,  Fig.  556,  in  which  the  primary  wire  is 
long  and  thin,  and  consequently  has  many  turns, 
as  compared  with  the  secondary  wire,  S,  S,  which 
is  short,  thick,  and  has  few  turns. 

To  prevent  heating  and  loss  of  energy  in  con- 
version, the  core  of  the  transformer  is  thoroughly 
laminated;  to  lower  the  resistance  of  its  mag- 
netic circuit,  the  transformer  is  usually  iron-clad. 

In  a  system  of  electrical  distribution  by  means 
of  transformers,  alternating  currents,  of  small 
Current  strength  and  comparatively  considerable 


difference  of  potential,  are  sent  over  a  line  from  a 
distant  station,  and  passing  into  the  primary  wire 
of  a  number  of  converters,  generally  connected 
to  the  line  in  multiple  arc,  produce,  by  induction 


Fig.  556.     Transformer. 

currents  of  comparatively  great  strength  and 
small  difference  of  potential  in  the  secondary 
wires. 

Various  electro -receptive  devices  are  connected 
in  multiple  arc  to  circuits  connected  with  the  sec- 
ondary wires. 

This  method  of  distribution  greatly  reduces  the 
cost  of  the  main  conducting  wires  or  leads  in  all 
cases  where  the  distance  is  considerable,  since 
considerable  energy  may  be  conveniently  sent 
over  a  comparatively  thin  wire,  with  but  a  trifling 
loss,  if  the  difference  of  potential  is  sufficiently 
great. 

The  general  arrangement  of  the  converters  on 
the  main  line,  and  the  connection  of  the  second- 
ary circuits  with  the  electro-receptive  devices  in 


_L_L 


Fig.  SS7-     Transformer  Circuits. 

such  a  system,  are  shown  in  Fig.  557.     The  trans- 
formers are  supported  on  the  line  poles,  as  more 


Tra.] 


530 


[Tra. 


dearly  shown  In  Fig.  558,  in  which  the  terminals 
of  the  primary  and  secondary  of  the  converter 
are  readily  seen. 

When  the  converter  is  properly  constructed, 
the  loss  of  conversion  at  full  load  is  but  small ; 
that  is  to  say,  the  number  of  watts  in  the  secon- 
dary is  very  nearly  equal  to  the  number  in  the 
primary.  A  current  of  IO  amperes,  at  2,000 
volts,  when  passed  into  a  converter  the  number 
of  whose  turns  in  the  primary  is  twenty  times  the 
number  in  its  secondary,  will  produce  in  its  sec- 
ondary a  current  whose  strength  is  about  twenty 
times  as  great,  that  is,  nearly  200  amperes,  but 
whose  voltage  is  only  about  one-twentieth,  or, 
loo;  the  watts  in  the  two  cases  are  nearly  the 
same,  or  theoretically  20,000  watts. 

The  ratio  between  the  windings  of  the  primary 
and  the  secondary  circuits  is  called  the  co-effi- 
cient of  transformation. 

In  general,  the  shorter  the  wire  on  the  second- 
ary, and  the  smaller  its  number  of  turns,  the 
greater  is  the  reduction  in  the  difference  of  po- 
tential, and  the  greater  the  current  produced. 
The  reduction  is  nearly  proportionate  to  the  ratio 
of  the  number  of  windings  of  the  two  coils. 


Transformer,  Constant-Current 


Fig.  338.     Transformer  Attached  to  Poles. 

Transformer,  Closed  Iron  Circuit 

— A  transformer  the  core  of  which  forms  a 
complete  magnetic  circuit. 

These  transformers  are  sometimes  called  iron- 
clad  transformers. 

Transformer,  Commuting A  term 

sometimes  applied  to  a  variety  of  motor  gen- 
erator in  which  neither  the  armature  nor  the 
field  magnets  revolve,  the  variations  in  the 
polarity  of  the  magnetic  circuit  being  obtained 
by  means  of  special  comrrutators. 


transformer  in  which  a  current  of  a  constant 
potential  in  the  primary  is  converted  into  a 
current  of  constant  strength  in  the  secondary, 
despite  changes  in  the  load  on  the  secondary. 

Transformer,  Core A  transformer 

in  which  the  primary  and  secondary  wires 
are  wrapped  around  the  outside  of  a  core 
consisting  of  a  bundle  of  soft  iron  wires  or 
plates. 

A  Ruhmkorff  coil  is  a  core  transformer. 

Transformer,  Efficiency  of" — The 

ratio  between  the  whole  energy  supplied  in 
any  given  time  to  the  primary  circuit  of  a 
transformer  and  that  which  appears  in  the 
form  of  electric  current  in  the  secondary 
circuit. 

The  energy  applied  to  the  primary  circuit  of  a 
transformer  is  dissipated: 

(i.)  By  eddy  currents  in  the  core  of  the  trans- 
former. (See  Currents,  Eddy.) 

(2.)  By  hysteresis,  or  magnetic  friction.  (See 
Hysteresis. ) 

(3.)  By  heating  of  the  primary  circuit. 

(4.)  By  heating  of  the  secondary  circuit. 

When  a  transformer  is  overloaded,  its  efficiency 
decreases.  There  is  a  certain  range  of  second- 
ary resistance  and  current,  within  which  a  trans- 
former is  most  advantageously  operated. 

Transformer  Guard. — (See  Guard,  Trans- 
former, Lightning?) 

Transformer,  Hedgehog A  name 

applied  to  a  particular  form  of  open-iron  cir- 
cuit transformer.  (See  Transformer^) 

The  advantages  claimed  for  the  hedgehog  trans- 
former are  that  it  can  be  made  to  give  a  higher 
all-day  efficiency,  since  it  insures  a  smaller  loss 
from  hysteresis  in  the  iron.  The  efficiency  for 
very  small  loads,  or  for  no  loads  is  greater  than  in 
the  closed-circuit  transformer. 

Transformer,  Leakage  Current  of 

A  term  sometimes  used  for  the  current  which 
escapes  from  the  primary  through  the  dielec- 
tric of  a  transformer  to  the  secondary  circuit. 

The  term  is  a  bad  one,  since  the  true  leakage 
current  would  be  the  current  which  represents 
the  leakage  between  the  primary  or  secondary 
circuit  and  the  ground. 


Tra.] 


531 


[Tra. 


Transformer  Lightning  Arrester.— (See 
Arrester,  Lightning,  Transformer?) 

Transformer,  Multiple Any  form 

of  transformer  which  is  connected  in  multiple 
to  the  primary  circuit. 

A  multiple  or  parallel  transformer  is  self-regu- 
lating under  variable  loads,  provided  the  electro- 
motive force  in  the  primary  is  maintained  con- 
stant. 

Transformer,  Oil A  transformer 

which  is  immersed  in  oil  in  order  to  insure  a 
high  insulation. 

Transformer,  Open-Iron  Circuit 

A  transformer  the  iron  of  which  does  not  form 
a  complete  magnetic  circuit,  but  is  formed 
instead  partly  of  iron  and  partly  of  air. 

Transformer,  Pilot A  small  trans- 
former, placed  at  any  desired  portions  of  a 
line  in  order  to  determine  the  drop  of  poten- 
tial. 

The  pilot  transformer  is  used  in  connection  with 
a  lamp  or  other  suitable  indicating  device.  Its  use 
is  similar  to  the  use  of  the  pilot  incandescent  lamp. 

Transformer,  Rotary-Current A 

transformer  operated  by  means  of  a  rotary 
current.  (See  Current,  Rotating?) 

The  rotary  current  transformer  for  a  rotary 
current  of  three  separate  alternating  currents  com- 
bined, transforms  all  three  currents  together. 
There  are  three  cores,  connected  at  one  set  of 
ends  and  at  the  other  to  the  circumference  of  an 
iron  ring.  Each  core  contains  a  primary  and 
secondary  wire. 

Transformer,  Rotary-Phase A  ro- 
tary current  transformer.  (See  Transfor- 
mer, Rotary-Current?) 

Transformer,  Series Transformers 

which  are  connected  in  series  with  the  pri- 
mary circuit. 

A  series  transformer  is  not  as  readily  made  self- 
regulating  under  variations  in  the  load  as  a  mul- 
tiple transformer.  If,  however,  its  core  is  not 
saturated,  and  the  electromotive  force  of  its 
secondary  is  small,  it  can  be  made  fairly  self-regu- 
lating. Series  transformers  are  used  in  the 
Jablochkoff  system  for  feeding  arc  lamps  in  the 
shape  of  Jablochkoff  candles. 

Transformer,  Shell A  transformer 


in  which  the  primary  and  secondary  coils  are 
laid  on  each  other,  and  the  iron  core  is  then 
wound  through  and  over  them  so  as  to  en- 
close all  the  copper  of  the  primary  and 
secondary  circuits  within  the  iron. 

The  iron  shell  surrounding  the  copper  may 
consist  of  the  thin  plates  of  iron,  built  up  so  as  to 
leave  a  rectangular  space  for  the  introduction  of 
the  primary  and  secondary. 

Transformer,  Step-Down A  trans- 
former in  which  a  small  current  of  compara- 
tively great  difference  of  potential  is  con- 
tverted  into  a  large  current  of  comparatively 
small  difference  of  potential. 

An  in  verted  Ruhmkorff  induction  coil. 

Transformer,  Step-Up  — A  trans- 
former in  which  a  large  current  of  compara- 
tively small  difference  of  potential  is  con- 
verted into  a  small  current  of  comparatively 
great  difference  of  potential. 

The  term  step-up  transformer  is  used  in  contra- 
distinction to  the  step -down  transformer. 

The  old  form  of  Ruhmkorff  coil  is  an  example 
of  a  step-up  transformer. 

Transformer,  Testing A  trans- 
former employed  in  any  system  of  distribu- 
tion for  the  purposes  of  testing  for  grounds, 
condition  of  line,  drop  of  potential,  etc. 

Transformer,  Welding A  trans- 
former suitable  for  changing  a  small  electric 
current  of  comparatively  high  difference  of 
potential,  into  the  heavy  currents  of  low 
difference  of  potential  required  for  welding 
purposes. 

Welding  transformers  have  in  general  a  very 
low  resistance  in  their  secondary  coils,  and  almost 
invariably  consist  of  a  single  turn  or  at  the  most 
of  a  few  turns  of  very  stout  wire. 

Transforming  Currents.— (See  Current, 
Transforming  a.) 

Transforming  Down.— Transforming  by 
means  of  a  step-down  transformer.  (See 
Transformer,  Step-Down?) 

Transforming  Station.— (See  Station, 
Transforming.) 

Transforming  Up.— Transforming  by 
means  of  a  step-up  transformer.  (See 
Transformer,  Step-Up?) 


Tra.] 


532 


[Tra. 


Transient     Currents.—  (See    Currents,          Transmission,  Multiple The  simul- 


Transient.) 

Transit,  Magnetic  Variation An 

apparatus  for  measuring  the  declination  or 
variation  of  the  magnetic  needle  at  any  place. 
The  variation  transit  generally  consists  of  an 
altitude  and  azimuth  instrument,  the  telescope  of 
which  is  so  arranged  as  to  be  readily  converted 
into  a  microscope. 

Transition  Resistance. — (See  Resistance, 
Transition.) 

Translator,    Double-Current A 

telegraphic  translater  or  repeater  designed  to 
operate  on  double  current  transmission. 

•  —A  tele- 


Translater,  Single-Current 

graphic   translater  or  repeater  designed   to 
operate  a  single-current  transmission. 


Translater,  Telegraphic A  term 

sometimes  applied  to  a  telegraphic  repeater. 
(See  Repeaters,  Telegraphic?) 

Translating  Device. — (See  Device,  Trans- 
lating?) 

Translating  Devices,  Multiple-Arc-Con- 
nected   (See  Devices,  Translating, 

Multiple-Arc-Connected.) 

Translating  Devices,  Multiple-Con- 
nected    —  (See  Devices,  Translating, 

Multiple-  Connected.) 

Translating  Devices,  Multiple-Series- 
Connected  (See  Devices,  Translat- 
ing, Multiple-Series-Connected?) 

Translating    Devices,   Series-Connected 

(See  Devices,   Translating,   Series- 
Connected.) 

Translating  Devices,  Series-Multiple- 
Connected  (See  Devices,  Translat- 
ing, Series-Multiple-Connected.) 

Translucent- Disc  Photometer.  —  (See 
Photometer,  Translucent-Disc.) 

Transmission,  Double  —  —The  simul- 
taneous sending  of  two  messages  over  a  sin- 
gle wire  in  opposite  directions.  (See  Teleg- 
raphy, Duplex,  Bridge  Method  of.) 


taneous  sending  of  more  than  two  messages 
over  a  single  line  or  conductor. 

Transmission  of  Energy.— (See  Energy, 
Electric,  Transmission  of.) 

Transmitter,    Carbon,    for    Telephones 

A  telephone  transmitter  consisting  of 

a  button  of  compressible  carbon. 

The  sound  waves  impart  to-and-fro  movements 
to  the  transmitting  diaphragm,  and  this  to  the 
carbon  button,  thus  varying  its  resistance  by  pres- 
sure. This  button  is  placed  in  circuit  with  the 
battery  and  induction  coil.  (See  Telephone.') 

Transmitter,  Double-Current The 

transmitting  instrument  employed  in  systems 
of  telegraphy,  by  means  of  which  the  direc- 
tion of  the  currents  on  the  line  is  alternately 
changed,  according  to  whether  the  key  rests 
on  its  front  or  on  its  back  stop. 

Double-current  transmitters  are  used  in  con- 
nection with  instruments,  such  as  polarized  re- 
lays, which  respond  to  change  in  the  direction  of 
the  current,  rather  than  to  changes  in  its  in- 
tensity. 

Transmitter,  Electric A  name 

applied  to  various  electric  apparatus  employed 
in  telegraphy  or  telephony  to  transmit  or  send 
the  electric  impulses  over  a  line  wire  or  con- 
ductor. 

The  sending  instrument  as  distinguished 
from  the  receiving  instrument. 

In  most  telegraphic  systems,  the  transmitting 
instrument  consists  of  various  forms  of  keys  for  in- 
terrupting or  varying  the  current.  In  the  tele- 
phone the  transmitter  consists  of  a  diaphragm 
operated  by  the  voice  of  the  speaker.  (See  Tele- 
phone.) 

Transmitter,  Water-Jet  Telephone  - 

— A  telephone  transmitter  consisting  of  a  jet 
of  water  issuing  vertically  downwards  from  a 
small  orifice. 

The  jet  forms  a  part  of  the  circuit  of  the  re- 
ceiving telephone.  In  order  to  reduce  its  resist- 
ance, the  water  is  rendered  acid  by  the  addition 
of  sulphuric  acid,  and  a  battery  of  high  electro- 
motive force  is  employed.  Since  the  jet  has  a 
high  resistance,  a  battery  of  high  resistance  can 
be  used  without  inconvenience. 


Tra.] 


533 


[Tre. 


Transposing. — In  a  system  of  telephonic 
communication  a  device  for  avoiding  the  bad 
effects  of  induction  by  alternately  crossing 
equal  lengths  of  consecutive  sections  of  the 
line.  (See  Connection,  Telephonic  Cross.) 

Transverse  Electromotive  Force. — (See 
Force,  Electromotive,  Transverse.} 

Treatment,  Hydro-Carbon,  of  Carbons 

— Exposing  carbons,  while  electrically 

heated  to  incandescence,  to  the  action  of  a 
carbonizing  gas,  vapor  or  liquid,  for  the  pur- 
pose of  rendering  them  more  uniformly  elec- 
trically conducting  throughout.  (See  Car- 
bons, Plashing  Process  for?) 

Tree,  Parallel,  Circuit (See  Cir- 
cuit, Parallel-  Tree.) 

Trembling  Bell.— (See  Bell,  Trembling.) 

Trigonometrical. — Of  or  pertaining  to 
trigonometry.  (See  Trigonometry.) 

Trigonometrical  Function. — (See  Func- 
tion, Trigonometrical^) 

Trigonometrically.— In  a  trigonometrical 
manner. 

Trigonometry. — That  branch  of  mathe- 
matical science  which  treats  of  the  methods 
of  determining  the  values  of  the  angles  and 
sides  of  a  triangle. 

There  are  in  every  triangle  three  sides  and 
three  angles.  If  any  three  of  these  parts  are 
given,  except  the  three  angles,  the  values  of  the 
remaining  parts  can  be  determined  by  means  of 


Fig.  SS9-    Dynamo  Brush  Trimmer. 
trigonometry,  by  what  is  called  the  solution  of 
ihe  triangle.     (See  Function,  Trigonometrical.) 


Trimmer. — An  employee  of  an  electric 
light  company  who  renews  the  carbons  in 
arc  lamps. 

Trimmer,  Dynamo  Brush A  de- 
vice for  insuring  rapid  and  accurate  trimming 
of  dynamo  brushes. 

The  brush  trimmer  consists  of  a  knife,  placed 
as  shown  in  Fig.  559  on  a  rigid  support.  The 
brushes  are  placed  under  a  clamp,  and  against  a 
straight  edge,  so  that  a  single  cut  with  the  knife 
blade  insures  a  clean  and  true  cut. 

Trimming. — A  term  sometimes  applied  to 
the  act  of  placing  the  carbons  in  an  electric 
arc  lamp. 

The  phrase,  carboning  a  lamp,  would  appear 
to  be  preferable  to  trimming  a  lamp. 

Triple-Carbon  Arc  Lamp. — (See  Lamp, 
Arc,  Triple-Carbon^ 

Tripod  Roof  Support.— (See  Support, 
Tripod  Roof) 

Trolley. — A  rolling  contact  wheel  that 
moves  over  the  overhead  lines  provided  for  a 
line  of  electric  railway  cars,  and  carries  ofl 
the  current  required  to  drive  the  motor  car. 

Trolley  Crossing. — A  device  placed  at  tha 
crossing  of  two  trolley  wires,  by  which  tha 
trolley  wheel  running  on  one  wire  may  cross 
the  other. 

Such  a  device  can  also  be  made  to  hold  the  two 
wires  together. 

Trolley  Crossing,  Insulated  — • A  de^ 

vice  used  at  the  crossing  of  two  trolley  wires, 
which  insulates  the  wires  from  each  other, 
but  which  permits  the  trolley  wheel  of  one 
line  to  cross  the  other  trolley  line. 

Trolley  Cross-Over. — (See  Cross-Over, 
Trolley) 

Trolley,  Double The  traveling  con- 
ductors, which  move  over  the  lines  of  wire  in 
any  system  of  electric  railways  that  employs 
two  overhead  conductors. 

In  one  form  of  double  trolley  a  bar  of  wood 
carries  two  hangers,  separated  from  each  other, 
and  furnished  with  diverging  feet,  with  clips  that 
embrace  the  two  conducting  wires.  These  wires 
serve  also  as  the  track  for  the  two-wheeled  trolley. 
The  trolley  consists  of  two  plates  connected  to  and 
insulated  from  each  other  under  the  conductors, 


Tro.J 


534 


[Tub. 


and  carrying  flanged  wheels,  extending  in  over 
the  conductors. 

Swinging  from  the  axles  of  the  poles  are  arms, 
which  form  a  bail-like  draft  loop,  with  insulated 
material  between  their  lower  ends,  and  furnish 
means  for  connection  with  the  car  motor.  In 
order  to  remove  this  trolley  from  the  conducting 
wires,  these  arms  are  pressed  together  at  points 
between  two  points  of  hangers,  which  allows 
them  to  pass  between  the  inner  ends  of  the  wheel 
axles. 

The  trolley  cannot  be  removed  from  the  wires 
except  at  the  end  of  the  track,  and  it  is  therefore 
found  in  practice  to  be  particularly  useful  in 
mines,  where,  from  the  nature  of  the  galleries,  the 
trolley  wheel  is  very  apt  to  become  detached  from 
the  trolley  wires. 

Trolley,  Drop The  trolley  wheel 

and  rod  for  an  electric  car  which  drops  away 
from  the  wire  on  slipping  from  the  wire,  and 
is  reset  upwards  through  proper  elastic  press- 
ure. 

Trolley  Fork.— (See  Fork,  Trolley) 
Trolley  Frog.— (See  Frog,  Trolley) 

Trolley  Frog,  Standard (See  Frog, 

Trolley,  Standard) 

Trolley  Hanger.— (See  Hanger,  Trolley) 
'    Trolley  Pole.— (See  Pole,  Trolley) 
Trolley  Section.— (See  Section,  Trolley) 

Trolley,  Single A  traveling  con- 
ductor or  wheel  which  moves  over  a  single 
conductor  in  a  system  of  electric  railways, 
and  takes  off  the  current  for  driving  the  elec- 
tric motor,  in  connection  with  an  earth  or 
grounded  return  conductor. 

Trolley  Wheel.— (See  Wheel,  Trolley) 
Trolley,  Wire (See  Wire,  Trolley) 

True  Contact  Force. — (See  Force,  True 
Contact) 

True  Resistance.  —  (See  Resistance, 
True) 

Trumpet,  Electric  — An  electro- 
magnetic buzzer,  the  sound  of  which  is 
strengthened  by  means  of  a  resonator  in  the 
shape  of  a  trumpet.  (See  Buzzer,  Electric. 
Resonator,  Electric) 


The  electric  trumpet  is  used  to  replace  electric 
bells.  It  gives  a  louder  and  more  penetrating 
sound  than  the  electric  bell. 

Trunking  Switch  Board. — (See  Board, 
Switch,  Trunking) 

Tube,  Crookes' A  tube  containing 

a  high  vacuum  and  adapted  for  showing  any 
of  the  phenomena  of  the  ultra-gaseous  state 
of  matter.  (See  Matter,  Radiant,  or  Ultra- 
Gaseous) 

Tube,  Insulating A  tube  of  insu- 
lating material  provided  for  covering  a  splice 
in  an  insulated  conductor. 

Tube,  Mercury Vacuous  glass  tubes 

in  which  a  flash  of  light  is  produced  by  the 
fall  of  a  small  quantity  of  mercury  placed  in- 
side it. 

The  light  is  caused  by  the  electricity  produced 
by  the  friction  of  the  mercury  in  falling  against 
the  sides  of  a  spiral  glass  tube  placed  inside  the 
vacuous  tube. 

Tube,  Pliicker  — : A  modification  of  a 

Geissler  tube  adapted  for  the  study  of  the 
stratification  of  the  light,  and  the  peculiar- 
ities of  the  space  adjoining  the  negative  elec- 
trode. (See  Tubes,  Geissler) 


Tube,  Spark 


— A  high  vacuum  tube, 


across  which,  when  the  vacuum  is  sufficiently 
high,  the  spark  from  an  induction  coil  will  not 
pass. 

A  spark  tube,  connected  with  incandescent 
lamps  while  undergoing  exhaustion,  acts  as  a 
simple  gauge  to  determine  the  degree  of  ex- 
haustion. When  an  induction  coil  discharge 
ceases  either  to  pass,  or  to  pass  freely,  the  vacuum 
is  considered  as  sufficient,  according  to  circum- 
stances. 

Tube,  Stratification An  exhausted 

glass  tube,  the  residual  atmosphere  of  which 
displays  alternate  dark  and  light  stria',  or 
stratifications,  on  the  passage  through  it  of 
an  induction  coil  discharge.  (See  Discharge, 
Luminous  Effects  of) 

Tubes,  Geissler Vacuum  tubes  of 

glass  containing  various  gases,  liquids  or 
solids,  provided  with  platinum  electrodes, 
passed  through  and  fused  into  the  glass,  de- 
signed to  show  the  various  luminous  effects 


Tub.] 


535 


[Twi. 


of  electric  discharges  through  gases  at  com- 
paratively low  pressures. 

Geissler  tubes  are  made  of  a  great  variety  of 
shapes,  and  often  include  tubes,  spirals,  spheres, 
etc.,  within  other  tubes.  These  enclosed  tubes 
are  made  either  of  ordinary  glass,  or  of  uranium 
glass  in  order  to  obtain  the  effects  of  fluorescence. 

The  vacuum  in  Geissler  tubes  is  by  no  means 
what  might  be  called  a  high  vacuum.  Indeed,  if 
the  exhaustion  of  the  tube  be  pushed  too  far, 
much  of  the  brilliancy  of  the  luminous  effects  is 
lost. 

Some  of  the  many  forms  of  Geissler  tubes  are 
shown  in  Fig.  560. 


Fig.  360.     Geisder  Tubes. 

Tubes  of  Force.— (See  Force,   Tubes  of.) 

Tubes  of  Induction.— (See  Induction, 
Tubes  of.) 

Tubes,  Yacuum Glass  tubes,  from 

which  the  air  has  been  partially  exhausted  and 
through  which  electric  discharges  are  passed 
fcr  the  production  of  luminous  effects.  (See 
Tubes,  Geissler) 

Tubular  Braid.— (See  Braid,   Tubular.} 
Tumbling  Box.— (See  Box,  Tumbling) 
Tuning-Fork  or  Reed  Interrupter. — (See 
Interrupter,     Tuning-Fork.      Interrupter, 
Reed) 

Turn,  Ampere A  single  turn  or 

winding  in  a  coil  of  \vire  through  which  one 
l/npere  passes. 

..Vn  ampere-turn  is  soinetiiues  called  an  ampere- 
winding.  Magneto-motive  force  in  a  magnetic 
circuit  is  proportioned  to  the  number  of  ampere- 
tarns  linked  with  it.  The  practical  unit  of  mag- 
neto-motive foice  is  _L_  x  ampere  turn  =  .0796 

4  "t 
ampere  turn.       Therefore  the    magneto-motive 


force,  m.  m.  f.,  is  found  by  multiplying  the  am- 
pere turns  by  4  it  or  12.57. 

The  number  of  amperes  multiplied  by  the 
number  of  windings  or  turns  of  wire  in  a  coil  give 
the  total  number  of  ampere-turns  in  the  coil. 

In  a  coil  of  fixed  dimensions  the  magnetizing 
force  developed  by  a  given  number  of  ampere-turns 
remains  the  same  as  long  as  the  product  of  the 
amperes  and  the  current  remains  the  same.  That 
is  to  say,  the  same  amount  of  magnetizing  force 
can  be  obtained  by  the  use  of  many  windings  and 
a  small  current,  as  in  shunt  dynamos,  or  by  a  few 
turns  and  a  proportionally  large  current,  as  in 
series  dynamos.  (See  Machine,  Dynamo-Elec- 
tric.} 

Turns,    Ampere,    Primary  — The 

ampere-turns  of  the  primary  of  an  induction 
coil. 

Turns,  AmpSre,  Secondary The 

ampere-turns  of  the  secondary  of  an  induc- 
tion coij. 


Turns,  Dead 


— The  number  of  revo- 


lutions a  self-exciting  dynamo  makes  before 
it  excites  itself. 

Turns,  Dead,  of  Armature  Wire 

Those  turns  of  the  wire  on  the  armature  of  a 
dynamo-electric  machine  which  produce  no 
useful  electromotive  force  or  resultant  current, 
on  the  movement  of  the  armature  through  the 
magnetic  field  of  the  machine. 

The  wire  on  the  inside  of  a  Gramme  or  ring 
armature  is  dead  wire,  but  not  dead  turns. 

Turns,  Series,  of  Dynamo-Electric  Ma- 
chines   The  ampere-turns  in  the 

series  circuit  of  a  compound-wound  dynamo- 
electric  machine.  (See  Machine,  Dynamo- 
Electric,  Compound-  Wound.) 

Turns,  Shunt,  of  Dynamo-Electric  Ma- 
chine   The  ampere-turns  in  the  shunt 

circuit  of  a  compound-wound  dynamo-elec- 
tric machine.  (See  Machine,  Dynamo-Elec- 
tric, Compound-  Wound.) 

Tnrn-Table,  Electric A  table,  suit- 
able for  show  windows,  revolved  around  a 
vertical  axis  by  means  of  an  electric  motor. 

Twig.— A  sub-branch.  (See  Branch, 
Sub.) 

Twin  Wire.— (See  Wire,  Twin.) 


Twi. 


536 


[Unl* 


Twist  in  Leads.— (See  Leads,  Armature, 
Twist  in.) 

Twisted  Bunched  Cable.— (See  Cable, 
Bunched,  Twisted.) 

Twisted-Pair  Cable.— (See  Cable,  Twisted- 
Pair.) 

Twisting  Force. — (See  Force,  Twisting.) 

Two-Fluid  Voltaic  Cell.— (See  Cell,  Vol- 
taic, Two-Fluid.) 

Two-Point  Switch.— (See  Switch,  Two- 
Point) 

Two,  Three,  Four,  etc.,  Conductor  Cable 

(See  Cable,  Two,  Three,  Four,  etc., 

Conductor.) 

Two-Way  Splice  Box.— (See  Box,  Splice, 
Two-  Way!) 


Two-Way  Switch.— (See  Switch,  TW+. 
Way.) 

Type-Printing  Telegraph. — (See  Teleg- 
raphy',  Printing!) 

Typewriter,  Electric A  typewrit- 
ing machine,  in  which  the  keys  are  intended 
to  make  the  contacts  only  of  circuits  of 
electro-magnets,  by  the  attraction  of  the  arzna* 
tures  of  which  the  movements  of  the  type 
levers  required  for  the  work  of  printing  ar* 
effected. 

Electric  typewriters  secure  a  uniformity  of  im- 
pression that  is  impossible  to  obtain  with  hand 
worked  machines.  They  also  greatly  lessen  the 
mechanical  labor  of  writing .  (See  Dynamograph . ) 


U. — A  contraction  sometimes  used  for  unit. 

Ultra-Gaseous  Matter. — (See  Matter, 
Radiant,  or  Ultra-Gaseous!) 

Underground  Cable.— (See  Cable,  Under- 
ground!) 

Underground  Conductor. — (See  Con- 
ductor, Underground!) 

Undulating  Currents. — (See  Currmf, 
Undulating!) 

Undulatory  Currents.— (See  Currents, 
Undulatory.) 

Undulatory  Discharge. — (See  Discharge, 
Undulatory.) 

Ungilding    Bath.— (See  Bath,    Ungild- 

Unidirectional  Discharge.  —  (See  Dis- 
charge, Unidirectional.) 

Unidirectional  Leak. — (See  Leak,  Uni- 
directional!) 

Uniform  Density  of  Field.— (See  Field, 
Uniform  Density  of.) 

Uniform  Magnetic  Field. — (See  Field, 
Magnetic,  Uniform!) 

Uniform  Magnetic  Filament. — (See  Fila- 
ment, Uniform  Magnetic!) 


Uniform  Potential.  —  (See  Potential. 
Uniform.) 

Uniformly  Distributed  Current— (See 
Current,  Uniformly  Distributed.) 

Unipolar  Armature. — (See  Armature, 
Unipolar!) 

Unipolar-Electric  Bath.— (See  Bath,  Un-:* 
polar-Electric!) 

Unipolar  Induction. — .'See  TrtJvct&n, 
Unipolar!) 

Unit  Angle. — (See  Angle,  Unit.  Velocity, 
Angular.) 

Unit  Angular  Velocity. — (See  Velocity^ 
Angular.) 

Unit,  B.  A. A  term  formerly  ap- 
plied to  the  British  Association  unit  of  re- 
sistance, or  ohm.  (See  Ofi*n.) 

Unit-Difference  of  Potential  or  Electro- 
motive Force (See  Potential,  Unit. 

Difference  of.) 

Unit,  Magnetic,  A A  term  some- 
times used  for  a  line  of  magnetic  force,  or 
the  amount  of  magnetism  irduccd  in  an  area 
of  one  square  centimetre  at  the  centre  of  a 
coil  having  a  diameter  of  10  centimetres  and 
carrying  a  current  of  7.9578  amperes. 

Unit,  Natural,  of  Electricity (See 

Electricity,  Natural  Unit  of.) 


2— Vol.  2 


Uni.] 


537 


[Uni. 


Unit  of  Acceleration. — (See  Acceleration, 
Unit  of.} 

Unit  of  Activity.— (See  Activity,  Unit  of.) 

Unit   of  Current,   Absolute (See 

Current,  Absolute  Unit  of.) 

Unit  of  Current,  Jacobi's  — (See 

Current,  Jacobi's  Unit  of.) 


These  units  are    more  frequently  called  the 
centimetre-gramme-second  units. 

Units,  Centimetre-Gramme-Second  

—  A  system  of  units  in  which  the  centimetre 
is  adopted  for  the  unit  of  length,  the  gramme 
for  the  unit  of  mass,  and  the  second  for  unit 
of  time. 


This  is  the  same  as  the   absolute   system   of 
units. 


Units,  C.  G.  S. The   centimetre- 

gramme-second  units.     (See  Units,  Funda- 
mental.) 

Units,  Circular Units  based  upon 

the  value  of  the  area  of  a  circle  whose  diame- 
ter is  unity. 

The  advantages  possessed  by  the  circular  units 
of  cross- section  arise  from  the  fact  that  in  these 
units  the  areas  are  equal  to  the  squares  of  the 
diameter.  No  necessity  exists,  therefore,  for  mul- 
tiplying by  .7854. 


Unit  of  Electrical  Supply.— (See  Supply, 
Unit  of,  Electrical.) 

Unit  of  Electromotive  Force,  Absolute 

(See  Force,  Electromotive,  Absolute 

Unit  of.) 

Unit    of   Electrostatic   Capacity. — (See 
Capacity,  Electrostatic,  Unit  of.) 

Unit  of  Heat— (See  Heat  Unit.) 

Unit  of  Inductance. — (See    Inductance, 
Unit  of.) 

UnitofMass.— (See  J/<m,  Unit  of  .) 

Unit   of   Photometric    Intensity. — (See 

Intensity,  Photometric,  Unit  of.) 

Units,  Circular  (Cross-Sections),  Table 
Unit  of  Power. — (See  Power,  Unit  of.)  of 

Unit  of  Pressure,  New TheBarad:       i  circular  mil  =   .78540  square  mil. 

(SeeBarad.)  "  "  =   .00064514  circular 

Unit    of    Resistance.-(See    Resistance,  millimetre. 

Unit  of.)  =   •0005o669     square 

millimetre. 

Unit  of  Resistance,  Absolute (See      i  square  mil  =  1.2732  circular  mils. 

Resistance,  Absolute  Unit  of.)  "  ««  =   .00082141  circular 

Unit  of  Resistance,  Jacobi's (See  millimetre. 

Resistance,  Unit  of,  facobi's.)  '  circular  millimetre =  1550.  i  circular  mils. 

TT   . ,     „  „  "  "          =  1217.4  square  mils. 

Unit  of  Resistance,  Matthiessen's „                 „                 =      ' £  s^uare  mim 

(See  Resistance,  Unit  of,  Afatthiessen's.)  metre. 

Unit  of  Resistance.  Varley's (See      I  square  millimetre  =1973. 6  circular  mils. 

Resistance,  Unit  of  ,  Var ley's.)  "  "        =1.2732  circular  mU- 

*T    •«.     *•  IT  -i      «j.     -HT  limetres. 

Unit  cf  Velocity,  New (See  Ve-        -,,.  ,    .    ,.      ,.  r       •    i 

,     ._  If  d,  is  the  diameter  of  a  circle,  the  area  in. 

loctty,  New  Unit  of.)  .,          .,    . 

J  '  other  units  is: 

Unit  Quantity  of  fllfcctricity.— (See  Elec-     If  d,  is  in  mils,  the  area  in 

tricity.  Unit  Quantity  of.)  square  millimetres.    ...=d»X    .00050669. 

Unit-Strength    of   Current— (See   Cur-          d' in  millimetres»  area  in 

rmt,  Unit  Strength  of.)  S5uare  mUs =  d*  x  I2I7-4- 

T     .  d,  in  centimetres,  area  in 

Units,  Absolute A  system  of  units  square  inches =  d,  x  I2I74< 

bas^d  on  the  centimetre  for  the  unit  of  length,  a,  in  inches,  area  in  square 

th^  gramme  for  the  unit  of  mass,  and  the  centimetres =dax  5.0669. 

second  for  the  unit  of  time.  (ffering.), 


Uni.] 


538 


[Uni. 


Units,  Derived  ---  Various  units  ob- 
tained or  derived  from  the  fundamental  units 
of  Length,  L.,  Mass,  M.,  and  Time,  T. 

The  derived  units  and  their  dimensions  are  as 
follows: 

Area,  L2.  —  The  square  centimetre. 

Volume,  L3.  —  The  cubic  centimetre. 

Velocity,  V.  —  Unit  distance  traversed  in  unit 
time,  or 

v  =  t.   (i) 

Acceleration,  A.  —  The  rate  of  change  which 
will  produce  a  change  of  velocity  of  one  centi- 
metre per  second. 

A  =  ^.     (2) 

Substituting  in  equation  (2)  the  value  of  V,  in 
equation  (i),  we  have 
L 

A       T_L 
~~ 


Force,  F.  —  The  dyne,  or  the  force  required  to 
act  on  unit  mass  in  order  to  impart  to  it  unit 
velocity. 

F=MXA.   (4) 

Substituting  the  value  of  A,  derived  from  equa- 
tion (2),  we  have 


Substituting  the  value  of  V,  derived  from  equa- 
tion (i),  we  have 

M      L  _  ML 

r  —  rp   X  Tj.  -  -p2  •       (5) 

Work  or  Energy,  \V.  —  The  erg,  or  the  work 
done  in  overcoming  unit  force  through  unit  dis- 
tance. 


Prwer,  P.  —  The  unit  rate  of  doing  work. 


p_W_ 

-  T  ~ 


Units,  Dimensions  of 


ML* 
:~T^~ 


(6) 


— The  values 


given  to  the  units  of  length,  L ;  mass,  M,  and 
time,  T.     (See  Units,  Derived^ 

Units,  Electro-Magnetic  —       — A  system 
of  units  derived  from  the  C.  G.  S.  units,  em- 


ployed   in    electro-magnetic   measurements. 
(See  Units,  Centimetre-Gramme-Second.  \ 

Units  based  on  the  attractions  or  repul- 
sions between  two  unit  magnetic  poles  at 
unit  distance  apart.  (See  Units,  Electro- 
static. ) 

Units,  Electro-Magnetic,  Dimensions  of 


Current  Strength  =  Intensity  of  FieldxLength  = 
v/ML 
T" 

Quantity  =  Current  X  Time=  ,/M  X  L  . 
Potential,    Difference    of    Potential,    Electromo- 


tive Force  =; 


W°rk     . 
Quantity 


Resistance  = 


Electromotive  Force      L 
Current  ~  T 


Capacity  =  Quantity  _  T^ 
Potential""  L 

Units,  Electrostatic Units  based 

on  the  attractions  or  repulsions  of  two  unit 
charges  of  electricity  at  unit  distance  apart. 

'Two  systems  of  electric  units  are  derived  from 
the  C.  G.  S.  system,  viz.,  the  electrostatic  and 
electro -magnetic.  These  units  are  based  re=pec- 
tively  on  the  force  exerted  between  two  quanti- 
ties of  electricity  and  between  two  magnet  poles. 
The  electrostatic  units  embrace  the  units  of 
quantity,  potential  and  rapacity.  No  particular 
names  have  as  yet  been  adopted  for  these  units. 

Unit  of  Quantity. — That  quantity  of  electricity 
which  will  repel  an  equal  quantity  of  the  san.e 
kind  of  electricity  placed  at  a  distance  of  or.e  i%cr.- 
timetre  from  it  with  the  force  of  one  dyne. 

Electrostatic  potential,  or  power  of  doing  elec- 
trostatic work,  is  measured  in  units  of  WO-K,  or 


difference  of  Poi'ntinl. — Such  a  differ- 
ence of  potential  between  two  points  as  requires 
the  expenditure  cf  one^rfof  work  to  bring  up 
a  unit  of  positive  electricity  from  one  point  to  the 
other  against  the  ele°<  •.  ;c  force. 

Unit  of  Cavd-My. — Such  a  capacity  of  conduc- 
tor as  will  take  a  charge  of  one  unit  of  electricity 
when  the  potential  is  unity. 

The  ratio  between  the  inducfive  cap^vityofa 
substance  and  that  of  air,  measured  under  pre 


Uiii.] 


539 


[Uni. 


cisely  similar  conditions,  is  called  the  specific  in- 
ductive capacity. 

The  specific  inductive  capacity  is  obtained  by 
comparing  the  capacity  of  a  condenser  filled  with 
the  particular  substance  and  the  capacity  of  the 
same  condenser  when  filled  with  air.  The  spe- 
cific inductive  capacity  of  air  is  taken  as  unity. 

Units,      Electrostatic,    Dimensions     of 


Quantity  =  v/Force  X  (Distance) «  =  \/F  X  L»  = 


Current  = 


Time 


Potential  — 


Work 


Resistance  = 


Quantity  T 

Potential 
Current 


Capacity  =  Q™°tity       L 
Potential  ~  *" 

Specific  Inductive  Capacity  = 

One  Quantity  • 

Another  Quantity  =  A  Simple  Ratio  or  Number. 

Electromotive  Intensity  = 

Force 
Quantity 

The  fractional  and  negative  exponents  used 
above  are  merely  convenient  methods  of  express- 
ing the  extraction  of  roots  and  division  respec- 
tively by  the  quantity  represented  by  these  expo- 
nents. 

Units,  Fundamental The  units  of 

length,  time   and  mass,  to  which   all   other 
quantities  can  be  referred. 

The  unit  of  length  is  now  generally  taken  as 
the  centimetre,  the  unit  of  time  as  the  second,  and 
the  unit  of  mass  as  the  gramme.  These  form  a 
system  of  measurement  known  as  the  centimetre- 
gramme-second  system,  or  the  C.  G.  S.  system,  or 
absolute  system.  (See  Units,  Derived.) 

The  dimensions  of  the  fundamental  units  are 
designated  thus: 

Length  =  L. 
Mass  =  M. 
Time  —  T. 

Units,    Heat Units   based  on   the 


quantity  of  heat  required  to  raise  a  given 
weight  or  quantity  of  a  substance,  generally 
water,  one  degree. 

The  principal  heat  units  are  the  English  heat 
unit,  the  greater  and  smaller  calorie  and  the 
joule.  (See  Calorie.  Joule.') 

The  following  table  gives  the  values  of  some  of  the  prin- 
cipal heat  units  : 

i  gram,  centigrade,  .001          kilogram  centigrade, 

i  pound  Fahrenheit,  1,047.03  joules. 

772.  foot-pounds. 

106.731          kilogram  metres. 
.55556      pound  centigrade. 
.25200      kilogram  centigrade. 
.29084      watt- hours. 
.0003953  metric  horse-power. 
.0003899  horse-power  hours, 
i  pound  centigrade,   1,884.66  joules. 

1,389.6  foot-pounds. 

192.116         kilogram  metres. 
1.800          pound  Fahrenheit. 
.4536        kilogram  centigrade. 
.52352      watt -hour. 
.0007115    metric     horse-powet 

hour. 

.0007018  horse  power  hour, 
i  kilogram  centigrade,  4, 1 54.95  j  oules. 

3,063.5  foot-pounds. 

423.54  kilogram  metres. 

3.9683       pound  Fahrenheit. 
2.2046       pound  centigrade. 
1.1542        watt-hour. 
.001569     metric      horse-powef 

hour. 

.0015472  horse-power  hour. 
— Her  ing. 

Units,  Magnetic Units  based  on 

the  force  exerted  between  two  magnet  poles. 

Unit  strength  of  a  magnetic  pole  is  such  a 
magnetic  strength  of  pole  that  repels  another 
magnetic  pole  of  equal  strength  placed  at 
unit  distance  with  unit  force,  or  with  the 
force  of  one  dyne. 

Magnetic  Potential. — Is  the  power  of  doing 
work  possessed  by  a  magnetic  pole. 

Magnetic  potential  is  measured  like  electro- 
static potential  in  units  of  work  or  in  ergs. 

Magnetic  Potential,  Unit  Difference  of.  —  Such 
a  difference  of  magnetic  potential  between  two 
points  that  requires  the  expenditure  of  one  erg  of 
work  to  bring  a  magnetic  pole  of  unit  strength 
from  one  to  the  other. 

Unit  Intensity  of  Magnetic  Field. — Such  an 
intensity  of  magnetic  field  as  acts  on  a  north  or 
south  seeking  pole  of  unit  strength  with  the  force 
of  one  dyne. 


Uni,] 


540 


Units,  Magnetic,  Dimensions  of 

Strength  of  Pole,  or  i 
Quantity  of  Magnetism  j 

=  V  Force  X  (Distance)8  =  v/ML 


Magnetic  Potential 


Work 


Strength  of  Pole  T 

Force  __     ^~M~. 

Intensity  of  Field  =  Strength  of  Pole      T  X  v/  L 

Units,  Practical  -  —Multiples  or  frac- 
tions of  the  absolute  or  centimetre-gramme- 
second  units. 

The  practical  units  have  been  introduced  be- 
cause the  absolute  units  are  either  too  small  or 
too  large  for  actual  use. 

Electromotive  Force.— The  Volt  =  100,000, - 
ooo  C.  G.  S.  or  absolute  units,  thaj:  is,  io8  abso- 
lute units  of  resistance.  (See  Volt.) 

Resistance.— The  Ohm  =  1,000,000,000  abso- 
lute units  of  electromotive  force,  or  io9  absolute 
units.  (See  Ohm.) 

Current.  —The  Ampere  =  fa  absolute  unit  of 
current.  (See  Ampere.) 

Quantity. — The  Coulomb  =  fa  absolute  unit  of 
quantity,  of  the  electro-magnetic  system.  (See 
Coulomb.) 

Capacity.— The    Farad  =    -  abso- 

*  *  I,OOO,OOO,OOO 

lute  unit  of  capacity,  or  io9  units  of  capacity. 
(See  Farad.     Henry.      Watt.     Joule.) 

Units,  Proposed  New The  follow- 
ing units  and  terms  have  recently  been  pro- 
posed by  Oliver  Heaviside. 

Some  of  these  have  been  generally  adopted. 

Conductance. — Capacity  for  conducting  elec- 
tricity. 

Numerically,  the  ratio,  in  absolute  measure,  ot 
the  current  strength  to  the  total  electromotive 
force  in  a  circuit  of  uniform  flow.  A  quantity 
with  the  nature  of  a  slowness  or  reciprocal  to  a 
Telocity.  The  practical  unit  is  called  the  mho. 

Conductivity. — Conductance  per  unit  volume. 

Elastance. — Capacity  of  a  dielectric  for  oppos- 
ing electric  charge  or  displacement. 

"Numerically,  the  ratio,  in  absolute  measure, 
of  the  difference  of  potential  in  an  electrostatic  cir- 
cuit to  the  total  charge  or  displacement  therein 
produced.  The  reciprocal  of  permittance  and  a 
quantity  of  the  inverse  nature  of  a  length." 

"  Elastivity.  —  Elastance  per  unit  volume  of  di- 
electric." 

Impedance. — Capacity  for  opposing  the  variable 
flow  of  electricity. 


"Numerically,  in  the  absolute  measure,  the 
ratio  of  the  total  electromotive  force  to  the  cur- 
rent  strength  at  any  instant  in  a  circuit  of  a  vari- 
able flow.  A  quantity  with  the  nature  of  a 
velocity  and  in  any  circuit  always  greater  than 
the  resistance." 

"Inductance. — Capacity  for  magnetic  induc- 
tion." 

"Numerically,  in  absolute  measure,  the  num- 
ber of  unit  lines  of  magnetic  force  linked  with  a 
circuit  traversed  by  the  unit  current  strength. 
Sometimes  alluded  to  as  the  co-efficient  of  self  in- 
duction. A  quantity  of  the  nature  of  a  length.'* 

"  Inductivity '. — Specific  capacity  for  magnetic 
induction. 

"The  numerical  ratio  of  the  induction  in  a 
medium  to  the  induction  producing  it." 

Permittance. — Electrostatic  capacity.  Capa- 
city of  a  dielectric  for  assisting  charge  or  displace- 
ment. 

"Numerically,  the  ratio,  in  absolute  measure, 
of  the  total  charge  or  displacement  in  the  electro- 
static circuit,  to  the  difference  of  potential  pro- 
ducing it.  A  quantity  with  the  nature  of  a 
length." 

"  Permittivity. — The  numerical  ratio  of  the 
permittance  of  a  dielectric  to  that  of  air. 

"  Also  known  as  specific  inductive  capacity." 

"Reluctance. — Capacity  for  opposing  mag- 
netic induction. 

"Numerically,  the  ratio,  in  absolute  measure, 
of  the  magneto-motive  force  in  a  magnetic  cir- 
cuit to  the  total  induction  therein  produced.  A 
quantity  with  the  nature  of  the  reciprocal  of  a 
length.  Sometimes  described  as  magnetic  resist- 
ance." 

Reluctancy  or  Reluctivity. — Reluctance  per  unit 
volume. 

"Sometimes  described  as  specific  magnetic  re- 
sistance. A  numeric,  the  reciprocal  of  induc- 
tivity." 

"  Resistance.  —  Capacity  for  opposing  the 
steady  flow  of  electricity. 

"Numerically,  in  absolute  measure,  the  -itio 
of  the  total  electromotive  force  to  the  current 
strength  in  a  circuit  of  uniform  flow.  A  quantity 
with  the  nature  of  a  velocity.  The  practical  unit 
is  called  the  ohm." 

"  Resistivity. — Resistance  per  unit  volume; 
sometimes  alluded  to  as  specific  resistance. ' ' 

Universal  Discharger.— (See  Discharger. 
Universal.} 

Upright      Galvanometer. -(See     Galva- 


Tac.] 


541 


[Var. 


V. — A  contraction  sometimes  used  for  volt. 

V. — A  contraction  sometimes  used  for  ve- 
locity. 

V. — A  contraction  sometimes  used  for  vol- 
ume. 

V.  A. — A  contraction  sometimes  used  for 
voltaic  alternative.  (See  Alternatives,  Vol- 
taic.} 

Vacuum,  Absolute A  space  from 

which  all  traces  of  residual  gas  have  been 
removed. 

A  term  sometimes  loosely  applied  to  a  par- 
tial vacuum. 

It  is  doubtful  whether  an  absolute  vacuum  is 
attainable  by  any  physical  means. 

Vacuum,  High A  space  from  which 

nearly  all  traces  of  air  or  residual  gas  have 
been  removed. 

Such  a  vacuum  that  the  length  of  the 
mean  free  path  of  the  molecules  of  the  residual 
atmosphere  is  equal  to  or  exceeds  the  di- 
mensions of  the  containing  vessel.  (See 
Layer,  Cr  cokes'.} 

Vacuum,  Low Such  a  vacuum  that 

the  mean  free  path  of  the  molecules  of  the 
residual  gas  is  small  as  compared  with  the 
dimensions  of  the  containing  vessel.  (See 
Tubes,  Geissler.} 

In  a  high  vacuum  groups  of  molecules  can 
move  across  the  containing  vessel  without  meet- 
ing other  groups  of  molecules.  In  a  low  vacuum 
such  a  group  of  molecules  would  be  broken  up  by 
collision  against  other  groups  before  reaching 
the  other  side  of  the  vessel. 

Vacuum,  Partial A  name  some- 
times applied  to  a  low  vacuum.  (See  Vac- 
uum, Low.} 

Vacuum,  Torricellian The  vacuum 

which  exists  above  the  surface  of  the  mercury 
in  a  barometer  tube  or  other  vessel  over  thirty 
inches  in  vertical  height. 

The  Torricellian  vacuum  is  high  only  when  the 
mercury  has  been  carefully  boiled  and  the  tube 
or  other  vessel  vigorously  heated,  so  as  to  thor- 


oughly drive  out  the  moisture  and  adherent  film 
of  air. 

Vacuum  Tubes. — (See  Tubes,  Vacuum} 
Valency. — The  worth  or  value  of  a  chem- 
ical atom  as  regards  its  power  of  displacing 
other  atoms  in  chemical  compounds.     (See 
Atomicity} 

The  worth  or  valency  of  an  atom  of  oxygen  is 
twice  as  great  as  that  of  hydrogen,  since  one 
atom  of  oxygen  is  able  to  replace  two  hydrogen 
atoms  in  chemical  combinations. 


Valve,    Electric 


— An    electrically 


controlled  or  operated  valve. 

In  systems  of  electro-pneumatic  signals,  gaseous 
or  liquid  pressure  controlled  by  electrically  oper- 
ated valves  is  employed  to  move  signals,  ring 
bells,  control  water  and  air  valves,  or  to  perform 
other  similar  work. 

Vapor  Globe  of  Incandescent  Lamp. — 

(See  Globe,  Vapor,  of  Incandescent  Lamp} 

Variable  Inductance.— (See  Inductance, 
Variable} 

Variable  Period  of  Electric  Current — 

(See  Current,  Variable  Period  of} 

Variable  Resistance. — (See  Resistance, 
Variable} 

Variable  Resistance,  Automatic 

(See  Resistance,  Variable,  Automatic} 

Variable  Resistance,  Non- Automatic 

— (See  Resistance,  Variable,  Non-Auto- 
matic} 

Variable  State  of  Charge  of  Telegraph 
Line. — (See  State,  Variable,  of  Charge  of 
Telegraph  Line} 

Variation,  Angle  of The  angle 

which  measures  the  deviation  of  the  magnetic 
needle  to  the  east  or  west  of  the  true  geo- 
graphic north. 

The  angle  of  declination  of  the  magnetic 
needle.  (See  Declination,  Angle  of} 

Variation,  Annual An  approxi- 
mately regular  variation  in  the  magnetic 


Var.] 


542 


[Vel. 


needle  which  occurs  at  different  seasons  of 
the  year. 

Variation  Chart  or  Map. — (See  Map  or 
Chart,  Isogonic.) 

Variation,  Cyclical  Magnetic Secu- 
lar magnetic  variations  occurring  during 
great  cycles  of  time.  (See  Variation, 
Secular.  Variation,  Magnetic.) 


Variation,  Diurnal 


— An  approxi- 


mately regular  variation  of  the  magnetic 
needle,  which  occurs  at  different  hours  of  the 
day.  (See  Declination.) 

Variation,  Irregular A  variation 

of  the  magnetic  needle  which  occurs  at  ir- 
regular intervals.  (See  Declination.} 

Variation,  Magnetic Variations  in 

the  value  of  the  magnetic  declination,  or 
inclination,  that  occur  simultaneously  over 
all  parts  of  the  earth. 

The  term  is  also  applied  to  the  magnetic  decli- 
nation itself. 

These  variations  are: 

(I.)  Secular,  or  those  occurring  at  great  cycles 
of  time. 

(2.)  Annual,  or  those  occurring  at  different 
seasons  of  the  year. 

(3.)  Diurnal,  or  those  occurring  at  different 
hours  of  the  day. 

(4.)  Irregular,  or  those  accompanying  mag- 
netic storms.  The  first  three  are  periodical ;  the 
last  is  irregular.  (See  Declination,  Angle  of. 
Chart,  Inclination.) 

Variation,  Secular A  variation  in 

the  magnetic  declination  which  occurs  at 
great  cycles  or  intervals  of  time.  (See  Dec- 
lination.) 

Varieties  of  Circuits. — (See  Circuits, 
Varieties  of) 

Variometer,  Magnetic An  instru- 
ment for  comparing  the  horizontal  compo- 
nent of  the  earth's  magnetism  in  different 
localities. 

Varnish,  Electric A  varnish  formed 

of  any  good  insulating  material. 
Shellac    dissolved    in    alcohol,   applied    to   a 


thoroughly  dried  surface  and  afterwards  hard- 
ened by  baking,  forms  an  excellent  varnish. 

Varnish,  Stopping-OfF A  varnish 

used  in  electro-plating  to  cover  portions 
which  are  not  to  receive  the  metallic  coaN 
ing. 

A  good  stopping-off  varnish  is  made  by  mixing 
together  10  parts  of  resin,  6  parts  of  beeswax, 
4  parts  of  sealing-wax  and  3  parts  of  rouge,  dis. 
solved  in  turpentine.  (See  Stopping- Off.) 

Vat,  Depositing The  vat  in  which 

the  process  of  electro-plating  is  carried  on. 
(See  Plating.  Electro.) 

The  depositing  vat  contains  the  plating  liquid, 
the  metallic  anode  and  the  object  to  be  plated. 

Vegetation,    Effects    of   Electricity    on 

Most  vegetable  fibres  contract  when 

an  electric  current  is  passed  through  them 
while  on  the  living  plant. 

Some  experiments  appear  to  show  that  electric 
charges  and  currents  hasten  the  germination  and 
growth  of  certain  plants.  Other  experiments 
seem  to  show  that  under  certain  circumstances 
electric  currents  retard  plant  growth.  The  di- 
rection of  the  currents  is  probably  of  main  im- 
portance. 

Velocimeter. — Any  apparatus  for  measur- 
ing the  speed  of  a  machine. 

Velocity,  Angular The  velocity  of 

a  body  moving  in  a  circular  path,  measured, 
not  as  usual,  by  the  length  of  its  path  divided 
by  the  time,  but  with  reference  to  the  angle 
it  subtends  and  to  the  length  of  the  radius. 

Unit  angle  is  that  angle  subtended  by  a  part 
of  the  circumference  equal  to  the  length  of  the 
radius,  or  57  degrees  17  minutes  44  seconds  .8 
nearly. — (Daniell.) 

Unit  angular  velocity  is  the  velocity  under 
which  a  particle  moving  in  a  circular  path,  whose 
radius  equals  unity,  would  traverse  unit  angle  in 
unit  time. 

Velocity,  New  Unit  of The  kine. 

(See  Kine) 

Velocity  of  Discharge.— (See  Discharge, 
Velocity  of) 

Velocity  Ratio.— (See  Ratio,  Velocity) 


Ven.J 


543 


[Vib. 


Ventilation  of  Armature. — (See  Arma- 
ture, Ventilation  of.} 

Vernier. — A  device  for  the  more  accurate 
measurement  of  small  differences  of  length 
than  can  be  detected  by  the  eye  alone,  by 
means  of  the  direct  reading  of  the  position 
of  a  mark  on  a  sliding  scale. 

The  sliding  scale  is  called  the  vernier.  There 
are  a  variety  of  vernier  scales  in  use. 

Vertical  Component  of  Earth's  Magnet- 
ism.— (See  Component,  Vertical,  of  Earth's 
Magnetism.) 

Vertical  Electrostatic  Voltmeter. — (See 
Voltmeter,  Vertical,  Electrostatic.} 

Verticity,  Poles  of,  Magnetic The 

earth's  magnetic  poles,  as  determined  by 
means  of  the  dipping  needle. 

The  point  of  the  north  where  the  angle  of  dip 
is  90  degrees.  (See  Map  or  Chart,  Inclination. ) 

Vibrating. — Moving  to-and-fro. 
Vibrating  Bell.— (See  Bell,  Vibrating} 

Vibrating  Contact. — (See  Contact,  Vibrat- 
ing.) 

Vibration. — A  to-and-fro  motion  of  the 
particles  of  an  elastic  medium.  (See  Wave} 

Vibration  or  Wave,  Amplitude  of 

The  ratio  that  exists  in  a  wave  between 
the  degree  of  condensation  and  rarefaction 
of  the  medium  in  which  the  wave  is  propa- 
gated. 

The  amplitude  of  a  wave  is  dependent  on  the 
amount  of  energy  charged  on  the  medium  in 
which  the  vibration  or  wave  is  produced. 

A  vibration  or  wave  is  a  to-and-fro  motion  pro- 
duced in  an  elastic  material  or  medium  by  the 
action  of  energy  thereon.  S-jund,  light  and  heat 
are  subjectively  effects  produced  by  the  action  of 
vibrations  or  waves,  which  in  the  case  of  sound 
are  set  up  in  the  air,  and,  in  that  of  light  and 
heat,  in  a  highly  tenuous  medium  called  the  lumi- 
niferous  ether.  Objectively  they  are  the  waves 
themselves. 

As  the  amplitude  of  a  sound  wave  increases,  the 
loudness  or  intensity  of  the  sound  increases.  As 
the  amplitude  of  the  ether  wave  increases,  the 
brilliancy  of  the  light  or  the  intensity  of  the  light 
or  heat  increases. 


Let  A  C,  Fig.  561  represent  an  elastic  cord  or 
string  tightly  stretched  between  A  and  C.  If 
the  string  be  plucked  by  the  finger,  it  will  move 
to-and  fro,  as  shown  by  the  dotted  lines.  Each 
to-and-fro  motion  is  called  a  vibration.  The 


Fig.  56  z.  Amplitude  of  Wave. 
vertical  distance  B  D,  or  B  E,  represents  the 
amplitude  of  the  vibration,  and  the  sound  pro- 
duced is  louder,  the  greater  the  amount  of  energy 
with  which  the  string  has  been  plucked,  or,  in 
other  words,  the  greater  the  value  of  B  D,  or 
BE. 

Vibrations  assume  various  forms  in  solid  or 
fluid  media,  but  in  all  cases  the  amplitude'  will 
increase  with  the  increase  in  the  energy  that 
causes  the  vibration. 

Vibration  Period. — (See  Period,  Vibra- 
tion} 

Vibration,  Period  of The  time 

occupied  in  executing  one  complete  vibration 
or  motion  to-and-fro. 

Vibration,  Phase  of The  position 

of  the  particles  in  motion  in  a  wave  or  vibra- 
tion at  any  instant  of  time  during  the  wave 
period,  as  compared  with  a  zero  line,  or  a  line 
passing  through  their  mean  or  middle  position. 


Vibrations,    Isochronous 


—Vibra- 


tions which  perform  their  to-and-fro  motions 
on  either  side  of  the  position  of  rest  in  equal 
times. 

The  vibrations  of  a  pendulum  are  practically 
isochronous,  no  matter  what  the  amplitude  of  the 
swing  may  be,  that  is,  whether  the  pendulum 
swings  through  a  large  arc  or  a  small  arc,  pro- 
vided this  arc  be  not  very  great. 

All  vibrations  that  produce  musical  sounds  may 
be  regarded  as  isochronous;  that  is,  in  any  case, 
the  time  required  to  complete  a  to-and-fro  motion 
is  the  same  at  the  beginning  when  the  sound  is 
loud,  as  at  the  end,  when  it  is  faint. 

Vibrations,  Sympathetic Vibra- 
tions set  up  in  bodies  by  waves  of  exactly  the 
same  wave  rate  as  those  produced  by  the 
vibrating  body. 

The  pitch  or  tone  of  the  note  produced  by  the 
body  set  into  sympathetic  vibration,  is  exactly  the 


Tib.] 


544 


[Vol. 


same  as  the  pitch  or  tone  of  the  exciting  waves  or 
vibrations. 

Hertz's  experiments  show  that  sympathetic  vi- 
brations are  excited  by  electro-magnetic  waves. 
(See  Electricity ',  Hertz's  Theory  of  Electro-Mag- 
netic Radiations  or  Waves.') 

Vibrations,  Sympathetic,  Electrical 

— Vibrations  set  up  in  circuits,  by  the  effect 
of  pulses  in  neighboring  circuits,  that  are  of 
exactly  the  same  mean  length. 

Vibrations,  Synchronous Vibra- 
tions that  are  performed  not  only  in  the  same 
time  as  one  another,  but  which  pass  through 
the  same  portions  of  their  to-and-fro  move- 
ment at  the  same  time. 

Vibrator,    Electro-Magnetic    — A 

lever,  or  arm,  automatically  moved  to-and- 
fro  by  the  alternate  attractions  of  an  electro- 
magnet and  an  opposing  spring,  or  by  the 
successive  action  of  two  electro-magnets. 

In  either  case  the  movement  of  the  lever  is 
utilized  to  permit  the  action  of  first  one  and  then 
the  other  device.  Automatic  or  trembling  bells 
are  operated  by  means  of  an  electro-magnetic 
vibrator. 

Villari  Critical  Point. — A  term  proposed 
by  Sir  William  Thomson  for  that  strength  of 
magnetic  field  at  which  the  reversal  of  the 
effects  of  tension  occurs. 

Both  magnetic  susceptibility  and  permeability 
are  affected  by  mechanical  stress,  vibration  and 
changes  of  temperature.  In  a  weak  magnetic 
field  the  susceptibility  of  iron  wire  is  increased  by 
longitudinal  tension,  while  in  a  strong  field  it 
may  be  decreased.  The  particular  strength  of 
field  at  which  the  reversal  occurs  is  called  the 
Villari  critical  point. 


Viscosity,  Magnetic 


— That  prop- 


erty of  iron  or  other  paramagnetic  substance 
in  virtue  of  which  a  certain  time  is  required 
before  a  given  magnetizing  force  can  pro- 
duce its  effects.  (See  Hysteresis,  Viscous.) 

Viscous  Hysteresis. — (See  Hysteresis, 
Viscous.) 

Vis- Viva. — The  energy  stored  in  a  moving 
body,  and  therefore  the  measure  of  the  amount 
of  work  that  must  be  performed  in  order  to 
bring  a  moving  body  to  rest. 


If  M,  is  the  mass  and  V,  the  velocity 

MV* 
The  Vis-Viva  = 

2 

Vitreous   Electricity. — (See   Electricity, 
Vitreous.) 
Vitrite. — An  insulating  substance. 

Volatilization,  Electric A  term 

sometimes  used  instead  of  electric  evapora-. 
tion. — (See  Evaporation,  Electric.) 

Volcanic  Lightning. — (See  Lightning, 
Volcanic.) 

Volt. — The  practical  unit  of  electro- 
motive force. 

Such  an  electromotive  force  as  is  induced 
in  a  conductor  which  cuts  lines  of  magnetic 
force  at  the  rate  of  100,000,000  per  sec. 

Such  an  electromotive  force  as  would 
cause  a  current  of  one  ampere  to  flow  against 
the  resistance  of  one  ohm. 

Such  an  electromotive  force  as  would 
charge  a  condenser  of  the  capacity  of  one 
farad  with  a  quantity  of  electricity  equal  to 
one  coulomb. 

io8  absolute  electro-magnetic  units  of  elec- 
tromotive force. 

Volt-Ammeter. — A  wattmeter. 

A  variety  of  galvanometer  capable  of  di- 
rectly measuring  the  product  of  the  difference 
of  potential  and  the  amperes.  (See  Watt- 
meter.) 

Volt  ArnpSre.— A  watt.    (See  Watt.) 

Volt-Coulomb. — The  unit  of  electric  work. 

The  joule.     (See/0#&.) 

Volt,  Mega One  million  volts. 

Volt,  Micro The  one-millionth  of  a 

volt. 

Voltage. — This  term  is  now  very  com- 
monly used  for  either  the  electromotive  force 
or  difference  of  potential  of  any  part  of  a 
circuit  as  determined  by  the  reading  of  a 
voltmeter  placed  in  that  part  of  the  circuit. 

Voltage,  Terminal The  electro- 
motive force  expressed  in  volts  of  a  dynamo 
or  other  electric  source,  as  indicated  by  a 
voltmeter  placed  across  its  terminals. 

The  terminal  voltage  is  greater  than  that  on 
the  leads  or  conductors  at  some  distance  from 


Vol.] 


545 


[Yol 


the  source  and  less  than  that  generated  by  the 
source. 

There  is  an  exception  to  this  general  statement 
in  the  case  of  ceitain  leads  connected  with  an 
•alternating  dynamo-electric  machine.  (See  Ef- 
fect',  Ferranti) 

Voltaic  Arc.— (See  Arc,  Voltaic) 
Voltaic  Battery.— (See  Battery,  Voltaic) 

Voltaic  Battery  Indicator. — (See  Indica- 
tor, Voltaic  Battery?) 

Voltaic  Battery  Protector. — (See  Pro- 
tector,  Voltaic  Battery) 

Voltaic  Cell.— (See  Cell,  Voltaic) 

Voltaic  Cell,   Bichromate —(See 

Cell,  Voltaic,  Bichromate.) 

Voltaic  Cell,  Bunsen's (See  Cell, 

Voltaic,  Bunsen's.) 

Voltaic  Cell,  Calland's (See  Cell, 

Voltaic,  Callaud's.) 

Voltaic  Cell,  Capacity  of  Polarization  of 

— (See  Cell,  Voltaic,  Capacity  of  Polar- 


ization of.) 

Voltaic  Cell,  Closed-Circuit (See 

Cell,  Voltaic,  Closed-Circuit.) 

Voltaic  Cell,  Contact  Theory  of 

(See  Cell,  Voltaic,  Contact  Theory  of) 

Voltaic    Cell,  Creeping  of (See 

Cell,  Voltaic,  Creeping  in) 

Voltaic  Cell,  Daniell's (See  Cell, 

Voltaic,  DanielFs) 

Voltaic  Cell,  Double-Fluid  -  —(See 
Cell,  Voltaic,  Double-Fluid) 

Voltaic  Cell,  Dry  -  —(See  Cell,  Vol- 
taic, Dry) 

Voltaic  Cell,  Gravity (See  Cell, 

Voltaic,  Gravity) 

Voltaic  Cell,  GrenSt (See  Cell, 

Voltaic,  Grenet.) 

Voltaic  Cell,  Grove (See  Cell,  Vol- 
taic, Grove) 

Voltaic  Cell,  Leclanchg (See  Cell, 

Voltaic',  Leclanche) 

Voltaic  Cell,  Local  Action  of —(See 

Action,  Local,  of  Voltaic  Cell) 


Voltaic  Cell,  Meidinger (See  Cell, 

Voltaic,  Meidinger) 

Voltaic  Cell,  Negative  Plate  of 

(See  Plate,  Negative,  of  Voltaic  Cell) 

Voltaic  Cell,  Open-Circuit (See 

Cell,  Voltaic,  Open-Circuit) 

Voltaic  Cell,    Poggendorff  —(See 

Cell,  Voltaic,  Poggendorff) 

Voltaic  Cell,  Polarization  of (See 

Cell,  Voltaic,  Polarization  of) 

Voltaic  Cell,   Positive  Plate  of  - 
(See  Plate,  Positive,  of  Voltaic  Cell) 

Voltaic    Cell,  Siemens-Halske  - 
(See  Cell,  Voltaic,  Siemens-Halske.) 

Voltaic  Cell,   Simple  -        —(See   Cell, 
Voltaic,  Simple) 

Voltaic  Cell,   Single-Fluid  -        —(See 
Cell,  Voltaic,  Single-Fluid) 

Voltaic  Cell,  Smee (See  Cell,  Vol- 
taic, Smee) 

Voltaic  Cell,  Standard (See  Cell, 

Voltaic,  Standard) 

Voltaic  Cell,  Standard,  Clark's  - 
(See  Cell,  Voltaic,  Standard,  Clark's) 

Voltaic  Cell,    Standard,    Clark's,  Ray- 

leigh's  Form  of (See  Cell,  Voltaic, 

Standard,  Rayleigh's  Form  of  Clark's) 

Voltaic   Cell,  Standard,  Fleming's 

—  (See  Cell,  Voltaic,  Standard,  Fleming's) 

Voltaic  Cell,  Standard,  Lodge's  — 
(See  Cell,  Voltaic,  Standard,  Lodge's) 

Voltaic  Cell,  Standard,  Sir  Win.  Thom- 
son's   (See  Cell,    Voltaic,  Standard 

Sir  William  Thomson's) 

Voltaic  Cell,  Standardizing (See 

Cell,  Voltaic,  Standardizing  a) 

Voltaic  Cell,  Two-Fluid (See  Cell, 

Voltaic,  Two-Fluid.) 

Voltaic   Cell,   Water (See    Cell, 

Voltaic,  Water) 

Voltaic    Cell,    Zinc-Carbon (See 

Cell,  Voltaic,  Zinc-Carbon) 

Voltaic   Cell,  Zinc-Copper  -  (See 

Cell,  Voltaic,  Zinc-Copper) 

Voltaic  Circle.— (See  Circle,  Voltaic.) 


Vol.] 


546 


[Vol. 


Yoltaic  Circuit.— (See  Circuit,  Voltaic} 
Voltaic  Couple.— (See  Couple,  Voltaic.} 
Yoltaic  Effect— (See  Effect,  Voltaic} 
Voltaic    Electricity. —  (See    Electricity, 
Voltaic.} 

Voltaic  Element. — (See  Element,  Vol- 
taic} 

Voltaic  or  Current  Induction. — (See  In- 
duction, Voltaic} 

Voltameter. — An  electrolytic  cell  em- 
ployed for  measuring  the  quantity  of  the 
electric  current  passing  through  it  by  the 
amount  of  chemical  decomposition  effected 
in  a  given  time. 

Various  electrolytes  are  employed  in  voltam- 
eters, such  as  aqueous  solutions  of  sulphuric 
acid,  copper  sulphate,  or  other  metallic  salts. 

In  the  sulphuric  acid  voltameter  shown  in  Fig. 
562,  the  battery  terminals  are  connected  with  pla- 
tinum electrodes,  immersed  in  water  slightly  acidu- 
lated with  sulphuric  acid,  and  placed  inside  glass 
tubes,  also  filled  with  acidulated  water.  On  the 
passage  of  the  current  hydrogen  appears  at  the 
kathode,  and  oxygen  at  the  anode,  in  nearly  the 
proportion  of  two  volumes  to  one.  (See  Ozone.} 


Fig.  562.    A  Sulphuric  Acid  Voltameter. 

In  the  case  of  water  containing  sulphuric  acid 
(hydrogen  sulphate)  the  decomposition  would  ap- 
pear to  be  that  of  the  sulphuric  acid  rather  than 
that  of  the  water.     The  reaction  is  as  follows: 
H2SO4=H,  +  SO4. 

The  hydrogen  appears  at  the  electro  negative 
terminal  or  kathode.  The  SO4  appears  at  the 
electro  positive  terminal  or  anode,  but  combines 
with  one  molecule  of  water,  thus,  SO4  -4-  H2O  = 
H2SO4-|-  O,  gaseous  oxygen  being  driven  off  at 
the  anode. 

Voltameters  are  not  as  well  suited  as  galva- 
nometers for  the  measurement  of  electric  currents, 
because  a  certain  electromotive  force  must  be 
reached  before  electrolysis  is  effected. 


The  voltameter  in  reality  measures  the  cou- 
lombs, and,  therefore,  is  valuable  as  a  current 
measurer  only  when  the  current  is  constant. 

Coulomb-meter  would,  therefore,  be  the  pref- 
erable term. 

Then,  again,  time  is  required  to  produce  the 
results,  and  considerable  difficulty  is  experienced 
in  maintaining  the  current  strength  constant, 
either  on  account  of  variations  in  the  electro- 
motive force  of  the  source,  or  of  variations  in  the 
resistance  of  the  voltameter. 

Voltameter,  Copper — A  voltameter 

in  which  the  quantity  of  the  current  passing 
te  determined  by  the  weight  of  copper  de- 
posited. 

A  current,  the  strength  of  which  is  constant,  is 
passed  through  the  voltameter  for  a  given  time. 
The  kathode,  preferably  of  platinum,  is  thor- 
oughly cleaned  and  dried  with  a  current  of  heated 
air  and  accurately  weighed  before  and  after. 
The  current  strength  is  then  deduced  from  the 
increase  in  weight  and  the  time. 

A  galvanometer  is  kept  in  the  circuit  of  the 
battery  and  voltameter.  If  a  Daniell  battery  is 
used,  it  should  be  kept  on  closed-circuit  through 
a  resistance  for  some  time  before  use,  in  order  to 
insure  normal  current. 

It  will  be  noticed  that  the  indications  of  this 
voltameter  are  based  on  the  gain  in  weight  of  the 
kathode.  The  loss  in  weight  of  the  anode  is  mis- 
leading, owing  to  secondary  chemical  action  and 
disintegration. 

Voltameter,  Gas A  term  sometimes 

used  for  volume  voltameter.  (See  Voltam- 
eter, Volume} 

Voltameter,  Siemens'  Differential  — 
A  form  of  voltameter  employed  by  Sir  Wil- 
liam Siemens  for  determining  the  resistance  of 
the  platinum  spiral  used  in  his  electric  pyrom- 
eter.    (See  Pyrometer,  Siemens'  Electric} 

Two  separate  voltameter  tubes,  provide!  with 
platinum  electrodes  and  filled  with  dilute  sulphu- 
ric acid,  are  provided  with  carefully  graduated 
tubes  to  determine  the  volume  of  the  decomposed 
gases.  (See  Voltameter,  Volume.} 

A  current  from  a  battery  is  divided  by  a  suit- 
able commutator  into  two  circuits  connected  re- 
spectively with  the  two  voltameter  tubes.  In  one 
of  these  circuits  a  known  resistance  is  placed,  in 
the  other  the  resistance  to  be  measured,  i.  t.,  the 
platinum  coil  used  in  the  electric  pyrometer. 


Tol. 


547 


[Vol. 


Voltameter,  Silver 


— A  voltameter 


in  which  the  quantity  of  the  current  passing 
is  determined  by  the  weight  of  silver  de- 
posited. 

A  solution  of  silver  nitrate  is  used  as  the  elec- 
trolytic liquid.  When  the  current  to  be  measured 
is  strong  the  strength  of  the  silver  nitrate  solution 
is  made  stronger. 

Voltameter,  Volume A  voltameter 

\n  which  the  quantity  of  the  current  passing 
>  determined  by  the  volume  of  the  gases 
r  olved. 

a  some  forms  of  volume  voltameter  in  which 
ailute  sulphuric  acid  is  electrolyzed,  both  the 
hydrogen  and  the  oxygen  are  measured,  either 
separately  or  together. 

In  one  form  of  volume  voltameter  the  hydrogen 
only  is  collected,  and  thus  the  error  in  volum- 
etric determinations  arising  from  the  decrease  in 
volume  from  the  formation  of  ozone  is  avoided. 
The  evolved  oxygen  is  isolated  from  the  hydrogen 
by  placing  a  porous  jar  between  the  electrodes. 
The  negative  electrode,  is  formed  of  platinum 
fused  in  the  tube,  which,  for  ease  of  connec- 
tion, is  partially  filled  with  mercury. 

The  graduated  glass  tube,  in  which  the  hy- 
drogen is  collected,  is  maintained  at  a  nearly  con- 
stant temperature  by  means  of  a  water  column. 
A  thermometer  is  provided  for  corrections  of 
volume  as  affected  by  temperature. 

The  voltameter  contains  dilute  sulphuric  acid, 
about  30  per  cent,  of  acid. 

Voltameter,  Weight  -  —A  voltameter 
in  which  the  quantity  of  the  current  passing 
is  determined  by  the  difference  in  the  weight 
of  the  instrument  after  the  circuit  has  passed 
for  a  given  time. 

A  weight  voltameter  consists  essentially  of 
platinum  electrodes  and  some  means  for  thor- 
oughly drying  the  evolved  gases.  A  vessel  filled 
with  pumice  stone  moistened  with  sulphuric  acid, 
or  a  chloride  of  calcium  tube,  may  be  used  for  this 
purpose.  The  voltameter  is  carefully  weighed 
before  and  after  the  decomposition.  The  differ- 
ence in  weight  gives  the  weight  of  the  sulphuric 
acid  decomposed. 

Voltametric  Law.— (See  Law,  Voltamet- 

rzc.) 

Voltmeter. — An  instrument  used  for  meas- 


uring  difference  of  potential.     (See    Galva- 
nometer.  Potential,  Difference  of.      Volt) 

A  voltmeter  may  be  constructed  on  the  principle 
of  a  galvanometer,  in  which  case  it  differs  from 
an  ammeter,  or  ampere  meter,  which  measures 
the  current,  principally  in  that  the  resistance 
of  its  coils  is  greater,  and  that  in  an  ampere  meter 
the  coils  are  placed  in  the  circuit,  while  in  a  volt- 
meter they  are  placed  as  a  shunt  to  the  circuit. 

The  difference  of  potential  is  determined  from 
the  reading  of  a  voltmeter,  by  the  fact  that  accord- 
ing to  Ohm's  law,  the  product  of  the  current  and 
the  resistance  is  equal  to  the  electromotive  force, 

E 

as  C  =  —  from  which  we  obtain  C  X  R  =  E. 
R 

In  the  ordinary  operation  of  a  voltmeter,  the 
action  of  the  current  in  passing  through  a  coil  of 
insulated  wire  is  to  produce  a  magnetic  field, 
which  causes  the  deflection  of  a  magnetic  needle. 
Since  the  resistance  of  the  voltmeter  is  constant 
the  current  passing,  and  hence  the  deflection  of 
the  needle,  will  vary  with  the  value  of  E.  The 
magnetic  field  produced  by  the  current  deflects 
the  magnetic  needle  against  the  action  of  another 
field,  which  may  be  either  the  earth's  field,  or  an 
artificial  field  produced  by  a  permanent  or  an 
electro-magnet.  Or,  it  may  deflect  it  against  the 
action  of  a  spring,  or  against  the  force  of  gravity 
acting  on  a  weight.  There  thus  arise  varieties  of 
voltmeters,  such  as  permanent-magnet  voltmeters, 
spring  voltmeters,  and  gravity  voltmeters. 

Or,  the  current  produced  by  a  given  difference 
of  potential  may  be  used  to  heat  a  wire,  and  the 
value  of  the  potential  difference  determined  by 
the  movement  of  a  needle  by  the  consequent 
expansion  of  a  wire.  Cardew's  voltmeter  operates 
on  this  principle.  (See  Voltmeter,  Cardew's.) 

Or,  the  potential  difference  to  be  measured 
may  be  utilized  to  charge  a  readily  movable 
needle,  and  thus  produce  electrostatic  attractions 
and  repulsions. 

This  form  of  instrument  is  in  reality  a  form  of 
electrometer.  (See  Electrometer,  Quadrant. 
Attraction,  Electrostatic.) 


Voltmeter,    Cardew's 


— A   form    of 


voltmeter  in  which  the  potential  difference  is 
measured  by  the  amount  of  expansion  caused 
by  the  heat  of  a  current  passing  through  a 
fixed  resistance. 

The   current    produced   by   the   difference   <  f 
potential  to  be  measured  is  passed  through  a  high 


Vol.] 


548 


resistance  wire  of  platinum  silver,  the  expansion  of 
which  is  caused  to  move  a  needle  across  a 
graduated  arc.  The  wire  is  thin  and  therefore 
quickly  acquires  the  temperature  due  to  the 
current. 

The  Cardew  voltmeter  possesses  an  advantage 
of  being  independent  of  changes  of  temperature. 
It  is  also  capable  of  being  used  to  measure  the 
potential  difference  of  alternating  currents. 

Toltmeter,  Closed-Circuit A  volt- 
meter in  which  the  points  of  the  circuit,  be- 
tween which  the  potential  difference  is  to  be 
measured,  are  connected  with  a  closed  coil 
or  circuit,  and  which  gives  indications  by 
means  of  the  current  so  produced  in  said 
circuit. 

All  galvanometer- volt  meters  are  of  the  closed- 
circuited  type. 

The  Weston  standard  voltmeter  shown  in  Fig. 
563  is  a  closed-circuit  voltmeter. 


Fig.  563-     Weston  Standard  Voltmeter. 


Voltmeter,   Electro-Magnetic 

form  of  voltmeter    in  which  the 


—A 


difference 

of  potential  is  measured  by  the  movement  of 
a  magnetic  needle  in  the  field  of  an  electro- 
magnet. (See  Voltmeter?) 

Yoltmeter,  Gravity A  form  of  volt- 
meter in  which  the  potential  difference  is 
measured  by  the  movement  of  a  magnetic 
needle  against  the  pull  of  a  weight. 

Sir  William  Thomson's  balance  instruments  are 
used  as  gravity  voltmeters.  (See  Voltmeter  ) 

Voltmeter,  Magnetic-Vane A  volt- 
meter in  which  the  potential  difference  is 
measured  by  the  repulsion  exerted  between  a 


fixed  and  a  movable  vane  of  soft  iron  placed 
within  the  field  of  the  magnetizing  coil. 

A  pointer,  fixed  to  the  moving  vane,  serves  to 
measure  the  amount  of  the  repulsion,  and  conse- 
quently the  potential  difference  producing 'the 
magnetizing  current.  The  moving  vane  moves 
under  the  magnetic  repulsion  against  the  action 
of  a  spring.  Discs  of  copper  for  damping  the 
movements  ®f  the  movable  vane,  are  placed  be- 
fore and  behind  it. 

Voltmeter,  Multi-Cellular  Electrostatic 

An  electrostatic  voltmeter  in  which  a 

series  of  fixed  and  movable  plates  are  used 
instead  of  the  single  pair  employed  in-  the 
quadrant  electrometer. 

The  movable  pairs  of  plates  are  connected  to  a 
movable  axis  and  placed  vertically  above  one 
another.  To  the  top  of  the  axis  is  fixed  a  light 
aluminium  needle  or  pointer,  which  moves  over  a 
graduated  scale.  A  series  of  fixed  plates,  suita- 
bly supported  and  insulated  from  the  ground, 
alternate  with  the  needle  plates. 

Voltmeter,  Open-Circuit A  volt- 
meter in  which  the  points  of  the  circuit  where 
potential  difference  is  to  be  measured  are 
connected  with  an  open  circuit  and  give  in- 
dications by  means  of  the  charges  so  pro- 
duced. 

Electrometer-voltmeters  are  of  the  open-cir- 
cuited type. 

Voltmeter,  Permanent  Magnet A 

form  of  voltmeter  in  which  the  difference  of 
potential  is  measured  by  the  movement  of  a 
magnetic  needle  under  the  combined  action 
of  a  coil  and  a  permanent  magnet,  against  the 
pull  of  a  spring.  (See  Voltmeter^) 

Voltmeter,  Beducteur  or  Resistance  for 

(See  Reducteur    or  Resistance  for 

Voltmeter?) 

Voltmeter,  Vertical    Electrostatic    - 

— A  form  of  voltmeter  the  needle  of  which 
moves  in  a  vertical  instead  of  in  a  horizontal 
plane. 

The  construction  of  the  vertical  electrostatic 
voltmeter  is,  in  general,  similar  to  that  of  the- 
quadrant  electrometer.  (See  Electrometer,  Quad- 
rant.) 


Vol.] 


549 


[Wat. 


The  fixed  and  movable  sectors,  the  pointer  and 
the  graduated  scale,  however,  are  in  vertical  in- 
stead of  horizontal  planes. 


Fig.  364.      I'erticai  t.lrctrostatic  loltmeter. 

The  general  arrangement  of  the  vertical  elec- 
trostatic voltmeter  will  be  readily  understood  by 
an  inspection  of  Fig.  564. 

Volume    Voltameter. — (See     Voltameter, 
Volume?) 
Vortex  Atom. — (See  Atom,  Vortex!) 


Vortex  Cylinder.— (See  Cylinder,  Vor- 
tex?) 

Vortex-Ring  Field.— (See  Field,  Vortex- 
Ring^ 

Vulcabeston. — An  insulating  substance 
composed  of  asbestos  and  rubber. 

Vulcanite. — A  variety  of  vulcanized  rub- 
ber extensively  used  in  the  construction  of 
electric  apparatus. 

Vulcanite  is  sometimes  called  ebonite  from  its 
black  color.  It  is  also  sometimes  called  hard 
rubber. 

Though  an  excellent  insulator,  vulcanite  will 
lose  its  insulating  properties  by  condensing  a  film 
of  moisture  on  its  surface.  This  can  be  best  re- 
moved by  the  careful  application  of  heat. 

The  surface  is  very  liable  to  become  covered  by 
a  film  of  sulphuric  acid,  due  to  the  gradual  oxi- 
dation of  the  sulphur.  Mere  friction  will  not  re- 
move this  film,  but  it  may  be  removed  by  wash- 
ing with  distilled  water.  A  thick  coating  of  var- 
nish will  obviate  this  last  defect. 

Vulcanized  Fibre. — (See  Fibre,  Vulcan- 
z'zed.) 


W. — A  contraction  sometimes  used  for 
watt. 

W. — A  contraction  sometimes  used  for 
work. 

W. — A  contraction  sometimes  used  for 
weight. 

Wall  Plug.— (See  Plug,  Wall.} 
Wall  Socket.— (See  Socket,  Wall.) 
Ward. — A  term  proposed  by  James  Thom- 
son for  a  line  and  direction  in  a  line. 

Sir  William  Thomson  thus  defines  the  ward  of 
magnetization:'  "  The  ward  in  which  the  magnet, 
izing  force  urges  a  portion  of  the  ideal  northern 
magnetic  matter  or  northern  polarity." 

Waring  Anti-Induction  Cable.  —  (See 
Cable,  Anti-Induction,  Waring!) 

Waste    Field.  —  (See    Field,    Magnetic, 
Wasted 
Watches,  Demagnetization  of Pro- 


cesses    for     removing      magnetism      from 
watches. 

C 


fO OOOOO  O 

AJOOOOOOO 
I  OOOOO  OO 
I  O  O  O  O  OOOOO 


Source   of  Alternating 
Current. 


Fig,  565.     Wright's  Demagnetization  Apparatus. 

The  demagnetization  of  watches  can  be  readily 
effected  by  a  method  proposed  by  J.  J.  Wright. 


Wat.] 


550 


[  Wat. 


The  watch  is  held  by  its  chain  and  slowly  lowered 
to  the  bottom  of  a  hollow  conical  coil  of  wire,  and 
then  slowly  withdrawn  from  the  coil. 

The  wire  is  wound  on  the  coil,  as  shown  in 
Fig.  565,  in  the  shape  of  a  cone,  viz.:  with  a 
single  turn  at  the  top,  and  gradually  increasing 
in  number  of  turns  towards  the  bottom.  The 
conical  coil  is  connected  with  a  source  of  rapidly 
alternating  currents. 

As  the  watch  is  lowered  into  the  coil,  it  gradu- 
ally becomes  more  and  more  powerfully  magnet 
ized  with  alternately  opposite  polarities,  thus 
completely  removing  any  polarity  it  previously 
possessed.  As  it  is  now  slowly  raised  from  out 
the  hollow  cone,  this  magnetization  becomes  less 
and  less,  until,  if  removed  from  the  conical  coil 
while  high  above  its  apex,  all  sensible  traces  of 
magnetism  will  have  disappeared. 

Watchman's  Electric  Register.  —  (See 
Register,  Watchman's  Electric?) 

Water  Battery.— (See  Battery,  Water.') 

Water-Dropping  Accumulator. — (See  Ac- 
cumulator,  Water-Dropping.} 

Water,  Electrolysis  of The  de- 
composition of  water  by  the  passage  through 
it  of  an  electric  current. 

Water  does  not  appear  to  conduct  electricity 
when  pure;  it  is  therefore  not  quite  certain  that 
pure  water  can  be  electrolytically  decomposed. 
The  addition  of  a  small  quantity  of  sulphuric 
acid,  or  of  a  metallic  salt,  however,  renders  its 
electrolysis  readily  accomplished.  (See  Vol- 
tameter. ) 

In  the  opinion  of  most,  it  is  the  sulphuric  acid 
that  is  decomposed  rather  than  the  water. 

Water  Horse-Power. — The  Indian  Gov- 
ernment's term  for  horse-power  developed 
by  falling  water. 

The  estimate  is  made  by  the  following  simple 
rule  :  15  cubic  feet  of  water  falling  per  second 
through  I  foot  equals  I  horse  power. 

Water- Jet  TelepSione  Transmitter.— (See 

Transmitter,  Water-Jet  Telephone?) 

Water -Level  Alarm. —  (See  Alarm, 
Water  or  Liquid  Level.} 

Water-Proof  Wire.— (See  Wire,  Water- 
Proof.) 

Water  Pyrometer.  —  (See  Pyrometer, 
Siemens'  Water.} 


Water  Rheostat.— (See  Rheostat,  Water} 

Water  Voltaic  Cell.— (See  Cell,  Voltaic, 
Water.} 

Watt.— The  unit  of  electric  power.  The 
volt-ampere. 

The  power  developed  when  44.25  foot- 
pounds of  work  are  done  per  minute,  or 
0.7375  foot-pounds  per  second. 

The  T£ff  of  a  horse-power. 

There  are  three  equations  which  give  the 
value  of  the  watts,  viz. : 

(i.)  C  E  =  The  watts. 

(2.)  C8R  =  The  watts. 

(3.)  E*  =  The  watts. 
R 

Where  C  =  the  current  in  amperes  ;  E  =  th*> 
electromotive  force  in  volts,  and  R  =  the  resist 
ance  in  ohms.  (See  Energy,  Electric.} 

Watt  Arc.— (See  Arc,  Watt} 

Watt  Generator. — (See  Generator,  Watt} 

Watt-Hour. — A  unit  of  electric  work. 

A  term  employed  to  indicate  the  expendi- 
ture of  an  electrical  power  of  one  watt,  for  an 
hour. 

Watt-Hour,  Kilo  -  -  The  Board  of 

Trade  unit  of  work  equal  to  an  output  of  one 
kilo-watt  for  one  hour. 

Watt,  Kilo  —       —One  thousand  watts. 

A  unit  of  power  sometimes  used  in  stating 
the  output  of  a  dynamo. 

A  dynamo  of  20  units,  or  a  2O-unit  machine,  is 
one  capable  of  giving  an  output  of  20  kilo-watts. 

Watt-Meter. — A  galvanometer  by  means 
of  which  the  simultaneous  measurement  of 
the  difference  of  potential  and  the  current 
passing  is  rendered  possible. 

The  watt-meter  consists  of  two  coils  of  insu- 
lated wire,  one  coarse  and  the  other  fine,  placet 
at  right  angles  to  each  other  as  in  the  ohm-metet, 
only,  instead  of  the  currents  acting  on  a  sus- 
pended magnetic  needle,  they  act  o:\  each  other 
as  in  the  electro-dynamometer. 

Watt-Minute. —A  unit  of  electric  work. 

An  expenditure  of  electric  power  of  one 
watt  for  one  minute. 

Watt-Second. — A  unit  of  electric  work. 

An  expenditure  of  electric  power  of  one 
watt  for  one  second. 


Web.] 


551 


[Wav. 


Wave. — A  disturbance  in  an  elastic  me- 
dium that  is  periodic  both  in  space  and 
time. 

Wave,  Electric An  electric  disturb- 
ance in  an  elastic  medium  that  is  periodic 
both  in  space  and  time.  (See  Oscillations, 
Electric?) 

Waves,  Amplitude  of The  ampli- 
tude of  a  vibration.  (See  Vibration  or 
Wave,  Amplitude  of.} 

Waves,  Displacement Waves  pro- 

duced  in  the  ether  of  dielectrics  by  means  of 
electric  displacement. 

The  electric  stress  applied  to  a  dielectric  to  pro- 
duce electric  displacement  soon  strains  it  to  its 
utmost  and  no  further  displacement  can  occur 
until  the  direction  of  the  electric  power  is  re- 
versed. A  rapidly  intermittent  current  therefore 
can  pass  through  a  dielectric  and  thus  produce  a 
series  of  displacement  waves. 

Dielectrics,  therefore,  may  be  considered  as 
pervious  or  transparent  to  rapidly  intermittent  or 
reversed  periodic  currents,  but  opaque  or  imper- 
vious to  continuous  currents.  A  condenser  inter- 
polated in  a  telephone  circuit  does  not  prevent  tele- 
phonic communication,  though  it  does  effectually 
stop  all  continuous  currents. 

Waves,  Electro-Magnetic Waves 

in  the  ether  that  are  given  off  from  a  circuit 
through  which  an  oscillating  discharge  is 
passing,  or  from  a  magnetic  circuit  under- 
going variations  in  magnetic  intensity. 

Waves,  Electro-Magnetic,  Interference 
of—  — Interference  effects  similar  to  those 
produced  in  the  case  of  waves  of  light,  ob- 
served in  the  case  of  electro-magnetic  radi- 
ations, or  waves,  in  which  one  system  of 
waves,  retarded  a  half  wave  length  behind 
another  system  of  equal  wave  length  and  am- 
plitude, results  in  a  complete  loss  of  motion 
of  the  particles  of  the  ether  they  tend  to 
simultaneously  affect. 

In  order  that  complete  interference  may  take 
place,  it  is  necessary 

(l.)  That  the  two  waves,  or  system  of  waves, 
must  meet  in  opposite  phases.  That  is,  that  one 
be  retarded -back  of  the  other  one-half  a  wave 
length,  or  some  odd  number  of  half  wave  lengths. 

(2.)  That  the  waves  simultaneously  affect  the 


same  particles  of  ether  in  which  they  are  mov- 
ing. 

(3.)  That  the  energy  charged  on  the  ether  in 
the  shape  of  waves  of  electro-magnetic  radiation, 
must  be  equal  in  the  case  of  each  system  of  waves. 

(4.)  That  the  two  systems  of  waves  must  have 
the  same  wave  length. 

These  conditions,  it  will  be  seen,  are  exactly 
the  same  as  in  the  case  of  the  interference  of 
light. 

It  will,  of  course,  be  readily  understood  that  if 
electro-magnetic  radiations  can  produce  the 
effect  of  resonance,  they  must  also  necessarily 
produce  interference  effects. 

Waves,  Electro-Magnetic,  Reflection  of 

Reflection  of  electro-magnetic  waves 

similar  to  the  reflection  of  waves  of  light. 

In  his  experiments  on  electro-magnetic  radia- 
tions, Dr.  Hertz  shows  that  true  reflection  of 
electro- magnetic  waves  occurs  from  the  surfaces 
of  certain  substances  placed  in  the  path  of  the 
waves. 

In  some  experiments  made  in  a  large  room, 
Dr.  Hertz  obtained  undoubted  indications  of  re- 
flection of  electro-magnetic  waves  from  the  walls 
of  the  room. 

Waves  of  Condensation  and  Rarefaction. 

— The  alternate  spheres  of  condensed  and 
rarefied  air  by  means  of  which  sound  is 
transmitted.  (See  Waves,  Sound.} 

Waves,  Sound Waves  produced  in 

air  or  other  elastic  media  by  the  vibrations 
of  a  sonorous  body.     (See  Sound.) 
Way  Line.— (See  Line,  Way.) 
Weather  Cross. — (See  Cross,  Weather.} 
Weber. — A   term   formerly  employed  for 
the  unit  of  electric  current,  and  replaced  by 
ampere.     (See  Ampere.} 

The  term  weber  was  originally  used  to  express 
a  quantity  of  electricity  equal  to  what  is  now 
called  one  coulomb,  and  a  current  designated  by 
one  weber  per  second.  It  was,  however,  used 
finally  as  a  unit  of  current. 

Weber. — A  term  proposed  by  Clausius  and 
Siemens  for  a  magnetic  pole  of  unit  strength, 
but  not  adopted. 

This  same  term  was  also  employed  to  derig. 
nate  the  unit  strength  of  current,  now  replaced 
by  the  term  ampdre. 


Web.] 


552 


[Wei. 


Weber's     Theory    of    Diamaguetism. — 

(See  Diamagnetism,  Weber's  Theoiy  of.) 

Weight,      Atomic The      relative 

weights  of  the  atoms  of  elementary  sub- 
stances. 

Since  the  atoms  are  assumed  to  be  indivisible, 
they  must  unite  or  combine  as  wholes  and  not 
as  parts.  Although  we  cannot  determine  exactly 
the  actual  weights  of  the  different  elementary 
atoms,  yet  we  can  determine  their  relative  weights 
by  ascertaining  the  smallest  proportions  in  which 
any  two  elements  that  combine  atom  for  atom 
will  unite  with  each  other.  Such  numbers 
will  represent  the  relative  weights  of  the  atoms 
as  compared  with  hydrogen. 

Weight  Voltameter.— (See  Voltameter, 
Weight?) 

Weights  and  Measures,  Metric   System 

of A  system  of  weights  and  measures 

adopted  by  almost  all  civilized  nations  except 
English-speaking,  and  by  the  scientific  world 
generally. 

For  measures  of  length,  the  one  ten -millionth 
part  of  the  quadrant  of  a  meridian  of  the  earth  is 
taken  as  the  unit  of  length.  This  unit  of  length 
is  called  a  metre,  and  various  subdivisions  and 
multiples  of  its  length  are  made  on  the  decimal 
system. 

For  a  system  of  weights,  the  weight  of  one 
cubic  centimetre  of  pure  water  at  39.2  degrees 
Fahr.,  the  temperature  of  the  maximum  density  of 
water,  is  taken  as  the  unit  of  weight.  This  is 
called  a  gramme,  and  various  multiples  and  sub- 
divisions of  this  unit  are  made  on  the  decimal 
system. 

The  following  table  of  French  measures  and 
their  corresponding  English  values  are  taken 
irom  Deschanel's  "  Elementary  Treatise  on 
Natural  Philosophy  ": 

Length. 

\  millimetre  =  .03937  inch,  or  about  ^  inch. 

i  centimetre  =  .3937  inch. 

I  decimetre  —  3.937  inches. 

I  metre  =  39.37  inches  =  3.281  feet  =» 
1.0936  yard. 

I  kilometre  =  1093.6  yards,  or  about  £  mile. 

Deschanel  gives  the  length  of  the  meter  as 
equal  to  39.370432  inches. 

U.  S.  Coast  Survey  Bull.  No.  9  of  1889,  gives 
value  of  meter  =  39.36980  inches.  Therefore, 
39.37  is  probably  as  accurate  as  any  other  figure. 


Area. 

I  square  millimetre  =  .00155  square  inch. 
I  square  centimetre  =  .155  square  inch. 
I  square  decimetre  =15.5  square  inches. 
I  square  metre  =1550  square  inches  =  10.764 
square  feet  =  1.196  square  yards. 

Volume. 

I  cubic  millimetre  =  .000061  cubic  inch. 

I  cubic  centimetre  =  .061025  cubic  inch. 

I  decimetre  =  61.0254  cubic  inches. 

Cubic  metre  =  61025  cubic  inches  =  35.3156 
cubic  feet  =  1.308  cubic  yards. 

The  litre  (used  for  liquids)  is  the  same  as  the 
cubic  decimetre,  and  is  equal  .to  1.7617  pint,  or 
.22021  gallon. 

Mass  and  Weight. 

i  milligramme  =  .01543  grain. 

I  gramme  =  15.432  grains. 

I  kilogramme  =  15432.3  grains  =  2.205  pounds 
avoirdupois. 

More  accurately,  the  kilogramme  is  2.20462125 
pounds. 

Miscellaneous. 

I  gramme  per  square  centimetre  =  2.0481 
pounds  per  square  foot. 

I  kilogramme  per  square  centimetre  =  14.223 
pounds  per  square  inch. 

I  kilogram  metre  =  7.2331  foot-pounds. 

I  force  de  cheval  •—  75  kilogrammetres  per 
second,  or  542^  foot  pounds  per  second,  nearly, 
whereas  i  horse-power  (English)  =  550  foot- 
pounds per  second. 

Conversion  of  English  into  French  measures; 
Length. 

i  inch  =  2.54  centimetres,  nearly. 

I  foot  =  30.48  centimetres,  nearly. 

i  yard  =  91.44  centimetres,  nearly. 

i  statute  mile  =  160933  centimetres,  nearly. 

More  accurately,  I  inch  =  2.5399772  centi 
metres. 

Area. 

I  square  inch  =  6.45  square  centimetres,  nearly. 

I  square  foot  =  929  square  centimetres,  nearly. 

i  square  yard  =  8361  square  centimetres, 
nearly. 

I  square  mile  =  2.59  X  lo1  °  square  centimetres, 
nearly. 

Volume. 

I  cubic  inch  =  16.39  cubic  centimetres,  nearly. 

I  cubic  foot  =  283 1 6  cubic  centimetres,  nearly. 


Wei.] 


553 


I  cubic  yard  =  764535  cubic  centimetres, 
nearly. 

I  gallon  =  4541  cubic  centimetres,  nearly. 

Mass. 

l  gr\in  =  .0648  gramme,  nearly. 
I  ounce  avoirdupois  =  28.35  grammes,  nearly. 
I  pound  avoirdupois  =  453. 6  grammes,  nearly. 
I  ton  =  1.016  X  io6  grammes,  nearly. 
More    accurately,     I     pound    avoirdupois  = 
453.59265  grammes. 

Velocity. 

i  mile  per  hour  =  44.704  centimetres  per 
second. 

I  kilometre  per  hour  =  27.7  centimetres  per 
second. 

Density, 

l  pound  per  cubic  foot  =  .016019  gramme  per 
cubic  centimetre. 

62.4  pounds  per  cubic  foot  =  I  gramme  per 
cubic  centimetre. 

Force  (assuming  g  =  981). 
Weight  of  I  grain  =  63.57  dynes,  nearly. 

"  I  ounce  avoirdupois  =  2.78  X    io4 

dynes,  nearly. 
"  I  pound  avoirdupois  =  4.45  X  io8 

dynes,  nearly. 

11  I  ton  =  9.97  X  ioa  dynes,  nearly. 

"  I  gramme  =  981  dynes,  nearly. 

41  I  kilogramme  —  9.81    X  io5  dynes, 

nearly. 

Work  (assuming  g  =  981). 
I  foot-pound  =  1.356  X  io7  ergs,  nearly. 
I  kilogrammetre  =  9.81  x  io7  ergs,  nearly. 
Work  in  a  second  by  one  theoretical  "horse- 
power" =  7.46  X  io9  ergs,  nearly. 

Stress  (assuming  g  =  981). 

I  pound  per  square  foot  =  479  dynes  per 
square  centimetre,  nearly. 

I  pound  per  square  inch  =  6.9  X  io4 dynes  per 
centimetre,  nearly. 

I  kilogramme  per  square  centimetre  =  9.81 
X  io5  dynes  per  square  centimetre,  nearly. 

760  millimetres  of  mercury  at  o  degree  C.  — 
1.014  X  lo15  dynes  per  square  centimetre,  nearly. 

30  inches  of  mercury  at  o  degree  C.  =  1.163 
X  io"  dynes  per  square  centimetre,  nearly.  • 

Welding,  Electric Effecting  the 

welding  union  of  metals  by  means  of  heat  of 
electric  origin. 

In  the  process  of  Elihu  Thomson,   the  metals 


are  heated  to  electric  incandescence  by  currents 
obtained  from  transformers,  and  are  subsequently 
pressed  or  hammered  together. 

Fig.  566,  shows  the  Thomson  apparatus  for  the 
direct  system  of  electric  welding.  The  dynamo 
is  combined  with  the  welding  apparatus.  The 
armature  contains  two  separate  windings;  one  of 
fine  wire,  in  series  with  the  field  magnet  coils, 
and  another  of  very  low  resistance,  being  fcrmeci 
of  a  U-shaped  bar  of -copper.  No  commutation 
is  used,  the  alternating  currents  being  welt 
adapted  for  heating  purposes.  The  terminals  of 
the  dynamo  are,  therefore  directly  co  mected  to- 
the  clamps  that  hold  the  bar  to  the  welder. 

Fig.  567,  shows  the  apparatus  for  the  Thomson 
Indirect  System  of  Electric  Welding.  This  sys- 
tem is  applicable  to  heavy  work,  and  to  cases 
where  more  than  one  welding  machine  is  operated 
by  the  current  from  a  single  dynamo. 

In  this  case  a  high  tension  current  is  converted 


Fig.  J66.     The  Thomson  Direct  Welder. 

into  the  large  welding  current  employed,  by  means 
of  a  suitably  proportioned  transformer. 

The  welding  process  is  the  same  in  either  sys- 
tem, and  consists  essentially  in  leading  the  weld- 
ing current  into  the  pieces  to  be  united  through 
their  points  of  junction  when  brought  into  firm 
end  contact.  As  the  current  is  led  across  the 
junction  the  temperature  rises  sufficiently  to  soften, 
the  metal,  when  the  pieces  are  firmly  pressed  to- 
gether by  the  motion  of  the  clamps  or  holders. 

In  the  process  of  Benardos  and  Olzewski,  the 
heat  of  the  voltaic  arc  is  employed  for  a  some- 
what similar  purpose,  but  by  a  different  process. 

In  the  Thomson  system  of  electric  welding 
alternating  currents  are  employed.  They  are 
either  supplied  by  an  alternating  current  dynamo 
or  by  a  transformer. 

The  process  of  welding  is  substantially  as  fol- 


Wei.] 


554 


[Win. 


lows,  viz.:  the  welding  junctions  are  made  slightly 
convex,  so  as  to  touch  in  but  one  part  of  their 
opposing  faces.  They  are  made  to  touch  near 
their  centres  and  the  welding  heat  is  first  reached 
near  their  points  of  junction.  Pressure  is  then 
applied  by  means  of  a  screw,  lever  or  hydraulic 
pre-sure  until  all  the  surfaces  are  at  the  welding 
temperature. 

This  operation  requires  in  practice  but  a  few 
seconds  for  small  work,  and  at  the  most  but  a 


Fig.  367.     The  Thomson  Indirect  Welder. 

few  minutes  for  larger  work.  The  heating  is 
practically  local,  extending  in  most  cases  a  dis- 
tance equal  to  about  the  diameter  of  the  weld. 

For  the  purpose  of  controlling  the  electro- 
motive force,  and  thus  adapting  the  same  welder  to 
different  classes  of  work,  when  a  transformor  is 
used,  a  second  transformer  provided  with  a  mov- 
able core  is  placed  in  series  with  the  first.  A 
number  of  coils  of  insulated  wire  are  placed  in  a 
segment  of  a  split-ring  laminated-core.  These 
may  be  connected  in  series  or  in  multiple  by  a 
switch.  An  iron  armature  placed  within,  the 
split  ring  encloses  the  annular  core  and  acts  as 
the  low-resistance  secondary.  When  this  is  placed 
so  as  to  embrace  the  primary  coils,  the  difference 
of  potential  will  be  different  than  if  moved  to  one 
side  or  the  other  of  the  ring. 

Welding  Transformer. — (See  Trans- 
former, Welding.} 

I      Wheatstone's    Electric    Balance. — (See 
Balance,  Wheatstone's  Electric.) 

Wheatstone's     Electric      Bridge. — (See 
Bridge,  Wheatstone's  Electric.} 
Wheel.  Barlow's  or  Sturgeon's A 

wheel  or  disc  of  metal  capable  of  rotation  on 
a  horizontal  axis,  that  is  set  into  rotation  when 
placed  between  the  poles  of  magnets  and 


traversed  by  a  current  of  electricity  from  the 
centre  to  the  circumference. 

Wheel,  Phonic  —  —A  wheel  maintained 
in  synchronous  rotation  by  means  of  timed 
electric  impulses  sent  over  a  line,  and  em- 
ployed in  Delany's  synchronous  multiplex 
telegraphic  system. 

The  phonic  wheel  was  invented  by  La  Cour,  but 
was  first  put  into  successful  operation  in  multiplex 
telegraphy  by  Delany  in  his  system  of  synchronous 
multiplex  telegraphy.  (See  Telegraphy,  Synchron- 
ous Multiplex,  Delany's  System.)  Delany  ob- 
tains the  exact  synchronism  of  the  phonic  wheel 
by  means  of  a  series  of  correcting  electric  impulses, 
automatically  sent  over  the  line  on  the  failure  of 
the  phonic  wheel  at  either  end  of  the  line  to  ex- 
actly synchronize  with  that  at  the  other  end. 

Wheel,  Reaction,  Electric  —  —A  wheel 
driven  by  the  reaction  of  a  convective  dis- 
charge. (See  Flyer,  Electric.) 

Wheel,  Trolley A  metallic  wheel 

connected  with  the  trolley  pole  and  moved 
over  the  trolley  wire  on  the  motion  of  the  car 
over  the  tracks,  for  the  purpose  of  taking  the 
current  from  the  trolley  wire  by  means  of 
rolling  contact  therewith. 

Whirl,  Electric A  term  employed 

to  indicate  the  circular  direction  of  the  lines 
of  magnetic  force  surrounding  a  conductor 
conveying  an  electric  current.  (See  Field, 
Electro-Magnetic^ 

This  is  more  correctly  called  a  magnetic  whirl. 
(See  Whirl,  Magnetic.) 

Whirl,  Expanding  Magnetic One 

of  the  magnetic  whirls  which  are  sent  out 
from  a  conductor  through  which  a  current  of 
gradually  increasing  strength  is  passing,  or 
from  a  magnet  whose  magnetism  is  increas- 
ing. 

These  magnetic  whirls,  according  to  Hertz, 
move  outward  through  free  ether  with  the  velo- 
city of  light. 

Whirl,  Magnetic The  lines  of  mag- 
netic force  which  surround  the  circuit  of  the 
conductor  conveying  an  electric  current. 

Whistle,  Steam,  Automatic  Electric 

— A  steam  whistle,  employed  on  foggy  days 
in  some  systems  of  railway  signals,  when  the 


Whi.] 


555 


[Wir 


visual  signals  cannot  be  seen,  in  which  the 
passage  of  the  steam  through  the  whistle  is 
automatically  obtained  by  the  closing  of  an 
electric  contact,  or  the  passage  of  the  loco- 
motive over  a  certain  part  of  the  track. 

White  Heat— (See  Heat,  White.) 

White  Hot.— (See  Hot,  White.} 

Wimshurst  Electrical  Machine. — (See 
Machine,  Wimshurst  Electrical.) 

Wind,  Electric  -  —The  convection 
stream  of  air  particles  produced  at  the  ex- 
tremities of  points  attached  to  the  surface  of 
charged,  insulated  conductors.  (See  Con- 
vection, Electric.  Flyer,  Electric.) 

Windage  of  Dynamo. — A  term  proposed 
for  the  air  gap  between  the  armature  and  the 
pole  pieces  of  a  dynamo. 

This  term  is  not  much  used. 

Winders,  Telegraphic  Paper Ap- 
paratus for  winding  or  coiling  the  paper  fillets 
used  on  telegraphic  registers. 

\Vhen  moved  by  means  of  a  spring  they  are 
genera.ly  styled  automatic  winders. 

Winding1,  Ampdre A  single  wind- 
ing or  turn  through  which  one  ampere  passes. 

Ampere-winding  is  used  in  the  same  significa- 
tion as  ampere-turn.  (See  Turn,  Ampere.) 

Winding,  Bifllar A  winding  of  a 

coil  of  wire  in  which,  instead  of  winding  the 
wire  in  one  continuous  length,  it  is  doubled 
on  itself  and  then  wound. 

This  method  is  employed  in  resistance  coils,  so 
as  to  avoid  the  induction  effects.  (See  Coil, 
Resistance.) 

Winding,  Compound,  of  Dynamo-Electric 

Machine A  method  of  winding  in 

which  shunt  and  series  coils  are  placed  on 
the  field  magnets.  (See  Machine,  Dynamo- 
Electric,  Compound-  Wound.) 

Winding,  Series  -  — A  winding  of  a 
dynamo-electric  machine  in  which  a  sin- 
gle set  of  magnetizing  coils  are  placed  on  the 
field  magnets,  and  connected  in  series  with 
the  armature  and  the  external  circuit.  (See 
Machine,  Dynamo-Electric,  Series-  Wound.) 

Window-Tube  Insulation. — (See  Insula- 
tor, Window-Tube.) 


Wipe  Spark.— (See  Spark,  Wipe.} 
Wiping  Contact. — (See  Contact,  Wiping^ 

Wire,  Air-Line —That  portion  of  c 

circuit  which  is  formed  by  air-strung  wires,  in 
contradistinction  to  the  portion  which  passes 
through  underground  or  submarine  cables. 

Wire,  Binding,  for  Telegraph  Lines  — 

—The  wire  used  for  securing  lines  of  ^vvire 
conductors  to  the  insulators. 

The  line  wire  rests  against  the  insulators  at  as 
small  an  area  of  contact  as  possible,  generally 
only  a  mere  edge.  In  order  to  attach  the  wire 
to  the  insulator,  and  protect  the  wire  from  chaf- 
ing, it  is  secured  to  the  insulator  by  binding  with 
wire. 

Wire,  Block A  line  or  wire  em- 
ployed in  a  block  system  for  railroads,  con- 
necting a  block  tower  with  the  next  tower 
on  each  side  of  it.  (See  Railroads,  Block 
System  for.) 

Wire,  Braided  —  — A  conducting  wire 
covered  with  a  braiding,  as  distinguished  from 
a  wire  that  is  merely  wrapped  with  insulating 
material. 

Cotton  or  silk  is  used  for  braiding.  The  cov- 
ering is  often  coated  by  a  layer  of  some  insu- 
lating gum  or  varnish  dissolved  in  a  rapidly 
drying  liquid.  It  is  sometimes  covered  with  melted 
paraffine. 


Fig.  568.     Braided  Wire. 

A  copper  wire  covered  with  insulating  material 
and  then  braided  is  shown  in  Fig.  568. 

Wire,  Calling A  wire  employed  in 

a  telegraphic  or  telephonic  system,  by  means 
of  which  a  subscriber  communicates  with  the 
central  office,  or  one  central  office  communi- 
cates with  another. 

This  wire  is  termed  the  calling  wire  in  order  to 
distinguish  from  the  wire  actually  used  ior  talking 
or  telegraphing. 

Wire,  Conductibility  and  Sizes  of 

For  tables  giving  the  resistance,  size,  weight 
per  foot,  etc.,  of  wire  according  to  some  of 
the  principal  wire  gauges  see  pages  254  and 
256. 


Wir.] 


556 


[Wir. 


Wire,  Copper,  Hard-Drawn Copper 

wire  that  is  drawn  three  or  four  times  after 
annealing. 

The  drawing  subsequent  to  annealing  renders 
the  wire  hard  and  elastic,  with  but  a  trifling  de- 
crease in  its  conductivity.  A  hard-drawn  wire, 
of  course,  possesses  greater  limits  of  elasticity 
than  soft-drawn  wire,  and,  therelore,  m  the  case 
of  air  lines,  permits  of  the  use  of  a  longer  distance 
between  adjacent  poles. 

Wire,  Copper,  Soft-Drawn  —  —Copper 
wire  that  is  softened  by  annealing  after 
drawing.  (See  Wire,  Copper,  Hard- 
Drawn,) 

Wire,  Dead,  of  Armature  -  —That 
part  of  the  wire  on  the  armature  of  a  dynamo 
which  produces  no  electromotive  force  or 
resultant  current. 

It  is  called  dead  because  it  does  not  move 
through  the  field  of  the  machine. 

Wire,  Duplex An  insulated  con- 
ductor containing  two  separate  parallel  wires. 

Wire,  Earth-Grounded  — A  wire 

one  terminal  of  which  is  grounded  or  put  to 
earth,  so  that  the  earth  forms  a  part  of  the 
circuit  in  which  the  wire  is  placed. 

Wire,  Feeding1  —  — A  term  sometimes 
applied  to  the  wire  or  lead  of  a  multiple  cir- 
cuit which  feeds  the  main. 

In  a  system  of  electric  railroads  the  feeding 
!«rires  feed  the  trolley  wires. 

Wire  Finder.— (See  Finder,  Wire.) 

Wire,  Fuse A  readily  fusible  wire 

employed  in  a  safety  catch  to  open  the  cir- 
cuit when  the  current  is  excessive.  (See 
Catch,  Safety.) 

Wire  Gauge,  Vernier (See  Gauge, 

Wire,  Micrometer) 

Wire,  Grounded (See  Ground  or 

Earth.) 

Wire,  House — In  a  system  of  in- 

:andescent  electric  lighting  any  conductor 
that  is  connected  with  a  service  conductor 
and  leads  to  the  meter  in  the  house. 

Wire,  Insulated  — Wire  covered 

with  any  insulating  material. 


Cotton  and  silk  are  generally  employed  for  in- 
snlating  purposes,  either  alone,  or  in  connection 
with  various  gums,  resins,  or  other  materials, 
which  are  rendered  plastic  by  heat,  but  which 
solidify  on  cooling.  India  rubber,  caoutchouc, 
and  various  mixtures  and  compounds  are  also  em- 
ployed for  the  same  purpose. 

For  most  of  the  purposes  of  line  wires,  high  in- 
sulating powers,  combined  with  a  low  specific 
inductive  capacity,  are  required  in  the  insulating 
materials. 

For  overhead  wires  a  waterproof  covering  is 
necessary.  In  the  neighborhood  of  combustible 
materials,  some  fireproof  covering  is  desirable. 

Wire,  Lead A  lead  fuse  wire. 

Wire,  Line  —  — In  telegraphy  the  wire 
that  connects  the  different  stations  with  om 
another. 

In  bell  and  annunciator  circuits,  the  term  lin». 
wire  is  sometimes  applied  to  all  circuits  other 
than  the  main  line. 

In  arc  light  circuits  the  term  line  wire  is  applied 
to  the  entire  metallic  circuit,  to  which  the  lamps 
are  connected  in  series. 

Wire,  Main The  principal  wire. 

In  any  system  of  bell  circuits,  the  mam  wire  is 
the  wire  which  runs  from  one  pole  of  the  battery 
to  one  of  the  springs  of  all  the  pushes,  in  distinc- 
tion from  the  line  wires,  or  the  rest  of  the  wires 
in  the  battery  circuit. 

Wire,  Message  -  — A  line  or  wire  em- 
ployed in  a  block  system  for  railroads,  ex- 
tending along  the  road  and  used  for  local 
traffic  or  business.  (See  Railroads,  Block 
System  for) 

Wire,  Negative —  — A  term  sometimes 
applied  to  that  wire  of  a  parallel  circuit  which 
is  connected  to  the  negative  pole  of  a  source. 

Wire,  Neutral The  middle  wire  of 

a  three-wire  system  of  electric  distribution 

Wire,  Omnibus An  onmibus.  bar. 

(See  Bars,  Omnibus) 

A  bus  bar  or  wire.     (See  Wires,  Bus) 

Wire,  Paraffined Wire  wrapped  or 

braided  with  some  textile  material  and  after- 
wards coated  with  paraffine. 

The  term  paraffined  wire  is  sometimes  limited 
to  a  wrapped  wire  that  is  afterwards  paraffine 
coated. 


Wir.] 


557 


fWir. 


Wire,  Positive 


— The  wire  or  con- 


ductor connected  to  the  positive  pole  or  ter- 
minal of  any  electric  source. 

Wire,  Potentiometer  —  — The  wire  of 
a  potentiometer  which  has  been  calibrated  in 
order  to  measure  the  drop  of  potential  in  any 
circuit.  (See  Potentiometer} 

Wire,  Return The  wire  or  con- 
ductor by  means  of  which  the  current  returns 
to  the  electric  source  after  having  passed 
through  the  electro-receptive  devices.  (See 
Sources,  Electric.  Device,  Electro-Recep- 
tive.} 

Wire,  Shade  Guard (See  Guard, 

Wire  Shade.} 

Wire,  Slide  -  —A  wire  of  uniform 
oiameter  employed  in  Wheatstone's  electric 
bridge  for  the  proportionate  arms  of  the 
bridge. 

A  sliding  contact  key  moves  over  the  slide 
wire  and  determines  the  length  of  the  arms. 
Some  forms  of  bridges  have  a  double  or  a  triple 
slide  wire.  (See  Bridge,  Electric,  Slide-Form  of.) 

Wire,  Span The  wire  employed  in 

systems  of  electric  railways  for  holding  the 
trolley  wire  in  place. 

The  span-wire  is  used  when  the  poles  are 
erected  on  both  sides  of  the  street  or  road-bed, 
and  the  trolley  wire,  suitably  insulated  from  the 
span  wire,  is  suspended  therefrom. 

Wire,  Suspending,  of  Aerial  Cable 

The  wire  from  which  an  aerial  cable  is  strung 
or  suspended. 

In  case  the  aerial  cable  is  unusually  heavy  the 
suspending  wire  is  replaced  by  a  wire  rope.  (See 
Cable,  A?rial.) 

Wire,  Taped  -  — A  conducting  wire 
covered  with  an  insulating  material  in  the 
shape  of  tape. 

A  wire  covered  with  an  insulating  material  and 
subsequently  taped  is  shown  in  Fig.  569. 


Taped  Wire. 

— Copper  wire  covered 
with  a  coating  of  tin  prior  to  its  being  insu- 
lated. 


Wire,  Tinned 


The  coating  of  tin  is  for  the  purpose  of  insur- 
ing  greater  ease  in  soldering.  It  is  also  useful 
in  case  vulcanized  rubber  is  used  for  the  insulator, 
to  prevent  the  sulphur  from  attacking  the  copper. 

Wire,  To To  fix  or  place  the  con- 
ductors or  mains  for  any  electric  circuit. 

Wire,  Train A  line  of  wire  em- 
ployed in  a  block  system  for  railroads,  con- 
nected with  the  general  dispatcher's  office, 
and  used  for  sending  train  orders  only.  (See 
Railroads,  Block  System  for} 

Wire,  Trolley The  wire  over  which 

the  trolley  passes  in  a  system  of  electric  rail- 
ways, and  from  which  the  current  is  taken  to 
drive  the  motors  on  the  cars. 

A  bare  conductor  or  wire,  supported  over- 
head on  suitable  hangers  and  provided  for 
transmitting  current  by  the  trolley  to  the 
motor  connected  with  the  car  on  the  passage 
of  the  trolley  wheel  over  its  surface.  (See 
Wheel,  Trolley} 

Trolley  wires,  being  necessarily  bare,  are 
carefully  insulated  at  their  points  of  attachment 
to  all  supports. 

Wire,  Trolley,  Continuous A  trol- 
ley wire  or  conductor  employed  in  overhead 
dependent  systems  of  electric  railways.  (See 
Railroads,  Electric,  Dependent  System  of 
Motive  Power  for.) 

Wire,  Trolley,  Sectional  or  Divided • 

— A  trolley  wire  or  conductor  for  systems  of 
electric  railroads  in  which  the  wire  is  divided 
into  a  number  of  separate  sections  that  are 
suitably  connected  with  the  generating  dyna- 
mo by  means  of  feeder  wires.  (See  Rail- 
roads, Electric,  Dependent  System  of  Motive 
Power  for.} 

Wire,  Trunk •  — A  main  line  or  wire, 

extending  between  two  distant  stations,  such 
as  between  two  large  cities,  and  provided 
solely  for  communication  between  them,  not 
being  tapped  at  intermediate  points. 

Wire,  Twin  -  — A  conductor,  consist- 
ing of  two  separately  insulated  wires,  bound 
together  by  an  additional  insulating  covering. 

Wire,  Water-Proof—  — A  wire  pro- 
tected from  the  weather  by  a  coating  of  any 
waterproof  material. 


Wir.J 


558 


[Wir. 


Wire,  Wrapped Wire  that  is  insu- 
lated by  placing  strands  of  some  insulating 
material,  like  cotton,  parallel  to  its  length, 
and  then  wrapping  a  number  of  strands 
around  the  wire. 

The  wrapped  wire  is  afterwards  either  coated 
with  paraffine  or  other  insulator,  or  is  used  with- 
out  such  coating. 

Wires,  Bus A  term  sometimes  used 

for  omnibus  bars  or  wires. 

The  wires  which  receive  the  full  current 
generated  by  the  electric  source,  and  carry 
it  to  the  feeders. 

The  bus-wires  collect  the  current  from  all  the 
sources,  hence  the  name. 

Wires,  Breaking- Weight  of The 

weight  required  to  be  hung  at  the  end  of  a 
wire  in  order  to  break  it. 

Ordinary  copper  wire  will  break  at  about  17 
tons  to  the  square  inch  of  area  of  cross  section. 
Common  wrought  iron  breaks  at  25  tons  to  the 
square  inch.  These  figures  are  to  be  regarded  as 
approximate  only,  since  almost  inappreciable 
differences  in  the  physical  condition  of  metals,  as 
well  as  slight  variations  in  their  chemical  com- 
position,  often  produce  marked  differences  in 
their  breaking  weights. 

Wires,  Cross (See  Cross,  Electric) 

Wires,  Crossing A  device  employed 

in  telegraphic  circuits  whereby  a  faulty  con- 
ductor is  cut  out  of  the  circuit  of  a  telegraph 
line  by  crossing  over  to  a  neighboring,  less 
used,  line. 

To  cut  out  a  faulty  section  of  wire  in  any  cir- 
cuit, such  as  C  D,  in  the  circuit  A  B  C  D  E,  Fig. 
570,  a  cross-connection  is  made  to  a  line  X  Y, 
running  near  it,  and  which  may  be  temporarily 
thrown  out  of  use.  By  this  means  the  interrup- 
tion of  an  important  circuit  may  be  repaired. 

ABODE 


Fig.  570.     Crossing  Wires. 

Wires,  Dead Disused  and  aban- 
doned electric  wires. 

The  term  dead  is  often  applied  to  a  wire 
through  which  no  current  is  passing.  The  term, 
however,  is  more  properly  applied  to  a  wire 
formerly  employed,  hut  subsequently  abandoned. 


Dead  wires  in  the  neighborhood  of  active  wires 
are  a  constant  menace  to  life  and  property,  and 
should  invariably  be  carefully  reimved. 

It  is  often  a  matter  of  considerable  importance 
to  be  able  to  determine  whether  or  not  a  current 
is  passing  through  a  wire.  When  the  wire  is  not 
enclosed  in  a  moulding,  or  fastened  against  a 
wall,  this  can  readily  be  ascertained  by  bringing 
a  small  compass  needle  near  the  wire,  when  it 
will  tend  to  set  itself  across  the  wire. 

The  term  dead  wire,  as  will  be  seen,  is  used  in 
two  distinct  senses. 

Wires,  Leading-In The  wires  OT 

conductors  which  lead  the  current  through 
(into  and  out  of)  an  electric  lamp. 

The  term  leading-in  wires  is  generally  applied 
to  incandescent  electric  lamps,  Geissler  or 
Crookes  tubes,  and  to  various  other  apparatus. 

Wires,  Leading-Tip — Wires  em- 
ployed for  raising  an  aerial  cable  to  the  cable 
hangers. 

Wires,  Omnibus A  term  sometimes 

used  for  bus  wires.  (See  Wires,  Bus.) 

Wires  or  Conductors,  Continuous 

Wires  or  conductors  free  from  joints. 

Wires  or  conductors  without  soldered  or 
twisted  joints  or  without  any  joints  whatso- 
ever. 

Wires,  the  entire  lengths  of  which  have 
been  taken  from  the  hitherto  uncut  coil  of 
wire  from  the  draw  plate. 

Strictly  speaking,  any  metallic  circuit  consists 
of  a  continuous  wire,  whether  in  one  piece  or  in 
several  sections  or  pieces.  The  preferable  term 
would  appear  to  be  un jointed  wires  or  conductors. 

Wires,  Phantom  —  — A  term  applied 
to  the  additional  circuits  or  wires  obtained  in 
any  single  wire  or  conductor  by  the  use  of 
some  multiplex  telegraphic  system.  (See 
Telegraphy,  Multiplex.  Telegraphy,  Syn- 
chronous-Multiplex, Delany's  System?) 


Wires,  Pilot 


— In  a  system  of  incan- 


descent lighting,  where  a  comparatively  low 
potential  is  employed  on  the  mains,  thin  wires 
leading  directly  from  the  generating  station 
to  different  parts  of  the  mains,  in  order  to 
determine  the  differences  of  potential  at  such 
points. 


Wir.] 


539 


[Wor. 


Pilot  wires  indicate  on  a  voltmeter  the  differ- 
ence of  potenti  il  at  the  various  points.  The  pilot 
wires  extend  to  the  various  seats  of  supply,  and 
so  give  instant  warning  of  any  change  in  the 
value  of  the  potential. 

Wires.  Pressure—  --  In  a  system  of 
incandescent  electric  lighting,  wires  or  con- 
ductors, series-connected  with  the  junction 
boxes,  and  employed  in  connection  with  suit- 
ible  voltmeters,  to  indicate  the  pressure  at 
the  junction  boxes. 

The  pressure  wires  are  sometimes  called  the 
wires. 


— The    joule.     (See 


Wires,  Tap  --  The  wires  or  conduc- 
tors used  to  carry  the  current  from  the  feed- 
ers or  mains  at  the  pole  to  a  near  point  on 
the  trolley  wire. 

Wiring1.  —  Collectively  the  wires  or  con- 
ducting circuits  used  in  any  system  of  electric 
distribution. 

Wiring1.—  Placing  or  establishing  the  wires 
or  conductors  for  any  electric  circuit. 

Wiring,  Case  --  Placing  or  establish- 
ing electric  conductors  or  wires  that  are  held 
in  place  on  the  walls  or  ceiling  of  a  room,  by 
means  of  continuous  cleats. 

Wiring,  Cleat  ----  Placing  or  estab- 
lishing electric  conductors  or  wires  that  are 
held  in  place  on  the  walls  or  ceiling  of  a 
room  by  means  of  suitably  shaped  insulating 
cleats. 


Wiring,    Inside 


— The     conductors 


that,  in  a  system  of  incandescent  electric 
lighting,  lead  to  the  interior  of  the  house  or 
area  to  be  lighted. 


Wirin-r,  Moulding 


— Electric   con- 


ductors or  wires  that  are  held  in  place  on  the 
walls  or  ceiling  of  a  room  by  means  of  suit- 
ably shaped  mouldings. 

Work.— The  product  of  the  force  by  the 
distance  through  which  the  force  acts. 

A  force  whose  intensity  is  equal  to  one  pound 
acting  through  the  distance  of  one  foot,  does  an 
amount  of  work  equal  to  one  foot-pound. 

Work  is  to  be  distinguished  from  the  more  gen- 
eral term  energy . 


Work,   Electric 

Joule.} 

The  product  of  the  volts  by  the  coulombs. 
I  joule  =  10,000,000  ergs,  or  .73732  foot-pounds. 

"         =  i  volt-coulomb. 

"         =1  watt  for  I  second. 

Work,  Electric,  Unit  of The  volt- 
coulomb  or  joule.  (See  Volt-Coulomb.  Joule?) 

Work,  Unit  of  -      —The  erg. 

The  amount  of  work  done  when  a  force  of 
one  dyne  acts  through  the  distance  of  one 
centimetre.  (See  Erg.} 

Raising  one  gramme  against  gravity,  through 
the  distance  of  one  centimetre,  requires  an 
amount  of  work  equal  to  980  ergs. 

Work,  Units  of Various  units  em- 
ployed for  the  measurement  of  work. 

The  following  table  of  Units  of  Work  is  taken 
from  Hering's  work  on  Dynamo-Electric  Ma- 
chines : 

WORK. 

I  erg =  i  dyne-centimetre. 

I     "     =  .0000001  joule. 

I  gramme-centimetre  . .  =981.00  ergs. 

I  "  . .  =  .ooooi  kilogr. -metre. 

I  foot-grain =  1937  5  ergs. 

f  10,000,000 

•737324 

pound,     .101937 
=  \      kilogram  -  metre, 
.0013592    metric 
horse  power    for 
i      one  second. 
.0013406  horse-power 

for  one  second. 
"  =.0009551      pound- 

"  Fah.,  heat  unit. 

"  =  .0005306     pound- 

Centig. ,  heat  unit. 

"  =  .OCO24O7    kilogr.- 

Centig..  heat  unit. 
•'  =  .0002778  wan -hour. 

I  foot-pound =  13562600  ergs. 

"  =  1.35626  joules. 

"  =  .  13825  kilogr.  metre. 

"  =.0018434       metric 

horse-power     for 

e  second. 

"  ..i, =.00181818     horse- 

power     for      one 
rrcond. 


i  joule,  or  i  volt-cou- ") 
lomb,  or  I  watt 
during  every  second 
or  i  volt-ampere 
during  every 
second  . . 


ergs, 
foot  - 


i   volt  ampere  during 
every  second 


i   _.« 


Wor. 


56U 


[Wor. 


I  foot-pound =  .0012953     pound- 

Fah.,  heat  unit. 

"  ,....  =  .0007196      pound- 

Centig.,  heat  unit. 

"  =  .0003264   k  i  1  o  g  r .  - 

Centig.,  heat  unit. 

"  =  .0003767  watt-hour. 

I  kilogram-metre =98 100000  ergs. 

"  =  9.81000  joules. 

"  =  7.23314  foot-pounds. 

"  =  .01333  metric  horse- 

power     for      one 
second. 

11  =.013151   horsepower 

for  one  second. 

"  =  .009369  pound-Fah., 

heat  unit. 

"  =.005205        pound- 

Centig.,  heat  unit. 

"  =  .002361      kilogr.- 

Centig.,  heat  unit. 

"  =  .002725  watt-hour. 

I  watt-hour =  3600  joules. 

"          =  2654.4  foot-pounds. 

"  =366.97   kilogram. 

metres. 

"          =3-4383    pound-Fah., 

heat  units. 

44          =  1.9102    pound- 

Centig.,  heat  units. 

"          =.8664        kilogr.- 

Centig.,  heat  units. 

"          =.0013592       metric 

horse- power-hour. 

"  =.0013406       horse. 

power-hour. 
I  metric  h.-p.-hour  . . . .  =  2648700  joules. 

"  . . . .  =  1952940  foot-pounds. 

"  ....=270000  kilogram- 

metres. 
"  . . . .  =  2529.7     pound-Fah., 

heat  units. 

41  ....  =  1405.4     pound- 

Centig. ,  heat  units. 

44  . . . .  =  637.5  kilogr. -Centig., 

heat  units. 

. . . .  =  735-75  watt-hours. 
•*  . . . .  =  .98634    horse-power* 

hour. 

I  norse-power-hour =  2685400  joules. 

kt  ....  =  1980000      foot- 

pounds. 

"  ....=273740    kilogram- 

metres. 


I  horse-power-hour =  2564.8     pound-Fah., 

heat  units. 

"  ....  =  1424.9      pound- 

Centig. ,  heat  units. 

"  =646.31       kilogr.- 

Centig.,  heat  units. 

"  =  745.941  watt-hours. 

"  =  1.01385  metric  horse- 

power-hour. 
HEAT. 

I  gram-Centig =  .001   kilogram -Centi- 
grade. 

I  pound-Fahr =  1047.03  joules. 

"  =  772  foot-pounds. 

"  =  106.731       kilogram- 

metres. 

"  =.55556   pound-Centi- 

grade. 

"  =.25200   kilogram- 

Centigrade 

"  =  .29084  watt-hour. 

*«  =  .0003953       metric 

horse  -  power-hour. 

"  =  .0003899       horse- 

power  hour. 

i  pound-Centig =  18.84.66  joules. 

"  =  1389.6  foot-pounds. 

"  =  192. 1 16        kilogram- 

metres. 

"  =  1.8000      pound- 

Fahrenheit. 

"  =  .4536  kilogram-Centi- 

grade. 

44  =  .52352  watt-hours. 

"  ... =.0007115       metric 

horse  -  power-hour. 

"  =.0007018       horse- 

power-hour. 

i  kilogram-Centig =  4154.95  joules. 

"  =  3063.5  foot-pounds. 

"  =423.54    kilogram- 

metres. 

•'  =3.9683     pound- 

Fahrenheit. 

•«  =2.2046    pound-Centi- 

grade. 

"  =  1.1542  watt  hours. 

•*  =  .001569  metric  horse- 

power-hour. 

"  .....=  .0015472       horse- 

power-hour. 


Working,   Direct 


— The     transmis- 


Wor.] 


561 


[Yok. 


sion  of  signals  over  a  telegraph  line  with- 
out the  use  of  relays  or  repeaters. 

Working,  Multiple,  of  a  Dynamo-Elec- 
tric Machine A  term  sometimes  used 

for  the  parallel  working  of  dynamo-electric 
machines.  (See  Working,  Parallel,  of  Dy- 
namo-Electric Machines.) 

Working:,  Parallel,  of  Dynamo-Electric 

Machines The  operation  of  working 

several  dynamo-electric  machines  as  a  single 
source,  by  connecting  them  with  one  another 
in  parallel  or  multiple  arc. 

The  effect  of  parallel  working  is  to  reduce  the 
internal  resistance  of  the  dynamo. 

If  a  current  be  required  in  a  circuit  at  an  electro- 
motive force  equal  only  to  that  of  a  single  machine, 
and  the  requirements  of  the  circuit  are  equal  to 
the  output  of  more  than  a  single  dynamo,  a  num- 
ber of  dynamos  must  then  be  coupled  in  mul- 
tiple. 

Working,  Reverse-Current  —  — A 

term  sometimes  used  in  telegraphy  for  a 
method  of  working  by  means  of  a  double 
current  in  place  of  a  single  current. 

The  double-current  system  of  working  was  de- 
vised by  Varley  to  permit  Morse  characters  to  be 
sent  rapidly  through  underground  conductors. 
In  order  to  avoid  the  retardation  due  to  induction, 
the  current  was  reversed  between  each  signal. 
This  reversion  in  the  conductor  hastened  the  dis- 
charge of  the  conductor. 


Working,  Series,  of  Dynamo-Electric 

Machines Such  a  coupling  of  several 

dynamo-electric  machines  as  will  deliver  the 
current  supplied  by  them  in  series.  . 

As  in  all  series  connections  of  sources,  there  re- 
sults an  electromotive  force  equal  to  the  sum  of 
the  electromotive  forces  of  the  different  dynamos. 

Worming,  Cable A  central  core  of 

hemp  or  jute  around  which  are  wrapped  the 
several  separate  conductors  of  a  cable  con- 
taining more  than  a  single  separate  conduc- 
tor. 

Wood's  Button  Repeater. — (See  Repeat- 
ers, Telegraphic.) 

Wrapped  Wire.— (See   Wire,   Wrapped.) 

Writing,  Electrolytic Imprinting 

written  characters  on  cloths,  or  other  textile 
fabrics,  by  the  electrolytic  decomposition  of  a 
dyeing  substance  with  which  they  are  im- 
pregnated. 

The  cloths,  etc.,  to  be  written  on,  are  impreg- 
nated with  an  aniline  salt,  and  placed  on  an  insu- 
lated metallic  plate  next  to  the  salt,  which  is  con- 
nected to  one  pole  of  an  electric  source.  The 
other  pole  is  connected  to  a  carbon  electrode, 
which  is  used  as  the  writing  stylus  or  pencil.  By 
suitably  connecting  the  terminals  the  writing  is 
obtained  in  color  on  a  white  ground,  or  in  white 
on  a  colored  ground.  (See  Dyeing,  Electric.) 

Writing  Telegraphy.— (See    Telegraphy, 
Writing.) 


T-Shaped  Sparks.  —  (See  Spark, 
Y-Shaped) 

Yale-Lock-Switch  Burglar  Alarm. — (See 
Alarm,  Yale-Lock-Switch  Burglar) 

Yoke,  Multiple-Brush  -  — A  term 
sometimes  applied  to  multiple  brush  rocker 
of  a  dynamo  or  motor.  (See  Rocker,  Mul- 
tiple-Pair Brush.) 

Yoke,'  Multiple-Pair  Brush A 

device  for  holding  a  number  of  pairs  of 
brushes  of  a  dynamo-electric  machine  in  such 


a  manner  that  they  can  be  readily  moved  or 
rotated  on  the  commutator  cylinder. 

The  brushes  are  placed  side  by  side  on  the  com- 
mutator cylinder.  In  such  cases  the  several  pairs 
of  brushes  are  so  arranged  that  they  can  be 
thrown  off  or  out  of  contact  with  the  commutator 
cylinder  while  cleaning  the  cylinder,  without  stop- 
ping the  machine. 

Yoke,  Single-Brush A  term  some- 
times used  for  single-brush  rocker.  (See 
Rocker,  Single-Brush.) 


Yok.] 


562 


[Zon. 


Yoke,  Single-Pair A  single-brush 

rocker.  (See  Rocker,  Single-Brush?) 

Yoke,  Single-Pair  Brush  —  — A  device 
for  holding  a  single  pair  of  collecting  brushes 
of  a  dynamo-electric  machine  in  such  a  way 


that  they  can  be  readily  moved  or  rotated  on 
the  commutator  cylinder. 

Yoked-Horseshoe   Electro-Magnet. — (See 
Magnet,  Electro,  Yoked-Horseshoe.} 


Z. — A  symbol  sometimes  used  in  electro- 
therapeutics for  contraction. 

The  use  of  Z,  is  for  the  purpose  of  avoiding 
the  letter  C,  which  has  already  been  used  for  cur- 
rent or  ampere  in  Ohm's  law.  Increasing 
strengths  of  contraction  are  represented  by  Z', 
Z",  Z'". 

Z. — A  symbol  for  electro-chemical  equiva- 
lent. 

Zero,  False •  — A  zero  taken  midway 

between  any  two  equal  and  opposite  deflec- 
tions of  a  measuring  instrument. 

Zero,  Inferred A  zero  deduced  or 

inferred  from  the  deflection  produced  by  a 
charge  that  is  to  be  measured  by  comparison 
with  the  value  of  the  deflection  by  means  of 
a  known  charge  in  an  electrical  measuring 
instrument. 

An  inferred  zero  is  usually  completely  off  the 
scale,  hence  its  name.  It  does  not  actually  exist. 

Zero  Methods. — (See  Method,  Null  or 
Zero.} 

Zero  Potential. — (See  Potential,  Zero.} 

Zero,  Shifting  —  — A  zero  that  changes 
or  shifts  in  position  ;  a  polar  zero  in  a  measur- 
ing instrument. 

Zigzag  Electro-Magnet. — (See  Magnet, 
Electro,  Zigzag} 

Zigzag  Electromotive  Force.— (See 
Force,  Electromotive,  Zigzag} 

Zigzag  Lightning.— (See  Lightning,  Zig- 
zag} 

Zinc,  Amalgamation  of  —  -  The  cov- 
ering or  amalgamation  of  zinc  with  a  layer 
of  mercury. 

To  amalgamate  a  plate  of  zinc,  its  surface  is 
first  thoroughly  cleaned  by  immersing  the  plate  in 
dilute  sulphuric  acid  of  about  I  part  of  acid  to 


10  or  12  parts  of  water.  A  few  drops  of 
mercury  are  then  rubbed  over  its  surface,  thus 
coating  it  with  a  bright  metallic  film  of  zinc 
amalgam.  Care  must  be  taken  not  to  use  too 
much  mercury,  since  the  zinc  plate  would  thus  be 
rendered  brittle. 

Zinc-Carbon  Voltaic  Cell.— (See  Cell, 
Voltaic,  Zinc-Carbon} 

Zinc-Copper  Voltaic  Cell.— (See  Cell, 
Voltaic,  Zinc-Copper} 

Zinc,  Crow-Foot  — A  crow-foot- 
shaped  zinc  used  in  the  gravity  voltaic  cell. 
(See  Cell,  Voltaic,  Gravity} 

The  term  "crow-foot  "  refers  to  the  shape  of 
the  claws.  It  is  hardly  a  happy  term. 

Zinc-Lead  Voltaic  Cell.— (See  Cell,  Vol- 
taic, Zinc-Lead} 

Zinc  Sender. — (See  Sender,  Zinc} 

Zincode  of  Voltaic  Cell.— A  term  for- 
merly employed  to  indicate  the  zinc  terminal 
or  electrode  of  a  voltaic  cell. 

The  negative  electrode  or  kathode  are  prefer- 
able terms. 

Zone,  Anelectrotonic — A  name 

sometimes  given  to  the  polar  zone.  (See 
Zone,  Polar} 

Zone,  Kathelectrotonic A  name 

sometimes  given  to  the  peripolar  zone.  (See 
Zone,  Peripolar} 

Zone,  Peripolar  —  — A  term  proposed 
by  De  Watteville  for  the  zone  or  region  sur- 
rounding the  polar  zone  on  the  body  of 
a  patient  undergoing  electro-therapeutic 
treatment. 

Zone,  Polar A  term  proposed  by 

De  Watteville  for  the  zone  or  region  surround- 
ing the  therapeutic  electrode  applied  to  the 
human  body  for  electric  treatment. 


APPENDIX 


References  to  Words,  Terms  and  Phrases  which  appear  in  the  Appendix  are  preceded  by  the 
words  "See  Appendix";  all  other  references  apply  to  the  main  portion  of  the  Dictionary. 


A.  —A  symbol  proposed  for  ampere,  the 
practical  unit  of  electric  current. 

a. — A  symbol  proposed  but  not  adopted 
for  acceleration. 

The  defining  equation  is  a  =  — 

This  letter  is  sometimes,  though  rarely, 
employed  as  the  symbol  for  ampere. 

a. — A  symbol  proposed  for  angle  ex- 
pressed in  circular  measure. 

SLTC 

The  defining  equation  is  a= : — 

radius 

A.  li. — An  abbreviation  used  for  ampere 
hour,  a  commercial  unit  of  electric  quan- 
tity. 

A.  t. — An  abbreviation  lor  ampere-turn, 
a  practical  unit  of  magneto-motive  force. 

Abscissas. — Plural  of  abscissa. 

Absorptive. — Possessing  the  power  of  ab- 
sorption. (See  Absorption.} 

Acceleration,  Angular The  time 

rate  of  change  of  angular  velocity. 

Accumulation  Method  for  Testing  Joints 
in  Electric  Cables. — (See  Appendix — 
Method,  Accumulation,  for  Testing  Joints 
in  Electric  Cables.} 

Accumulator,  Bi-Metallic A  term 

applied  to  a  secondary  or  storage  cell  in 
which  two  different  metallic  substances  are 
employed  in  connection  with  a  single  elec- 


trolytic fluid  composed  of  a  solution  of  a 
salt  of  one  of  the  metals  of  the  plates. 

Many  different  bi-metallic  accumulators 
have  been  designed;  for  example,  the  cop- 
per-lead accumulator,  in  which  plates  of 
copper  and  lead  are  immersed  in  an  electro- 
lyte of  copper  sulphate;  or  the  copper-zinc  ac- 
cumulator, in  which  plates  of  zinc  and  copper 
are  immersed  in  an  electrolyte  of  zinc  sul- 
phate; or  the  zinc-lead  accumulator,  in  which 
plates  of  zinc  and  lead  are  immersed  in  an 
electrolyte  of  zinc  sulphate. 

Accumulator,  Charge A  term 

sometimes  employed  for  a  Leyden  jar  or 
condenser.  (See  Jar,  Leyden.  Condenser.") 

Accumulator,  Copper-Lead  — An 

electro-chemical  or  electrolytic  accumula- 
tor consisting  of  plates  of  copper  and  lead 
immersed  in  a  solution  of  copper  sulphate. 

Accumulator,  Copper-Zinc —  An 

electro-chemical  or  electrolytic  accumu- 
lator consisting  of  plates  of  copper  and 
zinc  immersed  in  a  solution  of  zinc  sul- 
phate. 

Accumulator,  Current — A  term 

sometimes  employed  for  a  Barlow  wheel 
when  used  as  an  electrical  accumulator. 
(See  Accumulator.} 

A  series-wound  dynamo-electric  machine 

constitutes  in  reality  a  current  accumulator. 

Accumulator,    Electro-Chemical 


563 


Ace.  j  564 

The  name  generally  given  to  the  ordinary 
secondary  or  storage  battery,  in  which  the 
difference  of  potential  is  produced  by 
chemical  action.  (See  Cell,  Storage.} 

Accumulator,  Electrolytic An 

electro-chemical  accumulator.  (See  Appen- 
dix— Accumulator,  Electro-  Chemical.} 

Accumulator,  Storage — A  term 

sometimes  employed  for  storage  cell.  (See 
Cell,  Storage.} 

Accumulator,  Zinc-Lead An  elec- 
trolytic accumulator  consisting  of  plates  of 
zinc  and  lead  immersed  in  a  solution  oi 
line  sulphate. 

Acoustic  Interference. — (See  Appendix 
—Interference,  Acoustic.} 

Acoustic  Resonance. — (See  Appendix — 
Resonance,  Acoustic?) 

Acoustic  Telegraph. — (See  Appendix — 
Telegraph,  Acoustic.} 

Actinometer. — An  instrument  devised  to 
Measure  the  relative  intensity  of  the  sun's 
rays,  or  of  such  artificial  light  as  the  elec- 
tric light,  etc.,  etc, 

The  actinic  power  of  the  sun's  rays  to 
cause  chemical  decomposition  varies  with 
the  condition  of  the  atmosphere  and  the 
position  of  the  sun  above  the  horizon. 

Action,  Gyrostatic,  of  Dynamos  on  Ship- 
board   The  action  which  occurs  at 

the  bearings  of  a  dynamo  running  on  board 
a  tossing  ship,  whereby  gyrostatic  stresses 
are  set  up. 

Action,  Protective A  term  pro- 
posed for  the  protective  action  afforded  by 
a  magnetic  field  to  paramagnetic  metals 
when  exposed  to  chemical  action. 

The  proposed  term  is  not  good  in  view  of 
the  fact  that  it  is  used  to  cover  a  number  of 
other  kinds  of  protective  actions. 

Experiments  as  to  the  protective  action  of 
a  magnetic  field  on  iron,  nickel  and  cobalt 
were  undertaken  by  Prof.  Rowland  and  Dr. 
Bell.  The  results  of  these  experiments,  as 
stated  by  the  experimenters,  are  as  follows  : 


[Ala. 


"When  the  magnetic  metals  are  exposed 
to  action  in  a  magnetic  field,  such  action  is 
decreased  or  arrested  at  any  points  where 
the  ratio  of  the  variation  of  the  square  of  the 
magnetic  force  tends  towards  a  maximum." 

The  results  obtained  by  Rowland  and  Bell 
were  apparently  at  variance  with  some  more 
recent  experiments  of  Squier,  and  showed 
that  the  currents  produced  by  couples  of 
similar  metals  when  exposed  to  chemical 
action  in  a  magnetic  field  had  a  direction  of 
flow  through  the  liquid  from  the  magnetized 
to  the  non-magnetized  electrode — i.  e.,  in  the 
opposite  direction  to  that  pointed  out  by 
Squier  in  the  phenomena  of  the  protective 
throw.  (See  Appendix — Throw,  Protective.) 

Adielectric. — A  term  proposed  for  sub- 
stances that  are  not  dielectrics,  that  is, 
substances  whose  electric  conductivity  at 
ordinary  temperatures  decreases  as  the  tem- 
perature increases. 

Adjustable  Rheostat. — (See  Appendix — 
Rheostat,  Adjustable.} 

Aelotropic. — Heterogeneous  with  respect 
to  direction. 

Aelotropic  Medium. — (See  Appendix — 
Medium,  Aelotropic.) 

After-Working  of  Dielectric.— (See  Ap- 
pendix— Dielectric,  After-Working  of.} 

Age-Coating  of  Chamber  of  Incandescent 
Electric  Lamp. — (See  Appendix—  Chamber 
of  Incanaescent  Electric  Lamp,  Age-  Coat- 
ing of.} 

Ageing  of  Incandescent  Electric  Lamp. 
— (See  Appendix — Lamp,  Incandescent 
Electric,  Ageing  of.} 

Agglomerate  Leclanche'  Voltaic  Cell. — 
(See  Appendix — Cell,  Voltaic,  Agglomerate 
Leclanche.} 

Air  Telegraphy. — (See  Appendix—  Teleg- 
raphy, Air.} 

Alarm,  Frost An  alarm  sounded 

or  set  in  operation  by  means  of  mechan- 
ism operated  by  a  fall  of  temperature  to  or 
below  32°  F. 

Alarm,  Photo-Electric A  selenium 


All.] 


505 


[AH. 


cell  proposed  for  use  in  connection  with  the 
circuit  of  an  electric  source  and  suitable 
electro-receptive  devices,  so  as  to,  permit 
the  passage  of  a  stronger  current  through 
the  circuit  and  the  consequent  sounding  of 
an  alarm  on  the  exposure  of  one  of  its  faces 
to  the  light. 

By  means  of  this  device  a  burglar,  carry- 
ing a  light,  can  be  made  automatically  to  ring 
an  alarm  bell,  and  thus  call  the  attention  of 
a  watchman  or  policeman  to  his  presence. 

Allotropism. —  Allotropy.  (See  Allo- 
tropy.} 

Alternating  Current  Arc. — (See  Appendix 
— Arc,  Alternating  Current.} 

Alternating    Current    Potentiometer. — 

(See  Appendix — Potentiometer,  Alternat- 
ing Current.} 

Alternating  Current  Rotary  Transformer. 

— (See  Appendix — Transformer,  Alternat- 
ing Current  Rotary.} 

Alternating  Electromotive  Force. — (See 
Appendix — Force,  Electromotive,  Alternat- 
ing.} 

Alternation,   Periodicity    of The 

number  of  alternations  per  second  pro- 
duced by  a  generator. 

The  term  periodicity  of  alternation  is 
synonymous  with  frequency,  a  briefer  and 
more  commonly  employed  word. 

When  any  particular  periodicity  or  fre- 
quency is  spoken  of,  as,  for  example,  250 
alternations  per  second,  125  complete  periods 
or  cycles  per  second  are  meant. 

Commercially,  the  word  alternations  is 
used  for  half-periods  or  double-frequencies. 
A  dynamo  with  250  alternations  per  second 
has  125  periods  per  second. 

Alternations,  Co-phasal Alterna- 
tions whose  electromotive  forces  similarly 
and  simultaneously  vary. 

The  maximum  and  minimum  electromo- 
tive forces  of  co-phasal  alternations  are  both 
simultaneously  and  similarly  directed. 

Any  number  of  periodic  functions  are  said 


to  be  co-phasal  when  the  ratio  between  their 
instantaneous  values  is  constant ;  when  one 
is  a  maximum  all  the  remainder  will  be 
maxima,  and  when  one  is  a  minimum  all  the 
remainder  will  be  minima. 

Alternator,  Compensated An  al- 
ternating current  dynamo-electric  machine 
for  sustaining  a  uniform  voltage  at  some 
point  of  its  circuit  under  varying  loads, 
in  which  the  field  magnets  are  excited 
partly  by  rectified  or  commuted  currents 
taken  from  separate  armature  coils,  and 
partly  by  currents  furnished  by  the  com- 
muted current  from  a  small  transformer, 
whose  primary  coil  is  placed  in  the  main 
circuit. 

Alternator,  Compound An  alter- 
nating current  dynamo-electric  machine 
whose  field  magnets  are  compound-wound. 

The  current  from  the  machine  is  commonly 
run  through  a  series  transformer  whose  sec- 
ondary winding  is  connected  with  the  field 
magnets  through  a  commutator. 

Alternator,  Magnetic An  alter- 
nating dynamo-electric  machine  in  which 
permanent  field  magnets  are  employed. 

Alternator,   Magneto    — A  term 

sometimes  employed  for  magnetic  alter- 
nator. (See  Appendix — Alternator,  Mag- 
netic.} 

Alternator,  Multiphase An  alter- 
nating current  dynamo  capable  of  produc- 
ing multiphase  currents. 

Alternator,  Separate-Coil An  al- 
ternating current  dynamo-electric  machine 
in  which  the  field  magnets  are  excited  by 
means  of  current  taken  from  the  coils  on 
the  armature,  which  current  is  first  recti- 
fied, or  caused  to  flow  in  one  and  the  same 
direction,  by  means  of  a  commutator. 

Alternator,  Separately-Excited An 

alternating  current  dynamo-electric  ma- 
chine in  which  the  field  magnets  are  ex- 
cited by  means  of  current  furnished  from  a 
separate  source. 


JLU.] 


566 


[Amp. 


Alternator,  Two-Phase An  alter- 
nating current  dynamo  capable  of  produc- 
ing two-phase  currents. 

The  term  di-phase  alternator  would  appear 
to  be  preferable. 

Alternators,  Parallel  Connection  of 

— The  connection  of  two  or  more  alternat- 
ing current  dynamo-electric  machines  in 
parallel,  so  as  to  form  a  single  electric 
source. 

When  two  alternating  current  dynamo- 
electric  machines  are  connected  in  parallel, 
if  the  armature  self-induction  and  resistance 
are  not  too  high,  and  the  engines  driving  the 
dynamos  are  under  control,  or  in  other  words 
governed,  then  such  machines,  even  if  out  of 
synchronism,  when  connected,  will  almost 
immediately  pull  each  other  into  synchron- 
ism, each  promptly  exercising  an  automatic 
control  over  the  other. 

When  alternators  possess  marked  synchro- 
nizing power,  care  must  be  exercised  to 
adjust  them  fairly  to  equality  of  E.  M.  F. 
and  phase,  in  order  that  they  may  not  be  in- 
jured by  mechanical  shock  due  to  excessive 
cross  currents,  when  first  connected  in 
parallel.  A  certain  amount  of  armature  self- 
induction  is  therefore  desirable  to  render 
parallel  working  safe. 

It  is  a  matter  of  prime  importance  in  the 
parallel  running  of  alternators  that  the 
shape  of  the  wave  of  E.  M.  F.  is  the  same  in 
all  machines.  Otherwise  cross  currents  will 
flow  between  the  machines  under  all  adjust- 
ments. A  difficulty  is  occasionally  experi- 
enced in  the  parallel  connection  of  alternators 
of  different  size,  due  to  differing  wave  form. 

Alternators,  Parallel,  Hunting  of 

A  periodical  increase  and  decrease  in  the 
speed  of  alternators  when  running  in 
parallel  connection  as  motors  or  as 
dynamos  under  certain  conditions. 

Alternators,  Series  Connection  of 

The  connection  of  two  or  more  alternating 
current  dynamo-electric  machines  in  series, 
so  as  to  form  a  single  electric  source. 

The  series  connection  of  alternating  dyna- 
mo-electric machines  is  impracticable  in  or- 


dinary work;  for,  should  such  connection  be 
made  when  the  two  machines  are  furnishing 
currents  in  the  same  phase,  as  soon  as  either 
machine'  differs  in  the  slightest  degree  in 
phase  from  the  other  such  difference  would 
tend  to  rapidly  increase,  until  the  two  ma- 
chines were  in  opposite  phases,  when,  of 
course,  no  current  would  be  produced.  Hence, 
alternators  can  be  run  in  series  only  when 
their  armatures  are  mechanically  and  rigidly 
connected  with  each  other. 

Amalgamating  Solution. — (See  Appendix 
— Solution,  Amalgamating.) 

Amalgamator,  Electric Any  ap- 
paratus for  the  electrical  treatment  of  gold 
or  silver  ores  with  mercury. 

An  electric  amalgamator  consists  essen- 
tially of  an  amalgamator  driven  by  elec- 
tric instead  of  by  ordinary  mechanical  power. 

American  Morse  Code. — (See  Appendix — 
Code,  American  Morse.} 

Ammeter,  Steel-Yard A  form  of 

ammeter  in  which  the  strength  of  the  cur- 
rent is  measured  by  means  of  the  electro- 
magnetic forces  applied  to  one  extremity 
of  a  steel-yard  lever  provided  with  sliding 
weights  for  balancing  these  forces. 

Ampere,  B.  A. Such  a  current  as 

would  deposit  0.001118  gramme  of  silver 
per  second  from  a  neutral  solution  of 
nitrate  of  silver  in  distilled  water. 

This  value  of  the  ampere  was  adopted  by 
the  British  Association  at  its  meeting  held  in 
Edinburgh  in  August,  1892,  the  English 
Board  of  Trade,  and  by  the  Chicago  Congress 
of  1893. 

Equal  to  the  international  ampere. 

Ampere-Centimetre. — A  term  proposed 
as  a  unit  of  magnetism. 

The  ampere-centimetre  as  a  unit  of  mag- 
netism is  based  on  an  assumption  denied  by 
some  that  any  unit  length  of  circuit,  say  one 
centimetre,  conveying  a  unit  current  of  one 
ampere,  will  generate  a  constant  number  of 
lines  of  magnetic  force. 

The  proposed  unit  has  not  been  accepted. 

Ampere,  International r  —  The  value 


Amp.] 


567 


[App. 


of  the  international  ampere  adopted  by  the 
Chicago  Congress  ot  1893  as  equal  to  one- 
tenth  of  the  unit  of  current  of  the  C.  G.  S. 
system  of  electro-magnetic  units,  and 
which  is  represented  sufficiently  well  for 
practical  use  by  the  unvarying  current 
which  when  passed  through  a  solution  of 
nitrate  of  silver  in  water,  and  in  accord- 
ance with  certain  specifications,  deposits 
silver  at  the  rate  of  o.oomS  of  a  gramme 
per  second. 

Ampere  Meter,  Milli An  ampere 

meter,  which  measures  in  milli-amperes 
the  current  passing  through  it. 

Ampere  Yards. — (See  Appendix — Yards, 
Ampere.] 

Anaesthesia. — Insensibility,  especially  to 
pain. 

Anaesthesia,  Electric Nervous  in- 
sensibility produced  by  means  of  electricity. 

Local  anaesthesia  is  obtained  by  means  of 
induction  apparatus  in  which  the  number  of 
makes  and  breaks  can  be  readily  varied.  It 
has  been  found  in  certain  cases,  when  the 
makes  and  breaks  follow  one  another  with  a 
given  rapidity,  which  can  be  determined  by 
means  of  the  musical  note  produced,  that  such 
slight  operations  as  the  lancing  of  a  felon  can 
readily  be  performed  without  pain,  after  the 
part  has  been  subjected  to  the  action  of  the 
current  for  but  a  few  minutes. 

Anemograph,  Electric  —  An  ap- 
paratus for  electrically  registering  the  direc- 
tion and  velocity  of  the  wind. 

Angle  of  Maximum  Sensitiveness  of  Gal- 
vanometer.— (See  Appendix — Galvanom- 
eter, Angle  of  Maximum  Sensitive- 
ness of.) 

Angle,  Phase The  angle  com- 
prised between  two  different  current 
maxima. 

Angular  Acceleration. — (See  Appendix — 
Acceleration,  Angular.) 

Annunciator,  Speaking-Tube An 

oral  annunciator.  (See  Annunciator,  Oral.) 


Annunciator,  Swinging 


— A  pendu- 


lum annunciator.  (See  Annunciator,  Pen- 
dulum.) 

•  Annunciator     Wire. — (See     Appendix — 
Wire,  Annunciator.} 

Anodic  Kays  of  Vacuum  Tube. — (See  Ap- 
pendix— Rays,  Anodic,  of  Vacuum  Tube.) 

Anomalous  Helix.  —  (See  Appendix — 
Helix,  Anomalous.} 

Anomalous  Solenoid. — (See  Appendix — 
Solenoid,  Anomalous.} 

Anomalous  Spiral. — (See  Appendix — 
Spiral,  Anomalous.} 

Anti-Node. — The  point  on  a  vibrating 
body  midway  between  two  successive  nodes. 
(See  Appendix — Node.} 

The  point  of  maximum  motion  in  a  vibrat- 
ing body. 

Apparatus,  Individual  Signalling 

Any  apparatus  by  means  of  which  individ- 
ual signals  are  operated.  (See  Appendix — • 
Signal,  Individual.} 

Lockwood  arranges  the  different  methods 
according  to  which  individual  signals  can  be 
operated  underthe  following  heads,  namely: 

(i.)  Signals  operated  at  each  sub-station  or 
circuit  with  different  strengths  of  current. 

(2.)  Signals  operated  by  currents  of  op- 
posed direction. 

(3-)  Signals  operated  both  by  changes  in 
the  strength  and  direction  of  the  current. 

(4.)  Electro-magnetic  step-by-step  devices, 
acting  to  bring  the  sub-station  signals  to  a 
ringing  point  differing  for  each  sub-station, 
and  then  to  close  a  local  branch  or  shunt  cir- 
cuit, including  a  local  bell,  to  operate  alter, 
nating  mechanism,  or  in  some  way  to 
introduce  a  bell  magnet  into  the  circuit. 

(5.)  Signals  operated  by  means  of  various 
arrangements  of  clockwork  bells. 

(6.)  Signals  operated  by  means  of  galva- 
nometers, the  movements  of  whose  needles 
cause  bells  to  ring. 

To  which  may  be  added,  signals  operated 
by  currents  of  different  periodicity. 

Apparatus,  Polyphase Apparatus 


App.J 


568 


[Arm. 


operated  by  polyphase  currents.  (See  Ap- 
pendix— Currents,  Polyphase.} 

Apparatus,  Selective  Signalling  —  —A 
term  sometimes  used  in  place  of  indi- 
vidual signalling  apparatus.  (See  Appendix 
— Apparatus,  Individual  Signalling.} 

Apparent  Resistance.— (See  Appendix— 
Resistance,  Apparent.} 

Arc,  Alternating  Current  -  —An  arc 
formed  by  means  of  an  alternating  current. 

Since  in  the  alternating  current  the  elec- 
trodes become  alternately  positive  and  nega- 
tive, neither  carbon  in  the  case  of  a  carbon 
arc  is  markedly  brighter  than  the  other,  and 
the  rate  of  consumption  of  both  carbons  is 
the  same. 

Arc,  Carbon A  voltaic  arc  formed 

between  two  carbon  electrodes. 

The  carbon  voltaic  arc  is  the  one  ordina- 
rily employed,  and  is  formed  through  a  cloud 
of  volatilized  carbon.  (See  A  re,  Voltaic.} 

Arc,  Common,  of  Aurora  Glory 

The  inner  or  common  arc  of  an  aurora 
glory.  (See  Appendix—  Glory,  Aurora.} 

Arc,  Continuous  Current A  vol- 
taic arc  produced  by  means  of  a  continu- 
ous electric  current. 

In  a  continuous  current  arc  the  light  is 
principally  emitted  from  a  crater  in  the  posi- 
tive carbon. 

Arc,  Copper A  voltaic  arc  formed 

between  two  copper  electrodes. 

A  copper  arc  is  formed  through  a  cloud  of 
volatilized  copper.  Most  metallic  arcs  are 
longer  than  carbon  arcs.  They  possess  the 
characteristic  color  of  the  volatilized  metal; 
for  example,  the  copper  arc  is  green.  (See 
Arc,  Voltaic.} 

A  copper  or  other  metallic  arc  would  be 
formed  from  copper  or  other  metallic  rod  if  it 
formed  the.  positive  electrode,  and  a  block  of 
carbon  or  other  non-metallic  substance 
formed  the  negative  electrode,  since  it  is  the 
material  of  the  positive  electrode  that  is  vola- 
tilized. 


Arc  Lighting  Dynamo-Electric  Machine. 


3— Vol.  2 


— (See  Appendix  —  Machine,  Dynamo- 
Electric,  Arc  Lighting} 

Arc,  Two  Thousand  Candle  Power,  Pro- 
posed Definition  for  —  — The  light  of  an 
arc  produced  by  10  amperes  of  current 
and  45  volts  potential  difference  between  the 
carbons. 

A  45O-watt  arc  restricted  as  above. 

Such  an  arc  is  sometimes  called  a  full  arc. 

The  difficulty  in  measuring  the  photometric 
intensity  of  a  continuous  current  carbon  arc 
is  so  great  that  considerable  controversy  has 
arisen  as  to  whether  or  not  a  given  candle 
power  is  present  in  certain  cases.  This  dif- 
ficulty arises  not  only  from  the  fact  that  the 
light  is  of  much  greater  intensity  in  certain 
directions  than  in  others,  but  also  from  the 
fact  that  the  candle  power  of  an  arc  having 
a  certain  watt  value  may  differ  greatly  with 
the  quality  of  the  carbons  employed. 

The  adoption  of  the  above  definition  would, 
therefore,  seem  to  be  extremely  advisable.  , 

Armature,  Balanced An  armature 

of  an  electro-magnet  whose  motion  to- 
ward or  from  the  magnetic  poles  is  op- 
posed by  the  pull  of  a  spring,  or  the  action 
of  a  weight,  so  that  on  the  cessation  of  the 
magnetic  attraction  the  armature  will  be 
caused  to  assume  the  position  it  had  before 
the  magnetic  action  began. 

Strictly  speaking,  such  an  armature  is  not 
balanced;  the  term,  however,  is  a  convenient 
one. 

Armature,  Balanced An  armature 

of  a  dynamo-electric  machine  so  constructed 
or  adjusted  that  the  line  joining  the  centres 
of  inertia  of  all  its  cross  sections  practically 
coincides  with  the  axis  of  rotation. 

A  balanced  dynamo  armature  runs 
smoothly  and  without  mechanical  jars  or 
vibrations. 

Armature,  Balanced An  armature 

of  a  dynamo  or  motor  in  which  the  winding 
is  such  as  to  insure  electrical  symmetry. 

Armature,  Coreless,  of  Dynamo  or  Motor 

— An  armature  of  a  dynamo  or  motor 


Arm,] 


569 


[Ato. 


not  provided  with  a  core  of  iron  or  other 
magnetizable  material. 

Armature,  Di-Phase An  armature 

of  a  motor  wound  so  as  to  be  operated  by 
di-phase  currents. 

Armature,  Magnetic  Sticking  of  — 
The  adherence  of  the  armature  of  an  elec- 
tro-magnet to  the  poles,  after  the  current 
has  ceased  to  pass  through  the  magnetizing 
coils. 

The  cause  of  sticking  is  to  be  ascribed  to 
the  residual  magnetism. 

Sticking  is  sometimes  avoided  by  means 
of  core  pins,  or  by  a  non-magnetizable  coat- 
ing of  armature  or  core.  (See  Appendix — 
Pins,  Core.) 

Armature,  Polyphase •  An  arma- 
ture of  a  motor  wound  so  as  to  be  operated 
by  polyphase  currents. 

Armature  Reaction. — (See  Appendix — 
Reaction,  Armature,) 

Armature,  Three-Phase A  tri- 

phase  armature.  (See  Appendix — Arma- 
ture, Tri-Phase.} 

The  term  tri-phase  armature  would  appear 
to  be  preferable. 

Armature,  Tri-Phase  —  —  An  arma- 
ture of  a  motor  wound  so  as  to  be  operated 
by  tri-phase  currents. 

Armature,  Two-Phase A  di-phase 

armature.  (See  Appendix — Armature,  Di- 
Phase.) 

The  term  di-phase  armature  would  appear 
to  be  preferable. 

Arms,  Side A  term  applied  to  the 

supports  for  the  bearings  of  railway  mo- 
tors. 

Arrival  Curve  of  Telegraphic  Circuit.— 

(See  Appendix — Curve,  Arrival,  of  Tele- 
graphic Circuit.) 

Arriving  Current  of  Telegraphic  Circuit. 

— (See  Appendix — Current,  Arriving,  of 
Telegraphic  Circuit.) 

Asbestos-Porcelain. — A  porous  substance 
somewhat  resembling  ordinary  porcelain. 


Asbestos-porcelain  is  made  by  obtaining 
asbestos  fibres  in  an  exceedingly  fine  powder 
and  forming  this  powder  into  a  paste  with 
water,  consolidating  it  under  heavy  press- 
ure, and  subsequently  exposing  the  dried 
particles  to  the  effects  of  a  high  temperature. 

Asbestos-porcelain,  it  is  claimed,  forms  a 
material  which,  though  resembling  ordinary 
porcelain,  is  highly  porous.  It  has  been  suc- 
cessfully used  for  the  porous  cells  of  voltaic 
batteries,  for  which  purposes  it  is  claimed  to 
offer  a  better  conducting  path  for  the  current 
than  the  ordinary  unglazed  earthenware  gen- 
erally employed  for  such  purposes.  (See  Cell* 
Porous.} 

Astatic  Multiplier. — (See  Appendix — 
Multiplier,  Astatic.} 

Atmosphere,  Electric A  term  for- 
merly employed  for  a  space  filled  with 
electric  effluvia.  (See  Appendix — Effluvia, 
Electric.} 

A  term  sometimes  employed  for  an  elec- 
tro-static field. 

A  space  occupied  by  or  permeated  with 
electric  sparks  or  glow. 

Atmosphere,  Magnetic  —A  term 

formerly  employed  for  a  space  filled  with 
magnetic  effluvia.  (See  Appendix — 
Effluvia,  Magnetic.} 

A  term  sometimes  employed  for  a  mag- 
netic field. 

Atom,  Dyad An  atom  whose  val- 
ency, atomicity  or  combining  power  is  two. 
(See  Atomicity.  Element.} 

Atom,  Heptad An  atom  whose 

valency  or  atomicity  is  seven.  (See  Atom- 
icity. Element.} 

Atom,  Hexad An  atom  whose 

valency  or  atomicity  is  six.  (See  Atomicity. 
Element} 

Atom,  Monad An  atom  whose 

valency  or  atomicity  is  one.  (See  Atomicity. 
Element.) 

Atom,   Pentad An  atom    whose 

valency  or  atomicity  is  five.  (See  Atom- 
icity. Element.) 


Ato.] 


570 


[Bac. 


Atom,    Tetrad 


— An  atom  whose 


valency  or  atomicity  is  four.  (See  Atom- 
icity. Element?) 

Atom,  Triad  — An  atom  whose 

valency  or  atomicity  is  three.  (See  Atom- 
icity. Element.} 

Atomic. — Of  or  pertaining  to  the  atom. 
(See  Atom.) 

Attachment,  Electric  Clamp A 

device  employed  in  connection  with  a  floor 
push,  adapted  for  ready  clamping  to  a 
table  or  other  support  for  the  purpose  of 
holding  a  push  button  electrically  con- 
nected with  the  floor  push. 

Attachment  Plug. — (See  Appendix — Plug, 
Attachment.') 

Audible  Telegraphic  Signal.— (See  Ap- 
pendix— Signal,  Telegraphic,  Audible.} 

Audiometer. — A  word  sometimes  used  in 
place  of  Sonometer.  (See  Appendix — Sonom- 
eter.} 

Aura,  Electric A  term  formerly 

employed  for  the  breeze  produced  by  elec- 
tric convection.  (See  Convection,  Electric.} 

Aurora,  Electrostatic A  luminous 

phenomenon  attending  the  production  of  an 
electrostatic  corona.  (See  Appendix — 
Corona,  Electrostatic.} 

Aurora  Glory. — (See  Appendix — Glory, 
Aurora.} 


Aurora,  Polar A  term  sometimes 

used  indifferently  for  the  aurora  borealis, 
or  the  aurora  australis. 

Austral  Fluid. — (See  Appendix — Fluid, 
Austral.} 

Auto-Exciting. — Self-exciting. 

Auto-Induction. — (See  Appendix — Induc- 
tion, Auto.} 

Automatic  Guard  for  Series-Connected 
Incandescent  Lamps. — (See  Appendix — 
Guard,  Automatic,  for  Series-Connected 
Incandescent  Lamps.} 

Automatic  Photo-Electric  Switch. — (See 
Appendix — Switch,  Automatic  Photo-Elec- 
tric.} 

Automatic  Repeater. — (See  Appendix — 
Repeater,  Automatic?) 

Automatic  Telegraph. — (See  Telegraph, 
Automatic} 

Automatic    Telegraphic    Transmitter. — 

(See    Appendix — Transmitter,  Automatic 
Telegraphic.)  . 

Auto-Reyersible  or  Multiple  Tele-Radio- 
phone.— (See  Appendix — Tele-Radiophone, 
Auto-Reversible  or  Multiple.) 

Axial  Current. — (See  Appendix — Cur- 
rent, Axial} 


gg. — A  symbol  employed  for  magnetic 
induction. 

The  defining  equation  is  §$:=/* 3C 

B.  A.  Ampere. — (See  Appendix — Ampere, 
B.  A} 

B.  A.  Ohm.— (See  Ohm,  B.  A.)  (See  Ap- 
pendix—  Ohm,  B.  A.} 

B.  T.  U. — A  contraction  for  Board  of 
Trade  unit,  the  commercial  unit  of  elec- 
trical work  adopted  by  the  British  Board  of 


Trade,  viz.,  the  kilowatt-hour,  or  the  amount 
of  work  which  would  be  accomplished  in 
one  hour  at  the  rate  of  one  kilowatt. 

This  contraction  is  a  bad  one,  since  it  is 
already  employed  for  British  thermal  unit. 

B.  T.  U. — A  contraction  for  British 
thermal  unit. 

Back  Magnetization. — (See  Appendix— 
Magnetization,  Back.) 

Backing  Pan.— (See  Appendix — Pan, 
Backing.) 


Bac. 


571 


[Bat. 


Backward  Induction  of  Dynamo  Arma- 
ture. —  (See  Appendix  —  Induction,  Back- 
ward, of  Dynamo  Armature.} 

Bad  Earth.  —  (See  Appendix  —  Earth, 
Bad.} 

Balance,  Coulomb's  Electric  ---  A 
term  sometimes  employed  for  Coulomb's 
torsion  balance  when  used  for  measuring 
the  force  of  electric  repulsion.  (See  Bal- 
ance, Coulomb's  Torsion.} 

Balance,     Coulomb's    Magnetic   Torsion 

--  A  nam°.   sometimes  given  to  Cou- 

lomb's torsion  balance  when  employed  to 

measure  the  force,  of  magnetic  repulsion. 

(See  Balance,  Coulomb's  Torsion.} 

Balance,  Duplex  ---  The  condition 
of  a  line  in  duplex  telegraphy,  when  send- 
ing signals  leave  the  home  instruments  un- 
affected and  ready  for  response  to  received 
signals, 

Balance,  Electro-Dynamic  --  A  bal- 
ance form  of  electro-dynamometer.  (See 
Dynamometer,  Electro.  Balance,  Centi- 
Ampere.} 

Balanced  Armature.  —  (See  Appendix  — 
Armature,  Balanced.} 

Balancing  Wire  or  Conductor.  —  (See 
Appendix  —  Wire  or  Conductor,  Balanc- 


Barker's  Revolving  Contact  Breaker.  — 

(See  Appendix  —  Breaker,  Contact,  Barker's 
Revolving.} 

Barker's  Wheel.  —  (See  Appendix  — 
Wheel,  Barkers.} 

Base,  Socket  --  A  base  for  holding 
a  lamp  socket  in  position. 

Basket,  Dipping  --  —  A  perforated 
basket  of  non-corrosive  material,  em- 
ployed for  the  reception  ot  articles  that  are 
to  be  prepared  for  the  process  of  electro- 
plating by  dipping  them  in  the  cleansing 
bath.  (See  Dipping.} 

Basket,  Stoneware  Dipping  --  A 
stoneware  basket  in  which  the  articles  are 


placed  that  are  to  be  subjected  to  the  dip- 
ping process  in  electro-metallurgy.  (See 
Appendix — Basket,  Dipping.} 

Bath,  Electric  Light  —  — A  variety  of 
electro-therapeutic  bath,  in  which  all  the 
patient's  body,  except  the  head,  is  exposed 
to  the  radiant  light  and  heat  of  a  number 
of  incandescent  electric  lamps  placed  in- 
side a  closed  chamber  or  box. 

By  the  use  of  the  electric  light  bath  it  is 
claimed  that  the  temperature  of  the  body  is 
rapidly  increased,  and  that  the  effect  on  the 
skin  is  the  same  as  that  of  sunshine.  The 
therapeutic  value  of  such  a  bath  is,  perhaps, 
to  be  questioned. 

Battery,  Compound A  term  pro- 
posed by  Henry  for  a  number  of  separate 
voltaic  cells,  coupled  so  as  to  iorm  a 
single  cell,  in  contradistinction  to  a  single 
cell. 

The  term  battery  wasoriginally  sometimes 
loosely  applied  either  to  indicate  a  single 
voltaic  cell,  or  a  numberof  cells  so  joined  to- 
gether as  to  form  a  single  electric  source. 

Indeed,  the  term  is  still  loosely  employed 
even  at  the  present  day  by  some  writers.  In 
the  time  of  Henry  the  word  battery  was  ap- 
parently indifferently  applied  to  a  single 
cell  or  a  number  of  cells,  and  Henry  pro- 
posed the  term  compound  battery  to  distin- 
guish between  a  single  cell,  or,  as  he  called  it, 
a  battery,  and  a  number  of  cells  joined  so  as 
to  form  a  single  source,  which  he  terms  a 
compound  battery,  but  which  is  to-day,  by  all 
careful  writers,  termed  a  battery. 

Battery,  Distant A  battery  em- 
ployed in  a  telegraphic  system  at  the  re- 
ceiving end  of  the  line. 

Battery,  Dry A  number  of  sepa- 
rate dry  voltaic  cells  combined  so  as  to  act 
as  a  single  source. 

A  dry  pile.     (See  Pile,  Dry.} 

Battery,  Element  of (See  Ap- 
pendix— Element  of  Battery} 

Battery,  Home The  battery  em- 
ployed in  a  telegraphic  system  at  the  send- 
ing end  of  the  line. 


Bat.] 


572 


[Bic. 


Battery,      Polarization — A   term 

sometimes  employed  for  a  secondary  or 
storage  battery. 

The  term  secondary  or  storage  battery 
would  appear  to  be  preferable. 

Battery,  Secondary,  Current  Efficiency  of 
The  ratio  between  the  ampere- 
hours  of  the  discharge  and  the  ampere- 
hours  of  the  charge. 

Battery,  Secondary,  Efficiency  of 

The  ratio  between  the  amount  of  electrical 
work  given  out  by  a  battery  during  its  dis- 
charge, and  the  amount  of  work  expended 
in  charging  it. 

The  efficiency  of  a  secondary  battery  varies 
with  the  rates  of  charge  and  discharge  ;  the 
higher  these  rates  the  lower  the  efficiency. 

The  efficiency  of  a  secondary  battery  is  ob- 
tained by  dividing  the  amount  of  electrical 
work  in  joules  or  watt-hours,  which  a  battery 
will  produce  after  being  charged,  by  the 
amount  of  similarly  estimated  electrical  work 
expended  in  charging  it.  This  is  generally 
known  as  the  watt-efficiency. 

The  current-efficiency  is  obtained  by  divid- 
ing the  ampere-hours  of  the  discharge  by  the 
ampere-hours  of  the  charge. 

Battery,    Secondary,  Watt-Efficiency    of 

The  ratio  between  the  amount  of 

electrical  work  in  watt-hours  a  battery  will 
yield  after  being  charged,  and  the  amount 
of  work  in  watt-hours  expended  in  charg- 
ing it. 

Battery  Syringe. — (See  Appendix — 
Syringe,  Battery.} 

Battery  System  for  Electric  Railway.— 
(See  Appendix — Railway,  Electric,  Bat- 
tery System  for.} 

Bead,  Chain. — (See  Appendix — Chain, 
Bead} 

Bead  Lightning. — (See  Appendix — Light- 
ning, Bead.} 

Bearing,  Magnetic The  angle  in- 
cluded between  the  horizontal  line  from  an 
observer  to  an  object  and  the  observer's 
magnetic  meridian. 


Bega. — A  prefix  proposed  by  Houston 
and  Kennelly  for  a  thousand  million,  or  io9  • 

Begadyne. — A  term  proposed  by  Houston 
and  Kennelly  for  one  thousand  million 
dynes,  or  io9  dynes. 

Begerg. — A  term  proposed  by  Houston 
and  Kennelly  for  one  thousand  million  ergs, 
or  io9  ergs. 

Beginning  of  Current. — (See  Appendix — 
Current,  Beginning  of.} 

Begohm. — A  term  proposed  by  Houston 
and  Kennelly  for  one  thousand  million 
ohms  ;  i.e.,  io9  ohms. 

Bell,  Electric,  Continuous  Action 

An  electric  bell  which  continues  to  ring 
when  once  started  until  stopped  either  by 
hand  or  automatically. 

Bell,  Extension A  term  some- 

times  employed  for  extension  call  bell. 
(See  Bell,  Extension  Call.} 

Belt,  Creeping  of An  action  of  a 

belt  due  to  its  retractility,  whereby  the  driv- 
ing pulley  travels  somewhat  faster  than  the 
driven  pulley. 

Suppose  the  belt  possesses  true  elasticity 
or  retractile  power,  then  it  will  be  stretched 
on  the  work  side  and  come  back  to  its 
original  length  on  the  idle  side.  It  therefore 
reaches  the  driving  pulley  in  a  stretched  con- 
dition and  leaves  it  in  a  contracted  condition. 
It  also  reaches  the  driven  pulley  in  a  con- 
tracted condition  and  leaves  it  in  an  elongated 
condition.  Suppose  this  stretch  or  elonga- 
tion is  one  per  cent,  in  a  given  case,  the  driv- 
ing pulley  must  move  101  feet  for  every  100 
feet  of  the  driven  pulley,  then  there  is  no 
slip  of  the  belt,  only  a  creep. 

The  slip  of  a  belt  may  cause  a  consider- 
able loss  of  peripheral  velocity  in  the  pulley. 

Belt,  Slipping  of The  slipping  of 

a  belt  on  the  revolving  pulley  it  covers, 
causing  a  loss  of  speed. 

Bicro. — A  prefix  proposed  by  Houston 
and  Kennelly  denoting  the  thousand- 
millionth  part,  or  io~9- 


Bic.] 


573 


[Bon. 


Bicrofarad. — A  term  proposed  by  Hous- 
ton and  Kennelly  for  the  thousandth  part 
of  a  microfarad,  or  io-9  farad. 

Bierohenry. — A  term  proposed  by  Hous- 
ton and  Kennelly  for  the  thousand"- millionth 
part  ol  a  henry,  or  one  centimetre. 

Bi-Metallic  Accumulator. — (See  Appendix 
— Accumulator,  Si-Metallic.} 

Biologist,  Electro  —  — One  skilled  in 
the  art  of  electro-biology. 

Bioscopist,  Electro One  skilled  in 

the  science  of  electro-bioscopy. 

Blavier's  Formulae. — (See  Appendix — 
Fortuities,  Blavier's.} 

Blavier's  Test. — (See  Appendix — Test, 
Blavier's.') 

Block,  Ceiling  -  -  An  attachment 

fastened  to  ceilings  for  suspending  flexi- 
ble cords  and  connecting  them  with  the 
supply  wires  of  an  incandescent  system. 

Block,  Double,  Duplex  -  In  teleg- 
raphy, especially  in  submarine  telegraphy, 
duplex  transmission  obtained  by  the  aid  of  a 
condenser  inserted  in  each  arm  of  the  Wheat- 
stone  balance.  (See  Telegraphy,  Duplex, 
Bridge  Method  of.} 

Block,  Service  —  — The  set  of  termi- 
nals from  which  service  wires  are  taken 
to  the  interior  of  a  building,  usually  secured 
to  a  pole  or  to  the  exterior  of  a  building. 

Blow,  To A  phrase  frequently 

employed  to  indicate  the  fusion  of  a  safety 
fuse.  (See  Fuse,  Safety.} 

Blowing  of  Fuse. — (See  Appendix — Fuse, 
Blowing  of.} 

Blowing  Point  of  Fuse. — (See  Appendix 
— Fuse,  Blowing  Point  of.} 

Blue  Magnetic  Pole. — (See  Appendix — 
Pole,  Magnetic,  Blue.} 

Board,  Distributing — A  term 

sometimes  employed  in  a  system  of  tele- 
graphic or  telephonic  communication  for  a 
cross  connecting  board.  (See  Board,  Cross- 
Connecting.} 


Board,    Distributing    Switch A 

switch  board  employed  for  distributing 
electric  current  to  different  circuits. 

A  distributing  switch  board  is  usually  pro- 
vided with  wedge-plugs  and  spring-jacks. 

Board,  Lightning  Arrester In  a 

system  of  telephonic  or  telegraphic  com- 
munication the  board  to  which  the  light- 
ning arrester  is  connected. 

The  lightning  arrester  board  often  forms 
part  of  the  test-board. 

Board,  Test In  a  system  of  tele- 
phonic or  telegraphic  communication  the 
board,  provided  with  devices  for  readily 
connecting  testing  instruments  to  any  par- 
ticular line,  to  which  all  the  separate  lines 
are  connected. 

Bob,  Polishing  —  —A  disc  of  hard, 
tough  wood,  provided  on  its  edge  with  a 
ring  or  rim  of  tough  leather  or  hide,  and 
employed,  when  mounted  on  a  shaft  and 
put  into  rapid  rotation,  for  polishing  ar- 
ticles so  as  to  prepare  them  for  electro- 
plating. (See  Plating,  Electro.} 

The  polishing  bobs  are  charged  for  use  with 
any  suitable  abrasive  material,  such  as 
emery,  etc. 

Bobbed. — A  word  sometimes  employed 
to  characterize  a  surface  that  has  been 
polished  by  the  action  of  a  bob.  (See  Ap- 
pendix— Bob,  Polishing.} 

Body,  Induct  eons A  term  proposed 

by  Faraday  for  a  body  in  which  a  charge 
is  induced  by  the  action  of  a  neighboring 
charged  body. 

Body,  Inductric A  term  proposed 

by  Faraday  for  the  body  containing  the  in- 
ducing electric  charge. 

Bolognian  Stone. — (See  Appendix — Stone, 
Bolognian.} 

Bond,  Electric  Rail An  electric 

bond  or  connection  between  contiguous 
rails  of  a  road  using  a  grounded  return. 

In  a  system  of  electric  roads,  where  the 
return  circuit  is  grounded,  the  track  offers  an 


Bon.] 


574 


[Bro. 


excellent  return  provided  the  return  joints 
between  contiguous  rails  are  electrically  con- 
nected. To  do  this  thoroughly,  requires,  of 
course,  such  an  electric  connection  as  will 
render  the  bonds  of  no  higher  linear  resist- 
ance than  the  main  body  of  the  rails. 

Bony  Current. — (See  Appendix — Cur- 
rent, Bony.') 

Booster. — A  scarcely  euphonious  word 
employed  to  designate  a  dynamo  inserted 
in  a  special  feeder  or  group  of  feeders  ot 
an  Edison  incandescent  system  in  order  to 
raise  the  pressure  above  the  rest  of  the 
system. 

Boreal  Fluid.— (See  Appendix— Fluid, 
Boreal.') 

Bougie-Metre. — A  name  proposed  for  the 
practical  unit  of  illumination. 

A  unit  of  illumination  equal  to  the  normal 
illumination  from  the  bougie-decimale  at 
a  distance  of  one  metre. 

This  unit  was  proposed  by  a  Sub-Commit- 
tee of  the  American  Institute  of  Electrical 
Engineers  on  the  provisional  programme  of 
the  Chicago  International  Electrical  Con- 
gress of  1893,  on  the  occasion  of  the  World's 
Columbian  Exposition. 

The  bougie-decimale  is  practically  equal  to 
one  English  standard  candle.  By  making 
the  distance  equal  to  one  metre,  the  practical 
unit  of  illumination  will  be  approximately 
equal  to  y^  carcel-metre,  or  one  metre-candle, 
or  to  one  metre-kerze. 

Bow,  Yoltaic A  voltaic  arc.    (See 

Arc,  Voltaic.'] 

Bowl,  Stoneware  Dipping A  per- 
forated bowl  made  of  stone  or  earthen  ware 
in  which  articles  are  placed  that  are  to  be 
subjected  to  the  dipping  process  in  electro- 
metallurgy. (See  Dipping.} 

Box,  Section In  a  system  of  elec- 
tric street  railways  the  box  containing  the 
section  switches  and  fuses  used  for  the 
control  of  a  section  or  a  line  section. 

Box,   Starting,   of  Shunt-Wound  Motor 


A  box  provided  with  a  rheostat  or 

variable  resistance. 

The  armature  resistance  of  a  shunt-wound 
motor  is  generally  made  very  low,  in  order 
to  insure  high  efficiency  and  constancy  of 
speed.  In  starting  the  motor,  if  it  is  con- 
nected to  the  constant  potential  circuit  and 
the  driving  current  be  permitted  to  pass 
directly  through  its  armature,  the  rush  of 
current  would  be  sufficient  to  injure  the 
machine.  To  avoid  this  the  current  is  first 
sent  through  a  rheostat,  or  starting  box, 
and,  when  the  speed  of  the  motor  is  suffi- 
ciently high,  and  a  suitable  counter-electro- 
motive force  is  generated  in  the  armature, 
the  resistance  coils  are  gradually  cut  out 
until  the  motor  is  connected  directly  to  the 
constant  potential  mains. 

Branched  Series. — (See  Appendix — 
Series,  Branched.} 

Break  Key.  —  (See  Appendix  —  Key, 
Break.} 

Break,  Quick A  break  of  a  cir- 
cuit obtained  by  means  of  a  quick-break 
switch.  (See  Appendix — Switch,  Quick- 
Break.} 

Breaker,  Contact Any  device  for 

opening  or  breaking  an  electric  circuit. 

Breaker,   Contact,   Barker's    Revolving 

A  form  of  contact  breaker  in  which 

a  toothed  wheel  is  rapidly  revolved  so  that 
its  teeth  pass  successively  into  and  out  of  a 
mercury  surface,  and  a  rapid  making  and 
breaking  of  an  electric  circuit  connected 
therewith  is  thus  obtained. 

Breaking  Down  of  Dielectric. — (See  Ap- 
pendix— Dielectric,  Breaking  Down  of.} 

Bridge,  Thomson's A  modified 

form  of  Wheatstone's  bridge  proposed  by 
Kelvin  for  the  measurement  of  very  small 
resistances. 

Broiler,    Electric — A   device  for 

broiling  b'y  means  of  electrically  generated 
heat. 

Rods  of  insulated  metal  are  suitably  con- 
nected in  parallel,  and  raised  to  incandescence 


Biu. 


575 


[Bur. 


by  means  of  electrically  generated  heat.  (See 
Heat,  Electric.} 

In  one  form  of  apparatus  made,  when  a 
potential  difference  of  no  volts  is  applied  to 
the  terminals,  a  current  of  seven  amperes 
passes  and  heats  the  broiler  sufficiently  for 
use  in  about  three  or  four  minutes. 

Brush,  Cup A  brush  employed  in 

cleansing  surfaces  that  are  to  be  prepared 
for  electro-plating,  and  suitably  shaped  lor 
polishing  the  inside  of  a  cup  or  other  simi- 
lar hollow  surface. 


Brush,    Inside  Box 


— A  brush  em- 


ployed in  cleansing  surfaces  so  as  to 
prepare  them  for  electro-plating,  suitably 
shaped  for  polishing  the  inside  of  tubular 
surfaces. 


Brush,  Potash 


— A  brush  employed 


in  cleansing,  by  the  use  of  a  caustic,  sur- 
faces that  are  to  be  electro  plated. 

Brush, Thimble  —  — A  brush  employed 
in  cleansing  articles  that  are  to  be  pre- 
pared for  electro-plating,  and  suitably 
shaped  for  such  surfaces  as  the  inside  of  a 
thimble. 

Brushes,  Distributing,  of  Electric  Motor 

The  brushes  of  an  electric  motor 

corresponding  in  position  to  the  collecting 
brushes  of  a  dynamo-electric  machine. 

It  is  evident  that  the  brushes  of  an  electric 
motor  differ  somewhat  in  their  function  from 
the  collecting  brushes  of  a  dynamo-electric 
machine,  since  in  the  former  case  the  brushes 
act  to  distribute  a  current  generated  outside 
the  motor  to  certain  coils  on  the  armature  of 
the  motor,  while  in  the  laiter  case  they  com- 
mute the  direction  of  the  current  generated 
in  the  armature. 

Brushes,  Finishing A  term  em- 
ployed in  electro-plating  for  finer  brushes 
than  scratch  brushes. 

Bucking'. — A  word  employed  in  the 
operation  of  street  railway  passenger  cars 
for  the  sudden  stopping  of  a  car,  as  if  by  a 
collision. 


The  car  sometimes  refuses  to  go  further  ; 
it  often,  however,  stops  and  then  goes  ahead 
again  almost  immediately  as  if  nothing  had 
occurred.  The  cause  of  bucking  is  to  be  as- 
cribed to  the  fact  that  the  armature  being 
grounded,  if  a  second  ground  occurs  in  any 
part  of  the  machine,  between  the  armature 
and  the  trolley,  with  the  ordinary  method  of 
connecting  up,  a  heavy  current  flows,  produc- 
ing an  intensely  strong  magnetic  field  and 
at  the  same  time  the  armature  is  short  cir- 
cuited by  means  of  the  two  ground  connec- 
tions. Under  these  circumstances  the 
dynamo,  being  short  circuited,  operates  as  a 
powerful  electro-magnetic  brake.  This  effect 
also  occurs  when  the  armature  is  short-cir- 
cuiied  by  heavy  sparking  at  the  brushes,  or 
bad  insulation  (not  to  ground)  in  the  com- 
mutator. 

The  term  bucking  is  sometimes  used 
loosely  for  any  cause  which  prevents  an 
electric  motor  from  properly  operating. 

Buffing. — Preparing  surfaces  for  the  re- 
ception of  an  electro-plating  by  subjecting 
them  to  the  polishing  action  of  a  revolving 
wheel  covered  with  a  buff  on  the  surface  of 
which  rouge  has  been  spread. 

Building  Iron. — (See  Appendix — Iron, 
Building.} 

Building  Process  for  Moulds  of  Electro- 
types.— (See  Append  x — Process,  Build- 
ing, for  Moulds  of  hlectrotypcs.} 

Buoy,    Electrically    Illumined A 

buoy  illumined  by  means  of  an  electric  in- 
candescent lamp. 

The  electric  buoys  are  connected  with  the 
generating  station  on  the  shdre  by  means  of 
heavily  armored  cables.  Spar  buoys  have 
been  successfully  lighted  by  such  means. 

Burglar  Alarm  Contacts. — (See  Appendix 
— Contacts,  Burglar  Alarm.} 

Burglar  Alarm  Matting. — (See  Appendix 
— Matting,  Burglar  Alarm.} 

Burglar  Alarm  Trap. — (See  Appendix — 
Trap,  Burglar  Alarm.} 

Burned-Out   Incandescent    Lamp. — (See 


Bar.] 


576 


[Cal. 


Appendix — Lamp,     Burned-Out     Incan- 
descent.") 

Burnishing.  —  A  word  employed  in 
electro-plating  for  a  process  by  means  of 
which  surfaces  are  prepared  for  electro- 
plating by  subjecting  them  to  the  action  of 
burnishing  tools. 

The  burnishing  action  consists  essentially 
in  smoothing  and  brightening  a  surface  by 
crushing  down  the  small  inequalities  of  the 
surface.  The  burnishing  action  is  not  unlike 
the  smoothing  action  of  a  hot  iron  in  ironing. 

Button,     Commutator-Press    — A 

form  of  press  button  in  which  the  current 
from  a  Hittery  or  other  source  is  reversed 


in  direction  to  the  current  previously  flow- 
ing from  the  ordinary  signalling  button. 

Button,  Push,  Double-Contact A 

push  button  provided  with  two  contacts. 

Button  Repeater. — (See  Appendix — Re- 
peater, Button.} 

Buzz. — A  verb  expressive  of  the  action 
of  an  electric  bell  when  it  fails  to  strike  dis- 
tinctly and  only  gives  a  sound  something 
like  that  of  a  buzzer. 

An  electric  bell  will  "buzz"  if  the  con- 
tacts are  out  of  proper  adjustment,  or  if  the 
current  passing  is  too  strong. 

By-Pass  of  Discharge. — A  term  some- 
times employed  for  alternative  path.  (See 
Path,  Alternative.} 


C. — A  symbol  used  for  capacity. 
The  defining  equation  is  C=  ^ 

E! 

The  same  symbol  is  also  used  for  current. 

C. — A  symbol  used  for  coulomb,  the 
practical  unit  ot  electric  quantity. 

The  same  symbol  is  also  used  for  current 
and  proposed  for  capacity. 

cm. — An  abbreviation  frequently  em- 
ployed for  the  centimetre,  the  C.  G.  S.  unit 
of  length. 

cm12. — An  abbreviation  frequently  em- 
ployed for  square  centimetre,  the  C.  G.  S. 
unit  of  surface. 

cm3. — An  abbreviation  frequently  em- 
ployed for  cubic  centimetre,  the  C.  G.  S.  unit 
of  volume. 

cm  :  s. — An  abbreviation  frequently  em- 
ployed for  centimetre  per  second,  the  C.  G. 
S.  unit  of  velocity. 

cm  :  s2. — An  abbreviation  frequently  em- 
ployed for  centimetre  per  second  per  sec- 
ond, the  C.  G.  S.  unit  of  acceleration. 

C^  R  Loss. — (See  Appendix — Loss, 


Cable,  Concentric A  cable  pro- 
vided with  both  a  leading  out  and  a  return 
conductor,  one  forming  a  central  core  or 
conductor  and  the  other  an  enclosing 
tubular  conductor,  suitably  insulated  from 
each  other. 

In  a  concentric  cable  the  central  conductor 
is  heavily  insulated  and  enclosed  in  a  metallic 
tube  which  latter  acts  as  a  return  conductor. 

Cable,  Linear  Capacity  of The  quo- 
tient of  the  capacity  of  a  cable  by  its 
length. 

Cable,  Linear  Insulation  of The 

product  of  the  insulation  resistance  of  a 
cable  and  its  length. 

The  linear  insulation  is  preferably  meas- 
ured in  kilometre  megohms,  or  mile 
megohms. 

Cage  Protector  for  Lightning  Discharges. 
— (See  Appendix — Protector,  Cage,  for 
Lightning  Discharges.} 

( ;illan  Voltaic  Cell. — (See  Appendix — 
Cell,  Voltaic,  Callan,} 

Callan's  Electro-Magnetic  Repeater. — 
(See  Appendix — Repeater,  Electro-Mag' 
netic,  Callan's} 


Cal.] 


577 


LCel. 


Calorimetry. — The  science  of  measuring 
quantities  of  heat.  (See  Calorimeter.} 

Capacitance. — A  term  analogous  to 
resistance,  proposed  by  Hospitalier  for  the 
true  or  specific  capacity  of  a  medium. 

Capacity  for  Heat,  Mean  Thermal 

The  mean  thermal  capacity  for  heat  of  a 
body  between  two  stated  temperatures  is  the 
quantity  of  heat  required  to  raise  it  from 
the  lower  of  these  temperatures  to  the 
higher,  divided  by  the  difference  of  tem- 
peratures. (See  Heat,  Specific.} 

Capacity,  Kilometric,  of  Cable The 

capacity  of  a  cable  in  microfarads  per  kilo- 
metre. (See  Cable,  Electric.} 

Capacity,  Magneto-Inductive — A 

term  sometimes  employed  for  magnetic  per- 
meability. (See  Permeability,  Magnetic.} 

The  word  permeability  is  preferable. 

Capacity,  Specific  Dielectric A 

term  sometimes  employed  in  place  of 
specific  inductive  capacity.  (See  Capacity, 
Specific  Inductive.} 

Carbon  Arc. — (See  Appendix — Arc,  Car- 
bon.} 

Carbon  Pencil. — (See  Appendix — Pencil, 
Carbon} 

Carbons,  Skew  Adjustment  of,  in  Arc 
Lamp The  adjustment  of  the  car- 
bons of  an  arc  lamp  by  means  of  which  the 
positive  carbon  is  placed  a  short  distance 
in  front  of,  back  and  out  of  a  vertical  line 
with,  the  negative  carbon. 

The  skew  adjustment  is  employed  in  a 
projector  or  search  light  for  the  purpose  of 
insuring  the  formation  of  the  crater  on  the 
edge  of  the  positive  carbon  so  that  the  prin- 
cipal part  of  the  light  is  thrown  out  hori- 
zontally. 

Cardan's  Suspension  of  Compass  Needle. — 

(See  Appendix — Suspension  of  Compass 
Needle,  Cardan's} 

Carrying-  Capacity  of  Safety  Fuse. — (See 
Appendix  —  Fuse,  Safety,  Carrying 
Capacity  of} 


—  — A  process  for 
the  casting  of  metals  that  have  been  fused 
by  means  of  heat  of  electric  origin. 

The  metals  are  fused  by  heat  in  a  specially 
provided  furnace  from  which  all  the  air  has 
been  exhausted.  The  fused  metal  is  then 
run  into  moulds  from  which  the  air  has  also 
bedn  exhausted. 

The  vacuum  and  the  electric  melting,  it  is 
claimed,  produce  a  greater  liquidity  of  the 
metal  than  do  the  ordinary  methods,  and 
hence  insure  a  readier  flow  and  more  sharply 
marked  castings.  The  metal  of  the  casting 
is  also  for  the  same  reason  extremely  close 
and  fine  grained,  and  is  free  from  blow-holes. 

Castor  and  Pollux  Light. — (See  Appen- 
dix— Light,  Castor  and  Pollux} 

Cataphoric  Electrode. — (See  Appendix — 
Electrode,  Cataphoric} 

Cataphoric  Medication. — (See  Appendix 
— Medication,  Cataphoric^ 

Ceiling  Block. — (See  Appendix — Block, 
Ceiling.} 

Ceiling  Rosette. — (See  Appendix — 
Rosette,  Ceiling.} 

Cell,  Double-Liquid — A  term  some- 
times employed  in  place  of  double-fluid 
cell.  (See  Cell,  Voltaic,  Double-Fluid.} 

Cell,  Dry  Gelatine A  term  applied 

to  a  type  of  dry  voltaic  cell  in  which  the 
exciting  liquid  is  absorbed  by,  or  com- 
bined with,  a  variety  of  gelatinous  sub- 
stances. 

The  term  gelatine  dry  cell  is  by  no  means 
limited  to  cases  in  which  gelatine,  either  in 
whole  or  in  part,  forms  the  material  for  the 
retention  of  the  exciting  liquid.  On  the  con- 
trary, such  cells  most  frequently  contain  a 
mixture  of  various  mineral  substances  which 
on  standing  assume  a  gelatinous  or  semi- 
gelatinous  condition  from  the  water  com- 
bining with  the  substances. 

Cell,   Earth A  term  frequently 

applied  to  a  variety  of  cell  consisting  of 
any  voltaic  couple  buried  in  a  compara- 
tively moist  stratum  of  earth. 


Cel.] 


578 


[Cel. 


In  such  cases  the  moisture  of  the  earth 
acts  as  the  electrolyte  and  the  electromotive 
forces  developed  depend  on  the  character  of 
the  voltaic  couples  employed. 

The  term  earth  cell  is  sometimes  improp- 
erly applied  to  the  case  of  two  similar  metal- 
lic plates  buried  in  the  earth  at  considerable 
distances  from  one  another.  In  such  cases 
the  current  produced  is  obtain2d  in  part  at 
least  by  means  of  the  difference  of  potential 
caused  between  the  two  points  of  the  earth 
at  which  the  separate  plates  are  located. 

It  is  evident,  however,  that  the  current 
produced  by  such  earth  cells,  improperly  so- 
called,  is  in  reality  obtained  from  the  earth 
as  an  electric  source,  the  plates  with  their 
metallic  terminals  simply  forming  conduct- 
ors for  carrying  off  the  current  generated  by 
the  difference  of  potential  already  existing 
in  the  earth.  (See  Currents,  Earth.) 

Cell,  Galvanic A  term  sometimes 

employed  instead  of  voltaic  cell.  (See 
Cell,  Voltaic.) 

Cell,  Gas A  term  sometimes  ap- 
plied to  one  of  the  cells  of  a  gas  battery. 
(See  Battery,  Gas.) 

Cell,  Lead  Sulphate  of  Copper A 

form  of  storage  cell  in  which  two  plates  of 
lead  are  immersed  in  a  solution  of  copper 
sulphate. 

On  the  passage  of  the  charging  current 
one  lead  plate  becomes  coated  with  lead 
peroxide  and  the  other  with  metallic  copper. 
(See  Cell,  Storage.) 

Cell,    Lead  Sulphate  of   Zinc A 

form  of  storage  cell  in  which  two  plates  ot 
lead  are  immersed  in  a  solution  of  zinc 
sulphate. 

On  the  passage  of  the  charging  current 
one  plate  becomes  coated  with  lead  peroxide 
and  the  other  with  metallic  zinc. 

This  cell,  according  to  Reynier,  has  an 
electromotive  force  of  as  high  as  from  2.8 
to  2.6  volts,  but  soon  falls  to  from  2.3  to  2 
volts.  (See  Cell,  Storage.) 

Cell,  Light A  term  sometimes 

employed  for  a  photo-electric  cell.  (See 
Cell,  Photo- Electric.) 


Radiant  energy,  whether  of  the  luminous 
type,  as  in  the  case  of  light,  or  of  the  non- 
luminous  type,  as  in  the  case  of  heat,  pro- 
duces a  difference  of  potential  under  a  variety 
of  circumstances. 

In  some  cases  violet-colored  light  seems  to 
produce  the  most  marked  effects. 

Roughly  speaking,  photo-electric,  or  light 
cells,  can  be  grouped  into  two  fairly  sharply 
marked  classes,  namely: 

(i.)  Those  in  which  the  electricity  accom- 
panies some  chemical  decomposition  which 
acts  to  produce  a  current. 

(2.)  Those  in  which  slight  molecular 
changes  occur  which  result  in  the  production 
of  an  electric  current. 

The  production  of  electricity  in  cells  of  the 
latter  type,  by  the  action  of  light  alone,  is 
probably  analogous  to  the  production  of 
pyro-electricity  in  the  case  of  certain  crys- 
talline bodies.  (See  Electricity,  Pyro.) 

Cell,  Magneto-Chemical A  cell  in- 
vented by  Balsamo,  in  which  two  similarly 
magnetized  bars  are  immersed  with  the 
north  pole  of  one  and  the  south  pole  of  the 
other  in  a  solution  of  oxalic  acid. 

Under  these  circumstances  the  magnet 
having  its  north  pole  immersed  in  the  ex- 
citing liquid  acts  like  the  zinc  plate,  and  the 
one  having  its  south  pole  like  the  copper  of 
an  ordinary  zinc-copper  couple  immersed  in 
dilute  sulphuric  acid. 

The  influence  a  magnetic  fluid  exerts  on 
chemical  action  has  been  investigated  by 
Rowland  and  Bell,  and  by  Squier.  (See 
Appendix — Action,  Protective.  Throw,  Pro- 
tective. Throw,  Concentration.) 

Cell,  Photo-Electric  Impulsion A 

term  sometimes  applied  to  an  impulsion 
cell.     (See  Cell,  Impulsion.) 

Cell,  Primary A  term  sometimes 

employed  for  a  voltaic  cell.     (See  Cell,  Vol- 
taic.) 

The  term  primary  cell  is  employed  in  con- 
tradistinction  to  secondary  or  storage  cell. 
(See  Cell,  Storage.) 

Cell,  Regenerative A  term  pro- 
posed for  an  early  form  of  storage  or  sec- 


Cel.J 


[Cha. 


ondary  cell,  invented  by  Thomson  and 
Houston,  consisting  of  two  plates  of  cop- 
per immersed  in  a  solution  of  zinc  sul- 
phate. 

Two  plates  were  placed,  one  at  the  bottom 
of  the  solution,  and  the  other  near  the  top. 
On  the  passage  of  the  charging  current, 
one  of  the  plates  through  the  decomposition 
of  the  zinc  sulphate  was  partially  con- 
verted into  copper  sulphate  and  the  other 
plate  was  coated  with  metallic  zinc.  The  con- 
nections were  such  that  the  plate  partially 
converted  into  zinc  sulphate  was  placed  at 
the  bottom  of  the  cell,  and  the  one  partially 
converted  into  and  covered  by  metallic  zinc, 
at  the  top. 

The  passage  of  the  charging  current  thus 
produced  a  variety  of  gravity  cell.  On  the 
exhaustion  of  the  cell  there  remained  two  in- 
ert plates  of  copper  immersed  in  a  solution 
of  zinc  sulphate. 

Cell,  Thermo-Cheinical A  variety 

of  heat  cell  in  which  a  difference  of  po- 
tential is  produced  and  maintained  between 
two  plates  immersed  in  a  suitable  liquid 
when  one  plate  is  kept  at  a  higher  tem- 
perature than  the  other. 

A  heat  cell  forms  in  reality  a  species  of 
storage  battery  in  which  the  charging  of  the 
cell  is  obtained  by  the  expenditure  of  heat 
energy. 

In  true  heat  cells  a  chemical  action  occurs 
which  is  readily  and  completely  reversible 
by  heat. 

Cell,    Voltaic,    Agglomerate    Leclanche 

A    variety    of    Leclanche'    cell    in 

which  the  mixture  of  carbon  and  dioxide  of 
manganese  is  made  into  a  solid  mass  by 
pressure. 

The  advantage  claimed  for  the  agglomer- 
ate Leclanchfe  cell  is  that  the  porous  cup  em- 
ployed in  the  other  forms  of  this  cell  is  dis- 
pensed with. 

Cell,  Voltaic,  Callan A  zinc-iron 

couple,  the  elements  of  which  are  immersed 
respectively  in  an  electrolyte  of  dilute  sul- 
phuric acid,  and  an  electrolyte  consisting 


of  a  mixture  of  strong  nitric  and  sulphuric 
acids. 

In  the  Callan  cell  the  iron  plays  the  part  of 
the  negative  element.  It  is  not  attacked  by 
the  nitric  acid  provided  the  acid  be  suffi- 
ciently strong.  The  reasons  generally  as- 
signed for  the  non-action  of  the  acid  on  the 
iron  are  either  the  so-called  passive  state 
of  the  iron  or  the  formation  on  the  surface 
of  an  insoluble  oxide.  (See  Slate,  Passive.) 

This  cell  is  sometimes  called  the  iron  cell, 
or  the  Maynooth.  It  is  difficult  to  maintain 
this  cell  in  good  action,  owing  to  the  liability 
of  the  nitric  acid  to  act  on  the  iron  when- 
ever its  strength  falls  below  a  certain  point. 

Cell,  Toltaic,  Heat A  cell  in  which 

heat  energy  is  changed  or  converted  into 
electric  energy. 

Park  Benjamin  divides  heat  cells  into  three 
classes,  namely: 

(i.)  Those  in  which  heat  acts  upon  the 
materials  of  the  cell  by  causing  fusion  or  de- 
composition. 

(2.)  Those  in  which  heat  acts  to  set  free 
chemical  affinities  whereby  the  cell  is  caused 
to  operate,  regeneration  after  exhaustion 
taking  place  at  a  lower  temperature. 

(3)  Thermo-chemical  cells,  or  those  in 
which  the  difference  of  potential  is  maintained 
between  two  plates  immersed  in  a  liquid  by 
heating  one  plate  to  a  higher  temperature 
than  the  other. 

Cell,  Voltaic,  Maynooth 


— A  name 
sometimes  given  to  the  Callan  voltaic  cell. 
(See  Appendix — Cell,  Voltaic,  Callan.) 

Cell,  Voltaic,  Single-Liquid A  term 

sometimes  employed  in  place  of  a  single- 
fluid  cell.  (See  Cell,  Voltaic,  Single- 
Fluid.) 

Cessation  of  Current. — (See  Appendix — 
Current,  Cessation  of.) 

Chain,  Bead A  chain  employed  in 

connection  with  a  pendant  electric  burner. 
(See  Burner,  Plain  Pendant  Electric.) 

Chain,  Galvanic A  term  tormerly 

applied  to   a  galvanic,  or   more  properly 


Cha.] 


580 


LChr. 


speaking,  voltaic  circuit.  (See  Circuit, 
Voltaic.} 

Chamber  of  Incandescent  Electric  Lamp. 
Age-Coating  of The  gradual  darken- 
ing of  the  enclosing  glass  chamber  of  an 
incandescent  electric  lamp. 

This  coating  may  be  due  to  a  deposit  of 
carbon  or  a  hydrocarbon,  or  a  deposit  of  metal 
deflagrated  or  volatilized  by  the  heat  of  the 
filament. 

Charge  Accumulator. — (See  Appendix — 
Accumulator,  Charge.") 

Charge  Current  on  Telegraphic  Line. — 
(See  Appendix — Line,  Telegraphic,  Charge 
Current  on.) 

Charge,  Linear  Density  of The 

amount  of  electricity  per  unit  of  length  of 
conductor.  (See  Charge,  Electric.) 

Charge,  Minus A  negative  charge. 

(See  Charge,  Negative.) 

Charge,  Plus A  positive  charge. 

(See  Charge,  Positive.) 

Charge,  Sweeping-Out A  phrase 

employed  in  double-current  signalling  for 
the  freeing  of  the  line  from  a  charge  pro- 
duced by  the  sending  of  one  signal,  by  re- 
versing the  direction  of  the  current  through 
the  line. 

The  "sweeping-out"  of  the  charge  on  a 
telegraphic  line  decreases  the  amount  of  re- 
tardation. (See  Retardation.) 

Charge,  Volume  Density  of The 

amount  of  electricity  per  unit  of  volume. 
(See  Charge,  Electric.) 

Check,  Telephone  Time A  device 

by  means  of  which,  in  a  telephone  ex- 
change system,  a  drop  shutter  is  automati- 
cally released  at  a  particular  trunk  wire 
indicator,  at  the  beginning  of  the  time  that 
a  subscriber  is  given  the  use  of  the  trunk 
line,  and  automatically  disconnected,  and 
the  central  station  operator's  attention  is 
called  to  the  fact  of  such  disconnection. 

By  the  use  of  the  time-check,  disputes  as 


to  the  length  of  time  a  subscriber  is  given 
the  use  of  a  trunk  line  is  avoided. 

A  telephone  time-check  is  sometimes 
called  a  telephone  meter.  (See  Appendix — 
Meter,  Telephonic} 

Chemical  Generator  of  Electricity. — (See 
Appendix — Generator,  Chemical,  of  Elec- 
tricity.} 

Chemical  Telegraph. — (See  Appendix-^ 
Telegraph,  Chemical.} 

Chemism.  —  A  word  sometimes  em- 
ployed for  chemical  affinity.  (See  Affinity, 
Chemical.} 

Chemistry,  Thermo That  branch 

of  chemistry  which  treats  of  the  measure- 
ment of  chemical  energy  in  thermal  units. 

According  to  Berthelot  : 

(i.)  The  amount  of  heat  set  free  in  any 
chemical  reaction  is  a  measure  of  the  total 
work  done  during  that  reaction. 

(2.)  Changes  produced  in  any  system  not 
attended  by  external  effects  produce  an  evolu- 
tion of  heat  dependent  only  on  the  initial  and 
final  states  of  the  system. 

(3.)  Every  chemical  change  effected  in  a 
system  independent  of  external  energy  tends 
to  produce  that  body  or  system  of  bodies, 
the  formation  of  which  evolves  a  maximum 
heat. 

Choke  Magnet. — (See  Appendix — Mag- 
net, Choke} 

Chronograph,  Spark A  form   of 

electric  chronograph  in  which  the  time  of  a 
certain  event  is  indicated  by  means  of  the 
spark  of  a  Ruhmkorff  or  spark  coil. 

In  a  form  of  spark  chronograph  for  meas- 
uring the  time  in  which  a  falling  body  moves 
through  different  parts  of  its  path,  the  path 
of  the  body  is  marked  on  a  moving  sheet  of 
paper  by  means  of  a  series  of  sparks  frcm  a 
Ruhmkorff  coil. 

Chronometer,  Electric An  elec- 
trically controlled  or  operated  mechanism 
for  indicating  or  recording  time.  (See 
Clock,  Electric.) 


Cir.] 


581 


[CIo. 


Circuit  Closer. — (See  Appendix — Closer, 
Circuit.} 

Circuit  Closer  for  Pull  Bell.— (See  Ap- 
pendix— Pull  Bell,  Circuit  Closer  for.} 

Circuit,  Consumption A  circuit  in 

which  the  energy  of  the  electric  current  is 
consumed  or  utilized  for  energizing  electro- 
receptive  devices. 

Electric  energy  is  consumed  in  all  parts  of 
an  electric  circuit.  The  term  consumption 
circuit,  however,  is  limited  to  that  part  of  an 
electric  circuit  in  which  the  electro-receptive 
devices  are  placed  which  are  energized  by 
the  passage  of  the  electric  current  through 
them. 

Circuit,  Electrical  Tuning  of (See 

Appendix — Tuning  of  Electrical  Circuit.} 

Circuit,  Magnetic,  External A 

term  sometimes  employed  for  that  part  of 
a  magnetic  circuit  which  lies  outside  of  a 
magnet.  (See  Circuit,  Magnetic.} 

Circuit,  Magnetic,  Internal A 

term  sometimes  employed  for  that  part  of  a 
magnetic  circuit  which  lies  within  the  mag- 
net. (See  Circuit,  Magnetic.} 

Circuit,  Multiple-Parallel A  term 

sometimes  employed  for  a  multiple  of 
parallel  circuits.  (See  Circuit,  Multiple.} 

Circuit,  Parallel-Arc  —  — A  term 
sometimes  employed  in  place  of  parallel  or 
multiple  circuit.  (See  Circuit,  Multiple.} 

Circuit,  Resonant  —  — A  circuit  whose 
dimensions  are  such  as  to  bring  it  into  res- 
onance with,  or  to  tune  it  to,  the  period  ot 
another  circuit. 

Circuit,  Surging-^ An  electrical 

circuit  through  which  electrical  surgings 
are  passing. 

Lodge  employs  this  term,  surging  circuit, 
in  the  following  restricted  sense. 

'  I  have  been  accustomed  especially  to 
apply  the  name  '  surging  circuit '  to  the  case 
where  sparks  are  obtained  not  between  two 
distinct  parts  of  a  circuit,  but  between  two 
points  on  one  and  the  same  good  conductor. 


under  circumstances  when  it  does  not  form 
the  alternative  path  to  anywhere,  and  when 
it  would  ordinarily  be  supposed  that  there 
was  no  possible  reason  for  a  spark  at  all." 

The  term  surging  circuit  is  applied  gen- 
erally to  circuits  through  which  surging  dis- 
charges are  passing;  as,  for  example,  the 
condenser-motor  circuit  in  the  Stanley-Kelley 
system. 

Circuit,  Telegraphic,  Working  Efficiency 

of The  variation  or  margin  between 

the  joint  resistance  of  the  conductor  and  the 
resistance  of  the  insulator  by  which  the  con- 
ductor is  supported. 

According  to  F.  L.  Pope  the  working  effi- 
ciency may  be  increased  in  two  ways,  viz.: 

(i.)  By  increasing  the  insulation  resist- 
ance. 

(2.)  By  decreasing  the  resistance  of  the 
conductor. 

Circular  Magnetization. — (See  Appendix 
— Magnetization,  Circular.} 

Clamp,  Feeder Any  clamping  de- 
vice for  connecting  or  fastening  a  feeder 
wire  to  a  trolley  wire. 

Clip. — A  slight  break  in  the  signal  re- 
ceived in  a  system  of  duplex  telegraphy 
under  certain  circumstances. 

Clip,  Feeder In  a  system  of  elec- 
tric street  railways  a  clamp  furnished  with 
a  device  whereby  a  feeder  wire  may  be 
readily  connected  to  a  trolley  wire. 

Clips,  Stay-Eye  — Iron  bands 

clamped  to  the  string  beams  of  the  roof 
with  an  iron  ring  projecting  from  the  sur- 
face of  the  roof,  to  which  the  stay  rods  of 
telegraphic  or  telephonic  standards  are 
screwed. 

Clock,  Directing A  term  some- 
times employed  instead  of  controlling  or 
master  clock.  (See  Clock,  Electrical- 
Controlling^ 

Clock,  Electric,  Watchman's A 

watchman's  electric  register.  (See  Regis- 
ter, Watchman's,  Electric.} 


Clp.j 


582 


[Com. 


Clock,  Primary  Electric A  term 

sometimes  employed  in  place  of  the  con- 
trolling or  master  clock.  (See  Clock, 
Master?) 

Clock,  Standard — In  a  system  of 

time  telegraphy  the  master  clock.  (See 
Clock,  Master."] 

Closed-Circuit  Transformer. — (See  Ap- 
pendix— Transformer,  Closed-  Circuit?) 

Closed-Conducting  Sheath  for  Lightning 
Protection. — (See  Appendix  —  Sheath, 
Closed-Conducting,  for  Lightning  Protec- 
tion.} 

Closer,  Circuit Any  device  for 

completing  or  closing  a  circuit. 

Clown's-Hat  Curve. — (See  Appendix — 
Curve,  Clown' s-Hat} 

Code,  American  Morse A  term 

sometimes  employed  for  the  Morse  tele- 
graphic alphabet.  (See  Alphabet:  Tele- 
graphic, Morse's.} 

Code,  Dot-and-Dash A  term  some- 
times employed  for  the  Morse  telegraphic 
code.  (See  Code,  Telegraphic.} 

Code,  International  Morse A 

term  sometimes  employed  for  the  interna- 
tional telegraphic  alphabet.  (See  Alpha- 
bet, Telegraphic:  International  Code} 

Coil,  Faradic A  term  sometimes 

employed  in  place  of  a  F«radic  machine  or 
medical  induction  coil.  (See  Machine, 
Faradic.} 

Coil,  Ground A  small  rheostat 

employed  in  duplex  telegraphy  at  the  home 
station  for  the  purpose  of  giving  the  appara- 
tus in  such  station  an  equal  resistance  to 
the  currents  coming  from  the  distant  sta- 
tion. (Pope.) 

The  resistance  of  the  ground  coil  should 
be  equal  to  the  resistance  of  the  spark  coil, 
plus  the  internal  resistance  of  the  battery. 

Coil,  Induction  Ribbon An  induc- 
tion coil,  the  primary  and  secondary  cir- 


cuits of  which  are  made  of  metallic  ribbons 

instead  of  wires. 

Coil,  Induction,  Self A  coil  of  wire 

possessing  a  self  induction. 

A  choking  coil.     (See  Coil,  Choking} 
Coil,  Spark,  Telegraphic A  small 

rheostat  employed  in  duplex  telegraphy  at 

the  home   station   in  connection  with  the 

ground       coil.       (See       Appendix — Coil, 

Ground.} 

The  resistance  of  the  spark  coil  should 
be  made  sufficiently  great  to  prevent  the  po- 
larization of  the  battery  when  it  is  momenta- 
rily short-circuited. 

Coils,   Differential Coils  that  are 

differentially  wound.  (See  Appendix — 
Winding,  Differential.} 

Coils,  Field,  of  Dynamo The  coils 

of  wire  wound  on  the  field  magnet  cores 
for  the  production  of  the  magnetic  field. 

Coked  Core  of  Incandescent  Filament. — 

(See  Appendix — Core,  Coked,  of  Incandes- 
cent Filament} 

Coked  Filament. — (See  Appendix — Fila- 
ment, Coked.} 

Coking,  Electrical Subjecting  a 

carbon  to  the  coking  process.  (See  Ap- 
pendix— Process,  Coking,  for  Filament  of 
Incandescent  Electric  Lamp} 

Coking  of  Filament. — (See  Appendix — 
Filament,  Coking  of} 

Coking  Process  for  Filament  of  Incandes- 
centElectric  Lamp. — (See  Appendix — Proc- 
ess, Coking,  for  Filament  of  Incandescent 
Electric  Lamp} 

Collecting  Combs. — (See  Appendix — 
Combs,  Collecting} 

Comazant. — A  term  formerly  applied  to 
St.  Elmo's  fire. 

A  corposant.  (See  Corposant.  Fire, 
St.  Elmo's.} 

Combination  Fittings  for  Chandeliers, 
Brackets,  etc. — (See  Appendix — Fittings, 


Com.] 


583 


[Con. 


Combination,  for   Chandeliers,  Brackets, 
etc.} 

Combs,  Collecting A  term  some- 
times employed  for  the  collecting  points  of 
a  frictional  electrical  machine,  or  of  an 
electrostatic  induction  machine.  (See  Ma- 
chine, Frictional  Electric.  Machine, 
Electrostatic  Induction.} 

Common  Arc  of  Aurora  Glory. — (See  Ap- 
pendix— Arc,  Common,  of  Aurora  Glory.} 

Commutator  P^ress-Button. — (See  Ap- 
pendix— Button,  Commutator-Press^ 

Commutatorless. — Not  provided  with  a 
commutator.  (See  Commutator,  Dynamo- 
Electric  Machine.} 

Compass,  Declination — A  decli- 
nometer. (See  Declinometer.} 

Compensated  Alternator.  —  (See  Appen- 
dix— Alternator,  Compensated.} 

Compensating- Alternating  Dynamo-Elec- 
tric Machine. — (See  Appendix — Machine, 
Dynamo- Electric,     Compensating- Alter-  • 
nating.} 

Compensator,  Magnetic A  device 

for  neutralizing  the  effects  produced  on  a 
magnetic  needle  by  the  local  magnetism  of 
a  ship. 

Complex-Harmonic  Alternating  Electro- 
motive Forces. — (See  Appendix — Forces, 
Electromotive,  Complex-Harmonic  Alter- 
nating.} 

Complex-Harmonic  Curients. — (See  Ap- 
pendix—  Currents,  Complex-Harmonic.} 

Complex-Magnetic  Shell. — (See  Appen- 
dix— Shell,  Complex-Magnetic.} 

Compound  Alternator. — (See  Appendix — 
Alternator,  Compound.} 

Compound  Battery.  —  (See  Appendix — 
Battery,  Compound.} 

Compound  Electro-Magnet.  —  A  term 
sometimes  applied  to  an  induction  coil. 
(See  Appendix — Magnet,  Electro-Com- 
pound} 


Compound  Magnet.  —  (See  Appendix — 
Magnet,  Compound.} 

Concentration  Throw. — (See  Appendix — 
Throw,  Concentration} 

Concentric  Cable.  —  (See  Appendix — 
Cable,  Concentric} 

Concentric  Wiring. —  (See  Appendix  — 
Wiring,  Concentric} 

Conductance,  Specific Specific 

conductivity.  (See  Conductivity,  Specific.) 

Conductibility. — Possessing  the  power  of 
conducting  electricity. 

Conductivity. 

Conducting  Cord  and  Tip. — (See  Appen- 
dix—  Cord  and  Tip,  Conducting.) 

Conducting  Cord  Tip.— (See  Appendix — 
Tip,  Conducting  Cord.) 

Conduction  Lightning  Protection. — (See 
Appendix — Protection,  Conduction  Light- 
ning} 

Conduction  Lightning  Protector. — (See 
Appendix — Protector,  Conduction  Light- 
ning.) 

Conduction,    Metallic A    term 

sometimes  employed  for  the  conduction  of 
electricity  through  a  solid  conductor  in  con- 
tradistinction to  its  conduction  through  an 
electrolyte.  (See  Conduction,  Electrolytic.) 

Conduction  Resistance. — (See  Appendix 
— Resistance,  Conduction.) 

Conductivity,  Percentage,  of  Wire 

— The  conductivity  of  a  particular  copper 
wire  compared  with  the  conductivity  of 
another  wire  of  the  same  dimensions  of  pure 
material  at  a  standard  temperature. 

The  percentage  conductivity  is  readily  ob- 
tained by  multiplying  the  calculated  resist- 
ance of  the  pure  material  by  100  and  dividing 
the  result  by  the  measured  resistance  of  the 
particular  wire. 

Conductor,  Electric,  Glowing  of 

Emitting  light  from  any  conductor  heated 
to  electrical  incandescence. 


Con.] 


584 


[Con. 


The  current  strength  required  to  produce 
a  glow  in  a  conductor  varies  in  a  marked 
manner  with  the  character  and  density  of 
the  gas  surrounding  the  conductor. 

Conductor,  Electric,  Melting  of 

Fusion  of  a  conductor  by  means  of  the  heat 
of  electric  currents. 

The  strength  of  current  required  to  fuse 
or  melt  a  conductor  varies  with  a  number  of 
circumstances,  so  that  a  wire  which  will  not 
fuse  under  the  influence  of  a  certain  current 
strength  may  fuse  at  another  time  under  a 
much  smaller  current  strength  if  the  con- 
ditions are  different.  Among  these  influences 
may  be  mentioned  the  nature  of  the  medium 
surrounding  the  conductor,  as  well  as  the 
temperature  of  said  medium.  Sometimes, 
too,  a  coating  of  oxide  forms  on  the  surface 
of  the  conductor,  which  modifies  its  ability 
to  throw  off  or  radiate  its  heat. 

When  subjected  to  alternating  currents  a 
fuse  wire  has  its  fusing  point  gradually 
lowered. 

Conductor,  Electric,  Volatilization  of 

— The  volatilization  of  a  conductor  pro- 
duced by  the  passage  of  an  electric  current 
through  it. 

The  current  required  to  volatilize  a  con- 
ductor will  necessarily  vary  with  the  same 
circumstances  that  modify  its  electric  glow- 
ing or  melting.  (See  Appendix — Conductor, 
Electric,  Glowing  of.  Conductor,  Electric, 
Melting  of.) 

Conduct  or  or  Line  Wire,  Dip  of 

The  sag  of  a  telegraphic  or  telephonic  wire 
or  conductor  between  two  supports  due  to 
its  weight. 

Conductor  Resistance. — (See  Appendix — 
Resistance,  Conductor.) 

Conductor,  Semi A  term  some- 
times applied  to  substances,  such  as  acids, 
saline  salts,  water,  etc.,  whose  power  of 
conduction  for  electricity  is  neither  very 
high  nor  very  low. 

Substances  that  occupy  an  intermediate 
position  between  conductors  and  so-called 
non-conductors  for  electricity. 


Conductor,  Stranding  of Forming 

a  conductor  of  several  smaller  conductors 
for  the  purpose  of  reducing  the  self-induc- 
tion or  eddy  currents,  or  of  increasing  its 
flexibility.  (See  Induction,  Self.) 

Conductor  System  for  Railroad. — (See 
Appendix — Railroad,  Conductor  System 
for.) 

Conflict,  Electric -A  term  proposed 

by  Oersted  for  a  magnetic  field  surround- 
ing a  conductor  through  which  a  current 
of  electricity  is  flowing. 

Oersted  speaks  as  follows  of  his  discovery 
of  the  magnetic  qualities  of  the  region  around 
a  conductor  through  which  an  electrical  cur- 
rent is  flowing  :  "  That  this  conflict  performs 
circles  around  the  wire,  for  without  this  con- 
dition it  seems  impossible  that  one  part  of 
the  wire  when  placed  below  the  magnetic 
needle  shall  drive  its  pole  to  the  east,  and 
when  placed  above  it  to  the  west." 

Connector,  Copper A  particular 

form  of  connector  employed  in  the  gravity 
voltaic  cell  for  connecting  the  copper  ele- 
ment to  the  circuit  wire  or  conductor. 

A  name  applied  technically  to  a  form  of 
electric  light  fitting  or  coupler  for  connect- 
ing large  wires  or  conductors. 

Consonance. — Literally,  sounding  at  the 
same  time. 

Strictly  speaking,  two  sounds  are  said  to 
be  in  consonance  when  they  are  sounded  to- 
gether. In  this  sense  we  speak  of  pleasing 
consonances  or  harmonious  chords.  Often, 
however,  the  word  consonance  is  used  in 
contradistinction  to  dissonance  as  indicating 
two  sounds  that  are  in  unison  with  each 
other. 

The  word  consonance  is  also  frequently 
employed  in  the  sense  of  increasing  or  re- 
enforcing  a  sound;  such,  for  example,  as  the 
method  of  increasing  the  sound  produced  by 
a  vibrating  string  or  cord  by  stretching  the 
cord  over  an  elastic  body  like  a  table.  In 
such  cases  the  table  takes  up  the  motions  or 
vibrations  of  the  cord,  and,  by  thus  setting  in 
motion  a  greater  mass  of  air,  increases  the 


Con.] 


535 


[Con. 


amplitude  of  the  waves  and  consequently 
the  intensity  of  the  sound.  This  use  of  the 
word  consonance  is  to  be  distinguished  from 
resonance,  in  which  an  increase  in  the  inten- 
sity of  the  sound  is  also  produced  by  waves 
or  vibrations  set  up  in  another  body  with, 
however,  this  difference  :  in  the  case  of  reso- 
nance the  re-enforcement  is  effected  by  vibra- 
tions set  up  in  a  body  that  is  tuned  to  vibrate 
in  exact  unison  with  a  vibrating  body;  while 
in  the  case  of  consonance  no  such  tuning  is 
necessary  ;  or,  briefly,  consonant  vibration  is 
forced  vibration,  while  resonant  vibration  is 
natural  or  free  vibration  excited  by  the 
vibrating  body. 

Consonator. — Any  body  possessing  the 
power  of  increasing  the  strength  of  sound 
by  consonance.  (See  Appendix  —  Con- 
sonance.') 

This  use  of  the  word  consonator  is  analo 
gous  to  the  use  of  the  word  resonator;  viz., 
a  body  having  the  power  of  increasing  the 
strength  of  sound  by  resonance.  (See  Reso- 
nator?) A  consonator,  however,  differs  from 
a  resonator  in  the  manner  in  which  it 
strengthens  the  sound. 

Constant-Potential  Motor. — (See  Appen- 
dix— Motor,  Constant-Potential.} 

Constant,  Yerdet's  —  The  mag- 
neto-optic constant  of  a  transparent  sub- 
stance, usually  expressed  in  minutes  of  arc 
rotation  of  the  plane  of  polarization,  for  a 
luminous  ray  of  definite  wave  length  through 
the  magnetized  substance  at  a  definite 
temperature  between  points  on  the  ray 
path  whose  magnetic  potential  differs  by 
unity. 

Verdet's  constant  is  usually  taken  for  the 
D  line  at  the  temperature  of  I5°C.  Its  value 
for  monohydrated  sulphuric  acid  according 
to  Bichat,  and  Mascart  and  Joubert  equals 
0.0104  '• 

Consumption  Circuit. — (See  Appendix — 
Circuit,  Consumption.} 

Contact   Breaker.  —  (See    Appendix  — 
Breaker,  Contact.} 
Contact,  Drop  Relay A  form  of 


relay  contact  in  which  the  attraction  of 
an  armature  on  the  passage  of  a  current 
releases  a  drop  and  thus  completes  a  local 
circuit  which  remains  closed  until  the  drop 
is  replaced  or  reset. 

By  the  suitable  combination  of  a  drop  re- 
lay and  a  bell,  the  bell  may  become  a  con- 
tinuous ringing  bell. 

Contact,  Floor A  term  sometimes 

employed  in  place  of  floor  push.  (See 
Push,  Floor.} 

Contact,  Full A  variety  of  fault 

produced  by  a  part  of  the  circuit  being 
accidentally  placed  in  contact  with  a  good 
metallic  circuit.  (See  Contacts.} 

Contact,  Relay A  term  frequently 

applied  to  a  form  of  electro-magnetic  in- 
strument by  means  of  which  a  local  circuit 
is  co'mpleted  by  the  passage  of  a  current. 

A  relay  contact  is  in  reality  a  form  of  key 
or  push,  which,  instead  of  being  opened  or 
closed  by  means  of  the  hand,  is  closed  by 
means  of  an  electro-magnet.  Relay  contacts 
are  of  two  kinds,  namely,  spring  relay  con- 
tacts and  drop  relav  contacts. 

Contact  Resistance. — (See  Appendix — 
Resistance,  Contact.} 

Contact,  Spring  Relay A  form  of 

relay  contact  which  is  interrupted  by  the 
action  of  a  spring,  as  soon  as  the  current 
is  broken. 

Contact  Theory  of  Electricity.  —  (See 
Appendix — Theory,  Contact,  of  Elec- 
tricity} 

Contact,  Total A  term  sometimes 

employed  for  full  metallic  contact.  (See 
Contact,  Full-Metallic.} 

Contact,    Window    or    Blind A 

variety  of  burglar-alarm  contact  by  means 
of  which  an  alarm  bell  is  rung  by  a  slight 
pressure  against  a  blind  caused  by  any  at- 
tempt to  enter  from  without  after  having 
broken  'the  glass  in  the  window.  (See 
Alarm,  Burglar.} 


Con.] 


586 


[Cor. 


Contacts,  Burglar  Alarm  — Con- 
tacts by  means  of  which  the  opening  or 
closing  of  a  door  or  window,  or  the  passage 
of  a  person  across  a  given  space,  is  caused 
to  ring  an  alarm  bell.  (See  Alarm,  Burglar.} 

Continuous  Action  of  Electric  Bell. — (See 
Appendix — Bell,  Electric,  Continuous  Ac- 
tion of.) 

Continuous  Current  Arc. — (See  Appendix 
— Arc,  Continuous  Current.) 

Continuous  Current  Transformer. — (See 
Appendix — Transformer,  Continuous  Cur- 
rent.) 

Contracting  Magnetic  Whirl.— (See  Ap- 
pendix—  Whirl,  Contracting  Magnetic.) 

Contraction,  Over-Maximal An  in- 
crease in  the  electrical  stimulation  of  a 
motor  nerve  beyond  the  point  where  an 
apparent  maximum  stimulus  has  been 
reached. 

Between  the  condition  of  the  first  maxi- 
mum and  the  second  maximum  an  increase 
in  the  strength  of  the  current  is  followed  by 
a  decrease  in  the  stimulation.  On,  how- 
ever, a  further  increase  in  the  current 
strength  a  second  increase  in  the  contrac- 
tion, termed  the  over-maximal  contraction, 
occurs. 

Contraplex  Telegraph. — (See  Appendix — 
Telegraph,  Contraplex.) 

Convection  Transference. — (See  Appen- 
dix— Transference,  Convection.) 

Conversion  of  Electromotive  Force. — 
(See  Appendix  —  Force,  Electromotive, 
Conversion  of.) 

Conversion,  Ratio  of A  term  some- 
times employed  instead  of  ratio  of  trans- 
"  formation.  (See  Appendix — Transforma- 
\  tion,  Ratio  of.) 

Convert. — To  transform  or  change. 

Converter,  Rotary A  rotary  trans- 
former. (See  Appendix  —  Transformer, 
Rotary.) 

Converting. — Transforming  or  changing. 


Co-phasal.  —  Two  or  more  quantities 
which  vary  harmonically,  and  whose  rates 
of  increase  or  decrease  at  any  given  time 
maintain  a  constant  ratio. 

Co-phasal  Alternations. — (See  Appendix 
— Alternations,  Co-phasal.) 

Copper  Arc. — (See  Appendix — Arc,  Cop' 
per.) 

Copper  Connector. —  (See  Appendix  — 
Connector,  Copper.) 

Copper-Lead  Accumulator. — (See  Appen- 
dix— Accumulator,  Copper-Lead.) 

Copper  Resistance. —  (See  Appendix  — 
Resistance,  Copper.) 

Copper  Shell  of  Electrotype. — (See  Ap- 
pendix— Shell,  Copper,  of  Electrotype.) 

Copper-Zinc  Accumulator. — (See  Appen- 
dix— Accumulator,  Copper-Zinc.) 

Cord  and  Tip,  Conducting A  con- 
ducting cord  provided  at  one  of  its  ends 
with  a  tip  for  the  purpose  of  ready  inser- 
tion in  a  wall  socket. 

Cord,  Incandescent  Lamp A  flex- 
ible lamp  cord  of  two  strands  suitable  for 
use  with  a  pendent  incandescent  lamp. 

Core,  Coked,  of  Incandescent  Filament 
A  filament  for  an  incandescent  elec- 
tric lamp,  formed  of  a  core  of  electrically 
coked  carbon,  whose  surface  is  covered 
with  a  deposit  of  carbon  derived  from  the 
electrical  decomposition  of  a  hydrocarbon 
gas  or  vapor. 

Core  Loss  of  Transformer. — (See  Appen- 
dix— Loss,  Core,  of  Transformer.) 

Core  Pins  of  Magnet. — (See  Appendix — 
Pins,  Core,  of  Magnet.) 

Cores,  Krizik's  — Cores  for  magnetic 

solenoids  shaped  so  as  to  insure  an  ap- 
proximately uniform  pull  in  different  posi- 
tions in  the  solenoid.  (See  Bars,  Krizik's.) 

Coreless  Armature  of  Dynamo  or  Motor. 
— (See  Appendix — Armature,  Coreless,  of 
Dynamo  or  Motor.} 


Cor.] 


587 


[Cor. 


Corona,  Electrostatic A  luminous 

effect  produced  on  the  surface  of  a  thin 
sheet  of  mica,  or  other  similar  insulating 
material,  when  placed  between  two  elec- 
trodes between  which  discharges  of  com- 
paratively high  difference  of  potential  are 
passing. 

Steinmetz  describes  the  phenomena  of  the 
electrostatic  aurora  and  corona  in  the  Elec- 
trical Engineer  for  April  5,  1893,  as  follows  : 

"Very  interesting  luminous  effects  take 
place  when  a  thin  sheet  of  good  insulating 
material,  as  mica,  is  placed  between  the  elec- 
trodes. At  a  difference  of  potential  of  830 
volts  and  a  thickness  of  mica  of  1.8  milli- 
centimetres,  in  darkness  a  faint  bluish 
glow  becomes  visible  between  the  mica 
and  the  electrodes.  This  glow  is  very 
perceptible  at  970  volts,  and  faintly  visi- 
ble in  broad  daylight  at  1,560  volts.  With 
increasing  difference  of  potential,  this  bluish 
glow  increases  in  intensity,  forming  a  sharply 
defined,  smooth  blue  line  around  the  elec- 
trodes at  their  point  of  contact  with  the 
mica. 

"  At  a  difference  of  potential  of  4.5  kilo- 
volts — thickness  of  mica  of  2.3  milli-centi- 
metres — violet  creepers  of  about  two  mm. 
length  break  here  and  there  out  of  the  line 
of  bluish  glow.  These  creepers  are  distinctly 
different  from  the  blue  glow  surrounding  the 
electrodes  and  increasein  number  and  length 
with  increasing  potential,  until  they  form  a 
broad  electrostatic  aurora  surrounding  the 
electrodes  on  either  surface  of  the  mica 
sheet,  consisting  of  an  infinite  number  of 
small  violet  streamers,  rushing  with  a  hiss- 
ing noise  over  the  mica.  This  corona  in- 
creases rapidly  in  width  until  it  reaches  the 
edges  of  the  mica  sheet.  Then  white  sparks 
of  intense  brightness  pass  from  electrode  to 
electrode  over  the  surface  of  the  mica,  first 
few  in  number,  then  with  increasing  poten- 
tial, covering  the  whole  sheet  with  an  in- 
finite number  of  streaks  of  lightning  with  a 
roaring  noise.  The  amount  of  current  pass- 
ing through  these  sparks  is  exceedingly 
small,  for  no  perceptible  reaction  upon  the 
primary  circuit  was  noticed.  The  length  of 
these  sparks  is  many  times  larger  than  the 


sparking  distance  in  air,  being  tenfold  at  17 
kilovolts.  They  are  intensely  hot,  and  leave 
whitish  marks,  due  to  calcination,  on  the 
mica  when  passing  over  it.  The  sheet  of 
mica,  and  especially  the  electrodes,  become 
heated  very  rapidly,  the  mica  twists  and  be- 
gins to  splinter,  to  separate  into  sheets,  until 
finally  it  breaks  down. 

"  The  width  of  the  electrostatic  corona  is 
half  the  length  of  these  sparks.  The  length  of 
these  sparks  depends  somewhat  upon  fre- 
quency and  the  thickness  of  the  mica  sheet, 
being  greater  for  higher  frequency  and  thin- 
ner mica  disc,  but  apparently  only  in  so  far 
as  the  capacity,  or  rather  the  charging  cur- 
rent of  the  condenser,  represented  by  the 
mica  disc  as  dielectric,  is  increased  there- 
by." 

Corrosion,    Electrolytic A   term 

frequently  employed  for  the  corrosion  ot 
water  or  gas  pipes  or  other  masses  o.t 
metal  buried  in  the  earth  by  electrolytic 
action. 

In  the  case  of  such  large  currents  as  those 
employed  in  the  electric  railway  car  systems, 
or  other  similar  earth-connected  circuits,  the 
corrosion  may  become  marked.  In  such  cases 
electrolytic  corrosion  is  due  to  the  return 
current. 

The  amount  of  corrosion  varies  according 
to  whether  the  railroad  tracks  are  made  the 
positive  or  negative  terminal  of  the  driving 
source. 

It  is  claimed  by  some  that  electrolytic  cor- 
rosion is  lessened  by  connecting  the  trolley 
line  to  the  negative  terminal  of  the  battery 
and  the  tracks  to  the  positive  terminal. 

Perrine  describes  this  matter  as  follows  : 

"A  more  complete  system  of  ground- 
ing seems,  however,  to  offer  at  least  a  par- 
tial solution  of  this  difficulty,  which  may 
only  be  completely  worked  out  in  a  careful 
study  of  the  special  conditions  in  some  par- 
ticular case. 

"  For  such  a  complete  system  of  ground- 
ing, in  order  to  reduce  to  a  minimum  elec- 
trolytic corrosion,  the  negative  pole  of  the 
dynamo  should  be  connected  to  the  trolley 
and  feeder  line  ;  then  at  the  station  connec- 
tions should  be  made  not  only  with  the  rails 


Cos. 


588 


[Con. 


and  wells,  but  also  with  all  water  and  gas 
pipes,  which  piping  system  should  also  be 
frequently  connected  to  the  track  and  track 
feeder,  so  that  whatever  current  passes  by 
the  medium  of  these  pipes  should  flow  out  of 
the  earth  into  them,  and  thence  to  the  rails 
by  means  of  metallic  and  not  electrolytic 
conduction.  If  'this  be  completely  accom- 
plished there  can  be  no  corrosion  of  the  pipes 
caused  by  the  current  flowing  out  of  the 
pipes  to  the  rails,  and  the  only  corrosion 
possible  will  be  that  due  to  the  local  action 
caused  by  the  difference  of  potential  along 
the  pipes  themselves." 

It  would  appear  that  the  total  corrosion  of 
pipes  that  are  not  in  metallic  connection  with 
the  circuit  is  independent  of  the  polarity  of 
the  terminal,  since  the  same  amount  of  cur- 
rent which  enters  the  pipe  from  the  ground 
must  leave  it  by  again  passing  to  ground. 
In  this  manner  the  area  of  entrance  into  the 
pipe  is  protected  and  its  area  of  exit  cor- 
roded electrolytically.  By  changing  the 
terminals  the  protected  and  corroded  parts 
are  merely  interchanged. 

By  making  the  shunt  current  passing 
through  the  pipes  leave  the  pipes  by  means 
of  a  metallic  conductor  instead  of  by  the 
ground,  the  entire  system  of  pipes  is  brought 
below  the  potential  of  the  ground  and  a  pro- 
tection or  partial  protection  is  thus  effected. 

Experiments  made  on  the  West  End  Rail- 
road of  Boston  and  elsewhere,  appear  to 
show  that  it  makes  but  little  difference  which 
terminal  is  connected  to  earth.  It  is  by 
many  considered  best  to  alternately  connect 
the  positive  and  negative  terminals  to  earth 
for  a  period  of  a  week  at  a  time  and  not  to 
depend  on  the  earth  for  a  return,  or  make 
use  of  a  supplemental  wire,  but  to  double- 
bond  the  rails  with  heavy  copper  wire,  plac- 
ing the  connections  back  z\  to  3  feet  respect- 
ively from  the  end  of  the  rails  to  avoid  the 
motion  of  the  joint.  With  a  rail  70  pounds 
to  the  yard,  on  a  four  track  road,  this  is 
equivalent  to  about  28  inches  cross-section  of 
steel,  the  carrying  capacity  of  which  is  4^ 
square  inches  of  copper.  If,  therefore,  an 
equally  good  connection  is  made  from  the  rails 
to  the  generator  at  the  power  station,  there  is 
thus  provided  a  path  capable  of  carrying 


10,000  amperes  without  undue  heating.  Rails 
bonded  in  this  manner  and  used  as  returns, 
will  avoid  the  variable  resistance  of  the  earth 
arising  from  dry  weather,  poor  contact  with 
earth,  frost,  etc.,  and  will  consequently  avoid 
electrolytic  corrosion  in  neighboring  pipes. 

Cosine  Law  of  Illumination. — (See  Ap- 
pendix— Illumination,  Cosine  Law  of.} 

Coulomb,  International The  value 

of  the  international  coulomb  adopted  by  the 
Chicago  Congress  of  1893,  as  equal  to  the 
quantity  of  electricity  transferred  by  a  cur- 
rent of  one  international  ampere  in  one 
second. 

Coulomb  Meter. — (See  Appendix — Meter, 
Coulomb.} 

Coulomb's  Electric  Balance. — (See  Ap- 
pendix— Balance,  Coulomb's  Electric.} 
Coulomb's  Magnetic  Torsion  Balance. — 

(See  Appendix — Balance,  Coulomb's  Mag- 
netic Torsion.} 

Counter,  Electro-Chronometric 

An  apparatus  employed  in  a  system  of  elec- 
trical clocks  to  so  transmit  the  motion 
of  an  ordinary  clock  to  a  number  of  sepa- 
rate clocks  as  to  control  or  operate  them. 

Electro-chronometric  counters  consist  es- 
sentially of  two  parts,  namely, 

(l.)  The  indicator  or  apparatus  connected 
with  the  regulating  clock  and  operating  to 
periodically  make  and  break  the  current  of  a 
battery. 

(2.)  The  mechanism  that  moves  the  clock 
hands  when  actuated  by  the  current  sent  into 
the  line  by  the  indicator. 

Counter-Electromotive  Force  of  Elec- 
trolysis.— (See  Appendix  —  Electrolysis, 
Counter-Electromotive  Force  of.} 

Couple,  Molecular  Voltaic A  vol- 
taic couple  formed  of  the  atoms  or  radicals 
of  a  molecule. 

Lermantoff  has  shown  that  during  the 
development  of  the  photographic  image  in 
moist  collodion  a  true  electrolysis  occurs, 
each  silver  molecule  produced  by  the  action 
of  the  light  on  the  sensitized  plate  forming  a 


Cra.] 


589 


[Cur. 


voltaic  couple  with  a  molecule  of  silver 
nitrate  and  a  molecule  of  iron  sulphate  of  a 
developer. 

Crater  of  Arc. — A  crater  formed  in 
the  end  of  the  positive  carbon  electrode  in 
a  carbon  voltaic  arc.  (See  Arc,  Voltaic.') 

Creeping  of  Belt. — (See  Appendix — Belt, 
Creeping  of.") 

Cross-Fire. — A  term  employed  in  teleg- 
raphy for  an  escape  or  leakage  of  current 
from  one  telegraphic  line  to  another,  due  to 
defective  insulation. 

A  cross-fire  is  sometimes  called  a  weather 
cross.  (See  Cross,  Weather.) 

Cross-Induction  of  Dynamo  Armature. — 

(See  Appendix — Induction,  Cross,  of 
Dynamo  Armature.) 

Cross,  Metallic A  form  of  fault 

attended  by  a  leakage  or  escape  of  current 
from  a  telegraphic  line  due  to  the  absolute 
contact  between  two  or  more  wires  or  con- 
ductors, so  that  part  of  the  current  from 
one  line  passes  to  the  other. 

Cross-Over,  Trolley In  a  system 

of  electric  street  railways  a  device  permit- 
ting the  ready  passage  of  a  trolley  wheel  in 
a  continuous  direction  from  one  to  another 
of  two  adjacent  wires. 

Cross,  Peltier's A  cross  made  by 

placing  two  plates  of  dissimilar  metals  in 
contact  at  right  angles  to  each  other,  and 
employed  for  the  study  of  the  Peltier  effect. 
(See  Effect,  Peltier.) 

Crossing  Frog. — A  term  sometimes  em- 
ployed in  place  of  trolley  cross-over. 

Crystal,  Pyro-Electric Any  crys- 
talline substance  capable  of  producing 
pyro-electric  phenomena  on  being  unequally 
heated. 

Tourmaline,  electric  calamine,  boracite, 
quartz,  tartrate  of  potash,  and  sulphate  of 
quinine  are  examples  of  pyro-electric  crys- 
tals. 


Cubic  Energy. — (See  Appendix — Energy, 
Cubic.) 

Cup  Brush. — (See  Appendix — Brush, 
Cup.) 

Current  Accumulator. — (See  Appendix — 
Accumulator,  Current.) 

Current,  Arriving,  of  Telegraphic  Circuit 

A  term  employed  to  designate  the 

current  on  a  telegraphic  line  or  conductor 
near  the  distant  end  of  the  wire  close  to 
where  it  enters  the  ground  or  earth. 

Current,  Axial A  term  proposed 

for  a  current  whose  direction  coincides 
with  the  direction  of  the  lines  of  magnetic 
force. 

This  use  of  the  term  axial  current  is  in 
contradistinction  to  a  radial  current,  or  one 
whose  direction  is  at  right  angles  to  the 
direction  of  the  lines  of  magnetic  force. 

The  term  axial  current  is  employed  in  elec- 
tro-therapeutics in  a  different  sense  to  the 
above.  (See  Current,  Axial.) 

Current,  Beginning  of A  term 

sometimes  employed  for  the  making  or 
closing  of  the  current  in  any  circuit. 

Current,  Bony A  term  proposed 

by  Becquerel  for  the  electric  current  re- 
sulting ffom  the  difference  of  potential  ex- 
isting between  two  different  parts  of  a  bone 
of  a  recently  killed  animal. 

If  a  bone  be  taken  from  a  recently  killed 
animal  and  the  marrow  connected  by  means 
of  metallic  terminals  with  the  surface  of  the 
bone,  an  electric  current  will  flow  through 
the  circuit,  for  which  Becquerel  proposed  the 
'name  bony  current. 

This  term  is  not  generally  adopted. 

Current,  Cessation  of  — A  term 

sometimes  employed  for  the  breaking  oi 
the  current  in  any  circuit. 

Current,  Demagnetizing A  cur- 
rent whose  magnetic  field  is  employed  to 
decrease  the  strength  of  an  already  existing 
magnetic  field  by  directing  its  lines  of 
force  oppositely  to  that  of  the  existing  field. 


Cnr.] 


590 


[Cur. 


Current,  Effective 


— A  term  pro- 


posed  by  Ayrton,  but  not  accepted,  for  the 
current  producing  a  given  effect. 

This  term,  Ayrton  thinks,  is  an  unfortunate 
one,  since  the  effective  current  will  of  course 
depend  on  the  character  of  the  effect  the  cur- 
rent is  desired  to  produce. 

If,  however,  the  word  "effect"  be  under- 
stood to  mean  "  power,"  then  the  vagueness 
ceases,  and,  since  the  power  is  proportional 
to  the  square  of  the  current,  the  effective 
current  is  the  square  root  of  the  mean 
squares,  but  all  the  effects  produced  by  an 
alternating  current  are  proportional  to  the 
square  root  of  the  mean  squares. 

The  ordinary  meaning  of  effective  current 
is  that  given  it  by  the  definition  of  the  Elec- 
trical Congress  of  Paris,  in  1889,  viz.,  the 
square  root  of  the  time  average  of  the  square 
of  the  current. 

An  alternating  or  periodically  varying 
current  has  an  "effective"  strength  such 
that  if  this  effective  strength  were  steadily 
maintained  in  the  same  direction  through  a 
given  resistance  it  would  generate  as  much 
heat  in  a  given  length  of  time  as  the  periodi- 
cal current. 

When  electrolysis  or  the  magnetization  of 
iron  is  the  effect  produced,  the  effective  cur- 
rent is  identical  with  the  mean  current. 
Where  a  heating  or  dynamometric  effect  is  to 
be  produced,  the  effective  current  is  equal  to 
the  square  root  of  the  mean  square  of  the 
current. 

Current,  Effective  Starting,  of  Motor 

The  indicated  value  of  the  starting 


current  of  a   motor  as    observed    on   an 
ammeter. 

Current  Efficiency  of  Secondary  Battery. 

— (See     Appendix — Battery,     Secondary, 
Current  Efficiency  of.) 

Current,  Entering,  of  Telegraphic  Cir- 
cuit   A  term  employed  to  designate 

the  current  on  a  telegraphic  line  or  con- 
ductor near  the  battery. 

Current,  Harmonics  of A  term 

sometimes  used  for  the  upper  harmonics  of 


a  current.  (See  Appendix  —  Current, 
Upper  Harmonics  of.) 

Current,  M. A  term  proposed  by 

Ayrton  for  mean   current. 

This  term,  M.  current,  is  employed  to  sig- 
nify the  average  value  with  respect  to  time, 
and  is  obtained  by  dividing  the  total  quantity 
of  electricity  which  passes  through  a  given 
circuit  in  a  given  number  of  seconds  by  the 
number  of  seconds.  It  has  not  been  gen- 
erally accepted. 

Current,  M.  S. A  term  proposed 

by  Ayrton  for  mean  square  current. 

This  term  was  proposed  in  order  to  avoid 
the  use  of  the  alleged  vague  term,  effective 
current.  It  applies  to  cases  where  the  effec- 
tive current  has  a  value  equal  to  the  mean 
square  of  the  current.  It  has  not  been  gen- 
erally accepted. 

Current,  Maximum  Starting,    of  Motor 

The  highest  value  that  the  starting 

current  of  a  motor  attains. 

Current  of  Charge  on  Telegraphic  Line. 

—  (See  Appendix  —  Line,  Telegraphic, 
Charge  Current  on.) 

Current,  Polyphase A  term  now 

generally  employed  in  place  of  multiphase 
current.  (See  Current,  Multiphase.} 

Current,  Polyphase  Alternating,  Pro- 
posed A.  I.  E.  E.  Definition  for A 

combination  of  more  than  two  alternating 
currents  differing  in  phase. 

Current,  B.  M.  S. A  term  pro- 
posed by  Ayrton  tor  the  square  root  of  the 
mean  square  of  the  current. 

This  term  was  proposed  in  order  to  avoid 
the  use  of  the  alleged  vague  term,  effective 
current.  It  applies  to  cases  where  the  effec- 
tive current  has  a  value  equal  to  the  square 
root  of  the  mean  square  of  the  current.  It 
has  not  been  generally  accepted. 

Current,  Radial A  term  proposed 

for  a  current  whose  direction  is  at  right 
angles  to  the  direction  of  the  lines  of  mag- 
netic force. 


Car.] 


591 


[Cur. 


This  use  of  the  word  radial  current  is  in 
contradistinction  to  the  word  axial  current, 
whose  direction  coincides  with  that  of  the 
lines  of  magnetic  force.  (See  Appendix — 
Current,  Axial.) 

Current,  Simple  or  Two-Phase  Alternat- 
ing1   Two  alternating  currents  whose 

phases  differ  by  90°  or  by  270°. 

Current,  Sinusoidal A  term  some- 
times employed  for  sinuous  current.  (See 
Current,  Sinuous.) 

A  simple-harmonic  current  in  respect  to 
time. 

A  current  whose  strengths  graphically 
set  forth  as  ordinates  as  time  to  abscissas 
follow  a  sinusoidal  curve. 

Current,  Starting,  of  Motor The 

current  which  a  motor  requires  in  order  to 
start  from  a  state  of  rest. 

Current  Transformation. — (See  Appen- 
dix— Transformation,  Current.) 

Current,  Triphase A  term  some- 
times employed  in  place  of  three-phase 
current.  (See  Appendix — Currents,  Three- 
Phase.) 

Current,  Triphase  Alternating,  Proposed 
A.  I.  E.  E.  Definition  for Three  al- 
ternating currents  whose  phases  differ  by 
60°  or  120°. 

Current,  Tubular A  term  some- 
times applied  to  a  current  that  traverses 
the  superficial  portions  only  of  a  conductor. 

When  a  rapidly  intermittent  current  is  sent 
through  a  solid  conductor,  the  current  den- 
sity is  greater  at  the  surface  of  the  conductor 
than  in  the  central  portions,  and,  when  the 
rapidity  of  alternation  becomes  very  great, 
is  confined  to  an  exceedingly  thin  outer  layer. 

A  tubular  current  possesses  no  magnet- 
izing power  on  anything  placed  inside  the 
tube. 

Current,  Upper  Harmonics  of A 

series  of  higher  harmonic  currents  of 
greater-  frequency  than  the  fundamental 
current  impressed  on  a  simple-harmonic 


current  by  any  means.  (See  Appendix-^ 
Currents,  Complex-Harmonic.) 

Current,  Yirtual A  somewhat 

vague  term  sometimes  employed  for  a  cur- 
rent virtually  equivalent  to  something  else. 

A  term  employed  for  the  square  root  of 
the  mean  square  of  the  current  strength,, 

Current,  Working,  of  Motor The 

current  required  to  maintain  a  motor  when 
its  load  is  on. 

Currents,    Complex-Harmonic   — 

Currents  which  result  from  the  superposi- 
tion of  several  simple-harmonic  currents. 
(See  Current,  Simple-Harmonic.) 

Currents  resulting  from  the  co-existence 
of  the  higher  harmonic  currents  with  the 
fundamental  harmonic  current. 

Unless  certain  precautions  are  taken  the 
currents  produced  in  the  secondary  circuit  of 
a  transformer  or  induction  coil  are  by  no 
means  simple-harmonic  currents.  It  is  true, 
of  course,  that  the  fundamental  frequency 
has  the  same  frequency  as  that  of  the  cur- 
rents sent  through  the  primary  circuit,  but 
the  currents  so  induced  in  the  secondary, 
however,  are  complex-harmonic  currents, 
their  frequency  depending,  according  to  Pu- 
pin:  "  On  the  fundamental  frequency  of  the 
ohmic  resistance,  and  especially  on  the  self- 
induction  and  electrostatic  capacity  of  the 
primary  or  secondary  circuits." 

Complex-harmonic  currents  of  the  second- 
ary of  induction  coils  possess  a  fundamental 
frequency  the  same  as  the  frequency  of  the 
currents  impressed  on  the  primary,  but  they 
hav*e  associated  with  them  a  number  of 
higher  harmonic  currents,  which  correspond 
to  the  overtones  of  a  musical  note. 

These  overtones  are  due  to  rapid  elec- 
trical oscillations  accompanying  the  spark 
discharges.  The  association  of  these  higher 
harmonic  currents  with  the  fundamental 
harmonic  current  produces  what  are  called 
complex-harmonic  currents. 

Complex-harmonic  currents  always  exist 
when  there  is  iron  in  a  circuit,  especially  if 
the  iron  is  highly  magnetized,  when  they  are 
due  to  the  fact  that  the  magnetization  pro- 


Cur.J 


592 


[Cur. 


duced  is  not  proportional  to  the  magnetizing 
iorcc. 

It  is  only  In  circuits  of  constant  resistance, 
containing  no  iron,  that  the  current  produced 
by  a  simple  harmonic  or  sine  wave  of  E.  M. 
F.  is  a  sine  wave.  Magnetic  hysteresis,  or 
a  periodically  varying  resistance  as  by  an 
electric  arc,  causes  a  distortion  of  the  cur- 
rent  and  a  consequent  superposition  of 
higher  harmonics  on  the  fundamental  wave. 
Consequently  the  primary  currents  of  trans- 
formers at  open  secondary  circuit  or  very 
light  load  are  complex  harmonics,  and 
approach  more  nearly  to  true  sine  shapes  at 
increasing  loads.  When,  however,  the  second- 
ary £.  M.  Fs.  of  a  transformer  are  simply 
harmonics,  the  secondary  currents  are  also 
simply  harmonics,  in  circuits  without  iron  cored 
coils. 

Currents  produced  by  complex-harmonic 
E.  M.  F.  are  also  complex  harmonic  ;  gen. 
erally,  however,  the  higher  complex  harmonics 
of  the  E.  M.  F.  wave  are  larger  than  the  com- 
plex harmonics  of  the  current  wave. 

Currents,  Mutually-Induced  --  Cur- 
rents set  up  or  produced  by  means  of 
mutual  induction.  (See  Induction,  Mu- 


Currents,  Polyphase  -  —Currents 
4itfering  in  phase  from  one  another  and, 
therefore,  requiring  separate  circuits  for 
Hse. 

The  currents  may  differ  from  one  another 
by  one-half  phase,  by  one-third  of  a  phase, 
a  quarter  phase  and  so  on,  when  they  are 
respectively  called  di  phase  or  two  -phase 
currents,  triphase  or  three-phase  currents, 
and  four  -phase  currents.  An  ordinary  alter- 
nating current  is  called  a  single  phase  or  uni- 
phase  current.  The  latter  term  is  the.  prefer- 
able one. 

The  term  polyphase  currents  is  applied  to 
all  currents  over  three-phase,  though  some- 
times also  to  all  currents  over  two-phase. 

Currents,   Polyphased,  Alternating  - 

—  Two  or  more  alternating  currents  dif- 
fering in  phases  from  each  other. 

Currents,   Skin  --  A     term     some- 


times applied  to  the  currents  that  are  lim- 
ited to  the  surface  of  a  solid  conductor. 

Rapidly  alternating  currents  are  limited  to 
the  surface  of  solid  conductors  since  before 
any  such  currents  have  time  to  penetrate 
toward  the  centre  of  a  solid  conductor  their 
direction  is  reversed,  thus  limiting  them  to 
the  surface  portions. 

Currents,  Three  Phase Triphased 

currents.  (See  Appendix — Currents,  Tri- 
phased, Alternating.) 

Currents,    Triphased,    Alternating  

— Three  alternating  currents  differing 
1 20°  in  phase  from  each  other. 

In  the  two-phase  system  two  currents  differ- 
ing in  phase  90°  have  a  common  return  wire 
whose  area  should  be  V  2  greater  than  either 
leading  wire. 

In  the  three-phase  system  each  of  three 
currents  differing  in  phase  120°  uses  alter- 
nately one  or  two  of  the  three  wires  for  a 
return. 

Curve,     Arrival  of   Telegraph    Circuit 

A  curve  of  ordinates  and  abscissas 

which  represent  respectively  the  times  and 
the  gradual  increase  of  current  at  the  re- 
ceiving end  of  a  telegraph  circuit  from  the 
time  the  circuit  is  closed  until  the  time 
the  current  has  reached  its  full  strength. 

Curve,  Clown's  Hat A  term  pro- 
posed for  the  curve  of  a  current  or 
electromotive  force  in  which  the  pressure 
generated  increases  or  decreases  at  a 
maximum  rate  of  change, 

The  name  is  taken  from  the  shape  of  the 
curve  being  somewhat  similar  to  the  shape  of  a 
peaked  or  clown's  hat. 

Curve,  Top-Hat A  term  proposed 

for  the  current  or  E.  M.  F.  in  which  the 
pressure  generated  is  fairly  constant  for  a 
considerable  time  at  its  maximum  rise 
and  fall. 

The  name  is  taken  from  the  shape  of  the 
curve  being  somewhat  similar  to  that  of  a 
top-hat,  or  flat  crowned  hat.  A  current  for 
the  primary  of  a  transformer  «r  induction 


Cut.] 


593 


[Dec. 


coil,  however,  of  the  top-hat  type,  makes  a 
bad  form  of  secondary  current  curve,  for  in 
such  a  curve  the  rate  of  change,  whether 
increasing  or  decreasing,  would  be  small. 
The  current  whose  curve  of  electromotive 
force  is  sharp  and  peaked  like  a  clown's  hat 
would,  of  course,  be  preferable. 

Cut-In,  A A  term  sometimes 

employed  in  place  of  film  cut-out. 

An  automatic-guard  cut-out.  (See  Cut- 
Out,  Film.")  (See  Appendix — Guard,  Auto- 
matic, for  Series-  Connected  Incandescent 
Lamps.} 

Cut-Out,  D.  P. A  contraction 

for  double-pole  cut-out.  (See  Appendix — 
Cut-  Out,  Double-Pole,} 

Cut-Out,  Double-Pole A  cut-out 

which  provides  in  one  operation  the  cut- 
ting out  of  both  the  positive  and  the  nega- 
tive leads. 


Cut-Out,  Electro-Magnetic 


— A  term 


sometimes  employed  for  a  cut-out  operated 
by  means  of  an  electro-magnet.     (See  Cut- 
Out,    Automatic,    for    Series-Connected 
Electro-Receptive  Devices.) 
A  form  of  electro-magnetic  cut-out  is  used 


in  charging  accumulators  and  sometimes  in 
street  railway  circuits. 

Cut-Out,  S.  P. A  contraction  for 

single-pole  cut-out.  (See  Appendix — Cut- 
Out,  Single-Pole.) 

Cut-Out,  Single-Pole A  cut-out  by 

means  of  which  the  circuit  is  broken  or 
cut  in  one  of  the  two  leads  only. 

Cut-Out,  Wedge A  form  of  cut- 
out employed  on  telegraphic  circuits. 

The  ends  of  the  instrument  wire  are  con- 
nected to  the  opposite  sides  of  a  wedge 
formed  of  two  brass  plates  suitably  insulated 
from  one  another.  The  ends  of  the  line  wire 
or  conductor  are  suitably  connected  to  two 
metallic  pieces  that  are  maintained  in  elec- 
trical contact  by  means  of  a  spring  electri- 
cally connected  to  one  of  the  pieces  and 
caused  to  bear  with  elastic  pressure  against 
the  other  piece.  In  order  to  introduce  an 
instrument  into  the  line  circuit,  a  switch- 
wedge,  or  plug,  is  inserted  between  the  two 
pieces,  and,  thus  separating  them,  opens 
the  circuit  of  the  line  wire  or  conductor,  and 
at  the  same  time  connects  it  with  the  instru- 
ment thus  introduced. 

Cyclic. — Of  or  pertaining  to  a  cycle. 
(See  Cycle.) 


D.  B.  Switch. — (See  Appendix — Switch, 
D.B.) 

D.  P.  Cut-Out.— (See  Appendix — Cut- 
Out,  D.  P.) 

D.  P.  Switch. — (See  Appendix — Switch, 
D.  P.) 

Damping  Magnet. — (See  Magnet,  Damp- 
ing.) 

Dark  Discharge. — (See  Appendix — Dis- 
charge, Dark.) 

Dark  Segment  of  Aurora. — (See  Appen- 
dix— Segment,  Dark,  of  Aurora.) 

Dead  Ground. — (See  Appendix — Ground, 
Dead.) 


Declination  Compass. — (See  Appendix — 
Compass,  Declination.) 

Decomposition,  Electro-Chemical 

A    term  often  employed  for    electrolytic 
decomposition.     (See  Electrolysis.) 


Decomposition,    Molecular 


—The 


separation  or  breaking  up  of  a  molecule 
into  its  constituent  atoms  or  radicals. 

Molecular  decomposition  may  be  effected 
in  the  following  ways,  namely: 

(1)  By   electrolysis,   or  the   action   of   an 
electric  current. 

(2)  By  thermolysis,  or  the  action  of  heat. 

(3)  By  actinism,  or  the  action  of  light. 


Def.] 


594 


[Die. 


(4)  By  chemism,  or  the  action  of  superior 
chemical  affinity. 

(5)  By  pressure. 

Deflecting  Magnet. — (See  Appendix — 
Magnet,  Deflecting.} 

Degree,  Water-Gramme  — The 

amount  of  heat  required  to  raise  the  tem- 
perature of  one  gramme  of  water  at  4°  C., 
the  temperature  of  its  maximum  density, 
one  degree  centigrade. 

A  small  calorie.     (See  Calorie,  Small.} 

Delta  Triphase  System. — (See  Appendix 
— System,  Delta  Triphase.} 

Demagnetizing  Current. — (See  Appen- 
dix—  Current,  Demagnetizing.} 

Depolarizer. — The  material  employed  in 
a  voltaic  cell  for  the  purpose  of  depolarizing 
it.  (See  Cell,  Voltaic,  Polarization  of.} 

In  most  cases  the  depolarizer  is  a  different 
liquid  and  is  kept  separate  from  the  exciting 
liquid  or  electrolyte.  In  some  cases,  how- 
ever, the  depolarizer  is  mixed  with  the  excit- 
ing liquid. 

Deposit,  Electro  •  Metallurgical  Burnt 

— A  term  sometimes  applied  to  a  black 

deposit  of  metal  which  is  thrown  down 
when  the  intensity  of  the  depositing  cur- 
rent is  too  strong.  (See  Deposit,  Electro- 
Met  a  llurgica  I. } 

Deviation,  Quadrantal,  of  Mariner's  Com- 
pass   The  deviation  of  the  magnetic 

needle  due  to  the  induced  magnetism  in 
the  iron  of  a  ship  acting  as  a  mass  of  soft 
iron,  and  not  as  a  permanent  magnet. 

Quadrantal  deviation  changes  sign  and 
passes  through  successive  opposite  maxima 
four  times  in  one  complete  revolution  of  the 
ship. 

Quadrantal  deviation  is  corrected  by  plac- 
ing masses  of  soft  iron,  usually  spherical  in 
shape,  in  suitable  positions  on  each  side  of 
the  compass. 

Deviation,  Semi-Circular,  of  Mariner's 
Compass The  deviation  of  a  mag- 
netic needle  due  to  the  permanent  mag- 


netism in  the  iron  of  a  ship  having  its 
resultant  in  the  horizontal  plane. 

Semi-circular  deviation  passes  through 
two  opposite  maxima  and  two  zero  points  as 
the  ship  completes  a  revolution,  and  these 
zero  points  of  deviation  occur  when  the 
resultant  magnetic  axis  of  the  ship  coincides 
with  the  magnetic  meridian. 

Semi-circular  deviation  is  corrected  by 
fastening  a  permanent  magnet  in  the  proper 
position  near  the  compass  to  neutralize  the 
influence  of  the  ship's  iron. 

Diagram,  Load  —  A  diagram  or 

curve  representing  to  scale  the  load  or  ac- 
tivity of  a  plant  at  different  times. 

Dial,   Induced  Single-Needle  — A 

dial  employed  in  single-needle  telegraphy 
in  which  both  the  needle  and  its  axle  are 
formed  of  soft  iron  and  have  magnetism 
induced  in  them  by  means  of  permanent 
horseshoe  magnets  placed  so  as  to  act 
magnetically  on  the  needle. 

The  object  of  the  induced  single-needle 
telegraphic  dial  is  for  the  purpose  of  avoid- 
ing the  weakening  of  the  magnetism  of  the 
needle,  or  its  total  loss  or  reversal,  by  vari- 
ous means,  such,  for  example,  as  a  discharge 
of  lightning,  the  effect  of  earth  currents,  etc. 

Dial  Telegraph. — (See  Appendix — Tele- 
graph, Dial.} 

Dialyzing. — Subjecting  to  the  process  of 
dialysis.  (See  Dialysis.} 

Diamagnetized.  —  Endowed  with  dia- 
magnetic  properties.  (See  Diamagnetism.} 

Diamond  Drill. — (See  Appendix — Drill, 
Electric,  Diamond} 

Dielectric,  After- Working  of — A 

term  sometimes  employed  for  a  residual 
charge.  (See  Charge,  Residual.} 

The  term  after-working  of  a  dielectric  was 
proposed  by  Boltzmann.  It  is  not  much 
used  in  the  United  States. 

Dielectric,   Breaking-Down    of  - 
Such  a  weakening  of  a  dielectric  that  per- 
mits a  disruptive  discharge  to  pass  through 


Die.] 


595 


[Dis. 


its  substance.  (See  Appendix — Dielectric, 
Disruptive  Strength  of.} 

Dielectric,  Disruptive  Strength  of 

— The  resistance  which  an  insulating 
medium  or  dielectric  offers  to  the  disrupt- 
ive passage  of  an  electric  discharge 
through  it. 

According  to  Steinmetz  the  disruptive 
strength  of  different  materials  shows  no  re- 
lation to  their  electric  resistance. 

Dielectric  Hysteresis. — (See  Appendix — 
Hysteresis,  Dielectric.) 

Difference  of  Tension. — (See  Appendix — 
Tension,  Difference  of.) 

Differential  Coils. — (See  Appendix  — 
Coils,  Differential.) 

Differential  Electro-Dynamometer.- — (See 
Appendix — Dynamometer,  Electro,  Differ- 
ential.) 

Differential  Electro-Magnet. — (See  Ap- 
pendix— Magnet,  Differential,  Electro.) 

Differential  Winding. — (See  Appendix — 
Winding,  Differential.) 

Diffusing  Globes  for  Electric  Lights. — 

(See  Appendix  —  Globes,  Diffusing,  for 
Electric  Lights) 

Di-Phase  Armature. — (See  Appendix — 
Armature,  Di-Phase.) 

Di-Phase  Generator. — (See  Appendix — 
Generator,  Di  Phase.) 

Di-Phase  Motor,  —  (See  Appendix — 
Motor,  Di-Phase.) 

Diplex  Telegraph.  —  (See  Appendix  — 
Telegraph,  Diplex.) 

Dip  of  Line  Wire  or  Conductor. — (See 
Appendix — Conductor  or  Line  Wire,  Dip 
of-} 

Dipping  Basket. — (See  Appendix — Bas- 
ket, Dipping) 

Dipping  Hook. — (See  Appendix — Hook, 
Dipping.) 


Dips. — Acid  solutions  employed  in  elec- 
tro-plating in  which  articles  that  are  to  be 
plated  are  cleansed  by  dipping. 

Direct-Current  Dynamo-Electric  Ma- 
chine.— (See  Appendix — Machine,  Dyna- 
mo-Electric, Direct-  Current.) 

Direct-Current  Exciter. — (See  Appendix 
— Exciter,  Direct-  Current) 

Direct-Current  Rotary  Transformer. — 

(See  Appendix — Transformer,  Direct-Cur- 
rent Rotary.) 

Direct  Reading  Galvanometer.  —  (See 
Appendix — Galvanometer,  Direct  Read- 
ing.) 

Direct  Working  of  Telegraphic  Sounder. 

—  (See  Appendix —  Working,  Direct,  of 
Telegraphic  Sounder.) 

Directed  •  Streaming  Discharge.  — (See 
Appendix — Discharge,  Directed-Stream- 
ing.) 

Directing  Clock. — (See  Appendix —  Clock, 
Directing.) 

Disc,   Retarding A   copper  disc 

supported  on  a  rotating  shaft,  and  so 
placed  as  to  cut  the  lines  of  force  from  a 
magnet  for  the  purpose  of  retarding  the 
speed  of  rotation. 

In  Elihu  Thomson's  recording  electric 
meter  a  copper  disc,  moving  in  the  field  of  a 
permanent  magnet,  is  so  retarded  that  the 
resulting  number  of  revolutions  is  directly 
proportional  to  the  energy  to  be  measured. 

.    Discharge,  Dark A  term  applied 

by  Faraday  to  that  portion  of  a  convective 
discharge,  separating  the  positive  from  the 
negative  electrode,  that  occurs  under 
certain  circumstances  through  a  rarefied 
gas. 

Discharge,  Directed-Streaming 

A   Tesla    discharge   which    assumes    the 
shape  of  a  hollow  luminous  cone. 
The  discharge  takes  place  between  a  sphere  or 
ball  S  (Fig.  570),  and  a  ring-shaped  electrode. 


Dis.] 


596 


[Dis. 


W,  thereby  producing  a  hollow  luminous  cone 
such  as  is  shown  in  the  figure. 


57O.     Directed-Streaming  Discharge. 

Discharge,  Luminous  Disc-Shaped 

— A  name  given  to  a  variety  of  Tesla  dis- 
charge that  occurs  between  ring-shaped  ter- 
minals. 

The  terminals  are  arranged  as  shown  in  Fig. 
571.     On  the  passage  of  the  current  a  luminous 


Irfc 


shaped  terminals  C,  C,  which  presents  the  ap- 
pearance shown  in  the  figure. 

Discharge,  Slow,  Method  of An 

insulation  test  for  a  well-insulated  telegraphic 
line,  by  the  observation  of  the  rate  at  which 
a  charge  leaks  out  when  the  conductor  is  left 
insulated. 

A  well-insulated  cable  will  take,  say,  half  an 
hour  to  fall  to  half  charge,  and,  with  uniform 
cables,  this  time  is  independent  of  their  length. 

Discharge,  Spark  —  — An  electric  dis- 
charge effected  by  means  of  a  spark. 

A  disruptive  discharge.  (See  Discharge,  Dis- 
ruptive.) 

Discharge,  Tesla An  exceedingly 

high  frequency  discharge. 

The  Tesla  discharge  is  so  named  after  its  dis- 
coverer, Nikola  Tesla. 

Dish,  Chafing,  Electric An  elec- 
trically heated  chafing  dish. 

An  electric  heater  is  applied  to  an  ordinary 
chafing  dish,  so  as  to  permit  the  electrical  heat- 
ing to  take  the  place  of  ordinary  heating. 

A  form  of  electrically  heated  chafing  dish  is 
shown  in  Fig.  572,  and  will  be  readily  understood 
from  inspection.  (See  Heater,  Electric.) 


Fig.  5f  I.    Luminous  Disc-Shaped  Discharge. 

disc-shaped  discharge  occurs  between  the  ring- 


Fig.  572.    Electric  Chafing  Dish. 

Disruptive  Strength  of  Dielectric. — (See 
Appendix — Dielectric,  Disruptive  Strength 
of.) 

Dissonance,  Electric Electric  dis- 
agreement. 

Two  alternating  currents  are  in  electric  dis- 
sonanee  when  their  periods  are  different.  The 
term  electric  dissonance  is  employed  in  contra- 
distinction  to  electric  consonance. 

Distance,  Striking The  distance 

through  which  a  disruptive  discharge  will 
pass.  (See  Discharge,  Disruptive.) 

Distance,  Striking,  for  Various  Sub- 
stances   Tables  of  Steinmetz  give  the 

following  values  for  the  striking  distances  of 
various  mediums  under  certain  circumstances. 


Dis.] 


597 


[Dis. 


8  IN  MILLI-CENTIMETRES,  V  IN  KILO-VOLTS. 

Air S  =  36  (,  —i-3  V  _I)+54V  +  i.2V» 18  <  V  <  24.. 

Mica S=       .24V+.oi45V» 8  <  V  <  20.3 

Vulcanized  Fibre 8  =     7.66  V  +  2.3V* 2.2  <  V  <  22.5 

Dry  Wood  Fibre S  =    7.66  V 2.8  <  V  <  21.6 

Paraffined  Paper ; S  =    3  V 6.9  "5:  V   <  24.8 

Melted  Paraffin,  65°  C S  =  12.4  V 3.9  <  V   <  27.1 

Boiled  Linseed  Oil.  21°  C 8  =  12.5  V 7.6  <  V   <  21.3 

Turpentine  Oil 8  =  15.7  V 7.1  <  V   <  15.6 

Copal  Varnish S  =  30  V 9.7  "^  V   "^  20.4 

Crude  Lubricating  Oil S  =  60  V 4.4  "^  V   "f~  15.9 

Vulcabeston S  =  28  V 4.0  <  V  <  12.6 

Asbestos  Paper S  =  23  V 2.7  "^  V  "5:    5.0 

Creeping  discharge  over  surface  of  Mica S  =  55  (V  — 2)" 4.5  _V_  17.1 


In  the  above  table  d  equals  the  thickness 
of  the  dielectric  in  milli-centimetres,  or 
thousandths  of  a  cm.;  e  equals  the  Napierian 
base,  and  V  equals  the  potential  difference  in 
kilo-volts. 


The  last  column  gives  the  lowest  and  highest 
values  of  V  m  the  experiments  on  the  different 
materials. 

The  following  table  gives  the  data  concerning 
a  disruptive  discharge  through  air: 


TABLE  I. — DISRUPTIVE  DISCHARGE  THROUGH  AIR. 


S  =  36 


_t  1+54  V  +  1.2  V.« 


Maximum    Differ- 

Sparking Distance 

Electrostatic    Gra- 

Sparking     Distance 

Difference. 

Difference  in 

ence  of  Potential 
in  Kilo-  Volts. 

observed  in  Milli- 
centimetres. 

dient,    in    Kilo- 
Volts  per  cm. 

calculated  in  Milli- 
centimetres. 

8  —  8 

per  cent,  of 
8 

calc.  obs. 

calc. 

V 

8 

g 

8 

A 

% 

obs. 

calc. 

.18 

3-0 

60 

2.2 

—    .8 

(-36) 

.26 

4.6 

57 

3.8 

—    .8 

(-21) 

.29 

5.1 

57 

4.5 

—     .8 

—13-3 

.46 

8.1 

57 

8.9 

+     -8 

+  9-° 

.48 

9.1 

53 

9-5 

+     -4 

+   4-2 

•53 

ii 

48 

II.  O 

0 

0 

'•43 

16 
48 

44 
30 

17.1 

+  i.l 
+  1-3 

+  6,4 

+   2.6 

1.76 

68 

26 

66.4 

—  1.6 

—  2.4 

2.46 

100 

25 

105.7 

+  5-7 

+  5-4 

3.96 

190 

21 

197 

+  7 

+  3-5 

5-5 

287 

ig 

297 

+10 

+  3-4 

9-5 

575 

17 

584 

+  9 

+  1.6 

12.7 

860 

15 

—  16 

iS-7 

1150 

IIIO 

—40 

-3% 

19  6 

1440 

14 

1480 

+40 

+  2.7 

21.6 

173° 

13 

1800 

+70 

+  3-9 

24.0 

20IO 

12 

1950 

—60 

Average 

±14.7 

±4-2 

Distant   Battery. — (See  Appendix — Bat- 
tery, Distant?) 


Distortion    of    Magnetic    Field.— (See 

Appendix — Field,  Magnetic,  Distortion  of) 


Dis.] 


598 


Distributing  Board. — (See  Appendix — 
Board,  Distributing) 

Distributing  Brushes  of  Electric  Motor. 

— (See  Appendix — Brushes,  Distributing,  of 
Electric  Motor.) 

Distributing  Switch  Board. — (See  Appen- 
dix— Board,  Distributing-  Switch.) 

Distribution  of  Complex  Lamellar  Mag- 
netism.— (See  Appendix — Magnetism,  Com- 
plex Lamellar,  Distribution  of.) 

Disturbance,    Magnetic A    term 

sometimes  employed  for  the  temporary  varia- 
tions in  the  intensity  of  the  earth's  magnet- 
ism caused  by  a  magnetic  storm. 

Divided  Touch. — (See  Appendix—  Touch, 
Divided?} 

Door  Trigger. — (See  Appendix—  Trigger, 
Door.) 

Dot-and-Dash  Code.— (See  Appendix — 
Code,  Dot-and-Dash.) 

Double  Block,  Duplex. — (See  Appendix — 
Block,  Double  Duplex.) 

Double-Bronze  Wire. — (See  Appendix — 
Wire,  Double-Bronze.) 

Double-Contact  Push. — (See  Appendix — 
Push,  Double-Contact.) 

Double-Contact  Push  Button.— (See  Ap- 
pendix— Button,  Push,  Double-Contact) 

Double-Current  Telegraphic  Working.— 

(See  Appendix — Working,  Double-Current 
Telegraphic) 

Double-Curve  Pull-Off.— (See  Appendix— 
Pull-Off,  Double-Curve) 

Double-Curve     Trolley     Hanger.— (See 

Hanger,  Double-Curve  Trolley.) 

Double  Liquid  Voltaic  Cell.— (See  Cell, 
Voltaic,  Double  Liquid) 

Double-Pole  Cut-Out.— (See  Appendix— 
Cut-Out,  Double-Pole) 

Double-Wire  System  for  Electric  Light 

Leads.— (See     Appendix — Leads,    Doubt?- 
Wire  System  for  Electric  Light) 


Drifting  of  Zero  Point. — A  term  fre- 
quently employed  in  place  of  shifting  of  zero 
point.  (See  Appendix — Shifting  of  Spot  of 
Light) 

Drift  of  Needle. — (See  Appendix — Needle, 
Drift  of) 

Drill,  Electric  Diamond A  dia- 
mond drill  driven  by  electric  power. 

Drill,  Electro-Percussion A  drill 

for  quarrying  or  mining  purposes,  in  which 
the  reciprocating  motion  is  obtained  by  send- 
ing alternately  a  current  through  a  pair  of  sole- 
noids of  which  the  drill  stock  forms  the  core. 

Drill,  Electro-Keciprocating An 

electro-percussion  drill.  (See  Appendix — 
Drill,  Electro-Percussion) 

Drop  Relay-Contact — (See  Appendix — 
Contact,  Drop-Relay) 

Drop  Trolley.— (See  Trolley,  Drop) 

Dry  Battery. — (See  Appendix— Battery, 
Dry) 

Dry  Gelatine  Cell. — (See  Appendix — Cell, 
Dry  Gelatine) 

Duplex  Balance. — (See  Appendix — Bal- 
ance, Duplex) 

Duplex  Telegraph. — (See  Appendix — 
Telegraph,  Duplex) 

Duplex  Telephony. — (See  Appendix — 
Telephony,  Duplex?) 

Dust,  Electrical  Aggregation  of,  in  Dust- 
Laden  Air A  coalescence  of  a  great 

number  of  separate  particles  of  dust,  in  dust- 
laden  air,  by  means  of  the  action  of  an  elec- 
trical brush  discharge. 

If  a  brush  or  convection  discharge  be  passed 
through  dust  or  smoke-laden  air,  contained  for 
purposes  of  observation  in  a  glass  globe,  the 
electrical  aggregation  of  the  particles  of  dust  or 
smoke  rapidly  clears  the  air.  This  method  is 
practically  employed  in  the  manufacture  of  lamp- 
black. 

Dyad  Atom.  —  (See  Appendix — Atom, 
Dyad) 

Dynamic  Multiplier. — (See  Appendix — 
Multiplier,  Dynamic) 

Dynamics. — That  branch    of   mechanics 


Dyn.J 

which  treats  of  the  action  of  a  force  in  pro- 
ducing motions  or  pressures. 

Dynamo-Electric  Machine  for  Electro- 
Plating. — (See  Appendix — Machine,  Dy- 
namo-Electric, for  Electro-Plating!) 

Dynamo,  Idle  Wire  of (See  Appen- 
dix—  Wire,  Idle,  of  Armature  of  Dynamo!) 

Dynamometer,  Electro,  Differential 

— A  double  dynamometer  with  the  moving 
coils  rigidly  connected  and  oppositely  influ- 
enced, so  that  the  movement  of  the  suspen- 
sion system  can  be  reduced  to  zero  by  elec- 
trical adjustments  when  the  instrument  is 
under  operation. 

Dynamo,  Motor (See  Appendix— 

Motor,  Dynamo?) 

Dynamo  or  Motor  Frame. — (See  Appen- 
dix— Frame,  Dynamo  or  Motor!) 

Dynamo  Standards.— (See  Appendix— 
Standards,  Dynamo!) 

Dynamos  Coupled  in  Potential  Series. — 

(See  Appendix — Series,  Potential,  Dynamos 
Coupled  z'n.) 

Dynamotor. — A  continuous  current  trans- 
former. 


599 


[Eff. 


A  term  now  generally  employed  for  motor- 
generator.  (See  Generator,  Motor!) 

A  motor-dynamo,  or  motor-generator,  is  prac- 
tically a  dynamo  driven  by  means  of  an  electric 
current.  The  motor-dynamo  consists  of  two  dis- 
tinct or  separate  armatures  placed  on  the  same 
shaft,  or  two  separate  armature  windings  placed 
on  the  same  core.  On  sending  the  current 
through  one  armature  or  winding  it  acts  as  a 
motor  and  turns  the  shaft,  thus  producing  current 
in  the  other  armature  or  winding.  Such  a  ma- 
chine is  sometimes  called  a  rotary  transformer, 
though  this  name  is  preferably  limited  to  a  ma- 
chine containing  only  a  single  armature,  which 
acts  as  a  generator  and  motor  armature.  (See 
Transformer,  Constant  Current.') 

Such  a  machine  is  employed  for  transforming 
continuous  currents  into  continuous  currents  of 
different  potential,  or  for  transforming  alternating 
or  polyphase  currents  into  continuous  currents,  or 
vice  versa. 

Dyne  :  cm. — An  abbreviation  proposed  for 
dyne-centimetre,  the  C.  G.  S.  unit  of  moment 
of  couple. 

Dyne : cm2. — An  abbreviation  proposed  for 
dyne  per  square  centimetre,  the  C.  G.  S.  unit 
of  pressure. 


E. — A  symbol  proposed  for  electromotive 
force. 
The  defining  equation  is  E  =  RC. 

e. — A  symbol  proposed  for  difference  of 
potential. 

The  defining  equation  is  e  =  rC. 

E.  H.  P. — A  contraction  for  electrical  horse- 
power. 

Earth,  Bad A  term  sometimes  em- 
ployed for  a  ground  or  connection  to  earth, 
the  electric  resistance  of  which  is  compara- 
tively high.  (See  Earth  or  Ground. ) 

Earth  Cell.— (See  Appendix— Cell,  Earth.) 

Earth,  Good A  term  sometimes  em- 
ployed for  a  ground  or  connection  to  earth, 


the  electric  resistance  of  which  is  compara- 
tively low.     (See  Earth  or  Ground!) 

Earthed. — Connected  to  ground  or  earth. 

Easement. — A  permit,  obtained  from  the 
owner  of  a  property,  for  the  erection  of  poles 
or  attachments  for  telephonic,  telegraphic  or 
other  electric  lines. 

Effect,  Page The  faint  sounds  pro- 
duced when  a  piece  of  iron  is  rapidly  magnet- 
ized and  demagnetized. 

A  faint  click  is  produced  when  a  bar  of  iron  is 
magnetized  or  demagnetized.  When,  therefore, 
such  a  bar  undergoes  rapid  magnetization  and  de- 
magnetization these  separate  sounds  link  them- 
selves into  a  continuous  musical  note,  thus  pro- 
ducing what  is  known  as  the  Page  effect.  In  the 


Eff, 


600 


[Elo. 


larger  masses  of  iron  employed  in  transformer 
cores  and  alternator  armatures,  the  Page  effect 
sometimes  rises  to  a  loud  humming  noise. 

Effects  of  Temperature  on  the  Electric 
Resistance  of  Metals. — (See  Appendix — 
Resistance,  Electric,  of  Metals,  Effect  of 
Temperature  on.) 

Effective  Current. — (See  Appendix — Cur- 
rent, Effective?) 

Effective  Starting  Current  of  Motor.— 
(See  Appendix — Cur  rent,  Effective  Starting, 
of  Motor?) 

Efficiency  of  Electric  Lamp. — (See  Appen- 
dix— Lamp,  Electric,  Efficiency  of.) 

Efficiency  of  Electric  Motor. — (See 
Appendix — Motor,  Efficiency  of  Electric?) 

Efficiency  of  Radiation. — (See  Appendix 
— Radiation,  Efficiency  of.) 

Efficiency  of  Secondary  Battery.— (See 
Appendix — Battery,  Secondary,  Efficiency 
of.) 

Effluvia,  Electric A  term  em- 
ployed in  the  early  history  of  electricity  for 
supposed  effluvia  proceeding  from  an  electri- 
fied body  and  causing  electrical  phenomena. 

Effluvia,  Magnetic A  term  em- 
ployed in  the  early  history  of  magnetism  for 
assumed,  imponderable  effluvia  which  were 
supposed  to  be  given  off  by  magnets. 

The  doctrine  of  magnetic  effluvia  may  be  re- 
garded as  a  forerunner  of  the  doctrine  of  lines  of 
magnetic  force  introduced  into  science  by  Fara- 
day. 

In  some  of  his  earlier  writings  Boyle  framed 
the  hypothesis  of  a  magnetic  atmosphere,  or 
region  surrounding  a  magnet  He  conceived 
the  idea  that  magnetic  effluvia,  emitted  from 
one  of  the  poles  of  the  magnet,  passed  through 
the  space  surrounding  the  magnet  and  re-entered 
it  at  its  other  pole.  As  will  be  seen,  this  concep- 
tion closely  resembles  the  modern  conception  con- 
cerning the  flow  of  lines  of  magnetic  force,  or  of 
magnetic  flux. 

Egg,  Electric A  term  formerly  em- 
ployed for  an  egg-shaped  vessel  containing 
a  partial  vacuum  through  which  an  electric 
discharge  is  passed  for  the  purpose  of  obtain- 
ing luminous  effects. 


Elastance. — A  word  proposed  for  the  re- 
ciprocal of  permittance.  (See  Appendix — 
Permittance.) 

Elastivity. — The  elastance  of  a  dielectric 
referred  to  unit  volume. 

If  the  dielectric  possesses  great  permittance  it 
has  of  course  but  little  elastance. 

Electric  Amalgamator. — (See  Appendix— 
Amalgamator,  Electric?) 

Electric  Anaesthesia. — (See  Appendix — 
Ancesthesia,  Electric?) 

Electric  Anemograph. — (See  Appendix — 
Anemograph,  Electric?) 

Electric  Atmosphere. — (See  Appendix — 
Atmosphere,  Electric?) 

Electric  Aura.— (See  Appendix— Aura, 
Electric?) 

Electric  Broiler.  —  (See  Appendix— 
Broiler,  Electric?) 

Electric  Casting. — (See  Appendix—  Cast- 
ing, Electric^] 

Electric  Chaflng-Dish.— (See  Appendix— 
Dish,  Chafing,  Electric?) 

Electric  Chronometer.— (See  Appendix— 
Chronometer,  Electric?) 

Electric  Clamp  Attachment. — (See  Ap- 
pendix— Attachment,  Electric  Clamp?) 

Electric  Coil  Heater.— (See  Appendix— 
Heater,  Coil,  Electric?) 

Electric  Conflict. — (See  Appendix — Con- 
flict, Electric?) 

Electric  Deck-Planer.— (See  Appendix— 
Planer,  Electric  Deck?) 

Electric  Dissonance.— (See  Appendix— 
Dissonance,  Electric?) 

Electric  Door-Trip.— (See  Appendix— 
Trip,  Door,  Electric?) 

Electric  Effluvia.— (See  Appendix— Efflu- 
via, Electric?) 

Electric  Egg.— (See  Appendix— Egg  .Elec- 
tric?) 

Electric  Escapement— (See  Appendix— 
Escapement,  Electric.) 


4— Vol.  2 


Ele.] 


G01 


[Ele. 


Electric  Excitation. — (See  Appendix — 
Excitation,  Electric?) 

Electric  Flat-Iron. — (See  Appendix — 
Flat-iron,  Electric?) 

Electric  Fluid. — (See  Appendix — Fluid, 
Electric?) 

Electric  Forge. — (See  Appendix — Forge, 
Electric?) 

Electric  Glue-Pot. — (See  Appendix — 
Glue-Pot,  Electric?) 

Electric  Gnomon. — (See  Appendix — Gno- 
mon, Electric?) 

Electric  Harpoon. — (See  Appendix — Har- 
poon, Electric?) 

Electric  Horology.— (See  Appendix — 
Horology,  Electric?) 

Electric  Hummer. — (See  Appendix — 
Hummer,  Electric?) 

Electric-Light  Bath. — (See  Appendix — 
Bath,  Electric-Light?) 

Electric  Machine  Tool. — (See  Appendix 
—  Tool,  Electric  Machine?) 

Electric  Matter. — (See  Appendix — Mat- 
ter, Electric?) 

Electric  Meteorograph.— (See  Appendix 
— Meteorograph,  Electric?) 

Electric  Meteorology. — (See  Appendix — 
Meteorology,  Electric?) 

Electric  Mining. — (See  Appendix — Min- 
ing, Electric?) 

Electric  Pendulum.— (See  Appendix — 
Pendulum,  Electric?) 

Electric  Photo-Micography.— (See  Ap- 
pendix— Photo-Micography,  Electric?) 

Electric  Pocket  Gauge. — (See  Appendix — 
Gauge,  Electric  Pocket?) 

Electric  Pressure. — (See  Appendix — 
Pressure,  Electric?) 

Electric  Radiation. — (See  Appendix — 
Radiation,  Electric?) 

Electric  Radiator. — (See  Appendix — Ra- 
diator, Electric?)  ^ 

Electric  Rail  Bond. — (See  Appendix — 
Bond,  Electric  Rail.} 


Electric  Residue.— (See  Appendix— Rest- 
due,  Electric?) 

Electric  Spark. — (See  Appendix — Spark> 
Electric.)  \ 

Electric  Stopper  Lamp. — (See  Appendix — 
Lamp,  Electric  Stopper.) 

Electric  Stove-Plate. — (See  Appendix — 
Stove-Plate,  Electric?) 

Electric  Telegraph. — (See  Appendix — 
Telegraph,  Electric?) 

Electric  Tourniquet. — (See  Appendix — 
Tourniquet,  Electric?) 

Electric  Wand. — (See  Appendix —  Wand, 
Electric?) 

Electric  Windmill. — (See  Appendix— 
IVindmill,  Electric. ) 

Electrical  Aggregation  of  Dust  in  Dust- 
Laden  Air. — (See  Appendix — Dust,  Electri- 
cal Aggregation  of,  in  Dust-Laden  Air.) 

.  Electrical  Aggregation  of  Raindrops. — 

(See  Appendix — Raindrops,  Electrical  Ag- 
gregation of.) 

Electrical  Baking  Oven.— (See  Appendix 
— Oven,  Baking,  Electrical.) 

Electrical  Bombardment  Lamp. — (See 
Appendix — Lamp,  Bombardment,  Electri- 
cal?) 

Electrical  Coking. — (See  Appendix — Cok- 
ing, Electrical?) 

Electrical  Equivalent  of  Heat.— (See 
Appendix — Heat,  Electrical  Equivalent  of?) 

Electrical  Harmonics. — (See  Appendix— 
Harmonics,  Electrical?) 

Electrical  Stimulus  of  Nerve.— (See 
Appendix — Stimulus,  Electrical,  of  Nerve?) 

Electrically      Illumined      Buoy. — (See 

Appendix — Buoy,  Electrically  Illumined.) 

Electrically  Tuned  System.—  (See  Appen- 
dix— System,  Electrically  Tuned.) 

Electricity,  Reversible  Heating  Effect  of 

A  term  sometimes  employed  in  place 

of  the  Peltier  effect.     (See  Effect,  Peltier?) 


Ele.] 


602 


[Ele. 


An  effect  of  this  character  is  called  reversible, 
because  when  the  current  is  passed  across  an 
electro-thermal  junction  in  one  direction,  heat  is 
produced,  while  if  it  is  passed  in  the  opposite  di- 
rection, cold  is  produced. 

Electricity,  Spontaneous A  term 

formerly  employed  for  the  electricity  pro- 
duced by  the  melting  of  sulphur. 

This  term  is,  of  course,  not  employed  at  present, 
since  electricity  can  never,  properly  speaking,  be 
produced  spontaneously. 

Electrification,  Negative  —The 

charging  of  a  body  with  negative  electricity. 

The  negative  charge. 

Electrification,  Positive  —  —The 
charging  of  a  body  with  positive  electricity. 

The  positive  charge. 

Electripherous. — A  word  proposed  for 
anything  capable  of  bearing  or  transmitting 
electricity. 

This  word  is  unnecessary  and  its  use  should 
not  be  encouraged. 

Electrize,  To To  charge  or  electrify 

a  body. 

The  word  corresponds  to  magnetize,  to  render 
a  body  magnetic  or  endow  it  with  magnetic  prop- 
erties. 

The  word  is  sometimes  spelled  electrise. 

Electrizer. — That  which  electrizes  or 
charges  with  electricity. 

Electro-Biologist. — (See  Appendix — Biol- 
ogist, Electro?) 

Electro-Bioscopist.  —  (See  Appendix — 
Bioscopist,  Electro) 

Electro-Chemical  Accumulator.  —  (See 
Appendix — Accumulator,  Electro-Chemicaf.) 

Electro-Chemical  Decomposition. — (See 
Appendix — Decomposition,  Electro-Chemi- 
cal) 

Electro-Chemical  Filtration.— (See  Ap- 
pendix— Filtration,  Electro-Chemical.) 

Electro-Chronometric  Counter.  —  (See 
Appendix — Counter,  Electro-Chronometric.) 

Electro-Compound  Magnet. — (See  Appen- 
dix— Magnet,  Electro-Compound.) 

Electro-Culture.— Stimulating  the  growth 
of  vegetation  by  means  of  electricity. 


The  term  is  a  bad  one,  since  it  should  equally 
apply  to  a  similar  stimulation  of  animal  growth. 

The  term  electro-culture  has  been  proposed  to 
characterize  the  electric  stimulation  of  vegetation, 
which  consists  essentially  in  sending  an  electric 
current  either  through  the  plant  whose  growth  is 
to  be  stimulated,  or  through  the  earth  near  the 
plant. 

In  an  experiment  recently  tried  in  France,  a 
kilogramme  of  potatoes  placed  in  the  path  of  a 
weak  current,  under  conditions  exactly  similar  to 
those  of  an  equal  weight  of  potatoes  uninfluenced 
by  the  electric  current,  produced  21  kilogrammes 
of  healthy  tubers  as  compared  to  12 J  kilogrammes 
of  non -electrically  stimulated  tubers. 

These  experiments  developed  the  fact  that  if  a 
quantity  of  manure  be  planted  near  the  positive 
pole  of  an  electric  source,  the  assimilable  parts  of 
the  manure  are  transported  or  carried  towards 
the  negative  pole. 

The  phenomena  would,  therefore,  appear  to  be 
connected  with  those  of  electric  osmose  or  cata- 
phoresis.  (See  Osmose,  Electric.  C diaphoresis.) 

Electrode,  Cataphoric In  electro- 
therapeutics an  electrode  impregnated  with 
the  medicament  it  is  desired  to  introduce  into 
the  part  to  be  treated  by  cataphoric  medica- 
tion. (See  Appendix — Medication,  Cata- 
phoric.) 

Electro-Deposition. — A  term  sometimes 
employed  for  electric  deposition.  (See  Metal- 
lurgy, Electro.) 

Electro-Dynamic  Balance. — (See  Appen- 
dix— Balance,  Electro-Dynamic) 

Electro-Dynamic  Interrupter. — (See  Ap- 
pendix— Interrupter,  Electro-Dynamic) 

Electro-Dynamic  Rotation. — (See  Appen- 
dix— Rotation,  Electro-Dynamic) 

Electro-Dynamic  Whirls. — (See  Appen- 
dix—  Whirls,  Electro-Dynamic) 

Electro-Genesis. — A  word  proposed  for 
the  production  of  electricity. 

Electro-Genie. — Producing  electricity. 

Electro-Gilding. — (See  Appendix — Gild- 
ing, Electro) 

Electrograph. — A  curve  produced  by  a 
recording  electrometer. 

Electrography. — A  word  proposed  for  that 
branch  of  science  which  treats  of  electricity. 


Ele.] 


603 


[Ele. 


A  word  proposed  for  the  copying  of  fine  en- 
graving on  copper  or  steel  by  means  of  elec- 
tro-deposition. 

It  will  be  seen  that  the  word  electrography  has 
been  proposed  for  two  entirely  distinct  senses. 
The  first  use  of  the  word  would  appear  to  be 
entirely  unjustifiable. 

Electro-Kinetic  Energy. — (See  Appendix 
— Energy,  Electro- Kinetic?) 

Electro-Lithotrity.  —  (See  Appendix — 
Lithotrity,  Electro?) 

KIcrtrolizatioii. — The  act  of  being  elec- 
trolyzed. 
The  word  is  sometimes  spelled  electrolisation. 

Electrologist. — An  electrician. 

The  use  of  this  word  is  entirely  unnecessary. 

Electrolysis,     Counter  -  Electromotive 

Force  of — The  counter-electromotive 

force  produced  in  a  plating  bath  or  a  second- 
ary cell  by  electrolysis. 

Electrolyte. — The  exciting  liquid  in  a 
voltaic  cell. 

A  compound  liquid  which  is  separable  into 
its  constituent  ions  by  the  passage  of  elec- 
tricity through  it. 

Electrolytic  Accumulator. — (See  Appen- 
dix— Accumulator,  Electrolytic?) 

Electrolytic  Corrosion. — (See  Appendix 
— Corrosion,  Electrolytic?) 

Electrolytic  Meter. — (See  Appendix— 
Meter,  Electrolytic?) 

Electro-Magnetic  Cut-Ont. — (See  Appen- 
dix— Cut-Out,  Electro-Magnetic?) 

Electro-Magnetic  Gyroscope. — (See  Ap- 
pendix— Gyroscope,  Electro-Magnetic?) 

Electro-Magnetic  Interference.  —  (See 
Appendix — Interference,  Electro-Magnetic?) 

Electro-Magnetic  Multiplier. — (See  Ap- 
pendix— Multiplier,  Electro-Magnetic?) 

Electro-Magnetic  Separator. — (See  Ap- 
pendix— Separator,  Electro- Magnetic?) 

Electro-Magnetic  Sorter.- (See  Appen- 
dix— Sorter,  Electro-Magnetic?) 

Electro-Magnetic  Telegraph.— (See  Ap- 
pendix—  Telegraph,  Electro-Magnetic.) 


Electro-Metallurgical    Burnt    Deposit 

— (See   Appendix — Deposit,   Electro-Metal- 
lurgical Burnt?) 
Electrometer,  Heterostatic    -          — An 

electrometer  in  which  the  electrification  to 
be  tested  is  not  the  only  electrification  em- 
ployed. (See  Heterostatic?) 

Electrometer,  Idiostatic An  elec- 
trometer in  which  the  electrification  to  be 
tested  is  the  only  electrification  employed. 
(See  Idiostatic?) 

Electrometer,  Long-Range A  form 

of  attracted-disc  electrometer  in  which  the 
range  of  the  scale  is  comparatively  long. 

Electrometer,  Repulsion An  elec- 
trometer in  which  the  differences  of  potential 
are  measured  by  means  of  the  repulsion 
existing  between  two  similarly  charged 
bodies. 

Coulomb's  torsion  balance  is  an  instrument  of 
this  class.  A  gold-leaf  electrometer,  when  ar- 
ranged so  that  the  amount  of  deviation  can  be 
readily  measured,  is  also  a  repulsion  electrometer. 


form  of  electrometer  in  which  the  needle  is 
unaffected  when  it  is  placed  symmetrically  as 
regards  the  deflecting  segments. 

A  quadrant  electrometer  is  a  form  of  sym- 
metrical electrometer. 

Electrometer,  Thermo  — A  term 

sometimes  employed  for  an  electric  ther- 
mometer. 

This  use  of  the  term  probably  arose  from  the 
fact  that  such  an  instrument  may  be  employed  to 
measure  roughly  the  difference  of  potential  be- 
tween points  between  which  a  spark  passes. 

Electrometer  Voltmeter. — (See  Appen- 
dix—  Voltmeter,  Electrometer?) 

Electrometric. — Of  or  pertaining  to  an 
electrometer. 

Electromotive  Force,  Transformation  of 

(See  Appendix — Transformation,  as 

of  Electromotive  Force?) 

Electronome. — A  term  proposed  for  a 
measurer  of  electricity. 

This  term  is  not  only  unnecessary,  but  is  devoid 
of  any  precise  meaning  and  may  serve  as  an 


Ele.] 


604 


[End. 


illustration  of  the  thoughtless  manner  in  which 
electric  words  are  proposed. 

Electropath.— One  skilled  in  the  art  of 
electro-therapy. 

Electropathy.— A  word  proposed  for  the 
treatment  of  disease  by  means  of  electricity. 

The  word  electro-therapy  or  electro-thera- 
peutics is  generally  used. 

Electro-Percussion  Drill. — (See  Appen- 
dix— Drill,  Electro-Percussion.) 

Electrophone. — A  word  proposed  by  Ader 
for  a  form  of  telephone  employing  carbon 
contacts. 

Electro-Physiologist. — (See  Appendix — 
Physiologist,  Electro?) 

Electro-Potential  Energy. — (See  Appen- 
dix— Energy,  Electro-Potential?) 

Electro-Puncturation. — (See  Appendix — 
Puncturation,  Electro?) 

Electro-Reciprocating  Drill. — (See  Ap- 
pendix— Drill,  Electro-Reciprocating.) 

Electroscope,  Semaphoric  —  —A  name 
sometimes  given  to  Henley's  quadrant  elec- 
troscope. (See  Electroscope,  Quadrant, 
Henley's?) 

Electroscopic  Gauge. — (See  Appendix — 
Gauge,  Electroscopic?) 

Electrostatic  Aurora. — (See  Appendix — 
Aurora,  Electrostatic?) 

Electrostatic  Corona. — (See  Appendix— 
Corona,  Electrostatic?) 

Electrostatic  Influence. — (See  Appendix 
— Influence,  Electrostatic?) 

Electrostatic  Motion. — (See  Appendix — 
Motion,  Electrostatic?) 

Electrostatic  Motor. — (See  Appendix — 
Motor,  Electrostatic?) 

Electrostatic  Strain. — (See  Appendix — 
Strain,  Electrostatic?) 

Electro-Steeling. — (See  Appendix — Steel- 
ing, Electro?) 

Electro-Stereotype.  —  (See  Appendix — 
Stereotype,  Electro?) 

Electro-Synthesis.— (See  Appendix— Syn- 
thesis, Electro?) 


Electro-Thermancy.  —  (See  Appendix — 
Thermancy,  Electro?) 

Electro-Thermotic.  —  (See  Appendix — 
Thermotic,  Electro?) 

Electro-Tint.  —  (See  Appendix—  Tint- 
Electro?) 

Electrotome. — A  term  formerly  applied  to 
an  automatic  contact  breaker  which  vibrated 
with  sufficient  rapidity  to  produce  a  musical 
note.  (See  Contact  Breaker,  Automatic?) 

Electro-Tonicity.— (See  Appendix—  Toni- 
city,  Electro?) 

Electro,  Turtle-Back  —  —  An  electro- 
type curved  so  as  to  be  capable  of  being  em- 
ployed in  the  cylinder  of  a  rotary  newspaper 
press. 

Element  of  Battery.— A  term  sometimes 
applied  to  a  single  electric  source  or  a  battery 
of  sources. 

Element  of  Voltaic  Battery. — A  term 
sometimes  applied  to  a  single  cell  of  a  voltaic 
battery. 

The  term  element  is  properly  applied  to  a 
single  complete  voltaic  cell  only  when  such  a 
cell  forms  one  of  a  number  of  cells  so  connected 
in  a  battery  as  to  form  a  single  electric  source. 

It  would  appear  that  the  use  of  the  word  ele- 
ment in  the  case  of  a  single  voltaic  cell,  whether 
connected  with  the  battery  or  not,  is  inadvisable. 

Elliptical  Rotary  Magnetization. — (See 
Appendix — Magnetization,  Elliptical  Ro- 
tary?) 

Elongation,  Maximum  Negative 

The  position  of  a  vibrating  body  when  it  is 
at  the  extremity  of  its  path  on  the  negative 
side. 

Elongation,  Maximum  Positive 

The  position  of  a  vibrating  body  when  it  is 
at  the  extremity  of  its  path  on  the  positive 
side. 

Emission,    Selective A   selective 

radiation.  (See  Appendix — Radiation,  Se- 
lective?) 

End-to-End  Joint.— (See  Appendix— Joint, 
End-to-End?) 


End.] 


605 


[Fac. 


Endosmose,  Voltaic A  term  some- 
times employed  in  place  of  electric  osmose. 
(See  Osmose,  Electric.) 

Energetics. — That  branch  of  mechanics 
which  treats  of  the  transfer,  transformation 
or  modification  of  energy. 

Energy,  Cubic  —  —A  term  sometimes 
employed  for  volumetric  energy.  (See 
Appendix — Energy,  Volumetric?) 

Energy,  Electro-Kinetic Electric 

energy  that  is  actually  engaged  in  doing 
work.  (See  Energy,  Kinetic?) 

Energy,  Electro-Potential  — —  — Elec- 
tric energy  possessing  the  power  of,  but  not 
actually  doing,  work.  (See  Energy,  Poten- 
tial?) 

Energy,  Specific Volumetric  en- 
ergy. 

Energy,  Tolumetric A  term  pro- 
posed by  Hospitalier  for  a  quantity  equal  to 
the  work  divided  by  the  volume. 

Energy,  Volumetric,  C.  G.  S.  Unit  of 
An  erg  per  cubic  centimetre. 

Entering  Current  of  Telegraphic  Cir- 
cuit.— (See  Appendix — Current,  Entering, 
of  Telegraphic  Circuit?) 

Epoch. — The  time  reckoned  in  the  case  of 
a  vibrating  body  from  the  point  of  reckoning 
to  the  point  of  maximum  positive  elongation. 

Equalizing  Wires.  —  (See  Appendix  — 
Wires,  Equalizing?] 

Equatorial  Region  of  Magnet. — (See 
Appendix — Region,  Equatorial,  of  Magnet?) 

Ergometer.— A  term  proposed  for  an  in- 
strument for  measuring  the  amount  of  work 
done  by  a  machine. 


This  would  more  properly  be  called  an  erg- 
meter.  The  word,  however,  is  seldom  used. 

Erg  :  s. — An  abbreviation  proposed  for  erg 
per  second,  the  C.  G.  S.  unit  of  power. 
Error,  Heeling,  of  Mariner's  Compass 

The  error  in  deviation  of  the  mag- 
netic needle  produced  by  that  portion  of  the 
induced  and  permanent  magnetism  of  the 
iron  in  a  ship  brought  into  action  by  the  roll- 
ing or  heeling  of  the  vessel. 

Escape.— A  term  employed  in  telegraphy 
for  leakage  of  the  current  from  the  line  wire 
or  conductor,  from  the  effect  of  insufficient 
or  faulty  insulation,  or  from  contact  of  the 
line  with  wet  buildings  or  other  uninsulated 
bodies. 

Escapement,  Electric . An  electri- 
cally actuated  clock  escapement. 

Evanescent  Telegraphic  Signal. — (See 
Appendix — Signal,  Telegraphic,  Evanes- 
cent.) 

Exciter,  Direct  Current A  source 

of  direct  current,  generally  a  direct  current 
dynamo,  employed  for  exciting  the  field  mag- 
nets of  an  alternating  current  dynamo. 

Excitation,  Electric The  produc- 
tion of  electrification  by  any  means. 

Exhausted  Plates  of  Storage  Cell. — (See 
Appendix — Plates,  Exhausted,  of  Storage 
Cell?) 

Extension  Bell. — (See  Appendix—^//, 
Extension?) 

External  Magnetic  Circuit.— (See  Ap- 
pendix— Circuit,  Magnetic,  External?) 

External  Magnetic  Field. — (See  Appea- 
dix — Field,  Magnetic,  External?) 


F. — A   symbol    proposed   for  farad,    the 
practical  unit  of  capacity. 

F. — A  symbol  proposed  for  force. 
The  defining  equation  is  F  =  M  X  A.      The 
same  symbol  is  also  proposed  for  farad. 

eF. — A    symbol     proposed    for    magneto- 
motive force. 


The  defining  equation  is  eF  =  qit  N  I. 

F.  M. — A  contraction  sometimes  employed 
for  field  magnets. 

Fac-Simile  Telegraph.— (See  Appendix — 
Telegraph,  Fac-Simile?) 

Factor,  Power  -  —The  factor,  less 
than  unity,  which  must  be  applied  to  the  ap- 


Fal.] 


606 


[Fil. 


parent  activity  in  an  alternating  current  cir- 
cuit as  obtained  by  the  product  of  the  volts 
and  the  amperes,  in  order  to  obtain  the  true 
activity.  * 

With  sinusoidal  currents  and  electromotive 
forces,  the  power  factor  is  also  equal  to  the  cosine 
of  the  angle  of  lag  in  the  current  before  or  behind 
the  pressure. 

Fallback  Indicator. — (See  Appendix — 
Indicator,  Fallback?) 

Farad,  International The  value  of 

the  international  farad  adopted  by  the  Chi- 
cago Congress  of  1 893  as  equal  to  the  capac- 
ity of  a  conductor  charged  to  a  potential  of 
one  international  volt  by  one  international 
coulomb  of  electricity. 

Faradic  Coil. — (See  Appendix — Coil,  Far- 
adic?) 

Faradism. — A  word  sometimes  employed 
for  faradization. 

Faradization  would  appear  to  be  the  preferable 
word.  (See  Faradization. ) 

Fault,  Low  Test A  term  sometimes 

applied  to  a  fault  in  an  underground  cable 
when  the  insulation  resistance  falls  below  a 
certain  minimum  value,  say,  for  example,  5 
megohms  per  100  volts  per  mile. 

Fault,  Resultant  — The  apparent 

position  and  magnitude  of  a  fault  in  a  cable 
due  to  the  resultant  of  all  its  leakage  upon 
the  electrical  measurements  made. 

Feeder  Clamp. — (See  Appendix — Clamp, 
Feeder.) 

Feeder  Clip.  —  (See  Appendix  —  Clip, 
Feeder?) 

Feeder  for  Trolley  Conductor. — A  wire 
or  conductor  of  low  resistance,  employed  for 
transmitting  electric  current  directly  from  the 
power  station  to  the  trolley  wire,  and  serving 
to  maintain  the  potential  at  the  point  of  junc- 
tion. 

Ferro-Magnetic. — A  word  sometimes  em- 
ployed in  place  of  paramagnetic. 

Ferro-Magnetism.— A  word  sometimes 
applied  to  the  magnetism  possessed  by  iron, 
or,  in  general,  by  paramagnetic  substances. 
(See  Paramagnetic?) 


Field  Coils  of  Dynamo. — (See  Appendix, 
Coils,  Field,  of  Dynamo?) 

Field,  Magnetic,  Distortion  of A 

change  in  the  direction  or  grouping  of  lines 
of  magnetic  force,  in  the  field  of  a  dynamo- 
electric  machine  or  electric  motor,  produced 
by  the  reaction  of  the  armature,  or  the  mag- 
neto-motive force  of  the  armature  current. 

This  distortion  of  the  field  renders  it  necessary 
to  give  a  lead  to  the  collecting  or  distributing 
brushes.  (See  Lead,  Angle  of.  Lead  of 
Brushes  of  Dynamo-Electric  Machine. ) 

Field,  Magnetic,  External That 

portion  of  a  magnetic  field  which  lies  outside 
the  magnet  or  external  to  it.  (See  Field, 
Magnetic?) 

Field,  Magnetic,  Internal That 

portion  of  a  magnetic  field  which  lies  within 
the  magnet. 

Field  of  Force. — (See  Appendix — Force, 
Field  of?) 

Field  Plates. — (See  Appendix — Plates, 
Field?) 

Field  Spools  of  Dynamo-Electric  Ma- 
chine.— (See  Appendix,  Spools,  Field,  of 
Dynamo-Electric  Machine?) 

Figures,  Karsten's A  name  some- 
times given  to  electric  breath  figures.  (See 
Figures,  Breath?) 

Filament,  Coked A  carbon  fila- 
ment for  an  incandescent  electric  lamp  that 
has  been  subjected  to  electrical  heating  in  a 
vacuum,  not  only  until  thoroughly  freed  from 
its  occluded  gases,  but  also  until  its  carbon  is 
changed  into  a  variety  of  coke. 

The  coked  carbon  filament  is  the  invention  of 
Lodyguine.  The  coking  is  carried  on  in  a 
vacuum,  the  process  being  continued  for  about 
eight  seconds  after  the  occluded  gases  have  been 
driven  off. 

The  carrying  off  of  the  occluded  gas  is  effected 
in  the  usual  manner,  and  the  strength  of  the  cur- 
rent is  then  increased  considerably.  Under 
these  circumstances  the  carbon  of  the  filament 
becomes  changed  into  a  variety  of  coke. 

It  is  claimed  that  under  the  coking  process  the 
filament  has  its  permanent  or  cold  resistance 
greatly  decreased  until  it  becomes  approximately 


Fil.] 


607 


[Flu. 


of  the  same  value  as  that  of  the  hot  resistance  of 
the  filament  before  it  was  coked.  The  process  is 
sometimes  carried  further  than  this,  depending 
on  the  character  cf  the  original  carbonization. 

It  is  necessary,  however,  to  stop  the  coking 
treatment  when  this  point  of  resistance  has  been 
reached,  since,  if  the  heating  be  continued  beyond 
this,  the  resistance  of  the  filament  again  rises. 

Filament,  Coking  of Subjecting  a 

filament  to  the  coking  process.  (See  Fila- 
ment, Coked.) 

Filament,  Incandescent A  fila- 
ment that  is  rendered  incandescent  by  the 
passage  of  an  electric  current.  (See  Lamp, 
Incandescent,  Electric  Filament  of.) 

In  other  words,  a  filament  is  incandescent  only 
while  it  is  actually  emitting  its  own  light 

Filament,  Incandescing A  fila- 
ment that  can  be  rendered  incandescent  by 
the  passage  of  an  electric  current.  (See 
Lamp,  Incandescent,  Electric  Filament  of.) 

Filament,  Mounting  of A  suitable 

connection  for  the  filament  to  the  leading- 
in  wires  inside  the  chamber  of  an  incan- 
descent electric  lamp. 

Filament,  Treated  Coked A  car- 
bon filament  the  core  of  which  has  been  elec- 
trically coked  and  whose  surface  is  covered 
with  electrically  deposited  carbon  derived 
from  the  decomposition  of  a  hydrocarbon  gas 
or  vapor. 

Filtration,    Electro-Chemical A 

term  formerly  employed  in  place  of  electric 
endosmose.  (See  Osmose,  Electric.  Phe- 
nomena, Par  ret.) 

Finishing  Brushes.— (See  Appendix — 
Brushes,  Finishing) 

Fire  Alarm  Telegraph. — (See  Appendix — 
Telegraph,  Fire  Alarm) 

Fire  Glow. — (See  Appendix — Glow,  Fire) 

Fittings,  Combination,  for  Chandeliers, 

Brackets,  Etc. Fittings  that  provide 

for  the  use  of  both  gas  and  electricity 

Five- Wire  System. — (See  Appendix — Sys- 
tem, Fi've-  Wire) 

Flash,  Multiple  Lightning Several 


lightning  flashes  that  apparently  come  from 
the  same  cloud. 

Lodge  traces  the  cause  of  multiple  lightning 
flashes  to  the  same  circumstances  that  produce 
in  a  Leyden  jar  the  tendency  of  the  jar  to  neu- 
tralize its  charges  by  overflowing.  (See  Appen- 
dix— Jar,  Leyden,  Overflow  of .) 

Flashing. — A  process  to  which  carbons 
are  subjected,  in  order  to  give  them  a  uniform 
electrical  resistance  throughout  their  entire 
length.  (See  Carbons,  Flashing  Process 
for.) 

Flat-Iron,  Electric An  electrically 

heated  flat-iron. 

A  hollow  flat-iron  provided  with  a  suitably 
placed  electric  heater.  (See  Heater,  Electric.) 

Floor  Contact. — (See  Appendix — Contact, 
Floor) 

Fluid,  Austral — A  term  formerly 

employed  for  the  magnetic  fluid  that  was 
supposed  to  exist  around  or  emanate  from 
the  austral  pole  of  a  magnet.  (See  Pole, 
Magnetic  Austral.) 

Fluid,  Boreal A  term  formerly 

employed  for  the  magnetic  fluid  that  was 
supposed  to  exist  around  or  emanate  from 
the  boreal  pole  of  a  magnet.  (See  Pole, 
Magnetic,  Boreal.) 

Fluid,  Electric An  assumed  fluid 

which  was  formerly  believed  to  be  the  cause 
of  electric  excitement. 

A  belief  in  electric  fluids  no  longer  exists  among 
intelligent  electricians. 

Fluid,  Magnetic A  term  formerly 

employed  for  an  assumed  fluid  which  was  be- 
lieved to  cause  magnetic  phenomena. 

The  belief  in  magnetic  fluids  no  longer  exists. 

Fluid,  Negative A  specific  fluid 

which  was  formerly  believed  by  the  advo- 
cates of  the  double-fluid  electric  hypothesis 
to  be  the  cause  of  negative  electric  excite- 
ment. (See  Appendix — Fluid,  Positive.) 

A  deficit  of  an  assumed  single  electric  fluid. 
(See  Electricity,  Single-Fluid  Hypothesis 
of.) 

Fluid,  Positive  — A  specific  fluid 

which  was  formerly  believed  by  the  adherents 


Flu.] 


608 


[Fra. 


of  the  double-fluid  electric  hypothesis  to  be 
the  cause  of  positive  electric  excitement. 

A  surplusage  of  an  assumed  single  electric 
fluid. 

According  to  the  views  of  the  single-fluid  elec- 
tric hypothesis,  positive  excitement  was  supposed 
to  be  due  to  the  surplusage  of  an  assumed  single 
electric  fluid,  the  negative  excitement  being  as- 
sumed to  be  due  to  its  deficit.  (See  Electricity, 
Single- Fluid  Hypothesis  of.) 

Flush-Key  Switch.  —  (See  Appendix  — 
Switch,  Flush-Key.) 

Force,  Electric,  Transformation  of 

— Producing  or  effecting  a  change  in  the 
value  of  the  electromotive  force  by  means  of 
an  induction  coil,  transformer  or  condenser, 
or  by  electric  resonance.  (See  Transformer?) 

Force,  Electromotive,  Alternating 

— An  electromotive  force  periodically  passing 
through  zero  between  positive  and  negative 
values.  (See  Current,  Alternating?) 

Force,  Electromotive,  Conversion  of 

— A  change  in  the  value  of  the  electromo- 
tive force  produced  by  means  of  an  induction 
coil,-  transformer  or  condenser,  or  by  electric 
resonance.  (See  Transformer?) 

Force,  Electromotive,  Impressed,  Pro- 
posed A.  I.  E.  E.  Definition  for The 

ratio  of  the  total  activity  in  an  electrically 
conducting  circuit  to  its  instantaneous  cur- 
rent strength. 

Force,  Electromotive,  Opposing . 

A  term  sometimes  employed  for  counter- 
electromotive  force.  (See  Force,  Electro- 
motive, Counter?) 

Force,  Electromotive,  Voltaic A 

term  sometimes  employed  for  the  electromo- 
tive force  generated  at  the  electrodes  of  an 
electrolytic  cell,  in  contradistinction  to  the 
counter-electromotive  force  produced  at  such 
electrodes  by  their  polarization. 

Force,  Field  of  -  — The  space  trav- 
ersed or  crossed  by  the  lines  of  electrostatic 
or  magnetic  force. 

An  electrostatic  field.  (See  Field,  Elec- 
trostatic^) 

A  magnetic  field.     (See  Field,  Magnetic?) 


Force,  Magne-Crystallic A  name 

proposed  by  Faraday  for  the  force  assumed  as 
the  cause  producing  the  change  in  the  nature 
of  the  magnetism  of  certain  crystalline  bodies 
in  different  directions.  (See  Action,  Magne- 
Crystallic?) 

Force,  Volta  Electromotive An 

electromotive  force  produced  by  means  of 
the  voltaic  cell.  (See  Cell,  Voltaic.) 

Forces,  Electromotive,  Complex-Har- 
monic Alternating The  electromo- 
tive forces  producing  complex  harmonic  alter- 
nating currents.  (See  Appendix — Currents, 
Complex-Harmonic.) 

Forge,  Electric A  forge  so  ar- 
ranged that  the  metals  to  be  subjected  to 
forging  can  be  electrically  heated  while  in 
place  on  the  forge. 

Formulae,  Blavier's The  formulas 

employed  for  computing  the  Blavier  test 
(See  Appendix — Test,  Blavier's?) 

Formulas. — Plural  of  formula. 

Four-Pole  Dynamo-Electric  Machine. — 

(See  Appendix — Machine,  Dynamo-Electric, 
Four-Pole?) 

Fourth  State  or  Condition  of  Matter. — 

(See  Appendix — Matter,  Fourth  State  or 
Condition  of.) 

Four- Way  Switch.  —  (See  Appendix — 
Switch,  Four-  Way.) 

Four-Wire  System.  —  (See  Appendix — 
System,  Four-  Wire?) 

Frame,  Dynamo  or  Motor A  term 

applied  to  the  iron  body  of  a  dynamo  or 
motor,  including  the  pole  pieces  and  stand- 
ards of  the  machine,  but  exclusive  of  the 
base  plates  and  bearings.  (See  Machine, 
Dynamo-Electric.  Motor,  Electric?) 

Frame,  Trolley  Base A  frame  for 

receiving  the  standard  which  supports  the 
trolley  pole. 

Franklinism. — A  word  sometimes  em- 
ployed for  franklinization. 

Franklinization  would  appear  to  be  the  prefer- 
able word.  (See  Franklinization.) 


Fre.] 


609 


[Gal. 


Free  or  Insulated. — (See  Appendix — Insu- 
lated or  Free.) 

Frequencies,  Harmonic Frequen- 
cies higher  than  the  fundamental,  present  in 
complex-harmonic  currents.  (See  Appen- 
dix— Currents,  Complex-Harmonic.) 

Frequencies,  Tesla A  term  em- 
ployed for  exceedingly  high  frequencies. 

The  frequencies  employed  by  Tesla  amounted 
to  many  hundreds  of  thousands  per  second. 

Frequency,     Fundamental  — The 

nominal  or  lowest  frequency  of  a  current 
which  has  harmonics. 

Frequency,  Yibration — A  term 

expressing  the  number  of  vibrations  per 
second. 

In  the  case  of  a  musical  note  the  vibration  fre- 
quency corresponds  to  the  pitch  of  the  note. 

Frog  Crossing. — (See  Appendix — Cross- 
ing Frog.) 

Frost  Alarm. — (See  Appendix — Alarm, 
Frost) 

Full  Contact. — (See  Appendix — Contact, 
Full) 

Full  Load. — (See  Appendix — Load,  Full.) 

Fundamental  Frequency. — (See  Appen- 
dix— Frequency,  Fundamental.) 

Fuse,  Blowing  of A  term  some- 
times employed  for  the  fusing  or  volatiliza- 


tion of  a  fuse  wire  or  safety  plug.  (See 
Fuse,  Safety.) 

Fuse,  Blowing  Point  of The  tem- 
perature or  the  current  strength  at  which  a 
fuse  blows  out  or  melts. 

The  exact  current  strength  at  which  a  fuse 
blows  out  or  melts  varies,  not  only  with  the  tem- 
perature of  the  wire,  but  also  with  the  position 
in  which  the  fuse  wire  is  placed  in  the  fuse  block, 
and  the  nature  of  the  block,  its  size,  whether  the 
current  is  direct  or  alternating,  etc. 

The  ratio,  which  should  exist  between  the  carry- 
ing capacity  of  a  fuse,  and  the  condition  of  its 
ultimate  fusing,  will  of  course  depend  on  the 
character  of  the  circuit  the  fuse  is  intended  t» 
guard.  With  small  currents,  such  for  example  as 
are  employed  in  electric  lighting,  a  narrow  margin 
may  be  employed  without  detriment,  but  in  the 
case  of  railway  systems,  however,  a  wider  range 
is  necessarily  given  to  the  blowing  point  of  the 
fuse,  for  the  amount  of  current  required  in  such 
systems,  near  heavy  grades,  is  so  much  in  com- 
parison to  what  is  ordinarily  employed  that  if 
too  narrow  a  limit  were  given  to  the  fusing  point 
considerable  annoyance  would  be  experienced 
from  the  fuse  blowing  out  too  frequently. 

Fuse,  Safety,  Carrying  Capacity  of  - 

— The  current  strength  a  fuse  wire  or  plug 
can  carry  without  the  line  it  protects  becom- 
ing dangerously  heated. 


g. — An  abbreviation  proposed  for  one 
gramme,  the  C.  G.  S.  unit  of  mass. 

g.  cm2. — An  abbreviation  proposed  for 
gramme  centimetre  squared,  the  C.  G.  S.  unit 
of  moment  of  inertia. 

Galvanic  Cell. —  (See  Appendix — Cell, 
Galvanic) 

Galvanic  Chain.— (See  Appendix— Chain, 
Galvanic.) 

Galvanic  Ring.— (See  Appendix— Ring, 
Galvanic.) 

Galvanist— One  skilled  in  the  "art  of 
galvanism."  (Obsolete.) 


The  word  has  no  precise  meaning,  since  the 
word  galvanism  is  employed  in  two  entirely  dif- 
ferent senses  ;  namely,  as  current  electricity  and 
as  a  particular  method  of  applying  electricity  to 
the  curing  of  diseases. 

Galvanoglyphy. — The  process  of  produc- 
ing an  electrotype. 

This  word,  though  good  etymologically,  is  un- 
necessary ;  moreover,  the  word  electrotype  is 
almost  universally  employed. 

Galvanography. — A  term  proposed  for 
the  copying  of  fine  engravings  on  copper  or 
steel  plates  by  means  of  electro-deposition. 

Galvano-Magnetic. — A  word  proposed  for 
electro-magnetic. 


Gal.] 


610 


[Gen. 


The  use  of  this  word  is  unwarranted  and  should 
not  be  encouraged. 

Galvanometer,  Angle  of  Maximum  Sensi- 
tiveness of  —  — The  angle  of  deflection  at 
which  a  given  small  alteration  in  the  strength 
of  the  current  produces  the  greatest  change 
in  the  deflection  of  the  needle. 

Galvanometer,  Direct    Beading  — 
A  galvanometer  in  which  the  absolute  value 
of  the   deflection  in  current  strength  is  ob- 
tained directly  without  the  use  of  tables  or 
curves. 

Galvanometer,     Helmholtz    -  —  A 

double-ring  tangent  galvanometer,  the  two 
ring  coils  of  which  are  parallel  to  each  other 
and  are  placed  on  opposite  sides  of  the  mag- 
netic needle  at  such  positions  that  their  mag- 
netic field  at  the  needle  may  be  as  nearly 
uniform  as  possible,  and  much  more  nearly 
uniform  than  a  single  coil  could  produce. 

Galvanometer,  Optical A  form  of 

galvanometer  proposed  by  Potier  based  on 
the  magnetic  rotary  power  of  liquids.  (See 
Refraction,  Double,  Electric?) 

Galvanometer,  Pocket A  galvan- 
ometer small  enough  to  be  readily  carried  in 
the  pocket. 

Galvanometer  Voltmeter. — (See  Appen- 
dix—  Voltmeter,  Galvanometer?) 

Galvanotonus. — A  term  proposed  by 
Pfliiger  for  the  state  of  tetanus  produced  in  a 
muscle  that  has  been  overstimulated  electri- 
cally. 

Galvanotropism. — Movements  produced 
in  living  organisms  by  the  passage  of  elec- 
tricity through  them. 

The  word  galvanotropism  has  been  proposed 
to  describe  such  phenomena  as  the  movements 
observed  in  the  roots  of  plants,  when  placed  be- 
tween two  opposite  electrodes.  The  direction  of 
these  movements  seems  to  be  such  as  would  place 
the  longer  axis  of  the  root  in  the  direction  of  the 
plane  of  the  current. 

Gap,  Air,  Shunting An  air  gap  in 

a  circuit  placed  around  a  galvanometer  or 
other  instrument  for  the  purpose  of  affording 
protection  to  the  galvanometer  or  other  instru- 
ment from  the  effects  of  powerful  disruptive 
discharges. 


The  inductive  resistance  of  the  coil  to  the 
rapidly  varying  oscillatory  discharges  is  so  great 
that  the  discharges  take  instead  a  path  through 
an  air  gap.  Since  such  an  air  gap  thus  shunts  the 
discharge  from  the  galvanometer  or  other  coils,  it 
is  called  a  shunting  air  gap. 

Gas  Cell.— (See  Appendix— Cell,  Gas.) 

Gas  Polarization. — (See  Appendix — Po- 
larization, Gas.)  • 

Gauge,  Electric  Pocket A  gauge 

for  an  electric  battery  or  other  similar  source 
small  enough  to  be  readily  carried  in  the 
pocket. 

Gauge,  Electroscopic A  term  ap- 
plied by  Gaugain  to  a  form  of  discharging 
gold-leaf  electroscope.  (See  Electroscope, 
Gold-Leaf.) 

Gauss,  Proposed  A.  I.  E.  E.  Definition  for 

A  practical  unit  of  magnetic  intensity* 

the  value  of  which  is  equal  to  one  C.  G.  S. 
unit ;  that  is,  one  C.  G.  S.  line  per  square 
centimetre. 

This  unit  is  a  modification  of  that  proposed  by 
a  Sub-Committee  of  the  American  Institute  of 
Electrical  Engineers  on  the  Provisional  Pro- 
gramme for  the  International  Electrical  Con- 
gress, held  in  Chicago,  1893,  on  the  occasion  of 
the  World's  Columbian  Exposition. 

Generator,  Chemical,  of  Electricity 

— A  term  sometimes  employed  in  place  of  a 
voltaic  pile  or  battery. 

This  use  of  the  term  generator  is  sanctioned  by 
the  similar  use  of  the  word  in  other  connections. 
Of  course  it  will  be  understood  that  it  is  difference 
of  potential  and  not  electricity  that  is  generated. 

Generator,  Di phase A  generator 

which  delivers  two-phase  or  diphase  currents. 

Generator,  High-Voltage  Electro-Mag- 
netic   An  electro-magnetic  generator 

arranged  so  as  to  give  a  high  electromotive 
force. 

Generator,  Polyphase  -  — A  gener- 
ator which  delivers  more  than  single-phase 
currents. 

The  term  polyphase  is  frequently  employed 
only  in  the  sense  of  greater  than  diphase. 

Generator,   Railway A  dynamo- 


Gen.] 


611 


[Gro. 


electric  machine  which  develops  the  current 
employed  in  systems  of  electric  railways. 

Generator,  Self-Compounding  Polyphase 

— A   polyphase  generator  whose  field 

magnets  are  compound-wound. 

Generator,    Thermo-Electric A 

term  sometimes  employed  for  a  thermo-elec- 
tric pile.  (See  Pile,  Thermo-Electric^) 

The  term  is  equally  applicable  to  the  pyro- 
magnetic  generator. 

Generator,  Three-Phase A  tri- 

phase  generator.  (See  Appendix — Gener- 
ator, Tri-Phase^ 

The  term  tri-phase  generator  would  appear  to 
be  preferable. 

Generator,  Tri-Phase A  generator 

which  delivers  three-phase  or  tri-phase  cur- 
rents. 

Generator,  Two-Phase A  di-phase 

generator.  (See  Appendix — Generator,  Di- 
Phase.} 

The  term  di-phase  generator  would  appear  to 
be  preferable. 

Gilbert. — A  term  proposed  for  the  prac- 
tical unit  of  magneto-motive  force. 

A  unit  of  magneto-motive  force  having 
the  value  of  the  absolute  unit  or  equal  to 

—  ampere-turn. 
4* 

This  unit  is  a  modification  of  that  proposed  by 
a  Sub-Committee  of  the  American  Institute  of 
Electrical  Engineers  on  Provisional  Programme 
for  the  International  Electrical  Congress,  held 
in  Chicago,  in  1893. 

Gilding,  Electro Electric  gilding. 

Electro-plating  with  gold.  (See  Gilding, 
Electric^ 

Glass  Screw  Insulator. — (See  Appendix — 
Insulator,  Glass-Screw.) 

Globes,  Diffusing,  for  Electric  Lights. 

Globes  so  constructed  as  to  insure 

a  diffusion  of  the  light. 

The  diffusion  is  generally  obtained  by  means 
of  ground  glass.  In  order  to  avoid  the  loss  of 
light  that  attends  the  use  of  ground  glass,  diffusion 
globes  have  been  made  of  clear  glass  furnished 
with  a  number  of  refraction  or  total  internal  re- 


flecting lenses,  in  the  manner  of  the  well-known 
Fresnel  lens. 

Glory,  Aurora A  term  proposed 

by  Nordenskjb'ld  for  an  almost  constant 
crown  of  light,  single,  double  or  multiple, 
which  occupies  a  nearly  fixed  position  in  the 
heavens. 

Nordenskjold  describes  the  aurora  glory  as  fol- 
lows: 

"  Our  globe,  even  during  a  minimum  aurora 
year,  is  adorned  with  an  almost  constant  crown 
of  light,  single,  double,  or  multiple,  whose  inner 
edge  was  usually,  during  the  winter  of  1878-79, 
at  a  height  of  about  0.03  of  the  radius  of  the 
earth  (120  miles)  above  its  surface,  whose  surface 
was  somewhat  under  the  earth's  surface,  having 
its  centre  a  little  north  of  the  magnetic  pole,  and 
which,  with  a  diameter  of  about  0.32  radius  of 
the  earth  (about  1,280  miles),  extends  in  a  plane 
perpendicular  to  the  earth's  radius  which  passes 
through  the  centre  of  this  luminous  ring. " 

Glow,  Fire A  term   employed   by 

the  ancients  for  an  aurora.  (See  Aurora 
Borealis.  Aurora  Australis.) 

Glow  Illumination.  —  (See  Appendix — 
Illumination,  Glow?) 

Glow    Lamp. — (See    Appendix  —  Lamp, 

Glow.) 

Glowing  of  Electric  Conductor. — (See 
Appendix — Conductor,  Electric,  Glowing  of.) 

Glue-Pot,  Electric An  electrically 

heated  glue-pot. 

An  electric  heater  is  applied  to  a  glue-pot  of 
ordinary  construction.  (See  Heater,  Electric,} 

Gnomon,  Electric A  term  formerly 

applied  to  a  variety  of  pith  ball  electrometer. 

Good  Earth. — (See  Appendix  —  Earth, 
Good.) 

Ground  Coil. —  (See  Appendix  —  Coil, 
Ground?) 

Ground,  Dead A  term  sometimes 

applied  to  a  fault  or  interruption  in  a  tele- 
graphic line  in  which  the  escape  to  earth  or 
ground  is  so  great  that  it  is  impossible  to 
operate  the  line. 

Dead  earth.     (See  Earth,  Dead  or  Total.) 

Grounding. — A  word  sometimes  employed 


Gro.] 


612 


[Ear. 


n  electro-metallurgy  for  a  preparatory  pro- 
cess in  burnishing.  (See  Appendix— Bur- 
nishing^) 

Grouping  System  for  Electric  Light 
Leads. — (See  Appendix — Leads,  Grouping 
System  for  Electric  Light?) 

Guard,  Automatic,  for  Series-Connected 

Incandescent  Lamps A  device  placed 

on  each  series-connected  incandescent  elec- 
tric lamp  for  the  purpose  of  short  circuiting 


the  holder  should  the  lamp  filament  break, 
A  film  cut-out.     (See  Cut-Out,  Film?) 
An  automatic  guard  may  consist  of  a  sheet  of 

paraffine    paper    placed    between   two  metallic 

knobs. 

Gyroscope,   Electro-Magnetic A 

gyroscope  driven  by  an  electro-magnet. 

Gyrostatic  Action  of  Dynamos  on  Ship- 
board.— (See  Appendix — Action,  Gyrostatr'c, 
of  Dynamos  on  Shipboard?) 


H. — A  symbol  used  for  field  intensity. 

F 
The  defining  equation  is  H  =  — 

Here  F  =  the  force  and  m  the  strength  of  the 
pole. 

H. — An  abbreviation  proposed  for  henry, 
the  practical  unit  of  mutual  induction,  self- 
induction,  or  inductance. 

This  abbreviation  is  seldom  used. 

h. — An  abbreviation  for  hour,  one  of  the 
practical  units  of  time. 

3C. — A  symbol  proposed  for  magnetizing 
force. 

The  defining  equation  is  3C  =  4  *  N  \ 

\j 

Where  N,  is  the  number  of  windings,  and  L, 
the  length  of  the  solenoid  generating  the  mag- 
netizing force. 

HP  or  H* — A  contraction  for  horse-power. 
This  contraction  is  universally  employed  in  all 
English-speaking  countries. 

Harmonic  Frequencies. — (See  Appendix 
— Frequencies,  Harmonic?) 

Harmonic  Motion. — (See  Appendix — Mo- 
tion, Harmonic?) 

Harmonic  Telegraph. — (See  Appendix — 
Telegraph,  Harmonic?) 

Harmonics,  Electrical A  term 

sometimes  employed  in  place  of  the  upper 
harmonic  currents  generally.  (See  Appen- 
dix— Currents,  Complex-Harmonic?) 

Harmonics  of  Current. — (See  Appendix — 
Current,  Harmonics  of?) 


Harmonics,  Weeding-Out  of Get- 
ting rid  of,  or  removing  some  or  all  of  the 
upper  harmonic  currents  from  a  funda- 
mental harmonic  current. 

The  weeding-out  process  is  generally  effected 
by  means  of  electric  resonance.  The  presence  of 
self-induction  or  capacity  in  the  circuit  has  the 
same  effect.  It  is  partly  on  this  account  that  we 
cannot  yet  speak  across  the  Atlantic  cable,  the 
upper  harmonics  of  the  voice  being  weeded  out 
more  than  the  lower  and  made  to  lag  more. 
(See  Appendix — Harmonics,  Weeding.  Out  oj ',  by 
Electrical  Resonance.) 

Harmonics,  Weeding-Ont  of,  by  Electri- 
cal Resonance The  weeding-out  of 

the  upper  harmonics  of  a  complex-harmonic 
current  by  altering  the  natural  period  of  the 
system  until  it  is  in  unison  or  in  resonance 
with  the  fundamental  harmonic. 

"A  resonant  circuit,"  says  Pupin,  "behaves 
towards  a  complex-harmonic  electromotive  force 
just  the  same  as  an  acoustic  resonator  toward  a 
source  of  complex  sound.  It  brings  out  prom- 
inently that  harmonic  with  which  it  is  in  reso- 
nance. To  express  this  numerically,  say  that 
the  ratio  of  the  amplitude  of  the  fundamental  har- 
monic electromotive  force  to  that  of  the  next 
higher  harmonic  (supposing  it  to  be  even  no 
higher  than  an  octave)  is  2  to  I.  Then  the  cir- 
cuit can  be  easily  brought  into  resonance  with 
the  fundamental  harmonic  in  such  a  way  as  to 
increase  the  ratio  of  the  amplitudes  of  the  cor- 
responding simple  harmonic  currents  60  :  i .  The- 
oretically (and  to  a  great  extent  practically  also) 
that  ratio  can  be  made  anything  we  please  by  in- 
creasing continually  the  coefficient  of  self-indue- 


Har.J 


613 


[Her. 


tion  and  diminishing  the  capacity  without  de- 
stroying the  resonance.  In  other  words,  we  can, 
by  the  proper  single  tuning,  weed  out  the  upper 
harmonics  as  much  as  we  please.  But,  as  will  be 
indicated  later  on,  it  is  flot  always  advisable  to 
avail  ourselves  too  much  of  a  means  of  weeding 
out  the  upper  harmonics  by  using  very  large  self- 
induction.  The  best  method  of  tuning  depends 
on  the  nature  of  the  problem  before  us." 

Harpoon,  Electric A  harpoon  con- 
taining a  bomb,  that  is  electrically  fired  or 
exploded  by  the  harpooner  after  imbedding 
the  harpoon. 

Heat,  Electrical  Equivalent  of A 

quantity  representing  the  electrical  energy 
produced  by  the  action  of  a  given  amount  or 
quantity  of  heat  energy. 

Heater,  Coil,  Electric An  electric 

heater  in  which 
the  heat  is  pro- 
duced by  the  pas- 
sage of  an  electric 
current  through  a 
coiled  metallic  rib- 
bon. 

A  form  of  coil 
heater  is  shown  in 
Fig-  573- 

Heater,  Pri- 
mary Electric 

A       term 

proposed  for  the 
main  electric  heat- 
er in  a  building. 
(See  Heater,  Elec- 
tric) 

Heeling  Error 


573-    G>M Heater. 


of  Mariner's   Compass. — (See   Appendix — 
Error,  Heeling,  of  Mariner's  Compass. 

Helix. — A  word  sometimes  used  in  elec- 
tricity and  magnetism  in  place  of  coil  or  sole- 
noid. (See  Coil,  Electric?) 

Helix,    Anomalous   — A   helix  so 

wound  as  to  produce  an  anomalous  magnet. 
(See  Magnet,  Anomalous) 

Helix,  Left-Handed A  term  some- 
times employed  in  place  of  a  left-handed 


solenoid.  (See  Solenoid,  Left-Handed. 
Solenoid,  Practical) 

Helix,  Magnetic A  coil  that  is 

rendered  magnetic  by  the  passage  through  it 
of  an  electric  current.  (See  Coil,  Electric) 

Helix,  Magnetizing A  magnetiz- 
ing coil.  (See  Coil,  Electric) 

Helix,  Right-Handed  — A  term 

sometimes  employed  in  place  of  right-handed 
solenoid.  (See  Solenoid,  Right-Handed. 
Solenoid,  Practical) 

Helmholtz  Galvanometer. — (See  Appen- 
dix— Galvanometer,  Helmholtz) 

Henry,  International The  value 

of  the  international  henry  adopted  by  the 
Chicago  Congress  of  1893,  as  equal  to  the 
induction  in  a  circuit  when  the  electromotive 
force  induced  in  this  circuit  is  one  interna- 
tional volt,  while  the  inducing  current  varies 
at  the  rate  of  one  ampere  per  second. 

Henry,  Proposed  A.  I.  E.  E.  Definition 

for The  name  adopted  by  the  Elec- 
trical Congress  of  1 893  for  the  practical  unit 
of  inductance. 

A  unit  of  inductance  having  the  value  of 
io9  absolute  units,  or  nearly  the  length  of  an 
earth's  quadrant. 

This  name  was  proposed  by  a  Sub-Committee 
of  the  American  Institute  of  Electrical  Engineers 
on  Provisional  Programme  of  the  International 
Electrical  Congress,  in  Chicago,  1893,  on  the  occa- 
sion of  the  World's  Columbian  Exposition. 

This  name  was  adopted  by  the  said  Inter- 
national Electrical  Congress  in  August,  1893,  with 
the.  following  definition : 

A  henry  is  the  induction  in  a  circuit  when  the 
electromotive  force  induced  in  this  circuit  is  one 
international  volt,  while  the  inducing  current 
varies  at  the  rate  of  one  international  ampere  per 
second. 

Heptad  Atom. — (See  Appendix — Atom, 
Heptad) 

Hertz's  Axial  Oscillator. — (See  Appen- 
dix— Oscillator,  Hertz  s  Axial) 

Hertz's  Linear  Oscillator. — (See  Appen- 
dix— Oscillator,  Hertz's  Linear) 

Hertz's  Oscillator. — (See  Appendix— < 
Oscillator,  Hertz's) 


Her,] 


614 


[Idl. 


Hertzian  Waves. — (See  Appendix — 
Waves,  Hertzian.} 

Heterostatic  Electrometer. — (See  Appen- 
dix— Electrometer,  Heterostatic!) 

Hexad  Atom.  —  (See  Appendix — Atom, 
Hexad!) 

High-Frequency  Transformer. — (See  Ap- 
pendix—  Transformer,  High-Frequency!) 

High- foliage  Electro-Magnetic  Gener- 
ator.— (See  Appendix — Generator,  High- 
Voltage  Electro-Magnetic!) 

Home  Battery. — (See  Appendix— Battery, 
Home!) 

Hook,  Dipping A  metallic  hook 

provided  for  holding  articles  that  are  to  be 
cleansed,  in  order  to  prepare  them  for  electro- 
plating by  subjecting  them  to  the  dipping 
process.  (See  Dipping!) 

The  dipping  hook  should  be  made  of  metal  as 
nearly  resembling  the  article  to  be  plated  as  pos- 
sible, so  as  thereby  to  prevent  voltaic  action  tak- 
ing place  between  the  two  metals  with  a  conse- 
quent marking  at  the  points  of  contact. 

Horizontal  Intensity  of  Earth's  Magnet- 
ism.—  (See  Appendix — Magnetism,  Hori- 
zontal Intensity  of  Earth's!) 

Horology,  Electric That  branch  of 

electric  science  which  treats  of  the  applica- 
tions of  electricity  to  the  regulation  or  opera- 
tion of  clocks.  (See  Clock,  Electric!) 

Hummer. — A  word  sometimes  employed 
in  place  of  buzzer.  (See  Buzzer,  Electric!) 

If  inn  in  cr,  Electric A  term  some- 
times used  for  electric  buzzer. 


Hunting  of  Parallel  Alternators.— (See 

Appendix — Alternators,  Parallel,  Hunting 
of-) 

Hysteresis,  Dielectric A  term  pro- 
posed by  Steinmetz  for  a  variety  of  molecular 
friction,  analogous  to  magnetic  hysteresis,  pro- 
duced in  a  dielectric  under  changes  of  electro- 
static stress. 

The  losses  caused  by  dielectric  hysteresis  are 
probably  proportional  to  the  frequency  and  to  the 
square  of  the  E.  M.  F.,  i.  e,,  to  the  electrostatic 
field  intensity. 

Losses  ascribed  to  defective  insulation  are  often, 
in  the  opinion  of  Steinmetz,  caused,  at  least  in  part, 
by  dielectric  hysteresis. 

Hysteresis,  Magnetic A  variety  of 

molecular  friction  produced  in  the  molecules 
of  a  magnetizable  substance  during  changes 
of  magnetic  stress. 

According  to  Steinmetz,  the  loss  occasioned  by 
magnetic  hysteresis  is  proportional  to  the  fre- 
quency and  to  the  1. 6th  power  of  the  magnetic 
variation. 

According  to  Steinmetz,  for  a  magnetic  cycle 
performed  between  the  limits  of  magnetic  induc- 
tion Bx  and  B»,  the  loss  in  ergs  per  cubic  cm.  is 

,1.6 


•—(B*7Bf)1 


where  n,  the  coefficient  of  hysteresis,  averages 
.0033  in  average  good  sheet  iron,  .013  in  cast 
iron,  .003  to  .03  in  cast  steel,  and  reaches  as  high 
as  .08  in  hardened  steel. 

With  alternating  magnetism  the  formula  can 
be  written 

L=nB1'6 

The  actual  existence  of  magnetic  hysteresis  is 
denied  by  some  able  electricians. 


7. — A  symbol 
current. 


proposed    for  intensity  of 


E 


The  defining  equation  is  I  =  =r- 

3 A  symbol  used  in  France  and 

Germany  for  intensity  of  magnetization. 

_m 

The  defining  equation  is  c) y— 


Idiostatic  Electrometer. — (See  Appendix 
— Electrometer,  Idiostatic!) 

Idle  Wire  of  Armature. — (See  Appendix 
—  Wire,  Idle,  of  Armature!) 

Idle  Wire  of  Armature  of  Motor.— (See 
Wire,  Idle,  of  Armature  of  Motor!) 

Idle  Wire  of  Dynamo.— (See  Appendix— 
Wire,  Idle,  of  Armature  of  Dynamo!) 


IdL] 


615 


[Ind. 


Idle  Wire  of  Motor.— (See  Appendix — 
Wire,  Idle,  of  Armature  of  Motor.) 

Illumination,  Cosine  Law  of The 

intensity  of  the  illumination  emitted  from  or 
received  by  any  element  of  surface  is  propor- 
tional to  the  cosine  of  the  angle  between  its 
normal,  and  the  direction  of  the  radiation. 

Illumination,  Glow A  term  pro- 
posed for  an  illumination  similar  to  that  of 
the  glow-worm  ;  that  is,  illumination  without 
sensible  heat. 

All  artificial  sources  of  light,  such,  for  example, 
as  a  coal-oil  lamp,  a  gas  jet,  an  incandescent  elec- 
tric lamp,  or  an  arc  lamp,  contain  a  much  greater 
percentage  of  non-luminous  than  of  luminous 
radiation,  that  is,  of  heat  than  light,  being  at  the 
most  a  few  per  cent,  of  light,  and  considerably 
over  95  per  cent,  of  heat. 

The  most  economical  artificial  lighting  is,  of 
course,  impossible  under  these  circumstances. 

In  the  light  emitted  by  a  firefly  or  a  glow 
worm,    practically  all  the   radiation  consists  of. 
light  or  radiation  within  the  limits  of  visibility. 

The  term  glow  illumination  has  been  proposed 
for  illumination  by  light  such  as  is  furnished  by  a 
firefly  or  glow-worm;  viz.,  for  the  light  emitted 
by  any  source  which  is  capable  of  producing 
luminous  radiation  only.  In  some  forms  of  Tesla 
lamps  the  illumination  closely  approaches  glow 
illumination. 

Immediate  False  Zero. — (See  Appendix 
— Zero,  Immediate  False.) 
Incandescent    Bombardment    Lamp. — 

(See  Appendix — Lamp,  Incandescent  Bom- 
bardment.) 

Incandescent  Filament. — (See  Appendix 
— Filament,  Incandescent^) 

Incandescent  Lamp  Cord. — (See  Appen- 
dix— Cord,  Incandescent  Lamp.) 

Incandescent  Lighting  Dynamo-Electric 
Machine. — (See  Appendix — Machine,  Dy- 
namo-Electric, Incandescent  Lighting.) 

Incandescing  Filament. — (See  Appendix 
— Filament,  Incandescing.) 

Inclination  Magnetometer. — (See  Appen- 
dix— Magnetometer,  Inclination) 

Indicator,  Disc,  Mechanical  Replacement 

Of Such  a  replacement  or  resetting  of 


a  disc,  arm,  shutter  or  semaphore  of  an  indi- 
cator as  must  be  done  by  hand. 

A  non-automatic  replacement  of  an  indi- 
cator disc. 

Indicator,  Fall-Back A  term  some- 
times employed  in  place  of  drop  indicator. 

Indicator,    Light,   of  Railroad    Signal 

A  device  by  means  of  which  an  indi- 
cation is  given  as  to  whether  a  signal  lamp  is 
lighted  or  not. 

The  light  indicator  is  operated  by  means  of  a 
metallic  bar,  which  increases  in  length  by  means 
of  the  heat  of  the  lamp  when  lighted. 

Indicator,  Polarized A  term  some- 
times employed  for  an  indicator  provided 
with  a  polarized  armature. 

Indicator,  Pole An  apparatus  em- 
ployed for  readily  determining  whether  the 
poles  of  a  dynamo  battery  or  other  source 
are  positive  or  negative. 

A  convenient  form  of  pole  indicator  consists  of 
a  small  electrolytic  cell  filled  with  a  solution  of  a 
metallic  salt.  On  the  passage  of  the  current 
through  the  electrolyte  the  character  of  the  poles 
is  readily  determined  by  the  change  in  color  of 
the  liquid  adjacent  to  one  pole  of  the  indicator. 

There  are  other  well-known  forms  of  pole  in- 
dicators. 

Indicator,  Tele A  term  sometimes 

employed  in  place  of  telemeter.  (See  Telem- 
eter) 

Indicator,  Telephone An  indi- 
cator employed  on  a  telephone  circuit  to  indi- 
cate the  number  of  the  correspondent  calling. 
(See  Indicator,  Electric) 

A  telephone  indicator,  as  generally  constructed, 
consists  of  some  form  of  mechanical  drop  oper- 
ated by  the  attraction  of  the  armature  of  an 
electro-magnet  which,  permitting  the  fall  of  a 
drop  or  shutter,  exposes  the  particular  number  of 
the  correspondent  calling. 

Indicator,  Tri-Polar—  — An  electro- 
magnetic indicator,  with  three  poles. 

A  straight- bar  magnet  is  employed,  one  end  of 
which  forms  one  pole  and  the  other  end  is  con- 
nected with  a  U-shaped  piece  of  soft  iron,  so  as 
to  bring  the  two  free  ends  of  the  latter  up  to  the 


Ind.] 


616 


[Ind. 


line  on  the  other  pole.     There  are  thus  produced 
three  poles;  hence,  the  name,  tri-polar. 

Indifferent  Point— (See  Appendix — 
Point,  Indifferent?) 

Individual  Signal.  —  (See  Appendix  — 
Signal,  Individual!) 

Individual  Signaling  Apparatus.— (See 
Appendix — Apparatus,  Individual  Signal- 
ing. 

Induced  Electric  Surgings.— (See  Appen- 
dix— Surgings,  Induced  Electric!) 

Induced  Single-Needle  Dial.— (See  Ap- 
pendix— Dial,  Induced  Single-Needle!) 

Inductance,  Mutual,  Proposed  A.  I.  E.  E. 
Definition  for The  mutual  induc- 
tance of  one  electric  circuit  upon  another  is 
the  ratio  of  the  total  magnetic  induction 
linked  with  the  second,  due  to  a  uniform  cur- 
rent in  the  first,  to  the  strength  of  that 
current. 

The  mutual  inductance  between  two  electric 
circuits  is  reciprocally  equal  when  the  environ- 
ing medium  has  constant  inductivity. 

The  C.  G.  S.  unit  of  mutual  inductance  is  one 
centimetre;  the  practical  unit  of  self-inductance 
is  one  henry. 

The  following  modification  of  the  definition 
would  appear  to  be  preferable,  viz.  :  the  mutual 
inductance  of  one  circuit  on  another  is  the  ratio 
of  the  sum  of  the  linkages  of  lines  of  magnetic 
induction  with  the  second,  due  to  a  uniform  cur- 
rent in  the  first,  to  the  strength  of  that  current. 

Inductance,  Non-Ferric A  term 

proposed  to  distinguish  an  inductance  in 
which  no  iron  or  magnetic  metal  enters. 

A  coil  of  copper  forms  a  non-ferric  inductance  ; 
the  insertion  of  an  iron  core  into  the  coil  makes 
it  become  a  ferric  inductance. 

Inductance,  Self,  Proposed  A.  I.  E.  E. 

Definition  for The  ratio  of  the  total 

magnetic  induction,  linked  with  and  estab- 
lished by  an  electric  current,  to  the  uniform 
strength  of  the  same. 

The  inductance  of  a  conducting  circuit  is  con- 
stant when  its  environing  medium  has  constant 
inductivity.  A  modification  has  been  proposed 
for  this  definition  similar  to  that  proposed  for 
mutual  inductance. 


Inductance,  Specific A  term  pro- 
posed for  the  comparative  value  of  induc- 
tance. (See  Inductance,') 

Inductance  Speed.  —  (See  Appendix  — 
Speed,  Inductance!) 

Inducteous  Body. — (See  Appendix — Body, 
Inducteous!) 

Induction,  Auto A  term  sometimes 

employed  instead  of  self-induction.  (See  In- 
duction, Self.) 

Induction,  Backward,  of  Dynamo  Arma- 
ture   The  component  of  the  armature 

magnetization  opposing  the  magnetization  of 
the  field  magnets.  (See  Appendix — Induc- 
tion, Cross,  of  Dynamo  Armature.) 

Were  there  no  forward  lead  given  to  the 
brushes,  there  would  be  no  back  induction  ;  there 
would,  however,  be  cross  induction. 

Induction,  Cross,  of  Dynamo  Armature 

A  term  sometimes  employed  in  place 

•  of  the  induction  produced  in  the  armature  of 
a  dynamo-electric  machine  from  the  ampere 
turns  acting  across  the  main  magnetic  cir- 
cuit, /'.  e.,  those  due  to  the  ^current  in  the 
armature,  and  is  the  lead  of  the  brushes 
tending  to  produce  magnetic  poles  crosswise 
to  the  regular  poles  of  the  machine. 

Induction,  Magne-Electric A  term 

formerly  employed  for  magneto-electric  in- 
duction. (See  Induction,  Magneto-Electric!) 

Induction,  Magnetic,  Terrestrial 

The  production  of  magnetism  by  the  action 
of  the  earth's  magnetic  field. 

Induction  Motor. — (See  Appendix — Mo- 
tor, Induction!) 

Induction  Telegraph. — (See  Appendix— 
Telegraph,  Induction!) 

Indnctivity.— A  word  proposed  for  spe- 
cific inductance.  (See  Appendix — Induct- 
ance, Specific!) 

Inductivity,  Proposed  A.  I.  E.  E.  for 

The  inductivity  at  any  point  in  an 

isotropic  medium  is  the  ratio  added  to  unity 
of  4  n  times  the  intensity  of  the  magnetiza- 
tion there  existing  to  the  magnetizing  flux 
density. 


Ind.J 


617 


[Int. 


The  ratio  of  the  flux  density  to  the  mag- 
netizing force. 

The  conventional  symbol  is  fi  and  it  is  synony- 
mous with  permeability. 

Inductric  Body.— (See  Appendix — Body, 
Inductric.) 

influence,  Electrostatic A  word 

sometimes  employed  in  place  of  electro- 
static induction.  (See  Induction,  Electro- 
static.) 

There  would  appear  to  be  no  real  necessity 
for  the  abandonment  of  the  term  induction  for 
the  effects  produced  by  an  electrostatic  field. 
The  general  similarity  of  the  phenomena  would, 
indeed,  appear  to  render  it  advisable  to  retain 
the  word  electrostatic  induction,  to  show  its  close 
relation  to  electro-magnetic  induction. 

In-Put. — The  energy  absorbed  by  a  ma- 
chine in  driving  it  or  causing  it  to  perform  a 
certain  amount  of  work. 

This  word  is  used  in  contradistinction  to  out- 
put. 

Inside  Box  Brush. — (See  Appendix — 
Brush,  Inside  Box.) 

Instrument,  S.  N.,  Telegraphic A 

contraction  employed  for  single-needle  tele- 
graphic instrument. 

Insulated  or  Free A  term  em- 
ployed in  telegraphy. 

A  wire  is  said  to  be  free  insulated  when  it  is 
disconnected  from  its  apparatus  and  left  insu- 
lated. 

Insulation,  Kilometric,  of  Cable 

The  insulation  of  a  cable  measured  in  kilo- 
metre-megohms or  the  average  insulation  of 
one  kilometre  in  megohms. 

Insulation  Lightning  Protection. — (See 
Appendix — Protection,  Insulation  Light" 
ning.) 

Insulation  Lightning  Protector. — (See 
Appendix — Protector,  Insulation  Light- 
ning.) 

Insulator,  Glass-Screw A  glass  in- 
sulator provided  with  a  screw  thread  inside 
the  glass  for  the  purpose  of  ready  attach- 
ment to  the  insulator  pin. 

Insulator,  Shackle A  term  some- 

tfmes  employed  for  any  form  of  shackle  in- 


sulator.      (See    Insulator,    Single- Shackle. 
Insulator,  Double-Shackle.) 

Insulator,  Tree A  variety  of  insu- 
lator suitable  for  attachment  to  trees,  and 
designed  so  as  to  keep  the  conductor  from 
being  brought  into  contact  with  the  branches. 

The  insulator  -proper  is  mounted  on  a  shaft 
which  plays  in  a  ball  and  socket  joint,  the  cup 
of  which  is  fastened  to  the  tree  ;  the  line  is  there- 
fore kept  in  its  normal  position  despite  the  move- 
ments of  the  tree. 

In-Take. — A  word  sometimes  used  in  place 
of  In-Put. 

Intensity  of  Radiation. — (See  Appendix— 
Radiation,  Intensity  of.) 

Interference,  Acoustic Interfer- 
ence of  sound  waves. 

The  term  acoustic  interference  is  employed  in 
contradistinction  to  luminous  interference. 


Interference,  Electro-Magnetic 


—A 


term  sometimes  employed  for  the  interference 
of  electro-magnetic  waves. 

The  term  electro-magnetic  interference  is  em- 
ployed in  contradistinction  to  acoustic  or  lumi- 
nous interference,  even  though  it  be  granted  that 
luminous  waves  are  electro -magnetic  waves. 

Interference,  Luminous A  term 

sometimes  employed  for  the  interference  of 
light  waves. 

The  term  luminous  interference  is  used  in 
contradistinction  to  acoustic  or  electric  inter- 
ference. 

Internal  Magnetic  Circuit. — (See  Ap- 
pendix— Circuit,  Magnetic,  Internal.) 

Internal  Magnetic  Field. — (See  Appen- 
dix— Field,  Magnetic,  Internal.) 

International  Ampdre.— (See  Appendix 
— Ampere,  International?) 

International  Coulomb. — (See  Appendix 
— Coulomb,  International?) 

International  Farad.— (See  Appendix— 
Farad,  International?) 

International  Henry. — (See  Appendix— 
Ifenry,  International.) 

International  Joule. — (See  Appendix— 
Joule,  International?) 


Int.] 


618 


[Int. 


International  Morse  Code.— (See  Appen- 
dix— Code,  International  Morse?) 

International  Ohm.— (See  Appendix— 
Ohm,  International?) 

International  Volt— (See  Appendix— 
Volt,  International?) 

International  Watt— (See  Appendix— 
Watt,  International?) 

Interrupter,  Electro-Dynamic A 

name  proposed  by  Pupin  for  an  interrupter  for 
the  primary  circuit  of  an  induction  coil  con- 
sisting of  an  elastic  wire  stretched  like  the 
wire  of  a  sonometer  or  monochord  between 
the  poles  of  a  permanent  horseshoe  magnet. 

The  term  sonometer  interrupter  might,  per- 
haps, be  more  descriptive  of  the  apparatus  em- 
ployed. 

The  circuit  connections  are  such  that  when  the 
wire  is  set  into  vibration  these  vibrations  are  con- 
tinued under  the  action  of  the  field  produced  by 
the  magnet.  The  construction  and  operation  of 
an  electro-dynamic  interrupter  are  given  by  its 
inventor,  Pupin,  as  follows : 

"In  the  meantime  experience  suggested  the 
form  given  in  Fig.  574  as  best  suited  to  the  pur- 
pose for  which  the  interrupter  was  first  de- 
signed. The  diagram  of  Fig.  575  explains  the 


Fig.  574- 


A      /h 


Fig.  ^re- 

construction of  the  apparatus  more  clearly.  A 
stout  aluminium,  or  phosphor-bronze  wire,  the 
vibrator,  is  stretched  between  the  pole  pieces  d 
and  e,  of  two  permanent  Weston  magnets,  such 
as  this  distinguished  electrician  uses  in  his 
voltmeters. 


"  Fig-  576  £*ves  the  fr°nt  ^ew  °*  one  of  the 
magnets.  The  cross-section  of  the  vibrator  is 
seen  therebetween  the  pole  pieces  N,  S,  as  a  black 
dot.  The  short  line  a  b  extending  from  the  vi- 
brator to  the  mercury  cup  below  is  the  dipper,  a 
short,  thin,  amalgamated  copper  wire,  which  is 
soldered  to  the  vibrator.  The  vibrator  rests  on 


two  hard-rubber  bridges  f  g.  One  of  its  ends  is 
rigidly  attached  to  the  wooden  frame  of  the 
apparatus,  the  other  end  is  attached  to  a  lever  h, 
which,  worked  by  a  micrometer  screw,  varies 
the  tension  of  the  vibrator. 
There  are  three  mercury 
cups,  a,  b,  c,  and  three 
dippers  (which  unfortun- 
ately do  not  appear  in  Fig. 
574).  The  middle  cup  b,  is  I 
fixed  in  position,  and  the 
middle  dipper,  being  at  the 
nodal  point  of  the  vibrator, 
makes  a  permanent  contact 
there.  The  other  two  dippers  make  contact  with 
mercury  cups  which  can  be  raised  or  lowered  by 
means  of  a  nut  and  screw  as  represented  in  Fig. 
574,  and  indicated  in  diagram  575.  The  con- 
struction of  the  adjustable  mercury  cups  and  the 
stretching  lever  were  copied  from  Dr.  Max  Wien's 
magnetic  interrupter  (Wiedem.  Ann.  1891  and 
1892).  The  middle  cup  (see  Fig.  577)  is  connected 
to  one  pole,  F,  of  the  gravity  or  storage  cell,  the 
other  two  cups  are  connected  one  to  one  end  and 
the  other  to  the  other  end  of  the  primary  of  the 


Fig.  S7(>- 


Fig.  S77> 

small  coil  A  B.  From  the  middle  point,  C,  of  the 
primary  a  wire  leads  to  the  other  pole  of  the  cell. 
Auxiliary  small  coils,  E  and  D,  and  condensers, 
H  and  G,  are  inserted  in  the  circuits  as  indicated. 
Their  functions  will  be  explained  further  below. 

"The  vibrator  vibrates  with  a  node  at  the 
middle  dipper  as  soon  as  the  tension  has  reached  a 
certain,  by  no  means  high,  limit.  A  permanent 
contact  is  therefore  maintained  at  this  point,  and 
the  contact  is  made  at  one  of  the  cups  just  at 
about  the  same  moment  as  it  is  broken  at  the 
other  cup.  Leaving  the  condensers  out  of  con- 
sideration for  the  present,  it  is  evident  that  this 
form  of  the  current  make-and-break  produces 
the  same  effect  upon  the  iron  core  of  the  coil  as 
an  alternating  current  would.  The  advantage  of 
this  needs  no  comment ;  but  although  the  iron 
core  consists  of  the  finest  iron  wire  that  can  be 
obtained  in  the  market,  yet  it  must  be  remem- 


Int.] 


619 


[Iso. 


bered  that  the  vibrator  is  expected  to  work  some- 
times at  the  rate  of  512,  or  more,  complete  periods 
per  second.  Another  immediate  advantage 
which  this  interrupter  offers  is  a  considerable 
diminution  of  sparking.  The  addition  of  con- 
densers, besides  performing  other  functions 
which  will  be  discussed  presently,  reduces  the 
break  sparks  almost  to  invisibility,  even  when 
currents  as  large  as  half  of  an  ampere  are  used. 
Each  half  of  the  primary  coil  consists  of  532  turns 
of  No.  22  silk-covered  wire  wound  over  an  iron 
core  of  30  centimetres  in  length,  4  square  centi- 
metres in  cross-section,  and  consisting  of  very 
fine,  soft  iron  wire." 

Interrupter,  Sonometer A   term 

sometimes  employed  in  place  of  electro- 
dynamic  interrupter.  (See  Appendix — In- 
terrupter, Electro-Dynamic^) 

Interrupter,  Telegraphic A  de- 
vice for  making  and  breaking  a  circuit  at  a 
definite  rate. 

A  telegraphic  key  or  other  analogous  de- 
vice. 

Interrupter,  Telegraphic,  Mechanical 

A  form  of  mechanical  telegraphic 

sounder  for  learners  in  which  no  battery  is 
required. 

A  mechanical  telegraphic  interrupter  is  pro- 
vided  with  a  full-size  key  with  a  full  set  of  adjust- 
ments. In  fact,  it  resembles  an  ordinary  key, 
except  in  that  it  requires  no  battery  to  operate  it. 
It  differs,  therefore,  from  the  snappei  sounder, 
which  is  not  intended  to  resemble  a  sounder,  but 
merely  to  give  the  sounds  of  the  Morse  characters 
with  the  simplest  mechanism. 

Interruption,  Telegraphic A  term 

sometimes  employed  in  telegraphy  for  faults 
in  general. 

According  to  Pope,  telegraphic  faults  or  inter- 
ruptions  arise  from  the  following  causes,  viz. : 

(l.)  Disconnections  or  breaks. 

(2.)  Partial  disconnections  or  resistance. 

(3.)  Escapes. 

(4.)  Crosses. 

Ions,  Migration  of A  term  em- 
ployed to  express  the  movement  of  the  ions 
in  an  electrolyte  during  electrolysis. 

The  hypothesis  of  GrOthuss  attempts  to  explain 
the  fact  that  in  electrolysis  the  anions  and  kathions 
do  not  appear  in  any  part  of  the  electrolyte  ex- 


cept at  the  electrodes,  no  ions  apparently  being 
set  free  in  the  liquid.  (See  Hypothesis,  GrOtkuss' . ) 

When  copper  electrodes  are  employed  in  the 
electrolysis  of  a  solution  of  copper  sulphate,  the 
solution  becomes  from  two  to  three  times  weaker 
at  the  kathode  than  at  the  other  electrode. 
Hittorf  explains  this  fact  on  the  assumption  that 
during  the  migration  the  864  radical  moves 
through  the  liquid  more  rapidly  than  the  Cu 
radical. 

GrOthuss'  hypothesis  has  been  objected  to  be- 
cause it  requires  a  finite  force  to  bring  about  the 
decomposition  of  the  electrolyte,  and  the  experi- 
ments of  Helmholtz  prove  that  the  interior  of  an 
electrolyte  is  unable  to  withstand  the  slightest 
electrostatic  stress.  Clausius  has  modified  GrOt- 
huss'  hypothesis  so  as  to  bring  it  more  into 
accord  with  the  kinetic  theory  of  matter.  He 
believes  that  some  of  the  moving  molecules  of  the 
electrolyte  are  broken  up  into  their  constituent 
ions  as  a  result  of  occasional  molecular  impact,, 
and  that  it  is  these  separated  ions  only  that  appear 
at  the  electrodes.  Arrhenius  asserts  that  during 
electrolysis  the  greater  part  of  the  molecules  of 
the  electrolyte  are  thus  dissociated.  The  veloc- 
ity of  the  dissociated  ions  is  assumed  to  be  pro- 
portioned to  the  potential  gradient  in  the  elec- 
trolyte. According  to  this  theory  a  continuous 
movement  of  positively  charged  ions  occurs 
towards  the  negative  electrode  or  kathode  and  of 
negatively  charged  ions  towards  the  positive 
electrode  or  anode. 

Iron,  Building A  heated  iron  tool, 

by  means  of  which  the  mould  impressed  by 
the  printed  page,  it  is  desired  to  electrotype, 
is  built  up  preparatory  to  being  placed  in  the 
electroplating  bath. 

A  building  iron  consists  essentially  of  a  suitably 
shaped  iron  tool  which  is  employed  while  hot  in 
connection  with  strips  of  wax  for  bringing  up  or 
raising  the  blank  spaces  in  a  mould  between  the 
pages  and  paragraphs. 

Iron-Loss  in  Transformer. — (See  Ap- 
pendix—  Transformer,  Iron-Loss  in.) 

Isonisation. — A  term  proposed  for  a  de- 
crease in  the  strength  with  which  the  separate 
atoms  or  radicals  are  held  together  in  the 
molecules  of  an  electrolyte. 

A  term  proposed  for  that  modified  dis- 
sociation of  a  molecule  which  consists  in  a 


ISO.] 


620 


[Key. 


weakening  of  the  force  which  holds  the  ions 
of  the  molecules  together  in  an  electrolyte. 

The  term  isonisation  does  not,  as  might  be 
supposed,  refer  to  the  complete  separation  of  an 
electrolyte  into  its  ions  by  electrolysis,  but  to  a 
preparatory  weakening  of  the  bonds  which  hold 
the  ions  together  in  a  solution  in  which  elec- 
trolysis is  about  to  occur. 


This  term  was  proposed  by  Fitzgerald  for  the 
purpose  of  covering  the  peculiar  action  of  elec- 
trolysis so  far  as  its  behavior  to  aqueous  solutions 
of  metallic  salts  is  concerned. 

Isotropic. — Homogeneous  with  respect  to 
direction. 

Employed  in  reference  to  the  properties  of  a 
medium. 


Jack  Switch. — (See  Appendix — Switch, 
Jack) 

Jar,  Leyden,  Overflow  of A  term 

sometimes  employed  for  the  discharge  of  a 
Leyden  jar  by  a  disruptive  discharge  around 
its  edge. 

Joint,  End-to-End A  term  fre- 
quently employed  in  place  of  butt  joint.  (See 
Joint,  Butt) 

Joint,  Sliding An  expansion  joint. 

(See/iw»/,  Expansion) 

Joule,  International The  value 

of  the  international  joule  adopted  by  the  Chi- 
cago Congress  of  1893,  as  equal  to  io7  units 
of  work  in  the  C.  G.  S.  system,  and  which  is 


represented  sufficiently  well  for  practical  use 
by  the  energy  expended  in  one  second  by  one 
international  ampere  in  an  international  ohm. 

Joule-Meter. — Any  apparatus  capable  of 
measuring  energy  in  joules. 

An  energy  meter  as  distinguished  from  a 
watt-meter. 

Jumper. — A  temporary  shunt  or  circuit  put 
around  a  lamp  or  loop  on  a  series  circuit,  to 
enable  it  to  be  readily  removed  or  repaired. 

A  jumper  usually  consists  of  a  piece  of  wire  of 
sufficient  size  to  carry  the  current  past  the  faulty 
lamp  or  other  device  which  it  is  desired  to  tem- 
porarily remove  or  repair. 


K. — A  symbol  for  moment  of  inertia. 
The  defining  equation  is  M  X  L2. 
K  (Kappa). — A  symbol  proposed  for  mag- 
netic susceptibility. 

1  | 

The  defining  equation  is  K  =   j^-  i.  e.  •Q 

cH-          n 

kg.  — An  abbreviation  for  kilogramme,  the 
practical  unit  of  mass. 

kg:  cm2. — An  abbreviation  proposed  for 
kilogramme  per  square  centimetre,  the  prac- 
tical unit  of  pressure. 

kgni. — An  abbreviation  for  kilogrammetre, 
the  practical  unit  of  moment  of  a  couple  or 
of  work. 

kgm:  s. — An  abbreviation  proposed  for 
kilogrammetre  per  second,  the  practical  unit 
of  power. 


KR. — A  contraction  for  the  total  capacity 
of  a  telephone  wire  or  conductor  multiplied 
by  its  total  resistance. 

KB  Law. — (See  Appendix — Law,  The 
KR) 

Kapp  Line.  —  (See  Appendix  —  Line, 
Kapp) 

Karsten's  Figures.  —  (See  Appendix  — 
Figures,  Karsten's) 

Kathodic  Rays  of  Vacuum  Tube.— (See 
Appendix— Rays,  Kathodic,  of  Vacuum 
Tube) 

Kerite  Tape.  —  (See  Appendix  —  Tape, 
Kerite) 

Key,  Break A  key  which  breaks 

or  opens  the  circuit  when  depressed. 


Key.] 


621 


[Lam. 


•Key,    Strap  —  A    telegraphic    key 

formed  of  a  single  plate  of  elastic  material. 

The  elastic  strip  of  conducting  material  is 
fixed  at  one  end.  Its  motion  in  one  direction  is 
effected  by  the  hand  of  the  operator,  and  its  re- 
turn in  the  opposite  direction  by  the  elasticity  of 
the  material. 

Key,  Successive  Contact A  key  so 

arranged  as  to  make  or  break  one  contact 
after  another. 

A  successive  contact  key  is  frequently  used  in 
connection  with  a  Wheatstone  bridge  ;  where  it 
is  desirable  to  make  or  close  the  battery  circuit 
before  making  or  closing  the  galvanometer  cir- 
cuit, or  to  break  the  battery  circuit  after  break- 
ing or  opening  the  galvanometer  circuit.  This  is 
done  by  means  of  a  successive  contact  key.  A 
successive  contact  key  is  also  sometimes  called  a 
double  contact  key.  (See  Key,  Double-Contact 
Form  of  Bridge,  Spr ague's.  Key,  Double-Con- 
tact, Lambert's.) 

Key,  Tapper A  term    sometimes 

employed  in  place  of  Morse  tapper.     (See 
Appendix — Tapper,  Morse?) 


Kick  of  Relay. — A  momentary  effect, 
more  powerful  than  usual,  produced  on  the 
armature  of  a  relay  by  the  current  of  charge 
on  the  closing  of  the  circuit. 

The  kick  varies  in  its  amount  or  intensity  not 
only  with  the  electrostatic  capacity  ot  the  line, 
but  also  with  its  length  and  with  the  perfection  of 
its  insulation. 

Kilerg. — A  kilo-erg. 

Kilo-Erg. — One  thousand  ergs. 

Kilo-Volt. — One  thousand  volts. 

Kilometric  Capacity  of  Cable.  —  (See 
Appendix — Capacity,  Kilometric,  of  Cable?) 

Kilometric  Insulation  of  Cable. — (See 
Appendix — Insulation,  Kilometric,  of  Cable?) 

Kinematics. — That  branch  of  mechanics 
which  treats  of  motions,  irrespective  of  the 
mass  moved  or  the  forces  which  produce  or 
oppose  its  motion. 

Kinetics. — That  branch  of  dynamics  which 
treats  of  the  action  of  forces  in  producing  or 
modifying  motion. 

Krizik's  Cores.— (See  Appendix— Cores, 
Krizik's?) 


Lm. — A  symbol  proposed  for  co-efficient  of 
mutual  induction. 

Ls. — A  symbol  proposed  for  co-efficient  of 
self-induction  or  inductance. 

$ 
The  defining  equation  is  L,  =  Y 


Lag,  Translation 


-A  term  proposed 


by  Elihu  Thomson,  who  defines  it  as  follows : 
"  Lag  due  to  the  traverse  of  a  conductor  con- 
veying current  past  a  magnet  pole,  whereby 
the  action  of  the  current  in  that  conductor 
becomes  displaced  in  the  direction  of  the 
motion  and  produces  a  moving  field,  the  iron 
mass  or  body  tending  to  accommodate  itself 
to  the  direction  of  the  lines  of  force  in  the 
moving  field." 

The  phenomena  of  a  shifting  field  are  observed 
when  a  coil  with  an  iron  wire  core  is  energized 
by  an  alternating  current  so  as  to  produce  an 


alternating  field,  and  a  wheel  made  up  of  iron 
discs  around  which  is  a  rim  or  band  of  copper 
overhanging  the  edges  of  the  disc  is  placed  in 
such  field.  On  the  energizing  of  the  coil,  the 
wheel,  which  is  mounted  on  pivots,  when 
mechanically  started  in  rotation  in  either  direc- 
tion, will  increase  both  in  speed  and  torque  to  a 
degree  depending  on  the  frequency  of  the  current, 
the  friction  to  be  overcome  on  the  alternating 
field  and  on  the  iron  and  copper  of  the  wheel. 
(See  Field,  Magnetic,  Shifting. ) 

Lamp,  Arc,  Striking  Mechanism  of  — - 

— The  mechanism  in  an  arc  lamp  by  means 
of  which  the  carbons  are  separated  to  the 
distance  at  which  it  is  desired  the  arc  shall 
be  maintained  between  them. 

Lamp,  Bombardment,  Electrical A 

lamp  in  which  the  light  is  produced  in  a 
vacuous  space  by  means  of  the  bombard- 


Lam.] 


622 


[Law. 


ment  of  the  molecules  of  the  residual  gas  by 
the  passage  of  electrical  discharges. 

The  molecules  in  their  rapid  to-and-fro  motions 
are  caused  to  strike  against,  and  thus  raise  to  in- 
candescence, strips  or  bars  of  refractory  material, 
such  as  carbon,  etc. 

Tesla's  straight-filament  incandescent  electric 
lamp  is  a  form  of  electric  bombardment  lamp. 
(See  Lamp,  Incandescent,  Straight-Filament.} 

Lamp,  Burned-Out  Incandescent 

A  term  sometimes  employed  for  an  electric 
incandescent  lamp  which  is  no  longer  able 
to  furnish  efficient  electric  light. 

An  incandescent  electric  lamp  is,  strictly  speak- 
ing, to  be  regarded  as  burned  out  when  it  no 
longer  furnishes  a  suitable  light,  and  this, 
whether  the  filament  or  chamber  has  been 
actually  destroyed  or  not. 

Lamp,   Electcic,   Efficiency  of 

Strictly,  the  ratio  of  the  luminous  energy 
emitted  by  the  lamp,  to  the  energy  absorbed 
by  the  lamp. 

The  term  efficiency  of  a  lamp  is  less  accur- 
ately used  to  signify  its  relative  watts  per  candle 
power.  The  Edison  lamps  are  of  high  efficiency 
if  3.1  watts  per  c.  p.,  and  of  low  efficiency  if 
greater. 

Lamp,  Electric   Stopper A  term 

now  generally  em- 
ployed for  an  in- 
candescent elec- 
tric lamp  in  which 
the  chamber  is 
stopped,  not  as 
formerly  by  the 
fusion  of  the 
glass,  but  by  the 
action  of  a  glass 
stopper  hermeti- 
cally sealed  by 
the  use  of  suit- 
able cement. 

Fig.  578  shows  a 
lamp  of  this  type. 

Lamp,     Glow 

— A    lamp 

the  light  of  which  is  produced  by  glow 
illumination.  (See  Appendix — Illumination, 
Glow) 


The  term  glow  lamp  is  already  generally  em- 
ployed in  England  and  Germany  for  the  ordinary 
incandescent  electric  lamp.  It  would  appear  that 
the  term  incandescent  lamp  generally  employed 
in  America  is  preferable.  The  term  glow-lamp 
should  be  limited,  as  above,  to  a  lamp  producing 
an  approximately  cold  light ;  namely,  a  lamp 
operating  by  glow  illumination. 

Lamp,  Incandescent  Bombardment 

— An  electric  lamp  in  which  a  refractory 
material  is  rendered  incandescent  by  the 
molecular  bombardment  produced  by  the 
passage  of  an  electric  discharge  through  a 
rarefied  space. 

Most  of  Tesla's  lamps  are  of  the  bombardment 
type  and  are  of  a  great  variety  of  forms,  but  in 
all  of  them  refractory  substances  like  carbon  are 
rendered  incandescent  by  the  passage  of  very 
rapidly  alternating  currents  through  rarefied 
gases.  (See  Lamp,  Electric,  Incandescent  Ball. 
Lamp,  Incandescent,  Straight  Filament. ) 

Lamp,  Incandescent  Electric,  Ageing  of 

— A  term  sometimes  employed  for  a 


Fig.  51 8.     Electric  Stopper 
Lamp. 


gradual  decrease  in  the  economical  light 
emitted  by  an  incandescent  electric  lamp 
attending  its  continued  use. 

Lamp,    Phosphorescent A    lamp 

whose  light  is  obtained  by  means  of  the  phos- 
phorescent effects  attending  the  discharges  of 
electricity  through  a  rarefied  space. 

In  phosphorescent  lamps  the  phosphorescent 
effects  are  produced  by  causing  the  molecules  ot 
the  residual  gas  to  strike  against  some  readily 
phosphorescent  material.  Such  lamps  are  some- 
times called  bombardment  lamps.  But  the  term 
bombardment  lamp  is  [perhaps  more  properly 
restricted  to  cases  where  molecular  bombardment 
raises  a  substance  of  high  refractory  power,  such 
as  carbon,  to  incandescence;  while  the  term 
phosphorescent  lamps  is  limited  to  cases  where 
the  material  so  raised  to  luminescence  is  a  phos- 
phorescent material.  (See  Bombardment,  Molec- 
ular.} 

Law,  The   KR. A  generalization 

claimed  by  some  as  a  law,  but  denied  by 
most,  which  assigns  a  limit  to  the  distance 
through  which  intelligible  telephonic  com- 
munication can  be  carried  on  to  cases  where 
the  product  of  K,  the  capacity  of  the  tele- 


Lea.] 


623 


[Lig. 


phone  circuit,  multiplied  by  R,  its  resistance, 
does  not  exceed  a  certain  value. 

Preece  originally  fixed  the  limits  of  intelligible 
communication  of  speech  by  means  of  a  telephone 
to  cases  where  the  product  of  K  and  R  did 
not  exceed  15,000.  Preece's  figures  do  not  agree 
with  the  results  of  practical  telephone  work  in  the 
United  States ;  such,  for  example,  as  in  the  case  of 
the  line  now  in  actual  operation  between  Boston 
and  Chicago. 

Preece's  general  method  of  calculating  the  K 
R  of  a  metallic  circuit  was  by  multiplying  the 
total  capacity  of  the  line  by  its  total  resistance 
and  then  dividing  by  four,  since  the  capacity  of 
an  insulated  loop  is  taken  as  one-fourth  of  the 
capacity  of  the  entire  length  of  the  line  measured 
against  the  ground.  Even  when  calculated  in 
this  way  the  K  R  of  the  Boston-Chicago  con- 
ductor line  is  nearly  54,000. 

Lead  Sulphate  of  Copper  Cell.— (See  Ap- 
pendix— Cell,  Lead  Sulphate  of  Copper?) 

Lead  Sulphate  of  Zinc  Cell.— (See  Ap- 
pendix— Cell,  Lead  Sulphate  of  Zinc.) 

Leads,  Double-Wire  System  for  Electric 

Light A  term  employed  for  a  parallel 

or  multiple  system  of  leads  for  electric  light. 
(See  Circuit,  Parallel.  Circuit,  Multiple?) 

Leads,   Grouping    System   for   Electric 

Light A   term   sometimes   employed 

for  series-multiple  circuits.  (See  Circuit, 
Series-Multiple?) 

Leads,  Single  Wire  System  for  Electric 

Light A  term  sometimes  employed  for 

a  circuit  in  which  the  current  after  passing 
through  the  lamps  is  returned  by  means  of 
the  earth  or  ground. 

This  is  called  the  single  wire  system  for  electric 
light  leads  because  but  a  single  wire  or  con- 
ductor is  employed  in  the  circuit,  the  return  being 
made  through  the  ground  or  earth. 

Leak,  Telegraphic,  Resistance  of 

The  resistance  offered  by  a  leak  in  a  tele- 
graphic line  or  circuit. 

Leakance. — A  word  proposed  by  Heavi- 
side  for  leakage  conductance. 

It  will  be  seen  that  the  proposed  word  is  an 
abbreviation  or  contraction  for  leakage-conduct- 
ance. 


Lease,  Way A  permit  obtained  from 

the  owner  of  a  property  for  the  erection  of 
poles  or  other  attachments  for  telephonic  or 
telegraphic  lines. 

Left -Hand  Trolley  Switch.— (See  Ap- 
pendix— Switch,  Left-Hand  Trolley.) 

Left-Handed  Helix. — (See  Appendix — 
Helix,  Left-Handed?) 

Left-Handed  Rotation. — (See  Appendix— 
Rotation,  Left-Handed?) 

Left-Handed  Spiral. — (See  Appendix  — 
Spiral,  Left-Handed?) 

Lever  Switch. — (See  Appendix — Switch, 
Lever?) 

Light,  Castor  and  Pollux A  term 

formerly  used  in  place  of  St.  Elmo's  fire. 

Light  Cell. — (See  Appendix — Cell,  Light} 

Light  Indicator  of  Railroad  Signal. — 
(See  Appendix — Indicator,  Light,  of  Rail- 
road Signal.) 

Light  Load.  —  (See  Appendix  —  Load, 
Light.) 

Light,  Northern An  aurora  bore- 

alis. 

Lighting,  Vacuum-Tnbe Artificial 

illumination  obtained  by  the  passage  of  elec- 
tric discharges  through  vacuum  tubes. 

A  practical  system  of  electric  lighting  by  means 
of  vacuum  tubes  was  not  long  ago  regarded  as  an 
impossibility  ;  now,  however,  through  the  labors 
of  many  distinguished  men,  especially  those  of 
Tesla,  such  a  system,  which  seems  to  possess 
many  advantages,  bids  fair  in  event  of  certain- 
difficulties  being  overcome  to  become  a  formid- 
able rival  to  the  incandescent  electric  lighting. 

In  a  system  of  vacuum-tube  lighting,  some 
source  of  high  alternating  potential  furnishing 
from  50,000  to  100,000  volts  or  more  is  employed. 
Such  discharges  are  most  readily  obtained  by 
means  of  an  alternator  and  disruptive  discharges 
from  condensers  in  connection  with  an  oil  trans- 
former. The  oil  transformer  is  employed  on  ac- 
count of  the  high  resistance  of  the  oil  as  a  dielec- 
tric. One  of  the  most  important  advantages 
which  vacuum-tube  lighting  possesses  over  light- 
ing by  means  of  the  ordinary  incandescent  electric 
lamp  is  that  it  produces  a  cold  light  or  illumination 
of  the  type  of  glow  illumination.  (See  Appendix 
— Illumination,  Glow.) 


624 


[Lum. 


Lightning  Arrester  Board. — (See  Appen- 
dix— Board,  Lightning  Arrester?) 

Lightning,  Bead A  form  of  light- 
ning discharge  in  which  the  flash  produces  a 
discontinuous  line  of  light,  thus  causing  the 
discharge  to  assume  a  bead-like  appearance. 

Lightning  Tube.— (See  Appendix— Tube, 
Lightning?) 

Limit,  Magnetic A  term  sometimes 

employed  for  the  temperature  at  which  a 
magnetic  substance  loses  its  magnetism  on 
exposure  to  heat. 

Line,  Eapp A  term  proposed,  but 

not  generally  adopted,  for  the  English  unit  of 
magnetic  induction. 

This  term,  which  defines  the  lines  per  square 
inch  instead  of  per  square  centimetre,  does  not 
harmonize  with  the  C.  G.  S.  system  of  units, 
and,  therefore,  should  not  be  encouraged. 

Line,  Telegraphic,  Charge   Current  on 

The  current  produced  by  the  initial 

rush  of  electricity  into  a  telegraphic  line  on 
the  closing  of  the  circuit. 

Lines  of  Magnetization. — (See  Appen- 
dix— Magnetization,  Lines  of.) 

Linear  Capacity  of  Cable.— (See  Appen- 
dix—  Cable,  Linear  Capacity  of.*) 

Linear  Density  of  Charge. — (See  Appen- 
dix— Charge,  Linear  Density  of.) 

Linear  Insulation  of  Cable. — (See  Ap- 
pendix— Cable,  Linear  Insulation  of.) 

Liquid,  Quickening A  term  some- 
times applied  to  a  quicking  solution.  (See 
Solution,  Quicking.) 

Lithanode. — A  name  employed  for  a  solid 
highly  conducting  block  of  lead  peroxide  pre- 
pared by  a  certain  process  for  the  plate  of  a 
storage  cell.  (See  Cell,  Storage?) 

The  word  lithanode  is  properjy  applied  to  the 
product  produced  by  Fitzgerald's  process. 

Lithotrity,  Electro A  term   pro- 


posed for  a  crushing  or  removing  of  urinary 
calculi  by  means  of  electrolysis. 

Load. — The  work  thrown  upon  an  electro- 
magnetic system  or  machine. 

The  load  on  a  dynamo,  for  example,  means 
the  value  of  its  activity  or  rate  of  doing  work. 

Load  Diagram. — (See  Appendix — Dia- 
gram, Loaa.) 

Load,  Full A  term  indicating  the 

condition  of  running  with  a  comparatively 
large  amount  of  work. 

Load,  Light A  term  indicating  the 

condition  of  running  with  a  comparatively 
small  amount  of  work. 

Locomotive,  Telpher An  electric 

motor  by  means  of  which  telpher  cars  are 
drawn  on  a  telpher  line.  (See  Telpherage.) 

Long-Range  Electrometer.— (See  Appen- 
dix— Electrometer,  Long-Range.) 

Loop  Test. — (See  Appendix — Test,  Loop*) 

Loss,  C2  R A  term  for  the  loss  of 

energy  in  a  conductor  due  to  the  ohmic  re- 
sistance offered  by  the  conductor  to  its  pas- 
sage. 

The  product  C2  R  =  activity  in  watts.  In 
this  formula,  C,  is  the  current  in  amperes  and  R, 
is  the  ohmic  resistance  in  ohms,  and,  when  multi- 
plied by  the  proper  factor,  it  will  give  the  value  of 
the  loss  in  heat  units. 

Loss,  Core,  of  Transformer A  loss 

of  energy  in  the  core  of  a  transformer  due  to 
hysteresis  and  Foucault  or  eddy  currents,  etc. 

Low-Frequency  Transformer.— (See  Ap- 
pendix—  Transformer,  Low-Frequency.) 

Low-Test  Fault.  —(See  Appendix — Fault, 
Low-  Test?) 

Luminous  Disc-Shaped  Discharge. — (See 
Appendix — Discharge,  Luminous  Disc- 
Shaped.) 

Luminous  Interference. — (See  Appendix 
— Interference,  Luminous?) 


Mac.] 


625 


[Mac. 


9H. — A  symbol  for  magnetic  moment. 
The  defining  equation  is  9ft  =  m  /. 

m. — An  abbreviation  for  minute,  one  of 
the  practical  units  of  time. 

m. — A.  symbol  for  strength  of  magnetic 
pole. 

f  he  defining   equation   is  F  =  =r-g- 

m. — An  abbreviation  for  metre,  the  prac- 
tical unit  of  length. 

/*. — A  symbol  for  magnetic  permeability  or 
inductivity. 

OW 

GA2) 

The  defining  equation  is  n = -=- - 
erC 

m2. — An  abbreviation  for  square  metre, 
the  practical  unit  of  surface. 

m3. — An  abbreviation  for  cubic  metre,  the 
practical  unit  of  volume. 

m.  a. — A  contraction  for  milli-ampere. 
(See  Mzllz- Ampere,) 

m :  s. — An  abbreviation  proposed  for  metre- 
per-second,  the  practical  unit  of  velocity. 

m :  s2. — An  abbreviation  proposed  for 
metre-per-second-per-second,  the  practical 
unit  of  acceleration. 

M.  Current. — (See  Appendix— Current, 
M.) 

M.  P. — A  contraction  proposed  for  man- 
power. 

M.  S.  Current. — (See  Appendix — Current, 
M.  S.~) 

Machine,  Dynamo-Electric,  Arc  Lighting 

A  dynamo-electric  machine  suitable 

for  supplying  current  to  arc  lamps. 

Arc  lights  are  almost  invariably  connected  to 
the  circuit  in  series.  In  such  cases  the  series- 
wound  dynamo  is  preferable  for  feeding  such  cir- 
cuits. (See  Machine,  Dynamo-Electric,  Series- 
Wound.)- 

Machine,  Dynamo-Electric,  Compensat- 
ing-Alternating A  term  proposed 


for  a  compensating  alternator.  (See  Appen- 
dix— Alternator,  Compensated!) 

Machine,  Dynamo-Electric,  Direct  Cur- 
rent   A  term  sometimes  employed  in 

place  of  continuous  current  dynamo-electric 
machine.  (See  Machine,  Dynamo-Electric, 
Continuous  Current?) 

Machine,  Dynamo-Electric,  for  Electro- 
Plating  A  dynamo-electric  machine 

suitable  for  use  in  electro-plating.  (See  Ma- 
chine, Dynamo-Electric.  Plating,  Electro!) 

An  electro-plating  dynamo-electric  machine 
possesses  many  advantages  over  a  voltaic  battery 
for  the  ready  production  of  the  current  required 
in  electro-plating.  By  its  use  the  tedious,  expen- 
sive, and  often  unhealthy  charging  of  a  voltaic 
battery  is  entirely  dispensed  with,  since  the  mere 
running  of  a  belt  over  a  pulley,  and  the  proper 
speeding  of  the  machine,  is  all  that  is  required  to 
furnish  a  suitable  current. 

Dynamo-electric  machines  for  electro-plating 
should  be  furnished  with  a  device  for  the  purpose 
of  preventing  a  reversal  of  the  polarity  of  the 
dynamo  by  means  of  the  current  produced  by  the 
polarization  of  the  electrodes  or  articles  con- 
nected with  the  plating  bath.  The  tendency  of 
this  current  is  of  course  opposed  to  that  of  the 
current  furnished  to  the  bath,  and,  should  the  ma- 
chine be  continued  in  use  as  a  source  of  cur- 
rent for  plating  while  its  polarity  is  reversed,  the 
metal  already  deposited  on  the  articles  that  are 
being  electro-plated  will  be  removed. 

In  the  early  history  of  the  art,  considerable 
difficulty  was  experienced  with  series-wound 
machines  due  to  reversals  in  the  polarity  of  the 
dynamos,  by  means  of  the  current  sent  back- 
wards through  the  dynamo  by  the  counter  E. 
M.  F.  of  the  electro-plating  bath,  whenever,  by 
reason  of  a  decrease  of  current  strength,  or  a  de- 
crease of  the  speed  of  the  dynamo,  its  E.  M.  F. 
fell  below  the  counter  E.  M.  F.  of  the  bath. 

Weston  prevents  such  a  reversal  of  the  polarity 
of  the  dynamo  by  opening  the  circuit  of  the  ma- 
chine as  soon  as  the  speed  of  the  machine  falls 
below  a  certain  point.  He  does  this  by  means 
of  the  centrifugal  force  acting  on  a  small  quantity 
of  mercury  in  a  small  hollow  conical-shaped 
vessel. 


Mac.] 


626 


[Mag. 


Brush  first  accomplished  this  same  result  by 
means  of  a  shunt  which  he  called  a  ' '  teaser. ' ' 
His  early  plating  machine  containing  this  device 
was  the  prototype  of  the  compound  wound  dy- 
namo-electro machine.  In  it  the  coils  of  the  field 
magnets  are  excited  partly  by  the  main  current 
and  partly  by  a  current  shunting  across  the 
brushes  of  the  machine.  A  machine  so  con- 
.structed  possesses  the  great  advantage  of  render- 
ing  the  machine  self-regulating  under  certain 
circumstances.  This  additional  or  shunt  circuit 
takes  a  variety  of  forms.  (See  Machine,  Dynamo- 
Electric^  Compound-Wound.') 

The  difficulty  of  reversed  polarity  has  disap- 
peared since  the  introduction  of  the  shunt  or 
compound-wound  dynamo,  *'.  <?.,  a  dynamo  whose 
field  is  wholly  or  in  part  excited  by  a  current 
shunted  across  the  brushes  of  the  armature.  In 
such  a  machine,  even  if  the  E.  M.  F.  falls  below 
the  counter  E.  M.  F.  of  the  bath,  the  current  in 
the  shunt  field,  and  therefore  the  polarity,  re- 
mains unchanged,  and  the  current  reverses  only 
in  the  armature. 

Machine,    Dynamo-Electric,   Four-Pole 

A  term  sometimes  employed  for   a 

dynamo-electric  machine  in  which  the  field  is 
produced  by  two  separate  north  poles,  and 
two  separate  south  poles. 

Machine,  Dynamo-Electric,  Incandescent 
Lighting  — A  term  sometimes  em- 
ployed for  a  dynamo-electric  machine  suit- 
able for  furnishing  the  currents  employed  for 
incandescent  electric  lamps. 

For  all  cases  where  the  incandescent  electric 
lamps  are  connected  to  the  leads  in  multiple-arc, 
or  any  of  its  varieties,  any  machine  capable  of 
producing  and  maintaining  a  constant  potential 
at  its  terminals,  notwithstanding  changes  in  the 
load  on  it,  is  suitable  for  use  as  an  incandescent 
electric-lighting  dynamo-electric  machine.  Com- 
pound-wound machines  are  generally  employed 
for  such  purposes.  (See  Machine,  Dynamo- 
Electric,  Compound -Wound.) 

Machine,  Dynamo-Electric,  Separate- 
Coil  Alternating A  term  sometimes 

employed  for  a  separate  coil  alternator. 
(See  Appendix — Alternator,  Separate-Coil.} 

Machine,  Dynamo-Electric,  Separately 
Excited  Alternating  -  —A  term  some- 
times employed  for  separately  excited  alter- 


nator. (See  Appendix — Alternator,  Sepa- 
rately Excited?) 

Machine,     Dynamo-Electric,     Six-Pole 

A  term   sometimes  employed  for  a 

dynamo-electric  machine  in  which  the  field 
is  produced  by  six  poles,  i.  <?.,  three  separate 
north  poles  and  three  separate  south  poles. 
Machine,    Dynamo-Electric,    Two-Pole 

A  term  sometimes  employed  for  a 

dynamo-electric  machine  in  which  two  poles 
only  are  employed  for  producing  the  field. 

Such  a  machine  is  usually  called  a  bi-polar 
machine. 

Machine,  Magneto-Electric,  Alternating 

An  alternating  current  dynamo-elec- 
tric machine,  the  field  of  which  is  produced 
by  permanent  magnets. 

A  magneto  alternator.  (See  Appendix — 
Alternator,  Magneto.) 

Machine,  Speeding  of Obtaining 

the  requisite  number  of  rotations  of  an  arma- 
ture of  a  machine  per  second. 

Machines  as  ordinarily  constructed  produce 
their  most  economical  output  for  practical  pur- 
poses when  a  certain  speed  of  rotation  has  been 
obtained. 

Machines,  Dynamo-Electric,  Alternating, 

Parallel  Working  of The  working  of 

two  or  more  alternators  in  parallel.  (See 
Appendix — Alternators,  Parallel  Connection 
of.) 

Machines,  Dynamo-Electric,  Alternating, 
Series- Working The  series  connec- 
tion of  two  or  more  alternating  dynamo-electric 
machines.  (See  Appendix  —  Alternators, 
Series  Connection  of.) 

Magazine,  Magnetic A  term  some- 
times employed  for  a  compound  magnet. 
(See  Magnet,  Compound).  (Obsolete.) 

Magne-Crystallic  Force. — (See  Appendix 
— Force,  Magne-Crystallic.) 

Magne-Electric  Induction.  —  (See  Ap- 
pendix— Induction,  Magne-Electric} 

Magnet,  Choke A  term  proposed, 

for  choking  coil.  (See  Coil,  Choking} 

The  term  choking  coil  would  appear  to  be 
preferable. 


Mag.] 


627 


[Mag. 


Magnet,  Compound A  term  for- 
merly applied  to  an  induction  coil  with  two 
separate  circuits. 

The  use  of  this  word  is  inadvisable.  The  same 
word  is  already  correctly  employed  for  a  mag- 
net formed  of  a  number  of  separate  magnets. 
(See  Magnet,  Compound.) 

Magnet,  Deflecting The  perma- 
nent magnet  of  a  magnetometer  employed 
for  deflecting  a  small  magnetic  needle  sus- 
pended at  a  definite  distance  in  order  to  com- 
pare its  influence  with  that  of  the  earth's 
horizontal  magnetic  force. 

Magnet,  Differential,  Electro A 

differentially  wound  electro-magnet.  (See 
Appendix —  Winding,  Differential.) 

Magnet,  Electro-Compound  — A 

term  formerly  applied  to  an  electro-magnet 
the  core  of  which  is  wound  with  two  sepa- 
rate wires  or  conductors. 

Magnet,  Laminated,  Permanent 

A  term  sometimes  employed  in  place  of  com- 
pound magnet. 

Magnet,  North  Pole  of,  Proposed  A.  I. 
E.  E.  Definition  for  -  — The  pole  of  a 
magnet  which  seeks  the  geographical  north 
pole. 

Magnet,  South  Pole  of,  Proposed  A.  I. 
E.  E.  Definition  for  -  —The  pole  of  a 
magnet  which  seeks  the  geographical  south 
pole. 

Magnet,  Theoretical  —  — A  hypotheti- 
cal magnet  assumed  for  the  purpose  of 
mathematical  discussion,  as  fulfilling  the  fol- 
lowing conditions,  namely  :  An  infinitely  long 
and  thin,  uniformly  magnetized  bar. 

Magnet,  Voltaic A  term  some- 
times employed  for  a  solenoid  or  electro- 
magnetic helix.  (See  Solenoid.) 

Magnetic  Alternator. — (See  Appendix — 
Alternator,  Magnetic.} 

Magnetic  Atmosphere. — (See  Appendix — 
Atmosphere,  Magnetic} 

Magnetic  Bearing. — (See  Appendix — 
Bearing,  Magnetic.} 

Magnetic  Compensator.— (See  Appendix 
• — Compensator,  Magnetic?) 


Magnetic  Disturbance. — (See  Appendix — 
Disturbance,  Magnetic?) 

Magnetic  Effluvia.  —  (See  Appendix  — 
Effluvia,  Magnetic?) 

Magnetic  Fluid. — (See  Appendix — Fluid, 
Magnetic!) 

Magnetic  Flux  Path. — (See  Appendix — 
Path,  Magnetic  Flux?) 

Magnetic  Helix. — (See  Appendix— Helix, 
Magnetic.} 

Magnetic  Hysteresis. — (See  Appendix — 
Hysteresis,  Magnetic?) 

Magnetic  Limit. — (See  Appendix — Limit, 
Magnetic?) 

Magnetic  Magazine. — (See  Appendix — 
Magazine,  Magnetic} 

Magnetic  Phantom. — (See  Appendix — 
Phantom,  Magnetic?) 

Magnetic  Shading. — (See  Appendix— 
Shading,  Magnetic} 

Magnetic  Source.  —  (See  Appendix  — 
Source,  Magnetic} 

Magnetic  Spectrum. — (See  Appendix — 
Spectrum,  Magnetic?) 

Magnetic  Spiral.  —  (See  Appendix — 
Spiral,  Magnetic} 

Magnetic  Voltmeter. — (See  Appendix — 
Voltmeter,  Magnetic?) 

Magnetics. — That  branch  of  science  which 
treats  of  the  laws  and  phenomena  of  mag- 
netism. 

The  use  of  this  term  should  not  be  encouraged. 

Magnetician. — A  word  proposed  for  one 
skilled  in  the  science  of  magnetism  as  known. 

This  word  appears  to  be  a  good  one,  but  is 
little  used. 

Magnetine. — A  word  formerly  employed 
for  the  principle  of  magnetism,  or  for  the  im- 
ponderable, hypothetical  fluid  in  which  mag- 
netic phenomena  were  assumed  to  take  place. 

Magnetisation. — (See  Magnetization?) 

Magnetisation,  Back (See  Appen- 
dix— Magnetization,  Back} 

Magnetisation,  Lines  of— (See  Ap« 

pendix — Magnetization,  Lines  of.) 


Mag.] 


628 


[Mag. 


Magnetish. — Possessing  the  property  of 
magnetism  to  a  limited  degree. 

This  term  is  a  bad  one,  and  its  use  should  be 
avoided. 

Magnetism,  Complex-Lamellar,.  Distri- 
bution of The  distribution  of  the 

magnetism  of  a  finite  magnet  into  an  infinite 
number  of  complex  magnetic  shells. 

Magnetism,     Horizontal    Intensity    of 

Earth's The  force  which  causes  a 

magnetic  needle  to  come  to  rest  in  a  hori- 
zontal position  in  the  earth's  field. 

The  horizontal  intensity  of  the  earth's  mag- 
netism can  be  determined  by  means  of  a  magnet- 
ometer. The  horizontal  intensity  at  any  place  is 
proportional  to  the  square  root  of  the  number  of 
oscillations  which  a  needle  suspended  about  a 
vertical  axis  performs  at  that  place  in  a  given 
time,  when  disturbed  from  its  position  of  rest  in 
the  earth's  field. 

Magnetism,  Total  Intensity  of  Earth's 
The  entire  force  of  the  earth's  mag- 
netism. 

The  total  intensity  of  the  earth's  magnetism 
is  equal  to  the  resultant  of  the  horizontal  and 
vertical  intensities,  or  to  the  quotient  of  the  hori- 
zontal intensity  by  the  cosine  of  the  angle  of  dip. 

Magnetism,  Bemanent A  phrase 

sometimes  used  in  place  of  residual  magnet- 
ism.    (See  Magnetism,  Residual?) 

Magnetism,  Specific  — A  term  pro- 
posed for  the  quotient  of  the  magnetic  moment 
of  a  magnet  by  its  mass. 

Magnetism,  Vertical  Intensity  of  Earth's 

The  force  which  tends  to   cause  a 

magnetic  needle  to  assume  a  vertical  position. 

The  following  formula  gives  the  vertical  inten- 
sity of  the  earth's  magnetism  : 
V  =  H.  tan.  9 
Where  V  =  vertical  intensity. 

H  =  the  horizontal  intensity, 
and  0  =  the  angle  of  dip. 

Magnetist — A  magnetician. 

The  word  magnetician  is  preferable. 

Magnetizability. — Possessing  the  ability 
of  becoming  magnetized. 

Magnetization,  Back A  term  pro- 
posed in  place  of  back  or  backward  induc- 


tion.    (See    Appendix — Induction,    Back- 
•ward?) 

Magnetization,  Circular The  mag- 
netization which  exists  in  a  diphase  motor 
in  which  two  alternating  magnetic  fluxes  of 
equal  amplitude  are  produced  in  quadrature 
or  at  right  angles  to  each  other. 

Magnetization,  Elliptical  Botary  — 
The  magnetization  which  exists  in  a  diphase 
motor  in  which    two    alternating  magnetic 
fluxes  exist  out  of  phase  with  each  other. 

Magnetization,  Lines  of A  term 

sometimes  employed  for  lines  of  magnetic  in- 
duction. 

When  lines  of  magnetic  force  pass  through  air, 
the  number  of  lines  of  induction  are  the  same  as 
the  number  of  lines  of  magnetizing  force  ;  when, 
however,  the  lines  of  force  pass  through  iron,  the 
number  of  such  lines  of  induction  is  greatly  in- 
creased. 

Magnetizee. — A  word  proposed  to  desig- 
nate a  person  who  believes  he  is  placed 
under  the  power  of  animal  magnetism. 

Magnetizer. — A  word  proposed  to  desig- 
nate a  person  who  claims  to  place  another 
under  the  power  of  animal  magnetism. 

Magnetizing  Helix. — (See  Appendix — 
Helix,  Magnetizing?) 

Magnetizing  Spiral. — (See  Appendix — 
Spiral,  Magnetizing?) 

Magneto- Alternator.  —  (See  Alternator, 
Magneto?) 

Magneto-Chemical  Cell. — (See  Appendix 
— Cell,  Magneto-Chemical?) 

Magnetod. — A  word  employed  by  Reichen- 
bach  for  the  assumed  force  or  principle  of 
animal  magnetism. 

Magneto-Electric  Alternating  Machine. 

— (See  Appendix — Machine,  Magneto-Elec- 
tric Alternating?) 

Magneto-Inductive  Capacity. — (See  Ap- 
pendix— Capacity,  Magneto-Inductive?) 

Magnetology.— That   branch    of  science 
which  treats  of  magnetism. 
'  The   word  magnetism  would    appear  to  bt 
preferable. 


Mag.] 


[Mer. 


Magnetometer,    Inclination    — A 

form  of  magnetometer  suitable  for  measur- 
ing variations  in  the   magnetic  inclination  at 
Viy  place. 
Magnetometer,  Registering  Declination 

«-- A  form  of  magnetometer  in  which  the 

variations  of  the  declination  at  any  place  can 
be  automatically  registered. 

Magnetometer,  Variation A  form 

of  magnetometer  suitable  for  measuring 
changes  in  the  magnetic  variation  at  any 
place. 

Magneto-Metric. — Of  or  pertaining  to 
the  measurement  of  magnetic  force. 

Magnetometry. — That  branch  of  science 
which  treats  of  the  measurement  of  the 
strength  of  magnetic  fields. 

Magneto-Motor.— (See  Appendix— Motor, 
Magneto.) 

Magnetophone. — A  word  sometimes  used 
for  a  magneto  telephone. 

Magneto-Tapper. — (See  Appendix —  Tap- 
per, Magneto.) 

Man  Power. — (See  Appendix — Power, 
Man.)  , 

Manual  Repeater. — (See  Appendix — Re- 
peater, Manual?) 

Manual  Translation. — (See  Appendix — 
Translation,  Manual?] 

Marks,  Ripple,  Electrical Wave 

marks  produced  in  a  fine  powder  by  the  dis- 
charge of  a  Leyden  jar  in  its  neighborhood. 

These  ripple  marks  are  due  to  waves  set  up  in 
the  air  by  the  passage  of  the  discharge. 

The  same  discharge  that  produces  waves  in 
ether  also  sets  up  waves  in  the  surrounding  air. 
It  can  be  shown  that  the  same  discharge  that  can 
excite  ether  waves  i  kilometre  in  length  can 
excite  waves  in  the  air  about  I  millimetre  in 
length. 

Matt. — A  word  employed  in  electro-plating 
to  designate  the  appearance  presented  by  an 
electro-plating  of  silver  in  which  the  deposit 
is  interlaced  and  closely  massed  together. 
(See  Plating,  Electro?) 

Matter,  Electric A  term  formerly 

applied  to  the  matter  which  was  believed  to 


constitute  the  effluvia  formerly  assumed  to 
pass  off  from  an  electrified  body. 

Matter,  Fourth  State  or  Condition  of 

A  term  sometimes  employed  for  the 

ultra-gaseous  or  radiant  state  of  matter.  (See 
Matter,  Radiant  or  Ultra-Gaseous?) 

Matting,  Burglar  Alarm A  mat- 
ting provided  with  a  number  of  invisible  con- 
tacts connected  with  alarm  bells  whose  cir- 
cuits are  closed  by  treading  on  the  matting. 
(See  Matting,  Invisible  Electric  Floor?) 

Maximum  Negative  Elongation. — (See 
Appendix — Elongation,  Maximum  Nega- 
tive?) 

Maximum  Positive  Elongation. — (See 
Appendix — Elongation,  Maximum  Posi- 
tive?) 

Maximum  Starting  Current  of  Motor. — 

(See  Appendix — Current,  Maximum  Start- 
ing, of  Motor?) 

Maynooth  Voltaic  Cell. — (See  Appendix 
— Cell,  Voltaic,  Maynooth?) 

Mechanical  Replacement  of  Disc-Indi- 
cator.— (See  Appendix  —  Indicator,  Disc,. 
Mechanical  Replacement  of?) 

Mechanical  Telegraphic  Interrupter. — 
(See  Appendix— Interrupter,  Telegraphic, 
Mechanical?) 

Medication,  Cataphoric The  intro- 
duction of  drugs  or  other  medicaments  into 
the  body  through  its  tissues  by  the  cataphoric 
action  of  an  electric  current.  (See  Cata- 
phoresis.  Osmose,  Electric?) 

Medium,  Aelotropic A  medium 

which  manifests  different  actions  in  definite 
directions ;  /.  e.,  an  eolotropic  medium.  (See 
Medium,  Eolotropic?) 

Crystallized  bodies  are  in  general  notably 
aelotropic,  while  amorphous  substances  are  gen- 
erally isotropic. 

An  aelotropic  substance  may  be  expected  to 
possess  different  electrostatic  elastivity  and  in- 
ductive  capacity  in  different  directions. 

Melting  of  Electric  Conductor. — (See 
Appendix — Conductor,  Electric,  Melting  of.) 

Mercurial  Phosphorus. — (See  Appendix 
— Phosphorus,  Mercurial?) 


Met.] 


630 


[Mho. 


Metallic  Conduction. — (See  Appendix — 
Conduction,  Metallic.} 

Metallic  Cross.— (See  Appendix— Cross, 
Metallic?) 

Metallo-Chromes. — Colors  which  appear 
when  a  salt  of  lead,  such  as  the  acetate,  is 
electrolyzed  under  peculiar  circumstances. 

Metallo  chromes  are  produced  by  electrolytic 
deposits  of  peroxide  of  lead  in  the  neighborhood 
of  the  anode.  When  the  thickness  of  the  coating, 
which  is  deposited  on  a  plate  of  polished  steel,  is 
properly  regulated,  a  series  of  brilliant  colors 
appear. 

Gassiot  recommends  the  following  process  for 
obtaining  metallo-chromes. 

"  Place  the  polished  steel  plate  in  a  glass  basin 
containing  a  clear  solution  of  acetate  of  lead,  and 
over  it  a  piece  of  card.  A  small  rim  of  wood 
should  be  placed  over  the  card,  and  on  that  a 
circular  copper  disc.  On  contact  being  made 
from  5  to  20  minutes,  with  two  or  three  cells  of  a 
small  constant  battery,  the  steel  plate  being  con- 
nected with  the  positive  electrode,  and  the  cop- 
per disc  with  the  negative,  the  deposit  will  be 
effected,  and  a  series  of  exquisite  colors  will  ap- 
pear on  the  steel  plate.  The  colors  are  films  of 
peroxide  of  lead  thrown  down  on  the  surface  of 
the  steel,  and  the  varied  tints  are  occasioned  by 
the  varying  thicknesses  of  the  precipitated  film, 
the  light  being  reflected  through  them  from  the 
metallic  surface  below.  By  reflected  light  every 
prismatic  color  is  seen  ;  and  by  transmitted  light 
a  series  of  prismatic  colors  complementary  to  the 
first  series  appears,  occupying  the  place  of  the 
former  series. 

"  The  colors  are  seen  in  the  greatest  perfection 
by  placing  the  plate  before  a  window,  and  inclin- 
ing a  white  sheet  of  paper  at  45  degrees  over  it. " 

Similar  colorations  are  obtained  when  other 
substances  are  electrolytically  deposited.  Under 
certain  conditions  these  colorations  assume  the 
form  of  concentric  circles,  that  are  sometimes 
called  Nobili's  rings. 

Nobili's  rings  are  readily  obtained  by  placing 
a  drop  of  acetate  of  copper  on  a  silver  plate  and 
touching  the  middle  of  the  drop  with  a  piece  of 
zinc.  Under  these  circumstances  prismatically 
colored  rings  are  formed,  that  are  disposed 
concentrically  around  the  point  of  contact  of  the 
zinc. 

Meteorograph,  Electric.— An  apparatus 
for  automatically  registering  various  meteor- 


ological values,  such,  for  example,  as  the  in- 
dications of  a  barometer  or  thermometer,  the 
direction  and  velocity  of  the  wind,  or  the 
value  of  the  rainfall. 

Meteorology. — That  branch  of  physics 
which  treats  of  the  phenomena  of  the  atmos- 
phere. 

Meteorology,  Electric That  branch 

of  meteorology  which  treats  of  the  electric 
phenomena  of  the  atmosphere. 

Meter,  Coulomb Any  form  of  ap- 
paratus capable  of  measuring  the  number  of 
coulombs  that  pass  in  a  circuit  in  a  given  time. 

Any  form  of  galvanometer  which  gives  the  cur- 
rent in  amperes  will  give  the  number  of  coulombs 
that  pass  if  the  time  the  current  is  flowing  is 
known.  Various  forms  cf  electric  meters  will 
therefore  give  the  number  of  coulombs  that  pass 
in  a  circuit.  (See  Meter,  Electric.) 

Meter,  Electrolytic An  electro- 
chemical meter.  (See  Meter,  Electro-Chem- 
ical?) 

Meter,  Quantity A  coulomb  meter. 

Meter,  Telephonic A  meter  em- 
ployed for  recording  the  time  during  which  a 
telephone  is  in  use. 

The  telephonic  meter,  as  at  present  constructed, 
consists  essentially  of  a  clock,  the  pendulum  of 
which  is  caught  by  means  of  a  lever  connected  with 
the  telephone  lever.  By  such  means  the  clock  is 
stopped  while  the  telephone  is  out  of  use  or  is 
hung  on  its  hook. 

Method,  Accumulation,  for  Testing 

Joints  in  Electric  Cables A  sensitive 

method  of  testing  the  insulation  of  a  joint,  or 
of  a  few  feet  of  gutta-percha  core,  by  allowing 
the  leakage  of  the  joint  to  accumulate  through 
a  condenser  for  a  considerable  time  and  then 
measuring  the  condenser  discharge. 

Method  of  Slow  Discharge. — (See  Appen- 
dix— Discharge,  Slow,  Method  of.} 

Mho,  Proposed  A.  I.  E.  E.  Definition  for 

A  name  proposed  for  the  practical 

unit  of  conductivity. 

A  unit  of  electrical  conductance  of  the 
value  of  lo-9  absolute  units;  or,  in  other 
words,  having  a  value  equal  to  the  reciprocal 
of  the  ohm. 


Mho.] 


631 


[Mot. 


This  name  for  the  practical  unit  of  electrical 
conductance  was  proposed  by  a  Sub-Committee 
of  the  American  Institute  of  Electrical  Engineers 
on  Provisional  Programme  of  the  International 
Electrical  Congress,  held  in  Chicago,  U.  S.  A., 
in  1893,  on  the  occasion  of  the  World's  Columbian 
Exposition. 

Milometer. — An  instrument  for  measuring 
the  value  of  conductance  in  mhos.  (See  Con- 
ductance. Mho.} 

Micanite. — A  name  sometimes  given  to  a 
variety  of  insulating  material  made  from  pure 
mica  bound  together  by  some  cementing 
material. 

Micro-Ohm. — The  millionth  of  an  ohm. 
Microphone,    Plastic-Circuit  — A 

microphone  in  which  the  ordinary  variable 
contact  is  replaced  by  a  plastic  material  of 
low  conducting  power. 

The  plastic-circuit  microphone  is  the  invention 
of  Clammond.  In  it  the  ordinary  powder  form- 
ing the  loose  contact  is  obtained  by  means  of  a 
plastic  material  composed  of  a  mixture  of  a  good 
conducting  substance  with  some  plastic  non-con- 
ducting material. 

The  advantage  claimed  for  the  plastic-circuit 
telephone  transmitter  is  that  it  has  a  much  greater 
range  of  operation  than  the  ordinary  contact 
microphone,  being  able  to  transmit  either  faint  or 
loud  tones  with  equal  distinctness. 

Migration  of  Ions.— (See  Appendix— Ions, 
Migration  of.) 

Mile,  Ohm The  number  obtained 

by  multiplying  the  weight  of  i  mile  of  wire 
of  a  given  substance  by  its  resistance. 

The  ohm  mile  of  a  given  substance  is  the  mass 
of  a  mile  of  wire  of  that  substance  having  the 
resistance  of  an  ohm. 

Milli-Amnieter.— A  milli-ampere  meter. 

Milli-Aiiipere  Meter.— (See  Meter,  Milli- 
Ampere) 

Mining,  Electric Carrying  on  the 

various  operations  of  mining  by  means  of 
electric  power. 

Electricity  has  been  successfully  employed  in 
mining  for  the  driving  of  percussion  or  rotary 
drills,  for  electric  haulage,  for  pumping,  and  for 
purposes  of  communication,  ventilation,  power 
and  artificial  lighting. 


Minus  Charge.— (See  Appendix— Charge, 
Minus.") 

Molecular  Decomposition. —  (See  Ap- 
pendix— Decomposition,  Molecular?) 

Molecular  Voltaic  Couple. — (See  Ap- 
pendix— Couple,  Molecular  Voltaic?) 

Monad  Atom. — (See  Appendix — Atom, 
Monad.) 

Monochord. — A  single  stretched  wire  for 
measuring  the  relative  number  of  vibrations 
produced  by  different  musical  notes. 

The  instrument  takes  the  name  monochord, 
from  the  fact  that  it  consists,  practically,  of  a 
single  chord  stretched  between  two  points  <»f 
support  over  a  resonant  case,  and  provided  with 
means  for  suitably  adjusting  its  tension  so  as  to 
produce,  when  vibrating  as  a  whole,  a  note  of  a 
given  musical  pitch.  When  it  is  required  to  de- 
termine the  relative  number  of  vibrations  existing 
between  the  note  which  the  monochord  produces 
and  some  other  note,  a  sliding  bridge  is  placed 
in  some  intermediate  part  of  the  wire  so  as  to  cut 
off  a  part  of  its  length. 

When  the  length  of  the  original  wire  has  been 
shortened  by  means  of  a  sliding  bridge,  so  that 
it  produces  a  higher  note  whose  pitch  is  to  be 
compared  with  that  of  the  wire  vibrating  as  a 
whole,  the  relative  number  of  vibrations  are  then 
inversely  proportional  to  the  lengths  of  the  two 
wires. 

Mop,  Polishing  —  —A  disc  formed  of 
circular  pieces  of  calico,  felt,  or  similar  soft 
material  mounted  on  a  shaft  and  employed, 
when  put  in  rapid  rotation,  for  polishing 
articles  so  as  to  prepare  their  surfaces  for 
electro-plating.  (See  Plating,  Electro?) 

For  use,  mops  are  charged  with  fine  polishing 
material;  as,  rouge,  tripoli,  etc. 

Mopped. — Polished  by  the  action  of  a  mop. 
(See  Appendix — Mop,  Polishing?) 

Morse  Push.  —  (See  Appendix  —  Push, 
Morse?) 

Morse  Tapper. — (See  Appendix — Tapper, 
Morsel] 

Motion,  Electrostatic Motion  pro- 
duced by  means  of  an  electrostatic  field 
somewhat  similar  to  the  motion  produced  by 
means  of  a  magnetic  field. 


Mot.j 


632 


[Mot. 


Electrostatic  motion  may  be  produced  by  vary- 
ing electrostatic  fields  placed  at  right  angles  to 
each  other.  When  the  force  varies  in  accordance 
with  the  sine  law,  and  the  difference  in  phase 
varies  by  only  90  degrees,  a  uniform  tendency  to 
rotation  is  produced. 

Motion,  Harmonic A  term  some- 
times employed  in  place  of  simple-harmonic 
notion.  (See  Motion,  Simple-Harmonic!) 

Motion,  Periodic A  term  some- 
times employed  in  place  of  simple-periodic 
motion.  (See  Motion,  Simple-Periodic!) 

Motor,     Constant-Potential  —  A 

motor  designed  for  operation  by  means  of  a 
constant  potential  current. 

Where  the  motor  is  to  be  operated  at  a  constant 
speed,  or  by  a  constant-potential  circuit,  such, 
for  example,  as  an  incandescent  lighting  circuit, 
it  is  generally  made  a  plain,  shunt-wound  motor. 

Motor,  Diphase A  motor  which 

requires  for  its  operation  two  diphase  cur- 
rents. 

The  armature  of  such  a  motor  is  always  wound 
either  with  two  separate  circuits,  or  has  two 
separate  connections  to  the  same  common  wind- 
ing. 

This  term  would  appear  preferable  to  the  term 
two-phase  motor. 

Motor,  Dynamo A  constant  cur- 
rent transformer  or  dynamotor.  (See  Ap- 
pendix— Dynamotor!) 

Motor,  Efficiency  of  Electric The 

watts  delivered  at  the  motor  pulley,  divided 
by  the  watts  supplied. 

Motor,  Electric  Street  Railway,  Backing 
of (See  Appendix — Bucking!) 

Motor,     Electrostatic A     motor 

driven  by  means  of  the  induction  of  two 
varied  electrostatic  fields  at  right  angles  to 
each  other. 

Generally,  a  motor  driven  by  the  action  of 
electrostatic  fields. 

Motor,  Idle  Wire  of (See  Ap- 
pendix—  Wire,  Idle,  of  Armature  of  Motor!) 

Motor,  Induction A  motor  in  which 

the  magnetic  field  is  produced  entirely  by  the 


working  current, '  as  distinguished  from  a 
motor  in  which  the  field  magnets  are  inde- 
pendently maintained. 

An  induction  motor  consists  essentially  of  coils 
of  wire  and  laminated  iron  discs  so  related  to  one 
another  that  the  currents  in  the  moving  parts  are 
induced  by  currents  in  the  stationary  parts. 

Motor,  Magneto A  term  formerly 

employed  for  a  voltaic  battery  coupled  in 
parallel. 

The  current  furnished  by  such  a  battery  being 
capable,  when  employed  with  suitable  electro- 
magnets, to  produce  powerful  magnetism,  was 
called  a  magneto-motor.  This  word  is  generally 
used  as  below. 

Motor,  Magneto A  motor  whose 

field  is  produced  by  permanent  magnets. 

Motor-Man. — A  word  generally  applied  to 
the  person  who  operates  the  motor  car  of 
street  railway  systems. 

Motor,  Multiphase A  term  some- 
times employed  in  place  of  polyphase  motor. 
(See  Appendix — Motor,  Polyphase!) 

Motor,  Polyphase A  motor  ope- 
rated by  means  of  polyphase  currents. 

Motor,  Polyphase,  Unsymmetrical  — — 

— An  unbalanced  polyphase  motor;  /'.  e.,  a 
motor  where  one  circuit  carries  a  greater 
load  than  the  other  circuit  or  circuits. 

Motor,  Single-Phase A  uni-phase 

motor. 

The  term  uni-phase  is  preferable. 

Motor,  Synchronous,  Self-Starting 

— A  motor  of  the  synchronous  type  that  is 
capable  of  self-starting. 

Motor,  Three-Phase A  tri-phase 

motor.  (See  Appendix — Motor,  Tri-Phase!) 

The  term  tri-phase  motor  would  appear  to  be 
preferable. 

Motor,  Tri-Phase A  motor  which 

requires  for  its  operation  three  tri-phase  cur- 
rents. 

The  armature  of  such  a  motor  is  always  wound 
either  with  three  separate  circuits  or  has  three 
separate  connections  to  a  common  winding. 

Motor,     Two-Phase A     diphase 

motor.      (See  Appendix — Motor,  Diphase!) 


5— Vol.  2 


Mot.] 


633 


[Nip. 


The  term  diphase  motor  would  appear  to  be 
preferable. 

Motor,  Uni-Phase A  motor  which 

requires  for  its  operation  a  simple  alternating 
current ;  i.  e.,  a  current  which  is  uni-phase. 

The  term  uni-phase  is  preferable  to  the  term 
single-phase. 

Mounting  of  Filament. — (See  Appendix 
Filament,  Mounting-  of.) 

Multi-Phase  Alternator. — (See  Appendix 
— Alternator,  Multi-Phased) 

Multi-Phase  Motor. — (See  Appendix  — 
Motor,  Multi-Phased) 

Multiple  Auto-reversible  Tele-radio- 
phone.— (See  Appendix  —  Tele-radiophone, 
Auto-reversible  or  Multiple?) 

Multiple-Lightning  Flash.— (See  Ap- 
pendix— Flash,  Multiple-Lightning?) 

Multiple-Parallel  Circuit.  —  (See  Ap- 
pendix— Circuit,  Multiple-Parallel!) 


Multiplex  Telegraph.— (See  Appendix— 
Telegraph,  Multiplex?) 

Multiplex  Telephony.— (See  Appendix— 
Telephony,  Multiplex?) 

Multiplier,  Astatic A  term  some- 
times employed  for  an  astatic  galvanometer. 
(See  Galvanometer,  Astatic?). 

Multiplier,  Dynamic A  term  for- 
merly applied  to  a  self-induction  coil.  (See 
Appendix — Coil,  Induction,  Self.} 

Multiplier,    Electro-Magnetic A 

term    sometimes    employed  for  Sweigger's 
Multiplier.     (See  Multiplier,  Sweigger's.) 

Municipal  System  of  Incandescent  Elec- 
tric Lighting.— (See  Appendix—  System, 
Municipal,  of  Electric  Lighting?) 

Mutually  Induced  Currents.— (See  Ap- 
pendix— Currents,  Mutually  Induced?) 


N 


n. — A  symbol  sometimes  employed  for 
frequency. 

Natural  Period. — (See  Appendix — Period, 
Natural?) 

Needle,  Drift  of- The  failure  of  the 

needle  of  a  galvanometer  to  remain  at  its 
zero  point  when  no  current  is  passing  through 
its  coils,  usually  due  to  variation  in  the 
magnetic  condition  of  the  needle,  or  to 
variation  in  the  torsion  of  the  suspending 
fibre,  local  causes,  etc. 

Needle  Telegraph.  —  (See  Appendix — 
Telegraph,  Needle!) 

Needle,     Vertical     Magnetic A 

term    sometimes   employed    for    a   dipping 
needle.     (See  Needle,  Magnetic,  Dipping!) 
Negative  Electrification. — (See  Appendix 
— Electrification,  Negative!) 

Negative  Fluid.— (See  Appendix— Fluid, 
Negative!) 

Negative  Spark.— (See  Appendix— Spark, 
Negat-'v.!) 


Neutral  Zone  of  Electrically  Charged 
Insulated  Conductor. —  (See  Appendix— 
Zone,  Neutral,  of  Electrically  Charged  In- 
sulated Conductor?) 

Neutral  Zone  of  Magnet. — (See  Ap- 
pendix— Zone,  Neutral,  of  Magnet?) 

Nipple  on  Negative  Carbon. — A  small 
projection  formed  at  the  end  of  the  negative 
carbon  directly  opposite  the  positive  carbon 
of  a  voltaic  arc  that  has  been  established  for 
some  little  time. 

The  nipple  is  formed  at  the  end  of  the  nega- 
tive carbon  directly  opposite  the  crater  in  the  op- 
posing end  of  the  positive  carbon  by  the  de- 
position of  volatilized  carbon  from  the  positive 
electrode.  The  material  of  the  nipple  is  pure 
graphite  or  plumbago. 

If  the  ends  of  the  carbons,  that  are  thrown  away 
from  an  electric  arc  lamp  on  trimming  the  lamp, 
be  examined,  they  will  be  found  to  possess  either 
a  small  crater  or  a  small  projection  or  nipple  at 
their  burned  end. 


Nod.l 


634 


[Osc. 


Either  of  these  ends,  but  especially  the  nipple 
at  the  negative  caroon,  is  formed  of  pure  graphite 
sufficiently  soft  to  be  readily  used  for  some  con- 
siderable time  as  a  lead  pencil. 

Node. — A  point  of  comparative  rest  in  a 
vibrating  body. 

Since  the  position  of  an  anti-node  for  a  funda- 
mental tone  may  be  the  position  of  the  node  for 
one  of  its  harmonics,  it  is  clear  that  the  nodes  are 
often  necessarily  only  points  of  relative  rest. 


Non-Automatic  Repeater. — (See  Appen- 
dix— Repeater,  Non-Automatic?) 

Non-Ferric  Inductance. — (See  Appendix 
— Inductance,  Non-Ferric?) 

Non-Polar   Transformer. — (See   Appen- 
dix—  Transformer,  Non-Polar?) 

Northern  Light. — (See  Appendix — Light, 
Northern?) 


o. — An  abbreviation  sometimes  used  for 

ohm,  the  practical  unit  of  electric  resistance. 

oa. — A  symbol  sometimes  used  for  angular 

velocity. 

V 

The  denning  equation  is  00=  •=- 

o:  cm. — An  abbreviation  proposed  for 
ohm-centimeter,  the  practical  unit  of  resis- 
tivity. 

Oersted,  Proposed  A.  I.  E.  E.  Definition 

for A  name  proposed  for  the  practical 

unit  of  magnetic  reluctance. 

A  unit  of  magnetic  reluctance  having  a 
value  of  one  absolute  unit. 

This  name  was  proposed  by  a  Sub-Committee 
of  the  American  Institute  of  Electrical  Engineers 
on  Provisional  Programme  for  the  International 
Electrical  Congress,  held  in  Chicago,  V.  S.  A., 
in  1893,  on  the  occasion  of  the  World's  Columbian 
Exposition. 

Ohm,  B.  A. A  resistance  of  14.4521 

grammes  of  mercury  in  the  form  of  a  col- 
umn of  uniform  cross-section  (one  square 
millimetre)  and  104.8  centimetres  in  height 
at  o  degree  C. 

The  above  value  of  the  ohm  was  adopted  as 
the  unit  of  the  British  Association  at  its  meeting 
held  in  Edinburgh  in  August,  1892. 

Ohm,  International The  value 

of  the  international  ohm  adopted  at  the 
Chicago  Congress  of  1893,  as  being  the  re- 
sistance column  based  upon  the  ohm  equal 
to  io9  units  of  resistance  of  the  C.  G.  S. 
system  of  electro-magnetic  units,  and  is  rep- 
resented by  the  resistance  offered  to  an  un- 


varying electric  current  by  a  column  ot 
mercury  at  the  temperature  of  melting  ice 
14.4521  grammes  in  mass,  of  a  constant  cross 
sectional  area,  and  of  the  length  of  106.3 
centimetres. 

Ohm  Mile. — (See  Appendix— Mile,  Ohm?) 

Ohm,  Proposed  A.  I.  E.  E.  Definition  for 
The  resistance  offered  at  the  tempera- 
ture of  melting  ice  by  a  column  of  mercury, 
14.4521  grammes  in  mass,  of  a  constant  cross- 
sectional  area  and  of  a  length  of  106.3  centi- 
metres. 

One-Way  Door  Trigger.— (See  Appendix 
—  Trigger,  One-  Way  Door?) 

Open-Circuit  Transformer. — (See  Ap- 
pendix— Transformer,  Open-Circuit?) 

Opposing  Electromotive  Force. — (See 
Appendix — Force,  Electromotive,  Opposing?) 

Optical  Galvanometer. — (See  Appendix — 
Galvanometer,  Optical?) 

Oscillator,  Hertz's A  term  some- 
times employed  for  two  insulated  metallic 
plates,  to  which  are  attached  metallic  rods, 
terminated  by  rounded  knobs  or  balls  separ- 
ated by  an  air  gap  or  air  space,  through  which 
a  disruptive  discharge  passes. 

The  metallic  plates  represent  the  opposite  coat- 
ing of  a  Leyden  jar.  When  employed  as  Hertz's 
oscillator  each  plate  is  connected  to  the  terminal 
of  a  Ruhmkorffcoil,  and  at  each  discharge  elec- 
trical surgings  are  produced,  which  cause  waves 
to  radiate  from  the  plates  into  the  surrounding 
ether. 

Oscillator,  Hertz's  Axial A  term 

sometimes  employed  for  Hertz's  linear  oscil- 


Osc.] 


635 


lator.  (See  Appendix — Oscillator,  Hertz's 
Linear?) 

Oscillator,  Hertz's  Linear A  form 

of  Hertz's  oscillator  in  which  a  straight  or 
linear  conductor  is  employed  instead  of  a 
plate  as  in  the  ordinary  oscillator.  (See  Ap- 
pendix— Oscillator,  Hertz's!) 

According  to  Lodge,  a  thunder  cloud  con- 
nected to  the  earth  by  means  of  a  lightning  rod 
forms  a  linear  oscillator. 

Out-Put. — The  useful  energy  given  out  by 
a  machine. 

The  out-put  is  generally  taken  in  connection  or 
in  comparison  with  the  in-put.  When  the  use- 
ful or  available  electric  energy  of  any  source  is 


divided  by  the  total  electric  energy,  the  value  of 
a  ratio,  called  the  efficiency,  is  obtained.  In  this 
case  the  out-put,  when  divided  by  the  total  in-put, 
gives  the  efficiency.  (See  Efficiency,  Electric. ) 

Oven,  Baking,  Electrical An  elec- 
trically heated  oaking  oven. 

Almost  any  form  of  baking  oven  can  be  heated 
by  means  of  electric  heaters  suitably  placed 
therein. 

Overflow  of  Leyden  Jar. — (See  Appendix 
• — Jar,  Leyden,  Overflow  of.") 

Overlap  Test. — (See  Appendix —  Test, 
Overlap?) 

Over-Maximal  Contraction. — (See  Ap- 
pendix— Contraction,  Over-Maximal?) 


P. — A  symbol  proposed  for  power. 

W 

The  denning  equation  is  P  =  •= 

P. — A  symbol  proposed  for  electric  power. 

The  same  symbol  is  proposed  for  mechanical 
power. 
The  defining  equation  is  P  =  C  E. 

p. — A  symbol  proposed  for  pressure. 

jr 
The  defining  equation  is  p  =  -^ 

$. — A  symbol  employed  for  flux  of  mag- 
netic force. 
The  defining  equation  is  $  =  §g  X  S. 

Pacinotti  Teeth, — (See  Appendix—  Teeth, 
Pacinotti?) 

Page     Effect— (See     Appendix— Effect, 
Page.)       . 

Pair,  Thermo A  thermo   couple. 

(See  Couple,  Ther mo-Electric?) 

Pair,    Thermo-Electric A     term 

sometimes  employed  in  place  of  thermo-elec- 
tric couple.    (See  Couple,  Thermo-Electric.} 

Pair,  Voltaic A  term  sometimes 

employed  in  place  of  voltaic  couple.     (See 
Couple,  Voltaic?) 


Pan,  Backing A  pan  in  which  the 

copper  shell  of  an  electrotype  is  placed,  in 
order  to  receive  its  backing  of  type  metal. 

When  the  copper  shell  has  been  placed  in  the 
backing-pan,  for  the  purpose  of  receiving  its 
backing  of  type-metal,  it  has  its  back  covered 
with  sheets  of  tin-foil.  It  is  then  placed  along 
with  the  backing-pan  in  the  melting-pot,  a  pot 
filled  with  melted  type-metal,  on  which  it  is  per- 
mitted to  float  until  the  covering  of  tin- foil  is 
melted.  It  is  now  removed  and  placed  on  a  level 
table  where  the  molten  metal  from  the  melting 
pot  is  poured  over  it  until  a  layer  of  the  required 
thickness  is  obtained. 

Pan-Telephone. — (See  Appendix  — 'Tele- 
phone, Pan.) 

Parallel-Arc  Circuit. — (See  Appendix — 
Circuit,  Parallel-Arc?) 

Parallel  Connection  of  Alternators. — 

(See  Appendix — Alternators,  Parallel  Con- 
nection of.) 

Parallel  Working  of  Alternating  Dy- 
namo-Electric Machines. — (See  Appendix — 
Machines,  Dynamo-Electric,  Alternating, 
Parallel  Working  of?) 

Paramagnetized. — Endowed  with  para- 
magnetic properties.  (See  Paramagnetism.) 


Pas.] 


636 


[Pha. 


Passive  Resistance. — (See  Appendix — 
Resistance,  Passive?) 

Path,  Magnetic  Flux The  path  or 

circuit  taken  by  the  lines  of  magnetic  force 
or  flux. 

Pear  Push.  —  (See  Appendix  —  Push, 
Pear!) 

Peltier's  Cross.— (See  Appendix— Cross, 
Peltier's!) 

Pencil,  Carbon A  term  sometimes 

employed  for  a  carbon  rod. 

A  rod  or  cylinder  of  carbon,  as  distinguished 
from  a  plate. 

Pendant  Socket — (See  Appendix— Socket, 
Pendant?) 

Pendulnni,  Electric A  term  some- 
times employed  for  a  pith  ball  electroscope, 
so  arranged  as  to  move  to-and-fro  like  an 
ordinary  pendulum. 

This  use  of  the  term  is  to  be  avoided,  since  the 
word,  as  primarily  employed,  signifies  either  a 
pendulum  driven  by  electric  impulses,  or  a  pen- 
dulum so  arranged  as  to  produce  timed  impulses. 

The  term  electroscopic  or  electrostatic  pen- 
dulum  would  appear  preferable.  (See  Pendulum, 
Electric.) 

Pentad  Atom. — (See  Appendix  —  Atom, 
Pentad.) 

Percentage  Conductivity  of  Wire.— (See 
Appendix  —  Conductivity,  Percentage,  of 
Wire.) 

Period. — The  interval  of  time  between  two 
successive  passages  of  a  vibration  through 
a  given  point  of  its  path  taken  in  the  same 
direetion. 

Period,  Natural The  period  of 

harmonic  frequency  which  brings  it  to  the 
same  value  as  that  of  the  fundamental  fre- 
quency. 

The  natural  period,  according  to  Lodge,  is 
represented  by  the  following  formula. 

T  =  2 ic N/LC  X  io-3 
Where  T  =  the  period  in  seconds. 

L  =  the  coefficient  of  self-induction  in 

henries. 
C  =  the  capacity  in  micro-farads. 


The  natural  period  can  be  varied  either  by 
varying  the  self-induction  of  the  circuit  or  by 
varying  its  capacity. 

Period,  Variable,  of  Telegraph  Line 

— The  time  required  for  a  current  in  a  tele- 
graph line  to  reach  a  constant  strength 
after  the  circuit  through  it  is  closed. 

Periodic  Motion. — (See  Appendix — Mo- 
tion, Periodic!) 

Periodicity  of  Alternation. — (See  Ap- 
pendix— Alternation,  Periodicity  of.) 

Permanent  Laminated  Magnet. — (See 
Appendix  —  Magnet,  Laminated,  Perma- 
nent!) 

Permanent  Telegraphic  Signal. — (See 
Appendix  —  Signal,  Telegraphic,  Perma- 
nent!) 

Permeation. — A  word  sometimes  em- 
ployed for  the  number  of  lines  of  magnetic 
force  per  square  centimetre. 

Permittance. — A  word  proposed  for 
dielectric  capacity.  (See  Appendix — Capa- 
city, Specific  Dielectric!) 

Electrostatic  induction  takes  place  between  the 
two  coatings  of  a  condenser,  or  between  two 
copper  conductors  across  the  dielectric  between 
them.  Dielectrics  differ  greatly  in  their  ability 
to  permit  this  influence  to  pass  through  them,  and 
this  difference  has  been  called  the  dielectric 
capacity,  the  specific  inductive  capacity,  the  in- 
ductive capacity,  or  the  permittance.  (See 
Capacity,  Specific  Inductive.) 

Permittivity. — A  word  sometimes  em- 
ployed for  specific  permittance.  (See  Ap- 
pendix— Permittance!) 

Phantom,  Magnetic A  term  some- 
times employed  for  magnetic  figures.  (Se* 
Figures,  Magnetic.  Field,  Magnetic!) 

Phantom  Streams.  —  (See  Appendix  — 
Streams,  Phantom!) 

Phase.— The  fractional  part  of  a  period 
which  has  passed  since  a  vibrating  body  last 
passed  through  the  extreme  point  of  its  path 
in  the  positive  direction. 

Phase  Angle. — (See  Appendix— Angle, 
Phase.) 


Pha.] 


637 


[Plu. 


Phase  Windings.  —  (See  Appendix  — 
Winding's,  Phase.} 

Phenomena. — Plural  of  phenomenon. 

Phonogram. — A  dispatch  transmitted  by 
means  of  a  telephone. 

The  word  phonogram  corresponds  to  the  word 
telegram. 

This  word  is  also  used  for  the  record  produced 
by  a  phonograph. 

Phonoplex  Telegraph.— (See  Appendix— 
Telegraph,  Phonoplex!) 

Phosphorescent  Lamp.— (See  Appendix — 
Lamp,  Phosphorescent!) 

Phosphorus,  Mercurial A  term 

employed  by  Hawksbee  in  1795  for  the  light 
produced  by  the  motion  of  a  column  of  mer- 
cury in  an  exhausted  tube. 

The  light  so  produced  is  due  to  electricity 
caused  by  the  friction  of  the  mercury  against  the 
walls  of  the  tube.  Such  a  light  is  often  seen  in 
the  Torricellian  vacuum  which  exists  in  the  space 
above  the  mercurial  column  in  a  barometer  tube. 

Photo-Electric  Alarm. — (See  Appendix — 
Alarm,  Photo-Electric?) 

Photo-Electric  Impulsion  Cell. — (See 
Appendix — Cell,  Photo-Electric  Impulsion!) 

Photometer,  Spectro A  form  of 

photometer  suitable  for  measuring  the  rela- 
tive intensities  of  lights  of  different  qualities. 

A  spectro-photometer  consists  essentially  of 
means  by  which  the  two  parallel  beams  of  light 
that  are  to  be  compared  are  passed  side  by  side 
through  the  same  prism.  The  field  is  then 
limited  to  a  single  color,  and  the  respective 
intensities  of  the  two  lights  as  regards  this  par- 
ticular  character  of  radiation  are  then  compared. 

Photo-Micrography,  Electric The 

art  of  photographing  microscopic  images  by 
means  of  the  electric  light. 

Physiologist,  Electro One  skilled 

in  the  art  of  electro-physiology.  (See  Physi- 
ology, Electro!) 

Pins,  Core,  of  Magnet Small  pins 

of  copper  or  other  non-magnetic  material 
placed  in'the  cores  of  an  electro-magnet  at 
its  poles  for  the  purpose  of  preventing  stick- 
ing. 


Planer,    Electric  Deck 


— An   elec- 


trically driven  rotary  cutter  or  planer,  adapted 
for  the  ready  planing  of  the  deck  of  a  ship. 

Fig-  579  shows  an  electric  deck  planer.     The 
rotary  cutter  revolves  at  some  three  thousand 


579'    -An  Electric  Deck  Planer. 


revolutions  per  minute,  and  is  so  arranged  as  to 
be  readily  adapted  for  a  varying  depth  of  cut. 

Plastic-Circuit  Microphone. — (See  Ap- 
pendix— Microphone,  Plastic-Circuit!) 

Plates,  Exhausted,  of  Storage  Cell 

A  phrase  employed  to  characterize  the  condi- 
tion of  the  plates  of  a  storage  battery  when 
they  have  furnished  all  the  current  they  are 
capable  of  producing  without  being  injured. 
(See  Plates  of  Secondary  or  Storage  Cell, 
Forming  of!) 

Plates,  Field A  term   sometimes 

applied  to  the  plates  of  tin-foil,  on  a  Toppler- 
Holtz  influence  machine,  which  act  as  in- 
ductors. (See  Machine,  Toppler-Holtz!) 

Plates,  Formed,  of  Storage  Cell 

A  phrase  employed  to  characterize  the  condi- 
tion of  the  plates  of  a  new  storage  battery 
when  they  have  been  prepared  for  regular 
service  by  a  preliminary  process  of  charging, 
or  charging  and  discharging.  (See  Plates  of 
Secondary  or  Storage  Cell,  Forming  of!) 

Plating  Trough.  —  (See  Appendix  — 
Trough,  Plating!) 

Plug,  Attachment A  plug  for  at- 
taching and  connecting  a  flexible  cord  to  any 
lamp  socket  or  receptacle. 

Plus  Charge.— (See  Appendix — Charge, 
P!us!\ 


Poc.] 


638 


[Pot, 


Pocket  Galvanometer.-  (See  Appendix — 
Galvanometer,  Pocket?) 

Point,  Indifferent A  term  some- 
times employed  for  the  neutral  point  of  a 
magnet.  (See  Line,  Neutral,  of  a  Magnet?} 

Point,  Smashing,  of  Incandescent  Elec- 
tric Lamps The  point  in  the  life  of 

an  incandescent  electric  lamp  at  which  it  is 
said  to  be  more  economical  to  replace  it  by 
a  new  lamp  than  it  is  to  keep  it  any  longer 
in  use. 

The  life  of  an  incandescent  electric  lamp  can 
be  preserved  for  many  thousand  hours.  It  is 
claimed,  however,  that,  so  far  as  economy  is  con- 
cerned, it  is  more  economical  after  a  certain 
number  of  hours  burning  to  replace  it  by  another 
than  it  is  to  continue  it  any  longer  in  use.  This 
conclusion,  however,  is  by  no  means  generally 
accepted. 

The  length  of  life  will,  of  course,  depend  on 
the  make  of  the  lamp  and  the  potential  to  which 
it  has  been  exposed.  Cases,  however,  may  fre- 
quently arise  where  it  will  be  more  economical  to 
use  the  lamp  under  an  increased  difference  of  po- 
tential than  to  cease  using  it. 

Polar  Aurora. — (See  Appendix — Aurora, 
Polar.} 

Polar  Transformer. — (See  Appendix — 
Transformer,  Polar} 

Polarization  Battery. — (See  Appendix — 
Battery,  Polarization.} 

Polarization,  Gas A  term  some- 
times employed  for  that  form  of  polarization 
which  is  due  to  the  collection  of  a  gas,  gen- 
erally hydrogen,  on  the  negative  plate.  (See 
Cell,  Voltaic,  Polarization  of} 

Polarized  Indicator. — (See  Appendix — 
Indicator,  Polarized.} 

Pole  Indicator. — (See  Appendix— Indi- 
cator, Pole} 

Pole,  Magnetic,  Blue A  term 

sometimes  employed  for  that  pole  of  a  mag- 
net which  points  approximately  towards  the 
geographical  south  pole. 

The  natural  confusion  arising  from  this  non- 
descriptive  term  is  still  further  increased  by  the 
fact  that  some  writers  use  the  word  blue-pole  for 


the  pole  which  points  towards  the  geographical 
north  pole. 

Pole,  Magnetic,  Red A  term  some- 
times employed  for  the  pole  of  a  magnet 
which  points  approximately  towards  the  geo- 
graphical north  pole. 

Sometimes  used  in  opposite  sense.  (See  Ap- 
pendix— Pole,  Magnetic,  Blue.} 

Pole,    Magnetic,    Unmarked A 

term  sometimes  employed  for  the  south  pole 
of  a  magnet. 

Pole,  Resultant  Magnetic A  term 

sometimes  employed  for  a  consequent  pole. 
(See  Pole,  Consequent?) 

Polishing  Bob. — (See  Appendix  —  Bob, 
Polishing?) 

Polishing  Mop. — (See  Appendix — Mop, 
Polishing.} 

Polyphase  Apparatus. — (See  Appendix — 
Apparatus,  Polyphase.} 

Polyphase  Armature. — (See  Appendix— 
Armature,  Polyphase.} 

Polyphase  Currents. — (See  Appendix^- 
Currents,  Polyphase?) 

Polyphase  Generator. — (See  Appendix — 
Generator,  Polyphase.') 

Polyphase  Motor.  —  (See  Appendix  — 
Motor,  Polyphase} 

Polyphase  Working. — (See  Appendix — 
Working,  Polyphase.} 

Polyphased  Alternating  Currents. — (See 
Appendix — Currents,  Polyphased,  Alternat- 
ing} 

Positive  Electrification.— (See  Appendix 
— Electrification,  Positive?) 

Positive  Fluid.— (See  Appendix— Fluid, 
Positive} 

Positive  Spark. — (See  Appendix — Spark, 
Positive.) 

Potash  Brush. — (See  Appendix— Brush, 
Potash} 

Potential,  Scalar A  potential  pos- 
sessing magnitude  and  sign  without  directive 
signification,  as  distinguished  from  a  vector 
potential,  which  possesses  both  direction  and 


Pot.] 


639 


[Pro. 


magnitude.  (See  Appendix — Potential,  Vec- 
tor,} 

Potential,  Vector A  potential  pos- 
sessing directive  properties  and  one  that  may 
be  derived  by  the  process  of  summation 
from  vectors,  or  elementary  directed  quanti- 
ties, as  opposed  to  a  scalar  potential,  which 
possesses  undirected  magnitude.  (See  Ap- 
pendix— Potential,  Scalar!) 

Potentiometer,  Alternating  Current 

— A  form  of  potentiometer  designed  for 
measuring  the  differences  of  potential  in  al- 
ternating current  circuits. 

Power  Factor. — (See  Appendix — Factor, 
Power.) 

Power,  Man A  unit  of  power  equal 

to  YO  horse-power,  or  about  74^  watts. 

Pressure,  Electric A  term  some- 
times loosely  employed  for  difference  of  po- 
tential or  electromotive  force.  (See  Poten- 
tial, Difference  of.) 

The  terms  potential  difference  and  elec- 
tromotive force  are  preferable  terms.  The  use 
of  the  term  electric  pressure  can  well  be  aban- 
doned. The  term  electric  pressure,  however,  is 
much  to  be  preferred  to  the  very  objectionable 
term  electric  tension,  or  difference  of  tension. 

Primary  Cell.  —  (See  Appendix — Cell, 
Primary.) 

Primary  Electric  Clock. — (See  Appendix 
— Clock,  Primary  Electric?) 

Primary  Electric  Heater. — (See  Appendix 
— Heater,  Primary  Electric?) 

Primary  Spiral  of  Induction  Coil.— (See 
Appendix — Spiral,  Primary,  of  Induction 
Coil.) 

Process,  Building,  for  Moulds  of  Elec- 
trotypes   A  process  for  bringing  up 

the  blank  spaces  in  the  mould  of  an  electro- 
type by  the  use  of  wax,  melted  by  a  build- 
ing iron — the  high  places  thus  built  up 
becoming  depressions  in  the  finished  plate. 

Process,  Coking,  for  Filament  of  Incan- 
descent Electric  Lamp  — A  process 


for  converting  the  carbon  of  an  incandescent 
filament  into  coke,  by  subjecting  it,  while  in 
a  vacuum,  to  the  prolonged  heating  action  of 
a  powerful  electric  current.  (See  Appendix — • 
Filament,  Coked.) 

Process,  Qnicking A  term  em- 
ployed in  electro-plating  for  a  process  by 
means  of  which  an  article  that  is  to  be  electro- 
plated with  silver,  is  previously  coated  with  a 
layer  of  mercury  by  dipping  it  into  a  quicking 
solution,  z.  e.,  a  solution  of  salt  of  mercury. 
(See  Solution,  Quicking?) 

Process,   Stopping-Off A  process 

employed  in  electro-plating  by  means  of  which 
an  article  which  is  to  be  electro-plated  on  por- 
tions only  of  its  surface  with  one  metal,  and 
on  other  portions  with  another  metal,  is  first 
completely  covered  by  an  electro-plating  of 
the  cheaper  metal,  and  is  then  stopped-off,  by 
covering  with  a  coating  of  non-conducting 
varnish  such  portions  only  of  its  surface  as 
are  not  to  receive  the  deposit  of  the  dearer 
metal.  (See  Stopping-Off?) 

Process,  Stopping-Out >A  process 

employed  in  electrotyping  by  means  of  which 
those  parts  of  an  electrotype  mould  that  are 
not  to  be  copied  in  the  electrotype  are  covered 
with  clean  hot  wax. 

The  stopping-out  process  is  similar  to  the  stop- 
ping-off  process  in  electro-plating.  Wherever  the 
black  lead  or  plumbago  surface  is  covered  with 
clean  wax,  the  copper  fails  to  be  deposited. 

Proposed  A.    I.    E.    E.    Definition    for 

Impressed  Electromotive  Force. — (See  Ap- 
pendix—  Force,  Electromotive,  Impressed, 
Proposed  A.  I.  E.  E.  Definition  for?) 

Proposed  A.  I.  E.  E.  Definition  for  Gauss. 

— (See  Appendix — Gauss,  Proposed  A.  I.  E. 
E.  Definition  for?) 

Proposed  A.  I.  E.  E.  Definition  for 
Henry. — (See  Appendix — Henry,  Proposed 
A.  I.E.  E.  Definition  for?) 

Proposed  A.  I.  E.  E.  Definition  for  Iu- 
ductivity.  —  (See  Appendix  —  Inductivity, 
Proposed  A.  I.  E.  E.  Definition  for?) 


Pro.] 


640 


[Pul. 


Proposed  A.  I.  E.  E.  Definition  for  Mho. 

— (See  Appendix — Mho,  Proposed  A.  I.  E.  E. 
Definition  for -.) 

Proposed  A.  I.  E.  E.  Definition  for 
Mutual  Inductance. — (See  Appendix — In- 
ductance,  Mutual,  Proposed  A.  I.E.  E.  Defi- 
nition for?) 

Proposed  A.  I.  E.  E.  Definition  for  North 
Pole  of  Magnet. — (See  Appendix — Magnet, 
North  Pole  of,  Proposed  A.  I.  E.  E.  Defini- 
tion for?) 

Proposed  A.   I.    E.    E.    Definition    for 

Oersted. — (See  Appendix — Oersted,  Proposed 
A.  I.  E.  E.  Definition  for.) 

Proposed  A.  I.  E.  E.  Definition  for  Ohm. 

— (See  Appendix — Ohm,  Proposed  A.  I.  E. 
E.  Definition  for?) 

Proposed  A.  I.  E.  E.  Definition  for  Poly- 
phase Alternating  Current. — (See  Appen- 
dix— Current,  Polyphase  Alternating,  Pro- 
posed A.I.  E.  E.  Definition  for?) 

Proposed  A.  I.  E.  E.  Definition  for  Re- 
luctivity. —  (See  Appendix  —  Reluctivity, 
Proposed  A.  I.  E.  E.  Definition  for?) 

Proposed  A.  I.  E.  E.  Definition  for  Self- 
Inductance. — (See  Appendix — Inductance, 
Self,  Proposed  A.  I.  E.  E.  Definition  for?) 

Proposed  A.  I.  E.  E.  Definition  for  South 
Pole  of  Magnet. — (See  Appendix — Magnet, 
South  Pole  of,  Proposed  A.  I.  E.  E.  Defini- 
tion for?) 

Proposed  A.  I.  E.  E.  Definition  for 
Triphase  Alternating  Current. — (See  Ap- 
pendix— Current,  Triphase  Alternating, 
Proposed  A.  I.  E.  E.  Definition  for?). 

Proposed  A.  I.  E.  E.  Definition  for  Volt. 

— (See  Appendix  —  Volt,  Proposed  A.  I.  E.  E. 
Definition  for?) 

Proposed  A.  I.  E.  E.  Definition  for  Watt. 

—(See  Appendix —  Watt,  Proposed  A.  I.  E. 
E.  Definition  for?) 

Proposed  A.  I.  E.  E.  Definition  for  Web- 
er.—(See  Appendix  —  Weber,  A.  I.  E.  E. 
Definition  for?) 


Protection,  Conduction  Lightning 

— The  protection  of  any  instrument  from  the 
passage  of  a  current  due  to  lightning  around 
its  coils,  and  so  disturbing  the  magnetism  of 
the  needle. 

Protection,  Insulation  Lightning  

— The  protection  of  any  instrument  from  the 
jumping  of  a  spark  across  it  from  layer  to 
layer. 

Protective  Action.— (See  Appendix— Ac- 
tion, Protective?) 

Protective  Throw. —  (See  Appendix — 
Throw,  Protective?) 

Protector,  Cage,  for  Lightning  Dis- 
charges   A  term  sometimes  employed 

for  protecting  sheaths  for  lightning  dis- 
charges. (See  Sheath,  Protective?) 

The  method  consists  essentially  in  surrounding 
the  body  to  be  protected  by  conducting  wires  in 
the  form  of  a  cage. 

Protector,  Conduction  Lightning 

A  lightning  protector  by  means  of  which  a 
current  is  prevented  from  passing  around  the 
coil  of  a  galvanometer  or  other  needle  instru- 
ment, and  thus  disturbing  the  magnetism  of 
the  needle. 

Protector,  Insulation  Lightning 

A  lightning  protector  by  means  of  which  a 
discharge  is  prevented  from  jumping  across 
the  coil  of  an  instrument  from  layer  to  layer, 
and  thus  damaging  the  insulation. 

Pull  Bell,  Circuit  Closer  for A 

device  suitable  for  attachment  to  a  mechanical 
door  pull,  so  as  to  make  an  electrical  contact 
for  the  ringing  of  an  electric  bell,  without  pre- 
venting the  original  bell  from  being  operated 
by  the  mechanical  pull. 

Pull-Off,  Double  Curve In  a  system 

of  electric  street  railways  a  hanger  supported 
by  a  lateral  strain  in  opposite  directions,  used 
generally  at  the  ends  of  both  single  and 
double  curves  and  at  intermediate  points  on 
double  track  curves. 

A  double  curve  hanger. 

Pull-Off,  Single  Curve In  a  system 

of  electric  street  railways  a  hanger  supported 


Pill.] 


641 


[Baa. 


in  one  direction  by  a  lateral  strain  except  at 
the  ends  and  on  the  inside  curve  of  double 
tracks. 

A  single  curve  hanger. 

Puncturation,  Electro A  term  pro- 
posed for  electro-puncture. 

Electro-puncture  would  appear  to  be  the  .pref- 
erable term.  (See,  Puncture,  Electro.} 

Push,  Double-Contact A  push  pro- 
vided with  two  contacts,  so  arranged  that  the 
pressure  of  the  push  opens  one  contact  and 
closes  the  other. 

Push,  Morse A  terjn  sometimes 

employed  in  place  of  double-contact  push. 
(See  Appendix — Push,  Double-Contact!) 

Push,  Pear A  pear-shaped    push 


provided  for  attachment   to  a  flexible  con- 
ducting cord. 

Push,  Sounder An  apparatus,  con- 
sisting of  a  push  so  combined  with  a  sounder 
as  readily  to  enable  the  one  pushing  it  to 
know  whether  a  distant  bell  has  rung  or  not 
on  the  depression  of  the  push  button. 

Push  Switch.— (See  Appendix— Switch, 
Push) 

Pyro-Electric  Crystal.— (See  Appendix — 
Crystal,  Pyro-Electric!] 

Pyrogravure.— A  process  for  the  decora- 
tion of  wood,  copper  or  glass  by  the  burning 
action  of  an  electrically  or  otherwise  heated 
tool. 


Q 


Q. — A  symbol  used  for  quantity  of  elec- 
tricity. 
The  defining  equation  is  Q  =  CT. 

Quad. — An  abbreviation  sometimes  em- 
ployed for  a  unit  of  self-inductance.  (See 
Quadrant!) 

The  same  abbreviation  is  also  employed  for 
quadruplex,  but  the  context  will  generally  pre- 
vent any  confusion. 

Quadmeter. — A  secohmmeter.  (See  Sec- 
ohmmeter!) 

Quadrantal  Deviation  of  Mariner's  Com- 
pass.— (See  Appendix — Deviation,  Quad- 
rantal,  of  Mariner's  Compass!) 

Quadruplex  Telegraph.— (See  Appendix 
—  Telegraph,  Quadruplex!) 

Quality  of  Radiation.— (See  Appendix— 
Radiation,  Quality  of.} 


Quantity  Meter.— (See  Appendix— Meter 
Quantity!) 

Quick  Break.— (See  Appendix— Break, 
Quick!) 

Quick-Break  Switch.— (See  Appendix— 
Switch,  Quick-Break!) 

Quickened. — A  term  employed  in  electro- 
plating for  a  surface  which  has  been  prepared 
for  the  reception  of  a  deposit  of  silver,  by 
dipping  the  article  into  a  quickening  liquid. 
(See  Solution,  Quicking!) 

Quickening  Liquid.— (See  Appendix— 
Liquid,  Quickening!) 

Quickening  Solution. — A  quicking  solu- 
tion. (See  Solution,  Quicking!) 

Quicking  Process. — (See  Appendix — Pro- 
cess, Quicking!) 


R. — A  symbol  used  for  resistance. 

E 

The  defining  equation  is  R  =  -^ 

oft. — A  .symbol  proposed  for  magnetic  re- 
sistance or  reluctance. 

The  defining  equation  is  §f{,  =  v-^ 


p. — A  symbol  used  for  specific  electrical 
resistance  or  reluctivity. 

The  symbol  v  has  been  proposed  for  this  quan- 
tity by  Hospitalier. 

R.  M.  S.  Current — (See  Appendix— Cur- 
rent, R.  M*.  S.} 

Raad. — A  name    formerly  given    by  the 


Bad.] 


642 


[Rai. 


Arabians  to  the  torpedo  or  electrical  ray. 
(See  Torpedo,  Electric.  Ray,  Electric.} 

Radial  Current.— (See  Appendix— Cur- 
rent, Radial.} 

Radian.— Unit  angle. 
An  angle  such  that  its  circular  arc  is  equal 
in  length  to  its  radius. 
Its  value  in  degrees  is  approximately  57°  17' 

45"- 

The  radian  is  not  employed  in  practical  appli- 
cations, since  the  degree  is  the  unit  angle  in 
ordinary  use,  but  in  mathematics  angles  are 
nearly  always  discussed  in  terms  of  the  radian. 

Radian  Per  Second.  —  Unit  angular 
velocity  of  a  rotating  body. 

Radiation,  Efficiency  of A  term 

sometimes  employed  to  represent  the  ratio  of 
the  non-luminous  to  the  luminous  radiation  in 
the  case  of  a  body  emitting  light  and  heat. 

The  efficiency  of  the  ordinary  sources  of  arti- 
ficial light  is  very  low.  The  efficiency  of  the 
radiation  of  the  firefly  or  glow-worm  is  very 
high,  practically  all  its  radiation  belonging  to  the 
luminous  type. 

Radiation,  Electric The  transfer- 
ence of  electric  energy  by  means  of  waves 
set  up  in  the  surrounding  ether. 

During  the  oscillatory  discharge  of  a  Leyden  jar, 
or,  in  general,  during  any  disruptive  discharge, 
the  electricity  surges  or  rushes  to  and  fro,  send- 
ing out  or  radiating  its  energy  into  the  surround- 
ing ether  by  means  of  waves. 

It  does  this  until  all  its  energy  is  either  directly 
dissipated  in  this  manner,  or  is  converted  into 
heat  in  the  conductor,  which  is  afterwards  dis- 
sipated as  heat-waves. 

The  lengths  of  the  waves  thus  sent  out  into 
space  by  means  of  direct  radiation  of  the  electri- 
cal energy  depend  on  a  variety  of  circumstances, 
the  most  important  of  which  are  : 

(l.)  On  the  capacity  of  the  condensers. 

(2.)  On  the  self-induction  of  the  radiating 
system. 

Radiation,  Intensity  of The  ratio 

existing  between  the  amount  or  quantity  of 
radiation  and  the  surface. 

Radiation,  Quality  of Variations 

in  the  radiation  due  to  differences,  both  in  the 


various  wave  lengths  present  and  in  the 
polarization. 

Radiation,  Selective  — Radiation 

limited  to  waves  of  a  particular  wave  length. 

The  character  of  the  radiation  depends. 

(I.)  On  the  nature  of  the  body. 

(2.)  On  the  condition  of  its  surface. 

(3.)  On  the  temperature. 

Langley  has  shown  that  in  the  case  of  a  lumin- 
ous body  the  proportion  existing  between  the 
visible  radiation  and  the  invisible  radiation  varies 
greatly  in  different  cases.  In  the  case  of  a  gas 
flame,  2.4%  of  the  radiation  is  luminous.  In  the 
case  of  the  arc  light  about  10  per  cent,  is  lumin- 
ous, while  in  the  light  emitted  by  the  firefly  or 
the  glow-worm  practically  all  the  radiation  is 
luminous. 

Radiator,  Electric An  electric 

heater  so  placed  as  to  radiate  its  heat  into 
the  room  or  space  to  be  heated. 

Any  electric  heater  applied  to  heat  the  air  or 
space  that  surrounds  it  may  be  regarded  as  an 
electric  radiator. 

Electric  radiators  are  generally  so  placed  as  to 
prevent  direct  contact  with  their  heated  surfaces. 

Radiophonic  Sounds. — (See  Appendix — 
Sounds,  Radiophonic?) 

Railroad,  Conductor  System  for 

A  system  for  the  propulsion  of  cars  by 
means  of  electricity  taken  from  a  conductor 
placed  near  the  road.  (See  Railroads,  Elec- 
tric, Dependent  System  of  Motive  Power 
for} 

Railway,  Electric,  Battery   System  for 

• A  system  for  the  propulsion  of  cars 

by  means  of  electricity  derived  from  storage 
or  secondary  batteries  placed  on  the  cars. 
(See  Railroads,  Electric,  Independent  Sys- 
tem of  Motive  Power  for.} 

Railway  Generator.  —  (See  Appendix— 
Generator,  Railway} 

Raindrops,  Electrical    Aggregation    of 

The    coalescence    of    a    number  of 

separate  raindrops  into  a  single  drop  by  the 
action  of  electricity. 

Rayleigh  has  observed  the  fact  that  if  a  verti- 
cal water-jet  is  subjected  to  the  influence  of  an 
electrified  stick  of  sealing  wax  held  a  short  dis- 


Rat.J 


[Rep. 


tance  from  the  drop,  the  jet  at  once  shrinks  upon 
itself  and  greatly  changes  its  appearance,  a  great 
number  of  separate  drops  collecting  into  single 
larger  drops. 

Examining  the  drops  by  means  of  intermittent 
illumination  the  coalition  of  the  separate  drops 
can  be  readily  seen.  When  no  difference  of 
potential  exists  between  the  separate  drops  they 
do  not  unite  or  coalesce,  but  when  a  difference 
of  potential  exists,  coalescence  occurs,  and,  since 
such  coalescence  causes  an  increased  difference  of 
potential,  the  drops  rapidly  increase,  both  in  size 
and  potential  difference. 

Ratio  of  Conversion.— (See  Appendix — 
Conversion,  Ratio  of.) 

Ratio  of  Transformation. — (See  Appen- 
dix—  Transformation,  Ratio  of.) 

Bays,  Anodic,  of  Tacuum  Tube 

The  rays  of  light  which  appear  in  the  neigh- 
borhood of  the  anode  of  a  vacuum  tube 
through  which  a  rapid  electric  discharge  is 
passing. 

Bays,  Kathodic,  of  Vacuum  Tube 

The  rays  of  light  which  appear  in  the  neigh- 
borhood of  the  kathode  of  a  vacuum  tube 
through  which  a  rapid  electric  discharge  is 
passing. 

Reactance. — A  term  proposed  by  Hospital- 
ier  for  a  quantity  of  the  same  dimensions  as 
the  resistance,  which  does  not  absorb  energy, 
and  the  square  of  which  added  to  the  square 
of  the  resistance  gives  the  square  of  the  im- 
pedance to  simple  harmonic  currents. 

Calling  Ceff,  the  effective  current,  Eeff,  the 
effective  electromotive  force,  a?,  the  pulsation,  or 
2  TI  times  the  frequency,  then — 

Eeff 


Ceff  = 


The  factor  in  the  parenthesis  is  what  Hospital- 
ier  proposes  to  call  the  reactance. 

Reaction,  Armature The  reactive 

magnetic  influence  produced  by  the  current 
in  the  armature  of  a  dynamo  or  motor  upon 
the  magnetic  circuit  of  the  machine. 

Red    Magnetic    Pole. — (See  Appendix— 
Pole,  Magnetic,  Red?) 


Redressed. — Commuted  or  caused  to  take 
the  same  direction. 

The  commutator  redresses  or  commutes  the 
currents  in  the  armature  and  causes  them  to  flow 
in  the  same  direction. 

Regenerative  CelL— (See  Appendix — Cell, 
Regenerative.) 
Region,  Equatorial,  of  Magnet A 

term  sometimes  employed  for  the  portions  of 
a  magnet  which  lie  near  the  equator.  (See 
Magnet,  Equator  of.) 

Registering  Declination  Magnetometer. 

— (See  Appendix — Magnetometer,  Register- 
ing Declination.) 

Regulating  Socket. — (See  Appendix — 
Socket,  Regulating.) 

Relay  Contact. — (See  Appendix — Contact, 
Relay.) 

Relay,  Kick  of (See  Appendix  — 

Kick  of  Relay.) 

Relay,  Polar,  Telegraphic A  tele- 
graphic relay  provided  with  a  polarized  arma- 
ture. (See  Armature,  Polarized.) 

Reluctancy. — An  alternative  word  pro- 
posed for  reluctivity.  (See  Reluctivity.  Re- 
luctance, Magnetic.) 

Reluctivity,  Proposed  A.  I.  E.  E.  Defini- 
tion for The  reciprocal  of  permea- 
bility. 

Remanent  Magnetism. — (See  Appendix — 
Magnetism,  Remanent^) 

Repeater,  Automatic A  telegraphic 

repeater  which  acts  automatically.  (See  Re- 
peaters, Telegraphic.) 

Repeater,  Button A  form  of 

manual  repeater.  (See  Repeaters,  Tele- 
graphic.) 

Repeater,  Electro-Magnetic,  Callan's 

— A  term  formerly  applied  to  a  variety  of 
vibrating  contact  breaker. 

Repeater,  Manual A  telegraphic 

repeater  which  is  operated  by  hand.  (See 
Repeaters,  Telegraphic.) 

Repeater,  Non-Automatic A  term 

sometimes  employed  for  manual  repeater. 
(See  Repeaters,  Telegraphic.) 


Rep.] 


644 


[Rev. 


Repeating    Telegraphic    Station.— (See 

Appendix — Station,  Repeating  Telegraphic^) 

•Repulsion  Electrometer. — (See  Appendix 
— Electrometer,  Repulsion?) 

Residue,  Electric A  term  proposed 

for  residual  charge. 

The  term  electric  residue  would  appear  to  be 
entirely  unnecessary. 

Resistance,    Apparent  — A    term 

sometimes  employed  for  the  impedance  of  a 
circuit  or  the  resistance  it  offers  to  the  pas- 
sage of  an  alternating  current. 

Resistance,  Conduction The  re- 
sistance offered  by  a  conductor  to  the  pas- 
sage of  an  electric  current. 

Resistance,  Conductor A  term  fre- 
quently employed  for  cop  per  resistance.  (See 
Appendix — Resistance,  Copper?) 

Resistance,  Contact A  resistance 

produced  by  the  contact  of  two  surfaces. 

Resistance,  Copper A  term  fre- 
quently employed  for  expressing  the  resist- 
ance of  a  telegraphic  conductor. 

The  value  of  the  copper  resistance  is  generally 
expressed  in  ohms-per-mile,  ohms-per-knot  or 
ohms-per-kilometre. 

Resistance,  Electric,  of  Metals,  Effect  of 
Temperature  on A  change  in  the  re- 
sistance of  a  metal  following  a  given  change 
in  temperature. 

At  decreasing  temperatures  an  increase  occurs 
in  the  electric  conducting  power  of  the  metals. 

Dewar,  by  means  of  the  intense  cold  produced* 
by  liquefied  oxygen,  found  that  at  very  low  tem- 
peratures all  pure  metals  increase  in  their  conduct- 
ing power  as  the  temperature  decreases.  The 
temperature  curve  is  such  that,  the  resistivity  of 
pure  metals  would  be  zero  at,  or  even  before,  the 
absolute  zero  of  temperature.  In  such  a  case, 
if  a  wire  or  conductor  of  pure  metal  were  placed 
in  the  approximately  absolute  zero  of  inter- 
stellar space,  electricity  would  pass  through  it 
without  loss.  This  must,  however,  be  regarded 
only  as  a  hypothesis. 

According  to  Dewar,  most  non-conducting 
bodies  show  a  conductivity  decreasing  with  the 
temperature. 


Resistance  of  Telegraphic  Leak. — (Sec 
Appendix — Leak,  Telegraphic,  Resistance 
of.) 

Resistance,  Passive A  term  some- 
times employed  for  the  ohmic  resistance  of  a 
circuit.  (See  Resistance,  Ohmic.) 

Resistance,  Specific  Magnetic A 

word  proposed  for  reluctivity.  (See  Reluc* 
tivity.) 

Resistance,  Transition A  term 

formerly  employed  for  the  resistance  experi- 
enced by  a  voltaic  cell  shortly  after  closing  a 
circuit. 

The  transition  resistance  was  inferred  from  the 
decrease  in  the  current  strength,  and  was  for- 
merly attributed  to  a  change  in  the  character  of 
the  electrode.  It  is  now  generally  ascribed  to  the 
electromotive  force  of  polarization. 

This  term  is  also  employed  in  a  somewhat 
similar  sense  in  electro-therapeutics.  (See  Re- 
sistance, Transition.) 

Resistivity. — A  term  proposed  for  specific 
resistance.  (See  Resistance,  Specific) 

Resistivity  is  the  inverse  of  specific  conductivity. 

Resonance,  Acoustic  — The  excite- 
ment or  production  of  waves  or  vibrations  of 
sound  in  an  elastic  body  by  means  of  succes- 
sive impulses  received  by  such  body  from  the 
sound  waves  striking  it. 

Acoustic  resonance  is  a  particular  case  of  sym- 
pathetic vibrations.  Like  all  cases  of  such  vibVa- 
tions,  there  must  exist  between  the  sonorous  body 
in  which  the  waves  of  vibrations  are  excited,  and 
the  body  which  is  producing  the  exciting  waves, 
an  identity  of  wave  length;  or,  in  other  words, 
there  must  exist  between  the  two  strict  syn- 
chronism, so  that  the  effects  of  timed  impulses 
may  be  permitted. 

Resonant  Circuit. — (See  Appendix — Cir- 
cuit, Resonant^ 

Resultant  Fault. — (See  Appendix — Fault, 
Resultant.) 

Resultant  Magnetic  Pole.— (See  Appendix 
— Pole,  Resultant  Magnetic.) 

Retarding  Disc. — (See  Appendix — Disc, 
Retarding. 

Reversals. — In  telegraphy,  alternate  cur- 
rent signals  transmitted  for  the  purpose  of 


Key.] 


645 


[Sea. 


adjustment ;  as,  for  example,  in  obtaining  a 
duplex  balance. 

Reversible  Heating  Effect  of  Electric- 
ity.— (See  Appendix — Electricity,  Reversible 
Heating  Effect  of ".) 

Rheostat,  Adjustable An  adjustable 

resistance,  in  a  compound-wound  dynamo- 
electric  machine,  employed  to  adjust  com- 
pounding for  a  greater  or  less  than  tested 
speed  or  a  greater  or  less  wiring  loss. 

A  term  sometimes  employed  for  a  rheostat, 
or  a  resistance  that  can  readily  be  adjusted 
or  altered.  (See  Rheostat?) 

Strictly  speaking,  any  rheostat  is  an  adjustable 
resistance;  therefore,  this  latter  use  of  the  term 
adjustable  rheostat  would  seem  to  be  unnecessary. 

Ribbon  Induction  Coil. — (See  Appendix 
— Coil,  Induction  Ribbon!) 

Right-Hand  Trolley  Switch.— (See  Ap- 
pendix— Switch,  Right-Hand  Trolley?) 

Right-Handed  Helix.— (See  Appendix — 
Helix,  Right-Handed?) 

Right-Handed  Rotation. — (See  Appendix 
— Rotation,  Right-Handed?) 

Right-Handed  Spiral.— (See  Appendix— 
Spiral,  Right-Handed?) 

Ring,  (ial vanic A  term  sometimes 

applied  to  a  galvanic,  or,  more  properly  speak- 
ing, voltaic  circuit.  (See  Circuit,  Voltaic?) 

Ripple  Marks.— (See  Appendix — Marks, 
Ripple,  Electrical?) 

Rise. — In  interior  house  wiring  that  portion 
of  a  conductor  which  rises  vertically  from  one 
floor  to  another. 

Rocking  Switch.  —  (See  Appendix  — 
Switch,  Rocking?) 


Rosette,  Ceiling A  ceiling  block  of 

ornamental  and  rosiform  design. 

Rotary  Converter.— (See  Appendix—  Con- 
verter, Rotary?) 

Rotary  Transformer. — (See  Appendix — 
Transformer,  Rotary?) 

Rotation,  Electro-Dynamic "  The 

rotation  of  a  magnetic  field  produced  as  the 
resultant  of  two  or  more  magnetic  or  mag- 
netizing forces  of  variable  intensity  acting  at 
an  angle  to  one  another,  whose  maxima  do 
not  coincide,  but  whose  periods  are  the  same." 
— Gutmann. 

Rotation,  Left-Handed A  rotation 

the  direction  of  which  is  opposite  to  that  of 
the  hands  of  a  watch  when  one  looks  directly 
at  the  face  of  the  watch. 

Rotation,  Right-Handed A  rota- 
tion the  direction  of  which  is  the  same  as 
that  of  the  hands  of  a  watch  when  one  looks 
directly  at  the  face  of  the  watch. 

A  direction  the  same  as  that  of  an  ordinary 
right-handed  screw,  when  we  turn  the  upper  side 
of  the  right-hand  outwards. 

Rubber  Tape. — (See  Appendix — Tape, 
Rubber?) 

Rumble. — A  barrel  or  other  hollow  box 
revolved  by  mechanical  power  in  which  small 
articles  that  are  to  be  electro-plated  are 
placed  for  the  purpose  of  polishing  them. 

When  subjected  to  the  rotation  of  the  barrel 
the  articles  became  polished  by  friction  against 
one  another.  Some  dry  sawdust  is  frequently 
placed  in  the  barrel,  to  aid  in  the  polishing  pro- 
cess. 

Running  Torque  of  Motor. — (See  Appen- 
dix— Torque,  Running,  of  Motor.) 


s 


S.—  A  symbol  proposed  for  surface. 

The  defining  equation  is  S  =  L  X  L. 

8. — An  abbreviation  proposed  for  second, 
the  C.  G.  S.  unit  of  time. 

S.  N.  Telegraphic  Instrument.—  (See  Ap- 
pendix— Instrument,  S.  N.,  Telegraphic.) 


S.  P.  Cut-Out.— (See  Appendix— Cut-Out, 
S.P.) 

Sag  of  Conductor  or  Line  Wire. — (See 
A  ppendix — Conductor  or  Line  Wire,  Dip  of.) 

Scalar  Potential. — (See  Appendix — Po- 
tential, Scalar.) 


Sec.] 


646 


[Ser. 


Secondary  Spiral  of  Induction  Coil. — 

(See  Appendix — Spiral,  Secondary,  of  In- 
duction Coil.) 

Section  Box. — (See  Appendix — Box,  Sec- 
tion.) 

Segment,  Dark,  of  Aurora A  dark 

or  non-illumined  portion  of  the  sky  in  the 
neighborhood  of  an  aurora. 

Segment,  Unlighted,  of  Aurora 

A  term  employed  by  Nordenskjold  in  place  of 
dark  segment  of  aurora.  (See  Appendix — 
Segment,  Dark,  of  Aurora) 

Selective  Emission. — (See  Appendix — 
Emission,  Selective.} 

Selective  Radiation. — (See  Appendix — 
Radiation,  Selective.) 

Selective  Signal. — (See  Appendix — Sig- 
nal, Selective.) 

Selective  Signalling  Apparatus.— (See 
Appendix — Apparatus,  Selective  Signal- 
ling.) 

Self-Compounding  Polyphase  Genera- 
tor.— (See  Appendix — Generator,  Self -Com- 
pounding Polyphase.) 

Self-induction  Coil. — (See  Appendix — 
Coil,  Induction,  Self.) 

Self-Starting  Synchronous  Motor. — (See 
Appendix — Motor,  Synchronous,  Self-Start- 
ing.} 

Semaphoric  Electroscope. — (See  Appen- 
dix— Electroscope,  Semaphoric.) 

Semi-Circular  Deviation  of  Mariner's 
Compass. — (See  Appendix — Deviation,  Semi- 
Circular,  of  Mariner's  Compass?) 

Semi-Conductors.— (See  Appendix — Con- 
ductor, Semi?) 

Sensitiveness  of  Telephone.— (See  Ap- 
pendix—  Telephone,  Sensitiveness  of) 

Separable  Conducting  Cord  Tip.— (See 
Appendix — Tip,  Conducting  Cord,  Sep- 
arable.) 

Separate-Coil  Alternator. — (See  Appen- 
dix— Alternator,  Separate-Coil.) 

Separate  -  Coil  Alternating  Dynamo- 
Electric  Machine.— (See  Appendix— Ma- 


chine, Dynamo-Electric,  Separate-Coil  Al- 
ternating.) 

Separately-Excited  Alternating  Dynamo- 
Electric  Machine. — (See  Appendix — Ma- 
chine, Dynamo-Electric,  Separately  Excited 
Alternating.) 

Separately-Excited  Alternator.  —  (See 
Appendix — Alternator,  Separately-Excited) 

Separator,    Electro-Magnetic A 

device  for  separating  the  useful  ore  from  the 
dross  in  low  grade  finely  granulated  iron  ores. 
Septum. — A  wall  or  diaphragm  through 
which  osmotic  diffusion  can  take  place.  (See 
Osmose.  Osmose,  Electric) 

Series,  Branched A  term  some- 
times employed  in  place  of  series-multiple. 
(See  Series-Multiple.) 

Series  Connection  of  Alternators. — (See 
Appendix — Alternators,  Series  Connection 
of) 

Series,  Potential,  Dynamos  Coupled  in 

A  term  sometimes  employed  in  teleg- 
raphy for  a  particular  coupling  of  dynamo- 
electric  machines  in  series. 

In  the  application  of  a  number  of  dynamo-elec- 
tric machines  to  the  operation  of  telegraphic  lines 
in  a  central  station,  where  a  number  of  different 
lines  enter  or  leave  the  station,  different  voltages 
are  required  on  the  different  lines.  These  differ, 
ent  voltages  are  most  readily  obtained  by  coup- 
ling the  machines  in  what  is  called  potential 
series. 

In  potential-series  coupling,  the  dynamos  are 
connected  together  in  series,  that  is,  the  positive 
brush  of  one  dynamo  is  connected  to  the  negative 
brush  of  another,  its  positive  brush  to  the  nega- 
tive of  another,  and  so  on  throughout  the  series. 
One  terminal  of  the  battery  of  dynamos  is 
grounded,  and  the  other  connected  to  the  line. 
The  terminals  of  the  various  telegraphic  lines  are 
then  connected  to  points  of  junction  of  contiguous 
dynamos  where  their  opposite  brushes  are  con- 
nected. By  these  means  the  requisite  difference 
of  potential  is  readily  obtained. 

Series  Working  of  Alternating  Dynamo- 
Electric  Machines. — (See  Appendix — Ma- 
chines, Dynamo-Electric,  Alternating, Serif* 
Working) 


Sen] 


647 


[Sig. 


Service  Block.— (See  Appendix— Block, 
Service. 

Shackle  Insulator. — (See  Appendix— In- 
sulator, Shackle?) 

Shading,  Magnetic A  term  some- 
times employed  for  magnetic  screening.  (See 
Screening,  Magnetic. ) 

Sheath,  Closed-Conducting,  for  Light- 
ning Protection A  form  of  lightning 

conductor  proposed  by  Maxwell,  consisting 
essentially  of  a  net-work  or  cage-like  con- 
ductor surrounding  the  house  or  building  to 
be  protected. 

The  theory  for  the  protection  of  a  building  by 
means  of  a  conducting  sheath  is  based  on  the  well 
known  fact  that  there  is  no  trace  of  electrostatic 
charge  inside  a  hollow  conductor. 

It  is  now  well  known  that  there  are  circum- 
stances under  which  the  closed-conducting  circuit 
does  not  thoroughly  protect  a  building  on  which 
it  is  placed.  If  the  number  of  such  circuits  is  suf- 
ficiently great  so  as  to  form  a  close- meshed  cage, 
the  protection  thus  afforded  is  excellent.  Such  a 
sheath,  however,  might  be  dangerous  to  touch. 

Lodge,  who  has  studied  the  matter  of  lightning 
protection  very  thoroughly,  thus  humorously  re- 
marks concerning  the  system  of  sheath  lightning 
protection: 

"  It  would  be  unpleasant,  when  you  are  driven 
home  out  of  a  storm,  to  find  it  so  highly  charged 
as  to  knock  you  down  directly  you  tried  to  enter. 
An  earth  connection  is  necessary  as  well." 

Shell,  Complex-Magnetic A  mag- 
netic shell  whose  strength  varies  from  one 
part  to  another. 

A  complex  magnetic  shell  will  result  from  the 
overlapping  of  a  number  of  simple  magnetic 
shells. 

Shell,  Copper,  of  Electrotype A 

thin  sheet  of  electrolytically  deposited  copper. 

The  copper  shell  is  rendered  sufficiently  rigid 
for  use  by  being  covered  with  a  backing  of  type 
metal. 

In  order  to  permit  this  metal  readily  to  adhere 
to  the  back  of  the  shell  it  is  thoroughly  cleansed 
and  then  covered  on  the  back  with  sheets  of  tin- 
foil, which  are  melted  in  the  backing-pan  pre- 
paratory to  receiving  the  coating  of  type  metal. 


Shell,  Simple  Magnetic A  mag- 
netic shell  whose  strength  is  everywhere 
equal. 

Shifting  of  Spot  of  Light.— A  movement 
of  a  spot  of  light  on  a  scale  produced  by 
other  causes  than  those  acting  during  the 
proper  operation  of  the  instrument,  and  caus- 
ing the  spot  of  light  to  move  away  from  its 
true  zero  position. 

In  the  case  of  a  galvanometer  the  spot  of  light, 
instead  of  remaining  at  the  zero  point,  shifts  or 
moves  from  one  side  to  another  of  the  zero  point. 

This  movement  is  sometimes  called  the  drifting 
of  the  zero  point. 

The  shifting  of  the  spot  of  light  is,  of  course, 
caused  by  the  drift  of  the  needle. 

Shunting  Air  Gap.— (See  Appendix— 
Gap,  Air,  Shunting?) 

Shunt-Out. — A  cut-out  device  for  remov- 
ing an  electro-receptive  device  from  a  circuit, 
without  breaking  the  circuit,  by  providing  a 
short  circuit  between  its  terminals. 

An  electro- magnetic  cut-out  provides  a  shunt- 
out  of  the  device  it  is  desired  to  cut-out  It  will 
be  seen,  however,  that  all  a  shunt-out  does  is  to 
provide  a  by-path,  the  resistance  of  which  is  so 
small  as  compared  with  the  resistance  of  the  de- 
vice cut-out,  that  practically  all  the  current  flows 
past  the  device  through  the  shunt  path,  thus  prac- 
tically cutting  it  out  from  the  circuit ;  or,  more 
properly  speaking,  cutting  it  out  from  the  opera- 
tive  current. 

Side  Arms.  —  (See  Appendix  —  Arms, 
Side.) 

Signal,  Individual In  any  system 

of  electric  communication  devices  by  means 
of  which  bells  or  other  signals,  at  two  or 
more  stations  electrically  connected  in  the 
same  circuit,  are  not  operated  at  all  of  the 
stations  by  the  calls  sent  over  the  line  to  the 
call  bell  at  any  particular  station,  but  in  which 
each  particular  bell  is  only  operated  by  its  own 
call  to  the  exclusion  of  the  other  calls. 

Signal,  Selective A  term  some- 
times employed  in  place  of  individual  signal. 
— (See  Appendix — Signal,  Individual.) 

Signal,  Telegraphic,  Audible Tele- 
graphic signals  that  can  be  heard. 


Sig.] 


648 


[SoU 


Examples  of  audible  telegraphic  signals  are  to 
be  found  in  the  signals  given  by  various  sounders 
of  the  Morse  type. 

The  signals  of  electric  bells  are  also  audible 
signals. 

Signal,  Telegraphic,  Evanescent 

Telegraphic  signals  that  leave  no  permanent 
record. 

Examples  of  evanescent  telegraphic  signals  are 
found  in  the  audible  signals  produced  by  most 
forms  of  telegraphic  sounders. 

Signal,  Telegraphic,  Permanent 

Telegraphic  signals  that  are  recorded  by  any 
means  which  leaves  a  permanent  record. 

The  various  forms  of  recording  or  registering 
apparatus  employed  in  telegraphy  produce  per- 
manent signals. — (See  Recorder,  Morse.  Rec- 
order, Chemical,  Bain's.  Recorder,  Siphon.  Reg~ 
ister,  Telegraphic.) 

Signal,  Telegraphic,  Visual Tele- 
graphic signals  that  can  be  seen. 

Examples  of  visual  telegraphic  signals  are  to  be 
found  in  the  various  galvanometric  receiving  ap- 
paratus employed  in  cable  telegraphy,  or,  in  gen- 
eral, in  needle  telegraphy.  The  signals  received 
on  the  siphon  recorder,  for  example,  are  visible 
signals.  (See  Recorder,  Siphon.) 

Simple  Alternating  or  Two-Phase  Cur- 
rent.— (See  Appendix — Current,  Simple  or 
Two-Phase  Alternating?) 

Simple-Magnetic  Shell. — (See  Appendix 
— Shell,  Simple-Magnetic?) 

Single-Current  Telegraphic  Working. 
— (See  Appendix —  Working,  Single-Cur- 
rent, Telegraphic.} 

Single  Curve  Pull-Off.— (See  Appendix— 
Pull-Off,  Single  Curve?) 

Single-Liquid  Yoltaic  Cell.— (See  Cell, 
Voltaic,  Single-Fluid?) 

Single-Phase  Motor. — (See  Appendix — 
Motor,  Single-Phase?) 

Single-Pole  Cut-Out.— (See  Appendix— 
Cut-Out,  Single-Pole?} 

Single-Wire  System  for  Electric  Light 
Leads.— (See  Appendix  —  Leads,  Single- 
Wire  System  for  Electric  Light?) 

Sinusoidal  Current.— (See  Appendix  — 
Current,  Sinusoidal?) 


Six-Pole   Dynamo-Electric   Machine. — 

(See  Appendix — Machine,  Dynamo-Electric, 
Six-Pole?) 

Six-Wire  System. — (See  Appendix— Sys- 
tern,  Six-  Wire?) 

Skew  Adjustment  of  Carbons  in  Arc 
Lamp. — (See  Appendix — Carbons,  Skew  Ad- 
justment of,  in  Arc  Lamp?) 

Skin  Currents.  —(See  Appendix — Cur- 
rents, Skin?) 

Sliding  Joint. — (See  Appendix— -Joint, 
Sliding.} 

Slinging  Wires. — (See  Appendix —  Wires, 
Slinging?) 

Slipping  of  Belt. — (See  Appendix—^//, 
Slipping  of.) 

Smashing  Point  of  Incandescent  Elec- 
tric Lamps.— (See  Appendix — Point,  Smash- 
ing, of  Incandescent  Electric  Lamps.) 

Snapper  Sounder.  —  (See  Appendix  — 
Sounder,  Snapper.) 

Socket  Base.  —  (See  Appendix — Base, 
Socket?) 

Socket,  Pendant An  attachment  to 

a  socket  provided  with  a  chain  or  chains  for 
turning  on  or  off  a  lamp  not  readily  accessi- 
ble. 

Socket,  Regulating A  lamp  socket 

fitted  with  an  adjustment  under  control  of  a 
key  or  switch  for  regulating  the  degree  of 
incandescence  of  the  filament. 

Socket,  Temporary A  simple  and 

unfinished  form  of  socket  for  holding  a  lamp 
temporarily. 

Solenoid,     Anomalous A     term 

sometimes  applied  to  a  solenoid  with  conse- 
quent poles.  (See  Solenoid,  Practical.) 

Solution,  Amalgamating A  solu- 
tion of  mercury  employed  for  readily  amal- 
gamating the  zincs  of  a  voltaic  battery. 

Maycock  gives  the  following  as  a  good  amalga- 
mating solution: 

Two  pounds  mercury. 

Five  pounds  nitric  acid. 

Ten  pounds  hydrochloric  acid. 

The  mercury  and  nitric  acid  are  mixed  together, 


Son.] 


649 


[Spa. 


and,  after  the  mercury  is  dissolved,  the  10  pounds 
of  hydrochloric  acid  are  added. 

To  use  this  liquid  the  zincs  are  first  cleansed 
and  then  dipped  into  the  solution  and  afterwards 
rinsed  with  clean  water. 

Sonometer. — A  monochord.  (See  Appen- 
dix— Monochord?) 

Sonometer  Interrupter. — (See  Appendix 
— Interrupter,  Sonometer?) 

Sorter,  Electro-Magnetic An  elec- 
tro-magnetic separator,  sometimes  applied  to 
a  magnetic  separator.  (See  Appendix — Sep- 
arator, Electro-Magnetic?) 

Sounder  Push. — (See  Appendix— Push, 
Sounder?) 

Sounder,  Snapper A  sounder  for 

producing  the  sounds  corresponding  to  the 
Morse  characters,  as  they  are  heard  on  a 
sounder,  in  which  the  audible  signals  are 
produced  by  the  flexure  of  a  spring. 

A  sounder  snapper  consists  essentially  of  a 
dented  spring  plate  firmly  connected  at  one  end 
and  the  other  end  moved  to-and-fro  by  hand. 

It  is  used  to  produce  sounds  similar  to  those  of 
the  regular  electro-magnetic  sounder,  only,  in- 
stead of  being  operated  by  an  electric  current,  it  is 
operated  solely  by  hand. 

Sounder,    Telegraphic    Box A 

sounder,  the  receiving  magnets  of  which  are 
enclosed  in  a  hollow  box  for  the  purpose  of 
increasing  the  intensity  of  the  sound  by  means 
of  resonance. 

Sounds,  Radiophonic Sounds  re- 
sulting from  the  direct  action  of  radiation  on 
certain  bodies.  (See  Sonorescence.) 

It  is  the  photophonic  sounds,  produced  in  the 
receiving  instrument  of  a  photophone,  that  are 
employed  for  the  transmission  of  speech  or  other 
intelligence.  (See  Photophone. ) 

Mercadier  gives  the  following  conclusions  as 
the  result  of  his  experiments  on  radiophonic 
sounds: 

(i.)  "  The  radiophone  (radiophonic  sound) 
does  not  appear  to  be  an  effect  produced  by  the 
mass  of  the  receiving  plate  vibrating  transversely, 
like  an  ordinary  vibrating  plate.  The  nature  of 
the  molecules  of  the  receiver  and  their  mode  of 
aggregation  do  not  appear  to  exercise  a  predom- 
inant influence  on  the  production  of  sounds. 


"  The  radiophonic  phenomena  appear  to  result 
principally  from  an  action  exercised  at  the  sur- 
face of  the  receiver,  and  are  amplified  when  this 
surface  is  covered  with  substances  like  lamp- 
black,  platinum-black,  and  the  like. 

(2. )  "  Radiophonic  sounds  result  from  the  direct 
action  of  radiations  on  the  receivers.  Radiophonic 
sounds  are  produced  principally  by  the  undula- 
tions of  great  length  of  wave,  called  '  calorific.' 

(3.)  "  The  medium  in  which  radiophonic  vi- 
bration is  produced  is  the  layer  of  condensed  air 
on  the  surface  of  the  receivers.  This  layer  of  air, 
particularly  when  the  surfaces  are  smoked,  or 
covered  with  a  substance  absorbing  heat,  is  alter- 
nately heated  and  cooled  by  intermittent  radia- 
tions, with  the  result  that  periodic  and  regular 
dilatations  and  contractions  are  set  up  ;  hence  a 
vibratory  movement  communicated  to  the  ad- 
jacent gaseous  layers,  which  also  vibrate  directly 
under  the  same  influence. 

(4. )  "  Radiophonic  sounds  cannot  be  produced 
unless  the  medium  which  surrounds  the  receiving 
surfaces  is  gaseous.  A  liquid  or  solid  medium 
cannot  produce  them;  but  a  gaseous  medium 
containing  vapor,  particularly  vapor  of  am- 
monia or  ether,  develops  them  in  a  remarkable 
way  :  those  vapors  which  have  the  greatest  ab- 
sorbing thermic  power  give  out  the  greatest 
effects." 

Source,  Magnetic Any  arrangement 

of  parts  capable  of  producing  lines  of  mag- 
netic force. 

A  permanent  magnet,  an  electro-magnet,  or  a 
circuit  through  which  an  electric  current  is 
passing,  may  act  as  a  magnetic  source. 

Spark  Chronograph. — (See  Appendix— 
Chronograph,  Spark?) 

Spark  Discharge. — (See  Appendix — Dis- 
charge, Spark?) 

Spark,  Electric The   phenomena 

produced  by  a  disruptive  discharge  in  the  air 
space  or  gap  through  which  the  discharge 
passes. 

Spark,  Negative A  spark  produced 

by  the  discharge  of  a  negatively  charged  con- 
ductor. 

Spark,  Positive A  spark  produced 

by  the  disruptive  discharge  of  a  positively 
charged  conductor. 


Spav 


650 


[Sta. 


Sparking  Terminals. — (See  Appendix — 
Terminals,  Sparking?) 

Speaking  Telegraph. — (See  Appendix — 
Telegraph,  Speaking?) 

Speaking-Tube  Annunciator. — (See  Ap- 
pendix— Annunciator,  Speaking-  Tube?) 

Specific  Conductance. — (See  Appendix — 
Conductance,  Specific?) 

Specific  Dielectric  Capacity. — (See  Ap- 
pendix— Capacity,  Specific  Dielectric?) 

Specific  Energy. — (See  Appendix — En- 
ergy, Specific. 

Specific  Inductance. — (See  Appendix — 
•  Inductance,  Specific?) 

Specific  Magnetic  Resistance. — (See  Ap- 
pendix— Resistance,  Specific  Magnetic?) 

Specific  Magnetism.— (See  Appendix — 
Magnetism,  Specific?) 

Spectro-Photometer. — (See  Appendix — 
Photometer,  Spectre.) 

Spectrum,  Magnetic A  term  some- 
times employed  in  place  of  magnetic  figure 
or  magnetic  field. 

The  term  magnetic  spectrum  is  unfortunate 
since  magnetic  figures  so  produced  can  hardly  be 
regarded  as  spectra,  but  merely  as  collections 
of  iron  filings  arranged  in  the  order  which  the 
lines  of  magnetic  force  take  in  the  space  or  at- 
mosphere  outside  the  magnet. 

Speed,  Inductance A  term  pro- 
posed for  the  product  of  a  coefficient  of  self- 
induction  by  an  angular  velocity. 

Speeding  of  Machine. — (See  Appendix — 
Machine,  Speeding  of.) 

Spiral. — A  term  sometimes  employed  in 
electricity  and  magnetism  in  place  of  an  open 
coil.  (See  Coil,  Electric.) 

Spiral,  Anomalous A  term  some- 
times employed  in  place  of  an  anomalous 
helix  or  solenoid.  (See  Appendix — Solenoid, 
Anomalous.) 

Spiral,  Left-Handed A  term  some- 
times employed  in  place  of  left-handed 
solenoid.  (See  Solenoid,  Left-Handed.  Sole- 
noid, Practical.) 

Spiral,    Magnetic A  term   some- 


times employed  in  place  of  magnetic  helix. 
(See  Coil,  Electric?) 

Spiral,  Magnetizing A  term  some- 
times employed  in  place  of  a  magnetizing 
helix  or  coil.  (See  Coil,  Electric?) 

Spiral,  Primary,  of  Induction  Coil 

A  term  sometimes  employed  for  the  primary 
of  an  induction  coil.  (See  Coil,  Induction?) 

Spiral,    Right-Handed A    term 

sometimes  employed  in  place  of  right-handed 
solenoid.  (See  Solenoid,  Right-Handed. 
Solenoid,  Practical?) 

Spiral,  Secondary,  of  Induction  Coil 

— A  term  sometimes  employed  for  the  sec- 
ondary of  an  induction  coil.  (See  Coil,  In- 
duction?) 

Spontaneous  Electricity. — (See  Appendix 
— Electricity,  Spontaneous?) 

Spools,  Field,  of  Dynamo-Electric  Ma- 
chine   A  term  sometimes  employed 

for  the  forms  on  which  the  field  coils  are 
wound. 

Spring  Relay  Contact— (See  Appendix — 
Contact,  Spring  Relay?) 

Spring  Voltmeter.  —  (See  Appendix  — 
Voltmeter,  Spring?) 

Standard  Clock. — (See  Appendix—  Clock, 
Standard?) 

Standard  Trolley  Switch.— (See  Appen- 
dix— Switch,  Standard  Trolley?) 

Standards. — Telegraphic  or  -telephonic 
supports  placed  on  the  roof  of  a  building  for 
the  purpose  of  supporting  telegraphic  or 
telephonic  wires  or  conductors. 

Standards,  Dynamo A  term  ap- 
plied to  the  supports  for  the  bearings  of  a 
dynamo. 

Starting  Box  of  Shunt-Wound  Motor. — 
(See  Appendix— Box,  Starting,  of  Shunt- 
Wound  Motor?) 

Starting  Current  of  Motor.— (See  Appen- 
dix— Current,  Starting,  of  Motor?) 

Starting  Torque  of  Motor.— (See  Appen- 
dix—  Torque,  Starting,  of  Motor?) 

Static  Transformer.— See  Appendix— 
Transformer,  Static.) 


Sta.J 


651 


[Str. 


Station,  Repeating  Telegraphic 

A  station  situated  at  some  intermediate 
point  on  a  long  telegraphic  line  where  the 
currents  from  the  sending  station  are  passed 
through  a  relay  by  means  of  which  they  are 
sent  on  to  the  next  station  by  means  of  a 
current  from  a  local  battery. 

Station,    Translating    Telegraphic 

— A  receiving  station. 

The  station  at  which  the  signals  are  re- 
ceived. 

Stay-Eye  Clips. — (See  Appendix — Clips, 
Stay-Eye) 

Steeling,  Electro The  art  of  cover- 
ing copper  electros  with  hardened  iron. 

Steel-Yard  Ammeter. — (See  Appendix — 
Ammeter,  Steel-  Yard.) 

Steeps. — A  word  sometimes  employed  in 
electro-plating  for  dips  or  dipping  liquids  or 
solutions. 

Steno  -  Telegraphy.  —  (See  Appendix — 
Telegraphy,  Steno.) 

Stereotype,  Electro A  word  some- 
times employed  for  electrotype. 

The  term  electrotype  would  appear  to  be 
preferable. 

Sticking  of  Magnetic  Armature.— (See 
Appendix — Armature,  Magnetic  Sticking 
of.) 

Stimulation,  Unipolar,  of  a  Nerve 

— The  stimulation  of  a  nerve  produced  by 
the  application  of  a  single  electrode  to  the 
nerve. 

This  term  was  proposed  by  Du  Bois  Reymond, 
and  is  sometimes  employed  in  electro-therapeu- 
tics. According  to  Reymond  unipolar  stimula- 
tion of  a  nerve  is  due  to  the  action  of  the  to- 
and-fro  motions  of  the  electric  current  between 
the  free  ends  of  the  open  induction  circuit  at  the 
moment  of  induction. 

Stimulus,  Electrical,  of  Nerve 

The  effect  which  electricity  produces  by  its 

passage  through  a  nerve. 
Landois  and  Sterling  give  the  following  facts 

concerning  the  electric  stimulation  of  a  nerve  : 
The  stimulation  is  more  powerful — 
(I.)  At  the  moment  the  current  is  completed. 


(2.)  At  the  moment  the  current  ceases. 

(3.)  When  a  constant  electric  current  increases 
or  decreases  in  its  strength.  The  more  rapid  the 
variations,  the  more  energetic  the  stimulation. 

(4.)  To  stimulate  a  nerve,  the  current  must 
have  a  certain  duration. 

(5.)  The  electric  current  is  most  active  when 
applied  to  the  longer  axis  of  the  nerve,  and  be- 
comes inactive  when  applied  at  right  angles  to 
this  axis. 

(6.)  The  greater  the  length  of  nerve  treated  by 
the  current,  the  smaller  is  the  stimulus  that  is 
required. 

Stone,  Bologniau A  term  origin- 
ally applied  to  a  calcareous  substance  that 
became  phosphorescent  on  exposure  to  light. 

Stoneware  Dipping  Basket. — (See  Appen- 
dix— Basket,  Stoneware  Dipping.) 

Stoneware  Dipping  Bowl. — (See  Appen- 
dix— Bowl,  Stoneware  Dipping.) 

Stopping-Off  Process. — (See  Appendix — 
Process,  Stopping-Off?) 

Stopping-Out  Process.— (See  Appendix — 
Process,  Stopping-Out.) 

Storage  Accumulator. — (See  Appendix— 
Accumulator,  Storage) 

Storage  Battery,  Formed  Plates  of  - 
— (See  Appendix — Plates,  Formed,  of  Stor- 
age Cell?) 

Stove,  Plate,  Electric A  form  of 

electric  stove  in  which  the  heat  is  imparted 
to  the  plate  from  a  suitably  shaped  resist- 
ance. 

A  form  of  plate  stove  is  shown  in  Fig.  580,  a 


Fig.  580.    Electric  Plate  Stove. 

part  of  the  top  being  cut  away  to  show  the  elec- 
tric heater. 

Strain. — The  deformation  produced  by 
the  action  of  a  stress. 

Strain,  Electrostatic A  strain  or 

deformation  produced  in  any  medium  by 


Str.] 


652 


[Swi. 


means  of  the  stress  caused  by  an  electro- 
static field. 

Stranding  of  Conductor.— (See  Appendix 
— Conductor,  Stranding  of.) 

Strap  Key. — (See  Appendix— Key,  Strap.) 

Streams,  Phantom A  term  some- 
times applied  to  a  variety  of  the  Tesla  stream- 
ing discharge.  (See  Discharge,  Streaming.) 

Striking  Distance. — (See  Appendix — Dis- 
tance, Striking.) 

Striking  Distance  for  Yarious  Sub- 
stances.— (See  Appendix — Distance,  Strik- 
ing, for  Various  Substances.) 

Striking  Mechanism  of  Arc  Lamp. — (See 
Appendix — Lamp,  Arc,  Striking  Mechan- 
ism of.) 

Stroboscope. — An  instrument  employed 
in  the  study  of  periodic  motion. 

The  stroboscope  is  based  on  the  illumination  at 
frequent  intervals  of  the  body  whose  motion  is  to 
be  studied. 

Stroboscopic. — Of  or  pertaining  to  the 
stroboscope. 

Struck. — A  word  employed  in  electro- 
plating to  characterize  a  surface  that  has 
been  covered  with  a  film  of  electro-deposited 
nickel  by  being  placed  in  a  bath  and  exposed 
for  a  few  moments  to  the  action  of  a  strong 
current. 

When  the  surface  of  the  article  to  be  plated 
has  been  struck  or  covered  with  a  thin  film  of 
nickel,  the  remainder  of  the  coating  is  deposited 
on  the  surface  by  the  action  of  a  weaker  current. 

Successive  Contact  Key. — (See  Appendix 
— Key,  Successive  Contact?) 

Surging  Circuit.— (See  Appendix— Cir- 
cuit, Surging.) 

Surgings,  Induced  Electric Elec- 
trical surgings  induced  in  neighboring  con- 
ductors by  means  of  electrical  surgings  or 
oscillating  discharges.  (See  Discharge, 
Oscillating) 

Suspension  of  Compass  Needle,  Cardan's 

— A  term  sometimes  employed  for  gim- 
bal  suspension.     (See  Gimbals) 

Sweeping-Out  Charge.— (See  Appen#x— 
Charge,  Sweeping-Out.) 


Swinging  Annunciator. — (See  Appendix 
— Annunciafor,  Swinging.) 

Switch,  Automatic    Photo-Electric 

— A  switch  that  is  automatically  opened  or 
closed  on  the  exposure  of  its  face  to  differ- 
ences of  illumination. 

A  selenium  cell  is  so  placed  in  a  circuit  in  com- 
bination with  an  electro-magnetic  switch  that 
when  one  of  the  selenium  faces  is  exposed  to  the 
decreasing  illumination  of  approaching  night  a 
current  is  produced  by  such  decrease  of  light,  the 
direction  of  which  is  such  as  to  automatically 
turn  on  or  light  an  electric  lamp,  and  conversely, 
on  the  approach  of  daylight  and  the  consequent 
increase  of  solar  illumination,  to  turn  off  the 
light. 


A  contraction   for 

(See  Switch,  Double- 

A  contraction  for 

(See  Switch,  Double- 


Switch,  D.  B. — 

double-break  switch. 
Break?) 

Switch,  D.  P.  — 

double-pole  switch. 
Pole?) 

Switch,  Flush  Key A  switch  whose 

mechanism  is  contained  in  a  box,  the  face  of 
which  is  flush  with  the  wall  or  other  support 
to  which  the  switch  is  attached. 

The  switch  is  opened  or  closed  by  means  of  a 
key. 


Flush  Key  Switch. 

A  form  of  flush  switch  is  shown  in  Fig.  581 
in  which  a  removable  key,  instead  of  the  ordinary, 
fixed  key,  is  employed  for  opening  and  closing  the 
switch. 


Swi.] 


653 


[Sys. 


Switch,  Four- Way A  term  some- 
times employed  in  place  of  four-point  switch. 
(See  Switch,  Four-Point!) 

Switch,  Jack A  term  sometimes 

employed  in  place  of  spring-jack.  (See 
Spring-Jack!) 

Switch,  Left-Hand  Trolley In  a 

system  of  electric  street  railways  a  trolley 
switch  designed  for  use  at  a  point  where  a 
branch  trolley  leaves  the  main  line  to  the 
left-hand  side  in  the  going  direction. 

Switch,  LeYer Any  form  of  switch 

in  which  the  circuit  is  closed  or  opened  by 
means  of  the  movement  of  a  lever  arm. 

Switch,  Push A  switch  included  in 

a  push  case  and  operated  by  means  of  a  push 
button. 

In  push  switches  successive  motions  of  the  but- 
ton make  or  break  the  circuit. 

Switch,  Quick-Break A  switch  by 

means  of  which  a  circuit  is  rapidly  or  quickly 
broken. 

Switch,  Right-Hand  Trolley In  a 

system  of  electric  street  railways  a  switch  de- 
signed for  use  at  a  point  where  a  branch 
trolley  wire  leaves  the  main  line  to  the  right 
in  the  going  direction. 

Switch,  Rocking A  form  of  switch 

operated  by  means  of  an  electro-magnet  by 
which  storage  cells  are  automatically  removed 
from  the  circuit  of  the  charging  dynamo  to 
prevent  the  battery  from  discharging  through 
it  in  case  the  voltage  of  the  dynamo  falls 
below  the  E.  M.  F.  of  the  battery. 

Switch,    Standard    Trolley In    a 

system  of  electric  railways  the  device  em- 
ployed to  hold  together  the  trolley  wires  at 
any  point  where  the  wire  branches,  and  for 
automatically  guiding  a  trolley  wheel  along 
the  wire  over  the  track  taken  by  the  car. 

Switch,  T.  P. A  contraction  for 

Triple-Pole  Switch.  (See  Appendix — Switch, 
Triple-Poie, 

Switch,  Three-Way A  term  some- 
times employed  in  place  of  three-point  switch. 
(See  Switch,  Three-Point?) 


Switch,  Three- Way  Trolley In  a 

system  of  electric  street  railways,  a  trolley 
switch  designed  for  use  at  a  point  where  the 
line  branches  in  three  directions. 

Switch,  Triple-Pole A  switch  con- 
sisting of  a  combination  of  three  separate 
switches  for  opening  or  closing  the  three  cir- 
cuits at  the  same  instant. 

Symmetrical  Electrometer. — (See  Appen- 
dix— Electrometer,  Symmetrical?) 

Symphonance. — A  word  proposed  in  place 
of  resonance.  (See  Resonance,  Electric?) 
(See  Appendix — Resonance,  Acoustic?) 

Synchronous-Multiplex  Telegraph. — (See 
Appendix —  Telegraph,  Synchronous-Multi- 
plex?) 

Synthesis,  Electro The  combina- 
tion of  electro-positive  and  electro-negative 
radicals  under  the  influence  of  electricity. 

Syringe,  Battery A  syringe  ar- 
ranged to  readily  transfer  the  acid  or  spent 
liquids  from  a  voltaic  cell  or  batter}'  for  the 
introduction  of  fresh  liquid. 

System,  Delta  Tri-Phase A  tri- 

phase  system  in  which  the  terminal  connec- 
tions resemble  in  form  the  Greek  letter  delta. 

System,  Electrically  Tuned A 

term  sometimes  employed  for  a  circuit  or 
system  of  circuits  that  has  been  brought  into 
electrical  resonance  with  another  circuit  or 
system  of  circuits.  (See  Resonance,  Elec- 
tric.) 

System,  Fiye-Wire A  system  sim- 
ilar in  its  arrangements  to  the  three-wire 
system  in  which  four  dynamos  are  connected 
to  five  wires  or  conductors.  (See  System, 
Three-  Wire?) 

In  such  a  case  there  are  three  wires  or  con- 
ductors occupying  the  position  corresponding  in 
general  to  the  neutral  wire  or  conductor  in  a 
three-wire  system. 

System,  Four- Wire A  system  sim- 
ilar in  its  general  arrangement  to  the  three- 
wire  system,  in  which  three  dynamos  are 
connected  to  four  wires  or  conductors.  (See 
System,  Three-Wire?) 

In  such  a  case  there  are  two  wires  or  conduct- 
ors occupying  in  general  a  position  correspond- 


Sys.] 


654 


[Tel. 


ing  to  the  neutral  wire  of  the  three-wire  system. 
(See  System,  Three-  Wire.) 

System,  Municipal,  of  Electric  Lighting 

A  series  system  of  incandescent  light- 
ing invented  by  Edison  for  use  in  cities,  par- 
ticularly for  street  or  window  lamps,  and 
operated  at  a  total  continuous  current  pressure 
of  1,000  volts. 


System,  Six-Wire A  system  sim- 
ilar in  general  to  the  three-wire  system  in 
which  five  dynamos  are  connected  to  six 
conductors  or  leads.  (See  Appendix — Sys- 
tem, Five-  Wire?) 

System,  Y  Tri-Phase A  tri-phase 

system  in  which  the  terminal  apparatus  re- 
sembles in  form  the  capital  letter  Y. 


t. — A  symbol  used  for  time. 

t :  m. — An  abbreviation  proposed  for  revo- 
lutions per  minute,  a  practical  unit  of  angular 
velocity. 

T.  P.  Switch.— (See  Appendix— Switch, 
T.  P.) 

Tap  Wire  in  Quadruples  Telegraphy.— 
(See  Appendix—  Wire,  Tap,  in  Quadruplex 
Telegraphy?) 

Tape,  Kerite A  kerite  covered  in- 
sulating tape. 

Tape,  Rubber Insulating  tape 

made  of  rubber. 

Tapper  Key. — (See  Appendix — Key,  Tap- 
per.} 

Tapper,  Magneto A  term  some- 
times employed  in  place  of  magneto  key. 
(See  Key,  Magneto-Electric?) 

Tapper,  Morse A  form  of  tele- 
graphic key  provided  with  two  contacts,  one 
in  front  and  the  other  in  the  back,  arranged 
so  that  the  depression  of  the  key  makes  one 
contact  and  breaks  the  other. 

Teeth,  Pacinotti A  term  some- 
times employed  in  place  of  Pacinotti  pro- 
jections. (See  Projections,  Pacinotti?) 

Telegram. — A  telegraphic  dispatch  or  com- 
munication. 

Literally,  anything  written  by  means  of  a  tele- 
graph. 

Telegraph. — Any  instrument  or  combina- 
tion of  instruments  for  conveying  a  commu- 
nication or  dispatch  to  a  distance  by  means 
other  than  the  unassisted  voice. 


Telegraph,  Acoustic A  general 

term  embracing  the  apparatus  employed  in 
acoustic  telegraphy.  (See  Telegraphy, 
Acoustic?) 

Telegraph,  Automatic A  general 

term  embracing  the  apparatus  employed  in 
automatic  or  machine  telegraphy.  (See 
Telegraphy,  Automatic?) 

Telegraph,  Chemical A  general 

term  embracing  the  apparatus  employed  in 
chemical  telegraphy.  (See  Telegraphy 
Chemical?) 

Telegraph,  Contraplex A  general 

term  embracing  the  apparatus  employed  in 
contraplex  telegraphy.  (See  Telegraphy, 
Contraplex?) 

Telegraph,  Dial A  general  term 

embracing  the  apparatus  employed  in  dial 
telegraphy.  (See  Telegraphy,  Dial?) 

Telegraph,  Diplex A  general  term 

embracing  the  apparatus  employed  in  diplex 
telegraphy.  (See  Telegraphy,  Diplex?) 

Telegraph,  Duplex A  general  term 

embracing  the  apparatus  employed  in  duplex 
telegraphy.  (See  Telegraphy,  Duplex, 
Bridge  Method  of.  Telegraphy,  Duplex, 
Differential  Method  of.) 

Telegraph,  Electric An  electrical 

instrument  for  conveying  a  communication 
or  dispatch  to  a  distance  by  means  other  than 
the  unassisted  voice. 

Electric  telegraphs  are  of  a  great  variety  of 
forms.  They  may  be  divided  into  classes,  either 
according  to  the  number  of  dispatches  they  can 
simultaneously  transmit,  or  according  to  the 


Tel.J 


655 


[Tel. 


method  employed  for  transmitting  or  receiving 
the  dispatches. 

According  to  the  number  of  messages  they  can 
transmit  simultaneously,  telegraphs  are  divided 
into  duplex,  diplex,  contraplex,  quadruplex, 
multiplex,  phonoplex,  harmonic,  synchronous- 
multiplex,  etc.,  etc. 

According  to  the  differences  in  the  method  of 
transmitting  and  receiving  the  messages,  they  are 
divided  into  the  electro-magnetic,  the  needle, 
the  chemical,  the  dial,  the  fac-simile,  the  writing, 
the  acoustic,  the  speaking,  the  induction,  the 
automatic,  the  fire-alarm,  etc.,  etc. 

Telegraph,  Electro-Magnetic A 

general  term  embracing  the  apparatus  em- 
ployed in  the  various  systems  of  electro- 
magnetic telegraphy. 

Telegraph,  Fac-Simile A  general 

term  embracing  the  apparatus  employed  in 
fac-simile  telegraphy.  (See  Telegraphy,  Fac- 
similed) 

Telegraph,  Fire-Alarm A  general 

term  embracing  the  apparatus  employed  in 
fire-alarm  telegraphy.  (See  Telegraphy, 
Firt-Alarm.) 

Telegraph,  Harmonic A  general 

term  embracing  the  apparatus  employed  in 
harmonic  telegraphy.  (See  Telegraphy, 
Gray's  Harmonic  Multiple?) 

Telegraph,  Induction A  general 

term  embracing  the  apparatus  employed  in 
induction  telegraphy.  (See  Telegraphy,  In- 
duction?) 

Telegraph,  Multiplex A  general 

term  embracing  the  apparatus  employed  in 
multiplex  telegraphy.  (See  Telegraphy, 
Multiplex.} 

Telegraph,  Needle A  general  term 

embracing  the  apparatus  employed  in  needle 
telegraphy.  (See  Telegraphy,  Needle  Sys- 
tem of.) 

Telegraph,  Phonoplex A  general 

term  embracing  the  apparatus  employed  in 
phonoplex  telegraphy.  (See  Telegraphy, 
Phonoplex.') 

Telegraph,  Quadruplex A  general 

term  embracing  the  apparatus  employed  in 
quadruplex  telegraphy.  (See  Telegraphy, 


Quadruplex,  Bridge  Method  of.  Teleg- 
raphy, Quadruplex,  Differential  Method 
of.) 

Telegraph,  Speaking A  general 

term  embracing  the  apparatus  employed  in 
speaking  telegraphy.  (See  Telegraphy, 
Speaking.  Telephone?) 

Telegraph,  Synchronous-Multiplex 

— A  general  term  embracing  the  apparatus 
employed  in  synchronous-multiplex  teleg- 
raphy. (See  Telegraphy,  Synchronous- 
Multiplex?) 

Telegraph,  To To  write  or  com- 
municate at  a  distance  by  means  of  the  tele- 
graph. 

Telegraph,  Writing  — A  general 

term  embracing  the  apparatus  employed  in 
writing  telegraphy.  (See  Telegraphy, 
Writing?) 

Telegraphic  Box  Sounder. — (See  Appen- 
dix— Sounder,  Telegraphic  Box?) 

Telegraphic  Interrupter.— (See  Appen- 
dix— Interrupter,  Telegraphic?) 

Telegraphic  Interruption. — (See  Appen- 
dix— Interruption,  Telegraphic?) 

Telegraphic  Polar  Belay. — (See  Appen- 
dix— Relay,  Polar,  Telegraphic?) 

Telegraphic  Spark  Coil.— (See  Appendix 
— Coil,  Spark,  Telegraphic?) 

Telegraphist. — One  skilled  in  the  art  of 
transmitting  intelligence  by  means  of  the  tele- 
graph. 

Telegraphy,  Air A  term  some- 
times employed  for  induction  telegraphy. 
(See  Telegraphy,  Induction?) 

The  term  air  telegraphy  has  been  applied  on 
account  of  the  fact  that  the  electric  impulses  on 
one  line  wire  or  conductor  are  transmitted  across 
an  air  space  to  a  neighboring  line  wire  or  con- 
ductor, *'.  e.,  the  air  acts  as  the  dielectric  through 
which  the  induction  takes  place. 

Telegraphy,  Steno A  system  of 

telegraphy  in  which  the  sounds  of  a  word  are 
represented  by  characters  in  place  of  letters. 

Steno-telegraphy  differs  from  ordinary  telegra- 
phy in  the  same  manner  that  shorthand  writing 
differs  from  longhand  writing. 


Tel 


656 


[Ten. 


The  object  of  steno-telegraphy  is,  of  course,  to 
insure  increased  economy  in  speed. 

Tele-Indicator. — (See  Appendix — Indi- 
cator, Tele.) 

Tele-Meteorograph. — A  form  of  meteoro- 
graph. (See  Appendix — Meteorograph.} 

Telephone  Indicator. — (See  Appendix — 
Indicator,  Telephone.) 

Telephone,  Pan A  word  proposed 

for  a  certain  sensitive  form  of  telephone. 

The  particular  form  of  telephone  for  which  the 
name  pan-telephone  was  proposed  was  an  instru- 
ment with  a  microphone  transmitter. 

Telephone,  Sensitiveness  of The 

ability  of  a  telephone  properly  to  respond  to 
currents  much  smaller  than  those  required 
for  the  operation  of  some  other  telephonic 
apparatus. 

The  telephone  is  characterized  by  its  extreme 
sensitiveness,  requiring,  as  it  does,  for  its  opera- 
tion a  very  small  current.  It  is  for  this  reason 
that  the  current  produced  in  the  telephone  circuit 
by  the  induction  of  neighboring  conductors 
causes  the  annoying  cross-talk  in  the  telephone. 

Telephone,  Thermo A  telephone 

transmitter  consisting  of  a  tense  wire,  one  end 
of  which  is  connected  with  the  transmitting 
diaphragm,  placed  in  circuit  with  a  receiving 
telephone  battery,  and  having  a  current  pass- 
ing through  it  of  sufficient  strength  to  heat  it. 

On  speaking  near  the  wire  the  waves  in  the 
air  periodically  cool  the  wire,  and  its  resistance 
varies,  and  accordingly  the  current  in  the  line 
varies.  A  thermo  receiver  is  made  in  a  similar 
manner,  and  the  telephone  current  heats  the 
wire  periodically  and  sets  the  diaphragm  in 
motion. 

Telephone  Time  Check.— (See  Appendix — 
Check,  Telephone  Time) 

Telephonic  Meter. — (See  Appendix— 
Meter,  Telephonic) 

Telephonist. — One  skilled  in  the  art  of 
telephony.  » 

Telephony. — The  art  of  transmitting  intel- 
ligence by  the  use  of  the  telephone.  (See 
Telephone) 

Telephony,  Duplex A  system  of 

telephony  by  means  of  which  a  single  line 


wire  or  conductor  can  be  simultaneously  used 
by  two  subscribers. 

Telephony,  Multiplex A  system  of 

telephony  by  means  of  which  a  single  line 
wire  or  conductor  can  be  simultaneously 
used  by  a  number  of  subscribers. 

Tele-radiophone. — A  form  of  radiophone 
arranged  for  the  simultaneous  transmission 
of  telegraphic  and  telephonic  messages.  i 

Tele-radiophone,  Auto-reversible  or  Mul-  j 

tiple A  photo  phone  so  arranged  that 

a  number  of  telegraphic  communications  may 
be  simultaneously  sent  over  a  line  wire  or 
conductor  either  all  in  one  direction  or  part 
in  one  direction  and  the  remainder  in  oppo- 
site directions. 

The  adjectives  auto-reversible  and  multiple  refer 
to  the  fact  that  the  messages  can  be  transmitted 
either  all  in  the  same  direction,  or  a  number  in 
one  direction  and  the  remainder  in  the  opposite 
direction. 

A  multiple  auto-reversible  tele-radiophone  is  an 
invention  of  Mercadier's,  based  on  the  electrical 
properties  of  selenium. 

A  number  of  selenium  cells  of  variable  resist- 
ance are  employed  at  the  sending  station,  where 
they  are  placed  in  the  circuit  of  a  battery  of  a  few 
elements  and  of  a  line  wire  extending  to  the  re- 
ceiving station,  which  is  connected  with  a  number 
of  receivers  equal  to  the  number  of  selenium 
cells  of  variable  resistance. 

When  luminous  radiations  are  intermitted  so  as 
to  have  the  relative  succession  and  duration  of 
the  characters  of  the  Morse  alphabet,  and  these 
impulses  are  sent  over  the  line,  they  affect  the 
receivers  at  the  other  end.  Each  transmitter 
sends  into  the  line  impulses  of  a  definite  rate  and 
only  affects  that  receiving  instrument  at  the  other 
end  which  is  tuned  in  unison  with  it.  The  ap- 
paratus is  similar  in  its  general  action  to  Gray's 
system  of  multiple  harmonic  telegraphy.  (See 
Telegraphy,  Gray'' s  Harmonic  Multiple. ~) 

Telpher  Locomotive. — (See  Appendix — 
Locomotive,  Telpher) 

Temporary  Socket. — (See  Appendix — 
Socket,  Temporary) 

Tension,  Difference  of An  objec- 
tionable term  sometimes  employed  in  place 
of  difference  of  potential. 


Ter.J 


657 


[Tho. 


This  use  of  the  term  should  be  strictly  avoided, 
as  it  is  unnecessary  and  to  a  great  extent  mean- 
ingless. 

Terella.— Literally,  a  little  earth. 

A  sphere  of  hardened  steel,  or,  as  used  by  Gil- 
bert, of  loadstone,  having  marked  thereon  the 
poles  and  equator,  and  so  magnetized  that  the  dis- 
tribution of  its  magnetism  shall  resemble  the  dis- 
tribution of  the  earth's  magnetism. 

Terminals,  Sparking Terminals 

between  which  a  series  of  disruptive  dis- 
charges are  passed,, 

Sparking  terminals  are  generally  provided  with 
rounded  or  blunt  or  disc-shaped  ends  so  as  to  pre- 
vent a  convective  discharge  from  taking  place. 

Terrestrial  Magnetic  Induction. — (See 
Appendix — Induction,  Magnetic,  Terres- 
trial) 

Tesla  Discharge.— (See  Appendix— Dis- 
charge, Tesla?) 

Tesla  Frequencies. — (See  Appendix — Fre- 
quencies, Tesla.) 

Test,  Blavier's A  test  introduced 

by  Blavier  for  focalizing  a  single  fault  in  a 
single  telegraphic  line  or  conductor  by  meas- 
uring the  resistance  at  one  end  of  the  line 
when  the  other  end  is  alternately  freed  and 
earthed. 

Test  Board. — (See  Appendix— Board, 
Test.) 

Test,  Loop A  localization  test  for  a 

single  fault  in  a  loop  of  two  telegraphic  wires, 
or  in  a  complete  metallic  circuit. 

Test,  Overlap A  localization  test  for 

a  single  fault  in  a  single  telegraphic  line  by  ob- 
serving the  resistance  from  each  end  and 
deducing  from  the  amount  to  which  the  sum 
of  the  resistances  overlap  the  total  conductor 
resistance  of  the  line. 

Tetrad  Atom. — (See  Appendix—  Atom, 
Tetrad.) 

Theoretical   Magnet — (See    Appendix — 
Magnet,  Theoretical.) 
Theory,  Contact,  of  Electricity A 

theory  that  ascribes  the  production  of  elec- 
tricity in  a  voltaic  cell,  and  to  some  extent 


the  production  of  electricity  by  friction,  to  the 
contact  of  dissimilar  substances  or  surfaces. 

The  act  of  contact  is  assumed  to  produce  a 
difference  of  potential.  While  mere  contact  may 
unquestionably  produce  a  difference  of  potential, 
it  requires  the  liberation  of  the  chemical  potential 
energy  of  the  metal  of  the  positive  plate  of  a 
voltaic  couple  to  maintain  such  differences  of 
potential  as  to  produce  a  continuous  flow  of  a 
current. 

Thermancy,  Electro A  term  pro- 
posed for  that  branch  of  electricity  which 
treats  of  the  effects  produced  by  an  electric 
current  on  the  temperature  of  a  thermo- 
electric junction. 

Thenno-Chemical  Cell. — (See  Appendix — 
Cell,  Thermo-Chemical.) 

Thermo  Chemistry. — (See  Appendix — 
Chemistry,  Thermo.) 

Thermo-Electric  Generator. — (See  Ap- 
pendix— Generator,  Thermo-Electric?) 

Thermo-Electric  Pair. — (See  Appendix — 
Pair,  Thermo-Electric!) 

Thermo-Electrometer.—  (See  Appendix — 
Electrometer,  Thermo?) 

Thermo-Multiplier. — A  thermopile. 

Thermo  Pair. — (See  Appendix — Pair, 
Thermo?] 

Thermo-Phone. — An  electrical  instrument 
for  producing  sounds  by  means  of  electrically 
produced  heat. 

Thermostatic.  —  Of  or  pertaining  to  a 
thermostat. 

Thermo-Tetephone.  —  (See  Appendix — 
Telephone,  Thermo?) 

Thermotic,  Electro Of  or  pertain- 
ing to  heat  produced  by  electricity. 

Thimble  Brush. — (See  Appendix — Brush, 
Thimble?) 

Thomson. — A  name  proposed  for  the  unit 
of  conductivity. 

The  term  mho  is  to-day  generally  employed 
for  the  unit  of  conductivity.  The  plan  of  em- 
ploying the  names  of  celebrated  deceased  elec- 
tricians is  a  good  one  and  should  not  be  departed 
from,  no  matter  how  deservedly  great  the  name 
of  the  living  electrician. 


Tho.] 


658 


[Tip. 


Thomson's    Bridge.  — (See  Appendix  — 
Bridge,  Thomson's.} 

Three-Phase  Armature. — (See  Appendix 
— Armature,  Three-Phased] 

Three-Phase  Currents. — (See  Appendix — 
Currents,  Three-Phased) 

Three-Phase  Generator.— (See  Appendix 
•>— Generator,  Three-Phased] 

Three-Phase  Motor. — (See  Appendix — 
Motor,  Three-Phase^ 

Three-Way  Switch. — (See  Appendix — 
Switch,  Three-Way^) 

Three-Way  Trolley  Switch.— (See  Appen- 
dix— Switch,  Three- Way  Trolley?) 

Throw,  Concentration   — A  term 

proposed  by  Squier  for  the  deflection  of  a 
magnetic  needle  by  a  current  produced  under 
certain  circumstances  by  a  couple  formed  of 
similar  plates  of  iron  or  other  paramagnetic 
metals  when  exposed  to  chemical  action  while 
under  the  influence  of  a  magnetic  field. 

The  concentration  throw  is  a  phenomenon  mark- 
ing the  reversal  of  the  direction  of  current  pro- 
duced by  a  couple  of  paramagnetic  metals  when 
exposed  to  the  action  of  a  magnetic  field.  Squier 
has  observed  in  the  case  of  a  couple  formed  of 
similar  plates  of  iron  exposed  to  the  action  of 
nitric  acid  while  in  a  ir  >gnetic  field,  that  under 
certain  conditions  the  effect  of  suddenly  putting 
on  a  magnetic  field  was  to  produce  a  less  rapid 
deflection  of  the  galvanometer  in  the  opposite 
direction,  so  that  the  electrode  which  was  formerly 
protected,  by  being  the  negative  plate  of  the 
couple,  was  now  the  one  acted  on  by  becoming 
the  positive  plate. 

It  is  the  above  phenomenon  for  which  Squier 
proposes  the  term  of  concentration  throw. 

According  to  Squier,  "  The  '  protective  throw ' 
is  due  to  the  actual  attraction  of  the  magnet  for 
the  ion,  and  is  always  in  the  direction  to  protect 
the  more  strongly  magnetized  parts,  while  the 
'  concentrated  throw  '  is  always  in  the  opposite 
direction,  and  depends  upon  the  distribution  of 
the  iron  salts  present  in  the  solution,  and  the  con- 
vection currents  in  the  liquid.  The  concentration 
of  the  products  of  the  reaction  about  the  point, 
would  tend  to  produce  a  ferrous  reaction  instead 
of  a  ferric  reaction,  and  experiments  show  that  a 


higher  electromotive  force  is  obtained  with  cells 
in  which  a  ferrous  reaction  takes  place  than  with 
those  in  which  a  ferric  reaction  occurs,  and  this 
change  in  the  character  of  the  reaction  produced 
by  the  concentration  probably  accounts,  at  least 
in  part,  for  the  increased  electromotive  force  at 
the  point." 

Throw,  Protective A  term  pro- 
posed for  the  protection  afforded  by  a  mag- 
netic field  to  paramagnetic  metals  exposed  to 
chemical  action. 

When  two  similar  electrodes  of  iron,  or  other 
paramagnetic  metals,  are  exposed  to  chemical 
action  while  under  the  influence  of  a  strong  mag- 
netic  field,  they  act  as  a  voltaic  couple  and  the 
direction  of  the  current  produced  depends  on 
the  direction  of  the  lines  of  magnetic  force.  In 
the  case  of  iron  exposed  to  the  action  of  nitric 
acid,  one  electrode  being  in  the  shape  of  a  pointed 
cylinder  and  the  other  in  the  shape  of  a  disc, 
when  the  lines  of  magnetic  force  of  the  field  coin- 
cide in  the  direction  with  the  length  of  the  disc, 
the  current  produced  passes  through  the  liquid 
from  the  disc  to  the  electrode,  that  is,  from  the 
less  magnetized  electrode,  to  the  more  magnet- 
ized electrode,  the  presence  of  the  magnetic  field 
determining  the  direction  of  the  current  pro- 
duced. In  this,  as  in  all  similar  cases  of  voltaic 
couples,  the  negative  plate  or  electrode  is  pro- 
tected from  the  chemical  action,  the  positive  plate 
alone  being  acted  on. 

The  name  protective  throw  is  proposed  by 
Squier  for  the  protection  so  afforded,  who  has 
studied  the  phenomena.  The  proposed  term 
would  appear  to  be  an  unfortunate  one,  the  pro- 
tection not  being  afforded  by  the  throw  of  the 
needle. 

Tint-Electro. — A  term  proposed  for  a 
method  of  electric  engraving. 

Tip,  Conducting  Cord A  blunted 

or  rounded  conductor  placed  at  one  of  the 
ends  of  a  wire  for  the  purpose  of  readily  in- 
serting it  into  a  binding  post  or  into  a  hole  in 
a  plate. 

Tip,  Conducting  Cord,  Separable 

A  cord  and  tip  arranged  so  that  the  tip  is 
readily  detachable  from  the  cord. 

The  method  of  attachment  can  be  insured  ia 
a  variety  of  ways.  A  screw  thread  forms  one  of 
the  most  obvious. 


Ton.] 


659 


[Tra. 


Tonicity,  Electro A  term  some- 
times employed  for  electrotonus.  (See 
Electrotonus.) 

Tool,  Electric  Machine A  machine 

tool  of  any  character  driven  directly  by  elec- 
tric power. 

In  electric  machine  tools  the  motor  is  generally 
so  placed  that  the  moving  power  is  thus  connected 
directly  to  the  machine  instead  of  transmitted  to 
it  by  means  of  belting.  Among  the  many  advan- 
tages possessed  by  electric  machine  tools  is  that 
such  tools  do  away  entirely  with  lines  of  shafting. 

Top-Hat  Curve. — (See  Appendix — Curve, 
Top-Hat.) 
Torque,  Running',  of  Motor The 

torque  exerted  by  a  motor  while  running. 

Torque,  Starting-,  of  Motor The 

torque  exerted  by  a  motor  at  the  moment  of 
starting. 

The  starting  torque  in  a  well-constructed  motor, 
either  of  the  alternating  or  continuous  type,  is 
always  in  excess  of  the  torque  it  exerts  at  full  load. 

Total  Contact. — (See  Appendix — Contact, 
Total.} 
Total  Intensity  of  Earth's  Magnetism. — 

(See  Appendix — Magnetism,  Total  Intensity 
of  Earth's?) 

Touch,  Divided A  term  sometimes 

employed  in  place  of  separate  touch.  (See 
Touch,  Separate?) 

Tourniquet,  Electric A  term  some- 
times employed  in  place  of  electric  flyer.  (See 
Flyer,  Electric?) 

Transference,    Convection  — —   — The 

transference  of  electricity  in  a  liquid  sub- 
stance unattended  by  chemical  changes  in  the 
liquid. 

Convection  transference  of  electricity  appears  to 
partake  of  the  nature  of  atomic  convection,  the 
charge  being  carried  by  each  atom  or  group  of 
atoms  in  the  direction  in  which  the  electricity  is 
being  transferred. 

Transform.— To  change  or  convert. 

To  convert  or  change  the  electromotive 
force  and  consequently  simultaneously  to 
change  the  current  strength  of  the  circuit  by 
any  means. 


Strictly  speaking,  a  transformer  is  regarded  as 
changing  the  electromotive  force.  It  therefore 
produces  at  the  same  time  changes  in  the  value  of 
the  current  strength.  When  we  speak  of  a  step- 
down  transformer  we  refer  to  a  transformer  which 
lowers  or  decreases  the  value  of  the  electromotive 
force,  although,  of  course,  at  the  same  time,  it 
is  employed  to  raise  or  increase  the  strength  of 
the  current. 

Tranformation. — The  act  of  transforming 
or  changing. 

Transformation,  as  of  Electromotive 

Force A  change  in  the  value  of  the 

electromotive  force  by  means  of  an  induction 
coil  or  transformer.  (See  Transformer?) 

Electric  power  is  equal  to  the  product  of  the 
current  by  the  electromotive  force.  By  the  use 
of  a  transformer  the  electromotive  force,  and  con- 
sequently the  current  strength,  are  changed  or 
altered  in  value.  Since  in  a  well-constructed 
transformer  but  very  little  energy  is  lost  in  trans- 
formation,  the  product  of  C  E,  in  the  primary 
very  nearly  equals  the  product  of  C'  E',  in  the 
secondary.  It  follows,  therefore,  that  as  the  elec- 
tromotive force  increases  in  the  secondary,  the 
current  strength  decreases  and  vice  versa. 

In  the  case  of  a  transformer  the  transformation 
is  directly  proportional  to  the  ratio  of  the  number 
of  turns  of  the  primary  and  the  secondary  cir- 
cuits. 

Transformation,  Current The  act 

of  changing  the  value  of  the  current  in  any 
circuit  by  changes  effected  in  its  electromotive 
force.  (See  Transformer?) 

The  act  of  changing  the  character  of  the  cur- 
rent,  such,  for  example,  as  a  direct  into  an  alternat- 
ing current  or  the  reverse,  or  a  single  alternating 
current  of  short  wave  length  and  high  frequency 
into  triphase  or  polyphase  currents. 

It  will  be  observed  that  the  term  current  trans- 
formation is  employed  in  two  distinct  senses. 

Transformation  of  Electric  Force. — (See 
Appendix — Force,  Electric,  Transforma- 
tion of.) 

Transformation,  Ratio  of The  ratio 

between  the  electromotive  force  produced  in 
the  secondary  of  an  induction  coil  or  trans- 
former and  the  electromotive  force  impressed 
on  the  primary. 


Tra.] 


660 


[Tra. 


The  ratio  of  transformation  depends  on  the  rel- 
ative number  of  turns  of  the  secondary  and  pri- 
mary coils  of  the  transformer.  In  a  well-con- 
structed transformer  there  is  very  little  energy  lost 
in  producing  a  transformation  by  means  of 
mutual  induction.  Consequently  the  energy  pro- 
duced in  the  secondary  must  very  nearly  equal 
the  energy  that  has  been  expended  in  the 
primary.  Suppose,  for  example,  that  the  number 
of  turns  of  the  secondary  of  an  induction  coil  is 
one-fiftieth  that  of  the  primary ;  then  the  difference 
of  potential  induced  in  the  secondary  will  be  but 
one-fiftieth  that  impressed  on  the  primary.  In 
order  to  make  the  product  of  the  current  strength 
and  the  difference  of  potential  in  the  secondary 
equal  to  the  product  of  the  current  strength  and 
difference  of  potential  in  the  primary,  the  cur- 
rent  strength  in  the  secondary  will  have  to  be 
fifty  times  greater  than  the  current  strength  in 
the  primary;  or,  in  other  words,  the  product 
of  C  and  E,  in  the  primary  will  very  nearly 
equal  the  product  of  C'  and  E'  in  the  secondary, 
*'.  e.,  C  E  =  C'  E'  nearly,  assuming  their  lag 
factors  to  be  equal. 

Transformer,  Alternating-Current  Ro- 
tary — A  term  sometimes  employed  for 

an  alternating  current  motor  which  at  the 
same  time,  by  means  of  a  suitable  commu- 
tator, delivers  continuous  currents  on  a  sep- 
arate circuit. 

Transformer,  Closed-Circuit A 

term  sometimes  employed  for  closed-iron- 
circuit  transformer.  (See  Transformer, 
Closed  Iron  Circuit!) 

Transformer,  Continuous  Current 

— A  term  sometimes  used  for  motor-dynamo 
or  dynamotor.  (See  Transformer,  Constant 
Current!) 

Transformer,  Direct-Current  Rotary 

— A  term  sometimes  employed  for  a  motor- 
generator.  (See  Generator,  Motor.} 

Transformer,  High-Frequency A 

transformer  in  which  the  frequency  of  the 
currents  employed  is  high. 

Transformer,  Iron-Loss  in A  loss 

of  energy  in  a  transformer  due  to  magnetic 
hysteresis  or  molecular  magnetic  friction  and 
to  the  setting  up  of  eddy  or  Foucault  currents 
in  the  iron. 


According  to  Steinmetz,  there  is  no  sensible 
magnetic  viscosity  in  a  transformer  up  to  204.5 
complete  periods  per  second.  If  the  eddy  or 
Foucault  currents  are  excluded,  the  hysteresis  loss 
of  a  transformer  can,  up  to  200  complete  periods 
per  second,  be  exactly  predetermined  by  calcula- 
tions based  on  tests  at  slow  cycles,  magnetic 
viscosity  being  absent. 

Transformer,    Low-Frequency  — 

A  transformer  in  which  the  frequency  of  the 
currents  employed  is  low. 

Transformer,  Non-Polar A  term 

sometimes  employed  in  place  of  closed-iron- 
circuit  transformer.  (See  Transformer, 
Closed  Iron  Circuit!) 

Transformer,  Open-Circuit A  term 

frequently  employed  for  open-iron-circuit 
transformer.  (See  Transformer,  Open  Iron 
Circuit!) 

A  variety  of  open-circuit  transformer  is  shown 
in  Fig.  582. 


fig.  58 2.     Open- Circuited  Transformer, 


Transformer,  Polar A  term  some- 

times  employed  for  open-circuit  transformer. 
(See  Appendix — Transformer,  Open-Cir- 
cuit!) 

Transformer,  Rotary A  term  gen- 
erally employed  for  the  combination  of  a 
motor  and  generator  in  one  machine,  /.  e., 
one  armature  and  one  motor. 

Sometimes  employed  in  place  of  a  con- 
tinuous current  transformer.  (See  Trans- 
former, Constant  Current. 

The  rotary  transformer  is  employed  either  to 
transform  continuous  currents  into  continuous 
currents  of  different  potential,  in  which  case  its 
armature  contains  two  windings,  the  generator 


Tra.] 


661 


[Tri. 


winding  and  the  motor  winding,  and  the  ratio  of 
transformation  is  equal  to  the  ratio  of  the  turns 
of  the  two  windings;  or  for  converting  alternate 
or  polyphase  currents  into  continuous  currents, 
in  which  case  if  the  maximum  alternate  current 
potential  equals  the  continuous  current  potential, 
it  generally  contains  one  armature  winding  only, 
which  is  connected,  to  the  continuous  current 
commutator,  and  at  two,  three  or  four  equidistant 
points  to  collector  rings. 

Such  rotary  transformers  are  used  extensively 
in  long-distance  power  transmission  for  convert- 
ing the  alternating  or  polyphase  currents  into 
continuous  currents  for  railway  circuits,  or  for 
supplying  alternating  current  circuits,  or  for  elec- 
tric welding. 

The  term  rotary  transformer  should  not  be  con- 
founded with  rotary  current  transformer.  (See 
Transformer,  Rotary  Current.) 

Transformer,  Static A  term  some- 
times employed  for  an  ordinary  transformer 
as  distinguished  from  a  rotary  transformer. 
(See  Appendix —  Transformer,  Rotary?) 

Transforming. — Converting  or  changing 
the  electromotive  force  and  consequently  the 
current  strength  in  any  circuit. 

Transition  Resistance. — (See  Appendix— 
Resistance,  Transition?) 

Translating  Telegraphic  Station.— (See 

Appendix  —  Station,      Translating      Tele- 
graphic.} 

Translation  Lag.— (See  Appendix— Lag, 
Translation?) 

Translation,  Manual  — In  telegra- 
phy, especially  in  sub-marine  telegraphy,  the 
translation  of  a  message  from  one  circuit 
directly  to  another  by  an  operator,  who  trans- 
mits to  the  second  circuit,  direct  from  sig- 
nals received  on  the  first,  without  writing 
dowji  or  transcribing  the  message. 

Transmitter,     Automatic     Telegraphic 

An  apparatus  employed  in  a  system 

of  automatic  telegraphy  for  sending  or  trans- 
mitting the  prepared  messages. 

The  message  for  automatic  telegraphy  is  pre- 
pared by  properly  punching  or  perforating  a  slip 
or  fillet  of  paper.  This  fillet  is  passed  through 
a  transmitter  so  as  to  transmit  automatically. 


Transposition.— In  telephony  a  reversal  in 
the  relative  position  of  two  parallel  conductors. 

Transpositions  are  made  in  conducting  wires 
in  order  to  neutralize  the  electromotive  forces 
produced  by  neighboring  currents. 

Trap,  Burglar  Alarm A  spring 

burglar-alarm  contact  held  in  an  open  posi- 
tion by  the  pull  of  a  string  against  the  action 
of  a  spring. 

The  slightest  disturbance  of  the  spring 
draws  the  contact  in  one  direction,  and  the 
destruction  of  the  string  permits  the  spring 
to  draw  it  in  the  opposite  direction,  in 
either  case  insuring  the  closing  of  a  circuit 
and  the  ringing  of  an  alarm  bell. 

Treated  Coked  Filament. — (See  Appen- 
dix— Filament,  Treated  Coked?) 

Tree  Insulator. — (See  Appendix — Insu- 
lator, Tree?) 

Tregadyne. — A  term  proposed  by  Houston 
and  Kennelly  for  a  million  million  dynes,  or 
a  million  megadynes,  or  io12  dynes. 

Trega. — A  prefix  proposed  by  Houston 
and  Kennelly  for  a  million  million  or  io12. 

Tregerg.— A  term  proposed  by  Houston 
and  Kennelly  for  a  million  million  ergs,  or  a 
million  megergs,  or  io12  ergs. 

Tregohm.—  A  term  proposed  by  Houston 
and  Kennelly  for  a  million  million  ohms,  or 
a  million  megohms,  or  io12  ohms. 

Triad  Atom.  —  (See  Appendix  —  Atom, 
Triad.} 

Trico. — A  term  proposed  by  Houston  and 
Kennelly  for  the  million  millionth  part,  or 
io-12. 

Tricofarad. — A  term  proposed  by  Houston 
and  Kennelly  for  the  millionth  part  of  a 
microfarad,  or  io~12  farad. 


Trigger,  Door 


— A  device  by  means 


of  which  notice  is  given  of  the  opening  or 
closing  of  a  door  or  window. 

Trigger,  One-Way  Door A  door 

trigger  which  operates  on  the  opening  of  the 
door  only. 

Trigger,  Two-Way  Door A  door 

trigger  which  operates  both  when  the  door  is 
opened  and  when  it  is  closed 


Tri.] 


662 


Trip,  Door,  Electric A  device  for 

ringing  a  bell  so  as  to  announce  the  entrance 
of  a  customer. 

The  bell  is  rung  only  when  the  door  passes  the 
trip,  but  does  not  ring  when  the  door  is  opened, 
or  when  it  is  being  closed. 

Tri-Phase  Armature. — (See  Appendix — 
Armature,  Tri- Phase?) 

Tri-Phase  Current.  —  (See  Appendix  — 
Current,  Tri-Phase?) 

Tri-Phase  Generator. — (See  Appendix — 
Generator,  Tri-Phase. } 

Tri-Phase  Motor. — See  Appendix — Motor, 
Tri-Phase. } 

Triphased  Alternating  Currents.— (See 

Appendix — Currents,  Triphased,  Alternat- 
ing.} 

Turtle-Back  Electro. — (See  Appendix — 
Electro,  Turtle-Back?) 

Two-Phase  Alternator. — (See  Appendix — 
Alternator,  Two-Phase?) 

Two-Phase  Armature. — (See  Appendix — 
Armature,  Two-Phase?) 

Two-Phase  Generator. — (See  Appendix — 
Generator,  Two-Phase.} 

Two-Phase  Motor. — (See  Appendix — Mo- 
tor, Two-Phase?) 


Two-Pole  Dynamo-Electric    Machine. — 

(See  Appendix — Machine,  Dynamo-Electric, 
Two-Pole.) 

Two-Thousand  Candle-Power  Arc,  Defi- 
nition for (See  Appendix — Arc,  Two- 
Thousand  Candle-Power,  Proposed  Defini- 
tion for.} 

Two-Way  Door  Trigger. — (See  Appendix 
—  Trigger,  Two-  Way,  Door} 

Triple-Pole  Switch.— (See  Appendix— 
Switch,  Triple-Pole?) 

Tri-Polar  Indicator. — (See  Appendix — 
Indicator,  Tri-Polar} 

Trolley  Base  Frame. — (See  Appendix — 
Frame,  Trolley  Base} 

Trough,  Plating A  term  some- 
times employed  in  place  of  plating  bath. 
(See  Bath,  Electro-Plating} 

Tube,      Lightning A      fulgurite. 

(See  Fulgurite} 

Tubular  Current. — (See  Appendix— Cur- 
rent, Tubular.) 

Tuning  of  Electrical  Circuit.— Altering 

the  period  of  a  circuit  or  varying  the  capacity 
or  self-induction  of  the  circuit  so  as  to  bring 
it  into  resonance  with  another  circuit. 


Uui-Phase  Armature  Winding. — (See  Ap- 
pendix— Winding,  Uni-Phase  Armature} 

Uni-Phase  Motor. — (See  Appendix — Mo- 
tor, Um- Phase.} 

Unipolar  Stimulation  of  Nerve. — (See 
Appendix — Stimulation,     Unipolar,    of    a 

Nerve} 

Unit,  C.  G.  S.,  of  Volumetric  Energy 

— (See  Appendix — Energy,  Volumetric,  C.  G 
S.  Unit  of} 


Unlighted  Segment  of  Aurora. — (See 
Appendix — Segment,  Unlighted,  of  Aurora} 

Unmarked  Magnetic  Pole. — (See  Appen- 
dix— Pole,  Magnetic,  Unmarked} 

Unsymmetrical  Polyphase  Motor. — (See 
Appendix— Motor,  Polyphase,  Unsymmet- 
rical} 

Upper  Harmonics  of  Current. — (See 
Appendix — Current,  Upper  Harmonics  of.) 


Vac.] 


663 


[Yol. 


T.— A  symbol  used  for  volt  or  for  volume. 
The  defining  equation  is  V  =  L  X  L  X  L. 
The  same  symbol  is  also  employed  for  volt 

v.  — A  symbol  used  for  velocity. 
The  defining   equation  is  v  =  7= 

The  same  letter  is  proposed  as  a  symbol  for  volt. 
Its  use  should  be  limited  to  one  or  the  other 
quantity. 

v. — A  symbol  for  the  ratio  between  the 
units  of  resistance  in  the  electrostatic  and 
electromagnetic  C.  G.  S.  system  of  measure- 
ment ;  *'. e.,  for  velocity  ratio.  (See  Ratio, 
Velocity.) 

Yacuum-Tube  Lighting.— (See  Appendix 
— Lighting,  Vacuum-  Tube.) 

Yariable  Period  of  Telegraph  Line. — 

(See  Appendix — Period,  Variable,  of  Tele- 
graph Line.) 

Variation  Magnetometer. — (See  Appen- 
dix— Magnetometer,  Variation?) 

Vector  Potential. — (See  Appendix— Po- 
tential, Vector.} 

Verdet's  Constant.— (See  Appendix— Con- 
stant, Verdet's.) 

Vertical  Intensity  of  Earth's  Magnetism. 

— (See  Appendix — Magnetism,  Verticalln- 
tensity  of  Earth's.) 

Vertical  Magnetic  Needle.— (See  Appen- 
dix— Needle,  Vertical  Magnetic.) 

Vibration  Frequency. — (See  Appendix — 
Frequency,  Vibration.) 

Vibrator. — An  electromagnetic  device  pro- 
vided on  a  siphon  recorder  for  maintaining 
the  siphon  in  continual  vibration  so  that  ink 
is  thrown  down  upon  the  fillet  of  paper  be- 
neath. 

Virtual  Current— (See  Appendix— Cur- 
rent, Virtual.) 

Visual  Telegraphic  Signal.— (See  Appen- 
dix— Signal,  Telegraphic,  Visual.) 


Volatilization  of  Electric  Conductor. — 

(See  Appendix—  Conductor,  Electric,  Vola- 
tilization of.) 

Volt,  International The  value  of 

the  international  volt  adopted  by  the  Chicago 
Congress  of  1893  as  equal  to  such  an  electro- 
motive force  that,  steadily  applied  to  a  con- 
ductor whose  resistance  is  one  international 
ohm,  will  produce  a  current  of  one  interna- 
tional ampere,  and  which  is  represented  suffi- 
ciently well  for  practical  use  by  y^ff  of  the 
electromotive  force  between  the  electrodes  of 
the  voltaic  cell  known  as  Clark's  cell,  at  a 
temperature  of  15°  C.,  and  prepared  in  ac- 
cordance with  certain  specifications. 

Volt,  Proposed  A.  I.  E.  E.  Definition  ftt 

The  product  of  the  A.  I.  E.  E.  am 

pere  by  the  A.  I.  E.  E.  ohm. 

Volt-Ammeter. — A  term  proposed  for  any 
electric  instrument  capable  of  measuring 
either  the  volts  or  the  amperes  in  a  circuit,  or 
both. 

A  measurer  of  the  volt-amperes  or  the 
watts. 

A  wattmeter. 

The  word  wattmeter  would  appear  to  be  pref- 
erable. 

Volta-Electric.— Of  or  pertaining  to  voltaic 
electricity.  (See  Electricity,  Voltaic.) 

Volta-Electricity.— Voltaic  electricity. 
(See  Electricity,  Voltaic.) 

Yolta-Electrometer. — A  voltameter.  (See 
Voltameter.) 

Volta-Electrometric. — Producing  voltaic 
electricity.  (See  Electricity,  Voltaic.) 

Volta-Electromotire  Force.— (See  Ap- 
pendix— Force,  Volta-Electromoti-ve.) 

Volta-Plast— A  word  proposed  for  the 
voltaic  battery  employed  in  electrotyping. 

The  use  of  this  word  would  appear  to  be  en- 
tirely  unnecessary.  There  is  nothing  peculiar 
about  this  employment  of  the  voltaic  battery. 


Vol.] 


664 


[VoL 


Volta-Type.— A  word  proposed  for  elec- 
trotype. 

The  use  of  this  word  would  appear  to  be  en- 
tirely unnecessary.  The  word  electrotype  is  pref- 
erable. 

Voltagraphy. — Electrotypy. 
The  word  electrotypy  would  appear  to  be  far 
preferable. 

Voltaic  Battery,  Element  of (See 

Appendix — Element  of  Voltaic  Battery?) 

Voltaic  Bow. — (See  Appendix — Bow,  Vol- 
taic.} 

Voltaic  Cell,  Callan (See  Appen- 
dix— Cell,  Voltaic,  Callan.) 

Voltaic  Cell,  Maynooth (See  Ap- 
pendix— Cell,  Voltaic,  Maynooth?) 

Voltaic  Electromotive  Force. — (See  Ap- 
pendix— Force,  Electromotive,  Voltaic?) 

Voltaic  Endosmose. — (See  Appendix — 
Endosmose,  Voltaic?) 

Voltaic  Heat  Cell.— (See  Appendix— Cell, 
Voltaic  Heat?) 

Voltaic  Mag-net. — (See  Appendix— Mag- 
net, Voltaic?) 

Voltaic  Pair.  —  (See  Appendix — Pair, 
Voltaic?) 

Voltaism. — A  word  sometimes  employed 
in  electro-therapeutics  for  treatment  by  means 
of  the  voltaic  current. 

The  production  of  electricity  by  means  of 
voltaic  couples. 

The  latter  use  of  this  word  was  the  meaning 
given  to  it  by  Sturgeon  in  1842,  who  defined  it  as 
follows:  "The  production  of  electricity  by  the 
association  of  metals  and  other  organic  bodies  "by 
the  simple  contact  of  inorganic  bodies." 

Voltmeter,  Electrometer A  volt- 
meter in  which  the  difference  of  potential  to 
be  measured  charges  insulated  conductors, 
the  electrostatic  attractions  and  repulsions  of 
which  produce  a  deflection  of  a  suitably  sus- 
pended metallic  needle. 

A  term  frequently  employed  for  voltam- 
eter. (See  Electrometer.  Voltameter?) 


Voltmeter,    Galvanometer  — Any 

form  of  galvanometer  so  arranged  as  to 
readily  measure  difference  of  potential. 

A  term  sometimes  employed  for  a  galva- 
nometer. 

Galvanometer-voltmeters  may  be  constructed 
in  a  great  variety  of  forms. 

In  all  such  cases,  however,  the  difference  of 
potential  is  measured  by  the  deflection  of  a  needle 
of  a  galvano:-ieter  by  means  of  the  magnetic  field 
produced  by  the  current  which  flows  through  a 
conductor  connecting  the  two  points  whose  differ- 
ence of  potential  is  to  be  measured. 

In  any  galvanometer- voltmeter  a  magnetic  field 
produced,  as  above  described,  by  the  difference 
of  potential  which  is  to  be  measured,  may  deflect 
a  magnetic  needle  against  the  following  forces, 
namely: 

(i.)  Against  a  magnetic  field.  (See  Appendix 
—  Voltmeter,  Magnetic?) 

(2.)  Against  the  action  of  a  spring.  (See  Ap- 
pendix—  Voltmeter,  Spring. ) 

(3.)  Against  the  action  of  gravity  acting  on  a 
weight.  (See  Appendix — Voltmeter,  Weight.') 

Voltmeter,  Magnetic An  instru- 
ment in  which  the  magnetic  field  of  a  cur- 
rent, which  is  proportional  to  the  difference 
of  potential  to  be  measured,  deflects  a  mova- 
ble needle  against  the  action  of  the  field  of 
a  magnet.  (See  Voltmeter?) 

Voltmeter,  Spring An  instrument 

in  which  the  magnetic  field  of  a  current, 
which  is  proportional  to  the  difference  of  po- 
tential to  be  measured,  deflects  a  movable 
needle  against  the  action  of  a  spring.  (See 
Voltmeter?) 

Voltmeter,  Weight An  instrument 

in  which  the  magnetic  field  of  a  current,  which 
is  proportional  to  the  difference  of  potential 
to  be  measured,  deflects  a  movable  needle 
against  the  action  of  a  weight.  (See  Volt- 
meter?) 

Volume  Density  of  Charge. — (See  Appen- 
dix— Charge,  Volume  Density  of?) 


Volumetric    Energy. — (See    Appendix— 

Energy,  Volumetric?) 
6— Vol.  2 


Wan.] 


665 


[Whi. 


W 


W. — A  contraction  used  for  the  physical 
quantity  energy,  whether  it  be  electrical,  ther- 
mal, mechanical  or  chemical,  or,  in  general, 
to  represent  the  product  of  the  force  by  the 
distance. 

W. — A  symbol  used  for  electric  energy. 

The  defining  equation  is  W  =  C  E  T. 

The  same  letter  is  proposed  as  the  symbol  for 
work  and  moment  of  a  couple. 

W. — A  symbol  proposed  for  the  moment  of 
a  couple. 

This  letter  is  also  employed  as  the  symbol  for 
work. 

The  denning  equation  is  F  X  D. 

W.  h. — An  abbreviation  proposed  for  watt- 
hour,  the  practical  unit  of  electric  energy. 

Wand,  Electric A  term  some- 
times used  for  an  electrophorus  in  the  form 
of  a  torch. 

An  electric  wand  is  employed  for  gas  lighting 
by  a  spark  produced  by  means  of  a  small  static 
machine  in  the  handle  upon  the  electrophorus. 

Watchman's  Electric  Clock. — (See  Appen- 
dix— Clock,  Electric,  Watchman's} 

Water-Gramme  Degree. — (See  Appendix 
— Degree,  Water-Gramme!) 

Watt-Efficiency  of  Secondary  Battery. — 
(See  Appendix — Battery,  Secondary,  Watt- 
Efficiency  of.) 

Watt,  International The  value  of 

the  international  watt,  adopted  by  the  Chicago 
Congress  of  1893,  is  equal  to  io7  units  of 
power  in  the  C.  G.  S.  system,  and  which  is 
the  work  done  at  the  rate  of  one  joule  per 
second. 

Watt,  Proposed  A.  I.  E.  E.  Definition  for 

The  product  of  the  square  of  the 

A.  I.  E.  E.  ampere  and  the  A.  I.  E.  E.  ohm. 

Wares,  Hertzian A  term  sometimes 

employed  for  electro-magnetic  waves. 

Waves  in  the  ether  that  are  produced  by  oscil- 
latory discharges  passing  through  a  circuit  or  by 
a  magnetic  circuit  undergoing  variations  in  its 


magnetic  intensity.  (See  Electricity,  Hertz's 
Theory  of  Electro-Magnetic  Radiation,  or 
Waves.) 

Way  Lease.  —  (See  Appendix  —  Lease, 
Way.) 

Weber,  A.  I.  E.  E.  Definition  for 

A  name  proposed  for  the  practical  unit  of 
magnetic  flux, 

A  unit  of  magnetic  flux  having  the  value  of 
one  absolute  unit  or  line. 

This  unit  is  a  modification  of  that  proposed  by 
a  Sub-Committee  of  the  American  Institute  of 
Electrical  Engineers  on  Provisional  Programme 
for  the  International  Electrical  Congress  held  in 
Chicago,  U.  S.  A.,  in  1893,  on  the  occasion  of  the 
World's  Columbian  Exposition. 

The  term  weber  was  formerly  applied  to  the 
unit  of  current;  it  never,  however,  came  into 
very  extensive  use  in  the  United  States. 

Wedge  Cut-Out— -(See  Appendix— Cut- 
Out,  Wedge.} 

Weeding-Ont  of  Harmonics. — (See  Ap- 
pendix— Harmonics,  Weeding-Out  of.} 

Weeding-Out  of  Harmonics  by  Electrical 
Resonance. — (See  Appendix — Harmonics, 
Weeding-Out  of,  by  Electrical  Resonance?) 

Weight  Voltmeter. — (See  Appendix — 
Voltmeter,  Weight) 

Wheel,  Barker's  — A  term  some- 
times applied  to  a  Barker  revolving  contact 
breaker.  (See  Appendix — Breaker,  Contact, 
Barker's  Revolving.} 

Whirl,  Contracting  Magnetic A 

magnetic  whirl  which  is  decreasing  or  mov- 
ing in  towards  the  electro-magnet  or  circuit 
which  is  producing  it. 

When  variations  occur  in  the  strength  of 
the  magnetism  produced  by  variations  in  the 
strength  of  the  current,  expanding  or  contracting 
whirls  are  produced  around  the  conductor  which 
move  outwards  or  from  the  conductor  when  the 
strength  of  the  magnetism  is  increasing,  and  in- 
wards or  towards  the  conductor  when  such 
strength  is  decreasing.  These  whirls  produce 


Whi.] 


666 


[Wir. 


electro-magnetic  waves  in  the  surrounding  ether 
which  are  called  Hertzian  electro-magnetic 
waves.  (See  Whirl,  Expanding  Magnetic. 
Electricity,  Hertz's  Theory  of.) 

Whirls,  Electro-Dynamic A  whirl- 
ing or  rotary  motion  produced  in  a  cloud  of 
copper  oxide  in  a  voltameter  when  traversed 
by  a  powerful  electric  discharge  while  under 
the  influence  of  a  magnetic  field. 

The  direction  of  the  rotation  is  opposite  to  the 
hands  of  a  watch  before  a  north  magnetic  pole 
and  in  the  same  direction  as  the  hands  of  a  watch 
before  a  south  pole. 

Winding,  Differential A  — ny  double 

winding  of  the  magnet  coils  such  that  the 
two  fields  produced  thereby  are  opposed  to 
each  other. 

Winding,  Single-Phase  Armature 

— A  uni-phase  armature  winding. — (See  Ap- 
pendix—  Winding,  Uni-Phase  Armature?) 

Winding,  Uni-Phase  Armature 

The  winding  of  the  armature  of  a  motor  such 
as  to  enable  it  to  be  operated  by  uni-phase 
currents. 

Windings,  Phase  — The    separate 

windings  on  the  armature  of  a  polyphase 
motor.  (See  Appendix — Motor,  Polyphase?) 

Windmill,  Electric A  term  some- 
times employed  in  place  of  electric  flyer. 
(See  Flyer,  Electric?) 

Window  or  Blind  Contact — (See  Appen- 
dix— Contact,  Window  or  Blind?) 

Wire,  Annunciator Insulated  wire 

suitable  for  use  in  connection  with  annuncia- 
tors, or  other  similar  purposes. 

Wire,  Double  Bronze A  conduct- 
ing wire  furnished  with  an  aluminium-bronze 
core  and  a  copper-brass  envelope. 

A  double  bronze  wire  possesses  great  tensile 
strength,  extreme  toughness,  and  a  comparatively 
low  electrical  resistance. 

A  No.  1 1  standard  gauge  double  bronze  wire 
has  a  breaking  strain  of  850  pounds  and  a  re- 
sistance of  443  ohms  per  mile  at  60  degrees  Fahr. 

Such  a  wire  is  so  tough  that  it  will  stand  from 
eight  to  ten  bends  of  180  degrees  each  in  alter- 
nate directions  through  a  radius  of  5  millimetres. 


Wire,  Idle,  of  Armature A  term 

sometimes  employed  in  place  of  dead  wire. 
(See  Wire,  Dead,  of  Armature?) 

Wire,  Idle,  of  Armature  of  Dynamo 

— A  term  applied  to  that  part  of  the  wire  on 
the  armature  of  a  dynamo-electric  machine 
in  which  no  useful  electromotive  force  is  pro- 
duced. 

The  dead  wire  on  an  armature.  (See  Wire, 
Dead,  of  Armature?) 

Wire,  Idle,  of  Armature  of  Motor 

— A  term  applied  to  that  part  of  the  wire  on 
the  armature  of  a  motor  in  which  the  field  pro- 
duced by  the  driving  current  never  exercises 
useful  action  in  driving  the  motor,  in  so  far  as 
no  counter  electromotive  force  is  generated 
in  it. 

Wire  or  Conductor,  Balancing A 

term  sometimes  employed  for  a  neutral  wire 
or  conductor  of  a  three-wire  system. 
Wire,  Tap,  in  Quadruples  Telegraphy 

The  intermediate  wire  or  conductor, 

in  a  system  of  quadruplex  telegraphy,  which 
divides  the  battery  into  two  unequal  parts, 
called  respectively  the  long  end  and  the  short 
end. 

Wires,  Equalizing Two  wires  or 

conductors,  one  of  which  is  employed  for 
connecting  the  two  positive  brushes  and  the 
other  for  connecting  the  two  negative  brushes 
of  two  compounded  dynamos  when  coupled  in 
parallel. 

In  general,  wires  or  conductors  employed  for 
equalizing  electrical  pressure  or  difference  of 
potential  in  two  or  more  circuits. 

In  the  coupling  of  two  compound-wound 
dynamos,  the  equalizing  wires  are  connected  one 
to  the  two  positive  brushes  and  the  other  to  the 
two  negative  brushes  of  the  coupled  machines. 
By  these  means  the  electrical  pressure  or  differ- 
ence of  potential  at  the  terminals  of  the  two  dyna- 
mos is  made  equal,  and  consequently  the  currents 
in  the  two  fields  are  also  made  equal. 

Wires,  Slinging A  term  sometimes 

employed  in  electro-plating  for  the  wires  or 
conductors  by  which  the  articles  that  are  to 
be  electro-plated  are  hung  from  the  kathode 
in  the  plating  bath. 


Wir.] 


667 


I/on. 


Wiring,  Concentric Wiring  by 

means  of  concentric  cables.  (See  Ap- 
pendix— Cable,  Concentric.} 

Working  Current  of  Motor.— See  (Ap- 
pendix— Current,  Working,  of  Motor.} 

Working,  Direct,  of  Telegraphic  Sounder 

A  term  sometimes  employed  for 

the  method  in  which  a  telegraphic  sounder 
is  operated  by  means  of  the  current  re- 
ceived from  the  line  wire  or  conductor 
from  the  distant  station  in  contradistinc- 
tion to  the  method  where  the  receiving 
instrument  is  operated  by  means  of  a 
local  battery. 

Working,    Double-Current    Telegraphic 

A  term  sometimes  employed   for 

double-current  signaling.  (See  Signaling, 
Double  Current. ) 


Working  Efficiency  of  Telegraphic  Cir- 
cuit.—(See  Appendix — Circuit,  Tele- 
graphic, Working  Efficiency  of.) 

Working,    Polyphase  —A   general 

term  employed  to  express  the  actual  ap- 
plication of  polyphase  currents. 

In  polyphase  currents  the  armature  of  tht 
motor  is  provided  with  separate  sets  of  coils 
grouped  in  two's,  three's,  etc.,  and  put  success, 
ively  into  action  at  suitable  periods. 

Working,     Single-Current     Telegraphic 

A  term  sometimes  employed  for 

single-current  signaling.     (See  Signaling, 

Single-Current. ) 

• 

Writiug  Telegraph.— (See    Appendix — 

Telegraphy.   Writing. 


Y  Tri-Phase  System.— (See  Appendix — 
System,  Y Tri-Phase.} 

Yards,  Ampere The    prpduct    of 


the  current  in  amperes  by  the  distance  in 
yards  through  which  it  passes.  (See  Feet, 
Ampere.  Turn,  Ampere.} 


Zero,  Immediate  False A  term 

employed  in  Wheatstone  bridge  measure- 
ments for  an  observation  made  to  that 
position  of  the  galvanometer  needle  as 
zero,  which  is  assumed,  or  which  tends 
to  be  assumed,  immediately  after  the 
opening  of  the  circuit  of  the  testing  cur- 
rent. 

Zinc-Lead  Accumulator.—  (See  Appendix 
— Accumulator,  Zinc-Lead.} 


/one,  Neutral,  of   Electrically  Charged 

Insulated  Conductor That    portion 

of  an  insulated  conductor,  charged  by 
electrostatic  induction,  which  lies  approx- 
imately midway  between  its  positive  and 
negative  ends. 

Zone,  Neutral,  of  Magnet A  term 

sometimes  employed  for  equator  of  mag* 
net.  (See  Magnet,  Equator  of.} 


APPENDIX  B. 


A. — A  symbol  for  ampere  (Partly  Interna- 
tional usage). 

A.  or  An. — A  contraction  for  anode. 

a. — A  symbol  proposed  for  acceleration. 

a. — A  symbol  for  an  angle. 

A.  B.  C.  Telegraph  Instrument. — 
A  step-by-step  dial  telegraph  instrument 
marked  with  the  letters  of  the  alphabet. 

A.  C. — A  contraction  for  alternating  cur- 
rent. 

A.  C.  C. — A  contraction  for  anodic  closure 
contraction. 

A.  D.  C. — A  contraction  for  anodic  dura 

tion  contraction. 

A.  H. — A  contraction  for  ampere-hour. 
A.  H.  E. — A  contraction  for  ampere-hour 

efficiency. 
A.  O.  C. — A  contraction  for  anodic  opening 

contraction. 

A.  T. — A  contraction  for  ampere-turn. 
A.  W.  G. — A   contraction   for  American 

wire  gauge. 

Abnormal  Dispersion. — Anomalous  dis- 
persion. 

Abnormal  Earth-Current.— A  tempo- 
rary, stronger,  and  more  variable  earth 
current  than  usual. 

Abnormal  Magnetization. — Magnetiza- 
tion generally  in  concentric  layers  of  al- 
ternate polarity,  produced  by  oscillatory 
or  Leyden-jar  discharges.  (Obsolete.) 

Abnormal  Vapor  -  Densities.  —  Vapor 
densities  whose  values  do  not  appear  to 
conform  to  Avogadro's  hypothesis. 

Abreast. — Connected  in  multiple  or  paral- 
lel. 

Abscissa.— The  co-ordinate  of  a  point 
measured  along  the  axis  of  abscissas. 

Absolute.— (1)  Complete  in  itself.  (2)  Not 
dependent  on  secondary  bases. 

Absolute  Block  System  for  Railroads. 
A  block  system  in  which  one  train  only 
is  permitted  to  occupy  a  given  block,  or 
division  of  the  road,  at  any  one  time. 

669 


Absolute  Calibration. — The  determina« 
tion  of  the  absolute  reading  of  an  electro- 
meter, galvanometer,  voltmeter,  am- 
meter, or  other  instrument. 

Absolute  Electro-Dynamometer. — An 
electro-dynamometer  for  the  measurement 
of  electric  currents  in  C.  G.  S.  units  by 
reference  to  the  moment  of  a  bifllar 
suspension  and  constants  derived  from 
the  winding  of  the  coils. 

Absolute  Electrometer.— An  electrome- 
ter in  which  the  value  of  the  electromo- 
tive force  is  directly  determined  in  abso- 
lute units  from  the  deflection  of  its  mov- 
able index. 

Absolute  Expansion.— The  real  expan- 
sion of  a  liquid,  or  the  expansion  it  would 
have  independently  of  any  change  in  the 
dimensions  of  its  containing  vessel. 

Absolute  Galvanometer. — Any  galvano- 
meter whose  indications  are  directly  de- 
termined in  absolute  units  of  current. 

Abs9lute  Inductivity.— The  real  indue 
tivity  of  a  medium  as  distinguished  from 
the  ratio  of  its  inductivity  to  the  induc- 
tivity  of  vacuum. 

Absolute  Insulation.— The  total  insula- 
tion of  a  circuit  or  conductor  without 
reference  to  its  length. 

Absolute  Permittivity.— The  real  per- 
mittivity of  a  medium. as  distinguished 
from  the  ratio  of  its  permittivity  to  the 
permittivity  of  vacuum. 

Absolute  Photometric  Standard.— A 
term  for  a  fundamental  standard  of  light 
employed  in  photometric  measurements, 
in  contra-distinction  to  a  secondary 
standard. 


Absolute  Unit  of  Current.— (1)  A  cur- 
rent of  such  a  strength  that  when  passed 
through  a  wire  one  centimetre  in  length, 
bent  in  the  form  of  an  arc  of  a  circle  one 
centimetre  in  radius,  will  act  with  a  force 
of  a  dyne  on  a  magnetic  pole  of  unit 
strength  placed  at  the  centre  of  the  arc, 
(2)  A  current  of  10  amperes. 


4-bs.] 


670 


LACl. 


Absolute  Unit  of  Electromotive 
Force.— (1)  The  C.  G.  S.  unit  of  electro- 
motive force.  (2)  The  one-hundred  mil- 
lionth of  a  volt. 

Absolute  Unit  of  Inductance.— A 
length  equal  to  one  centimetre.  (2)  The 
one  billionth  (10-9)  part  of  a  henry. 

Absolute  Unit  of  Induction. — A  term 
sometimes  used  for  the  absolute  unit  of 
inductance. 

Absolute  Unit  of  Magnetomotive 
Force. — A  unit  of  magnetomotive  force 
equal  to  4ir  multiplied  by  unit  current 
of  one  turn. 

Absolute  Unit  of  Resistance.— (1)  The 
one  thousand  millionth  of  an  ohm.  (2)  A 
microhm. 

Absolute  Units. — The  centimetre- 
gramme-second  system  of  units. 

Absolute  Vacuum. — (1)  A  space  from 
which  all  traces  of  residual  gas  have  been 
removed.  (2)  A  term  sometimes  loosely 
applied  to  a  high  vacuum. 

Absolute     Zero    of    Temperature.— 

(1)  The  temperature  of  a  substance  in 
which  its  molecules  are  absolutely  at  rest, 
or  possess  no  kinetic  energy.  (2)  A  tem- 
perature of  approximately — 273°C. 
Absorption. — The  taking  in  or  drinking 
in  of  one  form  of  matter  by  another,  such 
as  a  gas,  a  vapor,  or  a  liquid  by  any  sub- 
stance, usually  a  solid ;  or  of  energy  of 
sound,  light,  neat  or  electricity  by  ordi- 
nary matter. 

Absorption  Current. — The  current  of 
diminishing  strength  which  flows  into 
a  dielectric  under  electrification,  and 
which  is  partly  capable  of  being  restored 
during  continued  discharge. 

Absorption  Dynamometer. — The  name 
given  to  a  dynamometer  in  which  me- 
chanical power  is  measured  and  at  the 
same  time  absorbed,  in  contradistinction 
to  a  transmission  dynamometer,  in  which 
the  power  to  be  measured  is  all  or  nearly 
all  transmitted. 

Absorption,  Electric. — The  apparent 
soaking  of  an  electric  charge  into  the 
glass  or  other  solid  dielectric  of  a  Leyden 
jar  or  condenser. 

Absorption  of  Sound. — Acoustic  absorp- 
tion. 

Absorption  Spectrum. — A  spectrum 
containing  gaps  or  dark  spaces  due  to  ab- 
sorption by  some  medium  which  the  radi- 
ation has  traversed. 

Absorptive. — Possessing  the  power  of  ab- 
sorption. 

Absorptive  Power. — The  power  possessed 


by  certain  substances  of  taking  in  and 
condensing  gases  within  their  pores. 
Acceleration. — (1)  The  time-rate  of  change 
of  velocity.      (2)  Increase  or  decrease  of 
velocity. 

Accumulated  Electricity. — Stored  elec- 
tricity, as  in  a  condenser. 

Accumulating  Electricity  .—S  t  o  r  i  n  g 
electricity. 

Accumulation  of  Electricity. — (1)  The 
collection  of  an  electric  charge  in  a  Ley 
den  jar  or  condenser.  (2)  The  increase  in 
an  electric  charge  by  devices  called  ac- 
cumulators. (3)  The  production  of  a 
charge  by  an  influence  machine.  (4)  The 
collection  of  electric  energy  by  storage 
batteries  or  accumulators. 

Accumulator. — ( 1)  A  word  sometimes  ap- 
plied to  a  current  accumulator.  (2)  A 
Leyden  jar  or  condenser.  (3)  A  secondary 
or  storage  battery. 

Accumulator  Distribution.— Distribu- 
tion of  electric  energy  by  means  of  ac- 
cumulators. 

Accumulator  Traction. — Car  traction  in 
which  the  motors  are  driven  by  storage 
batteries  carried  on  the  car. 

Acetometer. — (1)  A  hydrometer  gradua- 
ted for  determining  the  strength  of  com- 
mercial acetic  acid  or  vinegar.  (2)  A» 
acidometer. 

Acheson  Effect.— The  change  in  the  elec- 
tromotive force  of  the  secondary  of  a  trans- 
former due  to  changes  of  temperature  in 
its  core. 

Achromatic. — Free  from  false  coloration. 

Achromatic  liens. — A   lens   capable   of 

forming  images  free  from  false  coloration. 

Achromatic     Ocular. — An     achromatic 

eye-piece. 
Achromatisable.— Capable  of  being  freed 

from  false  coloration. 

Achromatise. — To  free  from  false  colora- 
tion. 

Achromatising. — Freeing  from  false 
coloration. 

Acidimeter. — An  acidometer. 

Acidometer. — A  hydrometer  for  measur- 
ing the  specific  gravity  of  an  acid  liquid, 
and  thereby  determining  its  degree  of 
acidity. 

Aclinic. — (1)  Of  or  pertaining  to  no  mag- 
netic inclination.  (2)  Devoid  of  magnetic 
inclination  or  dip. 

Aclinic  Line. — (1)  A  line  connecting 
places  on  the  earth's  surface  which  have 
no  magnetic  inclination.  (2)  The  mag- 
netic equator  of  the  earth. 


Aco.] 


671 


[Act. 


Acoustic.— Of  or  pertaining  to  sound. 

Acoustic  Absorption. — The  absorption 
by  a  vibrating  body,  of  the  energy  of  the 
sound  waves  produced  by  another  vibrat- 
ing body. 

Acoustic  Interference. — Interference  of 
sound  waves. 

Acoustic  Resonance. — (1)  The  increase 
in  the  intensity  of  the  sound  emitted  by 
a  sonorous  body  by  means  of  sympathetic 
vibrations  set  up  in  a  co-periodic  sounding 
body.  (2)  The  condition  by  virtue  of 
which  a  sonorous  body  is  capable  of  having 
sympathetic  vibrations  produced  in  it  by 
a  neighboring  sounding  body. 

Acoustic  Synchronizer. — An  instrument 
for  indicating  the  synchronism  of  two 
alternating  currents  or  alternators,  by  an 
acoustic  apparatus  in  which  silence  is 
produced  at  synchronism. 

Acoustic  Telegraph. — Any  telegraph 
whose  signals  are  appreciated  by  the  ear, 
as  distinguished  from  a  visual  telegraph. 

Acoustic  Telegraphy.— Sound  tele- 
graphy ;  or,  any  system  of  telegraphy  in 
which  the  signals  are  received  by  sound, 
in  contradistinction  to  being  received 
visually. 

Acoustic  Tetanus. — Tetanus  produced  by 
alternating  currents  from  an  induction 
coil,  when  its  contact  piece  is  vibrating 
with  sufficient  rapidity  to  produce  a  musi- 
cal note. 

Acoutemeter,  Electric. — An  apparatus 
for  electrically  testing  the  delicacy  of 
hearing. 

Actinic. — Of  or  pertaining  to  the  chemical 
effect  produced  by  light  or  other  form  of 
radiant  energy. 

Actinic  Photometer. — A  photometer  in 
which  the  intensity  of  light  is  measured 
by  the  amount  of  chemical  decomposition 
it  produces. 

Actinic  Ray. — A  ray  of  light,  or  other 
form  of  radiant  energy,  possessing  the 
power  of  producing  chemical  action. 

Actinism. — The  chemical  effects  of  light. 

Actino-Electricity. — Electricity  p  r  o- 
duced  in  crystalline  substances  by  the 
action  of  radiant  energy. 

Actinograph. — An  apparatus  for  measur- 
ing and  recording  the  intensity  of  the 
chemical  effects  of  light. 

Actinography. — The  method  of  produc- 
ing records  by  the  chemical  effects  of 
light. 

Actinometer. — (1)  An  apparatus  for  meas- 
uring the  intensity  of  the  chemical  effects 
of  light.  (2)  A  pyrheliometer. 


Actinometer,   Electric.— An   apparatus 

for  electrically  measuring  the  intensity  of 

the  chemically  active  rays  present  in  any 

radiation. 
Actinpmetry. — The  science  of  measuring 

the  intensity  of  the  chemical  effects  of 

radiant  energy. 
Action  Currents. — Physiological  currents 

produced  in  a  muscle  or  nerve  during  ita 

activity. 

Active  Coil  or  Conductor. — A  coil  or 
conductor  carrying  an  electric  current. 

Active  Component  of  Exciting  Cur- 
rent. (1)  The  active  current  in  an  alter- 
nating-current circuit  as  distinguished 
from  the  wattless  current.  (2;  In  an 
alternating-current  circuit  the  component 
of  current  which  is  in  phase  with  the  E. 
M.  F.  (8)  In  an  alternating-current  cir- 
cuit the  product  of  the  E.  M.  F.  and  the 
effective  or  apparent  conductance. 

Active  Current. — (1)  The  working  com- 
ponent of  a  current  in  an  alternating-cur- 
rent circuit  as  distinguished  from  the  wat- 
tless component  of  current.  (2)  The  com- 
ponent of  an  alternating-electric  current 
that  is  in  phase  with  the  impressed  electro- 
motive force. 

Active  Electromotive  Force. — In  an  al- 
ternating-current circuit  that  component 
of  the  impressed  electromotive  force 
which  is  expended  in  overcoming  the 
ohmic  resistance,  as  distinguished  from 
the  component  which  is  expended  in  over- 
coming the  induced  C.  E.  M.  F. 

Active  Loop. — Any  single  loop  in  a  circuit 
that  is  traversed  by  an  electric  current. 

Active  Mass. — In  electrolysis  the  quantity 
of  an  electrolyte  which  is  disassociated" 
into  its  ions,  and  which  is,  therefore, 
active  in  conveying  the  electrolysing  cur- 
rent. 

Active  Material  of  Storage  Cell.— The 
substance  or  substances  in  a  storage  or 
secondary  cell,  that  undergo  decompo- 
sition while  charging  or  discharging,  and 
which  serve  to  store  the  electric  en- 
ergy. 

Active  Molecules. — (1)  Those  molecules 
in  an  electrolyte  that,  during  the  passage 
of  an  electric  current,  are  resolved  into 
their  constituent  ions  and  which,  there- 
fore, alone  affect  the  molecular  conduc- 
tivity of  the  electrolyte.  (2)  The  dis- 
associated molecules  in  an  electrolyte. 

Active  Plate  of  Voltaic  Cell. — A  name 
sometimes  given  to  the  zinc  or  other  plate 
of  a  voltaic  or  primary  cell  which  is  dis- 
solved during  action. 

Active  Polar  Surface  of  Magnet. — That 


Act/ 


672 


[Ady, 


surface  oi  t,  magnet  from  which  the  use- 
ful flux  emerges,  or  into  which  it  enters. 

Active  Pressure. — In  an  alternating-cur- 
rent circuit  that  component  of  the  im- 
pressed pressure  which  is  expended  in 
overcoming  the  olimic  resistance. 

Active  Pressure — A  term  sometimes  em- 
ployed for  the  pressure  that  is  effective 
in  producing  a  current,  as  distinguished 
from  the  impressed  pressure. 

Active  Wire. — That  portion  of  the  wire 
on  the  armature  of  a  dynamo  or  motor 
that  is  passed  through  the  inducing  mag- 
netic flux  as  distinguished  from  the  re- 
mainder of  the  wire  sometimes  called 
"  idle  wire,"  which  does  not  pass  through 
such  flux. 

Activity. — (1)  Power.  (2)  Rate-of-doing- 
work.  (3)  The  work  done  per  second,  in 
uniform  working. 

Actual  Cautery. — A  cautery  produced  by 
the  agency  of  a  white  heat. 

Actual  Energy.— (1)  Energy  actually 
employed  in  doing  work,  as  distinguished 
from  energy  that,  though  possessing  the 
power  of  doing  work, 'is  in  the  latent  or 
potential  state.  (2)  Kinetic  energy. 

Actual  Efficiency. — Commercial  effici- 
ency. 

Acute  Angle. — Any  angle  less  than  a  right 
angle  or  90  degrees. 

Acute-Angled  Trolley-Crossing.— A 
contact  plate,suspended  at  the  point  of  in- 
tersection of*  two  trolley  wires  crossing 
at  an  acute  angle. 

Acyclic  Region. — (1)  A  region  devoid  of 
cyclosis.  (2)  A  simply  connected  region. 

Adapter. — (1)  A  screw-nozzle  fitted  to  an 
incandescent  electric  lamp  and  provided 
with  a  screw-thread  to  enable  it  to  be 
readily  placed  on  a  gas  bracket,  or  chan- 
delier, in  the  place  of  an  ordinary  gas 
burner.  (2)  A  device  whicli  permits  in- 
candescent electric  lamps  of  one  manufac- 
ture to  be  readily  placed  in  the  socket  of 
a  lamp  of  another  manufacture.  (3)  Ap- 
paratus designed  to  permit  the  ready  use 
of  a  continuous-electric  current  employed 
for  incandescent  lighting  to  produce  the 
feeble  continuous  currents  employed  in 
electro-therapeutic  work. 

Adherence. — The  quality  or  property  of 
adhesion. 

Adhesion. — The  mutual  attraction  which 
exists  between  unlike  molecules,  as  dis- 
tinguished from  the  attraction  of  like 
molecules,  or  cohesion. 

Adhesion,  Electric. — The  adhesion  be- 
tween surfaces  due  to  the  attraction  of 
unlike  electrostatic  charges. 


Adhesion,  Magnetic.— The  adhesion  be- 
tween surfaces  due  to  magnetic  flux. 

Adhesive  Tape. — A  tape  covered  with  in- 
sulating material  and  possessing  adhesive 
properties,  employed  for  covering  bared 
conductors,  at  joints,  or  other  similar 
places. 

Adiabatic  Expansion.— The  expansion  of 
a  gas  which  neither  receives  nor  gives  out 
heat  to  the  walls  of  the  chamber  in  which 
the  expansion  takes  place,  as  distin- 
guished from  isothermal  expansion. 

Adiathermancy.— Opacity  to  heat. 

Adiathermanic. — Of  or  pertaining  to 
adiathermancy. 

Adielectric. — (1)  Not  dilectric.  (2)  A  term 
proposed  for  substances,  not  dielectrics, 
whose  electric  conductivity  at  ordinary 
temperatures  decreases  as  the  temperature 
increases. 

Adjustable  Angle  Crossing.— A  form  of 
trolley  crossing  in  which  the  angle  of  in- 
tersection is  adjustable. 

Adjustable  Condenser. — A  condenser 
whose  capacity  can  be  readily  varied 
within  certain  limits. 

Adjustable  Resistance. — A  resistance 
whose  value  can  be  readily  varied  within 
certain  limits. 

Adjustable  Rheostat. — An  adjustable  re- 
sistance. 

Adjustable  Vacuum  Tube. — A  vacuum 
tube  employed  for  X-ray  work  whose 
vacuum  can  be  decreased  by  the  action 
of  heat  on  a  vaporizable  substance. 

Adjustable  Wire  Clip  for  Trolley 
Wire. — A  clip,  capable  of  adjustment  as 
to  its  position,  inserted  in  an  insulator 
and  designed  for  holding  a  trolley  wire  in 
place. 

Adjuster  for  Lamp  Pendant. — Any  de- 
vice for  adjusting  or  altering  the  height 
or  position  of  a  pendant  lamp. 

Adjusting  Cleat. — Any  cleat  that  is  ca- 
pable of  adjustment  as  to  alignment  or 
height. 

Adjustment. — Any  regulation  of  an  ap- 
paratus that  will  enable  it  properly  to 
perform  its  functions. 

Adjustment  of  Relay. — Such  a  regula- 
tion of  a  receiving  relay  as  will  permit  it 
to  readily  respond  to  signals  sent  over  the 
line. 

Admittance. — (1)  The  reciprocal  of  the 
impedance  in  an  alternating-current  cir- 
cuit. (2)  The  apparent  conductance  of 
an  alternating-current  circuit  or  con- 
ductor. 

Advanced  Quadrature. — In  an  alternate 


Ady.] 


673 


[Air. 


ing- current  circuit  the  condition  of  being 
90°  in  phase  ahead  of  some  particular 
E.  M.  F.,  flux,  or  current. 

Adynamia  System  of  Currents.— A  sys- 
tem of  currents  so  opposed  to  each  other 
in  direction  as  to  neutralize  one  another's 
magnetic  effects. 

Aeolotropic.  —  Heterogeneous  with  re- 
spect to  direction. 

Aeolotropic  Medium.— (1)  A  medium 
possessing  different  properties  in  different 
directions.  (2)  A  medium  in  which  equal 
stresses  applied  in  any  direction  do  not 
produce  equal  strains. 

jEpinus'  Condenser. — An  early  form  of 
air  condenser. 

Aerial  Cable. — An  electric  cable  sus- 
pended in  the  air. 

Aerial  Circuit. — (1)  That  portion  of  a  cir- 
cuit which  consists  of  aerial  conductors 
or  lines.  (2)  A  circuit  of  overhead  wire. 

Aerial  Conductor. — An  overhead  con- 
ductor. 

Aerial  Line. — An  overhead  line. 

Aerial  Telephone  Cable.— A  suitably 
supported  overhead  telephone  cable. 

Aerodromic  Transportation.  — Trans- 
portation by  means  of  a  balloon-supported 
car  over  a  suitable  support  guide. 

Aerodynamics. — The  science  which  treats 
of  the  forces  produced  by  air  in  motion. 

Aero-Ferric-Circuit  Transformer. — An 
open-circuit  transformer. 

Aero-Ferric  Inductance.— The  induct- 
ance possessed  by  a  coil  or  coils  whose 
magnetic  circuit  consists  partly  of  air  and 
partly  of  iron. 

Aero-Ferric  Magnetic  Circuit. — A 
magnetic  circuit  that  is  completed  partly 
through  air  and  partly  through  iron. 

Aerolite. — A  meteorite. 

Aero-Therapeutics. — Treatment  of  dis- 
ease by  means  of  air  under  pressures  other 
than  that  of  the  atmosphere. 

After  Currents. — Electric  currents  pro- 
duced in  nerve  or  in  muscular  tissue,  on 
the  cessation  of  a  constant  current  which 
has  been  flowing  through  it. 

After  Glow  of  Exhausted  Bulb.— A 
fluorescent  glow,  observed  in  an  ex- 
hausted glass  chamber,  after  its  with- 
drawal from  electrostatic  influence. 

Age-Coating  of  Electric  Incandescent 
Lamp  Chamber. —  A  blackening  of  the 
chamber  of  an  electric  incandescent  lamp 
due  to  the  deposit  thereon,  during  use,  of 
carbon,  or  other  opaque  substance. 

Ageing  of  Alcohol,  Electric.— Artifl- 
43 


cially  ageing  alcohol  by  exposing  it  to  tha 
action  of  electrically  generated  ozone. 

Ageing  of  Electric  Incandescent 
Lamp. — A  gradual  decrease  in  the  effi- 
ciency of  an  electric  incandescent  lamp 
due  either  to  the  age  coating  of  its  cham- 
ber, or  to  the  deterioration  of  its  filament. 

Ageing  of  Magnet. — Treating  a  perma- 
nent magnet  for  the  purpose  of  rendering 
its  magnetic  condition  more  permanent. 

Ageing  of  Transformer. — (1)  A  decrease 
in  the  efficiency  of  a  transformer  owing 
to  the  ageing  of  its  core.  (2)  Fatigue  of 
transformer. 

Ageing  of  Transformer  Core. — Increase 
in  the  hysteretic  coefficient  in  the  iron 
of  a  transformer  core,  during  the  first  few- 
months  of  its  commercial  operation,  from 
its  continued  magnetic  reversals  at  com- 
paratively high  temperature. 

Agglomerate  Leclanche  Cell. — A  form 
of  Leclanche  cell  which  dispenses  with 
the  porous  cup  by  employing  the  carbon 
and  black  oxide  of  manganese  formed 
into  a  solid  mass  by  pressure. 

Agitator  for  Plating  Vat. — A  device  for 
ensuring  a  uniformity  in  the  density  of 
the  plating  solution  in  a  depositing  vat, 
by  mechanical  stirring. 

Agonal. — Of  or  pertaining  to  an  agone. 

Agone. — (1)  A  line  connecting  places  on 
the  earth's  surface  where  the  magnetic 
needle  points  to  the  true  geographical 
north.  (2)  The  line  of  no  declination. 

Agonic. — Of  or  pertaining  to  an  agone. 

Agonic  Line. — (1)  A  line  connecting  ter- 
restrial points  having  no  declination  or 
variation.  (2)  The  agone. 

Air  Battery.— A  form  of  voltaic  battery 
whose  electromotive  force  is  increased  by 
the  direct  absorption  of  oxygen  from  the 
air. 

Air  Blast  for  Commutator.— A  jet  of  air 
applied  to  the  surface  of  the  commutator 
of  a  dynamo-electric  machine  to  prevent 
destructive  flashing. 

Air-Blast  Transformer.— A  transformer 
which  is  cooled  by  a  blast  of  air. 

Air  Churning. — The  movement  of  the  air 
that  occurs  in  the  vicinity  of  the  arma- 
ture of  a  dynamo  or  motor  during  rotation 
resulting  in  a  loss  of  energy  to  the  machine. 

Air  Condenser. — A  condenser  in  which 
air  is  the  dielectric. 

Air-Cooled  Transformer.— (1)  A  trans- 
former which  is  cooled  by  the  passage 
through  it  of  convection  currents  of  ait 
set  up  by  its  increase  of  temperature 
(2)  An  air-blast  transformer. 


Air.] 


674 


[AIL 


Air-Core  Solenoid.— A  solenoid  which 
has  no  core  other  than  air. 

Air-Core  Transformer.— A  transformer 
which  is  destitute  of  a  core  other  than 
that  of  air. 

Air-Expansion  Lightning  Arrester.— 
A  form  of  lightning  arrester  in  which  the 
arc,  when  formed,  is  blown  out  by  the 
expansion  of  a  mass  of  confined  air  under 
the  influence  of  the  heat  of  the  arc. 

Air  Field. — That  portion  of  a  magnetic 
field  in  which  the  magnetic  flux  passes 
through  air  only. 

Air  Film  of  Lamp  Chamber.— A  film  of 
condensed  air  that  tends  to  remain  on  the 
walls  of  an  exhausted  lamp  chamber  after 
the  action  of  the  air  pump. 

Air  Gap. — In  a  magnetic  circuit,  any  gap 
or  opening  containing  air  only. 

Air  Gap  of  Commutator.— The  air  space 
between  contiguous  segments  in  an  air- 
insulated  commutator. 

Air  Insulation. — An  insulation  obtained 
by  air,  or  by  the  action  of  air. 

Air  Ley  den. — An  air  condenser. 

Air-Line  Wire. — That  portion  of  a  circuit 
which  consists  of  overhead  wires,  in  con- 
tradistinction to  the  portion  which  passes 
through  underground  conduits,  or 
through  a  submarine  cable. 

Air  Magnetic  Circuit.— A  magnetic 
circuit  in  which  the  flux  passes  wholly 
through  air. 

Air  Path. — The  path  a  disruptive  discharge 
takes  through  the  air. 

Air  Pump. — A  device  for  removing  air  or 
other  gas  from  a  containing  vessel. 

Air  Reluctance.— The  reluctance  of  that 
portion  of  a  magnetic  circuit  which  con- 
sists of  air. 

Air  Resistance  of  Dynamo.— The  me- 
chanical resistance  to  the  rotation  of  a 
dynamo  due  to  the  surrounding  air. 

Air  Space.— (1)  The  space  that  exists  be- 
tween the  surface  of  an  armature  and  the 
polar  surface  within  which  it  rotates. 
(2)  The  space  between  opposed  surfaces 
of  a  comb  lightning-arrester. 

Air-Space  Cut-Out.— A  modified  form  of 
paper  cut-out  in  which  the  disc  of  paper 
or  mica  is  replaced  by  an  air-space. 

Air-Space  Submarine  Cable.— A  mul- 
tiple-conductor submarine  cable,  having 
a  core  in  which  an  internal  air  space  is 
provided  for  separating  the  conductors. 

Air  Telegraphy.— (1)  Aerial  telegraphy. 
(2)  Induction  telegraphy.  (3)  Wireless  tel- 
egraphy. 


Air- Washing  of  Lamp  Filament.— A 

deleterious  effect  produced  on  the  fila- 
ment of  an  incandescent  electric  lamp  by 
the  molecular  bombardment  of  the  resid- 
ual gaseous  atmosphere  of  its  chamber. 
Alarm,  Electric.— (1)  Any  automatic  elec 
trie  device  by  which  attention  is  calle* 
to  the  occurrence  of  certain  events,  suck 
as  the  opening  of  a  door  or  window,  the 
stepping  of  a  person  on  a  mat  or  stair- 
case, the  rise  or  fall  of  temperature  be- 
yond a  certain  predetermined  point,  etc., 
by  the  closing  or  opening  of  an  electric 
circuit.  (2)  A  device  for  calling  a  person 
to  a  telegraphic  or  telephonic  instru- 
ment. 

Alarm  Point.— In  a  system  of  fire  teleg- 
raphy, any  point  from  which  an  alarm 
is  sent  out. 

Alarm  Wires  of  Submarine  Cable.— 
Extra  insulated  wires  imbedded  in  the 
fibrous  serving  of  a  submarine  cable,  be- 
tween the  sheathing  wires  and  the  con- 
ductor core,  and  capable  of  giving  an 
alarm  when  their  insulation  is  affected 
through  injury  to  the  cable,  before  the 
working  conductor  or  central  core  may 
be  injured. 

Aligned  Magnetomotive  Force. — The 
magnetomotive  force  in  a  magnetic  cir- 
cuit containing  iron,  due  to  the  aligning 
of  the  molecular  magnets  of  the  iron 
under  the  influence  of  the  impressed 
magnetic  force  or  prime  flux. 

"  Alive." — (1)  A  name  sometimes  given 
to  a  live  wire  or  circuit.  (2)  An  active 
wire  or  circuit. 

All-Day  Efficiency  of  Transformer.— 

The  ratio  of  the  energy  commercially 
supplied  by  a  transformer  in  24  hours  to 
the  energy  absorbed  by  it  from  the  mains 
during  that  time. 

All-Night  Arc  Lamp.— A  double-carbon 
arc  lamp. 

Allotropic. — Of  or  pertaining  to  allo- 
tropism. 

Allotropic  State.— A  modification  of  a 
substance  by  means  of  which,  without 
any  change  in  chemical  composition,  it 
acquires  physical  or  chemical  properties 
differing  from  those  it  ordinarily  pos- 
sesses. 

Allotropism. — The  state  or  condition  re- 
sulting from  acquiring  the  allotropic 
state. 

Allotropy.— The  property  of,  or  capacity 
for,  acquiring  the  allotropic  state. 

Alloy. — A  combination  or  homogeneous 
mixture  of  two  or  more  metallic  sub- 
stances. 


All]. 


675 


[Alt. 


Alloy. — To  form  a  combination  or  homo- 
geneous mixture  of  two  or  more  metallic 
substances. 

Alphabetic  Telegraph. — (1)  A  telegraph 
in  which  the  letters  of  the  message  to  be 
sent  are  spelled  out  in  succession  from  a 
dial.  (2)  An  A,  B,  C,  telegraph. 

Alteration  Theory  of  Muscular  or 
Nerve  Currents.  —  A  theory  which 
traces  the  origin  of  electric  currents  in 
the  nerves  or  muscular  fibres  to  an  alter- 
ation from  their  original  condition. 

Alternate  Currents. — Alternating  cur- 
rents. 

Alternating. — Periodically  changing  in 
direction. 

Alternating  Arc.— (1)  An  alternating-cur- 
rent arc.  (2)  An  arc  supplied  from  an 
alternating-current  circuit. 

Alternating  Continuous-Current  Com- 
mutating  Machine. — A  secondary  gen- 
erator for  transforming  from  alternating 
to  continuous  currents  by  the  aid  of  a 
commutator. 

Alternating-Current  Arc. — A  voltaic  arc 
produced  by  alternating  electric  currents. 

Alternating-Current  Armature- Wind- 
ing.—  A.n  armature  winding  suitable  for 
the  production  of  alternating  currents. 

Alternating  -  Current  Dynamo  -  Elec- 
tric Machine. — A  dynamo-electric  ma- 
chine producing  alternating  currents  in 
its  external  circuit. 

Alternating-Current  Electric  Motor. 
— A  motor  driven  by  alternating  electric 
currents. 

Alternating-Current  Electro-Magnet. 
— An  electro-magnet  whose  coils  are 
traversed  by  alternating  Currents,  and 
which,  although  constantly  reversing  in 
magnetism,  yet  possesses  a  continued  at- 
traction for  its  armature. 

Alternating  -  Current  Phase  -  Meter.— 
An  apparatus  for  measuring  the  differ- 
ence between  the  phases  of  two  alternat- 
ing currents. 

Alternating  -  Current  Potentiometer. 
— A  potentiometer  suitable  for  measuring 
the  difference  of  pressure  in  an  alternat- 
ing-current circuit. 

Alternating-Current  Power.— (1)  Elec- 
tric power  supplied  through  the  medium 
of  alternating  currents.  (2)  The  product 
of  the  effective  alternating-current 
strength,  the  effective  pressure  under 
which  that  current  is  supplied,  and  the 
power  factor.  (3)  With  sinusoidal  elec- 
tromotive forces  and  currents,  the  pro- 
duct of  the  effective  current  strength, 


the  effective  pressure  under  which  that 
current  is  supplied,  and  the  cosine  of  the 
phase-difference  between  the  two. 

Alternating-Current  Pressure  Indi- 
cator. —  An  alternating  -  current  volt- 
meter. 

Alternating-Current  Regulator.— (1)  A 
regulator  for  maintaining  constant  the 
pressure  of  an  alternating-current  gen- 
erator. (2)  A  regulator  for  controlling 
the  strength  of  an  alternating  current. 

Alternating-Current  Rotary  Trans- 
former.— A  rotary  transformer  for 
transforming  alternating  into  continu- 
ous-currents, or  vice-versa. 

Alternating-Current  Transmission. — 
Transmission  of  power  or  energy  by 
means  of  alternating  currents. 

Alternating-Current  Rush. — (1)  A  term 
sometimes  applied  to  the  first  rush  or 
wave  of  alternating  current  passing  into 
the  primary  coil  of  a  transformer  at  the 
moment  it  is  connected  to  the  mains.  (2) 
A  term  sometimes  applied  to  the  oscilla- 
tory discharge  of  a  condenser. 

Alternating-Current  Working. — Feed- 
ing lamps,  motors,  or  other  receptive 
devices  by  means  of  alternating  cur- 
rents. 

Alternating  Currents.  —  (1)  Currents 
which  flow  alternately  in  opposite  direc- 
tions. (2)  Currents  whose  directions  are 
periodically  reversed. 

Alternating  Discharge. — (1)  A  dis- 
charge which  periodically  changes  its 
direction.  (2)  An  oscillatory  discharge. 

Alternating  Dynamo  -  Electric  Ma- 
chine.— An  alternating-current  dynamo- 
electric  machine. 

Alternating  Electromotive  Forces. — 
Electromotive  forces  whose  directions 
are  periodically  reversing. 

Alternating  Electrostatic  Field.— A 
field  of  electrostatic  flux  whose  direction 
is  periodically  reversing. 

Alternating  Electrostatic  Potential.— 
An  electrostatic  potential  whose  value  is 
periodically  changing  sign. 

Alternating  Influence  Machine. — An 
electrostatic  influence  machine  which  de- 
livers periodically  alternating  electric  dis- 
charges or  currents. 

Alternating  Magnetic  Field. — A  mag- 
netic field  the  direction  of  whose  flux 
periodically  changes. 

Alternating  Magnetic  Potential.— A 
magnetic  potential  whose  value  is  period- 
ically changing  sign. 

Alternating    Magnetic    Call-Bell.— A 


Alt]. 


676 


call-bell  operated  by  the  uncommuted 
currents  of  a  magneto-electric  machine. 
Alternating  Magneto  -  Electric  Ma- 
chine.— A  magneto-electric  generator 
that  produces  alternating  currents  in  its 
external  circuit. 

Alternating  Potential. — A  potential, 
whether  electrostatic,  electric,  or  mag- 
netic, that  is  periodically  changing  in 
sign. 

Alternating  Sparking  Distance. — The 
air  space  across  which  an  alternating- 
current  disruptive-discharge  would  pass. 

Alternation. — (1)  A  change  in  direction. 
(2)  A  change  or  reversal  in  the  direction 
of  an  electromotive  force  or  current.  (3) 
A  single  vibration  or  oscillation  as  distin- 
guished from  a  complete  cycle  or  double 
vibration. 

Alternation  of  Current. — A  change  in 
the  direction  of  a  current. 

Alternations. — Successive  changes  in  the 
direction  of  a  current  or  electro-motive 
force. 

Alternative  Air-Path  of  Magnetic 
Flux. — In  a  ferric  magnetic  circuit  a 
field,  outside  the  iron  of  the  circuit, 
through  which  a  portion  of  the  magnetic 
flux  passes. 

Alternative  Path. — The  path  or  circuit 
taken  by  an  impulsive  discharge  through 
an  insulator  in  preference  to  a  conducting 
path  or  circuit,  of  enormously  smaller 
ohmic  resistance,  open  to  the  discharge. 

Alternator. — The  name  generally  given 
to  an  alternating-current  dynamo  or  gen- 
erator. 

Amalgam.— A  combination  or  mixture  of 
a  metal  with  mercury. 

Amalgam,  Electric. — A  substance  with 
which  the  rubbers  of  the  ordinary  fric- 
tional  electric  machine  are  covered. 

Amalgamate. — To  form  into  an  amalgam. 

Amalgamating. — Forming  into  an  amal- 
gam. 

Amalgamating  Solution. — A  solution 
of  a  salt  of  mercury  employed  for  readily 
amalgamating  the  zincs  of  a  voltaic 
battery. 

Amalgamation. — The  act  of  forming  into 
an  amalgam  or  effecting  the  combina- 
tion of  a  metal  with  mercury. 

Amalgamation  of  Zinc. — Coating  the 
surface  of  the  zinc  of  a  voltaic  cell  with 
mercury. 

Amalgamator,  Electric.— An  electrically 
driven  amalgamator  for  the  treatment  of 
gold  or  silver  ores  with  mercury. 


Amazite. — The  name  given  to  a  particular 
kind  of  insulating  material. 

Amber. — A  resinous  substance  generally 
of  a  transparent  yellow  color. 

American  Morse  Code. — The  Morse  tele- 
graphic code  employed  in  America,  as 
distinguished  from  that  employed  in 
other  parts  of  the  world. 

American  System  of  Telegraphy. — 
The  Morse  system  of  telegraphy  as  em- 
ployed in  America. 

American  Telegraphic  Code.  —  The 
American  Morse  code  of  telegraphic  sig- 
nals. 

American  Twist  Joint. — A  joint  between 
two  conducting  wires  in  which  each  end 
is  twisted  around  the  other. 

American  "Wire  Gauge.— The  name  gen- 
erally given  to  the  Brown  and  Sharpe 
wire  gauge,  in  which  the  largest  wire, 
No.  0000,  has  a  diameter  of  0.46",  the  wire 
No.  36,  0.005",  and  all  other  diameters  are 
in  geometrical  progression. 

Ammeter. — Any  form  of  galvanometer 
which  is  capable  of  measuring  current 
strength  directly  in  amperes. 

Ammeter  Panel  of  Switchboard.— In  a 

central  station  the  panel  of  the  switch- 
board which  carries  the  principal  amme- 
ter or  ammeters. 

Ammunition  Hoist,  Electric. — An  elec- 
trically operated  hoist  employed  for  rais- 
ing ammunition  to  the  gun  deck  or  turret 
of  a  ship. 

Amorphous. — Possessing  no  definite  crys- 
talline form. 

Amperage. — The  number  of  amperes  pass- 
ing in  a  cirquit  in  a  given  time. 

Ampere.—  (1)  The  practical  un  ,  of  electric 
current.  (2)  A  rate  of  flow  of  electricity 
transmitting  one  coulomb  per  second.  (3) 
The  current  of  electricity  which  would 
pass  through  a  circuit  whose  resistance  is 
one  ohm,  under  an  electro-motive  force 
of  one  volt.  (4)  A  current  of  such  a 
strength  as  will  deposit  1.118  milli- 
grammes of  silver  per  second  from  a  spe- 
cifically prepared  solution  of  silver  ni- 
trate. 

Ampere-Arc. — A  single  conductor,  bent 
in  the  form  of  an  arc  of  a  circle,  and  used 
in  an  electric  balance  for  measuring  cur- 
rent. 

Ampere-Balance. — A  balance  form  of 
ammeter  which  measures  currents  of  a 
few  amperes,  or  which  determines  a  cur- 
rent strength  of  one  ampere. 

Ampere-Centimetre. — A  proposed  unit 
of  magnetic  flux  equal  to  the  flux  pro* 


Amp.] 


677 


[An*. 


duced  by  one  ampere  flowing  through  a 
circuit  one  centimetre  in  length. 

Ampere-Foot.— A  unit  of  current  strength 
multiplied  by  the  distance  to  which  said 
current  is  carried,  employed  in  calculat- 
ing the  fall  of  electric  pressure  in  distri- 
buting mains.  (2)  The  magnetic  flux  or 
flux  density  developed  in  a  coil. 

Ampere-Hour. — (1)  A  unit  of  electrical 
quantity  equal  to  the  quantity  of  elec- 
tricity conveyed  by  one  ampere  flowing 
for  one  hour.  (2)  A  quantity  of  elec- 
tricity equal  to  3600  coulombs. 

Ampere-Hour  Efficiency  of  Storage 
Battery. — (1)  In  a  cycle  of  charge  and 
discharge,  the  ratio  between  the  ampere- 
hours  taken  out  of  a  storage  battery  and 
the  ampere-hours  put  into  it.  (2)  The 
quantity  efficiency  of  a  storage  battery 
as  distinguished  from  the  energy  effi- 
ciency. 

Ampere-Hour  Meter. — A  meter  which  is 
capable  of  measuring  an  electric  supply 
in  ampere-hours. 

Ampere-Hour  Output  of  Storage  Bat- 
tery.— The  amount  of  useful  electric 
quantity  produced  by  a  storage  battery 
in  ampere-hours. 

Ampere-Meter. — An  ammeter. 

Ampere-Minute. — A  unit  of  electrical 
quantity  equal  to  the  electric  quantity 
conveyed  by  one  ampere  in  one  minute. 

Ampere-Ring. — A  word  sometimes  used 
for  ampere-turn. 

Ampere-Second. — (1)  A  unit  -of  electric 
quantity  equal  to  the  quantity  of  elec- 
tricity conveyed  by  one  ampere  flowing 
for  one  second.  (2)  A  coulomb. 

Ampere-Stream  in  Armature.— The  ag- 
gregate current  in  amperes  produced  by 
all  the  conductors  on  a  dynamo  armature. 

Ampere-Tap. — In  a  system  of  electric  dis- 
tribution a  tap  provided  in  a  branch  cir- 
cuit for  carrying  off  a  current  of  one  am- 
pere. 

Ampere-Turn.— A  unit  of  magneto-motive 
force  equal  to  that  produced  by  one  am- 
pere flowing  around  a  single  turn  of  wire. 

Ampere- Volt. — A  word  sometimes  used 
for  volt-ampere,  cr  watt. 

Ampere-Yard. — A  proposed  unit  of  elec- 
tric current  multiplied  by  distance 
through  which  said  current  is  carried, 
sometimes  employed  in  calculations. 

Ampere-Winding.— A  word  sometimes 
used  for  ampere-turn  ;  i.  e, ,  a  single  wind- 
ing or  turn  through  which  one  ampere 
passes. 

Ampere-per-Square-Centlmetre.  —  A 


unit  of  density  of  current  expressed  in 
amperes-per-square-centimetre  of  normal 
cross-section  of  conductor. 

Ampere-per-Square-Inch.— A  unit  of 
density  of  current  expressed  in  amperes 
per-square-inch  of  area  of  normal  cross- 
section  of  conductor. 

Ampere's  Rule  for  Deflection  of  Nee- 
dle.— The  north-seeking  pole  of  a  mag- 
netic needle  is  deflected  by  a  current  to 
the  left-hand  of  an  observer  who  is  sup- 
posed to  be  swimming  in  the  current 
while  facing  the  needle. 

Ampere's  Theory  of  Magnetism.— A 
theory  or  hypothesis  which  ascribes  the 
cause  of  magnetism  to  the  presence  of 
electric  currents  in  the  ultimate  particles 
of  a  magnet. 

Amperian  Currents. — The  electric  cur- 
rents that  are  assumed,  in  the  Amperian 
theory  of  magnetism,  to  flow  in  closed 
circuits  around  the  ultimate  particles  of 
a  magnet. 

Amphigenic  Charge. — A  name  proposed 
for  an  electric  charge,  whose  surface  den- 
sity varies  in  sign. 

Amplitude  of  Galvanometer  Swing.— 

(1)  In  a  series  of  ballistic  galvanometer 
deflections,  the  half  sum  of  the  deflection 
or  elongation  from  zero,  on  one  side  of  the 
scale,  and  the  means  of  the  preceding  and 
following  elongations  on  the  other  side. 

(2)  When  referred  to  radian  measure  the 
ratio  of  the  above  quantity  to  the  distance 
of  the  scale  from  the  mirror. 

Amplitude  of  Simple-Harmonic  Mo- 
tion.— The  maximum  cyclic  value  of  a 
simple-harmonic  or  simple-periodic  vibra- 
tion ;  or,  the  distance  in  a  straight  line 
from  the  median  position  to  the  position 
of  greatest  elongation. 

Amplitude  of  Vibration  or  "Wave. — 
The  extent  of  the  excursion  of  a  simply 
vibrating  particle  on  either  side  of  its  vi- 
brating point  or  point  of  rest. 

Amyl-Acetate  Standard.— (1)  A  photo- 
metric standard  lamp  of  definite  dimen- 
sions burning  amyl-acetate.  (2)  The- 
Hefner-Alteneck  standard  lamp. 

Amyloid. — (1)  A  substance  employed  in 
the  manufacture  of  incandescent  lamp 
filaments  produced  by  the  action  of  sul- 
phuric acid  on  cellulose.  (2)  Parchment- 
ized  cellulose. 

Amyloid  Filament. — An  incandescent 
lamp  filament  made  from  amyloid. 

Anaemic  Cataphoresis. — Cataphoretio 
medication  accompanied  by  the  applica- 
tion of  bandages  to  retard  local  circula- 
tion in  the  parts  treated. 


An*.] 


678 


[Ang. 


Anaesthesia. — Insensibility  to  pain. 

Anaesthesia,  Electric.— Nervous  insen- 
sibility obtained  by  electrical  means. 

Analogous  Pole.— In  a  pyro-electric  sub- 
stance like  tourmaline,  the  pole  that  ac- 
quires a  positive  electrification  while  the 
temperature  of  the  crystal  is  rising. 

Analysis. — The  determination  of  the  com- 
position of  a  compound  substance  by  sep- 
arating it  into  the  elementary  substances 
of  which  it  is  composed. 

Analysis,  Electric. — The  determination 
of  the  composition  of  a  compound  sub- 
stance by  electric  means. 

Analyzable.  — Capable  of  being  analyzed. 

Analyze. — To  separate  into  component 
parts. 

Analyzer,  Electric. — A  gridiron  of  me- 
tallic wires  which  is  transparent  to  per- 
pendicularly incident  electro-magnetic 
waves,  when  the  length  of  the  wires  is 
perpendicular  to  the  electric  oscillations, 
but  is  opaque  to  them,  that  is,  possesses 
the  ability  to  absorb  or  reflect  them,  when 
rotated  90°  from  its  former  position  :  i.  e., 
when  parallel  to  the  electric  oscillations. 

Analyzing. — Separating  into  component 
parts. 

Anaphoresis. — A  term  sometimes  applied 
for  the  electric  osmose  which  occurs  in 
the  neighborhood  of  the  anode. 

Anchor. — In  a  trolley  system  the  diagonal 
tie  wires  which  bind  the  trolley  wire 
longitudinally  to  adjacent  poles  in  order 
to  maintain  a  uniform  degree  of  tension 
in  the  trolley  wire. 

Anchor  Log. — A  log  partially  buried  in  the 
ground  and  serving  as  an  anchor  for  a  tel- 
egraphic pole. 

Anchor  Platform.— A  frame-work  at- 
tached to  an  anchor-pole  by  means  of 
which  the  pole  is  solidly  set  in  the  earth. 

Anchor  Pole. — (1)  A  pole  for  overhead 
wires  of  sufficient  stiffness  to  take  the  en- 
tire tension  at  points  where  an  abrupt 
angle  occurs,  or  where  the  conductors 
enter  underground  conduits.  (2)  A  ter- 
minal pole. 

Anchor-Ring  Core. — A  toroidal  core. 

Anchor  Strain-Ear. — In  an  overhead 
trolley  system  a  trolley  ear  or  insulator 
employed  for  anchoring  the  trolley  wire, 
or  maintaining  it  taut,  so  as  to  ensure 
good  and  continuous  contact  with  the 
trolley  wheel. 

Anchored.— (1)  Kept  in  position  by  means 
of  an  anchor  strain -ear.  (2)  Kept  in  posi- 
tion by  means  of  an  anchor,  as  a  buoy  or 
ship.  (3)  Maintained  in  a  given  position. 


Anchored  Filament. — An  incandescent 
lamp  filament  supported  at  its  centre  'to 
prevent  injury  to  it  by  excessive  vibra- 
tie" 

Aneiectric. — A  word  formerly  applied  to 
conducting  substances  which  it  was  be- 
lieved could  not  be  electrified  by  friction. 
(Obsolete.) 

Anelectrotonic  State. — The  state  or  con- 
dition of  electrotonus. 

Anelectrotonic  Zone.— The  polar  zone. 

Anelectrotonus. — The  decreased  func- 
tional activity  which  occurs  in  a  nerve  in 
the  neighborhood  of  the  anode  or  positive 
electrode. 

Anemograph. — A  recording  anemometer. 

Anemograph,  Electric. — An  electrically 
recording  anemometer. 

Anemometer. — An  apparatus  for  record- 
ing the  intensity  and  direction  of  the 
wind. 

Anemometer,  Electric. — An  apparatus 
for  electrically  recording  the  intensity 
and  direction  of  the  wind. 

Anemometry. — The  measurement  of  the 
direction  and  intensity  of  the  wind. 

Anemoscope. — An  instrument  which  in- 
dicates but  does  not  measure  the  inten- 
sity, or  record  the  direction  of  the  wind. 

Aneroid. — Devoid  of  liquid. 

Aneroid  Barometer. — An  apparatus  for 
measuring  atmospheric  pressure,  which 
operates  by  the  to-and-fro  movements  of 
one  of  the  walls  of  a  partially  exhausted 
elastic  metallic  box. 

Angle. — The  deviation  of  direction  be- 
tween two  intersecting  lines  or  planes. 

Angle  Cathetometer. — A  cathetometer 
suitable  for  measuring  angular  deviation. 

Angle  of  Declination.— (1)  The  angle 
which  measures  the  deviation  of  the  mag- 
netic needle  to  the  east  or  west  of  the  true 
geographical  north.  (2)  The  angle  of  va- 
riation of  a  magnetic  needle. 

Angle  of  Dielectric  Hysteretic  Lag.— 
In  a  condenser  traversed  by  an  alterna- 
ting current  the  angle  whose  tangent  is 
equal  to  the  ratio  of  the  hysteretic  con- 
ductance to  the  hysteretic  susceptance  of 
the  condenser,  or  to  the  angle  whose  co- 
tangent is  the  ratio  of  the  hysteretic  re- 
actance of  condensance  to  the  hysteretic 
resistance  of  the  condenser. 

Angle  of  Dip.— (1)  The  angle  which  a 
magnetic  needle,  free  to  move  in  both  a 
vertical  and  horizontal  plane,  makes  with 
the  horizontal  line  passing  through  its 
point  of  support.  (2)  The  angle  of  inclina* 
tion  of  a  magnetic  needle. 


Aug.] 


679 


[Ann. 


Angle  of  Hysteretic  Advance  of  Phase. 
The  angle  by  which  the  equivalent  sine 
wave  of  exciting  current  leads  the  sine 
wave  of  magnetism,  in  a  transformer  or 
choking  coil  containing  iron. 

Angle  of  Inclination. — The  angle  of  dip. 

Angle  of  Lag. — The  angle  of  lag  of  a  dy- 
namo-electric machine. 

Angle  of  Lag  of  Current.— (1)  An  angle 
whose  tangent  is  equal  to  the  ratio  of  the 

•  inductive  to  the  ohmic  resistance  in  a  cir- 
cuit. (2)  An  angle  whose  cosine  is  equal 
to  the  ohmic  resistance  divided  by  the 
impedance  of  a  circuit.  (3)  An  angle 
whose  cosine  is  the  ratio  of  the  real  to  the 
apparent  power  in  an  alternating-current 
circuit. 

Angle  of  Lag  of  Dynamo-Electric  Ma- 
chine.— (1)  The  angle  through  which  the 
axis  of  magnetization  of  the  armature  of 
a  dynamo-electric  machine  is  shifted  by 
reason  of  the  resistance  its  core  offers  to 
cyclic  reversals  of  magnetization.  (2) 
The  angle  through  which  the  axis  of 
magnetization  of  the  armature  of  a  dyna- 
mo-electric machine  is  shifted  by  reason 
of  both  hysteresis  and  armature  reaction. 
(3)  The  backward  angular  deviation  from 
the  normal  of  the  brushes  of  a  motor  in 
order  to  secure  sparkless  commutation. 

Angle  of  Lead. — The  forward  angular  de- 
viation from  the  normal  position  which 
must  be  given  to  the  collecting  brushes 
on  the  commutator  of  a  continuous-cur- 
rent generator  in  order  to  obtain  quiet 
commutation. 

Angle  of  Maximum  Sensitiveness  of 
Galvanometer. — The  angle  of  deflection 
at  which  a  given  small  alteration  in  the 
current  strength  produces  the  greatest 
deflection  of  the  change  in  the  needle. 

Angle  of  Polar  Span. — The  angular  dis- 
tance which  the  pole  pieces  extend  cir- 
cumferentially  around  the  armature  bore. 

Angle  of  Variation. — The  angle  of  de- 
clination of  the  magnetic  needle. 

Angular. — Of  or  pertaining  to  an  angle. 

Angular  Acceleration.. — The  time  rate 
of  change  of  angular  velocity. 

Angular  Couple . — The  angular  force.    . 

Angular  Currents. — Currents  flowing 
through  circuits  which  intersect  one  an- 
other at  any  angle. 

Angular  Energy. — The  product  of  one- 
half  the  square  of  the  angular  velocity 
and  the  moment  of  inertia. 

Angular  Force. — The  force  which  causes 
the  rate  pf  change  of  angular  momentum. 

Angular  Momentum. — The  product  of 


the  moment  of  inertia  at  any  instant  and 
the  angular  velocity. 

Angular  Torque. — The  angular  twist  or 
couple. 

Angular  Velocity.— (1)  The  velocity  of  a 
point  moving  relatively  to  a  centre  of 
rotation  or  to  some  selected  point,  and 
usually  measured  in  degrees  per  second,  or 
in  radians  per  second.  (2)  In  a  sinusoidal- 
current  circuit  the  product  of  6.2832  and 
the  frequency  of  the  current. 

Angular  Wire  Gauge. — A  wire  gaug^e 
measurer  formed  of  a  metallic  strip  con- 
taining a  tapering,  or  acute-angled  slot 
with  graduated  edges. 

Animal  Electricity. — Electricity  pro- 
duced in  the  bodies  of  animals  during 
life. 

Animal  Magnetism. — A  term  sometimes 
applied  to  hypnotism  or  artificial  som- 
nambulism. 

Anion. — The  electro-negative  ion  or  radical 
of  a  molecule. 

Anisptropic  Conductor. — A  conductor 
which  though  homogeneous  in  structure 
possesses  different  conductivities  in  dif- 
ferent directions. 

Anisotropic  Medium.— (1)  A  medium 
in  which  equal  stresses  do  not  produce 
equal  strains  when  applied  in  different 
directions.  (2)  An  eolotropic  medium. 

Annealing. — The  art  of  softening  metals 
by  heating  and  subsequent  gradual  cool- 
ing. 

Annealing,  Electric.— A  process  for  an- 
nealing metals  in  which  electric  heat  is 
substituted  for  ordinary  heat. 

Annual  Inequality  of  Earth's  Mag- 
netism.— (1)  A  variation  in  any  of  the 
elements  of  the  earth's  magnetism  de- 
pendent upon  the  relative  position  of  the 
sun  and  earth.  (2)  Annual  variations  in 
the  earth's  magnetism. 

Annual  Load-Factor.— (1)  The  ratio  be- 
tween the  mean  output  of  a  central  station 
in  one  year,  and  the  maximum  output  at 
any  time  during  the  year.  (2)  The  ratio 
between  the  mean  daily  output  of  a  cen- 
tral station  in  one  year,  and  the  mean 
daily  maximum  output  in  the  same  year. 

Annual  Variations  of  Magnetic 
Needle. — Variations  in  the  magnetic  de- 
clination that  occur  at  regular  periods  of 
the  year. 

Annunciator  Board. — A  board  on  which 
annunciator  drops  are  placed. 

Annunciator  Clock,  Electric.— A  clock 
employed  in  connection  'with  an  an- 
nunciator for  automatically  disconnect- 


Ann.] 


680 


[Ant. 


ing  certain  circuits  at  certain  predeter- 
mined times. 

Annunciator  Drop. — An  annunciator 
signal  whose  dropping  indicates  the  clos- 
ing or  opening  of  the  circuit  of  a  partic- 
ular electro-magnet  connected  therewith. 

Annunciator  Wire. — A  class  of  insulated 
wire  prepared  for  use  in  annunciator 
circuits. 

Anodal. — Of  or  pertaining  to  the  anode. 

Aiiodal  Diffusion. — A  word  sometimes 
*  used  for  cataphoretic  medication. 

A.node. — (1)  The  conductor  or  plate  of  a 
decomposition  cell  connected  with  the 
positive  terminal  of  a  battery  or  other 
electric  source.  (2)  The  terminal  of  an 
electric  source  out  of  which  the  current 
flows  into  the  electrolyte  of  a  decompos- 
ing cell  or  voltameter.  (3)  In  a  vacu- 
um tube,  electrolytic  cell,  bath,  or  re- 
ceptive device,  the  terminal  at  which  the 
current  enters,  as  distinguished  from  the 
cathode,  at  which  the  current  leaves. 

Anodic. — Of  or  pertaining  to  the  anode. 

Anodic  Closure  Contraction.  —  The 
muscular  contraction  produced  by  the 
closing  of  a  voltaic  circuit,  the  anode  of 
which  is  placed  over  a  nerve,  and  the 
cathode  at  some  other  part  of  the  body. 

Anodic  Contraction. — The  muscular  con- 
traction produced  in  the  neighborhood  of 
the  anode,  either  on  opening  or  closing 
the  circuit. 

Anodic  Currents. — In  a  polarized  voltaic 
couple  immersed  in  acidulated  water, 
the  electric  currents  produced  by  the 
agitation  of  the  plate  connected  with  the 
anode. 

Anodic  Duration  Contraction.— The 
time  during  which  a  muscle  continues 
contracted  on  the  opening  or  closing  of  a 
circuit  whose  anode  is  placed  over  the 
part  contracted. 

Anodic  Electro-Diagnostic  Reactions. 
The  characteristic  reactions  which  oc- 
cur at  the  anode  of  an  electric  source 
placed  over  any  part  of  a  living  body. 

Anodic  Opening  Contraction. — The 
muscular  contraction  produced  by  the 
opening  of  a  voltaic  circuit  the  anode  of 
which  is  placed  over  a  nerve  and  the 
cathode  at  some  other  part  of  the  body. 

Anodic  Rays. — The  radiation  claimed  to 
emanate  from  the  anode  of  an  X-ray  tube. 

Anodic  Zone. — The  zone  or  region  sur- 
rounding the  anode  when  employed  as  a 
therapeutic  electrode. 

Anodograph. — A  word  proposed  for  a 
radiograph. 


Anomalous.— (1)  Irregular.  (2)  Not  in 
accordance  with  the  ordinary  rule. 

Anomalous  Dispersion. — An  abnormal 
dispersion  in  which  the  order  of  the  wave 
frequencies  is  inverted  as  regards  their 
order  in  ordinary  dispersion. 

Anomalous  Helix. — A  helix  wound  so  as 
to  produce  an  anomalous  magnet. 

Anomalous  Magnet. — A  magnet  possess- 
ing more  than  two  free  poles. 

Anomalous  Magnetization. — (1)  The 
magnetization  produced  by  the  oscillatory 
discharge  of  a  condenser  or  Leyden  jar. 
(2)  Magnetization  which  produces  more 
than  two  free  poles  in  a  magnet. 

Anomalous  Pole. — A  name  sometimes 
given  to  those  poles  of  an  anomalous 
magnet  which  consist  of  two  similar 
adjacent  poles. 

Anomalous  Solenoid. — An  anomalous 
helix. 

Anomalous  Spiral. — An  anomalous  helix. 

Answer  Back  Signal. — A  return  signal. 

Answering  Call-Box. — A  call-box  at 
which  an  answering  signal  is  obtained, 
indicating  that  the  call  has  been  received 
at  the  central  station. 

Answering  Board. — In  a  telephone 
switchboard  the  board  holding  the  an- 
swering jacks. 

Answering  Jacks. — In  any  panel  of  a 
telephone  switchboard  the  jacks  con- 
nected with  the  subscribers  whose  calling 
drops  are  placed  in  that  panel,  so  that 
each  call  may  be  immediately  answered 
at  an  adjacent  jack. 

Answering  Key. — In  a  telephone  switch- 
board a  lever  contact  key  which  enables 
the  operator  to  bring  her  head  telephone 
into  connection  with  any  subscriber. 

Anti-Cathode  of  X-Ray  Tube.— (1)  A 
deflection  plate  placed  opposite  the  ca- 
thode of  an  X-ray  tube.  (2)  A  platinum 
plate  supported  inside  an  X-ray  tube  to 
receive  the  cathodic  bombardment. 

Anti-Conical  System  of  Distribution. 
A  system  of  conical  conductors  employed 
in  anti-parallel  feeding. 

Anti-Hum. — A  device  for  lessening  the 
humming  sound  due  to  the  vibration  of 
an  aerial  wire. 

Anti-Induction. — Opposing  or  preventing 
induction  and  its  effects. 

Anti-Induction  Cable.— A  cable  whose 
conductors  are  so  arranged  as  to  avoid 
the  effects  of  induction,  either  from  them- 
selves or  from  neighboring  conductors. 

Anti-Induction     Conductor. — A    con« 


Ant.] 


681 


[App. 


ductor  cQnstructed  so  as  to  avoid  injur- 
ious inductive  effects  from  neighboring 
circuits. 

Anti-Induction  Telephone  Cable. — 
(1)  A  telephone  cable  in  which  the  con- 
ductors are  so  arranged  as  to  neutralize 
the  effects  of  induction  produced  by 
neighboring  circuits.  (2)  A  telephone  cable 
in  which  the  effects  of  electrostatic  in- 
duction from  neighboring  circuits  is 
avoided  by  a  metallic  covering  or  sheath- 
ing that  is  grounded  at  suitable  inter- 
vals. 

Antilogous  Pole.— The  pole  of  a  pyro- 
electric  substance  like  tourmaline,  which 
acquires  a  negative  electrification  while 
the  temperature  of  the  crystal  is  rising. 

Antimonious  Lead. — An  alloy  of  lead 
and  antimony  employed  for  the  grid  of  a 
storage  battery  because  it  is  not  acted  on 
by  the  charging  current. 

Antinode. — The  point  in  a  vibrating  string, 
wire,  or  plate,  midway  between  adjacent 
nodes. 

Anti-Parallel  Feeding.— A  method  of 
feeding  in  a  system  of  parallel  distribu- 
tion in  which  the  pressure  at  the  ter- 
minals of  all  the  translating  devices  is 
kept  approximately  uniform  by  employ- 
ing mains  tapering  in  opposite  directions  ; 
that  is,  with  their  large  ends  connected 
to  the  generator  terminals  or  bus-bars, 
and  the  mains  proceeding  in  opposite 
directions  around  the  circuit  to  be  sup- 
plied. 

Anti-phase. — (1)  A  phase  relation  be- 
tween two  periodic  currents  such  that 
they,  tend  to  decrease  the  amplitude  of 
the  motion.  (2)  Phase  opposition. 

Anvil  of  Telegraph  Key.— The  front 
stop  of  a  Morse  telegraph  key,  upon  which 
the  lever  descends  in  signalling. 

Aperiodic.— (1)  Not  characterized  by 
periodicity.  (2)  Devoid  of  periodicity. 
(3)  Coming  to  rest  steadily  without  oscil- 
lations. 

Aperiodic  Galvanometer.— (1)  A  gal- 
vanometer whose  needle  comes  to  rest 
without  any  oscillation.  (2)  A  dead- 
beat  galvanometer. 

A-Pole.— A  telegraph  double-pole  shaped 
like  a  letter  A. 

Apparent  Electromotive  Force.— The 
E.  M.  F.  apparently  acting  in  a  circuit  as 
measured  by  the  drop  of  pressure  due  to 
the  resistance  of  the  circuit  and  the  cur- 
rent strength  passing  through  it. 

Apparent  Coefficient  of  Induction.— 
A  term 'sometimes  used  for  the  apparent 
inductance  in  a  circuit  which  either  en- 


velops iron,  or  is  inductively  associated 
with  secondary  circuits. 

Apparent  Coefficient  of  Magnetic  In- 
duction.— The  apparent  permeability  of 
a  substance  as  expressed  by  the  amount 
of  magnetic  flux  that  passes  through  it 
per  unit  of  normal  cross-sectional  area, 
differing  from  the  true  value  on  account 
of  the  presence  of  eddy  currents. 

Apparent  Conductor-Resistance. —The 
impedance  of  a  conductor  which  forms 
part  of  an  alternating-current  circuit  con- 
taining both  resistance  and  reactance. 

Apparent  Efficiency  of  Alternator. — 

The  ratio  of  the  electric  activity  delivered 
at  the  terminals  of  an  alternator,  as  the 
product  of  volts  and  amperes  supplied,  to 
the  activity  mechanically  absorbed  at  its 
pulley  or  shaft ;  in  contradistinction  to 
the  efficiency  determined  from  the  true 
electric  activity  delivered. 

Apparent  Efficiency. — The  efficiency  of 
a  generator,  motor,  or  other  apparatus,  in 
an  alternating-current  circuit  based  upon 
the  volt-amperes  or  apparent  power  as  dis- 
tinguished from  efficiency  based  on  real 
power. 

Apparent  Efficiency  of  Alternating- 
Current  Motor. — The  ratio  of  the  power 
mechanically  delivered  by  the  motor  to 
the  apparent  activity  it  receives  at  its  ter- 
minals ;  as  distinguished  from  the  effi- 
ciency based  upon  the  real  electric  activity 
received. 

Apparent  Energy. — (1)  The  product  of 
the  effective  current  and  the  effective 
pressure  in  an  alternating-current  circuit. 
(2)  Apparent  activity,  as  opposed  to  true 
activity.  (3)  In  a  sinusoidal-current  cir- 
cuit, or  simple  alternating-current  circuit, 
the  product  of  effective  volts  and  effective 
amperes  uncorrected  for  the  cosine  of  the 
angle  of  their  phase  difference. 

Apparent  Expansion. — The  increase  in 
the  volume  of  a  liquid  by  expansion  irre- 
spective  of  the  expansion  of  its  con- 
taining vessel. 

Apparent  Insulation.  —  The  insulation 
resistance  of  a  circuit,  uncorrected  for 
the  effect  of  leakage  in  the  measuring 
current. 

Apparent  Impedance. — (1)  In  an  alter- 
nating-current circuit  the  virtual  imped- 
ance in  a  primary  circuit  due  to  the 
presence  of  an  associated  secondary  cir- 
cuit. (2)  The  joint  impedance  of  a  net- 
work of  impedances. 

Apparent  Insulation  of  Telegraphic 

Line. — The  insulation  of  a  telegraph  line 


App.] 


682 


[Arc. 


uncorrected  for  its  conductor  resistance, 
or  for  the  drop  in  testing  potential  at  the 
more  remote  portions. 

Apparent  Magnetization. — The  magnet- 
ization due  to  the  superposition  of  two 
separate  magnetizations. 

Apparent  Power.  —  In  an  alternating- 
current  circuit,  the  apparent  watts,  or  the 
product  obtained  by  multiplying  the  volts 
by  the  amperes,  as  read  directly  from  a 
voltmeter  and  ammeter. 

Apparent  Reluctance. — The  reluctance 
of  a  magnetic  circuit,  or  portion  thereof, 
under  the  influence  of  a  complex  of  such 
superposed  magnetic  fluxes  as  may  prac- 
tically be  developed,  as  distinguished 
from  its  reluctance  under  a  single  mag- 
netising force. 

Apparent  Resistance. —  The  impedance 
in  an  alternating-current  circuit  or  por- 
tion thereof. 

Apparent  Torque  Efficiency. —  In  an 
alternating-current  motor,  the  ratio  of  the 
torque  actually  developed  to  the  torque 
which  it  would  give  at  the  same  volt- 
ampere  or  apparent  electric  input  in  volt- 
amperes  if  there  were  neither  internal 
losses  nor  phase  displacement  in  the  motor. 

Apparent  Watts. — The  apparent  power 
in  an  alternating-current  circuit  as  dis- 
tinguished from  the  real  power. 

Apron  Grapnel. — A  form  of  grapnel  for 
grappling  a  cable  in  which  the  prongs  are 
protected  from  breakage  on  rocks  by  an 
apron  or  covering,  only  a  sufficient  space 
being  left  between  the  apron  and  the 
prongs  for  the  entrance  of  the  cable. 

Aqueous  Solution. — A  solution  of  a  salt 
or  other  substance  in  water. 

Arago's  Disc. — A  disc  of  copper  or  other 
non-magnetic  metallic  substance  which, 
when  rapidly  rotated  under  a  magnetic 
needle  supported  independently  of  the 
disc,  causes  the  needle  to  be  deflected  in 
the  direction  of  rotation,  and,  when  the 
velocity  of  the  disc  is  sufficiently  great,  to 
rotate  with  it. 

Arborescent  Discharges.  —  Disruptive 
discharges  obtained  from  a  high-potential 
discharge  of  a  series-connected  battery. 

Arborescent  Deposits.  —  Tree-shaped 
electro-metallurgical  deposits. 

Arc. — (1)  A  voltaic  arc.  (2)  A  portion  of  a 
circle,  or  other  plane  conic  section. 

Arc. — To  discharge  in  the  form  of  a  voltaic 
arc. 

Arc  Ammeter. — An  ammeter  on  an  arc 
circuit. 

Arc  Blow-Pipe,  Electric.— A  blow-pipe 


in  which  the  air-blast  is  obtained  by  a 
convective  discharge. 

Arc-Circuit  Cut-Out. —  A  cut-out  placed 
in  a  series  arc-light  circuit  to  prevent  the 
extinguishment  of  any  lamp  from  break- 
ing the  entire  circuit. 

Arc-Circuit  Cut-Out  Box. — A  box  fo\ 
holding  an  arc-circuit  cut-out. 

Arc-Circuit  Indicator. — A  device  in  the 
form  of  a  simple  galvanometer  which  in- 
dicates when  the  current  is  passing 
through  an  arc-light  circuit. 

Arc  Crater  Photometric  Standard. — A 

photometric  standard  based  on  the  inten- 
sity of  light  normally  emitted  from  a 
definite  area  of  the  crater  of  a  carbon 
voltaic  arc. 

Arc,  Electric.  —  A  term  sometimes  em- 
ployed for  the  voltaic  arc. 

Arc-Lamp,  Electric. — (1)  An  electric  lamp 
whose  source  of  light  is  the  voltaic  arc. 
(2)  An  incandescent  electric  lamp,  em- 
ployed to  illumine  the  circles  of  telescopes 
or  other  instruments  in  an  observatory. 

Arc-Lamp  Compensator. — A  reactive  or 
choking  coil,  placed  in  the  circuit  of  a 
lamp  or  lamps  for  the  purpose  of  auto- 
matically regulating  the  amount  of  cur- 
rent passing  through  the  lamp  or  lamps. 

Arc-Lamp  Globe.  —  A  glass  globe  sur- 
rounding the  arc  of  an  arc  lamp. 

Arc-Lamp  Hand-Board.  —  An  arc-lamp 
hanger-board. 

Arc-Lamp  Hanger. — A  board  from  which 
an  arc  lamp  is  suspended,  provided  with 
electric  connections  for  readily  short-cir- 
cuiting the  lamp. 

Arc-Lamp  Spark-Arrester. — A  gauze 
chimney  surrounding  the  arc  and  em- 
ployed for  the  purpose  of  preventing  fires 
when  arc  lamps  are  placed  near  com- 
bustible materials,  .as  in  shop  windows. 

Arc-Lamp  Suspension-Board.  —  (1)  A 
board  for  suspending  an"  arc  lamp.  (2) 
an  arc-lamp  hanger-board. 

Arc-Light .  —  The  light  of  the  carbon 
voltaic  arc. 

Arc-Light  Circuit.  —  (1)  A  circuit  in 
which  arc-lights  are  placed.  (2)  Gen- 
erally, a  series-connected  circuit. 

Arc-Light  Cut-Out. — A  switch  for  short- 
circuiting  an  arc-lamp  and  so  cutting  it 
out  of  the  circuit.  (2)  A  cut-out  which 
automatically  removes  an  arc-lamp  from 
the  circuit. 

Arc-Light  Diffuser.  —  Any  diffuser  for 
scattering  or  diffusing  the  light  from  an 
arc  light  so  as  to  avoid  the  production  of 
intense  shadows. 


Arc.] 


683 


[Arm, 


Arc-Light  Generator. — A  dynamo-elec- 
tric machine  that  furnishes  current  for 
arc-light  circuits. 

Arc-Light-Points. — The  carbon  pencils 
between  which  the  arc  is  maintained  in 
an  arc  light. 

Arc- Light  Projector. — An  arc  lamp  pro- 
vided with  a  reflector  for  obtaining  a 
beam  of  approximately  parallel  rays  of 
light. 

Arc-Light  Meter. — A  form  of  electric 
current  timer. 

Arc-Light  Regulator. — A  device,  gene- 
rally automatic,  for  maintaining  the  car- 
bons of  an  arc-lamp  a  constant  distance 
apart  during  the  operation  of  the  lamp. 

Arc-Light  Tower. — A  tower  employed  in 
out-door  illumination  for  supporting  a 
number  of  arc  lamps. 

Arc-Light  Transformer.  —  A  transfor- 
mer which  supplies  alternating  currents 
to  arc-lamps. 

Arc-Lighter. — An  arc-light  generator. 

Arc-Lighting. — Artificial  illumination 
obtained  by  means  of  arc  lights. 

Arc-Lighting  Dynamo-Electric  Ma- 
chine.— An  arc-light  generator. 

Arc  Plug-Switchboard. — A  switchboard 
provided  with  spring-jack  contacts  con- 
nected with  the  terminals  of  different 
circuits,  and  plug  switches  connected  with 
the  dynamo  terminals,  by  means  of  which 
any  dynamo  can  be  connected  with  any 
circuit ;  or  a  number  of  circuits  connected 
with  the  same  dynamo  ;  or  a  number  of 
separate  dynamos  placed  in  the  same 
circuit. 

Arc  Micrometer. — An  apparatus  for 
measuring  the  length  of  a  voltaic  arc  by 
means  of  a  micrometer. 

Arc  Standard  of  Light. — A  photometric 
standard  based  on  the  intensity  of  the 
light  emitted  by  a  given  area  of  crater  of 
the  positive  carbon  in  a  carbon  arc. 

Arc  Switchboard. — An  arc  plug-switch- 
board. 

Arcing. — Discharging  by  means  of  voltaic 
arcs. 

Areometer. — An  instrument  for  readily 
determining  the  specific  gravity  of 
liquids. 

Areometry.— The  measurement  of  the 
specific  gravity  of  liquids  by  means  of 
areometers. 

Argand  Electric  Burner.— An  Argand 
burner  provided  with  a  device  for  elec- 
trically igniting  the  gas. 


Argand  Electric  Lighter.— An  Argand 
electric  burner. 

Argand  Valve-Burner  or  Lighter.— 
An  Argand  burner  provided  with  means 
.  whereby  the  gas  can  be  both  turned  on 
and  lighted  electrically. 

Argymometry. — The  art  of  determining 
the  weight  of  electrically  deposited  silver. 

Arithmetical  Mean  Value  of  Periodic 
Current  of  E.  M.  P.  Wave.— The  arith- 
metical average  of  all  the  instantaneous 
values  during  one  complete  period. 

Arm  of  Balance  or  Bridge.— One  of  the 
resistances  of  an  electric  balance  01 
bridge. 

Arms  of  Balance  or  Bridge. — Two  sepa- 
rate resistances,  the  value  of  one  of  which 
is  usually  a  decimal  multiple  of  the  other, 
employed  in  an  electric  bridge  or  balance, 
in  connection  with  a  known  resistance, 
to  determine  the  value  of  an  unknown 
resistance. 

Armature. — (1)  A  mass  of  iron  or  other 
magnetizable  material  placed  on  or  near 
the  poles  of  a  magnet.  (2)  The  armature 
of  a  dynamo-electric  machine. 

Armature  Bars.— (1)  Heavy  copper  bars 
of  rectangular  or  trapezoidal  cross-sec- 
tion, or  of  imbricated  rectangular  strips, 
or  of  rectangular  bars  of  compressed 
stranded  wire,  or  of  special  forgings,  em- 
ployed on  large  drum  armatures  in  place 
of  the  ordinary  wire  windings.  (2)  Heavy 
conductors  employed  for  armature  wind- 
ings. 

Armature  Binding  Wires. — Coils  of 
wire  bound  on  the  outside  of  the  armature 
wires  for  the  purpose  of  preventing  their 
separating  from  the  armature  core  by 
centrifugal  force. 

Armature  Bore. — The  space  between  the 
pole-pieces  of  a  dynamo  or  motor  provided 
for  the  rotation  of  the  armature. 

Armature  Chamber. — (1)  The  armature 
bore.  (2)  An  armature  pocket. 

Armature  Chambers. — Spaces  left  in  the 
armature  core  for  the  reception  of  the 
armature  coils. 

Armature  Core-Discs. — The  thin  discs 
of  sheet-iron  that  form,  when  assembled, 
the  laminated  core  of  the  armature  of  a 
dynamo  or  motor. 

Armature  Core  of  Dynamo.— The  masa 
of  laminated  iron  on  which  the  armature 
coils  or  conductors  of  a  dynamo  or  motoi 
are  placed. 

Armature  Covering. — A  covering  of  can- 
vas  or  other  suitable  material  placed  on 
an  armature  for  the  purpose  of  protecting 
its  conductors  from  injury  or  dirt. 


Arm.] 


C84 


[Art. 


Armature  Hole.-  (1)  The  armature  bore. 
(2)  A  hole  made  in  the  core  for  the  recep- 
tion of  an  armature  coil  or  winding. 

Armature  Inductors. — The  bars,  strips, 
or  coils,  placed  on  the  dynamo  armature 
core,  in  which  electromotive  forces  are 
induced  by  rotation. 

Armature  Loop. — The  single  conducting 
coil  or  loop  on  a  dynamo  or  motor  arma- 
ture. 

Armature  of  Cable. — The  sheathing  or 
protective  coat  placed  on  the  outside  of  a 
cable. 

Armature  of  Condenser. — A  term  some- 
times applied  to  the  metallic  plates  or 
coatings  of  a  condenser  or  Leyden  jar. 

Armature  of  Dynamo. — (1)  Coils  of  in- 
sulated wire  together  with  the  iron  core 
on  or  around  which  such  coils  are  wound. 
(2)  That  part  of  a  dynamo  in  which  useful 
differences  of  potential  or  useful  currents 
are  generated.  (3)  Generally  that  part  of 
a  dynamo  which  is  revolved  between  the 
pole-pieces  of  the  field  magnets.  (4)  That 
member  of  a  dynamo  in  which  the  mag- 
netic flux  is  caused  to  successively  fill 
and  empty  the  coils  and  thereby  gener- 
ate E.  M.  Fs. 

Armatures  of  Holtz  Machine.— The 
pieces  of  paper  that  are  placed  on  the 
stationary  plate  of  a  Holtz,  or  other  simi- 
lar electrostatic  induction  machine,  near 
the  openings  in  the  same. 

Armature  Pinion. — A  toothed  wheel 
.  placed  on  the  armature  shaft  of  a  street- 
car motor  for  engaging  the  teeth  of  the 
reducing  gear. 

Armature  Pockets. — Spaces  provided  in 
an  armature  core  for  the  reception  of  the 
armature  coils. 

Armature  Projections. — Those  portions 
of  the  armature  core  between  which  the 
armature  slots,  pockets,  or  chambers  are 
situated. 

Armature  Reaction.— The  reactive  mag- 
netic influence  produced,  by  the  current 
in  the  armature  of  a  dynamo  or  motor, 
on  the  magnetic  circuit  of  the  machine. 

Armature  Segment.— That  portion  of  an 
armature  winding,  or  armature  inductor, 
whose  circuit  is  included  between  two 
contiguous  segments  of  the  commutator. 

Armature  Slots. — Slots  provided  in  an 
armature '  core  for  the  reception  of  the 
armature  coils. 

Armature  Spider. — A  metal  frame-work, 
keyed  to  the  armature  shaft,  and  pro- 
vided with  radial  arms  for  firmly  holding 
the  armature  core. 


Armature    Stampings.— Stampings    of 

soft  sheet  iron  intended  for  the  core  discs 

of  a  laminated  armature  core. 
Armature  Turns. — The  separate  turns  of 

conductors  on  the  armature  of  a  dynamo 

or  motor. 

Armature  Varnish. — An  insulating  var- 
nish sometimes  applied  to  armature  wind- 
ings for  the  purpose  of  increasing  theil 
powers  of  resisting  moisture  and  friction. 

Armature  Winding-Space. — Longitu- 
dinal grooves  or  spaces  left  in  the  arma- 
ture core  for  the  reception  of  the  arma- 
ture coils. 

Armed  Magnet. — A  magnet  provided 
with  an  armature. 

Armor  of  Cable.— The  protecting  sheath- 
ing or  metallic  covering  of  a  submarine 
or  other  electric  cable. 

Armored. — Provided  with  armor,  as  of  the 
protective  sheathing  of  a  cable. 

Armored  Cable. — A  cable  provided  with 
a  protective  sheathing  or  armor. 

Armored  Conductor. — A  conductor  pro- 
vided with  a  protective  sheathing  or 
armor. 

Army  Telegraph.— The  telegraphic  ap- 
paratus employed  in  field  service  in  the 
army. 

Arrester  Plate  of  Lightning  Protec- 
tor.— The  ground -connected  plate  of  a 
comb  lightning-arrester. 

Arrester  Plates. — A  term  sometimes  ap- 
plied to  the  two  plates  of  an  ordinary 
comb  lightning-protector. 

Arrival  Curve  of  Current  in  Sub- 
marine Cable  or  Telegraphic  Cir- 
cuit.— A  curve  showing  the  gradual 
increase  in  the  strength  of  current  reach- 
ing the  receiving  end  of  a  submarine 
cable  under  a  given  condition  of  signal- 
ling. 

Articulate  Speech. — The  successive  tones 
of  the  human  voice  that  are  necessary  to 
produce  intelligible  words. 

Artificial  Cable. — A  circuit  containing 
associated  resistance  and  capacity,  and 
employed  in  a  system  of  duplex  sub- 
marine telegraphy  corresponding  to  the 
artificial  line  in  duplex  aerial  line  tele- 
graphy. 

Artificial  Cable  Leak. — A  leak  purpose- 
ly introduced  at  some  point  in  the  circuit . 
of  an  artificial  cable  employed  in  duplex 
cable  telegraphy. 

Artificial  Carbons. — Carbons  obtained 
by  the  carbonization  of  a  mixture  of  pul- 
verized carbon  with  a  carbonizable  liquid. 


Art.] 


685 


[AtOa 


Artificial  Fault  in  Cable. — A  fault  pur- 
posely made  in  an  artificial  cable  for  the 
purpose  of  studying  its  behavior  under 
tests. 

Artificial  Illumination. — The  employ- 
ment of  artificial  sources  of  light. 

Artificial  Line. — In  duplex  telegraphy  a 
combination  of  resistance  coils  and  con- 
densers which  serves  to  balance  an  actual 
telegraph  line. 

Artificial  Magnet.— A  magnet  produced 
by  induction  from  another  magnet  or 
from  an  electric  current. 

Asbestos  Porcelain.  —  A  porous  sub- 
stance, somewhat  resembling  ordinary 
porcelain,  employed  for  the  porous  cells 
of  voltaic  batteries. 

A-Side  of  Quadruplex  Table.— That 
side  of  a  quadruplex  system  which  is 
worked  by  means  of  reversed  currents. 

Asphyxia. — Suspended  respiration  event- 
ually resulting  in  death  from  non-aeration 
of  the  blood. 

Assumed  Direction  of  Flow  of  Cur- 
rent.— A  convention  which  regards  the 
current  as  leaving  an  electric  source  at 
its  positive  pole,  and  returning  to  it  at  its 
negative  pole. 

Assymmetrical. — Devoid  of  symmetry. 

Assymmetrical  Resistance. — A  resist- 
ance which  is  claimed  to  be  greater  to  a 
flow  of  current  in  one  direction  than  in 
another. 

Astatic. — Devoid  of  magnetic  directive 
power. 

Astatic  Circle. — A  term  sometimes  used 
for  astatic  circuit. 

Astatic  Circuit. — A  circuit,  consisting  of 
two  closed  curves  enclosing  equal  sur- 
faces, which  is  not  deflected  by  the 
earth's  field  on  the  passage  of  a  current 
through  it. 

Astatic  Couple. — Two  magnets  of  equal 
strength  so  placed  one  above  the  other  in 
a  vertical  plane  as  completely  to  neutral- 
ize each  other's  effects. 

Astatic  Galvanometer. — A  galvanometer 
provided  with  an  astatic  needle  or  cir- 
cuit. 

Astatic  Multiplier. — An  astatic  galvano- 
meter. 

Astatic  Needle. — (1)  A  compound  mag- 
netic needle  of  great  sensibility,  possess- 
ing little  or  no  directive  power.  (2)  An 
astatic  needle  consisting  of  two  separate 
needles  rigidly  connected  and  placed  par- 
allel one  directly  over  the  other  with 
opposite  poles  opposed. 

Astatic  Pair.— An  astatic  couple. 


Astatic  System. — An  astatic  combination 

of  magnets. 

Astaticizing. — Rendering  a  system  astatic. 
Astigmatism. — A  defect  in  the  lenses  of 

the  eye  which   prevents  horizontal  and 

vertical  lines  from  being  in  focus  at  the 

same  time. 
Astronomical  Meridian. — A  great  circle 

passing  through  any  point  of  the  heavens 

and  the  north  and  south  poles    of  the 

heavens. 

Asymptote  of  Curve. — A  straight  line 
which  continually  approaches  a  curved 
line,  but  which  meets  it  only  at  an  in- 
finite distance. 

Asynchronism. — Devoid  of  synchronism. 

Asynchronous.  —  Occurring  or  acting 
non-simultaneously. 

Asynchronous  Alternating-Current- 
Motor. — A  motor  whose  speed  is  not 
synchronous  with  that  of  its  driving  gen- 
erator, both  machines  having  the  same 
number  of  poles. 

Atmosphere. — (1)  A  unit  of  gaseous  or 
fluid  pressure  equal  to  14'73  pounds  per 
square  inch.  (2)  The  ocean  of  air  which 
surrounds  the  earth. 

Atmospheric. — Of  or  pertaining  to  the 
atmosphere. 

Atmospheric  Cathode  Discharge. — An 
X-ray  discharge  which  is  assumed  to  ac- 
company and  form  part  of  the  sun's 
radiation. 

Atmospheric  Electricity.  —  The  free 
electricity  which  is  present  in  the  atmos- 
phere. 

Atom. — (1)  An  ultimate  particle  of  mat- 
ter. (2)  The  smallest  quantity  of  ele- 
mentary or  simple  matter  that  can  exist. 

Atom  of  Electricity.  —  A  quantity  of 
electricity  equal  in  amount  to  that  pos- 
sessed by  any  chemical  monad  atom. 

Atomic. — Of  or  pertaining  to  the  atom. 
Atomic  Attraction. — (1)  The  attraction 

which  causes  the  atoms  to  combine.     (2) 

Chemical  affinity. 
Atomic   Capacity. — The  equivalence  or 

valency  of  an  atom. 

Atomic  Currents. — A  term  sometimes 
employed  instead  of  molecular  or  Ampe- 
rian  currents. 

Atomic  Energy.  —  Chemical  potential 
energy. 

Atomic  Heat. — A  constant  product  ob- 
tained by  multiplying  the  specific  heat  of 
an  elementary  substance  by  its  atomic 
weight- 


Ato.] 


686 


[Aut. 


Atomic  Weight. — The  relative  weight  of 
the  atoms  of  elementary  substances. 

Atomicity. — (1)  The  combining  capacity 
of  the  atoms.  (2)  The  relative  equiva- 
lence of  the  atoms,  or  their  atomic  ca- 
pacity. 

Atomization. — The  act  of  obtaining  li- 
quids in  a  spray  of  finely  divided  parti- 
cles. 

Atomize. — To  separate  into  a  spray  by 
means  of  an  atomizer. 

Atomizer. — An  apparatus  for  readily  ob- 
taining a  finely  divided  jet  or  spray  of 
liquid. 

Attachment  Plug. — A  plug  provided  for 
insertion  in  a  screw  socket  or  spring  jack, 
for  the  ready  connection  of  a  lamp  or 
other  receptive  device  to  a  circuit. 

Attract. — To  draw  together. 

Attracted-Disc  Electrometer. — A  form 
of  electrometer  in  which  the  force  is 
measured  by  the  attraction  existing  be- 
tween two  charged  discs. 

Attracting. — Drawing  together. 

Attraction. — Literally  the  act  of  drawing 
together. 

Attraction  of  Gravitation. — (1)  Mass  at- 
traction ;  or,  the  attraction  which  causes 
masses  of  matter  to  tend  to  move  towards 
one  another.  (2)  The  attraction  which 
causes  bodies  to  fall  to  the  earth.  (3)  Molar 
attraction. 

Attractions  and  Repulsions  of  Cur- 
rents.— The  tendency  of  active  circuits 
to  be  attracted  to  or  repelled  from  one 
another  by  the  mutual  action  of  their 
magnetic  fields. 

Audible  Code. — A  term  employed  in  rail- 
way signalling  for  a  code  of  audible  sig- 
nals in  railway  service. 

Audible  Telegraphic  Signal. — A  signal 
which  is  received  by  the  ear  in  contra- 
distinction to  a  visual  signal  or  one  re- 
ceived by  the  eye. 

Audiometer. — A  form  of  induction  bal- 
ance or  sonometer  employed  in  testing 
the  acuteness  of  hearing. 

Audiphone. — A  thin  plate  of  hard  rubber 
held  in  firm  contact  with  the  teeth  and 
maintained  at  a  certain  tension  by  strings 
attached  to  one  of  its  edges,  employed  for 
the  purpose  of  aiding  the  hearing. 

Auger. — A  boring  tool  for  cutting  holes 
for  telegraph  poles. 

Aura,  Electric. — A  term  sometimes  ap- 
plied to  an  electric  brush  or  convective 
discharge. 

Aural  Electrode. — An  electrode  suitably 


shaped  for  the  therapeutic  treatment  of 
the  ear. 

Aurora. — (1)  Luminous  sheets,  columns, 
arches,  or  pillars  of  pale  flashing  light, 
generally  of  a  reddish  color,  seen  in  the 
Northern  and  Southern  heavens.  (2)  The 
Northern  and  Southern  lights. 

Aurora  Australis.— (1)  The  Southern 
light.  (2)  A  name  given  to  an  appear- 
ance in  the  Southern  heavens  similar  to 
that  of  the  aurora  borealis. 

Aurora  Borealis. — The  Northern  light. 

Aurora  Glory. — A  term  proposed  for  the 
almost  constant  crown  or  crowns  of  light, 
which  occupy  a  nearly  fixed  position  in 
the  heavens  during  the  continuance  of 
an  aurora. 

Aurora  Polaris. — A  general  name  for  the 
aurora  borealis  or  the  aurora  australis. 

Auroral. — Of  or  pertaining  to  an  aurora. 

Auroral  Arch. — An  arch-like  form  some- 
times assumed  by  the  auroral  light. 

Auroral  Bands. — Approximately  parallel 
streams  of  light  that  are  sometimes  seen 
during  the  prevalence  of  an  aurora. 

Auroral  Coronse. — Crown-shaped  appear- 
ances sometimes  assumed  by  the  auroral 
light. 

Auroral  Curtain. — A  curtain-shaped 
sheet  of  auroral  light. 

Auroral  Plashes. — (1)  Sudden  variations 
in  the  intensity  of  the  auroral  light. 
(2)  Intermittent  flashes  of  auroral  light. 

Auroral  Light. — The  light  given  off  by 
an  aurora. 

Auroral  Storm. — An  unusual  prevalence 
of  auroras. 

Auroral  Streams. — Auroral  streamers. 

Auroral  Streamers. — Flashing  columns 
or  pillars  of  light  that  are  emitted  from 
portions  of  the  sky  during  the  prevalence 
of  an  aurora. 

Austral. — Of  or  pertaining  to  the  South. 

Austral  Fluid. — A  term  formerly  em- 
ployed for  that  magnetic  fluid  which  was 
supposed  to  exist  around  or  to  emanate 
from  the  austral  pole  of  a  magnet. 

Austral  Magnetic  Pole. — (1)  The  name 
formerly  employed  in  France  for  the 
north-seeking  pole  of  a  magnet.  (Not  in 
general  use.)  (2)  That  pole  of  a  magnet 
which  points  to  the  earth's  geographical 
north.  (Not  in  general  use.) 

Auto-Car.— -(I)  An  automobile  car.  (2) 
A  car  provided  with  storage  batteries. 

Auto-Converter. — (1)  A  choking  coil  con- 
nected across  a  circuit  and  tapped  at  va- 
rious points  to  enable  a  reduced  E.  M.  F. 


Aut.J 


687 


[Aut. 


to  be  obtained.  (2)  An  auto-transformer. 
(3)  A  choking  coil  connected  to  an  induc- 
tion motor  by  a  switch  in  such  a  manner 
as  to  facilitate  the  starting  of  the  motor 
under  load. 

Auto-Excitation.— Self-excitation. 

Auto-Exciting. — Self -exciting. 

Autographic  Telegraphy. — (1)  Fac- 
simile telegraphy.  (2)  A  writing  tele- 
graph. 

Auto-Induction. — A  word  sometimes  em- 
ployed instead  of  self-induction. 

Auto-Kinetic  System  of  Fire  Telegra- 
phy.— A  system  of  fire  telegraphy  in 
which  the  transmitters  are  connected  in 
series  in  a  pair  of  circuits,  so  that,  when 
an  alarm  is  being  transmitted  from  one 
alarm  point,  no  other  alarm,  received  at 
the  same  time,  will  be  transmitted  until 
the  first  has  been  recorded. 

Automatic  Annunciator  Drop. — An 
annunciator  drop  which  on  the  closing  of 
a  distant  circuit  falls  and  holds  the  cir- 
cuit closed  until  the  drop  is  raised. 

Automatic  Answer-Back. — An  auto- 
matic return-signal  call-box. 

Automatic  Argand   Burner. — An   Ar- 

gand  burner  furnished  with  a  device  by 
means  of  which  it  can  be  either  auto- 
matically lighted  or  extinguished  at  a 
distance. 

Automatic  Gas  Cut-Off.— A  device  for 
automatically  cutting  out  the  battery 
from  an  electric  gas-lighting  circuit,  on 
the  accidental  grounding  of  the  circuit. 

Automatic  Guard  for  Series-Con- 
nected Incandescent  Lamps. — (1) 
An  automatic  cut-out,  placed  on  a  series- 
connected  incandescent  lamp,  for  the 
purpose  of  short-circuiting  the  holder 
should  the  lamp  filament  break.  (2)  A 
film  cut-out. 

Automatic  Indicating-Grapnel. — A 
grapnel  which  automatically  completes 
the  circuit  of  an  electric  bell  or  indicator 
on  a  cable  ship,  as  soon  as  the  cable  is 
hooked. 

Automatic  Indicator. — Any  automatic 
device  for  electrically  indicating  the 
number  of  times  a  circuit  has  befin  opened 
or  closed,  thus  showing  the  number  of 
times  any  operation  has  occurred,  which 
has  caused  the  opening  or  closing  of  the 
circuit. 

Automatic  Indicator  for  Grapnel. — 
An  apparatus  employed  with  a  grapnel 
for  indicating  when  the  grapnel  conies 
off  the  sea  bottom. 

Automatic  Inker. — An  ink- writing  Morse 


recorder  which  is  automatically  self- 
starting  upon  its  operation  by  telegraphic 
currents. 

Automatic  Interrupter. — An  automatic 
contact-breaker. 

Automatic  Locking-Switch.— A  com- 
bined key  and  switch  employed  in  sub- 
marine cables,  whereby  the  switch  is 
automatically  locked  and  thus  prevented 
from  being  left  for  sending,  when  it 
should  be  left  for  receiving,  or  vice-versa. 

Automatic  Make-and-Break. — A  device 
whereby  the  to-and-f ro  movements  of  the 
armature  of  an  electro-magnet  are  caused 
to  automatically  make  and  break  its  cir- 
cuit. 

Automatic  Multiple-Transmitter. — In 
a  telegraphic  signalling  or  calling  system, 
the  means  whereby  the  requisite  number 
of  spacing  and  electric  impulses  for  any 
of  a  number  of  different  calls,  is  auto- 
matically sent  over  a  line,  in  order  to  pro- 
duce a  given  signal,  such  for  example,  in 
a  system  of  police  telegraphy,  as  a  call  for 
an  ambulance,  a  call  for  a  squad,  etc. 

Automatic  Oiler. — An  oil  cup  or  reservoir 
that  automatically  spreads  oil  over  the 
bearing  of  a  machine  in  motion. 

Automatic  Overload-Switch  for  Stor- 
age Battery. — An  automatic  electro- 
magnetic switch,  inserted  in  the  discharg- 
ing circuit  of  a  storage  battery,  by  means 
of  which,  when  the  discharging  current 
exceeds  a  certain  safe  limiting  strength,  it 
is  automatically  opened. 

Automatic  Paper-Winder. — An  appa- 
ratus for  carrying  and  automatically 
winding  the  paper  fillet  or  strip  used  on 
telegraphic  registers. 

Automatic  Photo-Electric  Switch. — 
A  switch  that  is  automatically  opened  or 
closed  on  the  exposure  of  its  face  to 
differences  of  illumination. 

Automatic  Regulation  of  Dynamo- 
Electric  Machine. — Such  a  regulation 
of  a  dynamo-electric  machine  as  will 
automatically  preserve  constant,  either 
the  current  strength  or  the  potential  dif- 
ference at  its  terminals. 

Automatic  Regulation  of  Motor.— Such 
a  regulation  of  a  motor  as  will  maintain 
constant  its  speed,  or  its  torque. 

Automatic  Regulator. — A  device  for 
securing  automatic  regulation  of  a  dy- 
namo or  motor,  as  distinguished  from 
hand  regulation. 

Automatic  Repeater. — A  telegraphic  re- 
peater  which  is  automatically  operated,  in 
contradistinction  to  a  manual  repeatei 
which  is  operated  or  controlled  by  hand. 


Aut.] 


688 


Automatic  Rheostat.— An  automatic 
variable  resistance. 

Automatic  Rheotome. — An  automatic 
contact-breaker. 

Automatic  Ringing  -  Through.  —  A 
means  by  which  in  junction  telephone 
working  the  attention  of  the  distant  ex- 
change can  be  secured  by  the  act  of  estab- 
lishing connection  at  the  originating  ex- 
change without  the  necessity  of  calling  up 
the  distant  exchange  after  connection 
has  been  made. 

Automatic  Search-Light.— A  search- 
light in  which  a  parallel,  or  slightly 
divergent  beam  of  light,  is  caused  au- 
tomatically to  sweep  the  horizon  and  thus 
disclose  the  approach  of  a  torpedo  boat  or 
other  similar  danger. 

Automatic  Signalling.  —  Telegraphic 
transmission  by  machine-made  contacts  as 
distinguished  from  telegraphic  signalling 
by  hand. 

Automatic-Call-Box.— A  form  of  tele- 
phone call-box  by  means  of  which  the 
service  of  a  telephone  exchange  can  be  ob- 
tained by  a  payment  made  into  a  box, 
thus  dispensing  with  the  services  of  an 
attendant. 

Automatic    Chemical    Telegraphy. — 

Automatic  telegraphy  in  which  the  sig- 
nals are  recorded  on  a  fillet  or  band  of 
chemically  prepared  paper. 

Automatic  Circuit-Breaker. — A  device 
for  automatically  opening  a  circuit  when 
the  current  passing  through  it  is  exces- 
sive. 

Automatic  Clearing  Indicator.— (1)  A 
self-restoring  drop.  ( 2 )  A  clearing  indica- 
tor at  a  telephone  exchange  on  a  junction 
line,  which  automatically  indicates  when 
the  conversation  has  terminated. 

Automatic  Contact-Breaker. — A  device 
for  causing  an  electric  current  to  rapidly 
make  and  break  its  own  circuit. 

Automatic  Counter. — In  railway  block- 
signalling,  an  electro-magnetic  device 
for  recording  and  indicating  the  signals 
of  an  audible  code. 

Automatic  Curb-Sender. — In  subma- 
rine telegraphy,  a  transmitter  in  which 
each  signal  is  curbed  automatically  ;  i.  e., 
each  signal  is  followed  by  one  or  more 
alternately  directed  impulses  before  earth- 
ing, for  the  purpose  of  clearing  the  line 
of  its  static  charge. 

Automatic  Cut-in. — Any  arrangement 
of  parts  that  will  automatically  introduce 
a  translating  device  or  an  electric  source 
into  a  circuit  on  the  occurrence  of  any 
predetermined  event. 


Automatic  Cut-Out.— Any  arrangement 
of  parts  that  will  automatically  cut-out 
or  remove  a  translating  device  or  an  elec- 
tric source  from  a  circuit  on  the  occur- 
rence of  a  predetermined  event. 

Automatic  Cut-Out  for  Storage  Bat- 
tery.— An  automatic  electro-magnetic 
switch,  inserted  into  the  charging  cir- 
cuit of  a  storage  battery,  so  arranged  that 
if  the  charging  current  falls  below  a  safe 
limiting  strength  the  charging  circuit 
will  be  opened. 

Automatic  Cut-Out  for  Multiple-Con- 
nected Electro-Receptive  Devices. 
— (1)  A  device  for  automatically  cutting 
an  electro-receptive  device,  such  as  a 
lamp,  out  of  a  circuit.  (2)  A  safety  catch 
or  safety  base. 

Automatic  Cut-Out  for  Series-Con- 
nected Electro-Receptive  Devices. 
Means  whereby  an  electro-receptive  de- 
vice, such  as  an  arc  lamp,  is  to  all  intents 
and  purposes  automatically  cut-out  of,  or 
removed  from,  a  circuit,  by  means  of  a 
shunt  of  low  resistance  which  permits  the 
greater  part  of  the  current  to  flow  past 
the  lamp. 

Automatic  Cut-Out  of  Magneto.— A 
cut-out  switch  for  automatically  remov- 
ing the  armature  of  a  magneto  from  the 
telephone  circuit  by  the  action  of  a  spring, 
as  soon  as  the  handle  is  released. 

Automatic  Drop. — An  automatic  annun- 
ciator drop. 

Automatic  Electric  Alarm-Bell.— An 
electric  alarm-bell  furnished  with  an 
automatic  contact-breaker. 

Automatic  Electric  Bell. — (1)  A  trem- 
bling or  vibrating  bell.  (2)  An  auto- 
matic electric  alarm-bell. 

Automatic  Electric  Gas-Burner.— An 

electric  device  for  both  turning  on  the 
gas  and  lighting  it,  and  turning  the  gas  off, 
and  thus  extinguishing  the  light,  by  alter- 
nately touching  different  buttons. 

Automatic  Electric  Safety  System  for 
Railroads. — A  system  for  automatically 
preventing  tne  approach  of  two  trains, 
whatever  their  speed,  beyond  a  pre- 
determined distance  from  each  other. 

Automatic  Fire- Alarm. —An  instrument 
for  automatically  telegraphing  an  alarm 
of  fire  from  any  locality  on  its  increase  in 
temperature  beyond  a  certain  predeter- 
mined point. 

Automatic  Fire- Annunciator. — An  an- 
nunciator for  automatically  indicating 
the  point  from  which  a  fire-alarm  has 
been  sent. 

Automatic  Steam- Whistle,  Electric.^ 


Aut.J 


689 


[Aux. 


A  steam-whistle  employed  in  absolute 
block  systems  for  railroads,  whereby, 
during  fogs  or  snow-storms,  when  the 
signals  are  hidden  from  view,  the  loco- 
motive, on  passing  over  a  portion  of  the 
road  at  a  convenient  distance  from  the 
signal,  is  caused  to  make  a  succession  of 
electric  contacts,  whereby  a  steam  whis- 
tle is  blown'  on  the  moving  train. 
Automatic  Switch. — (1)  A  switch  which 
is  automatically  opened  or  closed  on  the 
occurrence  of  certain  predetermined 
events.  (2)  In  double-current  telegraphy 
an  electro-magnetic  switch  which  enables 
the  distant  station  to  stop  the  sending 
operator  at  the  home  station. 

Automatic  Switch  for  Incandescent 
Electric  Lamps.— (1)  A  safety  fuse  or 
safety  cut-out.  (2)  Any  switch  by  means 
of  which  incandescent  lamps  can  be 
lighted  or  extinguished  at  a  distance.  (3) 
A  device  for  automatically  closing  the 
circuit  of  a  lamp  or  lamps  on  the  opening 
of  a  door,  or  passage  of  a  barrier.  (4)  A 
device  for  automatically  opening  the  cir- 
cuit of  a  lamp  or  lamps  after  the  expira- 
tion of  a  predetermined  time  or  at  the 
closing  of  a  door. 

Automatic  Telegraph. — A  general  term 
embracing  the  apparatus  employed  in 
automatic  or  machine  telegraphy. 

Automatic  Telegraph-Sounder.— A 
form  of  automatic  telegraphic  transmit- 
ter. 

Automatic  Telegraph-Transmitter.— 
(1)  A  device  for  automatically  transmit- 
ting signals  by  means  of  embossed  or  per- 
forated slips  drawn  under  suitable  con- 
tact devices.  (2)  A  transmitter  employed 
in  automatic  telegraphy  for  sending  pre- 
pared messages. 

Automatic  Telegraphy. — A  system  of 
telegraphy  by  means  of  which  a  tele- 
graphic message  is  automatically  trans- 
mitted over  a  line  by  the  motion  of  a  pre- 
viously perforated  fillet  of  paper,  the 
perforations  of  which  are  arranged  in  the 
order  and  length  required  to  form  the 
characters  to  be  transmitted. 

Automatic  Telephone-Exchange. — A 
system  of  telephony  in  which  the  sub- 
scribers are  able  to  secure  selective  inter- 
communication without  the  aid  of  an 
exchange  operator. 

Automatic  Telephone  Hook. — An  auto- 
matic telephone  switch,  operated  by  hang- 
ing up  the  telephone  used  in  connection 
with  it. 

Automatic  Telephone  Switch. — (1)  A 
device  for  automatically  transferring  the 
connection  of  the  main  line  from  the  tele- 
4-1 


phone  to  the  call-bell  by  the  weight  of 
the  telephone  when  hung  up.  (2)  A 
switch  operated  by  the  act  of  hanging  up 
or  taking  down  a  telephone  from  a  hook 
and  employed  to  introduce  or  remove  a 
call-bell  from  the  line. 

Automatic  Time  Cut-Out. — A  device 
which  automatically  cuts  a  translating 
device  or  an  electric  source  from  a  circuit 
at  a  certain  predetermined  time,  or  after 
the  lapse  of  a  predetermined  time. 

Automatic  Variable  Resistance. — A 
resistance  the  value  of  which  can  be  auto, 
matically  varied. 

Automatically  Regulable. — Capable  of 
automatic  regulation. 

Automatically  Regulate. — To  regulate 
in  an  automatic  manner. 

Automobile. — (1)  Self -movable.  (2)  Con- 
taining the  power  necessary  for  its  own 
motion. 

Automobile  Carriage. — A  horseless  car- 
riage. 

Automobile  Torpedo. — A  torpedo  which 
contains  the  power  required  for  its  pro- 
pulsion. 

Automobile  Vehicle. — An  automobile 
carriage. 

Auto-Reversible    Tele-Radiophone. — 

(1)  A  photophone  arranged  so  that  a  num- 
ber of  telegraphic  communications  may 
be  simultaneously  sent  either  all  in  the 
same  direcf  ion,  or  part  in  one  direction, 
and  the  remainder  in  the  opposite  direc- 
tion. (2)  A  multiple  tele-radiophone. 

Auto-Starter. — (1)  A  self -starting  mech- 
anism. (2)  A  self-starting  ink-writer. 
(3)  A  self-starting  motor. 

Auto-Telephone  System. — A  system  of 
multiple-circuit  telephony  in  which  a 
single  battery  is  employed,  whereby  a 
number  of  telephone  stations  can  be  con- 
nected by  a  single  cable  without  the  use 
of  a  distributing  board,  or  exchange. 

Auto-Transformer. — A  one-coil  trans- 
former consisting  of  a  choking  coil  con- 
nected across  a  pair  of  alternating-current 
mains,  and  so  arranged  that  a  current  or 
pressure  differing  from  that  supplied  by 
the  mains  can  be  obtained  from  it  by 
tapping  it  at  different  points. 

Auxiliary  Bus. — A  central-station  bus- 
bar connected  to  an  auxiliary  pressure  ; 
i.  e.,  a  pressure  different  from  the  main- 
station  pressure. 

Auxiliary  Alarm  Telegraph. — In  a  sys- 
tem of  fire-alarm  telegraphy,  where  an 
alarm  received  in  any  one  circuit  is  auto- 
matically repeated  over  all  the  other  cir» 


Ave.] 


690 


[Bac, 


cults,  means  whereby  the  repetition  of 
the  signals  are  prevented  from  interfering 
with  the  incoming  signals  of  any  of  the 
other  circuits. 

Average  Efficiency  of  Motor. — (1)  The 
efficiency  of  an  electric  motor  based  on 
its  average  or  mean  load.  (2)  The  ratio 
of  all  the  work  that  a  motor  delivers  in  a 
given  time  to  the  electric  energy  it  has 
absorbed  in  that  time. 

Average  Electromotive  Force. — The 
mean  electromotive  force. 

Average  Life  of  Incandescent  Lamp. 
The  mean  time  during  which  a  number 
of  incandescent  lamps  will  continue  to 
burn  without  breaking  when  connected 
with  a  circuit  of  given  pressure. 

Average  Value  of  Periodic  Current 
or  E.  M.  F. — The  arithmetical  mean 
value  of  a  periodic  current  or  E.  M.  F., 
with  respect  to  magnitude  and  without 
respect  to  sign  or  direction. 

Avogrado's  Hypothesis. — Equal  vol- 
umes of  different  gases  measured  at  the 
same  temperature  and  pressure  contain 
the  same  number  of  molecules. 

Axes  of  Co-Ordinates. — A  vertical  and  a 
horizontal  line,  usually  intersecting  each 
other  at  right  angles,  and  called  respec- 
tively the  axes  of  ordinates  and  abscissas, 
from  which  the  ordinates  and  abscissas 
are  measured. 

'Axial. — Of  or  pertaining  to  an  axis. 


Axial  Current. — In  electro-therapeutics, 

a  current  flowing  in  a  nerve  in  the  oppo. 

site  direction  to  the  normal  impulse  oi 

the  nerve. 
Axial  Magnet. — A  name  sometimes  given 

to  a  solenoid  with  a  straight  core. 
Axis  of  Abscissae  or  Abscissas. — The 

horizontal  line  in  the  axes  of  co-ordinates. 
Axis  of  Magnetic  Needle. — A  straight 

line  drawn  through  a  magnetic  needle, 

and  joining  its  poles. 

Axis  of  Ordinates. — The  vertical  line  in 
the  axes  of  co-ordinates. 

Azimuth. — In  astronomy,  the  apgle  sub- 
tended at  an  observer  between  the  plane 
of  an  azimuth  circle  and  the  plane  of  the 
meridian. 

Azimuth  Circle. — The  arc  of  a  great 
circle  passing  through"  the  zenith,  or  the 
point  of  the  heavens  directly  overhead, 
and  the  nadir,  or  the  point  directly  be- 
neath. 

Azimuth  Compass. — (1)  A  compass  used 
for  measuring  the  horizontal  angular  dis- 
tance of  any  distant  object  from  the  mag- 
netic meridian.  (2)  The  mariner's  com- 
pass. 

Azimuth  Telegraph.— On  a  war-ship  a 
telegraph  for  indicating  at  any  or  all 
guns  the  azimuth  of  a  target. 

Azimuth  and  Range  Telegraph. — On 
a  war-ship  a  combined  telegraph  to  the 
guns  of  the  azimuth  and  range  of  a  target. 


B 


§&. — A  symbol  for  magnetic  intensity,  or 
induction  density,  usually  expressed  in 
C.  G.  S.  units  per  normal  square  centi- 
metre. (Partly  International  usage. ) 

B. — (1)  A  symbol  for  magnetic  induction,  or 
the  amount  of  flux  per  normal  square 
centimetre  of  the  magnetized  material. 
(2)  A  symbol  for  susceptance  in  alter- 
nating-current circuits. 

B.  A.  Ampere. — The  British  Association 
ampere  in  a  circuit  whose  resistance  is 
one  B.  A.  ohm  under  an  E.  M.  F.  of 
one  B.  A.  volt. 

B.  A.  Balance. — A  type  of  balance  or 
bridge,  originally  employed  by  the  British 
Association  Committee  in  duplicating  B. 
A.  ohms. 

B.  A.  Ohm. — (1)  The  British  Association 
ohm.  (2)  The  resistance  of  a  column  of 
mercury  one  square  millimetre  in  area  of 
normal  cross-section,  and  104.9  centi- 
metres in  length,  at  the  temperature  of 
zero  centigrade. 


B.  A.  U. — A  contraction  for  British  Asso- 
ciation unit  or  ohm. 

B.  A.  Unit. — The  British  Association  unit 
of  resistance  or  ohm. 

B.  S.  G-. — A  contraction  for  British  stand- 
ard gauge. 

B.  &  S.  W.  G-. — A  contraction  for  Brown 
and  Sharpe's  wire  gauge. 

B.  T.  U. — (1)  A  contraction  for  Bi'itish 
thermal  unit.  (2)  A  contraction  for  Board 
of  Trade  unit. 

B.  W.  G. — A  contraction  for  Birmingham 
wire  gauge. 

Back  Ampere-Turns.— Ampere-turns  on 
a  dynamo  armature  which  tend  to  oppose 
the  flux  produced  by  the  field  magnets. 

Back   Electromotive   Force. — A   term 

sometimes  used  for  counter-electromotive 

force. 
Back  Induction. — An  induction  opposed 

to  the  field  and  tending  to  weaken  or 

neutralize  it. 


Bac.] 


691 


[Bal. 


Back  Magnetization.  —  A  term  some- 
times used  for  backward  or  back  induc- 
tion. 

Back  Magnetization  of  Armature. — 
Counter-magnetomotive  forces  acting  in 
the  main  magnetic  circuit  of  the  field 
coils,  and  tending  to  reduce  the  useful 
flux  passing  through  the  armature. 

Back  of  Electro-Magnet. — The  yoke  of 
an  electro-magnet. 

Back  Pitch. — The  backward  pitch  of  the 
armature  windings. 

Back  Stroke  of  Lightning. — The  return 
stroke  of  lightning. 

Back  Stop  of  Key. — A  stop  placed  on  the 
back  of  a  telegraph  key  in  order  to  limit 
its  motion  in  the  direction  of  release. 

Back-Turns  of  Armature.  —  (1)  Those 
turns  on  an  armature  whose  current 
tends  to  demagnetize  the  field.  (2)  The 
back  ampere-turns. 

Backing  Metal. — An  alloy  that  is  placed 
on  the  back  of  the  copper  shell  of  an  elec- 
trotype in  order  to  stiffen  it. 

Backing  Pan. — The  pan  in  which  the  cop- 
per shell  of  an  electrotype  is  placed  in 
order  to  receive  its  backing  of  type 
metal. 

Backward  Induction  of  Dynamo  Ar- 
mature.— The  component  of  the  arma- 
ture induction  that  opposes  the  induction 
of  the  field  magnets. 

Backward  Pitch  of  Armature  Wind- 
ings.— A  pitch  which  is  always  left- 
handed,  or  counter-clockwise,  when  re- 
garded from  the  commutator  side. 

Backward  Waves. — In  a  closed  circuit 
supplied  by  a  dynamo  or  other  source  of 
electromotive  force,  a  wave  of  potential 
that  is  assumed  to  start  from  the  negative 
pole  of  the  dynamo  and  travel  around 
the  circuit  in  the  opposite  direction  to  the 
forward  wave  of  positive  potential  from 
the  positive  pole  of  the  dynamo. 

Bad  Earth. — A  term  sometimes  applied  to 
a  bad  ground,  or  a  connection  to  earth 
whose  electric  resistance  is  comparatively 
high. 

Bain  Telegraph  Code.— An  old  form  of 
telegraphic  alphabet  originally  employed 
in  connection  with  the  Bain  printing 
instrument. 

Bain's  Chemical  Recorder. — An  appa- 
ratus for  recording  the  dots  and  dashes  of 
a  telegraphic  despatch  on  a  sheet  of  chemi- 
cally prepared  paper. 

Bain's  Chemical  Solution.— Bain's  print- 
ing solution. 


Bain's  Printing  Solution.— (1)  The  so- 
lution used  in  Bain's  chemical  recorder. 
(2)  A  solution  of  potassium  f  erro-cyanide 
and  water. 

Baking  Oven,  Electric. — An  electrically 
heated  baking  oven. 

Balance  Arm. — One  of  the  arms  of  an 
electric  balance. 

Balance  Arms. — The  arms  of  an  electric 
balance. 

Balance,  Electric. — A  term  sometimes 
used  for  an  electric  bridge. 

Balance  Galvanometer. — A  dynamo  gal- 
vanometer employed  for  indicating  when 
the  pressure  of  the  dynamo  is  equal  to 
the  pressure  on  the  bus-bars. 

Balance  Indicator. — Any  device  for  indi- 
cating when  an  electric  balance  has  been 
obtained. 

Balance  Indicator  of  Three-Wire  Sys- 
tem.— A  device  for  indicating  when  a 
balance  is  obtained  between  the  positive 
and  negative  leads  of  a  three-wire  system 
of  distribution. 

Balance  of  Induction  in  Cable. — The 
neutralization  of  induction  in  a  cable  by 
the  presence  of  equal  and  opposite  effects. 

Balance  of  Telegraphic  Circuit.— The 
condition  of  a  duplexed  telegraph  line 
when  the  home  relay  ceases  to  respond  to 
the  home  key. 

Balance  Photometer.  —  A  photometer 
based  on  the  decomposition  of  iodide  of 
nitrogen  by  the  action  of  light. 

Balanced  Armature. — (1)  An  armature 
whose  weight  is  symmetrically  distributed 
as  regards  its  axis  of  rotation.  (2)  An 
armature  that  has  been  so  adjusted  by 
the  addition  of  weights  that  its  weight  is 
symmetrically  distributed  with  reference 
to  its  axis  of  rotation. 

Balanced  Circuit. — A  telephonic,  tele- 
graphic, or  other  circuit  which  has  been 
so  erected  and  adjusted  as  to  be  free 
from  mutual  inductive  disturbances  from 
neighboring  circuits. 

Balanced  Load. — A  load  which  is  sym- 
metrically divided  between  two  or  more 
generating  units,  as  in  the  three-wire, 
five-wire,  multiple,  or  polyphase  systems 
of  distribution. 

Balanced  Magnetic  Circuits  of  Arma- 
ture.— The  magnetic  circuits  traversing 
the  armature  of  a  dynamo-electric  ma- 
chine through  which  the  magnetic  fluxes 
produced  by  the  field  are  symmetrically 
distributed  in  regard  to  flux  density,  total 
flux,  and  geometrical  distribution. 

Balanced  Metallic  Circuit. — A  metallic 


Bal.] 


692 


[Ban. 


circuit,  the  two  sides  of  which  have  sim- 
ilar electric  properties. 
Balanced  Polyphase  System.— A  poly- 
phase system  all  the  branches  of  which 
are  symmetrical  in  regard  to  their  electro- 
motive force,  current,  and  phase. 

Balanced  Reaction  Coil. — A  coil  em- 
ployed in  a  system  of  distribution  by 
alternating-current  transformers  for 
maintaining  a  constant  current  in  the  sec- 
ondary circuit  or  circuits  despite  changes 
in  the  load  placed  therein. 

Balanced  Resistance. — A  resistance  so 
placed  in  a  bridge  or  balance  as  to  be  bal- 
anced by  the  remaining  resistances  in  the 
bridge. 

Balanced  System.— An  electric  system 
of  distribution  or  communication  which 
is  so  adjusted  as  to  be  free  from  mutual 
inductive  disturbances  from  neighboring 
systems. 

Balancing.— Rendering  a  metallic  tele- 
phone circuit  free  from  inductive  dis- 
turbances from  other  lines. 

Balancing  Coil  of  Armature. — An  aux- 
iliary field-winding  in  series  with  an 
armature,  and  having  its  magnetomotive 
force  equal  and  opposite  to  that  of  the 
armature  current,  so  that  their  total  mag- 
netic effect  upon  the  field  is  zero,  and  the 
field  flux  remains  unchanged  at  all  loads. 

Balancing  of  Telegraph  Line.— In  du- 
plex or  quadruplex  telegraphy  the  opera- 
tion of  adjusting  the  balance  between 
the  real  and  artificial  lines,  whereby  the 
home  signals  do  not  affect  the  receiving 
instruments. 

Balancing  Relay  .—A  differentially  wound 
relay. 

Balancing  Resistance  for  Dynamos.— 
A  regulating  resistance  that  possesses  a 
sufficient  range  to  balance  one  dynamo 
against  another  with  which  it  is  operated 
in  parallel. 

Balancing  Thermopile.— (1)  A  double 
thermopile.  (2)  A  differential  thermo- 
pile. 

Balancing  Wire  or  Conductor.— A  term 
sometimes  employed  for  the  neutral  wire 
or  conductor  of  a  three-wire  system. 

Balata. — An  insulating  material. 

Ball  Lightning.  —  A  name  sometimes 
given  to  globular  lightning. 

Ballistic  Curve.— The  curve  actually  de- 
scribed by  a  projectile  thrown  through 
the  air  in  any  other  than  a  vertical  direc- 
tion. 

Ballistic  Galvanometer.— (1)  A  galvano- 
meter designed  to  measure  the  total  quan- 


tity of  electricity  in  a  discharge  lasting  for 
a  brief  interval,  as,  for  example,  the  cur- 
rent caused  by  the  discharge  of  a  conden- 
ser. (2)  A  galvanometer,  in  which  the 
movable  part  is  as  little  damped  as  pos- 
sible, suitable  for  measuring  electric 
charges  or  discharges,  and  usually  ad- 
justed to  have  a  long  period  of  vibration 
or  slow  swing. 

Ballistic  Pendulum.— A  pendulum  with 
a  heavy  bob  employed  to  determine  the 
velocity  of  a  projectile  fired  into  it. 

Balloon  Buoy. — A  buoy  used  in  submarine 
cable  work  somewhat  resembling  a  bal- 
loon in  shape. 

Balloon,  Electric.— (1)  A  balloon  or  air- 
ship provided  with  electric  power  so  as  to 
be  capable  of  being  started  or  moved 
against  the  direction  of  the  wind.  (2)  An 
electrically  dirigible  balloon. 

Balloon  Signalling  for  Military  Pur- 
poses.— Transmitting  intelligence,  as  of 
the  movements  of  an  enemy's  army, 
from  observations  made  in  balloons  by 
means  of  telephone  circuits  directly 
connected  with  the  balloons. 

Band  Arc  Lamp. — An  arc  lamp  in  which 
the  feeding  of  the  carbons  is  effected 
through  the  movements  of  a  band  of  cop- 
per, which  carries  the  upper  carbon  holder 
and  conducts  the  current  into  the  arc. 

Band  or  Banded  Spectrum.— The  con- 
dition assumed  by  the  spectrum  of  a  com- 
pressed gas  or  vapor  when  sufficiently 
heated,  in  which  the  lines  of  the  ordinary 
spectrum  are  broadened  into  bands. 

Banjo. — A  wooden  drum  fastened  upon  a 
kite-shaped  board,  employed  for  tighten- 
ing a  pole-strung  telephone  or  telegraph 
wire. 

Bank  Board.— A  small  switchboard  con- 
taining a  bank  of  lamps  used  in  an  alter- 
nating-current series-incandescent  system 
of  street  lighting,  and  usually  supplied 
with  an  ammeter  and  switch  for  intro- 
ducing one  or  more  relief  lamps. 

Bank  of  Lamps.— A  group  of  electric 
lamps  collected  together  in  a  common 
structure,  usually  for  the  purpose  of  ob- 
taining a  load. 

Bank  of  Transformers. — A  group  of 
transformers  collected  together  in  a  com- 
mon structure  usually  either  for  the  pur- 
pose of  obtaining  a  load,  or  for  readily 
varying  the  pressure. 

Banked  Battery.  —  A  term  sometimes 
applied  to  a  battery  from  which  a  num- 
ber of  separate  circuits  are  supplied  with 
current. 

Banking  Transformers.— (1)   Grouping 


Bar.] 


693 


[Bat. 


transformers  in  a  common  structure  either 
for  the  purpose  of  obtaining  a  load,  or 
for  readily  varying  the  pressure.  (2)  As- 
sociating transformers  in  parallel.  (3) 
Associating  transformers  in  series. 

Bar  Armature. — An  armature  whose  con- 
ductors are  formed  of  bars. 

Bar  Electro-Magnet. — An  electro-mag- 
net, the  core  of  which  is  in  the  foi-m  of  a 
straight  bar  or  rod. 

Bar  Windings.  —  Armature  windings 
composed  of  copper  bars. 

Bar-Wound  Armature. — An  armature 
in  which  the  conductors  have  the  form  of 
bars. 

Barad. — (1)  A  unit  of  intensity  of  pressure. 
(2)  A  dyne  per  square  centimetre. 

Bare  Arc-Light  Carbons. — Arc-light  car- 
bons or  pencils  unprovided  with  an  elec- 
tro-plating of  copper  or  other  conducting 
metal. 

Bare  Carbons. — Arc-light  or  battery  car- 
bons, unprovided  with  an  electro-plating 
of  copper. 

Barker's  Wheel. — An  early  form  of  reac- 
tion water  wheel. 

Barlow's  Wheel. — A  wheel  or  disc  of 
metal,  capable  of  rotation  on  an  axis, 
that  is  set  into  rotation  when  placed  be- 
tween the  poles  of  magnets  and  traversed 
between  its  centre  and  circumference  by 
a  current  of  electricity, 

Barometer. — An  apparatus  for  measuring 
the  atmospheric  pressure. 

Barometric  Column.— A  column,  usually 
of  mercury,  approximately  30  inches  in 
vertical  height,  sustained  in  a  barometer 
or  other  tube  by  the  atmospheric  pres- 
sure. 

Barometric  Gradient.— The  drop  or  fall 
of  atmospheric  pressure  per  unit  of  dis- 
tance as  measured  between  two  adjacent 
isobars. 

Barrel  of  Jack. — In  telephony  a  conduct- 
ing cylinder  in  a  jack  for  making  con- 
tact with  the  sleeve  of  a  plug. 

Barrow-Reel. — A  reel  supported  on  a 
barrow  for  convenience  in  paying  out  an 
overhead  conductor  during  its  installa- 
tion. 

Bar  Winding  of  Armature.— A  winding 
consisting  of  insulated  copper  bars  con- 
nected at  their  extremities. 

Base  Frame  of  Generator.— The  frame 
on  which  a  generator  is  supported. 

Basis  Metal  of  Electro-Plating.— The 

metal  on  whose  surface  an  electro-plating 
is  to  be  deposited. 


Batch  Working.— In  telegraphy  a  method 
of  operating  consisting  in  "sending  a 
plurality  of  messages  in  one  direction  over 
a  line,  and  then  a  plurality  of  messages 
in  the  opposite  direction,  as  distinguished 
from  up-and-down  working. 

Bathometer. — An  instrument  for  obtain- 
ing deep-sea  soundings  without  the  use 
of  a  sounding-line. 

Battery. — A  name  frequently  used  for  an 
electric-battery. 

Battery. — (1)  To  place  a  storage  battery 
on  a  storage-battery  car.  (2)  To  supply 
a  battery  to  a  station  or  circuit. 

Battery  Car. — A  storage-battery  car. 

Battery,  Electric. — A  general  name  ap- 
plied to  the  combination,  as  a  single 
source,  of  a  number  of  separate  electric 
sources. 

Battery  Gauge. — A  form  of  portable  gal- 
vanometer suitable  for  ordinary  battery 
testing  work. 

Battery  Jar. — A  jar  provided  for  holding 
the  electrolyte  of  each  of  the  separate 
cells  of  a  primary  or  secondary  battery. 

Battery  Lamp. — An  incandescent  lamp 
of  such  low  voltage  as  to  be  readily  oper- 
ated by  the  ordinary  voltage  of  a  battery 
of  a  few  series-connected  cells. 

Battery  Motor. — An  electric  motor  so 
wound  as  to  be  properly  operated  by  the 
comparatively  low  electromotive  force  Of 
an  ordinary  battery. 

Battery  of  Alternators. — A  number  of 
separate  alternators  so  connected  as  to  be 
capable  of  acting  as  a  single  alternator. 

Battery  of  Generators. — A  number  of 
separate  generators  so  connected  as  to  be 
capable  of  acting  as  a  single  generator. 

Battery  Pole-Changer. — A  form  of  trans- 
mitter employed  in  duplex  telegraphy  for 
readily  reversing  the  direction  of  the 
main  battery  so  as  to  send  signals  to  the 
line. 

Battery  Solution. — The  exciting  liquid 
or  electrolyte  of  a  primary  or  secondary 
cell. 

Battery  Stand. — The  insulating  or  insu- 
lated stand  provided  for  holding  a  pri- 
mary or  secondary  battery. 

Battery  Syringe. — A  syringe  for  either  re- 
moving the  acid  or  spent  liquids  from  a 
voltaic  battery,  or  for  introducing  fresh 
liquid. 

Battery  System  for  Electric  Railroads. 

A  system  for  the  propulsion  of  street  cars 
by  means  of  storage  batteries. 
Battery  Transformer. — A  step-up  trans- 
former so  wound  as  to  be  readily  operated 


Bat.] 


694 


[Bic. 


by  a  primary  battery  of  a  few  series-con- 
nected cells. 

Battle  Circuit. — A  circuit  on  a  warship, 
connected  with  the  conning  tower  and 
provided  for  use  during  action. 

Battle  Lantern. — A  form  of  safety  lantern 
for  use  in  action  on  board  a  warship. 

Bead.  Areometer. — A  form  of  hydrometer 
suitable  for  rapidly  testing  the  density  of 
the  exciting  liquid  in  a  storage  cell. 

Bead  Chain. — A  chain  of  metallic  beads 
sometimes  employed  for  the  pull  in  a 
pendant  electric-burner. 

Bead  Hydrometer. — A  bead  areometer. 

Bead  Lightning. — A  form  of  lightning 
discharge  in  which  the  flashes  produce  a 
discontinuous  line  of  light  possessing  a 
bead-like  appearance. 

Beaded  Cable. — A  form  of  cable  employed 
for  high-tension  transmission,  provided 
with  a  sheathing  of  strung  porcelain 
beads. 

Bec-Carcel. — The  carceL  or  French  photo- 
metric standard. 

Becquerel  Radiation. — An  invisible  ra- 
diation, discovered  by  Becquerel,  emitted 
by  certain  salts,  especially  those  of  ura- 
nium, capable  both  of  penetrating  many 
media  opaque  to  ordinary  light,  and 
affecting  a  photographic  plate. 

Becquerel  Bays. — Becquerel  radiation. 

Bed-Plate  of  Dynamo-Electric  Ma- 
chine.— The  base  or  frame  of  a  dynamo- 
electric  machine. 

Bega.— A  prefix  for  a  billion,  one  thousand 
million,  or  109. 

Begadyne. — One  billion  dynes,  or  roughly, 
the  earth's  gravitational  force  on  a  ton 
of  matter. 

Beg-Erg. — One  billion  ergs ;  or,  73.7  foot- 
pounds, approximately. 

Beg-Ohm. — One  billion  ohms,  or  one  thou- 
sand megohms. 

Begohm  Galvanometer. — A  galvano- 
meter which  gives  unit  deflection  through 
a  resistance  of  one  begohm  in  circuit  with 
one  volt. 

Bell  Box. — In  telephony  a  box  containing 
or  designed  to  contain  a  telephone  bell. 

Bell  Hanger's  Joint. — A  careless  form  of 
telegraphic  or  telephonic  joint  in  which 
the  ends  of  the  wires  are  merely  looped 
into  each  other. 

Bell  Mouth  of  Cable  Tank.— A  circular 
aperture  provided  in  the  top  of  a  cable 
tank,  through  which  a  cable  is  led  into 
or  taken  out  of  the  tank. 


Bell  Pull,  Electric. — Any  circuit-closing 
device  operated  by  a  pull. 

Bell-Shaped  Magnet. — A  modified  form 
of  horse-shoe  magnet  in  the  form  of  a 
split  tube,  and  in  which  the  approached 
poles  are  semi  circular  in  shape. 

Bell  Switch. — A  switch  connected  with  a 
telephone  alarm-bell  for  the  purpose  of 
throwing  it  in  or  out  of  circuit. 

Belt  Circuit. — A  series  lighting  circuit 
extending  in  the  form  of  a  wide  loop, 
belt,  or  circle,  as  opposed  to  a  circuit 
formed  of  two  closely  associated  parallel 
wires. 

Belt-Driven  Generator. — A  generator 
driven  by  means  of  belting,  as  distin- 
guished from  a  direct-driven  or  rope- 
driven  generator. 

Belt-Driving  or  Coupling.— Driving  or 

coupling  by  means  of  belts. 
Belt,  Electric.^A  belt  suitably  shaped 
so  as  to  be  capable  of  being  worn  on  the 
body,  consisting  either  of  imaginary  or 
real  voltaic  or  thermo-electric  couples, 
and  employed  for  its  alleged  therapeutic 
effects. 

Belt  of  Current. — The  total  current  gen- 
erated by  an  armature  at  any  moment, 
assumed  as  making  a  single  turn  around 
the  armature. 

Belt  Speed. — The  velocity  of  translation 
or  linear  speed  of  a  belt  in  the  transmission 
of  power. 

Bessel's  Functions. — A  series  of  mathe- 
matical functions  often  connected  with 
problems  in  electricity  and  satisfying  a 
certain  relation  first  enunciated  by  Bessel 
in  connection  with  an  astronomical  prob- 
lem. 

Bias  of  Relay  Tongue. — A  term  em- 
ployed to  signify  such  an  adjustment  of 
a  polarized  relay  that  on  the  cessation 
of  a  working  current  the  relay  tongue 
shall  always  rest  against  the  insulated 
contact,  and  not  against  the  other  con- 
tact, or  vice  versa. 

Bichromate  Voltaic  Cell.— A  zinc-car- 
bon couple  employed  with  a  solution  of 
bichromate  of  potash  and  sulphuric  acid 
in  water. 

Bicro. — A  prefix  for  one  billionth,  one 
thousand  millionth,  or  10-9. 

Bicro-Ampere. — The  billionth  of  an  am- 
pere. 

Bicro-Farad.— The  billionth  of  a  farad. 
Bicro-Henry.— The  billionth  of  a  henry. 
Bicron. — A  unit  of  length  equal  to  the 

billionth  of  a  metre,  and  indicated  by  the 

symbol  pp. 


Bic.] 


695 


[Bi-T. 


Bicycle  Car. — An  electrically  propelled 
car  whose  weight  rests  on  a  single  rail, 
and  which  is  kept  in  position  by  a  guide 
rail  supported  vertically  above  the  main 
rail. 

Bicycle  Electric  Lamp.— An  incandes- 
cent lamp  suitable  for  use  on  a  bicycle 
and  usually  operated  by  a  small  voltaic 
battery. 

Bifllar  Control  of  Galvanometer 
Needle. — The  control  of  a  galvanometer 
needle  whereby  it  returns  to  its  position 
of  rest,  on  the  removal  of  the  deviating 
force,  by  the  operation  of  a  bifilar  sus- 
pension. 

Bifilar  Suspension.— S  u  s  p  e  n  s  i  o  n  by 
means  of  parallel  vertical  wires  or  fibres 
as  distinguished  from  suspension  by  a 
single  wire  or  fibre. 

Bifllar  Winding.— The  method  of  wind- 
ing employed  in  resistance  coils  to  obviate 
the  effects  of  self-induction,  in  which  the 
wire,  instead  of  being  wound  in  one  contin- 
uous It^igth,  is  doubled  on  itself  before 
winding. 

Bight  of  Cable. — A  single  loop  or  bend 
of  cable. 

Bimetallic  Accumulator. — An  accumu- 
lator or  storage  cell  whose  positive  and 
negative  plates  are  formed  respectively 
of  two  different  metals. 

Bimetallic  Helix. — A  compound  helix  of 
two  metals  of  different  expansibilities, 
such  as  copper  and  steel,  firmly  riveted 
or  soldered  together,  so  that  the  helix  is 
twisted  or  moved  in  one  direction  by  un- 
equal expansion,  and  in  the  opposite  direc- 
tion by  unequal  contraction. 

Bimetallic  Thermometer. — A  thermom- 
eter whose  operation  depends  on  the  ex- 
pansion and  contraction  of  a  bimetallic 
helix. 

Bimetallic  Thermostat. — A  form  of  ther- 
mostat employed  for  opening  or  closing  a 
circuit  by  the  expansions  and  contractions 
of  a  bimetallic  arc-shaped  spring. 

Bimetallic  Wire. — A  compound  tele- 
phone or  telegraph  wire  consisting  of  a 
steel  core  and  a  copper  envelope,  suitable 
for  long-span  overhead-construction. 

Binary  Compound. — A  compound 
formed  by  the  union  of  two  different 
elements. 

Binding  Coils. — Coils  of  wire,  wound  on 
the  outside  of  the  armature  coils  and  at 
right  angles  thereto,  to  prevent  the  loosen- 
ing of  the  armature  coils  during  rotation 
by  centrifugal  force. 

Binding  Post. — A  metallic  binding  screw, 
rigidly  fixed  to  some  apparatus  or  support, 


and  employed  for  conveniently  making 
firm  electric  connections. 

Binding  Screw. — A  name  sometimes  ap- 
plied to  a  binding  post. 

Binding  Wire  for  Telegraph  Lines.— 

(1)  The  wire  employed  for  securing  a  tele- 
graph wire  to  the  insulator  which  sup- 
ports it.     (2)  A  tie  wire. 

Binnacle  Compass. — A  compass  on  board 
ship  placed  in  a  binnacle  for  use  in  steer- 
ing or  directing  the  vessel. 

Biograph. — An  apparatus  for  obtaining  on 
a  screen,  from  a  rapid  succession  of  suit- 
able pictures,  the  appearance  of  the  actual 
movements  of  natural  objects. 

Bioplasm.— (1)  Any  form  of  living  matter 
possessing  the  power  of  reproduction. 

(2)  Living  protoplasm. 
Bioscope. — A  biograph. 

Bioscopy,  Electric. — The  determination 
of  the  presence  of  life  or  death  by  the 
passage  of  electricity  through  the  nerves 
or  muscles. 

Bipolar. — Having  two  poles. 

Bipolar  Armature. — An  armature  suit- 
able for  use  in  a  bipolar  field. 

Bipolar  Armature-Winding. — Any  ar- 
mature winding  suitable  for  use  in  a 
bipolar  field. 

Bipolar  Bath. — An  electro-therapeutic 
bath,  the  current  supplied  to  which  enters 
at  one  part  of  the  bath-tub  and  leaves 
at  another. 

Bipolar  Dynamo-Electric  Machine. — 
A  dynamo-electric  machine  with  a  bi- 
polar field. 

Bipolar  Generator. — A  bipolar  dynamo- 
electric  machine. 

Bipolar  Magnetic  Field.— A  magnetic 
field  formed  by  two  opposite  magnetic 
poles. 

Bird  Cage,  Electric.— A  bird-cage-shaped 
wire  screen  employed  by  Hertz  in  his  in- 
vestigations on  the  propagation  of  electro- 
magnetic waves  for  screening  the  spark 
micrometer. 

Bird  Cage. — In  submarine  cable-work,  a 
mechanical  distortion  of  the  sheathing 
in  which  the  wires  are  locally  bulged  out- 
wards leaving  the  serving  or  core  visible 
or  exposed. 

Birmingham  Wire  Gauge.  —  An  En- 
glish wire  gauge. 

Bismuth  Spiral. — A  flat  spiral  of  bismuth 
wire  employed  for  the  measurement  of 
strong  magnetic  fields. 

Bi-Telephone. — A  term  sometimes  ap- 
plied to  a  double  telephone  receiver  ar- 


Biv.] 


696 


[Bol. 


ranged  so  as  to  permit  the  ready  applica- 
tion of  both  ears  of  the  listener  to  the 
receiving  instruments. 

Bivalent. — (1)  Possessing  an  atomicity  or 
valency  of  two.  (2)  Divalent. 

Bitite. — A  variety  of  insulating  material. 

Black  Electro-Metallurgical  Deposit. 
A  dark  electro-metallurgical  deposit  that 
is  thrown  down  from  the  metal  in  a  plat- 
ing bath  when  too  strong  a  current  is 
employed. 

Black  Lead. — Plumbago  or  graphite. 

Black  Leading  Machine  for  Electro- 
Types. — A  machine  for  covering  the 
printing  surface  of  the  wax  impression 
employed  in  electro-typing  with  an  elec- 
trically conducting  surface  of  black  lead. 

Black  Light. — Non-luminous  radiation. 

Blake      Telephone      Transmitter. — A 

form  of  carbon  telephone  transmitter. 

Blank  Panel. — A  panel  on  a  switchboard 
provided  for  the  support  of  extra  circuit 
connections  or  instruments. 

Blasting,  Electric. — The  electric  ignition 
of  powder  or  other  explosive  material  in 
a  blast. 

Blavier's  Formulae. — The  formulae  em- 
ployed in  the  Blavier  test. 

Blavier's  Test. — A  test  introduced  by 
Blavier,  for  localizing  a  single  fault  in  a 
single  telegraph  line  or  conductor,  by 
measuring  the  resistance  at  one  end  of 
the  line,  when  the  other  end  is  succes- 
sively freed  and  earthed. 

Bleaching,  Electric. — A  bleaching  pro- 
cess in  which  the  bleaching  agents  are 
liberated  as  required  by  electrolytic  de- 
composition. 

Block. — To  stop  or  check  by  means  of  a 
block  system. 

Block-Facing. — In  a  system  of  electric 
distribution  mains  a  section  of  conductors 
extending  in  front  of  a  city  block-facing. 

Block  System  for  Railroads. — A  sys- 
tem for  avoiding  the  collision  of  moving 
railroad  trains,  by  dividing  the  road  into 
a  number  of  separate  blocks  or  sections  of 
a  given  length,  and  so  maintaining  tele- 
graphic communication  between  towers 
located  at  the  ends  of  each  of  such  blocks, 
as  to  prevent,  by  the  display  of  suitable 
signals,  more  than  one  train  or  engine 
from  being  on  the  same  block  at  the  same 
time. 

Block  Wire. — The  line  or  wire  employed 
in  block  systems  for  railroads  connecting 
each  block  tower  with  the  next  tower  on 
each  side  of  it. 


Blooms. — Masses  of  wrought  or  cast  metal, 
generally  rectangular  in  shape  and  ap- 
proximately six  inches  square  and  three 
or  four  feet  in  length,  from  which  wires 
are  obtained  by  rolling. 

Blow. — To  melt  or  fuse  a  safety  fuse. 

Blow-Pipe,  Electric. — A  blow-pipe  in 
which  the  air-blast  is  obtained  by  a  con- 
vective  electric  discharge. 

Blower,  Electric. — An  electrically  driven 
blower.  • 

Blowing  a  Fuse. — The  fusion  or  volatili- 
zation of  a  fuse  wire  or  safety  strip  by 
the  current  passing  through  it. 

Blowing  Point  of  Fuse.— The  current 
strength  at  which  a  fuse  blows  or  melts. 

Blue  Magnetic  Pole. — A  term  sometimes 
employed  for  the  south-seeking  magnetic 
pole. 

Bluestone  Gravity  Cell.— A  voltaic  cell 
consisting  of  a  zinc-copper  couple  whose 
elements  are  immersed  respectively  in 
electrolytes  of  zinc  sulphate  &  nd  copper 
sulphate. 

Board  of  Trade  Unit.— (1)  A  unit  of  elec- 
tric supply,  or  the  energy  contained  in  a 
current  of  1.000  amperes  flowing  for  one 
hour  under  a  pressure  of  one  volt.  (2)  A 
kilowatt-hour. 

Boat,  Electric. — An  electrically  propelled 
boat. 

Bobbed. — A  word  employed  to  character- 
ize a  surface  that  has  been  polished  by 
the  action  of  a  bob. 

Bobbin,  Electric. — A  coil  of  insulated 
wire  suitable  for  the  passage  of  an  elec- 
tric current  for  any  purpose,  as,  for  ex- 
ample, energizing  an  electro-magnet. 

Body -Protector,  Electric. — A  device  for 
protecting  the  human  body  against  the 
accidental  passage  through  it  of  an  electric 
discharge. 

Boiler-Feed,  Electric. — A  device  for 
electrically  opening  a  boiler-feed  appa- 
ratus when  the  water  in  the  boiler  falls 
to  a  certain  predetermined  point. 

Boiling  of  Secondary  or  Storage  Cell. 

A  term  sometimes  applied  to  the  gassing 

of  a  storage  cell. 
Bole. — A  unit  of  momentum,  proposed  by 

the    British    Association,  equal    to    one 

gramme-kine. 
Bolognian  Stone. — A  name  formerlygiven 

to  a  calcareous  substance  that  becomes 

phosphorescent  on  exposure  to  light. 

Bolometer. — (1)  An  apparatus  for  electri- 
cally measuring  small  differences  of 
temperature.  (2)  A  fine  wire  or  thin  strip 


Bol.] 


697 


[Bra. 


of  metal  whose  resistance  is  altered  by 
incident  radiant  energy. 

Bolometric  Spectrum. — The  luminous 
and  non-luminous  spectrum  obtained  by 
the  use  of  a  rock-salt  prism,  or  a  diffraction 
grating,  for  the  measurement  of  radia- 
tion in  the  bolometric  spectrometer. 

Bolometric  Spectrometer. — A  spectro- 
meter designed  for  the  measurement  of 
radiation,  luminous  or  otherwise. 

Bolt. — A  lightning  discharge. 

Bombardment,  Electric. — M  o  1  e  c  u  1  a  r 

bombardment. 

Bombardment  Incandescent  Lamp, 
Electric. — An  electric  lamp  in  which  re- 
fractory material  is  rendered  incandes- 
cent by  molecular  bombardment  produced 
by  the  passage  of  an  electric  discharge 
through  a  rarefied  space. 

Bonded  Bails. — In  any  electric  system 
where  the  rails  are  used  as  a  part  of  the 
circuit,  as  in  a  trolley  system,  rails  con- 
nected at  their  joints  by  suitable  bonds 
for  the  purpose  of  bringing  them  into 
good  electric  contact  with  one  another. 

Bonding  Resistance  of  Bail. — The  resist- 
ance offered  in  a  rail  circuit  at  the 
bonded  joints. 

Bonsalite. — An  insulating  substance. 

Bony  Current. — The  electric  current  re- 
sulting from  the  difference  of  potential 
existing  between  the  different  parts  of  a 
bone  in  a  recently  killed  animal. 

Booster. — A  dynamo,  inserted  in  a  special 
feeder  or  group  of  feeders  in  a  distribu- 
tion system,  for  the  purpose  of  raising  the 
pressure  of  that  feeder  or  group  of  feed- 
ers, above  that  of  the  rest  of  the  system. 

Boreal  Fluid. — A  term  formerly  applied 
to  the  fluid  that  was  supposed  to  exist 
around,  or  to  emanate  from,  the  boreal 
pole  of  a  magnet. 

Boring,  Electric. — Forming  holes  in 
metajs  or  minerals  by  the  heat  of  the 
voltaic  arc. 

Bot. — A  contraction  sometimes  used  for 
Board  of  Trade  unit  of  electric  supply,  or 
the  kilowatt -hour. 

Boucherize.-— To  subject  to  the  boucher- 
izing  process. 

Boucherizing. — A  process  for  preserving 
wooden  telegraph  poles,  or  railroad  sleep- 
ers, by  injecting  a  solution  of  copper  sul- 
phate into  the  pores  of  the  wood. 

Bougte-Decimale.— (1)  The  standard 
French  candle.  (2)  A  standard  of  lumi- 
nous intensity  equal  to  the  l-20th  of  that 
of  the  Yiolle  molten-platinum  standard. 

Bougie-Metre. — A   unit  of  illumination 

7_ 


equal  to  the  normal  illumination  from 
a  bougie-decimale  at  the  distance  of  one 
metre,  sometimes  called  a  lux. 

Bound  Charge. — The  condition  of  a  charge 
on  a  conductor  placed  near  another  con- 
ductor, but  separated  from  it  by  a  me- 
dium through  which  electrostatic  induc- 
tion can  take  place. 

Bow  Gear.— The  gear  placed  at  the  bow  of 
a  cable  ship  for  the  ready  handling  of  a 
cable  or  the  ropes  used  in  cable  work. 

Box  Balance.  —  A  box  form  of  electric 
bridge. 

Box  Bridge. — A  commercial  form  of  elec- 
tric bridge  or  balance  in  which  both  the 
arms  of  the  bridge  and  the  known  resist- 
ances consist  of  standardized  resistance 
coils  placed  in  a  suitable  box. 

Box-Sounding  Belay.— A  relay  whose 
magnet  is  surrounded  by  a  resonant  case 
of  wood,  for  the  purpose  of  increasing  the 
intensity  of  the  sounds  made  by  the  ar- 
mature of  the  magnet. 

Boxing  the  Compass. — Naming  consec- 
utively all  the  different  points  or  rhumbs 
of  a  compass  from  any  one  of  them. 

Bracket- Arm. —  An  arm  supported  by  a 
bracket  for  carrying  a  line  insulator. 

Bracket- Arm  Hanger.— A  hanger  for  an 
overhead  trolley  line  supported  on  a 
bracket  arm. 

Bracket  Pole. — In  a  system  of  overhead 
wires,  a  pole  employed  for  the  support 
of  the  brackets  provided  for  the  suspen- 
sion of  the  overhead  wires  or  conductors. 

Bracket  Suspension-Ear.— A  trolley  ear 
supported  on  a  bracket  arm,  designed  for 
the  suspension  of  an  overhead  trolley 
wire. 

Brake  Arm. — An  arm  or  lever  connected 
with  the  brake  shoe,  and  by  which  the 
brake  power  is  applied. 

Brake  Disc.  —  An  electro-magnet  in  the 
form  of  a  disc,  employed  in  an  electric 
street-car  brake. 

Brake  Handle.  —  A  handle  projecting 
above  the  dasher  of  a  car  for  the  opera- 
tion of  the  hand  brake  mechanism. 


Brake  Shoe. — A  mass  of  metal  whose  out- 
line conforms  to  the  tread  of  a  car  wheel, 
which  is  pressed  against  the  circumfer- 
ence of  the  wheel  on  the  operation  of 
the  brake  mechanism,  for  the  purpose  of 
stopping  the  car. 

Braided  Wire. — A  wire  covered  with  a 
braiding  of  insulating  material. 

Branch. — (1)  In  a  system  of  parallel  distri- 
bution, any  conductor  from  which  outlets 

Vol.  2 


Bra.] 


698 


[Bre. 


are  taken  or  taps  made.  (2)  One  of  the 
divisions  of  a  divided  conductor. 

Branches. — (1)  Conductors  connected  to 
the  submains  or  supply  conductors  in  a 
system  of  incandescent  lighting.  (2) 
Wires  tapped  to  mains. 

Branch.  Block.— A  porcelain  block  pro- 
vided with  suitable  grooves  in  which  the 
terminals  or  conductors  are  placed  for 
connecting  a  pair  of  branch  wires  to  the 
mains. 

Branch  Box. — A  box  containing  a  branch 
block. 

Branch  Circuits. — (1)  Additional  circuits 
provided  at  points  of  a  circuit  where  the 
current  branches  or  divides,  part  of  the 
current  flowing  through  the  branch,  and 
the  remainder  flowing  through  the  origi- 
nal circuit.  (2)  A  shunt  circuit. 

Branch  Conductor.  —  (1)  A  conductor 
placed  in  a  branch  or  shunt  circuit. 
(2)  A  smaller  or  sub-conductor  tapping  a 
main. 

Branch  Coupling  Box.— In  a  system  of 
street  mains  a  coupling  box  suitable  for 
connecting  a  house  service  connection 
with  the  incandescent  mains  supplying 
the  house. 

Branch  Cut-Out. — A  safety  fuse  or  cut- 
out, inserted  between  a  pair  of  branch 
wires  and  the  mains  supplying  them. 

Branch  Fuse. — A  branch  cut-out  or  safety 
fuse. 

Branch  of  Multiple  Circuit. — Any  of 
the  separate  circuits  that  are  connected 
between  the  mains  in  a  multiple  circuit. 

Branch  Point  of  Circuit.— Any  point  of 
a  circuit  from  which  a  branch  is  taken 
off. 

Branch-Wire  Terminal  Telephone 
Switchboard.—  A  three-wire  multiple 
switchboard  for  a  telephone  in  which  the 
jacks  for  any  one  subscriber  are  connected 
in  successive  panels  in  parallel  instead  of 
in  series. 

Branched  Magnetic  Circuit. — A  mag- 
netic circuit  in  which  the  flux  sub- 
divides into  a  number  of  separate  mag- 
netic circuits. 

Branched  Series. — A  term  sometimes  em- 
ployed for  series-multiple. 

Branching  Boards.— Multiple  telephone 
switchboards  connected  on  the  branching 
or  multiple  system. 

Branching  Telephone  System.— (1)  A 
system  of  multiple  telephone  switchboards' 
employing  the  branching  or  three-wire 
switchboard.  (2)  A  system  of  multiple 
telephone  switchboard  in  which  the  vari- 


ous jacks  on  one  line  are  connected  in 
parallel  instead  of  in  series. 

Branding,  Electric. — The  process  where- 
by a  branding  tool  is  heated  to  incan- 
descence by  an  electric  current  instead 
of  by  ordinary  means. 

Bread-and-Butter  Cable.  —  A  name 
given  to  a  form  of  light  submarine  cable 
in  which  the  sheathing  consists  alter- 
nately of  yarns  and  wires. 

Breadth  Coefficient  of  Armature  Coil. 

The  ratio  of  the  effective  electromotive 
force  induced  in  an  armature  coil  to  the 
effective  electromotive  force  which  would 
be  induced  if  the  coil  had  no  breadth  ;  i.  e. , 
if  all  its  wire  could  be  compressed  into 
the  space  occupied  by  a  single  turn. 

Breadth  of  Coil. — The  angular  distance  to 
which  a  coil  extends  circumferentially 
around  an  armature  core. 

Break. — Any  lack  of  conducting  continuity 
in  a  circuit. 

Break-Down  Switch. —  A  panel  switch 
employed  in  small  three-wire  systems, 
for  connecting  the  positive  and  negative 
bus-bars  so  as  to  convert  the  system  into 
a  two-wire  system,  and  thus,  in  case  of 
a  break-down,  to  permit  the  system  to 
be  supplied  with  current  from  a  single 
dynamo. 

Break-Induced  Current. —  (1)  The  cur- 
rent induced  in  an  active  circuit  by 
breaking  or  opening  that  circuit.  (2)  The 
current  induced  in  a  secondary  circuit  on 
the  breaking  of  the  circuit  of  the  pri- 
mary. 

Break  Key. — A  key  which  opens  or  breaks 
the  circuit  when  depressed. 

Break  Shock. —  A  term  sometimes  em- 
ployed in  electro-therapeutics  for  the 
physiological  shock  produced  on  the  open- 
ing or  breaking  of  an  electric  circuit. 

Break  Signal.— In  telegraphy  a  name 
given  to  the  signal  which  separates  the 
preamble  from  the  text  of  a  message,  or 
the  text  from  the  signature. 

Breaking  Capacity  of  Switch.— The 
strength  of  current  which  can  be  safely 
and  effectively  interrupted  by  a  switch, 
as  distinguished  from  the  carrying  capac- 
ity of  the  same. 

Breaking  Down  of  Dielectric.— Such  a 
weakening  of  a  dielectric  subjected  to 
electric  pressure  as  permits  disruptive 
discharges  to  pass  through  its  substance. 

Breaking  Down  of  Insulation.  —The 
failure  of  an  insulating  material,  as  evi- 
denced by  the  disruptive  passage  of  an 
electric  discharge  through  it. 


Ere.] 


G99 


[Bri. 


Breaking  In. — (1)  An  interruption  in  the 
sending  of  a  telegraphic  despatch  by  an 
intermediate  operator  who  endeavors  to 
simultaneously  use  the  line.  (2)  Introduc- 
ing a  key  into  a  telegraph  circuit  by  open- 
ing its  switch.  (3)  Interrupting  the  con- 
tinuity of  a  circuit. 

Breaking  the  Primary.  —  Opening  or 
breaking  the  circuit  of  the  primary  of  an 
induction  coil  or  transformer. 

Breaking  Weight  of  Wire.— The  weight 
required  to  be  hung  on  the  end  of  a  wire 
in  order  to  break  it. 

Breast  Plate. — The  breast  support  for  the 
microphone  transmitter  of  a  central 
telephone  station  operator. 

Breast  Telephone  Transmitter. — A 
telephone  transmitter  supported  for  con- 
venience on  a  plate  placed  on  the  breast 
of  the  operator. 

Breath  Figures,  Electric. — Faint  figures 
of  condensed  vapor  produced  by  electrify- 
ing a  coin  or  other  conducting  object, 
placing  it  momentarily  on  the  surface  of 
a  clean,  bright,  glass  sheet,  and  then 
breathing  gently  on  the  spot  where  the 
coin  was  placed. 

Breeze,  Electric. — A  brush  discharge  em- 
ployed in  electro-therapeutics. 

Breguet's  Manipulator. — A  sending  in- 
strument employed  by  Breguet  in  his 
system  of  step-by-step,  or  dial  telegraphy. 

"  Bridge." — A  word  sometimes  employed 
for  multiple-arc. 

Bridge  Arms. — The  arms  of  an  electric 
bridge  or  balance. 

Bridge  Balance  of  Telegraph  Line. — 
Such  a  balance  of  a  duplexed  telegraph 
line,  obtained  by  an  electric  bridge,  in 
which  the  home  relay  ceases  to  respond 
to  the  home  key. 

Bridge  Duplex. — The  bridge  method  of 
duplex  telegraphy,  as  distinguished  from 
the  differential  method. 

Bridge,  Electric. — (1)  A  device  whereby 
an  unknown  electric  resistance  is  readily 
measured.  (2)  A  device  for  measuring 
an  unknown  resistance  by  comparison 
with  two  fixed  resistances  and  an  adjust- 
able resistance. 

Bridge  Method  of  Duplex  Teleg- 
raphy.— (1)  A  system  whereby  two 
telegraphic  messages  can  be  simultane- 
ously transmitted  over  a  single  wire  in 
opposite  directions,  when  a  bridge  balance 
of  the  line  has  been  obtained.  (2)  A  sys- 
tem of  duplex  telegraphy  by  means  of  a 
single-bridge  duplex-system. 

Bridge  of  a  Fuse.— A  small  gap  at  a  fuse 


in  a  metallic  circuit  filled  with  a  semi- 
conducting compound  in  which  heat  is 
developed  by  a  current. 

Bridge  System  of  Quadruplex  Teleg- 
raphy.— A  system  of  quadruplex  telegra- 
phy by  means  of  a  bridge  duplex  system. 

Bridges. — Heavy  copper  wires  suitably 
shaped  for  connecting  a  dynamo-electric 
machine  in  an  incandescent  lighting  sta- 
tion to  the  bus- bars. 

Bridge- Wire.— The  wire  in  a  Wheat- 
stone's  Bridge  in  which  the  galvanometer 
is  inserted. 

Bridge  with  Secondary  Conductors 
A  form  of  Wheatstone  bridge    employ- 
ing an  additional  pair  of  resistances,  and 
suitable  for  measuring   very  low  Resist- 
ances. 

Bridging  Bell. — A  polarized  electric  bell 
permanently  connected  across  the  circuit 
employed  in  the  bridging-bell  system  of 
telephony. 

Bridging-Bell  Telephone  System.— A 
system  of  telephone  communication  in 
which  the  call  bells  are  placed  in  multiple- 
arc,  permanently  bridging  the  two  line 
conductors  of  metallic  circuits,  or  legged 
to  the  ground  in  grounded  circuits,  so 
that,  when  a  call  is  sent  out,  every  bell 
in  the  line  rings,  the  particular  station 
needed  being  indicated  by  a  suitable  code 
of  signals. 

Bridging  Coils. — In  telephony,  coils  which 
are  connected  across  a  telephone  circuit, 
as  distinguished  from  coils  placed  in 
series  in  the  circuit. 

Bridging  Indicator.— In  telephony,  an 
indicator  connected  in  shunt  across  a 
circuit  instead  of  in  series. 

Bridging  Relay. — In  telephony  or  tele- 
graphy, a  relay  which  is  connected  in 
shunt  across  a  circuit  instead  of  in  series, 

Bridle  Chain. — In  submarine  cable  work, 
the  chain  on  a  buoy  which  is  connected 
to  the  buoy  rope,  and  by  which  the  buoy 
rope  maybe  picked  up  when  the  buoy 
is  released  at  the  slip  chain. 

Bridle  "Wires. — (1)  Wires  connecting  the 
separate  line  wires  with  a  cable  box  or 
tower.  (2)  Wires  for  looping  a  telegraph 
station  into  a  line  or  lines. 

Bright  Deposit. — In  the  electro-plating  of 
silver  a  bright  surface  of  deposited  metal 
produced  by  a  special  final  process  in  the 
plating. 

Bright  Dipping. — Cleansing  a  metal  sur- 
face by  dipping  it  in  acid  liquids  for  the 
purpose  of  ensuring  a  bright  electro- 
metallurgical  coating. 


Bri.] 


700 


[Bui. 


Bright  Dipping  Liquid. — The  liquid  em- 
ployed in  bright  dipping. 

Brilliancy  of  Light.— (1)  The  brightness 
of  a  luminous  source.  (2)  The  quantity 
of  light  that  is  emitted  normally  from 
unit  surface  of  a  luminous  source.  (3) 
The  intrinsic  intensity  of  a  luminous 
source. 

Britannia  Joint. — A  telegraphic  or  tele- 
phonic joint  in  which  the  ends  of  the 
wires  are  laid  side-by-side,  bound  to- 
gether, and  subsequently  soldered. 

British  Association  Unit. — A  term  for- 
merly applied  to  the  British  Association 
unit  of  resistance  or  ohm. 

Broiler,  Electric. — An  electrically  heated 
broiler. 

Broken  Circuit. — (1)  An  open  circuit. 
(2)  A  circuit  whose  electric  continuity 
has  been  disturbed,  and  through  which 
the  current  has,  therefore,  ceased  to  pass. 

Brother-in-Law. — A  bell  whose  sound  is 
the  same  as  that  of  the  car  indicator,  con- 
cealed by  a  dishonest  conductor  for  the 
purpose  of  avoiding  ringing  the  bell  of 
the  car  indicator  when  a  fare  has  been 
collected. 

Brush-and-Spray  Discharge. -A  stream- 
ing form  of  high-potential  discharge  pos- 
sessing the  appearance  of  a  spray  of 
silvery  white  sparks,  or  of  a  branchbf  thin 
silvery  sheets  around  a  powerful  brush, 
obtained  by  increasing  the  frequency  of 
the  alternations. 

Brush  Contact-Surface. — (1)  That  portion 
of  a  commutator  surface  which  is  in  con- 
tact with  the  brushes  at  any  moment  of 
time.  (2)  The  surface  area  of  a  brush 
applied  to  a  contact  surface. 

Brush  Discharge. — The  faintly  luminous 
discharge  which  takes  place  from  a 
positively  charged  pointed  conductor. 

Brush  Electrode. — A  conducting  brush- 
shaped  electrode  employed  in  electro- 
therapeutic  treatment. 

Brush-Holder  Cable. — A  stranded  con- 
ductor or  cable  employed  in  a  dynamo 
or  motor  for  direct  connection  to  the 
brushes. 

Brush  Holders  for  Dynamo-Electric 
Machine. — Devices  for  supporting  the 
collecting  brushes  of  a  dynamo-electric 
machine. 

Brush  Pressure.— (1)  The  electric  pressure 
at  the  brushes  of  a  dynamo-electric  ma- 
chine. (2)  Mechanical  pressure  on  a 
brush. 

Brush  Rocker. — In  a  dynamo  or  motor 
any  device  for  shifting  the  position  of  the 
Pushes  on  the  commutator  cylinder. 


Brush  Shifting  Device.— A  modified 
form  of  brush  rocker. 

Brushes  of  Dynamo-Electric  Ma- 
chines.— Strips  of  metal,  bundles  of  wire 
or  wire  gauze,  slit  plates  of  metal,  or 
plates  of  carbon,  that  bear  on  the  com- 
mutator cylinder  of  a  dynamo,  and  carry 
off  the  current  generated. 

B-Side  of  Quadruples  Table.— That 
side  of  a  quadruplex  table  which  is 
worked  by  means  of  strengthened  cur- 
rents. 

Bucking. — A  term  employed  in  the  opera- 
tion of  street-railway  passenger  cars  for  a 
sudden  stopping  of  the  car  as  if  by  a  col- 
lision, due  to  opposition  between  two 
motors. 

Buckled  Diaphragm. — A  fault  in  a 
telephonic  transmitter  or  receiver  due  to 
a  dent  or  warping  in  the  diaphragm. 

Buckling. — The  warping  or  irregularities 
produced  in  the  surface  of  the  plates  of 
storage  cells  by  a  too  rapid  discharge. 

Buffing. — Preparing  surfaces  for  the  re- 
ception of  electro-plating  by  subjecting 
them  to  the  polishing  action  of  a  revolv- 
ing wheel  covered  with  a  buff,  on  the 
surface  of  which  rouge  has  been  spread. 

Bug. — (1)  A  term  employed  in  quadru- 
plex telegraphy  to  designate  any  fault  in 
the  operation  of  the  apparatus.  (2)  Gen- 
erally, a  fault  in  the  operation  of  any 
electric  apparatus.  (3)  A  particular  fault 
or  difficulty  in  quadruplex  telegraphy 
consisting  of  an  interference  between  the 
A  and  B-sides. 

Bug-Trap. — A  device  employed  to  over- 
come the  bug  in  quadruplex  telegraphy. 

Building-Iron. — A  heated  iron  tool  by 
means  of  which,  the  mould  impressed  by 
a  printed  page,  which  it  is  desired  to 
electro-type,  is  built  up  preparatory  to  its 
being  placed  in  the  plating  bath. 

Building  Knife. — A  heated  knife-shaped 
tool  employed  in  removing  the  wax  that 
has  been  forced  up  around  the  sides  of 
the  matrix  during  the  taking  of  the  im- 
pression. 

Building  Process  for  Electro-Type 
Metals. — A  process  for  bringing  up  the 
blank  spaces  in  the  mould  of  an  electro- 
type by  the  addition  of  wax  plates  melted 

,  into  place  by  the  building-iron,  the  high 
spaces  thus  built-up  becoming  depressions 
in  the  finished  plate. 

Building  Switch. — A  switch  provided 
with  an  insulating  handle  for  cutting  a 
building  in  or  out  of  an  electric  circuit, 
usually,  a  series  circuit. 

Building  Tool. — A  form  of  building  iron 


Bui.] 


701 


[Bus 


"  Building-Up  "  of  Dynamo.— The  ac- 
tion whereby  a  dynamo-electric  machine 
rapidly  reaches  its  maximum  E.  M.  F. 
after  starting. 

"  Built-in  "  Underground  Conductor. 
An  underground  conductor  which,  in- 
stead of  being  placed  in  the  duct  of  a 
conduit  or  tube  so  as  to  be  capable  of  re- 
moval therefrom,  at  any  time,  is  perma- 
nently "built  in"  or  surrounded  by  the 
insulating  and  protective  material. 

"Built-Up"  Magnet. — A  composite  per- 
manent magnet. 

Bullet  Probe. — A  probe  containing  elec- 
trical conductors,  so  arranged  that  the 
contact  of  the  probe  with  a  bullet  closes 
an  electric  circuit  and  operates  an  electric 
signal. 

Bunched  Cable. — A  cable  containing 
more  than  a  single  wire  or  conductor. 

Bunsen  Screen. — The  screen  of  a  Bunsen 
or  translucent-disc  photometer. 

Bunsen  Voltaic  Cell. — A  zinc-carbon 
couple  whose  elements  are  immersed 
respectively  in  electrolytes  of  dilute  sul- 
phuric and  strong  nitric  acids. 

Buoy,  Electric. — A  buoy  on  which  elec- 
trically produced  luminous  signals  are 
displayed. 

Burette. — A  graduated  glass  tube  em- 
ployed for  readily  measuring  the  volume 
of  a  liquid. 

Burglar-Alarm,  Electric. — An  electric 
device  for  automatically  announcing  the 
opening  of  a  door,  window,  closet,  drawer 
or  safe,  or  the  passage  of  a  person  through 
a  hallway,  or  on  a  stairway. 

Burglar-Alarm  Annunciator,  Elec- 
tric.— An  annunciator  used  in  connec- 
tion with  a  system  of  burglar-alarms. 

Burglar-Alarm  Contacts. — Contacts  fit- 
ted to  windows,  doors,  tills,  safes,  floors, 
etc. ,  so  that  the  movements  of  the  various 
parts  from  their  natural  positions,  sound 
an  alarm. 

Burglar-Alarm  Matting. — A  matting 
provided  with  a  number  of  invisible  con- 
tacts connected  with  an  alarm  bell,  whose 
circuits  are  closed  by  treading  on  the 
matting. 

Buried  Cable  or  Conductor. — An  un- 
derground cable  or  conductor  placed  di- 
rectly in  the  earth,  in  contra-distinction 
to  one  placed  in  a  conduit  or  subway. 

Buried  Transformer. — A  transformer, 
provided  with  a  water-tight  cover  and 
placed  below  the  surface  of  the  ground. 

Burn-Out. — The  destruction  of  an  arma- 
ture, or  any  part  of  an  electric  apparatus, 


by  the  passage  of  an  excessive  current 
due  to  short-circuit  or  other  cause. 

Burned-Out  Incandescent  Lamp. — An 
incandescent  lamp  which  through  con- 
tinued use  is  no  longer  able  to  furnisb 
electric  light. 

Burner,  Electric.— A  gas-burner  that  is 
capable  of  being  electrically  lighted. 

Burnetize. — To  subject  to  the  burnetizing 
process. 

Burnetizing. — A  method  adopted  for  the 
preservation  of  wooden  telegraph  poles, 
by  injecting  a  solution  of  zinc-chloride 
into  the  pores  of  the  wood. 

Burning  at  Commutator  of  Dynamo. 
An  arcing  at  the  brushes  of  a  dynamo- 
electric  machine,  due  either  to  their  im- 
perfect contact  or  improper  position,  re- 
sulting in  the  loss  of  energy  to  the  circuit, 
and  the  destruction  of  the  commutator 
segments,  or  of  the  brushes. 

Burnishing. — A  process  by  means  of 
which  surfaces  are  prepared  for  electro- 
plating by  subjecting  them  to  the  action 
of  burnishing  tools. 

Burnt  Electro-Metallurgical  Deposit. 
The  black  deposit  of  metal  which  is 
thrown  down  when  the  intensity  of  the 
depositing  current  is  too  strong. 

Bus. — A  word  generally  used  instead  of 
omnibus. 

Bus-Bar  Connectors. — Connectors  em- 
ployed for  connecting  or  joining  the  ends 
of  bus-bars. 

Bus-Bar  Stand. — A  bus-bar  support  on  a 
switchboard. 

Bus-Bar  Voltmeter. — A  voltmeter  em- 
ployed in  a  central  station  for  measuring 
the  pressure  between  the  bus-bars. 

Bus-Bars. — Heavy  bars  of  conducting 
metal  connected  directly  to  the  poles  of 
one  or  more  dynamo-electric  machines, 
and,  therefore,  receiving  the  entire  cur- 
rent produced  by  the  machines. 

Bus  Field-Excitation. — Excitation  of  the 
field  of  a  generator  by  current  taken 
directly  from  the  bus-bai's. 

Bus-Rods  or  Wires. — Terms  frequently 
used  for  bus-bars. 

Bushing  of  Socket. — A  sleeve  or  cylinder 
of  insulating  material  inserted  at  the 
entrance  of  a  lamp  socket  for  the  pro- 
tection of  the  entering  conductors. 

Busy-Back. — A  jack  at  a  central  telephone 
exchange  connected  with  a  battery  and 
vibrator,  in  such  a  way  that  the  operator 
by  inserting  the  plug  of  an  incoming  line 
into  this  jack  can  notify  a  calling  operator 
that  the  subscriber  desired  is  busy. 


Bus.] 


702 


[Cab. 


Busy  Test. — A  simple  test  whereby  a  tele- 
phone operator  at  a  multiple  switchboard 
can  readily  tell  whether  any  wire  or  cir- 
cuit connected  with  the  switchboard  is 
or  is  not  in  use  at  any  moment  of  time. 

Butt  Joint. — (1)  An  end-to-end  joint.  (2) 
A  joint  effected  in  wires  by  placing  the 
wires  end  on  and  subsequently  soldering 
or  welding  them. 

Butt  Prop. — A  tool  sometimes  called  a 
"dead  man,"  used  in  the  erection  of 
telegraph  poles. 

Button  Repeater. — A  manual  telegraphic 
repeater  whereby  the  proper  connections 


are  made  for  repeating  a  message  in 
either  direction,  by  turning  a  button. 

Buzzer,  Electric. — (1)  A  call,  not  as  loud 
as  that  of  an  electric  bell,  employing  a 
humming  sound  by  the  use  of  a  suffi- 
ciently rapid  automatic  contact-breaker. 
(2)  A  telephone  receiver  for  morse  circuits 
employing  a  vibrating  contact  key. 

Buzzing  of  Bell. — An  improper  action  of 
an  electric  bell,  whereby  it  produces  a 
buzzing  sound  instead  of  its  proper  ring- 
ing. 

By-Pass  of  Discharge. — A  term  some- 
times employed  for  alternative  path. 


C.  —  A  contraction  for  Centigrade. 

C.  —  A  contraction  for  current. 

C.  —  A  symbol  for  capacity.  (Partly  inter- 
national usage.) 

C.-  -A  symbol  for  coulomb. 

C.  E.  M.  F.  —  A  contraction  for  counter 
electromotive  force. 

C.  G-.  S.  —  A  contraction  for  centimetre- 
gramme-second. 

C.  c.  —  A  contraction  for  cubic  centimetre, 
the  C.  G.  S.  unit  of  volume. 

cm.  —  An  abbreviation  for  centimetre,  the 
C.  G.  S.  unit  of  length. 

cm2.  —  An  abbreviation  for  square  centi- 
metre, the  C.  G.  S.  unit  of  surface. 

cm3.  —  An  abbreviation  for  cubic  centi- 
metre, the  C.  G.  S.  unit  of  volume. 

C.  M.  M.  Jfi1.  —  A  contraction  for  counter- 
magnetomotive  force. 

C.  P.  —  A  contraction  for  candle-power. 

C.  38,.  —  A  contraction  for  conductor-resist- 
ance. 

C2H  Activity.—  (1)  The  PR  activity. 
(2)  That  portion  of  the  electric  activity 
which  is  expended  in  heating  the  con- 
ductor, and  due  to  the  ohmic  resistance 
offered  by  the  conductor  to  the  passage 
of  the  current.  (3)  The  thermal  activity 
of  a  circuit  expressed  in  watts,  and  equal 
to  the  square  of  the  current  strength  in 
amperes  multiplied  by  the  resistance  in 
ohms. 


Loss.  —  The  loss  of  energy  in  a  con- 
ductor due  to  the  ohmic  resistance  and 
the  current  strength. 

'C.  G.  S.  Units.  —  The  centimetre-gramme- 
second  units. 

Cabinet  Seat  Contact.  —  A  contact 
placed  in  a  silence  telephone  cabinet, 
underneath  a  seat,  and  closed  by  the 
weight  of  a  person  on  the  seat. 


Cable. — (1)  An  electric  cable.  (2)  A  mes- 
sage transmitted  by  means  of  an  electric 
cable. 

Cable. — To  send  a  telegraphic  despatch  by 
means  of  a  cable. 

Cable  Alphabet. — The  code  or  telegraphic 
alphabet  employed  in  cable  signalling. 

Cable  Box. — A  box  provided  for  the  re- 
ception and  protection  of  a  cable  head. 

Cable  Buoy. — A  buoy  generally  secured 
by  a  mushroom  anchor  and  provided  for 
temporarily  holding  or  securing  an  end  of 
a  cable  during  its  laying  or  repair. 

Cable  Casing. — The  metallic  sheathing  of 
a  cable. 

Cable  Cell. — A  voltaic  cell  formed  by  an 
exposed  broken  end  of  a  submarine  copper 
conductor  and  the  iron  sheathing  of  the 
cable. 

Cable  Clearing-House  System. — A 
system  whereby  every  message  sent  over 
a  submarine  cable  is  returned  to  the  head 
office  and  a  comparison  effected  between 
the  original  message,  as  received  for 
transmission,  and  the  final  message,  as 
delivered  to  the  addressee. 

Cable  Clip. — A  term  sometimes  used  for 
cable  hanger. 

Cable  Closing  Machine.— A  machine  for 
covering  a  cable  with  its  sheathing. 

Cable  Code. — (1)  A  cable  alphabet.. 
(2)  A  cable  cipher. 

Cable  Core. — (1)  The  insulated  conducting 
wires  of  an  electric  cable.  (2)  The  elec- 
trically essential  portion  of  a  cable  as  dis- 
tinguished from  its  sheath  or  protection. 

Cable  Cross-Connecting  Board.— In  a 
telephone  exchange,  where  a  number  of 
cables  enter  the  building  from  the  outside, 
a  distributing  board,  placed  in  a  termi- 
nal room  to  facilitate  the  work  that  ia 


Cab.] 


703 


[Cab. 


constantly  going  on  of  making  and  chang- 
ing the  connections  of  the  subscribers' 
lines  to  the  switchboard  cables. 

Cable  Currents. — (1)  Various  currents  that 
exist  in  a  submarine  cable  and  interfere 
with  the  testing,  consisting  of  earth  cur- 
rents, electrostatic  charge  and  discharge 
currents,  and  polarization  currents  due  to 
a  fault  or  break.  (2)  A  current  flowing 
through  a  cable  in  the  absence  of  any  im- 
pressed E.  M.  F.  (3)  The  current  which 
tends  to  flow  in  a  broken  cable  from  the 
exposed  copper  conductor  at  the  fracture 
to  the  iron  sheathing  through  the  ap- 
paratus at  the  station. 

Cable  Despatch.— A  despatch  sent  by 
means  of  a  cable. 

Cable  Drum. — (1)  In  cable  machinery,  a 
drum  on  which  cable  is  wound  for  coil- 
ing, shipping,  laying,  or  turning  over. 
(2)  A  drum  or  reel  on  which  cable  is 
wound  for  transport. 

Cable,  Electric. — A  combination  of  an 
extended  length  of  a  single  insulated  elec- 
tric conductor,  or  of  two  or  more  sepa- 
rately insulated  electric  conductors,  cov- 
ered externally  with  a  metallic  sheathing 
or  armor. 

Cable  Fault. — Any  failure  in  the  proper 
working  of  a  cable  due  either  to  a  total 
or  partial  fracture  of  the  cable,  or  to  a 
heavy  electric  leakage. 

Cable  Float. — A  float  employed  for  tem- 
porarily relieving  the  tension  on  a  cable 
while  it  is  being  paid  out. 

Cablegram. — A  telegraph  message  re- 
ceived by  cable. 

Cable  Grapnel. — A  heavy  pronged  iron 
hook  provided  for  picking  up  a  cable  by 
grappling. 

Cable  Grip.— (1)  The  grip  provided  for 
holding  the  end  of  an  underground  cable 
while  it  is  being  drawn  into  a  duct. 
(2)  In  a  cable  road  the  grip  by  means  of 
which  a  car  is  driven  by  the  moving 
cable. 

Cable  Ground. — The  locality  of  a  cable 
operation  or  repair. 

Cable  Hanger. — A  hanger  or  hook  suit- 
ably secured  to  a  cable  and  designed  to 
sustain  its  weight  by  intermediately  sup- 
porting it  on  an  iron  or  steel  wire  strung 
above  the  cable. 

Cable  Hanger  Tongs. — Tongs  provided 
with  long  handles  for  attaching  the 
hangers  of  an  aerial  cable  to  the  suspend- 
ing wire  or  rope. 

Cable  Head. — A  rectangular  board  pro- 
vided with  binding  posts  and  fuse  wires 


for  the  purpose  of  receiving  the  wires  of 
overhead  lines  where  they  enter  a  cable. 

Cable  House. — A  hut  provided  for  secur- 
ing and  protecting  the  end  of  a  submarine 
cable  when  it  is  landed. 

Cable  Hut. — A  cable  house. 

Cable  Joint. — An  insulated  electric  con- 
nection made  between  the  cores  of  two 
separate  lengths  of  cable. 

Cable  Junction-Box. — A  junction  box  for 
holding  and  protecting  the  insulated 
connections  or  joints  between  cables. 

Cable  Laid-TJp-in-Layers.— A  cable  all 
of  whose  conducting  wires  are  in  layers. 

Cable  Laid-Up-in-Reverse-Layers.— A 
cable  the  alternate  layers  of  whose  con- 
ductors are  twisted  in  opposite  directions. 

Cable  Laid-up-in-Twisted-Pairs.—  A 
cable  every  pair  of  whose  wires  is  twisted 
together. 

Cable  Land  Line.— (1)  A  land  line  com- 
posed of  cable.  (2;  A  land  line  connected 
to  a  cable. 

Cable  Laying. — The  process  of  placing  a 
cable  on  the  sea-bottom. 

Cable  Lead. — A  lead  formed  of  a  cable 
of  several  stranded  conductors,  as  dis- 
tinguished from  a  lead  containing  a 
single  conductor. 

Cable  Message. — A  cable  despatch. 

Cable  Office. — An  office  connected  with  a 
cable. 

Cable  Protector.— (1)  A  device  for  the 
safe  discharge  of  the  charge  induced  in 
the  metallic  sheathing  of  a  cable,  or  in 
the  conductors  surrounding  or  adjacent 
to  the  cables,  consequent  on  changes  in 
the  electromotive  force  applied  to  the 
conducting  core  of  the  cable.  (2)  A  fuse 
device  provided  for  the  protection  of  each 
of  the  wires  of  an  aerial  cable,  placed  in 
the  cable  head  at  the  junction  where  an 
aerial  line  enters  the  cable  head. 

Cable  Rack.— A  rack  placed  at  the  back 
of  a  multiple  telephone  switchboard  f^r 
supporting  the  cabled  switchboard  con- 
ductors and  providing  ready  access  to  the 
same. 

Cable  Repairing.— The  process  of  repair- 
ing a  broken  or  faulty  cable. 

Cable  Resistor.— A  form  of  float  or  buoy 
provided  for  lessening  the  strain  on  a 
cable  while  paying  it  out. 

Cable  Road.— A  system  of  car  propulsion 
in  which  the  cars  are  drawn  by  the 
movement  of  an  underground  cable  to 
which  the  moving  cars  are  attached  by  a 
suitable  grip. 


704 


[Cal. 


Cable  Sending-Key. — A  key  employed 
for  readily  sending  the  positive  and  nega- 
tive current  impulses  required  to  trans- 
mit the  cable  alphabet  or  code. 

Cable  Serving. — A  covering  of  hemp  or 
jute  spun  around  the  insulated  core  of  a 
cable  in  order  to  protect  it  from  the  pres- 
sure of  the  iron  wire  armor  or  sheathing 
of  the  cable. 

Gaol©  Ship. — A  ship  provided  with  the 
apparatus  required  for  laying  or  repairing 
submai'ine  cables. 

Cable  Signals. — Signals  received  over  the 
circuit  of  a  cable. 

Cable  Speaking-Set. — The  apparatus 
used  in  signalling  over  a  cable. 

Cable  Spinning-Jenny.— A  device  for 
readily  binding  an  aerial  cable  to  a  sup- 
porting wire. 

Cable  Splice. — A  connection  between  the 
sheathing  or  armor  of  two  lengths  of 
cable. 

Cable  Stopper. — A  flexible  grip  applied 
to  a  cable  to  keep  it  from  moving  or 
slipping. 

Cable  Suspender. — A  device  for  suspend- 
ing an  aerial  cable. 

Cable  Switchboard. — A  switchboard  to 
which  the  cable  conductors  are  connected. 

Cable  Tank. — A  strong  water-tight  tank 

E laced  on  a  cable  ship  and  provided  for 
olding  a  coiled  section  of  cable  that  is 
ready  for  laying. 

Cable  Telegraph. — A  general  term  in- 
cluding all  the  apparatus  employed  in 
cable  telegraphy. 

Cable  Telegraphy.  —  Telegraphic  com- 
munication carried  on  over  a  submarine 
cable. 

Cable  Terminal. — A  water-tight  covering 
provided  at  the  free  end  of  a  telephone 
cable  to  prevent  injury  to  the  cable's  in- 
sulation by  the  moisture  of  the  air. 

Cable  Terminal-Pole. — The  terminal  pole 
of  an  aerial  line  provided  where  the  ends 
of  an  aerial  line  are  connected  with  an 
underground  cable  for  the  support  of  the 
cable  head. 

Cable      Terminal  -  Switchboard.  —  A 

board  in  a  cable  head  where  the  wires 
are  spread  out  and  connected  in  proper 
order  to  a  number  of  binding  posts  which 
in  their  turn  are  connected  through  fuse 
wires  to  binding  posts  receiving  the  ends 
of  overhead  wires. 

Cable  Transformer.  —  An  alternating- 
current  transformer  in  which  the  pri- 
mary and  secondary  conductors  have  the 


form  of  a  cable  overlaid  by  an  iron 
sheath  or  magnetic  circuit. 

Cable  Vault. — A  vault  provided  in  a 
building  where  cables  enter  from  under- 
ground conduits,  and  where  the  cables 
are  opened  and  connected  to  fusible  plugs 
or  safety  catches. 

Cable  Testing. — The  process  or  methods 
of  trying  or  measuring  the  electric  or 
mechanical  capabilities  of  a  cable. 

Cable  Well.— A  cable  tank. 

Cable  Winder. — A  cable  spinning-jenny. 

Cable  Work. — Any  operation  connected 
with  the  manufacture,  shipping,  laying, 
testing,  or  repair  of  cables. 

Cable  Worming.— A  central  core  of  hemp 
or  jute  around  which  are  wrapped  the 
several  separate  conductors  of  any  cable 
that  contains  more  than  a  single  con- 
ductor. 

Cabled. — Transmitted  by  means  of  cable 

telegraphy. 
Cabling. — Transmitting  by  means  of  cable 

telegraphy. 

Cadmium  Standard  Cell. — A  standard 
voltaic  cell  of  very  low  temperature 
coefficient  of  variation  in  E.  M.  F. ,  em- 
ploying a  cadmium-zinc  couple. 

Cage  Lightning-Protector.  —  A  term 
sometimes  employed  for  a  lightning  pro- 
tector consisting  of  wires  in  the  form  of 
a  cage  surrounding  the  body  to  be  pro- 
tected. 

Calamine,  Electric. — A  crystalline  va- 
riety of  silicate  of  zinc  that  possesses  pyro- 
electric  properties. 

Calculagraph. — A  machine  employed  in 
long-distance  telephony  for  registering 
the  time  during  which  the  use  of  a  line 
by  a  subscriber  continues. 

Gal-Electric  Generator.— A  generator 
whose  operation  depends  on  the  produc- 
tion of  electricity  in  the  secondary  coil  of 
a  transformer  by  changes  of  temperature 
in  its  iron  core. 

Gal-Electricity. — Electricity  produced  by 
changes  of  temperature  in  the  iron  core 
of  a  transformer. 

Calibrate. — To  determine  the  absolute  or 
relative  values  of  the  scale  divisions,  or  of 
the  indications  of  any  electrical  instru- 
ment, such  as  a  galvanometer,  electro- 
meter, voltmeter,  wattmeter,  or  other 
similar  instrument. 

Calibrating. — Determining  or  marking  off 
the  values  or  readings  of  a  galvanometer, 
electrometer,  voltmeter,  wattmeter,  or 
other  similar  electrical  instrument. 

Call.— (1)  In  telephony,  the  signal  or  call  of 


Cal.] 


705 


[€au. 


a  subscriber  for  connection  to  some  other 
subscriber.  (2)  In  telegraphy,  the  signal 
for  attention,  or  the  call  for  response  from 
the  distant  operator. 

Call-Bell,  Electric. — An  electric  bell  used 
to  call  the  attention  of  an  operator  to  the 
fact  that  his  correspondent  wishes  to 
communicate  with  him. 

Call-Key. — Any  suitable  key  for  sending 
an  electric  call. 

Callaud  Voltaic  Cell. — A  name  some- 
times given  to  the  blue-stone  gravity  cell. 

Calling  Circuit. — In  the  Law  system  of 
telephony,  a  common  calling- wire  circuit 
connecting  the  centi'al  exchange  through 
all  the  subscribers'  offices  in  a  given 
group,  and  employed  for  sending  calls  to 
the  central  office. 

Calling  Drops. — In  an  isolated-station 
switchboard,  drops  employed  for  indicat- 
ing the  particular  subscriber  calling. 

Calling  Plug. — That  plug  of  a  pair  of 
plugs,  at  a  central  telephone  switchboard, 
which  is  inserted  in  the  jack  of  the  sub- 
scriber wanted  and  through  which  that 
subscriber  is  called  up. 

Calling  Side  of  Telephone  Circuit. — 
That  side  of  a  telephone  circuit  over 
which  a  call  arrives. 

Calling  Station. — Any  station  that  desires 
to  be  placed  in  communication  with  an- 
other station. 

Calling  Wire. — A  wire  forming  the  call- 
ing circuit  in  a  system  of  telephony. 

Call  Signal.— In  telegraphy,  the  signal  or 
group  of  signals  indicating  the  particular 
station  called. 

Call  Wire. — (1)  A  speaking  wire.  (2)  A 
wire  connecting  two  telephone  exchanges, 
for  the  purpose  of  transmitting  instruc- 
tions, as  distinguished  from  a  wire  em- 
ployed for  establishing  communication 
between  subscribers.  (3)  A  wire  employed 
for  calling  the  attention  of  a  central- 
station  operator  by  a  subscriber,  as  dis- 
tinguished from  the  wires  through  which 
he  communicates  with  other  subscribers. 

Call- Wire  Key. — A  subscriber's  key  em- 
ployed to  call  the  operator  at  a  central 
telephone  station. 

Call- Wire  Switchboard. — A  switchboard 
at  a  telephone  station  auxiliary  to  a 
multiple  switchboard  in  a  call-wire 
system,  and  employed  for  suitably  divid- 
ing up  call-wires  among  the  operators, 
so  as  to  equalize  their  work. 

Call-Wire  System. — A  system  of  tel- 
ephony in  which  special  wires  are  em- 

45* 


ployed  to  call  the  operator  at  the  central 
station. 

Calorescence. — The  transformation  of  ob- 
scure heat  rays  into  luminous  rays  on 
impact  with  certain  solid  substances. 

Caloric. — A  term  formerly  applied  to  the 
assumed  fluid  that  was  believed  to  be  the 
cause  or  essence  of  heat. 

Calorie. — (1)  A  heat  unit.  (2)  The  quantity 
of  heat  required  to  raise  1  gramme  of 
water  1°  centigrade. 

Calorific  Intensity. — The  temperature  at- 
tained in  combustion. 

Calorimeter. — An  instrument  for  measur- 
ing the  amount  of  heat  contained  in,  or 
developed  by,  a  given  body. 

Calorimeter,  Electric. — An  instrument 
for  measuring  the  heat  developed,  in  a 
given  time,  in  any  conductor,  by  an  elec- 
tric current. 

Calorimetric. — Of  or  pertaining  to  the 
calorimeter. 

Calorimetric  Conductivity.  —  Specific 
heat  transference,  or  the  conductivity  of 
a  substance  based  on  the  quantity  of  heat 
transferred  in  a  given  time,  independently 
of  the  temperature  attained. 

Calorimetric  Measurement. — The  meas- 
urement of  heat  energy  by  means  of  a 
calorimeter. 

Calorimetric  Photometer.  —  A  photo- 
meter in  which  the  light  to  be  measured 
is  absorbed  by  the  face  of  a  thermo-pile, 
and  its  photometric  intensity  estimated 
from  the  strength  of  the  electric  current 
thereby  produced. 

Calorimetry. — The  art  of  measuring  heat 
energy  by  means  of  a  calorimeter. 

Calorimotor.  —  (1)  A  deflagrator.  (2)  A 
word  formerly  employed  for  a  number  of 
series-connected  voltaic  cells.  (Obsolete.) 

Calory.  —  A  less  preferable  orthography 
sometimes  employed  for  calorie. 

Canalization. — (1)  A  network  of  conduct- 
ors. (2)  A  system  of  electric  mains. 

Candle. — (1)  A  unit  of  photometric  inten- 
sity. (2)  The  photometric  intensity  which 
would  be  produced  by  a  standard  candle 
burning  at  the  rate  of  two  grains  per 
minute. 

Candle  Balance. — A  balance  support  pro- 
vided for  the  standard  candle  of  a  photo- 
meter, so  arranged  as  continuously  to 
weigh  the  candle  and  so  determine  its  rate 
of  consumption  while  in  use. 

Candle,  Electric. — A  Jablochkoff  candle. 

Candle-Foot. — A    unit     of    illumination 

equal  to  that  normally  produced  by  a 


Can.] 


706 


[Cap. 


standard  British  candle,  at  a  distance  of 
one  foot,  and  sometimes  called  a  lux. 

Candle-Power.— (1)  The  intensity  of  light 
emitted  by  a  luminous  body  estimated  in 
standard  candles.  (2)  The  photometric 
intensity  of  one  standard  candle . 

Canopy. — (1)  In  a  multiple  telephone  ex- 
change, an  overhanging  frame  suitably 
supported  from  above,  and  containing 
plugs  and  drops.  (2)  An  ornamental 
metallic  covering  employed  in  incandes- 
cent lighting  for  an  electrolier  or  pendant 
outlet. 

Canopy  Switch. — An  overhead  switch 
placed  at  each  end  of  a  trolley  car  for  the 
purpose  of  permitting  the  motorman  to 
turn  the  current  on  or  off  the  car  as  de- 
sired, when,  for  example,  he  wishes  to  in- 
spect a  fuse  block  or  controller  without 
pulling  down  the  trolley  pole. 

Cant  Hook. — A  tool  employed  in  the  erec- 
tion of  telegraph  poles  consisting  of  a  pole 
furnished  with  a  curved  pivoted  hook 
employed  for  turning  or  rolling  a  telegraph 
pole. 

Caoutchouc. —  (1)  A  resinous  substance 
possessing  high  powers  of  electric  insula- 
tion, obtained  from  the  milky  juice  of  cer- 
tain tropical  trees.  (2)  India  rubber. 

Cap  Wire. — An  overhead  wire  carried  on 
the  summit  of  a  pole,  as  distinguished 
from  an  overhead  wire  carried  on  a  cross 
arm. 

Capability  of  Dynamo  -  Electric  Ma- 
chine.— The  maximum  theoretical  activ- 
ity of  a  dynamo  as  expressed  by  the  square 
of  its  electromotive  force  divided  by  its 
resistance. 

Capacitance. — (1)  A  term  proposed  in 
place  of  capacity.  (2)  The  reactance  of 
a  condenser  in  an  alternating-current 
circuit. 

Capacity  Balance  of  Duplex  System.— 
The  balance  of  capacity  in  duplex  teleg- 
raphy as  opposed  to  a  balance  of  resist- 
ance. 

Capacity  Circuit. — A  circuit  containing 
capacity  but  no  inductance. 

Capacity  Current  of  Cable.— (1)  The 
current  in  a  cable  due  to  its  capacity. 
(2)  The  charging  or  discharging  current 
in  a  cable. 

Capacity  Load. — The  apparent  load  or 
current  of  a  high-tension  generator  due 
to  the  capacity  of  the  distributing  con- 
ductors as  distinguished  from  the  load  or 
current  usefully  distributed. 

Capacity  of  Accumulator. — The  avail- 
able output  of  a  storage  battery  expressed 
either  in  ampere-hours,  or  in  watt-hours. 


Capacity  of  Cable.— (1)  The  quantity  of 
electricity  required  to  raise  a  given  length 
of  cable  to  a  given  potential,  divided  by 
the  potential.  (2)  In  a  multiple  cable,  the 
amount  of  charge  at  unit  potential  which 
any  single  conductor  will  take  up,  the 
rest  of  the  conductors  being  grounded. 
(3)  The  ability  of  a  conducting  wire  or 
cable  to  permit  a  certain  quantity  of 
electricity  to  be  passed  into  it  before  ac- 
quiring a  certain  potential. 

Capacity  of  Cable  Tank.— The  accom- 
modation of  a  cable  tank  expressed  either 
voluminally  in  cubic  feet,  or  in  relation 
to  the  number  of  miles  of  a  given  type  of 
cable  which  can  be  practically  stowed 
away  in  it. 

Capacity  of  Condenser. — (1)  The  quan- 
tity of  electricity  a  condenser  is  capable 
of  holding  in  coulombs  when  charged  to 
a  pressure  of  one  volt.  (2)  The  ratio  be- 
tween the  quantity  of  electricity  in  cou- 
lombs on  one  coating  of  a  condenser  and 
the  potential  difference  in  volts  between 
the  two  coatings. 

Capacity  of  Leyden  Jar. — The  quantity 
of  electricity  a  Leyden  jar  will  take  under 
unit  difference  of  potential. 

Capacity  of  Line.— The  ability  of  a  line 
to  act  as  a  condenser,  and,  therefore,  like 
it,  to  possess  capacity. 

Capacity  of  Polarization  of  Voltaic 
Cell. — The  capacity  of  becoming  polar- 
ized when  subjected  to  a  steady  discharge. 

Capacity  of  Secondary  or  Storage  Cell. 
The  capacity  of  an  accumulator. 

Capacity  Pressure.— (1)  In  a  condenser 
connected  with  a  source  of  alternating 
currents,  a  pressure  in  phase  with  the 
condenser  current.  (2)  A  pressure  due 
to  a  capacity.  (3)  The  pressure  at  the 
terminals  of  a  condenser. 

Capacity  Reactance. — (1)  The  reactance 
of  a  condenser  due  to  its  capacity. 
(2)  The  condensance.  (3)  The  capacitance. 

Capacity  Resistance. — (1)  A  term  pro- 
posed for  the  resistance  which  a  conden- 
ser or  other  substance  possessing  electric 
capacity  offers  to  the  passage  of  an  alter- 
nating electric  current.  (2)  The  impe- 
dance of  a  condenser. 

Capillarity. — The  elevation  or  depression 
of  liquids  in  tubes  of  small  internal  diam- 
eter. 

Capillary.— Of  small  or  hair-like  diameter 
or  size. 

Capillary  Attraction.  —  The  molecular 
attractions  concerned  in  capillary  phe- 


Cap.] 

Capillary  Contact-Key.— A  form  of  fluid 
contact-key  in  which  the  circuit  is  closed 
or  broken  by  means  of  a  wire  which  is 
dipped  into  or  removed  from  the  surface 
of  a  mass  of  mercury. 

Capillary  Electrometer. — An  electro- 
meter in  which  difference  of  potential 
is  measured  by  the  movements  of  a  drop 
of  sulphuric  acid  in  a  tube  filled  with 
mercury. 

Capsizing  Thermometer. — A  thermom- 
eter employed  in  deep  sea  soundings  for 
cable  work,  which  is  caused  to  record  the 
temperature  at  the  moment  the  lead 
commences  to  ascend  from  the  bottom, 
by  causing  the  thermometer  to  be  re- 
versed or  capsized. 

Car  Annunciator.  —  An  annunciator 
placed  in  a  car  for  the  purpose  of  calling 
a  waiter  or  porter. 

Car  Barn. — A  covered  shed  provided  with 
tracks  in  which  trolley  cars  are  stored 
when  not  in  use. 

Car  Body. — The  wooden  framework  of  a 
street-railway  car  which  encloses  the 
space  provided  for  the  passengers. 

Car-Brake,  Electric. — A  car-brake  that 
is  operated  by  the  electric  current  pro- 
duced by  the  motor  acting  as  a  generator 
when  the  current  is  turned  off  and  the 
car  is  rapidly  moving. 

Car-Brake  Mechanism. — The  mechan- 
ism for  applying  the  brake  to  a  car- wheel. 

Car  Controller. — (1)  A  device  placed  at 
each  end  of  the  platform  of  a  trolley  car, 
under  the  control  of  the  motor  man  for 
starting,  stopping,  reversing  or  changing 
the  velocity  of  a  trolley  car.  (2)  A  series- 
parallel  car-controller. 

Car-Heater,  Electric. — An  electric  heat- 
er consisting  essentially  of  suitably  sup- 
ported coils  of  insulated  wire  traversed 
by  an  electric  current. 

Car-Lamp,  Electric. — An  incandescent 
lamp  generally  provided  with  an  anchored 
filament,  suitable  for  use  in  street-railway 
cars. 

Car-Propulsion,  Electric.— The  propul- 
sion of  cars  by  means  of  electric  motors. 

Car  Truck. — The  part  of  a  car  on  which 
the  car  body  rests. 

Car  Wiring. — The  distribution  of  conduct- 
ors on  an  electric  street  car. 

Carbon. — An  elementary  substance  which 
occurs  naturally  in  three  distinct  allo- 
tropic  forms  :  graphite,  charcoal  and  the 
diamond. 

Carbon  Arc. — A  voltaic  arc  formed  be- 
tween carbon  electrodes. 


rOT  [Car. 

Carbon  Brushes  for  Electric  Motors 
or  Generators.— Plates  of  artificial  car- 
bon employed  as  the  brushes  of  dynamos 
or  motors. 

Carbon  Button. — A  button-shaped  carbon 
mass  whose  resistance  varies  with  press- 
ure. 

Carbon  Cell. — (1)  A  silvered  plate  of  glass 

Erovided  on  its  silvered  side  with  a  num- 
er  of  zigzag  furrows  filled  with  carbon 
soot,  and  employed  as  the  receiving  in- 
strument in  a  photophone.  (2)  A  voltaic 
cell  employing  carbon  as  one  of  its  ele- 
ments. 

Carbon  Clutch  or  Clamp  for  Arc 
Lamps. — A  clutch  or  clamp  attached  to 
the  lamp  rod  or  the  support  of  the  positive 
or  upper  carbon  of  an  arc  lamp,  provided 
for  gripping  or  holding  the  carbon. 

Carbon  Diaphragm  of  Telephone. — 
A  thin  sheet  of  carbon  employed  as  the 
diaphragm  in  certain  forms  of  telephone 
transmitters. 

Carbon  Electrodes  for  Arc  Lamps. — 
The  carbons  of  an  electric  arc  lamp  be- 
tween which  the  arc  is  maintained. 

Carbon  Holder. — A  device  employed  in 
an  arc  lamp  for  supporting  the  lower  or 
negative  carbon. 

Carbon  Megohm. — A  resistance  of  ap- 
proximately one  megohm  composed  of  a 
thin  film  or  strip  of  graphite. 

Carbon  Motor  Brush. — A  carbon  brush 
employed  on  a  motor. 

Carbon  Pencils. — A  word  sometimes  used 
for  the  carbons  employed  in  arc  lamps. 

Carbon-Point  Lightning- Arrester. — A 
lightning  arrester  in  which  the  disruptive 
discharge  occurs  between  opposed  carbon 
points. 

Carbon  Points. — The  carbon  rods  or  pen- 
cils employed  in  arc  lamps. 

Carbon  B,heostat. — An  adjustable  resist- 
ance formed  of  carbon  plates  or  powder 
whose  resistance  can  be  varied  by  pres- 
sure. 

Carbon  Telephone  Transmitter.— A 
telephone  transmitter  whose  operation  is 
dependent  on  variations  in  the  resistance 
of  a  carbon  button,  or  of  a  mass  of  loose 
granulated  carbon,  on  the  to-and-fro 
movements  of  the  diaphragm. 

Carbon  Tongs. — A  pair  of  tongs  suitable 
for  gripping  arc-light  carbons. 

Carbon  Transmitter. — A  carbon  tele- 
phone transmitter. 

Carbons. — A  general  term  applied  to  the 
carbons  or  negative  elements  of  voltaio 
cells. 


Car.] 


708 


[Cat. 


Carbonic  Acid  Gas. — A  gaseous  substance 
formed  by  the  union  of  one  atom  of  car- 
bon with  two  atoms  of  oxygen. 

Carboning  Lamps. — Placing  carbons  in 
electric  arc  lamps. 

Carbonizable. — Capable  of  being  carbon- 
ized. 

Carbonization. — The  act  of  carbonizing. 

Carbonize. — To  reduce  a  carbonizable  sub- 
stance to  carbon. 

Carbonized  Cloth  Discs  for  High  Re- 
sistance.— Discs  of  cloth  carbonized  by 
heating  to  an  exceedingly  high  temper- 
ature while  out  of  contact  with  air. 

Carbonizer. — Any  apparatus  suitable  for 
reducing  a  carbonizable  material  to  car- 
bon. 

Carbonizing.— Subjecting  a  carbonizable 
substance  to  the  process  of  carbonization. 

Carbonizing  Box. — A  box  prepared  for 
holding  the  carbon  filaments  of  incandes- 
cent lamps  during  their  carbonization. 

Carbonizing  Frame.— A  suitably  shaped 
block  of  carbon  prepared  for  winding  the 
cotton  threads,  or  other  plastic  carboniz- 
able material,  employed  for  the  filaments 
of  incandescent  lamps,  before  submitting 
them  to  the  carbonizing  process. 

Carcass  of  Dynamo-Electric  Machine. 
A  term  sometimes  used  for  the  iron  f rame- 
work  of  a  dynamo. 

Carcel. —  (1)  A  French  photometric  stand- 
ard of  light.  (2)  The  light  emitted  by 
a  lamp  of  definite  dimensions  burning 
42  grammes  of  Colza  oil  in  an  hour,  with 
a  flame  40  millimetres  in  height. 

Carcel  Lamp. — An  oil  lamp  employed  in 
France  as  a  photometric  standard. 

Carcel  Standard. — The  carcel. 

Carcel  Standard  Gas-Jet.— A  lighted 
gas  jet  employed  for  determining  the  can- 
dle-power of  gas  by  measuring  the  height 
of  a  jet  of  gas,  burning  under  certain 
conditions,  when  used  in  connection  with 
the  light  of  a  larger  gas-burner  burning 
under  similar  conditions,  for  a  photo- 
metric measurement  of  electric  lights. 

Cardan  Suspension  of  Compass 
Needle. — The  gimbal  suspension  of  a 
compass  needle. 

Cardew  Voltmeter. — A  voltmeter  whose 
indications  are  obtained  by  the  expansion 
of  a  long  fine  wire  by  the  passage  through 
it  of  the  current  to  be  measured. 

Carnot's  Cycle. — A  cycle  of  steps  or  oper- 
ations proposed  by  Carnot  for  convenience 
in  studying  the  transformation  of  heat 
into  work. 


Carriers  of  Replenishes — The  moving 
conductors  of  a  replenisher  which  carry 
the  charges  and  thus  permit  an  accumu- 
lation of  such  charges. 

Carrying  Capacity. — The  maximum  cur- 
rent strength  that  any  conductor  can 
safely  transmit. 

Carrying  Capacity  of  Safety  Fuse.— 
The  maximum  current  strength  which  a 
fuse  wire  or  block  can  carry  without 
melting. 

Carrying  Hooks. — A  pair  of  curved  hooks 
pivoted  together  and  provided  with  han- 
dles, for  carrying  telegi'aph  poles. 

Cascade  Charging  of  Leyden  Jars  or 
Condensers. — A  method  of  charging 
Leyden  jars  or  condensers  by  means  of 
the  electricity  liberated  by  induction 
from  one  coating  when  a  charge  is  pass- 
ing into  the  other  coating. 

Cascade  Connection. — A  term  sometimes 
employed  for  series  connection. 

Cascade  Connection  of  Condensers. 
A  term  sometimes  employed  for  a  series- 
connection  of  condensers. 

Case-Hardening,  Electric.— S  u  p  e  r- 
ficially  hardening  a  piece  of  metal  by 
means  of  electrically  generated  heat. 

Case  Wiring. — A  wiring  in  which  the  elec- 
tric conductors  are  held  in  place  on  the 
walls  or  ceilings  of  a  room  by  means  of 
continuous  cleats. 

Casings.— Grooves  or  panelled  channels 
for  carrying  wires  in  a  house. 

Cast  Rail-Bond.— A  method  for  bonding 
the  successive  track  rails,  in  a  system  of 
trolley  propulsion,  by  casting  molten 
iron  around  all  except  the  upper  portions 
of  the  joint. 

Casting,  Electric. — A  process  for  casting 
metals,  in  which  the  metals  are  fused  by 
means  of  heat  of  electric  origin. 

Castor  and  Pollux  Light.— A  term  for- 
merly used  for  the  St.  Elmo's  fire. 

Catalisis. — An  objectionable  orthography 
sometimes  employed  for  catalysis. 

Catalysis. — The  influence  produced  on 
chemical  combination  or  decomposition, 
by  the  presence  of  certain  substances 
which,  without  undergoing  any  changes 
themselves,  produce  changes  in  the  affini- 
ties of  other  substances  by  their  mere 
contact  or  presence. 

Catalytic. — Of  or  pertaining  to  catalysis. 

Cataphoresis. — Electric  osmose. 

Cataphoretic. — Of  or  pertaining  to  cata- 
phoresis. 

Cataphoretic  A  c  t  i  o  n. — Cataphoretic 
medication  or  demedication. 


Cat.] 


709 


[Cei. 


Cataphoretic  Demedication. — A  means 
whereby  material  is  removed  from  differ- 
ent parts  of  the  body  by  means  of  cata- 
phoresis. 

Cataphoretic  Electrode. — (1)  An  elec- 
trode containing  in  solution  the  drug  or 
medicament  that  is  to  be  introduced  into 
the  body  by  cataphoresis.  (2)  The  anode. 

Cataphoretic  Medication. — The  intro- 
duction of  a  drug  or  medicament  into  the 
body  by  means  of  cataphoresis. 

Cataphoric. — Of  or  pertaining  to  cata- 
phoresis. 

Catelectrotonus. — An  orthography  some- 
times employed  for  cathelectrotonus. 

Catenary. — A  catenary  curve. 

Catenary  Curve. — The  curve  described 
by  the  sagging  of  a  wire,  under  its  own 
weight,  when  stretched  between  two 
points  of  support. 

Cathelectrotonic. — Of  or  pertaining  to 
cathelectrotonus. 

Cathelectrotonic  State. — The  condition 
of  increased  functional  activity  of  a 
nerve  in  the  neighborhood  of  the  cathode 
to  whose  influence  it  is  subjected. 

Cathelectrotonic  Zone. — A  name  some- 
times given  to  the  peripolar  zone. 

Cathelectrotonus. — In  electro-therapeu- 
tics the  condition  of  increased  functional 
activity  that  occurs  in  a  nerve  in  the 
neighborhood  of  the  cathode  or  negative 
electrode. 

Cathetometer. — An  instrument  for  the 
accurate  measurement  of  small  heights 
or  distances. 

Cathion. — The  electro-positive  ion,  atom, 
or  radical,  into  which  the  molecule  of  an 
electrolyte  is  decomposed  by  electrolysis. 

Cathodal. — Of  or  pertaining  to  the 
cathode. 

Cathode.— (1)  The  conductor  or  plate  of 
an  electro-decomposition  cell  connected 
with  the  negative  terminal  of  a  battery 
or  other  electric  source.  (2)  The  terminal 
of  an  electric  source  into  which  the  cur- 
rent flows  from  the  electrolyte  of  a  de- 
composition cell  or  voltameter.  (3)  The 
electrode  of  a  bath,  tube,  body,  or  device 
by  which  the  current  leaves  the  same. 
(4)  The  negative  electrode. 

Cathode  Cup. — (1)  A  cup-shaped  cathode 
of  an  X-ray  tube.  (2)  A  concave  mirror 
attached  to  the  cathode  of  an  X-ray  or 
other  high-vacuum  tube. 

Cathode  Pictures. — X-ray  or  Roentgen- 
ray  pictures. 

Cathode  Bay  Spectrum. — A  succession 
of  light  and  dark  phosphorescent  bands 


produced  on  a  screen,  in  an  exhausted 
Crookes  tube,  by  magnetically  deflected 
cathode  rays. 

Cathode  Rays.— Radiation  emitted  from 
the  cathode  or  negative  electrode  of  a 
Crookes  or  X-ray  tube. 

Cat  ho  die. — Of  or  pertaining  to  the 
cathode. 

Cathode  Streams. — Cathode  rays. 

Cathodic  Current. — In  a  polarized  vol- 
taic couple  immersed  in  acidulated  water, 
the  current  produced  by  the  agitation  of 
the  plate  connected  with  the  cathode. 

Cathodic  Electro-Diagnostic  Reac- 
tions.— The  reactions  which  occur  at  the 
cathode  placed  on  or  over  any  part  of  a 
living  body. 

Cathodic  Rays. — The  cathode  rays, 

Cathodic    Streamings.— Cathode    rays. 

Cathodogram. — A  Roentgen  or  X-ray 
picture. 

Cathodograph. — A  radiograph. 

Cation. — An  orthography  sometimes  em- 
ployed for  cathion. 

Catoptrics. — That  branch  of  optics  which 
treats  of  the  reflection  of  light. 

Cauterization.— The  act  of  cauterizing  or 
burning  with  a  heated,  solid  or  caustic 
substance. 

Cauterization,  Electric. — Subjecting  to 
cauterization  by  means  of  an  electrically 
heated  wire. 

Cauterize. — To  subject  to  cauterization. 

Cauterizer,  Electric.— A  name  some- 
times given  to  an  electric  cautery. 

Cautery  Battery. — A  term  sometimes 
employed  in  electro-therapeutics  for  a 
multiple-connected  voltaic  battery  adapt- 
ed for  producing  incandescence  for  cau- 
tery effects. 

Cautery  Cabinet. — A  cabinet  containing 
a  cautery  battery,  switchboard,  cautery 
knives  and  other  necessaries  for  electric 
cauterization. 

Cautery  Cell. — A  cell  suitable  for  use  in 
a  cautery  battery. 

Cautery,  Electric. — The  application  to 
the  human  body  of  variously  shaped  plat- 
inum wires,  heated  to  incandescence  by 
the  electric  current,  for  removing  dis- 
eased growths,  or  for  stopping  hemor- 
rhages. 

Cautery  Knife-Electrode.  —  A  knife- 
shaped  electrode  that  is  rendered  incan- 
descent by  the  passage  through  it  of  an 
electric  current. 

Ceiling  Block. — An  attachment  fastened 
to  the  ceiling  for  suspending  flexible 


Cei.] 


710 


[Can. 


cords,  and  connecting  them  with  the  sup- 
ply wires  of  an  incandescent  system. 
Ceiling  Board.  —  An  arc -light    hanger 
board. 

Ceiling  Bracket.— (1)  A  ceiling  canopy. 
(2)  A  bracket  for  supporting  an  insulated 
wire  or  wires  to  a  ceiling. 

Ceiling  Cut-Out. — A  cut-out  placed  in  a 
ceiling  block. 

Ceiling  Fan. — An  electrically  driven  fan 

suspended  from  the  ceiling. 
Ceiling  Rose.  —  An   ornamental  ceiling 

plate  from  which  an  electric  conductor 

passes. 

Ceiling  Rosette. —  An  ornamental,  rose- 
shaped  ceiling  block. 

Cell  of  Primary  or  Secondary  Battery. 
A  jar  of  a  primary  or  secondary  battery 
containing  a  single  couple  and  its  elec- 
trolyte. 

Celluloid  Lamp-Filament.  —  A  lamp 
filament  made  by  carbonizing  celluloid, 
a  modified  form  of  cellulose. 

Celluvert  Fibre. — A  variety  of  insulating 
material. 

Centi. —  A  prefix  for  the  one  hundredth 
part. 

Centi- Ampere.  —  The  hundredth  of  an 
ampere. 

Centi- Ampere  Balance.— An  ammeter  in 
the  form  of  a  balance,  capable  of  measur- 
ing current  strengths  readily  expressed  in 
centi-ampei'es  (i.  e.,  from  1£ff  ampere  to 
1  ampere). 

Centigrade  Thermometer  Scale.  —  A 
thermometer  scale  in  which  the  length 
of  the  thermometric  tube,  between  the 
melting  point  of  ice  and  the  boiling  point 
of  water,  is  divided  into  one  hundred 
equal  parts  or  degrees. 

Centigramme.  —  The  hundredth  of  a 
gramme  ;  or,  0. 1543  grains  avoirdupois. 

Centilitre. — The  hundredth  of  a  litre  ;  or, 
0.6102  cubic  inch. 

Centimetre. — The  hundredth  of  a  metre  ; 
or,  0.3937  inch. 

Centimetre-Gramme-Second  System. 
A  system  based  on  the  centimetre  as  the 
unit  of  length,  the  gramme  as  the  unit  of 
mass,  and  the  second  as  the  unit  of  time. 

Centimetre-Gramme-Second  Units.  — 
The  units  of  the  centimetre-gramme- 
second  system. 

Centipede  Cable-Grapnel.  —  A  grapnel 
whose  projecting  prongs  give  it  an  ap- 
pearance somewhat  resembling  a  centi- 
pede. 


Central. — A  name  given  to  any  central 
telephone  exchange  or  office. 

Central  Galvanization.  —  A  variety  of 
general  galvanization  in  which  the 
cathode  is  placed  over  the  epigastrium 
and  the  anode  moved  over  the  body. 

Central  Lighting-Station. — A  station 
where  the  generators  and  distributing 
apparatus  are  placed  for  producing  the 
current  which  lights  the  lamps  in  a  given 
district. 

Central-Station  Burglar- Alarm.  —  A 
burglar-alarm  whose  contacts,  situated  at 
the  place  to  be  protected,  are  connected 
by  suitable  circuits  with  alarms  placed  in 
a  centrally  located  station. 

Central-Station  Lighting.— The  lighting 
of  a  number  of  houses  or  other  buildings 
from  a  single  centrally  located  station. 

Central  -  Station  Multiple  -  Switch- 
Board. — A  switchboard  employed  in  a 
central  telephone  exchange,  in  which 
each  subscriber's  jack  appears  in  more 
than  a  single  panel. 

Central  Telephone  Exchange.— (1)  A 
central  telephone  office  connected  with 
a  plurality  of  subscribers  or  telephone 
stations.  (2)  A  central  exchange  con- 
nected with  a  plurality  of  local  exchanges. 

Central  -  Telephone  -  Exchange  Mul- 
tiple-Switchboard. —  Any  form  of 
switchboard  employed  in  a  central  tele- 
phone exchange,  by  means  of  which 
numerous  subscribers  connected  there- 
with can  be  readily  connected  to  one 
another. 

Centrally  Grounded  Wire  of  Railway 
Circuit. — A  conductor  or  wire  extending 
along  the  roadbed,  parallel  to  the  rails  of 
a  pair  of  tracks,  connected  to  the  bond 
wires,  and  itself  grounded  at  intervals. 

Cement-Lined  Conduit. — A  conduit  of 
wood,  stone  or  metal,  the  surfaces  of 
whose  ducts  are  lined  with  cement. 

Centre-Pole  Trolley  Line  Construc- 
tion.— A  form  of  aerial  line  construction 
in  which  the  trolley  wires  are  suspended 
from  poles  placed  in  the  middle  of  the 
street  or  road. 

Centre  of  Distribution. — In  a  system  of 
incandescent  distribution  any  point  at 
which  the  supply  current  is  branched  or 
radially  distributed  to  mains,  to  sub- 
mains,  or  to  translating  devices. 

Centre  of  Gravity.— The  centre  of  weight 
of  a  body. 

Centre  of  Oscillation. — A  point  in  a  body 
swinging  like  a  pendulum,  which  is 
neither  accelerated  nor  retarded,  during 
its  oscillations,  by  the  portions  of  the  pen- 


Ceil.] 


711 


[Che. 


dulum  that  are  situated  above  or  below 
it. 

Centre  of  Percussion. — That  point  in  a 
body,  suspended  so  as  to  move  as  a  pen- 
dulum, at  which  a  blow  perpendicular  to 
the  radius  would  produce  no  pressure 
at  the  axis. 

Centre-Pole  Construction. — In  a  double- 
track  trolley  system,  especially  on  broad 
streets,  a  system  of  pole  construction  in 
which  poles  are  placed  between  the  two 
tracks,  provided  with  bracket  arms  ex- 
tending over  each  track  for  the  support 
of  the  trolley  wire. 

Centre  Railway  Line— A  trolley  line  of 
centre-pole  construction. 

Centrifugal  Force. — That  force  which  is 
supposed  to  urge  a  rotating  body  directly 
away  from  the  centre  of  rotation. 

Centrifugal  Governor.  —  A  device  for 
maintaining  constant  the  speed  of  a  steam 
engine  or  other  prime  mover,  despite 
certain  changes  in  its  load  or  work. 

Centrifuge. — (1)  An  apparatus  for  separat- 
ing solids  from  liquids  or  liquids  of  differ- 
ent density  from  one  another  by  centri- 
fugal forces.  (2)  A  centrifugal  separator. 

Centrifuge,  Electric.  —  A  centrifuge 
driven  by  an  electromagnetic  motor. 

Centripetal. — Seeking  the  centre. 

Cerebration. — The  action  of  the  brain  in 
producing  thought. 

Chafe. — A  weak  or  worn  place  in  the 
sheathing  of  a  submarine  cable  due  to 
attrition. 

Chaflng-DishjElectric. — An  electrically- 
heated  chafing  dish. 

Chain  Cable-Grapnel. — A  grapnel  whose 
prongs  are  attached  to  the  linky  of  a 
chain. 

Chain  Lightning.  —  A  variety  of  light- 
ning flash  in  which  the  discharge  assumes 
a  rippling,  chain-like  appearance. 

Chain  Pull. — A  pendant  chain  attached  to 
a  pendant  burner  for  the  movement  of 
the  wipe-spark  spring  and  the  ratchet  in 
an  electrically-lighted  gas-burner. 

Chamber  of  Incandescent  Lamp. — The 
glass  bulb  or  chamber  of  an  incandescent 
lamp  provided  for  maintaining  a  high 
vacuum,  and  for  the  reception  of  the 
filament. 

Change-Over  Switch.  —  A  switch  pro- 
vided in  a  central  station  for  transferring 
a  working  circuit  from  one  dynamo  to 
another,  or  from  one  battery  of  dynamos 
to  another. 

Change  ,  Ratio  of  Transformer.  —  The 
ratio  of  transformation. 


Changing  Switch.  —  A  change  -  over 
switch. 

Characteristic  Curve.  —  (DA  diagram 
in  which  a  curve  is  employed  to  represent 
the  relation  of  certain  varying  values. 
(2)  A  curve  indicating  the  characteristic 
properties  of  a  dynamo-electric  machine 
under  various  phases  of  operation.  (3)  A 
curve  indicating  the  electromotive  force 
of  a  generator,  as  a  variable  dependent  on 
the  excitation. 

Characteristic  Curve  of  Dynamo.— A 
curve  showing  the  pressure  at  the  ter- 
minals of  a  dynamo  at  different  field  ex- 
citations. 

Characteristics  of  Sound. — (1)  The  pe- 
culiarities that  enable  different  musical 
sounds  to  be  readily  distinguished  from 
one  another.  (2)  The  tone  or  pitch,  in- 
tensity or  loudness,  and  the  quality  or 
timbre  of  sounds. 

Charge  Accumulator. —  A  word  some- 
times given  to  a  Leyden  jar  or  condenser. 

Charge  Current  onTelegraphic  Line. — 

The  current  produced  by  the  initial  rush 
of  electricity  into  a  telegraph  line  on  the 
closing  of  the  circuit. 

Charge,  Electric. — The  quantity  of  elec- 
tricity that  exists  on  the  surface  of  an 
insulated  electrified  conductor. 

Charged  Body.— A  body  containing  an 
electric  charge. 

Charged  Cell. — A  cell  of  a  storage  battery 
that  has  been  acted  on  by  a  charging  cur- 
rent. 

Charging  Accumulators  or  Storage 
Batteries. — Sending  an  electric  current 
into  storage  batteries  or  accumulators  for 
the  purpose  of  enabling  them  to  act  as 
electric  sources. 

Charging  Current.  —  The  current  em- 
ployed in  charging  a  storage  battery  or 
accumulator. 

Chatterton's  Compound. — An  insulat- 
ing compound  for  cementing  together  the 
alternate  coatings  of  gutta-percha  em- 
ployed on  a  cable  conductor,  or  for  filling 
up  the  space  between  the  stranded  con- 
ductors. 

Checking  Action. — A  term  sometimes 
employed  for  a  dampening  action. 

Checking  Instrument. — An  instrument 
in  a  cable  station  for  recording  sending  or 
out-going  signals  on  a  recorder  slip. 

Chemical  Affinity. —  (1)  Atomic  attrac- 
tion. (2)  The  force  that  causes  atoms  to 
unite  and  form  molecules. 

Chemical  Annunciator. — A  term  some- 


Che.] 


712 


[Ckr. 


times  employed  for  electrolytic  annun- 
ciator. 

Chemical  Battery. — A  name  sometimes 
given  to  a  voltaic  telegraph  battery  as 
distinguished  from  a  dynamo. 

Chemical  Change. — Any  change  in  mat- 
ter resulting  from  atomic  combination 
and  the  consequent  formation  of  new 
molecules. 

Chemical  Effect. — (1)  Any  effect  occa- 
sioned by  atomic  combination,  in  which 
the  substances  entering  into  combination 
lose  all  those  properties  and  peculiar- 
ities by  which  they  are  ordinarily  recog- 
nized. (2)  Atomic  combination  result- 
ing in  the  formation  of  new  molecules. 

Chemical  Equivalent. — (1)  The  quotient 
obtained  by  dividing  the  atomic  weight 
of  an  elementary  substance  by  its  atom- 
icity. (2)  The  ratio  between  the  quantity 
of  an  element  and  the  quantity  of  hy- 
drogen it  is  capable  of  replacing.  (3)  The 
quantity  of  an  elementary  substance  that 
is  capable  of  combining  with  or  replacing 
one  atom  of  hydrogen. 

Chemical  Galvano-Cautery. — A  term 
sometimes  applied  to  electro-puncture  or 
the  application  of  electrolysis  to  the  treat- 
ment of  diseased  growths. 

Chemical  Generator  of  Electricity. — 
A  term  sometimes  employed  in  place  of  a 
voltaic  pile  or  battery. 

Chemical  Phosphorescence. — A  variety 
of  phosphorescence  in  which  the  emitted 
light  is  produced  by  the  actual  combus- 
tion of  a  specific  chemical  substance  by 
the  oxygen  of  the  air,  as  in  the  phosphor- 
escence of  the  fire-fly,  or  the  glow-worm. 

Chemical  Photometer. —  A  photometer 
in  which  the  intensity  of  light  to  be  meas- 
ured is  determined  by  the  amount  of 
chemical  action  produced  in  a  given  time. 

Chemical  Potential  Energy.— The  po- 
tential energy  possessed  by  the  element- 
ary chemical  atoms. 

Chemical  Recording  Meter. — A  meter 
which  records  by  means  of  electrolysis 
the  quantity  of  electricity  supplied  in  a 
given  time. 

Chemical  Separation. — Chemical  decom- 
position. 

Chemical  Telegraph. — A  general  term 
for  the  apparatus  employed  in  chemical 
telegraphy. 

Chemical  Telegraphy.—  A  system  of 
telegraphy,  in  which  the  dots  and  dashes 
of  the  Morse  alphabet,  or  other  telegraphic 
code,  are  recorded  on  a  fillet  of  moistened 
paper  by  the  electrolytic  action  of  the 


current  on  some  chemical  substance  with 
which  the  paper  is  impregnated. 

Chemical  Telephone. — The  name  given 
to  a  telephone  operating  on  the  principles 
of  the  electro-motograph. 

Chemical  Velocity. — The  ratio  of  the 
amount  of  substance  transformed  in  any 
chemical  process  to  the  time  required  for 
its  transformation. 

Chemism. — A  word  sometimes  employed 
for  chemical  affinity. 

Chief  Operator. — The  senior  operator  on 
duty  in  a  telegraph  or  telephone  office. 

Chimes,  Electric. — A  chime  of  bells  rung 
by  the  attractions  and  repulsions  of  elec- 
trostatic charges. 

Chimney  Bracket. — A  bracket  for  sup- 
porting an  overhead  wire  fastened  to  a 
chimney  corner. 

Chloride  Storage  Cell. — A  name  given 
to  a  storage-cell  in  which  the  plates  are 
formed  of  grids  of  antimonious  lead,  cast 
around  pastilles  or  buttons  of  fused  chlo- 
ride of  lead,  which,  when  properly  sub- 
jected to  the  charging  current,  are  con- 
verted into  spongy  metallic  lead  and  lead 
peroxide,  on  the  negative  and  positive 
plates  respectively. 

Choke  Coil. — A  name  sometimes  given  to 
a  choking  coil. 

Choke  Magnet. — A  word  sometimes  used 
for  choking  coil. 

Choking  Coil. — A  coil  of  wire  so  wound 
on  a  core  of  iron  as  to  possess  high  self- 
induction  when  used  on  alternating-cur- 
rent circuits. 

Choking  Effect.  —  The  effect  produced 
by  a  choking  coil  in  obstructing  or  cut- 
ting off  an  alternating  current  with  a 
smaller  loss  of  power  than  would  its  use 
as  a  mere  ohmic  resistance. 

Chord  Armature  Windings.— (1)  Ar- 
mature windings  partly  formed  by  chords 
of  arcs  on  the  periphery  to  which  they 
are  applied.  (2)  An  armature  winding 
in  which  the  wire  is  carried  from  one 
point  on  the  surface  to  another  along  a 
chord  of  the  included  arc. 

Chromosphere. — An  intensely  hot  gaseous 
envelope  surrounding  the  central  lumin- 
ous nucleus  or  photosphere  of  the  sun. 

Chronograph,  Electric. — An  electric  ap- 
paratus for  automatically  measuring  and 
registering  small  intervals  of  time. 

Chronograph  Record. —  A  record  ob- 
tained oy  means  of  a  chronograph. 

Chronometer,  Electric. — An  electrically 
controlled  and  operated  mechanism  for 
indicating  and  recording  time. 


Clir.] 


713 


[Cir. 


Chronoscope,  Electric.— (1)  An  appa- 
ratus for  electrically  indicating  but  not 
measuring  small  intervals  of  time.  (2)  An 
electrically  operated  device  by  which 
small  intervals  of  time  can  be  measured. 

Cigar-Lighter,  Electric. — An  apparatus 
for  electrically  lighting  a  cigar. 

Cinematograph. — A  biograph. 

Cipher  Code. — A  code  in  which  a  number 
of  words  or  phrases  are  represented  by 
single  words,  or  by  arbitrary  words  or 
syllables. 

Cipher  Message. — A  code  message. 

Circle  of  Reference. — A  circle  by  refer- 
ence to  which  simple-harmonic  motion 
may  be  studied  by  comparison  with  uni- 
form motion  around  such  circle. 

Circuit  Breaker. — Any  device  for  open- 
ing or  breaking  a  circuit. 

Circuit  Closer. — Any  device  for  making 
or  closing  a  circuit. 

Circuit-Closer  Bell-Pull. — A  device, 
suitable  for  attachment  to  a  mechanical 
door  pull,  which  makes  a  contact  for  the 
ringing  of  an  electric  bell,  without  pre- 
venting the  original  bell  from  being 
operated  by  the  mechanical  pull. 

Circuit,  Electric. — The  path  in  which 
electricity  circulates  or  passes  from  a 
given  point  around  or  through  a  conduct- 
ing path  back  again  to  its  starting-point. 

Circuit  Indicator. — A  rough  form  of  gal- 
vanometer employed  to  indicate  the  pres- 
ence and  direction  of  a  current  in  a  cir- 
cuit, and,  in  some  cases,  to  roughly  indi- 
cate its  strength. 

Circuit  Loop-Break. — A  device  for  in- 
troducing a  loop  into  any  part  of  an 
aerial  line  circuit. 

Circuit  Loop-Break  Insulator. — An  in- 
sulator employed  in  a  circuit  loop-break. 

Circuital. — (1)  Of  or  pertaining  to  a  cir- 
cuit. (2)  Flowing  or  passing  in  a  closed 
circuit. 

Circuital  Flux. — (1)  A  term  sometimes 
employed  for  circular  flux.  (2)  The  flux 
surrounding  any  circuit.  (3)  Flux  com- 
pleting a  closed  circuit. 

Circuital  G-aussage. — The  gaussage  as 
measured  once  completely  around  a 
closed  magnetic  circuit. 

Circuital  Vector. — A  vector  quantity 
which  does  not  terminate  in  space  but 
forms  a  closed  curve  or  endless  chain. 

Circuital  Voltage.— The  voltage  as  meas- 
ured around  a  closed  circuit. 

Circuitation.— The  line  integral  of  a 
vector  quantity  taken  around  a  circuit. 


Circular  Bell.— A  term  sometimes  applied 
to  a  bell  so  constructed  that  all  of  its 
moving  parts  are  contained  in  the  gong. 

Circular  Current. — A  current  flowing 
through  a  circular  path. 

Circular  Flux. — (1)  A  term  sometimes 
employed  for  the  concentric  circular  flux 
which  surrounds  an  active  cylindrical 
wire  or  conductor.  (2)  Generally,  cir- 
cuital flux. 

Circular  Magnetic  Flux. — Circular  flux. 

Circular  Magnetism.— (1)  The  magnet- 
ism of  a  cylindrical  rod  of  iron  or  steel  one 
of  whose  poles  extends  circumferentially 
around  the  rod  while  the  other  pole  is 
situated  at  and  around  its  centre.  (2)  A 
circular  distribution  of  magnetic  flux. 

Circular  Magnetization. — The  magnet- 
ization producing  circular  magnetism. 

Circular  Mil. — (1)  A  unit  of  area  employed 
in  measuring  the  cross-section  of  wires, 
equal,  approximately,  to  0.7854  square 
mils.  (2)  The  area  of  a  circle  one  mil  in 
diameter. 

Circular  Millage. — The  areas  of  cross- 
sections  of  wires  or  conductors  expressed 
in  circular  mils. 

Circular  Scratch  Brush.— A  scratch 
brush  of  circular  shape,  'suitable  for 
being  set  in  rapid  rotation  by  a  lathe. 

Circular  Touch. — A  method  of  magnet- 
ization by  touch  in  which  four  bars  are 
placed  in  the  form  of  a  rectangle  and  the 
magnetizing  magnet  is  placed  in  contact 
at  any  point,  drawn  around  the  rectangle 
a  number  of  times,  and  removed  at  the 
point  where  its  motion  began. 

Circular  Type  of  Periodically  Alter- 
nating E.  M.  F. — A  periodically  alter- 
nating E.  M.  F.  having  a  curve  whose 
values  in  different  parts  of  a  cycle  are 
such  that  when  plotted  in  a  curve  they 
will  produce  a  circular  outline. 

Circular  Units  of  Area. — Various  units 
employed  for  measuring  areas  of  cross- 
section  by  reference  to  the  area  of  a  unit 
circle,  such,  for  example,  as  the  circular 
mil. 

Circulating  Power.— A  term  employed 
by  Hopkinson  for  the  method  of  taking 
power  out  of  a  machine  as  a  motor  and 
utilizing  this  power  to  drive  the  generator 
with  which  it  is  connected. 

Circumferential  Speed. — The  speed  of 
any  point  on  the  circumference  of  a  ro- 
tating wheel  or  armature. 

Circumflux. — A  term  sometimes  employed 
for  the  product  of  armature  current  and 
the  total  number  of  armature  conductors 
divided  by  the  number  of  poles. 


Cla.] 


714 


[Clo. 


Clamp  for  Arc  Lamps. — (1)  A  device  for 
gripping  the  lamp  rod  of  an  arc-lamp. 
(2)  The  carbon  clutch  or  clamp  of  an  arc- 
lamp. 

Clamp  Splicing-Ear. — A  trolley  splicing 
ear  in  which  the  two  ends  of  the  wire  are 
placed  in  the  jaws  of  a  clamp  and  then 
pressed  together  and  secured  by  a  bolt. 

Clamp  Terminals. — Simple  screw-clamps 
serving  as  terminals  for  connecting  the 
ends  of  flexible  cords  or  other  wires. 

Clark  Element.  —  A  name  sometimes 
given  to  a  Clark  standard  voltaic  cell. 

Clark's  Compound. — A  bituminous  and 
siliceous  compound  employed  on  the 
outer  casing  of  the  sheathing  of  a  sub- 
mai'ine  cable. 

Clark's  Standard  Voltaic  Cell.— A  form 
of  zinc-mercury  couple  employed,  in  con- 
nection with  electrolytes  of  mercurous 
sulphate  and  zinc  sulphate,  as  a  standard 
cell. 

Clay  Electrode. — A  therapeutic  electrode 
of  clay  shaped  so  as  to  fit  the  part  of  the 
body  to  be  treated. 

Clearance. — The  gap  space  between  the 
surface  of  a  rotating  armature  and  the 
opposed  polar  surface  of  the  field  magnets 
of  a  dynamo  or  motor. 

Clearance  Space. — The  clearance. 

Clearing. — In  telephony,  the  operation  of 
disconnecting  subscribers  who  have  been 
in  connection,  and  restoring  the  lines  to 
their  normal  conditions. 

Clearing-Out  Drops.  —  (1 )  Electro-mag- 
netic drop-shutters  placed  in  a  telephone 
exchange  in  circuit  with  a  pair  of  com- 
municating subscribers,  so  that  the  fall- 
ing of  the  shutter  when  they  "  ring  off  " 
indicates  that  the  conversation  is  ended. 
(2)  Ring-off  drops. 

Clearing-Out  Relays. — Relays  provided 
for  operating  clearing-out  drops. 

Clearing  Signal.— (1)  A  ring-off  signal. 

.  (2)  A  signal  in  a  telephone  exchange  to 
indicate  that  a  telephonic  conversation 
lias  ended. 

Cleat  Wiring. — Placing  or  establishing 
electric  conductors  or  wires  on  walls  or 
ceilings  by  means  of  suitably  shaped  in- 
sulating cleats. 

•Cleat,  Electric. — A  suitably  shaped  piece 
of  wood,  porcelain,  hard-rubber  or  other 
non-conducting  material  used  for  fasten- 
ing and  supporting  electric  conductors  to 
ceilings  and  walls. 

Cleavage  Electricity. — Electrification 
produced  by  the  cleavage  of  crystalline 
substances. 


Clepsydra,  Electric. — An  instrument  for 
measuring  time  by  the  escape  of  water  or 
other  liquid  under  electric  control. 

Click  Wire. —  (1)  A  wire  of  a  multiple 
telephone  switchboard  employed  for  the 
engaged  test,  by  which  a  click  is  heard 
in  the  operator's  telephone  when  the  sub- 
scriber asked  for  is  busy.  (2)  The  busy 
test  wire. 

Clip. — A  slight  break  in  signalling  where- 
by a  signal  is  unduly  shortened,  that  is 
likely  to  occur  with  an  imperfect  adjust- 
ment of  duplex  or  quadruplex  telegraphy. 

Clip  Switch. — A  switch  in  which  the 
switch-lever  enters  the  base  of  a  clip. 

Clipping  of  Telegraphic  Signal.— The 
curtailing  of  a  telegraph  signal  due  to 
defective  adjustments  or  to  disturbances 
on  the  line. 

Clock,  Electric. — A  clock  the  works  of 
which  are  moved,  controlled  or  regulated, 
either  entirely  or  partially,  by  the  electric 
current. 

Clock  Meter. — An  electric  meter  in  which 
clock-work  is  employed. 

Clock  Register. — A  register  employed 
in  connection  with  a  clock  for  recording 
the  time  of  an  occurrence. 

Clockwise  Motion. — A  rotary  motion 
whose  direction  is  the  same  as  that  of  the 
hands  of  a  clock,  viewed  from  the  face. 

Clockwork  Feed  for  Arc  Lamps. — An 
arc-lamp  mechanism  in  which  one  or  both 
carbons  are  fed  by  trains  of  wheel 
work. 

Closed  Car-Wheel. — A  car-wheel  in 
which  the  portion  of  the  wheel  between 
the  flange  and  the  axle  is  formed  of  an 
imperforate  mass. 

Closed  Circuit. — A  completed  circuit. 

Closed  -  Circuit  Burglar-Alarm. — A 
burglar  alarm  that  is  normally  on  closed 
circuit,  and  which  operates  on  the  open- 
ing of  the  circuit  by  the  opening  of  the 
contacts. 

Closed-Circuit  Signalling. — A  system 
of  single-circuit  signalling  in  which  the 
sending  batteries  are  placed  at  each  end 
of  the  line  and  are  so  connected  as  to 
remain  always  in  circuit. 

Closed-Circuit  Thermostat. — A  ther- 
mostat maintained  normally  on  closed 
circuit. 

Closed-Circuit  Transformer.— A  term 
sometimes  employed  for  closed  iron-cir- 
cuit transformer. 

Closed-Circuit  Voltaic  Cell  or  Bat- 
tery.— A  voltaic  cell  or  battery  that  can 
be  left  for  a  considerable  time  on  a  closed 


Clo.] 


715 


[Cod. 


circuit  of  comparatively  small  resistance 
without  serious  polarization. 
Closed-Circuit  Voltmeter.  —  A  volt- 
meter intended  to  be  in  permanent  con- 
nection with  the  pressure  it  is  designed 
to  measure. 

Closed-Circuited. — Placed  in  a  closed  or 
completed  circuit. 

Closed-Circuited  Conductor. — A  con- 
ductor connected  in  a  closed  or  completed 
.circuit. 

Closed-Circular  Current.  —  A  current 
flowing  in  a  circular  circuit. 

Closed-Circular  Solenoid. — A  circular 
solenoid  closed  upon  itself  so  as  to  form  a 
tore. 

Closed-Coil  Armature.— (1)  An  armature 
the  coils  of  which  are  never  on  open  cir- 
cuit during  rotation.  (2)  A  dynamo  ar- 
mature whose  coils  are  grouped  in  sec- 
tions and  connected  with  successive  bars 
of  a  commutator,  so  as  to  be  continuously 
connected  together  in  a  closed  circuit. 

Closed-Coil  Winding. —  Any  winding 
by  which  the  armature  coils  are  connect- 
ed in  closed  circuit  during  the  operation 
of  the  machine. 

Closed-Conducting  Sheath  for  Light- 
ning Protector.— A  method  for  light- 
ning protection  consisting  in  forming  a 
wire-sheathing  or  netting  around  the  ob- 
ject to  be  protected. 

Closed   Iron -Circuit  Transformer. — 

(1)  A  transformer,  the  core  of  which  forms 
a  completed  magnetic  circuit.  (2)  An 
iron-clad  transformer. 
Closed  Iron  -  Magnetic  Circuit.  —  A 
magnetic  circuit  all  of  whose  path  is 
completed  by  iron. 

Closed  Loop. — A  single  loop  of  wire  or 
conductor  placed  on  a  closed  circuit.  * 

Closed  -  Loop  Parallel  -  Circuit.  —  A 
variety  of  parallel  circuit  in  which  both 
the  leading  and  returning  conductors  form 
closed  loops,  between  which  the  trans- 
lating devices  are  bridged. 

Closed  Magnetic  Circuit.— A  magnetic 
circuit  which  lies  wholly  in  iron  or  other 
substance  of  high  magnetic  permeability. 

Closed  Magnetic  Circuit  of  Atom.— A 
closed  magnetic  circuit  whose  flux  is 
supposed  to  lie  entirely  within  the  atom. 

Closed-Magnetic  Circuit  of  Molecule. 
A  closed  magnetic  circuit  assumed  to 
lie  wholly  within  the  molecule. 

Closed  Magnetic  Core.— A  magnetic 
core  so  shaped  as  to  provide  a  complete 
iron  path  or  circuit  for  the  magnetic  flux 
of  its  field. 


Closet  System  of  Parallel  Distribu- 
tion.— A  system  of  parallel  distribution 
and  house  wiring  in  which  the  various 
receptive  devices  are  collected  in  groups 
each  of  which  is  supplied  with  a  separate 
and  independent  supply  circuit  back  to 
the  service  ;  as  distinguished  from  a  tree 
system. 

Closed  Trolley  Car.— A  trolley  car  en- 
closed from  the  outer  air  as  distinguished 
from  an  open  or  summer  car. 

Closure. — The  completion  of  an  electric 
circuit. 

Clown's  Hat  Curve.— A  curve  of  current 
or  electromotive  force  in  which  the  pres- 
sure generated  increases  or  decreases  at 
a  rapid  rate  of  change,  and  whose 
shape  is  somewhat  similar  to  the  shape  of 
a  peaked  hat  or  a  clown's  hat. 

Club  -  Footed     Electro-Magnet.  —  An 

electro-magnet  whose  core  is  in  the  form 
of  a  horse-shoe  and  is  provided  with  a 
magnetizing  coil  on  one  pole  only. 
Cluster  Call.— A  globe  of  metal  from 
which  a  cluster  of  incandescent  lamps 
radiate. 

Clutch  for  Arc  Lamps.  —  A  carbon 
clutch  or  clamp  for  arc  lamps. 

Clutching  Device.— (1)  Any  device  em- 
ployed for  clutching  or  holding  the  car- 
bons in  an  arc-lamp.  (2)  A  device  for 
clutching  or  holding  any  object  subjected 
to  occasional  motion. 

Coarse  Winding  of  Field  Magnets. — 
The  series-winding  of  a  compound-wound 
machine. 

Co-acting. — Acting  simultaneously  or  to- 
gether. 

Coating. — An  adherent  layer  or  covering. 

Coating  of  Condenser. — A  sheet  of  tin 
foil  placed  on  ona  side  of  a  Leyden  jar  or 
condenser,  directly  opposite  a  similar  sheet 
on  the  other  side,  for  the  purpose  of 
receiving  and  collecting  an  electric 
charge. 

Coatings  of  Leyden  Jar.— The  sheets  of 
tin  foil  or  other  conductor  placed  on  op- 
posite sides  of  a  Leyden  jar  or  condenser. 

Code  Name. — In  telegraphy,  the  symbol, 
word,  or  group  of  letters,  standing  for, 
or  representing  the  name  of  some  person, 
association,  or  thing,  according  to  a  pre- 
arranged code. 

Code  or  Coded  Telegraphy. — A  system 
of  telegraphy  employed  for  sending  de- 
spatches in  which  the  time  required  for 
transmitting  is  considerably  decreased 
by  employing  code  words  instead  of  the 
actual  words  of  the  message. 


Cod.] 


716 


[Coi. 


Coded  Telegraph  Messages  or  Code 
Messages. — Messages  that  are  sent  by 
the  use  of  prearranged  words,  any  one  of 
which  may  stand  for  a  group  of  words, 
a  phrase,  or  a  complete  sentence. 

Code  Time. — In  telegraphy,  the  code  sig- 
nals in  the  preamble  of  a  message  which 
signify  and  indicate  the  time  at  which  the 
message  was  received  for  transmission. 

Coefficient  of  Electro-Magnetic  Iner- 
tia.— A  term  sometimes  employed  in 
place  of  the  coefficient  of  inductance  or 
self-inductance  of  a  circuit. 

Coefficient  of  Expansion.— The  frac- 
tional increase  in  the  length  of  a  bar  or 
rod,  when  heated  from  32  to  33  degrees 
Fahr. ,  or  from  0  to  1  degree  Cent. 

Coefficient  of  Hysteresis.— (1)  The  work 
expended  hysteretically  in  a  cubic-centi- 
metre of  iron, or  other  magnetic  substance, 
in  a  single  cycle  of  unit  magnetic  flux 
density.  (2)  The  coefficient  which  multi- 
plied by  the  volume  of  iron,  the  frequency 
of  alternation,  and  the  l-6th  power  of  the 
maximum  flux  density  gives  the  hyster- 
etic  activity. 

Coefficient  of  Inductance.— (1)  A  con- 
stant quantity  such  that,  when  multiplied 
by  the  current  strength  passing  through 
any  coil  or  circuit,  will  numerically  rep- 
resent the  flux  linkage  with  that  coil  or 
circuit  due  to  that  current.  (2)  A  term 
sometimes  used  for  coefficient  of  self-in- 
duction. (3)  The  ratio  of  the  C.  E.  M.  F. 
of  self-induction  in  a  coil  or  circuit  to 
the  time-rate-of-change  of  the  inducing 
current. 

Coefficient  of  Induction. — A  term  some- 
times used  for  coefficient  of  magnetic  in- 
duction. 

Coefficient  of  Magnetic  Induction. — 
(1)  A  term  sometimes  used  instead  of 
magnetic  permeability.  (2)  The  ratio 
between  the  quantity  of  magnetic  flux 
that  passes  through  any  area  of  normal 
cross-section  of  a  magnetic  circuit  and 

'  the  magnetizing  force  producing  that 
flux. 

Coefficient    of  Magnetic    Leakage. — 

(1)  The  ratio  of  the  flux  through  a  leakage 
path  to  the  flux  through  an  armature. 

(2)  The  ratio  of  the  mutual  induction  in 
a  transformer  as  reduced  by  magnetic 
leakage  to  the  mutual  induction  in  the 
absence  of  magnetic  leakage. 

Coefficient  of  Magnetization.— A  num- 
ber representing  the  intensity  of  magneti- 
zation produced  in  a  magnetizable  body 
divided  by  the  magnetizing  force,  and 
usually  represented  by  the  symbol  K. 


Coefficient  of  Mutual  Inductance.— 

(1)  The  ratio  of  the  electromotive  force 
induced  in  a  circuit  to  the  rate-of -change 
of  the  inducing  current  in  a  magnetically 
associated  circuit.  (2)  The  ratio  of  the 
total  flux-linkage  with  a  circuit  proceed- 
ing from  an  associated  inducing  circuit, 
to  the  strength  of  current  flowing  in  the 
latter. 

Coefficient  of  Mutual  Induction.— The 

coefficient  of  mutual  inductance. 

Coefficient  of  Potential.— (1)  A  co- 
efficient which  multiplied  into  the  charge 
of  a  body  gives  its  potential.  (2)  The  ratio 
of  the  potential  of  an  electrified  body  to 
its  charge,  when  all  neighboring  bodies 
are  uncharged. 

Coefficient  of  Reflection. — The  percent- 
age value  expressing  the  ratio  of  the 
intensity  of  the  reflected  ray  to  the  in- 
tensity of  the  incident  ray. 

Coefficient  of  Self-induction.— (1)  Self- 
inductance.  (2)  The  ratio  in  any  circuit 
of  the  flux  induced  by  and  linked  with  a 
current,  to  the  strength  of  that  current. 
(3)  The  ratio  in  any  circuit  of  the  E.  M. 
F.  of  self-induction  to  the  rate-of-change 
of  the  current. 

Coercitive  Force. — A  name  sometimes 
employed  for  coercive  force. 

Coercive  Force. — (1)  The  power  of  resist- 
ing changes  in  magnetization.  (2)  In 
cyclic  magnetization  the  demagnetizing 
force  which  must  be  applied  to  a  mag- 
netic substance  in  order  to  completely 
demagnetize  it. 

Coherer. — A  detector  of  electro-magnetic 
waves  consisting  of  conducting  particles 
forming  a  semi-conducting  bridge  be- 
tween two  electrodes. 

Coil  and  Plunger  for  Electro-Magnet. 
A  movable  iron  core  which  is  attracted 
into  a  hollow  coil  or  solenoid  when  a  cur- 
rent passes  through  said  coil. 

Coil,  Electric. — (1)  A  convolution  of  insu- 
lated wire  through  which  an  electric 
current  may  be  passed.  (2)  A  number  of 
turns  of  wire,  or  a  spool  of  wire,  through 
which  an  electric  current  may  be  passed. 

Coil-Heater,  Electric. — A  heater  whose 
heat  is  obtained  by  the  passage  of  an 
electric  current  through  a  suitably  sup- 
ported coil  of  wire. 

Coil  Winding. — Loop  or  lap  winding. 

Coil  Winding  of  Alternator. — (1)  A 
form  of  winding  applied  to  the  armature 
of  an  alternator  in  which  the  wire  is 
made  into  coils  that  are  laid  upon  the 
surface  of  the  armature  core.  (2)  A  term 
sometimes  used  for  loop  winding. 


Coi.] 


717 


[Com. 


Coiling  Space  of  Cable  Tank.— The 
space  provided  in  a  cable  tank  for  the  re- 
ception of  a  cable. 

Coked  Core  of  Incandescent  Filament. 
An  incandescent  lamp  filament  formed 
of  a  core  -of  electrically  coked  carbon 
whose  surface  is  covered  with  a  deposit 
of  carbon  by  the  flashing  process. 

Coked  Filament. — A  carbon  filament  for 
an  incandescent  lamp  that  has  been  so  sub- 
jected to  electrical  heating  in  a  vacuum 
as  not  only  to  be  thoroughly  freed  from 
its  occluded  gases  but  also  to  have  its  car- 
bon changed  into  a  variety  of  coke. 

Coking,  Electric. — Subjecting  carbon  to 
the  coking  process. 

Coking  of  Filament. — Subjecting  a  fila- 
ment to  the  coking  process. 

Coking  Process  for  Filament  of  In- 
candescent Lamp. — A  process  for 
converting  the  carbon  of  an  incandescent 
filament  into  coke  by  subjecting  it,  while 
in  a  vacuum,  to  the  prolonged  heating 
action  of  a  powerful  electric  current. 

Cold  Light. — (1)  Luminous  radiation 
unaccompanied  by  obscure  radiation. 
(2)  Radiation  confined  within  the  limits  of 
the  visible  spectrum.  (3)  The  light  of  a 
fire-fly  or  glow-worm. 

Collapsing  Drum. — A  visual-signal  drum 
capable  of  manual  distension  and  collapse. 

Collation. — The  repetition  of  a  message  or  • 
important  parts  of  the  same  by  an  oper- 
ator at  a   telegraph  station  who  has  re- 
ceived it  over  the  line,  to  the  transmitting 
operator  at  the  sending  station. 

Collecting  Ammeter — An  ammeter  in  a 
central  station  which  collects,  and,  there- 
fore, indicates  the  total  current  received 
from  two  or  more  separate  generators, 
and  usually  employed  to  indicate  the  total 
current  output  of  a  station. 

Collecting  Brushes  of  Dynamo-Elec- 
tric Machine. — Conducting  brushes 
which  bear  on  the  commutator  cylinder 
of  a  dynamo  and  carry  off  the  current 
generated  by  the  E.  M.  F.  in  the  armature 
coils.  (2)  The  brushes  which  bear  on 
the  collecting  rings  of  an  alternator 
armature. 

Collecting  Combs. — The  collecting  points 
of  a  frictional  electric  machine,  or  of  an 
electrostatic  induction  machine. 

Collecting  Panel. — A  panel  in  a  switch- 
board which  collects  all  the  current  sup- 
plied by  the  generators  connected  to  that 
switchboard. 

Collecting   Rings   for   Alternators.— 

Metallic  rings  connected  with  the  ter- 
minals of  the  armature  coils  of  an  alter- 


nator on  which  brushes  rest  to  carry  off 
the  alternating  currents. 
Collectors,  Electric. — Devices  employed 
for  collecting  electricity  from  a  moving 
electric  source. 

Collectors  of  Alternators. — The  collect- 
ing rings. 

Collectors  of  Dynamo-Electric  Ma- 
chine.— The  brushes  that  rest  on  the 
commutator  cylinder  and  carry  off  the 
current  generated  on  the  rotation  of  the 
armature. 

Collectors  of  Frictional  Electric  Ma- 
chine.— The  metallic  points  that  collect 
the  charge  from  the  glass  plate  or  cylin- 
der of  a  frictional  electric  machine. 

Colloids. — One  of  the  two  classes  into 
which  substances  are  separated  by  dial- 
ysis. 

Colombin. — An  insulating  substance  con- 
sisting of  a  mixture  of  sulphates  of  barium 
and  calcium  placed  between  the  parallel 
carbons  of  the  Jablochkoff  candle. 

Column,  Electric. — A  term  formerly  ap- 
plied to  a  voltaic  pile. 

Colza  Oil. — The  oil  employed  in  the  Carcel 
standard  lamp. 

Comazant. — (1)  A  term  formerly  applied 
to  a  St.  Elmo's  fire.  (2)  A  corposant. 

Collector  Rings. — The  collecting  rings 
of  an  alternator. 

Comb  Lightning-Arrester. — A  form  of 
lightning-arrester  in  which  the  line  wires 
are  connected  to  two  metallic  plates  pro- 
vided with  serrations  like  the  teeth  of  a 
comb,  and  placed  near  to  another  ground- 
connected  plate,  which  may  or  may  not 
be  furnished  with  similar  serrations. 

Comb  of  Storage  Battery. — The  grid  of 
a  storage  battery. 

Comb  Protector. — A  comb  lightning-ar- 
rester. 

Combination  Anchor-Poles. —  (1)  An 
anchor  pole  intended  for  the  support  of 
both  aerial  wires  and  aerial  cables.  (2)  A 
composite  anchor-pole. 

Combination  Bracket. — (1)  A  bracket 
for  supporting  a  pair  of  insulators  side  by 
side.  (2)  A  bracket  for  supporting  both 
a  gas  lamp  and  an  incandescent  lamp. 

Combination  Fittings  for  Chandeliers. 
Fittings  that  provide  for  the  use  of  both 
gas  and  electricity. 

Combination  Gas-Fixtures. — Combina- 
tion fittings. 

Combination    Lightning-Protector. — 

A  form  of  combined  film  and  fuse  light- 
ning-protector   employed    on    telephone 


Com.] 


718 


[Com. 


circuits,  arranged  so  as  to  ground  the  cir- 
cuit either  under  the  action  of  high  pres- 
sures, or  under  the  action  of  an  unduly 
strong  current. 

Combination  Line-Protector. — A  com- 
bination lightning-protector. 

Combination  Protector. — A  combination 
lightning-protector. 

Combination  Rheostat. — A  form  of  box 
rheostat,  or  resistance  box,  which  con- 
tains within  its  cover  several  separate 
series  of  resistance  coils. 

Combination  Triphase- Winding.  —  A 
triphase  winding  combining  both  the  star 
winding  and  the  triangular  winding. 

Combined  Fibre  and  Spring  Suspen- 
sion.— A  suspension  of  a  needle  by  the 
combined  use  of  a  spiral  spring  and  a 
single  fibre. 

Combined  Tangent  and  Sine  Galvano- 
meter.— A  galvanometer  furnished  with 
two  magnetic  needles  of  different  lengths, 
one  a  small  needle  for  tangent  measure- 
ments, and  the  other  a  long  needle  for 
sine  measurements. 

"  Come  Along." — A  small  portable  vise 
capable  of  ready  attachment  to  an  aerial 
telegraph  or  telephone  cable,  and  used  in 
connection  with  a  line  dynamometer  to 
pull  up  the  wire  to  its  proper  tension. 

Commercial  Efficiency. — The  useful  or 
available  energy  produced  by  any  ma- 
chine or  apparatus  divided  by  the  total 
energy  it  absorbs. 

Commercial  Efficiency  of  Dynamo,  or 
Generator. — The  ratio  of  the  output  of 
a  dynamo,  or  the  useful  and  available 
electric  energy  delivered  at  its  terminals, 
divided  by  its  intake,  or  the  mechanical 
energy  required  to  drive  it. 

Commercial  Efficiency  of  Motor.— The 
ratio  between  the  mechanical  activity 
developed  at  a  motor  pulley  and  the  elec- 
tric activity  absorbed  at  its  terminals. 

Common  Arc  of  Aurora  Glory. — The 
inner  or  common  arc  of  an  aurora  glory. 

Common  Return. — A  return  conductor 
common  to  several  circuits. 

Common  Side  of  Quadruplex  System. 
In  quadruplex  telegraphy,  the  neutral  or 
No  2.  side,  as  distinguished  from  the  polar 
or  No  1.  side. 

Communicator,  Electric. — A  term  for- 
merly employed  for  a  telegraphic  key. 

Commutating  Machine. — A  rotary 
transformer. 

Commutation. — The  act  of  commuting  or 
causing  a  number  of  electromotive  forces 


or  currents  to  take  one  and  the  same 
direction. 

Commutation  Fringe. — A  term  em- 
ployed for  the  induction  produced  by  an 
edge  or  fringe  of  the  magnetic  flux  at  the 
pole  tip,  under  which  commutation  takes 
place. 

Commutator. — (1)  Any  device  for  chang- 
ing in  one  portion  of  a  circuit  the  direc- 
tions of  electromotive  forces  or  currents 
in  another  portion.  (2)  A  device  for 
changing  alternating  into  continuous 
currents,  or  vice  versa. 

Commutator. — A  name  sometimes  given 
to  a  universal  switch  or  pin  switchboard. 

Commutator  Bar. — One  of  the  insulated 
segments  of  a  commutator. 

Commutator  Coils. — Coils  wound  around 
an  armature  core  for  the  purpose  of  pre- 
venting sparking,  connected  at  one  of 
their  ends  to  the  main  windings  at  points 
between  the  coil  sections,  and  at  the 
other  end  to  the  commutator  segments. 

Commutator  Motor.— An  alternating, 
current  motor  in  which  the  armature  is 
provided  with  a  commutator. 

Commutator  of  Dynamo-Electric  Ma- 
chine.— The  device  employed  to  cause 
the  electromotive  forces  generated  in  an 
armature,  on  its  rotation  in  the  magnetic 
field,  to  take  one  and  the  same  direction 

•     externally. 

Commutator  Press  Button.— A  press 
button  employed  in  a  system  of  telephony, 
at  a  subscribers'  station,  for  calling  the 
central  station  by  reversing  a  battery. 

Commutator  Segments  or  Strips. — The 
insulated  bars  of  a  commutator. 

Commutatorless. — Devoid  of  a  commu- 
tator. 

Commutatorless  Continuous-Current 
Dynamo. — (1)  A  dynamo  that  furnishes 
continuous  currents  without  the  aid  of  a 
commutator.  (2)  The  so-called  unipolar 
dynamo. 

Commuted. — Caused  to  take  one  and  the 
same  direction. 

Commuted  Currents  or  Electromotive 
Forces. — Currents  or  electromotive 
forces  that  have  undergone  commutation. 

Commuted  Magneto-Generator.— A 
magneto-generator  whose  currents  are 
commuted. 

Commutated. — Commuted. 

Commutating. — Commuting. 

Commuting. — Changing  direction. 

Commuting  Transformer.— A  rotarj 
commutator. 


Com.] 


719 


[Com. 


Companion  Loops. — A  pair  of  telegraphic 
loop-circuits,  connecting  a  pair  of  branch 
offices  with  the  main  office,  in  which  there 
is  a  duplex  set,  so  connected  therewith, 
that  the  instruments  at  the  branch  offices 
are  made  the  virtual  duplex  instruments 
of  the  main  station  ;  one  branch  office 
sending  while  the  other  is  receiving. 

Comparator. — An  apparatus  for  compar- 
ing standards  of  lengths  or  gauges. 

Compartment  Man-Hole  of  Conduit. 
A  man-hole  provided  with  suitably  sup- 
ported shelves  or  compartments  that  pro- 
tect different  cable  sections. 

Compass. — A  mariner's  compass. 

Compass  Card. — A  card  used  in  a  mari- 
ner's compass  on  which  are  marked  the 
four  cardinal  points  of  the  compass ; 
North,  South,  East  and  West,  and  again 
sub-divided  into  32  points  called  rhumbs, 
and  also  frequently  divided  circumferen- 
tially  into  degrees. 

Compass  Sights. — Small  holes  or  narrow 
slits  made  in  opaque  plates,  affixed  to  the 
compass  box,  for  use  in  taking  bearings. 

Compensated  Alternator. — An  alterna- 
tor employed  for  sustaining  a  uniform 
voltage  at  some  point  of  its  circuit  under 
varying  loads,  whose  field  magnets  are 
excited  partly  by  constant  currents  taken 
from  a  separate  generator,  and  partly  by 
currents  supplied  by  the  load  current  in 
the  armature. 

Compensated  Excitation  of  Alterna- 
tor.— The  excitation  of  an  alternating- 
current  dynamo  whose  field  is  partly  sep- 
arately excited,  and  partly  excited  from 
the  main  circuit  of  the  machine. 

Compensated  Galvanometer. — A  dif- 
ferential- galvanometer  for  indicating 
pressure  at  a  distant  point  of  a  continu- 
ous-current circuit,  having  one  coil  in 
shunt  and  the  other  in  series  with  said 
circuit. 

Compensated  Meter-Bridge. — A  meter- 
bridge  so  arranged  that  its  indications 
are  compensated  for  the  effects  of  tem- 
perature. 

Compensated  Besistance-Coil. — A  re- 
sistance-coil so  arranged  as  to  be  compen- 
sated for  the  effect  of  temperature  upon 
its  resistance. 

Compensated  System  of  Currents. — 
In  telegraphy  with  the  Wheatstone  auto- 
matic apparatus,  a  system  of  double-cur- 
rent signalling  in  which  both  the  initial 
and  final  currents  are  weakened  before 
removal  by  the  interposition  of  a  resist- 
ance in  the  battery  circuit. 

Compensated   Voltmeter. — A   central- 


station  voltmeter  connected  to  the  bus- 
bars in  such  a  manner  that  its  indications 
are  automatically  corrected  for  the  drop  of 
pressure  in  some  particular  feeder  or  group 
of  feeders,  so  that  its  readings  correspond 
to  the  pressure  supplied  to  the  mains. 

Compensated  "Wattmeter. — A  watt- 
meter so  wound  as  to  be  compensated  for 
the  effect  of  reactance  in  its  shunt  circuit. 

Compensated  Coils. — A  term  sometimes 
applied  to  the  series  coils  placed  on  a 
shunt- wound  machine. 

Compensated  Condenser. — A  condenser 
employed  in  duplex  telegraphy  to  give  to 
the  artificial  line  a  static  capacity  equal 
to  that  of  the  main  line. 

Compensated  Potential-Indicator. — A 
compensated  voltmeter. 

Compensating  Line. — An  artificial  line 
employed  in  duplex  telegraphy. 

Compensating  Magnet.  —  A  magnet 
placed  over  a  galvanometer  or  other 
needle,  for  the  purpose  of  varying  the  di- 
rection and  intensity  of  the  earth's  mag- 
netic force  on  such  needle. 

Compensating  Pole. — A  small  bar  elec- 
tro-magnet, or  electro-magnetic  coil, 
placed  perpendicularly  between  the  pole- 
pieces  of  a  dynamo  to  compensate  for  the 
cross  magnetization  of  the  armature  cur- 
rents. 

Compensating  Wire. — In  a  system  of 
differential  duplex  telegraphy,  the  arti- 
ficial line  or  wire,  as  distinguished  from 
the  real  line  or  wire. 

Compensation  Photometer. — (1)  A  pho- 
tometer in  which  the  illumination  of  the 
two  parts  of  the  photometer  screen  is 
equalized  by  diminishing  the  intensity  of 
the  pencil  of  light  by  polarization.  (2)  A 
polarization  photometer. 

Compensator. — An  auto-transformer. 

Compensator  for  Alternating-Current 
Lamps. — A  choking  coil  or  compensator, 
placed  in  circuit  with  the  lamps  in  an 
alternating-current  circuit,  for  the  pur- 
pose of  automatically  regulating  the  cur- 
rent strength  in  the  lamps. 

Compensator  System.— A  system  of  al- 
ternating-current electric  distribution 
from  high-pressure  mains  to  low-pressure 
translating  devices,  in  which  the  latter 
are  connected  in  derived  circuits  between 
sections  of  choking  coils  connected  across 
the  mains. 

Complement  of  Angle.— What  an  angle 
lacks  to  make  its  value  equal  to  90°,  or 
a  right  angle. 

Complete  Fault.— Any  fault  which  com- 
pletely interrupts  telegraphic  or  telephon- 


Com.] 


720 


[Com. 


ic  communication  as  distinguished  from  a 
partial  fault. 

Complete  Wave.— (1)  Two  successive  al- 
ternations, or  a  double  alternation  of  a 
periodically-alternating  quantity.  (2)  A 
cycle. 

Completed  Circuit.— (1)  A  closed  cir- 
cuit. (2)  A  circuit  whose  conducting 
continuity  is  unbroken. 

Completing  a  Circuit. — Closing  a  circuit. 

Complex  Distribution  of  Lamellar 
Magnetism. — A  distribution  of  the  mag- 
netism of  a  finite  magnet  into  an  infinite 
number  of  complex -magnetic  shells. 

Complex-Harmonic  Motion.  —  Motion 
resulting  from  the  superposition  or  co- 
action  of  a  plurality  of  simple-harmonic 
motions. 

Complex-Harmonic  Alternating  E.  M. 
F.s. — Electromotive  forces  resulting 
from  the  combination  of  a  fundamental- 
harmonic  electromotive  force  and  its 
harmonics. 

Complex-Harmonic 

rents    produced    by 
electromotive  forces. 


Currents.  —  Cur- 
complex-harmonic 


Complex  -  Harmonic  Electromotive 
Forces . — Com plex-harmonic  alternating 
electromotive  forces. 

Complex-Magnetic  Shell.— (1)  A  mag- 
netic shell  whose  strength  varies  from 
one  part  to  another  of  its  surface.  (2)  A 
distribution  of  magnetization  equivalent 
to  an  association  or  superposition  of  a 
number  of  separate  magnetic  shells  of 
arbiti'ary  strength  and  area. 

Complex  Quantities. — Any  quantity 
made  up  of  two  parts,  one  of  which  is 
measured  along  an  axis  of  reference,  and 
the  other  in  a  direction  at  right  angles  to 
such  axis,  these  axes  being  sometimes 
described  as  the  real  and  imaginary  axes 
respectively. 

Component. — One  of  the  two  or  more 
separate  forces  into  which  any  single 
force  may  be  resolved  ;  or,  conversely,  the 
separate  forces  which  together  produce 
any  single  resulting  force. 

Component  Currents.— The  two  or  more 
currents  into  which  it  may  be  conceived 
that  a  single  current  may  be  divided  so 
as  to  be  the  equivalent  "of  that  single 
current. 

Component  Electromotive  Forces.— 
The  two  or  more  E.  M.  F.s  into  which 
any  given  E.  M.  F.  may  be  resolved. 

Component  Inductions.— The  two  or 
more  inductions  into  which  any  given 
magnetic  flux  may  be  resolved  so  as  to  be 
its  equivalent. 


Components  of  Impedance.— The  ener- 
gy component  or  effective  resistance,  and 
the  wattless  component  or  effective  re- 
actance. 

Composite  Anchor-Pole.— A  combina- 
tion anchor-pole. 

Composite  Balance.— A  balance  with  two 
pairs  of  fixed  coils  of  coarse  and  fine  wire 
respectively,  employed  for  measuring 
strong  or  feeble  currents  as  desired. 

Composite  Dynamo. — A  compound- 
wound  dynamo. 

Composite  Excitation. — Any  excitation 
of  the  field  magnets  of  a  dynamo  in  which 
more  than  a  single  winding  is  employed, 
such  as  a  shunt  and  a  series  winding. 

Composite  Field.— The  field  of  a  com- 
positely-excited  dynamo. 

Composite-Field  Dynamo.— (1)  A  dy- 
namo whose  field  has  a  composite  excita- 
tion. (2)  A  dynamo  whose  field  is  com- 
pound wound. 

Composite  Grid. — A  storage-battery  grid 
made  of  a  number  of  sheets  of  lead  foil 
covered  with  graphite,  placed  between 
two  plates  of  sheet  lead  which  are  held 
together  with  lead  rivets. 

Composite     Horse-Shoe    Magnet. — A 

compound  horse-shoe  magnet. 

Composite  Kilo-Ampere  Balance. — A 

balance  form  of  ammeter,  provided  with 
coarse  and  fine  windings,  so  arranged  that 
the  instrument  will  serve  as  a  kilo-ampere 
meter,  as  a  centi-ampere  meter,  or,  as  a 
voltmeter. 

Composite  Wire. — (1)  A  wire  provided 
with  a  steel  core  and  an  external  copper 
sheath,  possessing  sufficient  tensile 
strength  to  enable  it  to  be  u«ed  in  long 
spans  without  excessive  sagging.  (2)  A 
bimetallic  wire. 

Compositely-Excited  Dynamo. — (1)  A 
compound-wound  dynamo.  (2)  A  com- 
posite-field dynamo. 

Composition  of  Forces. — Finding  the 
direction  and  intensity  of  a  single  force 
which  represents  the  total  effect  of  two 
or  more  forces  that  are  acting  simultane- 
ously on  a  body. 

Compound. — An  asphaltic  composition 
employed  in  the  sheathing  of  submarine 
cables. 

Compound  Alternator. — A  compound- 
wound  alternator. 

Compound  Arc. — An  arc  formed  of  mora 

than  two  separate  electrodes. 
Compound  Battery. — A  term  formerly 

employed  for  a  battery  of  voltaic  cells,  as 


t'om.] 


721 


[Con. 


contradistinguished  from  a  single  cell. 
(Obsolete.) 

Compound  Cable. — A  multiple-core  cable. 

Compound  Circuit. — A  circuit  contain- 
ing more  -than  a  single  source,  or  more 
than  a  single  electro-receptive  device,  or 
both.  (Not  in  general  use.) 

Compound  Condenser. — (1)  A  name 
sometimes  given  to  subdivided  condenser. 
(2)  A  composite  condenser. 

Compound  Electro-Magnet. — A  word 
formerly  employed  for  an  electro-magnet 
consisting  of  an  iron  core  wound  with 
two  or  more  separate  magnetizing  cir- 
cuits. (Not  in  general  use.) 

Compound  Magnet. — A  number  of  single 
magnets  placed  parallel,  side  by  side, 
and  with  their  similar  poles  adjacent. 

Compound  Radical.— (1)  A  group  of  un- 
satura ted  atoms.  (2)  A  group  of  elemen- 
tary atoms  some  of  whose  bonds  are  in- 
terconnected or  joined  with  the  bonds  of 
other  atoms. 

Compound  Receiver. — A  telephone  re- 
ceiver employed  by  an  operator  at  a 
central  station,  and  composed  of  two 
separate  telephone  receivers  united  into 
one  common  frame  or  receptacle  with  a 
single  ear- piece,  for  the  purpose  of  afford- 
ing a  separate  distinct  circuit  and  dia- 
phragm, independently  of  the  speaking 
circuit  and  diaphragm. 

Compound  Telegraph-Wire. — A  bi- 
metallic telegraph  wire. 

Compound  Winding. — A  method  of 
winding  dynamos  or  motors  in  which 
both  shunt  and  series  coils  are  placed  on 
the  field  magnets. 

Compound  -  Wound. — (1)  Having  asso- 
ciated shunt  and  series  windings. 
(2)  Compositely  wound. 

Compound-Wound  Alternator. — An 
alternator  whose  fields  are  compound- 
wound. 

Compound-Wound  Continuous-Cur- 
rent Generator. — A  continuous-current 
generator  whose  fields  are  compound- 
wound,  for  the  purpose  of  maintaining 
the  pressure  constant  under  all  loads. 

Compound- Wound  Field. — A  field  pro- 
vided with  compound  windings. 

Compound-Wound  Motor. — A  motor 
whose  field  is  compound  wound,  for  the 
purpose  of  maintaining  its  speed  constant 
under  all  loads. 

Compound- Wound  Voltmeter.— (1)  A 
compensated  voltmeter.  (2)  A  voltmeter 
having  more  than  one  winding. 

Concealed  Wiring. — Interior  wiring 
46 


placed  out  of  sight,  and  either  built  in 
the  plaster  of  a  room  or  carried  through 
suitable  conduits  placed  therein. 
Concentration  of  Lines  of  Force.— 
Any  increase  in  the  intensity  of  a  mag- 
netic flux. 

Concentration  Throw.— The  deflection 
of  a  magnetic  needle  by  a  current,  pro- 
duced under  certain  circumstances  by  a 
couple  formed  of  plates  or  iron  or  other 
paramagnetic  metal,  when  exposed  to 
chemical  action  while  in  a  magnetic  field. 

Concentric  Cable.— (1)  A  cable  provided 
with  both  a  leading  and  return  conductor 
insulated  from  each  other,  and  forming 
respectively  the  central  core  or  conductor, 
and  the  enclosing  tubular  conductor. 
(2)  A  cable  having  concentric  conductors. 

Concentric-Carbon  Electrodes.— Con- 
centric-carbon electrodes  employed  in  a 
modified  form  of  Jablochkoff  candle. 

Concentric  Conductors.  —  Cylindrical 
coaxial  conductors  insulated  from  each 
other. 

Concentric-Cylindrical  Carbons .  —  A 
cylindrical  rod  of  carbon  placed  inside  a 
hollow  cylinder  of  carbon,  but  separated 
from  it  either  by  an  air  space,  or  by  some 
refractory  insulating  material,  employed 
in  a  form  of  Jablochkoff  candle. 

Concentric  Mains. — Mains  employing 
concentric  cables. 

Concentric  Wiring. — Wiring  by  means 
of  concentric  cables. 

Condensance. — Capacity  reactance. 

Condenser. — (1)  A  device  for  increasing 
the  capacity  of  an  insulated  conductor 
by  bringing  it  near  another  earth- 
connected  conductor  but  separated  there- 
from by  any  medium  that  will  permit 
electrostatic  induction  to  take  place 
through  its  mass.  (2)  Any  variety  of 
electrostatic  accumulator. 

Condenser  Capacity. — The  capacity  of  a 
condenser. 

Condenser  Circuit. — Any  circuit  in  which 
a  condenser  is  inserted. 

Condenser  Lightning- A  r  r  e  s  t  e  r.— A 
form  of  lightning  arrester  whose  opera- 
tion depends  on  the  connection  of  a  con- 
denser with  some  part  of  the  circuit  to  be 
protected. 

Condenser  Pressure. — The  difference  of 
potential  at  the  terminals  of  a  condenser. 

Condenser  Rheostat. — A  rheostat  in  the 
circuit  of  a  condenser  in  an  artificial 
line  of  a  duplex  or  quadruplex  system. 

Condenser    Signalling. — Any   form   of 


Con.] 


722 


[Con. 


telegraphic  or  telephonic  signalling  in 
which  condensers  are  employed. 

Condenser  Working. — Condenser  signal- 
ling. 

Condensing  Electroscope. — An  electro- 
scope provided  with  a  condenser  for 
the  purpose  of  rendering  evident  feeble 
charges. 

Conduct. — (1)  To  pass  electricity  through 
conducting  substances.  (2)  To  carry,  or 
to  possess  the  power  of  carrying,  an  elec- 
tric current. 

Conductance. — (1)  A  word  sometimes 
used  in  place  of  conducting  power. 
(2)  The  reciprocal  of  resistance.  (3)  In 
a  continuous-current  circuit  the  ratio  of 
the  current  strength  to  the  E.  M.  F. 
(4)  In  an  alternating-current  circuit  the 
quantity  whose  square  added  to  the' square 
of  the  susceptance  is  equal  to  the  square 
of  the  admittance. 

Conductance,  Electric. — Conducting 
power  for  electricity. 

Conductance  Leak.— A  leak  in  a  cable  or 
circuit  produced  by  conduction  as  dis- 
tinguished from  a  leak  possessing  induc- 
tion. 

Conductibility. — (1)  Possessing  the 
power  of  conducting  electricity.  (2)  Con- 
ductivity. 

Conducting  Cord. — A  small  insulated 
flexible  cable  usually  consisting  of  a 
stranded  conductor  or  conductors. 

Conducting  Cord  Tip. — A  blunted  or 
rounded  conductor  placed  at  one  of  the 
ends  of  a  cord  or  wire  for  the  purpose  of 
readily  inserting  it  into  a  binding  post  or 
into  a  plug  hole. 

Conducting  Loop. — A  loop  of  wire  or 
other  electric  conductor. 

Conducting  Power. — The  ability  pos- 
sessed by  a  given  length  and  area  of 
normal  cross-section  of  a  substance  for  con- 
ducting light,  heat,  electricity,  or  mag- 
netism, as  compared  with  that  possessed 
by  an  equal  length  and  area  of  normal 
cross-section  of  some  other  substance 
taken  as  a  standard. 

Conducting  Power  for  Electricity. — 
The  ability  possessed  by  a  given  length 
and  area  of  normal  cross-section  of  a  sub- 
stance to  conduct  electricity,  as  compared 
with  that  possessed  by  an  equal  length 
and  area  of  normal  cross-section  of  some 
other  substance  taken  as  a  standard, 
such,  for  example,  as  pure  copper. 

Conducting     Power    for    Heat. — The 

ability  possessed  by  a  substance  to  trans- 
mit heat  through  its  mass. 


Conducting  Power  for  Lines  of  Mag- 
netic Force. — (1)  Permeability.  (2)  In- 
due tivity. 

Conduction  Current.— The  current  that 
passes  through  a  metallic  or  other  con- 
ducting substance,  as  distinguished  from 
one  produced  in  a  non-conductor  or 
dielectric. 

Conduction,  Electric. — (1)  The  so-called 
flow  or  passage  of  electricity  through  a 
metallic  or  other  similar  substance. 
(2)  The  ability  of  a  substance  to  determine 
the  direction  in  which  electric  energy 
shall  be  transmitted  through  the  ether 
surrounding  it.  (3)  The  ability  of  a  sub- 
stance to  determine  the  direction  in  which 
a  current  of  electricity  shall  pass  from 
one  point  to  another. 

Conduction  Lightning-Protection.  — 
The  protection  of  any  instrument  from 
the  passage  of  a  current  due  to  lightning 
through  its  coils. 

Conduction  Lightning-Protector.  —  A 
lightning  protector  by  means  of  which  a 
current  is  prevented  from  passing  through 
the  coils  of  a  galvanometer,  or  other 
needle  instrument,  and  thus  injuriously 
disturb  the  magnetism  of  the  needle. 

Conduction  Besistance. — The  resistance 
offered  by  a  conductor  to  an  electric 
current. 

Conductive.  —  Possessing  the  power  of 
conducting. 

Conductive  Discharge. —  A  discharge 
effected  by  leading  the  charge  off  through 
a  conductor  placed  in  contact  with  the 
charged  body,  as  opposed  to  a  convective 
or  disruptive  discharge. 

Conductivity,  Electric. — (1)  The  recip- 
rocal of  electric  resistivity.  (2)  The  con- 
ductance of  a  substance  referred  to  unit 
dimensions. 

Conductivity  Resistance.  —  The  resist- 
ance offered  by  a  substance  to  electric 
conduction,  or  to  the  passage  of  elec- 
tricity through  its  mass. 

Conductor. — (1)  Any  substance  which 
will  permit  the  so-called  passage  of  an 
electric  current.  (2)  A  substance  which 
possesses  the  ability  of  determining  the 
direction  in  which  electric  energy  shall 
pass  through  the  ether  in  the  dielectric 
surrounding  it. 

Conductor  Resistance. — A  term  fre- 
quently employed  for  copper  resistance. 

Conductor  System. — A  net-work  of  in- 
terconnected conductors  employed  for 
distributing  electricity. 

Conduit  Cables. — A  cable  conductor  of 
set  of  conductors  laid  in  a  conduit. 


Con.] 


723 


[Con. 


Conduit  Conductors. — Conductors  in- 
tended for  use  in  underground  circuits, 
provided  with  an  insulation  suitable  to 
maintain  the  electric  integrity  of  the 
separate  circuits. 

Conduit,  Electric. — An  underground 
space,  either  single  or  provided  with  a 
number  of  separate  spaces  called  ducts, 
employed  for  the  reception  of  electric 
wires  or  cables. 

Conduit  Trolley-System. — A  single  or 
double-trolley  system  in  which  the  trolley 
wire  or  wires  are  placed  in  an  under- 
ground slotted  conduit,  the  trolley  wheel 
being  replaced  by  a  plow  or  sled  pushed 
or  drawn  through  the  slot. 

Coned  Plunger  for  Electromagnetic 
S  o  1  e  n  o  i  d. — A  cone-shaped  core,  em- 
ployed in  connection  with  a  solenoid  in- 
stead of  the  ordinary  cylindrical  core,  for 
the  purpose  of  obtaining  a  comparatively 
uniform  pull  through  a  fairly  extended 
movement  of  the  core. 

Conflict,  Electric. — A  term  proposed  for 
the  magnetic  field  surrounding  an  active 
conductor. 

Congelation. — The  act  of  freezing,  or  the 
change  of  a  liquid  into  a  solid  on  loss  of 
heat. 

Conical  Conductor. — (1)  A  cone-shaped 
conductor,  which  gradually  increases  or 
decreases  in  diameter,  thus  assuming  the 
form  of  a  tapering  cone,  employed  to 
obtain  an  approximately  constant  current 
density  through  a  system  of  parallel  dis- 
tribution. (2)  In  practice,  a  cylindrical 
conductor  that  tapers  by  sections,  the 
diameter  being  reduced  in  each  succeed- 
ing length. 

Conjoined  E.  M.  P.'s. — A  number  of  elec- 
tromotive forces  simultaneously  acting 
in  one  circuit. 

Conjugate  Coils. — Two  coils  whose  con- 
ductors are  conjugate  to  each  other. 

Conjugate  Conductors. — (1)  In  a  con- 
ducting net-work,  two  conductors  so  re- 
lated that  the  introduction  of  an  E.  M.  F. 
in  one  produces  no  current  in  the  other. 
(2)  Two  conductors  so  placed  as  regards 
each  other  that  an  interruption  of  the 
current  in  one,  produces  no  induced  cur- 
rent in  the  other. 

Conjugate  Functions. — The  real  and  im- 
aginary components  of  a  function  of  a 
complex  variable. 

Connect. — To  place  or  bring  into  electric 
contact. 

Connecting.— Placing  or  bringing  into 
electric  contact. 


Connecting  Bars. — Metallic  bars  at  a 
call-wire  multiple-switchboard,  for  con- 
necting the  operator's  set  with  the  call- 
wire  jacks  through  a  cord. 

Connecting  In  "Bridge." — A  phrase 
sometimes  employed  for  connecting  in 
multiple  arc  or  parallel. 

Connecting  Jack. — A  jack  for  introduc- 
ing a  loop  into  a  telephone  circuit. 

Connecting  Peg. — A  metallic  block  for 
bridging  an  air  gap  and  so  making  an 
electric  connection. 

Connecting  Screws. — A  term  sometimes 
employed  indifferently  for  connectors  or 
for  binding  posts. 

Connecting  Side  of  Telephone  Switch- 
board.— That  side  of  a  telephone  switch- 
board at  which  connections  are  made 
with  subscribers  wanted,  as  distinguished 
from  the  side  at  which  calls  are  received. 

Connecting  Sleeve. — A  metallic  sleeve 
employed  as  a  connector  for  readily  join- 
ing the  ends  of  two  or  more  wires. 

Connecting-Up.— (1)  In  telegraphy,  join- 
ing up.  (2)  The  operation  of  establishing 
an  electric  circuit. 

Connection. — The  act  of  placing  in  electric 
or  magnetic  contact. 

Connection  Board  of  Transformer. — A 
board  usually  located  in  an  accessible 
place  in  a  transformer  case,  and  provided 
with  binding  posts  for  conveniently  mak- 
ing or  changing  the  connections  of  the 
transformer  coils  with  the  external  cir- 
cuits. 

Connection  for  Intensity. — A  phrase 
formerly  employed  for  connection  in 
series.  (Nearly  obsolete.) 

Connection  for  Quantity. — A  phrase 
formerly  employed  for  connection  in  mul- 
tiple. (Nearly  obsolete.) 

Connection  in  Cascade. — A  term  some- 
times employed  for  connection  in  series. 

Connection  in  Sequence.— A  term  some- 
times used  for  connection  in  series. 

Connection  of  Battery  for  Intensity. 
A  term  formerly  employed  for  the  series- 
connection  of  the  cells  in  a  battery.  (Ob- 
solete.) 

Connection  of  Battery  for  Quantity. — 
A  term  formerly  employed  for  a  multiple 
or  parallel  connection  of  the  cells  in  a  bat- 
tery. (Obsolete.) 

Connector. — A  device  for  readily  connect- 
ing or  joining  the  ends  of  two  or  more 
conductors. 

Conning  Tower. — A  shell-proof  tower 
from  which  the  commander  on  a  turreted 


Con.] 


724 


[Coil. 


war-ship  directs  its  movements  when  in 
action. 

Consequent  Points. — The  points  or  places 
in  an  anomalous  magnet  where  its  conse- 
quent poles  are  situated. 

Consequent  Pole.— (1)  A  magnet  pole 
formed  by  two  free  north  or  two  free 
south  poles  placed  together.  (2)  A  mag- 
net pole  developed  at  some  point  of  a 
magnet  other  than  its  extremities. 

Consequent   Poles    of  Dynamo.— 

(1)  Dynamo  poles  formed  by  the  juxtapo- 
sition   of    two    similar   magnetic    poles. 

(2)  Dynamo  poles  developed  at  polar  pro- 
jections   unprovided    with    magnetizing 
coils. 

Consequent  Resistance. — A  term  pro- 
posed for  the  apparent  resistance  of  a 
conductor  traversed  by  alternating  cur- 
rents, as  modified  by  the  skin  effect,  and 
as  distinguished  from  its  ohmic  resist- 
ance or  its  inductive  resistance. 

Conservation  of  Energy.— (1)  A  term 
indicative  of  the  fact  that  energy  can 
never  be  annihilated,  so  that  if  it  disap- 
pears in  one  form,  it  must  reappear  in 
some  other  form.  (2)  The  indestructi- 
bility of  energy. 

Consonance. — (1)  A  phase  agreement  be- 
tween two  simple-periodic  waves  or  vibra- 
tions. (2)  The  reinforcement  of  sound 
waves,  or  their  increase  in  intensity,  by 
means  of  vibrating  bodies  that  are  not  in 
resonance  with,  or  are  tuned  to  vibrate 
in  unison  with,  the  sounding  body. 

(3)  Forced  unison. 

Consonance,  Electric. — In  an  alternat- 
ing-current circuit  the  co-phasing  of  the 
impressed  E.  M.  F.  with  the  primary  cur- 
rent, due  to  the  influence  of  capacity  in 
an  inductively  associated  secondary  cir- 
cuit. 

Consonant  Electric  Circuit.-^!)  An 
alternating-current  circuit  containing  re- 
sistance and  inductance,  and  inductively 
associated  with  a  secondary  circuit  con- 
taining resistance,  inductance,  and  capac- 
ity, in  such  a  manner  that  the  secondary 
inductance  and  capacity  neutralize  the 
inductance  of  the  primary  circuit.  (2)  A 
primary  alternating-current  circuit  devoid 
of  reactance  or  choking  effect,  owing  to 
the  presence  of  a  condenser  in  a  secondary 
circuit,  as  distinguished  from  the  effect 
of  a  condenser  inserted  in  the  primary 
circuit  directly. 

Consonator. — Any  body  capable  of  rein- 
forcing sound  by  consonance. 
Constant. — Possessing  an  invariable  value. 


Constant  Cell.— Any  voltaic  cell  which, 
under  certain  circumstances,  is  capable  of 
furnishing  a  constant  electromotive  force 
and  current. 

Constant  Current. — (1)  A  direct  current, 
or  one  that  always  flows  in  the  same  di- 
rection. (2)  A  current  whose  strength  is 
unvarying. 

Constant  -  Current  Alternating  -  Cur- 
rent Dynamo. — An  alternator  which 
supplies  a  constant  effective  current 
strength  in  its  circuit. 

Constant-Current  Arc-Lamp. — A  series- 
connected  arc-lamp. 

Constant-Current  Circuit. — A  circuit 
whose  current  strength  is  maintained 
constant  notwithstanding  changes  in  its 
resistance. 

Constant-Current  Dynamo. — A  con- 
stant-current generator. 

Constant-Current  Generator.— A  term 
applied  to  a  generator  intended  to  pro- 
duce a  constant  strength  of  current  de- 
spite changes  in  its  load. 

Constant-CurrentTransformation.— A 

change  or  transformation  in  the  strength 
of  a  constant  current. 
Constant-Current  Transformer. — (1)  A. 
transformer  which  is  intended  to  raise  or 
reduce  a  current  strength  in  a  given  con- 
stant ratio.  (2)  A  transformer  designed 
to  maintain  a  constant  strength  of  current 
in  its  secondary  circuit,  despite  changes 
of  load. 

Constant  Inductance. — (1)  The  induc- 
tance of  a  circuit  immersed  in  or  wholly 
surrounded  by  a  material  of  constant 
magnetic  permeability.  (2)  An  induc- 
tance which  does  not  vary  with  the  cur- 
rent strength. 

Constant-Potential  Alternating-Cur- 
rent Dynamo. — (1)  An  alternator  which 
supplies  a  constant  effective  pressure  at 
its  terminals.  (2)  A  compounded  alter- 
nator. 

Constant-Potential  Arc-Lamp. — An 
arc  lamp  employed  on  constant-potential 
or  incandescent  mains. 

Constant-Potential  Circuit. — (1)  A  cir- 
cuit whose  potential  is  maintained  ap- 
proximately constant.  (2)  A  multiple-arc 
or  parallel-connected  circuit. 

Constant-Potential  Dynamo.— (1)  A 
dynamo  that  furnishes  an  approximately 
constant  difference  of  potential  or  elec- 
tromotive force  despite  changes  in  its  re- 
sistance or  load.  (2)  A  shunt  or  com- 
pound-wound dynamo. 

Constant-Potential  Generator.— A  con- 
stant-potential dynamo. 


Con.] 


725 


[Con. 


Constant-Potential  Motor.— (1)  A  motor 
designed  for  operation  by  means  of  a  con- 
stant-potential current.  (2)  Generally,  a 
shunt-wound  or  compound-wound  motor. 

Consumer. — One  who  receives  electric 
supply. 

Consumer's  Terminals. — In  a  system  of 
electric  distribution  the  terminals  of  a 
house  service,  the  property  of  the  house, 
and  at  which  the  electric  supply  is  de- 
livered by  the  supply  company. 

Consumption  Circuit. — Any  circuit  in 
which  an  electro-receptive  device  is 
placed. 

Contact  Breaker. — A  device  for  breaking 
or  opening  an  electric  circuit. 

Contact  Electromotive  Force. — Elec- 
tromotive force  produced  by  the  mere 
contact  of  dissimilar  metals. 

Contact  Electricity. — Electricity  pro- 
duced by  contact  electromotive  forces. 

Contact  Force. — A  contact  electromotive 
force. 

Contact  Lamp. — A  name  sometimes  given 
to  a  semi-incandescent  lamp. 

Contact  Resistance. — Resistance  pro- 
duced at  the  contact  of  two  or  more  sur- 
faces. 

Contact  Ring  of  Telephone  Plug.— A 
plug  in  a  multiple  telephone  switchboard 
carrying  an  insulated  metal  ring  or  sleeve 
establishing  a  circuit  for  the  busy  test. 

Contact  Rings  of  Alternator. — The  col- 
lector rings  of  an  alternator. 

Contact  Series. — A  series  of  metals  ar- 
ranged in  such  an  order  that  each  becomes 
positively  electrified  by  contact  with  the 
one  that  follows  it. 

Contact  Screw. — A  screw  the  end  of 
which  is  provided  with  a  platinum  or 
other  contact,  employed  to  close  the 
circuit  of  any  electric  device  in  whose 
circuit  it  is  placed. 

Contact  Theory  of  Electricity. — A  the- 
ory that  ascribes  the  production  of  elec- 
tromotive forces,  or  of  electricity,  to  the 
contact  of  dissimilar  substances  or  sur- 
faces. 

Contact  Theory  of  Voltaic  Cell.— The 
contact  theory  of  electricity  applied  to 
the  production  of  electricity  in  a  voltaic 
cell. 

Contacts. — (1)  Conducting  pieces  or  plates 
introduced  into  electric  circuits  at  points 
where  it  is  desired  to  open  and  close  the 
circuit.  (2)  A  variety  of  fault  occasioned 
in  any  circuit  by  the  accidental  contact 
of  any  part  of  the  circuit  with  a  conduct- 
ing body.  (3)  A  metallic  cross  or  faulty 


connection  between  two  telegraphic  or 
telephonic  circuits. 

Containing  Cell. — (1)  A  jar  provided  for 
holding  or  containing  the  solution  or 
electrolyte  employed  in  connection  with 
a  primary  or  secondary  voltaic  couple. 
(2)  A  jar  or  receptacle  for  containing  any 
liquid  or  solution,  as  in  an  electro-plating 
bath. 

Continental  Telegraphic-Code. — A  tele- 
graphic-code employed  in  Europe  gener- 
ally. 

Continuator. — A  constant-current  dyna- 
mo. (Not  in  use.) 

Continuity  of  Circuit.— The  uninter- 
rupted conducting  condition  of  a  circuit. 

Continuity -Preserving  Transmitter.— 
A  transmitter  employed  in  duplex  teleg- 
raphy, so  arranged  that  the  line  wire 
may  be  transferred  from  the  battery  to 
the  earth  without  any  break  in  the  conti- 
nuity of  the  circuit. 

Continuous- Alternating  Transformer. 

(1)  A  secondary  generator  for  transform- 
ing continuous  into  alternating  currents. 

(2)  A  dynamotor,  motor-dynamo,  or  ro- 
tary transformer. 

Continuous  Current. — (1)  An  electric 
current  which  flows  in  one  and  the  same 
direction.  (2)  A  direct  current. 

Continuous-Current  Arc. — A  voltaic  arc 
produced  by  a  continuous  current,  as  dis- 
tinguished from  one  produced  by  alternat- 
ing currents. 

Continuous-Current  Armature- Wind- 
ings.— Armature  windings  suitable  for 
use  in  continuous-current  generators. 

Continuous-Current  Dynamo-Electric 
Machine. — A  continuous-current  gener- 
ator. 

Continuous-Current  Generator.— Any 
generator  capable  of  furnishing  contin- 
uous currents. 

Continuous-Current  Motor. — A  motor 
operated  by  continuous  or  direct  currents. 

Continuous-Current  Transformer. — (1) 
A  dynamotor  or  motor-dynamo.  (2)  A 
transformer  from  one  continuous  pressure 
and  current  to  another. 

Continuous  E.  M.  F.'s. — Electromotive 
forces  whose  direction  and  value  remain 
constant. 

Continuous  -  Sounding  or  Ringing 
Electric-Bell. — (l)An  electric  bell,  which 
on  completion  of  its  circuit  continues 
sounding  until  stopped.  (2)  A  trembling 
bell. 

Continuous  Spectrum. — (1)  A  luminous 
spectrum  that  is  devoid  of  the  Fraunhofer 


Coil.] 


726 


[Con. 


dark  lines,  or  which  contains  all  the  phys- 
iologically effective  luminous  frequencies. 
(2)  The  spectrum  of  a  sufficiently  heated 
incandescent  solid. 

Continuous- Surf  ace  Commutator. — A 
dynamo  commutator,  whose  surface  con- 
tains no  breaks  in  the  gaps  between  con- 
tiguous commutator  bars  ;  i.  e.,  whose 
gaps  are  tilled  with  an  insulating  material 
instead  of  being  left  with  air  spaces. 

Continuous  Trolley  Wire. — An  un- 
jointed  trolley  wire. 

Continuous  Winding. — A  term  fre- 
quently employed  for  wave  winding  or 
undulatory  winding  of  an  armatui'e. 

Continuous  Wire  or  Conductor. — An 
unjointed  wire  or  conductor. 

Continuously  Insulated  Cable.  —  A 
length  of  cable  extending  continuously 
between  two  points  without  any  taps. 

Contracting  Magnetic  Whirls. — Mag- 
netic whirls  which  are  decreasing  or  mov- 
ing in  towards  the  electro-magnet  or  cir- 
cuit producing  them. 

Contractures.  —  In  electro-therapeutics 
prolonged  muscular  spasms  or  tetanus 
caused  by  the  passage  of  electric  currents. 

Contraplex  Telegraph. — A  general  term 
embracing  the  apparatus  employed  in 
contraplex  telegraphy. 

Contraplex  Telegraphy. — Duplex  teleg- 
raphy in  which  transmissions  are  simul- 
taneously made  from  opposite  ends  of  the 
lino. 

Controlled  Clock. — A  clock  whose  works 
are  controlled  or  regulated  either  entirely 
or  partially,  by  an  electric  current. 

Controller. — (1)  The  magnet  employed  in 
a  system  of  automatic  constant-current 
regulation,  whose  coils  are  traversed  by 
the  main  current, employed  automatically 
to  throw  a  regulator  magnet  into  or  out 
of  the  main  circuit  on  changes  of  the  cur- 
rent passing.  (2)  Any  electric  mechanism 
for  controlling  a  circuit  or  system.  (3)  An 
electric  switching  mechanism  for  control- 
ling the  speed  of  a  motor  or  motors.  (4)  A 
street-railway  car-controller. 

Controller  Resistance. — Resistance  em- 
ployed in  connection  with  street-car  con- 
trollers for  starting  or  stopping  the  mo- 
tors, or  for  varying  their  speed. 

Controller  Switch.— (1)  The  switch  oper- 
ating the  switch  cylinder  of  a  street-car 
controller.  (2)  Any  switch  employed  in 
connection  with  a  street-car  controller. 

Controlling  Box.— The  box  holding  any 
controlling  rheostat  or  controller. 

Controlling  Block,  Electric. — In  a  sys- 
tem of  time-telegraphy,  the  master  clock 


whose  impulses  move  or  regulate  the 
secondary  clocks. 

Controlling  Magnet. — (1)  Any  magnet 
which  controls  some  particular  action, 
as,  for  example,  the  attraction  of  a  needle 
in  a  galvanometer.  (2)  A  name  some- 
times given  to  the  controller  in  an  auto- 
matic system  of  current  regulation. 

Controlling  Stand. — The  support  or  stand 
provided  for  holding  the  apparatus  em- 
ployed for  controlling  a  motor. 

Convection  Currents.  —  Currents  pro- 
duced by  the  bodily  carrying  forward  of 
static  charges  in  convection  streams. 

Convection,  Electric.— The  air  streams 
which  are  thrown  off  from  points  on  the 
surface  of  a  charged  insulated  conductor. 

Convection  of  Heat,  Electric. — (1)  A 
term  employed  to  express  the  dissymmet- 
rical distribution  of  temperature  that 
occurs  when  an  electric  current  is  sent 
through  a  metallic  wire,  the  middle  of 
which  is  maintained  at  one  constant  tem- 
perature, and  the  ends  at  another  constant 
temperature.  (2)  Distribution  of  heat 
which  attends  the  passage  of  an  electric 
current  through  an  unequally  heated  con- 
ductor. 

Convection  Streams.— Streams  of  elec- 
trified air,  or  other  gaseous  or  vaporous 
particles,  given  off  from  sharp  points  on 
the  surface  of  highly  charged  insulated 
conductors. 

Convection  Transference.  —  The  trans- 
ference of  electricity  by  means  of  convec- 
tion streams. 

Convective  Discharge. — The  discharge 
which  occurs  from  the  points  of  a  highly 
charged  conductor,  through  the  electro- 
static repulsion  of  similarly  charged  air 
particles,  which  thus  carry  off  minute 
charges. 

Converging  Magnetic  Flux.— Magnetic 
flux  that  converges  or  radiates  from  a 
point  or  points. 

Conversion  of  Electromotive  Force. — 
Any  increase  or  decrease  in  the  value  of 
an  electromotive  force  produced  by  means 
of  a  transformer. 

Convert. — To  transform  or  change  an  elec- 
tromotive force  or  current. 

Converted  Currents. — Electric  currents 
whose  strengths  have  been  increased  or 
decreased  by  means  of  a  transformer. 

Converter. — A  name  sometimes  given 
to  a  transformer. 

Converter  Bracket. — (1)  A  bracket  for 
holding  a  pair  of  insulators  and  a  single 
light  converter  and  shunt  box  in  an  alter- 
nating-current series-system  of  street  light- 


Con.] 


727 


[Cop. 


ing.  (2)  A  bracket  for  supporting  an  al- 
ternating-current converter. 

Converter  Fuse. — A  safety  fuse  connect- 
ed with  the  circuit  or  circuits  of  a 
converter  or  transformer,  and  usually 
mounted  in  the  transformer  case. 

Converting. — Transforming  or  changing 
an  electromotive  force  or  current. 

Converting  Currents. — (1)  Changing  the 
value  of  the  current  strength  by  means 
of  transformers.  (2)  Changing  a  contin- 
uous into  an  alternating  current,  or  vice 
versa. 

Converting  Station. — (1)  A  transform- 
ing station.  (2)  A  station  containing 
transformers. 

Conveyer,  Electric. — An  electrically  op- 
erated or  controlled  system  of  transport- 
ing material. 

Convolutions  of  Wire.  —  The  separate 
loops  or  turns  in  a  helix  or  coil. 

Cooling-Box  of  Hydro-Electric  Ma- 
chine.— A  box  provided  in  Armstrong's 
hydro-electric  machine  for  the  steam  to 
pass  through  before  leaving  the  nozzle. 

Cooling  Surface.  —  The  surface  from 
which  a  hot  body  can  dissipate  its  heat 
energy. 

Cooling  Surface  of  Armature. — That 
portion  of  an  armature  surface  from 
which  it  can  dissipate  into  the  surround- 
ing air,  the  heat  energy  produced  in  it 
by  the  passage  of  the  currents  generated 
during  its  rotation. 

Cooling  Tubes. — Tubes  inserted  in  the 
frame  or  casing  of  an  alternating-current 
transformer  for  the  supply  of  cold  water 
from  an  external  pump  or  source. 

Co-Periodic. — Possessing  the  same  peri- 
odicity. 

Co-Periodic  E.  M.  F.'s,  Currents  or 
Fluxes. — Electromotive  forces,  currents 
or  fluxes,  possessing  the  same  periodicity. 

Co-Phasal. — Possessing  the  same  phase. 

Co-Phasal  Alternations.  —  Alternations 
possessing  the  same  phase. 

Co-Phase. — (1)  Coincidence  in  phase  of 
co-periodic  motions.  (2)  Such  a  phase 
relation  between  two  periodic  but  non- 
co-periodic  quantities  as  tends  to  increase 
the  amplitude  of  the  motion. 

Copper  Arc.  —  An  arc  formed  between 
copper  electrodes. 

Copper  Bath.  —  An  electrolytic  bath 
containing  an  electrolyzable  solution  of  a 
copper  salt,  and  a  copper  plate  forming 
the  anode,  and  placed  in  an  electrolyte 
near  the  object  to  be  electroplated,  which 
forms  the  cathode. 


Copper  Battery.— A  battery  employed  in 
sending  copper  currents  to  line. 

Copper  Conductivity  Standard.— (1) 
According  to  rules  of  the  British  Institu- 
tion of  Electrical  Engineers,  a  metre- 
gramme  wire  of  standard  conductivity, 
whose  resistance  is  0.1519  international 
ohm  at!5°C.,  corresponding  to  Matthies- 
sen's  standard  for  hard  copper.  (2)  Ac- 
cording to  a  committee  of  the  American 
Institute  of  Electrical  Engineers,  a  copper 
metre-gramme,  of  Matthiessen  standard 
soft  copper  conductivity,  whose  resistance 
is  0.1501  ohm  at  15°C. 

Copper  Connector. — (1)  A  particular 
form  of  connector  employed  in  the  grav- 
ity voltaic  cell  for  connecting  the  copper 
element  to  the  circuit  wire  or  conductor. 
(2)  A  special  form  of  coupler  for  con- 
necting large  wires  or  conductors. 

Copper  Current. — A  term  sometimes 
used  in  telegraphy  for  a  positive  current. 

Copper  Efficiency.  —  The  ratio  of  the 
electric  energy  delivered  by  a  copper  con- 
ducting system,  to  the  energy  delivered 
to  that  system. 

Copper  Fuse- Wire  Terminals. — Copper 
terminals  provided  for  connection  with 
the  terminals  of  fuse  wires  or  safety 
catches. 

Copper  Heat. — The  heat  which  appears 
in  a  copper  conductor  due  to  the  passage 
through  it  of  an  electric  current. 

Copper-Lead  Accumulator.  —  An  ac- 
cumulator or  storage  battery  consisting 
of  plates  of  copper  and  lead  immersed  in 
a  solution  of  copper  sulphate. 

Copper  Loss. — The  total  loss  of  energy 
produced  by  the  passage  of  a  current 
through  the  copper  wire  of  a  dynamo, 
motor,  or  conducting  system  generally. 

Copper  Magnetic  Circuit. — That  portion 
of  a  magnetic  circuit  which  is  completed 
through  copper. 

Copper  Plating. — Electro  -  plating  with 
copper. 

Copper  Resistance. — In  submarine  tel- 
egraphy, conductor  resistance. 

Copper  Resistivity. — The  specific  re- 
sistance of  copper  of  Matthiessen  soft  cop- 
per standard  referred  to  the  resistance  of 
a  cube  one  centimetre  in  length  of  edge, 
such  a  cube  offering  between  parallel 
faces  a  resistance  of  1.594  microhms  at 
0°  C.  (2)  The  resistivity  of  a  copper  wire. 

Copper  Ribbon. — A  variety  of  strap  cop- 
per. 

Copper  Shell  of  Electro  -  Type.— The 
thin  electrolytic  deposit  of  copper  which, 
when  stiffened  by  the  backing  metal  and 


Cop.] 


728 


[Cos. 


suitably  mounted  on  a  block,  forms  the 
electro-type. 

Copper  Strap. — Copper  conductors  in  the 
form  of  straps  or  flat  bars. 

Copper  Tape.  —Rectangular  straps  or  bars 
of  copper  employed  for  armature  wind- 
ings. 

Copper  Voltameter.  —  A  voltameter 
whose  indications  are  dependent  on  the 
electrolysis  of  a  solution  of  a  copper  salt. 

Copper-Zinc  Accumulator.— An  accu- 
mulator or  storage  cell  consisting  of  a 
plate  of  copper  and  a  plate  of  zinc  im- 
mersed in  a  solution  of  zinc  sulphate. 

Coppered  Arc-Light  Carbons. — Carbons 
employed  in  arc-lamps,  covered  electro- 
lytically  with  copper. 

Coppered  Carbons. — Carbons  for  arc- 
lamps,  or  batteries,  that  are  electrolyti- 
cally  coated  with  copper. 

Coppered  Plumbago. — Powdered  plum- 
bago coated  with  copper  for  use  in  the 
metallization  of  objects  to  be  electro- 
plated. 

Copying  Telegraph. — A  fac-simile  or 
automatic  telegraph. 

Cord  Adjuster. — A  device  for  adjusting 
the  length  of  a  pendant  cord. 

Cord,  Electric. — A  flexible,  insulated  elec- 
tric conductor,  generally  containing  two 
parallel  wires. 

Cord  Peg.— A  cord  to  which  a  connecting 
peg  is  attached. 

Cord-Peg  Connection. — Connection  in  a 
switchboard  by  means  of  a  cord  peg. 

Cord  Pendant. — A  flexible  or  stranded 
conductor  employed  for  a  lamp  pendant. 

Cord  Shelf.— A  shelf  provided  for  the 
holding  of  the  cord  pegs  of  a  telephone 
switchboard. 

Core  Discs.  —  Stampings  or  cuttings  of 
sheet  iron,  employed,  when  suitably  as- 
sembled, for  the  laminated  core  of  a 
dynamo  or  motor  armature,  or  other 
dynamo-electric  apparatus. 

Core  Losses. — The  hysteresis  and  the 
Foucault  or  eddy-current  losses  of  the 
core  of  a  dynamo,  motor,  or  transformer. 

Core  Losses  of  Transformer.— (1)  The 
hysteresis  and  Foucault-current  losses  in 
the  core  of  a  transformer.  (2)  The  iron 
losses  in  a  transformer. 

Core  of  Cable. — (1)  The  insulated  wires  em- 
ployed for  the  transmission  of  the  current 
through  a  conducting  cable.  (2)  The  elec- 
tric conductor  and  insulator  as  distin- 
guished from  the  mechanical  serving  and 
sheathing  of  a  cable. 


Core  Pins  of  Magnet.-  -Pins  in  the  cores 
of  a  magnet  for  securing  their  firm 
mechanical  union  with  the  yoke. 

Core  Ratio  of  Cable.— The  ratio  between 
the  diameter  of  the  core  of  a  cable  and  the 
mean  diameter  of  the  conductor  strand. 

Core  Transformer. — (1)  A  transformer  in 
which  the  iron  forms  the  core  or  central 
portion  on  which  the  wire  windings  are 
placed.  (2)  A  transformer  possessing  a 
core  capable  of  insertion  or  removal. 

Cored  Carbons. — Arc-light  carbons  pro- 
vided with  a  soft  centre  of  carbon. 

Cored  Electrodes. — Cored  arc-light  car- 
bons. 
Coreless.— Devoid  of  a  core. 

Coreless  Armature  of  Dynamo  or 
Motor. — An  armature  of  a  dynamo  or 
motor  unprovided  with  the  usual  core 
of  iron. 

Corn-Plaster  Fuse. — A  strip  of  fusible 
metal  rolled  up  with  an  asbestos  tape  in 
the  form  of  a  cylinder  and  employed  as 
a  safety  catch  in  a  telephone  switchboard. 

Cornice  Bracket. — A  form  of  insulator 
bracket  for  use  on  the  under  side  of  cor- 
nices. 

Corposant. — A  name  sometimes  given  by 
sailors  to  the  St.  Elmo's  fire. 

Coronse.  —  (1)  Crown  -  shaped  masses  of 
light  sometimes  seen  during  the  preva- 
lence of  aurorse.  (2)  Auroral  coronee. 

Corpuscle. — (1)  An  ultimate  particle  in  an 
assumed  highly  tenuous  substance  that 
was  formerly  believed  to  be  emitted  by 
highly  heated  bodies.  (2)  Any  of  the 
ultimate  particles  of  the  matter  into 
which  it  has  been  assumed  that  the  ulti- 
mate elementary  atoms  may  be  divided. 

Correcting  Factor  of  Wattmeter. — 
The  correction  which  must  be  applied  to 
the  readings  of  an  alternating-current 
wattmeter  when  the  reactance  in  its 
shunt  circuit  cannot  be  neglected. 

Correcting  Relay  .—(1)  A  relay  employed 
in  the  Delaney  system  of  synchronous- 
multiplex  telegraphy  to  aid  in  obtaining 
synchronism.  (2)  In  a  quadruplex  sys- 
tem, a  relay  intermediate  between  the 
polarized  receiving  relay  and  its  sounder, 
for  the  purpose  of  preventing  false  signals 
or  kicks. 

Correlation  of  Energy.— A  term  some- 
times applied  to  the  different  phases  under 
which  energy  may  appear. 

Corrugated  Reflector.  —  A  reflector 
formed  of  silvered  corrugated  glass. 

Cosine. — (1)  One  of  the  trigonometrical 
functions.  <8)  The  ratio  of  the  base  to 


Cos.] 


7:>9 


[Cou. 


the  hypothenuse  of  a  right-angled  triangle 
in  which  the  hypothenuse  is  the  radius 
vector,  and  the  angle  between  the  base 
and  hypothenuse  the  angle  whose  cosine 
is  considered. 

Cosine  Law  of  Illumination. — The  in- 
tensity of  illumination,  of  a  surface 
illumined  by  a  single-point  source,  varies 
as  the  cosine  of  the  angle  of  the  rays 
incident  upon  the  surface  from  that 
source. 

Oosinusoid. — A  curve  of  cosines. 

Cotangent. — (1)  One  of  the  trigonometrical 
functions.  (2)  The  reciprocal  of  the  tan- 
gent of  an  angle. 

Coulomb. — (1)  The  practical  unit  of  elec- 
tric quantity.  (2)  Such  a  quantity  of 
electricity  as  would  pass  in  one  second 
through  a  circuit  conveying  one  ampere. 
(3)  The  quantity  of  electricity  contained 
in  a  condenser  of  one  farad  capacity, 
when  subjected  to  the  E.  M.  F.  of  one 
volt. 

Coulomb  Meter. — A  meter  for  measuring 
in  coulombs,  the  quantity  of  electricity 
which  passes  through  any  circuit. 

Coulomb's  Electric  Balance. — A  tor- 
sion balance  for  measuring  the  forces  of 
electric  01  magnetic  repulsion. 

Coulomb's  Torsion  Balance.  —  An  ap- 
paratus for  measuring  the  force  of  elec- 
tric or  magnetic  repulsion  between  two 
similarly  charged  bodies,  or  between  two 
similar  magnet  poles,  by  opposing  to  such 
forces  the  torsion  of  a  thin  wire. 

Coulomb- Volt. — A  word  sometimes  em- 
ployed for  the  volt-coulomb  or  joule. 

Counter-Clockwise  Motion.—  A  rotary 
motion  whose  direction  is  opposed  to  that 
of  the  hands  of  a  clock,  as  viewed  from 
the  clock  face. 

Counter  Communication  Telephone 
Switch.  —  A  switch  arranged  in  a  tele- 
phone system  in  connection  with  a  silence 
cabinet,  whereby  a  person  occupying  the 
cabinet  is  unable  to  call  up  the  exchange 
without  the  sanction  and  assistance  of  an 
attendant  in  the  office  outside  the  cabinet. 

Counter,  Electric.— (1)  A  device  for 
counting  and  registering  such  quantities 
as  the  number  of  fares  collected,  gallons  of 
water  pumped,  sheets  of  paper  printed, 
votes  polled,  revolutions  of  an  engine  per 
second,  etc.  (2)  Any  counting  device 
operated  or  controlled  by  electricity. 

Counter  Electro-Dynamic  Force.— The 
electro-magnetic  force  which  is  set  up  in 
a  dynamo  armature  opposing  the  im- 
pressed driving  force. 

8 — 


Counter-Electromotive  Force.— (1)  An 
opposed  or  reverse  electromotive  force 
which  tends  to  set  up  a  current  in  the 
opposite  direction  to  that  actually  pro- 
duced by  a  source.  (2)  In  an  electric 
motor,  an  electromotive  force  produced 
by  the  rotation  of  the  armature  and  op- 
posed to  that  produced  by  the  driving 
current. 

Counter-Electromotive  Force  Cell. — 
(1)  An  electrolytic  cell  inserted  in  the 
charging  circuit  of  a  storage  battery  to  re- 
duce the  charging  current  strength,  usu- 
ally composed  of  opposed  plates  or  grids  of 
antimomous  lead  from  the  surfaces  of 
which  gases  are  disengaged  by  electrol- 
ysis. (2)  Additional  cells,  generally  with- 
out active  material,  employed  with  a  stor- 
age battery  which  has  to  be  charged  at  a 
pressure  above  the  normal  pressure,  and 
inserted  between  the  dynamo  and  the 
mains  to  maintain  their  pressure  normal. 

Counter-Electromotive  Force  Light- 
ning-Arrester. — (1)  A  lightning-arrester 
in  which  the  passage  of  a  discharge 
through  the  instruments  to  be  protected 
is  opposed  by  a  counter  electromotive 
force  generated  by  induction  on  the  pas- 
sage of  the  lightning  discharge.  (2.)  A 
choking-coil  lightning-arrester. 

Counter-Electromotive  Force  of  Arc.— 

An  electromotive  force  produced  during 
the  formation  of  a  carbon  voltaic  arc  op- 
posed to  that  which  maintains  the  arc. 

Counter-Electromotive  Force  of  Con- 
vecti  /e  Discharge. — Resistance  to  the 
passage  of  an  electric  discharge  through 
a  high  vacuum,  somewhat  of  the  nature 
of  a  counter  electromotive  force. 

Counter-Electromotive  Force  of  Elec- 
trolysis.— A  counter  electromotive  force 
produced  by  electrolysis  in  the  plating 
bath  of  an  electrolytic  cell. 

Counter-Electromotive  Force  of  In- 
duction. —  The  counter  electromotive 
force  of  self  or  mutual  induction. 

Counter-Electromotive  Force  of  Mut- 
ual Induction.  —  (1)  Counter-electro- 
motive force  produced  by  mutual  induc- 
tion between  neighboring  circuits.  (2) 
Counter-electromotive  force  in  the  pri- 
mary circuit  of  a  transformer  produced  by 
the  mutual  induction  from  the  current 
in  the  secondary  circuit. 

Counter-Electromotive  Force  of  Polar- 
ization.— Electromotive  force  developed 
in  a  voltaic  cell  or  plating  bath  by  polar- 
ization, and  opposed  to  that  which  pro- 
duces the  current  of  the  cell. 

Counter-Electromotive  Force  of  Self- 
induction. — The  counter-electromotive 

Vol.  9. 


Cou.] 


730 


[Cri, 


force  produced  in  the  primary  circuit  of  an 
induction  coil  by  the  action  thereon  of  an 
alternating  electromotive  force. 

Counter-Electromotive  Force  of  Self- 
induction  of  the  Primary.  —  The 
counter-electromotive  force  produced  in 
the  primary  circuit  of  a  transformer  by 
the  action  of  induction  of  the  primary 
current  on  itself,  as  distinguished  from 
that  produced  by  mutual  induction  .from 
the  secondary  current. 

Counter-Electromotive  Force  of  Self- 
induction  of  the  Secondary.— The 
counter-electromotive  force  produced  in 
the  secondary  by  periodic  variations  in 
the  effective  electromotive  force  in  the 
secondary  circuit. 

Counter-Electromotive  Force  of  Stor- 
age Battery. —  The  electromotive  force 
in  a  storage  battery  which  opposes  the 
electromotive  force  employed  in  charging. 

Counter-Electromotive  Force  of  Volt- 
aic Cell.  —  The  counter-electromotive 
force  in  a  voltaic  cell  due  to  its  polariza- 
tion. 

Counter  Inductive  Effect. — An  opposal 
of  current  or  charge  by  means  of  an  elec- 
tromotive force  produced  by  induction. 

Counter  Pressure. — A  term  sometimes 
used  for  counter-electromotive  force. 

Couple. — (1)  In  mechanics,  two  equal  and 
parallel,  but  oppositely  directed  forces, 
not  acting  in  the  same  line,  and  tending  to 
produce  rotation.  (2)  The  two  elements 
in  a  voltaic  cell  or  thermo-electric  cell. 

Coupled  Cells. —  A  number  of  separate 
cells  so  connected  or  coupled  as  to  form 
a  battery  or  single  electric  source. 

Coupling  Box  for  Electric  Tubes. — A 

box  provided  for  the  ready  connection  of 
the  conductors  in  the  separate  lengths 
of  underground  electric  tubes. 

Coupling  Clamp  for  Underground  Con- 
ductors.— An  electric  coupling  between 
two  lengths  of  underground  conductors. 

Coupling  Joint  for  Underground 
Tubing. — A  joint  for  the  separate  con- 
ductors in  an  underground  tubing,  con- 
sisting generally  of  a  flexible  conductor 
and  connectors  for  ready  attachment  to 
the  ends  of  the  conductor. 

Coupling  of  Voltaic  Cells  or  Other 
Electric  Sources. — Connecting  a  num- 
ber of  separate  voltaic  cells,  or  other  sep- 
arate electric  sources,  so  as  to  enable  them 
to  act  as  a  battery  or  single  electric 
source. 

Coupling  Transformer. — A  transformer 
which  employs  polyphasal  coupling  of 
magnetic  circuits. 


Cradle  Dynamometer. — A  dynamometer 
in  which  the  dynamo  to  be  tested  is  sup- 
ported in  a  cradle,  and  the  mechanical 
energy  it  receives  or  transmits  is  measured 
by  the  torque  developed  by  the  cradle 
about  its  axis. 

Cradle  Suspension  of  Street-Car  Mo- 
tor.—  A  method  of  supporting  a  street- 
car motor  on  its  truck  upon  a  spring 
cradle. 

Crater  in  Positive  Carbon. — A  depression 
in  the  end  of  the  positive  carbon  of  an 
arc-lamp,  which  occurs  after  the  arc  has 
been  maintained  for  some  little  time. 

"Creep"  of  Belt. — A  term  sometimes 
used  for  the  slip  of  a  belt. 

Creepage. — The  residual  elastic  torsion  of 
a  suspension  fibre. 

Creeping,  Electric. —  A  term  sometimes 
applied  to  the  creeping  of  a  current. 

Creeping  in  Voltaic  Cell. — The  formation 
by  efflorescence  of  salts  on  the  sides  of 
the  porous  cup  of  the  voltaic  cell,  on  the 
binding  posts,  or  on  the  walls  of  the 
vessel  containing  the  electrolyte. 

Creeping  of  Belt. — (1)  An  action  of  a  driv- 
ing belt  due  to  its  retractility,  whereby  the 
driving  pulley  travels  somewhat  faster 
than  the  driven  pulley.  (2)  Belt  slip. 

Creeping  of  Current. — (1)  A  term  some- 
times employed  for  a  change  in  the  direc- 
tion of  the  path  of  a  current  from  a  direct 
line  between  the  points  of  connection  with 
the  source.  (2)  Electrification  or  polariza- 
tion currents  in  an  electrolyte.  (3)  The 
extension  of  a  glow  or  streamer  discharge 
over  the  surface  of  a  dielectric. 

Creosoting.— A  process  employed  for  the 
preservation  of  wood,  such,  for  example, 
as  telegraph  poles,  by  injecting  creosote 
into  the  pores  of  the  wood. 

Crevasse. — A  narrow  gap  or  slit  effected, 
or  imagined,  in  a  magnet  or  magnetized 
substance,  for  the  purpose  of  determining 
the  magnetic  forces  on  a  small  needle. 

Crith. — A  proposed  unit  of  mass,  or  the 
weight  of  one  litre  or  cubic  decimetre  of 
hydrogen  at  0°  Centigrade,  and  760  mil- 
limetres barometric  pressure. 

Critical  Angle. — The  angle  of  incidence  at 
which  a  ray  of  light  falling  upon  the 
surface  of  a  body  ceases  to  be  reflected 
and  is  wholly  absorbed  or  internally  re- 
flected and  refracted. 

Critical  Current. — The  current  strength 
at  which  a  certain  critical  result  is 
reached. 

Critical-Current  of  Dynamo. — That 
value  of  the  current  of  a  dynamo  at  which 


Cri.] 


731 


[Cro. 


its  characteristic  curve  begins  to  depart 
from  a  nearly  straight  line. 

Critical-Current  of  Magnetization. — 
The  current  strength  at  which  a  small 
increase  in  the  magnetizing  current  pro- 
duces a  great  increase  in  the  magnetiza- 
tion of  an  iron  core. 

Critical-Distance  of  Lateral  Discharge 
through  an  Alternative  Path. — The 
distance  at  whicli  a  discharge  will  take 
place  through  an  air  space  of  given  di- 
mensions, in  preference  to  passing  through 
a  metallic  circuit  of  comparatively  small 
ohmic  resistance. 

Critical  Pressure  of  a  Gas  or  Vapor. — 
(1)  The  lowest  pressure  at  which  a  sub- 
stance in  the  liquid  state  cannot  be  par- 
tially vaporized  by  increase  of  temper- 
ature, but  changes  wholly  into  a  gas.  (2) 
The  lowest  pressure  at  which  a  gaseous 
substance  when  cooled  is  condensed  to  a 
liquid  in  the  presence  of  its  vapor.  (3) 
The  pressure  above  which  no  amount  of 
chilling  will  liquefy  a  gaseous  substance. 

Critical-Speed  of  Compound- Wound 
Dynamo. — The  speed  at  which  both  the 
series  and  shunt  coils  of  a  dynamo  give 
the  same  difference  of  potential  when  the 
full  load  is  on  the  machine,  as  the  shunt 
coil  would  have  if  used  alone  on  open- 
circuit.  (2)  The  speed  at  which  a 
dynamo  commences  to  build  up  its  ex- 
citation. 

Critical  Temperature  of  a  Gas  or 
Vapor. — (1)  The  temperature  of  a  vapor 
at  a  given  pressure  above  which  no  pres- 
sure, however  great,  can  convert  the 
vapor  into  liquid.  (2)  The  temperature 
above  which  a  vapor  is  essentially  a  per- 
manent gas. 

Critical  Temperature  of  a  Substance. — 

(1)  The    temperature    above    which     no 
pressure  applied  to  the  substance  in  the 
gaseous    form    will    effect    liquefaction. 

(2)  The  temperature  below  which  a  gase- 
ous substance  is  a  vapor,  and  as  such  cap- 
able of  liquefaction  by  pressure. 

Critical  Volume  of  a  Gas  or  Vapor. — 
The  volume  of  a  substance  at  the  critical 
temperature  and  pressure. 

Crookes'  Dark-Space. — A  dark  space 
surrounding  the  negative  electrode  in  a 
rarified  space  through  which  electric  dis- 
charges are  passing. 

Crookes'  Effect.— The  effect  produced  in 
high-vacuum  tubes  due  to  the  charac- 
teristic motions  possessed  by  heated  or 
electrified  molecules  when  in  the  ultra- 
gaseous  or  radiant  state. 

Crookes'  Electric  Radiometer. — A  ra- 
diometer in  which  the  repulsions  of  the 


molecules  of  the  residual  atmosphere  take 
place  from  electrified  instead  of  from 
heated  surfaces. 

Crookes'  Layer. — The  dark  space  or  layer 
enveloping  the  cathode  of  an  excited 
Crookes'  tube. 

Crookes'  Radiometer. — An  apparatus 
for  demonstrating  the  action  of  radiant 
matter  in  producing  motion,  from  the 
effects  of  the  reaction  of  a  stream  of 
molecules  thrown  off  from  a  number  of 
easily  moved,  unequally  heated  surfaces. 

Crookes'  Tubes. — (1)  Glass  tubes  contain- 
ing high  vacua,  provided  with  platinum 
leading-in  wires  terminating  in  suitably 
shaped  metallic  surfaces,  employed  in 
demonstrating  the  peculiarities  of  the 
radiant  or  ultragaseous  condition  of  mat- 
ter. (2)  A  name  frequently  given  to 
X-ray  tubes. 

Cross. — (1)  A  connection  or  contact  between 
two  telegraph  circuits.  (2)  A  contact  be- 
tween two  conductors  or  circuits  which 
should  be  insulated  from  each  other. 

Cross- Ampere  Turns. — (1)  Ampere  turns 
on  a  dynamo  armature  possessing  u  cross- 
magnetizing  tendency  to  distort  the  mag- 
netic field.  (2)  Ampere  turns  whicli  tend 
to  produce  a  cross  magnetization,  at  right- 
angles  to  that  produced  by  the  field- 
magnets. 

Cross  Arm. — (1)  A  horizontal  beam  at- 
tached to  a  pole  for  the  support  of  the 
insulators  of  telegraph,  electric  light,  or 
other  electric  wires.  (2)  A  telegraphic 
arm. 

Cross-Arm  Bolts. — Bolts  employed  for 
attaching  the  cross-arms  to  a  pole. 

Cross-Arm  Brace. — Galvanized  iron 
braces  whose  ends  are  respectively  con- 
nected to  the  pole  and  the  cross-arm  for 
the  purpose  of  stiffening  them. 

Cross  Bonding. — In  an  electric  railway 
the  bonding  between  the  ground  feeder 
and  the  track  for  the  purpose  of  ensuring 
a  good  conducting  return  circuit. 

Cross-Connected  Dynamo. — A  dynamo 
the  ends  of  whose  armature  coils  are  con- 
nected to  corresponding  segments  all 
around  the  commutator. 

Cross-Connecting  Board. — In  a  system 
of  telegraphic  or  telephonic  communica- 
tion, a  board  to  which  the  line  terminals 
are  run,  before  entering  the  switchboard, 
so  as  readily  to  place  any  line  in  connec- 
tion with  any  desired  section  of  the  switch- 
board. 

Cross-Connecting  Conductors.— (1)  The 
conductors  on  a  cross-connecting  board 
which  serve  to  connect  the  sections  of  a 


Croo 


732 


LCry. 


switch-board  with  the  wires  leading  to  a 
cable.  (2)  The  conductors  which  connect 
corresponding  commutator  segments  in  a 
cross-connected  armature. 

Cross-Connecting  Telephone  Switch- 
board.— A  telephone  distributing  board. 

Cross-Connecting  Trough. — A  trough 
dividing  a  telephone  test  board  from  a 
distributing  board,  formed  for  holding  the 
joints  in  the  cross-connections  between 
them. 

Cross-Connection  of  Armature  Wind- 
ings.— Armature  windings  in  which  the 
wires  are  interconnected  at  the  corre- 
sponding segments  of  the  commutator. 

Cross-Connection  of  Commutator. — 
The  interconnection  of  the  armature  coils 
to  corresponding  commutator  segments. 

Cross  Current. — Current  passing  between 
the  armatures  of  alternating  current 
generators,  or  motors,  operated  in  parallel, 
and  due  to  differences  in  the  phase  or 
magnitude  of  the  E.  M.  Fs.  in  the  ma- 
chines. 

Cross  Fire.— (1)  A  term  employed  in  tel- 
ephony or  telegraphy  for  an  escape  or  leak- 
age of  current  from  one  line  to  another, 
due  to  defective  insulation.  (2)  Cross  talk. 

Cross,  Electric. — (1)  A  connection,  gen- 
erally metallic,  accidentally  established 
between  two  conducting  lines.  (2)  A  de- 
fect in  a  telegraph,  telephone,  or  other 
circuit,  caused  by  two  wires  coming  into 
contact  by  crossing  each  other. 

Cross  Induction. — (1)  An  induction  pro- 
duced by  the  armature  current  whose 
magnetization  is  at  right-angles  to  that 
produced  by  the  field.  (2)  Cross  magneti- 
zation. 

Cross-Induction  of  Dynamo  Arma- 
ture.— Cross  magnetization  produced  by 
a  dynamo  armature. 

Cross  Magnetization. — A  magnetization 
set  up  by  the  currents  circulating  in  the 
armature  turns,  which  is  at  right-angles 
to  the  magnetization  set  up  by  the  field 
flux. 

Cross-Over  Block. — A  device  to  permit 
the  safe  crossing  of  one  wire  over  another 
in  moulding  or  cleat  wiring. 

Cross  System. — A  system  of  running  over- 
head wires  for  the  purpose  of  preventing 
mutual  inductive  disturbances,  which  con- 
sists in  crossing  or  transposing  the  position 
of  wires  on  the  pole  arms  at  suitable  in- 
tervals, as  distinguished  from  the  twist 
system. 

Cross-Talk. — (1)  Cross-fire  conversation 
over  one  telephone  circuit  which  is  heard 
in  neighboring  telephone  circuit.  (2)  In- 


terference between  neighboring  tele- 
phone circuits. 

Cross- Wire-Suspension  for  Arc  Lamp. 

Suspension  of  an  arc-lamp  by  means  of 
a  pulley  and  cord,  attached  to  a  block  and 
tackle  suspended  from  a  suitably  sup- 
ported cross  wire. 

Crossing  Cleat. — A  cleat  so  arranged  as 
to  permit  the  crossing  of  one  pair  of  wires 
under  or  over  another  pair  without  con- 
tact with  each  other. 

Crossing  Prog. — A  frog  sometimes  em- 
ployed in  place  of  a  trolley  cross-over. 

Crossing  Wires. — (1)  A  device  employed 
in  telegraphic  circuits  whereby  a  faulty 
conductor  is  cut  out  of  the  line  circuit,  by 
crossing  it  over  to  a  neighboring  less- 
used  line.  (2)  In  telegraphy,  interchang- 
ing sections  of  wire  between  two  way 
stations,  so  as  to  remove  a  fault  from  a 
circuit  or  to  rearrange  a  circuit  passing 
through  the  stations. 

Crow-Foot  Zinc. — A  crpw-foot-shaped 
zinc  employed  in  the  gravity  voltaic  cell. 

Crown  Telephone  Receiver. — A  tele- 
phone receiver  in  which  a  number  of 
permanent  steel  magnets  are  arranged  in 
the  form  of  a  crown,  all  the  poles  of  the 
same  name  centring  at  the  soft-iron  pole- 
piece  carrying  the  coil,  and  the  opposite 
coils  being  joined  to  the  rim  of  the  dia- 
phragm. 

Crucible,  Electric. — (1)  A  crucible  suit- 
able for  electro-metallurgical  operations. 
(2)  A  crucible  in  which  the  heat  of  a  vol- 
taic arc,  or  of  electric  incandescence,  is 
employed,  to  perform  difficult  fusions,  to 
effect  the  reduction  of  metals  from  their 
ores,  or  to  form  alloys. 

Crystal. — A  solid  body  bounded  by  sym- 
metrically disposed  plane  faces. 

Crystalline  Electro-Metallurgical  De- 
posit.— A  non-adherent,  non-coherent 
film  of  electrolytically  deposited  metal. 

Crystallization. — Solidification  from  solu- 
tion or  fusion  in  definite  forms. 

Crystallization  by  Electrolytical  De- 
composition.— Crystalline  deposition  of 
various  metals  by  the  passage,  under  cer- 
tain conditions,  of  an  electric  current 
through  solutions  of  their  salts. 

Crystallize. — To  separate  from  a  liquid  or 
vapor  in  the  form  of  a  crystalline  solid. 

Crystalloid. — Those  portions  of  a  mixed 
substance  subjected  to  dialysis,  that  are 
capable  of  crystallization. 

Cryptoscope. — (1)  An  apparatus  consist- 
ing of  a  fluorescent  screen  placed  at  one 
end  of  a  light-tight  pasteboard.  tub«,  and 


Cry.]  733 

viewed  at  the  other  end  through  an  eye- 
piece. (2)  A  fluoroscope. 

Cryptoscopic  Screen. — (1)  The  screen 
employed  in  cryptoscopy.  (2)  A  fluores- 
cent screen. 

Cryptoscopy. — The  art  of  examining  the 
body  by  means  of  a  cryptoscope. 

Cube  Knot. — A  unit  of  volume  sometimes 
employed  in  calculations  of  insulation 
resistance  of  submarine  cables. 

Cubic  Energy. — A  term  sometimes  em- 
ployed for  voluminal  energy. 

Cup  Brush. — A  brush  suitably  shaped  for 
polishing  the  interior  surface  of  a  cup  or 
other  similar  surface  of  an  object  that  is 
to  be  electroplated. 

Cupric  Electrolysis. — In  electro-thera- 
peutic treatment,  electrolysis  performed 
with  copper  electrodes  whereby  a  salt  of 
copper  is  carried  into  the  tissues  under 
the  anode  by  cataphoric  action. 

Curb  Key. — A  telegraphic  key  employed 
in  curb  signalling. 

Curb  Sender. — An  automatic  transmitter 
employed  in  submarine  telegraphy,  which 
is  operated  by  a  punched  paper  strip  and 
which  sends  curbed  signals  into  the  cable. 

Curb  Signalling. — In  cable  telegraphy,  a 
system  for  reducing  the  effects  of  retarda- 
tion and  increasing  the  speed  of  signal- 
ling, by  following  each  signalling  current 
with  a  definite  sequence  of  reversed  cur- 
rents or  earthings. 

Curbed  Signals. — Signals  sent  by  means 
of  a  curb  key. 

Curbing. — Employing  curb  signalling. 

Curl. — (1)  The  vector  part  of  the  nabla  of  a 
vector  point-function.  (2)  The  line  inte- 
gral of  a  vector  once  around  any  closed 
loop,  and  equal  to  the  surface  integral  of 
a  related  vector  passing  through  the  loop. 
(3)The  rotation  or  spin  of  a  vector  point- 
function.  (4)  A  vector  which  indicates  by 
its  direction  the  plane,  and  by  its  length 
the  magnitude,  of  the  maximum  vector 
rate-of-change  of  a  vector  point-function 
in  the  neighborhood  of  a  given  point. 

Current  Accumulator. — Any  apparatus 
in  which  the  strength  of  an  electric  cur- 
rent is  increased  by  the  motion  past  it  of 
a  conductor,  the  currents  produced  in 
which  tend  to  strengthen  and  increase 
the  current  which  causes  the  induction. 

Current  Balance. — A  general  name  given 
to  a  variety  of  ampere  balance  which 
gives  readings  in  various  decimals  or  mul- 
tiples of  amperes,  and  which  determines 
the  strength  of  current  passing,  through 
its  action  on  a  movable  ring  or  coil  placed 
between  two  fixed  rings  or  coils. 


[Cur. 


Current  Calorimeter. — An  electric  ca- 
lorimeter. 

Current  Commuter.— (1)  Any  device  that 
causes  alternating  currents  to  flow  in  one 
and  the  same  direction.  (2)  A  commu- 
tator. 

Current-Conveying  Helix. — An  active 
helix. 

Current  Density.  —  (1)  The  current 
strength  which  passes  in  any  part  of  a  cir- 
cuit, divided  by  the  area  of  cross-section 
of  that  part  of  the  circuit.  (2)  The  ratio 
of  the  current  strength  through  any 
surface  of  section  of  active  conductor  to 
the  area  of  that  surface,  assumed  perpen- 
dicular to  the  current. 

Current  Distribution. — The  spreading  or 
ramification  of  electric  currents  through 
a  conducting  mass  or  network. 

Current  Direction-Indicator. — An  in- 
strument for  insertion  in  an  arc  or  other 
circuit  to  indicate  whether  the  proper 
direction  of  current  is  maintained. 

Current  Diverter  for  Electric  Bail- 
ways. — A  term  sometimes  given  to  the 
rheostat  employed  in  starting  and  regulat- 
ing a  street-car  motor. 

Current  Efficiency  of  Storage  Battery. 

The  ratio  between  the  total  useful  elec- 
tric quantity  delivered  by  a  charged  stor- 
age battery  to  the  working  circuit,  to  the 
total  electric  quantity  employed  in  charg- 
ing the  battery. 

Current,  Electric. — (1)  The  quantity  of 
electricity  per-second  which  passes 
through  any  conductor  or  circuit,  when 
the  flow  is  uniform.  (2)  The  rate  at  which 
a  quantity  of  electricity  flows  or  passes 
through  a  circuit.  (8)  The  ratio,  ex- 
pressed in  terms  of  electric  quantity  per- 
second,  existing  between  the  electro- 
motive force  causing  a  current  and  the 
resistance  which  opposes  it. 

Current  Equalizer  for  Storage  Bat- 
tery.— A  device  for  controlling  the 
strength  of  the  charging  or  discharging 
circuit  of  a  storage  battery. 

•Current  Filaments. — A  term  sometimes 
employed  in  place  of  current  streamlets. 

Current  Governor. — (1)  A  current  regu- 
lator. (2)  Any  device,  whether  auto- 
matic or  non-automatic,  for  maintaining 
constant  the  current  strength  in  any 
circuit. 

Current  Induction. — A  term  sometimes 
used  for  voltaic  induction. 

Current  Meter. — (1)  Any  form  of  current 
galvanometer.  (2)  An  indicating  amme- 
ter or  recording  ampere-hour  meter, 


Cur.] 


734 


[Cut, 


Current  Recording-Meter. — A  record- 
ing ammeter. 

Current  Retarder. — A  term  sometimes 
employed  for  rheostat. 

Current  Reverser. — (1)  A  switch  or  other 
apparatus  designed  to  reverse  the  direc- 
tion of  a  current.  (2)  A  current  changer. 

Current  Rush.. — The  impulsive  rush  of 
current  that  occurs  when  a  transformer 
is  first  switched  on,  or  connected  with,  an 
alternating-current  circuit. 

Current  Sheet. — The  area  of  active  con- 
ducting surface  carrying  a  current  con- 
sidered as  though  the  current  existed  as 
a  material  sheet. 

Current  Spiral. — A  conducting  helix  or 
spiral  provided  for  the  passage  of  a  cur- 
rent. 

Current  Streamlets. — A  conception  of  a 
series  of  parallel  current  streams  or  cur- 
rent filaments  flowing  through  a  solid  con- 
ductor. 

Current  Strength.-^!)  In  a  direct-cur- 
rent cii'cuit  the  quotient  of  the  total  elec- 
tromotive force  divided  by  the  total  re- 
sistance. (2)  The  time-rate-of-flow  in  a 
circuit  expressed  in  amperes,  or  coulombs 
per  second.  (3)  In  an  alternating  current 
the  quotient  of  the  total  electromotive 
force  divided  by  the  impedance. 

Current  System  of  Induction  Teleg- 
raphy.— A  system  of  induction  teleg- 
raphy on  railroads,  depending  on  current 
induction  between  a  fixed  circuit  along 
i  the  roadway,  and  a  parallel  circuit  on  the 
moving  train. 

Current  Teaser,  Electric. — A  coil  of 
thin  wire  placed  on  the  field  magnets  of 
a  dynamo-electric  machine  in  addition  to 
the  series  coils  wound  thereon,  and  con- 
nected as  a  shunt  across  the  main  cir- 
cuit. 

Current  Transformation. — (1)  The  act 
of  changing  the  strength  of  a  current  by 
changes  effected  in  its  electromotive  force. 
(2)  The  act  of  changing  a  direct  into  an 
alternating  current,  or  the  reverse,  or  a 
Uniphase-alternating  current  into  a  mul- 
tiphase-alternating current. 

Current  Transformer. — A  device  for 
changing  in  one  circuit  the  strength  of 
current  which  flows  in  another. 

Current  Turns.— (1)  The  product  of  the 
number  of  turns  in  a  coil  by  the  current 
flowing  through  them.  (2)  A  word  some- 
times used  for  ampere-turns. 

Current  Wave. — (1)  The  progressive  elec- 
tro-magnetic disturbance  in  the  ether  sur- 
rounding a  conducting  wire  forming  part 
of  a  circuit.  (2)  The  progressive  disturb- 


ance of  electric  flow  traversing  a  con- 
ducting circuit,  under  the  influence  of 
a  variation  in  its  impressed  electromotive 
force. 

Current  Weigher.— (1)  A  current  bal- 
ance. (2)  An  ammeter  in  which  the 
electro-magnetic  force  of  the  current  is 
compared  with  the  earth's  gravitational 
force  on  a  mass. 

Currents  of  Motion. — A  term  sometimes 
employed  in  electro-therapeutics  for  the 
electric  currents  that  are  asserted  to 
traverse  healthy  muscle  or  nerve  tissue, 
during  the  sudden  contraction  or  relaxa- 
tion of  such  muscle  and  nerve. 

Currents  of  Rest. — A  term  sometimes 
employed  in  electro-therapeutics  for  the 
electric  currents  that  are  asserted  to  trav- 
erse healthy  muscle  or  nerve  tissue  while 
the  muscles  are  passive. 

Curve  Guy-Poles. — Anchor  poles  or  pull- 
offs,  employed  in  an  overhead-trolley 
system,  placed  at  a  curve  or  turn-out,  to 
which  are  attached  the  wire  guys  em- 
ployed to  preserve  the  proper  tension  for 
the  conductor  at  these  points. 

Curve  of  Sines.— (1)  A  curve  representing 
at  continuous  successive  positions  the 
successive  values  of  the  sines  of  a  pro- 
gressively varying  angle.  (2)  A  sinusoid. 
(3)  When  drawn  to  rectangular  co-ordi- 
nates, a  curve  successively  rising  above 
and  falling  below  the  axis  of  abscissas  cor- 
responding to  the  sines  of  angles  measured 
along  said  axis. 

Curve  of  Cross-Over  System. — In  a  sys- 
tem of  transposition  for  overhead  wires, 
in  order  to  avoid  the  effects  of  induction, 
the  short  bend  of  wire  which  effects  the 
transposition  at  a  pole  cross-arm. 

Cushioning  Chamber. — In  a  dead-beat 
mirror  galvanometer,  a  chamber  before 
or  behind  a  suspended  mirror,  for  the 

Eurpose  of  dampening  the  motions  of  the 
itter. 

Cut-In. — To  introduce  an  electro-receptive 
device  into  the  circuit  of  a  source  by 
completing  or  closing  the  circuit  through 
it. 

Cut-In.— (1)  A  term  sometimes  employed 
for  filament  cut-out.  (2)  An  automatic 
guard  cut-out. 

Cut-Off. — Any  device  for  cutting  a  battery 
or  other  electric  source  from  a  circuit,  or 
from  part  of  a  circuit. 

Cut-Out. — To  remove  an  electro-receptive 
device  or  loop  from  the  circuit  of  an  elec- 
tric source. 

Cut-Out. — (1)  A  device  for  removing  an 
electro-receptive  device  or  loop  from  the 


Cut.] 


735 


[D.  P, 


circuit  of  an  electric  source.  (2)  A  safety 
fuse.. 

Cut-Out  Board. — A  board  supporting  a 
number  of  fuse  cut-outs. 

Cut-Out  Block. — A  block  containing  a 
fuse  wire  or  safety  catch. 

Cut-Out  Box. — A  box  containing  a  cut- 
out. 

Cut-Out  Cabinet. — Any  enclosed  space 
provided  in  a  building  for  the  reception 
of  cut-outs  or  fuses. 

Cut-Out  Switch. — A  short-circuiting 
switch  by  means  of  which  an  arc-light 
is  cut  out  from  its  feeding  circuit. 

Cutting  and  Holding  Grapnel. — In 
submarine  telegraphy,  a  grapnel  which, 
after  engaging  a  cable  on  the  sea  bottom, 
automatically  grips  the  cable,  and  cuts  it 
beyond  the  grip. 

Cutting  Lines  of  Magnetic  Force. — 
Passing  a  conductor  through  lines  of 
magnetic  force  or  flux,  or  passing  mag- 
netic lines  of  force  or  flux  through  a  con- 
ductor, so  as  to  cut  or  intersect  such  lines 
or  such  flux. 

Cycle. — (1)  A  succession  of  events  which 
periodically  recur,  reckoning  from  any 
stage  of  the  disturbance  to  the  moment 
at  which  that  stage  next  occurs.  (2)  A 
complete  recurrence  of  any  periodic 
change. 

Cycle  of  Alternations. — The  cycle  of 
a  periodically-alternating  electromotive 
force,  current  or  flux. 

Cycle  of  Magnetization. — A  single  com- 
plete passage  of  any  magnetic  substance 
through  the  successive  stages  of  a  period- 
ically-recurring magnetic  change. 

Cyclic. — Of  or  pertaining  to  a  cycle. 

Cyclic  Magnetization. — Magnetization 
produced  in  a  magnetic  substance  when 
subjected  to  periodic  cyclic  changes  in 
the  magnetizing  force. 

Cyclic  Magnetic  Variations. — Secular 
magnetic  variations  occurring  during 
great  cycles  of  time. 

Cyclic  Motion. — Any  motion  which  re- 
occurs in  a  cycle. 


Cyclic  Stability. — (1)  In  an  alternating- 
current  circuit  the  condition  of  uniform 
periodic  motion  in  alternating  quantities, 
such  as  pressure  and  current,  attained 
after  a  definite  number  of  cycles  from  the 
starting  of  the  motion  ;  as  distinguished 
from  the  variable  state  of  motion  when 
the  circuit  is  first  closed.  (2)  The  per- 
manent state  in  an  alternating-current 
circuit. 

Cyclometer. — An  instrument  for  record- 
ing the  number  of  turns  completed  by 
a  wheel,  shaft,  drum,  or  other  rotating 
device,  or  for  indicating  the  distance 
traversed  by  its  periphery. 

Cyclosis. — The  existence  of  independent 
cycles  in  a  diagram. 

Cyclotrope. — A  word  proposed  for  trans- 
former or  converter.  (Not  in  use.) 

Cylindrical  Armature. — A  term  some- 
times applied  to  a  drum  armature. 

Cylindrical  Carbon  Electrodes. — Car- 
bon cylinders  employed  for  the  electrodes 
of  arc  lamps  or  for  battery  plates . 

Cylindrical  Core. — (1)  A  cylindrical- 
shaped  mass  of  iron  employed  for  the 
core  of  a  solenoid  or  helix.  (2)  A  cylin- 
drical-shaped mass  of  soft  carbon  em- 
ployed in  cored  electrodes. 

Cylindrical  Electro-Magnet.— An  elec- 
tro-magnet whose  core  consists  of  a 
hollow  cylinder  provided  with  a  slot 
extending  parallel  to  its  axis. 

Cylindrical  Magnet. — A  cylindrically 
shaped  magnet. 

Cylindrical  Ring-Armature.— A  ring 
armature  whose  core  has  the  shape  of 
a  long  cylinder. 

Cylindrical  Vibrator. — A  weight  in  the 
form  of  a  cylinder  supported  by  a  suspen- 
sion for  the  purpose  of  measuring  its 
torsional  rigidity. 

Cymogene. — An  extremely  volatile  liquid 
hydrocarbon  given  off  from  crude  coal-oil 
during  the  early  stages  of  its  distillation. 

Cystoscopy,  Electric. — The  examination 
of  the  human  bladder  by  electric  illu- 
mination. 


D 


d.  —A  symbol  for  diameter. 

D.  B.  Switch. — A  contraction  for  double- 
break  switch. 

D.  C. — A  contraction  for  direct  current. 
D.   E.   M.  I1. — A  contraction  for  direct- 
electromotive  force. 
"D."  Operator. — A   term   employed   in 


mathematics  for  the  operator  which  ef- 
fects the  total  differentiation  of  a  func- 
tion with  respect  to  time. 

D.  P.  Cut-Out. — A  contraction  for  double- 
pole  cut-out. 

D.  P.  Switch. — A  contraction  for  double- 
pole  switch. 


D.Q.] 


[Dea. 


D.  Q. — In  submarine  telegraphy,  a  signal 
serving  to  separate  the  address  from  the 
text  of  the  message. 

Daily  Variation  of  Magnetic  Needle. 
The  diurnal  variation  of  the  magnetic 
needle. 

Damped  Galvanometer. — A  galvano- 
meter whose  movable  part — i.  e..  whose 
needle  or  coil — when  moved,  comes  to  rest 
as  quickly  as  possible. 

Damped  Magnetic  Needle. — A  magnetic 
needle  so  placed  as  to  come  quickly  to 
rest  after  it  has  been  set  in  motion. 

Damped  Vibrations. — (1)  Vibrations  that 
occur  under  circumstances  in  which  the 
vibratory  or  swinging  motions  can  be  at 
once  brought  to  rest,  instead  of  repeatedly 
swinging  to-and-fro,  on  the  removal  of  the 
force  causing  the  vibration.  (2)  Vibra- 
tions of  successively  diminishing  ampli- 
tude. 

Dampening  Factor. — The  property  of  an 
oscillatory  alternating-current  circuit  of 
diminishing  the  amplitude  of  its  oscilla- 
tions owing  to  the  influence  of  electric 
resistance  or  of  radiation. 

Damper. — (1)  A  metallic  cylinder  so  ar- 
ranged as  to  partially  or  completely  sur- 
round the  iron  core  of  an  induction  coil 
for  the  purpose  of  varying  the  intensity 
of  the  currents  produced  in  the  secondary. 
(2)  A  dash-pot,  or  similar  apparatus,  pro- 
vided for  preventing  the  too  sudden 
movements  of  a  lever  or  other  part  of 
a  moving  device.  (3)  Any  device  em- 
ployed for  damping  a  magnetic  needle. 

Damping. — (1)  The  act  of  stopping  a  sudden 
vibratory  motion  without  waiting  for  it 
to  cease  after  repeated  swingings  to-and- 
fro.  (2)  The  act  of  causing  a  periodically 
moving  body  to  lose  its  energy  of  motion 
by  the  application  of  retarding  forces. 

Damping  Coil  for  Galvanometer.— 
(1)  An  auxiliary  coil  employed  with  a  gal- 
vanometer for  receiving  transient  electric 
currents  from  a  key  under  the  control  of 
an  observer,  for  the  purpose  of  checking 
the  motion  of  the  needle.  (2)  A  short-cir- 
cuited coil,  on  or  near  a  movable  electro- 
magnetic system,  for  the  purpose  of 
damping  its  oscillations  by  the  action  of 
electric  currents  induced  therein. 

Damping,  Electric. — A  term  sometimes 
employed  for  the  decrease  in  the  intensity 
of  the  electric  oscillations  produced  in  a 
resonant  circuit  by  electric  resistance, 
under  circumstances  where  some  of  the 
higher  overtones  are  set  up  in  the  circuit. 

Damping  Magnet.  — Any  magnet  em- 
ployed for  the  purpose  of  checking  the 
motions  of  a  moving  body  or  magnet. 


Damping  Suspension.  —  A  suspension 
which  is  rendered  dead-beat,  or  aperiodic, 
by  the  application  of  any  retarding  force 
or  damping  mechanism. 

Damping  Tube. — (1)  A  tube  fitted  with  a 
glass  cap  and  placed  in  an  instrument  to 
diminish  the  cavity  in  which  a  movable 
system  swings,  and  thus  damp  its  motion. 
(2)  A  conducting  tube  attached  to  a 
movable  system  and  placed  in  the  vicin- 
ity of  fixed  permanent  magnets,  in  order 
to  damp  the  vibrations  of  the  system. 

Damping  Vessel. — A  dash-pot. 

Dani ell's  Voltaic  Cell. — A  zinc-copper 
couple  whose  elements  are  immersed  re- 
spectively in  electrolytes  of  dilute  sul- 
phuric acid  and  a  saturated  solution  of 
copper  sulphate. 

Dark  Discharge. — A  term  applied  by 
Faraday  to  that  portion  of  the  convective 
discharge  which  occurs,  under  certain  cir- 
cumstances, in  the  rarefied  gas  of  an 
exhausted  chamber  between  the  positive 
and  negative  electrodes. 

Dark-Light  Frequencies. — Ether  vibra- 
tions of  the  nature  of  light  whose 
frequencies  are  too  low  to  produce 
physiologically  effective  light. 

Dark-Segment  of  Aurora. — A  dark  or 
non-illumined  portion  of  an  aurora  glory, 
or  crown  of  auroral  light. 

Dash-Pot. — A  mechanical  device  for  pre- 
venting a  too  sudden  motion  in  the 
movable  part  of  any  apparatus. 

Day  Load. — A  load  on  an  apparatus, 
machine,  or  central  station,  occurring 
during  the  daytime  as  distinguished  from 
a  night  load. 

Day  of  Magnetic  Disturbance.— A  day 
during  which  the  mean  departure  of  the 
reading  of  a  declinometer  at  any  place, 
from  the  normal  monthly  value  at  that 
place,  is  at  least  one  and  one-half  times 
the  average. 

Daylight  Color-Values. — Such  values  of 
luminous  frequencies  as  correspond  to 
those  present  in  ordinary  sunlight  or  day- 
light. 

Dead  -  Beat. —  (1)  Heavily  damped.  (2) 
Aperiodic.  (3)  Such  a  motion  of  a  gal- 
vanometer needle,  or  other  suspension 
system,  in  which  the  needle  moves  sharply 
from  point  to  point  and  comes  quickly  to 
rest. 

Dead-Beat  Discharge.— A  non-oscilla- 
tory discharge. 

Dead-Beat  Galvanometer.— (1)  An  aperi- 
odic galvanometer,  or  one  whose  needle 
comes  quickly  to  rest  instead  of  repeat- 


Dea.] 


737 


[Dee. 


edly  swinging  to-and-fro.    (2)  A  heavily 
damped  galvanometer. 
Dead  Beatness. — Possessing  the  property 
of  aperiodicity. 

Dead  Dipping. — Dipping  in  acid  liquids 
for  the  purpose  of  obtaining  a  dead  or 
unpolished  surface  on  an  electro-metal- 
lurgical coating  or  deposit. 

Dead  Earth. — (1)  A  fault  in  a  telegraphic 
or  other  line,  in  which  the  line  is  thor- 
oughly grounded  or  connected  with  earth. 
(2)  A  total  earth.  (3)  An  earth  of  inap- 
preciable or  insignificant  resistance. 

Dead-Ended  Conductor  or  Wire.— A 
conductor  or  wire  whose  end  is  deliber- 
ately left  open  or  insulated,  as,  for  ex- 
ample, by  being  wound  around  an 
insulator. 

Dead  Ending.— Leaving  a  conductor 
dead-ended. 

Dead  Ground  or  Grounding. — Such  a 
grounding  as  will  ensure  a  ground  of 
negligible  resistance. 

Dead  Man. — A  support  for  raising  a  pole 
and  supporting  it  in  place  while  securing 
it  in  the  ground. 

Dead  Points  of  Motor  Armature. — Any 
positions  of  a  motor  armature  when  at 
rest,  in  which  the  driving  current  cannot 
start  it. 

Dead  Resistance  for  Testing  Bank. — 

(1)  A  resistance  for  a  testing  bank  devoid 
of  inductance.  (2)  An  inductionless  re- 
sistance. 

Dead  Wires. — (1)  Any  disused  wires  or 
abandoned  wires,  generally  aerial.  (2)  A 
term  applied  to  that  portion  of  the  wire  on  a 
dynamo  which  produces  no  electromotive 
force  on  its  movements  through  the  field 
flux.  (3)  That  part  of  the  wire  on  a  motor 
which  produces  no  useful  effect  on  the 
passage  through  it  of  a  driving  current. 

Dead  Wires  of  Dynamo  Armature. — 

The  wires  on  the  armature  of  a  dynamo 
or  motor  which  produce  no  useful  elec- 
tromotive force  or  resulting  current  on 
the  movement  of  the  armature  through 
the  field  of  the  machine. 

Dead  Wires  on  Motor  Armature. — The 
wires  on  the  armature  of  a  motor  which 
produce  no  useful  torque  on  the  passage 
through  them  of  an  electric  current. 

Death,  Electric.— Death  resulting  from 
the  passage  of  an  electric  discharge  or  cur- 
rent through  the  human  body. 

Decalescence. — An  absorption  of  sensible 
heat  that  occurs  at  a  certain  time  during 
the  heating  of  a  bar  of  steel. 
47 


Decay  of  Waves.— The  diminution  in  the 
amplitude  of  waves  due  to  obstruction  of 
any  kind. 

Deci. — A  prefix  for  the  one-tenth  part. 

Deci-Ampere. — One-tenth  of  an  ampere. 

Deci- Ampere  Balance. — A  balance  form 
of  ammeter  whose  scale  is  graduated  to 
give  direct  readings  in  deci-amperes. 

Deci-Lux. — The  one-tenth  of  a  lux. 

Deci-Polar  Dynamo. — A  dynamo  whose 
field  is  produced  by  ten  magnet  poles. 

Decimal  Candle. — A  photometric  stand. 

ard  equal  to  the  twentieth  part  of  the 

Violle  platinum  standard. 
Deck  Cable-Lead.  —  Guide  pulleys  or 

leads,  placed  at  suitable  intervals  on  the 

deck  of  a  cable  ship,  extending  from  a 

tank  to  the  bow  or  stern  sheaves,  to  aid  in 

laying  a  submarine  cable. 
Deck-Planer,  Electric. — An  electrically 

driven  rotary  cutter  or  planer,  suitable 

for  planing  the  deck  of  a  ship. 

Deflection  of  Magnet. — The  variation  of 
a  magnetic  needle  from  the  true  geograph- 
ical North. 

Deflection    Compass. — A   declinometer. 

Declinometer. — A  magnetic  needle  suita- 
bly arranged  for  the  measurement  of  the 
magnetic  declination  or  variation  of  any 
place. 

Decohere. — To  restore  or  regain  the  nat- 
ural condition  of  a  coherer. 

Decomposition.  —  The  separation  of  a 
molecule  into  its  constituent  ions  or  radi- 
cals, or  into  its  ultimate  atoms. 

Decomposition,  Ulectric. — Chemical  de- 
composition effected  by  means  of  an  elec- 
tric discharge  or  current. 

Decomposition,  Electrolytic. — The  sep- 
aration of  a  molecule  into  its  consti- 
tuent ions  or  radicals  by  the  action  of  an 
electric  current. 

Decorative  Series  Lamps. — Series-con- 
nected incandescent  lamps  employed  to 
obtain  decorative  effects. 

De-Energize.  —  To  deprive  an  electro- 
receptive  device  of  its  operating  current. 

De-Energizing.  —  Depriving  an  electro- 
receptive  device  of  its  operating  current. 

Deep  Sea-Cable. — That  portion  of  a  sub- 
marine cable  which  is  laid  in  the  deep 
water,  at  a  distance  from  the  coast  or 
shore. 

Deep  -  Seated   Eddy  -  Currents.  —  The 

eddy  currents  that  are  set  up  in  the  mass 
of  a  conductor  subjected  to  electro- 
dynamic  induction,  as  distinguished 


Dee.] 


738 


[Dem. 


from  the  superficially -seated    eddy -cur- 
rents. 

Deep- Water  Submarine-Cable.— A  deep 
sea  cable. 

Defective-Loop  Repeater.— <1)  A  device 
for  employing  the  good  wire  of  a  defective 
loop  to  an  office,  to  receive  and  transmit 
alternately,  on  a  duplex,  or  on  the  com- 
mon side  of  a  quadruplex  set.  (2)  A  re- 
peater connecting  a  branch  office  with  a 
duplex  or  quadruplex  set  at  a  main 
office,  and  arranged  to  operate  on  a  single 
wire  of  a  pair  or  loop  to  said  branch  office 
when  the  other  wire  becomes  defective. 

Deflagration. — A  violent  but  not  explo- 
sive combustion  of  a  substance. 

Deflagration,  Electric. — The  fusion  and 
volatilization  of  metallic  substances  by 
the  passage  through  them  of  an  electric 
current. 

Deilagrator. — The  name  given  to  a  partic- 
ular voltaic  battery  of  small  internal 
resistance,  employed,  in  the  early  history 
of  the  voltaic  battery,  for  the  electric  de- 
flagration of  metallic  substances. 

Deflecting  Magnet.— (1)  The  permanent 
magnet  of  a  magnetometer,  employed  for 
deflecting  a  small  magnetic  needle  sus- 
pended at  a  definite  distance,  in  order  to 
compare  its  influence  with  that  of  the 
earth's  horizontal  magnetic  force.  (2)  The 
compensating  magnet  of  a  galvanometer. 

Deflection  Method. — A  method  employed 
in  electrical  measurements  in  which,  as 
distinguished  from  the  zero  method,  the 
amount  of  the  deflection  produced  on  any 
instrument,  by  a  given  current  or  a  given 
charge,  is  utilized  for  determining  the 
value  of  that  current  or  charge. 

Deflection  of  Cable  Dynamometer. — 
(1)  The  sag,  or  distance  to  which  a  cable 
dynamometer  sheave  descends  below  the 
horizonal  line  corresponding  to  infinite 
tension.  (2)  The  sag  of  a  dynamometer 
sheave  which  increases  as  the  strain  on 
the  cable  diminishes. 

Deflection  of  Magnetic  Needle.— The 
movement  of  a  needle  out  of  a  position  of 
rest,  either  in  the  earth's  magnetic  field, 
or  in  the  field  of  another  magnet,  by  the 
action  of  the  flux  of  an  electric  current  or 
of  a  magnet. 

Deformation. — (1)  Any  displacement  of 
the  particles  of  a  solid  with  reference  to 
one  another,  produced  by  the  action  of  a 
stress.  (2)  A  strain. 

Degeneration  of  Cell. — Such  a  change 
in  the  muscular  or  cellular  structure  of  a 
cell  that  incapacitates  it  from  performing 
its  ordinary  functions. 


Degeneration  of  Energy.— A  degrada- 
tion of  energy. 

Deka. — A  prefix  signifying  ten  times. 

Deka- Ampere.— Ten  amperes. 

Deka- Ampere  Balance.— A  balance-form 

of  ammeter  measuring  tens  of  amperes 

(0  to  100  amperes. ) 

Deliquescence. — The  solution  of  a  crys- 
talline solid  arising  from  its  absorption  of 
the  vapor  of  water  from  the  atmosphere. 

Delivered  Power.— In  a  system  of  elec- 
trical transmission,  the  power  that  is 
delivered  at  one  end  of  a  line  as  distin- 
guished from  the  power  sent  into  the  line 
at  its  other  end. 

Delta  Connection.  —  The  connection  of 
circuits  employed  in  a  delta  triphase- 
systern. 

Delta  Current.— (1)  The  current  between 
adjacent  wires  or  terminals  of  a  triphase- 
system.  (2)  The  ring  current. 

Delta  Potential  of  Triphase  System. — 

(1)  The  effective  difference  of  potential, 
or  voltmeter  pressure,  between  adjacent 
wires  or  terminals  of  a  triphase-sj^stem. 

(2)  The  ring  potential. 

Delta  Triphase-System.  —  A  triphase 
system  in  which  the  terminal  connections 
resemble  the  Greek  letter  delta,  or 
triangle. 

Demagnetizable.— Capable  of  being  de- 
prived of  magnetism. 

Demagnetization.— The  act  of  depriving 
a  magnet  of  its  magnetism. 

Demagnetization  by  Successive  Re- 
versals. —  A  process  for  removing  the 
magnetism  from  a  mass  of  steel,  as  in  a 
watch,  by  subjecting  it  to  many  success- 
ive magneto-motive  forces  alternating 
in  direction  and  gradually  diminishing  to 
zero. 

Demagnetize. — To  deprive  of  magnetism. 
Demagnetizing. — Depriving   of  magnet- 
ism. 

Demagnetizing  Current.— The  current 
which  serves  to  remove  the  magnetization 
of  some  magnetic  device. 

Demagnetizing  Lines  of  Flux.— Mag- 
netic flux  produced  by  a  magnetized  bar 
in  a  direction  opposite  to  the  magnetizing 
force,  and  tending,  therefore,  to  demag- 
netize the  bar. 

Demand  Recording-Meter.— A  meter 
which  registers  the  maximum  demand 
for  electric  energy,  usually  a  meter  which 
registers  the  maximum  current  strength 
supplied  through  it,  in  addition  to  the 
total  quantity  of  electricity  delivered. 


Dem.] 


739 


[Dia. 


Demarcation  Current.— A  term  some- 
times applied  to  the  electric  current  ob- 
tained from  an  injured  muscle. 

Density,  Electric. — The  quantity  of  free 
electricity  on  any  unit  of  area  of  surface 
of  a  charged  body. 

Density  of  Charge. — The  quantity  of 
electricity  per-unit-of-area  at  any  part  of 
a  charged  surface. 

Density  of  Current. — The  quantity  of 
current  that  passes  per-unit-of-area  of 
cross-section  in  any  part  of  a  circuit. 

Density  of  Electrification. — The  density 
of  an  electrostatic  charge. 

Density  of -Field. — The  quantity  of  mag- 
netic flux  that  passes  through  any  field 
per-unit-of-area  of  cross-section. 

Dentiphone. — An  audiphone. 

Dephased.— (1)  Differing  in  phase.  (2) 
Caused  to  differ  in  phase. 

Depolarization. — The  act  of  reducing  or 
removing  the  polarization  of  a  voltaic 
cell  or  battery. 

Depolarize. — To  deprive  of  polarization. 

Depolarizer. — The  material  employed  in 
voltaic  cells  for  the  purpose  of  depolar- 
izing them. 

Depolarizing. — Depriving  of  polarization. 

Depolarizing  Fluid  or  Liquid.  —  An 
electrolytic  fluid  or  liquid  employed  in  a 
voltaic  cell  for  the  purpose  of  preventing 
or  lessening  polarization. 

Depositing  Cell  or  Vat. — Any  electro- 
lytic cell  in  which  an  electro-metallur- 
gical deposit  is  made. 

Deposition,  Electric.— The  deposit  of  a 
substance,  generally  a  metal,  by  the  action 
of  electrolysis. 

Deprez-D' Arson val  Galvanometer.— A 

form  of  dead-beat  galvanometer. 
Derivation. — (1)  A  shunt  or  derived  cir- 
cuit.    (2)  A  leak. 

Derivative  or  Derived  Current.— The 
current  that  flows  through  a  branch  or 
derived  circuit. 

Derived  Circuit.— (1)  A  branch  or  shunt 
circuit.  (2)  A  derivation. 

Derived-Circuit  Arc-Lamp.— The  name 
sometimes  employed  for  a  differential  arc- 
lamp. 

Derived  Units. — Various  secondary  units 
obtained  or  derived  from  the  fundamental 
units  of  length,  mass,  and  time. 

Desk  Loop. — (1)  In  telegraphy,  a  loop  or 
circuit,  running  to  a  desk  in  a  telegraph 
office,  and  connecting  the  apparatus  on 
such  desk  with  main-line  apparatus  at 
some  other  table.  (2)  A  circuit  connect- 


ing an  operator  at  one  desk  with  a  duplex 
or  quadruplex  set  of  apparatus  at  another 
desk  for  convenience  in  handling  the 
traffic. 

Desk  Push. — An  electric  push  attached 
to  a  desk  for  the  purpose  of  ringing  a  call- 
bell,  or  closing  some  other  electric  circuit. 

Desk  Set. — Telephone  apparatus  arranged 
for  use  on  a  desk. 

Destructive  Distillation. — The  action  of 
heat  on  an  organic  substance  while  out  of 
contact  with  air,  resulting  in  the  decom- 
position of  the  substance  into  simpler  and 
more  stable  compounds. 

Detector  Galvanometer. — Any  rough 
form  of  galvanometer  or  galvanoscope 
employed  for  detecting  the  presence  of 
electric  currents. 

Detector  Peg. — A  peg  used  in  connection 
with  a  detector  galvanometer. 

Detonating  Fuse.— (1)  A  fuse  that  is  ex- 
ploded by  a  percussion  or  blow.  (2)  A 
percussion  fuse. 

Detorsion  Bar. — A  bar  placed  in  a  mag- 
netic declinometer  for  the  purpose  of  re- 
moving the  torsion  on  the  suspending 
thread  of  the  magnet. 

Developed  Winding. — A  winding  of  a 
dynamo-electric  machine  developed  .  or 
expanded  upon  a  drawing  or  plane. 

Devil  Claws.— A  device  employed  in 
stringing  overhead  wires. 

Dextrorsal  Helix. — A  name  sometimes 
applied  to  a  dextrorsal  solenoid. 

Dextrorsal  Solenoid. — A  solenoid  whose 
winding  is  right-handed. 

Diacritical  Current.— Such  a  strength  of 
a  magnetizing  current  as  produces  a  mag- 
netization of  an  iron  core  equal  to  one- 
half  saturation. 

Diacritical  Number. — Such  a  number  of 
ampere  turns  at  which  a  given  core  would 
receive  a  magnetization  equal  to  one- 
half  saturation. 

Diacritical  Point  of  Magnetic  Satu- 
ration. —  A  term  proposed  for  such  a 
value  of  the  co-efficient  of  magnetic  satu- 
ration that  its  core  is  magnetized  to  ex- 
actly one-half  of  its  possible  maximum 
magnetization. 

Diagometer. — An  apparatus  in  which  an 
attempt  is  made  to  determine  the  chemi- 
cal composition,  and  consequent  purity,  of 
certain  substances  by  their  electrical  con- 
ducting powers. 

Dial  Bridge  or  Rheostat. — A  resistance 
bridge  or  rheostat  whose  contact  points 
are  arranged  in  the  shape  of  a  dial. 


Dia.] 


740 


[Die. 


Dial  Telegraph.— A  general  term  embrac- 
ing the  apparatus  employed  in  dial  teleg- 
raphy. 

Dial  Telegraphy.  —  A  system  of  teleg- 
raphy in  which  the  messages  are  received 
by  the  movements  of  a  needle  over  a  dial 
plate. 

Dialysis. — The  act  of  separating  a  liquid 
mixture  into  its  crystalloids  and  colloids 
by  passing  the  liquid  through  a  mem- 
brane. 

Dialyzing. — Subjecting  to  the  process  of 
dialysis. 

Diamagnetic. — The  property  possessed  by 
substances  like  bismuth,  phosphorus, 
antimony,  zinc  and  others,  of  being  ap- 
parently repelled  when  placed  between 
the  poles  of  powerful  magnets. 

Diamagnetic  Permeability. — The  per- 
meability to  magnetic  flux  possessed  by 
diamagnetic  substances. 

Diamagnetic  Polarity. — A  polarity,  the 
reverse  of  ordinary  magnetic  polarity,  the 
existence  of  which  was  assumed  to  ex- 
plain the  phenomena  of  diamagnetism. 

Diamagnetically.  —  In  a  diamagnetic 
manner. 

Diamagnetism. — A  name  sometimes  given 
to  the  magnetism  of  diamagnetic  bodies. 

Diamagnetized. — Subjected  to  the  action 
of  so-called  diamagnetism. 

Diamagnetometer.  —  A  magnetometer 
designed  for  the  study  of  diamagnetism. 

Diamagnets.  —  Diamagnetic  substances 
subjected  to  magnetic  induction,  and 
formerly  called  diamagnets  in  contra- 
distinction to  ordinary  or  paramagnets. 

Diameter  of  Commutation.  —  (1)  The 
diameter  of  the  commutator  cylinder  of  a 
dynamo  at  which  the  brushes  are  applied. 
(2)  That  diameter  on  the  commutator 
cylinder  of  an  open-circuited  armature, 
which  joins  the  points  of  contact  of  the 
collecting  brushes. 

Diaphragm. — (1)  A  sheet  of  an  elastic 
solid,  generally  circular  in  shape,  securely 
fastened  at  its  edges  and  capable  of  being 
set  into  vibration.  (2)  The  porous  wall  or 
septum  of  an  endosmometer.  (3)  The 
porous  partition  of  a  voltaic  cell.  (4)  A 
disc  of  blackened  metal  provided  with 
a  circular  aperture  and  employed  for 
cutting  off  all  the  light  from  a  lens  except 
that  falling  on  its  central  portions. 

Diaphragm  Currents. — Electric  currents 
produced  by  forcing  a  liquid  through  the 
capillary  pores  of  a  diaphragm. 

Diaphragm  of  Voltaic  Cell.  — (1)  The 
porous  partition  or  plate  of  a  voltaic  cell. 
(2)  Generally,  a  porous  cell. 


Diaphragm  Photometer.— A  photometer 
which  depends  on  the  equality  of  the 
brightness  obtained  on  the  two  halves  of  a 
diaphragm  or  screen,  either  by  varying 
the  distances  of  the  lights  from  the  screen 
or  by  varying  the  inclination  of  the 
luminous  rays  thereon. 

Dice-Box  Insulator. — A  name  sometimes 
applied  to  a  double-cone  insulator. 

Dielectric. — Any  substance  which  permits 
electrostatic  induction  to  take  place 
through  its  mass. 

Dielectric  Absorption. — The  absorption 
of  a  charge  or  current  by  a  dielectric. 

Dielectric  Capacity. — A  term  employed 
in  the  same  sense  as  specific  ijiductive 
capacity. 

Dielectric  Circuit. — A  circuit  formed  in 
whole  or  in  part  through  a  dielectric  as 
opposed  to  a  conducting  circuit. 

Dielectric  Constant. — A  term  sometimes 
employed  in  place  of  specific  inductive 
capacity. 

Dielectric  Current. — (1)  The  rate-of -in- 
crease of  the  polarization  of  a  dielectric 
produced  by  a  change  in  the  polariza- 
tion through  the  circuit.  (2)  A  displace- 
ment current. 

Dielectric  Density  of  a  Gas.— A  term 
sometimes  employed  instead  of  dielectric 
strength  of  a  gas. 

Dielectric  Displacement.— (1)  Electric 
displacement  taking  place  through  a  die- 
lectric. (2)  The  electromotive  intensity  in 
a  dielectric  multiplied  by  4?r  and  divided 
by  the  dielectric  co-efficient. 

Dielectric  Elasticity. — (1)  The  reciprocal 
of  the  dielectric  co-efficient.  (2)  The 
measure  of  the  electric  force  that  must  be 
exerted  upon  a  dielectric  in  order  to  effect 
unit  displacement. 

Dielectric  Energy  Current.— That  com- 
ponent of  an  alternating  current  passing 
through  a  condenser  which  is  in  phase 
with  the  impressed  E.  M.  F.  at  its  termi- 
nals. 

Dielectric  Hysteresis.— (1)  A  variety  of 
molecular  friction,  analogous  to  magnetic 
hysteresis,  produced  in  a  dielectric  under 
changes  of  electrostatic  stress.  (2)  That 
property  of  a  dielectric  by  virtue  of  which 
energy  is  consumed  in  reversals  of  electri- 
fication. 

Dielectric  Hysteretic  Admittance. — 
(1)  In  an  alternating-current  circuit  the 
apparent  component  of  admittance  due  to 
dielectric  hysteresis.  (2)  In  a  condenser 
traversed  by  an  alternating  current  the 
admittance,  which  is  the  geometrical  sum 
of  the  hysteretic  conductance  and  the  hy 


Die.] 


741  [Dif. 


steretic  susceptance,  or  whose  reciprocal  is 
the  vector  hysteretic  impedance. 

Dielectric  Hysteretic  Impedance. — In 
an  alternating-current  circuit,  the  ap- 
parent component  of  impedance  due  to 
dielectric  hysteresis. 

Dielectric  Hysteretic  Lag. — Lag  in  an 
alternating-current  circuit  due  to  dielec- 
tric hysteresis. 

Dielectric  Medium. — Any  medium  ca- 
pable of  acting  as  a  dielectric. 

Dielectric  Polarization. — (1)  The  polari- 
zation of  a  dielectric  by  means  of  which 
electric  induction  takes  place.  (2)  Dielec- 
tric displacement. 

Dielectric  Resistance.  —  (1)  The  resist- 
ance which  a  dielectric  offers  to  mechan- 
ical strains  produced  by  electrification. 
(2)  The  resistance  of  a  dielectric  to  dis- 
placement currents. 

Dielectric  Static  Hysteresis. — Hystere- 
sis occurring  in  a  dielectric  under  succes- 
sive electric  reversals,  and  due  to  a  quasi- 
electrostatic  friction  independent  of  the 
rate  of  reversal,  as  distinguished  from 
dielectric  viscous  hysteresis  which  varies 
with  the  frequency  of  cyclic  electric  re- 
versals. 

Dielectric  Strain. — (1)  The  strained  con- 
dition of  the  glass  or  other  dielectric  of  a 
condenser  produced  by  the  charging  of 
the  condenser.  (2)  The  deformation  of  a 
dielectric  under  the  influence  of  an  elec- 
tro-magnetic stress. 

Dielectric  Strength  of  Gas.— The  elec- 
tromotive intensity  a  gas  is  capable  of 
bearing  without  permitting  a  disruptive 
discharge  to  pass  through  it,  and  capable 
of  measurement  in  volts  per  centimetre. 

Dielectric  Stress.-^(l)  The  electro-mag- 
netic force  producing  a  deformation  or 
strain  in  a  dielectric.  (2)  Electromotive 
intensity. 

Dietrine. — A  name  given  to  a  variety  of 
insulating  material. 

Difference  of  Potential.— That  quanti- 
tative property  in  space  by  virtue  of 
which  work  is  done  when  a  mass  of  any 
kind  is  moved  from  one  point  to  another. 

Difference  of  Electric  Potential.— 
(1)  That  quantitative  property  in  space 
whereby  work  is  done  when  an  electric 
charge  is  moved  therein.  (2)  The  electric 
work  done  on  a  unit  charge  in  an  excur- 
sion between  two  points. 

Difference  of  Magnetic  Potential.— 
(1)  That  quantitative  property  in  space 
whereby  work  is  done  when  a  magnetic 
pole  moves  therein.  (2)  The  magnetic 


work  done  on  a  unit  magnetic  pole  in  an 
excursion  between  two  points. 
Difference  of  Tension. — A  term  some- 
tunes  incorrectly  employed  for  difference 
of  potential. 

Difference  of  Thermal  Pressure.—  A 
phrase  sometimes  employed  for  the  dif- 
ference of  temperature  between  any  two 
points  in  a  conducting  substance  that 
is  assumed  to  cause  the  flow  of  heat 
through  that  conductor  from  the  higher 
to  the  lower  temperature. 

Difference  Theory  of  Muscle  and 
Nerve  Currents. — A  theory  proposed 
to  explain  the  cause  of  the  electric  cur- 
rents in  living  tissues,  by  an  alteration  or 
change  in  the  protoplasm,  by  injury,  by 
differences  of  temperature,  or  by  polari- 
zation. 

Differential  Coils.— Coils  that  are  differ- 
entially wound,  or  that  act  differentially. 

Differential  Compound  Motor.  —  (1) 
A  compound  motor  in  which  the  mag- 
neto-motive force  of  the  working  current 
is  opposed  to  the  magneto-motive  force  of 
the  shunt  excitation,  for  the  purpose  of 
maintaining  the  speed  constant  under  all 
loads.  (2)  A  compound-wound  contin- 
uous-current motor. 

Differential  Electric  Arc-Lamp.— A 
term  formerly  employed  for  a  derived- 
circuit  arc-lamp,  in  which  the  lifting 
magnet  either  consists  of  a  core  or  sole- 
noid wound  with  series  and  shunt  coils, 
or  of  two  separate  and  opposed  cores,  one 
of  which  contains  the  series  and  the  other 
the  shunt  winding. 

Differential  Electric  Bell. — An  electric 
bell  whose  magnetizing  coils  are  differ- 
entially wound. 

Differential  Electro-Dynamometer. — 
(1)  A  double  dynamometer  with  two  mov- 
ing coils  rigidly  connected  and  oppositely 
acted  on,  so  that  the  movement  of  the  sus- 
pension system  can  be  reduced  to  zero  by 
electrical  adjustments  made  while  the  in- 
strument is  under  operation.  (2)  A  dyna- 
mometer for  measuring  the  difference 
between  two  electro-dynamic  forces. 

Differential  Electro-Magnet.— A  differ- 
entially-wound electro-magnet. 

Differential  Equation. — An  equation 
connecting  quantities  into  which  one  01 
more  differential  coefficients  or  differ- 
entials enter. 

Differential  Galyanometer.— A  gal- 
vanometer containing  two  coils,  so  wound 
as  to  tend  to  deflect  its  needle  in  opposite 
directions. 


Dif.] 


742 


[Dil. 


Differential  Induction  Coil.— (1)  An  in- 
duction coil  employed  in  duplex  and  quad- 
ruplex  telegraphy, '  having  two  differ- 
entially-wound primary  coils,  one  of 
which  is  placed  in  the  main  line  of  the 
circuit,  and  the  other  in  the  circuit  of  an 
artificial  line.  (2)  In  telephony,  an  induc- 
tion coil  which  sometimes  forms  part  of 
the  equipment  of  a  multiple  switchboard 
operator. 

Differential  Inductometer. — A  galvano- 
metric  apparatus  for  measuring  the  mo- 
mentary currents  produced  by  the  dis- 
charge of  a  cable. 

Differential  Magnetometer. — A  mag- 
netometer having  a  divided  magnetic  cir- 
cuit and  a  needle  differentially  acted  upon 
by  the  branches. 

Differential  Method  of  Duplex  Teleg- 
raphy.— A  system  of  duplex  telegraphy 
in  which  the  coils  of  the  receiving  and 
transmitting  instruments  are  differenti- 
ally wound. 

Differential  Method  of  Quadruplex 
Telegraphy. — A  system  of  quadruplex 
telegraphy  by  means  of  a  double-differ- 
ential duplex  system. 

Differential  Permeability.— The  differ- 
ential coefficient  of  flux  density  to  mag- 
netizing force  in  a  substance  undergoing 
magnetization. 

Differential  Relay. — A  telegraphic  relay 
containing  two  differentially  wound  coils 
of  wire  on  its  magnet  core. 

Differential  Speed.— In  an  induction 
machine,  the  angular  velocity  of  the  field 
relatively  to  the  rotor. 

Differential  Susceptibility.— The  differ- 
ential coefficient  of  the  magnetic  intensity 
to  the  magnetizing  force  in  a  substance 
undergoing  magnetization. 

Differential  Thermo-Pile. — A  thermo- 
pile whose  two  opposite  faces  are  exposed 
to  the  action  of  two  nearly  equal  sources 
of  heat,  in  order  to  determine  accurately 
the  difference  in  the  thermal  intensities 
of  such  sources  of  heat. 

Differential  Voltmeter.— A  voltmeter 
consisting  of  two  separate  decomposition 
cells,  one  placed  in  a  circuit  of  known 
resistance,  and  the  other  in  a  circuit 
whose  resistance  is  to  be  determined. 

Differential  Winding.— Such  a  double 
winding  of  magnet  coils  that  the  two 
poles  produced  thereby  are  opposed  to 
each  other. 

Differential  Winding  of  Field.— (1) 
A  field-magnet  winding  in  which  two  ex- 
citing currents  exert  opposing  magneto- 
motive forces.  (2)  A  form  of  winding 


in  which  the  magnetizing  flux  of  the 
series  coil  is  opposed  by  the  magnetizing 
flux  of  the  shunt  coils. 

Differentially- Wound  Dynamo-Elec- 
tric Machine. — A  compound-wound 
dynamo-electric  machine. 

Differentially-Wound  Motor.— A  com- 
pound-wound motor,  in  which  the  current 
in  the  shunt  coils  opposes,  in  its  magnet- 
izing effects,  the  current  in  the  series  coil, 
so  that  the  efficient  magnetizing  effect 
produce-d  is  the  difference  between  the 
magnetizing  effects  of  the  two  coils. 

Differentially  Wound  Translator. — 
In  telephony,  a  translator  having  one 
primary  and  two  equal  secondary  coils, 
employed  in  duplex  working. 

Diffraction  Grating. — A  plate  containing 
a  series  of  parallel  linear  openings,  slits  or 
scratches,  separated  by  opaque  or  smooth 
spaces,  employed  for  producing  spectra 
by  diffraction  or  interference. 

Diffusing  Globes  for  Electric  Lights. 
Globes  so  constructed  as  to  ensure  a  dif- 
fusion of  the  light  around  which  they  are 
placed. 

Diffusion  Creep. — A  term  sometimes  used 
for  the  diffusion  of  an  electric  current. 

Diffusion  of  Electric  Current.— The 
flow  of  an  electric  current  in  the  portions 
of  a  conducting  substance  that  lie  outside 
the  parts  in  the  direct  line  between  the 
points  where  the  terminals  of  an  electric 
source  are  applied,  so  that  a  difference 
exists  in  the  density  of  the  current  at  dif- 
ferent points  of  such  substance. 

Diffusion  of  Electric  Waves.— (1)  The 
scattering  of  electric  waves,  or  their 
deviation  from  a  parallel  beam.  (2)  The 
transmission  of  electric  waves  through  a 
medium. 

Diffusion  of  Electro-Therapeutic  Cur- 
rent.— The  differences  in  the  density  of 
current  in  different  portions  of  the  human 
body,  lying  between  electro-therapeutic 
electrodes. 

Diffusion  of  Lines  of  Force. — The  diffu- 
sion of  magnetic  flux. 

Diffusion  of  Magnetic  Flux.— The 
lateral  deflection  of  magnetic  flux  from 
the  direct  path  between  the  poles  that 
produce  it. 

Digging  Spoon. — A  spoon-shaped  shovel 
used  in  digging  holes  for  telegraph  poles. 

Dilation,  Electric. — Electric  expansion, 
or  an  increase  in  volume,  produced  in  a 
body  by  an  electric  charge. 

Dilatometer. — An  instrument  resembling 
a  thermometer,  employed  in  measuring 
the  expansion  of  a  liquid  by  heat. 


Dim.] 


743 


[Dip. 


Dimensions  of  Electro-Magnetic 
Units. — The  conventional  exponential 
values  of  electro-magnetic  units  in  terms 
of  the  fundamental  units  of  length,  mass, 
and  time. 

Dimensions  of  Electrostatic  Units. — 
The  exponential  values  given  convention- 
ally to  the  units  of  the  electrostatic 
system,  in  terms  of  the  fundamental 
units  of  length,  mass,  and  time. 

Dimensions  of  Magnetic  Units. — The 
exponential  values  given  conventionally 
to  the  units  of  the  magnetic  system,  in 
terms  of  length,  mass,  and  time. 

Dimensions  of  Units.— The  exponential 
values  given  conventionally  to  units  in 
terms  of  length,  mass,  and  time. 

Diminished  Electric  Irritability. — A 
decrease  in  the  irritability  of  nervous  or 
muscular  tissue  produced  by  a  suitable 
electric  current. 

Dimmer. — A  clicking  coil  employed  in  an 
alternating-current  system  of  distribution 
for  regulating  the  current  strength  pass- 
ing through  incandescent  lamps. 

Diode  Working. — A  term  employed  for 
the  two-way  mode  of  telegraphic  working 
established  by  the  Delany  Synchronous 
Multiplex  Telegraphic  System. 

Diopter. — A  unit  of  the  refracting  or  focal 
power  of  a  lens. 

Dioptre. — An  orthography  commonly  em- 
ployed for  diopter. 

Dioptric. — An  orthography  sometimes 
employed  for  diopter. 

Dioptric. — Of  or  pertaining  to  dioptrics. 

Dioptric  Shade.— A  shade  for  a  luminous 
source  made  of  refractive  material,  which 
prevents  the  light  from  passing,  in  cer- 
tain directions,  by  reason  of  its  refractive 
power. 

Dioptrics. — The  science  which  treats  of 
the  refraction  of  light. 

Dioptry . — An  orthography  frequently  em- 
ployed for  diopter. 

Dip. — The  inclination  of  a  magnetic  needle. 
Dip   Circle. — A  dipping  needle  provided 

with  means  for  accurately  measuring  the 

angle  of  dip. 

Dip  of  Line- Wire  or  Conductor.— The 
sag,  due  to  its  weight,  of  an  aerial  con- 
ductor between  any  two  of  its  adjacent 
supports. 

Diphase  -  Alternating  Currents.— (1) 
Two  separate  alternating  electric  currents 
whose  phase  difference  is  a  quarter  of  a 
cycle.  (2)  Two-phase  currents.  (3) 
Quarter-phase  currents. 


Diphase- Alternating  E.  M.  F's.— (l)Two 
separate  alternating-electromotive  forces 
whose  phase  difference  is  a  quarter  of  a 
cycle.  (2)  Two-phase  E.  M.  F.'s.  (3)  Quar- 
ter-phase E.  M.  F.'s. 

Diphase  Alternator.— An  alternator  that 
produces  diphase  E.  M.  F.'s. 

Diphase  Armature. — The  armature  of  a 
diphase  alternator,  or  diphaser. 

Diphase  Armature- Winding.— Any  ar- 
mature winding  capable  of  furnishing 
diphase  currents. 

Diphase  Circuit. — A  circuit,  consisting 
either  of  three  or  four  separate  wires,  em- 
ployed for  the  transmission  of  diphase 
currents. 

Diphase  Field.— A  diphase  magnetic  field. 
Diphase    Generator. — (1)    A    generator 

capable  of  producing  diphase  E.  M.  F.'s. 

(2)  A  diphase  alternator. 

Diphase  Inter-Connected  Circuit.— 
(1)  A  diphase  circuit  consisting  of  two 
outgoing  conductors,  one  for  each  phase  or 
side  of  the  system,  and  a  single  return- 
conductor  common  to  both.  (2)  A  di- 
phase system  in  which  the  two  diphase  cir- 
cuits are  not  electrically  separated  or  in- 
dependent. 

Diphase  Magnetic-Field. — A  magnetic 
field  produced  by  diphase  currents. 

Diphase  Motor. — A  motor  suitable  for  use 
with  diphase  electric  currents. 

Diphase  Rotary-Field.— (1)  A  magnetic 
field  produced  by  four  or  more  magnet 
poles  whose  coils  are  so  wound  that  their 
polarity  not  only  alternates  with  changes 
in  the  direction  of  the  current,  but  acts 
as  though  the  field  rotated.  (2)  A  rotat- 
ing magnetic  field  produced  by  diphase 
currents. 

Diphase  Transformer. — A  polyphase 
transformer  suitable  for  use  with  diphase 
currents. 

Diphase  -  Triphase    Transformer.  —  A 

transformer  for  converting  diphase  into 

triphase  currents. 
Diphaser. — A  word  sometimes  used  for 

diphase  alternator. 
Diplex  Circuit. — The  circuit,  including 

the  line  wire  and  apparatus,  employed  in 

any  diplex  system. 

Diplex  Telegraph. — A  general  term  em- 
bracing the  apparatus  employed  in  diplex 
telegraphy. 

Diplex  Telegraphy.— Any  method  by 
which  two  telegraphic  messages  can  be 
simultaneously  sent  in  the  same  direction 
over  a  single  wire. 


Dip.] 


744 


[Dh\ 


Diplex  Telephony. — Any  method  by 
which  two  telephone  messages  can  be 
simultaneously  sent  in  the  same  direction 
over  the  same  wire. 

Diplex  Transmission. — The  simulta- 
neous telegraphic  or  telephonic  transmis- 
sion of  two  messages  in  the  same  direction 
over  a  single  wire. 

Dipolar. — (1)  Possessing  two  poles.  (2)  Bi- 
polar. 

Dipping. — (1)  An  electro-metallurgical 
process  whereby  a  thin  coating  or  depos- 
it of  metal  is  obtained  on  the  surface  of 
another  metal  by  dipping  it  in  a  solution 
of  a  readily  decomposable  metallic  salt. 
(2)  Cleansing  surfaces  for  electro-plating, 
by  immersing  them  in  various  acid 
liquors. 

Dipping  Basket. — A  perforated  basket 
of  non-corrosive  material,  employed  in 
electro-plating,  for  the  reception  of 
articles  that  are  to  be  cleansed  by  dip- 
ping. 

Dipping  Hook. — A  metallic  hook  em- 
ployed in  electro-plating  for  holding  ar- 
ticles that  are  to  be  cleansed  by  dipping. 

Dipping  Magnetic-Needle. — (1)  A  mag- 
netic needle  suspended  so  as  to  be  free  to 
move  in  a  vertical  plane  only,  and  em- 
ployed to  determine  the  angle  of  dip  or 
magnetic  inclination.  (2)  An  inclination 
compass. 

Dipping  Needle. — A  term  sometimes  used 
for  a  dipping  magnetic  needle. 

Dipping  "Wire. — The  wire  employed  in 
electro-metallurgy  for  suspending  small 
articles  that  are  to  be  cleansed  by  dip- 
ping. 

Dips. — Acid  liquors  employed  in  dipping. 

Direct-Coupled  Dynamo. — A  dynamo 
whose  armature  shaft  is  directly  coupled 
to  the  driving  shaft. 

Direct  Coupling. — Coupling  the  shaft  of 
a  dynamo  armature  directly  to  the  driv- 
ing or  engine  shaft. 

Direct-Current. — (1)  A  current  whose  di- 
rection is  constant,  as  distinguished  from 
an  alternating  current.  (2)  A  continuous 
current. 

Direct-Current  Dynamo-Electric  Ma- 
chine.-~Any  dynamo-electric  machine 
capable  of  furnishing  direct  currents. 

Direct-Current  Electric  Motor.— An 
electric  motor  driven  by  means  of  direct 
or  continuous  currents,  as  distinguished 
from  a  motor  driven  by  alternating  cur- 
rents. 

Direct- Current  Rotary  Transformer. — 
(1)  A  term  sometimes  employed  for  a  ro- 


tating secondary  generator  of  continuous 
currents.  (2)  A  motor-dynamo  or  dyna- 
motor. 

Direct-Current  Transformer. — (1)  A 
transformer  intended  to  vary  the  strength 
of  continuous  currents.  (2)  A  direct-cur- 
rent secondary -generator. 

Direct-Driven  Dynamo  of  Generator. 
A  direct-coupled  dynamo  or  generator. 

Direct-Deflection  Method  of  Measur- 
ing Resistance. — A  method  of  measur- 
ing resistance  based  on  the  deflection  of 
a  galvanometer  in  circuit  with  a  resist- 
ance and  a  battery. 

Direct-Electromotive    Force.— (1)    An 

electromotive  force  acting  on  a  circuit  in 
the  same  direction  as  another  electromo- 
tive force  already  existing  in  that  circuit. 
(2)  The  electromotive  force  acting  on  any 
circuit  in  contra-distinction  to  the  coun- 
ter-electromotive force  set  up  in  such  cir- 
cuit. (3)  A  continuous-electromotive 
force  as  distinguished  from  an  alternat- 
ing-electromotive force. 

Direct  Excitation. — (1)  The  excitation  of 
a  muscle,  resulting  from  the  placing  of  an 
electrode  directly  on  the  muscle  itself. 
(2)  The  excitation  of  a  dynamo  electric 
machine  by  a  separate  source  of  direct 
currents,  as  distinguished  from  its  excita- 
tion by  commuted  currents  taken  from 
its  own  armature. 

Direct-Induced  Current. — The  break  in- 
duced current. 

Direct  Inker. — An  ink-writing  Morse  re- 
corder, wound  for  insertion  in  a  tele- 
graphic line,  as  distinguished  from  one 
wound  for  a  local  circuit. 

Direct  Lightning-Discharge. — The  act- 
ual lightning  discharge,  as  distinguished 
from  the  back  or  return-stroke  or  dis- 
charge. 

Direct-Reading  Galvanometer. — A  gal- 
vanometer in  which  the  absolute  value  of 
the  deflection  and  current  strength  are  in- 
dicated directly,  or  without  computation. 

Direct  Sounder.^-A  telegraphic  sounder 
wound  for  a  line  circuit  and  not  for  use  in 
the  local  circuit  of  a  relay. 

Direct-Reading  Potentiometer. — A  po- 
tentiometer which  indicates  directly  on 
its  scale  the  pressure  measured  at  its  ter- 
minals. 

Direct  Working  of  Telegraphic 
Sounder. — The  working  of  a  telegraphic 
sounder  without  the  use  of  a  telegraphic 
relay. 

Directed  Streaming-Discharge.— A 
Tesla  or  high-frequency  discharge  which 


Dir.] 


745 


[Di? 


assumes  the  shape  of  a  highly  luminous 
cone. 

Directing  Clock. — A  controlling  or  mas- 
ter clock. 

Directing  Magnet. — A  controlling  or  com- 
pensating magnet. 

Direction  of  Electric  Current. — A  con- 
vention whereby  an  electric  current  is 
regarded  as  leaving  a  source  at  its  positive 
pole,  and  re-entering  it  at  its  negative 
pole. 

Direction  of  Electrostatic  Flux. — A 
convention  whereby  it  is  assumed  that 
electrostatic  flux  leaves  a  positively 
charged  body  at  its  positive  pole,  and  ter- 
minates on  a  negatively  charged  body. 

Direction  of  Lines  of  Force.— The  direc- 
tion of  magnetic  or  electrostatic  flux. 

Direction  of  Magnetic  Flux. — A  con- 
vention whereby  it  is  assumed  that  mag- 
netic flux  issues  from  a  magnet  at  its 
north-seeking  pole,  and  returns  to  it  at  its 
south-seeking  pole. 

Direction   of  Negative  Rotation. — In 

the  conventionally  adopted  system  of 
kinetics,  a  clock-wise  rotation  about  an 
axis  as  viewed  from  the  front  side  of  the 
clock. 

Direction  of  Positive  Rotation. — In  the 
conventionally  adopted  system  of  kinet- 
ics the  counter-clockwise  direction  of 
rotation  about  an  axis  as  viewed  from 
the  front  face  of  the  clock. 

Directive  Tendency  of  Magnetic 
Needle. — The  tendency  of  a  magnetic 
needle  to  come  to  rest  in  the  direction  of 
the  earth's  magnetic  flux. 

Disc  Armature.— (1)  The  armature  of  a  dy- 
namo-electric machine  whose  windings 
consist  of  flat  coils  supported  on  the  sur- 
face of  a  disc.  (2)  An  armature  having 
the  form  of  a  disc. 

Disc  Electrodes. — Disc-shaped  carbon 
electrodes  formerly  employed  in  long- 
burning  or  all-night  arc-lamps. 

Discharge.— (1)  The  equalization  of  the 
difference  of  potential  between  the  ter- 
minals of  a  condenser  or  source,  on  their 
connection  by  a  conductor.  (2)  The  re- 
moval of  a  charge  from  a  conductor  by 
connecting  the  conductor  to  the  earth  or 
to  another  conductor.  (3)  The  removal 
of  a  charge  from  an  insulated  conductor, 
by  means  of  a  stream  of  electrified  air 
particles. 

Discharge. — To  equalize  differences  of 
potential  by  connecting  them  by  a  con- 
ductor. 


Discharge  Key. — A  key  employed  to  pass 
the  discharge  from  a  condenser  or  cable 
through  a  galvanometer. 

Discharge  of  Magnetism  of  Field 
Magnets. — A  term  sometimes  employed^ 
for  the  unbuilding  of  a  dynamo,  or  Or 
gradual  failure  to  produce  current  on  tin 
loss  of  magnetism  of  its  field  magnets. 

Discharging  Rate. — The  strength  of  the- 
discharging  current  of  a  storage  cell  or 
battery. 

Discharge  Resistance. — The  resistance 
that  is  placed  in  the  path  or  circuit  of  a 
discharge. 

Discharging  Rod. — A  jointed  metallic 
rod,  blunted  at  both  ends,  capable  of 
adjustment  as  to  the  distance  of  the  ends 
from  each  other,  and  provided  with  in- 
sulating handles,  employed  for  the  dis- 
ruptive discharge  of  Leyden  batteries  or 
condensers. 

Discharging  Tongs. — A  pair  of  discharg- 
ing I'ods  with  an  insulating  handle,  con- 
nected together  by  a  rivet  like  a  pair  of 
tongs,  for  effecting  the  disruptive  dis- 
charge of  a  Leyden  jar  or  condenser. 

Discoidal  Ring- Armature. — A  term 
sometimes  used  for  disc  armature. 

Discoidal  Winding. — The  flat-ring  wind- 
ing employed  in  a  disc  armature. 

Disconnect. — (1)  To  break  or  open  an  eleo 
trie  circuit.  (2)  To  remove  an  electro- 
receptive  device  from  a  circuit. 

Disconnecting. — The  act  of  opening  or 
breaking  a  circuit,  or  of  removing  elec- 
tro-receptive devices  therefrom. 

Disconnecting  Plug. — An  infinity  plug. 

Disconnection. — (1)  A  general  term  des- 
ignating a  variety  of  faults  caused  by  the- 
accidental  breaking  or  disconnection  of  a 
circuit.  (2)  The  intentional  opening  or 
breaking  of  a  circuit,  or  the  removal  of  an. 
electro-receptive  device  therefrom.  (3 )  A. 
discontinuity  in  a  circuit. 

Disconnector. — A  key  or  other  device  for 
opening  or  breaking  an  electric  circuit,  or 
for  removing  an  electro-receptive  device- 
therefrom. 

Discontinuity  Plug. — A  name  sometimes 
employed  for  an  infinity  plug. 

Discriminating  Lightning- Arrester.  — 
The  name  sometimes  applied  to  a  non- 
arcing  continuous-current  lightning-ar- 
rester. 

Diselectriflcation. — A  general  term  em- 
ployed for  the  act  of  causing  a  charged 
body  to  lose  its  electric  charge. 

Disguised  Electricity. — Dissimulated  6t 
latent  electricity. 


Dis.j 


746 


[Dis. 


Disintegration  of  Storage  Battery 
Plate. — The  gradual  loosening  or  separa- 
tion of  the  active  material  of  a  storage 
battery  plate  from  the  perforations  of  the 
grid. 

Disjunctor. — A  device  employed  in  a  sys- 
tem for  the  distribution  of  electric  en- 
ergy by  means  of  continuous  currents  in 
connection  with  condensers,  for  periodi- 
cally reversing  the  constant  current  sent 
over  the  line. 

Dispersing  Pad-Electrode. — A  thera- 
peutic pad-electrode,  suitable  for  use  with 
strong  currents,  applied  directly  to  the 
body,  for  diffusing  the  therapeutic  current 
through  a  large  tract  thereof. 

Dispersion  Photometer. — A  photometer 
in  which  the  light  to  be  measured  is  de- 
creased in  intensity  by  a  known  amount, 
so  as  to  be  more  readily  compared  with  a 
standard  light  of  much  smaller  intensity. 

Displacement  Current. — (1)  Therate-of- 
change  of  electric  displacement.  (2)  An 
electric  current  produced  in  a  dielectric 
by  electric  displacement,  as  opposed  to  a 
conduction  cm-rent. 

Displacement,  Electric.— A  displace- 
ment of  electricity  in  a  uniform  non- 
crystalline  dielectric  when  electrostatic 
flux  passes  through  it. 

Displacement  Flux. — (1)  The  flux  of  elec- 
tric displacement.  (2)  The  surface  inte- 
gral of  displacement  effected  through  the 
surface. 

Displacement  Lines. — The  lines  along 
which  displacement  flux  moves. 

Displacement  Waves. — Waves  produced 
in  the  ether  by  means  of  electric  displace- 
ments. 

Disruptive  Discharge. — A  sudden  and 
more  or  less  complete  discharge  that 
takes  place  across  an  intervening  non- 
conductor or  dielectric. 

Disruptive  Electric-Conduction . — The 
conduction  of  electric  energy  which  ac- 
companies a  disruptive  discharge. 

Disruptive  Strength  of  Dielectric. — 
The  strain  a  dielectric  is  capable  of  bear- 
ing without  suffering  disruption,  or  with- 
out permitting  a  disruptive  discharge  to 
pass  through  it. 

Dissipation  Function. — (1)  A  function 
expressing  the  rate  at  which  heat  is 
produced  by  the  passage  of  an  electric 
current  through  a  conductor.  (2)  A 
function,  which,  when  differentiated 
with  respect  to  a  velocity  as  the  inde- 
pendent variable.,  gives  the  applied 
"  force  required  to  overcome  the  dissipa- 
tive  resistance  to  motion. 


Dissipation  of  Charge. — The  gradual 
but  final  loss  of  charge  by  leakage  which 
occurs  even  in  a  well  insulated  conductor. 

Dissipation  of  Energy. — The  expendi- 
ture or  loss  of  available  energy. 

Dissipativity. — The  time-rate  of  dissipat- 
ing energy  as  heat  per-unit- volume  of  a 
substance. 

Dissimulated  Electricity. — (1)  A  term 
sometimes  applied  to  the  condition  of  an 
electric  charge  when  placed  near  an  op- 
posite charge,  as  in  a  Leyden  jar  or  con- 
denser. (2)  A  bound  charge. 

Dissociate. — To  separate  a  compound  sub- 
stance into  its  constituent  parts. 

Dissociation. — The  separation  of  a  com- 
pound substance  into  its  constituents. 

Dissonance,  Electric. — (1)  Electrical  dis- 
agreement. (2)  A  term  employed  in  con- 
tradistinction to  electric  consonance,  to 
alternating  electromotive  forces,  fluxes 
or  currents,  whose  phases  are  in  opposi- 
tion. 

Dissymmetrical  Alternating-Electro- 
motive Forces. — Alternating-electro- 
motive forces,  in  which  an  alternating 
semi-wave,  when  reversed  in  sign,  does 
not  reduplicate  the  preceding  or  suc- 
ceeding semi-wave. 

Dissymmetrical  Induction  of  Arma- 
ture. — Any  induction  produced  in  the 
armature  of  a  dynamo  that  is  unequal  in 
amount,  in  opposite  or  symmetrically  dis- 
posed portions  of  the  armature. 

Dissymmetrical  Magnetic  Field. — A 
field  whose  flux  is  not  symmetrically  dis- 
tributed. 

Dissymmetry  of  Commutation. — A 
commutation  in  which  the  neutral  line 
does  not  coincide  with  the  diameter  of 
commutation. 

Distant  Battery. — A  battery  employed 
in  any  telegraphic  system  at  the  distant 
receiving  end  of  the  line. 

Distant  Station. — A  term  applied  by  a 
telegraph  operator  to  the  distant  end  of 
the  line,  in  order  to  distinguish  it  from 
his  own,  or  the  home  end. 

Distillation,  Electric. — The  distillation 
of  a  liquid  in  which  the  effects  of  heat 
are  aided  by  the  electrification  of  the 
liquid. 

Distorsion. — The  change  in  the  shape 
or  configuration  of  a  medium,  or  an  en- 
tity, produced  by  the  action  of  a  stress 
or  disturbance. 

Distorsion  of  Magnetic  Field. — A 
change  in  the  direction  or  distribution  of 
the  magnetic  flux  in  the  field  of  a  dynamo 


Dis.j 


747 


[Dis. 


armature,  produced  by  the  magnetomo- 
tive force  of  the  armature  current. 
Distorsional  Elasticity.— Elasticity  in  a 
body,  due  to  its  distorsion  or  deformation. 

Distorsionless  Cable. — A  cable  that 
forms  part  of  a  distorsionless  circuit. 

Distorsionless  Circuit. — (1)  A  telegraph- 
ic circuit  in  which  leakage  and  con- 
ductor resistance  are  so  balanced  as  to 
leave  no  tailings.  (2)  A  telegraphic  cir- 
cuit in  which  there  is  no  distorsion  of 
signals  or  electric  waves. 

Distributed  Capacity. — The  capacity  of 
a  circuit  considered  as  distributed  over 
its  entire  length,  so  that  the  circuit  may 
be  considered  as  shunted  by  an  infinite 
number  of  infinitely  small  condensers, 
placed  infinitely  near  together,  as  distin- 
guished from  localized  capacity,  in  which 
the  capacity  is  distributed  in  discrete 
aggregations. 

Distributed  Inductance. — Inductance 
distributed  throughout  the  entire  length 
of  a  circuit  or  portion  thereof,  as  distin- 
guished from  inductance  interposed,  in  a 
circuit  in  bulk  at  some  one  or  more  points. 

Distributed  Winding  of  Dynamo  Elec- 
tric Armature. — A  winding  disposed 
regularly  over  the  surface  of  the  armature 
as  distinguished  from  a  pole  winding,  or  a 
winding  composed  of  a  few  localized  coils. 

Distributing  Board.— <1)  A  term  some- 
times employed  in  a  system  of  telephonic 
or  telegraphic  communication,  to  a  cross- 
connecting  board.  (2)  A  board  at  which 
the  wires  or  cables  from  a  telephone 
switchboard  terminate  and  at  which  con- 
nections are  made  with  the  circuit  wires. 
(3)  An  insulating  board  provided  with 
screw  connecting-pieces  for  readily  con- 
necting branch  circuits  to  mains  in  a  dis- 
tributing system,  with  or  without  fuse 
cut-outs. 

Distributing  Box. — (1)  A  box  containing 
means  for  readily  changing  the  connec- 
tions of  distribution  circuits  with  their 
source  of  supply.  (2)  A  device  by  means 
of  which  both  arc  and  incandescent  lights 
may  be  simultaneously  employed  on  the 
same  constant-current  circuit.  (3)  A 
device  for  cutting  into  or  out  of  an  arc 
circuit,  at  will,  a  group  of  series  incan- 
descent lamps. 

Distributing  Box  of  Conduit. — A  name 
sometimes  given  to  a  man-hole  of  a  con- 
duit. 

Distributing  Brushes  of  Motor. — The 
brushes  which  rest  on  the  commutator  of 
an  electric  motor  and  carry  the  driving 
current  to  it. 


Distributing  Mains.— The  mains  env 
ployed  in  a  feeder  system  of  parallel  dis- 
tribution. 

Distributing  Ppint.— A  point,  usually  at 
the  junction  of  risers  and  mains,  or  mains 
and  sub-main's,  where  all  the  fuses  or 
safety  catches,  belonging  to  that  part  of 
the  system,  are  collected. 

Distributing  Station. — (1)  A  station  from 
which  electricity  is  distributed.  (2)  A 
central  station. 

Distributing  Switch. — A  switch  for  clos- 
ing a  plurality  of  distributing  circuits  at 
will  upon  the  source  of  supply. 

Distributing  Switchboard.— (1)  A  mul- 
tiple switchboard.  (2)  A  device  for  dis- 
tributing electricity  over  any  of  a  number 
of  circuits. 

Distributing  Box.— A  box  placed  at  a 
distributing  point  for  holding  all  the  f  usea 
belonging  to  that  portion  of  the  distribut- 
ing system. 

Distributing  Box  for  Arc-Light  Cir- 
cuits.— A  device  by  means  of  which  both 
arc  and  incandescent  lights  may  be  sim- 
ultaneously employed  on  the  same  line 
from  a  constant-current  dynamo-electric 
machine. 

Distributing  Centre.— (1)  In  an  electrical 
distribution  system  a  centre  or  sub-centre 
of  distribution.  (2)  A  ramifying  point. 

Distribution  of  Charge.— The  diffusion 
or  dispersion  of  an  electric  charge  over 
the  surfaces  of  electrified  bodies. 

Distribution  of  Electricity.— The  divi- 
sion and  transmission  of  electric  energy 
by  means  of  various  combinations  of  elec- 
tric sources,  circuits  and  electro-receptive 
devices,  so  arranged  that  the  electricity 
generated  by  the  sources  is  carried  or  dis- 
tributed to  more  or  less  distant  electro- 
receptive  devices,  by  means  of  the  various 
circuits  connected  therewith. 

Distribution  of  Electricity  by  Alter- 
nating Currents. — A  system  of  electric 
distribution  in  which  the  Jamps,  motors 
or  other  receptive  devices,  are  operated 
by  means  of  alternating  currents  that 
are  sent  over  the  line  or  lines,  in  many 
cases  after  they  have  been  modified  by 
apparatus  called  transformers. 

Distribution  of  Electricity  by  Alter- 
nating Currents  by  Means  of  Con- 
densers.— A  system  of  alternating-cur- 
rent distribution  in  which  condensers  are 
employed  to  transform  currents  of  high 
potential,  received  from  an  alternating- 
current  dynamo,  to  currents  of  low  poten- 
tial which  are  fed  to  the  lamps  or  other 
electro-receptive  devices. 


Dis.] 


748 


[Div, 


Distribution  of  Electricity  by  Com- 
mutating  Transformers. — A  system  of 
electric  distribution  in  which  motor  gen- 
erators are  used,  but  neither  their  field- 
magnets  nor  armatures  are  revolved,  a 
.special  commutator  being  employed  to 
change  the  polarity  of  the  magnetic  cir- 
cuits. 

Distribution  of  Electricity  by  Con- 
stant-Currents.— Any  system  of  elec- 
tric distribution  employing  direct  cur- 
rents, as  distinguished  from  one  employ- 
ing alternating  currents. 

Distribution  of  Electricity  by  Con- 
stant Potential-Circuits. — A  system 
of  electric  distribution  in  which  the  re- 
ceptive devices  are  placed  in  multiple  or 
multiple-series  across  constant-potential 
mains. 

Distribution  of  Electricity  by  Con- 
tinuous Currents  by  Means  of  Con- 
densers.— A  system  of  distribution  in 
which  a  continuous  current  is  conducted 
to  certain  points  in  a  line,  where  a  dis- 
junctor  is  employed  to  reverse  it  period- 
ically, the  reversed  currents  so  obtained 
being  directly  used  to  charge  condensers 
in  the  circuit  of  which  induction  coils 
are  employed. 

Distribution  of  Electricity  by  Con- 
tinuous Currents  by  Means  of 
Transformers. — A  system  for  the  trans- 
mission of  electric  energy  by  means  of 
continuous  or  direct  currents  that  are  sent 
over  the  line  to  suitably  located  stations 
where  motor-dynamos  are  used  for  trans- 
formers. 

Distribution  of  Electricity  by  Motor- 
G-enerators. — A  system  of  electric 
distribution  in  which  a  continuous  high- 
potential  current,  distributed  over  the 
main  line,  is  employed  at  the  point  where 
its  energy  is  to  be  utilized  for  driving  a 
motor,  which  in  turn  drives  a  dynamo 
whose  current  is  employed  to  energize 
the  electro-receptive  devices. 

Distribution  of  Power,  Electric.— Any 
system  in  which  mechanical  energy  is 
first  converted  into  electro-magnetic  en- 
ergy and  then  distributed  over  a  line  wire 
or  circuit  to  electric  motors,  which  again 
change  the  electro-magnetic  energy  into 
mechanical  energy. 

Distributor. — A  word  sometimes  applied 
to  the  distributing  mains  in  a  parallel 
system  of  distribution. 

District  Call-Box. — A  box  by  means  of 
which  an  electric  signal  is  automatically 
sent  over  a  telegraph  line  and  received 
by  an  electromagnetic  device  at  the  other 
end  of  the  line. 


Diurnal  Currents.  —  Earth  currents 
through  telegraph  circuits  of  normal 
strength  and  executing  diurnal  cycles. 

Diurnal  Inequality  of  Earth's  Mag- 
netism.— Diurnal  variations  in  the  value 
of  the  earth's  magnetic  variation  or  in- 
clination. 

Diurnal  Load-Factor.— (1)  The  ratio  be- 
tween the  total  number  of  units  sent  out 
from  a  station  in  twenty-four  hours,  to 
the  amount  which  would  have  been  sent 
out  in  the  same  time  if  the  plant  were 
working  at  its  maximum  load  for  the 
whole  twenty-four  hours'.  (2)  The  ratio  of 
daily  average  to  daily  maximum  load. 

Diurnal  Variation. — An  approximately 
regular  variation  of  the  magnetic  needle 
which  occurs  at  different  hours  of  the 
day. 

Divalent. — (1)  Possessing  an  atomicity  or 
valency  of  two.  (2)  Bivalent. 

Divergence. — (1)  The  integral  of  outward- 
ly directed  flux  over  the  surface  of  an  ele- 
ment of  volume  divided  by  that  volume. 
(2)  The  opposite  of  convergence. 

Divergent  Flux.— (1)  Flux  that  diverges 
or  diffuses  as  it  proceeds.  (2)  Flux  that 
decreases  in  intensity  along  its  path. 

Divergent  Vector  Quantity. — A  vector 
point  function  in  space  having  diver- 
gence. 

Diverging-Lens  Photometer. — A  pho- 
tometer in  which  the  intensity  of  the 
light  to  be  measured  is  decreased  by 
means  of  a  diverging  lens. 

Diverging  Magnetic  Flux.— Magnetic 
flux  that  decreases  in  intensity  and  di- 
verges or  diffuses  in  direction  along  its 
path. 

Diversity  Factor. — A  term  proposed  for 
the  ratio  of  the  average  supply  of  electric 
power  to  a  consumer  to  the  maximum 
power  supplied. 

Diviance. — A  term  proposed  for  resistance 
to  the  flow  of  magnetic  induction. 

Divided  Circuit. — (1)  A  branched  or  bifur- 
cated circuit.  (2)  A  term  sometimes 
employed  for  multiple  circuit. 

Divided  Core.— A  laminated  core. 

Divided  Magnetic  Circuit.— A  mag- 
netic circuit  which  bifurcates  or  divides. 

Divided  Telephone-Switchboard.— A 
multiple  telephone  switchboard. 

Divided  Touch. — A  term  used  in  place 
of  magnetization  by  separate  touch. 

Divided  Trolley  Line.— A  term  some- 
times used  for  a  sectional  trolley  line. 

Dividing  Engine. — (1)  A  mechanical  de- 
vice for  dividing  a  thermometric,  galvanos* 


Div.] 


749 


[Dou, 


metric,  or  other  scale,  into  equal  parts. 
(2)  A  device  for  dividing  a  tube  or  a 
scale  into  equal  parts  of  a  length,  consist- 
ing essentially  of  a  horizontal  screw  by 
means  of  which  a  carriage  carrying  suit- 
able marking  gear  can  be  moved  along  a 
parallel  prismatic  guide. 

Division  Operator. — A  railway  telegraph- 
operator  in  charge  of  a  telegraph  division 
or  section  of  railway  telegraph. 

Doctor  for  Plating. — A  device  employed 
in  electro-plating  for  coating  surfaces 
that  are  too  extended  to  be  immersed  at 
once  in  the  plating  bath. 

Dolly. — A  polishing  brush  employed  in 
electro-plating,  consisting  of  a  number  ol 
calico  rings  suitably  clamped  together 
in  a  wooden  holder  for  attachment  to  a 
lathe. 

Domestic  Telephone-Switchboard. — 
(1)A  telephone  switchboard  located  in  a 
house  for  readily  connecting  different 
rooms.  (2)  A  local  telephone  switchboard 
for  connecting  apartments  in  a  residence. 

Door-Bell  Pull,  Electric. — A  circuit- 
closing  device  attached  to  a  bell-pull  and 
operated  by  the  ordinary  motion  of  the 
pull. 

Door-Contact  Lamp. — A  contact  which 
lights  a  lamp  and  permits  it  to  remain 
lighted  only  while  the  door  operating  its 
circuit  remains  in  a  certain  position. 

Door-Opener,  Electric.  —  An  electro- 
magnetic device  for  opening  a  door  from 
a  distance. 

Door  Push. — A  contact  closed  or  opened 
by  the  opening  or  shutting  of  a  door  to 
give  a  notice  of  the  movement  at  a  dis- 
tance, as  in  a  burglar-alarm  system. 

Door  Trigger. — A  device  by  means  of 
which  notice  is  given  of  the  opening  or 
closing  of  a  door  or  window. 

Dot-and-Dash  Code.— A  term  sometimes 
employed  for  the  Morse  telegraphic  code. 

Dotting  Contact. — An  electric  contact 
obtained  by  the  approach  of  one  contact 
point  towards  another. 

Double  Alternation.— (1)  A  complete 
cycle  or  double  vibration.  (2)  A  com- 
plete to-and-fro  movement. 

Double  Armature  "Windings.  —  Two 
separate  armature  windings  applied  sym- 
metrically to  a  core,  and  whose  ends  are 
connected  respectively  to  alternate  com- 
mutator bars. 

Double-Balance  Relay.— In  a  closed-cur- 
rent system  of  alarm  telegraphy,  a  pair 
of  relays  connected  in  series,  one  of  which 
will  close  a  local  circuit  if  the  main  line 
current  appreciably  weakens,  and  the 


other  of  which  will  close  a  local  circuit 
if  the  main  line  current  appreciably 
strengthens. 

Double-Bar  Switch. — A  switch  or  re- 
verser  consisting  of  a  pair  of  parallel 
metallic  bars  or  strips  which  move  to- 
gether upon  independent  centres  so  as  to 
make  contact  simultaneously  upon  one  or 
more  pairs  of  contacts. 

Double-Block  Duplex  System. — A 
system  of  duplex  telegraphy  in  which  a 
condenser  exists  in  both  arms  of  the 
duplex  bridge. 

Double-Break  Knife-Switch.— (1)  A 
knife  switch  which  breaks  a  circuit  at  two 
points.  (2)  A  knife  switch  provided  with 
a  contact  for  botli  poles. 

Double-Break  Switch. — A  term  some- 
times used  for  double-pole  switch. 

Double-Bracket  Pole. — A  pole  employed 
in  an  overhead  line  for  the  support  of  a 
double  bracket. 

Double-Bracket  Trolley  Suspension. 
In  a  double-track  trolley  road,  a  pole  pro- 
vided with  two  brackets,  one  extending 
over  each  track,  and  provided  for  holding 
the  two  trolley  wires. 

Double-Block  Duplex  System. — A  du- 
plex system  on  the  Wheatstone  bridge 
system,  employing  a  condenser  in  each 
arm  of  the  bridge. 

Double-Break  Switch. — (1)  A  double- 
pole  switch.  (2)  A  switch  which  breaks 
a  circuit  in  two  places,  as  distinguished 
from  a  switch  which  breaks  a  circuit  at  a 
single  point  only. 

Double-Bronze  Wire. — A  conducting 
wire  possessing  great  tensile  strength, 
provided  with  an  aluminium-bronze  core, 
and  a  copper-brass  envelope. 

Double-Carbon  Arc-Lamp. — An  arc- 
lamp  which  will  burn  all  night  without 
recarboning,  containing  two  sets  of  car- 
bon electrodes  so  arranged  that,  when  one 
set  is  practically  consumed,  the  current  is 
automatically  switched  to  the  other  set. 

Double-Circuit  Dynamo. — A  dynamo- 
electric  machine  provided  with  two  sepa- 
rate circuits. 

Double-Conductor  Cable  or  Wire.— A 
cable  or  wire  provided  with  two  separate 
insulated  conductors. 

Double-Cone  Insulator. — An  insulator 
in  which  the  line  wire  passes  through  and 
is  supported  by  means  of  a  tube  consist- 
ing of  two  inverted,  truncated  cones, 
joined  at  their  vertices. 

Double-Connector. — A  form  of  binding 
screw  suitable  for  readily  connecting  two 
wires  together. 


Dou.] 


750 


[Dou. 


Double-Contact  Key.— A  key  suitable 
either  for  making  two  separate  succes- 
sive contacts,  or  for  closing  either  of  two 
circuits. 

Double-Contact  Push. — A  push  provided 
with  two  contacts  so  arranged  that  the 
pressure  of  a  push  opens  one  contact  and 
closes  the  other. 

Double-Contact  Push  Button. — A  push- 
button provided  with  two  contacts. 

Double-Cord  Multiple-Switchboard. — 
A  multiple  telephone  switchboard  in 
which  connections  are  made  by  plugs  and 
cords  having  two  twin  wires,  as  opposed 
to  a  switchboard  in  which  single  cord 
plugs  are  used.  • 

Double  -  Cord  Switchboard.  —  (1)  A 
switchboard  employing  twin-wire  or 
double-conductor  connections.  (2)  A 
switchboard  in  which  each  connection  is 
established  through  a  pair  of  cords,  as 
distinguished  from  a  single-cord  switch- 
board. 

Double-Cup  Insulator. — (1)  An  insulator 
consisting  of  two  funnel-shaped  cups,' 
placed  in  an  inverted  position  on  the  sup- 
porting pin,  and  separated  from  each  other 
by  a  Free  air-space  except  at  the  ends 
which  are  connected.  (2)  A  double-petti- 
coat insulator. 

Double-Curb. — A  device  for  increasing 
the  speed  of  telegraphic  signalling  by 
ridding  the  line  of  its  charge  before  the 
next  signal  is  sent,  by  sending  more  than 
one  reversal  of  current  with  or  without 
grounding  the  line,  as  distinguished  from 
a  single-curb. 

Double-Curb  Signalling. — Signalling  by 
means  of  a  double  curb. 

Double-Current  Signalling.— (1)  Signal- 
ling by  means  of  currents  that  alternately 
change  their  direction.  (2)  Signalling  in 
which  the  marking  currents  have  one 
direction  and  the  spacing  currents  the 
opposite  direction. 

Double-Current  Telegraphic  -  Work- 
ing.— Telegraphing  or  operating  by  means 
of  double  currents. 

Double-Current  Translation.— (1)  The 
automatic  repetition  of  a  telegraphic  mes- 
sage by  means  of  double  currents.  (2) 
Telegraphic  translation  employing  double 
currents. 

Double-Current  Translator. — A  tele- 
graphic translator  or  repeater  designed  to 
operate  on  double-current  transmission. 

Double-Current  Transmitter. — A  trans- 
mitting instrument  employed  in  a  system 
of  telegraphy  in  which  the  direction  of 
the  line  current  is  alternately  changed, 


according  to  whether  the  key  rests  on  its 
front  or  on  its  back  stop. 
Double-Current  Working.— A  method 
of  telegraphic  working  or  transmission  by 
means  of  double  currents. 

Double-Curve  Pull-Off.— A  double-curve 
hanger. 

Double-Curve     Trolley     Hanger.— A 

hanger  provided  for  holding  an  overhead 
trolley  wire,  supported  by  a  lateral  strain 
in  opposite  directions,  and  employed,  gen- 
erally at  the  end  of  both  single  and  double 
curves,  and  on  intermediate  points  on 
double-track  curves. 

Double-Curve     Trolley-Suspension.— 

Suspension  by  means  of  a  double-curve 
trolley  hanger. 

Double-Deck  Switchboard. — A  switch- 
board arranged  in  two  rows  placed  one 
above  the  other. 

Double-Dielectric  Refraction.— Double 
electric  refraction  produced  in  a  dielectric 
by  the  action  of  an  electro-magnetic 
stress. 

Double-Duplex  Block. — In  submarine 
telegraphy,  duplex  transmission  obtained 
by  the  aid  of  a  condenser  inserted  in  each 
arm  of  a  Wheatstone's  balance. 

Double-Filament  Lamp. — (1)  An  incan- 
descent lamp,  frequently  employed  for 
the  side-light  of  a  ship,  and  provided  with 
two  carbon  filaments  so  arranged  that 
should  one  break,  the  other  will  continue 
burning.  (2)  A  twin-filament  lamp.  (3) 
An  incandescent  lamp  having  two  fila- 
ments connected  in  series,  and,  therefore, 
requiring  twice  the  electric  pressure  of  an 
ordinary  lamp. 

Double-Flexible  Conductor. — A  con- 
ductor consisting  of  two  separate  stranded 
flexible  conductors,  provided  with  an  in- 
sulating covering  common  to  both. 

Double-Fluid  Electrical  Hypothesis. — 
A  hypothesis  which  endeavors  to  explain 
the  causes  of  electrical  phenomena  by  the 
assumption  of  the  existence  of  two  dif- 
ferent electric  fluids. 

Double-Fluid  Voltaic  Cell.— (1)  A  vol- 
taic cell  in  which  two  separate  fluids  or 
electrolytes  are  employed.  (2)  A  two-fluid 
voltaic  cell. 

Double-Focus  X-Ray  Tube.— An  X-ray 
tube,  suitable  for  use  with  alternating 
electric  currents,  in  which  two  anti- 
cathodes  are  employed,  so  arranged  that 
they  act  as  a  common  source  of  X-rays. 

Double-Hatchet  Switch. — A  term  some« 
timer  used  for  a  double-knife  switch. 


Don.] 


751 


[Dout 


Double-Horseshoe  Field-Magnet. — A 
multiple  field-magnet  of  a  dynamo  formed 
by  two  separate  electro-magnets. 

Double  Insulation. — Insulation  of  a  con- 
ductor effected  at  two  distinct  points,  so 
that  if  one  insulation  should  fail  the  other 
will  serve. 

Double-Key  Tapper. — A  key  used  in  a 
system  of  needle  telegraphy  to  send  elec- 
tris  impulses  through  the  line  in  alter- 
nately opposite  directions. 

Double-Liquid  Voltaic  Cell. — A  double- 
fluid  voltaic  cell. 

Double-Loop. — (1)  In  telegraphy,  any  pair 
of  associated  loops.  (2)  A  pair  of  loops 
connecting  a  pair  of  branch  offices  with  a 
central  office. 

Double-Loop  Repeater. — In  telegraphy, 
a  pair  of  loops  connecting  a  pair  of  branch 
offices  with  a  central  office,  and  so  con- 
nected with  a  duplex  set,  or  with  the 
common  side  of  a  quadruplex  set,  in  the 
main  office,  that  one  branch  office  can  send 
messages  on  the  duplexed  line  while  the 
other  office  is  receiving. 

Double-Magnet  Dynamo-Electric  Ma- 
chine.— A  term  sometimes  applied  to  a 
dynamo-electric  machine,  whose  field 
magnets  have  two  consequent  poles. 

Double-Needle  Telegraphy.— A  system 
of  needle  telegraphy  in  which  two  sepa- 
rate and  independently  operated  needles 
are  employed  on  two  separate  circuits. 

Double-Peg. — A  split  peg  which  closes  two 
separate  contacts,  when  inserted  in  the 
switchboard  to  which  it  belongs. 

Double-Pen  Telegraphic-Register. — A 
telegraphic  register  provided  with  two 
separate  styluses  or  pens  for  recording 
the  message  on  a  paper  fillet. 

Double-Petticoat  Insulator.— (1)  A 
double  insulator,  placed  one  within  and 
beneath  the  other,  to  reduce  the  electric 
leakage  over  the  surface.  (2)  A  double- 
cup  insulator. 

Double-Plug. — A  double  peg. 

Double-Plug  Key.— A  plug  key  made  in 
two  separate  parts  that  are  insulated  from 
each  other. 

Double-Pole  Bell.— An  electro-magnetic 
bell  having  a  polarized  armature  which 
plays  between  a  pair  of  electro-magnetic 
poles. 

Double  Pole.— (1)  A  double  telegraph 
pole.  (2)  Two  telegraph  poles  placed 
side-by-side  and  braced  together.  (3)  An 
H-pole. 

Double-Pole  Cut-Out.— (1)  A  cut-out 
which  provides  in  a  single  operation  the 


cutting  out  of  both  the  positive  and  the 
negative  leads.  (2)  Two  safety  fuses, 
mounted  on  the  same  holder,  and  con- 
nected respectively  to  the  positive  and 
negative  mains. 

Double-Pole  Fusible  Cut-Out.— A  term 
sometimes  used  for  double-pole  cut-out. 

Double-Pole  Safety-Fuse.  —  An  auto- 
matic double-pole  cut-out. 

Double-Pole  Switch. — A  switch  which 
simultaneously  breaks  the  circuit  of  both 
positive  and  negative  leads. 

Double-Pole    Telephone-Receiver.— A 

telephone  receiver  in  which  both  poles  of 
a  small  electro-magnet  are  presented  to 
the  diaphragm. 

Double  Pull-Off.— (1)  A  pull-off  employed 
on  curves  to  hold  a  trolley  wire  in  posi- 
tion when  strain  in  both  directions  is  nec- 
essary to  hold  it  in  place.  (2)  A  double- 
curve  pull-off. 

Double-Reduction. — A  gear  wheel  veloc- 
ity reducer  employing  two  gear  wheels 
and  two  pinions,  or  oneintermediate  shaft. 

Double-Reduction  Car-Motor. — A  car- 
motor  provided  with  a  double-reduction, 
or  with  one  intermediate  gear  shaft  be- 
tween the  motor  shaft  and  car  wheel. 

Double-Reflection  Tube.— A  term  some- 
times employed  for  a  double-focus  X-ray 
tube. 

Double-Refraction. — The  property  pos- 
sessed by  certain  transparent  substances 
of  splitting  up  a  ray  of  light  passed 
through  them  into  two  separate  rays. 

Double-Refraction,  Electric. — The  prop- 
erty of  doubly  refracting  light  acquired 
by  some  transparent  substances  when 
subjected  to  the  stress  of  an  electrostatic 
or  electro-magnetic  field. 

Double  Ringing-Key. — In  a  multiple  tel- 
ephone switchboard,  a  pair  of  keys  form- 
ing part  of  an  exchange  operator's  set, 
employed  in  ringing  up. 

Double-Shackle  Insulator. — A  form  of 
insulator  employed  in  shackling  a  wire, 
consisting  of  two  single-shackle  insulators. 

Double-Shed  Insulator. — A  double-cup 
insulator. 

Double-Speaking  Telegraph.— A  term 
sometimes  employed  for  the  duplex  tele- 
graph as  employed  on  submarine  cables* 

Double-Style  Printing  Apparatus. — A 
double  Morse  receiver  employing  two 
printing  levers  or  styluses  marking  dots 
in  parallel  lines,  one  responding  to  posi- 
tive currents  and  representing  dots,  and 
the  other  responding  to  negative  currents 
and  representing  dashes. 


Don.] 


752 


[Dow. 


Double-Successive    Contact-Key.  —  A 

key  so  arranged  as  to  successively  close 
two  separate  circuits. 

Dpuble  Tapper  Key.— A  key  employed 
in  a  system  of  needle  telegraphy  to  send 
electric  impulses  over  the  line  in  alter- 
nately opposite  directions. 

Double  Telegraphic  Transmission. — 
Any  method  of  simultaneously  sending 
two  messages  over  a  single  line  wire  or 
conductor. 

Double  Telegraphy. — A  term  sometimes 
employed  for  duplex  telegraphic  working. 

Double-Throw  Switch. — (1)  A  switch 
capable  of  being  thrown  into  either  of 
two  contacts  or  pairs  of  contacts.  (2)  A 
switch  which  has  three  positions.  (3)  A 
throw-over  switch. 

Double-Touch. — Magnetization  by  double 
touch. 

Double-Transmission.  —  (1)  The  simul- 
taneous sending  of  two  messages  over  a 
single  wire  in  opposite  directions.  (2)  Du- 
plex or  contraplex  telegraphy. 

Double-Transmitter  for  Engine  Tele- 
graph.— A  transmitter  on  board  a  twin- 
scre%v  steamer  for  communicating  orders 
electrically  to  the  engine-room  for  both 
engines  simultaneously. 

Double-Trolley. — Two  separate  trolleys 
placed  on  the  same  car,  and  moving  over 
two  separate  trolley  wires  which  form  a 
metallic  circuit,  in  any  double-overhead 
system. 

Double-Trolley  Line. — A  metallic-circuit 
trolley  line  employing  two  trolleys,  one 
connected  with  the  positive  conductor  and 
the  other  with  the  negative  conductor. 

Double-Trolley  System  for  Electric 
Railroads. — An  electric  railroad  system 
employing  double  trolley  wires  and  double 
trolleys  so  as  to  provide  a  complete  metal- 
lic circuit. 

Double-Truck  Car. — A  car  supported  on 
two  separate  single  trucks,  and  employed 
with  long  cars  for  safety  and  ease  in  turn- 
ing around  sharp  curves. 

Double  Vibration. — (1)  A  to-and-fro  or 
complete  vibration.  (2)  A  complete  cycle 
of  vibratory  motion. 

Double- Winding  of  Armature.  —  An 
armature  winding  provided  with  two 
separate  windings  or  sets  of  coils,  in  which 
the  separate  windings  are  insulated  from 
each  otner  and  connected  to  the  com- 
mutator at  alternate  segments,  so  that  the 
brushes  rest  coincidently  upon  segments 
that  are  connected  with  each  winding, 
thus  permitting  each  winding  to  furnish 
half  the  current  strength  with  an  attend- 


ant decrease  in  the  inductance  of  each 
circuit. 

Double-Wire  Circuit. — A  metallic  cir- 
cuit. 

Double- Wire  Cleat. — A  cleat  for  support- 
ing a  pair  of  wires. 

Double-Wire  Moulding. — A  moulding 
for  containing  two  wires,  each  in  a  sepa- 
rate groove. 

Double-Wire  System  for  Electric- 
Light  Leads. — On  board  ship,  a  system 
of  electric-light  wiring,  in  which  going 
and  returning  conductors  are  provided, 
as  distinguished  from  a  single-wire  system 
in  which  the  hull  of  the  vessel  is  em- 
ployed as  a  common  return. 

Double-Wire  Telephone-Switchboard. 
A  switchboard  in  a  central  telephone  ex- 
change, employing  metallic  circuits,  in 
which  each  subscriber  is  connected  by 
an  independent  double  wire  or  metallic 
circuit. 

Double-Word.— In  telegraphy,  a  word  of 
more  than  the  prescribed  length  and, 
therefore,  counted  and  charged  as  two. 

Do  able -Wound    Gramme    King.— A 

gramme  ring  provided  with  two  inde- 
pendent and  symmetrically  interspersed 
windings. 

Double-Wound  Wire. — Wire  provided 
with  a  double  winding  of  cotton,  silk,  or 
other  insulating  thread. 

Doubler  of  Electricity.— An  early  form 
of  continuous  electrophorous. 

D9ubly  He-Entrant  Armature- Wind- 
ing.— (1)  A  winding  in  which  the  armature 
is  provided  with  two  separate  windings 
or  conducting  paths,  each  of  which  is  in- 
dependently re-entrant.  (2)  A  double- 
wound  armature,  each  winding  of  which 
is  re-entrant. 

Doubly-Wound  Resistance  Coils.— A 
resistance  coil  wound,  as  is  usual,  with 
the  wire  doubled  on  itself,  in  order  to 
minimize  self-induction. 

Douche,  Electric. — An  electrified  shower- 
bath. 

Down-Contact  of  Switch.— A  contact 
which  is  made  by  the  downward  move- 
ment of  a  switch. 

Down-Lines. — In  the  United  Kingdom  of 
Great  Britain  and  Ireland,  telegraphic 
lines  on  the  side  remote  from  the  prin- 
cipal station  of  the  circuit,  as  distin- 
guished from  up-lines. 

Down-Side.— In  Great  Britain,  that  side 
of  a  telegraphic  circuit  further  from  the 
metropolis  or  principal  town  of  the  cir- 
cuit, as  distinguished  from  the  up-side. 


Dra.] 


753 


[Dro. 


Drag. — In  submarine  cable  operations,  a 
haul  made  with  a  gi-apnel  across  a  line  of 
cable  in  ths  hope  of  hooking  said  cable. 

Drag  of  Magnetic  Field. — A  word  some- 
times employed  for  the  torque  or  electro- 
dynamic  force  produced  by  a  magnetic 
field  on  an  active  conductor  placed  in  it. 

Draw-Bar. — In  a  locomotive,  the  link 
or  bar  which  connects  it  with  its  load. 

Draw-Bar  Pull. — The  pull  delivered  by  a 
locomotive  at  its  draw-bar,  as  distin- 
guished from  the  pull  exerted  by  its  motor. 

Drawbridge  Frog.— A  trolley  frog  for  use 
at  the  point  of  overhead  contact  with  a 
drawbridge  wire. 

Draw  Tongs. — A  species  of  vise  employed 
in  connection  with  a  light  block-and- 
tackle  for  obtaining  the  required  tension 
on  an  aerial  line  wire. 

Draw  Vise. — (1)  A  device  employed  in 
stringing  overhead  wires.  (2)  A  portable 
vise  for  holding  and  drawing  up  an  over- 
head wire. 

Drawing-In-and-Out  Conduit. — A  con- 
duit provided  with  ducts,  so  as  to  readily 
permit  the  wires  or  conductors  to  be 
placed  in  the  conduit  or  removed  from 
after  they  have  been  placed  therein. 

Drawing-In  Box. — A  flush  box. 

Drifting  of  Needle.— (1)  The  failure  of  the 
needle  of  a  galvanometer  to  remain  at  its 
zero  point  when  no  current  is  passing 
through  its  coils,  due  usually  to  variation 
in  the  condition  of  the  magnetic  needle, 
to  variation  in  the  torsion  of  the  suspend- 
ing system,  or  to  local  or  other  causes. 
(2)  Elastic  fatigue  in  the  suspension  of  a 
magnetic  system. 

Drifting  of  Zero  Point.— A  term  fre- 
quently employed  for  the  shifting  of  the 
zero  point. 

Drilling,  Electric. — (1)  A  term  sometimes 
employed  for  the  use  of  the  voltaic  arc 
in  perforating  a  mass  of  metal  or  mineral. 
(2)  Drilling  by  means  of  an  electrically 
operated  tool. 

Drip  Loop. — A  loop  inclined  upwards  at 
the  point  where  outside  conductors  enter 
a  building,  so  that  the  rain-water  flows 
along  said  loop  from  the  building,  instead 
of  towards  it. 

Driven  Circuit  of  Transformer. — The 
secondary  circuit  of  a  transformer. 

Driven  Coil  of  a  Transformer.— The 
secondary  coil  of  a  transformer. 

Driven  Pulley. — A  pulley  which  receives 
its  motion  from  a  driving  shaft. 

Driven  Pulley  of  Dynamo.— The  pulley 
connected  with  the  armature  shaft  of  a 
dynamo. 


Driven  Shaft. — The  shaft  worked  by  a 
belt  from  the  driving  pulley. 

Driving  Circuit  of  Transformer. — The 
primary  circuit  of  a  transformer. 

Driving  Coil  of  a  Transformer. — The 
primary  coil  of  a  transformer. 

Driving  Current  of  Motor. — The  cur- 
rent which  operates  an  electric  motor. 

Driving  E.   M.  F. — The    impressed     or 

-  working  E.  M.  F. 

Driving  Gear  of  Magneto. — The  gear 
wheels  connecting  a  magneto  telephone- 
transmitter  armature  with  the  driving 
handle,  whereby  the  speed  of  revolution 
of  the  armature  is  increased. 

Driving  Horns. — In  a  smooth-cored  ar- 
mature, mechanical  projections  for  hold- 
ing the  armature  wires  in  place,  and  com- 
municating their  electro-magnetic  force 
to  the  armature. 

Driving  Pressure. — The  driving  or  im- 
pressed E.  M.  F. 

Driving  Pulley. — That  pulley  of  a  ma- 
chine which  is  mounted  on  the  driving 
shaft. 

Driving  Pulley  of  Motor. — The  pulley 
attached  to  the  shaft  -of  a  motor,  or  the 
pulley  through  which  a  motor  furnishes 
its  mechanical  power. 

Driving  Shaft. — The  shaft  connected  di- 
rectly with  a  prime  mover. 

Driving  Spider. — The  radial  arms  or 
spokes  connected  to  the  armature  of  a  dy- 
namo, and  keyed  to  its  shaft,  so  as  to  act 
as  a  driving  wheel  for  the  armature. 

Drop. — (1)  A  word  frequently  used  for  drop 
of  potential,  pressure,  or  electromotive 
force.  (2)  The  fall  of  potential  which 
takes  place  in  an  active  conductor  by 
reason  of  its  resistance. 

Drop. — A  shutter,  or  falling  armature,  of 
a  drop  annunciator. 

Drop  Annunciator.  —  An  electro-mag- 
netic annunciator,  which,  on  being  en- 
ergized, releases  a  shutter  and  allows  the 
same  to  drop. 

Drop-Handle.  —  In  single-needle  teleg- 
raphy, a  form  of  transmitter  handle. 

Drop  Indicator. — A  drop  annunciator. 

Drop  of  Magnetic  Potential. — A  fall  of 
magnetic  potential. 

Drop  of  Potential. — The  fall  of  potential, 
equal  in  any  part  of  a  circuit  to  the  pro- 
duct of  the  current  strength  and  the  re- 
sistance of  that  part  of  the  circuit. 

Drop  of  Telephone  Switchboard.— A 
small  electro-magnetic  annunciator  in- 
serted in  the  line  of  each  subscriber, 


Pro,] 


754 


[Dup. 


whereby  any  current  received  from  a  sub- 
scriber attracts  the  armature  of  the  elec- 
tro-magnet and  releases  the  shutter,  there- 
by indicating  the  number  of  the  particu- 
lar subscriber  calling. 

Drop  of  Voltage. — The  drop  or  difference 
of  potential  of  any  part  of  a  circuit. 

Drop  Relay -Contact. — A  form  of  relay- 
contact  in  which,  on  the  passage  of  a  cur- 
rent, the  attraction  of  an  armature  releases 
a  drop  and  thus  completes  a  local  circuit,' 
which  remains  closed  until  the  drop  is 
reset. 

Drop-Shutter  of  Annunciator.— The 
drop  of  an  electro-magnetic  annunciator. 

Drop-Trolley. — A  particular  form  of  trol- 
ley wheel  and  pole  which  employs  a 
swivel  joint  and  springs  forcing  the  trol- 
ley against  the  wire. 

Drop-Trolley  Stand. — A  support  for  a 
trolley  pole  or  mast  provided  •with  a  swivel 
joint  and  suitable  springs  for  ensuring  a 
firm  pressure  of  the  trolley  wheel  against 
the  trolley  wire. 

Drum. — A  reel  for  holding  wire  or  cable. 

Drum  Armature. — A  dynamo  armature 
whose  coils  are  wound  longitudinally  over 
the  surface  of  a  cylinder  or  drum. 

Drum  Armature- Winding. — The  wind- 
ing employed  on  a  drum  armature. 

Dry  Battery. — (1)  A  number  of  separate 
dry  voltaic  cells,  connected  so  as  to  act  as 
a  single  source.  (2)  A  dry  pile. 

Dry  Cable. — A  dry-core  cable. 

Dry  Cell. — A  dry  voltaic  cell. 

Dry-Core  Cable. — A  cable  whose  core  is 
wrapped  with  paper  or  cotton  which  is 
not  afterwards  filled  with  paraffine,  gutta- 
percha,  or  other  insulating  material,  and, 
consequently,  whose  dielectric  consists 
largely  of  dry  air. 

Dry  Distillation. — A  species  of  destruc- 
tive distillation. 

Dry  Electrode. — A  therapeutic  electrode 
applied  in  a  dry  state. 

Dry  Front  of  Microscopic  Objective. 
That  front  of  a  microscopic  object  glass 
which  is  turned  towards  the  object,  but 
is  separated  from  it  by  a  short  distance  or 
air  gap,  in  contradistinction  to  an  immer- 
sion lens. 

Dry  Gelatine  Cell. — A  type  of  dry  voltaic 
cell  in  which  the  fluid  electrolyte  is  ab- 
sorbed by,  or  combined  with,  a  suitable 
gelatinous  substance. 

Dry  Pile. — A  dry  battery. 

Dry  Transformer. — An  air-insulated 
transformer,  as  distinguished  from  an  oil- 
insulated  transformer. 


Dry  Voltaic  Cell. — (1)  A  misnomer  for  a 
voltaic  cell  in  which  the  fluid  electrolyte 
is  held  in  suspension  by  saw-dust,  gelatine, 
or  other  suitable  material.  (2)  A  sealed 
voltaic  cell,  which  can,  therefore,  be  in- 
verted without  danger  of  spilling  liquid. 

Dual  Electrolysis.— A  term  sometimes 
employed  to  denote  the  double  decom- 
position that  attends  the  electrolysis  of  a 
metallic  salt ;  viz.  that  of  the  salt  and  its 
solvent. 

Dub's  Laws. — A  set  of  experimentally  es- 
tablished laws  relating  to  the  tractive  and 
attractive  magnetic  forces  developed  by 
electro-magnets  under  various  conditions,  • 
of  which  the  following  are  two  : — ' '  The 
attraction  of  V-shaped  electro-magnets, 
with  an  equal  number  of  windings,  ispro- 

'  portional  to  the  square  of  the  magnetiz- 
ing current  strength."  "The  attraction 
of  V-magnets  is,  with  equal  currents,  pro- 
portional to  the  square  of  the  number  of 
windings  of  the  magnetizing  spirals." 

Duct. — A  space  left  in  an  underground 
conduit  for  a  separate  wire  or  cable. 

Duct  of  Conduit. — The  space  provided  in 
a  conduit  for  a  conductor  or  cable. 

Dumb-Bell  Vibrator. — An  electric  vi- 
brator consisting  of  two  spheres  con- 
nected by  a  straight  conductor  contain- 
ing an  air-gap. 

Dummy  Moulding. — A  moulding  not  in- 
tended for  the  reception  of  a  wire,  but  as 
part  of  an  ornamentation,  the  moulding 
being  symmetrically  arranged  on  the  ceil- 
ing with  an  electrolier  as  a  centre,  with 
only  one  or  a  few  of  the  mouldings  actu- 
ally having  wires  placed  in  them. 

Duopod. — A  two-legged  screw  support  for 
a  pendant  or  upright. 

Duplex  Balance. — The  condition  of  a 
duplex  telegraphic  line,  in  which  the 
home  instruments  are  unaffected  by  the 
sending  signals,  and  are,  therefore,  ready 
to  respond  to  the  received  signals. 

DupLex  Cable. — A  cable  containing  two 
separate  conductors  placed  parallel  to- 
each  other. 

Duplex  Circuit. — (1)  A  circuit  arranged 
for  duplex  transmission.  (2)  A  metallic 
circuit. 

Duplex  Cut-Out. — A  cut-out  so  arranged 
that  when  one  bar  or  strip  is  fused  or 
melted  by  an  abnormal  current,  another 
can  be  immediately  substituted  for  it. 

Duplex  Electrolysis.  —  A  term  some- 
times used  for  dual  electrolysis. 

Duplex  Flat-Cable. — A  flat  laid-up  cable 
containing  two  wires. 

Duplex  Loop. — A  loop  or  pair  of  wires 


Dup.] 


755 


[Dyn. 


leading  to  a  branch  office,  whereby  a 
branch  office  can  be  brought  into  con- 
nection with  a  duplex  set  placed  at  the 
main  office,  for  the  duplex  sending  and  re- 
ception of  messages  at  said  branch  office. 
Duplex  Telegraph. — A  general  term 
embracing  the  apparatus  employed  in 
duplex  telegraphy. 

Duplex    Telegraphic    Insulator.  —  A 

double  telegraph  insulator. 

Duplex  Telegraphy. — A  system  of  tel- 
egraphy whereby  two  messages  can  be 
simultaneously  transmitted  in  opposite 
directions  over  a  single  wire. 

Duplex  Telephony. — Duplex  telephonic 
transmission. 

Duplex  Transmission. — The  sending  of 
two  telegraphic  or  telephonic  messages 
simultaneously  in  opposite  directions  over 
the  same  wire. 

Duplex  Wire. — An  insulated  conductor 
containing  two  separate  parallel  wires. 

Duplex  Working. — Duplex  transmis- 
sion. 

Duplexed-Diplex  Telephony  or  Tel- 
egraphy.— Quadruplex  telephony  or  tel- 
egraphy. 

Duplicate  Arc. — A  multiple  arc  contain- 
ing but  two  branches. 

Duration  of  Electric  Discharge.— The 
time  required  to  effect  a  complete  dis- 
ruptive discharge. 

Dust  Telephone  -  Transmitter.— (1)  A 
form  of  microphone  transmitter  in  which 
finely  granulated  carbon  or  carbon  dust  is 
contained  within  a  suitably  shaped  box, 
connected  with  the  terminals  of  the  trans- 
mitter. (2)  A  granular  telephone  trans- 
mitter. 

Dyad. — (1)  A  chemical  element  which  has 
two  bonds  by  which  it  can  unite  or  com- 
bine with  other  elements.  (2)  A  biva- 
lent element. 

Dyad  Atom. — An  atom  whose  valency, 
atomicity,  or  combining  power,  is  two. 

Dyeing,  Electric.— The  application  of 
electricity  either  to  the  reduction  or  to 
the  oxidation  of  the  salts  used  in  dyeing. 

Dynamic  Electricity.— A  term  some- 
times employed  for  current  electricity,  in 
contradistinction  to  static  electricity. 
(Obsolete.) 

Dynamic  Induction. — (1)  A  term  some- 
times employed  for  mutual  induction. 
(2)  Kinetic  induction. 

Dynamic  Multiplier. — (1)  A  term  some- 
times employed  for  a  self-induction  coil 
or  a  coil  possessing  self-induction.  (2)  A 
spark  coil.  • 


Dynamic  System  of  Induction  Teleg- 
raphy.— A  term  sometimes  used  for  the 
current  system  of  induction  telegraphy, 
as  distinguished  from  an  electrostatic 
system  of  induction  telegraphy. 

Dynamics. — That  branch  of  mechanics 
which  treats  of  the  action  of  a  force  in 
producing  motions  or  pressures. 

Dynamo. — A  dynamo-electric  machine  or 
generator. 

Dynamo  Armature-Coils. — The  coils, 
employed  on  the  armature  of  .a  dynamo- 
electric  machine. 

Dynamo  Balancing-Rheostat. — An  ad- 
justable rheostat  whose  range  is  sufficient 
to  balance  the  current  of  one  dynamo 
against  that  of  another,  with  which  it  is 
required  to  operate  in  parallel. 

Dynamo  Battery. — The  combination  of 
several  separate  dynamos  to  act  as  a 
single  electric  source. 

Dynamo  Brush-Holders. — Devices  for 
supporting  the  collecting  brushes  of  dy- 
namo-electric machines. 

Dynamo  Brush-Trimmer. — A  device  for 
rapidly  ensuring  the  accurate  trimming 
of  dynamo  brushes. 

Dynamo  Changing-Switch. — A  switch 
designed  to  throw  a  dynamo  from  one 
circuit  to  another. 

Dynamo-Electric  Generator.— A  dy- 
namo-electric machine. 

Dynamo-Electric  Machine. — (1)  A  ma- 
chine for  the  conversion  of  mechanical 
energy  into  electric  energy,  by  means  of 
electro-dynamic  induction.  (2)  A  dy- 
namo. 

Dynamo-Electric  Machine  Battery. — 
A  dynamo  battery. 

Dynamo  or  Motor  Frame. — The  iron 
body  of  a  dynamo  or  motor,  including  the 
pole-pieces  and  standards,  but  excluding 
the  base-plates  and  bearings. 

Dynamo  or  Motor  Standards.— The  sup- 
ports on  which  a  dynamo  or  motor  arma- 
ture rests. 

Dynamo  Pole-Changer.— A  pole-chang- 
ing transmitter  employed  in  a  system  of 
duplex  or  quadruplex  telegraphy. 

Dynamo  Power. — The  power  of  a  motor 
to  act  as  a  generator. 

Dynamo  Power  of  a  Motor. — (1)  A  power 
possessed  by  an  electric  motor  of  produc- 
ing counter-electromotive  force.  (2) 
The  number  of  volts  of  counter-electro< 
motive  force  produced  by  a  motor  per- 
revolution  per-second. 


Dyn.] 


756 


[Ear. 


Dynamo  Regulator. — A  name  given  to  a 
form  of  rheostat  employed  in  the  regula- 
tion of  a  dynamo. 

Dynamo  Resistance  Box. — A  form  of 
rheostat  employed  in  the  regulation  of 
a  dynamo. 

Dynamo  Terminals. — The  main  termi- 
nals of  a  dynamo. 

Dynamograph. — A  term  sometimes  ap- 
plied to  a  typewriting  telegraph  that 
records  the  messages  in  typewritten  char- 
acters, both  at  the  receiving  and  trans- 
mitting ends  of  the  line. 

Dynamograph,  Electric. — A  device  for 
electrically  recording  the  work  done  by 
any  machine. 

Dynamometer. — A  general  name  given 
to  a  variety  of  apparatus  for  measuring 
power. 

Dynamometric  Governor.  —  A  dyna- 
mometer employed  on  the  shaft  of  an 


electric  motor  for  the  purpose  of  operat- 
ing a  regulating  apparatus. 

Dynamotor.— (1)  A  particular  type  of 
rotary  transformer.  (2)  A  motor-gener- 
ator, in  which  a  generator  and  motor 
armature-winding  are  rotated  through  a 
common  magnetic  field. 

Dynamotor  Windings.— Windings  re- 
quired for  the  armatures  of  the  dynamo 
and  motor  of  a  dynamotor. 

Dyne.  —(1)  The  C.  G.   S.    unit  of    force. 

(2)  The  force  which  in  one  second  can 

impart  a  velocity  of  one  centimetre-per- 

second  to  a  mass  of  one  gramme. 
Dyne-cm. — An  abbreviation  proposed  for 

a  dyne-centimetre,  the  C.  G.  S.  unit  of 

work. 
Dyne :    cm-. — An    abbreviation    proposed 

for  a  dyne-per-square-centimetre,  the  C. 

G.  S.  unit  of  pressure. 

Dyne-Centimetre-Per-Second. — The  C. 
G.  S.  unity  of  activity. 


E 


E.  or  e. — A  symbol  for  electromotive 
force. 

E. — A  contraction  sometimes  used  for 
earth. 

E.  H.  P. — A  contraction  for  electrical 
horse-power. 

E.  M.  P. — A  contraction  for  electromotive 
force. 

E.  M.  P.  of  Self-induction.— The  E.  M. 
F.  generated  in  a  loop  of  wire  during  the 
filling  or  emptying  of  that  loop  by  mag- 
netic flux  from  its  own  current. 

Ear. — (1)  A  metal  piece  supported  by  an 
insulator  to  which  the  trolley  wire  is 
fastened.  (2)  A  trolley  ear. 

Ear  Piece. — A  circular  opening  into  an 
air  chamber  placed  over  the  diaphragm 
of  a  telephone,  suitably  shaped  to  per- 
mit the  ready  application  of  the  listener's 
ear. 

Earth. — (1)  A  fault  in  a  telegraphic  or  other 
line  caused  by  the  accidental  contact  of 
the  line  with  the  ground  or  earth,  or 
with  some  other  ground-connected  con- 
ductor. (2)  That  part  of  the  earth  or 
ground  which  forms  a  part  of  an  electric 
circuit. 

Earth-Battery  Current. — A  current  on 
a  telegraph  line  caused  by  voltaic  action 
between  two  dissimilar  earth  plates,  as 
distinguished  from  a  true  earth  current. 


Earth  Cell. — A  term  frequently  applied  to 
a  variety  of  voltaic  cell,  consisting  of  any 
voltaic  couple  buried  in  a  comparatively 
moist  stratum  of  earth. 

Earth  Circuit. — A  circuit  in  which  the 
ground  or  earth  forms  part  of  the  con- 
ducting path. 

Earth-Circuited  Conductor.  —  A  con- 
ductor connected  to  the  ground  or  to  an. 
earth-connected  circuit. 

Earth  Coil  for  Magnetic  Measurement. 
A  coil  capable  of  being  moved  about  a 
fixed  axis,  or  fixed  axes,  employed  for 
generating  a  measurable  E.  M.  F.  from 
the  earth's  magnetic  field. 

Earth  Connection. — A  conductor  which 
establishes  a  connection  between  any 
apparatus  or  circuit  and  ground. 

Earth  Currents. — Electric  currents  flow- 
ing through  the  earth,  caused  by  the 
difference  of  potential  of  its  different 
parts. 

Earth  Currents  of  Cable.— Currents  in 
a  cable  due  to  natural  causes,  such  as 
climatic  conditions  or  magnetic  disturb- 
ances, as  distinguished  from  the  current* 
sent  through  the  cable  for  the  transmis- 
sion of  messages. 

Earthenware  Conduit. — A  conduit,  gen- 
erally multiduct,  made  of  glazed  earthen- 
ware. 


Ear.] 


757 


[Edu 


Earth-Grounded  Wire. — A  wire  one  ter- 
minal of  which  is  grounded  or  put  to 
earth,  so  that  the  earth  forms  a  part  of 
the  circuit  in  which  it  is  placed. 

Earth  Indicator. — An  instrument  suitable 
for  the  accurate  determination  of  the 
magnetic  inclination  and  the  calibration 
of  ballistic  galvanometers. 

Earth  Overlap  Test. — A  localization  test 
for  the  position  of  a  partial  earth  in  a 
telegraph  line,  conducted  alternately  by 
observers  at  each  end  of  the  line,  the  line 
being  grounded  at  one  end  while  its  re- 
sistance is  measured  at  the  other,  and 
resistance  is  added  to  one  end  until  the 
fault  is  brought  to  the  centre  of  the  cir- 
cuit. 

Earth  Plates. — Plates  of  metal,  buried  in 
the  earth  or  in  water,  connected  to  the 
terminals  of  earth  wires. 

Earth  Return. — That  portion  of  a  ground- 
ed circuit  in  which  the  earth  forms  its 
conducting  path. 

Earth  Strip. — In  a  multiple  telephone 
switchboard  a  strip  of  metal,  or  top  plate 
of  a  series  of  jacks,  permanently  connect- 
ed to  earth  through  a  battery,  to  furnish 
connections  for  the  busy  test. 

Earth-Switch  for  Telephone. — (1)  In  a 
single-cord  multiple  telephone-switch- 
board, a  device  for  maintaining  a  ground- 
connection  with  the  shank  of  a  plug  when 
out  of  use,  by  supporting  the  plug,  friction 
tight,  against  a  ground-connected  bar. 
(2)  A  switch  at  a  telephone  switchboard 
for  automatically  grounding  the  sleeve  of 
a  plug  when  out  of  use. 

Earth  Wires. — The  wires  that  lead  an 
earth-grounded  circuit  to  the  earth  plates. 

Earth's  Field. — The  magnetic  field  pro- 
duced in  any  place  by  the  earth's  flux. 

Earth's  Flux. — The  magnetic  flux  pro- 
duced by  the  earth  by  virtue  of  its  mag- 
netized condition. 

Earthed. — Connected  to  earth  or  ground. 

Earthing. — Connecting  a  line  or  conductor 
to  earth  or  ground. 

Earthing  Device. — An  instrument  for 
automatically  making  connection  be- 
tween a  system  of  wiring  and  the  earth, 
should  the  potential  between  them  rise  be- 
yond a  certain  predetermined  safe  limit. 

Earthkin. — A  terella. 

Easement. — A  permit  obtained  from  the 
owner  of  a  property  for  the  erection  of 
poles  or  attachments  for  telephone,  tele- 
graph, or  other  aerial  lines. 

Ebonite. — (1)  A  hard,  tough,  black  sub- 
stance, composed  of  India  rubber  and 


sulphur,  possessing  both  high  powers  of  in- 
sulation and  high  specific  inductive  capac- 
ity. (2)  Vulcanite. 

Economic  Coefficient. — The  ratio  be- 
tween the  net  electric  power,  or  the  out- 
put of  a  dynamo,  and  the  gross  electric 
power,  or  power  actually  converted  in  the 
dynamo. 

Economic  Coefficient  of  Dynamo-Elec- 
tric Machine.— (1)  The  ratio  between 
the  electric  power  produced  by  a  dyna- 
mo at  its  terminals,  and  the  mechanical 
power  expended  in  driving  it.  (2)  A 
term  sometimes  employed  for  the  ratio  of 
the  useful  electric  power  at  the  termi- 
nals to  the  total  electric  power  developed 
in  the  machine. 

Economy  Coil. — A  choking  coil  employed 
for  the  purpose  of  reducing  the  pressure 
on  arc  lamps  fed  by  step-down  trans- 
formers. 

Eddy  Conduction-Currents. — (1)  Eddy 
currents.  (2)  Foucault  currents. 

Eddy-Current  Loss. — The  loss  of  energy 
in  a  dynamo,  motor,  transformer,  or  simi- 
lar apparatus,  due  to  the  presence  of 
eddy  currents. 

Eddy  Currents. — Useless  currents  pro- 
duced in  the  pole-pieces,  armature,  and 
field-magnet  cores  of  dynamos  or  motors, 
or  in  metallic  masses  generally,  either  by 
their  motion  through  magnetic  flux,  or 
by  variations  in  the  strength  of  electric 
currents  flowing  near  them. 

Eddy  Displacement-Currents. — Eddy 
currents  produced  in  the  mass  of  a  di- 
electric or  insulator,  by  the  passage 
through  it  of  electrostatic  or  magnetic 
flux. 

Edgewise  System. — A  system  of  mount- 
ing central-station  switchboard  instru- 
ments, in  which,  for  the  purpose  of  econo- 
mizing space,  their  scales  are  presented 
edgeways  vertically  to  the  switchboard 
face. 

Edison  Distributing-Box.— A  distribut- 
ing box  employed  in  the  Edison  three- 
wire  system  of  distribution. 

Edison  Effect. — An  electric  discharge 
which  occurs  between  one  of  the  termi- 
nals of  the  incandescent  filament  of  an 
electric  lamp  and  a  metallic  plate  placed 
near  but  disconnected  from  the  filament 
as  soon  as  a  certain  difference  of  poten- 
tial is  reached  between  the  lamp  terminals. 

Edison  Electric-Tubes. — The  under- 
ground tubes  employed  in  the  Edison, 
three- wire  system  of  distribution. 

Edison  -  Lalande  Cell. — A  zinc-copper 
couple  in  which  the  copper  is  covered 


Eel.] 


758 


with  a  depolarizing  layer  of  copper-oxide, 
and  the  couple  immersed  'n  an  electrolyte 
of  caustic  soda  zr  r~tasr:. 
Eel,  Electric.— (1)  Ai:  eel  possessing  the 
power  of  giving  powerful  electric  shocks. 
(2)  The  gymnotus  electricus. 

Effective  Ampere-Turns.  — O  The  re- 
sultant magnetizing  force  v-  a  magnetic 
circuit.  (2)  The  square  root,  of  the  mean 
square  of  the  ampere-turr.s  in  a  periodi- 
cally-varying magnetizing  force. 

Effective  Conductance.— (1)  The  ratio  in 
an  alternating-current  circuit  of  the  real 
electric  power,  or  real  activity,  to  the 
square  of  the  effective  pressure.  (2)  The 
virtual  conductance  of  a  circuit.  (3)  In 
an  alternating-current  circuit  the  ratio  of 
the  energy  component  of  current  to  the 
total  E.  M.  F. 

Effective  Current-Strength.— (1)  The 
strength  of  an  alternating  or  sinusoidal- 
electric  current,  determined  by  its  heat- 
ing effect ;  or,  in  other  words,  the  therm- 
ally effective  current  strength.  (2)  That 
value  of  the  current  strength  of  a  sinusoi- 
dal or  alternating  current  which  is  equal 
to  the  square  root  of  the  mean  square 
of  the  instantaneous  values  of  the  current 
during  one  or  more  cycles.  (3)  The  square 
root  of  the  time  average  of  the  square  of 
the  current. 

Effective  Electromotive  Force. — (1) 
The  difference  between  the  direct  and  the 
counter-electromotive  force.  (2)  The 
square  root  of  the  time  average  of  the 
square  of  the  E.  M.  F.  (3)  The  virtual 
E.  M.  F. 

Effective  M.  M.  P.— The  square  root  of 
the  time  average  of  the  square  of  a  peri- 
odically-alternating M.  M.  F. 

Effective  Reactance.— (1)  In  an  alternat- 
ing-current circuit,  the  ratio  of  the  watt- 
less component  of  an  electromotive  force 
to  the  total  current.  (2)  Apparent  react- 
ance. 

Effective  Resistance. — In  an  alternat- 
ing-current circuit,  the  ratio  between  the 
energy  component  of  an  electromotive 
force  and  the  total  current. 

Effective      Secondary  -  Electromotive 

Force.— (1)  The  vector  difference  be- 
tween the  direct  and  counter-electromo- 
tive force  in  the  secondary  of  an  induc- 
tion coil.  (2)  The  E.  M.  F.  in  a  secondary 
circuit  expended  in  overcoming  resist- 
ance. (3)  The  square  root  of  the  time  aver- 
age of  the  square  of  a  secondary  E.  M.  F. 
Effective  Starting-Current  of  Motor.— 
The  indicated  value  of  the  starting  cur- 
rent of  a  motor  as  observed  on  an  am- 
-  meter. 


Effective  Susceptance. — (1)  In  an  alter- 
nating-current circuit,  the  ratio  between 
the  wattless  component  of  a  current  and 
its  total  electromotive  force.  (2)  Apparent 
susceptance. 

Efficiency. — The  ratio  between  an  effect 
produced  and  the  expenditure  required 
to  produce  that  effect. 

Efficiency  of  Voltaic  Battery.— (1)  The 
ratio  between  the  actual  ampere-hour  out- 
put per  gramme  of  zinc  dissolved,  and  the 
theoretical  ampere-hour  output.  (2)  The 
ratio  of  the  energy  delivered  at  the  ter- 
minals of  a  battery  to  the  theoretically 
computed  energy  liberated  within  it  elec- 
trochemically.  (3)  The  ratio  of  the  en- 
ergy at  terminals  to  the  total  electric  en- 
ergy. 

Effective  Value  of  Periodic  Current  or 
E.  M.  F.— (1)  The  square  root  of  the 
mean  square  of  the  current  or  E.  M.  F. 
extended  over  one  or  more  complete  cy- 
cles. (2)  The  virtual  current  or  E.  M.  F. 

Efficiency,  Electric.— The  useful  or  avail- 
able electric  energy  delivered  by  any 
source  to  its  external  circuit,  divided  by  the 
total  electrical  energy  within  the-source. 

Efficiency  of  Dynamo,  Electric.— The 
electrical  output  of  a  dynamo,  divided  by 
the  total  electric  activity  in  its  armature 
circuit. 

Efficiency  of  Conversion.— The  ratio  be- 
tween the  enei'gy  present  in  any  result 
and  the  energy  expended  in  producing 
that  result. 

Efficiency  of  Conversion  of  Dynamo.— 
The  total  electric  energy  developed  by  a 
dynamo,  divided  by  the  total  mechanical 
energy  required  to  drive  the  dynamo. 

Efficiency  of  Distribution.— The  ratio 
of  the  units  of  electric  quantity  or  elec- 
tric energy  sold,  or  distributed  to  consum- 
ers from  a  central  station,  to  the  units 
generated  in  that  station. 

Efficiency  of  Electric  Lamp.— (1)  The 
ratio  of  the  luminous  energy  emitted  by 
an  incandescent  lamp  to  the  energy  ab- 
sorbed by  the  lamp.  (2)  The  ratio  of  the 
number  of  candles  which  can  be  obtained 
from  an  electric  lamp  to  the  electric  ac- 
tivity in  the  lamp  expressed  in  watts.  (3) 
A  term  in  common  but  inaccurate  use  for 
the  ratio  of  the  number  of  watts  con- 
sumed by  a  lamp  to  the  number  of  can 
dies  it  produces,  expressed  in  watts  pei 
candle. 

Efficiency  of  Electric  Motor.— (1)  The 
ratio  of  the  power  delivered  at  a  motor 
pulley  to  the  electric  power  supplied  at 
its  terminals.  (2)  The  ratio  between  the 
useful  mechanical  power  delivered  by  a 


Elf.] 


759 


[Ele. 


motor  and  the  electrical  power  put  in  to 
drive  it. 

Efficiency  of  Radiation. — The  ratio  of 
the  luminous  activity  of  a  luminous  body 
to  its  radiation  activity. 

Efficiency  of  Secondary  Battery. — (1) 
The  ratio  of  the  electric  quantity  of  dis- 
charge in  ampere-hours  to  the  electric 
quantity  in  a  charge.  (2)  The  ratio  of  the 
electric  energy  of  discharge  in  watt-hours 
to  the  electric  energy  of  charge. 

Efficiency  of  Transformer  or  Con- 
verter.— The  ratio  of  the  power  supplied 
at  the  secondary  terminals  of  a  trans- 
former or  converter  to  the  power  supplied 
at  its  primary  terminals. 

Efflorescence. — (1)  Pulverulence  or  crum- 
bling of  crystalline  salts,  due  to  the  loss 
of  their  water  of  crystallization  on  drying. 
(2)  A  term  loosely  applied  to  the  deposi- 
tion of  solid  matter  above  the  line  of  liquid 
on  the  surface  of  a  vessel  containing  a  va- 
porizing saline  solution,  by  the  crystalli- 
zation of  the  salt. 

Effluvia. — The  name  given  to  a  variety  of 
assumed  highly  tenuous  imponderable 
forms  of  matter  that  were  formerly  be- 
lieved to  be  given  off  by  electrified  or 
magnetized  bodies. 

Effluvium,  Electric. — A  term  employed 
in  the  early  history  of  electricity  for  the 
supposed  highly-tenuous,  imponderable 
matter  given  off  from  an  electrified  body, 
which  was  assumed  to  be  the  cause  of 
electric  phenomena. 

Efflux. — The  flow  or  quantity  of  liquid  es- 
caping in  a  given  time  from  an  orifice  in 
a  containing  vessel. 

Egg,  Electric. — An  egg-shaped  vessel  con- 
taining a  partial  vacuum  through  which 
an  electric  discharge  is  passed,  for  the 
purpose  of  producing  luminous  effects. 

Elastance. — (1)  The  reciprocal  of  the  elec- 
trostatic capacity.  (2)  The  reciprocal  of 
permittance. 

Elastic. — (1)  Of  or  pertaining  to  elasticity. 
(2)  Possessing  elasticity. 

Elasticity. — That  property  of  a  body  in  vir- 
tue of  which  its  original  configuration  or 
form  is  regained,  after  a  strain  or  distor- 
tion has  been  produced  in  it  by  the  action 
of  a  stress. 

Elasticity,  Electric. — The  quotient  aris- 
ing from  dividing  the  electric  strain  by 
the  electric  stress. 

Elastivity. — The  reciprocal  of  permit- 
tivity. 


Elbow  Connection. — A  connection  at  an 
angle  more  or  less  approaching  90°. 

Elbow  Connector. — A  connector  suitable 
for  connecting  conductors  at  an  elbow. " 

Electrepeter.— An  old  term  for  switch, 
key,  or  pole-changer.  (Obsolete.) 

Electret. — (1)  A  name  proposed  for  a  sub" 
stance  possessing  natural  or  inherent  elec- 
trization. (2)  A  permanently  polarized 
body. 

Electric. — Of  or  pertaining  to  electricity. 

Electrical. — An  orthography  for  electric. 

Electrically. — In  an  electrical  manner. 

Electrically  Conducting. — Transferring 
electricity  by  electric  conduction. 

Electrically  Controlled  Clock.— A  clock 
that  is  controlled,  either  wholly  or  par- 
tially, by  electricity. 

Electrically  Discharging.  —Equalizing 
differences  of  potential  by  connecting 
them  with  a  conductor. 

Electrically  Energizing.— Causing  elec- 
tricity tc  produce  any  effect  in  an  electro- 
receptive  device. 

Electrically  Illumined  Buoy. —An  elec- 
trically lighted  buoy. 

Electrically  Retarded.— Decreased  speed 
of  telegraphic  signalling  by  means  of 
electrostatic  induction. 

Electrically  Tuned  System.— Any  cir- 
cuit or  system  of  circuits  that  have  been 
brought  into  electric  resonance  with  an- 
other circuit  or  system  of  circuits. 

Electrician. — One  versed  in  the  principles 
and  applications  of  electricity. 

Electricity. — The  name  given  to  the  un- 
known cause  of  electric  phenomena. 

Electricity  Driving-Force.  —  A  term 
sometimes  used  for  electromotive  force. 

Electricity  Meter.;— (1)  A  coulomb  meter. 
(2)  A  term  sometimes  used  for  electric 
meter. 

Electrics. — A  term    formerly  applied  to 

substances  capable  of  becoming  electrified 

by  friction.  (Obsolete.) 
Electrifiable. — Capable  of  being  endowed 

with  electric  properties. 
Electrification. — The  production  of  an 

electric  charge. 

Electrified. — Endowed  with  an  electric 
charge. 

Electrified  Body. — A  charged  body. 

Electrify. — To  endow  with  electric  prop- 
erties. 

Electrlne. — Of  or  pertaining  to  electrum 
or  amber. 


Ele.] 


760 


[Ele. 


Electripherous. — An  unnecessary  word 
proposed  for  anything  capable  of  bearing 
or  transmitting  electricity. 

Electrization. — Electrification. 

Electrize. — To  electrify  or  endow  with  an 
electric  charge. 

Electrizer. — Anything  which  electrifies  or 
charges  a  body  with  electricity. 

Electro  -  Anaesthesia.  —  Insensibility  to 
pain  produced  by  the  use  of  electricity. 

Electro-Ballistics. — The  application  of 
electricity  to  the  determination  of  the 
velocity  of  projectiles. 

Electro-Bath.. — The  liquid  or  fluid  em- 
ployed in  electro-plating. 

Electro-Biological. — Pertaining  to  elec- 
tro-biology. 

Electro-Biologist. — One  skilled  in  electro- 
biology. 

Electro-Biology. — That  branch  of  electric 
science  which  treats  of  the  condition  of 
living  animals  and  the  effects  of  electric- 
ity upon  them. 

Electro-Bioscopist. — One  skilled  in  elec- 
tro-bioscopy. 

Electro-Bioscopy. — The  determination  of 
the  existence  of  life  or  death  by  the  pas- 
sage of  electricity  through  the  muscles 
and  nerves. 

Electro-Brassing. — (1)  The  electrolytic 
deposition  of  brass  from  a  solution  con- 
taining salts  of  zinc  and  copper.  (2)  Coat- 
ing a  surface  with  a  layer  of  brass  by 
electro-plating. 

Electro-Calorimetry. — The  art  of  meas- 
uring the  quantity  of  heat  developed  in 
any  conductor  or  circuit  by  an  electric 
current. 

Electro-Capillarity. — The  science  which 
treats  of  the  mutual  effects  between  elec- 
tricity and  capillarity. 

Electro-Capillary. — Of  or  pertaining  to 
electro-capillarity. 

Electro  -  Capillary  Electrometer.  —  A 
capillary  electrometer. 

Electro-Capillary  Light. — A  bright  light 
obtained  by  the  discharge  of  an  induction 
coil  through  a  narrow  capillary  tube  pro- 
vided with  aluminium  or  copper  elec- 
trodes, and  filled  with  air  at  ordinary 
pressures. 

Electro-Capillary  Phenomena.  —  Elec- 
tric phenomena  observed  in  capillary 
tubes  at  the  contact  surfaces  of  two 
liquids. 

Electro-Capillary  Telephone.— A  tele- 
phone transmitter  whose  operation  de- 
pends on  the  electric  currents  produced 


by  forcing  a  liquid  through  a  bundle  of 
capillary  tubes,  by  the  to-and-fro  move- 
ments of  the  diaphragm. 
Electro-Chemical. — Of  or  pertaining  to 
electro-chemistry. 

Electro-Chemical       Accumulator. — A 

storage  battery. 

Electro-Chemical  Actinometer.— (1)  An 
actinometer  employing  electrolytic  ac- 
tion. (2)  An  electric  actinometer. 

Electro-Chemical       Decomposition. — 

Electrolytic  decomposition. 

Electro-Chemical  Filtration. — A  term 
formerly  employed  in  place  of  electric 
end  osmose. 

Electro-Chemical  Meter. — An  electric 
meter  in  which  the  current  passing  is 
measured  by  the  amount  of  electrolytic 
decomposition  it  effects. 

Electro-Chemical  Telephone. — A  name 
sometimes  given  to  the  Edison  electro- 
motographic  telephone. 

Electro-Chemical  Series. — A  list  of 
chemical  elements  so  arranged  that  each 
will  displace  from  its  compounds  any 
element  lower  in  the  list  than  itself. 

Electro  -  Chemically. — In  -  an  electro- 
chemical manner. 

Electro  -  Chemist. — One  skilled  in  the 
science  of  electro-chemistry. 

Electro-Chemistry. — (1)  That  branch  of 
electric  science  which  treats  of  electric 
combinations  and  decompositions  effected 
by  the  electric  current.  (2)  The  science 
which  treats  of  the  relation  between  the 
laws  of  electricity  and  chemistry. 

Electro-Chromic  Rings. — (1)  A  term 
sometimes  applied  to  metallochromes. 
(2)  Nobilli's  rings. 

Electro-Chronographic. — Of  or  pertain- 
ing to  the  electric  chronograph. 

Electro-Chronometric  Counter. — An 
apparatus  employed  in  a  system  of  elec- 
tric clocks  to  enable  the  master  clock 
electrically  to  control  or  operate  a  num- 
ber of  separate  or  secondary  clocks. 

Electro  -  Coppering.  —  Electro  -  plating 
with  copper. 

Electro-Crystallization.— Crystallization 
effected  during  electrolytic  deposition. 

Electro-Culture  of  Plants. — Stimulating 
the  growth  of  plants  by  electricity. 

Electro-Deposit. — A  coating  or  electro- 
plating of  metal. 

Electro-Depositer. — One  who  practises 
the  art  of  electro-deposition. 

Electro  -  Deposition. — (1)  The  deposit, 
usually  of  a  metallic  substance,  by  means 


761 


[Ele. 


of    electrolysis.     (2)  Electrolytic    deposi- 
tion. 

Electro-Deposits. — Electrolytic  deposits. 

Electro-Diagnosis. — Diagnosis  by  means 
of  the  exaggeration  or  diminution  of  the 
reaction  of  the  excitable  tissues  of  the 
body  when  subjected  to  the  varying  in- 
fluences of  electric  currents. 

Electro-Diagnostic. — Of  or  pertaining  to 
electro-diagnosis. 

Electro-Diapason. — An  electro-magnet- 
ically  operated  tuning-fork. 

Electro-Dynamic  Attraction.— The  mu- 
tual attraction  existing  between  electric 
currents,  or  between  conductors  through 
which  electric  currents  are  passing. 

Electro-Dynamic  Balance.— A  balance 
form  of  electro-dynamometer. 

Electro-Dynamic  Capacity.— A  term 
sometimes  employed  for  self-induction. 

Electro-Dynamic  Force.— A  mechanical 
force  exerted  on  the  substance  of  a  wire 
or  conductor  due  to  the  dissymmetrical 
•  distribution  of  magnetic  flux  in  its  neigh- 
borhood. 

Electro-Dynamic  Induction.— Electro- 
motive forces  set  up  by  induction  in  con- 
ductors which  are  either  actually  or  prac- 
tically moved  so  as  to  cut  magnetic  flux. 

Electro-Dynamic  Interrupter.— An  in- 
terrupter for  the  primary  circuit  of  an 
induction  coil,  consisting  of  an  elastic 
wire  stretched,  like  the  wire  of  a  sono- 
meter or  inonochord,  between  the  poles 
of  a  permanent  horse-shoe  magnet. 

Electro-Dynamic  Machinery.— Any  ap- 
paratus designed  for  the  production, 
transference,  utilization,  or  measurement 
of  energy  by  the  medium  of  electricity. 

Electro-Dynamic  Motor.— (1)  A  motor 
operated  by  electro-dynamic  force.  (2) 
An  electric  motor. 

Electro-Dynamic  Potential.— An  elec- 
tric potential  produced  by  electro-dyna- 
mic induction. 

Electro-Dynamic  Repulsion.— The  mu- 
tual repulsion  between  two  electric  cir- 
cuits whose  currents  are  flowing  in  op- 
posite directions. 

Electro-Dynamic  Rotation.— (1)  The  ro- 
tation of  a  magnetic  field  produced  as  the 
resultant  of  two  or  more  magnetic  fields 
or  magnetizing  forces  of  variable  inten- 
sity, acting  at  right  angles  to  one  another, 
whose  maxima  and  minima  do  not  coin- 
cide, but  whose  periods  are  the  same.  (2) 
Rotation  produced  electro-dynamically. 

Electro-Dynamic  Screen.— A  conduct- 
ing scr.een  employed  for  intercepting  the 

9— 


transmission  of  varying  electro-magnetic 
forces. 

Electro-Dynamic  Whirls.— Whirlings, 
or  rotary  motions  produced  in  a  cloud  of 
copper  oxide  in  a  voltameter,  when  the 
electrolyte  is  traversed  by  a  powerful 
discharge,  while  under  the  influence  of 
magnetic  flux. 

Electro-Dynamics.— That  branch  of  elec- 
tric science  which  treats  of  the  action  of 
electric  currents  on  one  another,  on 
themselves,  or  on  magnets. 

Electro-Dynamical.— Of  or  pertaining  to 
electro-dynamics. 

Electro-Dynamometer. — A  form  of  gal- 
vanometer suitable  for  the  measurement 
of  electric  currents. 

Electro  -  Dynamometer  Balance.  —  A 
name  sometimes  given  to  a  current  bal- 
ance. 

Electro-Etching. — A  term  sometimes  em- 
ployed for  electric  engraving. 

Electro-Extraction  of  Ores. — Various 
electric  processes  for  extracting  metals 
from  their  ores. 

Electro-Filtration. — A  term  sometimes 
employed  for  electric  osmose  or  cata- 
phoresis. 

Electro-Genesis. — A  word  proposed  for 
the  production  of  electricity.  (Not  in 
use.) 

Electro-Genie.  —  Producing  electricity. 
(Not  in  use.) 

Electro-Gild. — To  cover  with  a  metallic 
coating  of  gold  by  electro-plating. 

Electro-Gilder. — One  who  practises  the 
art  of  electro-gilding. 

Electro-Gilding.  —  (1)  Electric  gilding. 
(2)  Electro-plating  with  gold. 

Electro-Gilt. — Gilded  by  means  of  elec- 
tricity. 

Electro-Graphy. — Galvanography. 

Electro-Inductive  Repulsion.— Repul- 
sion between  bodies  due  either  to  the 
influence  of  electrostatically  induced 
charges,  or  electromagnetically  induced 
currents. 

Electro-Kinetic. — Of  or  pertaining  to  elec* 
tro-kinetics. 

Electro-Kinetic  Energy.  —  Electrical 
energy  that  is  actually  engaged  in  doing 
work. 

Electro-Kinetic  Units. — A  term  some- 
times used  for  C.  G.  S.  electro-magnetic 
units. 

Electro-Kinetics. — A  term  sometimes  ap- 
plied to  the  phenomena  of  electric  cur- 
rents, or  electricity  in  motion,  as  dis- 
Vol.  2 


file.] 


762 


tinguished  from  electrostatics,  or  the 
phenomena  of  electric  charges,  or  elec- 
tricity at  rest. 

Electro-Lithotrity. — A  term  proposed  for 
the  removal  of  urinary  calculi  by  elec- 
trolysis. 

Electro-Magnet. — (1)  A  magnet  produced 
by  the  passage  of  an  electric  current 
through  a  circuit  of  insulated  wire.  (2)  A 
magnetizing  coil  surrounding  a  soft  iron 
core,  that  is  capable  of  being  magnetized 
and  demagnetized  instantly  on  the  clos- 
ing and  opening  of  the  circuit. 

Electro-Magnetic. — Of  or  pertaining  to 
an  electro-magnet  or  to  electroTinag- 
netism. 

Electro-Magnetic  Ammeter. — A  form  of 
ammeter  in  which  a  magnetic  needle  is 
moved  against  the  field  of  an  electro- 
magnet by  the  field  of  the  current  it  is 
measuring. 

Electro-Magnetic  Annunciator.— An 
electro-magnetic  device  for  automatically 
indicating  the  points  or  places  at  which 
one  or  more  electric  contacts  have  been 
closed. 

Electro-Magnetic  Attraction. — The  mu- 
tual attraction  existing  between  the  un- 
like poles  of  electro-magnets. 

Electro-Magnetic  Bell. — An  electro- 
magnetically  operated  bell. 

Electro-Magnetic  Bell-Call.— A  bell-call 
operated  by  an  electro-magnet. 

Electro-Magnetic  Brake. — A  brake  for 
car  wheels,  whose  braking  power  is 
either  entirely  derived  from  electro-mag- 
netism, or  is  thrown  into  action  by  elec- 
tro-magnetic devices. 

Electro-Magnetic  Cam. — A  form  of  mag- 
netic equalizer  which  depends  for  its 
operation  on  the  lateral  approach  of  a 
suitably  shaped  polar  surface. 

Electro-Magnetic  Capacity  of  Line.— 
A  term  sometimes  used  for  the  self-induc- 
tion or  inductance  of  a  line. 

Electro-Magnetic  Cut-Out. — A  cut-out 
operated  by  means  of  an  electro-magnet. 

Electro-Magnetic  Dental  Mallet. — A 
mallet  for  filling  teeth,  the  blows  of  which 
are  struck  by  means  of  an  electro-mag- 
netically  driven  mechanism. 

Electro-Magnetic  Drill. — A  drum  em- 
ployed in  blasting  and  mining  operations, 
operated  by  means  of  electricity. 

Electro-Magnetic  Drum. — A  drum  used 
in  feats  of  legerdemain  operated  by 
means  of  an  automatic  electro-magnetic 
contact-breaker. 


Electro-Magnetic  Engine.— An  electric 
motor. 

Electro-Magnetic  Explorer. — An  appa- 
ratus operated  by  means  of  induced  cur- 
rents, and  formerly  employed  for  the  pur 
pose  of  locating  bullets,  or  other  foreign 
metallic  substances  in  the  human  body. 

Electro-Magnetic  Eye.— (1)  A  term  ap- 
plied to  a  certain  form  of  spark  micro- 
meter, employed  by  Hertz  in  his  experi- 
ments on  electro-magnetic  radiation. 
(2)  A  term  sometimes  applied  to  a  co- 
herer. 

Electro-Magnetic  Field.— The  field  pro- 
duced either  by  an  electro-magnet  or  by 
an  electric  current. 

Electro-Magnetic  Flux. — Magnetic  flux 
produced  by  means  of  an  electro-magnet 
or  by  an  electric  current. 

Electro-Magnetic  Gyroscope. — An  elec- 
tro-magnetically  driven  gyroscope. 

Electro-Magnetic  Helix. — An  electro- 
magnetic solenoid. 

Electro-Magnetic  Impulse. — An  im- 
pulse produced  in  the  ether  surrounding  a 
conductor  by  the  action  of  an  impulsive 
discharge,  or  by  a  pulsating  field. 

Electro-Magnetic  Induction. — A  va- 
riety of  electro-dynamic  induction  in 
which  electric  currents  are  produced  by 
the  motion  either  of  electro-magnets,  or 
electro-magnetic  solenoids. 

Electro-Magnetic  Inertia. — A  term 
sometimes  employed  for  the  inductance 
or  self-induction  of  a  current. 

Electro-Magnetic  Interference. — The 
interference  of  electro-magnetic  waves. 

Electro-Magnetic  Intermitter. — An 
electro-magnetic  vibrator. 

Electro-Magnetic  Medium. — Any  me- 
dium in  which  electro-magnetic  phe- 
nomena occur,  or  through  which  electro- 
magnetic waves  are  transmitted. 

Electro-Magnetic  Meter. — An  electric 
meter  in  which  the  current  passing  is 
measured  by  the  electro-magnetic  effects 
it  produces. 

Electro-Magnetic  Mine-Exploder.— A 

small  magneto-electric  machine  employed 
in  the  direct  firing  of  blasts. 
Electro-Magnetic      Momentum. — T  h  e 
product  of  the  inductance  of  a  circuit  and 
the  current  strength  it  carries. 

Electro-Magnetic  Motor. — An  electric 
motor. 

Electro-Magnetic  Multiplier. — A  term 
sometimes  employed  for  Schweigger's 
multiplier. 


Ele.] 


res 


[Ele, 


Electro-Magnetic  Optical-Strain. — Any 

optical  strain  produced  by  electro-mag- 
netic stress. 

Electro-Magnetic  Pop-Gun.— A  mag- 
netizing coil,  provided  with  a  tubular 
space  for  the  insertion  of  a  core  much 
shorter  than  the  length  of  the  coil,  •which 
is  violently  projected  when  the  coil  is  en- 
ergized by  a  current. 

Electro-Magnetic  Radiation. — The  radi- 
ation, from  any  conductor  through  which 
oscillatory  discharges  are  passing,  of 
electro-magnetic  waves  similar  in  all  re- 
spects to  those  of  light,  save  in  their  much 
greater  wave  length. 

Electro-Magnetic  Repeater. — A  word 
formerly  employed  for  a  form  of  vibrating 
contact-breaker. 

Electro-Magnetic  Repulsion. — The  mu- 
tual repulsion  produced  by  two  similar 
electro-magnetic  poles. 

Electro-Magnetic  Resonator.— A  term 
sometimes  applied  to  a  Hertz  spark  micro- 
meter, in  which  electro-magnetic  waves 
are  produced  by  electric  resonance. 

Electro-Magnetic  Retardation.— A  re- 
tardation in  the  magnetization  or  demag- 
netization of  a  substance. 

Electro-Magnetic  Rotation.— Rotation 
obtained  by  electro-magnetic  attractions 
and  repulsions. 

Electro-Magnetic  Separator.— (1)  A  de- 
vice for  separating  iron  ore  from  the 
dross,  in  finely-pulverized,  low-grade  iron 
ores.  (2)  A  device  for  magnetically  re- 
moving particles  of  iron  from  brass  filings 
or  other  non-magnetic  material,  and  thus 
freeing  such  material  from  impurities. 

Electro-Magnetic  Shunt.— (1)  In  a  sys- 
tem of  telegraphic  communication,  an 
electro-magnet  whose  coils  are  placed  in 
a  shunt  circuit  around  the  terminals  of 
the  receiving  instrument.  (2)  Any  shunt 
coil  provided  with  a  magnetic  core. 

Electro-Magnetic  Solenoid.— (1)  A  cy- 
lindrical coil  of  wire,  each  convolution  of 
which  is  circular.  (2)  An  electro-mag- 
netic helix.  (3)  A  cylindrical  current 
sheet. 

Electro-Magnetic  Sorter.— An  electro- 
magnetic sepai'ator. 

Electro-Magnetic  Strain.— The  effect 
produced  by  an  electro-magnetic  stress. 

Electro-Magnetic  Stress.— The  force  or 
pressure  in  an  electro-magnetic  field 
which  produces  a  strain  or  deformation  in 
a  piece  of  glass  or  other  substance  placed 
therein. 


Electro-Magnetic  Telegraph. — A  gen- 
eral term  embracing  the  apparatus  em- 
ployed in  a  system  of  electro-magnetio 
telegraphy. 

Electro-Magnetic  Telegraphy.— (1)  A 
system  of  telegraphy  employing  or  based 
upon  electro-magnetism.  (2)  The  ordi- 
nary Morse  telegraphy. 

Electro-Magnetic  Temperature-Regu- 
lator.— A  temperature  regulator  whose 
operation  is  dependent  on  the  action  of 
an  electro-magnet  which  is  thrown  into 
operation  by  the  expansion  or  contraction 
of  a  solid  liquid  or  gas. 

Electro-Magnetic  Twist  or  Pull.— The 
torque  of  an  electro-magnetic  motor. 

Electro-Magnetic  Units.— (1)  A  system 
of  C.  G.  S.  units  employed  in  electro-mag- 
netic measurements.  (2)  Units  based  on 
the  attractions  and  repulsions  capable  of 
being  exerted  between  two  unit  magnetic 
poles  at  unit  distance  apart,  or  between 
a  unit  magnetic  pole  and  a  unit  electric 
current. 

Electro-Magnetic  Vibrator. — A  name 
sometimes  given  to  an  automatic  contact- 
breaker. 

Electro-Magnetic  Waves. — Waves  in  the 
ether,  given  off  from  a  circuit  through 
which  an  oscillatory  discharge  is  passing, 
or  from  a  magnetic  circuit  undergoing 
variations  of  magnetic  intensity. 

Electro-Magnetic  Voltmeter. — A  form 
of  voltmeter  in  which  the  difference  of  po- 
tential is  measured  by  the  movements  of  a 
magnetic  needle  in  the  field  of  an  electro- 
magnet. 

Electro-Magnetics. — That  branch  of  elec- 
tric science  which  treats  of  the  relations 
that  exist  between  electric  circuits  and 
magnets. 

Electro  -  Magnetism. — Magnetism  pro- 
duced by  means  of  electric  currents. 

Electro-Magnetist. — One  skilled  in  the 
art  of  electro-magnetism.  (Not  in  use.) 

Electro  -  Massage. — The  application    of 
electricity  to  the  body  during  its  mas-' 
sage. 

Electro-Mechanical  Alarm. — A  mechan- 
ically operated  alarm,  that  is  started  or 
set  in  operation  by  means  of  an  electric 
current. 

Electro-Mechanical  Bell. — A  bell  whose 
striking  apparatus  is  mechanically  oper- 
ated, when  called  into  action  by  an  electro- 
magnet. 

Electro  -  Mechanical  Gong. — A  gong 
struck  or  operated  by  mechanical  force, 
at  times  which  are  dependent  on  the  pas- 
sage of  an  electric  current. 


Ele. 


764 


[Ele. 


Electro-Mechanical  Indicator.— A  me- 
chanical indicator  that  is  started  or  set 
into  action  by  electricity. 

Electro-Medical. — Of  or  pertaining  to 
electricity  employed  electro-therapeuti- 
cally. 

Electro-Medical  Apparatus. — A  general 
term  for  any  apparatus  employed  in  elec- 
tro-therapeutic treatment. 

Electro  -  Metallurgical  Circuit .  —  An 
electric  circuit  employed  in  electro-metal- 
lurgical processes. 

Electro-Metallurgical  Galvanization. 
A  process  of  covering  any  conducting 
surface  with  a  metallic  coating  by  elec- 
trolytic deposition,  such,  for  example,  as 
the  thin  copper  coating  deposited  on  the 
carbon  electrodes  used  in  arc-lights. 

Electro-Metallurgical  Deposit. — A  me- 
tallic deposit  thrown  down  on  a  conduct- 
ing surface  by  electrolysis. 

Electro-Metallurgical  Dipping. — A  pro- 
cess for  obtaining  an  electro-metallurgi- 
cal deposit  on  a  metallic  surface  by  dip- 
ping it  in  a  solution  of  a  readily  decom- 
posable metallic  salt. 

Electro-Metallurgical  Galvanization. 
The  electro-therapeutic  effects  produced 
on  nerves  or  muscles  by  the  passage  of  an 
electric  current. 

Electro-Metallurgy. — (1)  That  branch  of 
electric  science  which  relates  to  the  elec- 
tric reduction  or  treatment  of  metals.  (2) 
Electro-metallurgical  processes  effected 
by  the  agency  of  electricity.  (3)  Electro- 
plating or  electro-typing. 

Electro-Motion. — Motion  produced  by 
electricity. 

Electro-Motor. — A  term  sometimes  em- 
ployed for  a  voltaic  couple. 

Electro-Muscular. — Of  or  pertaining  to 
the  influence  of  electricity  on  the  mus- 
cles. 

Electro-Muscular  "Excitation.— In  elec- 
tro-therapeutics, the  galvanic  or  farad  ic 
excitation  of  a  muscle,  or  its  excitation 
by  the  continuous  current  from  a  voltaic 
battery,  or  by  the  alternating  currents 
from  an  induction  coil. 

Electro-U  egative. — (1)  In  such  a  state  as 
regards  electricity  as  to  be  repelled  by 
bodies  negatively  electrified,  and  attracted 
by  those  positively  electrified.  (2)  The 
ions  or  radicals  which  appear  at  the  anode 
or  positive  electrode  of  a  decomposition 
cell. 

Electro-Negative  Ions. — (1)  The  negative 
ions,  or  groups  of  atoms  or  radicals,  which 
appear  at  the  anode  or  positive  terminal 
of  a  decomposition  cell.  (2)  The  anions. 


Electro-Negative  Radicals. — The  elec- 
tro-negative ions. 

Electro-Negatively. — In  an  electro-neg- 
ative manner. 

Electro-Negatives. — (1)  The  anions  or 
electro-negative  ions  of  a  radical.  (2)  The 
atoms  or  radicals  that  appear  at  the  anode, 
or  positive  terminal  of  any  source,  during 
electrolysis. 

Electro-Nervous  Excitability.  —  The 
electro-therapeutic  excitation  of  a  nerve. 

Electro-Nickeling. — Electro-plating  with 
nickel. 

Electro-Optics. — That  branch  of  science 
which  treats  of  the  general  relations  ex- 
isting between  light  and  electricity. 

Electro-Pathic. — Of  or  pertaining  to  elec- 
tro-pathology. 

Electro-Pathology. — Diagnosis  by  means 
of  electricity. 

Electro-Percussion  Drill. — (1)  A  drill 
employed  for  quarrying  or  mining  in 
which  a  reciprocating  motion  for  the  drill 
is  obtained  by  sending  an  electric  current 
alternately  through  one  or  the  other  of  a 
pair  of  solenoids  of  which  the  drill  stock 
forms  the  core.  (2)  Any  reciprocating 
drill  operated  electrically. 

Electro-Photometer. — An  instrument  for 
measuring  the  intensity  of  light  by  means 
of  electricity. 

E 1  e  c  t  r  o-Photo-Micography.—  Photo- 
graphy of  the  magnified  images  of  micro- 
scopic objects  illumined  by  the  electric 
light. 

Electro-Physiological. — Of  or  pertain- 
ing to  electro-physiology. 

Electro-Physiologist. — One  skilled  in 
electro-phy  siology . 

Electro-Physiology. — The  study  of  elec- 
tric phenomena  of  living  animals  and 
plants. 

Electro-Plating. — The  process  of  covering 
any  conducting  surface  with  a  metal,  by 
the  aid  of  an  electric  current. 

Electro-Plating  Bath. — A  tank  contain- 
ing a  metallic  solution  in  which  articles 
are  placed  to  be  electro-plated. 

Electro-Pneumatic. — Of  or  pertaining  to 
the  combined  action  of  electricity  and 
air  pressure. 

Electro-Pneumatic  Block  System.— A 
block  system  for  railroads  in  which  the 
semaphores  are  operated  pneumatically 
under  the  control  of  electro-magnetically 
operated  valves. 

Electro-Pneumatic  Signals . —Signals 
operated  by  diaphragms  or  piston? 


Ele.] 


765 


[Ele. 


moved  by  compressed  air,  under  electric 
control. 

Electro-Pneumatic  Thermostat. — An 
instrument  for  automatically  indicating 
the  existence  of  a  given  temperature  by 
the  closing  of  an  electric  circuit,  on  the 
expansion  or  contraction  of  a  gas. 

Electro-Polar. — Possessing  electric  poles. 

Electro-Positive. — (1)  In  such  a  state,  as 
regards  an  electric  charge,  as  to  be  at- 
tracted by  a  body  negatively  electrified, 
and  repelled  by  a  body  positively  electri- 
fied. (2)  The  ions  or  radicals  which  ap- 
pear at  the  cathode  or  negative  electrode 
of  a  decomposition  cell. 

Electro-Positive  Ions. — The  cathions  or 
groups  of  atoms  or  radicals  which  appear 
at  the  cathode  of  a  decomposition  cell. 

Electro-Positively. — In  an  electro-posi- 
tive manner. 

Electro-Positives. — (1)  The  cathions  or 
electro-positive  ions  of  radicals.  (2)  The 
atoms  or  radicals  that  appear  during  elec- 
trolysis at  the  cathode,  or  negative  elec- 
trode. 

Electro-Positive  Radicals. — The  electro- 
positive ions. 

Electro-Potential  Energy. — Electric  en- 
ergy possessing  the  power  of  doing  work, 
but  not  actually  doing  work. 

Electro-Prognosis. — In  electro-therapeu- 
tics a  prognosis,  or  prediction  of  the  fatal 
or  non-fatal  termination  of  a  disease,  from 
an  electro-diagnosis  based  on  the  exagger- 
ated or  diminished  reactions  of  the  ex- 
citable tissues  of  the  body,  when  subjected 
to  the  varying  influences  of  electric  cur- 
rents. 

Elect  ro-Puncturation. — Electro-punct- 
ure. 

Electro -Puncture. — The  application  of 
electrolysis  to  the  treatment  of  aneurisms 
or  diseased  growths. 

Electro-Pyrometer. — An  apparatus  for 
the  determination  of  temperature  by  the 
measurement  of  the  electric  resistance 
of  a  platinum  wire  exposed  to  the  tem- 
perature which  is  to  be  measured. 

Electro-Receptive  Devices. — (1)  Vari- 
ous devices  suitable  for  being  placed  in 
an  electric  circuit  and  energized  by  the 
passage  of  an  electric  current  through 
them.  (2)  Translating  devices. 

Electro-Reciprocating  Drill. — An  elec- 
tro-percussion drill. 

Electro-Refining. — Various  processes  for 
the  electric  refining  of  metals. 

Electro-Skiagraph. — A  term  proposed  for 
a  radiograph  or  X-ray  picture. 


Electro-Semaphore. — A  semaphore  oper- 
ated by  means  of  electricity. 

Electro-Sensibility. — An  effect  produced 
on  a  sensory  nerve  by  its  electrization. 

Electro-Siliceous  Light. — An  effect  ob- 
tained by  the  discharge  of  a  powerful 
rheostatic  machine,  through  a  glass  tube 
traversed  by  a  platinum  wire,  and  plunged 
in  salt  water,  the  heat  of  the  discharge 
not  only  melting  and  volatilizing  the 
wire,  but  also  raising  the  glass  tube  to 
brilliant  incandescence. 

Electro-Silvering. — Covering  a  surface 
with  an  adherent  coating  of  silver,  by 
electro-plating. 

Electro-Smelting. — The  separation  or  re- 
duction of  metallic  substances  from  their 
ores,  by  means  of  the  heat  developed  by 
electric  currents. 

Electro  -  Statics.  —  That  branch  of  elec- 
tric science  which  treats  of  the  phenomena 
and  measurement  of  electric  charges. 

Electro-Steeling. — (1)  The  art  of  covering 
copper  electrodes  with  a  thin  coating  of 
hardened  iron.  (2)  Covering  a  printing 
surface  of  an  electro  with  a  thin  deposit 
of  copper,  for  the  purpose  of  hardening  it. 

Electro-Ster^ttype. — A  word  sometimes 
employed  for  electro-type. 

Electro-Stereotyping. — Electro-typing. 

Electro-Synthesis. — The  chemical  com- 
bination of  electro-positive  and  electro- 
negative radicals  under  the  influence  of 
electricity. 

Electro-Technics.  —  The  science  which 
treats  of  the  technical  applications  of  elec- 
tricity and  the  general  principles  involved 
therein. 

E 1  e  c  t  r  o-Telegraphy.  —  Electric  teleg- 
raphy. 

Electro-Therapeutic  Bath. — A  bath  fur- 
nished with  suitable  electrodes  for  use  in 
the  therapeutic  applications  of  electricity. 

Electro-Therapeutic  Breeze. — An  elec- 
tric breeze  or  convection  current  in  air 
produced  by  the  electrification  of  metallic 
points. 

Electro-Therapeutic  Diffusion  of  Cur- 
rent.— The  difference  in  the  density  of  a 
current  in  different  parts  of  the  human 
body  between  electrodes  applied  thera- 
peutically. 

Electro-Therapeutic  Dosage . — Propor- 
tioning the  strength  of  an  electro-thera- 
peutic current  and  the  duration  of  its  ap- 
plication to  the  body. 

Electro-Therapeutic  Electrode.  —  The 
electrode  mainly  concerned  in  the  electro 


Ele.] 


766 


[Ele. 


therapeutic  treatment  or  diagnosis  of 
diseased  or  disordered  parts  of  the  body. 
Electro  -  Therapeutic  Electrodes.  — 
Electrodes  of  various  shapes  employed  in 
electro-therapeutics. 

Electro-Therapeutic  Galvanization. — 
In  electro-therapeutics,  the  effects  pro- 
duced on  nervous  or  muscular  tissue  by 
the  passage  of  a  voltaic  current. 

Electro  -  Therapeutic  Head-Breeze.  — 
•A  form  of  electric  breeze  or  convective 
electric  discharge  applied  to  the  head. 

Electro-Therapeutic  Polarizing  -  Cur- 
rent.— The  current  which  produces  the 
phenomena  of  electro-tonus. 

Electro-Therapeutic  Electrician. — An 
electro-therapist. 

Electro-Therapeutics. — (1)  The  applica- 
tion of  electricity  to  the  human  body  for 
the  curing  of  disease  or  the  improvement 
of  health.  (2)  Electro-therapy. 

Electro-Therapeutist. — An  electro-ther- 
apist. 

Electro-Therapist. — (1)  One  skilled  in 
electro-therapy.  (2)  An  electro-medical 
practitioner. 

Electro-Therapy. — A  word  sometimes 
used  instead  of  electro-therapeutics. 

Electro-Thermal  Meter. — An  electric 
meter  in  which  the  current  is  measured 
by  means  of  the  heat  generated  by  the 
passage  of  the  current  through  a  resist- 
ance. 

Electro-Thermancy .  —  That  branch  of 
electricity  which  treats  of  the  effects 
produced  by  an  electric  current  on  the 
temperature  of  a  thermo-electric  junc- 
tion. 

Electro-Thermic. — Of  or  pertaining  to 
the  generation  of  heat  by  means  of  elec- 
tricity. 

Electro-Thermic  Lightning-Arrester. 
A  lightning  arrester  operated  by  the  ex- 
pansion of  a  high-resistance  shunt  wire 
permanently  connected  to  the  circuit. 

Electro-Thermotic. — Of  or  pertaining  to 
heat  generated  by  electricity. 

Electro-Tinning. — Covering  a  substance 
with  a  coating  of  tin  by  electro-plating. 

Electro-Tint. — An  etching  obtained   by 

electricity. 
Electro-Tinting. — A  term  proposed  for  a 

method  of  electric  engraving. 
Electro-Type. — To  produce  a  fac-simile 

by  electrolytically  depositing  metals  in 

a  mould. 


Electro-Type. — A  cast  or  impression  of 
type  obtained  by  means  of  electro-metal- 
lurgy. 

Electro-Type  Process. — The  process  of 
electro-typing. 

Electro-Typic.— Of  or  pertaining  to  elec- 
tro-typy. 

Electro-Typing.  —  Obtaining  casts  or 
copies  of  pages  of  type  by  depositing 
metals  in  moulds,  by  the  agency  of  elec- 
tric currents. 

Electro-Typographic.  —  Pertaining  to 
printing  by  means  of  electricity. 

Electro-Typy.— The  art  of  producing 
electro-types. 

Electro-Vection. — A  term  sometimes 
employed  for  electric  endosmose. 

Electro-Vital. — Pertaining  to  the  rela- 
tions between  electricity  and  vitality. 

Electrocesis. — A  word  proposed  for  curing 
disease  by  electricity.  (Not  used.) 

Electro  Compound-Magnet. — A  term 
formerly  applied  to  an  electro-magnet 
whose  core  was  wound  with  two  separate 
wires  or  conductors.  (Obsolete.) 

Electro  Contact-Mine. — A  submarine 
mine  that  is  automatically  fired  on  the 
completion  of  the  current  of  a  battery 
placed  on  shore,  on  the  closing  of  floating 
contact  points  by  passing  vessels. 

Electrocution. — Capital  punishment  by 
means  of  electricity. 

Electrode.— (1)  Either  of  the  terminals  of 
an  electric  source.  (2)  Either  of  the 
terminals  of  an  electric  source  that  are 
placed  in  a  solution  in  which  electrolysis 
is  taking  place.  (3)  Either  of  the  electro- 
therapeutic  terminals  of  an  electric 
source. 

Electrodes. — The  positive  and  negative 
terminals  of  an  electric  source,  at  their 
points  of  application  to  a  receptive  de- 
vice. 

Electrodeless  Discharge.— The  dis- 
charge obtained  through  the  rarified  gas 
of  any  vacuum  tube  that  is  unprovided 
with  electrodes. 

Electrogen. — A  name  sometimes  applied 
to  the  unknown  cause  of  electricity.  (Not 
in  general  use.) 

Electrograph. — (1)  A  curve  produced  by 
a  recording  electrometer.  (2)  A  word 
sometimes  used  for  radiograph. 

Electrographics. — (1)  The  science  of  geo- 
metrically solving  electrical  problems  by 
graphical  methods.  (2)  The  science 
which  treats  of  the  graphical  representa- 
tion of  electric  quantities. 


Ele.] 


767 


[Ele. 


Electrolier. — A  chandelier  for  holding 
electric  lamps,  as  distinguished  from  a 
chandelier  for  holding  gas  burners. 

Electrolier  Arm. — An  electric  fixture 
employed  for  attaching  incandescent  elec- 
tric lamps  to  gas  fixtures  or  electroliers. 

Electrolier  Cut-Out. — Any  cut-out  con- 
nected in  the  circuit  of  an  electrolier. 

Electrolier  Switch. — A  switch  conven- 
iently located  for  lighting  or  extin- 
guishing lamps  in  an  electrolier. 

Flectrization.— The  act  of  being  electri- 
fied, or  electrifying. 

Electrologist.  —  An  unnecessary  word 
proposed  for  electrician. 

Electrologist. — One  skilled  in  the  science 
of  electricity.  (Not  in  general  use.) 

Electrology.  —  That  branch  of  science 
which  treats  of  electricity.  (Obsolete.) 

Electrolysis.  —(1)  Chemical  decomposi- 
tion effected  by  means  of  an  electric  cur- 
rent. (2)  The  decomposition  of  the  mol- 
ecule of  an  electrolyte  into  its  ions  or 
radicals.  (3)  Electrolytic  decomposition. 

Electrolysis  by  Means  of  Alternating 
Currents. —  Electrolytic  decomposition 
effected,  under  certain  circumstances,  by 
alternating  currents. 

Electrolysis  of  Salts.— The  electrolytic 
decomposition  of  a  salt  into  its  constit- 
uent ions  or  radicals. 

Electrolyte.  — <1)  Any  compound  liquid 
which  is  separable  into  its  constituent 
ions  or  radicals  by  the  passage  of  elec- 
tricity through  it.  (2)  The  exciting 
liquid  in  a  voltaic  cell. 

Electrolytic. — Of  or  pertaining  to  elec- 
trolysis. 

Electrolytic  Accumulator.— A  word 
sometimes  applied  to  a  secondary  or  stor- 
age battery. 

Electrolytic  Analysis.— A  term  some- 
times used  for  electric  analysis. 

Electrolytic  Annunciator. — An  annun- 
ciator consisting  of  a  number  of  separate 
electrolytic  cells,  provided  with  a  trans- 
parent cover,  and  so  arranged  that  on  the 
closing  of  the  circuit  of  any  particular 
cell  by  a  distant  push-button,  a  chemical 
decomposition  is  effected  in  the  liquid 
of  the  electrolytic  cell  and  a  reddish- 
brown  film  formed  over  the  surface  of  the 
electrode  connected  therewith. 

Electrolytic     Assaying. — Assaying    by 

means  of  electrolysis. 

Electrolytic  Bath.— An  electrolytic  cell. 
Electrolytic  Cell.— (1)  A  cell  or  vessel 

containing  an  electrolyte  in  which  elec- 


trolysis is  carried  on.    (2)  A  plating  cell 
or  vat. 

Electrolytic  Clock. — A  timepiece  in. 
which  the  rotation  of  the  clock-work  is 
obtained  by  the  rotation  of  a  delicately 
pivoted  and  well  balanced  wheel  by  the- 
difference  in  weight  of  its  two  halves  im- 
mersed in  an  electrolytic  bath,  on  the- 
passage  of  an  electrolyzing  current. 

Electrolytic  Condenser. — A  condenser 
consisting  of  a  number  of  iron  plates  im- 
mersed in  a  solution  of  carbonate  of  soda, 
and  inserted  in  a  branch  circuit  for  the 
purpose  of  giving  the  current  in  that  cir- 
cuit a  lead,  by  increasing  the  capacity. 

Electrolytic  Conduction. — A  term  some- 
times employed  to  indicate  the  passage  of 
electricity  through  an  electrolyte  by 
means  of  charges  imparted  to  its  free 
ions  or  radicals. 

Electrolytic  Conductivity. — The  recip- 
rocal of  the  electrolytic  resistance. 

Electrolytic  Convection. — A  term  pro- 
posed for  explaining  the  apparent  con- 
duction of  electricity  by  an  electrolyte, 
without  decomposition. 

Electrolytic  Corrosion. — The  corrosion 
by  electrolytic  action  of  water-pipes,  gas- 
pipes,  or  other  masses  of  metal,  buried  in 
moist  earth. 

Electrolytic  Coulomb-Meter. — A  cou- 
lomb-meter whose  operation  depends  on 
electrolytic  decomposition. 

Electrolytic  Diaphragm. — A  diaphragm 
in  an  electro-plating  bath. 

Electrolytic  Decomposition. — The  sep- 
aration of  a  molecule  into  its  constituent 
ions  or  radicals  by  the  action  of  an  elec- 
tric current. 

Electrolytic  Dissociation. — Electrolytic 
decomposition.  • 

Electrolytic  Epilation. — The  removal  of 
hair  by  electrolysis. 

Electrolytic  Etching.— (1)  Etching  by 
means  of  electrolytic  corrosion.  (2)  A 
form  of  electric  etching. 

Electrolytic  Exchange.— Electrolysis. 

Electrolytic  Generator. — A  continuous- 
current  dynamo-electric  generator  de- 
signed for  supplying  electricity  for  elec- 
trolytic purposes. 

Electrolytic  Heating. — A  method  of  elec- 
tric heating  consisting  in  plunging  the 
metal  to  be  heated  beneath  the  surface  of 
a  conducting  liquid,  while  held  in  a  metal 
clamp  that  is  connected  to  the  negative 
pole  of  a  continuous-current  source,  while 
the  positive  pole  of  such  source  is  con- 
nected, to  the  metal  lining  of  the  vessel 
containing  the  conducting  liquid. 


Ele.l 


768 


[Ele. 


Electrolytic  Hydrogen.— Electrolytical- 
ly  liberated  hydrogen. 

Electrolytic  Meter. — An  electro-chemical 
meter. 

Electrolytic  Moulding. — A  term  some- 
times employed  for  electro-typing. 

Electrolytic  Refining. — The  refining  of 
metals  by  electrolysis. 

Electrolytic  Removal  of  Hair. — Elec- 
trolytic epilation. 

Electrolytic  Separation. — Molecular  dis- 
sociation produced  by  electrolysis. 

Electrolytic  Synthesis. — Synthesis  of  a 
substance  by  electrolytic  means. 

Electrolytic  "Writing. — Imprinting  writ- 
ten characters  on  cloths  or  other  textile 
fabrics  by  the  electrolytic  decomposition 
of  a  dyeing  substance  with  which  they 
are.  impregnated. 

Electrolytically. — In  an  electrolytic  man- 
ner. 

Electrolyzability. — Possessing  the  power 
of  being  electrolyzed. 

Electrolyzable. — Capable  of  being  elec- 
trolyzed or  decomposed  by  means  of  elec- 
tricity. 

Electrolyzation. — The  act  of  electroly- 
zing. 

Electrolyze. — To  separate  or  decompose 
by  means  of  electricity. 

Electrolyzed. — Separated  or  decomposed 
by  means  of  electricity. 

Electrolyzer.  —  (1)  One  who,  or  that 
which,  causes  electrolysis.  (2)  An  elec- 
trolyzing  apparatus. 

Electrolyzing. — Causing  or  producing 
electrolysis. 

Electrolyzing  Cell. — An  electrolytic  cell. 

Electrolyzing  Chamber. — A  chamber  or 
space  in  which  electrolysis  occurs. 

Electrometer. — An  apparatus  for  measur- 
ing differences  of  electric  potential. 

Electrometer  Fatigue. — The  failure  of 
the  needle  of  an  electrometer  to  return  to 
the  zero  point,  due  to  the  elastic  fatigue 
of  its  suspension. 

Electrometer  Gauge.— A  device  em- 
ployed in  connection  with  some  hetero- 
static  electrometers,  to  ascertain  whether 
the  needle  connected  with  the  layer  of 
acid,  that  acts  as  the  inner  coating  of  a 
Leyden-jar  used  in  connection  therewith, 
is  at  its  normal  potential. 

Electrometer- Voltmeter. — A  voltmeter 
in  which  the  differences  of  potential  to 
be  measured  are  employed  to  charge  in- 
sulated conductors,  the  electrostatic  at- 
tractions and  repulsions  of  which  result 


in  the  deflection  of  a  suitably  suspended 
metallic  needle. 

Electrometric. — Of  or  pertaining  to  an 
electrometer. 

Electrometrical. — (1)  Of  or  pertaining  to 
the  measuring  of  electrical  forces.  (2)  Of 
or  pertaining  to  an  electrometer. 

Electromotive  Arrangement  or  De- 
vice.— An  electromotive  source. 

Electromotive  Force. — (1)  The  force 
which  starts  or  tends  to  start  electricity 
in  motion.  (2)  The  maximum  or  total 
generated  difference  of  potential  which 
exists  in  a  circuit. 

Electromotive  Force  of  Induction.— 

The  electromotive  force  developed  by  any 
inductive  action. 

Electromotive  Impulse. — An  impulse 
producing  an  impulsive  rush  of  elec- 
tricity. 

Electromotive  Intensity. — The  vector 
electric  force  at  a  point,  as  measurable  by 
the  mechanical  force  that  would  be  ex- 
erted upon  a  unit  electric  charge  at  that 
point. 

Electromotive  Series. — A  name  some- 
times given  to  a  contact  series. 

Electromotive  Source. — Any  source  such 
as  a  dynamo,  or  voltaic  cell,  capable  of 
producing  an  electromotive  force. 

Electromotograph. — An  apparatus  in 
which  the  friction  of  a  platinum  point 
against  a  rotating  cylinder  of  chalk  is  re- 
duced by  electrolytic  action,  consequent 
on  the  passage  of  an  electric  current. 

Electromotographic  Telephone.  —  A 
loud-speaking  telephone  operating  on  the 
principle  of  the  electromotograph. 

Electron. — (1)  A  word  formerly  used  for 
amber.  (2)  The  electric  atoms  whose  pro- 
jection from  the  cathode  of  a  high-vacu- 
um tube  is  supposed  to  constitute  the 
cathode  rays  or  streamings.  (3)  An  alloy 
of  gold  and  silver. 

Electronecrosic. — Pertaining  to  capital 
punishment  by  means  of  electricity. 

Electronecrpsis. — A  word  proposed  for 
capital  punishment  by  means  of  electric- 
ity. (Not  in  use.) 

Electronome. — A  name  proposed  for  a 
measurer  of  electricity.  (Not  in  use.) 

Electropath. — One  skilled  in  the  art  of 
electro-therapy. 

. — A  word  sometimes  em- 


Electropathy 
ployed  for  ele 


ectro-therapeutics. 

Electrophanic. — Pertaining     to     capital 
punishment  by  means  of  electricity. 


Ele.] 


769 


[Ele. 


Electrophanical. — Pertaining  to  capital 
punishment  by  means  of  electricity. 

Electrophanize. — To  inflict  capital  pun- 
ishment by  means  of  electricity. 

Electrophany. — A  word  proposed  for  cap- 
ital punishment  by  means  of  electricity. 
(Not  in  use.) 

Electrophila.— A  word  proposed  for  capi- 
tal punishment  by  means  of  electricity. 
(Nut  in  use.) 

Electrophobia. — A  word  proposed  for  un- 
necessary fear  of  electricity. 

Electrophone. — A  word  proposed  for  a 
carbon-contact  telephone  transmitter. 

Electrophor. — An  orthography  sometimes 
employed  for  electrophorous. 

Electrophoric. — Of  or  pertaining  to  an 
electrophorous. 

Electrophoric  Medium.— A  word  some- 
times employed  for  a  dialectric  medium. 

Electrophorous. — A  simple  form  of  elec- 
trostatic induction  apparatus. 

Electropoion  Liquid. — An  exciting 
liquid,  consisting  of  one  part  of  bichro- 
mate of  potash  dissolved  in  ten  parts  of 
water,  to  which  two  and  a  half  parts  of 
sulphuric  acid  have  been  gradually  added. 

Electroscope. — An  apparatus  for  showing 
the  presence  of  an  electric  charge,  or  de- 
termining its  character,  whether  positive 
or  negative,  but  not  for  measuring  its 
amount  or  value. 

Electroscopic  Gauge.— A  term  formerly 
applied  to  an  early  form  of  discharging 
gold-leaf  electroscope. 

Electroscopically. — By  means  of  an  elec- 
troscope. 

Electroscopy.— The  art  of  determining, 
by  means  of  an  electroscope,  the  character 
of  an  electric  charge. 

Electrostatic. — Of  or  pertaining  to  elec- 
trostatics. 

Electrostatic  Attraction.— The  mutual 
attraction  existing  between  unlike  elec- 
tric charges. 

Electrostatic  Aurora. — Luminous  phe- 
nomena attending  the  production  of  an 
electrostatic  corona. 

Electrostatic  Balance.— A  form  of  bal- 
ance employed  for.  the  measurement  of 
high,  direct,  or  alternating  electromotive 
forces,  by  the  electrostatic  effects  pro- 
duced by  their  charges. 

Electrostatic  Capacity.— The  quantity 
of  electricity  which  must  be  imparted  to 
a  given  conductor  as  a  charge,  in  order 
to  raise  its  potential  to  unity,  all  neigh- 
boring conductors  being  at  zero  potential. 
49 


Electrostatic  Capacity  of  a  Line.— The 
power  possessed  by  an  electric  line  wire 
or  conductor  to  act  as  a  condenser.  (2)  The 
capacity  of  a  line  or  conductor  for  holding 
an  electric  charge,  as  a  condenser. 

Electrostatic  Charge-Current  of  Cable. 
A  momentary  and  violent  rush  of  cur- 
rent that  occurs  on  the  application  of  an 
electromotive  force  to  a  submarine  cable. 

Electrostatic  Circuit. — A  circuit  formed 
bylines  of  electrostatic  flux  with  an  elec- 
tric source. 

Electrostatic  Corona. — A  luminous  effect 
produced  on  the  surface  of  a  thin  sheet 
of  mica,  or  other  insulating  material,  when 
placed  between  two  electrodes,  subjected 
to  a  compai'atively  high  difference  of  po- 
tential. 

Electrostatic  Current. — The  time-rate- 
of-flow  of  electrostatic  flux. 

Electrostatic  Difference  of  Potential. 
The  difference  of  potential  due  to  elec- 
tric charges. 

Electrostatic  Discharge. — A  term  some- 
times employed  for  a  disruptive  dis- 
charge. 

Electrostatic  Field.— (1)  The  region  of 
electrostatic  influence  surrounding  a 
charged  body.  (2)  A  region  traversed  by 
electrostatic  flux. 

Electrostatic  Flux. — A  stress  in  the 
ether  which  proceeds  from  a  charged 
body  along  definite  curved  lines  or  paths. 

Electrostatic  Flux-Paths.— The  paths 
traversed  by  electrostatic  flux. 

Electrostatic  Force.— The  force  which 
produces  the  attractions  or  repulsions  of 
charged  bodies. 

Electrostatic  Generator.  —  A  general 
term  applied  to  various  forms  of  influence 
machines. 

Electrostatic  Hysteresis.— (1)  The  en- 
ergy consumed  in  an  alternating-electro- 
static field  by  the  dielectric  medium.  (2) 
Dielectric  hysteresis. 

Electrostatic  Indicator. — A  name  some- 
times applied  to  an  electrometer. 

Electrostatic  Induction. — The  induction 
of  an  electric  charge  produced  in  a  con- 
ductor brought  into  an  electrostatic  field. 

Electrostatic  Induction-Machine.  —  (1) 
A  machine  in  which  a  small  initial  charge 
produces  a  greatly  increased  charge  by 
its  inductive  action  on  a  rapidly  rotated 
disc  of  glass  or  other  dielectric.  (2)  An 
electrostatic  influence  machine. 

Electrostatic  Influence. — A  term  some- 
times used  instead  of  electrostatic  induc- 
tion. 


Ele.] 


770 


[Ele. 


Electrostatic  Leakage. — The  gradual  dis- 
sipation of  a  charge  due  to  insufficient  in- 
sulation. 

Electrostatic  Lines  of  Force. — (1)  Lines 
of  force  produced  in  the  neighborhood  of 
a  charged  body,  by  the  presence  of  the 
charge.  (2)  Lines  extending  in  the  direc- 
tion in  which  the  force  of  electrostatic  at- 
traction or  repulsion  acts. 

Electrostatic  Motion. — Motion  produced 
by  an  electrostatic  field  somewhat  simi- 
lar to  motion  produced  by  a  magnetic 
field. 

Electrostatic  Motor.— (1)  A  motor  driven 
by  means  of  the  induction  of  two  varying 
electrostatic  fields  at  right  angles  to  each 
other.  (2)  Generally,  a  motor  driven  by 
the  interaction  of  two  or  more  electro- 
static fields. 

Electrostatic  Optical  Strain. — A  strain 
or  deformation  produced  in  an  optical 
medium  by  the  stress  of  an  electrostatic 
field. 

Electrostatic  Potential.— (1)  The  power 
of  doing  electric  work  possessed  by  a  unit 
quantity  of  positive  electricity  residing 
on  the  surface  of  an  insulated  body.  (2) 
That  property  in  space  by  virtue  of  which 
work  is  done  when  an  electric  charge  is 
moved  therein. 

Electrostatic  Repulsion. — The  mutual 
repulsion  produced  by  two  similar  elec- 
trostatic charges. 

Electrostatic  Resistance.  —  The  resist- 
ance offered  by  any  medium  to  the  passage 
of  an  electrostatic  flux  or  an  electrostatic 
current. 

Electrostatic  Retardation. — Retardation 
in  signalling,  on  long  telegraphic  lines, 
due  to  electrostatic  capacity. 

Electrostatic  Screening. — Screening  or 
shielding  from  the  inductive  effects  of  an 
electrostatic  charge. 

Electrostatic  Strain. — Strain  produced 
by  the  stress  of  an  electrostatic  field. 

Electrostatic  Stress. — The  force  or  pres- 
sure in  an  electrostatic  field  which  pro- 
duces electrostatic  strain  in  any  sub- 
stance placed  therein. 

Electrostatic  Time,  Constant. — In    an 

electric    circuit  or  condenser,  possessing 

capacity  and  resistance,  the  product  of 

k    the  capacity  and  the  resistance,  usually 

expressed  in  seconds  or  farad-ohms. 

Electrostatic  Units. — Units  based  on  the 
attractions  or  repulsions  of  two  unit 
charges  of  electricity  at  unit  distance 
apart. 

Electrothanasing. — Producing  accidental 
death  by  means  of  electricity. 


Electrothanasis. — A  word  proposed  for 
accidental  death  produced  by  electricity. 
(Not  in  use.) 

Electrothanasise. — To  produce  accidental 
death  by  electricity. 

Electrothanatose. — A  word  proposed  for 
capital  punishment  inflicted  by  means  of 
electricity.  (Not  in  use.) 

Electrothanatosic. — Of  or  pertaining  to 
capital  punishment  by  means  of  elec- 
tricity. 

Electrothanatosing. — A  word  proposed 
for  execution  by  electricity. 

Electrotisis. — A  word  proposed  for  capital 
punishment  by  means  of  electricity.  (Not 
in  use.) 

Electrotome. — A  term  sometimes  applied 
to  an  automatic  contact-breaker  which 
vibrates  with  sufficient  rapidity  to  pro- 
duce a  musical  sound. 

Electrotonic. — Of  or  pertaining  to  electro- 
tonus. 

Electrotonic  Currents. — In  electro-ther- 
apeutics, a  current  due  to  the  internal 
polarization  of  a  nerve  fibre  between  the 
conducting  core  of  the  nerve  and  its  en- 
closing sheath. 

Electrotonic  Effect.— An  altered  con- 
dition of  excitability  produced  in  a  nerve 
when  in  the  electrotonic  state. 

Electrotonic  Excitability. — The  actual 
excitability  of  a  nerve  when  in  the  elec- 
trotonic state. 

Electro-Tonicity.  —  A  term  sometimes 
employed  for  electrotonus. 

Electrotonus. — The  condition  of  altered 
functional  activity  which  occurs  in  a 
nerve  when  subjected  to  the  action  of  an 
electric  current. 

Electrozemia. — A  word  proposed  for  cap- 
ital punishment  by  means  of  electricity. 
(Not  in  use.) 

Electrum. — A  name  given  by  the  ancients 
to  various  substances  that  could  be  readily 
electrified  by  friction. 

Element.— (1)  Any  kind  of  matter  which 
cannot  be  decomposed  into  simpler  mat- 
ter. (2)  Matter  that  is  formed  or  com- 
posed of  but  one  kind  of  atoms. 

Element  of  Current. — A  term  employed 
in  mathematical  discussions  to  indicate 
a  very  small  part  of  a  current,  for  ease  in 
considering  its  actions. 

Element  of  Storage  Battery.— (1)  A 
single  set  of  positive  and  negative  plates 
of  a  storage  cell,  so  connected  as  to  be 
ready  for  placing  in  the  acid  liquid  of  the 
containing  jar  or  vessel.  (2)  A  term  some- 


Ele.] 


771 


[End. 


times  applied  to  one  of  the  storage  cells 
of  a  battery. 

Element  of  Voltaic  Cell.— Either  of  the 
substances  forming  the  couple  of  a  voltaic 
cell. 

Elements  of  Armature  Winding. — The 
separated  conductors  forming  the  parts  of 
an  armature  winding. 

Elementary  Matter. — Matter  which  can- 
not be  decomposed  into  simpler  matter. 

Elevator  Annunciator. — An  annunciator 
connected  with  an  elevator  to  indicate 
the  floor  from  which  a  signal  is  sent. 

Elevator,  Electric. — An  elevator  oper- 
ated by  means  of  an  electric  motor. 

Elevator  Switch. — A  switch  operated 
from  an  elevator  for  controlling  the  op- 
eration of  the  elevator  motor. 

Elliptical  Rotary-Magnetization.— The 
magnetization  which  exists  in  a  diphase 
motor  when  two  alternating-magnetic 
fluxes  coexist  while  out  of  phase  with 
each  other. 

Elliptical  Rotation. — A  rotation  as  of  a 
point  on  an  ellipse. 

Elliptically  Rotating  Magnetic  Field. 
(1)  A  magnetic  field  which  is  subject  to 
elliptical  rotation.  (2)  The  rotation  of 
magnetic  flux  produced  by  two  diphase 
currents  of  unequal  intensity,  or  of  equal 
intensity,  but  not  of  90°  phase  difference, 

Elongated  Ring-Core. — A  hollow  cylin- 
drical core  of  comparatively  great  length. 

Elongation  of  Needle. — A  phrase  some- 
times used  for  the  maximum  angular 
deflection  of  a  needle,  or  the  maximum  de- 
flection of  the  spot  of  light  on  a  galva- 
nometer scale,  when  making  one  or  more 
swings. 

Embedded  Coils. — (1)  Coils  or  windings 
placed  in  grooves  or  perforations  on  the 
armature  of  a  dynamo  or  motor.  (2)  Iron- 
clad armature  coils. 

Embossing  Telegraphic  Instrument. 
A  registering  telegraphic  instrument  in 
which  the  signal  is  recorded  in  embossed 
characters  on  a  paper  fillet. 

Emergency  Brake.-^-(l)  A  brake  on  a  ve- 
hicle employed  only  in  emergency.  (2)  In 
an  electrically  propelled  vehicle  a  brake  of 
greater  power  than  the  ordinary  brake, 
and  used  only  in  emergency,  as,  for  ex- 
ample, a  reversing  switch  to  reverse  the 
direction  of  rotation  of  the  motors. 

Emergency  Cable. — A  small,  compara- 
tively inexpensive  and  easily  handled 
cable,  employed  in  the  case  of  breaks  in  a 
pole  line  due  to  floods,  railroad  wrecks. 


etc.,  for  opening  up  communication  dur« 
ing  repairs  of  the  break. 

Emergency  Crew. — A  crew  or  gang  in  a 
power  distribution  system  for  service  in 
case  of  a  break-down,  emergency,  or  fault 
on  the  line. 

Emergency  Switch.  —  An  accessory 
switch  placed  on  a  car  controller  for 
reversing  the  motion  of  a  car  when 
necessary. 

Electrotisic. — Pertaining  to  capital  pun- 
ishment by  means  of  electricity. 

Electrotising. — Inflicting  capital  punish- 
ment by  means  of  electricity. 

Emissivity. — The  specific  radiating  power 
of  a  surface,  or  its  ability  to  emit  or  throw 
out  radiant  energy,  usually  expressed  in 
ergs  per  sq.  cm. 

Emissivity  of  Filament. — The  ability  of 
a  filament  to  emit  or  radiate  light  and 
heat  when  traversed  by  an  electric  cur- 
rent. 

Emmetropic  Eye. — The  normal  human 
eye,  or  the  human  eye  in  its  normal  adjust- 
ment and  capability  of  accommodation. 

Empanelled  Wires. — Wires  placed  inside 
mouldings,  or  behind  panels. 

Emptied. — A  term  sometimes  applied  to  a 
discharged  secondary  or  storage  battery, 
or  to  a  discharged  condenser. 

Enamelled  Rheostat. — A  rheostat  whose 
coils  consist  of  wires  imbedded  in  a  mass 
of  enamel,  in  close  juxtaposition  to  a  mass 
of  iron  or  other  heat-conducting  material. 

Enclosed  Arc-Lamp . — An  arc-lamp 
whose  carbons  are  enclosed  by  a  closely  fit- 
ting globe,  so  as  to  maintain  an  atmosphere 
around  the  arc  practically  devoid  of  oxy- 
gon, thus  diminishing  the  rate  of  con- 
sumption of  the  carbons. 

Enclosure  of  Magnetic  Flux.— (1)  Link- 
age of  magnetic  flux.  (2)  Confining  mag- 
netic flux  in  a  ferric  magnetic  circuit. 

End  Connections. — End  windings. 

Endlessness. — The  condition  of  a  closed 
ring  of  uniform  cross-section  in  which  the 
magnetizing  coils  are  wound  uniformly 
all  around  it,  and  a  practically  endless  or 
uniform  magnetic  field  is  obtained 
throughout  the  length  of  the  ring. 

Endoscopie  Lamp. — A  lamp  provided  for 
the  examination  of  a  bodily  cavity 
through  its  natural  outlet. 

Endosmometer. — An  apparatus  for  meas- 
uring the  strength  of  endosmotic  currents. 

Endosmose. — The  unequal  mixing  of  two 
different  liquids  or  gases  through  the 
pores  of  an  interposed  medium. 


End.] 


772 


[Ent. 


Endosmose,  Electric.— (1)  The  unequal 
mixing  of  two  liquids  through  the  pores  of 
an  interposed  septum  on.  the  passage  of 
an  electric  current  through  the  septum. 
(2)  The  transfer  of  liquid  through  an  im- 
mersed septum  traversed  by  an  electric 
current. 

Endosmosis. — A  word  frequently  employ- 
ed in  place  of  endosmose. 

Endosmotic  Equivalent. — The  ratio  be- 
tween the  amount  of  water  that  passes 
through  a  porous  membrane  into  a  saline 
solution,  and  the  amount  of  salt  that 
passes  in  the  opposite  direction. 

Endothactic  Cut-out. — A  cut-out  ar- 
ranged to  throw  a  device  into  a  circuit. 

Endothactic  Switch.. — A  switch  which  is 
arranged  to  cut  a  device  into  a  circuit. 

Endothermic. — Of  or  pertaining  to  the 
absorption  of  beat. 

Endothermic  Reaction. — A  chemical  ac- 
tion attended  with  the  absorption  of  heat. 

End-to-End  Joint. — A  term  frequently 
employed  in  place  of  butt-joint. 

End  Windings.  —  (1)  End  connections. 
(2)  Conductors  for  connecting  up  bar 
windings  at  the  end  of  an  armature. 

Energetics. — That  branch  of  mechanics 
which  treats  of  the  transfer  of  energy  or 
of  its  transformation. 

Energy. — The  power  of  doing  work. 

Energy  Component  of  Current. — (1)  In 
an  alternating-current  circuit  the  com- 
ponent of  current  which  is  in  phase  with 
the  impressed  E.  M.  F.  (2)  In  an  alter- 
nating-current circuit,  the  product  of  the 
E.  M.  F.  and  the  effective  conductance. 

Energy  Component  of  E.  M.  F.— (1)  In 
an  alternating-current  circuit  the  com- 
ponent of  E.  M.  F.  which  is  in  phase  with 
the  current.  (2)  In  an  alternating-cur- 
rent circuit,  the  product  of  the  current 
and  the  effective  resistance. 

Energy  Current. — (1)  A  term  sometimes 
used  for  active  component  of  current  in 
an  alternating-current  circuit,  as  dis- 
tinguished from  the  wattless  component 
of  current.  (2)  The  product  in  an  alter- 
nating-current circuit  of  the  effective  con- 
ductance and  the  E.  M.  F. 

Energy  Efficiency  of  Storage  Battery. 
The  watt-hour  efficiency. 

Energy,  Electric.  —  The  power  which 
electricity  possesses  of  doing  work. 

Energy  Electromotive  Force. — (1)  The 
energy  component  of  E.  M.  F.  in  an  alter- 
nating-current circuit.  (2)  The  compon- 
ent of  E.  M.  F.  which  is  in  phase  with  the 
current  strength. 


Energy  Flux.— (1)  A  stream  of  energy 
transfer.  (2)  A  surface  integral  of  energj 
transferred  through  a  surface. 

Energy  Meter.— A  term  sometimes  ap- 
plied to  a  wattmeter. 

Energy  of  Motion. — A  word  sometimes 
used  for  kinetic  energy. 

Energy  of  Position.— A  word  sometimes 

used  for  potential  energy. 
Energy   of  Strain. — A  term   sometimes 

used  for  potential  energy  of  deformation 

elasticity. 

Energy  Resistance. — In  an  alternating- 
current  circuit,  the  energy  component  of 
impedance. 

Energy  Storage-Capacity.  —  The  total 
amount  of  energy  which  a  storage  cell 
can  store  up  expressed  in  watt-hours. 

Energy  Transforming-Deviee.  —  Any 
device  which  will  transform  or  change 
energy  from  one  form  to  another. 

Engaged  Test.— (1)  In  telephony,  the  busy 
test.  (2)  A  test  made  by  the  operator  at  a 
central  exchange  to  ascertain  whether  the 
subscriber  desired  is  already  engaged  in 
telephonic  communication. 

Engine. — In  telephony,  a  name  sometimes, 
used  for  a  ringer  or  magneto-generator. 

Engine  Dynamo. — A  direct-connected 
dynamo. 

Engine  Plane  Signal. — In  a  system  of 
mine  signalling  a  circuit  containing  a 
battery  and  bell  at  the  engine  house,  and 
a  pair  of  uncovered  iron  wires  along  the 
engine  plane,  or  hoist  run.  for  the  purpose 
of  giving  signals  to  the  man  at  the  engine. 

Engine-Room  Indicator. — An  indicator 
placed  in  an  engine-room. 

Engine-Room  Tachometer. — A  tacho- 
meter suitable  for  permanent  attachment 
to  an  engine,  dynamo,  or  other  rotating 
machine  situated  in  an  engine-room. 

Engine  Telegraph. — A  telegraph  on  board 
ship  for  communicating  orders  to  the 
engine-room. 

English  Heat  Unit.— <1)  The  British  heat 
unit.  (2)  The  heat  necessary  to  raise  a 
pound  of  water  1°  F. 

Engraving,  Electric. — A  method  for  elec- 
trically etching  or  engraving  a  metallic 
plate  by  covering  it  with  wax,  tracing 
the  design  on  the  wax  so  as  to  expose  the 
metal,  connecting  the,  metal  with  the 
positive  terminal  of  a  battery,  and  placing 
it  in  a  bath  opposite  another  plate  of  metal, 
so  that  it  will  be  electrically  corroded  on 
its  exposed  parts. 

Entering  Current  of  Telegraphic  Cir- 
cuit.— A  term  employed  to  designate  the- 


Ent.] 


773 


[Equ. 


current  on  a  telegraphic  line  or  conductor 
near  the  battery. 

Entrefer. — (1)  The  gap  of  non-magnetic 
material  through  which  the  field  flux  has 
to  pass  at  the  surface  of  the  armature 
of  a  dynamo-electric  machine,  composed 
either  of  an  air-gap  or  of  air  and  copper. 
(2)  The  width  of  the  non-magnetic  gap, 
as  distinguished  from  the  width  of  the 
clearance  or  simple  air-gap  of  a  smooth 
cored  armature. 

Entropy. — (1)  In  thermo-dynamics  the 
non-available  energy  in  any  system. 
(Clausius  and  Mayer.)  (2)  In  thermo- 
dynamics the  available  energy  in  any 
system.  (Tait,  Thomson,  Maxwell.) 

Entropy,  Electric. — A  term  proposed  by 
Maxwell  for  use  in  thermo-electric  phe- 
nomena, to  include  the  doctrine  of  entropy 
in  electric  science. 

Environment. — The  accompaniments  or 
surroundings  of  any  thing  or  condition. 

Eolotropic. — (1)  Heterogeneous  with  re- 
spect to  direction.  (2)  A  medium  in  which 
equal  stresses  applied  in  different  direction 
do  not  produce  equal  and  similar  strains. 

Eolotropic  Dielectric. — A  dielectric  pos- 
sessing eolotropic  properties. 

Eolotropic  Medium. — Any  medium  pos- 
sessing eolotropic  properties. 

Eolotropic  "Wire-Grating.  —  An  eolo- 
tropic screen  employed  by  Hertz  in  his 
experiments  on  electric  radiation. 

Eolotropism.  —  The  possession  of  eolo- 
tropic properties. 

Eolotropy.-The  doctrine,  theory,  or  condi- 
tion of  eolotropism. 

Epoch. — In  the  case  of  a  vibrating  body, 
the  time  or  the  angle  reckoned  from  the 
point  of  starting  to  the  point  of  maximum 
positive  elongation. 

Equal    Arms    Electric   Balance.— An 

electric  Wheatstone  bridge  or  balance  em- 
ploying equal  arms. 

Equal  Deflection  Method.— A  method 
of  measuring  a  resistance,  electromotive 
force  or  current  which  consists  in  obtain- 
ing the  same  deflection  on  a  galvanometer 
in  the  circuit  with  a  given  shunt. 

Equalizer.— (1)  An  equalizing  bar.  (2)  A 
term  employed  for  an  equalizer  wire.  (3) 
A  device  for  equalizing  electric  pressure 
over  a  system. 

Equalizer  Feeder.— A  feeder  whose  sole 
or  principal  purpose  is  to  equalize  the 
pressure  between  the  ends  of  two  or  more 
other  feeders,  as  distinguished  from  sup- 
plying current  to  feeding  points. 


Equalizer  Feeder-Switch.— A  switch 
employed  to  throw  a  feeder  equalizer  in 
or  out  of  circuit. 

Equalizer  S witch. — A  switch  governing 
a  resistance  suitable  for  feeder  regulation. 

Equalizer  Wire. — (1)  An  equalizing  bar. 
(2)  A  wire  connecting  the  series  windings 
of  two  or  more  compound-wound  genera- 
tors operated  iii  parallel. 

Equalizing  Bar. — A  bar  joining  the  series 
coils  of  two  parallel-connected, compound- 
wounds  generators,  so  that  any  excess  of 
current  supplied  by  the  armature  of  one 
machine  must  necessarily  excite  the 
other  machine  to  the  same  extent. 

Equalizing  Current. — The  current  pass- 
ing through  an  equalizing  bar  between 
two  dynamos. 

Equalizing  Dynamo. — A  dynamo  em- 
ployed in  systems  of  three  or  five-wire 
distribution  to  supply  one  pair  of  mains 
which  may  be  unduly  loaded  so  as  to 
equalize  the  pressure. 

Equalizing  Resistance-Coils.  —  Resist- 
ance coils  employed  in  a  system  of  feeder 
regulation. 

Equalizing  Wires.-^(l)  Two  wires  or  con- 
ductors, one  of  which  is  employed  for 
connecting  the  positive  brushes  and 
the  other  for  connecting  the  negative 
brushes  of  compound-wound  dynamos, 
when  connected  in  parallel.  (2)  Wires 
connecting  corresponding  segments  in  a 
multipolar  armature  winding. 

Equator  of  Magnet. — (1)  A  point  ap- 
proximately midway  between  the  poles 
of  a  straight  bar  magnet,  or  nearly  mid- 
way from  the  poles  of  a  horse-shoe  mag- 
net, if  measured  along  the  bar  from  each 
pole.  (2)  A  line  of  neutral  points  on  a 
magnet. 

Equatorial. — Of  or  pertaining  to  the 
equator. 

Equatorial  Region  of  Magnet. — The 
portions  of  a  magnet  which  lie  near  the 
magnetic  equator. 

Equatorially. — In  the  direction  of  the 
equator. 

Equiangular  Impedances.  —  Imped- 
ances which  have  the  same  angle. 

Equilibrium. — The  condition  of  a  body 
on  which  several  forces  are  acting,  so  that 
their  resultant  is  zero. 

Equilibrium  of  Radiation.— The  condi- 
tion of  a  radiating  body  in  which  the 
radiant  energy  it  absorbs  is  equal  to  that 
which  it  emits. 

Equimolecular  Solutions.  —  Solutions 
which  contain,  in  the  same  quantity  of 


Equ.] 


774 


[Eth. 


tlie  solvent,  quantities  of  the  dissolved 
substance  proportional  to  their  molecular 
weights. 

Equipotential. — Of  or  pertaining  to  an 
equality  of  potential. 

Equipotential  Electrostatic-Surfaces. 
(1)  Surfaces  on  or  surrounding  charged 
bodies,  all  points  of  which  are  at  the  same 
electric  potential.  (2)  Electric  surfaces 
perpendicular  to  the  lines  of  electric 
force,  over  which  a  quantity  of  electricity, 
considered  as  being  concentrated  at  a 
point,  may  be  moved  without  doing  work. 

Equipotential  Magnetic-Surfaces. — 
Surfaces  surrounding  the  poles  of  a  mag- 
net or  system  of  magnets,  where  the 
magnetic  potential  is  the  same. 

Equivalent  Air-Gap. — An  air-gap  which 
would  have  the  same  magnetic  resist- 
ance as  a  joint,  assuming  the  permeabil- 
ity of  the  metal  to  be  unaffected  by  the 
cutting. 

Equivalent  Conductance. — (1)  A  con- 
ductance such  that  if  inserted  in  a  sinu- 
soidal-current circuit  would  absorb  en- 
ergy at  the  same  rate  as  the  actual 
conductance  in  a  non-sinusoidal  current 
circuit.  (2)  Virtual  conductance.  (3) 
The  effective  conductance  of  an  alternat- 
ing-current system  or  conductor. 

Equivalent  Conductivity. — The  mole- 
cular conductivity  of  a  solution  divided 
by  the  valency. 

Equivalent  Impedance. — Such  an  im- 
pedance in  a  simple-harmonic-current  cir- 
cuit as  would,  with  the  same  effective 
current  strength,  absorb  energy  at  the 
same  rate  as  an  actual  impedance  in  a 
complex-harmonic-current  circuit. 

Equivalent  Heactance.— Such  a  react- 
ance in  a  simple-harmonic-current  circuit 
as  would  permit  energy  to  be  absorbed, 
with  the  same  effective  current  strength, 
at  the  same  rate  as  an  actual  reactance 
in  a  complex-harmonic-current  circuit. 

Equivalent  Resistance. — (1)  A  single 
resistance  which  may  replace  a  number 
of  resistances  in  a  circuit  without  alter- 
ing the  current  traversing  it.  (2)  Such  a 
resistance  in  a  simple-harmonic-current 
circuit  as  would  permit  energy  to  be  ab- 
sorbed, with  the  same  effective  current 
strength,  at  the  same  rate  as  an  actual  re- 
sistance in  a  complex-harmpnic-current 
circuit.  (3)  The  effective  resistance  of  an 
alternating-current  system  or  conductor. 

Equivalent  Resistance  and  Induct- 
ance.— In  an  alternating-current  circuit, 
or  system  of  circuits,  such  a  resistance 
and  inductance  as  would,  if  substituted 
for  the  actual  system,  cause  the  same 


strength  and  activity  of  current  to  pusa 
through  the  conducting  leads. 

Equivalent  Resistance  and  Reactance. 
Such  a  resistance  and  reactance  in  a 
simple  alternating-current  circuit,  as 
would  cause  the  same  current  both  in 
magnitude  and  phase  to  flow  in  the  main 
leads,  as  when  a  number  of  multiple  arc 
circuits  are  connected  to  them. 

Equivalent  Sinusoid. — A  curve  repre- 
senting a  sinusoid,  which,  for  purposes  of 
analytical  investigation,  has  been  takenas 
the  equivalent  in  power  of  a  curve  ol 
pressure  or  current  which  is  not  sinu- 
soidal. 

Equivolt. — A  term  proposed  for  unit  ot 
electric  energy  applied  especially  to 
chemical  decomposition.  (Not  in  general 
use.) 

Erb's  Standard  Size  of  Electrodes.— 
Standard  sizes  of  electrodes,  generally 
adopted  in  electro-therapeutics. 

Erg.— (1)  The1  C.  G.  S.  unit  of  work,  or 
the  work  done  when  unit  C.  G.  S.  force 
is  overcome  through  unit  C.  G.  S.  dis- 
tance. (2)  The  work  accomplished  when 
a  body  is  moved  through  a  distance  of 
one  centimetre  with  the  force  of  one 
dyne.  (3)  A  dyne-centimetre. 

Erg-Meter. — (1)  An  apparatus  for  meas- 
uring the  work  of  an  electric  current  in 
ergs.  (2)  An  energy-meter. 

Ergometer. — An  erg-meter. 

Erg  :  s. — An  abbreviation  proposed  for  erg- 
per-second,  the  C.  G.  S.  unit  of  power. 

Erg-Ten. — (1)  A  term  proposed  for  ten  mil- 
lion ergs ;  1010  ergs,  or  one  erg  multiplied 
by  low.  (2)  A  kilo-joule. 

Error. — In  telegraphy,  a  blunder  or  inac- 
curacy either  of  transmitted  signals,  as  in 
sending  a  message,  or  of  deciphered,  re- 
transmitted, or  recorded  signals,  as  in  re- 
ceiving a  message. 

Escape,  Electric. — (1)  A  partial  loss  of 
current  to  earth  by  imperfect  insulation. 
(2)  A  loss  of  charge  on  an  insulated  con- 
ductor. 

Escapement,  Electric. — An  electrically 
actuated  clock  escapement. 

Essential  Resistance. — A  term  some- 
times used  for  internal  resistance. 

Etching,  Electric. — A  term  sometimes 
used  for  electric  engraving. 

Ether. — The  highly  tenuous,  elastic  fluid 
that  is  assumed  to  fill  all  space,  and  by 
whose  vibrations  or  waves,  light,  radiant 
heat,  and  electro-magnetic  radiation  are 
transmitted. 


Eth.] 


775 


[Exp. 


Ether  Flow  Vortices. — Vortices  in  the 
ether  upon  whose  alleged  existence  is 
based  a  hypothesis  for  the  explanation  of 
magnetic  phenomena. 

Ether  Path  of  Reluctivity. — A  concep- 
tion employed  in  studying  the  reluctivity 
of  a  magnetic  medium  which  regards  the 
magnetic  flux  as  taking  two  multiple- 
connected  paths,  one  the  path  of  metallic- 
reluctivity  through  the  mass  of  the  sub- 
stance, and  the  other  the  path  of  ether- 
reluctivity,  through  its  associated  ether. 

Ether  Streamings. — Streamings  that  are 
assumed  to  exist  in  the  ether  around  a 
magnet,  or  around  a  charged  conductor. 

Ethereal. — Of  or  pertaining  to  the  ether. 

Eudiometer. — (1)  A  voltameter  in  which 
separate  graduatedvesselsare  prepared  for 
the  reception  and  measurement  of  the 
gaseous  products  evolved  during  electro- 
lysis. (2)  A  graduated  glass  tube  for  hold- 
ing and  measuring  the  volume  of  the 
evolved  gas. 

Eudiometric.— Of  or  pertaining  to  an 
eudiometer. 

Eudiometrically. — By  means  of  an  eudio- 
meter. 

Evanescent  Telegraphic  Signal. — Any 
telegraphic  signal  which  is  not  perma- 
nently recorded. 

Evaporation. — The  change  from  the  liquid 
to  the  vaporous  state. 

Evaporation,  Electric. — The  formation 
of  vapors  on  the  surfaces  of  solid  or 
liquid  substances  by  the  influence  of  neg- 
ative electrification. 

Even  Harmonics. — In  a  complex  harmon- 
ically-varying quantity,  the  harmonics 
whose  frequencies  are  even  multiples  of 
the,  fundamental  frequency. 

Ewing's  Theory  of  Magnetism. — A 
theory  of  magnetism  proposed  by  Ewiug, 
based  on  the  assumption  of  originally 
magnetized  particles. 

Excitability  of  Nerve  or  Muscular 
Fibre,  Electric.— The  effect  produced 
by  an  electric  current  in  stimulating  a 
nerve  of  a  living  animal,  or  in  producing 
an  involuntary  contraction  of  a  muscle. 

Excitant.  —  (1)    That     which       excites. 

(2)  The  electric  or  magnetic  force  which 
energizes  a  receptive  device. 

Excitation. — (1)  The  production  of  elec- 
trification by  any  means.  (2)  The  pro- 
duction of  magnetism  by  any  means. 

(3)  The  energizing  of  any  electro  or  mag- 
neto-receptive device.     (4)   The  produc- 
tion of  the  magnetic  field  in  a  dynamo 


or  motor.      (5)    The    stimulation    of   a 
muscle  or  nerve  fibre. 

Exciter. — Anything  which  causes  an  ex- 
citation. 

Exciter  Dynamo. — A  dynamo  used  for 
the  separate  excitation  of  another  dynamo. 

Exciter  of  Field. — A  dynamo,  or  othel 
electric  source,  employed  in  the  separate 
excitation  of  tne  field  of  a  dynamo. 

Exciting  Ampere-Turns.— The  ampere- 
turns  in  the  field-winding  of  a  generator 
or  motor  employed  for  the  excitation  of 
its  field. 

Exciting  Fluid  or  Liquid  of  Voltaic 
Cell. — The  electrolyte  of  a  voltaic  cell. 

Execution,  Electric. — Inflicting  capital 
punishment  by  electricity. 

Exhaust  Fan,  Electric. — An  electrically 
driven  exhaust  fan. 

Exhaust  Wheel,  Electric. — An  electri- 
cally driven  rotary  device  Tor  drawing  or 
exhausting  the  air  from  an  apartment. 

Exhausted  Storage  Cell.— An  emptied 
storage  cell. 

Exhausted  Voltaic  Cell. — A  voltaic  cell 
in  a  state  of  exhaustion. 

Exhaustion,  Electric. — Physiological  ef- 
fects resembling  those  produced  by  sun- 
stroke, resulting  from  prolonged  exposure 
to  powerful  voltaic  arcs. 

Exhaustion  of  Primary  Voltaic  Cell. 
The  inability  of  a  primary  voltaic  cell 
to  furnish  any  further  current,  unless 
fresh  electrolyte,  or  new  positive  ele- 
ments, or  both,  are  supplied  to  it. 

Exhaustion  of  Secondary  Voltaic 
Cell. — The  inability  of  the  cell  to  furnish 
any  further  current  until  again  acted  on 
by  a  charging  current. 

Exosmosis. — The  osmotic  current  which 
is  directed  towards  the  lower  level. 

Exothactic  Cut-Out. — A  cut-out  de- 
signed to  remove  a  device  from  a  circuit. 

Exothatic  Switch.— A  switch  designed  to 
cut  a  device  out  of  circuit. 

Exothermic. — Of  or  pertaining  to  an  exo- 
thermic reaction. 

Exothermic  Reaction. — A  chemical  re- 
action attended  by  the  evolution  of  heat. 

Expanding  Magnetic  Whirls. — Mag- 
netic whirls  sent  out  from  a  conductor 
through  which  a  current  of  gradually  in- 
creasing strength  is  passing,  or  from  a 
magnet  whose  magnetism  is  gradually  in- 
creasing. 

Expanding  of  Magnetic  Field. — The 
increase  in  the  strength  of  a  magnetic 
flux  and  of  the  region  traversed  by  it. 


Exp.] 


776 


[Eye. 


Expansibility. — (1)  The  quality  of  being 
expansible.  (2)  Possessing  the  capacity 
for  expansion. 

Expansion. — The  act  of  increasing  in 
length,  surface,  or  volume. 

Expansion,  Electric. — The  increase  in 
volume  produced  in  a  body  by  giving  it 
an  electric  charge. 

Expansion  Joint. — A  joint  suitable  for 
tubes  or  pipes  exposed  to  considerable 
changes  of  temperature,  in  which  a  slid- 
ing joint  is  provided  to  safely  permit  a 
change  in  length  on  expansion  or  contrac- 
tion. 

Expended  Energy.— The  energy  em- 
ployed to  produce  any  result. 

Exploder,  Electric. — A  small  magneto- 
electric  machine  used  to  produce  a  high 
electromotive  force,  employed  in  the 
direct  firing  of  blasts. 

Exploration     of    Magnetic     Field. — 

Mapping  out  the  location  and  density  of 
a  magnetic  field  by  any  suitable  means. 

Explorer,  Electric. — An  apparatus  oper- 
ated by  means  of  induced  currents  for 
the  purpose  of  locating  bullets  and  other 
foreign  metallic  substances  in  the  human 
body. 

Exploring  Needle. — (1)  A  form  of  ex- 
ploring probe.  (2)  A  magnetic  needle 
employed  in  exploring  a  magnetic  field. 

Explosive  Distance. — A  term  sometimes 
employed  for  sparking  distance. 

Extension  Bell. — (1)  An  extension  call- 
bell.  (2)  A  call-bell  situated  at  a  distance 
from  the  apparatus  to  which  it  calls  at- 
tention. 

Extension  Call-Bell. — An  additional  bell 
connected  with  the  call-bell  of  a  telephone 
or  other  device,  and  placed  in  some  other 
portion  of  a  building,  for  the  purpose  of 
calling  the  subscriber  to  the  instrument 
when  he  may  be  in  a  distant  part  of  the 
house. 

Extension  Plates  for  Poles.— Double 
plates  forming  between  them  a  loop  for 
an  upper  extension  or  branch  of  a  guy- 
rod  supporting  a  pole. 

Extension  Push-Button. — An  auxiliary 
push-button  placed  at  a  distance  from  a 
main  push-button. 

Extensometer. — A  form  of  apparatus  for 
measuring  the  elongation  of  a  substance 
under  stress. 

External  Armature  Generator.  — A 
generator  in  which  the  armature  is  ex- 
ternal to  the  field  frame. 


External  Characteristic  of  Dynamo.— A 
curve  showing  the  E.  M.  F.  at  the  termi- 
nals of  a  dynamo  under  varying  currents, 
as  distinguished  from  an  internal  charac- 
teristic showing  the  internal  E.  M.  F. 

External  Circuit. — That  part  of  a  circuit 
with  which  an  electric  source  is  con- 
nected that  is  external  to  that  electric 
source. 

External  Magnetic  Circuit. — (1)  That 
portion  of  a  magnetic  circuit  which  lies 
outside  the  magnetic  source.  (2)  That 
portion  of  the  circuit  of  a  magnet  which 
lies  outside  its  mass  or  core. 

External  Magnetic  Field. — That  portion 
of  a  magnetic  field  which  lies  outside  the 
body  of  a  magnet. 

External  -  Secondary  Resistance.  —  In 
the  secondary  circuit  of  a  transformer, 
the  resistance  external  to  the  transformer. 

Extra-Current  Direct. — A  term  some- 
times employed  for  the  current  produced 
in  the  primary  of  a  transformer  on,  the 
breaking  of  its  circuit. 

Extra-Current  Inverse. — A  term  some- 
times employed  for  the  current  produced 
in  the  primary  current  of  a  transformer 
on  the  making  of  its  circuit. 

Extra-Current  Neutralize!*.— A  device 
for  reducing  electro-magnetic  retardation 
which  consists  of  a  shunted  condenser  in- 
serted in  the  main  circuit. 

Extra  Currents. — Currents  produced  in  a 
circuit  by  self-induction. 

Extra-High-Potential  System. — In  the- 
National  Electric  Code  a  potential  above 
3000  volts. 

Extra-High-Potential  "Wires. — Wires 
suitable  for  use  in  extra-high-potential 
systems.  . 

Extraneous  Field. — A  leakage  magnetic 
field. 

Extraordinary  Resistance. — A  term 
sometimes  used  for  external  resistance. 
(Not  in  use.) 

Extra-European  Message. — In  Europe  a 
message  sent  to  or  received  from  some 
point  beyond  the  geographical  limits  of 
Europe. 

Extra-Polar. — Lying  beyond  or  outside 
the  poles. 

Extra-Polar  Region. — In  electro-thera- 
peutics, the  region  which  lies  outside  or 
beyond  the  therapeutic  electrodes. 

Eye-Piece. — The  ocular  of  a  telescope  o* 
microscope. 


*••] 


777 


[Fan. 


F. — A  symbol  proposed  for  farad,  the  prac- 
tical unit  of  capacity. 

F. — A  symbol  proposed  for  force. 

of. — A  symbol  for  magnetomotive  force. 
(Partly  international  usage.) 

f. — A  symbol  proposed  for  force.  (Partly 
international  usage.) 

P.  M. — A  contraction  for  field  magnets. 

F.  W.  G-. — A  contraction  for  French  wire 
gauge. 

Fac-Simile  Telegraph. — A  general  term 
embracing  the  apparatus  employed  in 
fac-simile  telegraphy. 

Fac-Simile  Telegraphy. — (1)  A  system 
whereby  a  fac-simile  or  copy  of  a  chart, 
diagram,  picture,  or  signature,  is  tele- 
graphically transmitted  from  one  station 
to  another.  (2)  Pan-Telegraphy. 

Factor. — Each  of  the  several  quantities 
which  are  multiplied  together  to  form  a 
product. 

Factor  of  Safety.— (1)  The  ratio  of  the 
computed  or  measured  strength  of  a 
structure  to  the  maximum  strength  it 
will  be  called  upon  to  exert.  (2)  An 
amount  by  which  the  breaking  load  or 
stress  in  any  system  must  be  divided  in 
order  to  obtain  the  safe  load  or  stress.  (3) 
A  multiple  of  the  calculated  strength  re- 
quired of  a  structure  adopted  to  ensure 
safety. 

Factor  of  Safety  of  Demagnetization.— 
The  ratio  of  the  demagnetizing  force  in 
an  aero-ferric  magnetic  circuit  corre- 
sponding to  an  actually  existing  residual 
flux  density,  to  the  actually  existing 
mean  demagnetizing  force. 

Fahrenheit  Thermometric  Scale.— The 
thermometric  scale  in  which  the  length  of 
the  thermometer  tube,  between  the  melt- 
ing point  of  ice  and  the  boiling  point  of 
water,  is  divided  into  180  equal  parts  or 
degrees. 

Fall-Back  Indicator.— A  term  sometimes 
employed  for  drop  indicator. 

Fall  of  Potential.— The  drop  of  poten- 
tial. 

Fall  of  Pressure.— The  drop  of  pressure. 

Fall  of  Pressure  in  Active  Conductor. 
The  fall  of  pressure  due  to  the  passage 
of  the  current,  and  equal  to  the  product 
of  the  current  strength  by  the  resistance. 


False. — (1)  Untrue.  (2)  Provisionally  as- 
sumed. 

False  Discharge  of  Submarine  Cable. 
An  oscillatory  discharge  produced  in  a 
cable  as  distinguished  from  an  aperiodic 
discharge. 

False  Electric  Current. — A  virtual  elec- 
tric current  distribution  which  has  no  ac- 
tual existence,  but  which  is  assumed  in 
order  to  comply  with  the'  conditions  of 
an  electro-magnetic  field. 

False  Electrification. — A  virtual  electri- 
fication having  no  real  existence,  but 
which  may  be  assumed  in  order  to  deter- 
mine a  given  distribution  of  electro-mag- 
netic energy  in  a  medium. 

False  Magnetic  Currents. — Virtual  mag- 
netic currents  having  no  real  existence 
but  assumed  for  the  purpose  of  conform- 
ing to  the  requirements  of  a  given  electro- 
magnetic distribution. 

False  Magnetic  Poles  of  Earth. — A 
term  proposed  to  designate  the  place  or 
places  on  the  earth  which  apparently  act 
as  magnetic  poles,  in  addition  to  two  true 
magnetic  poles  in  the  neighborhood  of 
the  earth's  geographical  poles. 

False  Resistance. — A  resistance  arising 
from  a  counter  electromotive  force,  and 
not  directly  from  the  dimensions  of  the 
circuit,  or  from  its  specific  resistance. 

False  Zero. — (1)  A  zero  of  a  measuring  in- 
strument accepted  at  the  position  it  nat- 
urally assumes  under  the  action  of  forces 
other  tha.n  those  impressed  in  the  meas- 
urement. (2)  A  zero  taken  midway  be- 
tween two  unequal  and  opposite  deflec- 
tions of  a  measuring  instrument.  (3)  Iu 
Wheatstone-Bridge  measurement,  the  po- 
sition of  the  galvanometer  needle  natu- 
rally assumed  under  the  influence  of  E. 
M.  F.  in  the  bridge  before  the  application 
of  the  testing  battery.  (4)  In  cable  test- 
ing the  position  of  the  spot  of  light  when 
the  testing  battery  is  disconnected  and  the 
galvanometer  short-circuit  key  is  open. 
(5)  A  cable  zero,  or  zero  to  the  existing 
current  in  a  cable.  (6)  The  natural  zero. 

Fan  Guard. — A  wire  guard  placed  around 
an  electric  fan,  to  prevent  the  revolving 
blades  from  coming  in  contact  with  sur- 
rounding objects. 

Fan  Motor. — (1)  An  electric  motor  suit- 


Far.] 


778 


[Fee. 


able  for  driving  a  fan.  (2)  An  electric 
motor  carrying  a  fan. 

Far-Leading  Dynamo. — A  motor-dyna- 
mo placed  as  a  shunt  across  a  pair  of  long 
mains,  to  compensate  for  their  drop  in 
voltage. 

Farad.-^-(l)  The  practical  unit  of  electric 
capacity.  (2)  Such  a  capacity  of  a  con- 
ductor or  condenser  that  one  coulomb  of 
electricity  is  required  to  produce  therein 
a  difference  of  potential  of  one  volt. 

Faraday  Effect. — The  rotation  of  the 
plane  of  polarization  of  a  beam  of  plane 
polarized  light  on  its  passage  along  a 
magnetic  field. 

Faraday's  Cube. — An  insulated  room  or 
cube  covered  on  the  inside  with  tin-foil, 
which,  when  charged  on  the  outside,  gives 
no  electrical  indications  to  an  observer  on 
the  inside  even  to  delicate  instruments. 

Faraday's  Dark  Space.— The  gap  in  the 
continuity  of  the  luminous  discharges 
that  occur  between  the  positive  and  nega- 
tive electrodes. 

Faraday's  Disc. — A  metallic  disc  movable 
in  a  magnetic  field  on  an  axis  parallel  to 
the  direction  of  the  flux. 

Faraday's  Net. — An  insulated  net  of  cot- 
ton, gauze,  or  other  similar  conducting 
material,  capable  of  being  turned  inside 
out  without  being  thereby  discharged, 
and  employed  for  demonstrating  the  fact 
that  the  charge  of  an  insulated  conductor 
is  limited  to  its  outer  surface. 

Faradic. — Of  or  pertaining  to  Faraday. 

Faradic  Adapter. — A  device  for  readily 
permitting  commercial  incandescent- 
light  circuits  to  be  employed  for  electro- 
therapeutic  work,  with  an  induction 
coil. 

Faradic  Battery. — A  term  erroneously 
used  for  a  faradic  coil,  or  induction  coil. 

Faradic  Brush. — A  brush-shaped  elec- 
trode employed  in  the  medical  applica- 
tion of  electricity. 

Faradic  Coil. — A  term  sometimes  used  for 
a  faradic  machine,  or  medical  induction 
coil. 

Faradic  Current. — (1)  In  electro-thera- 
peutics, a  current  produced  by  an  induc- 
tion coil,  or  magneto-electric  machine. 
(2)  A  rapidly  alternating  current,  as  dis- 
tinguished from  a  direct  current. 

Faradic  Excitability. — Muscular  or  ner- 
vous excitability  produced  by  the  em- 
ployment of  faradic  currents. 

Faradic  Excitation. — The  excitement  of 
muscle  or  nerve  fibre  by  faradio  cur- 
rents. 


Faradic  Induction  Apparatus. — An  in- 
duction coil  apparatus  for  producing  fara- 
dic currents. 

Faradic  Irritability. — Muscular  contrac- 
tions produced  by  the  action  of  faradia 
currents  on  a  nerve. 

Faradic  Machine. — Any  machine  for 
producing  faradic  currents. 

Faradism. — A  word  sometimes  employed 
for  faradization. 

Faradization.  —  In    electro-therapeutics, 

the  effects  produced  on  the  nerves   or 

muscles  by  the  use  of  faradic  currents. 
Faradization  of  Skin. — Treatment  of  the 

skin  by  faradic  currents. 
Fast  Repeater. — A  telegraphic  repeater 

or  translator  especially  designed  for  rapid 

signalling. 
Faradometer. — A   term  proposed  for  an 

instrument  designed  for  the  measurement 

of  faradic  currents. 
Fast-Speed  Telegraphy. — Automatic  or 

machine  telegraphy. 
Fathom. — (1)  A  unit  of  length  equal  to  six 

feet  or  two  yards.    (2)  Approximately,  the 

one-thousandth  part  of  a  nautical  mile. 

Fault. — Any  defect  in  the  proper  working 
of  a  circuit,  due  to  ground  contacts,  cross 
contacts,  or  disconnections. 

Fault  Resistance. — The  resistance  of  a 
fault. 

Fault  Searcher.  —  An  instrument  em- 
ployed in  connection  with  a  telephone  or 
other  sensitive  current-detector,  for  de- 
termining the  moment  when  a  portion  of 
the  cable  containing  the  fault  comes  011 
board  ship,  while  the  same  is  being  picked 
up  for  purposes  of  repair. 

Feather  Edge. — A  strip  of  wood  laid  by 
the  side  of  a  layout  of  cable  in  a  cable 
tank  to  protect  it  from  the  pressure  of 
superincumbent  flakes. 

Feed. — (1)  To  supply  with  an  electric  cur- 
rent. (2)  To  move  or  regulate  one  or 
both  of  the  carbon  electrodes  in  an  arc- 
lamp. 

Feed-Line. — A  feeder. 

Feed- Wire  Insulator. — An  insulator  em- 
ployed for  the  support  of  a  feed-wire. 

Feeder. — One  of  the  conducting  wires 
through  which  the  current  is  distributed 
to  the  main  conductors,  as  distinguished 
from  a  conductor  which  supplies  trans- 
lating devices  directly. 

Feeder-and-Main  System  of  Distri- 
bution.— A  system  for  the  transfer  of 
electric  energy  in  which,  for  the  pur- 
pose of  preventing  too  great  a  drop  of 


Fee.] 


779 


[Fer. 


pressure  on  the  mains,  they  are  connected 
at  suitable  points  to  the  feeder  wires,  in- 
stead of  to  the  generator  or  generators. 

Feeder  Ammeter. — An  ammeter  placed 
in  the  circuit  of  a  feeder,  usually  at  a 
switchboard. 

Feeder  Block. — A  block  containing  a 
feeder  cut-out. 

Feeder  Box. — A  distribution  box  supplied 
by  a  feeder,  into  which  a  feeder  enters  to 
receive  its  distributing  connections. 

Feeder  Clamp. — Any  clamping  device  for 
connecting  or  fastening  a  feeder  wire  to  a 
trolley  wire  or  to  a  main. 

Feeder  Cleat. — A  clamp  furnished  with  a 
device  whereby  a  feeder  wire  may  be 
readily  connected  to  a  trolley  wire. 

Feeder  Distribution.  —  A  feeder  -  and- 
main  system  of  distribution. 

Feeder  Equalizer. — A  resistance  coil  in- 
serted in  the  circuit  of  a  feeder,  with  or 
without  means  for  adjustment,  for  the 
purpose  of  equalizing  the  pressure  at  the 
feeding  points. 

Feeder  -  Equalizer  Resistance. — A 
feeder  regulator. 

Feeder-Equalizer  Switch. — An  equa- 
lizer switch  employed  in  feeder  systems. 

Feeder  for  Trolley  Conductor. — A  wire 
or  conductor  of  low  resistance  employed 
for  transmitting  elec.tric  pressure  direotly 
from  the  power  station  to  some  distant 
point  of  the  trolley  wire,  for  the  purpose 
of  maintaining  the  potential  at  that  point. 

Feeder-Mechanism  for  Arc-Lamps. — 

An  arc-lamp  feeding  mechanism. 

Feeder  Panel  of  Switchboard. — A  panel 
of  a  switchboard,  furnished  with  the 
necessary  switches,  voltmeters,  ammeters, 
and  safety  devices,  to  which  the  feeder 
wires  are  connected. 

Feeder  Plug.— A  metallic  bolt  which, 
when  inserted  in  a  trolley  car  in  place  of 
an  insulated  bolt,  establishes  connection 
between  the  trolley  wire  and  a  feeder 
through  the  span  wire. 

Feeder  Potential.— (1)  The  electric  poten- 
tial of  any  feeder  relatively  to  ground.  (2) 
The  difference  of  potential  between  any 
pair  of  feeder  conductors. 

Feeder  Regulators. —  (1)  Artificial  re- 
sistances introduced  into  the  circuit  of 
idle  feeders,  so  as  to  increase  the  drop  of 
pressure  existing  in  them.  (2)  A  form  of 
special  transformer,  whose  primary  is  con- 
nected across  the  mains  and  its  secondary 
is  in  series  with  one  feeder  wire,  and  is 
employed  to  produce  a  pressure  which, 
by  means  of  a  suitable  reversing  switch, 


either  aids  or  opposes  the  alternating  pres- 
sure on  the  mains.  (3)  A  term  sometimes 
applied  to  boosters. 

Feeder  Switch.— Any  switch  placed  on  a 
feeder  panel  that  is  connected  with  the 
separate  feeders  and  employed  for  the 
purpose  of  connecting  or  disconnecting  a 
generator  with  such  feeder. 

Feeder  System.— A  system  of  distribution 
in  which  the  service  wires  are  connected 
by  means  of  feeders  to  certain  centres  of 
distribution. 

Feeder  Tubes. — Underground  tubes  pro- 
vided for  the  reception  of  the  feeder  wires. 

Feeders. — Wires  supplying  currents  to 
main  conductors  at  different  points,  to 
equalize  their  potential  under  load,  as 
distinguished  from  wires  supplying  cur- 
rents directly  to  the  load. 

Feeding  Centre.— (1)  A  centre  of  distri- 
bution supplied  by  a  feeder.  (2)  A  feed- 
ing point. 

Feeding  Conductors  or  Wires. — Feed- 
ers. 

Feeding  Device  or  Mechanism  for 
Electric  Arc-Lamps.  —  A  device  for 
maintaining  the  carbon  electrodes  of  an 
arc-lamp  at  a  constant  distance  apart  dur- 
ing their  consumption. 

Feeding  Point. — (1)  A  point  of  connection 
between  a  feeder  and  the  mains.  (2)  A 
feeding  centre. 

Fender. — A  device  placed  in  front  of  a 
street  car  for  preventing  accidental  in- 
jury to  pedestrians  passing  in  front  of  the 
moving  car. 

Ferranti  Effect. — (1)  An  increase  in  the 
electromotive  force  or  difference  of  po- 
tential of  mains  or  conductors  carrying 
alternating  currents,which  exists  towards 
the  end  of  the  same  furthest  from  the 
terminals  that  are  connected  with  the 
source.  (2)  A  negative  drop  in  pressure. 

Ferric  Circuit. — A  ferric-magnetic  cir- 
cuit. 

Ferric  Inductance  Coil. — An  inductance 
coil  provided  with  an  iron  core. 

Ferric  Magnetic  Circuit. — A  magnetic 
circuit  composed  wholly  of  iron. 

Ferric  Path  of  Reluctivity. — That  por- 
tion of  the  flux  paths  through  iron  or 
other  magnetic  material,  in  which  the 
flux  passes  through  the  metal  proper,  as 
distinguished  from  that  which  is  assumed 
to  pass  through  the  ether  lying  within 
such  material. 

Ferro-Magnet.— A  word  sometimes  em- 
ployed for  an  ordinary  magnet  made  of 
paramagnetic  material,  as  distinguished 


Fer.] 


780 


[Fil. 


from  a  diamagnet,  or  one  formed  of  dia- 
magnetic  material. 

Ferro-Magnetic. — A  word  sometimes  em- 
ployed for  paramagnetic. 

Ferro-Magnetic  Substances.  —  Para- 
magnetic substances. 

Ferrp-Magnetism. — Magnetism  possessed 
by  iron  or  other  paramagnetic  substances. 

Ferro-Manganese  Alloys.— Various  al- 
loys employed  for  the  wires  of  resistance 
coils,  whose  electric  resistance  is  not  sen- 
sibly affected  by  changes  of  temperature. 

Fibre  Suspension. — Suspension  of  a 
needle  or  other  system  by  a  fibre  of  un- 
spun  silk,  quartz  or  other  suitable  ma- 
terial. 

Fibrone. — A  variety  of  insulating  ma- 
terial. 

Fictive  Layers. — Layers  in  a  dielectric 
possessing  equipotential  surfaces  due  to 
the  accumulation  of  charges  insufficient 
to  produce  a  constant  potential  within  the 
dielectric,  but,  nevertheless,  capable  of 
modifying  its  potential. 

Fiducial  Point.— (1)  A  fixed  point  or  refer- 
ence point  in  the  scale  or  indications  of 
a  galvanometer  or  other  measuring  in- 
strument. (2)  A  temporary  zero  point. 

Field. — (1)  A  term  sometimes  used  for  a 
magnetic  field.  (2)  A  term  sometimes 
used  for  an  electrostatic  field. 

Field  Coils.— The  field-magnet  coils  of  a 
dynamo-electric  machine  or  motor. 

Field,  Electric. — A  term  sometimes  used 
in  place  of  electrostatic  field. 

Field  Frequency. — The  frequency  of 
revolution  in  a  rotating  magnetic-field. 

Field-Magnet  Coils. — The  magnetizing 
coils  on  the  field  magnets  of  a  dynamo  or 
motor. 

Field-Magnet  Regulating  Box.— (1) 
The  field  regulating  box.  (2)  A  resistance 
box  inserted  in  the  circuit  of  the  field 
magnets. 

Field  Magnets. — The  magnets  which  pro- 
duce the  magnetic  field  or  flux  in  which 
the  armature  of  a  dynamo  or  motor  ro- 
tates. 

Field  of  Force. — (1)  The  space  traversed 
by  electrostatic  or  magnetic  flux.  (2)  An 
electrostatic  or  magnetic  field. 

Field  of  Vortex  Ring.— The  field  of  in- 
fluence possessed  by  a  vortex  ring. 

Field  Poles.— The  poles  of  the  field  mag- 
nets of  a  dynamo  or  motor. 

Field-Regulating  Box.;— (1)  A  resistance 
box,  inserted  in  series  with  the  field  mag- 
net coils,  for  the  purpose  of  varying  the 


strength  of  the  magnetizing  current.  (2) 
A  regulating  box  or  rheostat  connected 
with  the  field  circuit  of  a  generator,  for 
the  purpose  of  controlling  its  pressure. 

Field  Rheostat. — A  field-regulating  box. 

Field  Spools  of  Dynamo  or  Motor. — 
The  magnetizing  coils  of  the  field-mag- 
nets of  a  dynamo  or  motor. 

Field  Strength.— The  magnetic  intensity 
of  a  field. 

Field  Telegraph  Line. — A  semi-perma- 
nent telegraph  line  employed  in  army 
telegraphy,  connecting  headquarters  with 
the  divisional  generals,  and  such  other 
stations  as  may  be  required. 

Field  Windings  of  Induction  Motor. 

Field  windings  so  arranged  as  to  produce 
a  rotating  magnetic  field  when  supplied 
by  multiphase  or  uniphase  currents. 

Fieldless  Motor. — A  form  of  motor  in 
which  the  torque  is  obtained  by  the  mu- 
tual attraction  of  separate  armatures. 

Figure-of-Eight  Wire. — A  trolley  wire 
whose  cross-section  resembles  in  outline 
the  figure  8. 

Figure  of  Merit  of  Galvanometer. — 

The  reciprocal  of  the  current  strength  re- 
quired to  produce  a  deflection  of  a  gal- 
vanometer needle  through  one  division  of 
the  scale. 

Figures,  Electric. — Figures  of  various 
shapes  produced  on  electrified  surfaces 
by  the  arrangement  of  dust  particles,  or 
vapor  vesicles,  under  the  influence  of  elec- 
tric charges. 

Filament. — A  slender  thread  or  fibre. 

Filament  of  Incandescent  Lamp. — The 
incandescing  conductor  of  an  incandes- 
cent electric  lamp. 

Filament  Shadows. — Markings  produced 
on  the  inner  surface  of  an  incandescent 
lamp  chamber  by  the  deposition  thereon 
of  carbon  from  the  filament. 

Filamentous  Armature  Core.— A  lam- 
inated armature  core  formed  of  iron 
wire. 

Filar  Micrometer. — A  micrometer  ocular 
in  which  an  angular  or  linear  distance  is 
measured  by  the  movement  of  a  fibre 
across  the  field  of  view,  under  the  control 
of  a  screw  adjustment. 

Film. — (1)  A  thin  pelicle  or  layer.  (2)  A 
name  sometimes  given  to  an  electro-plat- 
ing or  deposit. 

Film  Cut-Out. — (1)  A  cut-out  in  which  a 
film  or  sheet  of  paper,  or  mica,  is  inter- 
posed between  a  line  plate  and  the  earth 
plate,  which,  when  punctured  by  a  spark, 
short-circuits  the  instruments  on  the 


Fil.] 


781 


[Fiv. 


line.  (2)  A  cut-out  for  a  series  incan- 
descent lamp,  in  which  a  film  of  paper  or 
other  insulator  is  interposed  between  the 
lamp  terminals,  so  that  when  the  filament 
breaks,  the  pressure  rises  at  the  termi- 
nals, and  both  punctures  and  short  cir- 
cuits the  film,  thus  cutting  out  the  broken 
lamp. 

Film  Lightning-Arrester. — A  film-cut- 
out lightning-arrester. 

Filter  Pump. — A  pump  employed  for  in- 
creasing the  rapidity  of  filtration  of  a 
liquid  by  atmospheric  pressure. 

Filtration. — The  separation  of  a  liquid 
from  an  undissolved  solid  or  solids  me- 
chanically suspended  therein. 

Final  Cable  Test.— (1)  The  test  made 
after  a  cable  is  laid,  to  ascertain  if  the 
electrical  specifications  have  been  met. 

Final  Cable  Splice. — (1)  The  splice  in  a 
cable  which  completes  it.  (2)  The  last 
splice. 

Finding  Earth. — In  telegraphy,  making 
earth. 

Finishing  Brushes. — In  electro-plating, 
finer  brushes  than  scratch  brushes,  em- 
ployed for  polishing. 

Fire-Alarm  Annunciator. — An  annun- 
ciator used  in  connection  with  a  system 
of  fire  alarms. 

Fire-Alarm  Contact. — A  contact  so  ar- 
ranged that  an  alarm  is  automatically 
given  when  a  predetermined  temperature 
is  reached. 

Fire-Alarm  Signal-Box. — A  signal  box 
placed  in  a  street,  or  other  convenient 
position,  by  means  of  which  an  alarm  of 
fire  can  be  sent. 

Fire-Alarm  Telegraph. — A  general  term 
embracing  the  apparatus  employed  in 
fire-alarm  telegraphy. 

Fire-Alarm  Telegraphy. — A  system  of 
telegraphy  by  means  of  which  alarms  can 
be  sent  to  a  central  station,  or  to  the  fire- 
engine  houses  in  a  district,  from  call-boxes 
placed  on  the  line,  or  from  automatic  fire- 
alarm  contacts. 

Fire  Ball. — A  term  sometimes  applied  to 
globular  lightning. 

Fire  Cleansing. — Removing  grease  by  the 
action  of  fire  from  articles  that  are  to  be 
electro-plated. 

Fire  Extinguisher,  Electric. — A  ther- 
mostat or  mercurial  contact,  which  auto- 
matically completes  a  circuit  and  thus 
turns  on  a  water  jet  for  extinguishing  a 
fire,  on  a  certain  predetermined  increase 
of  temperature. 


Fire-Fly  Radiation. — Any  form  of  lumi- 
nous radiation  containing  a  small  propor- 
tion of  non-luminous  frequencies,  and,  in 
this  respect,  similar  to  the  radiation  of 
the  fire-fly  or  glow-worm. 

Fire-Glow. — A  term  employed  by  the  an- 
cients for  an  aurora. 

Fire  Telegraph. — A  fire-alarm  telegraph. 

Firing  Battery. — A  battery  employed 
in  mining,  in  military,  or  in  naval  opera- 
tions for  firing  a  fuse. 

Firing  Filament. — (1)  Subjecting  suitably 
shaped  carbonizable  material  to  the  car- 
bonizing process,  so  as  to  prepare  it  for 
use  as  the  filament  of  an  incandescent 
lamp.  (2)  Carbonizing  a  filament. 

Firing  Rheostat. — A  rheostat  in  the  firing 
circuit  of  a  fuse  detonator. 

Fish  Plate. — In  a  system  of  electric  rail- 
roads, the  plate  connecting  contiguous 
rails  by  bolts. 

Fished  Wires. — Wires  that  have  been  in- 
troduced into  ducts  by  the  application  of 
the  fishing  process. 

Fishes,  Electric. — Various  fishes,  such  as 
the  eel  and  the  ray,  which  possess  the 
ability  of  either  protecting  themselves,  or 
securing  their  prey,  by  giving  electric 
shocks  to  the  objects  touching  them. 

Fishing  Box. — A  term  sometimes  used 
for  junction  box. 

Fishing  Conductors. — The  process  of 
threading  conductors  through  the  spaces 
left  for  them  in  floors,  walls,  tubes,  or 
conduits  by  securing  their  ends  to  the 
end  of  a  convenient  length  of  wire  and 
hauling  the  latter  through  in  advance. 

Fishing  Process. — The  process  employed 
for  the  fishing  of  wires. 

Fishing  of  Wires. — The  process  of  draw- 
ing a  wire  into  its  place  in  a  building 
through  floors,  walls,  or  ceilings  by 
placing  a  wire  in  a  hole  at  one  end  and 
engaging  it  by  a  hook  from  the  other,  so 
as  to  draw  it  through. 

Fiske's  Electric  Range-Finder. — A  de- 
vice by  means  of  which  the  distance  of  an 
object  can  be  readily  obtained. 

Fiske's  Electric  Range-Finder . — A  de- 
vice by  means  of  which  the  exact  distance 
of  an  enemy's  ship  or  other  target  can  be 
readily  determined. 

Fittings.— {!) — The  sockets,  holders,  arms, 
etc.,  required  for  holding  and  supporting 
incandescent  electric  lamps.  (2)  Incan- 
descent light  fixtures. 

Five-Point  Jack. — In  a  multiple  tele- 
phone switchboard,  a  jack  having  five 
separate  contact  points. 


Fiv.] 


782 


[Fie, 


Piye-Point  Branching  Jacks.— In  a  mul- 
tiple telephone  branching  switchboard, 
five-point  jacks  connected  in  parallel  to 
a  subscriber's  line. 

Five- Wire  System. — A  system,  similar 
in  its  arrangement  to  the  three-wire  sys- 
tem, in  which  four  series-connected  dy- 
namos are  suitably  connected  to  five 
wires  or  conductors. 

Fixed  Call-Boxes. — District  call-boxes  so 
arranged  with  burglar-alarm  circuits,  that 
the  alarm  is  sent  to  the  district  station 
connected  therewith. 

Fixed  Electric  Lamp. — A  stationary  in- 
candescent lamp  as  distinguished  from  a 
portable  lamp. 

Fixed  Resistance. — A  resistance  whose 
value  is  approximately  constant,  as  dis- 
tinguished from  a  regulable  resistance. 

Fixed  Secondary. — The  secondary  of  an 
induction  coil  that,  as  is  common  in  such 
coils,  is  fixed,  in  contradistinction  to  a 
movable  secondary. 

Fixture  Cut-Out. — A  cut-out  or  safety 
plug  attached  to  an  electric  lamp. 

Fixture  Electric. — (1)  Fittings  for  electric 
light.  (2)  A  support  or  electrolier  for  one 
or  more  incandescent  lamps  rigidly  fas- 
tened to  a  wall  or  ceiling.  (3)  Any  elec- 
tric apparatus  forming  part  of  a  perman- 
ent installation. 

Fixture  Wire. — A  class  of  insulated  wire 
suitable  for  use  in  electric  fixtures. 

Flag  of  Balance. — A  small  arm  pivoted 
friction-tight  upon  the  movable  coils  of 
an  electro-dynamometer  balance,  and 
capable  of  adjustment  for  the  purpose  of 
obtaining  a  correct  initial  balance. 

Flag  Signalling. — A  system  of  semaphoric 
signalling  in  which  a  light  flag,  held  in 
the  hand,  is  waved  to  the  left  for  the 
dots,  and  to  the  right  for  the  dashes,  of 
the  Morse  or  Continental  Code. 

Flake  of  Cable. — A  single  horizontal  layer 
of  a  coiled  cable. 

Flame. — A  mass  of  imflammable  gas  in  a 
state  of  combustion. 

Flaming  Discharge. — The  white,  flam- 
ing, arc-light  discharge  that  occurs  be- 
tween the  terminals  of  a  high-frequency, 
high-potential  induction  coil,  when  the 
current  through  the  primary  is  increased 
in  strength  beyond  that  required  for  the 
sensitive-thread  discharge. 

Flaming  of  Carbon  Arc. — An  irregular 
burning  of  a  voltaic  arc,  which  occurs 
when  the  carbons  are  too  far  apart,  and 
the  current  strength  somewhat  exceeds 
the  normal. 


Flash  Signalling. — A  method  of  sema« 
phoric  signalling  by  means  of  a  lantern, 
or  torch. 

Flashed  Carbon  Filaments.  —  Carbon 
filaments  that  have  been  subjected  to  the 
flashing  process. 

Flashing.  —  Subjecting  carbons  to  the 
flashing  process. 

Flashing  Lights.— (1)  Lights  employed 
in  light -house  illumination,  that  are 
periodically  shaded,  so  as  to  produce  an 
intermittence  of  the  light,  and  thus  to 
permit  such  light  to  be  readily  distin- 
guished from  adjacent  lights.  (2)  Any 
light  whose  intensity  is  periodically  in- 
termitted. 

Flashing  of  Dynamo  -  Electric  Ma- 
chine.— A  name  given  to  long  flashing 
sparks  at  the  commutator  of  a  dynamo, 
due  to  the  short-circuiting  of  the  external 
circuit  at  the  commutator. 

Flashing  Process  for  Carbon  Fila- 
ments.— A  process  for  improving  the 
electrical  homogeneity  of  carbon  fila- 
ments by  the  deposit  of  carbon  in  their 
pores  and  over  their  surfaces,  by  exposing 
the  filaments  to  a  gradually  increasing 
electrical  incandescence,  while  surround- 
ed by  a  carbonaceous  gas  or  liquid. 

Flat  Board.  —  A  multiple  telephone- 
switchboard  whose  surface  lies  in  a  hor- 
izontal plane,  as  distinguished  from  a 
vertical  board. 

Flat  Cable. — A  cable  the  separate  con- 
ductors of  which  are  laid  up  side-by-side, 
so  as  to  form  a  flat-conductor. 

Flat  Commutator-Segment.  —  A  com- 
mutator segment  that  has,  through  wear 
or  otherwise,  acquired  a  flat  surface. 

Flat  Duplex-Cable. — A  flat  cable  con- 
taining two  separate  conductors  which 
are  laid  up  side-by-side. 

Flat-Iron,  Electric.  —  An  electrically 
heated  flat-iron. 

Flat-Ring  Armature.  —  An  armature 
whose  core  has  the  shape  of  a  short  cylin- 
drical ring. 

Flats. — Those  parts  of  commutator  seg- 
ments, the  surfaces  of  which,  through  wear 
or  otherwise,  have  become  lower  than  the 
other  portions. 

Fleeting  Knife  of  Cable  Gear.— The 
adjustable  guide  on  the  drum  of  a  cable 
machine,  which  leads  the  cable  to  the  sur- 
face of  the  drum. 

Flexible. — Capable  of  being  readily  flexed 
or  bent. 

Flexible  Cable.  —  A  stranded  cable,  of 
one  which  can  be  readily  flexed  or  bent. 


Fie.] 


783 


[Flu. 


Flexible  Conduit-System. — A  system 
of  conduits  for  underground  wires,  so 
constructed  that  the  conductors  or  cables 
it  is  to  cozitain  can  be  introduced  at  any 
time  after  its  completion. 

Flexible  Electric  Heater. — An  electric 
heater  made  of  flexible  material,  so  as  to 
permit  its  local  application  to  different 
parts  of  the  body. 

Flexible  Electric-Light  Pendant. — 
A  pendant  for  an  incandescent  lamp, 
formed  by  its  flexible  supporting  conduc- 
tors. 

Flexible  Lamp-Cord.— (1)  A  flexible  cord 
provided  for  supporting  an  incandescent 
lamp.  (2)  A  flexible  cord  maintaining 
electric  connection  with  a  semi-portable 
incandescent  lamp. 

Flexible  Lead. — A  conductor  that  is 
stranded  for  the  purpose  of  obtaining 
flexibility. 

Flexible  Twin-Lead. — A  lead  containing 
two  separate  parallel  stranded  conduc- 
tors. 

Float  Dynamometer. — A  dynamometer 
for  measuring  the  mechanical  activity  of 
a  dynamo  or  motor  in  which  the  machine 
is  supported  in  a  floating  cradle  and  con- 
nected to  its  driver  or  load  through  a  flex- 
ible coupling. 

Floor-Contact.— A  contact  placed  on  the 
floor  and  arranged  so  as  to  be  readily 
operated  by  the  foot. 

Floor  Push.— A  form  of  floor  contact. 

Flow. — (1)  The  quantity  of  liquid  escaping 
from  an  orifice  in  a  given  time.  (2)  The 
quantity  of  a  fluid  that  flows  past  a  given 
point  in  a  given  time. 

Flow,  Electric.— Electric  current. 

Flow  of  Energy.— The  transmission  of 
energy  through  the  medium  or  dielectric 
surrounding  a  conductor,  now  regarded 
as  causing  the  current  of  electricity  which 
was  formerly  assumed  to  flow  through 
the  conductor. 

Flow  Of  Electrostatic  Flux.— The  trans- 
ference of  electrostatic  flux  which  con- 
stitutes, in  reality,  the  so-called  flow  of 
electric  current  through  a  conductor. 

Flow  of  Heat.— The  quantity  of  heat 
which  passes  through  a  thermal  conductor 
when  subjected  to  a  certain  difference  of 
temperature. 

Flow  of  Magnetic  Flux.— (1)  The  quan- 
tityof  magnetic  flux  which  passes  through 
any  magnetic  circuit,  under  a  given  mag- 
neto-motive force,  against  a  given  mag- 
netic reluctance.  (2)  The  time-rate  of 
change  of  magnetic  flux  through  a  mag- 
netic circuit. 


Flow   of    Magnetic    Induction.— The 

transmission  of  magnetic  flux  from  one 
point  of  a  magnetic  circuit  to  another. 
Fluctuating  Electromotive  Force  or 
Current. —  An  electromotive  force  or 
current  which  varies  periodically  in  mag- 
nitude. 

Fluid. — (1)  Any  substance  which  readily 
flows.  (2)  A  liquid  or  a  gaseous  sub- 
stance. 

Fluid  Depolarizer.— A  fluid  substance 
employed  in  a  voltaic  cell  as  a  depolar- 
izer. 

Fluid,  Electric. — Either  of  the  assumed 
fluids  which  were  formerly  believed  to  be 
the  cause  of  electric  excitement. 

Fluid  Insulator. — An  oil  insulator. 

Fluidity. — Possessing  the  properties  of 
fluids. 

Fluorimeter. — A  fluoroscope. 

Fluoresce. — To  become  luminous  when 
exposed  to  radiant  energy. 

Fluorescence. — The  property  possessed 
by  certain  solid  and  liquid  substances  of 
becoming  luminous  when  exposed  to 
radiant  energy. 

Fluorescent. — Possessing  the  capability 
of  fluorescing. 

Fluorescent  Screen. — A  screen  covered 
with  fluorescent  materials. 

Fluorescing. — Emitting  fluorescent  light. 

Fluorograph,  Electric. — A  visible  X-ray 

picture  obtained  on  a  fluorescent  screen. 

Fluoroscopic  Examination. — An  X-ray 
examination  of  the  human  body  by  means 
of  a  fluorescent  screen. 

Fluoroscopic  Screen. — A  screen  covered 
with  fluorescent  material,  and  used  in 
connection  with  the  X-rays  for  fluoro- 
scopic  examination. 

Fluoroscopy. — The  art  of  examining  the 
body  by  X-rays  in  connection  with  a 
fluoroscopic  screen. 

Flush. Box. — A  box  or  space,  flush  with 
the  surface  of  a  roadbed,  provided,  in  a 
system  of  underground  wires  or  conduits, 
to  facilitate  the  introduction  of  a  con- 
ductor into  the  conduit,  or  the  examina- 
tions of  the  conductors. 

Flush  Key-Switch.— A  key  switch  that 
is  flush  with,  or  does  not  project  beyond, 
the  surface  of  the  wall  in  which  it  is 
placed. 

Flush  of  Current  of  Arc-Lamp.— The 
current  that  flows  into  an  arc-lamp  on 
starting,  and  which  greatly  exceeds  in 
strength  that  which  flows  after  the 
normal  arc  has  been  established. 


.Flu.] 


784 


[Foo. 


Plush  Plate. — A  plate  on  which  flush 
push-buttons  are  mounted. 

Plush  Push. — A  push  the  upper  surface 
of  whose  button  or  buttons  are  flush 
with  the  surface  of  the  wall  or  plate  in 
which  it  is  placed. 

Plush  Switch. — Any  switch  sunk  in  a 
wall,  so  that  its  plane  outer  surface  is 
flush  with  the  surface  of  the  wall. 

Fluviograph,  Electric. — An  apparatus 
for  electrically  registering  the  varying 
height  of  water  in  a  tidal  stream,  or  in 
the  ocean,  or,  in  general,  for  any  differ- 
ences of  water  level. 

Flux. — (1)  Magnetic  or  electric  flux.  (2)  A 
surface  integral  of  a  vector  quantity. 

Plux  Density. — The  quantity  of  magnetic 
flux  per  unit  of  area  of  normal  cross- 
section. 

Plux  Density  per-Square-Centimetre 
or  per-Square-Inch. — The  quantity  of 
magnetic  flux  passing  through  a  circuit 
per  square  inch  or  square  centimetre  of 
area  of  normal  cross-section. 

Plux  of  Displacement. — The  surface  in- 
tegral of  electric  displacement  passing 
through  a  closed  curve. 

Plux,  Electric. — Electrostatic  flux. 

Plux  Horn. — A  term  proposed  for  the 
leading  horn  or  polar  edge  of  a  generator 
which  supplies  the  magnetic  flux  neces- 
sary for  reversing  the  current  in  the 
armature  coil  under  commutation. 

Plux  Intensity. — (1)  The  density  of  a 
flux.  (2)  The  surface  density  of  a  vector 
quantity  at  a  point. 

Plux  Leakage. — Any  failure  of  flux  to 
pass  through  its  proper  receptive  device. 

Plux  Lines  of  Electrostatic  Force.— 
The  lines  or  paths  traversed  by  electro- 
static force. 

Plux  of  Heat. — The  flow  of  heat  per  unit 
of  time  through  a  given  area. 

Plux  of  Light.— (1)  The  total  quantity  of 
light  emitted  through  a  given  area  by  a 
luminous  source.  (2)  The  total  quantity 
of  light  emitted  from  a  point  source. 

Plux  of  Magnetic  Induction. — The  flow 
of  magnetic  induction. 

Plux  of  Magnetism. — (1)  The  flow  of 
magnetic  induction.  (2)  The  surface  in- 
tegral of  magnetic  induction  through  a 
given  surface. 

Plux  Oscillations. — Oscillations  in  the 
intensity  of  electrostatic  or  of  magnetic 
flux. 

Plux  Phase. — The  phase  of  a  simple-har- 
monic magnetic  flux. 


Ply  or  Flyer,  Electric.— A  light  wire 
wheel  provided  with  pointed  radial  arms, 
which  is  set  into  rapid  rotation  by  the 
escape  of  convection  streams  from  its 
points,  when  connected  with  a  charged 
body. 

Plying  Break  of  Armature  Conductor. 
A  discontinuity  in  an  armature  wire  that 
can  only  be  detected  when  the  armature 
is  rotating,  owing  to  the  influence  of 
centrifgual  force. 

Plying  Soundings. — Approximate  sound- 
ings, in  depths  not  exceeding  two  hundred 
fathoms,  obtained  without  decreasing  the 
speed  of  the  ship  below  five  or  six  knots 
per  hour. 

Pocal  Length. — (1)  The  distance  of  a  focus 
from  a  lens.  (2)  When  not  otherwise 
specified,  the  principal  focal  length  of  a 
lens  or  mirror.  (3)  The  distance  from 
the  optical  centre  of  a  mirror  or  lens  at 
which  parallel  rays  are  brought  to  a 
focus. 

Pocometer. — An  apparatus  for  readily  de- 
termining the  focus  of  a  lens  or  optical 
combination. 

Focus. — A  point  before  or  back  of  a  mir- 
ror or  lens,  where  all  the  rays  of  light 
coming  from  the  lens  or  mirror  either 
meet,  or  seem  to  meet. 

Focusing. — Altering  the  distance  between 
an  object,  and  a  lens  or  mirror,  in  order 
to  obtain  a  sharp  image  of  the  object. 

Focusing  Arc-Lamp. — An  arc-lamp  de- 
signed for  use  in  connection  witli  a  re- 
flector or  lens,  whose  mechanism  feeds 
both  carbons,  and  so  permits  the  arc  to 
be  maintained  at  the  focus  of  the  reflector 
or  lens. 

Fog,  Electric. — A  dense  fog  which  some- 
times occurs  when  there  is  an  unusually 
large  quantity  of  free  electricity  in  the 
atmosphere. 

Foiled  Conductor. — A  term  applied  to  a 
conductor  whose  insulating  coating  is 
covered  by  a  thin  coating  or  layer  of  tin 
foil  or  lead. 

Following  Edges  of  Pole-Pieces  of 
Motor. — Those  edges  of  the  pole-pieces  of 
a  motor  which  the  armature  is  leaving. 

Following  Horns  of  Pole-Pieces  or 
Dynamo. — Those  edges  or  terminals  of 
the  pole-pieces  of  a  dynamo  which  the 
armature  is  leaving. 

Foot-Candle. — A  unit  of  illumination 
equal  to  the  normal  illumination  pro- 
duced by  a  standard  candle  at  the  dis* 
tance  of  one  foot. 

Foot-Grain. — A  standard  for  comparing 
the  resistances  of  wires  at  a  given  tern- 


Too.] 


785 


[Foil. 


perature,  the  length  of  the  wire  being  one 
foot,  and  its  weight  one  grain. 

Foot-Pound.—  <1)  A  unit  of  work.  (2)  The 
amount  of  work  required  to  raise  one 
pound  vertically  through  a  distance  of  a 
foot. 

Foot-Pound-per-Second.-^-{l)  A  unit  of 
activity.  (2)  A  rate-of  -doing-work  equal 
to  the  expenditure  of  one  foot-pound  per 
second. 

Foot-Switch.  —  A  switch  capable  of  being 

readily  operated  by  the  foot. 
Force.  —  Anything  which  changes  or  tends 

to  change  the  condition  of  rest  or  motion 

in  a  body. 

Force,  Electric.  —  The  force  exerted  be- 
tween electrostatic  charges. 

Force  of  Field.  —  The  force  in  a  magnetic 
or  electric  field  independent  of  the  im- 
pressed magnetic  or  electric  force. 

Force  of  Flux.  —  The  total  magnetic  or 
electric  force  in  a  magnetic  or  electric 
field,  as  distinguished  from  the  impressed 
magnetic  or  electric  forces  or  from  the 
force  of  a  field. 

Force  Pump.—  A  pump  provided  with  a 
solid  piston,  and  employed  for  raising 
liquids  through  greater  vertical  heights 
than  that  through  which  such  liquids 
could  be  raised  directly  by  atmospheric 
pressure. 

Forced  Electromagnetic  Vibrations. 

Electro-magnetic  vibrations  that  are  set 
up  in  a  system  independently  of  its  elec- 
tro-magnetic dimensions. 

Forced  Vibrations.  —  A  term  employed 
for  vibrations  set  up  in  a  body  independ- 
ently of  its  nature  and  form,  and  other 
than  the  free  vibrations  which  the  body 
would  acquire,  if  disturbed  and  then  left 
to  itself. 

Forge,  Electric.  —  A  forge  in  which  the 
metal  to  be  operated  on  is  electrically 
heated. 


for  Trolley  Wheel.—  The  mechan- 
ism which  connects  the  trolley  wheel  to 
the  trolley  pole. 

Forked  Circuits.—  (1)A  term  used  in  teleg- 
raphy for  a  number  of  circuits  that  ra- 
diate from  a  given  central  point.  (2)  In 
telegraphy,  a  circuit  which  divides  into 
two  branches,  thus  connecting  three  ter- 
minal stations. 

Forked  Lightning.—  A  variety  of  light- 
ning flash,  in  which  the  discharge,  on 
meeting  the  earth  or  other  object,  divides 
into  two  or  more  branches. 

Form  Factor  of  Alternating-Current 
Curve.  —  A  factor  equal  to  the  square 
50 


root  of  the  mean  square  divided  by  the  true 
mean  value  of  the  alternating  electro- 
motive force  or  current. 

Formal  Inductance  of  Circuit.— That 
part  of  the  counter-electromotive  force  of 
a  circuit  which  depends  on  the  form  of 
the  circuit. 

Formed  Armature- Windings. — Arma- 
ture coils  that  are  wrapped  on  a  suitable 
form  and  afterwards  placed  on  the  arma- 
ture core. 

Formed  Plates  of  Secondary  Cell. — 
Plates  that  have  been  submitted  to  the 
forming  process. 

Formers. — The  forms  employed  in  obtain- 
ing formed  armature  or  other  windings. 

Forming  Block.— A  block  for  holding  the 
jack  connections  of  a  set  or  row  in  a  mul- 
tiple telephone  switchboard,  for  conveni- 
ence in  soldering  their  contacts  with  cable 
conductors,  before  inserting  the  set  in  the 
switchboard  panel. 

Forming  Storage  -  Battery  Plates.— 
Obtaining  thick  coatings  of  peroxide  of 
lead  and  of  spongy  lead  respectively,  on 
the  lead  plates  of  a  storage  battery,  by 
repeatedly  sending  the  charging  current 
between  them  in  alternately  opposite 
directions,  while  immersed  in  dilute  sul- 
phuric acid. 

Formulae. — Mathematical  expressions  for 
some  general  law,  rule,  or  principle. 

Forward  Induction. — An  induction  in 
the  field  of  a  motor  or  dynamo,  in  which 
the  current  in  the  armature  coils  produces 
an  induction  which  assists  the  field,  in 
centra-distinction  to  the  back  induction, 
which  opposes  the  field. 

Forward  Lead  of  Dynamo  Brushes. — 
A  displacement  of  the  brushes  on  the 
commutator  of  a  dynamo  in  the  direction 
of  rotation  of  the  armature. 

Forward  Pitch  of  Armature  Winding. 
A  pitch  which  is  always  directed  right- 
handedly,  or  clockwise,  when  viewed  from 
the  commutator  side. 

Forward  Waves. — In  a  closed-current 
circuit  supplied  by  a  dynamo  giving  a 
harmonic-alternating  electromotive  force, 
the  wave  of  induced  potential  that  is  as- 
sumed to  travel  through  the  circuit,  from 
the  positive  pole  of  the  dynamo  to  its 
negative  pole. 

Foucault  Currents. — (1)  A  name  some- 
times applied  to  eddy  currents,  especially 
when  in  armature  cores.  (2)  Useless  cur- 
rents developed  in  a  conducting  mass, 
through  which  varying  magnetic  flux  is 
moving. 


Fou.] 


786 


[Fre. 


Foucault  Losses.— Losses  of  energy  in  a 
dynamo  or  motor,  due  to  Foucault  cur- 
rents. 

Foundation  Trench. — A  trench  dug  to 
receive  the  masonry  employed  in  a  foun- 
dation. 

Fountain,  Electric. — A  fountain  oper- 
ated by  electric  motors,  provided  with  a 
variety  of  jets  that  are  electrically  illu- 
mined by  different  colored  lights. 

Fountain  Projector. — An  arc-light  pro- 
jector employed  in  illumining  the  jets  of 
an  electric  fountain. 

Four-Conductor  Cord.— A  flexible  oord 
containing  four  separate  insulated  con- 
ductors. 

Four-Pole  Switch.— (1)  A  switch  em- 
ployed for  making  or  breaking  four  con- 
tacts. (2)  A  switch  employed  to  open  or 
close  a  pair  of  diphase  circuits.  (3)  A 
double  double-pole  switch  for  diphase  cir- 
cuits, one  double-pole  switch  being  pro- 
vided for  each  circuit. 

Fourier's  Series. — A  series  of  sines  or  of 
cosines  of  multiple  arcs. 

Four-Piece  Electro-Magnet.— An  elec- 
tro-magnet -constructed  in  four  pieces  ; 
namely,  two  cores,  a  yoke  and  an  arma- 
ture. 

Four-Point  Switch.— (1)  A  switch  whose 
circuit  can  be  completed  through  four 
points,  either  singly,  or  simultaneously. 
(2)  A  four-pole  switch. 

Four-Pole  Dynamo-Electric  Machine. 
A  dynamo-electric  machine  whose  mag- 
netic field  is  produced  by  four  magnet 
poles. 

Four-Speed  Regulator. — A  regulator 
provided  with  a  motor  by  which  four  dif- 
ferent speeds  can  be  obtained. 

Four- Way  Splice-Box.— A  splice-box 
provided  with  four  ways  or  tubular  con- 
duits. 

Four- Way  Switch. — A  four-point  switch. 

Four  -  Wire  Diphase  -  Circuit.  —  A  di- 
phase circuit,  employing  four  wires  in 
contradistinction  to  a  three-wire  diphase 
circuit. 

Four- Wire  System. — A  system  similar 
in  its  general  arrangement  to  the  three- 
wire  system,  in  which  three  dynamos  are 
connected  to  four  wires  or  conductors. 

Four- Wire  Transmission. — A  system  of 
electric  transmission  employing  four  con- 
ductors. 

Fourth  State  or  Condition  of  Matter. 
The  ultra-gaseous  or  radiant  condition  of 
matter 


Fractional  Distillation.— (1)  A  method 
adopted  for  the  separation  of  two  or  more 
liquids  in  solution,  by  first  raising  the 
liquid  to  the  boiling  point  of  the  most 
volatile  liquid,  and  retaining  that  temper- 
ature until  all  that  liquid  is  evaporated, 
and  then  raising  the  temperature  to  that 
of  the  next  most  volatile  liquid,  and  so  on 
throughout.  (2)  The  successive  separa- 
tion by  distillation  of  liquids  that  volatil- 
ize at  different  temperatures. 

Fractional  Electrolysis.  —  Successive 
electrolysis  of  different  substances  by 
gradually  raising  the  E.  M.  F. 

Fracture  of  Cable.  —A  parting  or  rupt- 
ure of  a  submarine  cable. 

Frame  of  Dynamo  or  Motor. — A  dy- 
namo or  motor  frame. 

Franklinic  Alternating  E.  M.  F.'s. — 
Alternating  -  electromotive  forces  ob- 
tained by  means  of  a  frictional  or  electro- 
static-induction machine. 

Franklinic  Currents. — The  currents  pro- 
duced by  a  frictional  or  electrostatic-in- 
duction machine. 

Franklinic  Electricity. — A  term  some- 
times employed  in  electro-therapeutics 
for  the  electricity  produced  by  a  frictional 
or  electrostatic-induction  machine.  ,  I 

Franklinism. — A  word  sometimes  em- 
ployed for  franklinization. 

Franklinization. — A  term  employed  in 
medical  electricity  for  electrization  by 
means  of  a  frictional  machine,  as  distin- 
guished from  faradization  or  electrization, 
by  means  of  an  induction-coil. 

Franklin's  Kite. — The  kite  employed  by 
Franklin  in  demonstrating  the  identity  of 
lightning  and  electricity. 

Fraunhofer's  Dark  Lines. — Spaces  in 
the  otherwise  continuous  spectrum  of  the 
sun  where  certain  frequencies  are  absent. 

Free  Charge. — The  condition  of  an  elec- 
tric charge  on  a  conductor  isolated  from 
other  conductors. 

Free  Ether. — A  term  sometimes  em- 
ployed for  the  ether  that  exists  in  the 
inter-planetary  spaces,  as  distinguished 
from  the  inter-molecular  or  inter-atomic 
ether. 

Free  Electricity. — (1)  In  the  old  double- 
fluid  hypothesis,  a  term  employed  for 
either  the  positive  or  the  negative 
electricity  when  it  is  freed  from  the  in- 
fluence of  the  other.  (2)  A  term  some- 
times employed  for  a  charge  on  an  insu- 
lated conductor  that  is  isolated  from 
other  conductors.  (3)  A  term  sometimes 
employed  for  the  electricity  contained  in 
a  free  charge. 


Fre.J 


787 


[Ful. 


Free  Insulated. — The  condition  of  a  tele- 
graph wire  when  it  is  disconnected  from 
its  apparatus  and  left  insulated. 

Free  Magnet  Pole^ — A  pole  in  a  piece  of 
iron  or  other  paramagnetic  substance 
which  acts  as  if  it  existed  as  one  magnetic 
pole  only. 

Free  Magnetism. — (1)  In  the  theory  of 
magnetic  matter,  magnetism  resident 
upon  the  polar  surface  of  a  magnet  and 
not  neutralized  by  opposite  polarity.  (2) 
That  portion  of  the  imaginary  magnetic 
matter  of  a  magnet  that  is  distributed 
over  the  surface  of  the  magnet. 

Free  Path. — That  path  of  a  gaseous  mol- 
ecule in  which  it  does  not  collide  or  strike 
against  another  molecule. 

Free  Vibrations. — Vibrations  dependent 
on  the  elasticity  and  shape  of  a  body  ac- 
quired when  the  body  is  acted  on  by  a 
disturbing  force  and  then  left  to  itself. 

Freezing. — Congealing  or  assuming  the 
solid  state  by  loss  of  heat. 

Freezing  Mixtures. — Various  mixtures, 
such  as  salt  and  ice,  which  melt  or  dis- 
solve on  being  mixed,  and  thus  absorb 
sensible  heat  from  themselves,  or  from 
surrounding  substances. 

Freezing  of  Shaft  in  Bearing. — The  fix- 
ing of  a  shaft  in  its  bearing  by  the  lique- 
fication  and  subsequent  cooling  of  its 
anti-friction  metal. 

Freezing  Point. — The  point  of  congela- 
tion of  a  liquid. 

French  Measures  and  Weights.  —  A 
system  of  measures  and  weights  em- 
ployed generally  in  physical  science, 
based  on  the  metre  as  the  unit  of  length, 
and  the  gramme  as  the  unit  of  weight. 

French  Standard  Candle. — The  bougie- 
decimale  or  the  twentieth  part  of  a  Violle. 

Frequency  of  Alternation.  —  (1)  The 
number  of  cycles  or  periods  executed  by 
an  alternating  current  in  unit  time. 
(2)  The  periodicity.  (3)  The  number  of 
alternations  or  half -cycles  executed  by  an 
alternating  current  in  a  second  or  in  a 
minute. 

Frequency  Setter. — In  an  alternating- 
current  circuit  having  induction  ma- 
chines, an  alternator  which  supplies  them 
with  a  definite  frequency. 

Frequency  Teller. — A  device  for  deter- 
mining the  frequency  of  an  alternating 
current. 

Friable. — Easily  crumbled  or  pulverized. 
Friction.— Resistance    to    the    sliding  or 
rolling  motion  of  one  body  over  another. 


Friction  Brake.  —  (1)  A  Prony  brake. 
(2)  Any  form  of  brake  dependent  for  its 
operation  on  friction. 

Fringe  of  Lines  of  Force. — A  term  some- 
times used  for  fringe  of  magnetic  field. 

Friction,  Electric. — A  term  sometimei 
employed  for  electric  resistance. 

Frictional  Electric  Machine. — A  ma- 
chine for  the  development  of  electricity 
by  friction. 

Frictional  Electricity. — The  electricity 
developed  by  friction. 

Frictional  Torque. — (1)  Torque  developed 
by  friction.  (2)  In  a  motor  the  torque 
necessary  to  exert  on  the  armature  in 
order  to  overcome  its  friction. 

Fringe  of  Magnetic  Field.— The  lateral 
extension  or  diffusion  of  magnetic  flux 
from  the  edge  of  a  pole  piece  whereby 
the  field  is  not  restricted  to  the  space 
covered  by  the  pole,  but  extends  with 
diminishing  intensity  to  a  greater  area. 

Frog. — (1)  A  metallic  guide  placed  on  one 
side  of  a  single  track,  where  a  car  has  to 
be  driven  from  one  track  to  another,  so  as 
to  guide  the  car  in  the  required  direction. 
(2)  A  grooved  piece  of  metal,  serving  as 
a  guide,  at  the  intersection  of  two  rails 
in  a  track-crossing.  (3)  A  trolley  frog. 

Front  Door  Pull. — A  circuit-closing  de- 
vice operated  by  a  pull  at  a  front. 

Front  Stop  of  Key. — A  stop  placed  on  the 
front  of  a  telegraphic  key  in  order  to  re- 
strict its  motion  in  a  downward  direction. 

Frost  Alarm. — An  electric  alarm  sounded 
or  set  in  operation  by  means  of  a  mechan- 
ism operated  by  a  fall  of  temperature  to 
or  below  the  freezing  point  of  water. 

Frying  of  Arc. — The  frying  sound  .that 
accompanies  a  voltaic  arc  when  the  car- 
bons are  too  near  together. 

Fulgurite. — A  tube  of  vitrified  sand  be- 
lieved to  be  formed  by  a  lightning  dis- 
charge into  the  ground. 

Full  Battery. — A  complete  battery  em- 
ployed in  the  quadruplex  system,  as  dis- 
tinguished from  a  reduced  battery. 

Full  Contact. — A  complete  contact.  . 

Full  Load.— (1)  An  entire  load.  (2)  The 
maximum  load  which  a  machine  is  de- 
signed to  carry  permanently. 

Full-Load  Current.  —  The  current  of 
maximum  load  of  a  source  or  station. 

Full-Load  Efficiency  of  Motor.— The 
efficiency  of  a  motor  when  operating  at 
full  load. 

Full-Load  Efficiency  of  Transformer. 
The  efficiency  of  a  transformer,  or  the 
ratio  of  the  power  yielded  at  secondary 


Ful.] 


788  [Gal. 


terminals  to  the  power  absorbed  at  pri- 
mary terminals,  when  operating  at  full 
load. 

Full  Metallic -Contact. — A  contact 
which,  from  its  small  resistance,  estab- 
lishes a  complete  connection. 

Fuller  Voltaic  Cell. — A  zinc-carbon  cou- 

Ele  immersed  in  a  solution  of  electropoion 
quid  and  provided  with  a  layer  of  mer- 
cury around  the  lower  part  of  the  zinc. 
Fulminate. — A  name  given  to  a  class  of 
highly  explosive  compounds. 

Fundamental  Frequency. — The  nominal 
or  lowest  frequency  of  a  complex  har- 
monic electromotive  force,  flux  or  current. 

Fundamental  Tone. — The  lowest  or  dom- 
inant tone,  or  that  on  which  the  pitch  of 
a  musical  note  is  dependent. 

Fundamental  Units. — (1)  The  units  of 
length,  time,  and  mass,  to  which  all  other 
quantities  can  be  referred.  (2)  Units  of 
length,  time,  and  mass,  as  distinguished 
from  their  derivations,  or  derived  units. 

Furnace,  Electric. — A  furnace  in  which 
electrically  generated  heat  is  employed 
for  effecting  difficult  fusions,  for  the 
extraction  of  metals  from  their  ores,  or 
for  other  metallurgical  operations. 

Fuse  Block. — A  block  containing  a  safety 
fuse  or  fuses. 

Fuse  Board. — A  board  of  slate,  or  other 
infusible  material,  on  which  the  safety 


fuses  in  a  given  installation  are  assem- 
bled. 

Fuse  Box. — (1)  A  box  containing  a  safety 

fuse.     (2)  A  box  containing  fuse  wires. 
Fuse  Carrier. — A  fuse  block. 

Fuse,  Electric.— (1)  A  device  for  elec- 
trically igniting  a  charge  of  powder,  by 
the  heat  generated  in  a  small  strip,  wire 
or  mass  of  poorly  conducting  material. 
(2)  A  safety  wire  or  catch. 

Fuse  Holder. — A  device  for  holding  or 
protecting  a  safety  fuse. 

Fuse  Links. — Strips  or  plates  of  fusible 
metal  in  the  form  of  links  employed  for 
safety  fuses. 

Fuse  Panel. — A  panel  in  a  switchboard 
provided  for  the  support  of  safety  fuses. 

Fuse  Ribbons,  Strips,  or  Wires.— Ma- 
terial for  safety  fuses  in  the  form  of  ru> 
bons,  strips,  or  wires. 

Fused  Electrolytic  Bath. — An  electroly- 
tic bath  in  which  the  electrolyte  is  main- 
tained in  a  state  of  fusion  during  elec- 
trolysis by  means  of  heat. 

Fusible  Arrester. — A  safety  catch. 

Fusible  Plug. — A  term  sometimes  applied 
to  a  safety  plug. 

Fusible  Protector.— A  safety  fuse  which 
acts  as  a  line  protector. 

Fusing  Current.— A  term  sometimes  ap- 
plied to  the  current  which  causes  a  fuse 
to  blow  or  melt. 


G 


g. — (1)  An  abbreviation  or  symbol  for  the 
gravitation  constant,  or  the  force  with 
which  the  earth  acts  upon  unit  mass  at  any 
locality.  (2)  An  abbreviation  proposed  for 
gramme,  the  unit  of  mass  in  physical  in- 
vestigations. 

g. — In  telegraphy,  an  abbreviation  for  "  go 
ahead." 

g.  cm2. — An  abbreviation  proposed  for  the 
gramme  centimetre-squared,  the  centi- 
metre-gramme-second unit  of  moment  of 
inertia. 

G.  M.  D. — A  contraction  for  geometrical 
mean  distance. 

G.  M.  T. — A  contraction  for  Greenwich 
mean  time,  the  standard  time  used  in 
submarine  telegraphy. 

G.  P. — A  contraction  for  gutta-percha. 

Gain  Plate  of  Copper  Voltameter.— The 
plate  of  a  copper  voltameter  that  increases 
in  weight  due  to  the  deposition  on  it  of 
metallic  copper. 


Gains. — The  spaces  cut  in  the  faces  of  tel- 
egraph poles  for  the  support  and  placing 
of  the  cross  arms. 

Galvanic  Adapter.  —  An  apparatus  for 
obtaining  from  an  electric  light  circuit 
feeble  continuous  currents  such  as  are 
used  in  electro-therapeutic  applications. 

Galvanic  Arc. — A  term  sometimes  used 
for  a  voltaic  arc.  (Not  in  general  use.) 

Galvanic  Battery. — An  unadvisable  term 
sometimes  used  in  place  of  voltaic  battery. 

Galvanic  Cabinet. — A  suitably  shaped 
box  provided  with  a  voltaic  battery  and 
all  the  accessories  necessary  for  its  use  in 
electro-therapy. 

Galvanic  Cautery. — A  term  sometimes 
used  in  place  of  electric  cautery. 

Galvanic  Cell. — A  name  sometimes  used 
in  place  of  voltaic  cell. 

Galvanic  Chain. — A  galvanic  circuit. 


Gal.] 


789 


[Gal. 


Galvanic  Circle. — A  term  sometimes  used 
for  galvanic  circuit. 

Galvanic  Circuit. — A  name  sometimes 
used  for  voltaic  circuit. 

Galvanic  Couple. — A  name  sometimes 
given  to  a  voltaic  couple. 

Galvanic  Dosage. — A  name  sometimes 
given  to  electro-therapeutic  dosage. 

Galvanic  Electricity. — A.n  unadvisable 
term  sometimes  used  in  place  of  voltaic 
eler  tricity. 

Galvanic  Etching. — A  term  sometimes 
used  for  electric  engraving. 

Galvanic  Excitability. — A  term  some- 
times used  for  electric  excitability  of  nerv- 
ous or  muscular  fibre. 

Galvanic  Induction. — A  term  sometimes 
used  for  voltaic  induction. 

Galvanic  Irritability.  —  Muscular  con- 
tractions produced  by  the  action  of  vol- 
taic currents. 

Galvanic  Multiplier. — A  term  formerly 
applied  to  a  galvanometer. 

Galvanic  Polarization. — A  term  some- 
times applied  to  the  polarization  of  a  vol- 
taic cell. 

Galvanic  Ring. — A  term  sometimes  ap- 
plied to  a  voltaic  circuit. 

Galvanic  Taste. — The  sensation  of  taste 
produced  when  a  voltaic  current  is  passed 
through  the  tongue. 

Galvanism. — An  inelegant  term  some- 
times employed  to  express  the  effects  pro- 
duced by  voltaic  electricity. 

Galvanist. — One  skilled  in  the  art  of  gal- 
vanism. (Obsolete.) 

Galvanized.— (1)  Subjected  to  the  influ- 
ence of  galvanism.  (2)  Covered  with  a 
coating  of  zinc  by  immersion  in  a  bath  of 
molten  zinc. 

Galvanized  Iron. — Iron  coated  with  zinc. 

Galvanized  Iron  Wire. — A  zinc-coated 
iron  wire. 

Galvanizing. — (1)  Covering  iron  with  an 
adherent  coating  of  zinc  by  dipping  it 
in  a  bath  of  molten  metal.  (2)  Subject- 
ing a  nerve  or  muscle  to  the  action  of  gal- 


Galvanizing  Wire. — Covering  wire  with 
a  coating  of  zinc  by  dipping  it  in  a  bath 
of  molten  metal. 

Galvano. — A  word  sometimes  used  in  place 
of  electro,  either  for  an  electro-type  or  for 
an  article  reproduced  in  copper  by  electro- 
metallurgy. 

Galvano-Caustic  Loop. — (1)  A  loop  of 
platinum  wire  suitably  supported,  so  as  to 
be  shortened  at  will,  and  employed  for  re- 


moving diseased  growths  by  drawing  it, 
while  heated  to  electric  incandescence, 
through  the  parts  to  be  removed.  (2)  An 
electric  cautery. 

Galvano-Caustics. — A  term  sometimes 
employed  for  the  destruction  of  diseased 
tissues  by  electrolysis. 

Galvano-Causty. — A  term  sometimes  em- 
ployed for  galvano-cautery. 

Galvano-Cautery. — An  electric  cautery. 
Galvano-Electric  Cautery. — An  electric 
cautery. 

Galvano-Faradization. — (1)  In  electro- 
therapeutics, the  simultaneous  excitation 
of  a  nerve  or  muscle,  by  both  a  voltaic  and 
a  faradic  current.  (2)  A  pulsating,  con- 
tinuous current. 

Galvanoglyphy. — A  word  proposed  for 
the  process  of  producing  an  electro-type. 
(Not  in  use.) 

Galvanography . — The  process  of  building 
up  a  picture  in  colored  varnish,  whose 
varying  thickness  gives  the  necessary  gra- 
dations of  light  and  shade  ;  subsequently 
black-leading  the  picture,  and  depositing 
a  layer  of  copper  by  electro-plating,  and 
employing  the  finished  picture  as  an  en- 
graved plate  for  printing. 

Galvano-Magnet. —  A  word  sometimes 
used  for  electro-magnet.  (Not  in  use.) 

Galvano-Magnetic. — A  word  proposed 
for  electro-magnetic.  (Not  in  use.) 

Galvano-Magnetism. — A  word  proposed 
for  electro-magnetism.  (Not  in  use.) 

Galvanometer. — (1)  An  apparatus  for 
measuring  the  strength  of  an  electric 
current  by  the  deflection  of  a  magnetic 
needle.  (2)  A  current  measurer. 

Galvanometer  Constant. — (1)  The  con- 
stant of  calibration  of  the  galvanometer 
scale.  (2)  The  numerical  factor  connect- 
ing a  current  passing  through  a  galvan- 
ometer with  the  deflection  produced  by 
such  current.  (3)  The  value  of  one  divi- 
sion of  the  galvanometer  scale  in  terms  of 
resistance  or  current  strength. 

Galvanometer  Shunt. — A  shunt  placed 
around  a  sensitive  galvanometer  in  order 
to  protect  it  from  the  effects  of  a  strong 
current,  or  for  reducing  its  sensibility. 

Galvanometer  Switch. — A  switch  em- 
ployed with  a  dynamo  balance-galvan- 
ometer. 

Galvanometer  Voltmeter. — Any  form 
of  galvanometer  arranged  so  as  to  readily 
measure  a  difference  of  potential. 

Galvanometric. — Of  or  pertaining  to  a 
galvanometer. 


Gal.] 


790 


[Gea. 


Galvanometrical. — Of  or  pertaining  to  a 
gal  vanometer. 

Galvanometrically.— In  the  manner  of  a 
galvanometer. 

Galvanometry . — The  determination  of  the 
current  strength  by  means  of  a  galvan- 
ometer. 

Galvano-Plastic  Adhesion. —  Adhesion 
to  surfaces  produced  by  a  galvano-plastic 
deposit  between  them. 

Galvano-Plastic  Bath. — A  plating  bath. 

Galvano-Plastic  Matrix. — A  mould  in 
which  a  galvano-plastic  deposit  is  made. 

Galvano-Plastic  Soldering.  —  Uniting 
two  metallic  surfaces  by  a  metallurgical 
deposit. 

Galvano-Plastics. — (1)  A  term  some- 
times employed  for  eleotrotyping,  or  for 
producing  an  electrolytic  deposit  suffi- 
ciently thick  to  permit  of  its  ready  sep- 
aration from  the  object  on  which  it  has 
been  deposited.  (2)  Literally,  the  cold 
moulding  or  shaping  of  metals  by  electro- 
typing. 

Galvano-Plasty. — Galvano-plastics. 

Galvano-Puncture. — A  term  sometimes 
used  for  electro-puncture. 

Galvanoscope. — (1)  A  galvanometer  in- 
tended to  show  the  existence  of  a  current 
rather  than  to  measure  its  strength.  (1) 
A  crude  or  simple  form  of  galvanometer. 

Galvanoscopic  Prog. — The  hind  legs  of 
a  recently  killed  frog,  employed  as  an 
electroscope  or  galvanoscope,  by  sending 
electric  currents  from  the  nerves  to  the 
muscles. 

Galvano-Therapeutics. —  An  objection- 
able term  sometimes  employed  for  elec- 
tro-therapeutics. 

Galvano-Thermal  Cautery—  A  term 
sometimes  used  for  electric  cautery. 

GalvanotomiS. — A  term  proposed  for  the 
state  of  tetanus  produced  in  a  muscle 
that  has  been  over-stimulated  electrically. 

Galvanotropism. — Movements  produced 
in  living  organisms  by  the  passage  of 
electricity  through  them. 

Gap  Space. — The  air-gap  or  entrefer. 

Gap  Wire  Gauge. — A  form  of  wire  gauge 
in  which  a  gap  or  set  of  gaps  is  left  in  a 
plate  of  metal  which  may  be  bridged  or 
filled  by  the  wire  to  be  measured. 

Gas  Battery. — A  battery  formed  of  gas 
cells. 

Gas-Burner,  Electric. — An  electric  gas- 
burner  that  can  be  electrically  turned  on 
and  lighted,  or  electrically  lighted  after 
it  has  been  turned  on  by  hand. 


Gas  Cell. — A    voltaic  couple    formed    of 

metals  in  the  presence  of  gases  instead  of 

solids  as  usual. 
Gas  Engine. — An  engine  whose  motive 

power  is  derived  from  the  heat  of  burning 

gas. 

Gas-Flame  Photometric-Standard.— A 

gas-jet  photometer. 

Gas- Jet  Photometer. — A  photometer  in 
which  the  standard  of  light  is  a  gas  jet 
burning  with  or  without  a  diaphragm  at  a 
definite  height  under  standard  conditions 
of  volume  and  pressure. 

Gas-Lighting,  Electric.  —  The  electric 
ignition  of  a  gas  jet  from  a  distance. 

Gas-Lighting  Torch. — A  gas-lighting  ap- 
pliance, consisting  of  the  combination  of 
a  portable  voltaic  battery  and  a  spark 
coil. 

Gas  Polarization.  —  A  term  sometimes 
employed  for  that  form  of  polarization 
which  is  due  to  the  collection  of  hydrogen 
gas  on  the  negative  plate  of  a  voltaic 
cell. 

Gas  Voltameter. — A  voltameter  whose 
indications  are  based  on  the  volume  of 
gas  liberated  at  a  fixed  pressure  and 
temperature. 

Gassing. — The  evolution  of  gas  from  the 
plates  of  a  secondary  or  storage  battery. 

Gastroscope,  Electric.— An  electric  ap- 
paratus for  the  illumination  and  inspec- 
tion of  the  human  stomach. 

Gastroscopy. — The  examination  of  the 
stomach  by  the  gastroscope. 

Gauge,  Electric. — Any  form  of  portable 
galvanometer  suitable  for  ordinary  test- 
ing work. 

Gauss. — (1)  The  name  proposed  in  1894  by 
the  American  Institute  of  Electrical  En- 
gineers for  the  C.  G.  S.  unit  of  magnetic 
flux  density.  (2)  A  unit  o'f  intensity  of 
magnetic  flux,  equal  to  one  C.  G.  S.  unit 
of  magnetic  flux  per-square-centi metre  of 
area  of  normal  cross-section.  (3)  A  name 
proposed  for  the  C.  G.  S.  unit  of  magnetic 
potential  or  magnetomotive  force  by  the 
British  Association  in  1895. 

Gaussage. — (1)  The  value  of  the  magnetic 
intensity  in  gausses.  (2)  A  name  proposed 
for  the  value  of  the  M.  M.  F.  in  gausses. 

Gauze  Brushes  for  Dynamo  or  Motor. 

Dynamo  or  motor  brushes  formed  of  wire 

gauze,  or    of  bundles  of  parallel  plates 

of  thin  woven  wire. 
Gear  Clutch  Arc-Lamp. — An  arc-lamp 

provided  with  a  gear  clutch. 
Gearless  Car  Motor. — A   motor  whose 

speed  is  such  as  to  permit  it  to  be  con- 


Oei.] 


791 


[Glo. 


nected  directly,  without  intermediate 
gearing,  on  the  car-wheel  axle. 
Geissler  Mercurial  Pump. — A  mercurial 
air  pump  in  which  the  exhaustion  is  ob- 
tained by  the  aid  of  a  Torricellian  vac- 
uum. 

Geissler  Tubes.  —  Glass  tubes,  provided 
with  platinum  electrodes  passed  through 
and  fused  into  the  glass,  containing  the 
residual  atmospheres  of  gases  at  a  com- 
paratively low  vacuum,  either  with  or 
without  fluorescent  liquids,  or  solids,  or 
both,  employed  to  obtain  various  luminous 
effects  on  the  passage  of  electric  dis- 
charges. 

General  Alternating- Current  Trans- 
former.— Any  form  of  alternating-cur- 
rent apparatus  ift  which  secondary  cur- 
rents are  induced,  such  as  an  induction 
motor  or  induction  generator,  as  well  the 
ordinary  transformer. 

General  Faradization.  —  A  method  of 
employing  the  faradic  current  similar  to 
its  use  in  general  galvanization. 

General  Galvanization. — A  method  of 
employing  an  electric  current  therapeut- 
ically  by  the  use  of  electrodes  of  suffi- 
cient size  to  direct  the  current  practically 
through  the  entire  body. 

Generator. — A  dynamo-electric  machine. 
Generator    Ammeter.  —  An    ammeter 

measuring  the  total  current  output  of  a 

generator. 

Generator  Bus-Bars.  —  The  bus-bars 
which  receive  the  total  generated  pressure 
of  a  number  of  dynamos,  or  of  a  station. 

Generator  Panels  of  Switchboard.— 
That  panel  or  set  of  panels  of  a  central- 
station  switchboard  which  contains  the 
generator  bus-bars,  and  supports  the  gen- 
erator ammeters  voltmeters  and  switches. 

Generator  Switch. — A  switch  provided 
for  the  purpose  of  connecting  or  discon- 
necting a  generator  from  the  bus-bars. 

Generator  Unit. — (1)  A  dynamo-electric 
generator  in  a  central  station.  (2)  One 
of  a  number  of  independent  generating 
machines  in  a  central  station. 

Generator  Voltmeter. — A  voltmeter  con- 
nected with  the  circuit  of  a  generator, 
and  employed  to  measure  its  pressure. 

Geographical  Equator.— The  great  circle 
of  the  earth  midway  between  its  poles. 

Geographical   Meridian.  —  Any   great 

circle  of  the  earth  passing  through  its 

poles. 
Geomantic  Lines  of  Force. — the  lines 

of  the  earth's  magnetic  force.    (Not  in 

general  use.) 


German-Silver  Alloy.  —  An  alloy,  em- 
ployed for  the  wires  of  resistance  coils, 
usually  consisting  of  fifty  parts  of  copper, 
twenty-five  of  zinc  and  twenty-five  of 

.  nickel. 

Gig,  Electric.— An  electrically  propelled 
gig- 

Gilb. — A  name  proposed  for  the  gilbert. 

Gilbert. — (1)  A  name  proposed  for  the  C. 
G.  S.  unit  of  magnetomotive  force. 
(2)  A  unit  of  magnetomotive  force  equal 
to  that  produced  by  — j^  of  one  ampere- 
turn. 

Gilbertage.— The  value  of  the  magneto- 
motive force  of  a  circuit  expressed  in 
gilberts. 

Gilding,  Electric.— Electro-plating  with 
gold. 

Gilt  Plumbago.  —  Powdered  plumbago 
whose  conducting  power  for  electricity 
has  been  increased  by  electro-  plating  it 
with  gold,  used  for  rendering  non-con- 
ducting surfaces  electrically  conducting. 

Gimbals. — Concentric  rings  of  brass,  sus- 
pended on  pivots  in  a  compass  box,  on 
which  the  compass  is  so  supported,  as  to 
enable  it  to  remain  horizontal  notwith- 
standing the  movements  of  the  ship. 

Girder  Armature.  —  An  armature  with 
an  H — or  girder-shaped  core. 

Girder  Joint  for  Rail  Bond.— A  name 
given  to  a  joint  in  steel  rails  consisting  of 
two  side-clamped  girders  supporting  a  tee- 
bar  and  double  clamped. 

Glass-Bead  Hydrometer.— A  bead  areo- 
meter. 

Glass  Fuse. — A  fuse  contained  in  a  glass 
tube  with  metallic  ends. 

Glass  Screw  Insulator.  —  A  glass  in- 
sulator provided  with  an  inside  screw 
thread  for  attachment  to  the  insulator 
pin. 

Globe  Holder  for  Arc-Lamp.—  A  sup- 
port provided  for  holding  the  globe  of  an 
arc-lamp. 

Globe  Net  for  Arc-Lamp.— A  thin  wire 
netting  placed  on  the  outside  of  an  arc- 
light  globe. 

Globe  Strain  -  Insulators.  —  Insulators 
provided  for  the  support  of  the  strain 
wires  in  an  overhead  trolley  system. 

Globular  Lightning. — A  rare  form  of 
lightning  in  which  a  globe  of  fire  ap- 
pears quietly  floating  in  the  air  for  a 
while  and  then  explodes  with  great  vio- 
lence. 


Glo.] 


792 


[Gra. 


Globular  Spark.  —  An  experimentally 
produced  globular  discharge  obtained 
from  a  large  condenser. 

Glow  Discharge. — A  form  of  convective 
discharge. 

Glow  Illumination.—  (1)  A  term  pro- 
posed for  an  illumination  similar  to  that 
of  a  glow-worm  ;  that  is,  luminous  radia- 
tion unaccompanied  by  non-luminous 
radiation.  (2)  A  term  sometimes  used 
for  illumination  by  incandescent  electric 
lamps. 

Glow-Lamp,  Electric. — (1)  A  lamp  whose 
light  is  produced  by  glow  illumination. 
(2)  A  term  sometimes  used  for  incandes- 
cent lamps. 

Glow- Worm  Radiation. — (1)  The  radia- 
tion of  the  glow-worm  or  fire-fly.  (2)  Ra- 
diation that  is  practically  confined 
within  the  limits  of  the  visible  spectrum. 

Glowing  of  Electric  Conductor. — The- 
incandescence  of  an  electric  conductor. 

Glue-Pot,  Electric. — An  electrically  heat- 
ed glue-pot. 

Glyphography. — The  art  of  forming  an 
electro-type  block,  whose  impressions  will 
produce  relief  outlines  on  a  flat  sur- 
face, by  covering  a  flat  copper  plate 
with  a  suitable  insulating  material,  cut- 
ting through  the  same  until  the  copper  is 
exposed,  and  then  coating  the  surface 
with  plumbago  and  electro-plating. 

Gnomon,  Electric. — A  term  formerly  ap- 
plied to  a  variety  of  pith-ball  electro- 
meter. 

Gold  Bath. — An  electrolytic  bath  consist- 
ing of  a  readily  electrolyzable  solution  of 
a  gold  salt,  a  gold  plate  acting  as  the 
anode  and  placed  in  the  liquid  opposite 
the  object  to  be  electroplated,  which  forms 
the  cathode. 

Gold-Leaf  Electroscope. — An  electro- 
scope in  which  a  pair  of  leaves  of  beaten 
gold  is  employed  to  detect  the  presence 
of  an  electric  charge,  or  to  determine  its 
character,  whether  positive  or  negative. 

Gold-Plating. — Electroplating  with  gold. 
Gong   Signalling    for    Railroads.—  A 

system  of  railroad  signals  employing  a 

code  dependent  on  the  sounds  produced 

by  gongs. 
Good  Earth.— (1)  Total    or   dead-earth. 

(2)  An  earth  connection  whose  resistance 

is  negligibly  small. 

Goose-Neck  Double-Pull-Off.— An  in- 
sulator with  a  support  shaped  like  a  goose 
neck  provided  with  two  points  for  the 
attachment  of  the  strain  wires  and  em- 


ployed on  curves  to  hold  the  trolley  wire 
in  position. 

Goose  -  Neck  Pull  -  Off. — An  insulator, 
with  a  support  shaped  like  a  goose  neck, 
employed  on  curves  to  hold  the  trolley 
wire  in  position,  and  provided  with  a 
single  point  for  the  attachment  of  the 
strain  wire. 

Governor,  Electric. — A  device  for  elec- 
trically controlling  the  speed  of  a  steam 
engine,  the  direction  of  a  current  in  a 
plating  bath,  the  speed  of  an  electric 
motor,  the  resistance  of  an  electric  cir- 
cuit, the  flow  of  a  liquid  or  gas  into  or 
from  a  containing  vessel,  or  for  other 
similar  purposes. 

Graded  Cyclic-Magnetization. — A  reg- 
ularly expanding  or  contracting  cylic 
magnetization . 

Graded  Winding  of  Galvanometer. — 
A  galvanometer  winding  composed  of 
more,  than  one  size  of  insulated  wire 
provided  with  a  view  to  increasing  the 
sensibility  of  the  galvanometer,  and  in 
which  the  finest  wire  is  placed  nearest 
the  axis  of  the  coil. 

Gradient. — (1)  The  increase  or  decrease  of 
an  elevation  or  quantity  with  reference  to 
some  constant  quantity.  (2)  The  space- 
rate-of -change  in  a  quantity. 

Gradient,  Electric. — (1)  The  rapidity  of 
increase  or  decrease  of  the  strength  of  an 
electromotive  force  or  current.  (2)  The 
vector  space-rate  of  descent  of  electric 
potential  at  any  point. 

Graduators. — Devices,  generally  electro- 
magnetic, employed  in  systems  of  simul- 
taneous telegraphic  and  telephonic  trans- 
mission over  the  same  wire,  so  inserted 
in  the  line  circuit  as  to  gradually  ob- 
tain the  makes  and  breaks  required  in  a 
system  of  telegraphic  communication, 
so  that  they  fail  sensibly  to  influence  the 
diaphragm  of  a  telephone  placed  in  the 
same  circuit. 

Gramme. — (1)  A  unit  of  mass  equal  to 
15.43235  grains.  (2)  The  mass  of  a  cubic 
centimetre  of  water  at  the  temperature 
of  its  maximum  density. 

Gramme  Armature  -  Winding.  —The 
winding  originally  employed  by  Gramme 
on  the  armature  of  his  dynamo-electric 
machine. 

Gramme  Atom.  —  Such  a  number  of 
grammes  of  any  elementary  substance 
as  is  numerically  equal  to  the  atomic 
weight  of  that  substance. 

Gramme-Calorie.  —  (1)  The  amount  of 
heat  required  to  raise  a  gramme  of  water 
one  degree  Centigrade.  (2)  The  gramme- 
degree-Centigrade. 


Gra.J 


793 


[Gro. 


Gramme  Equivalent. — Such  a  number 
of  grammes  of  any  substance  as  is  nu- 
merically equal  to  the  electro-chemical 
equivalent  of  that  substance. 

Gramme  Molecule. — A  weight  of  any 
substance,  taken  in  grammes,  numerical- 
ly equal  to  its  molecular  weight. 

Gramme-Ring  Transformer.  —  (1)  A 
transformer  whose  primary  and  secondary 
coils  are  placed  on  a  closed  iron  ring.  (2)  A 
transformer  resembling  a  Gramme-ring 
armature. 

Gramaphone. — An  apparatus  for  record- 
ing and  reproducing  articulate  speech. 

Gramaphone  Record. — A  record  of  ar- 
ticulate speech  obtained  by  means  of  a 
gramaphoue. 

Granular -Carbon  Telephone  -  Trans- 
mitter.— A  dust  telephone  transmitter. 

Granular  Telephone. — A  word  some- 
times used  for  a  granular  carbon  tele- 
phone transmitter. 

Graphite. — A  variety  of  soft  carbon  suit- 
able for  writing  on  paper  or  on  similar 
surfaces. 

Grapnel  Toes. — The  prongs  of  a  grapnel 
employed  in  grappling  for  a  submarine 
cable. 

Graphophone. — A  form  of  apparatus  for 
recording  and  reproducing  articulate 
speech. 

Graphophone  Record. — A  record  of  ar- 
ticulate speech  received  on  a  graph- 
ophone. 

Grappling. — Recovering  a  sunken  object, 
such  as  a  cable,  by  means  of  a  grapnel. 

Grapnel. — A  device  for  hooking  and  re- 
covering a  submerged  object,  such  as  a 
cable. 

Gratings. — A  plate  of  glass  or  metal  cov- 
ered with  closely-ruled,  parallel  lines, 
employed  for  obtaining  diffraction  spec- 
tra. 

Gravitation. — Mutual  attraction  produced 
between  two  masses  of  matter  by  the 
force  of  gravity. 

Gravity. — The  force  which  causes  masses 
of  matter  to  move  or  to  tend  to  move 
towards  one  another. 

Gravity  Ammeter. — A  form  of  ammeter 
in  which  the  magnetic  needle  is  moved 
against  the  force  of  gravity  by  the  mag- 
netic influence  of  the  current  it  is  measur- 
ing. 

Gravity  Annunciator-Drop. — An  an- 
nunciator drop  which  is  operated  by 
gravity  under  the  influence  of  an  electric 
current. 

10- 


Gravity-Drop  Annunciator. — An  a» 
nunciator  whose  signals  are  operated  by 
the  fall  of  a  drop. 

Gravity -Feed  Arc-Lamp. — An  arc-lamp 
in  which  the  upper  or  positi'*d  carbon  is 
fed,  or  permitted  to  drop  towards  the 
negative  carbon  under  the  influence  of 
gravity,  on  the  operation  of  the  feeding 
mechanism. 

Gravity  Needle-Drop. — A  needle  annun- 
ciator furnished  with  a  gravity  drop. 

Gravity  Voltaic  Cell. —A  blue-stone 
gravity  cell. 

Gravity  Voltmeter.— A  form  of  volt- 
meter in  which  the  potential  difference 
is  measured  by  the  movement -of  a  mag- 
netic needle  against  the  pull  of  a  weight. 

Grease-Spot  Photometer.— (1)  A  translu- 
cent-disc photometer.  (2)  A  Bunsen 
photometer. 

Greater  Calorie. — The  amount  of  heat 
required  to  raise  the  temperature  of  one 
kilogramme  of  water  from  0°  Centigrade 
to  1°  Centigrade. 

Green  Candle. — A  standard  candle  em- 
ployed  in  connection  with  a  screen  o! 
green  glass  in  order  more  readily  to  com- 
pare the  light  of  an  arc  with  that  of  a 
standard  candle. 

Grenet  Voltaic  Cell. — A  name  sometimes 
given  to  the  bichromate  cell. 

Grid  Indicator.— (1)  In  telephony,  £, 
clearing  indicator  in  which  the  armaturo 
is  painted  with  alternate  white  and  black 
horizontal  stripes  and  fronted  by  a  bras;? 
grid.  (2)  A  form  of  telephone  visual 
clearing  indicator. 

Grid. — (1)  A  lead  plate  provided  with  per- 
forations or  other  irregularities  of  sur- 
face, and  employed  in  storage  cells  for 
the  support  of  the  active  material. 
(2)  The  support  provided  for  the  active 
material  on  the  plate  of  a  secondary  or 
storage  cell. 

Grid  Plugs. — Plugs  of  active  material,  or 
of  material  that  is  readily  rendered  active 
by  a  charging  current,  inserted  in  the 
perforations  of  a  grid  for  the  purpose  of 
decreasing  the  time  required  for  the 
forming  of  the  plates  of  a  storage  cell. 

Grip  of  Belt.— The  hold  of  a  belt  on  the 
driving  pulley. 

Grothuss'  Hypothesis. — A  hypothesis 
proposed  to  account  for  the  electrolytic 
phenomena  that  occur  on  closing  the  cir- 
cuit of  a  voltaic  cell. 

Ground. — A  general  term  for  the  eaivh 

when  employed  as  a  return  conductor. 
Vol.  2 


•Gro.J 


794 


<3round  Circuit. — A  circuit  in  which  the 
ground  forms  part  of  the  path  through 
which  the  current  passes. 

Oround  Coil. — A  small  rheostat  employed 
in  duplex  telegraphy  at  the  home  station, 
for  the  purpose  of  obtaining  the  balance 
of  the  line  at  that  station. 

Ground  Detector.— ^{1)  In  a  system  of  in- 
candescent-lamp distribution,  a  device 
placed  in  a  central  station  for  indicating, 
by  the  brightness  of  a  lamp,  the  existence 
of  a  ground  on  the  system.  (2)  An  instru- 
ment for  detecting  or  measuring  grounds 
or  leaks. 

Ground  Indicator. — (1)  A  tell-tale  device 
employed  on  a  line  carrying  a  current,  to 
instantly  indicate  any  fault  in  the  insu- 
lation. (2)  An  apparatus  for  detecting  a 
loss  of  insulation. 

Ground  Plate  of  Lightning  Arrester. 
— That  plate  of  a  comb  lightning-arrester 
which  is  connected  to  the  ground  or  earth. 

ground-Return. — (1)  A  general  term 
used  to  indicate  the  use  of  the  ground  or 
earth  for  part  of  an  electric  circuit. 
(2)  The  earth  or  ground  which  forms  part 
of  the  return  path  of  an  electric  circuit. 

Ground  Shield  of  Transformer.— (1)  A 
metallic  plate  or  shield  in  a  transformer 
separating  the  primary  and  secondary 
coils  and  connected  to  ground  so  as  to 
protect  the  secondary  circuit  from  any 
possibility  of  becoming  crossed  with  the 
primary.  (2)  A  cylinder  of  slotted  copper 
placed  between  the  primary  and  secon- 
dary windings  of  a  transformer,  so  that 
there  can  be  no  accidental  contact  be- 
tween the  high  pressure  and  the  low  pres- 
sure circuits. 

Ground  Wire. — The  wire  or  conductor 
leading  to  6r  connected  with  the  ground 
or  earth  in  a  grounded  circuit. 

Grounded  Circuit. — A  circuit,  part  of 
whose  path  is  completed  through  the 
ground. 

Grounded  Dynamo. — A  dynamo  whose 
circuit  is  accidentally  or  intentionally 
grounded. 

Grounding. — (1)  A  word  sometimes  em- 
ployed in  electro-metallurgy  for  the  pre- 
paratory process  of  burnishing.  (2)  Con- 
necting a  circuit  to  earth  or  ground. 

Group  Incandescent  Switch. — A  switch 
which  governs  a  portion  or  group  of  the 
lamps  on  an  electrolier,  or  in  a  room. 

Grouping  System  for  Switchboard 
Circuits. — A  system  of  central-tele- 
phone-station distribution  in  which  the 
subscribers  are  divided  into  a  convenient 


number  of  groups,  and  each  group  given 
to  the  charge  of  a  single  operator. 

Growth  of  Lines  of  Force.— The  expan- 
sion of  lines  of  force. 

Grove's  Voltaic  Cell. — A  zinc-platinum 
couple  immersed  respectively  in  electro- 
lytes of  sulphuric  and  nitric  acid. 

Guard  Arm. — In  telegraphic  pole-setting, 
a  short  upright  secured  to  a  pole  croos- 
arm  so  as  to  catch  a  wire  should  it  become 
detached  from  the  pole. 

Guard  Ring  of  Electrometer  or  Con- 
denser.— A  conducting  ring  constructed 
to  form  the  annular  extension  of  a  plate 
or  disc  in  an  air-condenser,  for  the  purpose 
of  preventing  any  disturbance  of  electric 
flux-distribution  at  the  edge  of  such  disc 
or  plate. 

Guard  Suspension  Wire. — In  a  trolley 
system,  a  wire  supported  on  the  tops 
of  opposite  poles  for  the  suspension  of  a 
running  guard  wire,  or  guard- wires. 

Guard  Wire. — A  wire  hung  above  any 
active  conductor,  such  as  a  trolley  wire, 
in  order  to  prevent  it  from  coming  into 
electric  contact  with  falling  wires. 

Guard-Wire  Hanger. — A  hanger  em- 
ployed for  the  suspension  of  a  guard  wire. 

Gutta-Percha. — A  resinous  gum  obtained 
from  a  tropical  tree,  and  valuable  elec- 
trically for  its  high  insulating  powers  and 
for  its  indestructibility  when  employed 
in  submarine  cables. 

Gutter  of  Insulator. — A  channel  on  the 
side  of  an  insulator,  designed  to  carry  off 
the  rain  water. 

Guy. — A  rod,  chain,  rope  or  wire  employed 
for  supporting  or  stiffening  any  structure 
such  as  a  telegraph  pole. 

Guy-Rod  Bands. — Bands  by  which  a  guy- 
rod  is  fastened  to  a  pole. 

Guy  Rods. — Metallic  rods  employed  as 
guys. 

Guy  Rope. — A  rope  employed  as  a  guy. 
Guy    Stubs. — (1)   A  stub    or  anchor  to 

which  a  guy  is  secured.     (2)  The  stub  of 

a  pole  set  in  the  earth  at  an  angle  away 

from  the  pole  to  be  guyed. 
Guy  Wire. — A  wire  employed  as  a  guy. 
Guying. — Stiffening  by  means  of  guys. 
Guys. — Stays,  suitably  secured  to  a  posl  ->«• 

anchor,  for  the  purpose  of  steadying  *n 

overhead  wire  system. 
Gymnoticus    Electricus.— The   electric 

eel. 
Gyration. — The  act  of  turning  around  an 

axis. 
Gyrometer. — A  rotary  speed-indicator. 


Gyr.] 


795 


[Man. 


Gyroscope,  Electric.  —  A  gyroscope 
driven  by  an  electro-magnetic  motor. 

Gyrostat. — (1)  A  revolving  flywheel  de- 
signed to  display  gyrostatic  action.  (2)  A 
flywheel  possessing  considerable  moment 
of  inertia,  suitably  supported  on  pivots 
within  a  case,  so  as  to  permit  of  being 
carried  about,  and  employed  to  show  the 


resistance  which  rotating  bodies  offer  to 
changing  their  plane  of  rotation. 
Gyrostatic  Action  of  Dynamo  on  Ship- 
board.— The  action  which  occurs  at  the 
bearings  of  a  dynamo  running  on  board  a 
tossing  ship,  whereby  gyrostatic  stresses- 
are  produced. 


H 


H. — A  symbol  for  the  horizontal  intensity 
of  the  earth's  magnetism. 

H. — A  contraction  for  the  henry  or  practi- 
cal unit  of  self  induction. 

H. — A  contraction  for  the  magnetizing 
force  that  exists  at  any  point ;  or,  gen- 
erally, for  the  intensity  of  magnetic 
force. 

II . — A  symbol  for  field  intensity. 

3C. — A  symbol  proposed  for  magnetizing 
force.  (Partly  international  usage.) 

h. — An  abbreviation  for  hour,  a  practical 
unit  of  time. 

"H.  B."  Curves. — (1)  Curves  indicating 
the  relations  between  magnetizing  force 
and  magnetic  flux  density  in  a  magnetic 
substance.  (2)  A  term  sometimes  em- 
ployed for  magnetization  curves. 

H.P.  or  St. — A  contraction  for  horse- 
power. 

H.R. — A  contraction  for  high  resistance. 

H- Armature  Core.  —  (1)  An  armature 
core  in  the  shape  of  the  letter  H.  (2)  A 
girder,  shuttle,  or  I-armature. 

H-Poles. — In  telegraphy  a  pair  of  parallel 
vertical  poles  braced  together  to  form  one 
structure,  resembling  the  letter  H. 

Hsematocrit,  Electric. — An  electrically 
driven  device  for  separating  the  white 
blood  corpuscles  from  the  red  corpuscles 
by  centrifugal  force. 

Half-Deflection  Method.— A  method  of 
measuring  an  electromotive  force,  current 
or  resistance,  by  adjusting  the  circuit  in 
such  a  way  as  to  halve  the  galvanometer 
deflection. 

Half-Gate.— The  condition  of  a  turbine 
when  operating  with  the  gate  half  open. 

Half-Hoop  Magnet. — A  magnet  in  the 
form  of  a  semi-circle. 

Half-Load  Efficiency.— The  efficiency 
which  a  device  possesses  at  half  its  full 
load. 

Half-Shade  for  Incandescent  Lamp. — 
A  reflecting  shade  whose  outline  conforms 


to  that  of  the  lamp  chamber,  and  covers 
but  half  of  its  surface. 

Half- Wire  Guard  for  Incandescent 
Lamp. — A  wire  guard  which  covers  but 
half  of  an  incandescent  lamp. 

Hall  Effect. — A  transverse  electromotive 
force  produced  by  a  magnetic  field  in 
substances  undergoing  electric  displace- 
ment. 

Halleyan  Lines. — A  term  sometimes  used 
for  isogonal  lines. 

Halpine-Savage  Torpedo.— A  form  of 
torpedo  in  which  electricity  is  both  the 
propelling  and  the  directing  power,  and 
in  which  the  electric  source  furnishing 
the  propelling  current  is  contained  within 
the  torpedo. 

Hand-Brake  Mechanism. — A  car  brake 
operated  by  hand. 

Hand  Dynamo  Machines. — A  hand  gen- 
erator. 

Hand  Generator. — (1)  A  hand-driven  dy- 
namo. (2)  A  hand-driven  telephone  mag- 
neto generator. 

Hand-Hole  of  Conduit. — A  box  or  open- 
ing, communicating  with  an  underground 
cable,  provided  for  readily  tapping  the 
cable,  and  of  sufficient  size  to  permit  the 
introduction  of  the  hand. 

Hand-Lighting  Electric  Burner. —  A 
name  sometimes  applied  to  a  plain  pen- 
dant burner. 

Hand-Operated  Alarm. — Any  electric 
alarm  operated  by  hand,  as  distinguished 
from  an  automatically  operated  electric 
alarm. 

Hand  Regulation. — Any  regulation  of  a> 
dynamo  effected  by  the  hand,  in  contradis- 
tinction to  automatic  regulation,  such  as 
will  preserve  constant  either  the  current; 
or  the  potential. 

Hand  Regulator. — A  resistance  box, 
whose  separate  coils  can  be  readily  placed 
in  or  removed  from  the  circuit  by  means 
of  a  hand-operated  switch. 

Hand  Scratch-Brush. — A  scratch  brush. 


Han.] 


796 


[Hea. 


operated  by  hand,  as  distinguished  from 
one  operated  by  means  of  a  lathe. 
Hand-Signalling.  —  Telegraphic    signal- 
ling by  hand,  as  distinguished  from  auto- 
matic or  machine  signalling. 

Hand  Telegraphic  Transmission.  — 
Manual  telegraphic  transmission. 

Hand  Telephone. — (1)  A  telephone  re- 
ceiver held  in  the  hand,  as  distinguished 
from  a  head  telephone  receiver.  (2)  An 
ordinary  telephone  receiver. 

Hanger  Board. — A  form  of  board  provided 
for  the  ready  replacement  or  removal  of 
an  arc-lamp  from  a  circuit. 

Hanger  Cut-Out. — A  cut-out  switch  for 
an  arc  lamp  placed  under  a  hanger. 

Hard-Drawn  Copper  Wire.— <1)  Copper 
wire  that  is  hardened  by  being  drawn 
three  or  four  times  without  annealing. 
(2)  Copper  wire  not  annealed  after  leaving 
the  die. 

Hard  Porous  Cell. — A  hard-baked  porous 
cell,  whose  use  in  a  voltaic  cell  renders 
its  resistance  comparatively  high,  but 
which  is  better  able  to  stand  the  disinte- 
grating action  arising  from  the  crystalli- 
zation of  saline  substances  present  in  the 
battery. 

Hardening. — Increasing  the  hardness  of 
certain  metals  by  heating  them  to  a  high 
temperature  and  then  suddenly  cooling. 

Hardness. — That  property  of  a  body  in 
virtue  of  which  it  resists  scratching  or 
cutting. 

Harmonic  Analyzer. — (1)  A  device  for 
automatically  resolving  a  complex  har- 
monic into  its  simple-harmonic  com- 
ponents. (2)  A  harmonic  receiver.  (3)  A 
receiving  instrument  responding  to  a  sin- 
gle harmonic  frequency  and  which  selects 
that  frequency  from  a  complex-harmonic 
current. 

Harmonic  Capacity. — The  capacity  of  a 
condenser  to  a  charge  or  current  received 
from  a  harmonically  varying  E.  M.  F. 

Harmonic  Currents.— (1)  Periodically  al- 
ternating currents  varying  harmonically. 
(2)  Currents  which  are  harmonic  functions 
of  time.  (3)  Sinusoidal  currents. 

Harmonic  Electromotive  Forces.— 
(1)  Periodically  alternating  E.  M.  F.'s  vary- 
ing harmonically  ;  or  harmonic  functions 
of  time.  (2)  Sinusoidal  E.  M.  F.'s. 

Harmonic  Frequencies.  —  A  series  of 
frequencies  whose  values  are  integral 
multiples  of  the  frequency  of  their 
fundamental. 

Harmonic  Motion. — (1)  Simple-harmonic 
motion.  (2)  Simple-periodic  motion. 


Harmonic  Receiver.— (1)  The  receiver  em- 
ployed in  systems  of  harmonic  telegraphy, 
consisting  of  an  electro-magnetic  rod 
tuned  to  vibrate  to  a  single  note  or  rate 
only.  (2)  A  receiver  designed  to  respond 
to  a  single  harmonic  frequency  in  a  com- 
plex-harmonic current. 

Harmonic  Telegraph. — A  general  term 
embracing  the  apparatus  employed  in 
harmonic  telegraphy. 

Harmonic  Telegraphy.— (1)  A  system  for 
the  simultaneous  transmission  of  a  num- 
ber of  separate  and  distinct  musical 
sounds  over  a  single  wire,  employed  for 
simultaneously  transmitting  an  equal 
number  of  telegraphic  messages.  (2)  A 
system  of  telegraphy  employing  harmonic 
currents. 

Harmonic  Vibrations. — The  over-tones 
or  higher  vibrations  into  which  a  com- 
plex-periodic vibration  may  be  resolved. 

Harmonics. — The  higher  component  tones 
into  which  any  complex  tone  can  be  re- 
solved. 

Harmonics,  Electric.— Currents  of  higher 
frequencies  into  which  any  complex-har- 
monic current  may  be  resolved. 

Harmonics  of  Current. — The  harmonic 
currents  into  which  a  complex-harmonic 
current  may  be  resolved. 

Harmonics  of  Sound  Waves.— The  over- 
tones or  harmonics  into  which  any  com- 
plex tone  may  be  resolved. 

Harmonograph. — A  mechanical  device 
for  compounding  any  number  of  simple- 
harmonic  motions  of  different  amplitudes 
and  phases. 

Harness. — (1)  The  head  and  breast  equip- 
ment of  an  exchange  operator.  (2)  A  term 
used  by  telephonists. 

Harpoon,  Electric. — A  harpoon  contain- 
ing a  bomb  that  is  electrically  fired  or 
exploded  by  the  harpooner  after  the  im- 
bedding of  the  harpoon. 

Harveyizing. — A  method  of  superficially 
hardening  a  steel  plate. 

Haulage,  Electric.  —  Locomotion  of  a 
vessel  or  car  by  the  agency  of  electricity. 

Head  -  Bath,  Electric.  —  A  variety  of 
electric  breeze  applied  therapeutically  to 
the  head  of  a  patient. 

Head-Gear  Telephone.  —  A  telephone 
receiver  held  to  the  ear  by  means  of  a 
suitable  head  supporting-gear,  thus  leav- 
ing the  hands  of  the  operator  free. 

Head-Board  of  Dynamo. — An  insulating 
board  of  a  dynamo-electric  machine  for 
the  reception  of  terminals  or  switches. 

Head-Board  of  Motor. — A  switchboard 


Hea.] 


797 


[Hel. 


connected  with  a  motor  for  use  in  start- 
ing it. 

Head  Guy. — A  guy  attached  to  the  top  of 
a  pole. 

Head  Guying. — A  method  of  pole  guying 
for  checking  lateral  vibrations,  in  which 
the  top  of  each  pole  is  guyed  to  the 
bottom  of  the  next  succeeding  pole  for 
a  distance  of  several  poles. 

Head-Lamp. — An  electric  lamp  placed 
in  the  focus  of  a  reflector  supported  on 
the  head. 

Head-Light,  Electric. — An  electric  light 
placed  in  the  focus  of  a  parabolic  reflector 
in  front  of  an  engine  or  car. 

Head  of  Liquid. — (1)  The  vertical  distance 
from  the  level  of  a  liquid  in  a  containing 
vessel  to  the  centre  of  gravity  of  an  orifice 
placed  therein.  (2)  Difference  of  liquid 
elevation  or  level. 

Head  Receiver. — A  head-gear  telephone- 
receiver. 

Hearing  Tubes. — Tubes  connecting  a 
telephone  receiver  with  the  ears  of  the 
listener. 

Heat.— (1)  A  form  of  energy.  (2)  A  mode  of 
motion.  (3)  A  vibratory  motion  impressed 
on  the  molecules  of  matter  by  the  action 
of  any  form  of  energy.  (4)  A  wave  mo- 
tion impressed  on  the  universal  ether  by 
the  action  of  some  form  of  energy. 

Heat  Alarm. — A  temperature  alarm. 

Heat  Coil. — (1)  A  form  of  protector  for 
switchboards  or  receptive  apparatus  gen- 
erally, consisting  of  a  coil  of  fine  German 
silver  wire  wrapped  around  a  small  me- 
tallic plug,  held  in  its  place  by  a  drop  of 
readily  fusible  solder,  and  so  arranged 
that  on  the  melting  of  the  solder  a  spring 
is  permitted  to  act  so  as  to  dead-ground 
the  system.  (2)  A  form  of  sneak-current 
arrester. 

Heat,  Electric.— The  heat  developed  by 
the  passage  of  an  electric  current  through 
a  conductor. 

Heat  Insulator. — Any  non-conductor  of 
heat. 

Heat  Lightning.— A  variety  of  lightning 
flash  unaccompanied  by  audible  thunder, 
in  which  the  discharge  lights  up  the  sur- 
faces of  neighboring  clouds. 

Heat  Unit.— (1)  The  quantity  of  heat  re- 
quired to  raise  a  given  mass  of  water 
through  one  degree  of  the  thermometric 
scale.  (2)  The  calorie. 

Heat  Units.— Units  based  on  the  quantity 
of  heat  required  to  raise  a  given  mass  of 
a  substance,  generally  water,  through 
one  degree  of  the  thermometric  scale. 


Heater,  Electric. — A  device  for  the  con- 
version of  electricity  into  heat,  employed 
for  purposes  of  artificial  heating. 

Heating  Effects  of  Current.— The  heat 
generated  by  the  passage  of  an  electric 
current  through  any  circuit. 

Heavy  Escape. — A  term  employed  for  a 
rapid  loss  of  current  on  a  telegraphic  line, 
due  to  its  accidental  connection  with  the 
ground,  as  distinguished  from  a  slight 
loss  of  current. 

Hedgehog  Transformer  or  Converter. 
A  name  applied  to  a  particular  form  of 
open-circuited  iron-core  transformer,  in 
which  a  core  of  iron  wire  projects  diver- 
gingly  from  each  end  of  the  coil. 

Heeling  Error  of  Compass  Needle. — 
The  error  in  a  ship's  compass  needle  due 
to  the  induced  and  permanent  magnet- 
ism of  the  ship  in  a  vertical  plane,  which 
produces  no  influence  upon  the  needle 
until  the  ship  heels  over,  either  under  a 
press  of  canvas,  or  from  any  other  cause. 

Hefner-Alteneck  Amyl-Acetate  Stan- 
dard.— (1)  The  arayl-acetate  standard  of 
luminous  intensity.  (2)  A  standard  lamp 
of  definite  dimensions  consuming  amyl- 
acetate. 

H  e  f  n  e  r-A  1 1  e  n  e  c  k  Amyl-Acetate 
Lamp. — The  lamp  employed  in  the  Hef- 
ner-Alteneck amyl-acetate  standard. 

Heilmann  Locomotive. — An  electrically 
propelled  locomotive  which  carries  not 
only  the  steam  plant  necessary  for  the 
operation  of  the  dynamo  that  furnishes 
its  driving  current,  but  also  the  motor 
propelling  the  truck. 

Hekto. — A  prefix  for  one  hundred. 
Hekto-Ampere. — One  hundred  amperes. 

Hekto- Ampere     Balance. — A    balance 

form  of  ammeter  measuring  hundreds  of 

amperes. 
Hekto-Watt   Hour. — (1)   One    hundred 

watt-hours.     (2)  A  unit  of  work  equal  to 

one  hundred  watt-hours. 
Helical   Coil. — A  wire  coil  containing  a 

number  of  convolutions  or  spirals. 

Heliograph. — (1)  An  instrument  for  tele- 
graphic communication,  that  operates  by 
employing  flashes  of  sunlight  to  repre- 
sent the  dots  and  dashes  of  the  Morse 
alphabet.  (2)  A  portable  instrument  for 
visual  telegraphic  communication  con- 
sisting essentially  of  a  mirror  supported  so 
as  to  reflect  a  beam  of  sunlight  to  the  dis- 
tant station,  and  means  to  intercept  the 
beam  at  intervals  corresponding  to  Morse 
code  signals. 

Heliographic  Transmission. — A  system 


Hel.] 


798 


[Met. 


of  telegraphic  communication  employing 
the  heliograph. 

Heliography. — (1)  A  description  of  the 
sun.  (2)  A  term  sometimes  applied  to  the 
fixing  of  images  in  the  camera  obscura. 
(3)  Transmitting  or  receiving  telegraphic 
signals  by  means  of  the  heliograph. 

Holiostat. — A  mirror  mounted  on  an  axis 
parallel  to  the  axis  of  the  earth  and  so 
rotated  by  clock-work  as  to  keep  a  beam 
of  light  reflected  from  its  surface  in  a 
constant  position,  notwithstanding  the 
rotation  of  the  earth. 

Heliotropism. — A  bending  and  twisting 
action  produced  on  the  growth  of  stalks 
and  stems  by  their  exposure  to  any  source 
of  light. 

Helix. — A  word  sometimes  used  in  place 
of  coil  or  solenoid. 

Holm  Indicator. — An  electrical  indicator 
on  board  ship  for  indicating  the  position 
at  which  the  helm  or  rudder  stands. 

Helmholtz's  Galvanometer. — A  double- 
ring  tangent-galvanometer,  whose  two 
ring  coils  are  parallel  to  each  other,  and 
so  placed  on  opposite  sides  of  the  mag- 
netic needle  that  their  magnetic  field  at 
the  needle  may  be  as  nearly  uniform  as 
possible,  and  much  more  nearly  uniform 
than  a  single-coil  ring  can  produce. 

Hemihedral  Crystal. — A  crystal  whose 
shape  or  form  has  been  modified  by  the 
replacement  of  half  of  its  edges  or  solid 
angles. 

Hemispherical  Pole-Pieces.  —  Pole- 
pieces  of  a  dynamo-electric  machine  that 
provide  between  them  a  spherical  space 
for  the  revolution  of  an  armature. 

Hen. — A  word  proposed  for  henry.  (Not 
•  in  use.) 

Henley's  Quadrant  Electroscope.— 
A  form  of  swinging-pendulum  electro- 
scope formerly  employed  for  indicating 
powerful  charges  of  electricity. 

Henry. — (1)  The  practical  unit  of  self-in- 
duction. (2)  An  earth-quadrant,  or  109 
centimetres. 

Henry's  Coils. — A  number  of  separate  in- 
duction coils  sp'connected  that  the  cur- 
rents induced  in  the  secondary  of  the  first 
coil,  induce  currents  in  the  secondary  of 
the  second  coil  with  whose  primary  it  is 
connected  in  series,  and  so  on  throughout 
all  the  coils. 

Heptad  Atom. — An  atom  whose  valency, 
atomicity,  or  combining  power,  is  seven. 

Hercules'  Stone. — A  name  given  by  the 
ancients  to  the  lodestone. 

Hermetical  Seal. — A  seal  obtained  in  a 


glass  vessel  by  the  fusion  of  its  walls,  so 
as  to  enable  it  to  hold  either  a  vacuum  or 
a  pressure  greater  or  less  than  that  of  the 
atmospheric  pressure. 

Hertzian  Waves. — (1)  Electro-magnetic 
waves  given  off  by  an  electro-magnet 
whose  intensity  is  undergoing  rapid  pe- 
riodic variations,  or  by  a  current  whose 
strength  is  undergoing  rapid  periodic 
variations.  (2)  Electro-magnetic  waves 
given  off  from  a  circuit  through  which 
an  oscillatory  discharge  is  passing. 

Hertz's  Axial  Oscillator. — A  term  some- 
times employed  for  Hertz's  linear  oscil- 
lator. 

Hertz's  Linear  Oscillator. — A  form  of 
Hertz's  oscillator  in  which  a  straight  or 
linear  conductor  is  employed  instead  of  a 
plate  as  in  the  ordinary  oscillator. 

Hertz's  Oscillator. — A  term  sometimes 
employed  for  two  insulated  metallic 
plates  to  which  are  attached  metallic 
rods,  terminated  by  rounded  poles  or 
knobs,  and  separated  by  an  air-gap  or 
space  through  which  disruptive  dischar- 
ges pass. 

Hertzian  Oscillations.— Hertzian  waves. 

Heterochromatic  Photometry.  —  (1) 
Photometric  measurements  made  when 
the  light  chosen  as  a  photometric  standard 
emits  rays  whose  frequencies  differ  from 
that  of  the  light  which  is  to  be  measured. 
(2)  Photometry  not  restricted  to  light  of 
one  color  as  distinguished  from  mono- 
chromatic photometry. 

Heterogeneous  Conductor. — (1)  A  con- 
ductor which  does  not  possess  the  same 
power  of  electric  conduction  in  all  direc- 
tions. (2)  A  non-isotropic  conductor,  or 
non-homogeneous  conducting  medium. 

Heterogeneous  Dielectric.  —  A  non- 
homogeneous  dielectric,  or  one  which 
possesses  different  powers  of  induction  in 
different  directions. 

Heteropolar  Dynamo.— (1)  A  dynamo 
whose  conductor  moves  successively  past 
opposite  magnet  poles.  (2)  A  bipolar  or 
multipblar  dynamo,  as  distinguished  from 
a  commutatorless  dynamo. 

Heterostatic. —  (1)  Diversely  electrified. 
(2)  A  term  employed  to  distinguish  a  form 
of  electrometer  in  which  the  electrifica- 
tion is  measured  by  determining  the 
mutual  influence  of  the  attraction  exerted 
by  the  charge  to  be  measured,  and  the 
attraction  of  a  fixed  charge  imparted  to 
the  instrument  by  a  source  independent 
of  the  charge  to  be  measured. 

Heterostatic  Electrometer. — (1)  An 
electrometer  in  which  the  electrification 


flex.] 


799 


[Hig. 


to  be  measured  is  not  the  only  electrifica- 
tion employed.  (2)  An  electrometer  pro- 
vided with  an  independent  charge. 

Hexad  Atom. — An  atom  whose  valency 
or  atomicity  is  six. 

Hexode  Working. — A  term  employed  for 
a  six- way  mode  of  working  by  the  Delany 
synchronous  multiplex  telegraph. 

Hick's  Automatic  Button  Repeater. — 
A  manual  form  of  telegraphic  repeater. 

High-Admittance  Motor. — An  alternat- 
ing-current induction  motor  characterized 
by  high  admittance. 

High  Commutator  Bars. — A  term  ap- 
plied to  those  commntator  segments,  or 
parts  of  commutator  segments,  which, 
through  less  wear,  faulty  construction,  or 
looseness,  are  higher  than  the  adjoining 
segments. 

High-Economy  Lamp. — Any  lamp  of 
high  efficiency. 

High  Frequency. — Any  frequency  much 
higher  than  that  ordinarily  employed. 

High-Frequency  Currents. — Currents 
produced  by  electromotive  forces  of  high 
frequency. 

High-Frequency  Induction  Motor. — 
An  induction  motor  operated  by  high- 
frequency  currents. 

High  -  Frequency  Transformer.  —  A 
transformer  suitable  for  employment  in 
connection  with  high-frequency  electro- 
motive forces  or  pressures. 

High  Insulation. — An  unusually  good  in- 
sulation. 

High-Potential  Current. — A  term  loose- 
ly applied  for  a  current  produced  by  high 
electromotive  forces. 

High-Potential  Insulator. — An  insula- 
tor suitable  for  use  on  high-potential  cir- 
cuits. 

High-Potential  Push-Button. — A  push 
button  provided  for  safe  use  on  a  high- 
pressure  system. 

High-Potential  Switch. — A  switch  suit- 
able for  use  on  high-pressure  circuits. 

High-Potential  System. — In  the  Na- 
tional Electric  Code,  any  pressure  of  from 
300  to  3,000  volts. 

High-Potential  Testing  Transformer. 
An  alternating-current  transformer  for 
obtaining  from  an  ordinary  alternating- 
current  circuit,  a  high  alternating  pres- 
sure suitable  for  testing  insulation. 

High-Potential  Wires. — Circuit  wires 
provided  with  high  insulation,  and,  there- 
fore, suitable  for  connection  with  high- 
potential  sources. 


High  Resistance. — A  resistance  for  any 
circuit  or  apparatus,  much  higher  than 
that  ordinarily  employed  on  such  circuit 
or  apparatus. 

High-Resistance  Arrester. — A  form  of 
lightning  arrester  consisting  of  a  number 
of  thin  metallic  plates  separated  from  one 
another  by  means  of  thin  sheets  of  mica, 
or  other  refractory  insulating  substance. 

High-Resistance  Magnet.— A  term  some- 
times used  for  a  long-coil  magnet  of  fine 
wire,  possessing  a  high  electric  resistance. 

High-Resistance  Telephone. — A  tele- 
phone having  an  unusually  high  resist- 
ance. 

High-Pressure  Incandescent  Lamp. — 
An  incandescent  lamp  provided  with 
long,  thin  filaments  whose  electric  resist- 
ance is  high,  and  which,  therefore,  re- 
quires a  comparatively  high  pressure  for 
its  operation. 

High-Reactance  Motor. — An  alternating- 
current  induction  motor  possessing  com- 
paratively high  primary  reactance. 

High-Speed  Electric  Motor. — (1)  An  or- 
dinary electric  motor,  as  distinguished 
from  a  motor  designed  to  run  at  a  slow 
speed.  (2)  A  motor  which  has  its  greatest 
efficiency  when  running  at  high  speed. 

High-Susceptance  Motor. — An  alter- 
nating-current motor  possessing  compara- 
tively high  susceptance. 

High-Tension  Accumulator. — An  ac- 
cumulator consisting  of  a  number  of 
series-connected  secondary  cells. 

High-Tension  Bus. — A  bus-bar  supplied 
by  a  high  pressure. 

High-Tension  Cable. — A  cable  possessing 
high  insulation  and,  therefore,  suitable 
for  bearing  high  electric  pressures. 

High-Tension    Circuit. — A  circuit  em- 
ployed in  connection  with  high  electric  . 
pressures.  t 

High-Tension  Fuse. — A  fuse  for  igniting 
an  explosive,  that  is  operated  by  the 
heating  power  of  an  electric  discharge  of 
high  tension. 

High-Tension  Switch. — A  switch  suit- 
able  for  use  in  high-tension  circuits. 

High  Vacuum. — (1)  A  space  from  which 
nearly  all  traces  of  air  or  residual  gas  have 
been  removed,  as  distinguished  from  a  low 
or  imperfect  vacuum.  (2)  Such  a  vacuum 
that  the  length  of  the  mean  free-path  of 
the  molecules  of  the  residual  atmosphere 
is  equal  to  or  exceeds  the  dimensions  of  the 
containing  vessel.  (3)  A  nearly  perfect 
vacuum. 

High- Voltage  Electro-Magnetic  Gen- 


Hig.] 


800 


[Hor. 


erator. — An  electro-magnetic  generator 
arranged  so  as  to  produce  a  high  electro- 
motive force. 

High- Voltage  Incandescent  Lamps. — 
Incandescent  lamps  constructed  for  more 
than  the  usual  pressure  ;  usually  lamps  for 
more  than  120  volts. 

Hissing  Arc. — A  voltaic  arc  that  emits  a 
hissing  sound,  due  to  its  carbons  being 
too  near  together. 

"  Hitching  Up." — A  term  sometimes  em- 
ployed for  boosting. 

Hittorf  Effect.— The  effect  produced  by  a 
Hittorf  tube. 

Hittorf  Rays. — The  rays  emitted  by  a 
Hittorf  tube. 

Hittorf  Tubes. — Various  forms  of  high- 
vacuum  tubes  employed  by  Hittorf  in  his 
researches  in  electrical  discharges  through 
high  vacua. 

Hold-Off  Spring. — A  spring  which  acts  to 
keep  one  thing  away  from  another,  in  op- 
position to  some  force  tending  to  keep  it 
in  contact  with  such  thing. 

Hold-On  Spring. — A  spring  which  acts  to 
keep  one  thing  against  or  in  contact  with 
another,  in  opposition  to  some  force  tend- 
ing to  pull  it  away  from  such  thing. 

Holder  for  Incandescent  Lamp. — An 
incandescent  lamp-socket. 

Holder  for  Safety  Fuse.— A  support, 
generally  of  porcelain  or  other  infusible 
material,  employed  for  holding  a  safety 
fuse  and  for  catching  the  metal  when 
fused. 

Holders  for  Brushes  of  Dynamo-Elec- 
tric Machine. — Devices  for  holding  the 
collecting  brushes  of  a  dynamo-electric 
machine. 

Holohedral  Crystal.— A  crystal  whose 
shape  or  form  has  been  modified  by  the 
replacement  of  all  its  edges  or  solid  an- 
gles. 

Holophane. — A  form  of  glass  globe  or 
enclosing  chamber  for  a  source  of  light, 
which  has  its  external  surface  cast  into 
lenticular  ridges  for  the  more  general 
diffusion  of  the  emerging  light. 

Holophotometer. — A  photometer  based 
on  the  employment  of  a  Bunsen  screen 
with  a  system  of  mirrors,  so  combined  as 
to  avoid  errors  due  to  the  movements 
which  the  lights  undergo  while  being 
compared. 

Holtz  Influence  Machine. — A  particular 
form  of  electrostatic  influence  machine. 

Home  Battery. — The  battery  in  a  sending 
station  on  a  telegraphic  line,  as  distin- 
guished from  a  distant  battery. 


Home  Station. — The  near  or  sending  sta- 
tion on  a  telegraphic  line,  as  distinguished 
from  a  distant  or  receiving  station. 

Homogeneous  Conductor. — A  c  o  n  - 
ductor  possessing  the  same  resistivity 
throughout  its  length. 

Homogeneous  Current-Distribution. — 
Such  a  distribution  of  current  through  a 
conductor  in  which  there  is  an  equal 
density  of  current  in  all  parts  of  a  nor- 
mal cross-section  of  the  conductor. 

Homogeneous  Dielectric.— (1)  A  die- 
lectric possessing  similar  properties  in  all 
directions.  (2)  A  uniform  dielectric. 

Homogeneous  Light.— (1)  A  light  con- 
sisting practically  of  but  a  single  fre- 
quency. (2)  Monochromatic  light. 

Homopolar  Dynamo. — (1)  A  dynamo 
whose  conductor  moves  continuously  past 
poles  of  one  polarity  only.  (2)  A  com- 
mutatorless  dynamo.  (3)  A  so-called 
unipolar  dynamo. 

Hood  for  Arc  Lamp. — A  hood  provided 
for  the  double  purpose  of  protecting  the 
body  of  an  arc  lamp  from  the  weather, 
and  for  throwing  its  light  in  a  downward 
direction. 

Hood  Suspension  for  Arc  Lamp.— A 

suspension  of  an  arc  lamp  from  a  hanger- 
board  placed  inside  a  suitably  supported 
hood. 

Hop  System  of  Space  Relations.— A 

system  of  space  relations,  employed 
by  some  electrical  writers,  which  "fol- 
lows the  hop  tendril ;  i.  e.,  which  consid- 
ers advance  accompanied  by  left-hand  ro- 
tation as  positive  ;  or  that  a  rotation  is 
positive  when  accompanied  by  transla- 
tion in  the  manner  of  a  female  screw  :  or, 
that  clockwise  rotation  is  positive  when 
viewed  from  the  front  of  the  clock. 
Horizontal  Candle  Power.  —  (1)  The 
intensity  of  light  emitted  by  any  source 
in  a  horizontal  direction.  (2)  Tlie  lumin- 
ous intensity  of  a  source  taken  in  a  hori- 
zontal direction,  as  measured  in  units  of 
luminous  intensity. 

Horizontal  Component.— That  portion 
of  a  force  which  acts  in  a  horizontal 
direction. 

Horizontal  Component  of  Earth's  Mag- 
netism.—(1)  That  portion  of  the  earth's 
directive  force  which  acts  in  a  horizontal 
direction.  (2)  That  portion  of  the  earth's 
magnetic  force  which  acts  to  produce 
motion  in  a  compass  needle  free  to  move 
in  a  horizontal  plane  only. 

Horizontal  Force  of  Needle.— The  hori- 
zontal component  of  the  earth's  magnetic 
force  or  magnetism. 


Hor.] 


801 


[Hug. 


Horizontal  Intensity  of  Earth's  Mag- 
netism.— (1)  The  horizontal  component 
of  the  earth's  magnetic  intensity  at  any 
point.  (2)  The  earth's  horizontal  mag- 
netic force  upon  a  unit  magnetic  pole. 

Horizontal  Intensity  of  Light. — (1)  The 
intensity  of  a  light  measured  in  a  horizon- 
tal direction.  (2)  The  flux  of  a  light  con- 
tained in  a  small  horizontal  beam  issuing 
from  a  source,  divided  by  the  solid  angle 
of  the  beam. 

Horizontal  Slit  Photometer. — A  form  of 
spectro- photometer  whose  slit  is  horizon- 
tal, lying  in  a  straight  line  joining  the 
sources  of  light. 

Horns  of  Pole-Pieces  of   Dynamo.— 

(1)  The  edges  or  terminals  of  the  pole-pieces 
of  a  dynamo  towards  or  from  which  the 
armature  is  carried  during  its  rotation. 

(2)  The  following  or  leading  horns  of  the 
pole-pieces  of  a  dynamo. 

Horology,  Electric.  —  That  branch  of 
electric  science  which  treats  of  the  appli- 
cation of  electricity  to  the  regulation  and 
operation  of  electric  clocks. 

Horse. — A  support  for  a  dynamo-armature 
in  the  process  of  winding  it. 

Horseless  Carriage. — An  automobile  car- 
riage. 

Horse-Power. — (1)  A  commercial  unit  of 
power,  activity,  or  rate-of-doing-work. 
(2)  A  rate-of-doing-work  equal  to  33,000 
pounds  raised  one  foot-per-minute,  or  550 
pounds  raised  one  foot-per-second.  (3)  A 
rate-of-doing-work  equal  to  4,562  kilo- 
grams raised  one  metre  per  minule. 

Horse-Power,  Electric. — Such  a  rate-of- 
doing  electrical  work  as  is  equal  to  746 
watts,  or  746  volt-coulombs  per  second. 

Horse-Power-Hour. — (1)  A  unit  of  work 
equal  to  the  work  done  by  one  horse- 
power acting  for  an  hour.  (2)  1,980,000 
foot-pounds. 

Horseshoe  Electro-Magnet. — An  elec- 
tro-magnet whose  core  has  the  shape  of  a 
horseshoe,  or  the  letter  U. 

Horseshoe  Magnet. — A  magnetized  bar  of 
steel  or  hardened  iron,  bent  in  the  form 
of  a  horseshoe,  or  letter  U. 

Hot  Saint  Elmo's  Fire. — A  term  proposed 
by  Tesla  for  a  form  of  flaming  brush-dis- 
charge between  the  secondary  terminals 
of  a  high-frequency,  high-potential  induc- 
tion coil. 

Hot  -  Wire  Ammeter.  —  An  ammeter 
whose  readings  are  based  on  the  expan- 
sion of  a  wire  due  to  an  increase  of  tem- 
perature, by  the  passage  through  it  of 
the  current  that  is  to  be  measured. 

5* 


Hot- Wire  Thermometer. — A  thermom- 
eter whose  indications  are  dependent  on 
the  expansion  of  a  bi-metallic  wire  or 
spiral. 

Hot  -  Wire  Voltmeter.  —  A  voltmeter 
whose  indications  are  based  on  the  in- 
crease in  the  length  of  a  metallic  wire 
placed  in  the  circuit  of  the  electromotive 
force  that  is  to  be  measured. 

Hotel  Annunciator.  —  An  annunciator 
connected  with  the  different  rooms  of  a 
hotel. 

House  Annunciator. — An  annunciator 
connected  with  the  different  rooms  of  a 
house. 

House  Mains. — The  conductors  connect- 
ing the  service  wires  with  the  street 
mains,  in  a  system  of  multiple-incandes- 
cent lamp  distribution. 

House  Regulator. — An  alternating-cur- 
rent apparatus  for  insertion  in  the  circuit 
of  a  group  of  lamps  in  a  house  for  the 
purpose  of  controlling  the  candle-power 
of  that  group. 

House-Service  Conductor. — In  a  system 
of  multiple-incandescent  lamp  distribu- 
tion, that  portion  of  the  service  wire 
which  is  included  between  the  street 
mains  and  the  cut-out  within  the  house. 

House  Telephone  System.— (1)  A  do- 
mestic telephone  system.  (2)  A  system 
for  establishing  telegraphic  communica- 
tion between  different  places  in  a  house. 

House  Wiring. — The  wiring  in  a  house 
for  distributing  electric  currents  therein. 

House  Wires. — The  circuit  wires  em- 
ployed in  a  house  in  a  system  of  distribu- 
tion. 

Howler. — A  term  sometimes  used  for  a 
loud  buzzer. 

Hughes'  Electro-Magnet.- (1)  An  elec- 
tro-magnet in  which  a  U-shaped  perma- 
nent magnet  is  provided  with  pole-pieces 
of  cast  iron  on  which  only  are  placed  the 
magnetizing  coils.  (2)  A  quick-acting 
electro-magnet  whose  magnetizing  coils 
are  placed  on  soft-iron  pole-pieces  that  are 
connected  with  and  form  the  prolonga- 
tion of  the  pole-pieces  of  a  permanent 
horseshoe  magnet. 

Hughes'  Induction-Balance. — An  ap- 
paratus for  the  detection  of  the  presence 
of  a  metallic  conducting  substance  in  the 
body  by  the  aid  of  induced  electric  cur- 
rents. 

Hughes'  Theory  of  Magnetism. — A 
theory  proposed  to  account  for  the  phe- 
nomena of  magnetism  by  the  presence  of 
originally  magnetized  particles  or  mole- 
cules. 


Hum.] 


802 


[Hys. 


Hummer,  Electric. — A  word  sometimes 
employed  for  an  electric  buzzer. 

Hunning's  Transmitter. — The  original 
form  of  dust  telephone  transmitter. 

Hunting  of  Parallel-Connected  Alter- 
nators.— (1)  Aperiodic  increase  and  de- 
crease in  the  speed  of  alternators,  when 
running  under  certain  conditions  in  paral- 
lel connection  as  motors  or  dynamos.  (2) 
Imperfect  synchronous  running. 

Hydraulic  Gradient.— (1)  The  gradient 
representing  the  drop  of  pressure  between 
the  surface  of  a  liquid  in  a  containing 
vessel  and  a  discharging  orifice  connected 
therewith.  (2)  The  rate-of-drop  of  pres- 
sure in  a  hydraulic  system  of  distribution. 

Hydraulic  Power  Dynamometer,— 
Any  dynamometer  suitable  for  measuring 
hydraulic  power. 

Hydraulic  Storage. — A  method  of 
storage  of  energy  consisting  in  forcing 
water  into  elevated  reservoirs. 

Hydraulic  Transmission.— The  trans- 
mission of  power  by  means  of  pipes  con- 
taining water  under  pressure. 

Hydraulics. — That  branch  of  science 
which  treats  of  the  transmission  of  water 
through  pipes  and  the  apparatus  required 
for  raising  or  moving  water. 

Hydro-Carbon  Treatment  of  Fila- 
ments.— Treatment  of  incandescent  lamp 
filaments  by  means  of  the  flashing  pro- 
cess. 

Hydro-Dynamics.: — That  branch  of  nat- 
ural philosophy  which  treats  of  the  con- 
ditions of  rest  and  motion  in  fluid  bodies. 

Hydro-Electric  Bath. — An  electro-thera- 
peutic bath  in  which  one  electrode  is  ap- 
plied to  the  metallic  lining  of  the  bath 
tub,  and  the  other  to  the  body  of  the  pa- 
tient. 

Hydro-Electric  Generator. — A  term 
sometimes  used  for  voltaic  battery. 

Hydro-Electric  Machine. — A  term 
sometimes  used  for  a  machine  in  which 
electricity  is  developed  by  the  friction  of 
a  jet  of  steam  over  a  water  surface. 

Hydro-Electro-Therapeutics.  —  Cura- 
tive processes  combining  electro-pathic 
and  electro-therapeutic  treatment. 

Hydrogen  Voltmeter. — A  voltmeter 
whose  indications  are  based  on  the  quan- 
tity of  hydrogen  evolved  under  a  constant 
pressure  and  temperature. 

Hydro-Generator,  Electric.— An  appa- 
ratus for  the  electrical  development  of 
the  nascent  hydrogen  employed  in  the 
electrical  rectification  of  alcohol. 

Hygrometer. — (1)  An  apparatus  for  de- 


termining the  specific  gravity  of  liquids.. 
(2)  An  areometer. 

Hydrometric  Telegraph. — A  form  of  in- 
strument by  means  of  which  signals  ar« 
transmitted  by  means  of  water  pressure. 

Hydro-Plastics. — The  art  of  electrically 
shaping  or  depositing  metals  in  the  wet, 
by  electro-plating. 

Hydro-Plasty. — The  art  of  hydro-plastics. 

Hydro-Platinum  Rheostat. — A  water 
rheostat  furnished  with  platinum  elec- 
trodes. 

Hydrostatic  Wire-Testing  Machine. 
A  machine,  operated  by  hydraulic  pres- 
sure, for  testing  the  tensile  strength  of 
wires. 

Hydrotasimeter,  Electric. — An  elec- 
trically operated  apparatus  designed  to 
show  at  a  distance  the  exact  position  of 
any  water  level. 

Hydrometer. — An  apparatus  for  deter- 
mining the  amount  of  moisture  present 
in  the  atmosphere. 

Hydrometrical. — Of  or  pertaining  to  a 
hygrometer. 

Hydrometrically. — In  the  manner  of  a 
hygrometer. 

Hyperphosphorescence. — (1)  A  nam« 
applied  to  a  variety  of  phosphorescence  in 
which,  after  due  stimulus,  the  body  ex- 
hibits a  persistent  emission  of  invisible 
rays,  not  included  in  the  hitherto  recog- 
nized spectrum.  (2)  A  phosphorescence 
accompanied  by  the  emission  of  the 
Becquerel  rays. 

Hypothesis. — A  provisional  assumption  of 
facts  or  causes,  the  real  nature  of  which 
is  still  unknown,  for  the  purpose  of  study- 
ing their  effects. 

Hypothetical. — Of  or  pertaining  to  a  hy- 
pothesis* 

Hypsometer. — (1)  An  apparatus  for  deter- 
mining the  height  of  a  mountain  or  other 
elevation  by  ascertaining  the  temperature 
at  which  water  boils  on  such  elevation. 
(2)  a  hydro-barometer. 

Hypsometrical. — Of  or  pertaining  to  a 
hypsometer. 

Hypsometrically. — In  the  manner  of  a 
hypsometer. 

Hysteresial  Dissipation  of  Energy.— 
The  dissipation  of  energy  by  means  of 
hysteresis. 

Hysteresis. — (1)  A  lagging  behind  of 
magnetization  relatively  to  magnetizing 
force.  (2)  Apparent  molecular  friction 
due  to  magnetic  changes  of  stress.  (3)  A 
retardation  of  the  magnetizing  or  demag- 
netizing effects  as  regards  the  causes 


Hys.] 


803 


[Ice. 


which  produce  them.  (4)  That  quality 
of  a  paramagnetic  substance  by  virtue  of 
which  energy  is  dissipated  on  the  reversal 
of  its  magnetization. 

Hysteresis  Coefficient.— (1)  The  hystere- 
tic  coefficient.  (2)  The  energy  dissipated 
in  a  cubic  centimetre  of  magnetic  ma- 
terial by  a  single  cyclic  reversal  of  unit 
magnetic  density. 

Hysteresis  Conductance. — The  effec- 
tive conductance  in  a  transformer  or 
condenser  due  to  the  effects  of  hysteresis. 

Hysteretetic  Constant. — The  hysteretic 
coefficient. 

Hysteresis  Loop. — The  looped  curve 
which  forms  the  outlines  of  the  graphic- 
ally represented  hysteretic  cycle  to  rec- 
tangular co-ordinates  of  magnetizing 
force  and  magnetic  intensity  or  magneti- 
zation. (2)  A  cyclic  magnetization  curve, 
forming  a  closed  loop. 

Hysteresis  Losses. — Losses  of  useful 
energy  due  to  hysteresis. 

Hysteresis  Measurer. — An  apparatus 
for  conveniently  estimating  or  measuring 
the  hysteretic  coefficient  of  a  magnetic 
material. 

Hysteresis  Meter.— A  hysteresis  meas- 
urer. 

Hysteresis  Tester. — A  hysteresis  meas- 
urer. 

Hysteretic  Activity. — Activity  expended 
in  producing  hysteretic  effects. 

Systeretie  Coefficient. — The  activity  in 
watts  which  would  be  expended  in  one 
cubic  centimetre  of  a  metal  when  magnet- 
ized and  demagnetized  to  a  flux  density 
of  one  gauss  at  one 'complete  cycle  or 
double-reversal  per  second. 


Hysteretic  Condensance. — In  a  con- 
denser  traversed  by  an  alternating 
current,  the  apparent  reactance  of  the 
condenser,  due  to  or  modified  by  hyster- 
esis. 

Hysteretic  Conductance. — In  a  con- 
denser traversed  by  an  alternating  cur- 
rent, the  apparent  conductance  of  the 
condenser,  due  to  or  modified  by  hyster- 
esis. . 

Hysteretic  Cycle. — A  cycle  of  complete 
magnetization  and  reversal. 

Hysteretic  Energy  Current. — The  com- 
ponent of  current  in  phase  with  the  im- 
pressed E.  M.  F.  at  the  primary  terminals 
of  a  transformer  representing  the  power 
expended  in  hysteresis.  (2)  The  energy 
component  of  the  exciting  current  of  a 
transformer. 

Hysteretic  Energy  Electromotive 
Force. — The  energy  component  of  the 
E.  M.  F.  of  excitation  in  a  transformer. 

Hysteretic  Lag. — The  lag  in  the  magnet- 
ization of  a  transformer  due  to  hysteresis. 

Hysteretic  Resistance. — In  a  condenser 
traversed  by  an  alternating  current,  the 
apparent  resistance  of  the  condenser  due 
to  or  modified  by  hysteresis. 

Hysteretic  Susceptance.— In  a  con- 
denser traversed  by  an  alternating  cur- 
rent, the  apparent  susceptance  of  the 
condenser,  due  to  or  modified  by  hys- 
teresis. 

Hysteretic  Torque. — That  portion  of  the 
torque  of  a  dynamo-electric  machine  due 
to  the  influence  of  hysteresis,  whereby 
mechanical  work  must  be  expended  in  de- 
veloping hysteretic  energy  as  heat  in  the 
iron  undergoing  magnetic  reversal. 


I 


I. — (1)  A  symbol  for  strength  of  current. 
(2)  A  symbol  for  intensity  of  magneti- 
zation. 

<D. — A  symbol  for  intensity  of  magneti- 
zation. (Partly  international  usage.) 

I.  H.  P. — A  contraction  for  indicated  horse- 
power. 

I.  I. — In  telegraphy,  a  signal  serving  to 
separate  the  text  of  a  message  from  the 
signature,  or  the  name  of  the  sender. 

I.  B. — A  contraction  for  India  rubber. 

I,  B. — A  contraction  sometimes  employed 
for  the  drop  in  an  electric  circuit,  equal  to 
the  product  of  the  current  in  amperes  by 
the  resistance  in  ohms. 


I.  8.  W.  Gr. — A  contraction  for  Imperial 

standard  wire  gauge. 
I.  W.  Gr. — A  contraction  for  Indian  wire 

gauge. 

I.2  B.  Activity. — (1)  The  activity  expended 
in  a  circuit,  equal  to  the  square  of  the 
current  strength  in  amperes  by  the  resist- 
ance in  ohms.  (2)  The  C2  R.  activity. 

I.2  B.  Loss. — (1)  The  loss  of  power  in  any 
circuit  equal  to  the  square  of  the  current 
in  amperes  by  the  resistance  in  ohms. 
(2)  The  C2  R.  loss. 

I- Armature. —An  I,  or  H-shaped  armature. 

Ice   Clearer    for   Trolleys.— A    trolley 


He.] 


804 


I  IMIII. 


wheel  designed  to  remove  aggregations  of 
ice  from  a  trolley-wire. 

Ideal  Solenoid. — A  solenoid  consisting  of 
a  cylinder  built  up  of  a  number  of  true 
circular  currents,  all  independent  of  one 
another,  and  all  of  whose  faces  of  like 
polarity  are  similarly  directed. 

Identical-Electrode  Cell. — A  term  some- 
times employed  for  a  double-fluid  voltaic 
cell,  both  of  whose  electrodes' are  formed 
of  the  same  metal,  and  whose  electro- 
motive forces  are  dependent  on  the  col- 
lection of  unlike  ions  around  such  plates. 

Idio-Electrics. — A  term  formerly  applied 
to  such  bodies  as  amber,  resin,  or  glass, 
which  are  readily  electrified  by  friction, 
and  which  were  then  supposed  to  be  elec- 
tric in  themselves.  (Obsolete.) 

Idiostatic. — Possessing  one  kind  of  elec- 
trification only. 

Idiostatic  Electrometer. — An  electro- 
meter in  which  the  electrification  is  whol- 
ly due  to  the  potential  difference  to  be 
measured,  as  distinguished  from  a  heter- 
ostatic  electrometer,  in  which  an  auxiliary 
charge  is  employed  from  an  independent 
source. 

Idle  Coil. — (1)  Any  coil  through  which 
for  the  time  no  current  is  passing.  (2) 
Any  coil  which  is  not  passing  through 
a  magnetic  field  or  generating  an  E.  M.  F. 

Idle  Current. — A  wattless  current. 

Idle  Current  of  Alternating-Current 
Dynamo.^— The  wattless  current  of  an 
alternating-current  circuit,  as  distin- 
guished from  the  active  or  working  cur- 
rent. 

Idle  Plug. — In  a  telephone  switchboard,  a 
plug  not  in  use. 

Idle  Poles. — Poles  or  electrodes  in  Crookes' 
tubes  between  which  no  discharge  is  tak- 
ing place. 

Idle  Wire. — (1)  Any  wire  through  which 
either  no  current  at  all,  or  no  useful  cur- 
rent, is  passing.  (2)  Any  open-circuited 
armature  wire  not  generating  an  E.  M.  F. 

Idle-Wire  of  Armature. — A  term  some- 
times employed  in  place  of  dead  wire. 

Idle  Wire  of  Armature  of  Dynamo.— 
(1)  That  part  of  the  wire  on  a  dynamo 
armature  in  which  no  useful  electro- 
motive force  is  produced.  (2)  The  dead 
wire  of  an  armature. 

Idle- Wire  of  Armature  of  Motor. — 
That  part  of  the  wire  on  the  armature  of 
a  motor  in  which  the  field  produced  by 
the  driving  current  exercises  no  useful 
action  in  driving  the  motor,  since  no 
counter-electromotive  force  is  generated 
in  it. 


Igniter. — A  carbonaceous  material  placed 
between  the  free  ends  of  a  Jablochkoff 
candle,  which  becomes  incandescent  on 
the  passage  of  the  current  and  so  enables 
the  arc  to  be  formed. 

Ignition,  Electric. — The  explosion  of  a 
powder,  or  the  lighting  of  a  combustible 
substance,  by  electrically  generated  heat. 

Illuminant. — Any  source  of  light. 

Illuminated. — A  somewhat  inelegant  or- 
thography for  illumined. 

Illuminated  Dial  Instrument. — An  in- 
strument for  engine-room  or  central- 
station  use,  provided  with  a  translucent 
dial  illumined  from  the  back  to  render 
the  position  of  the  pointer  visible  at  a 
great  distance. 

Illuminating  Power. — The  amount  of 
illumination  produced  by  any  luminous 
source. 

Illumination. — The  quantity  of  light  re- 
ceived on  a  surface  per-unit-of-area, 
either  directly  from  a  luminous  source  or 
indirectly  by  reflection  and  diffusion  from 
surrounding  objects. 

Illumined. — Lighted  up  or  rendered  vis- 
ible by  means  of  light. 

Illumined-Dial  Measuring  Instru- 
ment.— A  name  applied  to  any  electri- 
cal measuring  instrument  whose  dial  is 
so  illumined  that  its  scale  divisions  can  be 
readily  seen  at  a  distance. 

Illumined  Electrode. — That  electrode  of 
a  selenium  cell  which  on  exposure  to 
light  develops  an  E.  M.  F. 

Illuminometer.  —  An  instrument  for 
measuring  the  illumination  of  a  surface. 

Image. — The  picture  of  an  object  formed 
by  rays  from  its  several  points,  brought 
or  focused  by  any  suitable  means,  either 
on  the  retina,  or  on  a  screen,  so  as  to  per- 
mit the  image  to  become  visible. 

Image,  Electric. — (1)  A  term  sometimes 
applied  to  the  charge  produced  on  a 
neighboring  surface  by  induction  from  a 
known  charge.  (2)  An  electrified  point, 
or  system  of  points,  on  one  side  of  a  sur- 
face, which  would  produce  on  the  other 
side  of  that  surface  the  same  electrical 
action  that  the  actual  electrification  of 
the  surface  really  produces. 

Imbibition  Currents.  —  Currents  pro- 
duced in  tissues  by  the  imbibition  or 
absorption  of  a  fluid. 

Immediate  False  Zero. — A  term  em- 
ployed in  Wheatstone-bridge  measure- 
ments in  an  observation  made  with  ref- 
erence to  that  position  of  the  galvano- 
meter needle,  as  zero,  which  is  assumed, 


I  111  111.] 


805 


[Imp. 


or  which  tends  to  be  assumed,  immedi- 
ately after  the  application  of  the  testing 
E.  M.  F. 

Immersion  Front  of  Microscopic  Ob- 
ject Glass. — That  front  of  a  high-power 
or  immersion  objective,  to  which  the 
object  is  attached,  by  a  drop  of  transpar- 
ent liquid. 

Immersion  Gilding. — A  gilding  or  elec- 
tro-plating obtained  by  a  process  of  sim- 
ple immersion  in  a  suitable  solution  of 
gold. 

Immersion  Objective. — An  object  glass 
of  high  magnifying  power. 

Impact. — A  shock  or  collision  caused  by 
the  meeting  of  two  bodies  when  one  or 
both  are  in  motion. 

Impedance. — (1)  Generally,  opposition  to 
current  flow.  (2)  The  sum  of  the  ohmic 
resistance,  and  the  spurious  resistance  of 
a  circuit,  measured  in  ohms.  (3)  In  a 
simple-harmonic  current  circuit  the 
square  root  of  the  sum  of  the  squares  of 
the  resistance  and  reactance.  (4)  The 
apparent  resistance  of  a  circuit  contain- 
ing both  resistance  and  reactance. 

Impedance  Circuit. — A  circuit  contain- 
ing impedance. 

Impedance  Coils. — A  term  sometimes 
applied  to  choking  coils,  reactance  coils, 
or  economy  coils. 

Impedance  Factor. — The  ratio  of  the  im- 
pedance of  a  conductor  or  circuit  to  its 
ohmic  resistance. 

Impedance  Bush.— (1)  The  rush  of  cur- 
rent produced  on  closing  an  inductive 
circuit.  (2)  An  impulsive  current  rush. 

Impediment. — A  term  proposed  for  the 
apparent  resistance  of  a  circuit  contain- 
ing resistance,  self-induction,  and  capac- 
ity. 

Impenetrability.— That  property  which 
prevents  any  two  particles  of  matter 
from  occupying  the  same  space  at  the 
same  time. 

Imperfect  Earth. — Partial  earth. 

Imperfect  Linkage.— (1)  Magnetic  flux 
linkage  between  two  coils  or  circuits,  such 
that  some  linkage  of  one  circuit  is  not 
associated  with  the  other  circuit.  (2) 
Coils  or  circuits  possessing  mutual  induc- 
tion but  also  possessing  magnetic  leakage. 

Imperfect  Magnetic  Circuit.— A  term 
sometimes  employed  for  a  magnetic  cir- 
cuit in  which,  from  the  magnetizing  coils 
being  placed  on  one  part  of  the  core 
only,  the  intensity  of  the  flux  is  greater 
through  some  portions  of  the  ferric  cir- 
cuit than  through  others,  so  that  some  of 


the  lines  of  induction  complete  their  cir- 
cuits by  passing  through  the  space  sur- 
rounding the  core  instead  of  through  the 
core  itself. 

Impermeability. — The  reciprocal  of  the 
permeability. 

Impermeance. — The  reciprocal  of  the  per- 
meance. 

Imponderable.— (1)  Possessing  no  weight. 
(2)  A  term  formerly  applied  to  the  lumi- 
niferous  or  universal  ether. 

Impressed. — Caused  to  act  or  forced  upon. 

Impressed  Electromotive  Force.  — 
(1)  The  electromotive  force  brought  to 
act  in  any  circuit  to  produce  a  current 
therein.  (2)  In  an  alternating-current 
circuit,  the  impressed  electromotive  force 
due  to  an  impressed  source,  in  contradis- 
tinction to  the  effective  electromotive 
force,  or  that  which  is  active  in  produc- 
ing current,  or  the  electromotive  forces 
due  to,  or  opposed  to,  self  or  mutual  induc- 
tion. (3)  An  applied  E.  M.  F.  as  distin- 
guished from  a  resultant,  active,  or  watt- 
less E.  M.  F. 

Impressed  Field. — An  electric  or  mag- 
netic field  brought  to  bear  upon  any  sub- 
stance or  space  as  distinguished  from  sec- 
ondary fields  thereby  set  up. 

Impressed  Pressure.  —  The  impressed 
electromotive  force. 

Impulse. — (1)  Any  single  or  momentary 
force  acting  on  a  body.  (2)  The  motion 
produced  by  a  suddenly  communicated 
force. 

Impulse  of  Couples. — The  product  of  the 
magnitude  of  a  couple,  and  the  time  it  is 
acting. 

Impulsion  Cell. — A  photo-electric  cell 
whose  sensitiveness  to  light  may  be  re- 
stored or  destroyed  by  slight  impulses 
given  to  the  plate,  either  by  mechanical 
blows  or  taps,  or  by  electro-magnetic  im- 
pulses. 

Impulsion  Effect. — The  restoration  or 
loss  of  sensitiveness  of  a  photo-electric 
cell  to  the  action  of  light,  produced  by 
means  of  an  impulse,  such  as  a  mechan- 
ical tap  or  blow,  or  an  electro-magnetic 
impulse. 

Impulsive.  —  Communicated  by  an  im- 
pulse. 

Impulsive  Current-Rush  in  Inductive 
Circuit. — An  abnormal  rush  of  current 
which  sometimes  occurs  when  a  trans- 
former is  suddenly  switched  on  to  an 
active  main. 

Impulsive  Discharge. — A  discharge  pro- 
duced in  conductors  by  suddenly  created 
differences  of  potential. 


Imp.] 


806 


[Inc. 


Impulsive  Impedance. — The  impedance 
encountered  by  an  oscillatory  discharge. 

Impulsive  Inductance. — The  apparent 
inductance  of  a  conductor  or  circuit  when 
subjected  to  an  impulsive  discharge. 

Impulsive  Permittance. — The  apparent 
permittance  of  a  conductor  or  circuit 
through  which  an  impulsive  discharge  is 
passing. 

Impulsive-Rush  Discharge.  —  An  im- 
pulsive discharge. 

"  In  Bridge." — In  multiple  to  a  circuit,  as 
distinguished  from  being  inserted  in 
series  with  a  circuit. 

Inactive  Molecules.— (1)  Those  molecules 
of  an  electrolyte  which,  during  the  pas- 
sage of  an  electric  current,  are  not  re- 
solved into  their  constituent  ions,  and 
which,  therefore,  have  no  effect  on  the 
molecular  conductivity  of  the  electrolyte. 
(2)  The  non-dissociated  molecules  of  an 
electrolyte. 

Incandesce. — To  glow  or  shine  by  means 
of  incandescence. 

Incandescence. — The  shining  or  glowing 
of  a  substance,  usually  a  solid,  by  reason 
of  its  elevation  to  a  sufficiently  high  tem- 
perature. 

Incandescence,  Electric. — The  shining 
or  glowing  of  a  substance,  generally  a 
solid,  by  means  of  heat  of  electric  origin. 

Incandescent. — Shining  or  glowing  with 
heat. 

Incandescent-Ball  Electric  Lamp. — An 
incandescent  electric  lamp  in  which  the 
light  is  produced  by  a  sphere  or  ball  of 
carbon  placed  in  an  exhausted  glass 
chamber  and  subjected  to  electrostatic 
waves  of  high  frequency. 

incandescent  Bombardment-Lamp. — 
An  electric  lamp  in  which  a  refractory 
material  is  rendered  incandescent  by  the 
molecular  bombardment  produced  by  the 
passage  of  an  electric  discharge  through 
a  rarefied  space. 

Incandescent  Circuit.— A  circuit  pro- 
vided for  the  operation  of  incandescent 
electric  lamps. 

Incandescent-Cut-Out. — (1)  A  cut-out 
suitable  for  use  in  an  incandescent  light 
circuit.  (2)  A  safety-fuse  cut-out. 

Incandescent  Filament.— The  incandes- 
cing conductor  of  an  incandescent  electric 
lamp,  whether  of  small  or  of  compara- 
tively large  cross-section,  though  gener- 
ally of  the  former. 

Incandescent  Electric  Lamp.— An  elec- 
tric lamp  whose  light  is  produced  by  the 
electric  incandescence  of  a  strip  or  fila- 


ment of  some  refractory  substance,  almost 
invariably  carbon. 

Incandescent  Electric  Lighting. — 
Artificial  lighting  obtained  by  means  of 
incandescent,  electric  lamps. 

Incandescent  Generator. — A  dynamo- 
electric  machine  suitable  for  operating 
incandescent  lamps. 

Incandescent  Lamp. — An  incandescent 
electric  lamp. 

Incandescent  Lamp-Base.— The  base  of 
an  incandescent  electric  lamp. 

Incandescent  Lamp-Cord. — A  flexible 
lamp  cord  containing  two  separate  con- 
ductors, suitable  for  use  with  a  pendant 
incandescent  electric  lamp. 

Incandescent  Lamp-Shade.— A  shade 
provided  for  use  in  connection  with  an  in- 
candescent electric  lamp. 

Incandescent  Lamp-Socket.— A  socket 
provided  for  the  reception  of  an  incan- 
descent lamp. 

Incandescent  Lighting.  —  Artificial 
lighting  produced  by  the  use  of  incandes- 
cent lamps. 

Incandescent  Lighting  Dynamo-Elec- 
tric Machine. — An  incandescent  gener- 
ator. 

Incandescent  Mantle-Burner. — (1)  A 
gauze  skeleton,  or  mantle,  employed  for 
artificial  illumination,  made  of  refractory 
materials  and  rendered  incandescent  by 
the  heat  of  a  Bunsen  flame.  (2)  The  man- 
tle of  a  Welsbach  burner. 

Incandescing. — Producing  light  by  incan- 
descence. 

Incandescing  Filament. — A  lamp  fila- 
ment that  is  producing  light  by  incandes- 
cence. 

Incandescing  Lamp.— (1)  An  incandes- 
cent lamp  that  is  actually  producing  light. 
(2)  An  incandescent  lamp  emitting  light. 

Inclination  Chart. — A  map  or  chart  on 
which  the  isoclinic  lines  are  marked. 

Inclination  Compass.— (1)  A  magnetic 
needle,  free  to  move  in  a  single  vertical 
plane  only,  and  employed  for  determining 
the  angle  of  dip  at  any  place.  (2)  An  in- 
clinometer or  dipping  circle. 

Inclination  Magnetometer. — An  incli- 
nation compass  or  inclinometer. 

Inclination  Map. — A  map  or  chart  on 
which  isogonal  lines,  or  lines  connecting 
places  which  have  the  same  magnetic  dip 
or  inclination,  are  drawn. 

Inclination  of  Magnetic  Needle.— (1) 
The  deviation  of  a  mechanically  balanced 
magnetic  needle  from  a  horizontal  posi- 
tion. (2)  The  dip  of  a  magnetic  needle. 


lue.J 


807 


[lud. 


Inclinometer. — An  inclination  compass. 
(2)  A  word  sometimes  used  for  a  dipping 
circle. 

Incoming  Call. — A  call  received  at  an  ex- 
change from  a  subscriber  or  from  another 
exchange,  as  distinguished  from  an  out- 
going call. 

Incoming  Call  Trunk  Line. — A  trunk 
line  entering  a  central  telephone  station 
and  employed  for  the  reception  of  calls, 
as  distinguished  from  an  outgoing  call 
trunk  line  upon  which  calls  are  trans- 
mitted. 

Incoming  End. — The  end  of  a  junction 
telephone  wire  at  which  calls  are  received. 

Incoming  Junction  Board. — A  switch- 
board at  a  central  exchange  at  which  in- 
coming junction  wires  are  received  and 
distributed. 

Incoming  Lines. — Lines  at  a  telephone 
exchange  at  which  calls  are  received,  as 
distinguished  from  outgoing  lines. 

Incoming  Signals. — The  signals  that  are 
received  at  the  home  end  of  a  telegraphic 
circuit. 

Incoming  Wires. — Wires  leading  into  a 
building,  room,  switchboard,  or  other  de- 
vice. 

Incomplete  Circuit. — An  open  or  broken 
circuit. 

Inconductivity. — A  word  sometimes  used 
for  non-conductivity. 

Increased  Electric  Irritability. — Irrita- 
bility of  nervous  or  muscular  tissue  pro- 
duced'by  a  much  weaker  electric  current 
than  that  required  to  produce  it  in  nor- 
mal tissue. 

Increment  Key. — A  telegraphic  key  so 
connected  that  an  increase  or  increment 
in  the  line  current  occurs  -whenever  the 
key  is  depressed,  as  distinguished  from  a 
key  which  opens  or  closes  a  circuit. 

Increment  Key  of  Quadruples  Tele- 
graphic System.— A  key  employed  to 
increase  the  strength  of  a  current  and  so 
operate  one  of  the  distant  instruments  in 
a  quadruples  system,  by  an  increase  in 
the  strength  of  the  current. 

Independent  Circuits.— (1)  Separate  cir- 
cuits or  those  which  have  no  electric  con- 
nection with  other  circuits.  (2)  Circuits 
in  electric  connection,  but  acting  inde- 
pendently, as  though  insulated  from  each 
other. 

"In-Current"  of  Telephone  Relay.— 
The  current  which  is  received  by  a  tele- 
phone relay,  for  transmission  to  another 
circuit. 

Independent-Biphase      System.  —  A 


phrase  sometimes  used  for  the  four-wire 
diphase  system. 

Indestructibility  of  Energy  or  Mat- 
ter.— A  theory  which  assumes  that 
energy  or  matter  can  never  be  destroyed, 
and  that,  consequently,  when  either  dis- 
appears in  one  form  or  phase,  it  must  re- 
appear in  some  other  form  or  phase. 

Index  of  Refraction.— (1)  The  ratio  of 
the  sine  of  the  angle  of  incidence  to  the 
sine  of  the  angle  of  refraction  for  the 
light  passing  from  a  vacuum  into  a  mate- 
rial medium.  (2)  A  quantity  represent- 
ing the  amount  of  deviation  of  a  ray  of 
light  from  its  original  course,  on  its  pas- 
sage from  a  standard  medium,  or  vacuum, 
to  another  of  different  density.  (3)  A 
quantity  representing  the  ratio  of  the 
velocity  of  wave-propagation  in  a  vacuum 
to  the  velocity  in  a  material  medium. 
(4)  In  the  electro-magnetic  theory  of  light 
the  geometric  mean  of  the  specific  induc- 
tive capacity  and  the  magnetic  induc- 
tivity  of  a  medium  to  electro-magnetic 
waves  of  a  given  frequency. 

India  Rubber. — (1)  A  resinous  substance 
obtained  from  the  milky  juices  of  a 
tropical  tree.  (2)  Caoutchouc. 

Indicating  Bell.— An  electric  bell  which, 
in  order  to  distinguish  between  different 
bells  in  the  same  office,  is  provided  with 
an  annunciator  drop  which  is  released  by 
each  bell  when  it  rings. 

Indicating-Bell  Annunciator.— An  an- 
nunciator provided  for  an  indicating  bell. 

Indicating  Lamp. — A  lamp  connected 
with  a  circuit,  which  is  lighted  or  extin- 
guished, or  the  intensity  of  whose  light 
is  caused  to  vary,  on  the  occurrence  of  a 
predetermined  change  in  the  pressure  or 
resistance  of  the  circuit. 

Indicating  Push  Button. — A  push  but- 
ton which  leaves  an  indication  of  its 
having  been  depressed. 

Indicating  Switch. — A  switch  provided 
with  an  indicator  which  shows  whether 
the  circuit  of  the  switch  is  closed  or  open. 

Indicator. — A  term  sometimes  employed 
for  annunciator. 

Indicator  Card. — The  card  of  a  steam- 
engine  indicator,  on  which  are  traced  the 
curves  of  pressure,  by  means  of  which  the 
indicated  horse-power  of  the  engine  may 
be  calculated. 

Indicator  Dial,  Electric. — In  a  system 
of  railway  block  signalling  by  electricity, 
an  electro-magnetic  indicator  having  a 
dial  which  shows  the  condition  of  a  sec- 
tion of  railway. 

Indicator,  Electric. — (1)  A  general  terra 


Ind.] 


808 


[Ind. 


applied  to  various  devices  operated  by  the 
deflection  of  a  magntic  needle,  or  the 
ringing  of  a  bell,  or  by  both,  for  indicat- 
ing, at  some  distant  point,  the  condition 
of  an  electric  circuit,  the  strength  of  cur- 
rent passing  through  any  circuit,  the 
head  of  water  or  other  liquid,  the  pressure 
on  a  boiler,  the  temperature,  the  speed  of 
an  engine  or  lines  of  shafting,  the  work- 
ing of  a  machine,  or  other  similar  events 
or  occurrences.  (2)  A  term  sometimes 
used  in  place  of  annunciator.  (3)  Any 
electric  or  magnetic  signalling  apparatus. 

Indicator  Flap. — A  light  metal  disk  or 
cover,  hinged  over  a  self-restoring  indi- 
cator, in  a  branching  multiple  telephone 
switchboard. 

Indifferent  Electrode. — In  electro-thera- 
peutics, the  electrode  that  is  employed  to 
merely  complete  the  circuit  through  the 
organ  or  part  of  the  body  subjected  to  the 
electric  current,  and  not  directly  con- 
cerned in  the  treatment  or  diagnosis  of 
the  diseased  part,  and  which,  therefore, 
may  be  located  at  any  convenient  point. 

Indifferent  Point. — A  point  in  the  intra- 
polar  regions  of  a  nerve,  where  the  ane- 
lectrotonic  and  cathelectrotonic  regions 
meet,  and  where  the  excitability  is,  there- 
fore, unchanged. 

Indirect  Distribution. — A  system  of 
electric  distribution  in  which  intermedi- 
ate contrivances  for  the  transformation 
or  accumulation  of  electric  energy  are 
employed  between  the  generator  and  the 
receptive  devices. 

Indirect  Electrolysis. — Chemical  react- 
ions effected  as  a  consequence  of  electro- 
lytic action,  as  distinguished  from  electro- 
lytic actions  themselves. 

Indirect  Excitation. — The  excitation  of 
a  muscle  obtained  by  placing  an  electrode 
on  its  nerve  instead  of  directly  on  the 
muscle. 

Indirect  Welder. — A  step-down  trans- 
former employed  in  electric  welding. 

Individual  Electric  Motors. — A  term 
sometimes  employed  for  electric  motors 
that  are  coupled  directly  to  the  shaft  of 
each  machine  to  be  driven  or  operated. 

Individual  Signal. — A  selective  signal,  or 
one  in  which  a  given  signal  only  is  sound- 
ed a.t  a  distant  point  on  a  circuit  with 
which  more  than  one  signal  is  connected. 

Individual  Signalling  Apparatus. — 
Signalling  apparatus  provided  with  indi- 
vidual signals. 

Individual  Telephone  Switchboard.— 
A  single  section  of  a  multiple  switch- 
board. 


Individual  Transformer.— A  transform- 
er employed  solely  for  the  supply  of  some 
particular  translating  device  or  group  of 
devices,  as  distinguished  from  a  trans- 
former which  supplies  a  number  of  cir- 
cuits or  groups. 

"  In-Door  "  Transformer.  — A  trans- 
former designed  for  use  inside  a  building. 

Induced. — (1)  Set  up  or  caused  by  induc- 
tion. (2)  Not  produced  by  metallic  com- 
munication. 

Induced  Atomic  or  Molecular  Cur- 
rents.— Currents  supposed  to  be  induced 
in  the  atoms  or  molecules  of  a  magnetiz- 
able substance  when  brought  into  mag- 
netic flux. 

Induced  Circuit. — An  inductive  circuit. 

Induced  Current. — A  current  produced 
by  electro-dynamic  induction. 

Induced  Current  of  Transformer. — A 
term  sometimes  employed  for  the  second- 
ary current  of  a  transformer. 

Induced  Direct-Current.— (1)  The  cur- 
rent produced  in  an  active  circuit  on  the 
breaking  of  such  circuit,  having  the  same 
direction  as  the  active  current  and  tend- 
ing to  prolong  and  strengthen  it.  (2)  The 
break-induced  current. 

Induced  Electromotive  Forces. — E.  M. 
F.'s  set  up  by  electro-dynamic  induction. 

Induced  Electric  Surgings. — Electric 
surgings  induced  in  neighboring  conduct- 
ors by  means  of  electric  surgings,  oscilla- 
tory discharges,  or  impulsive  current- 
rushes  in  their  vicinity. 

Induced  Electrostatic  Charge.  —  A 
charge  produced  by  bringing  a  body  inta 
an  electrostatic  field. 

Induced  Lightning  Discharge. — (1)  A 
lightning  discharge  produced  in  a  sub- 
stance by  induction  from  a  neighboring 
lightning  flash.  (2)  A  back  or  return 
lightning  stroke. 

Induced  M.  M.  F. — (1)  Any  magneto- 
motive force  produced  by  induction.  (2) 
The  aligned  or  structural  magneto-motive 
force,  as  distinguished  from  the  prime 
magneto-motive  force. 

Induced  Magnetic  Flux. —  Magnetic 
flux  produced  in  any  body  by  induction. 

Induced  Reverse  Currents.— (1)  The 
currents  induced  in  an  active  conductor 
at  the  moment  of  making  or  closing  the 
circuit  in  the  opposite  direction  to  the  in- 
ducing current,  and,  therefore,  tending  to 
check  its  flow.  (2)  The  current  induced 
in  the  secondary  on  making  or  breaking 
the  circuit  of  the  primary. 


Ind.] 


809 


[Ind. 


Induced  Spiral  or  Conductor. — A  term 
sometimes  used  for  the  secondary  spiral  or 
conductor  of  a  transformer. 

Inducing. —  Producing  electromotive 
forces,  currents,  or  fluxes,  by  means  of  in- 
duction. 

Inducing  Circuit. — Any  circuit  which 
causes  induction. 

Inducing  Current  of  Transformer. — A 
term  sometimes  employed  for  the  primary 
current  of  a  transformer. 

Inducing  Magnet. — The  permanent  mag- 
net of  a  relay. 

Inducing  Spiral  or  Conductor. — A  term 
sometimes  used  for  the  primary  spiral  or 
conductor  of  a  transformer. 

Inductance.— (1)  The  capacity  for  induc- 
tion possessed  by  an  active  circuit  on  itself, 
or  on  neighboring  circuits.  (2)  Self-in- 
duction. (3)  That  property,  in  virtue 
of  which  a  finite  electromotive  force 
impressed  on  a  circuit  does  not  im- 
mediately generate  the  full  current  due 
to  the  resistance  of  the  circuit,  and 
which,  when  the  electromotive  force 
is  withdrawn,  requires  a  finite  time 
for  the  current  strength  to  fall  to  its 
zero  value.  (4)  A  property,  by  virtue  of 
which  the  passage  of  an  electric  current 
is  necessarily  accompanied  by  the  absorp- 
tion of  electric  energy  in  producing  a 
magnetic  field.  (5)  A  constant  quantity 
in  a  circuit  at  rest,  and  devoid  of  iron,  de- 
pending only  upon  its  geometrical  ar- 
rangement, and  usually  expressed  in 
henrys,  or  in  centimetres. 

Inductance  Box. — A  box  containing  a 
number  of  graded  inductances,  and  em- 
ployed for  the  measurement  of  the  in- 
ductance of  a  circuit. 

Inductance  Bridge.  —  An  apparatus 
similar  to  a  Wheatstone's  bridge,  for 
measuring  the  inductance  of  a  circuit. 

Inductance  Coil. — (1)  An  impedance,  re- 
actance, or  choking  coil.  (2)  A  coil  placed 
in  a  circuit,  for  the  purpose  of  prevent- 
ing an  impulsive  current-rush  in  that 
circuit,  by  means  of  the  counter-electro- 
motive force  developed  in  the  coil  on 
being  magnetized. 

Inductance-Reactance. — The  reactance 
of  a  self-inductive  coil,  as  distinguished 
from  the  reactance  of  a  condenser,  or  a 
capacity-reactance. 

Inductance-Resistance. — Reactance. 

Inductance  Speed. — (1)  A  term  proposed 
for  the  product  of  the  co-efficient  of  self- 
induction  by  an  angular  velocity,  corre- 
sponding to  a  simple-harmonic  frequency. 
(2)  In  an  alternating-current  circuit,  the 


product  of  an  inductance  and  STT  times  the 
frequency. 

Inductanceless. — Devoid  of  inductance. 

Inductariceless  Circuit.— (1)  A  circuit 
practically  devoid  of  inductance.  (2)  A 
circuit  whose  magnetic  field  is  negli- 
gible, such,  for  example,  as  an  ordinary 
incandescent  lamp,  or  a  double-wound  re- 
sistance coil. 

Inducteous  Body. — A  term  proposed  by 
Faraday  for  a  body  in  which  a  charge  is 
induced  by  the  action  of  a  neighboring 
charge. 

Induction. — (1)  The  influence  exerted  by 
a  charged  body,  or  by  a  magnetic  field, 
on  neighboring  bodies  without  apparent 
communication.  (2)  The  influence  pro- 
duced through  a  dielectric  by  the  action 
of  electrostatic  or  magnetic  flux. 

Induction  Alternator. — A  name  some- 
times given  to  an  inductor  alternator. 

Induction  Booster. — An  ordinary  induc- 
tion m'otor  whose  field  coils  are  in  series 
with  the  mains,  employed  in  an  alternat- 
ing-current circuit  as  a  booster  or  feeder 
regulator. 

Induction  Bridge. — (1)  A  balance  in 
which  electro-magnetically  induced  cur- 
rents are  equilibrated.  (2)  An  induct- 
ance bridge. 

Induction  Coil. — An  apparatus  consisting 
of  two  associated  coils  of  insulated  wire 
employed  for  the  production  of  currents  by 
mutual  induction. 

Induction  Factor. — In  an  alternating- 
current  circuit  the  ratio  of  the  wattlesa 
component  of  current  to  the  total  current 
strength. 

Induction-Finder. — A  term  sometime* 
used  for  a  magnetic  explorer. 

Induction  Flux. — Total  magnetic  flux  iir 
any  portion  of  a  magnetic  circuit. 

Induction  Generator.— (1)  A  generator 
supplying  currents  which    are  received 
from  the  line  and  reinforced  within  its 
coils.     (2)  A  generator  which  operates  by 
induction  from  currents  in  a  short-cir- 
cuited armature.     (3)  An  induction-motor- 
driven  above  synchronism.     (4)  An  alter- 
nating-current dynamo  itself  incapable  of 
generating  currents  but  becoming  excited 
y  currents  received  from  the  line. 

Induction  Killer. — Any  anti-inductioa 
device. 

Induction  Motor. — (1)  An  asynchronous 
alternating-current  motor,  in  which  cur- 
rents are  induced  in  a  short-circuited  ele- 
ment or  armature.  (2)  A  polyphase  or 
uniphase  motor  operating  by  the  action 


Ind.] 


810 


[Ind. 


of  a  rotary  magnetic  field  upon  a  short- 
circuited  armature. " 

Induction  Multiphase-Motor. — An  al- 
ternating-current induction,  or  .asynchro- 
nous motor,  operated  by  multiphase  cur- 
rents. 

Induction  Plates  of  Condenser.— The 
metallic  plates  of  a  condenser  on  which 
the  charges  reside. 

Induction  Regulator. — A  term  some- 
times employed  for  an  alternating-current 
regulator. 

Induction  Resistance. — An  inductive 
resistance. 

Induction  Rotary. — A  term  sometimes 
employed  for  a  rotary  converter  without 
field  excitation. 

Induction  Screen. — (1)  A  plate  of  metal 
placed  between  two  adjacent  electrified 
bodies,  or  magnetic  coils,  for  the  purpose 
of  preventing  or  modifying  the  inductive 
action  they  exert  on  one  another.  (2)  A 
conducting  screen  wholly  or  -partially 
opaque  to  inductive  action. 

Induction  Telegraph. — A  general  term 
embracing  the  apparatus  employed  in  in- 
duction telegraphy. 

Induction  Telegraphy.— (1)  A  system  for 
telegraphing,  between  moving  trains  and 
fixed  stations  on  a  railroad,  by  means  of 
impulses  transmitted  by  induction  be- 
tween the  car  and  a  wire  parallel  with 
the  track.  (3)  Wireless  telegraphy. 

Induction  Top. — A  top  consisting  of  a 
copper  disc  supported  on  a  vertical  axis, 
which,  when  spun  before  the  poles  of  a 
steel  magnet,  assumes  an  inclined  posi- 
tion, by  reason  of  the  currents  produced 
therein. 

Induetional  Igniting  Device. — A  de- 
vice for  producing  ignition  by  an  induced 
electric  discharge. 

Inductionless. — Devoid  of  induction. 

Inductionless  Circuit. — A  circuit  devoid 
of  induction. 

Inductionless  Resistance.— <1)  A  resist- 
ance devoid  of  self-induction.  (2)  A 
double-wound  resistance. 

Inductive. — Capable  of  producing  induc- 
tion. , 

Inductive  Capacity  of  Line. — The  elec- 
trostatic capacity  of  a  line. 

Inductive  Circuit. — Any  circuit  in  which 
induction  occurs. 

Inductive  Connection. — A  connection  of 
one  circuit  with  another  by  means  of  in- 
duction only,  as  distinguished  from  me- 
tallic connection. 

Inductive  Disturbance. — Any   disturb- 


ance in  the  operation  of  a  telephone  o* 
telegraph  line  produced  by  induction. 

Inductive   Electromotive  Force. — An 

electromotive  force  produced  by  induc- 
tion. 

Inductive  Interference. — Inductive  dis- 
turbance on  a  line. 

Inductive  Leak. — A  leak  containing  in- 
ductance provided  in  a  cable  or  circuit  as 
distinguished  from  a  leak  containing  re- 
sistance only. 

Inductive  Leakance. — (1)  Leakage  tak- 
ing place  through  inductive  shunts.  (2) 
Leakage  artificially  produced  in  a  tele- 
graph or  telephone  circuit  through  in- 
duction coils. 

Inductive  Pole. — An  induced  pole. 
Inductive-Reactance. — Reactance  due  to 

self  induction  as  distinguished  from  re- 

a  ctance  due  to  a  condenser. 

Inductive  Retardation. — A  retardation 
in  the  appearance  of  a  signal,  at  the  dis- 
tant end  of  a  cable  or  circuit,  produced 
by  the  action  of  induction. 

Inductive  Resistance. — (1)  A  resistance 
possessing  self-induction.  (2)  The  react- 
ance of  a  circuit. 

Inductive  Resistance  Regulator. — Any 
regulator  suitable  for  altering  the  imped- 
ance of  a  circuit  or  conductor  by  varying 
its  inductance. 

Inductivity. — (1)  A  word  proposed  for 
specific  inductance.  (2)  Magnetic  perme- 
ability. 

Inductivity.— (1)  The  magnetic  perme- 
ability of  a  magnetic  medium.  (2;  The 
dielectric  constant  of  an  electric  medium. 

Inductively  Associated  Circuit. — Such 
a  position  of  a  circuit  as  regards  another 
circuit,  that  any  electric  change  in  one 
circuit  produces  a  corresponding  change 
in  the  other  circuit  by  induction 

Inductize. — To  subject  a  body  to  the  effects 
of  induction. 

Inductometer. — An  instrument  capable 
of  measuring  inductance. 

Inductpphone.— A  device  for  obtaining 
electric  communication  between  moving 
trains  and  fixed  stations  by  means  of  in- 
duction currents. 

Inductor  Alternator. — (1)  An  inductor 
dynamo  for  alternating  currents.  (2)  An 
alternator  in  which  both  armature  and 
field  are  fixed,  but  in  which  a  rotating 
frame  is  so  placed  in  relation  to  each  as  to 
generate  E.  M.  F.'s  in  conducting  loops 
or  coils  on  the  armature. 

Inductor  Alternating  Generator. — An 
alternator  in  which  neither  the  field  coils 


Incl.] 


811 


Tins. 


nor  the  armature  rotates,  but  an  iron 
frame  rotates  in  such  a  manner  as  to 
periodically  fill  and  empty  the  armature 
loops  with  magnetic  flux. 
Inductor  Dynamo.— (1)  A  generator  in 
which  the  field  and  armature  coils  are 
stationary,  and  the  magnetic  flux  through 
them  is  altered  by  the  motion  of  inductors 
past  them.  (2)  A  dynamo-electric  gener- 
ator in  which  the  differences  of  potential 
causing  the  currents  are  obtained  by  mag- 
netic changes  in  the  cores  of  the  armature 
and  field  coils  by  the  movements  of  in- 
ductors past  them. 

Inductor  Generators.— Inductor  alter- 
nators or  dynamos. 

Inductors  of  Electrostatic  Machine. — 
The  electrified  parts  of  an  electrostatic 
influence  machine,  which  exert  inductive 
influence. 

Inductors. — The  laminated  masses  of  iron 
employed  in  inductor  dynamos  for  the 
purpose  of  producing  variations  in  the 
magnetic  flux  of  the  core  and  armature. 

Inductprium. — A  name  sometimes  given 
to  an  induction  coil. 

Inductoscope. — Any  apparatus  for  de- 
tecting the  presence  of  induction  between 
two  circuits. 

Inductric. — Capable  of  producing  induc- 
tion. 

Inductric  Body. — A  term  proposed  by 
Faraday  for  the  body  containing  the  in- 
ducing electric  charge. 

Inefficiency  of  Incandescent  Lamp. — 
The  number  of  watts  that  have  to  be  sup- 
plied to  an  incandescent  lamp  per-candle- 
power  emitted,  very  commonly,  but  inac- 
curately, called  the'efficiency  of  the  lamp. 

Inertia.— The  inability  of  a  body  to  change 
its  condition  of  rest  or  motion  until  some 
rorce  acts  on  it. 

Inertia,  Electric. — A  term  sometimes 
used  for  electro-magnetic  inertia. 

Inertia  Factor.— The  factor  in  a 'dynami- 
cal system  in  virtue  of  which  the  moving 
system  possesses  kinetic  energy. 

Inferred  Zero.— (1)  A  zero  deduced  or 
inferred  from  the  deflection  produced  by 
a  charge  that  is  to  be  measured,  by  com- 
parison with  the  value  of  the  deflection 
obtained  by  a  known  charge.  (2)  A  zero 
on  the  scale^of  an  instrument,  too  remote 
to  be  mechanically  obtainable,  but  as- 
sumed as  virtually  existing  for  the  pur- 
poses of  calculation. 

Infinity  Plug.— (1)  A  plug  provided  for 
a  hole  in  a  resistance  box  in  which  the 
two  pieces  of  brass  the  plug  connects  are 
not  connected  by  any  resistance  coil,  and 


which,  therefore,  when  withdrawn,  leaves 
an  open  circuit  of  a  practically  infinite 
resistance.  (2)  A  discontinuity  plug. 
Inflection.— The  bending  by  diffraction  of 
rays  of  light  or  radiant  energy  on  their 
passage  past  a  sharp  edge. 

Inflexible  Conduit  System.— A  conduit 
system  which  will  not  permit  the  intro- 
duction or  removal  of  its  conductors, 
after  the  structure  is  completed. 

Influence. — A  word  sometimes  used  in- 
stead of  electrostatic  induction. 

Influence  Charge. — A  charge  produced 
by  electrostatic  induction. 

Influence,  Electric.— Electrostatic  induc- 
tion. 

Influence  Machine. — A  name  sometimes 
used  for  an  electrostatic-induction  ma- 
chine. 

Infra-Red  Frequencies.  — Frequencies 
lower  or  smaller  in  Dumber  than  those  of 
red  light. 

Infra-Bed  Light.— A  term  applied  to  radi- 
ation frequencies  below  the  reds  of  the 
spectrum. 

Infra-Red  Spectrum.— That  portion  of 
the  spectrum  which  lies  below  the  red,  or 
whose  frequencies  are  smaller  than  those 
of  the  red. 

Initial.  — Placed  or  occurring  at  the  be- 
ginning. 

Initial  Magnetization.  —  Magnetization 
originally  produced  or  imparted. 

Injection  of  Telegraph  Poles.— Impreg- 
nating telegraph  poles  with  any  preser- 
vative liquid. 

Injector. — An  apparatus  for  the  introduc- 
tion of  a  condenser  or  other  device  into  an 
electric  circuit  at  a  definite  moment  and 
for  a  definite  interval  of  time. 

Inners. — In  telephony,  the  internal  pair  of 
springs  of  a  jack. 

In-Put. — The  power  absorbed  by  any  ma- 
chine in  causing  it  to  perform  a  certain 
amount  of  work. 

Inside  Box-Brush. — A  brush  suitably 
shaped  for  polishing  the  inside  of  tubular 
surfaces,  for  the  purpose  of  cleansing  such 
surfaces  so  as  to  prepare  them  for  electro- 
plating. 

Inside  Wiring.— (1)  In  a  system  of  incan- 
descent lighting,  the  conductors  that  lead 
to  the  interior  of  a  house  or  other  building 
to  be  lighted.  (2)  Any  conductors  placed 
inside  a  building. 

Inside  Work. — Indoor  wiring. 

Insulation,  Electric. — A  term  sometimes 
employed  for  electric  sun-stroke  or  elec- 
trie  prostration. 


Ins.] 


812 


[Ins. 


.Inspection  Boxes. — Man-holes  provided 
for  the  inspection  of  electric  mains. 

-Installation. — (1)  A  general  term  embrac- 
ing the  entire  plant  and  accessories  re- 
quired to  perform  any  specified  work. 
(2)  The  act  of  placing,  arranging  or  erect- 
ing a  plant  or  apparatus. 

Installation,  Electric. — (1)  The  establish- 
ment of  any  electric  plant.  (2)  A  plant. 

Instantaneous. — Occurring  at  an  instant. 

Instantaneous-Contact  Method.  —  A 
method  of  determining  the  form  of  an 
alternating-current  wave  by  making  con- 
tacts with  the  circuit  at  definite  instants 
in  each  cycle. 

Instantaneous  Current. — The  current 
strength  taken  at  any  given  moment  of 
time. 

Instantaneous  Electromotive  Force. — 
The  value  of  the  electromotive  force  taken 
at  any  given  instant  of  time. 

Instantaneous  Efficiency  of  Trans- 
former.— The  efficiency  of  a  transformer 
taken  at  any  instant  of  time,  as  distin- 
guished from  its  mean  efficiency,  or  its 
efficiency  extending  over  a  fairly  consid- 
erable time. 

Instantaneous  Pressure.— The  instan- 
taneous electromotive  force. 

Instantaneous  Value  of  Periodic  Cur- 
rent or  E.  M.  P.— The  value  of  a  peri- 
odic current  or  E.  M  F.  at  any  given  in- 
stant of  time  as  distinguished  from  an 
average  or  effective  value. 

Instantaneous  Values. — Values  meas- 
ured at  a  given  instant  of  time,  as  dis- 
tinguished from  average  values. 

Instrument  Bars. — In  a  multiple  tele- 
phone switchboard  the  conducting  bars 
connected  to  an  operator's  set. 

Instrument  Zero. — The  true  zero  of  an 
instrument  scale,  as  distinguished  from  a 
zero  selected  at  some  other  point  or  a 
false  zero. 

Insulate. — To  so  insulate  a  body  as  to  pre- 
vent electricity  from  being  conducted  to 
or  removed  from  it. 

Insulated  Body. — A  body  supported  on 
or  surrounded  by  an  insulator,  or  non- 
conductor of  electricity. 

Insulated  Conductors.  —  Conducting 
wires  provided  with  an  insulating  coating 
or  covering. 

Insulated. — A  term  sometimes  employed 
in  telegraphy  for  a  free  wire,  or  a  wire 
that  is  disconnected  from  its  apparatus 
and  left  insulated. 

Insulated  Pliers. — A  pair  of  pliers  whose 


handles  are  encased  in  insulating  ma- 
terial. 

Insulated  Trolley-Crossing. — A  cross- 
ing placed  at  the  intersection  of  two 
streets  where  trolley  wires  cross  each 
other,  provided  with  an  insulating  mate- 
rial to  prevent  the  contact  of  the  crossing 
wires. 

Insulated  Turn-Buckle.— (1)  A  turn- 
buckle  carrying  a  shackle  insulator  at  one 
end.  (2)  A  device  supported  by  suitable 
insulators  employed  on  overhead  circuits' 
for  straightening  the  wires  by  increasing 
the  stress  on  them. 

Insulated  Wires. — Wires  provided  with 
insulating  coverings  or  coatings. 

Insulating. — Providing  with  insulation. 

Insulating  Bushing. — A  bushing  made 
of  insulating  material. 

Insulating  Cements. — Various  mixtures 
of  gums,  resins  and  other  substances  pos- 
sessing the  ability  not  only  of  binding  two 
or  more  substances  together,  but  also  of 
electrically  insulating  them  from  one 
another. 

Insulating  Coating. — A  coating  or  cover- 
ing of  insulating  material. 

Insulating  Covering.— An  insulating 
coating. 

Insulating  Joint. — A  joint  in  an  insulat- 
ing material  or  covering  in  which  the 
continuity  of  the  insulating  material  is 
ensured. 

Insulating  Sleeve.— A  sleeve  formed  of 
insulating  material,  and  provided  for 
covering  splices  in  an  insulated  con- 
ductor. 

Insulating  Stool. — A  stool  provided  with 
insulating  supports  of  vulcanite,  or  simi- 
lar high-insulating  substance,  employed 
to  afford  a  convenient  insulating  stand  or 
support. 

Insulating  Tape. — A  ribbon  of  flexible 
material  impregnated  with  okonite,  rub- 
ber, or  other  similar  material,  and  gen- 
erally containing  some  adhesive  sub- 
stance, employed  for  insulating  wires  or 
electric  conductors  at  joints,  or  other  ex- 
posed places. 

Insulating  Tube. — (1)  A  tube  of  insulat- 
ing material  provided  for  covering  a  splice 
in  an  insulated  conductor.  (2)  A  tube 
of  insulating  material  provided  for  slii> 
ping  over  an  insulated  conductor  where  it 
passes  through  a  partition,  and  employed 
for  preventing  the  abrasion  of  the  insu- 
lating material  at  that  point. 

Insulating  Varnish. — An  electric  varnish 
formed  of  any  good  insulating  material. 


Ins,] 


813 


Insulating  Washer. — A  washer  formed 
of  insulating  material. 

Insulation.  —  Any  medium  or  material 
that  will  prevent  a  body  from  gaining  or 
losing  light,  heat,  electricity,  etc. 

Insulation  Bracket. — A  bracket  of  insu- 
lating material,  provided  with  an  insu- 
lator. 

Insulation  Break-Down. — Any  failure 
of  the  insulation  which  prevents  it  from 
insulating. 

Insulation,  Electric. — A  non-conducting 
material  so  placed  with  respect  to  a  con- 
ductor as  to  prevent  either  the  loss  of  its 
charge,  or  the  leakage  of  its  current. 

Insulation  Joint. — A  joint  in  an  insu- 
lating material  or  covering  in  which  con- 
tinuity is  preserved  both  in  the  conducting 
and  in  the  insulating  substance. 

Insulation  Lightning-Protection. — The 
protection  of  an  instrument  by  means  of 
an  insulating  lightning-protector  from  the 
jumping  of  a  spark  across  it  from  layer 
to  layer. 

Insulation  Lightning-Protector.  —  A 
lightning  protector  by  means  of  which  a 
discharge  is  prevented  from  jumping 
across  the  coils  of  an  instrument  from, 
layer  to  layer,  and  thus  damaging  its 
insulation. 

Insulation  Materials.  —  (1)  Materials 
whose  resistivity  is  high.  (2)  Non-con- 
ductors. 

Insulation  Resistance. — (1)  The  resist- 
ance existing  between  a  conductor  and 
the  earth,  or  between  two  conductors 
in  a  circuit  through  insulating  materials 
lying  between  them.  (2)  The  resistance 
taken  between  a  line  or  conductor  and 
the  earth  through  the  insulators,  or  be- 
tween two  separate  wires  of  a  cable 
through  the  insulating  materials  separ- 
ating them.  (3)  A  terin  sometimes  applied 
to  the  resistance  of  the  insulating  ma- 
terial of  a  covered  wire  or  conductor. 
(4)  The  resistance  of  any  insulation. 

Insulator. — Any  device  employed  for  in- 
sulating a  wire  or  other  body. 

Insulator  Bracket. — A  frame  of  wood  or 
metal  for  holding  the  insulator  of  an 
overhead  wire,  and  of  such  simple  form 
as  to  be  readily  attached  to  a  wall  or 
support. 

Insulator  Cap. — A  cover  or  cap  placed 
some  distance  above  an  insulator,  but 
separated  from  it  by  an  air  space. 

Insulator  Pin. — The  bolt  by  which  an 
insulator  is  attached  to  a  bracket,  pole- 
arm,  or  support. 

Intaglio. — (1)  An  engraving  in  which  the 


surface  is  so  hollowed  out  that  an  im 
pression  therefrom  would  give  the  ap- 
pearance of  a  bas-relief.  (2)  The  copy  ol 
a  coin  or  other  similar  object  obtained 
in  an  electro. 

Intake. — A  word  sometimes  used  instead 
of  input. 

Intake  of  Dynamo. — The  mechanical 
activity  which  a  dynamo  absorbs  when 
running. 

Intake  of  Machine. — The  activity  re- 
quired to  operate  a  machine. 

Intake  Wires. — The  wires  which  feed  a 
distribution  box. 

Integrating  Meter. — Any  meter  which 
leaves  a  record  of,  and  sums  up,  or  inte- 
grates, some  quantity  with  respect  to 
time. 

Integrating  Wattmeter. — (1)  A  watt- 
hour  meter,  or  a  meter  which  integrates 
the  power  which  passes  through  it  with 
respect  to  time.  (2)  An  energy  meter. 

Integrator. — An  apparatus  for  automat- 
ically performing  the  operation  of  inte- 
gration, or  th.e  continuous  summing  up 
of  instantaneous  values. 

Intensity.— (1)  The  surface  density  of  a 
vector  or  directed  quantity.  (2)  The  de- 
gree of  concentration  with  which  a  num- 
ber of  forces  act. 

Intensity  Armature. — A  term  formerly 
employed  for  an  armature  with  coils  of 
many  turns,  and,  consequently,  of  a  com- 
paratively high  resistance.  (Obsolete.) 

Intensity  Current. — A  term  formerly 
employed  for  the  current  produced  by  a 
series-connected  battery.  (Obsolete.) 

Intensity  of  Current. — (1)  A  term  taken 
from  the  French  language  to  indicate  cur- 
rent strength.  (2)  Current  density,  or  cur- 
rent strength  per-unit-area  of  normal 
cross-section. 

Intensity  of  Field. — The  strength  or 
density  of  a  magnetic  field  as  measured 
by  the  quantity  of  magnetic  flux  that 
passes  through  it  per-unit-of-area  of  nor- 
mal cross-section. 

Intensity  of  Illumination. — The  quan- 
tity of  light  received  per-unit-of -surface . 

Intensity  of  Light. — (1)  In  a  given  direc- 
tion of  emission,  the  ratio  of  the  flux  of 
light  in  a  small  solid  angle  containing 
that  direction  to  the  solid  angle.  (2)  The 
candle-power  of  a  light. 

Intensity  of  Magnetic  Flux.;— (1)  The 
quantity  of  magnetic  flux  per-unit-of-area 
of  normal  cross-section.  (2)  The  density 
of  magnetic  flux. 

Intensity   of  Magnetization.  —  (1)   A 


Int.] 

quantity  which  represents  the  intensity 
of  magnetization  produced  in  a  sub- 
stance. (2)  A  quantity  which  represents 
the  intensity  with  which  a  magnetizable 
substance  is  magnetized.  (3)  Magnetic 
moment  per-unit-volume.  (4)  The  sur- 
face density  of  imaginary  magnetic  mat- 
ter on  any  surface  normal  to  the  direc- 
tion of  magnetization. 


Intensity  of  Radiation. — (1)  The  ratio 
existing  between  the  amount  or  quantity 
of  radiation,  and  the  surface  from  which 
that  radiation  takes  place.  (2)  The  ratio 
of  the  flux  of  energy  in  any  small  solid 
angle  of  a  beam  to  the  solid  angle. 

Interactance. — In  an  induction  coil  oper- 
ated on  a  simple  alternating-current 
circuit,  the  product  of  the  mutual  in- 
ductance and  the  angular  velocity  cor- 
responding to  the  frequency  of  the  cur- 
rent, and  expressible  in  ohms. 

Inter  Air-Space.  —  A  term  sometimes 
employed  for  the  air-space  or  entrefer. 

Inter-Atomic  Ether. — A  term  sometimes 
used  for  the  ether  existing  between  the 
constituent  atoms  of  the  molecules. 

Tnter-Connected  Armature-Winding. 
(1)  Such  a  connection  of  the  separate 
circuits  in  a  multipolar  armature  as  will 
permit  a  single  pair  of  brushes  to  be 
employed  on  the  commutator.  (2)  A 
cross-connected  armature. 

Inter-Connection. — The  cross-connection 
of  an  armature. 

Inter-Crossing.  —  In  a  system  of  tele- 
phonic circuits,  a  device  for  avoiding  the 
disturbing  effects  of  induction,  by 
alternately  crossing  equal  sections  of  the 
line  wires. 

Inter-Exchange  Working.  —  (1)  Tele- 
phonic communication  effected  through 
the  medium  of  more  than  a  single  ex- 
change (2)  Telephone  communication 
passing  between  two  exchanges,  or  be- 
tween two  subscribers  connected  there- 
with. 

Interference  of  Electro-Magnetic 
Waves. — Interference  effects,  similar  to 
those  produced  in  the  case  of  light  and 
sound,  observed  in  electro-magnetic 
waves  when  two  systems  of  waves  of  equal 
frequency  simultaneously  act,  in  opposed 
phases,  on  the  same  medium. 

Inter-Ferric  Gap. — (1)  An  air-gap  in  an 
aero-ferric  magnetic  circuit  between  iron 
and  iron.  (2)  The  entrefer. 

Inter-Ferric  Space.— An  inter-ferric  gap. 

Interflange. — The  distance  between  the 
two  flanges  of  a  bobbin,  measured  par- 
allel to  the  bobbin's  axis,  and  represent- 


814  [Int. 

ing  the  length  of  the  cylindrical  spaca 
which  may  be  occupied  by  wire  w  hen  tha 
bobbin  is  wound. 

Inter-Induction. — Mutual  induction. 

Interior  Conduit. — (1;  A  conduit  provided 
inside  the  walls  of  a  house,  or  in  other 
convenient  spaces  within  a  house,  for  the 
reception  of  the  house  wires.  (2)  A  con- 
duit in  the  walls  or  floors  of  a  building, 
provided  for  accommodating  electrio 
conductors. 

Interior-Conduit  Junction-Box. — The 
box  provided  in  a  system  of  interior  con- 
duits to  receive  the  terminals  of  the  feed- 
ers, and  in  which  connection  is  made 
between  the  feeders  and  the  mains,  or 
the  mains  and  branches. 

Interior-Pole  Dynamo. — A  dynamo  hav- 
ing field  poles  in  the  interior  of  a  cylin- 
drical or  Gramme-ring  armature. 

Inter-Linked      Diphase-System.  —  A 

three-wire  diphase-system. 

Inter-Linked    Polyphase-System. — A 

polyphase  system  of  conductors  so  inter- 
connected that  one  wire  serves  as  the 
return  for  another,  and  distinguished 
from  a  polyphase  system  in  which  each 
phase  is  provided  with  a  separate  circuit. 

Inter-Locking  Apparatus. — A  device  for 
mechanically  operating  railroad  switcheg 
and  semaphoric  signals  from  a"  distant  sig- 
nalling tower,  for  the  purpose  of  indicat- 
ing the  position  of  such  switches,  by 
means  of  a  system  of  inter-locking  levers, 
so  inter-locked  as  to  render  it  impossible, 
af  !;er  a  route  has  once  been  set  and  a  sig- 
nal given,  to  clear  a  signal  for  a  route 
that  would  conflict  with  the  one  previ- 
ously set  up. 

Inter-Locking  Magnet.— A  magnet  em- 
ployed in  a  system  of  electric  railroad 
signals  for  crossings,  whereby  a  gong  ig 
caused  to  ring  at  the  crossings  on  the  ap- 
proach of  a  train,  and  is  automatically 
stopped  by  the  same  train  after  it  has 
passed  the  crossing. 

Intermediate  Cable. — A  type  of  cable 
intermediate  between  a  shore-end  cable 
and  a  deep-sea  cable. 

Intermediate  Station.— Any  station  be- 
tween the  terminal  stations  of  a  telegraph 
line. 

Intermediate  Switch. —  A  switch  em- 
ployed at  an  intermediate  telephone 
station  for  communicating  with  either 
terminal  station  at  will,  without  inter- 
rupting the  line. 

Intermittent.  —  (1)  Acting  at  interval* 
only.  (2)  Fluctuating  or  pulsating. 


Int.] 


815 


Intermittent  Contact. — The  occasional 
contact  of  a  telegraphic  or  other  line 
with  other  wires  or  conductors,  by  swing- 
ing, or  by  alternate  contractions  and  ex- 
pansions, occasioned  by  changes  of  tem- 
perature. 

Intermittent  Cross. — (1)  An  accidental 
contact,  generally  metallic,  occasioned  by 
wires  being  brought  into  occasional  con- 
tact with  one  another,  or  with  some  other 
conductor  by  the  intermittent  action  of 
the  wind.  (2)  A  swinging  cross. 

Intermittent  Current. — A  current  that 
does  not  flow  continuously,  but  which . 
flows  and  ceases  to  flow  at  intervals,  so 
that  electricity  is  practically  alternately 
present  and  absent  from  the  circuit. 

Intermittent  Currents  of  Wheatstone 
System. — In  the  Wheatstone  automatic 
system  the  transmission  of  short  initial 
and  final  currents  in  each  signal. 

Intermittent  Disconnection. — Any 
fault  in  a  line  which  occurs  at  intervals 
or  intermittently. 

Intermittent  Electromotive  Force. — 
An  electromotive  force  which  acts  inter- 
mittently. 

Intermittent  Earth. — (1)  A  fault  in  a 
telegraphic  or  other  line  in  which,  by  the 
action  of  the  wind,  or  by  occasional  ex- 
pansion by  heat,  the  line  is  brought 
into  intermittent  contact  with  the  earth. 
(2)  A  swinging  earth. 

Intermittent  Integrating  Meter.  —  A 
meter  which  does  not  take  a  reading  of 
the  current  or  .power  continucusly,  but 
at  regular  intervals,  and  then  adds  up 
the  result. 

Intermittent  System  of  Currents. — A 
system  of  currents  employed  in  teleg- 
raphy, in  which  the  initial  and  final 
currents  are  separated  by  an  interval  or 
insulation. 

Intermitter. — An  interrupter. 

Inter-Molecular.  —  Between  the  mole- 
cules. 

Inter-Molecular  Ether. — A  term  some- 
times used  for  the  ether  that  exists  be- 
tween the  molecules  of  matter. 

Internal  Armature  Generator.— A  gen- 
erator in  which  the  armature  is  situated 
within  the  field-poles,  as  distinguished 
from  a  generator  whose  armature  is  exter- 
nal to  the  field. 

Internal  Characteristic  of  Dynamo. — 
A  curve  showing  the  E.  M.  F.  generated 
in  a  dynamo  under  varying  excitation,  as 
distinguished  from  the  external  charac- 
teristic showing  the  E.  M.  F.  at  terminals. 


Internal  Circuit. — That  part  of  a  circuit 
which  is  included  within  the  electric 
source. 

Internal  Magnetic-Circuit.  —  A  term 
sometimes  employed  for  that  part  of  a 
magnetic  circuit  which  lies  within  the 
magnetic  core. 

Internal  Magnetic-Field. — That  portion 
of 'a  magnetic  field  produced  by  a  magnet 
which  lies  within  the  magnetic  core. 

Internal  Polarization  of  Moist  Body. — 
A  polarization  exhibited  by  such  moist 
bodies  as  nervous  or  muscular  fibres, 
the  juicy  parts  of  vegetables  and  animals, 
or  in  general,  by  all  bodies  possessing  a 
firm  structure  and  filled  with  a  liquid,  on 
the  passage  through  them  of  a  strong 
electric  current. 

Internal  Poles  of  Dynamo. — (1)  The  in- 
wardly projecting  field  poles  of  a  dy- 
namo. (2)  Magnetic  field-poles  internal 

•   to  an  armature. 

International  Ampere. — (1)  The  value 
of  the  ampere  as  adopted  by  the  Inter- 
national Congress  of  1893,  at  Chicago. 
(2)  The  value  of  an  ampere  equal  to  the 
one-tenth  of  a  unit  of  current  in  the  C. 
G.  S.  system  of  electro-magnetic  units, 
and  represented  with  sufficient  accuracy 
for  practical  purposes,  by  the  unvarying 
current,  which,  when  passed  through  a 
solution  of  nitrate  of  silver  in  water,  in 
accordance  with  certain  specifications, 
deposits  silver  at  the  rate  of  0.001118  of  a 
gramme-per-second. 

International  Coulomb. — (1)  The  value 
of  the  coulomb  as  adopted  by  the  Inter- 
national Electrical  Congress  of  1893,  at 
Chicago.  (2)  The  quantity  of  electricity 
equal  to  that  transferred  through  a  cir- 
cuit by  a  current  of  one  International 
ampere  in  one  second. 

International  Farad.— (1)  The  value  of 
the  farad  as  adopted  by  the  International 
Electrical  Congress  of  1893,  at  Chicago. 
(2)  The  capacity  of  a  conductor  charged 
to  a  potential  of  one  International  volt  by 
one  International  coulomb  of  electricity. 

International  ?Tenry.— (1)  The  value  of 
the  henry  as  adopted  by  the  International 
Electrical  Congrest.  cf  1893,  at  Chicago. 
(2)  The  value  of  the  induction  in  a  circuit, 
when  the  electromotive  force  induced  in 
the  circuit  is  one  International  volt,  and 
the  inducing  current  varies  at  the  rate  of 
one  ampere  per  second. 

International  Joule.— (1)  The  value  of 
the  joule  as  adopted  by  the  International 
Electrical  Congress  of  1893,  at  Chicago. 
(2)  A  value  equal  to  107  units  of  work  of 


Int.] 


816 


[Iny. 


the  C.  G.  S.  system  and  represented  with 
sufficient  accuracy  for  practical  purposes 
by  the  energy  expended  in  one  second  by 
one  ampere  in  one  International  ohm. 

-International  Morse  Code. — A  term 
sometimes  employed  for  the  International 
telegraphic  alphabet,  as  distinguished 
from  the  American  Morse  Code. 

International  Ohm. — (1)  The  value  of 
the  ohm  as  adopted  by  the  International 
Electrical  Congress  of  1893,  at  Chicago. 
(2)  A  value  of  the  ohm  equal  to  109  units 
of  resistance  of  the  C.  G.  S.  system  of 
electro-magnetic  units,and  represented  by 
the  resistance  offered  to  an  unvarying 
electric  current  by  a  column  of  mercury 
at  the  temperature  of  melting  ice,  14.4521 
grammes  in  mass,  of  a  constant  cross-sec- 
tional area,  and  of  the  length  of  106.3 
centimetres. 

International  Telegraphic  Code. — The 
International  Morse  Code. 

International  Unit  of  Activity. — The 

International  watt. 

International  Unit  of  Work.— The  In- 
ternational joule. 

International  Volt.— (1)  The  value  of  the 
volt  as  adopted  by  the  International 
Electrical  Congress  of  1893,  at  Chicago. 
(2)  Such  an  electromotive  force  that 
steadily  applied  to  a  conductor  whose 
resistance  is  one  International  ohm,  will 
produce  a  current  of  one  International 
ampere,  and  which  is  represented  with 
sufficient  accuracy  for  practical  use  by 
^4$  of  the  electromotive  force  between 
the  poles  or  electrodes  of  the  voltaic  cell 
known  as  Clark's  cell,  at  a  temperature  of 
15°  Cent,  when  prepared  in  accordance 
with  certain  specifications. 

International  Watt.— (1)  The  value  of 
the  watt  as  adopted  by  the  International 
Electrical  Congress  of  1893,  at  Chicago. 
(2)  A  value  equal  to  107  units  of  activity 
in  the  C.  G.  S.  system,  and  equal  to  the 
work  done  at  the  rate  of  one  joule-per- 
second. 

Inter-Node. — The  space  between  two  ad- 
jacent nodes. 

Inter-Polar. — Between  the  poles. 

Inter-Polar  Gap. — An  air-gap  or  space 
between  the  faces  of  opposing  pole-pieces. 

Inter-Polar  Space. — The  inter-polar  gap. 

Interpolated  Commutator  Segments. 
Blank  commutator  segments. 

Interrupted. — Broken  or  opened. 

Interrupted  Current  System.— A  sys- 
tem of  electric  distribution  effected  by 
the  aid  of  periodically  interrupted  contin- 
uous currents. 


Interrupter. — Any  device  for  interrupt- 
ing or  breaking  a  circuit. 

Inter-Urban  Communication.— Tele« 
graphic  or  telephonic  communication  be- 
tween adjacent  cities. 

Inter-Urban   Electric    Railway.— An 

electric  railway  suitable  for  use  between 

adjacent  cities. 
Inter  -  Urban    Telephony.—  Telephonic 

communication  carried  on  between  adja- 

cent  cities. 
Intra-Molecular. — (1)  Inter-molecular,  01 

between  the  molecules.    (2)  Within  the 
*    confines  of  a  molecule. 

Intra-Polar  Electrolysis.—  Electrolytic 
action  taking  place  in  the  region  between 
the  electrodes,  as  distinguished  from  that 
which  occurs  in  their  immediate  vicinity. 

Intrinsic  Brilliancy  of  Luminous 
Source. — (1)  At  any  point  of  a  luminous 
surface  the  ratio  of  the  luminous  intensity 
along  the  normal  to  the  small  surface  area 
from  which  it  is  emitted.  (2)  Luminous 
intensity  per-unit-area  of  normal  lumi- 
nous surface. 

Intrinsic  Electrization. — A  term  pro- 
posed for  permanent  impressed  electriza- 
tion in  a  substance  from  internal  causes. 

Intrinsic  Intensity  of  Light.— The 
quantity  or  flux  of  light  emitted  normally 
from  a  unit  of  surface  of  a  luminous 
source. 

Intrinsic  Magnetization.  —  Magnetiza- 
tion due  to  impressed  magnetic  force,  as 
distinguished  from  magnetization  due  to 
electric  currents. 

Intrinsic  Radiation  of  Luminous 
Source. — (1)  The  radiation  of  a  luminous 
source  expressed  in  lumens-per-square- 
centimetre.  (2)  The  flux  density  of  light 
issuing  normally  from  a  luminous  source. 

Invariable  Calibration  of  Galvano- 
meter.— In  a  galvanometer  with  absolute 
calibration,  a  method  for  preventing  the 
occurrence  of  variations  in  the  intensity 
of  the  field  of  a  galvanometer,  due  to  the 
neighborhood  of  masses  of  iron. 

Inverse  Current. — (1)  The  current  which 
tends  to  be  produced  by  a  current  in  its 
own  circuit  on  making  or  closing  the  cir- 
cuit. (2)  The  current  produced  in  the 
secondary  of  an  induction  coil  on  the  mak- 
ing or  completion  of  the  circuit  of  the 
primary.  (3)  The  make-induced  current. 

Inverse  Electromotive  Force. — An  elec- 
tromotive force  which  acts  in  the  oppo- 
site direction  to  another  already  existing 
electromotive  force. 

Inverse  Secondary  Current.— Thn 
make-induced  current. 


IllV.] 


817 


[Iro, 


Inversion,  Electric. — The  determination 
of  electric  disti'ibution  over  the  surfaces  of 
neighboring  electrified  conductors  by  the 
geometrical  method  of  inversion. 

Invert  Insulator. — An  insulator  support- 
ed in  an  inverted  position. 

Inverted  Arc. — An  inverted  arc-lamp. 

Inverted  Arc-Lamp. — An  electric  arc- 
lamp  in  which  the  positive  carbon  is 
lowermost,  or  inverted,  as  compared  with 
its  position  in  the  ordinary  arc-lamp. 

Inverted  Dynamo. — A  dynamo  whose 
armature  bore  or  chamber  is  placed  below 
the  field-magnet  coils. 

Inverted  Induction-Coil. — A  term  some- 
times employed  for  a  step-down  trans- 
former. 

Invisible  Electric-Contact  Matting.— 
A  matting  or  other  floor  covering,  pro- 
vided with  a  series  of  invisible  electric 
contacts,  which  are  closed  by  a  person 
walking  over  them. 

Invisible  Spectrum. — That  portion  of  the 
spectrum  which  is  incapable  of  affecting 
the  eye  as  light. 

Ionic. — Of  or  pertaining  to  the  ions. 

Ions. — The  groups  of  atoms  or  radicals  into 
which  a  molecule  is  separated  by  electro- 
lytic decomposition. 

Ionic  Attraction. — The  mutual  ( attrac- 
tion produced  by  the  cathions  and  the 
anions. 

Ionic  Conductivities. — Specific  conduc- 
tivities of  ions,  so  selected  that  their  sums 
give  molecular  conductivities  for  any 
combination  of  ions. 

lonisation.  —  (1)  The  decrease  in  the 
strength  with  which  the  separate  atoms 
or  radicals  are  held  together  in  the  mole- 
cules of  an  electrolyte.  (2)  A  modified 
dissociation  of  the  molecule  of  an  elec- 
trolyte which  consists  in  the  weakening 
of  the  force  which  holds  together  its  ions 
or  radicals. 

Iron-Armored  Conduit.— (1)  A  conduit 
provided  with  an  exterior  iron  casing  or 
covering.  (2)  A  conduit  in  which  each 
duct  has  an  iron  casing  or  covering. 

Iron-Clad. — Surrounded  by  iron. 

Iron-Clad  Armature.— (l)The  armature  of 
a  dynamo  or  motor,  whose  insulated  coils 
are  entirely  or  nearly  surrounded  by  the 
iron  of  the  armature  core.  (2)  An  arma- 
ture in  which  the  conductors  are  buried 
in  slots,  grooves,  or  tunnels  below  the 
surface  of  the  armature  core. 

Iron-Clad  Armature  Windings. —  Ar- 
mature windings  that  are  entirely  or 
nearly  surrounded  by  iron. 

52 


Iron-Clad  Coil. — An  iron-clad  magnet. 
Iron  -  Clad   Drop. — An   annunciator   o« 

telephone  drop  whose  electro-magnet  is 

iron-clad. 

Iron-Clad  Dynamo.— (1)  A  dynamo  whose 
armature  is  iron -clad.  (2)  An  iron-en- 
cased dynamo. 

Iron-Clad  Electro-Magnet. — An  electro- 
magnet whose  magnetizing  coil  is  almost 
entirely  surrounded  by  iron — in  some 
cases  to  increase  its  portative  power,  i» 
others  to  increase  its  inductance,  and  i> 
yet  others  to  shield  its  magnetic  varia- 
tions. 

Iron-Clad  Generator. — An  iron-clad  dy- 
namo. 

Iron-Clad  Inductance. — An  inductance 
associated  with  a  ferric  or  aero-ferric  mag' 
netic  circuit,  as  distinguished  from  an 
inductance  associated  with  a  non-ferric 
magnetic  circuit. 

Iron-Clad  Magnet. — (1)  An  electro-mag- 
net whose  magnetic  resistance  is  lowered 
by  a  casing  of  iron  connected  with  the 
core,  and  provided  for  the  passage  of  the 
magnetic  flux.  (2)  An  iron-clad  electro- 
magnet. 

Iron-Clad  Motor. — A  motor  whose  ar- 
mature is  iron-clad.  (2)  An  iron-encased 
motor. 

Iron-Clad  Rheostat. — A  rheostat  whose 
resistance  coils  are  provided  •with  an 
enamelled  insulation,  and  imbedded  in  a 
mass  of  iron. 

Iron  Core. — The  mass  of  iron  on  which 

are  placed  the  magnetizing  coils  of  an 

electro-magnet  or  solenoid. 
Iron-Core  Loss. — The  hysteretic  and  Fou- 

cault  losses  due  to  the  presence  of  an  iron, 

core. 
Iron     Covered     Cable. — A     submarine 

cable  provided  with  an  iron  sheathing. 

Iron-Enclosed  Electro-Magnet.  —  An 
iron-clad  electro-magnet. 

Iron-Loss  in  Transformer. — The  loss  of 
energy  in  a  transformer  due  both^to  mag- 
netic hysteresis  or  magnetic  friction,  and 
to  the  setting  up  of  eddy  or  Foucault 
currents  in  the  iron. 

Iron  Magnetic  Circuit.— A  ferric  mag- 
netic circuit. 

Iron  Reluctance. — (1)  The  reluctance  in 
a  magnetic  circuit  due  to  the  presence  of 
iron  in  that  circuit.  (2)  Reluctance  in 
iron. 

Iron- Work  Fault  of  Dynamo.  —  A 
ground  or  connection  between  the  circuit 
of  a  dynamo  and  any  part  of  its  iron 
frame. 


Irr.] 


818 


[Iso.. 


Irrationality  of  Dispersion.— A  lack  of 
proportionality  in  the  dispersions  of  spec- 
tra produced  by  different  refractive  media. 

Irreciprocal  Conduction. — (1)  Conduc- 
tion in  which  the  magnitude  of  the  cur- 
rent is  altered  when  its  direction  is  re- 
versed. (2)  The  electric  conduction  in 
an  assymmetrical  resistance. 

Irregular  Magnetic  Flux. — Magnetic 
flux  which  is  not  uniform,  but  is  either 
converging  or  diverging,  as  distinguished 
from  uniform  magnetic  flux. 

Irregular  Variation. — Any  variation  of 
the  magnetic  needle  which  occurs  at  ir- 
regular intervals. 

Irreversible  Heat. — (1)  Heat  produced  in 
a  homogeneous  conductor  by  the  passage 
of  electricity  through  it  in  any  direction. 
(2)  In  an  electric  circuit,  the  joulean  heat- 
ing effect  as  distinguished  from  the 
Peltier  effect.  (3)  In  an  electric  circuit 
any  development  of  heat  by  the  current, 
which  does  not  depend  upon  its  direction. 

Iridescence. — Interference  effects  pro- 
ducing rainbow-colored  tints  by  the  re- 
fraction of  light  from  thin,  transparent, 
finely  striated  surfaces. 

Irritability,  Electric. — The  irritability 
of  nerves  or  muscles  produced  by  an  elec- 
tric current  or  discharge. 

Irrotational  Stress. — (1)  Stress  unac- 
companied by  rotation.  (2)  A  stress  de- 
void of  curl. 

Isobaric  Lines. — Isobars. 

Isobarometric  Lines. — The  isobaric  lines. 

Isobars. —  (1)  Lines  connecting  places  on 
the  earth's  surface  which  simultaneously 
have  the  same  barometric  pressure. 
(2)  The  isobaric  lines. 

Isochasmen  Curves. — Curves  drawn  on 
the  earth's  surface  between  zones  having 
equal  frequency  of  auroral  discharges. 

Isochronism. — Equality  of  time-vibration 
or  motion. 

Isochrqnize. — To  produce  equality  of  time- 
vibration  or  motion. 

Isqchronizing. — Producing  equality  of 
time- vibration  or  motion. 

Isochronous  Oscillations. — Isochronous 
vibrations. 

Isochronous  Vibrations.  —  Vibrations 
or  oscillations  which  perform  their  to- 
and-fro  motions  on  either  side  of  the 
position  of  rest  in  equal  times. 

Isoclinal. — Possessing  the  same  inclina- 
tion. 

Isoclinal  Lines. — Lines  connecting  places 


on  the  earth's  surface  which  have  tha 

same  magnetic  inclination  or  dip. 
Isoclinal    Chart.— A   map  or   chart    on 

which  isoclinal  lines  are  marked. 
Isoclinic.  — Of     or     pertaining     to     the 

isoclinals. 

Isodynamic. — Possessing  equal  force. 
Isodynamic  Chart  or  Map. — A  map  or 

chart    on  which    isodynamic    lines  are 

marked. 

Isodynamic  Lines. — Lines  connecting 
places  which  have  the  same  total  mag- 
netic intensity. 

Iso-Electric  Points. — A  term  sometimes 
used  in  electro-therapeutics  for  points  of 
equal  potential. 

Isogonal. — Of  or  pertaining  to  the  isogonal 
lines. 

Isogonal  Chart  or  Map.— A  chart  or 
map  on  which  the  isogonal  lines  are 
marked. 

Isogonal  Lines. — Lines  connecting  places 
on  the  earth's  surface  which  have  the 
same  magnetic  declination. 

Isqgonic. — Of  or  pertaining  to  the  isogonal 
lines. 

Isolated  Electric  Lighting.— Electric 
lighting  in  which  the  plant  is  located  on 
the  premises  that  are  to  be  lighted,  as 
distinguished  from  a  plant  located  at  a 
station,  central  either  to  a  number  of 
buildings,  or  to  an  extended  area  to  be 
lighted. 

Isolated  Plant. — An  electric  plant  or  dis- 
tribution system  confined  to  a  building 
or  group  of  buildings  as  distinguished 
from  a  central-station  system. 

Isolated-Station  Telephone  Switch- 
board.— A  switchboard  established  for 
the  inter-communication  of  a  number  of 
telephoners,  where  the  distance  separating 
them  is  considerable,  or  where  privacy 
in  the  communication  is  essential.  (2)  A 
small  sub-station  telephone  switchboard. 
(3)  A  domestic  telephone  switchboard. 

Isqlatine. — A  variety  of  insulating  mate- 
rial. 

Isolating  Switch  for  Lamps.— A  short- 
circuiting  switch  designed  to  cut  a  lamp 
completely  out  of  connection  with  a  cir- 
cuit and  without  opening  or  breaking  the 
circuit  of  other  lamps. 

Isolux.-j— (1)  A  line  connecting  points  of 
equal  illumination  on  any  illumined  sur- 
face. (2)  A  line  of  equal  illumination. 

Isothermal  Expansion  of  Gas.— The  ex- 
pansion of  a  gas  whose  temperature  is 
maintained  constant. 


ISO.] 


[Joe. 


Isomorphism.— The  quality  of  possessing 
the  same  crystalline  form. 

Isomerism. — A  state  or  condition  of  com- 
pound substances  which,  though  identical 
in  composition,  yet  possess  entirely  dif- 
ferent properties. 

Isothermal  Surfaces. — Surfaces  on  a 
body,  all  points  of  which  have  the  same 
temperature. 

Lsothermals. — Lines  connecting  places  on 
the  earth's  surface  which  have  the  same 
mean  annual  temperature. 

Isotropic. — Possessing  equal  elasticity  in 
all  directions. 

Isotropic  Conductor.— (1)  A  substance 
which  possesses  the  same  powers  of  elec- 
tric conduction  in  all  directions.  (2)  An 
electrically  homogeneous  conducting 
medium. 


Isotropic  Dielectric.— A  dielectric  pos- 
sessing the  same  powers  of  inductive 
capacity  in  all  directions. 

Isotropic  Medium. — A  medium  possess- 
ing the  same  properties  in  all  directions. 

Isotropism. — The  quality  of  possessing 
equal  elasticity  in  all  directions. 

Isthmus  Method  of  Magnetization. — 
A  method  of  obtaining  an  exceedingly 
strong  magnetization  by  so  placing  the 
body  to  be  magnetized  that  it  forms  a 
narrow  isthmus  between  the  pole-pieces 
of  a  powerful  electro-magnet. 

Isynchronous  Vibrations. — (1)  Vibra- 
tions possessing  equality  of  time  of  vibra- 
tion or  motion.  (2)  Isochronous  vibra- 
tions. 


J. — A  contraction  proposed  for  joule. 

JablochkofF  Candle.  —  An  electric  arc 
light  in  which  the  two  carbon  electrodes 
are  placed  parallel  to  each  other,  and 
maintained  at  a  constant  distance  apart 
by  means  of  a  strip  of  an  insulating  sub- 
stance placed  between  them. 

Jablochkoff 's  Igniter. — A  small  strip  of 
carbon  or  carbonaceous  material  that  is 
readily  rendered  incandescent  by  a  cur- 
rent, placed  between  the  free  ends  of  the 
parallel  carbons  of  a  Jablochkoff  candle, 
for  the  formation  of  an  arc  on  the  passage 
of  the  current. 

Jack  Hole. — In  a  telephone  switchboard 

the  hole  leading  into  a  jack. 
Jack  Panel. — The  panel  of  a  telephone 

switchboard  provided  for  the  support  of 

the  jacks. 
Jack    Switch.  —  A   switch   operated   by 

means  of  a  spring  jack. 
Jacketed    Magnet. — A  term  sometimes 

applied  to  an  iron-clad  magnet. 
Jacobi's  Law. — The  maximum  activity  is 

performed  by  an  electric  motor  when  its 

counter-electromotive  force  is  equal  to 

one-half  of  the  impressed  electromotive 

force. 

Jacobi's  Unit  of  Current. — Such  a  cur- 
rent that  when  passed  through  a  volta- 
meter will  liberate  a  cubic  centimetre  of 
oxygen  and  hydrogen  per  second  at  zero 
Cent.,  and  760  millimetres  barometric 
pressure. 

Jacobi's  Unit  of  Resistance.— (1)  The 


electric  resistance  of  25  feet  of  a  certain 
copper  wire  weighing  345  grains.  (2)  The 
resistance  of  a  copper  wire  one  metre  in 
length  and  one  millimetre  in  diameter  of 
cross-section. 

Jar,  Electric. — A  name  formerly  given  to 
a  Leyden  jar. 

Jar  of  Secondary  Cell. — The  jai  in 
which  the  electrolyte  and  plates  of  a  sec- 
ondary cell  are  placed. 

Jaws  of  Switch. — The  metallic  clips  pro- 
vided for  the  reception  of  the  knife-blades 
of  a  switch. 

Jet  Photometer. — An  apparatus  for  de- 
termining the  candle-power  of  an  illu- 
minating gas  by  means  of  the  height  of  a 
jet  of  such  gas  when  burning  under  con- 
stant conditions  of  pressure  and  tempera- 
ture. 

Jewelry,  Electric. — Minute  incandescent 
lamps  substituted  for  gems  in  articles  of 
jewelry.  " 

Jockey  Gear. — The  cable  gear  through 
which  a  cable  has  to  pass  when  entering 
or  leaving  a  picking-up  or  paying-out 
drum,  and  in  which  it  passes  under 
weighted  wheels,  called  jockey  wheels, 
for  the  purpose  of  maintaining  a  uniform 
tension  of  the  cable  upon  the  drum  so  as 
to  prevent  slip. 

Jockey  of  Relay. — A  form  of  extension 
tongue  pivoted  friction-tight  upon  the 
tongue  of  a  sensitive  relay  employed  in 
submarine  telegraphy. 

Jockey  Wheel. — A  weighted  wheel  riding 
over  a  cable  on  a  grooved  wheel  in  a 


Joi.] 


820 


[Jun. 


cable  ship  for  the  purpose  of  preserving 
uniformity  of  tension  in  the  cable. 
Joining-Tip. — (1)  Connecting  in  series  or 
multiple-arc.     (2)  Generally,  connecting 
or  placing  in  a  circuit. 

Joining-Up  a  Wire. — Connecting  a  wire 
to  an  apparatus  or  circuit  after  it  has 
been  disconnected  or  grounded. 

Joint. — (1)  The  junction  of  two  or  more 
pieces  or  conductors.  (2)  The  place 
where  the  junction  of  two  or  more  pieces 
or  conductors  is  effected. 

Joint  Admittance. — The  total  or  com- 
bined admittance  of  a  number  of  separate 
admittances  connected  in  parallel. 

Joint  Conductance. — The  combined  con- 
ductance of  a  number  of  separate  con- 
ductances connected  in  parallel. 

Joint-Cooling  Tray. — A  tray  employed 
for  cooling  a  cable  core-joint  by  a  cooling 
mixture. 

Joint  Magnetomotive  Force. — The  re- 
sultant magnetomotive  force  of  a  number 
of  simultaneously  acting  magnetomotive 
forces. 

Joint  Reluctance. — The  combined  reluc- 
tance of  a  number  of  parallel-connected 
reluctances. 

Joint  Reluctivity. — The  reluctivity  of  a 
number  of  parallel-connected  reluctivi- 
ties. 

Joint  Resistance. — The  combined  resist- 
ance of  a  number  of  parallel-connected 
resistances. 

Joint  Trough. — A  trough  of  water  or 
cooling  solution  in  which  a  submarine 
cable  joint  is  submerged  for  cooling. 

Jointless  Conductor. — A  conductor  in 
a  single  length  and  without  joint. 

Joulad. — A  term  proposed  for  joule.  (Not 
in  use.) 

Joule. — (1)  A  volt-coulomb  or  unit  of 
electric  energy  or  work.  (2)  The  amount 
of  electric  work  required  to  raise  the 
potential  of  one  coulomb  of  electricity 
one  volt.  (3)  Ten  million  ergs. 

Joule  Effect. — The  heating  effect  pro- 
duced by  the  passage  of  an  electric  cur- 
rent through  a  conductor,  arising  from 
its  resistance  only. 

Joulean  Effect. — A  word  sometimes  used 
for  joule  effect. 

Joule  Meter. — (1)  Any  apparatus  capable 
of  measuring  energy  in  joules.  (2)  An 
energy  meter,  as  distinguished  from  a 
wattmeter. 

Joule-Per-Second. — A  unit  of  activity, 


equal  to  the  expenditure  of  one  joule  in 
each  second. 

Joule's  Cylindrical  Electro-Magnet.^ 
An  electro-magnet  provided  with  a  hoi* 
low  cylindrical  core. 

Joule's  Equivalent.  —  The  mechanical 
equivalent  of  heat. 

Joule's  Law. — The  heating  power  of  a 
current  is  proportional  to  the  product  of 
the  square  of  its  strength  and  the  resist- 
ance of  the  circuit  through  which  it 
passes. 

Journal. — That  portion  of  a  shaft  which 
revolves  on  a  bearing. 

Journal  Friction. — Friction  produced  by 
the  rotation  of  a  shaft  on  a  bearing. 

Jumper. — A  temporary  shunt  or  short  cir- 
cuit put  around  a  source,  lamp  or  receptive 
device  on  a  series-connected  circuit,  to  en- 
able it  to  be  readily  removed  or  repaired. 

Jump  Spark. — A  disruptive  spark  ob- 
tained between  two  opposed  conducting 
surfaces,  as  distinguished  from  a  spark 
obtained  by  or  following  a  wiping  contact. 

Jump-Spark  Burner. — A  term  some- 
times applied  to  a  gas  burner  in  which  the 
issuing  jet  is  ignited  by  means  of  a  high- 
tension  spark  obtained  between  two  op- 
posed points. 

Junction. — In  telephony,  a  wire  or  circuit, 
connecting  two  exchanges. 

Junction  Board. — In  telephony,  a  switch- 
board at  which  junction  wires  terminate. 
Junction    Box. — A    moisture-proof   box 

Provided  in  a  system  of  underground  con- 
uctors  to  receive  the  terminals  of  the 
feeders,  and  in  which  connection  is  made* 
between  the  feeders  and  the  mains,  and 
through  which  the  current  is  distributed 
to  the  individual  consumers. 

Junction  Calls. — Telephonic  calls  arriving 
on  a  junction  line. 

Junction  Circuit. — In  telephony,  a  line 
connecting  a  trunk  circuit  with  a  local 
subscriber. 

Junction  Line. — (1)  In  telephony,  a  junc- 
tion. (2)  A  line  connecting  two  telephone 
exchanges. 

Junction-Line  Plug. — In  a  central  tele- 
phone exchange,  a  plug  connected  with  a 
junction  line. 

Junction  Lines. — Lines  connecting  two: 
or  more  telephone  exchanges,  as  dis- 
tinguished from  subscribers'  lines. 

Junction  Operator. — In  telephony,  an 
operator  at  a  junction  board. 


Jan.] 


821 


[Key. 


Junction  Surface  of  Voltaic  Cell.— The 
contact  surface  between  the  elements  of 
a  voltaic  cell  and  the  electrolyte. 

Junction  Wires. — Junction  lines. 


Junction    Working. — Inter-exchange 

telephone  working. 
Just    Non-Oscillatory    Discharge.— A 

discharge  which  is  just  non-oscillatory. 


K 


K. — A  symbol  for  electrostatic  capacity. 

K. — A  symbol  for  moment  of  inertia. 

K. — A  symbol  for  magnetic  susceptibility. 

K.  C.  C. — A  contraction  for  cathodic  clos- 
ure contraction. 

K.  D.  C. — A  contraction  for  cathodic  dura- 
tion contraction. 

K.  W. — A  contraction  for  kilowatt, 
kg. — An  abbreviation  for  kilogramme,  a 
practical  unit  of  mass. 

kg  :  cm2. — An  abbreviation  for  kilo- 
gramme-per-square-centimetre,  a  practi- 
cal unit  of  pressure. 

kgm. — An  abbreviation  for  kilogramme- 
metre,  a  practical  unit  of  the  moment  of 
a  couple  or  of  work. 

kgm  :  s. — An  abbreviation  proposed  for 
kilogramme-meter-per-second,  a  practical 
unit  of  power. 

KB,. — A  contraction  for  the  total  capacity 
of  a  telegraph  or  telephone  wire  or  con- 
ductor, multiplied  by  its  total  resistance. 

KB  Law. — (1)  A  well-recognized  law  that 
the  limiting  speed  of  signalling  through 
a  submarine  cable,  assuming  a  given  re- 
ceiving and  sending  apparatus  in  uniform 
adjustment,  varies  inversely  as  the  KR  of 
the  cable.  (2)  A  generalization  claimed 
as  a  law  by  some,  but  denied  by  most, 
which  assigns  the  distance  through  which 
intelligible  telephonic  communication  can 
be  carried,  to  cases  where  the  product  of 
K,  the  capacity  of  the  telephone  circuit 
and  R,  its  resistance,  does  not  exceed  a 
certain  value. 

Kaolin. — A  variety  of  white  clay  some- 
times employed  for  insulating  purposes. 

Kapp  Lines. — A  term  proposed  for  unit 
lines  of  magnetic  force  or  flux. 

Karsten's  Figures. — A  name  sometimes 
applied  to  electric  breath  figures. 

Kartavert. — A  variety  of  insulating  mate- 
rial. 

Katalysis. — An  orthography  sometimes 
employed  for  catalysis. 

Katelectrotonus. — Catelectrotonus. 

Kathelectrotonic  State. — The  cathelec- 
trotonic  state. 


Kathelectrotonus  Zone.— Cathelectro- 
tonic  zone. 

Kathelectrotonus. — Cathelectrotonus. 

Kathetometer. — A  cathetometer. 

Kathion. — A  cathion. 

Kathodal.— Cathodal. 

Kathode. — A  cathode. 

Kathodic.— Cathodic. 

Kathodic  Electro-Diagnostic  Beac- 
tions. — Cathodic  electro-diagnostic  reac- 
tions. 

Kathodic  Bays. — Cathodic  rays. 

Kations. — Cathions. 

"  Keeper  "  of  Inductor  Alternator. — A 
word  sometimes  employed  for  inductor. 

Keeper  of  Magnet. — A  mass  of  soft  iron 
applied  to  the  poles  of  a  magnet,  and 
through  which  its  magnetic  flux  passes. 

Kelvin. — (1)  A  word  proposed,  but  not 
adopted,  for  a  kilowatt-hour  or  one  thous- 
and watt  hours.  (2)  A  word  proposed  for 
the  Board  of  Trade  unit. 

Kelvin  Balance. — A  form  of  electro-dyna- 
mometer balance  designed  by  Lord  Kelvin. 

Kerite. — A  variety  of  insulating  material. 

Kerite  Tape. — A  kerite-covered  insulating 
tape. 

Kerr  Effect. — The  elliptical  polarization 
of  a  beam  of  plane  polarized  light,  pro- 
duced by  its  passage  across  an  electrized 
dielectric. 

Key-Board. — Any  board  to  which  electric 
keys  or  switches  are  connected. 

Key-Board  Transmitter. — The  trans- 
mitter employed  in  a  step-by-step  or  print- 
ing telegraph. 

Key  Lamp-Socket. — A  lamp-socket  pro- 
vided with  a  key  for  lighting  or  extin- 
guishing the  lamp. 

Keyless. — Devoid  of  a  key. 

Keyless  Fire- Alarm  Box. — A  fire-alarm 
box  covered  with  a  glass  window  which 
requires  to  be  broken  in  order  to  send  the 
alarm. 

Keyless  Lamp-Socket.— A  lamp-socket 
unprovided  with  a  key,  and  whose  lamp, 
therefore,  requires  to  be  lighted  and  ex* 
tinguished  by  a  switch  placed  elsewhere* 


Key.] 


822 


[Kuo. 


Keyless  Wall-Socket.— A  socket  placed 
on  a  wall,  provided  for  the  reception  of  a 
plug  switch  for  the  introduction  of  a 
lamp. 

Kick. — A  recoil. 

Kick  of  Coil. — The  discharge  from  an  elec- 
tromagnetic coil. 

Kick  of  Relay. — An  impulse  communicat- 
ed to  the  tongue  of  a  relay  by  a  discharge 
from  the  line. 

Kicking  Coil. — A  choking  coil. 

Kicks. — In  telegraphy,  sudden  impulses  of 
a  mirror  spot,  or  siphon,  due  to  a  momen- 
tary earth  current  or  discharge. 

Kilerg. — One  thousand  ergs. 

Killing  Wire. — (1)  A  method  formerly  ad- 
opted for  removing  kinks,  bends  and  flaws 
in  iron  by  stretching  it  on  the  line  in  long 
lengths.  (2)  A  method  of  straightening 
wire  by  subjecting  it  to  tension.  (3)  A 
term  sometimes  applied  to  loss  of  elasti- 
city of  contact  springs  of  switches,  due  to 
their  over-heating  by  the  current. 

Kilo. — A  prefix  for  one  thousand  times. 

Kilo-Ampere. — One  thousand  amperes. 

Kilo- Ampere  Balance. — A  balance  form 
of  ammeter  which  measures  thousands  of 
amperes. 

Kilo-Dyne. — One  thousand  dynes. 

Kilo-Erg. — One  thousand  ergs. 

Kilo -Gauss. — One  thousand  gausses. 

Kilogramme.— One  thousand  grammes,  or 
2.2046  pounds  avoirdupois. 

Kilogramme-Metre.  —  A  unit  of  work 
equal  at  Washington,  D.C.,  to  9.81  multi- 
plied by  101  ergs. 

Kilo-Henry. — One  thousand  henrys. 

Kilo-Joule. — One  thousand  joules. 

Kilo-Lines. — One  thousand  lines  of  force. 

Kilometre. — One  thousand  metres. 

Kilometric  Capacity  of  Cable. — The  ca- 
pacity of  a  cable  in  micro-farads  per  kilo- 
metre. 

Kilometric  Insulation  of  Cable. — The 
insulation  of  a  cable  measured  in  meg- 
ohm-kilometres, or  the  average  insulation 
of  one  kilometre  in  megohms. 

Kilo-Volt. — One  thousand  volts. 

Kilo-Watt. — One  thousand  watts. 

Kilo- Watt-Hour.  —  (1)  The  amount  of 
work  equal  to  that  performed  by  an  activ- 
ity of  one  kilowatt  maintained  steadily 
for  one  hour.  (2)  An  amount  of  work 
equal  to  3.600,000  joules. 

Kilo-Watt  Hour  Meter. — A  form  of  re- 
cording watt-meter. 

Kilo- Weber. — One  thousand  webers. 


Kine. — A  unit  of  velocity,  proposed  by  the 
British  Association,  equal  to  a  centimetre- 
per-second. 

Kinematics. — That  branch  of  science 
which  treats  of  motion,  irrespective  ot 
the  mass  moved,  or  of  the  forces  which 
produce  or  oppose  the  motion. 

Kinetic  Energy. — Energy  producing  mo- 
tion, as  distinguished  from  potential 
energy,  or  energy  capable  of  producing 
motion. 

Kinetic  Induction. — Dynamic  or  mutual 
induction. 

Kinetic  Theory  of  Matter.— A  theory 
which  assumes  that  the  molecules  of  mat- 
ter are  in  a  constant  state  of  motion  or 
vibration  towards  or  from  one  another,  in 
paths  that  lie  within  the  spheres  of  their 
mutual  attractions  or  repulsions. 

Kinetics.  —  That  branch  of  dynamics 
which  treats  of  the  action  of  forces  in 
producing  or  modifying  motion. 

Kinetoscope. — A  means  for  obtaining  the 
effect  of  moving  objects  by  means  of  a 
rapid  succession  of  suitable  pictures. 

Kinetograph. — (1)  A  term  at  one  time 
applied  to  a  device  proposed  for  the  simul- 
taneous reproduction  of  a  distant  stage 
and  its  actors  under  circumstances  such 
that  the  actors  can  be  heard  at  any  dis- 
tance from  the  theatre.  (2)  An  apparatus 
for  reproducing  on  a  screen  the  image  of 
a  moving  object. 

KirehofPs  Laws. — The  Laws  for  the  pres- 
sures and  currents  in  branched  or  divided 
circuits. 

Kneading  Tools. — Tools  for  shaping  hot 
gutta-percha  laid  on  a  joint  between  gut- 
ta-percha covered  wires. 

Knife-Break  Switch. — A  knife  switch. 

Knife-Edge  Suspension. — The  suspen- 
sion of  a  needle  or  system  on  knife-edges, 
supported  on  steel  or  agate  plates. 

Knife-Edge  Switch. — A  term  sometimes 
used  for  knife-switch. 

Knife-Switch. — (1)  A  switch  which  is 
opened  or  closed  by  the  motion  of  a  knife 
contact  between  parallel  contact  plates. 
(2)  A  knife-edge  switch  or  knife  switch. 

Knob  Insulator. — An  insulator  shaped 
like  a  knob  and  divided  into  two  parts 
suitable  for  supporting  a  single  wire  when 
clamped  together  by  its  supporting 
screw. 

Knot. — (1)  A  nautical  mile,  or  6087  feet. 
(2)  A  length  equal  to  one  minute  of  arc  in 
terrestrial  latitude.  (3)  A  unit  of  velocity 
at  sea  equal  to  one  naut  per  hour,  ob- 


Kno.] 


823 


[Lam. 


tained  from  an  observation  of  a  knotted 
log-cord  thrown  overboard. 

Knot-Pound. — A  standard  of  conductivi- 
ty of  copper  referred  to  a  length  of  one 
knot  and  a  conductor  weight  of  one 
pound,  and  sometimes  employed  in  sub- 
marine telegraphy. 

Kohlrausch's  Law. — In  electrolytic  con- 
duction, the  rate  of  motion  of  each  atom 
in  a  given  liquid  is  independent  of  the 
element  with  which  it  may  have  been 
combined. 

Krizik's  Bars  or  Cores. — Iron  bars  or 


cores  of  various  shapes,  provided  for  sole- 
noids, in  which  the  distribution  of  the 
metal  is  so  proportioned  as  to  ensure  a 
nearly  uniform  attraction  or  pull  in  dif- 
ferent positions  of  the  solenoid. 

Kruss'  Optical  Scale.— A  scale  employed 
for  measuring  the  height  of  a  flame. 

Kyanized. — Subjected  to  the  kyanizing 
process. 

Kyanizing. — A  process  employed  for  the 
preservation  of  wooden  telegraph  poles, 
or  railroad  ties  or  sleepers,  by  injecting  a 
solution  of  corrosive  sublimate  into  the 
pores  of  the  wood. 


Ii. — A  symbol  for  coefficient  of  inductance. 

L. — A  contraction  for  length. 

L. — A  symbol  for  the  coefficient  of  induc- 
tance or  self-induction.  (Partly  inter- 
national notation.) 

Lm. — A  symbol  proposed  for  coefficient  of 
mutual-induction,  or  mutual  inductance. 

Ls. — A  symbol  proposed  for  coefficient  of 
self-induction,  or  self-inductance. 

Labile  Galvanization. — A  term  employed 
in  electro-therapeutics,  in  contra-distinc- 
tion  to  stabile  galvanization,  to  designate 
the  method  of  applying  the  current  by 
keeping  one  electrode  at  rest,  in  firm  con- 
tact with  one  part  of  the  body,  and  con- 
necting the  other  electrode  to  a  sponge 
which  is  moved  over  the  parts  of  the 
body  that  are  to  be  treated. 

Lag.— (1)  Falling  behind.  (2)  To  fall  be- 
hind. 

Lag  of  Motor  Brushes. — A  movement  of 
the  brushes  of  a  motor  to  a  position  on 
the  commutator,  in  the  opposite  direction 
to  its  rotation,  in  order  to  obtain  freedom 
from  sparking. 

Lag  of  Resultant  Flux.— The  displace- 
ment in  phase  of  the  magnetic  flux  in  an 
induction  motor  behind  the  impressed 
magneto-motive  force. 

Lagging  Electromotive  Force.— An 
electromotive  force  or  component  of  elec- 
tromotive force  lagging  behind  a  current 
or  flux. 

Lagging  Current. — A  periodic  current 
lagging  behind  the  impressed  electromo- 
tive force  which  produces  it. 

Lagging  of  Current.— An  alternating 
current;  which  is  retarded  in  phase  be- 
hind the  pressure  which  produces  it. 

Tagging  of  Magnetization.— (1)  A  re- 


tardation in  the  magnetization  as  com- 
pared with  the  magnetizing  electromotive 
force.  (2)  A  cyclic  retardation  of  mag- 
netization in  a  transformer  due  to  hys- 
teresis. 

Lambert's  Discharge  Key.— A  highly 
insulated  form  of  double-contact  key, 
used  in  testing. 

Lamellar. — Composed  of  parallel  plates  or 
laminae. 

Lamellar  Distribution  of  Magnetism. 

(1)  The  distribution  of  magnetism  in 
magnetic  shells.  (2)  Such  a  distribution 
of  magnetism  in  a  thin  plate  that  the 
magnetized  particles  are  arranged  with 
their  greatest  lengths  in  the  direction  of 
the  thickness  of  the  plate,  so  that  all  the 
poles  are  situated  at  or  near  the  faces  of 
the  plate,  and,  consequently,  the  extent 
of  such  polar  surfaces  is  great  when  com- 
pared with  the  thickness  of  the  plate. 
Lamellar  Magnet. — A  magnet  whose 
magnetism  is  characterized  by  lamellar 
distribution, 

Laminated. — Built  up  or  composed  of 
laminae. 

Laminated  Core. — An  iron  core  that  has 
been  sub-divided  in  planes  parallel  to  its 
magnetic  flux-paths,  in  order  to  avoid  the 
injurious  production  of  Foucault  or  eddy 
currents. 

Laminated  Magnet. — A  magnet  provided 
with  a  laminated  core. 

Laminating. — Sub-dividing  into  laminae. 
Lamination.— The  sub-division  of  an  iron 
core  into  laminae. 

Lamination  of  Armature  Core. — The 
sub-division  of  the  iron  core  of  a  dynamo 
or  motor  armature  into  a  number  of  in- 


Lam.] 


824 


[Lam. 


sulated  parallel  strips  or  plates,  for  the 
purpose  of  avoiding  eddy  currents. 
Lamination  of  Conductors.— (1)  The 
division  of  a  conductor  into  a  number  of 
parallel  strands  or  wires,  for  the  purpose 
either  of  lessening  the  eddy  currents  pro- 
duced in  its  mass,  or  for  reducing  the 
skin  effect  when  alternating  currents  are 
employed.  (2)  A  stranded  conductor. 

Lamp  Adapter.-;— (1)  A  device  which 
permits  an  electric  lamp  to  replace  an  or- 
dinary gas  burner  on  a  gas  bracket  or 
chandelier.  (2)  A  device  which  permits 
an  electric  lamp  base  of  one  manufacturer 
to  be  readily  inserted  in  the  socket  of  an- 
other manufacturer. 

Lamp  Base. — The  portion  of  an  incandes- 
cent lamp  chamber  through  which  the 
leading-in  wires  are  passed,  provided  with 
two  metallic  plates  or  parts,  suitably  in- 
sulated from  one  another,  and  electrically 
connected  to  the  ends  of  the  leading-in 
wires. 

Lamp  Bracket,  Electric. — A  device 
similar  to  that  employed  for  a  gas  burner, 
suitable  for  the  support  of  an  incandes- 
cent lamp. 

Lamp  Bulb.— The  chamber  or  globe  in 
which  the  filament  of  an  incandescent 
lamp  is  placed. 

Lamp  Cap. — The  base  of  an  incandescent 
lamp. 

Lamp  Chamber. — The  bulb  of  an  incan- 
descent lamp. 

Lamp  Circuit. — A  circuit  containing  an 
electric  lamp  or  lamps. 

Lamp  Clamp. — A  suitable  grip  for  hold- 
ing the  rod  that  supports  the  electrode  of 
an  arc-lamp. 

Lamp  Contacts. — Metallic  plates  or  rings 
placed  in  an  incandescent  lamp  base,  and 
connected  to  the  terminals  of  the  filament. 

Lamp  Cord. — A  flexible  cord  containing 
two  separately  insulated  wires  suitable 
for  use  in  connection  with  an  incandescent 
lamp. 

Lamp  Cut-Out.— (1)  A  device  so  arranged 
as  to  automatically  cut  a  series-con- 
nected arc-lamp  out  of  the  circuit,  as  soon 
as  the  carbons  are  entirely  consumed. 
(2)  A  safety  catch  or  safety  fuse  con- 
nected with  the  circuit  of  a  multiple-con- 
nected incandescent  lamp. 

Lamp  Dimmer. — A  reactive  coil,  em- 
ployed on  an  'alternating  circuit  for  the 
purpose  of  varying  the  intensity  of  incan- 
descent lights  connected  with  such 
circuit. 

Lamp    Efficiency. — (1)  Commonly,    but 


illogically,  the  watts  consumed  by  a  lamp 
per  candle-power  delivered.  (2)  More 
nearly  correctly,  the  reciprocal  of  this  ;  or 
the  number  of  candles  obtained  from  an 
incandescent  lamp  per  watt  supplied  to 
it. 

Lamp  Feet. — (1)  In  a  conducting  loop,  cir- 
cuit, or  system,  the  product  of  the  number 
of  lamps  supplied  and  the  distance  at 
which  they  are  supplied  ;  each  lamp  being 
multiplied  by  its  distance,  and  the  sum  of 
such  products  being  taken.  (2)  A  quan- 
tity sometimes  used  in  computing  dis- 
tribution systems  of  electric  lighting. 

Lamp  Filament.— The  filament  of  an  in- 
candescent lamp. 

Lamp  Fittings.— (1)  The.sockets,  holders, 
brackets,  etc.,  required  for  holding,  or 
supporting,  incandescent  electric  lamps. 
(2)  Lamp  fixtures. 

Lamp  Frame. — The  frame  of  an  arc-lamp 
provided  for  the  support  of  the  feeding 
mechanism,  globe,  etc. 

Lamp  Hanger.— A  device  provided  for 
the  suspension  of  an  arc-lamp. 

Lamp  Hood. — A  hood  employed  to  protect 
an  arc-lamp  from  rain  or  snow,  and  gen- 
erally so  arranged  as  to  throw  its  light  in 
a  downward  direction. 

Lamp-Hour.— (1)  Such  a  service  of 
electric  current  as  is  required  to  main- 
tain one  electric  lamp  during  one  hour. 
(2)  Such  a  quantity  of  electricity,  or  of 
electric  energy,  as  will  maintain  one 
standard  lamp  in  normal  operation  for 
•  one  hour. 

Lamp  Indicator.— (1)  An  apparatus  e*m- 
ployed  in  a  central  station  to  indicate  the 
presence  of  the  proper  voltage,  or  poten- 
tial difference,  on  the  mains.  (2)  A 
lamp  employed  on  a  telephone  switch- 
board to  indicate  when  the  subscriber  is 
calling,  or  when  he  has  rung  off.  (3)  A 
pilot  lamp.  (4)  Any  indicating  apparatus 
employing  an  electric  lamp  as  signalling 
device. 

Lamp  Pendant. — A  flexible  cord  em- 
ployed for  the  support  of  a  pendant 
lamp. 

Lamp  Pillar. — (1)  A  pillar  supporting  one 
or  more  lamps.  (2)  A  lamp  post. 

Lamp  Posts. — Posts  provided  for  the  sup- 
port of  lamps. 

Lamp  Protector. — A  lamp  hood,  cover  or 
guard. 

Lamp  Receptacle. — (1)  A  lamp  socket 
or  holder.  (2)  A  receptacle  for  a  flex- 
ible connection  leading  to  a  lamp. 

Lamp  Bod,— (1)  The  rod  provided  in  an 


Lam.] 


825 


[Law. 


ordinary  arc-lamp  for  the  support  of  the 
positive  carbon.  (2)  In  a  focussing 
lamp,  the  rods  provided  for  the  support 
of  the  two  carbons. 

Lamp  Socket. — A  support  provided  for 
the  reception  of  an  incandescent  lamp,  so 
arranged  that  the  introduction  of  the 
lamp  therein,  automatically  connects  the 
lamp  terminals  with  the  terminals  of  the 
supply  wires. 

Lamp-Socket  Rheostat. — A  regulable  re- 
sistance placed  in  the  socket  of  an  incan- 
descent lamp  for  the  purpose  of  altering 
the  quantity  of  light  it  emits. 

Lamp -Socket    Switch. — (1)  A   switch 

E laced  in  the  socket  of  an  incandescent 
imp,  provided  for  lighting  and  extin- 
guishing the  lamp.  (2)  A  lamp-socket  key. 

Lamp  Switches. — Switches  placed  in  the 
circuit  of  a  group  of  incandescent  lamps, 
either  in  the  branches,  or  in  the  mains, 
for  the  purpose  of  simultaneously  lighting 
or  extinguishing  a  number  of  lamps. 

Land  Line. — (1)  A  telegraph  line  on  land, 
either  aerial  or  buried,  as  distinguished 
from  a  submarine  cable.  (2)  An  aerial 
telegraph  line.  (3)  That  portion  of  a  sub- 
marine-cable circuit  which  extends  over 
the  land. 

Lantern  Lamp. — An  incandescent  lamp 
provided  with  a  lantern-shaped  chamber 
surrounding  the  lamp  chamber. 

Lantern  Projector.  —A  focussing  arc-lamp 
employed  in  connection  with  a  projecting 
apparatus. 

Lap  Joint.— (1)  The  joint  effected  by  over- 
lapping short-  portions  near  the  ends  of 
the  things  to  be  joined,  and  securing 
them  to  each  other  while  in  that  posi- 
tion. (2)  A  joint  between  the  ends  of  two 
conducting  wires  in  which  the  two  ends 
after  being  laid  together,  side  by  side,  are 
lapped  firmly  together  by  a  piece  of  separ- 
ate wire. 

Lap-Joint  for  Wires. — A  joint  between 
two  wires,  made  by  over-lapping  their 
ends  and  subsequently  soldering. 

Lap  Winding.— A  winding  for  a  drum 
armature,  in  which  the  successive  con- 
ducting loops  are  arranged  on  the  surface 
of  the  armature  over-lapping  one  an- 
other. 

Large  Calorie. — (1)  A  term  sometimes  used 
for  the  great  calorie.  (2)  A  kilogramme- 
degree-centigrade.  (3)  One  thousand 
lesser  calories. 

Latent. — Hidden,  concealed. 

Latent    Electricity.— A    term   formerly 

applied  to  bound  electricity. 
Lateral. — Ah  offset  from  a  conduit  system 

11— 


for  connecting  services  with  the  con- 
ductors of  a  conduit. 

Lateral  Bracket. — A  form  of  bracket  for 
running  wires  from  corner  to  corner  of 
buildings,  and  for  supporting  an  insulator 
in  an  upright  position. 

Lateral  Discharge.— (1)  A  Leyden-jar  or 
other  impulsive  discharge  occurring  be- 
tween parts  of  the  circuit  not  in  the 
direct  path  of  the  main  discharge.  (2)  A 
discharge  occurring  through  an  alterna- 
tive path. 

Lateral  Induction. — (1)  Induction  occur- 
ring between  closely-approached  portions 
of  a  circuit,  through  which  an  impulsive 
discharge  is  passing.  (2)  The  induction 
produced  by  an  impulsive  discharge  as 
manifested  in  a  lateral  discharge. 

Lateral  Magnetic-Leakage.  —  (1)  The 
failure  of  magneto  flux  to  pass  in  ap- 
proximately parallel  paths  through  a  bar 
of  iron  or  other  magnetizable  material, 
which  has  come  to  rest  in  a  field  in  which 
it  is  free  to  move.  (2)  The  escape  of 
magnetic  flux  from  the  sides  of  a  bar 
magnet,  or  other  similar  magnet,  instead 
of  from  the  poles  at  its  ends. 

Lattice  Pole. — A  form  of  structural-iron 
pole  designed  for  the  support  of  overhead 
wires  or  conductors,  made  in  the  form  of 
a  light,  strong  lattice. 

Lattice  Work  of  Pole. — A  composite 
pole  whose  upper  portion  consists  of 
structural  lattice  work,  employed  in  cases 
where  the  stresses  produced  on  the  top  of 
the  pole  are  excessive  by  reason  of  the 
weight  of  the  cables,  or  the  number  of 
lines  or  aerial  wires  supported  thereon. 

Launch,  Electric. — A  launch  whose  mo- 
tive power  is  electric. 

Law. — (1)  In  physics,  any  relation  existing 
between  natural  phenomena  and  their 
causes.  (2)  The  invariable  manner  in 
which  physical  causes  produce  their 
effects.  (3)  Any  observed  relation  of 
sequences  in  the  universe. 

Law  of  Electro-Chemical  Equiva- 
lence.— The  amount  of  electrolytic  libera- 
tion produced  by  an  electric  current 
passed  through  various  chemical  sub- 
stances is  proportional  to  the  chemical 
equivalent  of  each  substance,  that  is,  to 
its  atomic  weight  divided  by  its  valency. 

Law  of  Illumination. — The  illumination 
produced  by  a  single-point  source  of  light, 
varies  inversely  as  the  square  of  the  dis- 
tance from  that  source. 

Law  of  Ohm. — (1)  The  law  of  non-varying 
current  strength  in  a  circuit  not  subject 
to  variation.     (2)  Ohm's  law. 
Vol.  2 


Law.] 


826 


[Lea. 


Law  of  Volta.— (1)  The  law  of  contact 
series.  (2)  Volta's  law. 

Laws  of  Becquerel. — Laws  for  the  mag- 
neto-optic rotation  of  the  plane  of  polari- 
zation. 

Laws  of  Coulomb. — Laws  for  the  force 
of  attraction  and  repulsion  existing  be- 
tween charged  bodies,  or  between  neigh- 
boring magnet  poles. 

Laws  of  Faraday. — Laws  of  electrolytic 
decomposition . 

Laws  of  Joule. — Laws  expressing  the  de- 
velopment of  heat  in  a  circuit  by  an 
electric  current. 

Laws  of  Reflection. — (1)  The  angle  of  in- 
cidence is  equal  to  the  angle  of  reflection. 
(2)  Both  the  incident  and  the  reflected 
rays  lie  in  the  same  plane. 

Lay. — The  helical  disposition  of  wires  in  a 
strand  or  sheath,  in  which  each  wire 
makes  a  complete  revolution  about  the 
axis. 

Lay  Torpedo.  —  A  moving  torpedo,  in 
which  the  motive  power  is  either  carbonic 
acid  gas  or  compressed  air,  and  the  guid- 
ing power  electricity. 

Layer. — A  name  sometimes  applied  to  an 
electro-plating  deposit. 

Lay-Outof  Cable  in  Tank.— (1)  The 
starting  of  a  new  flake  in  coiling  a  cable 
in  a  tank,  by  proceeding  from  the  eye  at 
the  end  of  the  finished  flake,  directly  out- 
ward to  the  edge  of  the  tank.  (2)  That 
part  of  a  cable  which  connects  the  inside 
of  one  flake  with  the  outside  of  the  suc- 
ceeding flake  in  a  cable  tank. 

Laying-Up  Cables. — Placing  or  disposing 
separate  cables  or  conductors  in  a  bunched 
cable. 

Lead. — (1)  An  insulated  conductor  leading 
to  or  from  an  electric  source.  (2)  In 
telegraphy , an  insulated  conductor  leading 
to  an  instrument,  battery,  circuit,  or  sta- 
tion. (3)  In  a  multiple  or  parallel-con- 
nected circuit,  a  conductor  or  main  con- 
nected to  the  positive  terminal  of  the 
source.  (4)  In  a  system  of  electric  distri- 
bution, an  insulated  conductor  leading  to 
a  main,  feeder,  source,  station,  testing 
apparatus,  or  device.  (5)  A  connecting 
wire. 

Lead  Accumulator. — An  accumulator  or 
storage  cell  which  has  been  formed  from 
two  plates  of  lead  immersed  in  dilute 
sulphuric  acid. 

Lead  Burning.  —  Effecting  a  metallic 
junction  between  two  lead  plates  or  strips 
by  partially  fusing  them  together. 

Lead-Covered  Conductors. — Insulated 
conductors  sheathed  in  lead. 


Lead-Encased  Cable.— A  cable  provided 
with  a  sheathing  or  coating  of  lead  on  its 
external  surface. 

Lead  of  Brushes  of  Dynamo-Electric 
Generator. — An  angular  deviation  from 
the  normal  position,  forwards,  or  in  the 
direction  of  rotation  of  the  'armature, 
which  is  given  to  the  brushes  on  the 
commutator,  in  order  to  obtain  sparkless 
commutation. 

Lead  of  Current. — An  advance  in  the 
phase  of  an  alternating  current  beyond 
that  of  the  electromotive  force  producing 
the  current. 

Lead  of  Motor  Brushes. — The  angular 
displacement  from  the  normal  position 
in  the  direction  contrary  to  that  of  the 
rotation  of  the  armature,  which  it  is 
necessary  to  give  the  brushes  on  an  elec- 
tric motor,  when  its  load  is  increased,  in 
order  to  obtain  freedom  from  sparking. 

Lead  Scoring  Tool.— A  tool  for  readily 
scoring  the  surface  of  a  lead-covered 
cable,  for  the  purpose  of  obtaining  a  clean 
surface  preparatory  to  making  a  joint. 

Lead  Sheathing. — The  coating  of  lead 
placed  on  the  outside  of  a  lead-covered 
cable. 

Lead  Sleeve. — A  lead  tube  provided  for 
making  a  joint  in  a  lead-covered  cable. 

Lead-Tin  Alloys. — Alloys  of  lead  and  tin, 
of  low  melting  point,  employed  for  safety 
fuses. 

Lead  Tree. — An  arborescent  deposit  of 
lead  obtained  by  the  electrolysis  of  a  solu- 
tion of  a  lead  salt. 

Lead  Voltameter. — A  voltameter  consist- 
ing of  lead  electrodes  immersed  in  a  dilute 
solution  of  sulphuric  acid  and  water. 

Leaded  Cable. — A  cable  provided  with  a 
lead  sheathing. 

Leading  Current. — An  alternating-cur- 
rent wave  or  component,  in  advance  of 
the  electromotive  force  producing  it 

Leading  Edge  of  Pole-Pieces  of  Arma- 
ture.— Those  edges  or  terminals  of  the 
field-magnet  pole-pieces  which  the  arma- 
ture is  approaching  in  its  rotation. 

Leading  Horn  of  Pole-Pieces  of  Dy- 
namo.— Those  edges  or  terminals  of  the 
field-magnet  pole-pieces  towards  which 
the  armature  of  a  dynamo-electric  ma- 
chine is  carried  during  its  rotation. 

Leading-In  Insulator. —  The  insulator 
provided  for  the  support  of  the  wires 
leading  into  a  building  from  an  aerial  cir- 
cuit. 

Leading-In  Tube.y-(l)  A  tube  of  insulat- 
ing material  provided  for  the  reception 


Lea.] 


827 


[Lef. 


of   the  leading-in  wires   in  a  building. 
(2)  An  insulating  tube. 


Leading-In  Wires  .-^(1)  The  wires  that 
pass  from  an  aerial  circuit  into  a  house  or 
building.  (2)  The  wires  or  conductors 
which  lead  the  current  through  an  in- 
candescent electric  lamp;  i.e.,  into  and 
out  of  a  lamp.  (3)  Wires  leading  a  cir- 
cuit into  a  house,  room,  box,  or  apparatus. 

Leading  Pole  of  Dynamo  or  Motor.— 

The  pole  of  a  dynamo  or  motor  approached 
by  points  on  the  surface  of  the  revolving 
armature  which  lie  between  the  poles  at 
any  instant. 

Leading-Up  Wires.—  Wires  employed 
for  raising  an  aerial  cable  to  the  cable 
hangers. 

Leads.  —  (1)  In  a  system  of  parallel  distri- 
bution. the  conductors  connected  to  the 
positive  and  negative  terminals  of  a 
source.  (2)  Generally,  the  conductors  in 
any  system  of  electric  distribution.  (3) 
Conductors  which  lead  the  current  to  or 
from  any  source,  circuit  or  device.  (4) 
In  electric  testing  the  insulating  conduc- 
tors leading  the  testing  current  to  the  cir- 
cuit or  conductor  tested. 

Leak.  —  (1)  Any  loss  or  escape  by  leaking. 
(2)  The  point  or  place  where  a  leak  occurs. 

Leakage.  —  A  loss  or  escape  by  leaking. 

Leakage  Conductance.  —  Insulation  con- 
ductance, or  the  reciprocal  of  the  insula- 
tion resistance. 

Leakage  Conductor.  —  (1)  A  conductor 
placed  on  a  telegraphic  circuit  for  the 
purpose  of  preventing  the  disturbing  ef- 
fects of  leakage  into  a  neighboring  line 
by  providing  a  direct  path  for  such  leak- 
age to  the  earth.  (2)  A  conductor  placed 
on  a  telegraphic  line  for  the  purpose  of 
lessening  the  retardation  of  the  line  by 
assisting  in  its  discharge. 

Leakage  Current  of  Primary  .—^(1)  The 
magnetizing  current  which  flows  into  the 
primary  circuit  of  a  transformer  when 
the  secondary  circuit  is  open,  (2)  A  cur- 
rent employed  in  magnetizing  only,  as 
distinguished  from  a  current  usefully 
transformed. 

Leakage  Current  of  Transformer.  —  (1) 
The  current  which  flows  into  the  primary 
circuit  of  a  transformer  when  the  secon- 
dary circuit  is  opened.  (2)  The  mag- 
netizing current. 

Leakage  Drop.  —  The  drop  produced  in  a 
circuit  by  leakage. 

Leakage,  Electric.  —  The  gradual  dissipa- 
tion of  a  charge  or  current  due  to  insuf- 
ficient insulation. 


Leakage  Factor. — In  a  dynamo-electric 
machine,  the  ratio  of  the  total  flux,  which 
passes  through  the  field-magnet  cores  of 
a  dynamo  or  motor,  to  the  total  useful  flux 
passing  from  them  through  the  armature. 

Leakage  Flux. — (1)  That  portion  of  the 
field  flux  which  does  not  pass  through  the 
armature  of  a  dynamo  or  motor,  and 
which,  therefore,  produces  no  useful  ef- 
fect. (2)  The  stray  flux,  or  that  from 
which  no  useful  effect  is  obtained. 

Leakage  Indicator.-^!)  A  magnetic  ex- 
plorer. (2)  An  electric  testing  apparatus 
for  revealing  the  presence  of  leakage  in 
any  circuit  or  system. 

Leakage  Interference. — Interference  be- 
tween two  or  more  circuits  due  to  their 
mutual  leakage. 

Leakage  Magnetic  Resistance. — The  re^ 
luctance  to  leakage  magnetic  flux. 

Leakage  Method  of  Measuring  Insu- 
lation.— A  method  of  measuring  the  in- 
sulation of  a  conductor  or  condenser  by 
determining  the  rate  at  which  it  loses 
charge  by  leakage. 

Leakage  Paths. — The  paths  traversed  by 
leakage  magnetic  flux. 

Leakance. — A  term  proposed  for  leakage- 
conductance  in  a  circuit. 

Leclanche's  Voltaic  Cell. — A  zinc-car- 
bon couple  whose  elements  are  used  in 
connection  with  a  solution  of  sal-ammo- 
niac, and  a  quantity  of  finely  divided 
black  oxide  of  manganese  surrounding 
the  carbon. 

Lecture  Galvanometer.— A'form  of  gal- 
vanometer suitable  for  showing  the 
movements  of  a  galvanometer  needle  to 
an  audience  at  a  considerable  distance 
from  the  instrument. 

Left-Hand  Trolley-Frog.— A  trolley- 
frog  so  arranged  as  to  switch  a  car  to  the 
left. 

Left-Hand  Trolley-Switch. — A  switch 
arranged  to  divert  a  car  to  the  left  of  a 
main  line. 

Left-Handed  Armature-Windings.— 
Armature  windings  applied  to  the  core 
in  a  left-handed  or  sinistrorsal  helix. 

Left-Handed  Dynamo.  —  A  dynamo 
which  runs  left-handedly,  or  counter- 
clockwise, when  regarded  from  the  pulley 
end. 

Left-Handed  Helix.— (1)  A  left-handed 
solenoid.  (2)  A  helix  wound  left-hand- 
edly, or  counter-clockwise. 

Left-Handed  Motor. — A  motor  which 
runs  left-handedly,  or  counter-clockwise, 
when  regarded  from  the  pulley  end. 


Lef.] 


828 


[Ley. 


Left-Handed  Rotation. — A  rotation  in  a 
positive  or  counter-clockwise  direction. 

Left  -  Handed  .  Solenoid.—  A  solenoid 
whose  winding  is  left-handed,  or  counter- 
clockwise. 

Left-Handed  Spiral. —  A  left-handed 
helix. 

Left-Handed  Winding.— The  winding  of 
a  solenoid  or  helix  in  a  counter-clockwise 
direction. 

Leg. — In  a  system  of  telephonic  exchange, 
where  a  ground-return  is  used,  a  single 
wire  ;  or,  where  a  metallic  circuit  is  em- 
ployed, two  wires,  provided  for  connect- 
ing the  subscriber  with  the  main  switch- 
board, so  that  any  subscriber  may  be 
placed  directly  in  circuit  with  two  or 
more  other  subscribers. 

Leg  Key. — A  Morse  telegraphic  key  having 
long  screw  in  its  base  for  passing  through 
a  table. 

Leg  of  Circuit. — (1)  A  branch  of  a  bifur- 
cated or  divided  circuit.  (2)  A  loop  or 
offset  in  a  series  circuit. 

Leg  of  Electro-Magnet. — One  of  the 
cores  of  an  electro-magnet. 

Legal  Earth  Quadrant. — (1)  A  practical 
unit  of  inductance  as  denned  by  the  Elec- 
trical Congress  of  1884,  at  Paris,  and  as 
distinguished  from  the  true  earth  quad- 
rant. (2)  The  legal  quadrant. 

Legal  Ohm. — (1)  An  ohm  whose  value  is 
in  accordance  with  the  definition  of  the 
Electrical  Congress  of  1884,  in  Paris.  (2) 
The  resistance  of  a  uniform  column  of 
mercury  one  square  millimetre  in  area 
of  cross-section,  and  106  centimetres  in 
length,  at  the  temperature  of  0°  Cent.,  or 
32°  Fahr.  (3)  The  concrete  standard  ohm 
as  defined  by  the  Electrical  Congress  of 
1884,  at  Paris,  as  distinguished  either  from 
the  B.  A.  ohm,  the  true  ohm,  or  the  In- 
ternational ohm. 

Legal  Quadrant. — (1)  The  legal  earth 
quadrant.  (2)  The  unit  of  self-induction 
based  upon  the  definitions  of  the  Electrical 
Congress  of  1884,  in  Paris. 

Legged. — Placed  in  a  circuit  by  means  of 
a  leg. 

Legging  Key-Board. — A  key-board  em- 
ployed for  the  purpose  of  legging  an  oper- 
ator into  a  circuit  containing  two  or  more 
subscribers. 

Legless  Key. — (1)  A  name  sometimes  given 
to  a  Morse  telegraphic  key  provided  with 
a  flat  base.  (2)  A  self-closing  key. 

Length  of  Spark. — The  air  distance  trav- 
ersed by  a  disruptive  discharge. 

Lenard  Effect. — The  effect  produced  by 


the  Lenard  Rays,  in  causing  fluorescence, 
and  in  passing  through  some  substances 
that  are  opaque  to  light. 

Lenard  Rays. — The  peculiar  radiation 
emitted  from  that  external  portion  of  a 
Lenard  tube  that  is  directly  opposite  the 
cathode. 

Lenard  Tube. — A  form  of  high-vacuum 
tube  provided  with  an  aluminium  plate, 
hermetically  sealed  in  that  portion  of  the 
wall  of  the  tube  lying  directly  opposite 
the  cathode,  and  employed  for  producing 
Lenard  rays. 

Lens. — A  medium,  transparent  to  radiant 
energy,  provided  with  a  curved  face  or 
faces,  and  employed  to  bring  a  beam  or 
pencil  of  light  to  a  single  point  or  focus. 

Lens  Lamp. — A.n  incandescent  lamp  pro- 
vided with  a  small  lens  hermetically  fixed 
in  a  portion  of  its  wall,  opposite  a  suitably 
placed  reflector. 

Lens-Mirror  Projector. — A  form  of  pro- 
jector whose  operation  is  dependent  on 
the  combined  action  of  a  mirror  and  a  lens. 

Lenz's  Laws. — Laws  for  determining  the 
direction  of  currents  produced  by  electro- 
dynamic  induction. 

Lesser  Calorie. —  (1)  The  small  calorie. 
(2)  The  therm.  (3)  The  water-gramme- 
degree-centigrade  . 

Letter-Box,  Electric. — A  device  that 
announces  tho  deposit  of  a  letter  in  a  box 
by  the  ringing  of  a  bell,  or  by  the  moving 
of  a  needle  or  index. 

Letter  Printing  Instrument. — A  type- 
printing  telegraphic  instrument. 

Level,  Electric. — An  equipotential  elec- 
tric surface. 

Level  of  Earth,  Electric. — A  term  some- 
times employed  for  the  potential  of  the 
earth. 

Lever  Brake  for  Car. — A  form  of  car 
brake  operated  by  means  of  a  brake 
handle. 

Lever  Hook. — (1)  The  hook  in  an  auto- 
matic telephone  switch  on  which  a  tele- 
phone receiver  is  hung  when  not  in  use. 
(2)  A  contact  lever  provided  with  a  hook 
for  supporting  a  telephone. 

Lever  Switch. — (1)  A  switch  mounted 
upon  a  fulcrum  axis  like  a  lever.  (2)  A 
switch  operated  by  the  movements  of  a 
lever.  (3)  A  telephone  switch  of  a  multi- 
ple telephone  switch-board,  operated  by 
a  lever. 

Leyden-Jar. — A  condenser  in  the  form  of 
a  jar,  in  which  the  metallic  coatings  are 

'  placed  opposite  each  other  respectively  on 
the  outside  and  inside  of  the  jar. 


Ley.] 


829 


I  Urn. 


Leyden-Jar  Battery. — The  combination 
of  a  number  of  separate  Leyden  jars  so  as 
to  act  as  a  single  jar. 

Leyden-Jar  Discharge.— (1)  The  dis- 
ruptive discharge  produced  by  a  Leyden 
jar.  (2)  A  name  sometimes  given  to  an 
oscillatory  discharge. 

Leydic  Resistance. — A  term  proposed  for 
the  resistance  offered  by  various  metallic 
circuits  to  condenser  discharges. 

Lichtenberg's  Dust-Figures.—  Figures 
obtained  by  writing  on  a  sheet  of  shellac 
with  the  knob  of  a  charged  Leyden  jar, 
and  then  sprinkling  over  the  sheet,  dried, 
powdered  sulphur  and  red  lead,  which 
have  been  previously  mixed  together  and 
are  thereby  rendered  respectively  nega- 
tive and  positive. 

Lichtenberg's  Electric  Figures.— A 
term  sometimes  applied  to  Lichtenberg's 
dust-figures. 

Life  Curve  of  Incandescent  Electric 
Lamp. — A  curve  in  which  the  life  of  an 
incandescent  electric  lamp  is  represented 
by  means  of  abscissae  and  ordinates  that 
are  respectively  equal  to  the  life  in  hours 
and  the  candle-power  at  constant  pressure, 
or  the  pressure  at  constant  candle-power. 

Life  of  Electric  Incandescent  Lamp. — 
The  number  of  hours  that  an  incandes- 
cent electric  lamp  will  continue  to  fur- 
nish a  good  commercial  light  when  oper- 
ated at  normal  pressure. 

Lift,  Electric. — An  electrically  operated 
lift  or  elevator. 

Light. — (1)  That  particular  form  of  radiant 
energy  by  means  of  which  objects  are 
rendered  visible.  (2)  The  flow  or  flux  of 
light  emitted  from  a  luminous  source. 

Light  Bath,  Electric. — A  form  of  electro- 
therapeutic  bath  in  which  the  patient  is 
exposed  to  the  radiation  of  a  number  of 
incandescent  lamps. 

Light  Cell. — A  term  sometimes  employed 
for  a  photo-electric  cell. 

Light,  Electric. — Light  produced  by  the 
action  of  electric  energy. 

Light  Escape.  —  A  partial  ground  or 
earth. 

Light-House  Illumination,  Electric. — 
The  application  of  the  electric  arc-light 
to  light-houses. 

Light  Indicator  of  Railroad  Signal. — 
A  device  by  means  of  which  an  indica- 
tion is  given  electrically,  at  a  distance,  as 
to  whether  a  signal  lamp  is  lighted  or  not. 

Light  Load  of  Machine. — A  partial  load, 
or  a  load  which  is  small  by  comparison 
with  the  capacity  of  the  machine. 


Light  Cable,  Electric. —  A  cable  em- 
ployed for  furnishing  the  current  required 
for  the  maintenance  of  electric  lights. 

Lighting  Circuits. — Any  electric  circuit 
for  the  distribution  of  light. 

Lightning. — A  spark  or  discharge  that 
results  from  the  disruptive  discharge  of  a 
cloud  to  the  ground,  or  to  a  neighboring 
cloud. 

Lightning  Arrester. — A  device  by  means 
of  which  the  apparatus  placed  in  any- 
electric  circuit  is  protected  from  the  de- 
structive effects  of  a  flash  or  discharge  of 
lightning. 

Lightning  -  Arrester  Board.  —  The 
board  to  which  the  lightning  arresters  of 
a  system  of  telephonic  or  telegraphic 
communication  are  connected. 

Lightning-Arrester  Earth.— The  earth 
provided  for  the  grounding  of  the  earth- 
plate  of  a  lightning  arrester. 

Lightning  Bolt. — A  lightning  flash  or  dis- 
charge. 

Lightning  Conductor. — A  lightning  rod. 

Lightning  Deviator. — A  term  sometimes 
used  for  lightning  arrester. 

Lightning  Discharger. — A  term  some- 
times used  for  lightning  protector. 

Lightning  Flash. — A  lightning  discharge. 

Lightning  Guard. — A  term  sometimes 
used  for  lightning  rod. 

Lightning  Jar.  —  A  Leyden-jar  whose 
coatings  consist  of  metallic  filings  in  the 
gaps  between  which  an  irregular  series 
of  sparks,  somewhat  resembling  a  light- 
ning flash,  appear  on  the  discharge  of  the 
jar. 

Lightning  Rod. — A  rod,  strap,  wire,  or 
stranded  cable,  of  good  conducting  mate- 
rial, placed  on  the  outside  of  a  house  or 
other  structure,  in  order  to  protect  it 
from  the  effects  of  a  lightning  discharge. 

Lightning  Rods  for  Ships.— A  system  of 
rods  or  conductors  designed  to  afford 
electric  protection  for  vessels  at  sea. 

Lightning  Stroke. — (1)  A  disruptive  dis- 
charge occurring  between  two  oppositely 
charged  clouds,  or  between  a  cloud  and 
the  earth.  (2)  A  lightning  flash. 

Lightning  Tube. — A  fulgurite. 

Lime  Light. — A  source  of  light  obtained 
by  the  incandescence  of  a  cylinder  of 
lime  under  the  influence  of  the  oxy-hy- 
drogen  blow-pipe. 

Limit  Switch. — A  small  automatic  switch 
on  an  electric  street  car,  connected  in  series 
with  the  brake  discs,  and  so  arranged  as 
to  be  capable  of  cutting  out  the  fields  ot 


Lim.] 


830 


[Lin. 


both  motors  when  the  braeking  current  is 
excessive. 

Limiting  Distance  of  Speech. — (1)  The 
length  of  circuit,  or  the  distance  to  which 
a  circuit  may  be  carried  in  a  straight  line, 
at  which  telephonic  conversation  is  just 
practicable.  (2)  The  limiting  length  of 
line  to  which  telephonic  speech  can  be 
carried  successfully,  depending  upon  the 
electric  conditions  of  the  circuit,  and  the 
nature  of  the  apparatus  employed. 

Limiting  Speed  of  Cable. — The  speed 
to  which  the  transmission  of  signals 
through  a  cable  is  limited,  by  reason  of  its 
electrostatic  capacity  and  resistance. 

Limiting  Stop. — A  stop  set  so  as  to  limit 
the  motion  of  an  electrically  vibrating  or 
oscillating  bar  to  any  pre-determined 
extent. 

Limiting  Temperature-Elevation.— A 
temperature  elevation  of  any  apparatus 
which  is  not  to  be  exceeded  during  its 
prolonged  operation. 

Line.  —  Generally,  a  wire  or  conductor 
connecting  any  distant  points  or  stations. 

Line  Adjuster. — An  instrument  employed 
for  overcoming  the  effects  of  leakage  on 
the  adjustment  of  the  relays  in  a  tele- 
graphic circuit. 

Line  Arrester.  —  The  lightning  arrester 
connected  to  a  line  or  circuit. 

Line  Circuit.  —  (1)  The  wires  or  other 
conductors  in  the  main  line  of  a  tele- 
graphic or  other  circuit.  (2)  A  trans- 
mission circuit  for  electric  energy. 

Line  Crosses. — Electric  crosses  occurring 
on  lines. 

Line  Crossing. — (1)  The  place  where  two 
overhead  trolley  conductors  cross  each 
other.  (2)  A  metallic  plate  uniting  the 
ends  of  trolley  wires,  where  one  wire 
crosses  another. 

Line  Cross-Over. — (1)  A  trolley  crossing. 
(2)  A  trolley  cross-over. 

Line  Drop. — In  a  telephone  switchboard, 
an  electro-magnetic  drop  connected  to  a 
line. 

Line  Dynamometer.  —  A  dynamometer 
employed  during  the  erection  of  an  over- 
head line,  in  order  to  determine  whether 
it  has  been  pulled  up  to  its  proper  tension. 

Line  Insulator. — An  insulator  employed 
for  the  support  of  an  aerial  line. 

Line  Integral. — A  continuous  summing 
up  of  some  instantaneous  quantity  exe- 
cuted or  conducted  along  a  continuous 
line. 

Line  Jacks. — In  a  telephone  switchboard, 
a  jack  connected  to  a  line. 


Line  of  Least  Sparking. The  diameter 

of  sparkless  commutation. 

Line  Peg. — A  peg  or  plug  in  a  switchboard 
connecting  the  line  with  translating 
devices  or  with  another  line. 

Line-Pressure  Compensator.— A  device 
for  attachment  to  a  voltmeter  in  an  alter- 
nating-current system,  whereby  the  volt- 
meter indications  are  compensated  for 
the  drop  of  pressure  in  the  feeder,  and 
are  such  as  would  be  obtained  if  the 
instrument  were  directly  connected  to 
the  mains. 

Line  Reactance. — The  reactance  of  a  line 
conductor. 

Line  Section  of  Electric  Railroad.— 

Any  part  of  a  trolley,  or  other  railroad 
line,  so  insulated  from  other  parts  as  to 
permit  of  the  separate  control  of  its  sup- 
ply of  electric  power. 

Line  Selector. — A  wire  selector. 

Line  Wire. — In  telegraphy,  the  wire  that 
connects  the  different  stations  with  one 
another. 

Line-Wire  Tier.  —  A  tie  wire  of  soft 
copper  or  soft  iron  employed  for  holding 
the  line  wire  to  the  insulator. 

Lines  of  Electric-Displacement. — Lines 
of  electric  flux,  along  which  electric  dis- 
placement takes  place. 

Lines  of  Electric-Induction. — The  lines 
along  which  electric  induction  takes 
place. 

Lines  of  Electrostatic-Flux. — The  lines 
along  which  electrostatic  flux  passes. 

Lines  of  Electrostatic-Force.— (1)  Lines 
of  force  produced  in  the  neighborhood  of 
a  charged  body  by  the  presence  of  the 
charge.  (2)  Lines  extending  in  the  direc- 
tion in  which  the  force  of  electrostatic 
attraction  or  repulsion  acts. 

Lines  of  Inductive- Action. — Lines  of 
electrostatic  force. 

Lines  of  Magnetic-Force. — (1)  Lines  in 
which  magnetic  force  acts.  (2)  Lines 
extending  in  the  direction  in  which  the 
force  of  magnetic  attraction  or  repulsion 
acts. 

Lines  of  Magnetic-Induction.— (1)  Mag- 
netic flux-paths.  (2)  The  lines  in  which 
magnetic  induction  proceeds. 

Lines  of  Magnetization. — (1)  A  term 
sometimes  applied  for  lines  of  magnetic 
induction.  (2)  A  term  sometimes  applied 
to  those  portions  of  the  lines  of  magnetic 
force  which  lie  within  the  magnetized 
substance. 

Lineants. — A  term  proposed  as  a  unit  of 
magnetic  flux  in  place  of  webers,  and 


Lin.] 


831 


[Loc. 


equal  to  the  pressants  divided  by  the 
resistants,  or  to  the  magneto-motive  force 
divided  by  the  reluctance.  (Not  used.) 

Linear  Capacity. — The  quotient  of  the 
capacity  of  a  line  or  conductor  by  its 
length. 

Linear  Capacity  of  Cable.— The  electro- 
static capacity  of  a  cable  per-unit-of- 
length. 

Linear  Coefficient  of  Expansion.— The 
increase  in  a  unit  length  of  a  substance 
when  subjected  to  unit  difference  of  tem- 
perature. 

Linear  Density,  Electric. — The  amount 
of  electrification  per  unit  of  length. 

Linear  Density  of  Charge. — The  density 
of  charge  per-unit-of-length. 

Linear  Insulation. — The  product  of  the 
total  insulation  of  a  line  by  its  length. 

Linear  Insulation  of  Cable. — The  prod- 
uct of  the  insulation  resistance  of  a  cable 
by  its  length. 

Linear  Spectrum. — A  spectrum  consist- 
ing of  a  few  isolated  frequencies. 

Line-Man. — One  who  puts  up  and  repairs 
line  circuits,  and  attends  to  the  receptive 
devices  connected  therewith. 

Link-Fuse. — A  link-shaped  leaden  plate, 
provided  with  suitable  ends  for  connection 
•with  the  copper  fuse- wire  terminals. 

Link-Fuse  Cut-Out. — A  cut-out  employ- 
ing a  link-fuse. 

Linkages. — In  a  coil  traversed  by  a  cur- 
rent, the  sum  of  the  magnetic  flux  due  to 
that  current  linked  with  the  coil,  obtained 
by  considering  the  quantity  of  flux  linked 
with  each  turn,  separately  and  succes- 
sively, and  adding  the  fluxes  so  obtained. 

Linked  Magnetic  and  Electric  Cir- 
cuits.— A  phrase  sometimes  employed  to 
represent  the  interlinked  condition  of 
magnetic  and  electric  circuits. 

Liquid  Compass. — A  form  of  ship's  com- 
pass in  which  the  compass-needle  is  sus- 
pended, not  only  by  the  usual  gimbals,  but 
is  also  so  arranged  that  its  oscillations  are 
checked  by  a  surrounding  liquid. 

Liquid  Flow. — The  quantity  of  liquid 
that  escapes  from  an  orifice,  or  passes 
through  any  cross-section  of  a  pipe  or 
channel,  in  a  given  time. 

Liquid-Level  Alarm,  Electric. — A  de- 
vice for  electrically  sending  an  alarm 
when  a  liquid  level  differs  materially 
from  a  given  level. 

Liquid  Resistance  Load. — An  artificial 
load  for  a  dynamo  consisting  of  a  mass 
of  liquid  interposed  between  suitable 
electrodes: 


Liquid  Thermostat. — A  thermostat 
whose  operation  depends  on  the  expan- 
sion of  a  liquid. 

Liquefaction. — The  conversion  of  a  solid 
into  a  liquid  by  the  addition  of  heat,  or 
of  a  gas  into  a  liquid,  either  by  the  removal 
of  heat,  or  by  the  combined  influence  of 
low  temperature  and  pressure. 

Listening  Cam. — In  a  telephone  system  a 
metallic  cam  or  lever-key  by  means  of 
which  an  operator  readily  places  her  tele- 
phone in  circuit  with  a  subscriber. 

Listening  Key. — In  a  telephone  switch- 
board, a  listening  cam. 

Lithanode. — Highly  conducting  lead  per- 
oxide in  a  solid  form  suitably  prepared  for 
the  plate  of  a  storage  cell. 

Line  Trolley-Crossing. — (1)  The  point  or 
plate  where  two  trolley  wires  cross  each 
other  at  a  street  crossing.  (2)  A  line 
crossing. 

Live  Wire. — (1)  A  wire  through  which 
current  is  passing.  (2)  A  wire  connected 
with  an  electric  pressure  or  source. 

Liverpool  Repeater. — A  name  given  to 
a  form  of  telephone  repeating  induction 
coil  in  which  the  iron  core  is  constructed 
of  thin  wires  bent  around  over  the  coils, 
so  as  to  overlap  at  the  ends,  and  form  a 
complete  magnetic  circuit. 

Load. — The  work  thrown  on  any  machine. 

Load-Diagram  of  Station. — A  curve 
which  represents  the  output  of  a  station 
for  a  given  time,  say  for  the  twenty-four 
hours  of  the  day. 

Load-Factor. — The  ratio  of  the  average 
to  the  maximum  load. 

Load  of  Dynamo. — The  current  delivered 
by  a  dynamo. 

Load-Panel.  —  The  panel  of  a  central- 
station  switchboard  provided  with  appa- 
ratus for  indicating  the  total  station-load. 

Loadstone. — An  objectionable  orthogra- 
phy sometimes  employed  for  lodestone. 

Local  Action  of  Dynamo-Electric  Ma- 
chine.— The  loss  of  energy  in  a  dynamo 
by  the  establishment  of  eddy  currents  in 
its  pole-pieces,  cores,  or  other  conducting 
masses. 

Local  Action  of  Voltaic  Cell.— An  irreg- 
ular consumption  of  the  zinc,  or  positive 
element  of  a  voltaic  cell,  by  the  fluid  or 
electrolyte  when  the  circuit  is  opened  or 
broken,  as  well  as  when  it  is  closed  or  in 
regular  action. 

Local  Battery. — A  voltaic  battery  thrown 
into  or  out  of  action  by  a  relay  and  em- 
ployed at  a  station  on  a  telegraphic  line, 


Loc.] 


832 


[Lon. 


to  operate  a  sounder,  or  a  registering  or 
recording  apparatus,  at  that  point  only. 
Local  Battery  Circuit. — The  circuit  in  a 
telegraphic  system  in  which  is  placed  the 
local  battery,  as  distinguished  from  the 
main  battery. 

Local  Calls. — At  a  central  telephone  ex- 
change, a  call  received  from  a  subscriber 
connected  directly  therewith,  as  distin- 
guished from  a  call  received  from  another 
exchange. 

Local  Currents. — A  term  sometimes  used 
for  eddy  currents. 

Local  Faradization. — A  method  of  thera- 
peutically  applying  the  voltaic  current, 
similar  in  general  to  that  employed  in 
local  galvanization. 

Local  Galvanization.— The  application 
of  galvanization  to  portions  of  the  body 
only,  in  contradistinction  to  general  gal- 
vanization. 

Local  Jack.— In  a  multiple  telephone 
switchboard,  an  answering  jack  corre- 
sponding to  a  local  line  drop,  or  a  jack 
separated  from  the  main  body  of  the 
switchboard  and  set  in  a  local  row  for  the 
convenience  of  the  operator  in  answering 
calls. 

Localization  of  Faults.  —  Determining 
the  position  of  a  fault  on  a  telegraphic  line 
or  cable  by  electrical  tests  applied  at  one 
or  both  ends. 

Localization  Test. — A  test  of  a  faulty  cir- 
cuit made  to  determine  the  position  of 
the  fault. 

Localized  Capacity. — Capacity  inserted 
in  a  circuit  in  one  or  more  condensers,  as 
distinguished  from  distributed  capacity, 
or  that  which  is  present  throughout  the 
entire  circuit. 

Localized  Inductance. — Inductance  in- 
serted in  a  circuit  at  one  or  more  points, 
as  distinguished  from  distributed  induct- 
ance which  is  present  throughout  the 
entire  circuit. 

Localized  Vector. — (1)  A  vector  function 
of  space.  (2)  A  vector  point-function. 
(3)  A  vector  quantity  which  is  a  property 
of  every  point  of  a  region. 

Locally  Inter-Connected  Switchboard. 

A  switchboard  sub-divided  into  sections, 
each  provided  with  auxiliary  jacks  which 
are  interconnected  among  the  different 
sections. 

Lock,  Electric. — A  lock  that  is  automati- 
cally released  by  the  aid  of  a  distant  push- 
button. 

Locomotive,  Electric. — (1)  A  locomotor 
whose  motive  power  is  electricity.  (2)  An 
electrically-driven  locomotive  engine. 


Locomotive  Head-Light,  Electric.— An 

electric  light  placed  in  the  focus  of  a  par- 
abolic reflector  in  front  of  a  locomotive 
engine. 

Locomotor. — A  travelling  motor,  as  dis- 
tinguished from  a  stationary  motor. 

Locomotor,  Electric.  —  An  electrically 
driven  locomotor. 

Lodestone. — A  name  given  to  a  piece  of 
naturally  magnetized  iron  ore. 

Lodge's    Standard   Voltaic  Cell.  —  A 

standard  form  of  Daniell's  cell. 

Log,  Electric. — An  electric  device  for 
measuring  the  speed  of,  or  the  distance 
traversed  by,  a  vessel. 

Logarithm.— The  exponent,  or  the  power 
to  which  it  is  necessary  to  raise  a  fixed 
number  called  the  base,  in  order  to  pro- 
duce a  given  number. 

Logarithmic. — Of  or  pertaining  to  a  loga- 
rithm. 

Logarithmic  Curve. — A  curve  in  which 
the  rate  of  increase  or  decrease  of  the  or- 
dinate  is  proportional  to  the  ordinate  it- 
self. 

Logarithmic  Decrement  of  Galvano- 
meter .-— •(!)  In  a  series  of  galvanometer 
swings  or  deflections,  the  ratio  of  any 
pair. of  successive  amplitudes.  (2)  The 
ratio  of  any  two  successive  total  swings 
or  deflections  of  a  galvanometer  needle. 

Logging  Motor,  Electric. — (1)  An  elec- 
tric locomotor  employed  for  hauling  logs. 
(2)  A  form  of  telpher  motor  moving  over 
a  cable  way,  usually  over  a  swamp,  for 
hauling  logs  out  of  the  same. 

Long- Arc  System  of  Electric  Lighting. 
A  system  of  arc  lighting  employing  long 
arcs  and,  consequently,  high  electro-mo- 
tive forces. 

Long-Closed  Circuit. — A  series  circuit  in 
which  all  the  devices  are  included  as  dis- 
tinguished from  a  series  circuit  in  which 
some  of  the  electro-receptive  devices  are 
cut-out. 

Long-Coil  Magnet.— (1)  An  electro-mag- 
net whose  magnetizing  coil  consists  of 
many  turns  of  fine  wire.  (2)  A  high- 
resistance  magnet. 

Long-Connection  Armature-Winding. 
Such  a  connection  of  a  two-circuit  arma- 
ture winding  that  in  each  circuit  electro- 
motive forces  are  produced  by  field  pole& 
of  one  polarity  only. 

Long  Connection  of  Two-Circuit 
Gramme-Windings.  —  A  form  of 
Gramme  winding  in  which  the  two  cir- 
cuits from  brush  to  brush  consist  of  con- 
ductors that  are  influenced  by  only  one- 
half  the  poles. 


Ion.] 


833 


[Loo. 


Long-Core  Electro-Magnet. — An  electro- 
magnet with  a  long  core. 

Long-Distance  Carbon  Telephone 
Transmitter. — A  form  of  microphonic 
telephone  transmitter  suitable  for  use  on 
long-distance  circuits. 

Long-Distance  Telephone  Cabinet. — 
An  approximately  sound-tight  cabinet 
employed  for  convenience  and  secrecy  in 
telephonic  communication. 

Long-Distance  Transmission.  — Trans- 
mission of  electric  energy  over  fairly  con- 
siderable distances. 

Long  End  of  Quadruplex  Battery. — 
The  end  of  a  quadruplex  battery  that  is 
further  from  the  point  of  intermediate 
connection  than  the  short  end. 

Long-Range  Electrometer. — An  electro- 
meter the  range  of  whose  scale  is  compar- 
atively long. 

Long-Shunt  Compound-Winding.— A 
compound  winding  of  a  dynamo-electric 
machine  in  which  the  shunt  coil  is  con- 
nected directly,  or  through  resistance, 
with  the  terminals  of  the  machine,  as  dis- 
tinguished from  a  short-shunt  compound- 
winding. 

Long-Shunt  Compound-Wound  Dy- 
namo-Electric Machine.  —  A  com- 
pound-wound dynamo,  in  which  the 
shunt-field  magnet  coils  form  a  shunt  to 
the  binding  posts  of  the  machine. 

Longitudinal  Magnetization. — Such  a 
magnetization  of  a  bar  or  rod,  that  its 
separate  magnetic  particles  are  arranged 
with  their  axes  lying  in  the  direction  of 
the  length  of  the  bar. 

Longitudinal  Vibrations.  — Vibrations 
set  up  in  an  elastic  medium  in  the  direc- 
tion of  propagation  or  transmission,  as  dis- 
tinguished from  transverse  vibrations 
which  occur  at  right  angles  to  the  direc- 
tion of  propagation. 

Loom,  Electric. — An  electrically  operated 
loom ,  in  which  the  Jacquard  cards  of  the 
ordinary  loom  are  replaced  by  simple  per- 
forated metal  plates,  whose  perforations 
correspond  to  those  in  the  Jacquard  cards. 

Loop  Bracket. — (1)  A  insulating  bracket 
from  which  a  conducting  loop  can  con- 
veniently be  run  so  as  to  include  a  source 
or  translating  device.  (2)  A  bracket  for 
holding  two  insulators  and  wires,  such  as 
might  form  a  loop. 

Loop-Break. — A  device  for  introducing  a 
loop  in  a  break  made  at  any  part  of  a  cir- 
cuit. 

Loop-Circuit. — (1)  A  term  sometimes  ap- 
plied to  a  circuit  in  parallel  or  multiple- 
arc.  (2)  A  metallic  circuit.  (3)  A  circuit 

53 


having  two  wires,  one  out-going  and  the 
other  returning,  as  distinguished  from  an 
earth-return  circuit. 

Loop  Cut-Out. — A  cut-out  placed  in  a 
loop. 

Loop,  Electric. — A  portion  of  a  main  cir- 
cuit consisting  of  a  wire  going  out  from 
one  side  of  a  break  in  the  main  circuit  and 
returning  to  the  other  side  of  the  break. 

Loop-Mile. — (1)  A  mile  of  going  and 
return  conductor  in  a  loop  circuit.  (2)  A 
mile  of  double  conductor.  (3)  A  double 
mile  of  conductor.  (4)  A  distance  of  one 
mile  traversed  by  a  pair  of  conductors. 

Loop  or  Spreader  Bracket. — A  bracket 
used  on  cross-arms  for  taking  off  loops 
that  are  to  be  carried  to  service  wires, 
branch  mains,  or  transformers. 

Loop  Switch. — A  switch  for  opening  or 
closing  a  loop,  or  for  throwing  a  loop  into 
or  out  of  a  main  circuit.  (2)  A  switch 
for  connecting  a  branch  office  with  a  du- 
plex or  quadruplex  switch  at  a  main  of- 
fice, so  that  the  branch  office  assumes 
control  of  one  set  of  apparatus  ;  i.  e., 
sends  and  receives  messages  on  the  duplex 
or  quadruplex  system. 

Loop  System  of  Distribution. — A  system 
of  distribution  employed  in  the  early  his- 
tory of  electric  lighting,  in  which  each  of 
a  number  of  lamps  was  furnished  with  cur- 
rent through  a  single  machine  by  means 
of  a  separate  and  independent  loop  or  cir- 
cuit connected  with  the  terminals  of  such 
machine. 

Loop-System  of  Parallel  Distribution. 
A  system  of  parallel  distribution  in 
which  a  pair  of  mains  is  connected  to  a 
generator  in  a  manner  designed  to  equal- 
ize the  drop  of  pressure  ;  one  main  being 
connected  at  the  home  end  directly  to 
the  generator,  and  the  other  being  con- 
nected at  its  distant  end  to  the  generator 
through  a  separate  wire. 

Loop  Test. — A  localization  test  for  a  fault 
in  a  loop  of  two  telegraphic  wires,  or  in  a 
complete  metallic  circuit. 

Loop  Winding.— A  term  sometimes  used 
for  lap-winding. 

Loop-Winding  of  Alternator.— (1)  Coil 
winding.  (2)  An  alternator  armature- 
winding  in  which  the  wire  is  laid  on  the 
surface  of  the  armature  core  in  loops  or 
coils. 

Loops  of  Force. — A  term  sometimes  ap- 
plied for  lines  of  force. 

Loops  of  Induction. — A  term  sometimes 
applied  for  lines  of  magnetic  induction. 

Loops  of  Mutual-Induction.— Loops  or 
lines  of  induction  produced  in  any  cir- 


Loo.] 


834 


[Lum. 


cuit  by  variations  in  the  intensity  of  the 
current  flowing  in  a  neighboring  circuit. 
Looping-In. — A  term  sometimes  employed 
for  a  method  adopted  in  grounded  tele- 
phone or  telegraph  circuits  for  connect- 
ing Several  instruments  in  series  in  a  loop 
in  that  circuit,  so  that  any  conversation 
must  be  transmitted  through  all  the  in- 
struments which  happen  to  be  in  the  cir- 
cuit between  the  parties  connected. 

Loss  Plate  of  Voltameter.— (1)  That  plate 
of  a  voltameter  from  which  the  metal 
is  electrolytically  dissolved  during  the 
passage  of  the  current.  (2)  The  plate  con- 
nected with  the  anode  or  positive  ter- 
minal. 

Loose  Carbon  Transmitter.— (1)  A  tele- 
phone transmitter  employing  loose  car- 
bon or  carbon  dust.  (2)  A  dust  telephone 
transmitter. 

Loose  Contact. — A  contact  effected  by 
two  or  more  surfaces  that  rest  loosely  on 
one  another,  or  by  means  of  their  weight 
only. 

Loose-Handle  Switch. — A  form  of  switch 
in  which  the  handle  after  it  has  been 
moved  a  short  distance  falls  into  a  new 
position  of  equilibrium. 

Loss  of  Continuity. — A  disconnection  or 
interruption  of  a  circuit. 

Loud-Speaking  Telephone.— (1)  A  name 
given  to  any  telephone  characterized  by 
the  intensity  of  the  sounds  produced  by 
its  receiver.  (2)  A  name  sometimes  given 
to  the  electro-motographic  telephone. 

Loudness. — That  quality  of  a  sound  which 
depends  on  the  amplitude  of  its  vibra- 
tions. 

Low-Frequency.— (1)  A  frequency  of  but 
comparatively  few  alternations  per  sec- 
ond. (2)  Any  frequency  lower  than  that 
usually  employed. 

Low-Frequency  Trans  forme  r. — A 
transformer  designed  for  operation  on  a 
low-frequency  circuit. 

Low-Potential  Current. — A  term  some- 
times used  for  a  current  on  a  low-pressure 
circuit. 

Low-Potential  System.— In  the  National 
Electric  Code,  a  system  having  a  pressure 
less  than  300  volts. 

Low  Pressure.— A  comparatively  small 
pressure  or  electromotive  force. 

Low-Pressure  Circuit. — A  circuit  de- 
signed for  use  in  connection  with  low 
electric  pressure. 

Low-Pressure  Incandescent  Lamp.— 
An  incandescent  lamp  whose  filament  is 
short  and  thick,  and,  consequently,  of 


low  electric  resistance  suited  for  a  lo\* 
pressure. 

Low-Resistance  Magnet.  —  A  magnet 
wound  with  low-resistance  magnetizing 
coils. 

Low-Speed  Electric  Motor.— An  elec- 
tric motor  designed  to  run  normally  at 
low  speeds. 

Low  Tension. — A  term  sometimes  used 

for  low  pressure. 
Low-Tension  Bus.— In  a  central  station 

any  bus-bar  connected  witli  a  low-tension 

generator. 

Low-Tension  Electric  Fuse.— A  fuse 
that  is  ignited  by  heating  a  wire  to  in- 
candescence by  the  passage  of  an  electric 
current  of  low  pressure,  as  distinguished 
from  a  high-tension  fuse. 

Low-Tension  Switch.  —  A  switch  de- 
signed for  use  on  low-tension  circuits. 

Low  Vacuum. — (1)  A  vacuum  in  which 
the  mean-free-path  of  the  molecules  of 
the  residual  gas  is  small  as  compared  with 
the  dimensions  of  the  containing  vessel. 
(2)  A  space  from  which  only  a  portion  ot~ 
the  air  or  residual  gas  has  been  removed. 

Loxodograph. — An  apparatus  for  elec- 
trically recording  on  paper  the  actual 
course  of  a  ship,  by  the  combined  action 
of  magnetism  and  photography. 

Lubricating. — Reducing  friction  by 
means  of  lubrication. 

Lubrication. — The  reduction  of  friction 
between  surfaces,  by  rendering  them 
slippery. 

Luces. — A  plural  of  lux. 

Lumen. — (1)  A  unit  of  flux-of-light  equal 
to  the  light  received  by  a  square  metre  of 
spherical  surface,  from  a  point  source  of 
unit  intensity,  placed  at  the  centre  of  a 
sphere  one  metre  in  radius.  (2)  The  flux 
of  light  through  a  steradian  from  a  point 
source,  whose  intensity  is  one  pyr.  (3)  A 
pyr-steradian. 

Lumen-Meter. — An  instrument  for  meas- 
uring the  flux  of  light. 

Lumen-Second. — A  rad. 
Lumination.  —  A   term    proposed  for    il- 
lumination.   (Not  in  use.) 

Luminescence.  —  A  limited  power  for 
emitting  light  possessed  by  certain  bodies 
which  have  previously  acquired  potential 
energy  by  exposure  to  light  or  radiant 
energy. 

Luminescence  Lamp. — (1)  A  fluorescent 
lamp.  (2)  A  lamp  rendered  luminescent 
by  bombardment.  (3)  An  X-ray  lamp. 
(4)  A  vacuum-tube  lamp. 


Lum.] 


835 


[Mac. 


Luminiferous.  —  Bearing     or     carrying 

light. 
Luminosity. — A  term  sometimes  used  for 

the  brightness  of  a  source. 
Luminous  Absorption.— The  absorption 

of  luminous  energy  in  its  passage  through 

bodies. 
Luminous  Efficiency. — The  ratio  which 

the  luminous  radiation  emitted  by  a  source 

bears  to  the  total  radiant  energy  emitted 

by  such  source  in  a  given  time. 
Luminous    Flux.— A  phrase  sometimes 

employed  for  flow  of  light. 

Luminous  Frequencies. — Physiological- 
ly effective  frequencies,  or  those  capable 
of  producing  the  sensation  of  light. 

Luminous  Heat. — Heat  radiation  accom- 
panied by  or  containing  physiologically 
effective  frequencies. 

Luminous  Intensity. — The  amount  of 
visible  radiation  emitted  from  a  luminous 
source  per-unit-of-area  of  surface. 

Luminous  Interference.  —  Interference 
produced  by  light  waves  of  the  same 
frequency  when  out  of  phase  with  each 
other. 

Luminous  Radiation. — Radiation  capa- 
ble of  affecting  the  eye. 

Lummer-Brodhun  Screen. — A  form  of 
photometric  screen  requiring  the  use  of 


but  one  eye,  thus  eliminating  any  errors 
due  to  the  varying  sensibility  of  the  two 
eyes,  each  of  the  two  sources  of  light 
that  are  being  compared  illumining  its 
own  field  only,  and  these  two  fields 
being  presented  to  the  eye  as  a  disc  and 
circle  respectively,  the  latter  surround- 
ing the  former,  and  yet  having  a  sharp 
line  of  separation  from  it. 

Lunar-Inequality  of  Earth's  Magnetic 
Variation. — Small  changes  in  the  value 
of  the  magnetic  variation  or  inclination, 
dependent  on  the  position  of  the  moon 
as  regards  the  magnetic  meridian. 

Lunar-Inequality  of  Earth's  Magnet- 
ism.— Small  variations  in  the  value  of 
the  earth's  magnetic  elements  dependent 
on  the  position  of  the  moon  as  regards 
the  magnetic  meridian. 

Lux. — (1)  A  unit  of  illumination  equal  to 
the  light  received  on  each  square  metre  of 
the  interior  of  a  sphere  whose  radius  is 
one  metre,  from  a  bougie-decimale  placed 
at  its  centre.  (2)  An  illumination  equal 
to  a  lumen-per-square-metre.  (3)  The 
normal  illumination  produced  by  one 
carcel  at  a  distance  of  a  metre. 

Lux-Second. — (1)  The  time-illumination 
of  one  lux  during  one  second.  (2)  A  unit 
of  time-illumination  employed  in  photo- 
graphy. (3)  A  phot. 


M 


M. — A  contraction  sometimes  employed  to 

express  a  pressure  of  the  millionth  of  an 

atmosphere. 

m. — A  symbol  for  magnetic  moment. 
m. — A  symbol  for  strength  of  magnetic 

pole. 
m. — An  abbreviation  for  metre,  a  practical 

unit  of  length. 
m. — An  abbreviation  for  minute,  a  practical 

unit  of  time. 
p. — A  symbol  for  magnetic  permeability  or 

inductivity.     (International  notation.) 
ft. — A  symbol  for  micron,  the  millionth  of  a 

metre,  or  one  thousandth  of  a  millimetre. 

pp. — A  symbol  for  bicron,  the  millionth  of 
a  millimetre,  or  thousandth  of  a  micron. 

m2. — An  abbreviation  for  square  metre,  a 
practical  unit  of  surface. 

m3. — An  abbreviation  for  cubic  metre,  a 
practical  unit  of  volume. 

m.a. — A  contraction  for  milli-ampere. 


m  :  s. — An  abbreviation  proposed  for  metre- 
per-second,  a  practical  unit  of  velocity. 

m :  s2. — An  abbreviation  proposed  for 
metre-per-second-per-second,  a  unit  of 
acceleration. 

mm. — A  contraction  for  millimetre. 

M.  Current. — A  term  proposed  for  mean 
current. 

M.  M.  F. — A  contraction  for  magneto- 
motive force. 

M.  P. — A  contraction  for  man-power. 

M.  P.  H. — A  contraction  sometimes  em- 
ployed in  railroad  work  for  miles-per- 
hour. 

M.  S.  Current. — A  term  proposed  for 
mean-square-current. 

Mac  or  Mack. — A  term  at  one  time  pro- 
posed for  the  practical  unit  of  self-induct- 
ance, after  Maxwell. 

Machine  Seal  of  Lamp  Chamber. — A 
hermetical  seal  effected  mechanically  be- 


Mac.] 


836 


[Mag. 


tween  the  glass  support  of  an  incandes- 
cent lamp  and  the  walls  of  the  lamp 
chamber. 

Machine  Telegraphic  Transmission.— 
High-speed  telegraphic  transmission  ef- 
fected by  means  of  an  automatic  tele- 
graphic transmitter. 

Machine  Telegraphy. — Automatic  or 
high-speed  telegraphy. 

Machine  Tool,  Electric. — An  electrically 
driven  machine  tool. 

Made  Circuit. — A  completed  circuit. 

Magazine  Fuse. — A  safety  fuse  contain- 
ing a  number  of  spare  fuses,  so  arranged 
as  to  readily  permit  the  replacement  of 
the  fuse  when  blown,  either  automatic- 
ally, or  by  hand. 

Magic  Pane. — A  condenser  formed  of  a 
sheet  of  glass,  covered  on  one  side  with 
pieces  of  tin-foil,  with  small  spaces  left 
between  them  disposed  in  some  design  on 
the  glass,  which  design  becomes  lumin- 
ous on  the  discharge  of  the  condenser. 

Magne-Crystallic  Action. — A  term  pro- 
posed by  Faraday  to  express  differences 
in  the  action  of  magnetism  on  crystalline 
bodies  in  different  directions. 

Magne-Crystallic  Force.— The  force 
which  produces  magne-crystallic  actions. 

Magne-Electric  Induction. — A  variety 
of  electro-dynamic  induction  in  which 
electric  currents  are  produced  by  the 
motion  of  permanent  magnets  past  con- 
ductors, or  of  conductors  past  permanent 
magnets. 

Magnes  Stone. — An  old  name  for  mag- 
netite or  for  a  natural  magnet. 

Magnet. — (1)  Any  body  producing  mag- 
netic flux.  (2)  A  body  possessing  the 
power  of  attracting  the  unlike  pole  of  an- 
other magnet,  or  of  repelling  the  like 
pole,  or  of  inducing  magnetism  in  mag- 
netizable bodies. 

Magnet  Coil. — A  coil  of  insulated  wire 
surrounding  the  core  of  an  electro-mag- 
net, through  which  the  magnetizing  cur- 
rent is  passed. 

Magnet  Cores. — Bars  or  cylinders  of  iron 
on  which  the  magnetizing  coils  of  wire 
are  placed. 

Magnet  Operation. — The  use  of  a  magnet 
for  the  purpose  of  removing  particles  of 
iron  from  the  eye. 

Magnetic  or  Magnetical. — Of  or  pertain- 
ing to  a  magnet. 

Magnetic  A-B-C-Instrument.—  A  step- 
by-step  dial  telegraph  instrument  employ- 
ing magneto-induced  currents. 

Magnetic     Adherence.— Adhesion    be- 


tween surfaces,  due  to  their  mutual  mag- 
netic attractions. 

Magnetic  Aelotropy.— A  difference  in 
the  magnetic  susceptibility  of  a  mass  of 
iron  in  different  directions. 

Magnetic  Air-Circuit. — That  portion  of 
a  magnetic  circuit  which  passes  wholly 
through  air. 

Magnetic  Air-Gap. — Any  gap  in  an  aero- 
ferric  magnetic  circuit  filled  with  air. 

Magnetic  Alternator. — A  magneto-alter- 
nator. 

Magnetic  Atmosphere. — (1)  A  term  for- 
merly  employed  for  a  space  filled  with 
the  assumed  magnetic  effluvia.  (2)  A 
magnetic  field. 

Magnetic  Attraction. — The  mutual  at- 
traction exerted  between  unlike  magnetic 
poles. 

Magnetic  Axis. — (1)  The  line  along  which 
a  magnetic  needle,  free  to  move,  but 
which  has  come  to  rest  in  a  magnetic 
field,  can  be  turned  without  changing  the- 
direction  in  which  it  comes  to  rest.  (2) 
The  line  connecting  the  poles  of  a  bar 
magnet  or  needle. 

Magnetic  Axis  of  Straight  Needle. — 
A  straight  line  drawn  through  a  mag- 
netic needle  joining  its  poles. 

Magnetic  Azimuth. — (1)  The  arc  inter- 
cepted on  the  horizon,  between  a  mag- 
netic meridian  and  a  great  circle  passing 
through  the  observed  body.  (2)  A  mag- 
netic bearing. 

Magnetic  Battery. — The  combination  of 
a  number  of  separate  magnets  so  as  to  be 
capable  of  acting  as  a  single  magnet. 

Magnetic  Bearing. — The  horizontal  angle 
included  between  a  horizontal  line  from 
an  observer's  eye  to  an  object  and  the 
observer's  magnetic  meridian. 

Magnetic  Bearing  Compass. — A  com- 
pass provided  with  means  for  taking  bear- 
ings. 

Magnetic  Belting. — A  method  of  driving 
machinery  in  which  the  belt  is  provided 
at  frequent  intervals  with  strips  of  sheet 
iron  riveted  to  it  perpendicularly  to  its 
length  and  the  iron  driving  pulley  mag- 
netized, so  that  the  magnetic  attraction 
increases  the  friction  or  grip  on  the  pulley. 

Magnetic  Blow-Out.— (1)  A  device  for 
extinguishing  an  arc  by  an  electro-mag- 
net. (2)  A  device  employed  for  extin- 
guishing an  arc  formed  between  the  con- 
tact pieces  of  a  street-car  controller,  or 
other  similar  device,  by  means  of  the  flux 
produced  by  an  electro-magnet  which  i& 
placed  in  the  circuit  of  the  current  pro- 
ducing the  arc. 


Mag.] 


837 


[Mag. 


Magnetic  Blow-Out  Lightning-Ar- 
rester.— A  lightning  arrester  in  which 
the  arc,  when  formed,  is  blown  out  by 
the  action  of  the  flux  of  an  electro-mag- 
net placed  in  the  circuit  of  the  arc. 

Magnetic  Bridge. — An  apparatus  for 
measuring  magnetic  resistance,  similar 
in  principle  to  Wheatstone's  electric 
bridge. 

Magnetic  Centre  of  Gravity. — A  con- 
ception respecting  the  existence  of  a 
point  from  which  the  magnetic  flux  pro- 
ducing a  magnet  pole  issues,  similar  to 
the  conception  of  a  centre  of  gravity  in 
an  unequally  loaded  plane. 

Magnetic  Circuit. — The  path  through 
which  magnetic  flux  passes. 

Magnetic  Circuit-Breaker. — A  circuit 
breaker  operated  by  means  of  an  electro- 
magnet. 

Magnetic  Circuit-Closer.  —  A  circuit 
closer  operated  by  means  of  an  electro- 
magnet. 

Magnetic  Closed-Circuit. — A  ferro-mag- 
netic  circuit. 

Magnetic  Clutch. — (1)  A  form  of  clutch 
in  which  magnetic  attraction  is  substi- 
tuted for  ordinary  mechanical  force,  to 
obtain  the  friction  required  in  the  clutch. 
(2)  A  clutch  operated  electro-magnetic- 
ally. 

Magnetic  Coercivity. — A  term  some- 
times used  for  coercive  force. 

Magnetic  Compensator. — A  device  for 
neutralizing  the  effects  produced  by  the 
local  magnetism  of  a  ship  on  a  magnetic 
needle. 

Magnetic  Concentration.— The  separa- 
tion of  the  useful  ore  from  the  dross  in 
low-grade  ores,  by  the  use  of  an  electro- 
magnetic separator. 

Magnetic  Conduction  -  Current. —  ( 1 ) 
Time-rate  of  increase  of  magnetic  flux 
through  a  boundary.  (2)  Time-rate  of 
flow  of  magnetism. 

Magnetic  Conductivity. — Magnetic  per- 
meability. 

Magnetic  Connection. — (1)  A  term  some- 
times employed  for  inductive  connection. 
(2)  The  connection  of  one  circuit  with 
another  by  means  of  inter-linked  mag- 
netic flux. 

Magnetic  Control  of  Galvanometer 
Needle. — The  alteration  in  the  sensibility 
of  a  galvanometer  needle  effected  by 
means  of  a  compensating  magnet. 

Magnetic  Couple. — The  couple  which 
turns  or  tends  to  turn  a  magnetic  needle, 
placed  in  the  earth's  field,  into  the  plane 
of  the  magnetic  meridian. 


Magnetic  Creeping. — A  term  used  for 
a  gradual  increase  in  the  magnetization, 
following  a  sudden  increase  in  magnet- 
izing force. 

Magnetic  Cross-Flux  of  Transformer. 
A  magnetic  flux  across  the  direction  of 
main  or  working  flux  and  representing 
magnetic  leakage. 

Magnetic  Current. — The  time-rate  of  in- 
crease of  magnetic  flux  through  a  sur- 
face. 

Magnetic  Curve-Tracer.—  An  instru- 
ment for  graphically  recording  the  varia- 
tions of  magnetic  intensity  in  a  mass  of 
iron  subjected  to  cyclic  variations  of  mag- 
netizing force. 

Magnetic  Curves. — (1)  Curved  lines  ex- 
tending in  the  direction  of  the  flux-paths 
of  a  magnetic  field,  obtained  by  gently 
tapping  a  sheet  of  paper  or  glass  sprinkled 
with  iron  filings  and  held  in  the  field.  (2) 
Magnetic  figures. 

Magnetic  Cycle. — A  cycle  of  magnetiza- 
tion. 

Magnetic  Day  of  Disturbance.— A  day 
of  magnetic  disturbance. 

Magnetic  Declination. — The  variation  of 
a  magnetic  needle  from  the  true  geo- 
graphical north. 

Magnetic  Deep-Sea  Thermometer. — A 
deep-sea  thermometer  containing  small 
steel  maximum  and  minimum  limit 
markers  which  are  reset  by  a  permanent 
magnet. 

Magnetic  Density. —  The  strength  of 
magnetism  as  measured  by  the  amount  of 
magnetic  flux  which  passes  through  unit 
area  of  normal  cross-section.  (2)  Inten- 
sity of  magnetic  induction. 

Magnetic  Deviation. — (1)  The  local  mag- 
netic variation  due  to  the  presence  of 
iron  in  the  vicinity,  as  distinguished  from 
the  true  magnetic  variation  of  the  local- 
ity considered.  (2)  On  board  ship,  that 
part  of  the  total  magnetic  variation  due 
to  iron  in  or  on  board  the  ship. 

Magnetic  Diffusion. — Magnetic  leakage. 

Magnetic  Dip. — (1)  The  deviation  of  a 
freely  suspended  magnetic  needle  from  a 
true  horizontal  position.  (2)  The  mag- 
netic inclination. 

Magnetic  Discontinuity. — The  more  or 
less  marked  change  in  the  permeability 
of  a  magnetic  circuit  produced  by  any 
joint  in  such  circuit. 

Magnetic  Displacement. — (1)  An  imag- 
inary stress  in  the  ether  when  subjected 
to  magnetization  and  corresponding  to 
electric  displacement  in  electrostatics. 
(2)  Magnetic  induction. 


Mag.] 


838 


[Mag. 


Magnetic  Dissymmetry.— (1)  A  lack  of 
uniformity  of  the  magnetic  flux  in  a 
magnetic  circuit,  or  in  portions  of  that 
circuit.  (2)  A  lack  of  uniformity  pro- 
duced in  the  flux  through  the  armature 
core  of  a  dynamo  or  motor  during  its  op- 
eration. 

Magnetic  Disturbance. — A  term  some- 
times employed  for  temporary  variations 
in  the  intensity  of  the  earth's  magnetism. 

Magnetic  Divining  Rod. — A  small  dip- 
ping needle  employed  for  the  purpose  of 
locating  approximately  the  position  of 
beds  of  iron  ore. 

Magnetic  Effluvia. — (1)  A  term  employed 
in  the  early  history  of  magnetism  for 
assumed  imponderable  effluvia  which 
were  supposed  to  be  given  off  by  magnets. 
(2)  Magnetic  flux. 

Magnetic  Elements  of  a  Place.— The 
values  of  the  magnetic  intensity,  the 
magnetic  declination  or  variation,  and 
the  magnetic  inclination  or  dip  of  any 
place. 

Magnetic  Equalizer.  —  A  device  for 
equalizing  the  otherwise  unequal  force 
exerted  between  a  magnet  pole  and  its 
armature  at  varying  distances. 

Magnetic  Equator.  —  (1)  The  line  con- 
necting places  on  the  earth's  surface  where 
a  magnetic  needle  remains  horizontal, 
when  suspended  so  as  to  be  free  to  move  in 
a  vertical  as  well  as  in  a  horizontal  plane, 
(2)  An  irregular  line  passing  around  the 
earth,  approximately  midway  between 
its  magnetic  poles. 

Magnetic  Excitation. — Magnetization. 

Magnetic  Explorer.— (1)  A  small  flat 
coil  of  insulated  wire,  used,  in  connection 
with  the  circuit  of  a  galvanometer  or 
telephone,  to  determine  the  position  and 
extent  of  the  magnetic  leakage  of  a 
dynamo,  or  other  similar  apparatus.  (2)  A 
search  coil  so  connected  to  a  ballistic 
galvanometer  that  its  movements  through 
magnetic  flux  will  be  indicated  by  the 
galvanometer. 

Magnetic  Fatigue. — An  increase  in  the 
hysteretic  coefficient  of  iron  due  to  an 
assumed  fatigue  after  many  cyclic  re- 
versals. 

Magnetic  Fatigue  of  Transformer. — 
(1)  An  increase  in  the  hysteretic  loss  of  a 
transformer  with  time.  (2)  The  ageing 
of  a  transformer  core. 

Magnetic  Field.— (1)  The  region  of  mag- 
netic influence  surrounding  the  poles  of 
a  magnet.  (2)  The  space  or  region  trav- 
ersed by  magnetic  flux.  (3)  A  space 
traversed  by  magnetic  flux  in  which  a 


magnet  needle,  free  to  move,  will  assume 
a  definite  position. 

Magnetic  Figures. — A  name  sometimes 
applied  to  the  groupings  of  iron  filings 
obtained  when  a  sheet  of  paper  or  glass, 
sprinkled  with  filings,  is  so  held  in  a  mag- 
netic field  as  to  permit  the  filings  to  be 
grouped  or  arranged  under  the  influence 
of  the  magnetic  flux. 

Magnetic  Filament. — A  polarized  line  or 
chain  of  ultimate  magnetic  particles. 

Magnetic  Flow.  —  A  term  sometimes  em- 
ployed for  magnetic  flux. 

Magnetic  Fluids. — A  term  formerly  em- 
ployed for  the  assumed  fluids  which  were 
believed  to  be  the  cause  of  magnetic 
phenomena. 

Magnetic  Austral  Fluid. — The  assumed 

magnetic  fluid  existing  at  the  south  pole 

of  any  magnet. 
Magnetic  Boreal  Fluid. — The  assumed 

magnetic  fluid  existing  at  the  north  pole 

of  any  magnet. 

Magnetic  Flux. — (1)  The  streamings  that 
issue  from  and  return  to  the  poles  of  a 
magnet.  (2)  The  total  number  of  lines 
of  magnetic  force  in  any  magnetic  field. 
(3)  The  magnetic  flow  that  passes  through 
any  magnetic  circuit. 

Magnetic  Flux-Density. — The  quantity 
of  magnetic  flux  in  any  part  of  a  mag- 
netic circuit  per-unit-of-area  of  normal 
cross-section. 

Magnetic  Flux-Intensity. — The  density 
of  magnetic  flux. 

Magnetic  Flux-Paths. — Paths  taken  by 
magnetic  flux  in  any  magnetic  circuit. 

Magnetic  Force. — The  force  which  causes 
the  attractions  and  repulsions  of  mag- 
netic poles. 

Magnetic  Friction. — A  term  sometimes 
used  for  magnetic  hysteresis. 

Magnetic  Fringe  at  Edge  of  Dynamo 
Pole-Pieces. — The  lateral  dispersion  or 
diffusion  of  magnetic  flux  through  the 
air  space  which  produces  an  apparent 
fringe  of  magnetic  flux  in  the  air  sur- 
rounding the  poles. 

Magnetic  Gearing. — A  form  of  friction 
gearing  employing  magnetic  adhesion. 

Magnetic  Generator. — A  magneto-elec- 
.    trie  generator. 

Magnetic  Helix. — A  magnetizing  coil. 

Magnetic  Hysteresis. — (1)  Apparent  mo- 
lecular friction  due  to  magnetic  change 
of  stress.  (2)  A  lagging  of  magnetization 
behind  the  magnetic  force  producing  it. 
(3)  That  quality  of  a  magnetic  substance 


Mag.] 


839 


[Mag. 


in  virtue  of  which  energy  is  absorbed  on 
the  reversal  of  its  magnetization. 

Magnetic  Image. — The  analogue  in  mag- 
netism of  an  electric  image  in  electro- 
statics. 

Magnetic  Impermeability.  —  A  term 
sometimes  used  for  magnetic  reluctivity. 

Magnetic  Inclination. — (1)  The  angular 
deviation  from  a  horizontal  position  of 
a  freely  suspended  magnetic  needle. 

(2)  Magnetic  dip. 

Magnetic  Inductipn.  —  (1)  In  air,  the 
density  of  magnetic  force ;  in  iron  or 
other  magnetic  material  the  sum  of  the 
prime  flux,  or  magnetic  force,  and  the 
magnetic  flux  thereby  produced  in  the 
iron.  (2)  Total  magnetic  flux-density. 

(3)  The  production  of  magnetism  in  a 
magnetizable    substance    on    its    being 
brought  into  magnetic  flux. 

Magnetic  Inertia. — The  inability  of  a 
magnetic  core  to  instantly  lose  or  acquire 
magnetism. 

Magnetic  Intensity.— (1)  Magnetic  flux- 
density.  (2)  The  quantity  of  magnetic 
flux  per-unit-of-area  of  normal  cross-sec- 
tion. (3)  Magnetic  induction. 

Magnetic  Joint. — A  joint  effected  be- 
tween contiguous  pieces  of  iron  forming 
portions  of  a  magnetic  circuit. 

Magnetic  Lag.  —  (1)  Magnetic  viscosity 
manifested  by  the  sluggishness  with 
which  a  magnetizing  force  produces  its 
magnetizing  effects  in  a  mass  of  iron. 
(2)  The  tendency  of  an  iron  core  to  resist, 
and,  therefore,  to  retard  its  magnetiza- 
tion. (3)  Hysteresis  in  iron. 

Magnetic  Lag  Motor.— A  form  of  motor 
whose  torque  depends  on  magnetic  lag  or 
hysteresis. 

Magnetic  Latitude.— (1)  The  meridional 
angular  distance  of  a  place  north  or  south 
of  the  magnetic  equator.  (2)  The  lati- 
tude as  deduced  from  the  magnetic  dip. 

Magnetic  Leakage.— (1)  A  useless  disper- 
sion of  magnetic  flux  of  a  dynamo  or 
motor  by  its  failure  to  pass  through  the 
armature.  (2)  Any  useless  dispersion  of 
magnetic  flux  by  its  failure  to  pass 
through  a  magneto-receptive  device 
placed  in  the  magnetic  circuit. 

Magnetic  Leakage  Factor.— The  ratio 
of  the  total  flux  generated  in  a  magnetic 
circuit  to  the  quantity  usefully  passing 
through  an  armature  or  magneto-recep- 
tive device. 

Magnetic  Lightning-Arrester.— (1)  An 
electro-magnetic  blow-out  lightning-ar- 
rester. (2)  Any  lightning-arrester  em- 
ploying an  electro-magnet. 


Magnetic  Limbs.  — (1)  Magnetic  cores. 
(2)  Magnetic,  arms. 

Magnetic  Limit.  —A  term  sometimes  em- 
ployed for  the  temperature  at  which  a 
magnetic  substance  loses  its  magnetism 
on  exposure  to  heat. 

Magnetic  Line-Protector.— An  electro- 
magnetic device  placed  on  a  telegraphic 
or  other  line  for  the  purpose  of  protect- 
ing its  instruments  from  lightning  dis- 
charges. 

Magnetic  Lines  of  Force.— (1)  Lines  of 
magnetic  force.  (2)  Flux  paths.  (3)  The 
lines  along  which  a  free  magnetic  pole 
would  be  urged. 

Magnetic  Magazine. — A  term  sometimes 
employed  for  a  compound  magnet.  (Ob- 
solete.) 

Magnetic  Mass. — The  quantity  of  mag- 
netism or  imaginary  magnetic  mattei 
resident  on  a  polar  surface. 

Magnetic  Memory.— (1)  That  deviation 
of  a  magnetic  condition  of  a  magnetic 
substance  from  the  complete  response  to 
an  impressed  magnetic  force  which  is  a 
function  of  antecedent  magnetic  states. 
(2)  A  term  proposed  for  magnetic  reten- 
tivity.  (3)  The  .  power  possessed  by  a 
magnetic  substance,  in  virtue  of  hyster- 
esis, to  retain  in  any  magnetic  state,  the 
history  of  antecedent  states. 

Magnetic  Meridian.— (1)  The  great  circle 
which  passes  through  a  place  and  through 
the  poles  of  a  magnetic  needle  at  that 
place,  when  in  a  position  of  rest  under  the 
free  influence  of  the  earth's  magnetism. 
(2)  The  terrestrial  great  circle  coinciding 
in  plane  with  the  direction  of  the  earth's 
local  magnetic  force. 

Magnetic  Moment. — (1)  The  product  of 
the  strength  of  one  of  the  poles  of  a  mag- 
net into  the  distance  between  them. 
(2)  The  sum  of  the  two  forces  of  the 
directive  couple  of  a  magnet  multiplied  by 
half  the  perpendicular  distance  between 
the  directions  of  these  forces.  (3)  The 
length  of  a  magnet  multiplied  by  the  in- 
tensity of  one  of  its  poles. 

Magnetic  Needle. — (1)  A  magnetized 
steel  needle,  or  thin  straight  strip  or  rod. 
(2)  A  straight  bar  of  magnetized  steel, 
supported  at  or  above  its  centre  of  grav- 
ity, and  free  to  move  in  a  horizontal 
plane  only,  in  a  vertical  plane  only,  or  in 
both. 

Magnetic  North.— That  point  of  the  hori- 
zon which  is  indicated  by  the  north-seek- 
ing pole  of  a  magnet. 

Magnetic  Observatory. — An  observatory 
in  which  observations  are  made  of  the 


Mag.] 


840 


[Mag. 


variations  in  the  direction  and  intensity 
of  the  earth's  magnetic  field. 

Magnetic  Oscillation. — A  magnetic  vi- 
bration, or  to-and-fro  variation. 

Magnetic  Output. — The  product  of  the 
magnetic  flux  produced  by  any  source  and 
its  magneto-motive  force. 

Magnetic  Parallels. — Lines  connecting 
places  on  the  earth's  surface  at  right 
angles  to  the  isogonal  lines,  or  lines  of 
equal  declination  or  variation. 

Magnetic  Permeability.— (1)  Conductiv- 
ity for  magnetic  flux.  (2)  The  ratio  be- 
tween the  magnetic  induction  produced 
in  a  magnetic  substance,  and  the  magnet- 
izing force  producing  such  magnetic  in- 
duction. 

Magnetic  Permeance. — Magnetic  perme- 
ability. 
Magnetic  Permeation. — The  passage  of 

magnetic  flux   through   any  permeable 

substance. 
Magnetic  Perturbations.  —  Abnormal 

magnetic  variations,  or  disturbances. 
Magnetic  Phantom.— A  term  sometimes 

employed  for  magnetic  figures. 
Magnetic  Points  of  Cbnvergence. — The 

magnetic  paths  of  the  earth  around  which 

the  isogonic  lines  are  drawn. 
Magnetic  Polar-Area. — The  active  area 

of  the  pole-pieces  of  a  magnet. 

Magnetic  Polar-Intensity. — The  intens- 
ity of  the  magnetic  flux  produced  at  the 
pole-pieces  of  a  magnet. 

Magnetic  Polarization. — That  condition 
of  a  magnetizable  substance  when  it  is 
subjected  to  polarization. 

Magnetic  Polar-Surface. — The  magnetic 
polar  area. 

Magnetic  Polarity. — Polarity  acquired 
by  a  magnetizable  substance  when 
brought  into  magnetic  flux. 

Magnetic  Poles. — Those  parts  of  a  mag- 
netic source  from  or  at  which  the  flux 
emerges  or  enters. 

Magnetic  Potential. — (1)  That  property 
of  any  space  by  virtue  of  which  magnetic 
work  is  done  when  a  magnet  pole  is 
moved  therein.  (2)  The  amount  of  work 
required  to  bring  up  a  unit  north-seeking 
magnetic  pole  from  an  infinite  distance 
to  a  given  point  in  a  magnetic  field. 
(3)  The  line  integral  of  magnetic  force  on 
a  unit  pole  in  coming  from  an  infinite 
distance  to  the  point  considered. 

Magnetic  Proof-Piece. — A  magnetized 
ellipsoidal  or  square  rod  employed  for  as- 
certaining the  distribution  of  magnetism 


over  a  magnet  by  the  force  required  to 
detach  the  same. 

Magnetic  Proof-Plane. — A  small  coil  of 
wire  placed  in  the  circuit  of  a  delicate 
galvanometer,  and  used  for  exploring  a 
magnetic  field. 

Magnetic  Reactance. — In  an  alternating- 
current  circuit  the  reactance  of  a  coil  as 
distinguished  from  the  reactance  of  a 
condenser. 

Magnetic  Reluctance. — The  resistance 
offered  by  a  medium  to  the  passage 
through  it  of  magnetic  flux. 

Magnetic  Remanence. — The  magnetic 
flux-density  left  in  iron  or  other  magnetic* 
substance  after  the  removal  of  a  mag- 
netizing force. 

Magnetic  Repulsion. — Mutual  repulsion 
exerted  between  two  similar  magnet 
poles. 

Magnetic  Resistance. — A  term  formerly 
used  for  magnetic  reluctance. 

Magnetic  Resistivity. — (1)  Magnetic  re- 
luctivity. (2)  The  reluctance  of  a  medium 
referred  to  the  reluctance  offered  between 
parallel  faces  of  a  unit  cube.  (3)  The 
magnetic  analogue  of  electric  resistivity. 

Magnetic  Retardation. — A  retardation 
in  the  magnetization  or  demagnetization 
of  a  substance  due  to  magnetic  lag. 

Magnetic  Retentiveness. — A  name  some- 
times applied  to  magnetic  retentivity. 

Magnetic  Retentivity. — (1)  The  resist- 
ance a  body  offers  to  change  of  mag- 
netization. (2)  Hysteretic  retention  of 
magnetism  when  the  magnetizing  force 
is  changed  or  wholly  withdrawn.  (3) 
That  quality  of  iron  or  other  magnetic 
substance  in  virtue  of  which  it  retains  its 
magnetic  flux  after  the  withdrawal  of  the 
magnetizing  force.  (4)  Magnetic  rema- 
nence. 

Magnetic  Ringer. — A  magnetic  call-bell. 

Magnetic  Rotary  -  Polarization.  —  (1) 
Rotary  polarization  of  a  beam  of  plane 
polarized  light,  produced  by  its  passage 
through  magnetic  flux.  (2)  Magneto- 
optic  rotation. 

Magnetic  Safety  Factor. — The  factor  of 
safety  of  demagnetization. 

Magnetic  Saturation. — (1)  The  maximum 
magnetization  which  can  be  imparted  to 
a  magnetic  substance.  (2)  The  condition 
of  iron,  or  other  magnetic  substance,  when 
its  intensity  of  magnetization  is  so  great 
that  it  fails  to  be  further  magnetized  by 
any  magnetizing  force,  however  great. 

Magnetic  Screen.  —  (1)  A  hollow  box 
whose  sides  are  made  of  thick  iron  placed 


Mag.] 


841 


[Mag. 


around  a  magnet  or  other  body,  so  as 
to  shield  its  interior  from  a  magnetic 
field  external  to  the  box.  (2)  A  magnetic 
shield. 

Magnetic  Screening. — Preventing  mag- 
netic induction  from  taking  place  by  in- 
terposing either  a  thick  iron  plate,or  a  plate 
of  good  conducting  material,  between 
the  body  producing  the  magnetic  field  and 
the  body  to  be  magnetically  screened. 

Magnetic  Self-induction.— (1)  Electro- 
magnetic self-induction.  (2)  The  power 
possessed  by  a  magnet  of  inducing  an  op- 
posite polarity  in  its  own  particles.  (3)  Self- 
demagnetizing  power  in  a  magnet. 

Magnetic  Sense. — A  name  sometimes  ap- 
plied to  the  assumed  sense  by  means  of 
which  magnetic  influences  are  claimed  to 
be  perceived. 

Magnetic  Shade. — A  term  sometimes  used 
for  a  magnetic  screen. 

Magnetic  Shells. — Sheets  or  layers  con- 
sisting of  magnetic  particles  in  each  of 
which  all  the  north  poles  are  situated  in 
one  of  the  flat  surfaces  of  the  layer,  and 
all  the  south  poles  in  the  opposite  surface. 

Magnetic  Shield  for  Watches. — A  hol- 
low case  of  iron  in  which  a  watch  is  per- 
manently kept  in  order  to  partially  shield 
it  from  the  influence  of  external  magnetic 
flux. 

Magnetic  Shunt. — An  additional  path  of 
magnetic  material  provided  in  a  magnetic 
circuit  for  the  passage  of  magnetic  flux. 

Magnetic  Shunt-Circuit. — An  additional 
or  branch  circuit  through  which  some  of 
the  flux  is  diverted  from  the  main  mag- 
netic circuit. 

Magnetic  Shunt-Transformer.— (1)  A 
transformer  provided  with  a  magnetic 
shunt  of  regulable  value,  for  the  purpose 
of  regulation.  (2)  A  transformer  situated 
in  a  magnetic  shunt. 

Magnetic-Siren  Telephone-Call.  —  A 
magnetophone  employed  as  a  telephone 
call. 

Magnetic  Solenoid. — A  spiral  coil  of  wire, 
which  acts  like  a  magnet  when  an  electric 
current  is  sent  through  it. 

Magnetic  Sounds. — Faint  clicks  heard  on 
the  magnetization  and  demagnetization 
of  a  readily  magnetizable  substance. 

Magnetic  Source.— Anything  capable  of 
producing  magnetic  flux. 

Magnetic  Spectrum.— (1)  A  term  some- 
times employed  in  place  of  magnetic 
figures  or  a  magnetic  field.  (2)  The  suc- 
cession of  bright  and  dark  fluorescent 
bands  produced  upon  a  suitable  screen  in 


a  Crookes  tube  when  the  cathode  rays 
are  deflected  by  magnetic  flux. 

Magnetic  Spin. — A  term  sometimes  em- 
ployed for  magnetic  field. 

Magnetic  Spiral. — A  magnetizing  spiral 
or  helix. 

Magnetic  Sticking  of  Armature. — The 
magnetic  adhesion  of  the  armature  to  the 
magnet  poles  under  the  influence  of  hys- 
teresis. 

Magnetic  Storm.  —  (1)  Any  unusually 
marked  irregularity  occurring  in  the  dis- 
tribution of  the  earth's  magnetism  result- 
ing in  a  variation  in  the  value  of  its  mag- 
netic elements.  (2)  A  comparatively 
violent  and  widespread  temporary  pertur- 
bation of  the  earth's  magnetic  elements  in 
some  way  associated  with  solar  disturb- 
ances and  electric  earth  currents. 

Magnetic  Strain. — The  result  of  subject- 
ing any  medium  to  magnetic  stress  or 
magnetic  flux. 

Magnetic  Stream-Lines. — (1)  Magnetic 
flux-paths.  (2)  Lines  of  magnetic  flux. 
(3)  The  curved  paths  along  which  a  free 
magnetic  pole  would  be  urged  in  different 
parts  of  the  field. 

Magnetic  Stress.— (1)  The  mechanical 
stress  exerted  by  the  attraction  of  magnet- 
ized bodies.  (2)  That  property  of  flux 
which  produces  magnetic  strain  or  mag- 
netic phenomena  in  bodies  subjected  to  its 
influence. 

Magnetic  Susceptibility.— (1)  The  ratio 
existing  between  the  induced  magnetiza- 
tion and  the  magnetizing  force  producing 
such  magnetization.  (2)  The  intensity  of 
magnetism  divided  by  the  magnetic  force. 

Magnetic  Telephone.— (1)  A  name  some- 
times given  to  an  electro-magnetic  tele- 
phone. (2)  A  magneto  telephone. 

Magnetic  Telephone-Transmitter  or 
Receiver. — A  magneto-telephone-trans- 
mitter or  receiver. 

Magnetic  Theodolite. — An  apparatus  for 
measuring  the  declination  or  variation  of 
the  magnetic  needle  at  any  place. 

Magnetic  Tick. — (1)  A  metallic  click  heard 
on  the  magnetization  and  demagnetiza- 
tion of  a  bar  of  iron  or  steel.  (2)  The  Page 
effect. 

Magnetic  Time-Constant.— In  an  electric 
circuit  or  conductor,  the  ratio  of  the 
inductance  to  the  resistance,  usually  ex- 
pressed in  henrys  per  ohm,  or  seconds. 

Magnetic  Traction.— (1)  Tractive  or  sup- 
porting power  exerted  by  a  magnet. 
(2)  Hauling  or  carrying  effected  magneti- 
cally. 


842 


[Mag. 


Magnetic  Unit  Pole. — An  imaginary  free 
magnetic  pole  situated  at  a  point,  of  such 
strength  that  it  would  act  with  a  force  of 
a  dyne  on  a  similar  unit  pole  distant  from 
it  one  centimetre. 

Magnetic  Units.— (1)  Units  based  on  the 
force  exerted  between  magnet  poles. 
(2)  Units  employed  in  dealing  with  mag- 
nets and  magnetic  phenomena.  (3)  The 
magnetic  system  of  C.  G.  S.  electro- 
magnetic units,  as  distinguished  from  the 
electrostatic  system. 

Magnetic-Vane  Ammeter.  —  An  am- 
meter in  which  the  strength  of  a  magnetic 
field  produced  by  the  current  that  is  to  be 
measured  is  determined  by  the  repulsion 
exerted  between  a  fixed  and  a  movable 
iron  vane  placed  inside  the  field  and 
magnetized  thereby. 

Magnetic-Vane  Voltmeter.  —  A  volt- 
meter in  which  the  potential  difference  is 
measured  by  the  repulsion  exerted  be- 
tween a  fixed  and  a  movable  vane  of  soft 
iron  placed  within  the  field  of  the  mag- 
netizing coil. 

Magnetic  Variations. — Variations  in  the 
value  of  the  magnetic  elements  of  a  place. 

Magnetic  Variation-Transit. — An  ap- 
paratus for  measuring  the  magnetic  decli- 
nation or  variation  at  any  place. 

Magnetic  Variometer. — An  instrument 
for  comparing  the  horizontal  component 
of  the  earth's  magnetism  at  different 
localities. 

Magnetic  Viscosity. — A  property  of  iron 
or  other  paramagnetic  substance  in  virtue 
of  which  a  certain  time  is  required  before 
a  given  magnetizing  force  can  produce 
its  full  effects. 

Magnetic  Voltmeter — (1)  An  instrument 
in  which  the  magnetic  field  of  a  current 
proportional  to  the  difference  of  potential 
to  be  measured  deflects  a  movable  needle 
against  the  action  of  the  field  of  a  magnet. 
(2)  A  voltmeter  employing  a  permanent 
magnet. 

Magnetic  Vortices. — Imaginary  vortices 
in  the  ether  postulated  to  account  for 
magnetic  phenomena. 

Magnetics. — A  word  sometimes  used  for 
that  branch  of  science  which  treats  of  the 
laws  and  phenomena  of  magnetism. 

Magnetician. — A  word  proposed  for  one 
skilled  in  the  science  of  magnetism. 

Magnetification.  —  The  production  of 
magnetism  in  any  body. 

Magnetine. — A  word  formerly  applied  for 
the  assumed  principle  of  magnetism  ;  i.e., 
the  imponderable,  hypothetical  fluid  to 


the  presence  of  which  magnetic  pheno- 
mena were  believed  to  be  due. 

Magnetisation. — An  orthography  some- 
times used  for  magnetization,  and  in 
similar  words  where  the  z  is  replaced  by  s. 

Magnetish. — Possessing  the  property  of 
magnetism  to  a  limited  degree.  (Very 
rarely  used.) 

Magnetism.— (1)  That  property  or  condi- 
tion of  matter  which  accompanies  the 
production  of  magnetic  flux.  (2)  Mag- 
netic.flux  or  streamings.  (3)  That  branch 
of  science  which  treats  of  the  nature  and 
properties  of  magnets  and  of  magnetic 
flux. 

Magnetism  of  Rotation. — A  conception 
at  one  time  entertained  that  revolving 
bodies  became  magnetized,  as  a  deduction 
from  Arago's  experiment. 

Magnetist.  —  A  magnetician.  (Seldom 
used.) 

Magnetite. — A    name   given   to  mineral 

magnetic  oxide  of  iron. 
Magnetizability.— Possessing  the  ability 

of  becoming  magnetized. 

Magnetizable. — Capable  of  being  mag- 
netized. 

Magnetization.— The  act  of  imparting  or 
acquiring  magnetization. 

Magnetization  by    Double-Touch.  - 

A  magnetization  effected  by  placing  two 
magnets  with  their  opposite  poles  to- 
gether on  the  middle  of  the  bar  to  be 
magnetized,  moving  them  to  one  end  of 
the  bar,  then  moving  them  over  the  sur- 
face of  the  bar  to  the  other  end,  and 
continuing  these  to-and-fro  movements  a 
number  of  times,  observing  to  stop  in  the 
middle  of  the  bar,  and  when  the  mag- 
netizing magnets  are  moving  in  the  oppo- 
site direction  to  that  in  which  they  began 
to  move. 

Magnetization  by  Separate-Touch. — 
Magnetization  obtained  by  placing  two 
magnetizing  bars  with  their  opposite 
poles  at  the  middle  of  the  bar  to  be  mag- 
netized, drawing  them  away  from  each 
other  towards  its  ends,  returning  them 
through  tire  air  to  the  middle  of  the 
magnet,  and  repeating  this  a  number  of 
times. 

Magnetization  by  Touch. — The  produc- 
tion of  magnetic  poles  in  a  magnetizable 
substance  by  touching  it  with  a  magnet. 

Magnetization  Curves. — Curves  which 
graphically  represent  the  relation  of  a 
magnetizing  force  to  the  intensity  of 
magnetization  or  to  the  magnetic  flux. 

Magnetization  Cycle.— (1)  A  cycle  of 
magnetization.  (2)  A  succession  of  mag- 


843 


[Mag. 


netic   states    which    terminate    in   the 
original  state. 

Magnetize. — To  endow  with  the  property 
of  magnetism. 

Magnetized. — Endowed  with  the  property 
of  magnetism. 

Magnetizee. — A  word  proposed  to  desig- 
nate a  person  who  believes  he  is  placed 
under  the  power  of  animal  magnetism. 

Magnetizer. — (1)  One  who,  or  that  which, 
magnetises.  (2)  A  word  proposed  to  desig- 
nate a  person  who  claims  that  he  can 
place  another  under  the  power  of  his 
animal  magnetism. 

Magnetizing.  —  Endowing  a  body  with 
magnetic  qualities. 

Magnetizing  Ampere-Turns. — The  am- 
pere-turns of  a  magnetizing  coil. 

Magnetizing  Currents. — Currents  that 
are  employed  in  producing  magnetization. 

Magnetizing  Flux. — Flux  which  is  in- 
tended to  magnetize  a  body,  or  to  keep  it 
magnetized,  as  distinguished  from  mag- 
netic flux  which  performs  any  other 
functions. 

Magnetizing  Force,  —  (1)  The  vector 
space- rate  of  descent  of  magnetic  poten- 
tial. (2)  The  prime  flux-density  impressed 
upon  a  body,  and  which  may  induce 
magnetism  in  the  same.  (3)  The  force  at 
any  point  with  which  a  unit  magnetic 
pole  would  be  acted  on.  (4)  The  impressed 
flux-density  of  a  field  as  distinguished 
from  the  total  flux-density. 

Magnetizing  Helix.  —  A  magnetizing 
spiral  or  solenoid. 

Magnetizing  Spiral.  —  A  magnetizing 
helix  or  solenoid. 

Magnetizing  Turn. — A  single  turn  in  a 
magnetizing  coil. 

Magneto.  —  (1)  A  magneto-generator. 
(2)  A  small  magneto-electric  dynamo 
machine. 

Magneto-Alternator.  —  An  alternator 
whose  field  flux  is  produced  by  perma- 
nent magnets. 

Magneto-Blasting  Machine.  —  A  mag- 
neto-electric machine  employed  for  gen- 
erating the  currents  used  in  electric 
blasting. 

Magneto  Call-Bell. — A  call-bell  operated 
by  a  magneto-electric  machine. 

Magneto-Chemical  Cell.  —  A  cell,  the 
voltaic  couple  of  which  consists  of  two 
magnetized  steel  bars,  whose  north  and 
south  poles  are  respectively  immersed  in 
a  solution  of  oxalic  acid. 

Magnetod. — A  name  employed  by  Reich- 


enbach  for  the  assumed  force  or  principle 
of  animal  magnetism. 

Magneto-Dynamic  Force.  —  The  force 
exerted  between  magnets,  or  between 
magnets  and  electric  currents.  , 

Magneto-Dynamics.  —  That  branch  of 
dynamics  which  treats  of  the  influence  of 
magnet  poles  on  one  another. 

Magneto  -  Electric  Alternating  Ma- 
chine.— A  magneto-alternator. 

Magneto-Electric  Bell.— An  electric  bell 
whose  actuating  current  is  obtained  from 
a  magneto-electric  machine. 

Magneto-Electric  Brake.— (1)  A  device 
for  checking  the  swing  of  a  galvanometer 
consisting  of  means  for  sending  slight 
inverse  currents  through  the  coils  of  the 
galvanometer.  (2)  An  electro-magnetic 
brake. 

Magneto-Electric  Call-Bell.  —  A  call 
bell  operated  by  a  magneto-electric  ma- 
chine. 

Magneto-Electric  Dynamo.— A  dynamo- 
electric  machine  whose  field  magnets  are 
formed  of  permanent  magnets. 

Magneto-Electric  Faradic- Apparatus. 
A  small  magneto-electric  machine  em- 
ployed in  electro-therapeutics  for  produc- 
ing faradic  currents. 

Magneto-Electric  Force.— A  theoreti- 
cally-assumed mechanical  force  exerted 
between  a  magnetic  current  and  an  elec- 
tric field,  corresponding  to  the  electro- 
magnetic force  known  to  be  exerted  be- 
tween an  electric  current  and  a  magnetic 
field. 

Magneto-Electric  Generator. — A  mag- 
neto-generator. 

Magneto-Electric  Induction.  —  A  va- 
riety of  electro-dynamic  induction  in 
which  electric  currents  are  produced  by 
the  motion  of  pel-man  ent  magnets  past 
conductors,  or  of  conductors  past  perma- 
nent magnets. 

Magneto-Electric  Key. — A  telegraphic 
key  so  arranged  that  a  coil  of  wire  on  an 
armature  connected  with  a-  key  lever, 
through  the  movements  of  the  key  to- 
wards and  from  the  poles  of  a  permanent 
magnet,  produces  currents  that  are  sent 
into  the  line. 

Magneto-Electric  Machine. —  A  mag- 
.  neto-generator. 

Magneto-Electrical  Medical  Appara- 
tus.— A  small  magneto-alternator  em- 
ployed in  medical  electricity  for  the  pro- 
duction of  alternating  or  pulsating  cur- 
rents. 

Magneto-Electric  Multiplier.— An  early 
form  of  induction  coil  employed  by  Page. 


Mag.] 


844 


[Mai. 


Magneto-Electricity.  —  (1)  Electricity 
produced  by  the  motion  of  magnets  past 
conductors  or  of  conductors  past  magnets. 
(2)  Electricity  produced  by  magneto- 
electric  induction. 

Magneto-Generator. — A  dynamo-electric 
machine  whose  field  flux  is  obtained  from 
permanent  magnets. 

Magnetogram. — Any  automatic  record 
obtained  by  means  of  a  magnetic  instru- 
ment. 

Magnetograph. — A  permanent  record  ob- 
tained by  the  action  of  a  self-recording 
magnetometer. 

Magneto-Induction  Key.— A  magneto- 
electric  telegraph  transmitter  so  arranged 
that  the  movements  of  a  key  produce  the 
electric  currents  that  are  sent  into  the 
line. 

Magneto-Inductor. — An  inductor  con- 
sisting of  a  permanent  magnet  as  distin- 
guished from  an  inductor  consisting  of 
an  electro-magnet. 

Magneto-Inductive  Capacity. — A  term 
sometimes  employed  for  magnetic  per- 
meability. 

Magneto  Instrument.— (1)  A  name  for- 
merly applied  to  a  magneto  machine. 
(2)  In  telegraphy,  a  name  sometimes  em- 
ployed for  a  machine .  operating  or  oper- 
ated by  magnetically-induced  currents. 

Magnetology . — (1)  A  name  sometimes  ap- 
plied to  the  science  of  magnetism.  (Not 
in  general  use.)  (2)  That  branch  of 
science  which  treats  of  magnetism.  (Very 
seldom  used.) 

Magnetometer. — (1)  An  apparatus  for  the 
measurement  of  magnetic  force.  (2)  Any 
apparatus  for  measuring  the  elements  of 
the  earth's  magnetic  force. 

Magnetometric. — Of  or  pertaining  to  a 
magnetometer. 

Magnetometry. — That  branch  of  science 
which  treats  of  the  measurement  of  the 
strength  of  magnetic  fields. 

Magn eto-Motive.— Producing  magnetic 
effects. 

Magneto-Motive  Force. — (1)  The  force 
which  produces  magnetic  flux.  (2)  The 
force  that  moves  or  tends  to  move  mag- 
netic flux. 

Magneto-Motive  Intensity. — A  term 
sometimes  used  for  the  slope  of  magneto- 
motive force. 

Magneto-Motor. — (1)  A  term  formerly  ap- 
plied to  a  voltaic  battery  coupled  in  par- 
allel. (2)  A  motor  whose  field  is  pro- 
duced by  permanent  magnets. 

Magneto-Optic  Rotation.— A  rotation  of 


the  plane  of  polarization  of  a  beam  of 
plane  polarized  light  on  its  passage 
through  a  transparent  medium,  when 
placed  in  a  strong  magnetic  field  in  the 
direction  of  the  beam. 

Magnetophone. — A  species  of  magnetic 
siren  with  which  sounds  are  produced  in 
a  telephone  by  the  periodic  currents  pro- 
duced in  its  coils  by  the  rotation  of  a  per- 
forated metallic  disc  in  a  magnetic  field. 

Magneto-Pointer.— A  dial  of  a  printing 
telegraph. 

Magneto-Polar.  —  Possessing  magnetic 
polarity. 

Magneto-Receptive  Device.— A  device 

that  is  capable  of  being  energized  when 

placed  in  magnetic  flux. 
Magnetoscope. — Any  apparatus   for   the 

detection  of  the  presence  of  magnetism, 

but  not  for  measuring  it. 

Magneto-Signals. — Any  signals  operated 
by  a  magneto-electric  machine. 

Magneto-Static  Ammeter. — An  ammeter 
whose  magnet  is  acted  on  by  a  uniform 
field  of  force  with  two  coils,  while  at- 
tracted by  two  systems  of  powerful  per- 
manent magnets. 

Magneto-Static  Current-Meter.  —  A 
magneto-static  ammeter. 

Magneto-Static  Screening. — Screening 
from  the  inductive  effects  of  a  stationary 
magnetic  field. 

Magneto-Statics.  —  The  science  which 
treats  of  magnetic  forces  at  rest. 

Magneto-Tapper. — (1)  A  term  sometimes 
employed  for  a  magneto-key.  (2)  Aeon- 
tact  key  which  closes  the  circuit  of  a 
magneto. 

Magneto-Telephone    Transmitter. — A 

telephone  transmitter  formed  of  a  power- 
ful compound  magnet  provided  with  a 
coil  of  insulated  wire  supported  in  front 
of  one  of  its  poles,  and  an  iron  core  form- 
ing the  pole-piece  of  the  magnet. 

Magneto-Therapy.  —  Alleged  electro- 
therapeutic  effects  produced  by  the  ap- 
plication of  magnets  to  the  human  body. 

Magnet  Wire. — Insulated  wire  suitable 
for  winding  magnets  and  usually  cotton- 
covered. 

Magpie  Cable. — A  name  given  to  a  form 
of  telephone  cable  in  which  the  wires  or 
conductors  are  arranged  in  double  pairs. 

Main  Battery. — The  battery  employed  in 
telegraphic  systems  for  sending  the  signals 
over  the  main  line,  as  distinguished  from 
a  battery  employed  for  any  other  work. 

Main-Battery  Circuit. — ( 1 )  A  term  some- 
times used  for  line  circuit.  (2)  The  cir- 


Mai.] 


845 


[Man. 


cult  of  the  main  battery  in  any  conduct- 
ing system. 

Main-Circuit  Fuse. — A  safety  fuse  pro- 
vided for  the  protection  of  the  main  cir- 
cuit. 

Main-Circuit  Switch. — A  switch  inserted 
in  a  main  circuit. 

Main  Cut-Out. — Any  cut-out  placed  in 
the  circuit  of  a  main. 

Main  Feeder. — (1)  The  feeder  to  which 
the  standard  pressure-indicator  is  con- 
nected, and  whose  pressure  controls  the 
pressure  at  the  ends  of  all  the  other 
feeders.  (2)  A  standard  feeder.  (3)  A 
principal  feeder  supplying  a  group  of  sub- 
feeders. 

Main  Fuse. — A  main-circuit  fuse. 

Main- Line-Circuit  Switch.  —  A  main 
switch. 

Main-Line  Cut-Out. — A  main  cut-out. 

Main-Line  Relay. — A  relay  suitable  for 
use  in  connection  with  a  main  telegraphic 
line. 

Main-Line  Sounder. — A  sounder  suitable 
for  use  in  connection  with  a  main  tele- 
graphic line. 

Main  Switch.— (1)  A  switch  connected 
with  the  electric  mains,  (2)  A  principal 
switch  controlling  a  group  of  subsidiary 
switches.  (3)  A  main-line-circuit  switch. 

Main  Telegraphic-Circuit. — The  princi- 
pal or  line  telegraphic  circuit. 

Main  Telegraphic-Current. — The  cur- 
rent employed  on  a  main  telegraphic  line 
or  circuit. 

Main  Terminals  of  Machine. — (1)  The 
principal  terminals  of  a  machine.  (2)  The 
terminals  connected  with  the  external  cir- 
cuit of  a  machine. 

Main-to-Dynamo  Bonding. — A  phrase 
employed  for  a  method  of  bonding  the 
rails  in  an  electric  car  system,  in  which 
the  bonding  is  between  a  positive  water 
main,  or  buried  metallic  system,  and  the 
negative  terminal  of  the  dynamo. 

Main-to-Track  Bonding. — A  phrase  em- 
ployed for  a  method  of  bonding  of  the  rails 
in  an  electric  car  system  in  which  the 
bonding  is  between  a  positive  water  main 
and  a  negative  track. 

Main-Trunk  Telephone-Line.— (1)  A 
main  telephone  line  connecting  two  cities 
and  usually  erected  with  considerable 
care,  as  to  conducting  power,  insulation, 
and  freedom  from  electrical  disturbance, 
so  as  to  serve  as  a  general  link  of  com- 
munication either  for  communication  be- 
tween those  cities,  or  for  communication 
through  those  cities.  (2)  A  term  used  in 


contradistinction  to  a  local  telephone  line 
connecting  two  stations. 

Main  Tubes. — The  tubes  in  an  under- 
ground system,  provided  for  the  mains. 

Main  Voltmeter. — (1)  A  voltmeter  in  a 
central  station  connected  with  the  mains. 
(2)  A  principal  or  standard  voltmeter. 

Main  Wire.— (1)  Wire  used  in  or  intended 
for  electric  mains.  (2)  Wire  constituting 
part  of  an  electric  main.  (3)  The  prin- 
cipal electric  conductor  in  a  distribution 
or  conducting  system. 

Mains. — (1)  In  a  parallel  system  of  distri- 
bution the  parallel  conductors  carrying 
the  main  current,  and  to  which  translat- 
ing devices  are  connected.  (2)  In  a  sys- 
tem of  parallel  distribution,  the  principal 
conductors  which  extend  from  the  risers, 
or  service  wires,  along  the  corridors  or 
passages  along  the  floor  to  be  lighted. 

Mains  of  Electric  Railroads. —The 
mains  from  which  the  driving  current  is 
supplied  to  the  cars. 

Make. — To  complete  or  close  a  circuit. 

Make-and-Break. — The  operation  of  al- 
ternately completing  and  opening  a  cir> 
cuit. 

Make-Induced  Current. — (1)  The  cur 
rent  produced  by  self-induction  on  tin 
making  or  closing  of  a  circuit.  (2)  Thu 
current  produced  by  mutual  induction  in 
the  secondary  of  an  induction  coil  or 
transformer,  on  the  making  or  comple- 
tion of  the  circuit  of  the  primary. 

Making  Earth. — In  telegraphy,  ground- 
ing. 

Making  the  Primary. — Closing  the  cir- 
cuit of  the  primary. 

Making-Up  Batteries. — Joining  voltaic 
cells  in  series  or  in  parallel. 

Manganin.— A  high-resistivity  metal  of 
very  low  resistivity  temperature-coeffi- 
cient. 

Mangin  Projector. — A  special  form  of 
search-light  projector. 

Mangin  Reflector. — A  special  form  of 
dioptric  reflector  employed  in  connection 
with  the  Mangin  projector,  consisting  of 
a  circular  glass  reflector,  silvered  at  the 
back,  and  whose  inner  and  outer  or  front 
and  back  surfaces  are  both  spherical. 

Manganin  Resistance.  —  A  resistance 
made  of  manganin  wires,  strips,  or  sheets. 

Man-Hole  Compartment  of  Conduit. 
A  man-hole  provided  in  a  conduit  for 
affording  access  to  the  same. 

Man-Hole  of  Conduit. — An  opening  com- 
municating from  the  surface  of  the  road* 


Man.] 


846 


Mas. 


bed  with  an  underground  conduit,  of  suf- 
ficient size  to  admit  a  man. 

Manometer. — An  apparatus  for  measur- 
ing the  tension  or  pressure  of  gases. 

Manometric. — Of  or  pertaining  to  a  mano- 
meter. 

Man-Power. — A  unit  of  power  equal  to 
the  one-tenth  of  a  horse-power,  or  about 
75  watts. 

Manual  Alarm. — A  fire  alarm  operated 
by  hand-power. 

Manual  Igniting  Device. — (1)  A  pen- 
dent electric  gas-lighting  burner.  (2)  An 
electric  gas  igniter  operated  by  hand. 
(3)  A  manual  mine  exploder. 

Manual  Repeater. — A  telegraphic  re- 
peater which  is  controlled  or  operated  by 
hand,  as  distinguished  from  an  automatic 
repeater. 

Manual  Telegraphic  Transmission. — 
Transmission  by  hand,  as  distinguished 
from  automatic  or  machine  transmission. 

Manual  Translation. — The  translation, 
especially  in  submarine  telegraphy,  of  a 
message  from  one  circuit  to  another,  by 
an  operator  who  transmits  to  the  second 
circuit,  direct  from  signals  received  on  the 
first,  without  writing  down  or  transcrib- 
ing the  messages. 

Marconi  Rays. — Electro-magnetic  waves 
employed  in  the  Marconi  system  of  wire- 
less telegraphy. 

Marconi  "Waves.  —  Electromagnetic 
waves  employed  in  the  Marconi  system 
of  wireless  telegraphy. 

Margin  of  Relay  Adjustment.— The 
range  of  alteration  permissible  in  the  ad- 
justment of  the  armature  of  a  relay  with- 
out interfering  with  the  working  of  the 
instrument. 

Marine  Galvanometer. — (1)  A  form  of 
Thomson  reflecting  galvanometer,  heavily 
encased  in  iron,  devised  for  use  on  steam- 
ships where  the  motion  of  magnetized 
masses  of  iron  would  seriously  disturb 
the  reading  of  ordinary  instruments. 
(2)  Any  form  of  galvanometer  suitable 
for  use  on  board  ship. 

Marine  Junction-Box. — A  water-tight 
junction  box  for  effecting  junctions  be- 
tween mains,  or  mains  and  branches,  on 
board  ship. 

Marine  Lamp-Socket. — A  form  of  spring 
socket  for  flexibly  supporting  an  incan- 
descent lamp  on  board  ship. 

Marine  Search-Light  or  Lamp. — An 
electric  search-light  suitable  for  use  at 
sea. 

Marine  Switch. — A  water-tight  switch  in 


an  incandescent  lamp,  fixture,  or  circuit, 
on  board  ship. 

Marine  Voltmeter. — A  form  of  voltmeter 
suitable  for  use  on  a  ship. 

Mariner's  Compass.— (1)  A  compass 
mounted  in  such  a  manner  as  to  be  service- 
able on  board  ship.  (2)  A  name  often  ap- 

•  plied  to  an  azimuth  compass. 

Mark  Buoy. — In  submarine  cable  work,  a 
buoy  moored  to  the  bottom  of  the  sea  by  a 
mushroom  anchor,  and  placed  to  mark 
a  certain  position,  ,as  distinguished  from 
a  cable  buoy  which  is  moored  to  the  end 
of  a  cable. 

Marked  End  of  Magnet. — A  name  for- 
merly applied  to  the  north-seeking  pole  of 
a  magnet. 

Marked  Pole  of  Magnet.— A  term  some- 
times applied  to  the  north-seeking  pole 
of  a  magnet. 

Markers. — Colored  flags  or  signal  lights, 
usually  green,  displayed  in  systems  of 
block  railroad-signalling,  in  order  to  avoid 
accident  from  the  train  breaking  in  two. 

Marking  Current. — The  current  em- 
ployed in  automatic  telegraphy  to  produce 
the  dots  and  dashes  of  the  Morse  alphabet, 
as  distinguished  from  the  spacing  current 
or  that  employed  to  leave  spaces  between 
such  characters. 

Marking  Disc. — In  a  Morse  ink-writer, 
the  rotating  inking  disc,  which  marks  the- 
signals. 

Mass. — The  quantity  of  matter  contained 
in  a  body. 

Mass  Attraction. — The  mutual  attraction 
exerted  between  masses  of  matter. 

Mass  Specific-Resistance.— (1)  Specific 
resistance  referred  to  unit  mass  instead  of 
unit  volume.  (2)  The  resistance  taken  be- 
tween the  ends  of  a  cylindrical  wire  of 
definite  length,  usually  one  metre,  con- 
taining a  mass,  usually  a  gramme.  (3) 
The  resistance  of  a  metre-gramme. 

Massage. — The  treatment  of  the  body  by 
kneading,  rubbing  or  friction,  for  the 
purpose  of  effecting  changes  in  its  general 
nutrition. 

Mass,  Electric.  —A  mathematical  concep- 
tion for  quantities  of  electricity  which  are 
so  distributed  as  to  produce  electrostatic 
forces  in  conformity  with  the  laws  of 
gravitational  forces,  and,  therefore,  cor- 
responding to  material  masses. 

Mass  Specific  Resistance. — (1)  The  re- 
sistance of  a  known  mass  of  a  material ; 
namely,  one  gramme,  in  the  form  of  a 
circular  sectioned  wire  one  metre  in 
length.  (2)  The  resistance  of  a  foot-grain. 


Mas.] 


847 


[Mea. 


Mast-Arm  for  Arc-Lamp. — A  movable 
arm  or  bracket  provided  at  the  top  of  a 
pole  for  the  support  of  a  lamp  arranged 
for  the  ready  lowering  of  the  lamp  for 
re-carboning. 

Mast  Compass. — A  compass  secured  to  the 
mast  of  a  ship,  at  an  elevation  sufficient 
to  considerably  reduce  the  component  of 
local  attraction  from  the  ship's  magnetiza- 
tion. 

Master  Clock. — A  central  or  controlling 
clock  employed  in  a  system  of  electric 
time  distribution,  from  which  time  is 
transmitted  to  the  secondary  clocks  in  its 
circuit. 

Mate  of  Wire  in  Twisted  Pair.— (1)  One 
of  the  wires  of  a  twisted  pair.  (2)  The 
conjugate  member  of  a  wire  in  a  twisted 
pair. 

Matt. — (1)  A  word  employed  in  electro- 
plating to  designate  the  appearance  pre- 
sented by  an  electro-plating  of  silver  in 
which  the  deposit  is  interlaced  and  closely 
massed  together.  (2)  A  fused  mass  of  im- 
pure copper  employed  as  the  raw  material 
in  electrolytic  refinement. 

Matter. — Anything  which  occupies  space 
in  three  dimensions  and  prevents  other 
matter  from  simultaneously  occupying 
the  same  space. 

Matter,  Electric. — A  term  formerly  ap- 
plied to  the  matter  which  was  believed  to 
constitute  the  effluvia  formerly  assumed 
to  pass  off  from  an  electrified  body. 

Matteucci's  Muscular  Pile.— A  pile 
formed  by  arranging  a  series  of  muscles 
so  that  their  exterior  and  interior  surfaces 
are  alternately  connected. 

Matthiessen's  Metre-Gramme-Stand- 
ard..— 0)  A  standard  of  resistivity  or  con- 
ductivity in  metallic  wires.  (2)  The  re- 
sistance of  a  wire  one  metre  in  length, 
and  of  such  a  diameter  as  would  cause  the 
wire  to  weigh  one  gramme.  (3)  Accord- 
ing to  the  American  Institute  of  Electrical 
Engineers  Committee,  the  standard  estab- 
lished by  Matthiessen  for  a  metre-gramme 
of  soft  copper,  0.1417  international  ohm  at 
0°  C.,  or  0.1501  international  ohm  at  15°  C. 

Matthiessen's  Mile-S  t  a  n  d  a  r  d. — A 
standard  of  resistance  equal  to  the  resist- 
ance of  one  mile  of  pure  copper  wire  one- 
sixteenth  of  an  inch  in  diameter,  at  15.5° 
Cent.  (No  longer  used.) 

Matthiessen's  Unit  of  Resistance.— 
Matthiessen's  mile-standard. 

Maturing  of  Call.— In  a  system  of  tele- 
phony where  a  number  of  calls  have  been 
received  at  an  exchange  and  recorded  for 


execution  in  order,  the  time  at  which  any 
particular  call  is  reached  in  its  order. 

Maximum. — (1)  Possessing  the  greatest 
value.  (2)  In  a  continuous  succession  of 
values,  a  value  greater  than  that  which 
precedes  or  follows  it. 

Maximum  Activity  of  Motor.— <1)  The 
activity  of  a  motor  when  working  at  its 
greatest  possible  rate,  or  the  activity  when 
the  useful  work  done  is  equal  to  half  the 
energy  expended.  (2)  The  full-load  ac- 
tivity of  a  motor.  (3)  The  maximum 
available  activity  of  a  motor. 

Maximum  Efficiency  of  Transformer. 

The  highest  efficiency  obtainable  from  a 
transformer. 

Maximum    Horizontal    Intensity   of 
Light. — The  greatest  intensity  of  light 
.  emitted  by  a  source  in  a  horizontal  direc- 
tion. 

Maximum  Magnetization. — A  term 
sometimes  used  for  magnetic  saturation. 

Maximum  Negative-Elongation.— The 
position  of  a  vibrating  body  when  it  is  at 
the  extremity  of  its  path  on  the  negative 
side. 

Maximum    Positive-Elongation. — The 

position  of  a  vibrating  body  when  it  is  at 
the  extremity  of  its  path  on  the  positive 
side. 

Maximum  Starting-Current  of  Motor. 
The  highest  value  the  starting  current 
of  a  motor  attains. 

Maximum  Traction  Truck. — A  form  of 
double  car-truck. 

Maxwell's  Electro-Magnetic  Theory 
of  Light. — (1)  A  hypothesis  for  the  cause 
of  light  based  on  the  relations  existing 
between  the  phenomena  of  light  and 
those  of  electro-magnetism.  (2)  A  hy- 
pothesis that  regards  light  as  a  purely 
electro-magnetic  phenomenon. 

Mclntire's  Parallel-Sleeve-Telegraph- 
ic Joint. — A  joint  for  telegraphic  or  other 
wires,  in  which  the  ends  to  be  joined  are 
slipped  into  sleeves  or  parallel  tubes,  which 
are  afterwards  filled  with  solder. 

Mean. — (1)  Average.  (2)  A  quantity  hav- 
ing an  intermediate  value  between  others. 

Mean  Annual  Station-Current. — The 
average  current  delivered  by  a  station 
throughout  the  year. 

Mean  Current.— (1)  The  time  average  of 
a  current  strength.  (2)  In  an  alternating- 
current  circuit,  the  time  average  of  a  cur- 
rent strength  without  regard  to  sign  or 
direction. 

Mean  Electromotive  Force. — (1)  The 
average  electromotive  force.  (2)  In  an 


Mea.] 


848 


[Med. 


alternating-current  circuit,  the  time  aver- 
age of  the  E.  M.  F.  without  regard  to  sign 
or  direction. 

Mean  Horizontal  Intensity  of  Light. — 
The  average  intensity  of  light  in  a  hori- 
zontal plane  containing  the  source. 

Mean  Illumination. — The  average  illu- 
mination. 

Mean  Load-Current. — The  average  load- 
current. 

Mean  Spherical  Candle-Power.— (1)  An 
average  candle-power  numerically  equal 
to  the  total  quantity  of  light  emitted  by 
a  point  source  divided  by  12.566.  (2)  The 
average  candle-power  of  a  source  taken 
at  all  points  of  the  surface  of  a  sphere. 

Mean  Spherical  Intensity  of  Light. — 
The  mean  spherical  candle-power. 

Mean  Quadratic  Current. — A  term  pro- 
posed for  the  effective  strength  of  an 
alternating  current. 

Mean  Thermal  Capacity  for  Heat. — The 

average  capacity  for  heat. 
Measurement  of  Resistance. — The  de- 
termination of  the  value  of  an  electric 
resistance  by  any  suitable  means. 

Measurements,  Electric. — Determina- 
tions of  the  values  of  the  electromotive 
force,  resistance,  current,  capacity, 
energy,  etc.,  in  any  electric  circuit  or 
instrument. 

Measuring  Current. — (1)  The  current  by 
which  an  electrical  measurement  is  made. 
(2)  A  testing  current. 

Mechanical  Air  Pump. — A  mechanical 
device  for  exhausting  or  removing  the  air 
from  any  vessel. 

Mechanical  Characteristic  of  Motor. — 
A  term  sometimes  employed  for  the  curve 
of  the  torque  and  speed  of  a  motor  as  co- 
ordinates. 

Mechanical  Circuit-Closer.  —  (1)  Any 
circuit-closer  not  operated  electrically. 
(2)  An  automatic  circuit-closer  not  oper- 
ated electrically. 

Mechanical  Closer. — A  mechanical  cir- 
cuit-closer. 

Mechanical  Cut-Out — (1)  Any  cut-out 
not  operated  electrically.  (2)  An  auto- 
matic cut-out  not  operated  electrically. 

Mechanical  Depolarizer  of  Voltaic 
Cell. — A  method  for  removing  the  gas 
collected  on  the  negative  plate  of  a  voltaic 
cell  by  the  mechanical  agitation  of  the 
liquid. 

Mechanical  Equivalent  of  Heat. — The 

amount  of  mechanical  energy  converted 
into  heat  that  would  be  required  to  raise 
the  temperature  of  a  unit  mass  of  water 


one  degree  of  the  thermometric  scale. 

(2)  The  quantity  of  energy  mechanically 

equivalent  to  one  heat  unit. 
Mechanical  Equivalent  of  Light.— The 

quantity  of  energy  contained  in  one  unit 

of  light. 
Mechanical   Frictions   of  Dynamo. — 

The  journal,  brush  and  air  frictions  of  a 

dynamo. 

Mechanical  Magnet  Lightning  -  Ar- 
rester.— A  mechanical  device  operated 
by  an  electro-magnet  for  the  extinguish- 
ment of  the  arc  established  by  a  light- 
ning flash. 

Mechanical  Mine. — A  submarine  mine 
that  is  fired  when  struck  by  a  passing 
ship  through  the  action  of  some  contriv- 
ance contained  within  the  torpedo  itself, 
and  having  no  connection  whatever  with 
the  shore. 

Mechanical  Recording  Meter. — A  me- 
chanically operated  recording  meter. 

Mechanical  Seal. — A  mechanically  made 
seal  of  the  chamber  of  an  incandescent 
lamp. 

Mechanical  Telegraph. — Any  form  of 
telegraphy  by  which  communication  is 
established  by  mechanical  means. 

Mechanical  Telegraphic  Interrupter. 
A  form  of  mechanical  telegraphic 
sounder  for  learners,  where  no  battery  is 
required. 

Mechanical  Telephone.— A  wire  or 
string  telephone,  operated  by  longitudinal 
vibrations  transmitted  through  a  wire  or 
string. 

Mechanical  Throwback  -  Indicator. — 
An  annunciator  drop  provided  with  a 
drop  that  is  mechanically  replaced. 

Mechanical  Torpedo.— A  torpedo  that 
is  exploded  by  percussion  against  any 
obstacle. 

Mechanical  Vibrator. — (1)  A  mechani- 
cally operated  contact-breaker.  (2)  A 
mechanical  means  for  obtaining  the  ejec- 
tion of  the  ink  from  the  siphon  in  a  siphon 
recorder. 

Mechanical  Work. — (1)  The  product  of  a 
force  by  the  distance  through  which  the 
force  acts.  (2)  The  expenditure  of  energy 
required  for  any  change  in  the  configura- 
tion of  a  material  system. 

Medical  Battery. — A  medical  induction 
coil. 

Medical  Electrician. — An  electro-thera- 
pist. 

Medical  Induction-Coil.— An  induction 

coil  used  for  medical  purposes. 
Medical  Magneto-Electric  Apparatus. 


Meg.] 


849 


[Met. 


A  terra  applied  to  small  magneto-electric 
machines  employed  in  electro-therapeutics 
for  the  production  of  uncommuted  or  far- 
adic  currents. 

Meg  or  Mega. — A  prefix  for  one  million 
times. 

Mega-Dyne. — One  million  dynes. 

Mega- Joule. — One  million  joules. 

Mega-Lines. — One  million  lines. 

Megalascope,  Electric. — An  apparatus 
for  the  medical  exploration  of  the  cavi- 
ties of  the  body. 

Mega- Volt. — One  million  volts. 

Mega- Weber. — One  million  webers. 

Megerg. — One  million  ergs. 

Megohm. — One  million  ohms. 

Megohm  Box. — A  resistance  box  contain- 
ing a  resistance  or  resistances  equal  to  a 
megohm. 

Megohm  Galvanometer. — A  galvano- 
meter which  gives  unit  deflection  through 
a  resistance  of  one  megohm  in  circuit 
with  one  volt. 

Megohm  Mile. — A  unit  of  linear  insula- 
tion resistance  equal  in  value  to  the  pro- 
duct of  a  megohm  by  a  mile,  and  such  as 
is  possessed  by  a  mile  of  wire,  the  insula- 
tion of  which  is  one  megohm. 

Melting  Points  of  Metals. — Tempera- 
tures at  which  metals  fuse. 

Membrane  Diffusion. — Osmose. 

Membrane  Telephone-Receiver. — An 
early  form  of  telephone  receiver  whose 
diaphragm  was  formed  of  a  sheet  of  gold- 
beater's skin. 

Mercurial  Air-Pump.— (1)  A  device  for 
obtaining  a  high  vacuum  by  the  use  of 
mercury.  (2)  The  Geissler  or  Sprengel 
mercury  pumps. 

Mercurial  Connection. — A  form  of  read- 
ily adjustable  connection  obtained  by 
providing  the  poles  of  one  piece  of  appa- 
ratus with  cups  or  cavities  filled  with 
mercury,  in  which  the  terminals  of  anoth- 
er piece  of  apparatus  are  dipped,  in  order 
readily  to  place  them  in  circuit  with  each 
other. 

Mercurial  Contact. — An  electric  contact 
effected  through  the  medium  of  mercury. 

Mercurial  Phosphorescence. — A  term 
formerly  employed  for  the  light  produced 
by  the  motion  of  a  column  of  mercury  in 
an  exhausted  tube. 

Mercurial  Temperature  -  Alarm. — An 
instrument  for  automatically  telegraph- 
ing an  alarm  by  means  of  a  mercurial 
contact,  on  a  pre-determined  change  of 
temperature. 

,54 


Mercurial  Thermostat. — A  thermostat 
operating  by  the  expansion  of  a  mercury 
column. 

Mercury  Break. — A  form  of  circuit 
breaker  operated  by  the  removal  of  a  con- 
ductor from  a  mercurial  surface. 

Mercurial  Commutation. — A  change  in 
the  direction  of  a  current  obtained  by 
means  of  a  mercurial  connection. 

Mercury  Cup. — A  cup  partly  filled  with 
mercury  employed  as  a  mercurial  contact. 

Mercury  Gauge. — A  vacuum  or  pressure 
gauge  whose  indications  are  dependent 
on  the  height  of  a  mercury  column. 

Mercury  Piezometer. — An  instrument 
employed  in  cable  work  for  measuring 
the  depth  of  the  ocean,  by  recording  the 
pressure  at  the  lowest .  point  reached  by 
the  sounding  lead,  and  used  as  a  check 
upon  the  length  of  sounding  line. 

Mercury  Switchboard. — A  switchboard 
in  which  connections  are  effected  by  mer- 
curial contacts. 

Mercury  Tube.— (1)  A  sealed  glass  tube 
containing  mercury  arranged  to  emit 
fluorescent  light  when  agitated.  (2)  A 
resistance  formed  of  a  thread  of  mercury 
contained  in  a  tube. 

Meridional. — Of  or  pertaining  to  a  meri- 
dian. 

Mesh  Grouping  of  Polyphase  Circuit. 
A  triangular  or  delta-connection  of  three- 
phase  coils  as  distinguished  from  a  star 
connection. 

Message  Wire. — A  line  or  wire  employed 
in  block  systems  for  railroads  extending 
along  the  road  and  used  for  local  tele- 
graphic business. 

Messenger  Call-Box. — A  district  call- 
box. 

Messenger  Rope. — (1)  In  cable- work  a 
rope  drive  for  operating  a  drum  or  winch 
at  a  distance.  (2)  A  rope  supporting 
guide  sheaves. 

Messenger  Strand. — A  strand  in  a  mes- 
senger wire. 

Messenger  Wire  of  Aerial  Cable.— The 
supporting  wire  or  rope  from  which  the 
cable  clips  employed  in  the  suspension  of 
an  aerial  cable  are  supported. 

Metal-Cased  Blake  Transmitter.— A 
form  of  telephone  transmitter  provided 
with  a  metallic  covering. 

Metallic. — Of  or  pertaining  to  a  metal. 

Metallic  Arc. — An  arc  formed  between 
metallic  electrodes. 

Metallic  Circuit. — A  circuit  which  is 
metallic  throughout,  in  contradistinction 
to  an  earth-return  circuit. 


Met.] 


850 


[Met. 


Metallic-Circuit  Plug.— In  a  telephone 
switchboard,  a  plug  which  makes  contact 
both  at  its  tip  and  at  its  sleeve,  so  as  to 
close  a  double  or  metallic  circuit  con- 
nected therewith  by  a  twin  cord. 

Metallic  Coating. — An  electrolytically 
deposited  coating  of  metal. 

Metallic  Connection. — Connection  by 
means  of  a  metallic  conductor. 

Metallic  Conducting  Joint. — A  joint  in 
a  conductor  in  which  a  continuity  of  con- 
ducting power  is  secured. 

Metallic  Conduction. — The  conduction 
of  electricity  through  a  metal,  in  contra- 
distinction to  its  conduction  through  an 
electrolyte. 

Metallic  Conductor. — A  conductor 
formed  of  a  metal. 

Metallic  Contact. — (1)  A  contact  of  a 
metallic  conductor  obtained  by  bringing 
it  into  firm  connection  with  another 
metallic  conductor.  (2)  Contact  between 
metal  and  metal. 

]V  Metallic  Contact  of  Cable.— A  complete 
"cntact  between  the  copper  conductor  of  a 
s  marine  cable  and  its  metallic  sheath. 

Metallic  Cross. — A  fault  due  to  the  actual 
contact  between  two  or  more  wires  or 
conductors,  so  that  the  current  from  one 
line  passes  to  another. 

Metallic  Electric  Conduction. — (1)  A 
conduction  of  electric  energy  by  means 
GJ.  metallic  substances.  (2)  Metallic  con- 
duction. 

Metallic  Electrodes. — Variously  shaped 
pieces  of  metal  employed  for  electro- 
therapeutic  electrodes. 

Metallic  Electrolysis.— A  form  of  cata- 
phoretic  medication  in  which  a  metallic 
electrode,  connected  to  the  positive  pole 
of  a  continuous-current  source,  is 
brought  into  contact  with  the  part  to  be 
treated,  while  the  negative  pole  is  applied 
to  some  other  part  of  the  body,  and  the 
metallic  salt  formed  by  electrolysis  at  the 
anode  is  cataphoretically  driven  into  the 
tissues  beneath  the  electrode. 

Metallic  Filament. — A  metallic  wire  em- 
ployed as  a  filament  of  an  incandescent 
lamp. 

Metallic  Reluctivity. — (1)  The  reluc- 
tivity of  a  metallic  substance.  (2)  In  a 
magnetic  substance  the  reluctivity  of  the 
substance  as  considered  independently  of 
the  reluctivity  of  the  ether  in  its  mass. 

Metallic  Resistance. — A  term  some- 
times applied  to  the  resistance  of  wires 
or  conductors,  in  contradistinction  to 
the  resistance  of  insulating  materials. 


Metallic  Resistivity.— The  resistivity  of 
a  metallic  substance. 

Metallic  Solution.— A  solution  of  a 
metallic  salt. 

Metallization. — Rendering  a  non-conduct- 
ing surface  electrically  conducting  by 
covering  it  with  a  metallic  coating  so  as 
to  enable  it  to  be  readily  electro-plated. 

Metallizing.— Subjecting  to  the  process  of 
metallization. 

Metallo-Chromes.— (1)  A  name  some- 
times given  to  Nobili's  rings.  (2)  Pris- 
matic colors  which  appear  when  a  salt  of 
lead,  such  as  an  oxide,  is  electrolyzed 
under  certain  circumstances. 

Metallurgy.— That  branch  of  science 
which  treats  of  the  reduction  or  treat- 
ment of  metallic  ores  or  metals. 

Metamerism. — (1)  A  variety  of  isomerism. 
(2)  The  quality  possessed  by  some  chem- 
ical substances,  differing  in  their  proper- 
ties, although  similar  in  their  quantita-. 
tive  composition,  owing  to  a  difference  of 
molecular  construction  or  arrangement  of 
atoms  in  the  molecule.  (3)  A  term  used 
in  distinction  to  polymerism. 

Meteorites.  —  Fragmentary  eolids  that 
when  attracted  to  the  earth  become  in- 
candescent on  their  passage  through  its 
atmosphere. 

Meteorograph,  Electric. — An  appa- 
ratus for  automatically  registering  by 
electricity  various  meteorological  values 
such  as  the  indications  of  a  barometer  or 
thermometer,  the  direction  and  velocity 
of  the  wind,  the  value  of  the  rain-fall, 
etc. 

Meteorology.— That  branch  of  physics 
which  treats  of  the  phenomena  of  the 
atmosphere. 

Meteorology,  Electric. — That  branch 
of  physics  which  treats  of  the  electric 
phenomena  of  the  atmosphere. 

Meter,  Electric. — Any  apparatus  for  meas- 
uring commercially  the  quantity  of  elec- 
tricity that  passes  in  a  given  time  through 
a  consumption  circuit. 

Meter-Motor. — (1)  A  small  motor  em- 
ployed in  operating  an  electric  meter. 
(2)  A  meter  comprising  a  small  motor. 

Meter  Sealing  Tool. — A  tool  for  stamping 
a  leaden  seal  which  prevents  the  unin- 
dicated  opening  of  a  meter  by  an  un- 
authorized person. 

Method  of  Recoil.— A  method  of  measur- 
ing a  discharge  through  a  ballistic  gal- 
vanometer by  reversing  the  direction  of 
its  swing. 

Method  of  Slow  Discharge. — An  insu« 


Met.] 


851 


[Mic, 


lation  test  for  a  telegraphic  line,  based  on 
the  rate  at  which  a  charge  leaks  out 
when  the  conductor  is  left  insulated. 

Methven  Carburetter. — A  device  employ- 
ed in  connection  with  a  Methven  screen, 
consisting  of  troughs  of  fine  wire  gauze 
filled  with  gasoline,  so  that  the  gas  pas- 
sing through  becomes  charged  with  the 
vapor. 

Methven' s  Screen. — A  vertical  rectangu- 
lar metallic  screen  used  in  connection  with 
a  standard  Argand  burner  as  a  photomet- 
ric standard. 

Metre. — A  unit  of  length  equal,  approxi- 
mately, to  one  ten-millionth  part  of  a 
quadrant  of  a  meridian  of  the  earth  taken 
through  Paris  ;  or,  approximately,  to 
39.37  inches, 

Metre-Bridge. — A  slide  form  of  Wheat- 
stone's  bridge  in  which  the  slide  wire  is 
one  metre  in  length. 

Metre-Candle. — (1)  The  illumination  pro- 
duced by  a  standard  candle  at  the  distance 
of  one  metre.  (2)  A  unit  of  illumination. 

Metre-Gramme. — (1)  A  unit  of  resistance 
equal  to  that  of  the  resistance  of  a  wire 
one  metre  in  length  weighing  one 
gramme.  (2)  A  standard  of  comparison 
of  resistivity  or  conductivity.  (3)  Mat- 
thiessen's  metre-gramme  standard  of 
copper  wire,  which  for  soft  copper  wire, 
according  to  the  committee  of  the  Ameri- 
can Institute  of  Electrical  Engineers,  is 
0.1501  International  ohm  at  15°  C. 

Metre-Millimetre. — A  resistance  stan- 
dard, consisting  of  a  length  of  wire  or 
other  conductor,  one  metre  long  and 
having  a  diameter  of  one  millimetre. 

Metric  Factors. — The  factors  employed 
for  the  conversion  of  the  metric  system 
units  into  those  of  other  systems. 

Metric  Horse-Power. — A  unit  of  power 
in  which  the  rate-of -doing-work  is  equal 
to  75  kilogramme-metres  per  second. 

Metric  System  of  Weights  and  Meas- 
ures.— A  system  of  weights  and  meas- 
ures based  on  the  metre  and  the 
gramme. 

Mho. — (1)  The  practical  unit  of  conduct- 
ance. (2)  Such  a  conductance  as  is  equal 
to  the  reciprocal  of  one  ohm.  (3)  A  unit 
of  electric  conductance  of  the  value  of 
10-9  absolute  units. 

Mho-Box. — A  conductance  box,  or  box 
containing  adjustable  conductance, 
graduated  in  mhos. 

Mhometer. — An  insti-ument  for  measur- 
ing the  value  of  a  conductance  in  mhos. 

Mica. — (1)  A  refractory,  mineral  substance 
employed  as  an  insulator.  (2)  A  double 


ilicate    of    alumina  or    magnesia    and 
potash  or  soda. 

Micanite. — A  variety  of  insulating 
material  made  from  and  built  up  of  small 
mica  sheets  bound  together  by  some  in- 
sulating cement. 

Micro. — A  prefix  for  the  one-millionth. 

Micro- Ampere. — The  millionth  of  an  am- 
pere. 

Micro-Coulomb.  —  The  millionth  of  a 
coulomb. 

Micro-Farad. — The  millionth  of  a  farad. 

Micro-Gilb. —  A  contraction  for  micro- 
gilbert. 

Micro-Gilbert. — The  millionth  of  a  gilbert. 

Micro  Glow-Lamp. — A  miniature  incan- 
descent lamp. 

Micro-Graphophone. — A  modification  of 
the  phonograph,  in  which  a  number  of 
separate  non-metallic  diaphragms  are 
caused  to  act  on  a  single  diaphragm,  for 
the  purpose  of  obtaining  stronger  vibra- 
tions of  the  same. 

Micrometer  Caliper. — A  micrometer  wire 
gauge. 

Micrometer  Eye-Piece. — An  eye-piece  of 
a  telescope,  microscope  or  other  optical 
apparatus  provided  with  a  micrometer. 

Micrometer  Microscope. — A  microscope 
provided  with  a  micrometer  eyepiece. 

Micrometer  Wire-Gauge. — A  sensitive 
form  of  wire  gauge,  usually  constructed 
with  a  fine  thread  screw,  having  a  gradu- 
ated head  for  close  measurements  of  wire 
diameters. 

Micron. — A  unit  of  length  equal  to  the 
millionth  part  of  a  meter. 

Microhm. — The  millionth  of  an  ohm. 

Microphone. — A  form  .of  contact  tele- 
phone-transmitter employed  in  connec- 
tion with  a  telephone  for  rendering  faint 
or  distant  sounds  distinctly  audible. 

Microphone  Induction-Coil.  —  An  in- 
duction coil  employed  in  connection  with 
a  mici'ophonic  telephone  transmitter. 

Microphone  Relay. — A  device  for  auto- 
matically repeating  a  telephonic  message 
over  another  wire. 

Microphonic.  —  Of  or  pertaining  to  the 
microphone.- 

Microphonic  Contact. — A  loose  contact 
capable  of  being  employed  for  a  telephone 
transmitter. 

Microscope. — An  optical  instrument  for 
the  examination  of  objects  too  minute 
to  be  seen  by  the  unaided  eye. 

Microscopic. — (1)  Of  or  pertaining  to  the 


me.] 


852 


[Mix. 


microscope.     (2)  Of  very  minute  dimen- 
sions. 

Microscopy. — The  art  of  microscopic  ex- 
amination. 

Micro-Seismograph. — An  electric  appa- 
ratus for  graphically  recording  the  direc- 
tion and  intensity  of  faint  earthquake 
shocks  or  earth  tremors. 

Micro  -  Tasimeter.  —  An  apparatus  in- 
vented by  Edison  for  measuring  minute 
differences  of  temperature,  or  of  moisture, 
by  the  resulting  differences  of  pressure 
upon  a  carbon  button. 

Micro-Telephone.  —  (1)  A  convenient 
form  of  writing  table-set  telephone  used 
by  some  exchange  operators  in  quiet  ex- 
changes, or  in  busy  exchanges,  at  night. 
(2)  A  form  of  combined  transmitter  and 
receiver.  (3)  A  small  semi-portable  tele- 
phone set. 

Micro-Volt. — The  one-millionth  of  a  volt. 

Migration  of  Ions. — A  term  employed  to 
express  the  movement  of  the  ions  in  an 
electrolyte  undergoing  electrolysis. 

Migration  Values  of  Ions. — The  veloci- 
ties of  the  ions. 

Mil. — A  unit  of  length  used  in  measuring 
the  diameter  of  wires  equal  to  the  one- 
thousandth  of  an  inch. 

Milammeter. — A  milli-ammeter. 

Mild  Steel. — A  term  employed  for  soft 
steel. 

Mil-Foot. — (1)  A  resistance  standard  con- 
sisting of  a  foot  of  wire,  or  other  con- 
ducting material,  one  mil  in  diameter. 
(2)  A  standard  of  comparison  of  resistiv- 
ity or  conductivity  of  wires. 

Milli. — A  prefix  for  the  one-thousandth 
part. 

Milli- Ammeter. — A  milli-ampere  meter. 

Milli-Ampere. — The  thousandth  of  an 
ampere. 

Milli-Ampere  Meter.— An  ampere  meter 
graduated  to  read  in  milli-amperes. 

Milli-Calorie. — (1)  The  thousandth  of  a 

calorie.    (2)  The  small  calorie. 
Milli-Oersted. — The   thousandth  of   an 

oersted. 

Milli-Volt.— The  thousandth  of  a  volt. 
Mimosa   Sensitiva. — A    sensitive   plant 

whose  leaves  fold  or  shut  up,  either  when 

touched,  or  when  traversed  by  electric 

currents. 
Mine    Explorer,    Electric.  —  A   small 

magneto-electric  generator  employed  in 

the  direct  firing  of  blasts. 
Miniature    Incandescent     Lamp. —  A 

very  small  incandescent  lamp,  suitable  for 


decorative,  microscopic,  dental  or  surgical 
purposes. 

Mining,  Electric.— The  application  of 
electricity  to  mining. 

Milling  Locomotive,  Electric.— An  elec- 
tric locomotive  employed  in  mining  opera- 
tions. 

Minotto's  Voltaic  Cell.— A  form  of  Dan- 
iells'  cell  employing  a  flat  copper  plate  at 
the  bottom  of  the  cell  beneath  a  mass  of 
copper  sulphate  crystals,  the  cell  being 
then  filled  with  wet  sand,  or  wet  sawdust, 
on  which  rests  the  zinc  plate. 

Minus  Charge. — A  negative  charge. 

Miophone. — An  apparatus,  based  on  the 
use  of  the  microphone,  employed  for  the 
medical  examination  of  the  muscles. 

Mirror  Galvanometer. — A  galvanometer 
whose  readings  are  obtained  by  the  move- 
ments of  a  spot  of  light  reflected  from 
a  mirror  attached  to  the  needle  or  its  sus- 
pension system. 

Mirror  Magnetometer.  —  A  magneto- 
meter whose  needle  or  suspension  system 
is  provided  with  a  mirror. 

Mirror  Receiver  in  Cable  Telegraphy. 
In  cable  telegraphy,  a  mirror  galvano- 
meter employed  as  a  receiver. 

Mirror  Receiving-Instrument.— (1)  A 
receiving  signalling  instrument  employed 
in  submarine  telegraphy,  whose  needle  or 
suspension  system  is  provided  with  a 
mirror.  (2)  A  mirror  galvanometer  mod- 
ified for  use  in  telegraphing. 

Mirror  Speaking  -  Instrument.  —  A 
mirror  receiving-instrument. 

Mixed  Charge  Test  for  Capacity. — A 
test  employed  for  determining  the  capac- 
ity of  a  submarine  cable,  in  which  an 
unknown  capacity  is  charged  to  one  po- 
tential, a  known  capacity  is  charged  to 
an  opposite  potential,  and  the  two  charges 
are  then  mixed  with  the  object  of  neutral- 
ization. 

Mixed  Circuit. — (1)  In  telephony,  a  circuit 
partly  metallic  and  partly  earth-circuited. 
(2)  A  term  sometimes  applied  to  the  com- 
bination of  a  series  and  a  multiple  circuit. 

Mixed-Circuit  Board. — (1)  A  telephone 
switchboard  arranged  for  the  reception 
and  inter-connection  of  metallic  circuits 
and  ground-return  circuits.  (2)  A  mixed- 
circuit  switchboard. 

Mixed-Circuit  Switchboard. — A  tele- 
phone switchboard  connected  with  mixed 
circuits  or  circuits  of  which  some  are 
metallic  and  others  are  provided  with 
ground  return. 

Mixed  Distribution. — (1)  A  distribution 


Mix.] 


853 


[MoU 


of  electric  energy  which  combines  both 
series  and  parallel  distribution.  (2) 
Series-parallel  or  parallel-series  distribu- 
tion. 

Mixing  Key. — The  key  employed  in  simul- 
taneously charging  a  cable  and  a  con- 
denser for  producing  the  mixed  charge 
employed  in  the  mixed-charge  test  for 
capacity. 

Mixture  Photometer.  —  A  photometer 
combining  the  principles  of  the  compensa- 
tion and  the  polarization  photometer. 

Moderate-Speed.  Generator. — A  gener- 
ator designed  to  be  run  at  a  moderate 
speed,  as  distinguished  from  a  slow-speed 
generator. 

Moderate-Speed  Motor.— A  motor  de- 
signed to  work  at  a  moderate  speed,  as 
distinguished  from  a  slow-speed  motor. 

Modulus  of  Elasticity . — (1)  The  ratio  of 
the  simple  stress  required  to  produce  a 
small  elongation  or  compression  in  a  rod 
of  unit  area  of  normal  cross-section,  to 
the  proportionate  change  of  length  pro- 
duced. (2)  Young's  modulus. 

Moist  Electrode.  —  A  therapeutic  elec- 
trode moistened  with  water  or  some  other 
liquid. 

Moist  Voltaic  Cell. — A  form  of  the  so- 
called  dry  voltaic  cell. 

Moisture-Proof  Insulation. — (1 )  Water- 
proof insulation.  (2)  A  type  of  insulation 
which  is  not  strictly  water-proof,  but 
which  is  capable  of  being  immersed  for 
a  short  time  without  suffering  serious  loss 
of  insulation. 

Molar  Attraction. — (1)  Mass  attraction, 
as  distinguished  from  molecular  attrac- 
tion or  cohesion.  (2)  Gravitation. 

Molar  Vibration  of  Telephone  Dia- 
phragm.— The  mass  vibration  of  a  tele- 
phone diaphragm,  as  distinguished  from 
molecular  vibration. 

Molecular. — Of  or  pertaining  to  the  mole- 
cules. 

Molecular  Accommodation.  —  A  re- 
arrangement of  the  molecules  of  a  para- 

'  magnetic  substance  resulting,  by  constant 
repetition,  in  a  decrease  in  the  hysteretic 
friction  in  cyclic  magnetization. 

Molecular  Agitation. — Rapid  mechanical 
vibration  given  to  a  mass  of  iron  for  the 
purpose  of  reducing  its  magnetic  hyster- 
esis. 

Molecular  Attraction. — (1)  The  mutual 
attraction  existing  between  neighboring 
molecules.  (2)  Cohesion  or  adhesion. 

Molecular  Bombardment. — (1)  The  col- 
lisions which  occur  between  neighboring 


molecules,  and  which  are  accentuated  and 
accelerated  by  heat.  (2)  The  forcible  rec- 
tilinear projection  from  the  negative 
electrode  of  the  residual  gaseous  molecules 
in  an  exhausted  vessel,  on  the  heating  of 
the  same,  or  on  the  passage  through  it  of 
an  electric  discharge. 

Molecular  Chain. — A  polarized  chain  of 
molecules  that  is  assumed  by  Grothuss* 
hypothesis  to  exist  in  an  electrolyte  during 
its  electrolytic  decomposition,  or  in  a  vol- 
taic cell  on  the  closing  of  the  circuit. 

Molecular  Conductance. — The  conduct- 
ance offered  by  a  mass  of  an  electrolyte 
equal  to  its  molecular  weight  in  grammes, 
when  contained  in  an  insulating  vessel 
furnished  with  two  opposite  parallel  con- 
ducting sides  or  faces,  distant  one  centi- 
metre apart. 

Molecular  Conductivity  of  Electro- 
lyte.— (1)  The  conductance  possessed  by 
one  gramme-molecule  of  an  electrolyte 
when  placed  between  electrodes  one 
centimetre  apart.  (2)  A  term  sometimes 
used  for  molecular  conductance. 

Molecular  Configuration. — A  term  for 
the  molecular  groupings  or  the  relative 
position  of  the  molecules  in  a  magnetizable 
substance. 

Molecular  Currents. — (1)  A  term  some 
times  employed  for  Amperian  currents. 
(2)  Atomic  currents. 

Molecular  Decomposition.— Decomposi- 
tion of  a  molecule. 

Molecular  Dissociation.— (1)  Molecular 
decomposition.  (2)  The  disruption  of 
molecules  into  ions,  or  atoms. 

Molecular  Encounter. — A  collision  be- 
tween two  molecules  of  a  gaseous  sub- 
stance that  takes  place  during  the  to-and- 
fro  movements  they  describe  in  accord- 
ance with  the  kinetic  theory  of  gases. 

Molecular  Heat. — The  number  of  calories 
of  heat  required  to  raise  one  gramme- 
molecule  of  a  substance  one  degree  Cen- 
tigrade. 

Molecular  Kinetics. — The  kinetics  of  the 
molecules. 

Molecular  Magnetomotive  Forces. — 
(1)  The  magnetomotive  forces  inherently 
possessed  by  the  molecules.  (2)  The 
aligned  or  structural-magnetomotive 
force  as  distinguished  from  the  prime 
magnetomotive  force. 

Molecular  Magnetism.— (1)  The  mag- 
netism resulting  from  molecular  magneto- 
motive forces.  (2)  The  inherent  magnetic 
flux  in  a  molecule  of  a  magnetic  substance. 

Molecular    Magnetization.  —  The    in- 


Mol.] 


854 


[Mou. 


herent  magnetization  possessed  by  the 
molecules. 

Molecular  Magnets.  —  The  inherently 
magnetized  molecules. 

Molecular  Oscillations.  —  To-and-fro 
movements  or  oscillations  of  the  mole- 
cules. 

Molecular  Range. — The  distance  at  which 
the  molecules  of  matter  continue  to  exert 
a  sensible  attraction  on  one  another. 

Molecular  Repulsion. — The  mutual  re- 
pulsion existing  between  molecules  arising 
from  their  kinetic  energy. 

Molecular  Resistance. — (1)  The  resistance 
offered  by  a  mass  of  an  electrolyte  equal 
to  its  molecular  weight  in  grammes,  when 
contained  in  an  insulating  vessel  having 
two  opposite  parallel  conducting  faces 
distant  one  centimetre  apart.  (2)  The  re- 
sistance of  one  gramme-molecule  of  an 
electrolyte  when  brought  between  two 
electrodes  one  centimetre  apart. 

Molecular  Rigidity. —  The  resistance 
offered  by  the  molecules  of  a  substance 
to  rotation  or  displacement. 

Molecular  Shadows. — The  comparatively 
dark  spaces  on  those  portions  of  the  walls 
of  a  Crookes  tube,  which  have  been  pro- 
tected by  molecular  bombardment  by 
suitably  interposed  screens. 

Molecular  Streams.— Rectilinearly  di- 
rected streams  of  molecules,  thrown  off 
from  the  cathode  of  a  high-vacuum  tube, 
under  the  influence  of  heat  or  electric 
discharges. 

Muscular  Theory  of  Muscle  and 
Nerve  Currents. — A  theory  which  re- 
gards every  muscle  or  nerve  fibre  as 
formed  of  a  number  of  series-connected 
electromotive  molecules  surrounded  by  a 
neutral  conducting  fluid. 

Molecular  Transfer  of  Heat.— The 
transfer  of  heat  by  means  of  molecular 
vibrations. 

Molecular  Vibration  of  Telephone 
Diaphragm.— The  molecular  vibration 
of  a  telephone  diaphragm  under  the  in- 
fluence of  the  changes  in  the  magnetiza- 
tion of  the  telephone  magnet,  as  distin- 
guished from  its  molar  vibration. 

Monochromatic  Photometry.— (1)  The 
photometry  of  monochromatic  lights. 
(2)  Photometry  in  which  the  spectra  or  the 
compositions  of  the  lights  to  be  compared 
are  similar. 

Molecular  Voltaic-Couple. — A  voltaic 
couple  formed  of  the  atoms  or  radicals  of 
a  molecule. 

.Molecular  Vortices. — The  vortices  in  the 
ether  which,  according  to  a  particular 


theory,  are  assumed  to  constitute  the 
molecules,  atoms  or  ultimate  particles  of 
matter. 

Molecule.— (1)  The  smallest  quantity  of  a 
compound  substance  that  can  exist  as  such. 
(2)  A  group  of  atoms  whose  chemical  bonds 
or  affinities  are  completely  satisfied. 

Molten-Platinum  Lamp.— The  violle  or 
molten  platinum  standard. 

Molten-Platinum  Standard  of  Light.— 

(1)  The  violle.     (2)  The  practical  standard 
of  white  light  adopted  at  the  Electrical 
Congress  of  Paris,  in  1884,  and  defined  as 
the  total  quantity  of  light  emitted  by  a 
square  centimetre  of  molten  platinum  at 
the  temperature  of  its  solidification. 

Moment.— (1)  Torque.  (2)  The  product  of 
any  quantity,  directed  with  respect  to  an 
axis,  and  the  perpendicular  distance  of  its 
direction  from  that  axis. 

Moment  of  a  Couple.— (1)  The  torque  or 
effective  power  of  a  couple.  (2)  The  in- 
tensity of  one  of  the  forces  in  a  couple, 
multiplied  by  the  perpendicular  distance 
between  the  direction  of  the  forces. 

Moment  of  a  Magnet.— The  polar  length 
of  a  magnet  multiplied  by  the  intensity 
of  magnetism  of  one  of  its  poles. 

Momentary  Current.— (1)  A  current  that 
continues  flowing  but  for  a  short  time. 

(2)  A  current  of  brief  duration. 

Momentum.— (1)  The  product  of  the  mass 
of  a  moving  body  by  its  velocity.  (2) 
Quantity  of  motion  in  a  system. 

Monad  Atom. — An  atom  whose  valency 
or  atomicity  is  one. 

Moniyalent. — (1)  Possessing  a  valency  or 
atomicity  of  one.  (2)  Univalent,  or  mono- 
valent. 

Monochord. — A  sonometer. 

Monocular. — An  eye-piece  or  glass,  pro- 
vided for  a  single  eye. 

Monophotal  Arc-Light  Regulator. — 
A  term  sometimes  employed  for  an  elec- 
tric are-lamp  in  which  the  whole  current 
passes  through  the  arc-regulating  mech- 
anism, and  which  is  usually  operated 
singly  in  circuit  with  a  dynamo. 

Monocycler. — A  monocyclic  generator. 

Monocyclic. — Of  or  pertaining  to  a  mono- 
cycler,  or  to  a  monocyclic  system. 

Monocyclic  Alternator. — A  monocyclic 
generator. 

Monocyclic  Armature. — The  armature 
of  a  monocyclic  generator,  provided  with 
two  sets  of  windings,  one  of  which  con- 
stitutes the  main  winding  and  corresponds 
to  that  of  an  ordinary  uniphaser,  while 


Mon.] 


855 


[Mot. 


the  second  is  of  smaller  cross-section  and 
fewer  turns,  and  is  connected  to  the  centre 
of  the  main  winding  in  diphase  relation 
to  it. 

Monocyclic  Circuit. — The  circuit  of  a 
monocyclic  generator. 

Monocyclic  Generator. —  A  form  of 
polyphase  generator  provided  with  a  mo- 
nocyclic armature. 

Monocyclic  Motor. — A  form  of  induc- 
tion motor  suitable  for  use  on  monocyclic 
circuits. 

Monocyclic  System.;— (1)  A  system  of 
alternating-current  distribution  suitable 
for  electric  lighting  with  the  additional 
capability  of  operating  triphase  induction 
motors.  (2)  A  system  for  the  distribution 
of  alternating  currents  employing  three 
•wires,  between  two  of  which  an  ordinary 
uniphase  pressure  is  maintained,  while 
between  either  of  them  and  the  third, 
there  is  a  diphased  pressure. 

Monogenic  Charge. — A  name  proposed 
for  such  a  distribution  of  an  electric 
charge  in  which  the  sign  of  the  surface 
density  is  everywhere  the  same. 

Monophase  Generator. — An  alternator 
producing  uniphase  or  monophase  cur- 
rents. 

Monophase  Motor. — A  uniphase  motor. 

Mooring  Chain. — A  chain  employed  for 
the  mooring  of  a  cable  buoy. 

Mopped. — Subjected  to  the  action  of  a  pol- 
ishing mop. 

Mordey  Effect. — A  decrease  in  the  value 
of  the  hysteresis  in  the  iron  of  a  dynamo 
armature  at  full  load. 

Morse  Alphabet. — The  Morse  telegraphic 
alphabet. 

Morse  Code. — The  Morse  telegraphic  al- 
phabet. 

Morse  Embosser. — A  Morse  register. 

Morse  Ink-Writer. — The  name  some- 
times given  to  a  Morse  inker. 

Morse  Inker. — A  form  of  telegraphic  ink- 
writer  printing  signals  in  the  Morse  code. 

Morse  Push. — A  term  sometimes  employed 
for  a  double-contact  push. 

Morse  Recorder. — An  apparatus  for  au- 
tomatically recording  the  dots  and  dashes 
of  the  Morse  telegraphic  dispatch,  on  a 
fillet  of  paper  drawn  under  an  indenting 
or  marking  point  on  a  striking  lever  con- 
nected with  the  armature  of  an  electro- 
magnet, as  distinguished  from  a  Morse 
inker. 

Morse  Register. — A  Morse  recorder. 

Morse  System  of  Telegraphy. — A  sys- 


tem of  telegraphy  in  which  makes  and 
breaks,  occurring  at  intervals  corre- 
sponding to  the  dots  and  dashes  of  the 
Morse  alphabet,  are  received  by  an  electro- 
magnetic sounder,  or  other  receiver. 
Morse  Tapper.— A  form  of  telegraphic 
key  provided  with  two  contacts,  one  in 
front,  and  another  on  the  back,  so  arranged 
that  the  depression  of  the  key  makes  one 
contact  and  breaks  the  other. 

Morse  Writer. — A  form  of  telegraphic 
Morse  ink-writer. 

Morse  Telegraphic- Alphabet. — Various 
groupings  of  dots  and  dashes  or  deflec- 
tions of  a  needle  to  the  right  and  left,  em- 
ployed for  representing  the  letters  of  the 
alphabet  or  other  signs. 

Morse  Telegraphic-Sounder. — An  elec- 
tro-magnet, the  movements  of  whose  ar- 
mature lever  produce  the  audible  sounds 
corresponding  to  the  dots  and  dashes  of 
the  Morse  code. 

Motional  Electric  Force.— The  electric 
force  induced  by  the  motion  of  magnetic 
flux,  or  of  the  medium  supporting  the 
flux. 

Motional  Magnetic  Flux.  —  Magnetic 
flux  produced  by  the  motion  of  an  elec- 
trostatic charge,  or  of  electrostatic  flux. 

Motorneer. — A  word  proposed  for  motor- 
man.  (Not  in  general  use.) 

Motor  Armature. — The  armature  of  an 
electric  motor. 

Motor  Car,  Electric.  —  An  electrically 
propelled  car. 

Motor  Circuit. — A  circuit  containing  an 
electric  motor. 

Motor-Controlling  Rheostat. — A  rheo- 
stat connected  with  a  motor,  and  em- 
ployed for  starting  the  motor  or  for 
regulating  its  speed. 

Motor  Cut-Out. — A  cut-out  provided  in 
the  circuit  of  a  motor  for  the  purpose  of 
throwing  it  out  of  circuit. 

Motor  -  Dynamo.  —  (1)  An  electrically 
driven  motor,  rigidly  connected  to  the 
armature  of  a  dynamo,  and  employed  for 
transforming  or  changing  the  pressure  of 
a  direct-current  circuit.  (2)  The  combi- 
nation, in  a  continuous-current  generator 
of  a  motor  and  a  dynamo,  in  separate 
structures,  mechanically  connected  to 
form  a  single  machine  or  structure. 

Motor-Electromotive  Force. — A  term 
proposed  for  the  counter-electromotive 
force  of  a  motor. 

Motor,  Electric. — A  device  for  transform- 
ing electric  power  into  mechanical  power. 

Motor-Generator. — (1)  A  motor  coupled 


Mot.] 


856 


[Mul. 


to  a  generator.      (2)  A    motor-dynamo. 
(3)  A  form  of  secondary  generator. 

Motorman.  —  The  man  who  operates  a 
trolley  car. 

Motor-Meter. — (1)  An  electric  meter  whose 
operations  depend  on  the  movements  of 
an  electric  motor.  (2)  A  meter  con- 
nected with  the  supply  circuit  of  an  elec- 
tric motor. 

Motor  Slip. — The  deviation  of  an  induc- 
tion motor  from  synchronous  speed,  or 
the  proportional  loss  of  synchronous  speed 
due  to  load  and  losses  of  energy. 

Motor  Standards. — The  supports  for  the 
bearing  of  an  electric  motor. 

Motor  Starter. — A  term  proposed  for  a 
motor  starting-rheostat. 

Motor  Starting-Box. — A  box  containing 
a  starting  rheostat  or  controller. 

Motor  Starting-Rheostat. — An  adjusta- 
ble rheostat  provided  for  preventing  an 
abnormal  rush  of  current  through  a  shunt- 
wound  motor,  on  the  starting  of  the  same. 

Motor  Suspension. — The  suspension  pro- 
vided for  the  electric  motors  on  a  street- 
car truck. 

Motor  Switch. — A  switch  provided  for 
the  control  of  a  motor. 

Motor  Telegraph  Printing  System. 
A  printing  telegraph  system  in  which 
two  motors,  one  at  the  transmitting,  and 
one  at  the  receiving  end  of  the  line,  are 
maintained  in  synchronous  rotation. 

Motor  Torque. — The  rotary  effort  de- 
veloped by  an  electric  motor. 

Motor-Transformer.— (1)  A  transformer 
or  secondary  generator  operated  by  a 
motor.  (2)  A  motor-generator,  dynamo- 
tor,  or  rotary-transformer.  (3)  A  dyn- 
amo-electric machine  having  two  arma- 
ture windings,  one  to  receive  current  as  a 
motor,  and  the  other  to  deliver  current  to 
a  secondary  circuit  as  a  generator. 

Motor  Truck.— The  truck  of  an  electric 
car  provided  with  supports  for  the  sus- 
pension of  an  electric  motor  or  motors. 

Motoring  at  Brushes. — A  term  proposed 
for  flashing  at  the  brushes  of  a  motor. 

Moulded  Carbons.  —  Artificial  carbons 
made  by  moulding  mixtures  of  carbona- 
ceous substances  under  pressure. 

Moulded  Filaments.— The  formation  of 
an  incandescent  filament  by  moulding  a 
suitable  carbonaceous  paste  by  hydraulic 
pressure. 

Moulded  Mica. — An  insulating  substance 
consisting  of  finely  divided  mica,  made 
into  a  paste  with  some  f  used  insulating 


material,  and  moulded  into  the  desired 
shape  before  cooling. 

Moulding  Wiring.— Electric  conductor* 
or  wires  that  are  held  in  place  on  the 
walls  or  ceiling  of  a  room  by  means  of 
suitably-shaped  mouldings. 

Mouldings,  Electric.  —  Mouldings  of 
dried  non-conducting  wood,  provided 
with  longitudinal  grooves  for  the  recep- 
tion and  support  of  insulated  wires. 

Mounted  Filament. — The  filament  of  an 
incandescent  lamp  placed  on  its  support, 
ready  for  introduction  into  the  lamp 
chamber. 

Mounting  of  Filament. — Providing  the 
filament  and  leading-in  wires  of  an  incan- 
descent lamp  with  a  suitable  glass  sup- 
port ready  for  introduction  into  the 
chamber  of  an  incandescent  lamp,  and 
its  hermetical  sealing  therein. 

Mouse-Mill  Dynamo. — A  form  of  dyna- 
mo-electric machine  employed  to  drive  a 
replenisher  or  influence  machine. 

Mouse-Mill  Machine. — A  form  of  induc- 
tion machine  employed  as  a  replenisher 
or  high-tension  source. 

Mouth-Pieces.  —  Circular  openings  into 
air  chambers,  placed  over  the  diaphragms 
of  telephones,  phonographs,  gramophones, 
or  graphophones,  to  permit  the  ready 
application  of  the  mouth  in  speaking, 
so  as  to  set  the  diaphragm  in  vibration. 

Movable.— Capable  of  being  moved. 

Movable  Secondary. — The  secondary  of 
an  induction  coil,  which,  instead  of  being 
fixed,  as  in  most  coils,  is  movable. 

Multi  -  Cellular  Electrostatic  Volt- 
meter.— An  electrostatic  voltmeter  in 
which  a  series  of  fixed  and  movable  plates 
are  employed,  instead  of  the  single  pair  of 
plates  of  the  quadrant  electrometer. 

Multi-Circuit  Arc-Dynamo.— A  dynamo 
whose  armature  is  provided  with  several 
circuits  designed  to  avoid  too  high  an 
electromotive  force  on  any  single  circuit. 

Multi-Circuit  Arc-Light  Generator. — 
(1)  An  arc-light  generator  designed  to 
supply,  several  series-connected  arc-cir- 
cuits, as  distinguished  from  a  generator 
designed  to  supply  a  single  circuit.  (2)  A 
multi-circuit  arc  dynamo. 

Multi-Coil  Alternating-Current  Ar- 
mature-Winding.— An  alternator  arma- 
ture-winding containing  on  its  surface 
more  than  one  coil  or  group  of  conduc- 
tors per  pole  of  the  field  frame,  as  distin- 
guished from  a  uni-coil  winding. 

Multi-Conductor  Cable.— A  cable  pro- 
vided with  a  plurality  of  conducting 
circuits. 


Mul.] 


857 


[Mul.. 


Multi-Duct  Conduit. — A  conduit  con- 
taining a  plurality  of  ducts. 

Multi-Periodic  Current. — (1)  A  current 
composed  of  a  number  of  associated  com- 
ponent currents  of  different  frequencies. 
(2)  A  complex-harmonic  current. 

Multiphase. —  Containing  more  than  a 
single  phase. 

Multiphase  Alternating-  Currents . — A 
number  of  separate  alternating  currents 
which  differ  in  phase  by  a  fixed  amount. 

Multiphase  Alternator. — An  alternator 
capable  of  producing  multiphase  cur- 
rents. 

Multiphase  Apparatus. — A  general  term 
for  multiphase  alternators,  motors,  or 
other  receptive  apparatus,  suitable  for 
use  on  multiphase  circuits. 

Multiphase  Circuits. — The  circuits  em- 
ployed in  a  system  of  multiphase  distri- 
bution. 

Multiphase  Dynamo.  —  A  multiphase 
alternator. 

Multiphase  Generator. — A  multiphase 
alternator. 

Multiphase  Induction-Motor. — An  in- 
duction motor  suitable  for  use  in  con- 
nection with  multiphase  currents,  and 
operated  by  rotating  magnetic  fields. 

Multiphase  Synchronous-Motor.  —  A 
synchronous  alternating-current  motor 
supplied  with  multiphase  currents  as  dis- 
tinguished from  an  asynchronous  or  in- 
duction multiphase  motor. 

Multiphase  System. — A  system  for  the 
distribution  of  energy  by  multiphase  cur- 
rents. 

Multiphaser. — A  multiphase  alternator. 

Multiple-Arc  Circuit. — A  term  often 
used  for  multiple  circuit. 

Multiple- Arc-Connected  Electro-Re- 
ceptive Devices. — Electro-receptive  de- 
vices connected  with  the  driving  circuit 
in  multiple  arc. 

Multiple- Arc-Connected  Sources.  —  A 
battery  of  multiple-connected  sources. 

Multiple-Arc-Connected  Translating 
Devices. — Multiple-arc  connected  elec- 
tro-receptive devices. 

Multiple- Arc  Resistance  Box.— A  re- 
sistance box  whose  resistances  are  capable 
of  being  inter-connected  in  multiple  arc. 

Multiple  Armature-Windings.  —  (1)  A 
term  sometimes  used  for  multiple-circuit 
armature-windings.  (2)  A  term  some- 
times used  for  multiple-wound  armature 
windings. 

Multiple  Cable.  —  A  cable  containing 

12— 


more  than  a  single  conducting  wire  or 
circuit. 

Multiple  Cable-Core. — A  cable  contain- 
ing more  than  a  single  conducting  wire 
or  core. 

Multiple  Call-Box. — A  call-box  capable 
of  automatically  transmitting  a  number 
of  different  calls. 

Multiple  Circuit. — A  circuit  in  which  a 
number  of  separate  sources  or  separate 
receptive  devices,  or  both,  have  all  their 
positive  poles  connected  to  a  single  posi- 
tive lead  or  conductor,  and  all  their  neg- 
ative poles  connected  to  a  single  negative 
lead  or  conductor. 

Multiple  -  Circuit  Multiple  -  Wound 
Armature. — An  armature  providing  a 
plurality  of  circuits  between  the  brushes, 
and  also  a  plurality  of  independent  wind- 
ings connected  to  symmetrically  inter- 
spersed independent  commutator  bars. 

Multiple  Circuit  Winding  of  Arma- 
ture.— Such  a  winding  as  provides  a  mult- 
iplicity of  circuits  in  parallel  through  an, 
armature. 

Multiple  Conduit. — A  conduit  provided 
with  a  number  of  separate  ducts. 

Multiple  -  Connected.  —  Connected  in 
multiple-arc. 

Multiple-Connected  Battery.— A  bat- 
tery whose  separate  cells  are  connected 
in  multiple-arc. 

Multiple  -  Connected  Electro  -  Recep- 
tive Devices.  —  Multiple-arc-connected 
translating  devices. 

Multiple- Arc-Connected  Sources.  —  A 
number  of  separate  sources  connected  in 
multiple-arc,  so  as  to  act  as  a  single 
source. 

Multiple  Connection.  —  Connection  in 
parallel  or  in  multiple-arc. 

Multiple-Contact  Carbon  Telephone 
Transmitter. — (1)  A  telephone  trans- 
mitter provided  with  a  number  of  sep- 
arate contacts.  (2)  A  dust  telephone- 
transmitter. 

Multiple  Converter. — A  multiple  trans- 
former. 

Multiple  Electric  Gas-Lighting.  —  A 
system  of  electric  gas-lighting  in  which 
a  number  of  gas  jets  are  ignited  by  high 
electromotive  force  discharges  obtained 
from  a  Ruhmkorff  coil  or  static  induction 
machine. 

Multiple  Electrode  Telephone.  —  A 
telepnone  transmitter  possessing  a  plural- 
ity of  active  contacts. 

Multiple  Electrolysis.— Electrolysis  pro- 
Vol.  2 


Mul.] 


858 


[Mul. 


ducing  or  accompanied  by  secondary 
chemical  reactions. 

Multiple  -  Harmonic  Telegraph.  —  A 
general  term  embracing  the  apparatus 
employed  in  multiple-harmonic  teleg- 
raphy. 

Multiple  -  Harmonic    Telegraphy. — A 

system  for  the  simultaneous  transmission 
of  a  number  of  separate  and  distinct  mus- 
ical notes  over  a  single  wire,  which 
separate  notes  are  utilized  for  the  simul- 
taneous transmission  of  an  equal  number 
of  independent  telegraphic  messages. 

Multiple  Jacks. — The  reduplicating  jacks 
of  a  multiple  telephone  switchboard. 

Multiple  Lightning  Flash.  —  Several 
lightning  flashes  apparently  coming  from 
the  same  cloud, 

Multiple-Pair  Brush-Rocker.  — A  term 
sometimes  used  for  multiple-pair  brush- 
yoke. 

Multiple-Pair  Brush-Yoke. — A  device 
for  holding  a  number  of  pairs  of  brushes 
on  the  commutator;  so  that  they  can  all  be 
simultaneously  moved  oj-  rotated  thereon. 

Multiple-Parallel  Circuit.  —  A  term 
sometimes  employed  for  a  multiple  of 
parallel  circuits. 

Multiple  Quadruples. — A  system  of  re- 
peating from  more  than  one  quadruplex 
circuit  to  a  brancli  office,  or  repeating 
from  one  quadruplex  circuit  to  another. 

Multiple  Resonance. — The  partial  re- 
sonance of  a  primary  conductor  devoid  of 
a  definite  period  of  oscillation,  and,  there- 
fore, capable  of  performing  all  possible 
oscillations  lying  within  wide  limits. 

Multiple  Rheostat. — A  form  of  rheostat 
whose  resistances  are  capable  of  being 
thrown  into  a  circuit  in  multiple,  so  that 
the  carrying  capacity  increases  as  the  re- 
sistance is  decreased. 

Multiple  Running. — The  operation  of 
generators  in  parallel. 

Multiple-Series. — A  multiple  connection 
of  series  groups. 

Multiple-Series  Circuit. — A  circuit  in 
which  a  number  of  separate  sources,  or 
receptive  devices,  or  both,  are  connected 
in  a  number  of  separate  groups  in  series, 
and  these  separate  groups  subsequently 
connected  in  multiple. 

Multiple-Series  Condenser. — (1)  An  ar- 
rangement of  groups  of  condensers  in 
series,  which  groups  are  connected  in 
multiple.  (2)  A  condenser  divided  into 
parts  capable  of  being  connected  either 
in  multiple,  or  in  series,  or  in  both. 

Multiple-Series-Connected  Receptive 
or  Translating  Devices. — A  number  of 


receptive  or  translating  devices  connected 
in  multiple-series. 

Multiple-Series-Connected  Sources. — 
A  number  of  separate  electric  sources  so 
connected  in  multiple-series,  as  to  be 
capable  of  acting  as  a  single  source. 

Multiple-Series  Connection. — Connec- 
tion in  multiple-series. 

Multiple  Switch. — A  switch  provided 
with  a  number  of  separate  contact  plates 
for  controlling  a  plurality  of  circuits. 

Multiple  Switchboard. — A  switchboard 
to  which  the  numerous  circuits  employed 
in  systems  of  telegraphy,  telephony,  an- 
nunciators, or  electric  light  and  power 
circuits,  are  connected. 

M  u  1 1  i  p  1  e-Tablet  Switchboard.— A 
switchboard  provided  with  a  number  of 
separate  tablets  or  panels. 

Multiple    Telegraphic  -  Repeater.— A 

telegraphic  repeater  which  repeats  from 
one  circuit  to  two  or  more  Morse  circuits. 
Multiple  Telegraphy.— A  system  for  the 
simultaneous  telegraphic  transmission 
over  the  same  wire  of  more  than  a  single 
message  in  the  same  direction. 

Multiple  Telephone  Receiver. — (1)  A 
telephone  receiver  in  a  multiple  tele- 
phone circuit.  (2)  A  composite  tele- 
phone receiver. 

Multiple  Telephone  Switchboard.— A 
switchboard  consisting  in  reality  of  a 
number  of  separate  switchboards,  each 
provided  with  separate  operators  and 
bearing  transmitter  keys,  switches  and 
generators,  employed  when  the  number 
of  subscribers  connected  with  the  switch- 
board exceed  a  number  such  as  can  be 
handled  by  a  single  switchboard. 

Multiple  Telephony.— The  simultaneous 
transmission  over  the  same  wire  of  a  num- 
ber of  separate  telephonic  despatches,  in 
the  same  direction. 

Multiple  Transformer. — (1)  Any  form  of 
transformer  the  coils  or  circuits  of  which 
are  connected  in  multiple.  (2)  The  or- 
dinary alternating-current  transformer 
connected  across  a  supply  circuit,  as  dis- 
tinguished from  a  series  transformer. 

Multiple  Transmission.— The  simulta- 
neous sending  of  two  or  more  messages 
over  a  single  conductor  in  the  same  direc- 
tion. 

Multiple  Unit  System  of  Railway 
Traction. — A  system  of  electric  railways 
in  which  each  traction  unit  is  provided 
with  its  own  independent  motors,  in  such 
a  manner  that  all  the  units  may  be  oper- 
ated collectively  from  a  single  point. 


Mul.] 


859 


[Mus. 


Multiple  Valued  Function. — A  func- 
tion which  has  more  than  one  value  for  a 
single  value  of  its  variable. 

Multiple  Wheel  Printing  Telegraph. 
A  printing  telegraph  instrument  pro- 
vided with  a  plurality  of  printing  wheels. 

Multiple  Windings. — Independent  wind- 
ings symmetrically  disposed  upon  the 
same  armature,  insulated  from  each  other, 
but  brought  to  different  segments  of  the 
commutator. 

Multiple-Wound  Multiple-Circuit 
Armature.  —  A  multipolar  armature 
having  a  plurality  of  windings,  and  each 

•  winding  having  a  plurality  of  circuits 
between  the  brushes. 

Multiple- Wound  Two-Oircuit  Arma- 
ture-Windings.— A  multipolar  arma- 
ture having  a  plurality  of  windings,  each 
winding  having  two  circuits  between  the 
brushes. 

Multiple  Working  of  Dynamo-Elec- 
tric Machines. — A  term  sometimes  used 
for  parallel  working  of  dynamo  electric 
machines. 

Multiples. — The  jacks  in  the  various  sec- 
tions of  a  multiple-telephone  switchboard, 
which  are  connected  to  the  same  line  or 
subscriber. 

Multiplex  Telegraph.— A  general  term 
embracing  the  apparatus  employed  in 
multiplex  telegraphy. 

Multiplex  Telegraphy.— (1)  A  system  of 
telegraphy  for  the  simultaneous  transmis- 
sion in  opposite  directions  of  more  than 
two  separate  messages  over  a  single  wire 
from  each  end.  (2)  A  term  sometimes  used 
for  multiple  telephony  or  simultaneous 
transmission  of  more  than  one  message 
in  the  same  direction  over  a  single  wire. 

Multiplex  Telephony. — A  system  of  tele- 
phony for  the  simultaneous  transmission 
in  opposite  directions  of  more  than  two 
separate  messages  over  a  single  wire  from 
each  end. 

Multiplex  Working. — Multiplex  trans- 
mission. 

Multiplicatpr. — A  term  sometimes  used 
for  multiplier. 

Multiply. — In  a  multiple  telephone  switch- 
board to  reduplicate  or  to  repeat  at  each 
section  of  the  switchboard. 

Multiply  Re-Entrant  Armature- Wind- 
ing.— An  armature-winding  provided 
with  a  plurality  of  separate  conducting 
paths  or  windings,  each  of  which  is  in- 
dependently re-entrant. 

Multiplying  Power  of  Shunt. — A  quan- 
tity by  which  the  current  flowing  through 


a  galvanometer  or  other  device  provided 
with  a  shunt,  must  be  multiplied,  in  order 
to  give  the  total  current. 
Multi-Point  Secondary.— A  secondary 
coil  arranged  so  that  it  can  be  readilj 
tapped  at  different  points. 

Multipolar  Armature.— An  armature 
suitaole  for  use  in  a  multipolar  field. 

Multipolar  -  Drum  Armature  -  Wind- 
ings.— Windings  of  a  drum  armature 
suitable  for  a  multipolar  field ;  i.  e.  pro- 
ducing more  than  two  poles  on  the  arma- 
ture surface. 

Multipolar  Dynamo. — A  dynamo  pro- 
vided with  a  multipolar  field. 

Multipolar  Electric  Bath. — An  electro- 
therapeutic  bath  in  which  more  than  two 
electrodes  are  employed. 

Multipolar  Field. — A  field  produced  by 
more  than  two  separate  magnet  poles. 

Multipolar  Generator. — A  multipolar 
dynamo. 

Multipolar  Motor. — A  motor  whose  field- 
magnets  contain  more  than  two  separate 
magnet  poles. 

Multipolar  Railway  -  Generator. — A 
generator  having  a  multipolar  field,  em- 
ployed for  furnishing  current  to  trolley 
cars. 

Multipolar-Ring  Armature- Winding. 
The  winding  of  a  ring  armature  adapted 
to  a  multipolar  field. 

Multipolar  Winding. — A  winding  suit- 
able for  use  in  multipolar  generators  or 
motors. 

Multi-Slot  Armature  -  Winding.  —  A 
multi-coil  armature  winding. 

Multi-Slot  Alternating-Current  Iron- 
Clad- Armature. — An  iron-clad  arma- 
ture having  more  than  one  slot  per  field 
pole  and  furnishing  alternating  currents. 

Municipal  Series  Circuit.— A  series  cir- 
cuit employed  for  the  distribution  of  in- 
candescent lights  and  suitable  for  lighting 
streets. 

Municipal  System  of  Incandescent 
Electric  Lighting. — A  system  for  the 
distribution  of  incandescent  electric 
lights,  in  which  the  separate  lamps  are 
connected  to  the  circuit  in  series,  each 
lamp  being  provided  with  a  film  or  other 
automatic  cut-out. 

Muscle  Currents. — In  electro-therapeu- 
tics the  electric  currents  flowing  through 
a  muscle  during  its  stimulation  or  ac- 
tivity. 

Muscular  Pile. — Matteucci's  muscular 
pile. 


Jttus.] 


860 


[Nat. 


Mushroom  Anchor. — An  anchor  resem- 
bling a  mushroom  in  form  and  used  for 
mooring  buoys  in  submarine  cable-work, 
so  as  to  resist  dragging  along  the  sea-bot- 
tom and  yet  avoid  becoming  tightly  en- 
gaged in  rocks. 

Mushroom  Deposit  on  Negative  Car- 
bon.— A  flat  deposit  of  graphitic  carbon 
of  a  mushroom  shape,  that  forms  on  the 
negative  carbon  of  an  enclosed  arc-lamp. 

Musket,  Electric. — A  gun  whose  charge 
is  ignited  by  a  platinum  wire  rendered 
incandescent  by  the  action  of  a  battery 
placed  in  the  stock  of  the  gun. 

Mutual  Flux    of   Transformer.— The 

magnetic  flux  which  passes  through  both 
coils  in  a  transformer  as  distinguished 
from  magnetic  flux  which  may  traverse 
one  coil,  when  excited  to  the  exclusion  of 
the  other. 


Mutual  Inductance. — (1)  The  coefficient 
of  mutual  induction  between  two  con- 
ductors. (2)  The  flux  linkages  in  one 
circuit  due  to  unit  current  in  the  other. 

Mutual  Induction. — (1)  Induction  pro- 
duced on  each  other  by  two  neighboring 
circuits  through  the  mutual  inter-con- 
nection of  their  magnetic  fluxes.  (2)  In- 
duction produced  in  neighboring 
charged  conductors  by  the  inter-connec- 
tion of  their  electrostatic  fluxes. 

Myograph. — An  instrument  for  measur- 
ing nervous  sensibility. 

Myopia. — Near-sightedness. 

Myopic. — Of  or  pertaining  to  near-sighted- 
ness. 

Myria. — A  prefix  for  ten  thousand  times. 


N 


N. — A  symbol  for  the  whole  number  of  lines 
of  magnetic  flux  or  induction  in  any  mag- 
netic circuit- 

N. — In  submarine  telegraphy,  a  code  signal 
at  the  end  of  a  message  to  indicate  that 
there  are  no  more  messages  to  follow. 

N. — A  contraction  for  north-seeking  mag- 
netic pole. 

n. —  (1)  A  symbol  employed  for  frequency. 
(2)  A  contraction  for  a  number. 

N.  H.  P. — A  contraction  for  nominal  horse- 
power. 

Name  Plate.— A  plate  fastened  to  a 
dynamo-electric  machine  and  bearing  the 
name  of  the  maker  and  other  particulars 
such  as  the  speed,  power,  weight,  pres- 
sure, and  current  of  the  machine. 

Narrow-Gauge  Street-Railway  Mo- 
tor.— A  street-railway  car  motor  of  less 
breadth  than  usual,  suitable  for  use  on 
narrow-gauge  tracks. 

Nasal  Electrode. — An  electrode  suitable 
for  introduction  into  the  nostril  for  its 
therapeutic  treatment. 

Nascent  State. — A  term  used  in  chemistry 
to  express  the  state  or  condition  of  an 
elementary  atom  or  radical  when  just 
liberated  from  chemical  combination, 
when  it  possesses  chemical  affinities  or 
attractions  more  energetic  than  after- 
wards. 

Natural  Current  from  Fault  in  Cable. 
The  feeble  current  originating  from  the 
voltaic  couple  formed  at  a  break  or  fault 
in  a  cable. 


Natural  Currents. — A  term  sometimes 
applied  to  earth  currents. 

Natural-Draught  Transformer. — (1)  An 
alternating-current  transformer  in  which 
an  air-space  is  left  between  the  primary 
and  secondary  coils,  through  which  a  con- 
vection current  of  air  passes  on  the  heat- 
ing of  the  coils.  (2)  A  transformer  cooled 
by  radiation  and  convection,  as  distin- 
guished fi'om  an  air-transformer. 

Natural  Electret.— A  body  whose  mole- 
cules are  inherently  electrized,  as  distin- 
guished from  a  body  whose  molecules  be- 
come electrized  by  induction. 

Natural  Law. — (1)  A  law  of  nature. 
(2)  An  observed  co-relation  of  phenomena 
such  that  when  one  phenomenon  or  group 
of  phenomena  occurs  in  a  certain  definite 
way,  another  phenomenon  or  group  of 
phenomena  invariably  follows. 

Natural  Magnet.— The  name  sometimes 
given  to  a  lodestone. 

Natural  Period.— (1)  The  time  in  which 
a  cyclic  phenomenon  naturally  completes 
itself.  (2)  The  time  of  complete  free  os- 
cillation of  a  vibrating  substance  or  con- 
dition, when  not  subjected  to  external 
restraint. 

Natural  Resultant  Fault. — In  any  cir- 
cuit, a  fault  which  is  the  electrical  equiv- 
alent in  position  and  magnitude  of  all  the 
actual  small  faults  or  leakages  which  may 
be  present  in  that  circuit. 

Natural  Unit  of  Electricity.— (1)  A 
term  sometimes  used  in  place  of  an  atomic 


Nat.] 


861 


[Neg. 


charge  of  electricity.  (2)  The  quantity  of 
electricity  carried  by  a  single  monad  atom 
of  any  elementary  substance. 

Natural  Unit  of  Quantity  of  Electric- 
ity.— The  quantity  of  electricity  pos- 
sessed as  a  charge  by  any  elementary 
monad  atom. 

Naut. — A  nautical  mile. 

Nautical  Mile. — (1)  A  knot  or  naut,  or  a 
distance  of  6,087  feet ;  or  nearly  1.15  stat- 
ute miles.  (2)  The  ^iJ^th  of  the  earth's 
equatorial  circumference,  or  /ffth  of  a  de- 
gree of  longitude  at  the  equator. 

Nautical  Telegraphy.— Telegraphy  con- 
ducted at  sea  or  over  the  sea,  either  be- 
tween different  vessels  or  on  board  a 
single  vessel, 

Near-Sightedness. — (1)  Inability  to  see 
objects  distinctly  unless  they  are  com- 
paratively near  the  eye.  (2)  Myopia. 

Nebula. — A  misty  appearance  in  the 
heavens  often  resolved  by  a  telescope  in- 
to clusters  of  innumerable  stars. 

Needle. — A  word  frequently  used  for  a 
magnetic  needle. 

Needle  Annunciator. — An  annunciator 
whose  indications  are  obtained  by  the 
movements  of  a  needle,  instead  of  by  the 
fall  of  a  drop. 

Needle  Electrode.  —  A  needle-shaped 
therapeutic-electrode  employed  for  elec- 
trolytic treatment. 

Needle  Instrument. — A  single-needle 
instrument. 

Needle  of  Oscillation. — A  small  mag- 
netic needle  employed  for  measuring  the 
intensity  of  a  magnetic  field  by  the  num- 
ber of  oscillations  it  makes  in  a  given 
time  when  disturbed  from  its  position  of 
rest  in  such  field. 

Needle  System  of  Telegraphy.— A  sys- 
tem of  telegraphy  in  which  the  letters  of 
the  alphabet  and  numerals  are  indicated 
by  the  to-and-fro  movements  of  a  mag- 
netic needle. 

Needle  Telegraph. — A  general  term  em- 
bracing the  apparatus  employed  in  needle 
telegraphy. 

Needle  Telegraphy. — The  needle  system 
of  telegraphy. 

Negative  Brush  of  Dynamo.— The  brush 
connected  with  the  negative  terminal  of 
a  dynamo. 

Negative  Brush  of  Motor.— The  brush 
connected  with  the  negative  terminal  of 
the  driving  source. 

Negative  Bus-Bars. — The  negative  om- 
nibus bars. 


Negative  Charge.— (1)  According  to  the 
double-fluid  hypothesis,  a  charge  of  nega- 
tive electricity.  (2)  According  to  the 
single-fluid  hypothesis,  any  deficit  of  an 
assumed  electric  fluid.  (3)  An  electric 
charge  of  the  same  character  as  that  pro- 
duced on  silk  when  rubbed  by  glass. 

Negative  Conductor. — The  conductor 
connected  to  the  negative  terminal  of  an 
electric  source. 

Negative  Currents. — In  telegraphy,  a 
term  applied  to  the  currents  sent  over  a 
line  from  the  negative  pole  of  the  battery. 

Negative  Direction  of  Electrical  Con- 
vection of  Heat. — A  direction  in  which 
heat  is  transmitted  by  electric  convection, 
through  an  unequally  heated  conductor 
opposite  to  that  of  an  electric  current. 

Negative  Direction  of  Simple-Har- 
monic Motion. — Simple-harmonic  mo- 
tion in  which  the  generating  circle  is 
moved  over  in  the  negative  direction. 

Negative  Electricity.— (1)  One  of  the 
phases  of  electric  excitement.  (2)  The 
kind  of  electric  charge  produced  on  resin 
when  rubbed  with  cotton. 

Negative  Electromotive  Force.— Such 
an  E.  M.  F.  as  is  produced  at  the  free  pole 
of  a  battery  or  other  source  whose  posi- 
tive pole  is  grounded. 

Negative  Electrification.  —  (1)  The 
charging  of  a  body  with  negative  electric- 
ity. (2)  A  negative  charge. 

Negative  Electrode. — The  electrode  con- 
nected with  the  negative  terminal  of  a 
source. 

Negative  Element   of   Electrolyte.— 

(1)  The  element  which  in  electrolysis  ap- 
pears at  the  positive  electrode.  (2)  The 
cathion. 

Negative  Element  of  Voltaic  Cell.— 

(1)  That    element    of    a    voltaic    couple 
which  is,not  acted  on  by  the  electrolyte. 

(2)  The  element  which  forms  the  positive 
pole  of  the  cell  above  the  surface  of  the 
electrolyte. 

Negative  Feeders. — The  feeders  con- 
necting the  negative  mains  with  the 
negative  poles  of  the  generators. 

Negative  Fluid.— (1)  A  specific  fluid 
which  was  formerly  believed  by  the  ad- 
vocates of  the  double-fluid  electric 
hypothesis  to  be  the  cause  of  negative 
excitement.  (2)  A  deficit  of  an  assumed 
single  electric  fluid. 

Negative  Inductance. — A  capacitance. 

Negative  Lightning. — A  name  given  to 
a  variety  of  lightning  discharge  whose 
existence  is  apparent  in  some  photo- 


862 


[Neiu 


graphic  negatives  of  lightning  flashes, 
as  black  branches  coming  out  from  the 
main-lightning  stem. 

Negative  Omnibus-Bar. — The  bus-bar 
connected  to  the  negative  terminals  of 
the  generators. 

Negative  Phase  of  Electrotonus.— A 
decrease  in  the  electromotive  force  of  a 
nerve,  produced  by  sending  an  electric 
current  through  the  nerve  in  the  opposite 
direction  to  the  nerve  current. 

Negative  Plate  of  Storage  Cell.— (1) 
That  plate  of  a  storage  cell  which  is  con- 
verted into  or  partly  covered  with  a  coat- 
ing of  spongy  lead  by  the  action  of  the 
current.  (2)  That  plate  of  a  storage  cell 
which  is  connected  with  the  negative 
terminal  of  the  charging  source,  and 
which  is,  therefore,  the  negative  pole  of 
the  cell  on  discharging. 

Negative  Plate  of  Voltaic  Cell.— (1) 
The  electro-negative  element  of  a  voltaic 
couple.  (2)  That  element  of  a  voltaic 
couple  which  is  negative  in  the  electro- 
lyte of  the  cell.  (3)  That  portion  of  the 
pla,te  of  a  voltaic  cell  above  the  liquid, 
which  becomes  the  positive  pole  of  the 
cell. 

Negative  Pole  of  Receptive  Device.— 
That  pole  of  a  receptive  device  which  is 
connected  to  the  negative  pole  of  a 
source. 

Negative  Pole  of  Source.— That  pole  of 
an  electric  source  through  which  the 
current  is  assumed  to  enter,  or  flow  back 
into  the  source,  after  having  passed 
through  the  circuit  connected  to  the 
source. 

Negative  Potential. — (1)  A  potential  such 
as  determines  a  tendency  of  electricity  to 
flow  towards  it  from  the  earth  or  from 
any  point  of  positive  potential.  (2)  Gen- 
erally, the  lower  potential  or  lower  level. 
(3)  That  property  of  a  point  in  space  by 
virtue  of  which  electric  work  is  done  by 
the  movement  of  a  small  positive  charge 
to  that  point  from  an  infinite  distance. 

Negative  Rays. — The  molecular  streams 
given  off  at  the  negative  electrode  or 
cathode  of  an  induction  tube,  on  the  pas- 
sage of  electric  discharges  through  the 
tube. 

Negative  Resistance. — A  property  of  a 
circuit  or  conductor  containing  an  E.  M. 
F. ,  whereby  a  current  flowing  through  the 
conductor  rises  in  pressure  instead  of 
falling. 

Negative  Rotation. — Right-handed  or 
clockwise  rotation,  as  viewed  from  in 
ront  of  the  clock. 


Negative  Side  of  Circuit. — (1)  The  side 
of  a  circuit  opposite  to  the  positive  sides. 
(2)  That  side  of  a  circuit  bent  in  the  form 
of  a  circle,  from  which,  if  an  observer 
stood  with  his  head  in  the  negative  region, 
he  would  see  the  current  pass  around  him 
clockwise,  or  right-handedly.  (3)  The 
side  of  a  circuit  connected  with  the 
negative  pole  of  the  source. 

Negative  Spark. — The  spark  produced 
by  the  discharge  of  a  negatively  charged 
conductor. 

Negative  Terminal. — (1)  The  terminal 
of  a  voltaic  cell  connected  with  the  posi- 
tive plate  or  element.  (2)  The  terminal 
of  a  source  connected  with  the  negative 
pole.  (3)  The  terminal  of  a  translating 
device  connected  with  the  negative  pole 
of  the  source. 

Negative  Wire. — (1)  A  wire  charged,  or 
intended  to  be  charged,  negatively.  (2) 
A  wire  connected  with  the  negative  pole 
of  a  source.  (3)  A  wire  of  negative 
potential. 

Negatively  Excited.— Endowed  with  a 
negative  charge. 

Net  Efficiency.— The  final  or  ultimate 
efficiency  of  a  series  of  machines  or 
translating  devices,  through  which  en- 
ergy, or  any  other  quantity,  has  to  suc- 
cessively pass,  as  distinguished  from  the 
separate  efficiency  of  each  machine  or 
device. 

Netted  Globe. — A  globe  surrounding  an 
arc-lamp  and  provided  with  an  external 
netting. 

Netting  Wire. — A  wire  net-work-shield 
inclosing  the  globe  of  an  arc-lamp,  both 
to  protect  it  from  mechanical  injury  and 
to  prevent  glass  from  falling  in  case  of 
fracture. 

Network  of  Conductors. — A  term  ap- 
plied to  a  number  of  interconnected  con- 
ductors which  may  resemble  a  net  in  ap- 
pearance. 

Network  of  Currents.— A  term  some- 
times applied  to  a  number  of  shunts  or 
derived  circuits,  or  to  the  currents  which 
flow  in  a  network  of  conductors. 

Neutral  Armature. — A  non-polarized 
armature. 

Neutral  Ampere-Meter. — An  ampere- 
meter connected  with  the  neutral  bus-bar 
in  a  three- wire  system  of  distribution. 

Neutral  Conductor. — The  neutral  wire 
in  a  three- wire  system. 

Neutral  Feeder. — In  a  three-wire  system » 
a  feeder  connected  with  the  neutral  bus- 
bar. 


Neu.] 


863 


[Nip. 


Neutral-Line  of  Magnet.— The  equator 
of  a  magnet. 

Neutral-Line  of  Commutator  Cylin- 
der.— A  line  on  the  commutator  cylin- 
der of  a  dynamo  connecting  the  neutral 
points  or  points  of  zero  potential. 

Neutral-Line  of  Dynamo  Armature.— 

(1)  A  line  passing  through  the  armature, 
symmetrically    disposed    as    regards    its 
entering  and  emerging  flux.     (2)  A  line  of 
zero  polarity. 

Neutral  Omnibus-Bar,  or  Bus-Bar.— 
In  a  three- wire  system  of  distribution, 
the  bus-bar  connected  with  the  neutral 
dynamo  terminals,  or  the  terminals  unit- 
ing the  positive  and  negative  dynamos. 

Neutral  Point. — A  term  sometimes  em- 
ployed in  electro-therapeutics  for  indiffer- 
ent point. 

Neutral  Points  of  Magnet. — (1)  Points 
approximately  midway  between  the  poles 
of  a  magnet.  (2)  Points  of  zero  polarity. 

Neutral  Points  of  Dynamo-Electric 
Machine. — (1)  Two  points  situated  on 
the  commutator  cylinder  at  opposite  ends 
of  its  diameter  at  which  the  collecting 
brushes  must  rest  in  order  to  obtain 
sparkless  com  mutation.  (2)  Points  of  zero 
potential  on  a  commutator. 

Neutral  Points  of  Thermo-Electric 
Diagram. — (1)  The  points  on  a  thermo- 
electric diagram  where  the  lines  repre- 
senting the  thermo-electric  powers  of  any 
two  metals  cross  each  other.  (2)  A  mean 
temperature  for  any  two  metals  in  a 
thermo-electric  series,  at  which,  if  their 
two  junctions  are  slightly  over  or  slightly 
under  the  mean  temperature,  the  one 
as  much  above  as  the  other  is  below,  no 
effective  electromotive  force  is  developed. 

Neutral  Relay-Armature. — (1)  A  relay 
armature  consisting  of  a  piece  of  soft  iron 
which  closes  a  local  circuit  whenever  its 
electro-magnet  receives  an  impulse  over 
the  main  line.  (2)  A  normally  unmag- 
netized  relay  armature. 

Neutral  Section  of  Magnet. — A  section 
passing  through  the  neutral  line  or  equa- 
tor of  a  magnet. 

Neutral  Salt. — A  salt  possessing  neither 

acid  nor  basic  properties. 
Neutral  Solution. — A  solution  of  neutral 

salt. 

Neutral  Wire. — (1)  In  a  three-wire  system 
of  electric  distribution  the  wire  con- 
nected to  the  neutral  dynamo-terminal. 

(2)  The  balance    wire    of    a    three- wire 
system. 

Neutral- Wire  Ampere-Meter. — An  am- 


pere meter  placed  in  the  circuit  of  a 
neutral  wire,  in  a  three-wire  system,  for 
the  purpose  of  showing  the  excess  of  cur- 
rent passing  over  one  side  of  the  system 
as  compared  with  the  other  side,  when  a 
balance  between  the  two  is  no  longer 
maintained. 

Neutral  Zone  of  Charged  Insulated 
Conductor. — That  portion  of  an  insu- 
lated conductor,  charged  by  electrostatic 
induction,  which  lies  approximately  mid- 
way between  its  positive  and  negative 
end. 

Neutral  Zone  of  Magnet. — A  term  some- 
times employed  for  equator  of  magnet. 

Neutralization. — The  act  or  quality  of 
rendering  neutral,  as  in  the  discharge  of 
an  electrified  body. 

New  Ohm. — A  term  sometimes  used  for 
the  international  ohm. 

Nib  on  Carbon  Electrode. — A  term 
sometimes  employed  for  the  graphitic 
deposit  on  one  side  of  the  negative  carbon, 
when  the  arc  has  been  maintained  be- 
tween the  sides  of  two  parallel  carbon 
electrodes. 

Nickel  Bath. — An  electrolytic  bath  con- 
taining a  readily  electrolyzable  salt  of 
nickel,  a  plate  of  nickel  acting  as  the 
anode  of  the  battery,  and  placed  in  a 
liquid  near  the  object  to  be  coated,  which 
forms  the  cathode. 

Nickel  Facing  of  Electro-Type.  —  A 
thin  electro-plating  of  nickel  deposited  on 
the  surface  of  an  electro-type  for  the  pur- 
pose of  hardening  it. 

Nickel  Plating. — Electro-plating  with 
nickel. 

Niello-Work. — An  enamelling  process  in 
which  a  pattern  is  traced  upon  a  bright 
silver  surface  with  a  silver  sulphide,  or 
with  mixtures  of  lead,  copper  and  silver 
sulphide,  artificially  prepared,  and  which 
is  afterwards  fixed,  by  heating  to  the 
fusion  point. 

Nigger. — A  term  sometimes  employed  for 
a  fault  in  any  electric  apparatus  or  sys- 
tem. 

Night-Bell. — In  a  hotel  or  telephone  ex- 
change, a  bell  switched  into  connection 
with  a  shunted  circuit  of  an  annunciator 
case,  and  intended,  by  its  constant  ring- 
ing, to  call  the  attention  of  the  night 
operator  to  the  falling  of  a  drop. 

Night-Switch  for  Telephone.— A  switch 
so  arranged  that,  when  turned  to  the  on- 
position,  any  or  all  of  the  drops  will,  on 
falling,  ring  a  bell,  and  thus  call  the  atten- 
tion of  the  operator. 

Nipple  of  Negative    Carbon.— A  tiny 


No.] 


864 


[Noil. 


projection  of  graphitic  carbon,  deposited 
during  the  maintenance  of  the  arc,  on 
the  surface  of  the  negative  carbon  oppo- 
site the  crater  of  the  positive  carbon. 

No.  1  Side  of  Quadruples  System.— 
That  side  of  the  quadruplex  system  which 
is  employed  in  operating  the  polar  duplex 
system.  , 

No.  2  Side  of  Quadruplex  System.— 
That  side  of  a  quadruplex  system  which 
contains  the  increment  key  and  neutral 
relay. 

Nobili's  Rings.— Metallo-chromes. 

Nodal  Point. — A  point  in  a  vibrating 
string  or  wire  free  from  vibration. 

Node. — A  nodal  point. 

Nodes,  Electric. — (1)  Points  in  a  circuit 
or  conductor  through  which  electric 
oscillations  are  passing,  which  possess 
a  constant  value  of  potential,  while  the 
potential  at  the  internode  alternates  be- 
tween two  fixed  limits.  (2)  Points  in  a 
conductor  where  the  strength  of  the  in- 
duced oscillatory  current  is  equal  to  zero. 

Ifodular  Electro  -  Metallurgical  De- 
posit.— A  coherent  electro-metallurgical 
deposit,  of  irregular  outline,  which  occurs 
whenever  the  current  density  falls  below 
its  normal  value. 

Noise. — (1)  Any  discordant  assemblage  of 
musical  tones.  (2)  Any  sound  of  too  short 
duration  to  permit  its  pitch  to  be  readily 
distinguished. 

Noisy  Arc. — A  voltaic  arc  whose  mainte- 
nance is  attended  by  frying,  hissing  or 
spluttering  sounds. 

Nominal  Candle-Power. — A  term  some- 
times applied  to  the  candle-power  of  a 
luminous  source  taken  in  a  favorable 
direction. 

Non-Arcing  Arrester.— A  non-arcing 
lightning  arrester. 

Non-Arcing  Fuse. — A  fuse  wire  formed 
of  non-arcing  metal,  which,  therefore, 
blows  without  the  formation  of  a  voltaic 
arc. 

Non-Arcing  Metal. — An  alloy  formed  of 
mixtures  of  a  certain  group  of  metals, 
which,  under  certain  conditions,  will  not 
permit  the  maintenance  of  an  alternating- 
current  ai'c  between  them. 

Non-Arcing-Metal  Lightning- Arrest- 
er.—A  lightning  arrester  employing 
electrodes  of  non-arcing  metals. 

Non- Arcing  Metals. — Metals  forming 
non-conducting  oxides  such  that  an 
alternating-current  arc  is  interrupted 
between  them  under  certain  conditions. 


Non-Automatic  Repeater. — A  manual 
repeater. 

Non-Automatic  Variable  Resistance. 
A  resistance,  the  value  of  which  is  regu- 
lated by  hand. 

Non-Conductor. — Any  substance  whose 
conductivity  is  low,  or  whose  electric  re- 
sistance is  great. 

Non-Coperiodic. — (1)  Non-synchronous. 
(2)  Devoid  of  coperiodicity.  (3)  Not 
isochronous.  (4)  Having  a  period  differ- 
ing from  the  period  considered. 

Non-Coperiodic  Electromotive  Forces, 
Currents  and  Fluxes. — Electromotive 
forces,  currents,  or  fluxes  that  are  of  dif- 
ferent periods  or  frequencies. 

Non-Electrics. — A  term  formerly  applied 
to  substances  like  the  metals  or  other 
good  conductors,  which  appeared  not  to 
be  capable  of  electrification  by  friction. 

Non-Ferric. — Devoid  of  iron. 

Non-Ferric  Inductance. — (1)  The  in- 
ductance possessed  by  a  circuit  which 
does  not  contain,  or  is  not  magnetically 
associated  with,  iron.  (2)  The  inductance 
of  a  coil  with  a  non-magnetic  core. 

Non-Ferric  Inductance-Coil. — An  in- 
ductance coil  devoid  of  iron. 

Non-Ferric  Magnetic  Circuit.— (1)  A 
magnetic  circuit  devoid  of  iron.  (2)  A  mag- 
netic circuit  containing  only  air,  wood, 
copper  or  other  non-magnetic  materials. 

Non-Homogeneous  Current-Distribu- 
tion.— (1)  A  distribution  of  current  pass- 
.ing  through  a  conductor,  in  which  there 
is  an  unequal  density  of  current  over  any 
cross  section  of  the  conductor.  (2)  The 
skin  effect. 

Non-Illumined  Electrode. — That  elec- 
trode of  a  selenium  cell  which  is  pro- 
tected from  the  direct  action  of  light. 

Non-inductive  Load. — (1)  An  induction- 
less  load.  (2)  A  load  consisting  of  re- 
sistance. 

Non-Interfering  Fire  Telegraph. — A 
system  of  fire-alarm  telegraphy  in  which 
two  calls,  simultaneously  delivered,  are 
incapable  of  interfering  with  each  other. 

Non-Interfering  Street  Signal  Box. — 
A  street  signal  box  connected  with  a  cen- 
tral station  for  the  delivery  of  an  alarm, 
in  such  a  manner  that  two  signals  given 
at  the  same  time  from  two  different  boxes 
will  not  interfere  with  each  other. 

Non-inductive  Resistance. — A  resist- 
ance devoid  of  self-induction. 

Non-Isotropic  Expansion. — A  property 
possessed  by  some  crystalline  substance  of 
unequal  expansion  along  different  axes. 


Non.] 


865 


[Nos. 


Non-Luminous  Radiation. — Radiation 
incapable  of  affecting  the  eye. 

Non-Luminous  Heat  Radiation. — (1) 
Heat  radiation  devoid  of  frequencies  ca- 
pable of  exciting  or  producing  the  sensa- 
tion of  light.  (2)  Heat  radiation  devoid 
of  luminous  frequencies. 

Non-Magnetic  Steel. — Certain  alloys  of 
iron,  such  as  manganese  steel,  or  nickel 
steel,  that  are  practically  devoid  of  the 
ability  of  being  magnetized. 

Non-Multiple  Telephone  Switch- 
board.—  (1)  A  telephone  switchboard 
which  is  either  not  so  large  as  to  have 
rendered  reduplication  necessary,  or 
which  operates  upon  a  system  in  which 
reduplication  is  dispensed  with.  (2)  A 
single  telephone-switchboard. 

Non-Oscillatory. — (1)  Not  characterized 
by  oscillations.  (2)  Maintaining  the  same 
direction  of  motion  throughout. 

Non-Oscillatory  Charge. — A  charge  ob- 
tained by  means  of  non-oscillatory  electro- 
motive forces  or  currents. 

Non-Oscillatory  Charging.— Charging 
uniformly  by  currents  which  are  always 
of  the  same  direction,  as  opposed  to  charg- 
ing with  oscillations  in  which  the  currents 
alternate. 

Non-Oscillatory  Current.— (1)  A  cur- 
rent that  is  devoid  of  periodic  oscillation. 
(2)  A  uniform  current. 

Non-Oscillatory  Discharge.— A  steady 
discharge,  or  one  characterized  by  free- 
dom from  periodic  oscillation. 

Non-Oscillatory  Intermittent  -  Cur- 
rent.— A  current  which  is  intermittent, 
but  always  in  the  same  direction,  as  dis- 
tinguished from  an  oscillatory  current 
whose  direction  alternates. 

Non- Overlapping  Winding  of  Alter- 
nator.— A  winding  in  which  the  coils 
are  mechanically  separate  and  do  not 
overlap. 

Non-Periodic  Alternating-Current. — 
An  alternating  current  whose  intensity 
varies  non-periodically. 

Non-Periodically  Varying  -  Current. 
A  continuous  current  whose  strength  is 
subject  to  non-periodical  oscillations. 

Non-Polar  Transformer. — A  term  some- 
times used  for  a  closed  iron-circuit  trans- 
former. 

Non-Polarizable. — Incapable  of  polariza- 
tion. 

Non-Polarizable  Electrodes. — Electro- 
therapeutic  electrodes  constructed  so  as 
to  avoid  the  effects  of  polarization. 

Non-Polarized  Armature. — An  arma- 
55 


ture  of  soft  iron  which  is  attracted  to- 
wards the  poles  of  an  electro-magnet  on 
the  completion  of  the  circuit,  no  matter 
in  what  direction  the  current  passes 
through  the  coils. 

Non-Reactive  Circuit. — A  circuit  which 
possesses  neither  inductance  nor  capacity, 
and,  therefore,  has  ohmic  resistance  only. 

Non-Sinusoidal  Currents.— Alternating 
currents  that  are  not  of  the  true  sinusoi- 
dal type. 

Non-Synchronous  Motor. — (1)  An  asyn- 
chronous motor.  (2)  An  alternating-cur- 
rent motor  capable  of  starting  at  any 
load.  (3)  An  induction  motor.  (4)  An 
alternating-current  motor  which  is  not 
compelled  to  run  in  synchronism  with  its 
driving  current. 

Non-Uniform  Magnetic  Flux. — Mag- 
netic flux  whose  density  varies  in  differ- 
ent portions  of  the  magnetic  circuit. 

Non-Vibrating  Filament  Lamp. — An 
incandescent  lamp  with  an  anchored  fila- 
ment. 

Normal. —  (1)  Perpendicular  to.  (2)  In 
accordance  with  rule.  (3)  Regular. 

Normal  Current. — The  current  strength 
at  which  a  system  or  apparatus  is  de- 
signed to  be  operated. 

Normal  Earth-Current.— The  usual  earth 
current. 

Normal  Magnetic-Day.— A  day  during 
which  the  values  of  the  earth's  magnetic 
elements  do  not  vary  greatly  from  their 
mean  value. 

Normal  Voltage. — The  voltage  at  which 
a  system  or  apparatus  is  designed  to  be 
operated. 

Normal  Voltaic-Arc. — A  voltaic  arc 
whose  characteristic  properties  are  those 
possessed  by  the  ordinary  arc. 

North  Magnetic  Pole.— That  pole  of  a 
magnetic  needle  which  points  approxi- 
mately to  the  earth's  geographical  north. 

North-Seeking  Magnetic  Pole.— (1)  The 
north  magnetic  pole.  (2)  That  pole  of  a 
magnet  which  turns  towards  and  approx- 
imately points  to  the  north  geographical 
pole  of  the  earth. 

Northern  Lights. — (1)  Luminous  sheets, 
columns,  arches  or  pillars  of  pale,  flash- 
ing light,  generally  of  a  reddish  color, 
seen  in  the  northern  heavens.  (2)  The 
aurora  borealis. 

Nose  Suspension  of  Motor. — The  sus- 
pension of  a  motor  in  a  car  truck  by  a 
projecting  hook  or  nose  from  above,  as 
distinguished  from  a  suspension  by  a  bar 
and  spring  from  beneath. 


Nul.] 


866 


[Ohm. 


Null  or  Zero  Method. — (1)  Any  method 
employed  in  electrical  measurements  in 
which  the  values  are  determined  by  bal- 
ancing against  them  equal  similar  values, 
and  ascertaining  such  equality  not  by  the 
deflection  of  the  needle,  but  by  the  ab- 
sence of  such  deflection.  (2)  Any  method 
of 'measurement  in  which  the  criterion  is 
no  indication  on  the  instrument  em- 
ployed, as  distinguished  from  a  method 


depending  upon  the  amounts  or  quantita- 
tive values  of  such  indications. 
Null  Point. — (1)  Such  a  point  on  a  micro- 
meter circuit  that  when  joined  or  con- 
nected with  the  secondary  circuit  of  an 
induction  coil,  the  sparks  in  the  micro- 
meter circuit  are  either  very  greatly  de- 
creased, or  are  entirely  absent.  (2)  A 
nodal  point.  . 


o 


O. — An  abbreviation  for  ohm,  the  practical 
unit  of  resistance. 

O.  K. — A  telegraphic  signal  of  acquiescence 
meaning  "all  right,"  and  said  to  be  a 
perversion  of  the  initial  letters  of  the 
phrase  "  all  correct." 

Q. — A  contraction  for  megohm. 

u. — A  contraction  for  ohm. 

o. — A  symbol  sometimes  employed  for  an- 
gular velocity. 

O.  cm.  —  An  abbreviation  proposed  for 
ohm-centimetre,  a  standard  of  resistivity 
or  conductivity. 

Oblique  Induction. — In  the  air  gap  of  a 
dynamo,  magnetic  induction  which  is 
deflected  from  the  perpendicular  to  the 
polar  surface  by  armature  reaction. 

Obscure  Heat. — Non-luminous  heat. 

Observation  Mine.  —  A  variety  of  sub- 
marine mine  that  is  fired  from  a  distant 
point  when  an  enemy's  vessel  is  observed 
to  be  within  its  destructive  area. 

Obtuse  Angle. — Any  angle  whose  value, 
is  greater  than  90°. 

Occluded-Gas  Process. — A  process  for 
the  removal  of  the  residual  atmosphere 
from  a  vacuum  tube,  or  from  the  cham- 
ber of  an  incandescent  electric  lamp, 
consisting  in  heating  the  same  to  a  high 
temperature  while  connected  with  the 
pumps,  before  sealing  off. 

Occlusion  of  Gas.  —  The  absorption  or 
condensation  of  a  gas  in  the  pores  or  on 
the  surfaces  of  various  substances. 

Ocean  Cable. — A  submarine  cable. 

Octo-Polar  Dynamo. — A  multi-polar  dy- 
namo whose  field  has  eight  poles. 

Octo-Polar  Field. — A  field  produced  by 
the  flux  of  eight  separate  magnet  poles. 

Od. — The  name  given  by  Reichenbach  to 
the  assumed  force  which  he  claimed  to 
be  the  cause  of  animal  magnetism. 

Odd  Harmonics. — In  a  complex  harmon- 
ically varying  quantity,  the  harmonics 


whose  frequencies  are  odd  multiples  of 
the  fundamental  frequency. 

Odorscope. — An  apparatus  in  which  the 
determination  of  an  odor  was  attempted 
by  the  measurement  of  the  effect  its  vapor 
or  effluvia  produced  on  a  contact  resist- 
ance. 

Odylic. — Of  or  pertaining  to  the  od  force. 

Odylic  Rays. — Rays  accompanying  the 
od  force,  which,  according  to  Reichen- 
bach, were  emitted  from  magnet  poles, 
and  various  other  bodies,  and  were  capa- 
ble of  producing  faint  luminous  sensa- 
tions in  people  sufficiently  sensitive  to 
their  influence. 

Oersted. — (1)  The  name  proposed  for  the 
C.  G.  S.  unit  of  magnetic  reluctance. 
(2)  The  reluctance  offered  to  the  passage 
of  magnetic  flux  by  a  cubic  centimetre  of 
air  when  measured  between  parallel  faces. 

Off  Position  of  Switch.— (1)  That  posi- 
tion of  a  switch  in  which  it  throws  a 
device  or  a  portion  of  a  circuit  off  from 
the  working  circuit.  (2)  The  break  posi- 
tion of  a  switch. 

Office  Cable. — (1)  A  cable  of  insulated 
wires  suitable  for  indoor  office-work. 
(2)  A  cable  leading  to  a  telegraph  office. 

Office  Loop. — (1)  In  telegraphy,  a  loop,  or 
two  wires  running  to  an  office.  (2)  In 
telegraphy,  a  loop  or  pair  of  wires  running 
from  a  circuit  in  an  office  to  some  desk  in 
the  same  office,  as  distinguished  from  a 
loop  running  to  some  distant  point. 

Offset. — A  side  connection,  or  lateral,  taken 
from  a  conduit  or  cable  for  connection  to 
a  service. 

Ohm. — (1)  The  practical  unit  of  electric 
resistance.  (2)  Such  a  resistance  as  would 
limit  the  flow  of  electricity  under  an 
electromotive  force  of  one  volt,  to  a  cur- 
rent of  one  ampere,  or  one-coulomb-per- 
second.  (3)  A  value  equal  to  109  or 
1,000,000,000  absolute  electro-magnetic 
units.  (4)  A  value  which  is  represented 


Ohm.] 


867 


[Ope. 


conventionally  in  C.  G.  S.  units  by  a  veloc- 
ity of  109  or  1,000,000,000  centimetres  per 
second. 

Ohmage. — The  value  of  an  electric  resist- 
ance expressed  in  ohms. 

Ohmic. — (1)  Of  or  pertaining  to  the  ohm. 
(2)  Having  the  nature  of  an  electric  re- 
sistance. 

Ohmic  Drop. — The  drop  in  pressure  due 
the  olimic  resistance. 

Ohmic  Resistance. — (1)  The  true  resist- 
ance of  a  conductor  due  to  its  dimensions 
and  conductivity,  as  distinguished  from 
the  spurious  resistance  produced  by 
counter-electromotive  force.  (2)  A  re- 
sistance such  as  would  be  measurable  in 
ohms  by  the  usual  methods  of  continuous- 
current  measurement. 

Ohm-Meter. — A  commercial  galvanome- 
ter employed  for  practically  measuring, 
by  the  deflections  of  a  magnetic  needle, 
the  resistance  of  any  part  of  a  circuit  to 
which  it  is  connected,  and  through  which 
a  current  flows. 

Ohm  Mile. — (1)  A  standard  of  conductivity 
of  wires  one  mile  in  length  and  having  a 
resistance  of  one  ohm  at  a  standard  tem- 
perature. (2)  The  product  of  the  weight 
of  a  mile  of  wire  and  its  resistance  in 
ohms  at  a  given  temperature.  (3)  Such 
a  mass  of  a  substance,  at  a  standard  tem- 
perature, as  would  enable  a  uniform  wire 
of  that  substance,  one  mile  in  length,  to 
offer  a  resistance  of  one  ohm. 

Ohm's  Law. — The  strength  of  a  continuous 
electric  current  in  any  circuit  is  directly 
proportional  to  the  electromotive  force 
acting  on  that  circuit,  and  inversely  pro- 
portional to  the  resistance  of  the  circuit. 

Oil-Cooled  Transformer.  —  A  trans- 
former that  is  cooled  by  means  of  oil. 

Oil  Cup. — A  cup  filled  with  lubricating 
oil,  so  supported  that  its  oil  is  slowly  fed 
to  a  shaft  and  bearing,  or  in  general,  to 
the  rubbing  parts  of  a  machine. 

Oil  Guard. — (1)  A  guard  of  sheet  metal  sup- 
ported so  as  to  catch  any  drops  of  oil  that 
may  be  thrown  upon  its  surface,  and  thus 
protect  any  person  or  apparatus.  (2)  A 
guard  placed  over  a  direct-driven  dynamo, 
to  prevent  oil  from  being  thrown  on  it 
by  the  revolving  engine. 

Oil-Insulated. — Insulated  by  means  of  oil. 

Oil  Insulator. — A  fluid  insulator  con- 
taining oil. 

Oil  Insulator  for  Storage  Battery.— An 
oil  insulator  provided  for  the  support  of 
a  storage  battery. 

Oil  Paper. — An  insulating  material  con- 


sisting of  paper  that  has  been  soaked  in 
an  insulating  oil. 

Oil  Transformer. — (1)  A  transformer  im- 
mersed in  oil  in  order  to  ensure  and 
maintain  high  insulation.  (2)  An  oil- 
insulated  transformer. 

Okonite. — A  variety  of  insulating  material. 

Olivette  Box. — A  box  containing  an  arc= 
lamp  provided  with  an  aperture  closed  by 
colored  glass,  and  employed  for  the  pur- 
pose of  obtaining  a  uniform  field  of  color 
over  a  large  surface,  such  as  a  stage  scene. 

Omnibus  Bars. — (1)  Heavy  bars  of  cop- 
per connected  directly  to  the  poles  of  a 
dynamo  in  a  central  station,  and,  there- 
fore, receiving  their  entire  current. 
(2)  Main  conductors  common  to  two  or 
more  dynamos  in  an  electrical  generating 
plant. 

Omnibus  Wires. — 'A  word  sometimes 
used  for  bus-bars. 

On  Position  of  Switch.— (1)  That  posi- 
tion of  a  switch  in  which  it  throws  a  de- 
vice, or  portion  'of  a  circuit,  on  to  a  work- 
ing circuit.  (2)  The  make  position  of  a 
switch. 

One-Coil  Transformer.— A  word  some- 
times employed  for  auto-transformer. 

One-Fluid  Voltaic  Cell. — A  name  some- 
times given  to  a  single-fluid  voltaic  cell. 

One-Layer  Armature- Winding.— (1)  An 
armature  winding  consisting  of  but  a 
single  layer  of  wire.  (2)  A  winding 
which,  although  it  may  consist  of  several 
layers,  would  be  possible  of  application 
in  a  single  layer,  as  distinguished  from  a 
two-layer  armature  which  must  be  laid 
in  two  layers. 

One-Metal  Cell. — An  identical  electrode 
cell.  (2)  A  cell  in  which  both  elements 
are  composed  of  one  metal. 

One- Way  Door-Trigger.— A  door-trigger 
which  operates  on  the  opening  of  the  door 
only. 

Opacity.— Possessing  the  property  of  non- 
transparency  to  radiation. 

Open-Arc. — A  non-enclosed  voltaic  arc. 

Open-Box  Conduit.— A  conduit  consist- 
ing of  an  open  box  of  wood  placed  in  a 
trench  and  closed  with  a  wooden  cover, 
after  the  introduction  of  the  cable. 

Open  Car- Wheel. — A  form  of  car-wheel 
in  which  the  space  between  the  flange 
and  the  axle  is  provided  with  symmetri- 
cal perforations. 

Open  Circuit. — A  broken  circuit,  or  a  cir- 
cuit whose  conducting  continuity  is 
broken. 

Open-Circuit  Battery.— A  voltaic   bat- 


Ope.] 


868 


[Ope. 


tery  which  is  normally  on  open  circuit, 
and  which  is  used  continuously  on  closed 
circuit  only  for  comparatively  small  por- 
tions of  time. 

Open-Circuit  Burglar-Alarm. — A  bur- 
glar alarm  whose  battery  is  normally  on 
open  circuit,  and  is  brought  into  action 
on  the  closing  of  such  circuit  as  a  door, 
window,  or  other  point. 

Open-Circuit  Current  of  Transformer. 
A  term  sometimes  employed  for  the  leak- 
age current  of  a  transformer. 

Open-Circuit  Electric  Oscillations.— 
Electric  oscillations  produced  in  open  cir- 
cuits by  the  presence  of  electric  surgings 
in  neighboring  circuits. 

Open-Circuit  Induction. — The  induction 
produced  in  an  open  circuit  by  means  of 
electric  surgings  in. neighboring  circuits. 

Open-Circuit  of  Triphase  Connections. 
The  star-connection  of  triphase  circuits. 

Open-Circuit  Single-Current  Signal- 
ling.— A  system  of  single-current  signal- 
ling in  which  the  sending  batteries  placed 
at  each  station  are  in  circuit  during  sig- 
nalling only. 

Open-Circuit  Thermostat.— A  thermo- 
stat maintained  normally  on  an  open-cir- 
cuit. 

Open-Circuit  Transformer.— (1)  A  trans- 
former whose  magnetic  circuit  is  partly 
completed  through  air.  (2)  An  aero-fer- 
ric-circuit transformer. 

Open-Circuit  Voltaic  Cell. — A  voltaic 
cell  that  cannot  be  kept  on  closed  circuit 
with  a  comparatively  small  resistance, 
for  any  considerable  time,  without  seri- 
ous polarization. 

Open-Circuit  Voltmeter.— (1)  A  volt- 
meter in  which  the  points  of  a  circuit 
where  the  potential  difference  is  to  be 
measured,  are  connected  with  an  open- 
circuit  to  give  indications  by  means  of 
the  charges  so  produced.  (2)  An  electro- 
meter-voltmeter. 

Open-Circuited.— Provided  with  an  open 
or  broken  circuit. 

Open-Circuited  Conductor.— (1)  A  con- 
ductor not  forming  a  closed  circuit.  (2) 
A  conductor  not  closed  on  itself,  and 
whose  metallic  continuity,  therefore,  is 
not  complete,  but  through  which  an 
oscillatory  discharge  is  capable  of  passing. 

Open  -  Circuited  Discharge.  —  A  dis- 
charge taking  place  through  a  circuit 
whose  metallic  continuity  is  incomplete. 

Open-Circuited  Oscillation.— An  elec- 
tric oscillation  or  surging  taking  place  in 
an  open-circuited  conductor. 


Open-Circuit  Thermostat. — A  thermo- 
stat maintained  normally  on  an  open-cir- 
cuit. 

Open  -  Circuited  Transformer.  —  An 
aero-ferric-circuit  transformer. 

Open-Coil  Armature.  —  An  armature, 
some  of  whose  coils  are  on  open-circuit 
during  a  portion  of  the  rotation  of  the 
armature. 

Open-Coil  Armature- Windings. — The 
windings  of  an  open-coil  dynamo  arma- 
ture. 

Open  -  Coil  Disc  Dynamo  -  Electric 
Machine. — (1)  A  disc- wound  dynamo- 
electric  machine  whose  armature  coils  are 
open-circuited  during  part  of  each  revo- 
lution. (2)  An  open-coil  dynamo-elec- 
tric machine,  the  armature  of  which  is 
disc  shaped. 

Open  -  Coil  Drum  Dynamo  -  Electric 
Machine. — An  open-coil  dynamo-electric 
machine,  the  armature  of  which  is  drum- 
wound. 

Open-Coil  Dynamo. — A  dynamo  pro- 
vided with  an  open-coil  armature. 

Open  -  Coil  Ring  Dynamo  -  Electric 
Machine. — An  open-coil  dynamo-electric 
machine,  the  armature  of  which  is  ring- 
wound. 

Open  -  Iron  -  Circuit  Converter.  —  An 
open-iron-circuit  transformer. 

Open-Iron-Circuit  Transformer. — An 
aero-ferric  transformer. 

Open-Iron-Magnetic  Circuit. — An  aero- 
ferric  magnetic  circuit. 

Open  Magnetic  Core. — Any  iron  core 
which  forms  a  portion  of  an  aero-ferric 
circuit. 

Open  Trolley-Car. — A  trolley-car  open 
on  the  sides  and  ends. 

Open-Wire  Symmetrical  Twist. —  A 
system  of  stringing  aerial  telephone  wives, 
so  as  to  avoid  cross  talk,  in  which  all  the 
wires  on  a  pole  are  helically  twisted  right- 
handedly  along  the  line,  one  step  being 
taken  at  each  successive  pole. 

Open  Wiring. — (1)  Wiring  that  has  been 
purposely  left  exposed  to  view.  (2)  Wir- 
ing supported  on  cleats  or  insulators  as 
distinguished  from  channelled,  panelled, 
or  covered  wiring. 

Open  Work. — Open  wiring. 

Opening  a  Circuit. — Breaking  a  circuit. 

Opening  Shock. — The  physiological  shock 
produced  on  opening  or  breaking  an  elec- 
tric circuit  containing  self-induction. 

Operator's  Head  Telephone.— A  head- 
gear telephone. 


Ope.j 


869 


[Osc. 


Operator's  Position. — The  space  or  posi- 
tion allotted  to  each  operator  in  front  of 
a  multiple  telephone  switchboard. 

Operator's  Set. — A  telephone  set  at  a 
central  station  employed  by  the  operator. 

Operator's  Shelf. — A  shelf  at,  on,  or 
above  a  multiple  telephone  switchboard 
for  supporting  the  apparatus  used  by  the 
operators. 

Ophthalmoscope.— An  apparatus  for  ex- 
amining the  living  retina. 

Ophthalmoscopic. — Of  or  pertaining  to 
the  ophthalmoscope. 

Opposed  Electromotive  Forces. — Elec- 
tromotive forces  that  are  opposed  either 
to  each  other  or  to  some  other  already 
existing  electro-motive  force. 

Opposed    Magnetomotive    Forces.  — 

Magnetomotive  forces  that  are  opposed 
either  to  each  other,  or  to  some  other  al- 
ready existing  magnetomotive  force. 

Optic  Angle.— The  angle  contained  be- 
tween the  optical  centres  of  both  eyes  at 
any  point  to  which  they  may  be  directed. 

Optic  Axis. — (1)  The  right  line  passing 
through  the  eye,  so  that  the  eye  is  sym- 
metrical on  all  of  its  sides.  (2)  The  axis 
of  symmetry  of  a  crystal.  (3)  The  prin- 
cipal axis  of  the  eye,  or  its  axis  of  figure. 

Optic  Nerve. — The  nerve  of  vision. 

Optics.— That  branch  of  physics  which 
treats  of -the  properties  and  phenomena  of 
light. 

Optical  Bench. — A  graduated  support  em- 
ployed for  varying  the  distance  between 
fixed  and  movable  optical  appliances. 

Optical  Efficiency  of  Light.— The  ratio 
between  the  obscure  and  the  luminous 
radiation. 

Optical  Galvanometer. — A  galvanometer 
whose  indications  are  based  on  the  mag- 
netic rotary  power  of  liquids. 

Optical  Strain. — A  deformation  produced 
in  a  plate  of  glass,  or  other  transparent 
medium,  by  the  action  of  a  stress,  attended 
by  a  change  in  some  of  the  optical  prop- 
erties of  such  medium. 

Optical  Telegraph. — A  name  sometimes 
applied  to  a  semaphore. 

Oral  Annunciator. — An  electric  annun- 
ciator that  is  operated  by  a  puff  of  breath 
transmitted  through  an  ordinary  speak- 
ing tube. 

Ordinary  Jacks.— In  a  multiple  tele- 
phone-switchboard, the  reduplicated  jacks 
of  each  subscriber  appearing  successively 
in  each  section,  as  distinguished  from  the 
local  or  answering  jack,  which  appears 
at  a  single  panel. 


Ordinary  Lines.— The  lines  used  for  con- 
versation in  a  call-wire  system  of  tel- 
ephony, as  distinguished  from  the  wires 
employed  for  calling. 

Ordinate. — In  graphics,  a  distance  taken 
on  a  line  called  the  axis  of  ordinates 

Ordinary  Relay. — A  non-polarized  relay. 

Organ,  Electric.— A  wind  organ  in  which 
the  escape  of  air  into  the  different  pipes 
is  electrically  controlled,  or  propelled. 

Orientation  of  Magnetic  Needle.— The 
coming  to  rest  of  a  magnetic  needle  in 
the  direction  of  the  earth's  magnetic  flux. 

Originating  Call.— The  call  t>f  the  sub- 
scriber who  asks  to  be  connected  with 
some  other  subscriber,  as  distinguished 
from  any  other  call  which  may  follow  in 
the  process  of  securing  connection. 

Originating  Operator. —  In  telephonic 
communication  passing  through  more 
than  one  exchange,  the  operator  who  is 
nearest  to  the  calling  subscriber,  and  con- 
sequently the  operator  who  first  delivered 
the  call,  as  distinguished  from  other  oper- 
ators whose  assistance  may  have  been 
called  in. 

Oscillating  Current.— (1)  An  oscillatory 
current.  (2)  A  periodically  alternating 
current  usually  of  diminishing  ampli- 
tude. 

Oscillating-Current  Transformer.— A 
transformer  operated  by  an  oscillating 
current. 

Oscillating  Discharge. — An  oscillatory 
discharge. 

Oscillating  Needle.— A  needle  of  oscilla- 
tion. 

Oscillation. — A  to-and-f  ro  motion  or  vibra- 
tion. 

Oscillation  of  a  Function.— The  differ- 
ence between  the  greatest  and  the  least 
values  which  a  function  assumes  in  a 
given  interval. 

Oscillations,  Electric.— (1)  The  series  of 
partial  intermittent  discharges  of  which 
the  apparent  instantaneous  disruptive  dis- 
charge of  a  Leyden  jar,  through  a  small 
resistance,  consists.  (2)  Free  electric 
vibrations  of  a  disturbed  electric  system. 
(3)  Electric  surgings. 

Oscillator. — Any  device  for  producing 
oscillations. 

Oscillator,  Electric.— A  device  for  pro- 
ducing electric  currents  of  a  constant 
period,  independently  of  variations  in  its 
driving  force. 

Oscillatory. — Vibratory,  or  characterized 

by  periodic  to-and-fro  movements. 
Oscillatory    Charging.  —  Charging    by 


Osc.] 


870 


[Out. 


means  of  an  oscillatory  electromotive 
force  or  current. 

Oscillatory  Current. — A  current  which 
oscillates  or  performs  periodic  vibrations 
usually  of  diminishing  amplitude. 

Oscillatory  Discharge. — (1)  An  appar- 
ently instantaneous  discharge  of  a  Ley  den 
jar  or  condenser,  which  in  reality  consists 
of  a  number  of  successive  discharges.  (2) 
A  discharge  which  periodically  decreases 
by  a  series  of  oscillations. 

Oscillatory  Dynamo. — A  dynamo  whose 
armature  coils  have  electromotive  forces 
generated.in  them  by  a  vibratory  or  oscil- 
latory motion  through  a  magnetic  field, 
instead  of  the  usual  rotary  motion. 

Oscillatory  Electric  Displacement. — A 
displacement  of  an  oscillatory  character 
produced  in  a  dielectric. 

Oscillatory  Electric  Inductance.— Os- 
cillatory  inductance. 

Oscillatory  Electromotive  Force. — A 
rapidly  periodic  electromotive  force, 
usually  rapidly  diminishing  in  amplitude. 

Oscillatory  Generator. — An  oscillatory 
dynamo. 

Oscillatory  Inductance. — Inductance  in 
the  circuit  of  electric  oscillations. 

Oscillatory  Induction. — A  name  some- 
times applied  to  open-circuit  induction. 

Oscillatory  Intermittent  Currents.— 
Intermittent  currents  which  are  oscillat- 
ory in  character,  such  as  the  oscillatory 
discharges  of  a  static  machine. 

Oscillograph. — (1)  An  instrument  for  re- 
cording rapid  variations  of  an  electrical 
current  or  pressure,  usually  consisting  of 
a  combination  of  a  suitable  form  of  gal- 
vanometer with  a  photographic  recording 
apparatus.  (2)  A  cathode-ray  tube  in 
which  the  cathode  rays  are  deflected  by 
the  application  of  a  magnetic  field. 

Osmometer. — An  apparatus  for  measuring 
osmose. 

Osmose. — An  unequal  mixing  of  liquids  of 
different  densities  through  the  pores  of  a 
separating  medium. 

Osmose,  Electric. — The  unequal  differ- 
ence of  diffusion  between  two  liquids 
placed  on  opposite  sides  of  a  diaphragm, 
produced  by  the  passage  of  an  electric 
current  through  the  diaphragm. 

Osmosis. — A  term  sometimes  used  for 
osmose. 

Osmotic. — Of  or  pertaining  to  osmose. 

Osmotic  Pressure.— (1)  The  pressure  pro- 
duced by  osmose.  (2)  The  virtual  gas- 
eous pressure  of  a  dissolved  substance. 

Osmotic  Pressure. — (1)  Pressure  produced 


by  osmose.  (2)  Pressure  in  a  solution 
due  to  the  presence  of  a  dissolved  sub- 
stance. 

Osteotome,  Electric.  —  An  electrically 
propelled  circular  saw  employed  in  the 
surgical  cutting  of  bones. 

Outboard  Bearing. — (1)  A  journal  bearing 
projecting  beyond  the  base  frame  of  a 
machine  for  giving  adequate  support  to  a 
long  or  heavy  shaft.  (2)  A  separate 
journal  bearing  supported  outside  the 
frame  of  a  machine. 

Outboard  Bearing  of  Dynamo-Electric 
Machine. — (1)  A  bearing  projecting  be- 
yond the  base  frame  of  a  dynamo-electric 
machine  for  the  purpose  of  adequately 
supporting  the  rotor.  (2)  A  bearing  for 
the  shaft  of  a  dynamo  rotor  supported 
independently  of  the  base  of  the  dynamo. 

"  Out-Current "  of  Telephone  Relay. 
The  current  which  is  sent  out  by  a  tele- 
phone relay  or  repeater. 

"Out-Door"  Transformer. — A  trans- 
former placed  outside  a  building  on  the 
sides  of  its  walls,  or  on  suitably  selected 
posts. 

Outers. — (1)  The  outside  conductors  of  a 
three-wire  system  as  distinguished  from 
the  neutral  conductor.  (2)  In  telephony, 
the  external  pair  of  springs  of  a  telephone 
jack. 

Outgoing  Call. — A  call  issued  from  an  ex- 
change, as  distinguished  from  an  incom- 
ing call. 

Outgoing-Call  Trunk-Line. — A  trunk 
line  terminating  at  a  central  telephone 
station  and  conveying  calls  which  are 
transmitted  from  the  station,  as  distin- 
guished from  an  incoming  call  line  on 
which  such  calls  are  received. 

Outgoing  Current. — The  current  sent  out 
over  a  line  from  a  station  as  distinguished 
from  the  received  current,  or  the  return- 
ing current. 

Outgoing  End. — The  end  of  a  junction 
telephone  wire  at  which  calls  are  trans- 
mitted. 

Outgoing  Lines. — (1)  Lines  in  a  tele- 
phone exchange  on  which  calls  are  for- 
warded or  transmitted,  as  distinguished, 
from  incoming  lines.  (2)  Outgoing 
wires. 

Outgoing  Side  of  Telephone  Switch- 
board.— (1)  The  side  of  a  switchboard  at 
which  the  conductors  leave  it.  (2)  The 
side  of  a  switchboard  to  which  calls  are 
transferred  or  from  which  calls  are  trans- 
mitted. 

Outgoing  Signals.— Signals  sent  out  over 


Out.] 


871 


[Ove. 


a  telegraphic  line  by  the  outgoing  cur- 
rents. 

Outgoing  "Wires.  —  Wires  by  means  of 
which  the  current  is  led  out  from  a  gen- 
erator or  station. 

Outlet. — (1)  A  place  where  branch  wires 
come  out  in  a  wall  or  ceiling  for  connec- 
tion to  a  switch,  lamp  or  other  device. 
(2)  In  a  system  of  incandescent-lamp  dis- 
tribution, the  places  in  a  building  where 
the  fixtures  or  lamps  are  attached. 

Outlet  Block. — (1)  A  fuse  block  placed  at 
or  near  an  outlet.  (2)  A  block  containing 
an  outlet  fuse  wire. 

Outlet  Box. — A  box  placed  at  or  near  an 
outlet  for  the  ready  making  or  changing 
of  electric  connections  with  the  outlet 
conductors. 

Outlet  Insulator. — Any  insulator  em- 
ployed at  an  outlet. 

Output. — The  useful  energy  or  activity 
given  out  by  any  machine. 

Output  of  Dynamo-Electric  Machine. 
(1)  The  electric  power  of  the  current 
developed  by  a  dynamo-electric  generator 
or  transformer,  at  its  delivery  terminals 
expressed  in  volt-amperes,  watts,  or  kilo- 
watts. (2)  The  available  mechanical 
power  developed  by  a  motor,  or  the  power 
delivered  at  its  pulley  or  shaft. 

Output  Wires. — Wires  connected  with  a 
distribution  box  which  take  their  supply 
from  the  box. 

Outrigger. — An  arm  horizontally  fastened 
to  a  pole  for  the  purpose  of  trussing  it. 

Outrigger  for  Arc-Lamp. — A  device  for 
suspending  an  electric  arc-lamp  so  as  to 
cause  it  to  stand  out  from  the  wall  of  a 
building. 

Outrigger  Torpedo. — A  pole  or  spar  tor- 
pedo. 

Outside  Wiring. — (1)  Any  wiring  for  a 
circuit  outside  of  a  house  or  other  build- 
ing. (2)  Out-door  wiring. 

Outside  Work. — Out-of-door  wiring. 

Over-Compounded. — Such  a  compound- 
ing of  a  dynamo-electric  machine  as  pro- 
duces under  an  increase  of  load  an  increase 
of  voltage  at  its  terminals. 

Over-Compounded  Dynamo. —  A  dy- 
namo in  whicli  the  magneto-motive  force 
of  its  series  coils  not  only  compensates 
for  the  drop  in  the  armature,  but  also  for 
the  drop  in  a  conductor  leading  from  the 
generators  to  the  motors  or  translating 
devices,  thus  permitting  the  external 
conductors  to  be  regarded  electrically  as 
forming  an  extension  of  the  armature 
winding,  and  thus  permitting  the  genera- 


tor to  deliver  a  constant  pressure  at  its 
final  terminals  at  the  motor  or  device. 
Overflow  of  Leyden  Jar.— A  term 
sometimes  employed  for  the  discharge  of 
a  Leyden  jar  by  a  disruptive  discharge 
around  its  edge. 

Overhead  Conductor.— An  aerial  con- 
ductor. 

Overhead  Feeders.— Aerial  feeders,  as 
distinguished  from  buried  or  under- 
ground feeders. 

Overhead  Lines. — A  term  applied  to 
aerial  telegraph,  telephone,  electric  light 
or  power  lines,  that  run  overhead,  in  con- 
tradistinction to  similar  underground 
lines. 

Overhead  Mains.— Any  system  of  aerial 
mains. 

Overhead  Switch.— (1)  A  switch  con- 
trolling an  overhead  circuit.  (2)  A  can- 
opy switch.  (3)  A  switch  placed  over- 
head. (4)  A  switch  placed  above  a  motor- 
man  on  a  car  so  as  to  be  within  his  reach. 

Overhead  Trolley-System.— (1)  An  aerial 
trolley  wire  system.  (2)  A  system  of 
electric-street-car  propulsion  in  which  the 
required  current  is  taken  from  an  over- 
head trolley- wire. 

Overhead  Trolley- Wire.— An  ordinary 
aerial  trolley  wire. 

Overhead  Trolley. — A  trolley  employed 
in  an  overhead  trolley-system. 

Overhead  Wires. — Aerial  wires. 

Overland  Telegraph. — Any  telegraphic 
circuit  provided  with  aerial  conductors, 
as  distinguished  from  a  submarine  or  an 
underground  telegraph. 

Overlap  Test. — A  localization  test  for  a 
single  fault  in  a  single  telegraph  line,  by 
observing  the  resistance  from  each  end 
and  deducting  therefrom  half  of  the 
amount,  by  which  the  sum  of  these  resist- 
ances overlap  the  total  conductor  resist- 
ance of  the  line,  to  determine  the  posi- 
tion occupied  by  the  fault. 

Overlap  Splice. — A  splice  of  a  rope  or 
cable  in  which  the  strands  of  one  part 
overlap  the  parts  of  the  other,  as  distin- 
guished from  a  splice  in  which  the  strands 
of  both  parts  interlace. 

Overlapping  Block  System. — An  elec- 
trically operated  block  system  in  which 
the  signals  automatically  delivered  by  a 
train  occupying  one  section,  appear  at  a 
considerable  distance  behind  the  train  on 
the  preceding  section. 

Overlapping  Winding  of  Alternator 
Armature. — A  winding  in  which  the 
successive  coils  overlap,  as  distinguished 


Ove.] 


872 


[Pac. 


from  a  winding  in  which  successive  coils 
are  mechanically  separated. 
Overload. — (1)  Any  load  whose  value  ex- 
ceeds that  of  the  normal.    (2)  An  exces- 
sive load. 

Overload  of  Electric  Motor. —  (1)  A 
load  greater  than  that  which  an  electric 
motor  can  carry  with  its  greatest  effi- 
ciency of  operation.  (2)  Any  load  which 
causes  injurious  heating  of  a  motor.  (3) 
Any  load  exceeding  the  full  load  for 
which  a  motor  is  designed. 

Overload  Storage-Battery  Switch. — 
A  switch  placed  in  a  discharging  circuit 
of  a  storage  battery,  arranged  so  as  to 
automatically  break  the  circuit  of  the 
battery  should  the  discharge  become  ex- 
cessive. 

Overload  Switch. — A  switch  designed  to 
automatically  open  a  circuit  upon  the 
occurrence  of  an  overload. 

Over-Load  Switch  of  Accumulator. — 
(1)  A  switch  inserted  in  the  circuit  of  a 
storage  battery  which  automatically 
opens  or  introduces  resistance  into  the 
circuit  when  the  current  becomes  exces- 
sive. (2)  An  overload  storage-battery 
switch. 

Overloaded  Conductor. — A  conductor 
carrying  any  electric  current  heavier 
than  the  normal  current  for  which  it  was 
intended. 

Over-Maximal  Contraction. —  An  in- 
crease in  the  electric  stimulation  of  a 
motor  nerve  beyond  the  point  where  an 
apparent  maximum  stimulus  has  been 
reached. 

Over-Running  of  Incandescent 
Lamps. — The  operation  of  incandescent 
lamps  at  a  pressure  above  the  normal. 

Over-Running  Trolley. — An  overhead 
trolley,  as  distinguished  from  an  under- 
ground trolley. 


"  Overshoot." — To  err  in  compensation 
by  exceeding  in  adjustment,  so  as  to  over- 
pass the  limit. 

Overtone  Currents. — Electric  currents 
of  harmonic  frequencies  accompanying  a 
fundamental  periodic  current. 

Overtones. —  Additional  faint  tones  of 
higher  frequency  than  the  fundamental, 
and  some  multiple  thereof,  associated 
with  the  fundamental  and  tending  to  give 
it  its  characteristic  quality. 

Overtones,  Electric. — Electric  upper  har- 
monics or  rates  of  alternation  higher  than 
the  fundamental  rate. 

Overtype  Dynamo. — A  dynamo-electric 
machine  whose  armature  bore  or  cham- 
ber is  placed  above  the  field-magnet  coils 
instead  of  below  them. 

Overtype  Magnet.— A  form  of  horseshoe 
bi-polar  electro-magnet,  standing  verti- 
cally over  the  armature  between  its  poles. 

Over-Winding  of  Series  Motor. — A 
series  motor  whose  series-field  winding  is 
unduly  strong. 

Over-Wound  Motor  Field. — (1)  A  motor 
field  so  wound  that  its  full  strength  is 
nearly  attained  with  considerably  less 
than  the  normal  current.  (2)  A  term 
sometimes  employed  for  an  over-com- 
pounded motor  field. 

Oyster  Pitting. — A  form  of  incandescent 
lamp-fitting  employed  on  board  a  ship  for 
water-tight  bulkheads  which  cannot  be 
pierced. 

Ozite. — A  form  of  insulating  material. 

Ozokerite. — A  form  of  insulating  material. 

Ozone. — An  allotropic  modification  of  oxy- 
gen which  possesses  more  powerful  oxy 
dizing  properties  than  ordinary  oxygen, 
and  formed  by  electric  discharges  in  air. 

Ozonizer. — An  apparatus  for  producing 
ozone  by  means  of  electric  discharges. 


P. — A  symbol  for  power. 

P. — A  symbol  for  electric  power. 

P. — A  symbol  proposed  for  pressure. 

4>. — A  symbol  for  quantity  of  magnetic  flux. 

P.  C. — A  contraction  for  primary  current. 

P.  D.  or  p.  d. — A  contraction  frequently 
employed  for  potential  difference. 

P.  P.  D. — A  contraction  for  primary  po- 
tential difference. 

Pacinotti    Projections.— Radial   projec- 


tions or  teeth,  in  an  armature  core,  so  ex- 
tending from  the  central  shaft  as  to  form 
slots,  pockets  or  armature  chambers,  for 
the  reception  of  the  armature  coils. 

Pacinotti  Ring. — A  ring-shaped  arma- 
ture-core provided  with  projections  em- 
ployed by  Pacinotti  to  receive  the  arma- 
ture windings  in  his  generator. 

Pacinotti  Teeth. — A  term  sometimes  used 
for  Pacinotti  projections. 

Packing  of  Telephone  Dust  Transmit- 


Pag.] 


873 


[Par. 


ter. — The  partial  cohering  of  the  parti- 
cles of  granulated  carbon  in  a  dust  trans- 
mitter into  a  solid  cake,  thus  seriously  in- 
juring the  delicacy  of  the  apparatus. 

Page  Effect. — Faint  sounds  produced 
when  a  piece  of  iron  is  rapidly  magnet- 
ized and  demagnetized. 

Palladium. — A  metal  of  the  platinum 
group. 

Palladium  Alloys. — Various  alloys  of 
palladium  with  other  metals,  some  of 
which  are  entirely  devoid  of  paramag- 
netic properties,  and  are,  therefore,  em- 
ployed for  the  hair-springs  of  watches,  in 
order  to  render  them  free  from  the  dis- 
turbing influence  of  strong  magnetic 
fields. 

Palette  Combination  Wire-Gauge. — A 
wire-gauge  measurer  consisting  of  a 
graduated  cam  pivoted  in  a  frame  hook, 
so  that  the  wire  to  be  measured  is  gripped 
between  the  hook  and  cam. 

Pan-Cake  Armature-Coil. — A  flat  arma- 
ture coil  applied  to  and  secured  upon  the 
surface  of  an  armature. 

Panel  Board. — A  switchboard  which  is 
not  prepared  in  one  piece,  but  which  is 
constructed  and  connected  in  panels. 

Panel  Feeder. — The  feeder  connected 
with  the  bus-bars  of  any  particular  panel 
on  a  switchboard. 

Panel  Fuse. — A  fuse  placed  in  the  circuit 
of  a  particular  panel  on  a  switchboard. 

Panel  of  Switchboard. — One  of  the  sep- 
arate vertical  sub-sections  of  a  composite- 
ly  constructed  switchboard. 

Panel  Pressure. — The  pressure  which  is 
maintained  at  a  particular  switchboard 
panel. 

Panel  Reflector. — A  reflector  composed 
of  strips  or  panels  of  silvered  glass,  or 
other  good  reflecting  material. 

Panelled  Conductors.  —  Conductors 
placed  in  mouldings. 

Panelled  "Wire. — Wire  placed  inside 
mouldings  or  panels. 

Pan-Telegraphy. — Fac-simile  or  auto- 
matic telegraphy. 

Pan-Telephone. — A  name  proposed  for  a 
certain  sensitive  form  of  telephone. 

Paper  Cable.-^-(l)  A  paper-insulated  cable. 
(2)  A  cable  in  which  paper  is  the  solid 
insulator  employed. 

Paper  Carbons. — Incandescent  lamp  fila- 
ments formed  of  carbonized  paper. 

Paper  Condenser. — A  condenser  in  which 
sheets  of  paper  covered  by  some  good  in- 
sulating material  are  employed  as  a 
dielectric. 


Paper  Cut-Out. — A  term  sometimes  used 

for  film  cut-out. 
Paper-Film  Cut-Out.— A  paper  or  film 

cut-out. 

Paper  Insulation. — Insulation  obtained 
•by  paper. 

Paper  Perforator. — An  apparatus  em- 
ployed in  automatic  telegraphy  for  punch- 
ing in  a  strip  of  paper,  the  circular  or 
elongated  spaces  that  produce  the  dots 
and  dashes  of  the  Morse  alphabet. 

Paper  Telephone  Cable. — A  paper-insu- 
lated telephone  cable. 

Parabolic. — Of  or  pertaining  to  a  parabola. 

Parabola. — A  conic  section  formed  by  the 
intersection  of  a  right  cone  by  a  plane 
parallel  to  any  side. 

Parabolic  Reflector.— (1)  A  reflector  or 
mirror  the  surface  of  which  is  a  parabo- 
loid, or  such  as  would  be  obtained  by  the 
revolution  of  a  parabola  around  its  axis. 
(2)  A  reflector  employed  in  connection 
with  electro-magnetic  radiation  of  which 
the  section  perpendicular  to  the  long  axis 
has  the  form  of  a  parabola,  the  focus  of 
which  is  occupied  by  the  electric  oscil- 
lator. 

Paradox. — (1)  Something  which  seems  to 
contradict  the  ordinary  laws  of  nature, 
but  which  is  in  reality  the  expression 
of  such  law.  (2)  A  seeming  inconsistency, 
or  self-contradiction. 

Paraffine. — A  solid  hydro-carbon  possess- 
ing high  insulating  powers. 

Paraffined  Wire. — Wire  wrapped  or 
braided  with  some  textile  material  and 
afterwards  coated  with  paraffine. 

Paraffining. — Coating  or  covering  with 
paraffine. 

Paragrele. — A  French  term  for  a  light- 
ning rod,  intended  to  protect  a  field 
against  the  destructive  action  of  hail. 

Parallax. — The  apparent  displacement  of 
the  position  of  an  object,  relatively  to 
points  in  front  or  behind  it,  due  to  a  dif- 
ference in  the  point  of  view. 

Parallax  Error. — An  error  in  reading  the 
position  of  a  pointer  on  a  scale  due  to  par- 
allax. 

Parallel  Arc-Circuit. — A  word  sometimes 
used  for  multiple  circuit. 

Parallel  Circuit. — A  term  sometimes  used 
for  multiple  circuit. 

Parallel  Conical  Conductors. — A  sys- 
tem of  conical  conductors,  or  of  conduc- 
tors successively  diminishing  in  diameter, 
employed  in  parallel  distribution. 

Parallel  Connected  Sources.— A  num- 
ber of  separate  sources  connected  in 


Par.] 


874 


[Par. 


parallel,  so  as  to  be  capable  of  acting  as  a 
single  source. 

Parallel-Connected  Triphasers.— Two 
or  more  triphasers  connected  in  parallel 
to  a  common  .set  of  triphase  bus- bars  or 
mains. 

Parallel-Connections  of  Alternators.— 
A  number  of  alternators  connected  to 
a  single  pair  of  leads  or  bus-bars  in  paral- 
lel or  multiple-arc. 

Parallel  Coupling. — A  term  sometimes 
employed  for  the  parallel  connection  of 
alternators. 

Parallel  Distribution.— A  distribution 
of  electric  energy  in  which  the  receptive 
devices  are  arranged  between  one  or  more 
pairs  of  parallel  conductors,  extending 
to  the  limits  of  the  system. 

Parallel  Feeding.— (1)  Furnishing  the 
current  required  for  the  operation  of  a 
number  of  receptive  devices  connected 
in  parallel.  (2)  Multiple-arc  distribution 
in  which  a  pair  of  mains  is  supplied  at 
one  end  as  distinguished  from  an  anti- 
parallel  system. 

Parallel-Series.— A  term  sometimes  ap- 
plied to  a  multiple-series  connection. 

Parallel  Transformer.— (1)  A  trans- 
former connected  with  a  parallel-system 
of  distribution.  (2)  A  transformer  that 
is  connected  to  mains  in  parallel.  (3)  A 
transformer  whose  secondary  coils  are 
connected  in  parallel. 

Parallel  Tree-Circuit.— A  system  of 
parallel  distribution  in  which  the  dis- 
tributing mains  diverge  and  ramify  from 
a  common  centre  or  central  station,  di- 
minishing in  size  as  they  proceed. 

Parallel- Wire  Stretcher.— A  clamping 
tool  for  gripping  and  stretching  wire. 

Parallel-Working  of  Dynamo-Electric 
Machines. — The  working  of  two  or  more 
dynamos  in  pai'allel. 

Parallelogram  of  Forces.— A  parallo- 
gram  whose  sides  represent  in  length  and 
direction  the  intensity  and  direction  of  two 
co-acting  forces,  and  whose  intermediate 
diagonal  represents  the  resultant  force. 

Paramagnet.— (1)  A  magnet  produced  by 
iron  or  other  magnetic  substance.  (2)  A 
ferromagnet. 

Paramagnetic. — (1)  Possessing  the  proper- 
ties ordinarily  recognized  as  magnetic. 
(2)  Possessing  the  power  of  concentrat- 
ing lines  of  magnetic  force.  (3)  Ferro- 
magnetic. 

Paramagnetic  Permeability.  —Perme- 
ability to  magnetic  force. 

Paramagnetic  Polarity.— Magnetic  po- 


larity, or  the  polarity  possessed  by  para- 
magnetic substances. 

Paramagnetically.— In  a  paramagnetic 
manner. 

Paramagnetism.  —  The  magnetism  of 
paramagnetic  substances. 

Parasitical  Currents. — A  name  some- 
times applied  to  eddy  currents. 

Paratonnere. — A  French  term  for  light- 
ning rod,  sometimes  employed  in  English 
technical  works. 

Parcel  of  Wire. — A  word  sometimes  em- 
ployed for  any  quantity  of  manufactured 
wire  presented  at  one  time  and  in  one 
piece  for  examination  or  testing. 

Parchmentized-Thread  Filament. — A 
filament  for  an  incandescent  lamp  made 
from  the  carbonization  of  parchmentized 
thread. 

Parchmentizing  Process. — A  process  for 
converting  cellulose  thread  into  artificial 
parchment  by  treating  it  with  dilute  sul- 
phuric acid. 

Partial  Contact. — (1)  A  high-resistance 
or  imperfect  contact  between  two  tele- 
graphic lines  or  circuits.  (2)  An  incom- 
plete contact. 

Partial  Disconnection.— (1)  A  partial 
discontinuity.  (2)  A  loss  of  complete 
metallic  connection.  (3)  An  imperfect 
metallic  contact. 

Partial  Earth. — The  fault  in  a  telegraphic 
or  other  line  in  which  the  line  is  in  par- 
tial connection  with  the  earth. 

Partial  Fault.— In  telegraphy  or  tele- 
phony, a  fault  due  to  an  imperfect  ground- 
contact,  a  cross-contact  or  a  disconnec- 
tion, as  distinguished  from  a  complete 
fault  or  one  that  interrupts  communica- 
tion. 

Partial  Reaction  of  Degeneration.— 
That  form  of  alteration  to  electric  stim- 
ulation in  which  the  nerves  show  no  ab- 
normal reaction  to  electric  stimulation, 
while  the  muscles,  when  directly  stimu- 
lated by  a  constant  current,  exhibit  the 
reaction  of  degeneration. 

Partial  Vacuum. — An  incomplete  vac- 
uum. 

Partially  Overlapping  Winding  of 
Alternator  Armature.— A  winding  in 
which  some  of  the  coils  overlap  each 
other  and  some  of  the  coils  do  not  over- 
lap. 

Parting  of  Cable. — A  complete  rupture 
or  breaking  of  a  submarine  cable. 

Party  Lines  for  Telephone  Service.— 
(1)  Lines  which  connect  several  sub- 
scribers in  one  circuit,  as  opposed  to  lines 


Par.] 


875 


[Pen. 


devoted  to  a  single  subscriber.  (2)  Lines 
connecting  permanently  together  several 
telephonic  stations,  as  distinguished  from 
lines  connecting  each  telephone  station 
through  an  exchange. 

Partz  Gravity  Cell.  —  A  zinc-carbon 
couple  employed  with  electrolytes  of  sul- 
phate of  magnesia  or  common  salt,  and 
sulpho-chromic  salt,  in  which  the  liquids 
are  kept  apart  by  their  difference  of 
density. 

Passive  Resistance.— A  term  sometimes 
used  for  ohmic  resistance. 

Passive  State. — A  condition  of  a  metallic 
substance  in  which  it  may  be  placed  in 
liquids  that  would  ordinarily  combine 
with  it,  without  being  attacked  or  cor- 
roded. 

Paste  Joint  for  Lamp  Filament.— A 
form  of  joint  between  the  leading-in 
wires  and  the  ends  of  the  lamp  filament 
obtained  by  the  employment  of  a  moist 
hydro-carbon  paste  which  is  subsequently 
carbonized. 

Pasted  Secondary  Cell. — A  secondary 
cell  in  which  the  active  material  is  applied 
to  the  surface  of  the  grid  or  support  in 
the  form  of  a  paint,  paste,  or  cement. 

Path  of  Magnetic  Leakage. — A  side 
path  taken  by  deviating  magnetic  flux, 
as  distinguished  from  the  main  path  of 
usefully  employed  flux. 

Patrol  Alarm-Box. — In  a  system  of  sig- 
nal telegraphy  or  telephony,  a  box  from 
which  a  call,  communication,  or  alarm 
can  be  given  by  a  patrol. 

Paying-Out. — The  operation  of  passing 
submarine  cable  out  of  the  ship  while 
laying  it. 

Paying-Out  Drum. — A  drum  employed 
in  laying  a  submarine  cable  and  over 
which  the  cable  takes  several  turns, 
whereby,  by  means  of  brakes,  tension  may 
be  applied  to  the  cable  as  it  leaves. 

Paying-Out  Leg. — In  a  bight  of  cable  at 
the  bows  of  a  cable  ship,  that  side  or  leg 
which  is  paid  out,  as  distinguished  from 
the  side  or  leg  which  is  held  stationary  or 
picked  up. 

"  Pea  "  Lamp. — A  term  sometimes  given 
to  a  particular  form  of  miniature  incande- 
scent lamp. 

Peaked  Type  of  Periodically-Alter- 
nating Electromotive  Force.  —A  type 
of  electromotive  force  whose  curve  of 
graphical  representation  has  a  peaked 
shape,  as  opposed  to  a  smooth  or  a  flat 
shape. 

Pear  Push. — A  pear-shaped  push-contact, 


usually  provided  with    a    flexible  cord 
pendant. 

Pedestal  of  Armature. — A  supporting 
pillar  for  an  armature  bearing. 

Peg-Circuit. — A  circuit  that  is  opened 
or  closed  by  means  of  metallic  pegs. 

Peg-Switch.— (1)  A  switch  that  is  opened 
or  closed  by  means  of  a  peg.  (2)  A  pin 
switch. 

Peg-Switchboard. — A  switchboard  whose 
circuits  are  capable  of  being  variously 
inter-connected  by  means  of  peg  switches. 

Peltier  Effect.— The  heating  effect  pro- 
duced by  the  passage  of  an  electric  cur- 
rent across  a  thermo-electric  junction,  or 
surface  of  contact  between  two  different 
metals,  as  distinguished  from  a  Joulean 
effect  or  heat  due  to  resistance  merely. 

Peltier's  Cross.— A  cross,  made  by  placing 
two  plates  of  dissimilar  metals  in  contact 
at  right-angles  to  each  other,  employed 
for  the  study  of  the  Peltier  effect. 

Pen  Carriage. — The  carriage  in  an  elec- 
tric chronograph  which  carries  the  pen 
and  moves  over  the  sheet  of  paper  on 
which  the  record  is  made. 

Pen,  Electric. — A  device  for  manifold 
copying,  in  which  a  sheet  of  paper  is  made 
into  a  stencil  by  minute  perforations  ob- 
tained from  a  needle  driven  by  a  small 
electric  motor,  the  stencil  being  after- 
wards employed  in  connection  with  an 
ink  roller  for  the  production  of  any  re- 
quired number  of  copies. 

Pencil  Microphone. — A  carbon  micro- 
phone in  which  the  loose  carbon  is  in  the 
form  of  one  or  more  pencils. 

Pendant  Argand. — An  Argand  burner  so 
arranged  as  to  be  lighted  or  extinguished 
by  the  pulling  of  a  pendant. 

Pendant  Cord. — A  flexible  conductor  pro- 
vided for  conveying  the  current  to  a 
pendant  lamp  or  push. 

Pendant,  Electric. — A  hanging  fixture 
provided  with  'a  socket  for  the  support 
either  of  an  incandescent  lamp,  or  of  a 
contact. 

Pendant  Electric-Lamp. — An  incandes- 
cent lamp  supported  on  a  pendant  cord. 

Pendant  Pull-Switch.— A  switch  which 
is  operated  by  pulling  upon  a  pendant 
cord  or  loop. 

Pendant  Socket. — An  attachment  pro- 
vided with  a  chain  or  chains  for  turning 
on  or  off  a  lamp  not  readily  accessible. 

Pendulum  Annunciator.— (1)  An  an- 
nunciator whose  indicating  arm  consists 
of  a  pendulous  or  swinging  arm  which, 
when  at  rest,  assumes  a  vertical  position, 


Pen.] 


876 


[Per. 


and  which  is  moved  to  the  right  or  left 
by  the  action  of  the  current.  (2)  A 
swinging  annunciator. 
Pendulum,  Electric. — (1)  A  pendulum 
so  arranged  that  its  to-and-fro  motions 
send  electric  impulses  over  a  line,  either 
by  making  or  breaking  contacts.  (2)  An 
electric  tuning  fork  whose  to-and-fro 
movements  are  maintained  by  electric 
impulses. 

Pendulum  Indicator. — A  term  sometimes 
employed  for  a  pendulum  annunciator. 

Pendulum  Myograph.  —  An  electric 
pendulum  employed  for  physiological 
and  chronographic  purposes. 

Pendulum  Selector. — In  a  system  of  se- 
lective telephony,  a  pendulum  which  is 
adjusted  to  vibrate  at  different  rates  and 
thereby  actuate  the  call-bell  of  some  par- 
ticular station  selectively. 

Pendulum  Signaller.  —  A  pendulum 
armed  with  a  contact  maker  for  closing 
a  circuit  and  transmitting  signals. 

Pentad  Atom. — An  atom  whose  valency 
or  atomicity  is  five. 

Pentane  Standard. — A  standard  source 
of  light  obtained  from  the  burning  of 
pentane,  and  used  in  photometric  meas- 
urements in  place  of  a  Methven  screen. 

Penthode  Working. — A  five-way  mode 
of  telegraphic  working  obtained  by  the 
use  of  the  Delany  synchronous  multi- 
plex telegraph. 

Penumbra. — A  region  of  partial  shadow 
surrounding  the  umbra  or  complete 
shadow,  obtained  when  the  source  of 
light  causing  the  shadow  has  an  appreci- 
able area. 

Percentage  Conductivity. — The  conduc- 
tivity of  a  wire  expressed  in  percentage 
of  the  conductivity  of  Mathiessen's 
standard. 

Percentage  Conductivity  of  Wire.— 
(1)  The  conductivity  of  a  wire  in  terms  of 
the  conductivity  of  pure  copper.  (2)  The 
conductivity  of  a  particular  copper  wire 
compared  with  the  conductivity  of  a 
standard  wire  of  the  same  dimensions. 
(3)  The  conductivity  of  a  wire  referred 
to  Matthiessen's  standard  of  conductivity 
for  copper. 

Perfect  Linkage. — Linkage  of  magnetic 
flux  between  two  associated  coils  or  cir- 
cuits unaccompanied  by  magnetic  leak- 
age, or  such  that  all  of  the  flux  is  linked 
with  all  the  turns  of  each  circuit. 

Perforated  Armature.  —  An  armature 
provided  with  perforations  for  the  in- 
sertion of  the  coils. 


Perforated  Core-Discs.  —  The  separate 
core  discs  of  a  laminated  armature  core 
provided  with  perforations  for  the  in- 
sertion of  armature  wires. 

Perforator.— (1)  A  paper  perforator.  (2)  In 
automatic  telegraphy,  an  apparatus  for 
perforating  paper. 

Perforator  Mallet. — A  mallet  used  with 
a  perforator  for  striking  its  keys. 

Perforator  Slip. — The  slip  of  paper  pre- 
pared for  use  in  a  perforator. 

Period. — (1)  The  interval  of  time  between 
two  successive  passages  of  a  vibration 
through  a  given  point  of  its  path  taken  in 
the  same  direction.  (2)  The  time  occu- 
pied in  performing  a  complete  cycle. 

Period  of  Open-Circuit  Oscillation. — 
The  time  in  which  the  oscillation  set  up 
in  an  open  circuit  by  electric  resonance 
requires  to  make  one  complete  to-and-fro 
motion. 

Period  of  Simple-Harmonic  Motion. — 

The  interval  of  time  which  elapses  be- 
tween two  successive  passages  of  a  moving 
particle  over  the  same  point  in  the  same 
direction. 

Period  of  Vibration. — The  time  occupied 

in  executing  one  complete  vibration  or 

motion  to-and-fro. 

Periodic. — Of  or  pertaining  to  a  period. 
Periodic    Alternating    Electromotive 

Force. — An  electromotive    force  whose 

direction  periodically  varies. 

Periodic  Current. — (1)  A  current  whose 
strength  and  direction  periodically  vary. 
(2)  A  simple  harmonic  or  sinusoidal  cur- 
rent. (3)  A  periodically  alternating  cur- 
rent. 

Periodic  Discharge.— (1)  An  electric  dis- 
charge which  periodically  changes  its 
direction.  (2)  An  alternating  discharge. 

Periodic  Governor. — A  form  of  governor 
for  an  electric  motor,  in  which  the  cur- 
rent is  automatically  cut  off  for  a  certain 
portion  of  each  revolution. 

Periodic  Motion. — A  term  sometimes  em- 
ployed for  simple-periodic  motion. 

Periodically  Alternating  Discharge.— 
An  alternating  discharge. 

Periodically  Decreasing  Discharge.— 
An  oscillatory  discharge  whose  successive 
oscillations  decrease  in  intensity. 

Periodicity.— (1)  The  number  of  periods 
executed  per  second  by  a  periodically 
alternating  quantity.  (2)  The  number  of 
cycles  executed  in  unit  time  by  an  alter- 
nating current.  (3)  The  frequency  of  an 
alternating  current. 

Periodicitv   of  Alternation.  —  (1)  The 


Per.] 


number  of  alternations  per  second.  (2) 
The  frequency.  (3)  The  number  of  alter- 
nations executed  per  second  or  per  minute. 

Periodicity  of  Auroras,  Magnetic 
Storms,  and  Sunspots. — Coincidences 
between  the  occurrence  of  auroras,  mag- 
netic storms  and  sun-spots. 

Peripheral  Speed. — The  speed  of  a  point 
on  the  circumference  of  a  rotating  cylin- 
der or  wheel. 

Peripheral  Velocity.— (1)  The  rate  of 
linear  peripheral  speed.  (2)  The  tan- 
gential velocity  at  a  periphery. 

Periphratic  Region. — A  region  which 
encloses  other  regions  within  itself. 

Peripolar  Zone. — The  zone  or  region  sur- 
rounding the  polar  zone  on  the  body  of 
a  patient  undergoing  electro-therapeutic 
treatment. 

Periscopic  Eye-Piece  of  Microscope. 
An  eye-piece  consisting  of  a  triple  eye- 
lens  and  a  single  field-lens,  possessing  a 
very  large  and  flat  field. 

Permanency,  Electric. — The  property 
possessed  by  most  metallic  substances, 
while  in  a  solid  state,  of  retaining  a  con- 
stant electric  conducting  power  at  the 
same  temperature. 

Permanent  Charge  by  Induction. — An 
induced  charge  permanently  communi- 
cated to  a  conductor,  as  distinguished 
from  a  temporarily  induced  charge. 

Permanent  Currents  of  Wheatstone 
System. — (1)  In  the  Wheatstone  auto- 
matic system  the  use  of  a  signalling  cur- 
rent during  the  whole  period  in  which  a 
signal  is  transmitted.  (2)  The  continued 
application  of  current  in  one  or  other 
direction  oil  the  line. 

Permanent  Current  Telephone  Work- 
ing.— A  system  of  telephony  employing 
a  constant  normal  strength  of  current 
on  the  line. 

Permanent  Electret. — A  body  whose 
molecules  are  permanently  and  inherently 
electrized,  as  distinguished  from  a  body 
whose  molecules  are  only  inherently  elec- 
trized while  under  the  influence  of  some 
change  of  state. 

Permanent  Intensity  of  Magnetiza- 
tion.— A  term  employed  for  the  intensity 
of  a  permanent  magnetism  produced  in 
hard  steel,  as  distinguished  from  the 
magnetization  produced  temporarily  in 
soft  iron. 

Permanent  Laminated  -  Magnet. — A 
term  sometimes  employed  in  place  of 
compound-magnet. 

Permanent  Magnet. — A  name  sometimes 


877  [Per. 

given  to  a  magnet  composed  of  hardened 
steel,  whose  magnetic  retentivity  is  high. 
Permanen t-Magnet  Voltmeter. — A 
form  of  voltmeter  in  which  difference 
of  potential  is  measured  by  the  movement 
of  a  magnetic  needle  under  the  combined 
action  of  a  coil  and  a  permanent  magnet, 
against  the  pull  of  a  spring. 

Permanent  Magnetism. — M agnetism 
possessed  by  permanent  magnets. 

Permanent  Magnetization. — (1)  A  term 
employed  for  the  magnetization  produced 
in  a  mass  of  steel  or  hardened  iron  when 
brought  into  a  magnetic  field.  (2)  The 
magnetization  of  a  permanent  magnet. 

Permanent  Magneto-Motive  Force. — 
The  magneto-motive  force  of  a  permanent 
magnet. 

Permanent  State  of  Charge  on  Tele- 
graphic Line. — (1)  The  condition  of  the 
charge  on  a  telegraphic  line  during  the 
time  the  current  passing  is  at  full  strength 
in  all  parts.  (2)  The  charge  in  a  telegraph 
line  when  insulated  at  one  end  and  con- 
nected to  an  E.  M.  F.  at  the  other. 

Permanent  System  of  Currents. — (1)  A 
term  sometimes  used  in  telegraphy  to 
represent  the  current  sent  into  a  line  by 
a  double-current  key.  (2)  In  a  Wheat- 
stone's  automatic  telegraph  system  the  usf 
of  double  currents,  whereby  a  current  is 
always  flowing  on  the  line. 

Permanent  Telegraphic  Line. — A  term 
employed  for  a  telegraphic  line  that  is  in- 
tended to  remain  in  use  for  an  indefinite 
time,  in  contra  distinction  to  a  semi-per- 
manent line  which  is  only  designed  for 
use  during  a  comparatively  limited  time. 

Permanent  Telegraphic  Signals.— Tele- 
graphic signals  that  are  permanently  re- 
corded as  distinguished  from  transient  or 
unrecorded  signals. 

Permeability  Bridge. — A  device  for 
measuring  the  magnetic  permeability  of 
a  medium,  operating  on  the  principle  of 
a  Wheatstone  bridge. 

Permeability  Curve. — A  curve  repre- 
senting the  permeability  of  a  magnetic 
substance. 

Permeameter. — An  apparatus  for  deter- 
mining magnetic  permeabilities  by  the 
measurement  of  the  tractive  force  re- 
quired to  detach  a  mass  of  soft  iron 
having  a  plane  surface,  from  a  magnetic 
pole  whose  magnetic  flux  passes  perpen- 
dicularly through  the  surface. 

Permeance,  Magnetic. — (1)  The  recipro- 
cal of  magnetic  reluctance.  (2)  The  con- 
ductance of  a  medium  to  magnetic  flux. 

Permeating.— (1)   The   passage  of    mag- 


Per.] 


878 


[Pha. 


netic  flux  through  a  magnetizable  sub- 
stance, or  of  electrostatic  flux  through  a 
dielectric.  (2)  Intimately  traversing  the 
depths  of  a  medium. 

Permeation. — The  passage  of  magnetic 
flux  through  any  permeable  substance. 

Permissive  Block-System  for  Rail- 
roads.—-A  block-system  in  which  two  or 
more  trains  are,  under  certain  conditions, 
permitted  to  occupy  the  same  block  sim- 
ultaneously. 

Permissivity. — A  word  frequently  used 
for  permittivity. 

Permittance. — (1)  Electrostatic  capacity. 
(2)  The  capability  of  a  condenser  or  di- 
electric to  hold  a  charge. 

Permittivity. — (1)  Specific  permittance. 
(2)  The  dielectric  constant. 

Perpendicular.— (1)  At  right  angles  to. 
(2)  A  line  at  right  angles  to  one  or  more 
other  lines. 

Persistence  of  Energy.— The  indestruc- 
tibility of  energy. 

Personal  Equation. — A  constant  obser- 
vational error  peculiar  to  an  observer,  and 
depending  upon  his  psychological  condi- 
tion. 

Perviability. — A  word  proposed  for  per- 
meability to  electrostatic  flux. 

Perviance. — (1)  Conductance  to  electric 
lines  of  force.  (2)  The  reciprocal  of  divi- 
ance. 

Petticoat  Insulator. — (1)  An  insulator 
provided  with  a  petticoat,  or  deep  internal 
groove,  around  its  lower  extremity,  or 
stalk.  (2)  A  line-wire  vertical  insulator 
provided  with  an  insulating  inverted  cup 
having  a  form  resembling  a  petticoat.  (3) 
An  ordinary  telegraph  or  telephone  single- 
cup  insulator. 

Pflugers  Law. — A  given  tract  of  nerve  is 
stimulated  by  the  appearance  of  cathelec- 
trotonus  and  the  disappearance  of  anelec- 
trotonus,  but  not  by  the  disappearance  of 
cathelectrotonus  and  the  appearance  of 
anelectrotonus. 

Phantom  Circuit. — (1)  Any  of  the  addi- 
tional circuits  established  on  a  telegra- 
phic line  by  means  of  any  variety  of  mul- 
tiplex telegraphy.  (2)  An  imaginary  cir- 
cuit virtually  created  by  multiplexing  a 
telegraph  circuit. 

Phantom  Streams. — A  term  sometimes 
applied  to  a  variety  of  the  Tesla  streaming 
discharge. 

Phantom  Wires.— (1)  A  term  sometimes 
applied  to  the  virtual  additional  circuits 
or  wires  obtained  in  any  single  wire  or 
conductor  by  the  use  of  any  multiplex 


telegraphic    system, 
cuits. 


(2)    Phantom  cir- 


Phase. — The  fractional  part  of  a  period, 
which  has  elapsed  since  a  vibrating  body 
last  passed  through  the  extreme  point  of 
its  path  in  the  positive  direction. 

Phase  Angle. — The  angle  of  phase,  in 
a  simple-harmonic  motion,  or  the  angular 
distance  through  which  the  corresponding 
circularly  moving  point  has  passed  from 
the  point  of  last  maximum  positive  elonga 
tion. 

Phase  Detector. — A  device  for  determin- 
ing the  phase  of  an  alternating  current, 
electromotive  force,  or  flux. 

Phase  Diagram. — A  diagram  representing 
the  magnitude  and  relative  phase  position 
of  electric  pressures  or  currents. 

Phase-Difference  Measurer. — A  device 
for  measuring  difference  of  phase,  be- 
tween any  periodically  alternating  quan- 
tities. 

Phase  Indicator.— (1)  A  device  for  indi- 
cating when  the  pressure  of  an  alternator 
is  in  phase  and  synchronism  with  the 
pressure  of  the  circuit  with  which  it  is 
to  be  connected.  (2)  A  term  sometimes 

-  employed  for  a  synchronizer. 

Phase  Meter. — A  phase-difference  meas- 
urer. 

Phase  Modification. — The  alteration  of 
the  phase  of  any  periodically  alternating 
quantity. 

Phase  of  Simple-Harmonic  Motion. — 

The  angle  through  which  the  correspond- 
ing circularly  moving  point  has  moved 
from  the  point  of  maximum  positive  elon- 
gation. 

Phase  of  Vibration. — (1)  The  position 
of  the  particles  in  motion  in  a  wave  or 
vibration  at  any  instant  of  time  during 
the  wave  period,  as  compared  with  their 
mean  position.  (2)  The  phase  angle  of 
vibration  considered  as  simple-harmonic 
motion. 

Phase  Regulation. — The  regulation  of  the 
phase  or  phases  of  alternating  currents 
or  E.  M.  F.'s. 

Phase-Splitter .-7(1)  Any  apparatus  which 
so  acts  upon  an  incoming  alternating  cur- 
rent that  the  same  current  goes  out  in 
different  branches  as  a  plurality  of  cur- 
rents differing  in  phase.  (2)  A  device  for 
producing  a  difference  of  phase  between 
two  currents,  so  as  to  enable  a  single-phase 
induction-motor  to  be  self -star  ting.  (3)  A 
device  for  making  an  alternating  current 
split  into  two  or  more  dephased  compo- 
nents. 

Phase  Splitting. — The  quality  or  opera' 


Pha.] 


879 


[Pho. 


tion  cf  causing  a  single  alternating  cur- 
rent to  split  into  a  plurality  of  relatively 
dephased  components. 

Phase  Transformation. — A  change  of 
phase  obtained  by  a  transformer  whereby 
two-phase  currents  may  be  transformed 
into  three-phase  currents,  or  vice-versa. 

Phase- Windings. — The  separate  wind- 
ings on  the  armature  of  a  polyphase 
motor. 

Phasing  Current. — The  current  produced 
between  two  dynamos  when  thrown  into 
parallel,  which  arises  from  their  being 
either  not  perfectly  in  phase,  or  not  per- 
fectly equal  in  pressure,  or  both. 

Phasing  or  Wattless-Component.— A 

component  of  alternating  current,  90°  out 
of  phase  with  respect  to  a  pressure,  and, 
therefore,  indifferent  to  it  in  respect  to 
energy. 

Phasing  Transformer.— (1)  A  trans- 
former capable  of  effecting  a  change  of 
phase.  (2)  A  transformer  for  the  supply 
of  multiphase  secondary-currents  from 
Uniphase  primary-currents,  or,  vice-versa. 

Phelp's  Stock  Printer. — A  form  of  print- 
ing telegraph  employed  in  sending  stock 
quotations  telegraphically. 

Phenakistoscope. — An  optical  toy  de- 
pending on  the  persistence  of  a  retinal 
image,  in  which  the  appearance  of  life  is 
obtained  from  a  succession  of  suitable 
pictures  that  are  caused  to  rapidly  pass 
before  the  eye. 

Phenomenon. — Any  event  observed  or 
known  to  occur  in  nature. 

Pherope. — A  name  sometimes  applied  to  a 
telephote. 

Philosopher's  Egg. — A  name  given  to 
the  ovoid  or  egg-shaped  mass  of  light,  that 
appears  when  a  convective  discharge  is 
taken  between  two  electrodes  in  a  partial 
vacuum. 

Phonautograph. — An  apparatus  for  the 
automatic  production  of  the  visible  trac- 
ings of  the  vibrations  produced  by  any 
sounds. 

Phone. — (1)  A  contraction  frequently  em- 
ployed for  telephone.  (2)  A  message  sent 
by  telephone. 

Phone. — To  send  a  message  by  telephone. 

Phoned. — Communicated  by  telephone. 

Phonic  Wheel. — A  wheel  maintained  in 
synchronous  rotation  by  timed  electric 
impulses  sent  over  a  telegraphic  line,  and 
employed  in  the  Delany  synchronous 
multiplex  telegraph  system. 

Phoning. — Communicating  by  telephone. 

Phonogram. — A  term  proposed  for  a  de- 


spatch transmitted  by  means  of  a  tele- 
phone. 

Phonograph. — An  apparatus  for  the  re- 
cording and  reproduction  of  articulate 
speech,  or  of  sounds  of  any  character,  at 
any  time  after  their  occurrence,  and  for  a 
number  of  times. 

Phonograph  Record. — A  record  obtained 

by  means  of  a  phonograph. 
Phonographic.— Of  or  pertaining  to  the 

phonograph. 

Phonophore. — A  modified  form  of  har- 
monic telegraph. 

Phonoplex. — A  general  term  embracing 
the  apparatus  employed  in  phonoplex 
telegraphy. 

Phonoplex   Telegraphic-Receiver.— A 

special  form  of  telephone  receiver  em- 
ployed in  phonoplex  telegraphy,  which 
responds  to  brief  current  impulses  but 
not  to  prolonged  impulses. 

Phonoplex  Telegraphy. — A  system  of 
double  telegraphic  transmission,  in  which 
telephonic  currents,  superposed  on  the 
ordinary  Morse  currents,  actuate  a  modi- 
fied telephonic  receiver,  and  thus  permit 
the  simultaneous  transmission  of  two 
separate  messages  over  a  single  wire 
without  interference. 

Phonoplex  Transmission. — Double  tele- 
graphic transmission  obtained  by  the 
superposition  of  telephonic  and  Morse 
currents. 

Phonozenograph. — An  instrument  de- 
vised to  indicate  the  direction  of  a  distant 
sound. 

Phosphoresce. — To  emit  phosphorescent 
light. 

Phosphorescence. — The  power  of  emit- 
ting light,  or  becoming  luminous  by 
simple  exposure  to  radiant  energy. 

Phosphorescence,  Electric. — Phosphor- 
escence  caused  in  a  substance  by  the 
passage  of  an  electric  discharge. 

Phosphorescent. — Possessing  the  quality 
of  phosphorescence. 

Phosphorescent  Glow. — A  phosphores- 
cent light  emitted  by  the  residual  atmos- 
phere of  a  vacuum  tube  several  seconds 
after  an  electric  discharge  has  ceased  to 
pass  through  it. 

Phosphorescent  Lamp. — A  lamp  whose 
light  is  obtained  by  means  of  the  phos- 

Shoresceut    effects    attending    electrical 
ischarges  through  a  rarified  space. 
Phosphorescing.  —  Emitting    phosphor- 
escent light. 
Phosphoroscope. — An      apparatus      fol 


Pho.J 


880 


[Pho. 


measuring  the  phosphorescent  power  of 
any  substance. 

Phot. — (1)  A  unit  of  time-illumination,  or 
the  total  illumination  produced  by  one 
hi*  for  one  second  of  time.  (2)  The  lux- 
second. 

Photo-Chemical.  —  Relating  to  photo- 
chemistry. 

Photo-Chemical  Effect.— Chemical  ef- 
fects produced  by  the  action  of  radiant 
energy. 

Photo-Chemistry. — The  chemistry  of  the 
effects  of  radiant  energy. 

Photo-Chronograph. — An  electric  instru- 
ment for  automatically  recording  the 
transit  of  a  star  across  the  meridian. 

Photo-Electric. — Pertaining  to  the  com- 
bined action  of  light  and  electricity. 

Photo-Electric  Alarm.— (1)  An  alarm 
operated  by  means  of  a  photo-electric  cell. 
(2)  A  selenium  cell  proposed  for  use  in 
connection  with  the  circuit  of  an  electric 
source  and  suitable  electro-receptive  de- 
vices, so  as  to  cause  the  sounding  of  an 
alarm  on  the  exposure  of  one  of  the  faces 
of  the  cell  to  light. 

Photo-Electric  Battery.  —  Several  pho- 
to-electric cells  so  combined  as  to  be 
capable  of  acting  as  a  single  source. 

Photo-Electric  Cell. — A  cell  capable  of 
producing  difference  of  potential  when  its 
opposite  faces  are  unequally  exposed  to 
radiant  energy. 

Photo-Electric  Impulsion-Cell.  —  A 
photo-electric  cell  whose  sensitiveness  to 
light  may  be  restored  by  slight  impulses, 
such  as  mechanical  blows  or  taps,  or  by 
electro-magnetic  impulses. 

Photo-Electricity . — Difference  of  electric 
potential  produced  by  the  action  of  light. 

Photo-Electromotive  Force. — An  elec- 
tro-motive force  produced  by  the  action 
of  light. 

Photo-Engraving. — Engraving  effected 
by  the  agency  of  light. 

Photo-Fluoroscopy.— The  photography 
of  the  image  obtained  on  a  fluoroscopic 
screen. 

Photographic  Meter. — An  electric  meter 
producing  a  photographical  record. 

Photographic  Negative . — A  photo- 
graphic picture  whose  lights  and  shadows 
are  reversed  with  reference  to  the 
original. 

Photographic  Positive. — A  photographic 
picture  whose  lights  and  shadows  corres- 
pond to  those  in  the  natural  object. 

Photometer. — An  apparatus  for  measur- 
ing the  intensity  of  the  light  emitted  by 
any  luminous  source. 


Photometer  Bar. — A  graduated  horizon- 
tal bar  designed  to  carry  a  photometer 
screen  and  to  indicate  by  the  distance  of 
the  screen  from  the  sources  of  light,  the 
relative  intensities  of  the  lights  com- 
pared. 

Photometer  Bench. — A  photometer  bar, 
with  or  without  accessory  photometric 
apparatus. 

Photometer  Box. — A  darkened  box  in 
which  is  placed  the  photometer  screen  or 
disc. 

Photometer  Disc. — The  photometer 
screen. 

Photometer,  Electric. — An  electric  in- 
strument for  measuring  the  intensity  of 
light  or  illumination. 

Photometer  Gallery. — A  name  some- 
times given  to  a  photometric  bench. 

Photometer  Screen. — An  opaque  or  trans- 
lucent screen,  employed  in  a  photometer 
for  measuring  the  intensity  of  light,  and 
which  receives  the  two  illuminations  to 
be  compared. 

Photometric. — Of  or  pertaining  to  a  pho- 
tometer. 

Photometric  -  Surface  of  Luminous 
Source. — A  surface  formed  by  the  locus 
of  points  at  the  ends  of  lines,  obtained  by 
laying  off  lines  in  various  directions  pas- 
sing through  the  luminous  source,  whose 
lengths  measure  the  intensity  of  the  rays 
emitted  in  these  directions. 

Photometrically. — In  a  photometric  man- 
ner. 

Photo-Micrography.— The  photography 
of  microscopic  objects. 

Photo-Micrography,  Electric. — The  art 
of  photographing  microscopic  images  by 
means  of  the  electric  light. 

Photophone. — An  instrument  for  the  tele- 
phonic transmission  of  articulate  speech 
along  a  ray  of  light  instead  of  along  a 
conducting  wire. 

Photophone  Transmitter. — The  trans- 
mitter employed  in  radiophony,  in  con- 
nection with  the  photophone. 

Photophore. — An  apparatus  in  which  the 
light  of  a  small  incandescent  lamp  is  em- 
ployed for  purposes  of  medical  explora- 
tion. 

Photosphere. —  The  luminous  envelope 
which  surrounds  the  sun,  and  which  is  the 
source  of  its  luminous  radiation.  , 

Photo-Telegraphy.— (1)  Telegraphic  com- 
munication carried  on  by  means  of  light. 
(2)  Heliography.  (3)  Radiophony. 

Photo-Voltaic  Cell.— A  photo-electric- 
cell. 


Pho.] 


881 


[Pis. 


Photo- Voltaic  Effect. — A  change  in  the 
resistance  of  selenium  or  other  substance 
produced  by  its  exposure  to  light. 

Physical  Change. — Any  change  in  matter 
resulting  from  a  re-arrangement  of  its 
molecular  groupings,  without  the  forma- 
tion of  new  molecules,  as  distinguished 
from  a  chemical  change. 

Physical  Equator. — The  geographical 
equator. 

Physical  Phosphorescence . — Phosphor- 
escence produced  in  matter  by  the  impact 
of  light  waves,  resulting  in  a  vibratory 
motion  of  the  molecules,  of  a  rapidity  suf- 
ficient to  cause  them  to  emit  light. 

Physical. — (1)  Of  or  pertaining  to  nature. 
(2)  Natural. 

Physiological. — Of  or  pertaining  to  phy- 
siology. 

Physiological  Coefficient  of  Illumina- 
tion.— The  illuminating  value  of  one  watt 
of  activity  at  frequencies  within  visible 
limits  of  the  spectrum. 

Physiological  Rheoscope. — A  sensitive 
nerve-muscle  preparation  employed  to 
determine  the  presence  of  an  electric  cur- 
rent. 

Physiologically. — In  a  physiological  man- 
ner. 

Physiologically  -  Effective  Flux  of 
Light. — The  physiologically-effective  il- 
lumination received  by  any  surface. 

Physiologically-Effective  Radiation. 
That  portion  of  the  radiation  which  con- 
sists of  physiologically  active  or  luminous 
frequencies. 

Physiology,  Electro. — The  study  of  the 
electric  phenomena  of  living  animals  and 
plants. 

Piano,  Electric. — A  piano  whose  strings 
are  struck  by  hammers  actuated  by 
means  of  electro-magnets. 

Picking-TJp  Gear. — The  gear  provided  in 
a  cable  ship  for  the  recovery  of  a  sub- 
merged cable. 

Pickle. — An  acid  solution  in  which  metal- 
lic objects  are  dipped  in  order  to  thor- 
oughly cleanse  their  surfaces  before  being 
electro-plated. 

Piece  of  Wire. — A  single  length  of  wire 
without  a  joint  or  splice  of  any  descrip- 
tion. 

Pierced-Core  Armature. — A  perforated 
armature  core. 

Piezo-Electricity. —  Electrification  pro- 
duced in  certain  crystalline  substances  by 
pressure. 

Piezometer. — An  apparatus  for  determin- 
ing the  compressibility  of  a  liquid. 
$6 


Pike  Pole. — A  straight  pole  armed  at  one 
end  with  a  metal  point  or  pike,  for  use  in 
setting  up  telegraph  poles. 

Pile. — (1)  A  word  frequently  used  for  voltaic 
or  thermo-electric  pile,  though  more  fre- 
quently for  the  former.  (2)  A  voltaic  or 
thermo-electric  battery. 

Pilot  Brush. — A  small  accessory  brush 
placed  on  the  commutator  cylinder  for 
the  purpose  of  determining  the  variations 
in  the  electromotive  force  produced  in 
various  segments. 

Pilot-Hquse  Controlling-Gear. — Gear 
placed  in  the  pilot  house  for  the  control 
of  a  search-light  projector. 

Pilot  Lamp. — (1)  A  lamp  connected  across 
the  terminals  of  a  dynamo  to  show  roughly 
the  pressure  which  it  is  producing.  (2)  A 
lamp  placed  in  a  central  station,  generally 
on  the  dynamo  itself,  to  indicate  the  dif- 
ference of  potential  at  the  dynamo  ter- 
minals by  means  of  the  intensity  of  the 
emitted  light. 

Pilot  Motor. — (1)  A  small  motor  which 
goes  ahead  of  and  serves  to  set  in  opera- 
tion a  larger  or  working  motor.  (2)  A 
small  motor  whose  sole  duty  is  to  actuate 
contacts  for  controlling  the  operation  of 
a  large  motor. 

Pilot  Transformer. — A  small  transformer 
placed  at  any  desired  portion  of  a  line  in 
order  to  determine  its  pressure. 

Pilot  Wires. — (1)  The  wires  leading  di- 
rectly to  the  generating  station  from  dif- 
ferent parts  of  the  mains,  in  order  to  de- 
termine the  difference  of  potential  at 
such  parts.  (2)  Wires  provided  for  con- 
nection to  a  pilot  lamp,  or  other  device 
for  indicating  the  maintenance  of  normal 
pressure. 

Pins. — Wooden  pegs  for  supporting  pole 
line  insulators. 

Pin  Plug. — A  plug  consisting  of  a  single 
metallic  pin  with  or  without  an  insulat- 
ing head,  for  bridging  a  discontinuity  in 
a  resistance  box  or  switchboard.  • 

Pipe  Conduit. — A  conduit  formed  of  suit- 
ably prepared  metallic  pipes  surrounded 
either  on  the  interior  or  the  exterior  with 
a  cementing  compound. 

Pipe  Pole. — (1)  A  pole  for  aerial  wires, 
formed  of  iron  pipes,  usually  in  lengths  or 
sections  of  tapering  diameter.  (2)  A  pole 
of  iron  or  steel  in  tubular  form. 

Pipette. — A  glass  tube  suitable  for  holding 
and  removing  small  quantities  of  liquid 
for  analytical  or  other  purposes. 

Piston  Manometer. — A  manometer 
whose  operation  is  dependent  on  the  prin- 
ciple of  hydraulic  pressure. 


Pit.] 


882 


[Pla. 


Pitch.-^(l)  The  frequency  of  vibration  of 
a  musical  tone.  (2)  The*  frequency  of  an 
electrically  produced  tone.  (3)  The  dis- 
tance between  successive  corresponding 
points  of  symmetry  in  a  mechanical  sys- 
tem, such  as  of  screw  threads  or  propeller 
blades.  (4)  The  distance  between  succes- 
sive corresponding  conductors  on  a  dyna- 
mo armature.  (5)  In  an  armature  wind- 
ing divided  into  coils  or  segments,  the 
number  of  coils  through  which  advance 
must  be  made  in  making  end  connections 
between  the  coils. 

Pitch  Line.— (1)  A  circle  upon  the  periph- 
ery of  which  the  pitch  is  measured. 
(2)  A  circle  drawn  around  the  external 
surface  of  an  armature  through  the  mid- 
dle of  the  length  of  the  inductors  placed 
thereon. 

Pitch,  of  Poles. — The  distance  measured 
along  the  pitch  line  between  the  centres 
either  of  a  pair  of  poles  of  opposite  sign, 
or  of  a  pair  of  poles  of  the  same  sign. 

Pitch  of  Windings. — (1)  In  alternators, 
usually  the  distance  measured  along  the 
pitch  line  between  the  centres  of  a  pair  of 
successive  poles  of  opposite  sign ;  or,  in 
some  alternators,  half  this  distance.  (2)  , 
In  a  continuous-current  armature,  the 
pitch. 

Pitch-Ratio  of  Alternator.— The  ratio  of 
the  width  of  a  pole-piece,  or  an  armature 
coil,  to  the  pitch  of  the  machine,  or  dis- 
tance between  successive  field-pole  cen- 
tres as  measured  on  the  pitch  line. 

Pith.  —  A  light  cellular  substance  that 
forms  the  central  portions  of  the  stalls  of 
certain  plants. 

Pith  Balls. — Two  balls  of  pith,  suspended 
from  an  insulated  conductor  by  conduct- 
ing threads  of  cotton,  or  other  semi-con- 
ducting substance,  and  employed  for 
showing  the  presence  of  a  charge  on  the 
same  by  their  mutual  repulsion. 

Pith-Ball  Electroscope.  —  An  electro- 
scope whose  indications  are  obtained  by 
the  attractions  or  repulsions  of  pith  balls. 

Pivot  Suspension.  —  Suspension  of  a 
needle  by  means  of  a  jewelled  cup  and  a 
metallic  pivot. 

Pivotal  Trolley.— A  trolley  stand  in 
which  the  pole  is  supported  on  a  pivot,  so 
as  to  be  capable  of  rotation,  for  the  pur- 
pose of  reversing  the  direction. 

Plain-Pendant  Argand  Electric  Burn- 
er. —  A  plain-pendant  electric  burner 
suitable  for  lighting  an  Argand  gas 
burner. 

Plain-Pendant  Electric  Burner.— A  gas 
burner  provided  with  a  pendant  for  the 


purpose  of  lighting  the  gas  by  means  of  a 
spark,  after  the  gas  has  been  turned  on 
by  hand. 

Plaited  Electrode  Accumulator. — A 
form  of  storage  cell  or  accumulator,  in 
which  the  electrodes  consist  of  plaited 
strips  or  ribbons  of  lead. 

Plane  Angle.  —  (1)  An  angle  contained 
between  two  straight  lines.  (2)  An  angle 
lying  in  a  plane. 

Plane  of  Polarization  of  Light.— (1)  The 
plane  of  incidence  in  a  ray  of  light  polar- 
ized by  reflection.  (2)  A  plane  perpen- 
dicular to  the  plane  of  vibration  of  plane 
polarized  light. 

Plane  Vector.  —  A  quantity  which  pos- 
sesses not  only  magnitude  but  also  direc- 
tion in  a  single  plane. 

Planimeter.  —  An  instrument  for  auto- 
matically integrating  the  areas  of  plane 
curves,  around  the  contour  of  which  a 
fiducial  point  on  the  instrument  is  carried. 

Piano-Concave.  —  Flat  on  one  side  and 
concave  on  the  other. 

Piano-Convex. — Flat  on  one  side  and  con- 
vex on  the  other. 

Plant. — An  installation. 

Plant  Efficiency.— (1)  The  efficiency  of  a 
plant  or  electric  installation.  (2)  The  ef- 
ficiency of  a  plant  as  distinguished  from 
the  distribution  system  which  it  operates* 
or  by  which  it  may  be  operated. 

Plant  Efficiency  of  Motor.— The  effi- 
ciency of  a  motor,  as  distinguished  from 
the  efficiency  of  the  system  with  which 
it  is  connected. 

Plant  Electricity.— Electricity  produced 
by  plants  during  their  growth. 

Plastic. — Possessing  the  property  of  plas- 
ticity. 

Plastic-Circuit  Microphone. — A  micro- 
phone which  operates  by  varying  the  re- 
sistance of  a  plastic  circuit. 

Plastic  Rail-Bond. —In  street-railway 
systems,  a  rail-bond  in  which  contact  is 
secured  with  the  rail-ends  by^  sodium 
amalgam,  or  other  conducting  material 
applied  in  a  plastic  condition. 

Plasticity.— (1)  The  property  of  readily 
changing  form  under  continuous  stress. 
(2)  The  property  of  possessing  small  re- 
sistance to  distortional  stress. 

Plate  Condenser. — (1)  A  condenser,  the 
metallic  coatings  of  which  are  placed  on 
suitably  supported  dielectric  plates.  (2)  A 
condenser  made  up  of  one  or  more  pairs  of 
conducting  plates  separated  by  a  plate  or 
plates  of  non-conducting  material. 


Pla.] 


883 


[Pin. 


Plated.— Electro-plated,  or  covered  with 
an  electro-metallurgical  coating. 

Platform  Controller. — An  electrical  car- 
controller  placed  on  the  platform  of  a  car 
for  the  purpose  of  starting,  stopping  and 
regulating  the  speed  of  the  car. 

Platform  Coupling.— An  electric  coup- 
ling connecting  two  cars  and  placed  on 
or  beneath  the  platform  of  the  cars. 

Platinating. — Covering  a  conducting  sur- 
face electrolytically  with  platinum. 

Plating. — A  word  frequently  used  for  elec- 
tro-plating. 

Plating  Balance. — An  automatic  device 
for  disconnecting  the  current  from  an 
article  to  be  plated,  as  soon  as  a  certain 
Increase  in  weight  has  been  reached. 

Plating  Dynamo. — A  dynamo  employed 
for  furnishing  the  current  required  for  a 
plating  process. 

Plating  Trough. — A  term  sometimes  em- 
ployed for  plating  bath. 

Platinoid. — An  alloy  consisting  of  German 
silver  with  one  or  two  per  cent,  of  metal- 
lic tungsten,  whose  electric  resistivity  is 
only  slightly  affected  by  changes  of  tem- 
perature. 

Platinum. — A  heavy,  refractory  and  not 
readily  oxydizable  metal  of  a  tin-white 
color. 

Platinum  Alloy. — An  alloy  of  platinum, 
commonly  a  platinum-silver  alloy. 

Platinum  Black. — Finely  divided  plati- 
num that  possesses  in  a  marked  degree 
the  power  of  absorbing  or  occluding 
gases. 

Platinum  Fuse. — A  thin  platinum  wire 
rendered  incandescent  by  the  passage  of 
an  electric  current,  and  employed  for  the 
ignition  of  a  charge  of  powder. 

Platinum-Iridium  Alloy. — An  alloy  of 
platinum  and  iridium  employed  for  the 
manufacture  of  wire  sometimes  used  in 
resistance  coils  on  account  of  its  low  tem- 
perature coefficient  of  resistivity. 

Platinum  Lamp. — (1)  A  lamp  whose  in- 
candesjcent  filament  is  formed  of  a  plati- 
num wire.  (2)  A  lamp  of  molten  plati- 
num. (3)  A  violle. 

Platinum-Silver  Alloy. — A  name  usually 
applied  to  a  particular  alloy  of  one  part 
of  platinum  and  two  parts  of  silver,  pos- 
sessing a  low  temperature-coefficient  of 
resistivity. 

Platinum  Standard  Light,  —  (1)  The 
luminous  intensity  emitted  perpendicu- 
larly by  a  surface  of  platinum  one  square 
centimetre  in  area,  at  its  temperature  of 
fusion.  (2)  The  Violle  standard. 


Platinum  Sulphuric  Acid  Voltameter. 
A  platinum  voltameter. 

Platinum  Voltameter. — (1)  A  voltameter 
employing  platinum  electrodes.  (2)  A 
voltameter  furnished  with  platinum  elec- 
trodes immersed  in  a  dilute  solution  of 
sulphuric  acid  and  water. 

Platining.— (1)  Covering  a  surface  elec- 
trolytically with  platinum.  (2)  Platinum 
plating ;  or,  electro-plating  with  plati- 
num. 

Platinizing.— (1)  Obtaining  a  platinum 
coating  of  a  conducting  surface  by  simple 
immersion  in  a  solution  of  a  platinum  salt. 
(2)  Platining. 

Platymeter.  —  An  instrument  employed 
for  comparing  the  capacity  of  two  con- 
densers, or  the  specific  inductive  capaci- 
ties of  two  dielectrics. 

Plow. — A  term  sometimes  employed  for 
the  sliding  contact  and  its  support  that  is 
pushed  before  a  car,  along  the  trolley 
conductors  in  an  underground  trolley 
system. 

Plow,  Electric. — An  electrically  propelled 
plow  employed  in  agriculture. 

Plucker  Tube.  —  A  modification  of  a 
Geissler  tube  employed  for  studying  the 
stratification  of  the  light,  and  the  pecul- 
iarities of  the  space  adjoining  the  nega- 
tive electrode. 

Plug. — (1)  A  suitably-shaped  metallic  key 
provided  with  an  insulating  handle  and 
employed  for  closing  or  making  contacts. 
(2)  An  incompetent  telegraph  operator. 

Plug  Cut-Out.  —  A  cut-out  employing 
fuse-plugs. 

Plug  Hole. — The  hole  provided  in  a  plug 
switch  for  the  introduction  of  a  plug. 

Plug  Key. — A  key-shaped  plug. 

Plug  Operator.  —  A  term  of  contempt 
sometimes  applied  to  an  inefficient  tele^ 
graphic  operator. 

Plug  Resistances. — (1)  A  number  of  separ- 
ate resistances  that  can  be  introduced  into 
a  circuit  by  unplugging.  (2)  The  resist- 
ances of  the  ordinary  resistance  box. 

Plug  Sleeve. — The  contact  cylinder  on 
the  surface  of  a   telephone-switchboard 
plug- 
Plug  Switch. — A  switch  operated  by  the 
insertion  of  a  metallic  plug  between  two 
insulated  metallic  segments  connected  to 
a  circuit,  and  separated  by  air-spaces  for 
the  reception  of  the  plug  key. 
Plug    Switchboard.  —  A    switchboard 
whose  various  circuits  are  inter-connected 
by  means  of  plug  keys. 
Plugging. — (1)  Completing   a   circuit  by 


Plu.] 


884 


[Pol. 


means  of  plugs.  (2)  In  a  telephone 
switchboard,  the  operation  of  making 
the  connections  by  inserting  plugs  in  the 
proper  jacks. 

Plumbago. — (1)  An  allotropic  modifica- 
tion of  carbon.  (2)  Graphite. 

Plunge  Battery. — The  couples  of  a  vol- 
taic battery  so  supported  on  a  horizontal 
bar  as  to  be  capable  of  being  simultane- 
ously placed  in  or  removed  from  the  ex- 
citing liquid. 

Plunger  Door-Contact. — A  form  of  elec- 
tric contact  for  doors  in  which  the  closing 
of  the  door  forces  in  a  small  plunger 
against  the  tension  of  a  spring,  thereby 
either  making  or  breaking  an  electric 
alarm  circuit. 

Plunger  Floor  -  Contact. — A  form  of 
plunger  contact  suitable  for  being  placed 
on  the  floor  and  operated  by  the  foot. 

Plunger  Switch. — A  switch,  the  operat- 
ing lever  cylinder  of  which  passes  through 
a  bushing  in  a  switchboard,  so  as  to  make 
and  break  contacts  at  the  back  of  the 
switchboard. 

Plus  Charge. — A  positive  charge. 

Pneumatic. — Of  or  pertaining  to  pneuma- 
tics. 

Pneumatic  Car-Brake  Mechanism. — A 
car-brake  operated  by  air-pressure. 

Pneumatic  Perforator.— A  paper  perfor- 
ator operated  by  compressed  air. 

Pneumatic  Rodding. — A  method  of  in- 
troducing a  cable  or  wire  into  the  duct  of 
a  conduit  by  the  movement  of  a  dart 
driven  through  the  duct  by  air  pressure. 

Pneumatic  Telegraph. — A  form  of  in- 
strument for  transmitting  signals  by 
means  of  air  pressure. 

Pneumatic  Transmission.  —  Transmis- 
sion of  objects  or  of  power,  effected  by 
means  of  compressed  air. 

Pneumatics. — That  branch  of  physics 
which  treats  of  the  properties  of  gases 
either  at  rest  or  in  motion. 

Pocket  Galvanometer. — A  galvanometer 
suitable  for  carrying  in  the  pocket. 

Pocket  Gauge,  Electric. — A  rough  form 
of  pocket  galvanometer. 

Pocket  Telegraphic-Relay.— A  relay 
sufficiently  small  to  be  readily  carried  in 
the  pocket. 

Pockets  in  Inside  Wiring  System.— 
Hollow  spaces  provided  in  the  walls, 
floors  or  ceilings  of  a  building  for  draw- 
ing wires  in,  for  making  connections,  or 
for  inserting  safety  devices. 

Poggendorff's  Voltaic  Cell.— The  name 
sometimes  given  to  the  Grenet  cell. 


Point  Discharge.— A  term  sometimes  ap- 
plied to  a  convective  discharge. 

Point  of  Origin. — (1)  In  graphics,  the 
point  where  the  axes  of  co-ordinates  start. 
(2)  The  point  at  which  a  curve  starts. 

Points  on  Lightning  Rod. — Points  of 
unoxydizable  metal  placed  on  lightning 
rods  to  effect  the  quiet  discharge  of  a 
cloud  by  convection  streams. 

Points  of  Compass. — (1)  The  thirty-two 
points  into  which  the  edge  or  periphery 
of  a  compass  card  is  divided.  (2)  The 
rhumbs  of  a  compass. 

Polar. — Of  or  pertaining  to  a  pole. 

Pointer  Telegraph.— A  term  sometimes 
used  for  a  dial  telegraph. 

Polar  Aurora. — A  general  term  for  the 
Northern  or  Southern  light. 

Polar  Bore  of  Field  Frame.— The  bore 
or  cylindrical  hollow  space  excavated  in 
a  field  frame  for  the  reception  of  an  ar- 
mature. 

Polar  Duplex.— A  system  of  differential 
duplex-telegraphy  employing  polar-re- 
ceiving relays. 

Polar  Duplex-Telegraphy  .—Telegraphic 
communication  obtained  by  means  of  a 
differential  duplex  in  which  the  current 
flowing  from  the  home  battery  to  line  is 
reversed  when  the  home  key  is  depressed. 

Polar  Electrolysis.— (1)  A  form  of  elec- 
trolysis attended  by  destruction  of  the 
tissues.  (2)  Galvano- Caustics. 

Polar  Relay. — In  telegraphy,  a  relay  hav- 
ing a  normally  polarized  armature,  as 
distinguished  from  a  neutral  relay,  in 
which  the  armature  is  normally  in  neu- 
tral magnetic  condition. 

Polar  Surface  of  Magnet.— (1)  The  sur- 
faces of  one  or  both  poles  of  a  magnet. 
(2)  A  surface  of  magnetic  material  from 
which  or  into  which  magnetic  flux 
passes. 

Polar  Tips.— The  free  ends  of  the  field- 
magnet  pole-pieces  of  a  dynamo-electric 
machine. 

Polar  Transformer. — A  term  sometimes 
employed  for  an  open-circuit  transformer. 

Polar  Variation  Diagram. — A  diagram 
drawn  to  polar  co-ordinates  and  represent- 
ing some  relation  between  periodically 
varying  quantities. 

Polar  Zone. — The  zone  or  region  in  the 
human  body  surrounding  a  therapeutic 
eleotrode. 

Polariscope,  Electric. — An  electric  ap- 
paratus for  polarizing  electro-magnetic 
waves  and  for  revealing  the  presence  of 
polarization. 


Pol., 


885 


[Pol. 


Polarity. — (1)  The  possession  of  poles,  or 
of  opposite  properties,  at  opposite  ends. 
(2)  The  condition  of  electric  or  magnetic 
differentiation  between  properties  of  elec- 
tric or  magnetic  flux  depending  on  and 
inherent  in  the  direction  of  such  flux. 

Polarity  Indicator. — Any  device  for  de- 
termining the  direction  of  a  current  or 
the  polarity  of  a  magnet. 

Polarization  Battery. — A  term  some- 
times employed  for  a  secondary  or  storage 
battery. 

Polarization  Current. — In  electro-thera- 
peutics the  constant  current  which,  when 
passed  through  a  nerve,  produces  therein 
the  electro-tonic  state. 

Polarization  Current  from  Fault  in 
Cable. — A  current  due  to  the  polarization 
of  a  fault  or  break  in  a  cable  under  the 
action  of  a  testing  current. 

Polarization,  Electric.--(l)  In  dielectrics, 
the  condition  of  being  subjected  to  elec- 
trification. (2)  In  dielectrics,  the  condi- 
tion of  containing  or  restoring  a  residual 
charge.  (3)  In  electrolysis,  the  condi- 
tion of  having  free  ions  liberated  at  the 
electrodes,  whereby  a  C.  E.  M.  F.  is  set  up. 

Polarization  Fault-Current  of  Cable. — 
A  current  produced  in  a  cable  due  to  the 
counter-electromotive  force  set  up  in  a 
fault  under  the  action  of  a  signalling, 
testing,  or  natural  current. 

Polarization  of  Dielectric. — (1)  A  molec- 
ular strain  produced  in  the  dielectric  of 
a  Leyden  jar,  or  other  condenser,  by  the 
attraction  of  the  electric  charges  on  its 
opposite  faces,  or  by  electrostatic  stress. 
(2)  A  term  sometimes  employed  for  elec- 
tric displacement. 

Polarization  of  Electrolyte. — An  as- 
sumed formation  of  molecular  groups  or 
chains  in  which  the  poles  of  all  the  mole- 
cules of  any  chain  are  turned  in  the  same 
direction,  that  is  with  their  positive  poles 
facing  the  negative  plate,  and  their  nega- 
tive poles  facing  the  positive  plate. 

Polarization  of  I^ight. — The  condition  of 
a  ray  of  light  in  which  the  vibrations  of 
the  ether  by  which  the  light  is  propagat- 
ed are  all  limited  to  a  single  plane,  the 
plane  perpendicular  to  which  is  called  the 
plane  of  polarization. 

Polarization  of  Voltaic  Cell. — The  col- 
lection of  a  gas,  generally  hydrogen,  on 
the  surface  of  the  negative  element  of  a 
voltaic  cell. 

Polarization  Battery. — A  term  some- 
times used  for  secondary  or  storage  bat- 
tery. 

Polarization     Photometer.— A    photo- 


meter in  which  the  illumination  of  the 
stronger  of  two  luminous  sources  to  be 
compared  is  reduced  by  polarization. 

Polarized  Armature.  —  An  armature 
which  possesses  a  polarity  independently 
of  that  imparted  by  the  working  cur- 
rent. 

Polarized  Bell.  —  An  electro-magnetic 
bell  provided  with  a  polarized  armature. 

Polarized  Indicator. — Any  electro-mag- 
netic indicator  employing  a  polarized 
armature. 

Polarized  Ink-Recorder.— An  ink-re- 
corder employing  a  polarized  armature. 

Polarized  Radiation.  —  Any  radiation 
whose  waves  are  polarized,  or  restricted 
to  a  particular  plane  of  vibration. 

Polarized  Relay. — (1)  A  telegraphic  re- 
lay provided  with  a  permanently  magnet- 
ized armature  in  place  of  the  ordinary 
soft-iron  armature.  (2)  A  polar  relay. 
(3)  A  non-polarized  or  neutral  relay,  as 
distinguished  from  a  polarized  relay. 

Polarized  Ring-Off  Drop.— A  ring-off 
drop  in  a  telephone  switchboard  having 
a  polarized  armature. 

Polarized  Sounder.  —  A  telegraphic 
sounder  employing  a  polarized  armature. 

Polarizing  Current. — A  current  which 
produces  polarization. 

Polarizing  Spectro-Photometer.  —  A 
spectro-photometer  employing  a  polari- 
scope. 

Pole  Armature. — (1)  An  armature  whose 
coils  are  wound  on  separate  poles  that 
project  from  the  periphery  of  a  disc, 
drum,  or  ring  armature.  (2)  An  armature 
having  polar  projections. 

Pole  Bands.  —  Metallic  bands  placed 
around  a  pole  for  the  purpose  of  support- 
ing guy-rods  or  brackets. 

Pole  -  Changing  and  Interrupting 
Electrode  Handle. — A  handle  provided 
for  the  ready  insertion  of  the  electro- 
therapeutic  electrodes,  containing  means 
for  interrupting  or  changing  the  direction 
of  the  current. 

Pole  Changer. — (1)  A  switch  or  key  for 
reversing  the  direction  of  a  current. 
(2)  A  reverser.  (3)  A  generator  of  alter- 
nating currents  at  a  telephone  exchange, 
consisting  of  an  electro-magnetically 
driven  pendulum  which  periodically  re- 
verses a  call  battery. 

Pole-Changing  Key. — (1)  A  pole  changer. 
(2)  A  key  which  effects  a  reversal. 

Pole-Changing  Switch. — A  switch  em- 
ployed for  changing  the  direction  of  the 
current  in  any  circuit. 


Pol.] 


886 


[Pol. 


Pole  Clamp. — An  iron  clamp  on  a  pole 

employed  for  the  support  of  span  wires  or 

brackets. 
Pole    Climbers.— Devices    employed    by 

line-men  for  climbing  wooden  telegraphic 

poles. 

Pole  Clip. — A  pole  clamp. 

Pole  Counter. — A  hand-operated  register- 
ing device  employed  for  counting  tele- 
graph or  other  poles. 

.Pole  Guys. — A  guy  employed  for  the  stif- 
fening of  a  pole. 

Pole  Hood. — A  hood  or  cover  placed  at 
the  top  of  a  pole. 

Pole  Indicator. — Any  device  for  readily 
determining  the  polarity  of  a  pole,  of  a 
magnet,  or  of  an  electric  source. 

Pole-Pieces  of  Dynamo  or  Motor. — 
A  mass  of  iron  or  steel  connected  with  the 
poles  of  the  field-magnets  of  a  dynamo 
or  motori  and  shaped  to  conform  to  the 
outline  or  contour  of  the  armature. 

Pole  Platform. — A  platform,  capable  of 
supporting  one  or  more  men,  placed  on  a 
terminal  pole,  and  provided  with  a  cable 
box  for  the  purpose  of  affording  a  ready 
means  of  inspecting  and  arranging  the 
conductors  in  the  box. 

Pole  Roof. — A  metallic  cap  or  roof  of  a 
telegraph  or  telephone  pole. 

Pole  Shoe. — A  plate  of  iron  or  steel 
mounted  on,  and  forming  the  pole-piece 
of  a  field  magnet,  and  sometimes  used 
for  supporting  a  field  coil. 

Pole  Steps. — Steps  permanently  fastened 
to  a  wooden  or  iron  pole  to  facilitate 
climbing. 

Pole  Support  for  Arc-Lamps.— A  sup- 
port placed  on  the  top  or  end  of  a  pole  for 
the  reception  of  an  arc-lamp. 

Pole  Tips. — A  name  sometimes  employed 
for  the  horns  of  a  dynamo  field  pole. 

Pole  Top. — A  fixture  for  the  top  of  an 
aerial  pole  provided  with  a  number  of 
arms  and  insulators  for  the  support  of 
additional  aerial  circuits. 

Poles  of  Condenser. — The  terminals  of  a 
condenser. 

Poles  of  Magnetic  Intensity.  —  The 
earth's  magnetic  poles  as  determined  by 
means  of  observations  of  magnetic  inten- 
sity. 

Poles  of  Magnetic  Verticity.— The 
earth's  magnetic  poles  as  determined  by 
means  of  a  dipping  needle. 

Poling  Boards.— Short  rough  boards  laid 
vertically  against  the  sides  of  an  excava- 
tion, in  packed  soil,  and  kept  in  place  by 
cross  struts. 


Polishing  Bob.— A  disc  of  tough  wood 
provided  on  its  edge  with  a  ring  or  rim  of 
leather  or  hide,  on  which  finely  divided 
emery  is  placed,  employed,  when  mounted 
on  a  shaft  and  put  in  rapid  rotation,  for 
polishing  articles  so  as  to  prepare  them 
for  electro-plating. 

Polishing  Mop.— A  disc  formed  of  circu- 
lar pieces  of  calico,  felt,  or  other  similar 
soft  material,  mounted  on  a  shaft  and  em- 
ployed, when  put  in  rapid  rotation,  for 
polishing  surfaces  for  electro-plating. 

Polycyclic  System.— A  multiphase  sys- 
tem. 

Polymerism. — A  species  of  isomerism  in 
which  chemical  compounds  of  the  same 
proportional  constitution,  as  determined 
by  analysis,  have  different  properties,  due 
to  having  different  numbers  of  atoms  in 
their  molecules. 

Polymorphic  Instrument. — A  term 
sometimes  used  for  a  polymorphic  ma- 
chine. 

Polymorphic  Machine. — An  apparatus 
capable  of  effecting  the  transformation  of 
alternating-currents  from  one  species  to 
another. 

Polyphasal  Coupling  of  Magnetic  Cir- 
cuits.— The  inter-linking  of  magnetic 
circuits  traversed  by  polyphase  magnetic 
fluxes. 

Polyphase. — Possessing  more  than  a  single 
phase. 

Polyphase  Alternator. — An  alternator 
capable  of  supplying  polyphase  currents. 

Polyphase  Apparatus. — Apparatus  oper- 
ated by  polyphase  currents. 

Polyphase  Armature. — An  armature  so 
wound  as  either  to  produce  polyphase  cur- 
rents, or  to  be  operated  by  such  currents. 

Polyphase  Armature- Windings. — 
Windings  of  polyphase  generators. 

Polyphase  Asynchronous  Motor.— (1) 
An  asynchronous  motor  operated  by  mul- 
tiphase currents.  (2)  A  multiphase  in- 
duction motor. 

Polyphase  Choking-Coil. — (1)  A  choking 
coil  in  a  polyphase  system.  (2)  A  click- 
ing coil  operated  by  polyphase  currents. 

Polyphase  Circuits. — The  circuits  em- 
ployed in  polyphase-current  distribution. 

Polyphase  Currents. — Currents  differing 
in  phase  from  one  another  by  a  definite 
amount,  and  suitable  for  the  operation  of 
polyphase  motors  or  similar  apparatus. 

Polyphase  Dynamo. — A  polyphase  gen- 
erator. 
Polyphase    Generator. — An    alternator 


Pol.] 


887 


[Pos. 


which  delivers  two  or  more  alternating 
currents  definitely  differing  in  phase. 

Polyphase  Inductor  -  Alternator. — An 
inductor  alternator  suitable  for  producing 
polyphase  currents. 

Polyphase  Inductor-Generator. — (1)  A 
polyphase  genei'ator  of  the  inductor  type 
in  which  no  conductor  or  winding  is 
rotated.  (2)  A  polyphase  inductor-alter- 
nator. 

Polyphase  Motor. — A  motor  operated  by 
means  of  polyphase  currents. 

Polyphase  Power. — Power  transmitted 
by  means  of  polyphase  currents. 

Polyphase  Rotary  -  Converter. — A  ro- 
tary converter  operated  by  or  producing 
polyphase  currents. 

Polyphase  Switchboard.  —  A  switch- 
board suitable  for  controlling  polyphase 
circuits. 

Polyphase  Synchronous  -  Motor. — A 
synchronous  motor  operated  by  polyphase 
currents. 

Polyphase  Transformer. — A  transform- 
er suitable  for  use  in  connection  with 
polyphase  circuits. 

Polyphase  Transmission.  — Transmis- 
sion of  power  by  means  of  polyphase 
currents. 

Polyphase  Working. — A  general  term 
employed  to  express  the  application  of 
polyphase  currents. 

Polyphased  Alternating-Currents. — A 
term  employed  for  polyphase  currents. 

Polyphaser. — (1)  A  term  sometimes  em- 
ployed for  a  polyphase  alternator,  or 
generator.  (2)  A  multiphaser. 

Polyphotal  Arc-Light  Regulator.— A 
regulator  for  arc-lamps  suitable  for  use 
in  a  number  of  series-connected  arc 
lamps. 

Poacelet. — A  name  proposed  for  a  unit  of 
activity  equal  to  100  kilogramme-metres 
per  second  ;  or,  approximately,  one  kilo- 
watt. 

Pondermotive  Force. — The  force  re- 
quired for  the  movement  of  gross  matter. 

Pony  Insulators. — A  name  given  to  a  par- 
ticular type  of  glass  telegraph  insulator. 

Pony  Telegraphic  Relay.— A  name  ap- 
plied to  a  particular  form  of  telegraphic 
relay. 

Porcelain. — A  variety  of  insulating  sub- 
stance, made  from  kaolin. 

Porcelain  Insulator.— Any  insulator  of 
porcelain  for  supporting  a  wire. 

Porcelain  Wire-Tube.— A  porcelain  tube 


employed    for  passing  an  electric  wire 
through  a  partition. 

Porosity. — A  property  of  matter  in  virtue 
of  which  spaces  or  pores  are  left  between 
its  constituent  atoms  and  molecules. 

Porous  Cell. — A  jar  of  unglazed  earthen- 
ware employed  in  a  double-fluid  voltaic 
cell  to  mechanically  separate  the  two 
electrolytes. 

Porous  Cup. — A  porous  cell. 

Porous  Insulation. — An  insulating  ma- 
terial containing  air  or  other  gas. 

Porous  Jar  or  Pot. — A  porous  cell. 

Porret's  Phenomenon. — An  increase  in 
the  diameter  of  a  nerve  fibre  in  the  neigh- 
borhood  of  the  positive  pole,  when  trav- 
ersed by  a  voltaic  current. 

Portable  Conductors. — Flexible  cords 
containing  insulated  wires  suitable  for 
use  with  portable  lamps,  motors,  or  other 
devices. 

Portable  Electrometer. — A  form  of  read- 
ily transportable  Thomson  electrometer. 

Portable  Igniting  Device. — (1)  A  porta- 
ble electric  mine-exploder.  (2^  A  porta- 
ble electric  gas-igniter.  • 

Portable-Lamp  Guard. — A  guard  pro- 
vided for  the  protection  of  a  portable 
lamp. 

Portable  Tachometer. — A  portable  speed 
indicator. 

Portative  Power  of  Magnet.— The  lift- 
ing  or  sustaining  power  of  a  magnet. 

Portelectric. — (1)  An  electric  carrier.  (2} 
A  system  of  electric  transportation  by 
means  of  the  successive  attractions  of  a 
number  of  hollow  helices  of  insulated 
wire  on  a  moving  iron  core. 

Portrait,  Electric. — A  portrait  formed  on 
paper  by  the  electric  volatilization  of  gold 
or  other  metal. 

Position-Finder,  Electric. — An  electric 
device  by  means  of  which  the  position  of  a 
distant  object  can  be  determined. 

Positive  Brush  of  Dynamo. — The  brush 
of  a  dynamo  out  from  which  flows  the 
current  generated  in  the  armature. 

Positive  Brush  of  Motor. — The  brush 
connected  to  the  positive  terminal  of  a 
driving  source. 

Positive  Carbon. — That  carbon  of  a  vol- 
taic arc  out  from  which  the  current  flows 
into  the  arc. 

Positive  Charge. — (1)  According  to  th« 
double-fluid  hypothesis,  a  charge  of  posi- 
tive electricity.  (2)  According  to  the 
single-fluid  hypothesis,  any  excess  of  an 
assumed  electric  fluid.  (3)  A  charge  of 
electricity  having  a  positive  potential. 


Pos.] 


[Pot. 


Positive  Currents. — A  term  employed  in 
telegraphy  for  currents  sent  over  a  line 
from  the  positive  pole  of  a  battery. 

Positive-Direction  of  Lines  of  Mag- 
netic Force. — The  direction  in  which  a 
free  north-seeking  pole  would  move  along 
the  lines  of  force  when  placed  in  a  mag- 
netic field. 

Positive  -  Direction  of  Simple  -  Har- 
monic Motion. — The  motion  which  a 
body  moving  with  simple-harmonic  mo- 
tion has,  when  its  corresponding  circularly 
moving  point  moves  counter-clockwise. 

Positive-Direction  of  Electric  Con- 
vection of  Heat. — A  direction  in  which 
heat  is  transmitted  through  an  unequally 
heated  conductor  by  electric  convection 
during  the  passage  of  electricity  through 
the  conductor,  the  same  as  that  of  the 
current. 

Positive-Direction  Round  a  Circuit. — 
In  a  plane  circuit  looked  at  from  the  posi- 
tive side,  a  direction  opposed  to  that  of 
the  hands  of  a  clock. 

Positive-Direction  Through  a  Circuit. 
In  a  plane  circuit  carrying  a  positive  cur- 
rent, a  direction  through  the  circuit  simi- 
lar to  that  of  the  advance  of  a  corkscrew 
which  is  twisted  round  in  the  direction 
of  the  current. 

Positive  Electricity.^— (1)  One  of  the 
phases  of  electric  excitement.  (2)  That 
kind  of  electric  charge  produced  on  cot- 
ton when  rubbed  against  resin. 

Positive  Electrification. — (1)  The  charge 
of  a  body  with  positive  electricity.  (2)  A 
positive  charge.  (3)  An  electrification  of 
positive  potential. 

Positive  Electrode. — The  electrode  con- 
nected with  the  positive  pole  of  an  elec- 
tric source. 

Positive  Electromotive  Force. — An 
E.  M.  F.  which  will  communicate  a  posi- 
tive charge. 

Positive  Feeders. — The  feeders  that  are 
connected  with  the  positive  terminal  of 
a  dynamo. 

Positive  Fluid.— (1)  The  specific  fluid  that 
was  formerly  believed  by  the  adherents 
of  the  double-fluid  electric  hypothesis  to 
be  the  cause  of  electric  excitement.  (2) 
The  surplusage  of  an  assumed  single 
electric  fluid. 

Positive  Lead. — In  a  system  of  parallel 
distribution,  a  lead  connected  with  the 
positive  generator-terminal,  or  with  the 
positive  bus-bars. 

Positive  Omnibus-Bars.— The  bus-bars 
that  are  connected  with  the  positive  ter- 
minal of  a  dynamo. 


Positive  Phase  of  Electrotonus. — An 
increase  in  the  electromotive  force  of  a 
nerve  produced  by  sending  a  current 
through  the  nerve  in  the  same  direction 
as  the  nerve  current. 

Positive  Plate  of  Storage  Cell.— (1)  That 
plate  of  a  storage  cell  which  is  converted 
into,  or  covered  by,  a  layer  of  lead  peroxide 
by  the  action  of  the  charging  current. 
(2)  That  plate  of  a  storage  cell  which  is 
connected  with  the  positive  terminal  of  a 
charging  source,  and  which  is,  therefore, 
the  positive  pole*  of  the  cell  on  dis- 
charging. 

Positive  Plate  of  Voltaic  Cell.— (1)  The 
electro-positive  element  of  a  voltaic 
couple.  (2)  That  element  of  a  voltaic 
couple  which  is  positive  in  the  electrolyte 
of  the  cell.  (3)  The  plate  which  forms 
above  the  surface  of  the  electrolyte,  the 
negative  pole  of  the  cell. 

Positive  Pole. — That  pole  of  an  electric 
source  out  of  which  the  current  is  as- 
sumed to  flow. 

Positive  Potential.— (1)  That  potential  in. 
a  circuit  external  to  a  source  from  which 
the  electric  current  flows.  (2)  The  higher 
potential  or  higher  electric  level. 

Positive  Rotation. — Left-handed  or  coun- 
ter-clockwise rotation. 

Positive  Side  of  Circuit. — That  side  of  a 
circuit  bent  in  the  form  of  a  circle  in 
which,  if  an  observer  stood  with  his  head 
in  the  positive  region,  he  would  see  the 
current  pass  around  him  counter-clock- 
wise. 

Positive  Spark. — A  spark  produced  by 
the  disruptive  discharge  of  a  positively 
charged  conductor. 

Positive  Terminal. — The  terminal  con- 
nected with  the  positive  pole  of  a  source. 

Positive  Wire. — The  wire  connected  with 
the  positive  pole  of  a  source. 

Positively  Excited. — Charged  with  posi- 
tive electricity. 

Pot  Operator. — (1)  The  operator  which  i» 
the  double  inverse  of  the  curl  operator. 
(2)  The  operator  which  acting  upon  a 
point  function  in  space  produces  its  vector 
potential. 

Potash  Brush. — A  brush  employed  in 
cleansing,  by  the  use  of  a  caustic  solution, 
surfaces  which  are  to  be  electro-plated. 

Potential  Dynamometer. — An  electro- 
dynamometer  suitably  arranged  for  the 
measurement  of  electric  potential  differ- 
ences. 

Potential,  Electric. — (1)  The  power  of 
doing  electric  work.  (2)  Electric  level. 


Pot.] 


889 


[Pra. 


Potential   Energy. — (1)   Stored   energy. 

(2)  Potency  or  capability  of  doing  work. 

(3)  Energy  possessing  the  power  or  potency 
of  doing  work,  but  not  actually  perform- 
ing such  work. 

Potential  Function. — A  point  function 
of  space,  whose  space  differentiation 
gives  a  vector  point-function. 

Potential  Galvanometer. — A  term  some- 
times applied  to  a  voltmeter. 

Potential  Gradient.— (1)  The  rate-of-fall 
of  potential  at  a  point.  (2)  A  line  repre- 
senting the  fall  of  potential  in  a  circuit. 

Potential  Indicator. — An  apparatus  for 
indicating  potential  difference. 

Potential  of  Conductors. — (1)  The  rela- 
tion existing  between  the  quantity  of 
electricity  in  a  conductor  and  its  ca- 
pacity. (2)  That  property  of  a  conductor 
whereby  electric  work  is  done  when  an 
electric  charge  is  moved  towards  it. 

Potential  Beceptacle.— A  receptacle  in 
a  switchboard,  wall,  cover,  base,  or  other 
device,  for  receiving  a  plug  connected  to 
a  potential-indicator,  or  voltmeter. 

Potentiometer. — An  apparatus  for  the 
galvanometric  measurement  of  electro- 
motive forces,  or  differences  of  potential, 
by  a  zero  method,  and  by  relation  to  a 
standard  E.  M.  F. 

Potentiometer  Voltmeter.— A  voltmeter 
operating  on  the  potentiometer  principle 
and  employing  a  standard  voltaic  cell  as 
its  basis  of  measurement. 

Potentiometer  Wire.— A  graduated  wire 
employed  in  a  potentiometer  for  the  pur- 
pose of  securing  proportionate  linear  re- 
sistances and  thereby  proportional  poten- 
tial differences. 

Pounds-Per-Mile-Ohm.— (1)  A  standard 
of  conductivity  of  telegraph  or  telephone 
wires.  (2)  The  weight  of  a  uniform  wire 
offering  one  ohm  per  mile  at  standard 
temperature. 

Poundal.— (1)  The  -weight  of  a  pound,  or 
the  earth's  attraction  upon  the  mass  of  a 
pound  of  matter,  at  any  terrestrial  locality. 
(2)  A  gravitational  unit  of  force. 

Power. — (1)  Rate-of-doing-work,  express- 
ible in  watts,  joules-per-second,  foot- 
pounds-per-hour,  etc.  (2)  Activity. 

Power  Cable.— A  cable  employed  for  the 
electric  transmission  of  power. 

Power  Circuits. — Circuits  employed  for 
the  electric  transmission  of  power. 

Power  Coefficient.— (1)  In  an  alternat- 
ing-current circuit,  the  ratio  of  the 
power  component  of  electromotive  force 
to  the  power  component  of  current.  (2) 

13— 


The  apparent  resistance  of  an  alternating- 
current  circuit. 

Power  Cylinder.—  The  commutating 
cylinder  of  a  street-car  controller  as  dis- 
tinguished from  the  reversing  cylinder. 

Power,  Electric. — Power  developed  by 
means  of  electricity. 

Power  Electromotive  Force. — A  term 
sometimes  employed  for  that  component 
of  the  E.  M.  F.  acting  in  the  same  direc- 
tion with  the  current,  or  in  phase  with  it, 
and  expended  in  overcoming  effective  or 
ohmic  resistance. 

Power  Factor.— The  ratio  of  the  true 
watts  to  the  apparent  volt-amperes  in  an 
alternating-current  conductor,  circuit,  or 
device. 

Power-Factor  of  Transformer.— The 
ratio  of  the  true  watts  absorbed  by  a 
transformer  under  a  given  load  to  the  ap- 
parent watts  absorbed. 

Power  Generator. — A  generator  of  alter- 
nating currents  at  a  central  telephone  ex- 
change. 

Power-House. — A  house  provided  with 
the  plant  necessary  for  the  production  of 
the  electric  power  required  in  a  system 
of  electric  distribution. 

Power  Measurer,  Electric. — A  watt- 
meter. 

Power  Meter. — A  wattmeter. 

Power  of  Periodic  Currents. — With 
simple-harmonic  currents,  the  product  of 
effective  current  strength,  the  driving 
effective  pressure,  and  the  cosine  of  the 
difference  of  phase  between  them. 

Power-Wire  of  Monocyclic  System. 
The  wire  or  circuit  of  a  monocyclic  sys- 
tem employed  for  supplying  currents  for 
the  operation  of  triphase  electric  motors. 

Poynting's  Law. — At  any  point  in  space, 
electro-magnetic  energy  moves  perpen- 
dicularlv  to  the  plane  containing  the  lines 
of  electric  force  and  the  lines  of  magnetic 
force,  and  the  amount  of  energy  per  second 
crossing  the  unit  area  of  this  plane  is 
equal  to  the  product  of  the  intensities  of 
the  two  forces,  multiplied  by  the  sine  of 
the  angle  between  them,  and  divided  by 

4T. 

Practical  Current. — A  term  sometimes 
employed  for  the  effective  current  in  an 
alternating-current  circuit. 

Practical  Solenoid. — A  name  applied  to 
an  ordinary  solenoid,  in  order  to  distin- 
guish it  from  an  ideal  solenoid. 

Practical  Unit  of  Inductance. — (1)  A 
unit  of  length  equal  to  the  earth's  quad- 
rant, or  109  centimetres.     (2)  The  henry. 
Vol.  2 


Pra.] 


890 


[Pri. 


Practical  Unit  of  Magneto-Motive 
Force. — A  value  of  magneto-motive  force 
equal  to  4?r  multiplied  by  an  ampere  of  one 
turn,  or  equal  to  one-tenth  of  an  absolute 
unit  of  M.  M.  F. 

Practical  Unit  of  Self-induction.— A 
term  frequently  used  for  the  practical 
unit  of  inductance. 

Practical  Units. — Definitely  related  mul- 
tiples or  sub-multiples  of  the  absolute  or 
centimetre-gramme-second  units. 

Preamble. — In  telegraphy,  the  opening 
words  of  a  despatch  containing  the  names 
of  the  sending  and  delivery  stations,  the 
number  of  words  in  the  message,  the 
code  time,  and  other  service  instructions, 
as  distinguished  from  the  text  of  the  mes- 


Prefix. —  In  telegraphy,  a  code  letter  or 
group  of  letters  prefixed  to  a  message  to 
indicate  its  nature  or  relative  importance. 

Prepayment  Meter. — A  device  whereby 
a  certain  electric  service  is  given  by 
means  of  an  electric  penny-in-the-slot  ap- 
paratus. 

Presbyopic. — Far-sighted. 

Press  Button. — A  push-button. 

Press  Message. — (1)  A  message  directed 
to  a  newspaper  or  daily  publication.  (2) 
A  news  message. 

Press  Telegram. — A  press  message. 

Pressant. — A  name  proposed  for  a  unit  of 
magneto-motive  force. 

Pressel. — (1)  A  press  switch  or  push  con- 
nected to  the  end  of  a  flexible  pendant 
conductor.  (2)  A  pendant  press-button. 

Pressure,  Electric. — A  term  sometimes 
employed  for  difference  of  potential,  or 
electromotive  force. 

Pressure  Equalizer. — (1)  An  automatic 
device  employed  in  connection  with  a 
storage  battery  to  maintain  a  uniform 
pressure  at  its  terminals  under  different 
loads.  (2)  A  regulating  device  employed 
in  a  system  of  electric  distribution  for 
maintaining  the  pressure  uniform. 

Pressure  Indicator. — Any  device  for  in- 
dicating the  electric  pressure  in  a  circuit. 

Pressure  Panel  of  Switchboard.— That 
panel  in  a  switchboard  which  contains 
apparatus  for  measuring  the  mean  electric 
pressure  in  the  power  house. 

Pressure  Recording-Gauge. — Any  form 
of  recording  voltmeter. 

Pressure  .Wires. — Small  insulated  copper 
conductors,  employed  in  a  system  of  un- 
derground street  mains,  extending  from 
points  of  junction  between  the  feeders 
and  the  mains  to  the  central  station,  to 


indicate  in  the  central  station  the  pres- 
sure supplied  to  the  mains. 

Pricking  Wires. — A  method  sometimes 
adopted  for  locating  a  wire,  by  connect- 
ing a  battery  with  one  pole  to  earth  and 
the  other  pole  to  the  wire  sought  for,  by 
means  of  a  brad-awl  or  needle  inserted 
through  the  gutta-percha  insulating  ma- 
terial. 

Primary  Admittance. — The  admittance 
of  the  primary  coil  or  coils  of  an  alternat- 
ing-current transformer  or  induction  ma- 
chine. 

Primary  Ampere-Turns. — The  ampere- 
turns  in  the  primary  coil  of  a  transformer. 

Primary  Battery. — The  combination  of  a 
number  of  separate  primary  cells  to  form 
a  single  electric  source. 

Primary  Cell. — A  term  sometimes  em- 
ployed for  a  voltaic  cell. 

Primary  Coil  of  Transformer.— (1)  That 
coil  of  an  induction  coil  or  transformer 
on  which  the  primary  electromotive  force 
is  impressed.  (2)  The  driving  coil  of  a 
transformer.  (3)  The  coil  which  receives 
energy  prior  to  transformation. 

Primary  Currents. — Currents  flowing  in 
a  primary  circuit,  as  distinguished  from 
currents  flowing  in  a  secondary  circuit. 

Primary  Cut-Out. — A  cut-out  placed  in 
the  primary  circuit  of  a  transformer. 

Primary  Electric  Clock. — A  term  some- 
times employed  in  place  of  controlling  or 
master  clock. 

Primary  Electric  Heater. — A  term  pro- 
posed for  the  main  electric  heater  in  a 
building. 

Primary  Electromotive  Force. — The 
electromotive  force  applied  to  the  pri- 
mary coil  of  a  transformer. 

Primary  Element  of  Induction  Motor. 
The  element  connected  with  the  line  or 
lines,  as  distinguished  from  the  element- 
closed  upon  itself. 

Primary  Fuse  Box. — A  fuse  box  placed 
in  the  primary  circuit  of  an  induction 
coil  or  transformer. 

Primary  Impedance. — (1)  The  imped- 
ance of  the  primary  coil  of  a  transformer, 
or  of  an  induction  machine.  (2)  The 
impedance  'of  the  primary  coil  of  a  trans 
former,  or  of  an  induction  machine,  in- 
dependent of  the  reactance  of  mutual 
inductance,  or  the  C.  E.  M.  F.  of  mutual 
linkage. 

Primary  Plate  of  Condenser.— That 
plate  of  a  condensing  transformer  in 
which  the  inducing  charge  is  placed  in 
order  to  induce  a  charge  of  different 
potential  in  the  secondary  plate. 


Pri.] 


891 


[Pro. 


Primary  Spiral  of  Induction  Coil.— The 
primary  of  an  induction  coil  or  trans- 
former. 

Prime  Conductor. — The  positive  conduc- 
tor of  a  frictional  electric  or  electrostatic 
machine. 

Prime  Flux-Density. — The  magnetic 
density  of  the  prime  magnetic  flux  in  a 
ferric  circuit. 

Prime  Magneto-Motive  Force. — The 
magneto-motive  force  due  to  the  magnet- 
izing current  in  a  ferric  circuit. 

Prime  Magnetic  Flux. — (1)  A  term  em- 
ployed for  the  flux  produced  in  a  ferric 
circuit  by  the  prime  magneto-motive 
force,  as  distinguished  from  the  induced, 
aligned,  or  structural  magneto-motive 
force.  (2)  Magnetizing  force  as  distin- 
guished from  magnetic  induction. 

Prime  Motor. — A  prime  mover. 

Prime  Mover. — A  motor  which  drives  the 
secondary  motors  or  movers. 

Primordial  Atoms. — The  atoms  or  com- 
pounds into  which  it  has  been  assumed 
that  the  so-called  elementary  atoms  of 
ordinary  matter  are  broken  up  by  means 
of  the  cathode  rays. 

Principal  Circuit. — A  main  circuit  as  dis- 
tinguished from  a  derivation  circuit. 

Principal  Current. — A  main  current  as 
distinguished  from  a  derivation  current. 

Principal  Telegraphic  Circuit. — A  term 
sometimes  used  for  the  main  circuit. 

Principal  Telegraphic  Current.— A 
term  sometim.es  employed  for  the  main 
current. 

Printing  Telegraphy. — A  system  of  teleg- 
raphy in  which  the  messages  received 
are  printed  on  a  paper  fillet. 

Prism  Error  of  Compass. — The  error  in 
a  magnetic  bearing  due  to  an  inaccurate 
setting  of  the  prism  relatively  to  the  com- 
pass card. 

Probable  Error  of  an  Observation.— A 
magnitude  of  accidental  error  in  the  re- 
peated observation  of  a  quantity,  such 
that  it  is  just  as  probable  that  the  real 
accidental  error  is  greater  as  that  it  is  less 
than  this  magnitude. 

Probe,  Electric. — A  metallic  conductor 
inserted  in  the  body  of  a  patient  in  order 
to  ascertain  the  position  of  a  bullet  or 
other  foreign  metallic  substance. 

Process  of  Carbonization. — Means  for 
carbonizing  carbonizable  material. 

Production  of  Cold  by  Electricity.— 
The  absorption  of  energy,  and  consequent 
reduction  of  temperature  at  a  thermo- 
electric junction,  by  the  passage  of  an 


electric  current   in  a  certain    direction 
across  such  junction. 

Production  of  Electricity  by  Light. — 
The  production  of  electric  difference  of 
potential  by  the  action  of  light. 

Prognosis,  Electric. — A  prognosis  or  pre- 
diction of  the  fatal  or  non-fatal  termina- 
tion of  a  disease  from  an  electric  diagno- 
sis, based  on  the  exaggerated  or  dimin- 
ished reactions  of  the  excitable  tissues  of 
the  body,  when  subjected  to  the  varying 
influences  of  electric  currents. 

Progression  of  Magnetic  Flux.— In  a 
polyphase  motor,  the  circular  motion  of 
the  magnetic  flux  around  the  field  or 
armature. 

Projecting  Power  of  Magnet. — (1)  The 
range  within  which  a  magnet  produces 
sensible  attraction  or  repulsion.  (2)  The 
power  of  an  electro-magnet  to  repel  a 
suitably  placed  armature. 

Projection  Arc-Lamp.  —  An  arc- lamp 
suitable  for  use  in  a  projector  or  search- 
light. 

Projector,  Electric. — A  projector  or 
search-light  provided  with  an  electric  arc- 
light  at  its  focus. 

Projection  Armatures. — Slotted  arma- 
tures in  which  the  width  of  the  slot  is  suf- 
ficiently great  to  leave  a  distinct  projec- 
tion in  the  armature  surface  as  distin- 
guished from  tunnel  armatures  in  which 
the  slot  is  very  narrow. 

Prony  Brake. — A  mechanical  device  for 
measuring  the  power  of  a  driving  shaft 
by  the  application  of  a  brake  to  the  periph- 
ery of  a  wheel  firmly  keyed  on  the  shaft. 

Proof-Plane. — A  small  insulated  conduc- 
tor employed  to  take  and  carry  electric 
charges  from  the  surfaces  of  insulated 
charged  conductors. 

Proportional  Coils. — Pairs  of  resistance 
coils,  generally  of  10,  100  and  1,000  ohms 
each,  forming  the  proportional  arms  of 
a  balance  or  bridge,  and  employed  in  the 
box  or  commercial  form  of  Wheatstone's 
bridge. 

Proportionate  Arms. — The  two  resist- 
ances or  arms  of  an  electric  bridge,  whose 
relative  or  proportionate  resistances  only 
are  required  to  be  known,  in  order  to  de- 
termine in  connection  with  a  known  re- 
sistance, the  value  of  an  unknown  resist- 
tance  placed  in  the  remaining  arm  of  the 
bridge. 

Proposed  Definition  for  2,000  Candle- 
Power  Arc. — (1)  Such  an  arc  as  will  re- 
quire at  ordinary  pressures  450  watts  ac- 
tivity to  maintain  it.  (2)  A  450- watt  arc. 


Pro.] 


892 


[Puin. 


Propulsion,  Electric. — A  general  term 
for  driving  by  electric  power. 

Prostration,  Electric.— Physiological  ex- 
haustion or  prostration,  resembling  that 
produced  by  sun-stroke,  resulting  from 
exposure  to  an  unusually  powerful  arc. 

Protecting  Battery. — In  submarine  cable 
telegraphy,  a  battery  permanently  con- 
nected to  a  faulty  cable  through  a  high  re- 
sistance, for  the  purpose  of  sending  a 
negative  current  through  the  fault  in 
order  to  keep  the  exposed  surface  of  the 
conductor  free  from  corrosion  salts. 

Protection  of  Houses,  Ships  or  Build- 
ings, Electric. — Means  for  protection 
from  the  destructive  effects  of  a  lightning 
discharge,  consisting  essentially  in  the 
use  either  of  lightning-rods  or  of  an  en- 
closing conducting  shell. 

Protection  of  Metals,  Electric.— The 
protection  of  a  metal  from  corrosion  by 
placing  it  in  connection  with  another 
metal,  which,  when  exposed  to  the  cor- 
roding liquid,  vapor  or  gas,  will  form 
with  the  surrounding  liquid  the  positive 
element  of  a  voltaic  couple  and  will, 
therefore,  alone  be  corroded. 

Protection  of  Ship's  Sheathing,  Elec- 
tric.— Attaching  pieces  of  zinc  to  the 
copper  sheathing  of  a  ship  for  the  purpose 
of  preventing  the  corrosion  of  the  copper 
by  the  water. 

Protective  Action. — (1)  The  electric  pro- 
tection of  metals.  (2)  The  protection  of 
structures  from  lightning  by  lightning 
protectors. 

Protective  Sheath. — A  device  attached 
to  a  transformer  or  converter,  consisting 
of  a  copper  strip  or  plate  connected  to 
the  earth  and  interposed  between  the 
primary  and  secondary  windings,  to  pre- 
vent any  connection  from  taking  place 
between  the  high-potential  primary  and 
the  low-potential  secondary  circuit. 

Protective  Throw. — A  term  proposed  for 
the  protection  afforded  by  a  magnetic 
field  to  paramagnetic  metals  exposed  to 
chemical  action. 

Protoplasm. — Bioplasm. 

Psychrometer. — A  form  of  recording  hy- 
grometer. 

Public  Supply  Instruments. — Electric 
meters  designed  for  registering  the  cur- 
rent or  energy  supplied  to  a  consumer. 

Pull. — A  contact-maker  similar  in  general 
construction  to  a  push-button,  but  oper- 
ated by  a  pull  instead  of  by  a  push. 

Pull  Contact.— Any  contact  that  is  ef- 
fected by  the  movement  of  a  pendant  or 
pull. 


Pulley. — A  wheel  placed  on  a  shaft  for  the 
driving  of  the  same  by  means  of  a  belt. 

Pull-Off. — (1)  An  insulator  employed  on 
curves  to  hold  the  trolley  wire  in  proper 
position.  (2)  A  steel  wire  attached  to  a 
trolley  wire  through  an  insulator,  and 
employed  to  pull  the  trolley  wire  into 
position  over  a  curve  in  the  track. 

Pull-Off  Pole.— A  pole  provided  for  the 
suspension  of  a  pull-off  wire,  or  wires. 

Pulsating  Current. — A  pulsatory  current. 

Pulsating  Electromotive  Force.— An 
electromotive  force  whose  direction  is 
pulsatory. 

Pulsating  Motor. — A  motor  employing  a 
reciprocating  movement  in  its  armature 
as  opposed  to  the  ordinary  rotary  motion. 

Pulsation. — (1)  A  quantity  of  the  nature 
of  an  angular  velocity,  equal  to  2  TT  mul- 
tiplied by  the  frequency  of  the  oscillation, 
or  to  2  TT  divided  by  the  duration  of  a 
single  period.  (2)  In  a  simple-harmonic 
current  circuit,  the  angular  velocity  of 
the  corresponding  circularly  moving 
point. 

Pulsation,  Electric. — An  electric  pulse 
or  oscillation. 

Pulsation  of  Reactance.  —  Variations 
periodically  occurring  in  the  apparent 
reactance  of  an  alternating-current  cir- 
cuit or  machine. 

Pulsation  of  Resistance. — Periodic  vari- 
ations in  the  apparent  resistance  of  an 
alternating  current  circuit  or  apparatus. 

Pulsatory  Continuous-Current.  —  A 
current  whose  direction  remains  constant, 
but  whose  intensity  is  subject  to  steady 
changes. 

Pulsatory  Electromotive   Force. — An" 
electromotive  force  whose  value  is  sub- 
ject to  pulsatory  changes. 

Pulsatory  Magnetic-Field.  —  A  field 
whose  strength  pulsates  in  such  a  man- 
ner as  to  induce  oscillatory  currents  in 
neighboring  circuits. 

Pulsatory  Magnetism. — Magnetism  pro- 
duced by  pulsatory  currents. 

Pulse,  Electric.— (1)  An  electric  oscilla- 
tion. (2)  A  momentary  flow  of  electricity 
through  a  conductor  which  gradually 
varies  from  zero  value  to  the  maximum, 
and  then  to  zero  value  again,  like  a  pulse 
or  vibration  in  an  elastic  medium. 

Pumping  of  Alternating-Current  Dy- 
namo.— A  pulsation  in  the  motion  of  a 
synchronously-running  alternating-cur- 
rent generator  or  motor,  due  to  imperfect 
synchronism. 

Pumping  of  Electric  Lights.— A  term 


Pun.] 


893 


sometimes  applied  to  a  pulsatory  or  peri- 
odic increase  or  decrease  iu  the  brilliancy 
of  lights. 

Punched  -  Clip  Switch.— A  form  of 
switch  in  which  the  clips  are  punched  out 
of  sheet  metal. 

Puncher.— In  automatic  telegraphy,  a  per- 
forator. 

Punning  of  Telegraph  Pole.— The  proc- 
ess of  packing  the  earth  around  the  base 
of  a  telegraph  pole. 

Pupillary  Photometer. — A  photometer 
whose  operation  is  dependent  on  the 
diminution  of  the  diameter  of  the  pupil 
of  the  eye  with  the  intensity  of  the  light 
striking  the  eye. 

Pure  Spectrum. — A  single  spectrum  or 
distribution  of  luminous  frequencies  as 
distinguished  from  a  spectrum  which  is 
formed  by  the  superposition  of  a  number 
of  .spectra  slightly  displaced  with  refer- 
ence to  one  another. 

Push. — A  term  sometimes  applied  to  a 
push  button. 

Push  Box. — A  box  provided  for  the  recep- 
tion of  the  mechanism  of  a  push  button 
or  push. 

Push  Button. — A  device  for  closing  an 
electric  circuit  by  the  movement  of  a 
button. 

Push-Button  Battler.— (1)  A  device  con- 
nected with  a  push-button  to  show  that  a 
bell  connected  at  a  distant  point  in  the  cir- 
cuit of  the  button  rings  when  the  button 
is  pressed.  (2)  A  push-button  combined 
with  an  electro-magnetic  vibrator. 

Push-Button  Socket. — A  socket  provided 
with  a  push-button  for  the  closing  of  a 
circuit. 

Push-Button  Socket-Key. — An  incan- 
descent lamp-socket  so  provided  with  a 
push-button  key  as  to  permit  the  lamp  to 
be  readily  lighted  or  extinguished  by  the 
same  hand  that  holds  it. 

Push-Button  Switch.— A  switch  oper- 
ated by  a  push-button. 

Push  Contact. — A  name  sometimes  ap- 
plied to  a  push  button. 

Putting  Straight.— The  operation  of  re- 
storing the  normal  condition  of  wires 
which  have  been  crossed  at  two  way 
stations. 

Pyknometer. — A   term   sometimes  used 


for  a  specific  gravity  bottle,  employed  in 
determining  the  specific  gravity  of  a 
liquid. 

Pyr. — (1)  A  bougie-decimale.  (2)  A  pro- 
posed unit  of  luminous  intensity  equal  to 
the  one-twentieth  of  the  Violle  standard. 
(3)  A  proposed  name  for  the  one-twen- 
tieth of  the  Violle  standard. 

Pyrheliometer. — An  apparatus  for  meas- 
uring the  energy  of  solar  radiation. 

Pyro-Electric. — Pertaining  to  pyro-elec- 
tricity. 

Pyro-Electric  Crystal. — Any  crystalline 
substance  capable  of  producing  pyro- 
electric  phenomena  on  being  unequally 
heated. 

Pyro-Electricity.— Electricity  produced 
in  certain  crystalline  bodies  by  their  un- 
equal heating  or  cooling. 

Pyrogravure. — A  process  for  the  decora- 
tion of  wood,  copper,  or  glass,  by  the  burn- 
ing action  of  an  electrically  or  otherwise 
heated  tool. 

Pyro-Magnetic.  —  Of  or  pertaining  to 
pyro-magnetism. 

Pyro-Magnetic  Electric  Device. — Any 
device  operated  by  or  employing  pyro- 
magnetism. 

Pyro-Magnetic  Generator  or  Dynamo. 
An  apparatus  for  producing  electricity 
directly  from  the  heat  derived  from 
burning  fuel. 

Pyro-Magnetic  Motor. — A  motor  con- 
sisting of  an  armature  formed  of  a  disc 
or  ring  of  thin  steel,  which  is  set  in  mo- 
tion when  unequally  heated,  by  reason  of 
the  difference  in  the  coercive  force  so 
produced. 

Pyro-Magnetism.  —  A  term  sometimes 
applied  to  the  phenomena  of  the  com- 
bined effects  of  magnetism  and  heat. 

Pyrometer. — An  instrument  for  deter- 
mining temperatures  higher  than  those 
which  can  be  readily  measured  by  ther- 
mometers. 

Pyrometer,  Electric. — A  device  for  de- 
termining the  temperature  of  a  body  by 
the  measurement  of  the  electric  resist- 
ance of  a  platinum  wire  exposed  to  the 
heat  to  be  measured. 

Pyr-Steradian.— (1)  The  flux  of  light  cor- 
responding to  the  luminous  intensity  of 
one  pyr  extending  over  the  solid  angle  of 
one  steradian.  (2)  A  term  sometimes 
used  for  lumen. 


Q.] 


894 


[Qua. 


Q  or  q. — A  contraction  for  electric  quantity. 

Quad. — (1)  A  contraction  for  quadruplex 
telegraphy.  (2)  An  abbreviation  some- 
times employed  for  the  quadrant  or  the 
unit  of  self-inductance. 

Quad-Meter. — (1)  A  secohm  meter.  (2) 
An  instrument  for  measuring  inductance. 

Quadrant. — A  term  proposed  for  the  earth 
quadrant  or  practical  unit  of  self-induc- 
tion, now  officially  recognized  as  the 
henry.  (2)  The  length  of  the  arc,  from 
the  pole  to  the  equator,  on  a  terrestrial 
meridian  circle  extending  through  Paris, 
or  very  nearly  10,000  kilometers. 

Quadrant  Electrometer. — An  electro- 
meter in  which  an  electrostatic  charge  is 
measured  by  the  attractive  and  repulsive 
force  exerted  by  four  plates  or  quadrants 
on  a  light  needle  of  aluminium  suspended 
between  them. 

Quadrantal  Deviation  of  Mariner's 
Compass. — (1)  The  deviation  of  a  mag- 
netic needle  due  to  the  induced  mag- 
netism in  the  iron  of  a  ship  acting  as  a 
mass  of  soft  iron,  and  not  as  a  permanent 
magnet.  (2)  The  deviation  of  a  compass 
needle  on  board  ship  which  changes  sign 
once  in  each  quadrant. 

Quadrantal  Error. — The  quadrantal  de- 
viation of  a  mariner's  compass  as  dis- 
tinguished from  either  the  semicircular  or 
the  heeling  error. 

Quadrature. — A  term  applied  to  express 
the  fact  that  one  simple-harmonic  quan- 
tity lags  90°  behind  another. 

Quadruplex  Circuit.  —  A  circuit  em- 
ployed in  quadruplex  telegraphy. 

Quadruplex  Connector. — Any  connec- 
tor suitable  for  connecting  the  four  ends 
of  four  wires. 

Quadripolar  Dynamo  or  Generator. — 
A  multipolar  dynamo  having  four  poles 
in  its  field  frame,  or  four  magnetic  cir- 
cuits through  its  armature. 

Quadripolar  Field. — A  field  produced  by 
four  separate  magnet  poles. 

Quadruplex. — Of  or  pertaining  to  quad- 
ruplex telegraphy. 

Quadruplex  Balance. — The  balance  ob- 
tained in  a  quadruplex  circuit  in  order  to 
permit  quadruplex  transmission. 

Quadruplex  Circuit. — Any  single  circuit 
over  which  four  separate  messages  can 
be  simultaneously  transmitted,  two  in  one 


direction  and  the  remaining  two  in  the 
opposite  direction, 

Quadruplex  Telegraph.  —  A  general 
term  embracing  the  apparatus  employed 
in  quadruplex  telegraphy. 

Quadruplex  Telegraphy. — A  system  for 
the  simultaneous  transmission  of  four 
messages  over  a  single  wire,  two  in  one 
direction,  and  two  in  the  opposite  direc- 
tion. 

Quadruplex  Telephony.— The  simulta- 
neous transmission  of  four  telephonic 
messages,  two  in  one  direction  and  the  re- 
maining two  in  the  opposite  direction. 

Quadruplex  Transmission.  —  Tele- 
graphic or  telephonic  transmission  ef- 
fected by  means  of  a  quadruplex  system. 

Quadruplex  "Working.  —  Operating  a 
telegraph  or  telephone  line  by  quadruplex 
apparatus. 

Quadruplex  Re-Entrant  Armature 
Winding.— An  armature  provided  with 
four  independent  conducting  paths  or 
windings,  each  of  which  is  independently 
re-entrant. 

Qualitative  Analysis. — A  chemical  an- 
alysis which  merely  ascertains  the  kind* 
of  elementary  substances  present. 

Quality  of  Musical  Sound.— (1)  That 
property  of  a  musical  note  which  enables 
it  to  be  distinguished  from  another  which 
possesses  the  same  wave  length  and  am- 
plitude ;  i.  e.,  the  same  pitch  and  loudness. 
(2)  The  timbre  of  sound. 

Quality  of  Radiation.— The  character  of 
radiation  in  regard  to  the  frequency  and 
amplitude  of  the  vibration  it  contains. 

Quantitative  Analysis.— Chemical  an- 
alysis which  ascertains  the  different  pro- 
portions in  which  the  component  sub- 
stances enter  into  a  compound  substance. 

Quantity  Armature. — An  old  term  for  an 
armature  wound  with  a  few  coils  and  of 
comparatively  low  resistance. 

Quantity  Connection  for  Condensers. 
A  term  formerly  employed  for  the  mul- 
tiple connection  of  a  number  of  con- 
densers. 

Quantity  Current. — An  old  term  for  a 
current  pi'oduced  by  a  voltaic  battery  con- 
nected in  multiple-arc. 

Quantity  Efficiency  of  Storage  Bat- 
tery.— (1)  The  ratio  of  the  number  of 
ampere-hours  taken  out  of  a  storage  bat- 


Qua.] 


895 


[Raa. 


tery  to  the  number  of  ampere-hours  put 
in  the  battery  in  charging  it.     (2)    The 
ampere-hour  efficiency. 
Quantity,  Electric. — The  amount  of  elec- 
tricity present  in  any  current  or  charge. 

Quantity  Meter,  Electric. — A  coulomb 
meter. 

Quantity  of  Light.— (1)  Flux  of  light. 
(2)  The  product  of  the  luminous  intensity 
and  the  solid  angle  through  which  it  is 
emitted. 

Quantivalence. — A  general  term  for  the 
combining  capacity  of  the  elements. 

Quarter-Load  Efficiency  of  Trans- 
former.— The  efficiency  of  a  transformer 
at  quarter -load. 

Quarter-Period. — The  time  in  which  a 
vibrating  body,  or  alternating  quantity, 
completes  one  quarter  of  its  cycle. 

Quarter  -  Phase. — The  condition  of  di- 
phase  relationship  or  the  separation  of 
two  alternating  quantities  by  a  quarter 
period. 

Quarter-Phase  Armature. — A  polyphase 
armature  which  will  produce  quarter- 
phase  currents. 

Quarter-Phase  Armature-Winding. — 
Such  a  winding  of  a  polyphase  armature 
as  will  permit  it  to  produce  quarter-phase 
currents. 

Quarter-Phase  Bar- Winding  for  Ar- 
mature.— A  form  of  bar  winding  em- 
ployed in  the  armature  of  a  quarter-phase 
generator. 

Quarter-Phase  System. — A  two-phase 
system  of  alternating-current  distribution 
employing  two  currents  dephased  by  a 
quarter  period. 

Quartz  Fibre.— A  suspension  fibre  ob- 
tained by  drawing  a  thread  from  a  fused 
crystal  of  quartz. 

Quasi-Resonance. —  (1)  Imperfect  reso- 
nance. (2)  The  production  of  resonance  in 
a  primary  alternating-current  circuit  by 


the  adjustment  of  a  secondary  circuit  or 
circuits. 

Quega. — A  prefix  for  a  quintillion,  or  1015. 

Quegohm. — A  quintillion  ohms,  or  a  thou- 
sand million  megohms. 

Quick. — To  cover  with  an  adherent  film  of 
mercury. 

Quick-Break. — A  break  of  a  circuit  ob- 
tained by  means  of  a  quick-break  switch. 

Quick-Break  Switch.  —  A  switch  by 
means  of  which  a  circuit  may  be  rapidly 
broken. 

Quickened. — A  term  employed  in  electro- 
plating for  a  surface  which  has  been  pro- 
vided for  the  reception  of  a  deposit  of 
silver  by  dipping  the  article  in  a  quicken- 
ing liquid. 

Quickening  Liquid. — A  term  sometimes 
applied  to  the  quickening  solution. 

Quickening  Process. —  A  process  em- 
ployed in  quickening. 

Quickening  Solution. — A  solution  of  a 
salt  of  mercury  in  which  objects  to  be 
electro-plated  are  dipped  after  cleansing, 
just  before  being  placed  in  a  plating 
bath. 

Quicking.— Subjecting  to  the  quicking 
process. 

Quicking  Solution. — A  quickening  solu- 
tion. 

Quiet  Arc. — A  noiseless  arc. 
Quiet  Commutation. — Commutation  de- 
void of  sparking. 

Quiet  Discharge. — A  name  given  to  a 
convective  discharge  in  order  to  distin- 
guish it  from  a  noisy  disruptive  discharge. 

Quintuple  Harmonic. — A  harmonic  of 
five  times  the  frequency  of  the  funda- 
mental. 

Quivering  of  Magnetic  Field.— The  pul- 
sation of  magnetic  flux  either  under  the 
leading  pole-piece  of  a  generator,  or  the 
trailing  pole-piece  of  a  motor,  due  to  the 
successive  commutations  of  the  advan- 
cing armature  coils. 


R. — A  contraction  for  ohmic  resistance. 

R. — A  symbol  proposed  for  magnetic  resist- 
tance  or  reluctance. 

r. — A  symbol  for  radius. 

p. — A  symbol  for  specific  electric  resistance 
or  resistivity. 

R.  M.  S.  Current.— (1)  A  term  proposed 


for  the  square  root  of  the  mean  square  of 

the  current.     (2)  The  effective  current. 
R.  P.  M. — An  abbreviation  for  revolutions 

per  minute. 
R.  Q. — In  submarine  telegraphy,  a  request 

for  repetition  of  a  doubtful  word,  phrase, 

or  sentence. 
Raad. — A  name    formerly  given    by  the 

Arabians  to  the  torpedo  or  electric  ray. 


Rac.} 


896 


[Rad. 


Raceway. — A  continuous  space  provided 
in  a  conduit  for  the  insertion  or  removal 
of  a  conductor  or  conductors. 

Racing  of  Dynamo. — A  general  term  for 
any  excessive  speed  produced  in  a  dynamo- 
electric  machine  by  the  sudden  removal  of 
its  load,  as  by  the  breaking  of  a  belt. 

Racing  of  Motor. — An  increase  in  the 
speed  of  an  electric  motor  when  the  load 
is  suddenly  removed. 

Rack-Rail-Incline  Electric  Railway.— 
A  means  adopted  for  the  passage  of  a 
trolley  or  other  car  over  a  steep  grade  by 
the  use  of  a  rack  rail  to  be  operated  by 
the  ordinary  incline  system  where  the 
line  is  too  long.  • 

Racking  of  Armature  Conductors. — A 
term  sometimes  applied  to  a  sudden  drag 
exerted  on  the  armature  conductors  of  a 
dynamo  or  motor  during  operation. 

Rad. — (1)  A  unit  quantity  of  time-flux  of 
light.  (2)  A  lumen-second  or  one  lumen, 
maintained  during  one  second.  (3)  A 
name  proposed  for  the  lumen-second. 

Radial  Armature. —  A  term  sometimes 
used  for  pole  armature. 

Radial  Current.— A  term  proposed  for  a 
current  which  radiates  from  a  centre. 

Radial  Photometer.  —  A  photometer 
whose  bench  is  movable  about  a  vertical 
axis,  so  as  to  be  readily  turned  into  any 
azimuth,  and  employed  to  determine  the 
intensity  of  the  light  emitted  by  a  lum- 
inous source  in  various  directions. 

Radial  Truck.— A  triple-truck  support  for 
a  car-body,  in  which  the  car  is  supported 
on  the  centres  of  the  end  trucks  in  such  a 
manner  that  they  may  swivel  freely, 
carrying  the  middle  truck  between  them. 

Radially-Laminated  Armature.  —  An 
armature  core  whose  iron  consists  of  thin 
discs  suitably  supported  on  the  shaft. 

Radian.-^(l)  A  unit  angle.  (2)  An  angle 
whose  circular  arc  is  equal  in  length  to 
its  radius  ;  or.  approximately,  57°  17'  45". 

Radian-per-Second. — A  unit  of  angular 
velocity  of  a  rotating  body. 

Radiant  Efficiency.— The  ratio  of  the 
light-giving  radiation  to  the  total  radia- 
tion. 

Radiant  Energy. — Energy  transferred  or 
charged  on  the  universal  ether. 

Radiant  Matter.— (I)  That  condition  of 
the  gaseous  matter  that  constitutes  the 
residual  atmosphere  of  high  vacua.  (2) 
Ultra-gaseous  matter. 

Radiant  Vector. — A  vector  point-func- 
tion which  represents  the  rate  and  direc- 


tion at  and  in  which  energy  is  being  trans- 
ferred in  space. 

Radiophonic  Transmission. — (1)  Trans- 
mission by  means  of  a  photophone.  (2) 
Transmission  of  articulate  speech  along 
rays  of  light. 

Radiate. — (1)  To  transfer  energy  by  means 
of  waves.  (2)  To  issue  radially,  or  by 
rectilinear  divergence,  from  a  common 
centre. 

Radiating. — (1)  Transferring  energy  by 
means  of  waves.  (2)  Issuing  radially. 

Radiation. — (1)  A  transference  of  energy 
by  means  of  waves.  (2)  Issuing  radially 
from  a  common  centre. 

Radiation  Constant. — The  amount  of 
heat  lost  by  radiation  in  unit  time  when 
the  temperature  of  the  radiating  body  is 
one  degree  of  the  thermometric  scale 
above  that  of  the  surrounding  air. 

Radiation,  Electric.— (1)  The  transfer- 
ence of  electric  energy  by  means  of  elec- 
tro-magnetic waves  set  up  in  the  surround- 
ing ether.  (2)  That  property  of  a  rapidly 
oscillating  or  alternating-current  circuit 
by  virtue  of  which  energy  is  expended 
by  the  circuit  in  the  form  of  electro-mag- 
netic waves. 

Radiation  Meter. — (1)  An  instrument 
for  measuring  radiation.  (2)  A  meter 
employed  for  the  measurement  of  the 
radiation  emitted  by  an  electric  oscilla- 
tion, whose  operation  is  dependent  on  the 
elongation  produced  in  a  stretched  wire 
by  the  heat  developed  therein  by  cur- 
rents induced  by  the  rapidly  oscillating 
field  of  force. 

Radiation  of  Electricity. — The  radiation 
of  electric  energy  by  means  of  electro- 
magnetic waves. 

Radiation  of  Magnetic  Flux.— (1)  The 
passage  of  magnetic  flux  out  of  the  north- 
seeking  pole  of  a  magnet  or  solenoid.  (2) 
The  issue  of  magnetic  flux  from  a  mag- 
netic pole  in  approximately  radial  paths. 

Radiator,  Electric.  —  (1)  An  electric 
heater  so  placed  as  to  radiate  its  heat  into 
a  room  or  other  space  to  be  heated.  (2)  An 
electric  circuit  which  radiates  or  produces 
electro-magnetic  oscillations  or  waves. 

Radicals. — (1)  Unsaturated  atoms  or  groups 
of  atoms,  in  which  one  or  more  of  the 
bonds  are,  left  open  or  free.  (2)  Ions. 

Radiograph. — The  word  now  generally 
employed  for  a  picture  taken  by  means  of 
X-rays. 

Radiography. — (1)  The  process  of  taking 
radiographs,  or  X-ray  pictures.  (2)  X-ray 
photography. 


Kad.] 


897 


[Rat. 


Radiometer. — (1)  A  word  frequently  em- 
ployed for  the  Crookes  radiometer.  (2) 
An  instrument  in  which  the  rotation  of 
a  light  set  of  vanes  is  produced  in  an 
ultragaseous  space,  by  radiant  energy. 

Radio-Micrometer. — An  electric  appara- 
tus for  measuring  the  intensity  of  radiant 
heat. 

Radiophone. — A  name  sometimes  given 
to  a  photophone. 

Radiophonic. — Of  or  pertaining  to  the 
radiophone. 

Radiophonic  Sounds. — Sounds  resulting 
from  the  direct  action  of  radiation  on  cer- 
tain bodies. 

Radiophony. — The  production  of  sound 
by  a  body  capable  of  absorbing  radiant 
energy,  when  an  intermittent  beam  of 
heat  or  light  falls  on  it. 

Radius  of  Gyration.— In  a  rotating  body, 
a  radial  distance  from  the  centre  of  rota- 
tion at  which,  if  the  entire  mass  of  the 
body  were  collected,  its  moment  of  inertia 
would  remain  the  same. 

Rail-Bond,  Electric. — Any  device  where- 
by the  ends  of  contiguous  rails  are  placed 
in  good  electrical  contact  with  one 
another,  so  that  the  resistance  of  the  rails, 
employed  as  a  portion  of  the  return- 
circuit,  may  be  as  small  as  possible. 

Rail  Bonding. — Connecting  rails  by  elec- 
tric bonds,  for  the  purpose  of  effecting  in- 
timate electric  contact  between  them.  • 

Rail  Joint. — A  rail  bond. 

Railroad,  Electric.— A  railroad  or  rail- 
way on  which  the  cars  are  driven  or  pro- 
pelled by  means  of  electric  motors  placed 
on  the  cars,  or  on  locomotives. 

Railroad  Switchboard. — A  switchboard 
employed  in  a  railroad  power-house,  to 
which  the  generator  and  feeder  terminals 
are  attached. 

RailwayCircu.it. — A  circuit  for  operating 
an  electric  railway. 

Railway  Current-Controller.  —  (1)  A 
term  formerly  given  to  a  form  of  switch- 
board employed  for  controlling  the  output 
of  an  electric  power-house.  (2)  A  rail- 
road motor-controller  for  starting  and 
stopping  the  cars,  and  for  varying  their 
speed. 

Railway,  Electric. — An  electric  railroad. 

Railway  Generator. — A  dynamo-electric 
machine  which  develops  the  current  em- 
ployed in  systems  of  electric  railways. 

Railway  Line-Crossing. — (1)  Means  pro- 
vided for  supporting  the  separate  trolley 
•wires  at  places  where  two  or  more  wires 
cross  one  another.  ^  A  trolley  crossing. 
'  57 


Railway  Line-Section.— One  of  the  in- 
dependent divisions  into  which  the  trolley 
wire  and  its  feeder  system  are  divided  by 
means  of  section  insulators,  for  the  pur- 
pose of  preventing  an  accidental  ground 
at  one  point  from  interrupting  the  traffic 
over  a  considei-able  portion  of  the  road. 

Railway  Motor. — An  electric  motor  em- 
ployed for  the  propulsion  of  an  electric 
street  or  trolley  car. 

Railway  Power-Generator.  —  A  term 
sometimes  used  for  railway  generator. 

Railway  Return  Circuit.— (1)  A  term 
frequently  employed  for  the  ground-re- 
turn of  a  trolley  system.  (2)  The  return 
circuit,  generally  a  grounded  circuit,  em- 
ployed in  trolley  systems. 
Railway  Return- Wire.— (1)  A  copper 
.  wire  employed  for  the  purpose  of  aiding 
and  re-inforcing  the  ground-return,  so  as 
to  decrease  the  wasteful  expenditure  of  en- 
ergy due  to  the  poor  quality  of  the  rail 
and  track,  with  its  numerous  joints,  as  a 
conductor.  (2)  A  term  sometimes  em- 
ployed for  a  railway  return-circuit. 

Railway  Section-Insulators. —Insulators 
employed  for  the  purpose  of  dividing  the 
trolley  wire  or  line  into  a  number  of  inde- 
pendent sections. 

Railway  Turn-Out.— (1)  In  a  single-track 
road,  an  extra  track  provided  to  permit 
the  passage  of  a  car  in  the  opposite  direc- 
tion. (2)  A  local  section  of  track  into 
which  a  car  can  be  run,  so  as  to  leave  the 
main  line  clear. 

Range  Finder,  Electric. — Fiske's  electric 
range  finder. 

Range  Indicating  System. — On  war- 
ships a  telegraphic  indicating-system  for 
announcing,  at  any  or  all  of  the  guns,  the 
range  or  distance  of  the  target  as  signalled 
from  the  range  finder. 

Ratchet -Pendant  Argand  Electric 
Gas-Burner.— A  ratchet-pendant  electric 
burner  adapted  for  lighting  an  Argand 
gas  burner. 

Ratchet-Pendant  Electric  Gas-Burner. 
A  gas  burner  in  which  one  pull  on  a 
pendant  turns  on  the  gas  and  ignites  it  by 
means  of  an  electric  spark  from  a  spark 
coil,  and  the  next  pull  turns  it  off. 

Ratchet  -  Pendant  Electric  Candle 
Burner. — A  pendant  for  both  lighting 
and  extinguishing  a  candle  gas-jet. 

Rate-of-Doing-Work.— (1)  Activity.  (2) 
Power. 

Rated  Candle  -  Power.  —  A  nominal 
candle-power. 

Ratio  Arms  of  Bridge. — A  name  some- 


Rat.] 


898 


[Rea. 


times  given  to  the  proportionate  arms  of 
a  bridge. 

Ratio  of  Conversion. — A.  term  sometimes 
employed  instead  of  ratio  of  transforma- 
tion. 

Ratio  of  Transformation. — The  ratio  be- 
tween the  electromotive  force  produced 
at  the  secondary  terminals  of  an  induc- 
tion coil,  or  transformer,  and  the  electro- 
motive force  impressed  on  the  primary 
terminals. 

Ray. — (1)  A  term  sometimes  employed  for 
a  single  line  of  light  or  other  form  of  radi- 
ant energy,  as  distinguished  from  a  pen- 
cil of  rays  or  a  beam.  (2)  A  line  of  radiant 
energy  flux. 

Ray,  Electric. — (1)  A  species  of  fish 
which  possesses  the  power  of  producing 
electricity.  (2)  A  single  line  of  electric 
flux-energy. 

Rayleigh's  Current-Weigher. — A  form 
of  electro-dynamometer  balance. 

Rayleigh's  Form  of  Clark's  Standard 
V oltaic  Cell.  —  A  modified  form  of 
Clark's  standard  voltaic  cell. 

Reactance. — (1)  The  inductance  of  a  coil 
or  circuit  multiplied  by  the  angular  ve- 
locity of  the  sinusoidal  current  passing 
through  it.  (2)  A  quantity  whose  square 
added  to  the  square  of  the  resistance 
gives  the  square  of  the  impedance,  in 
a  simple-harmonic  current  circuit. 

Reactance  Factor. — The  ratio  of  the  re- 
actance of  a  coil,  conductor,  or  circuit, 
to  its  ohmic  resistance. 

Reactance  of  Condenser. — (1)  The  recip- 
rocal of  the  product  of  the  capacity  of  a 
condenser,  and  the  angular  velocity  of 
the  simple-harmonic  pressure  with  which 
it  may  be  connected.  (2)  A  quantity 
which  divided  into  the  alternating-cur- 
rent pressiire  at  condenser  terminals, 
gives  the  current  strength  in  the  con- 
denser. 

Reactance  of  Mutual  Inductance. — In 
an  alternating-current  circuit,  the  prod- 
uct of  a  mutual  inductance  and  the  an- 
gular velocity. 

Reacting  Inductive  Electromotive 
Force  of  Primary  Circuit.— (1)  The  C. 
E.  M.  F.  of  self-induction  in  a  primary 
alternating-current  circuit.  (2)  The  C. 

E.  M.  F.  of  mutual-induction  in  a  primary 
alternating-current  circuit,  or  the  C.  E.  M. 

F.  due  to  current  in  the  secondary  circuit. 

Reaction. — In  electro-therapeutics,  mus- 
cular contractions  following  the  closing 
or  opening  of  an  electric  circuit  through 
the  nerves  or  muscles. 

Reaction  Coil. — (1)  A  magnetizing  coil 


surrounded  by  a  conducting  covering  of 
sheathing  which  opposes  the  passage  of 
rapidly  alternating  currents  less  when 
directly  over  the  magnetizing  coil  than 
when  a  short  distance  from  it.  (2)  A 
choking  coil. 

Reaction  Machine.  —  An  induction  ma- 
chine. 

Reaction  Motor. — An  induction  motor. 

Reaction  of  Degeneration. — An  altera- 
tion in  the  behavior  of  nerves  and  muscles 
under  electric  stimulation,  due  to  disease. 

Reaction  of  Exhaustion. — A  condition 
of  nervous  or  muscular  irritability  to 
electric  excitation,  when  a  certain  reac- 
tion produced  by  a  given  current  strengtli 
cannot  be  reproduced  without  an  increase 
in  current  strength. 

Reaction  Principle  of  Dynamo-Elec- 
tric Machine. — The  mutual  interaction 
between  the  current  generated  in  the 
armature  coils  and  the  field  coils  of  a  con- 
tinuous-current dynamo-electric  machine, 
each  strengthening  the  other  until  the 
full-working  current  which  the  machine 
is  capable  of  developing  is  produced. 

Reaction  Telephone. — An  electro-mag- 
netic telephone  in  which  the  currents  in- 
duced in  a  coil  of  fine  wire  attached  to 
the  diaphragm  are  passed  through  the 
coils  of  an  electro-magnet,  each  thus  re- 
acting  on  and  strengthening  the  other. 

Reaction  Time. — The  time  required  for 
the  effects  of  an  electric  current  to  pass 
from  a  nerve  to  a  muscle. 

Reaction- Wheel,  Electric.  —  A  wheel 
driven  by  the  reaction  of  a  convective 
discharge. 

Reactive  Circuit. — A  circuit  containing 
either  inductance  or  capacity  alone,  or 
both  inductance  and  capacity. 

Reactive  Coil. — A  reaction  coil. 

Reactive  Drop. — The  drop  in  a  circuit  or 
conductor  "due  to  its  reactance,  as  dis- 
tinguished from  the  drop  due  to  its  ohmio 
resistance. 

Reactive  Effect. — The  choking  effect  of 
reactance  in  an  alternating-current  cir- 
cuit. 

Reactive  Electromotive  Force. — In  an 
alternating-current  circuit,  that  com- 
ponent of  the  electromotive  force  that  is 
in  quadrature  with  the  current  and  is 
employed  in  balancing  the  C.  E.  M.  F.  of 
inductance. 

Reading  Microscope. — A  form  of  micro- 
scope employed  for  the  measurement  of 
very  small  distances. 

Reading  Telescope.  —  A  telescope  em« 


Kea.] 


899 


[Rec. 


ployed  in  electric  measurements  for  read- 
ing the  deflections  of  a  galvanometer. 

Real  Cable. — In  duplex  submarine  cable- 
telegraphy  the  actual  cable,  as  distin- 
guished from  the  artificial  cable. 

Real  Efficiency  of  Storage  Battery.— 
(1)  The  ratio  of  the  number  of  watt-hours 
taken  out  of  a  storage  battery  to  the 
number  of  watt-hours  put  into  the  bat- 
tery in  charging  it.  (2)  The  energy  effi- 
ciency, or  watt-hour  efficiency,  of  a  stor- 
age battery,  as  distinguished  from  its 
quantity  efficiency,  or  ampere-hour  effi- 
ciency. 

Real  Hall  Effect. — A  transverse  electro- 
motive force  produced  by  magnetic  flux 
through  conductors  conveying  electric 
currents  in  a  manner  somewhat  similar 
to  that  in  which  the  Faraday  effect  is 
produced. 

Real  Image. — (1)  An  image  formed  by 
rays  of  light  that  actually  meet  in  the 
various  visible  points,  as  distinguished 
from  a  virtual  image.  (2)  An  image 
which  is  capable  of  being  received  on  a 
screen. 

Rebabbitting. — The  operation  of  replac- 
ing the  Babbitt  metal  in  the  b  earings  of 
a  machine. 

Recalescence. — A  property  possessed  by 
a  bar  or  a  mass  of  cooling  incandescent 
steel,  of  again  becoming  incandescent 
after  having  cooled  sufficiently  to  no 
longer  emit  luminous  heat. 

Recalibration. — A  new  calibration  of  an 
instrument. 

Received  Current. — A  term  used  in  teleg- 
raphy to  distinguish  the  currents  that 
come  in  over  a  line  from  a  distant  station, 
from  those  that  are  sent  out  to  a  distant 
station. 

Receiver. — A  name  sometimes  given  to  a 
receiving  instrument  of  a  gramophone, 
graphophone,  telephone,  or  telegraph  in- 
strument. 

Receiver  Magnet.— A  receiving  magnet. 

Receiving  End  of  Line. — That  end  of  a 
line  at  which  the  currents  arrive,  as  dis- 
tinguished from  the  end  at  which  they 
are  sent  out. 

Receiving  Leg  of  Telegraphic  Loop. 
The  wire  of  a  telegraphic  loop  upon 
•which  messages  are  received,  as  distin- 
guished from  the  sending  leg. 

Receiving  Magnet. — (1)  A  name  some- 
times given  to  the  relay  of  a  telegraphic 
system.  (2)  In  general,  any  magnet  used 
directly  in  the  receiving  apparatus  at  the 
receiving  end  of  a  telegraph  or  telephone 
line- 


Receiving  Signaller.  —  (1)  A  receiving 
operator.  (2)  An  operator  engaged  in  re- 
ceiving a  telegraphic  message. 

Receiving  Transformer.— A  transformer 
at  the  receiving  end  of  a  circuit. 

Receptacle. — In  incandescent  lighting  a 
permanent  device  for  receiving  an  at- 
tachment plug. 

Receptive  Device. — (1)  A  translating  de- 
vice. (2)  In  electrotechnics,  a  magneto- 
or  electro-receptive  device.  (3)  A  device 
for  receiving  energy  and  utilizing  or 
transforming  it. 

Reciprocal. — The  quotient  arising  from 
dividing  any  quantity  into  unity. 

Reciprocating  Motor. — A  motor  with,  a 
reciprocating  action,  or  with  a  motion 
alternately  in  opposite  directions,  as  dis- 
tinguished from  a  rotary  motor. 

Reciprocal  Vectors. — Two  vectors  whose 
product  is  equal  to  the  numeric  unity. 

Recoil  Circuit. — A  term  sometimes  ap- 
plied to  the  circuit  that  lies  in  the  alter- 
native path  of  a  discharge. 

Recoil  Kick  of  Disruptive  Discharge. 
A  kick  or  reaction  produced  by  a  disrup- 
tive discharge. 

Recorder. — A  word  sometimes  used  for 
either  a  telegraphic  recorder,  or  a  siphon 
recorder. 

Recorder  Ammeter. — An  ammeter  whose 
indications  are  permanently  recorded. 

Recorder  Battery.  —  The  local  battery 
supplying  the  magnets,  or  mouse-mill,  of 
a  siphon  recorder. 

Recorder  Circuit.  —  The  circuit  of  a 
siphon  recorder. 

Recorder  Coil. — The  receiving  coil  of  a 
siphon  recorder. 

Recorder  Magnets. — The  magnets  which 
supply  the  magnetic  flux  in  which  moves 
the  receiving  coil  of  a  siphon  recorder. 

Recorder  Shunt. — A  shunt  of  low  resist- 
ance placed  across  the  terminals  of  the 
coil  of  a  siphon-recorder  during  sending. 

Recorder  Signals.— Signals  received  on  a 
siphon  recorder  by  the  projection  of  ink 
upon  a  moving  strip  of  paper  from  a  small 
glass  siphon  connected  with  the  receiving 
coil. 

Recorder  Slip.— The  strip  of  paper  re- 
cording, or  prepared  for  recording,  siphon- 
recorder  signals. 

Recorder  Switch.— The  switch  employed 
in  connection  with  a  siphon  recorder  for 
changing  from  sending  to  receiving  con- 
nections. 

Recorder  -  Vibrator.  —  An     electronic- 


Rec.] 


900 


[Red. 


chanical  vibrator  for  forcing  an  inter- 
mittent flow  of  ink  from  the  siphon  of  a 
recorder  on  to  a  band  of  paper  moving 
beneath  it. 

Recording  Compass.— A  compass  so  ar- 
ranged as  to  record  the  directions  of 
the  needle,  and  to  sound  an  alarm  in  case 
the  course  of  the  vessel  deviates  any  pre- 
determined number  of  degrees. 

Recording  Drum. — A  cylindrical  drum 
covered  by  a  sheet  or  strip  of  paper  on 
which  a  chronographic  or  other  record,  is 
made. 

Recording  Meter.— Any  form  of  electric 
meter  that  records  its  indications. 

Recording  Voltmeter.  —  A  voltmeter 
whose  indications  are  permanently  re- 
corded. 

Recording  Wattmeter. — (1)  A  recording 
form  of  wattmeter.  (2)  A  dial  watt-hour 
or  kilowatt-hour  meter. 

"Recovery"  of  Condenser. — The  con- 
dition of  a  condenser  whose  dielectric  has 
regained  its  neutral  condition  after  having 
been  strained  by  a  charge. 

Rectal  Electrode. — An  electrode  suita- 
ble for  the  treatment  of  the  rectum. 

Rectangular  Curve. — A  curve  whose  out- 
line approximates  or  conforms  to  a  rec- 
tangular shape. 

Rectangular  Type  of  Periodically  Al- 
ternating Electromotive  Force. — An 
electromotive  force  whose  variations  of 
strength  are  represented  by  a  curve  of 
rectangular  outline. 

Rectangular  Variation  -  Diagram . — A 
diagram  drawn  to  rectangular  co-ordi- 
nates, and  representing  the  variation  of 
any  quantity  or  quantities. 

Rectification  of  Alcohol,  Electric. — A 
process  whereby  the  bad  taste  and  odor 
of  alcohol,  due  to  the  presence  of  alde- 
hydes, are  removed  by  the  electrical  con- 
version of  the  aldehydes- into  true  alcohol 
through  the  addition  of  hydrogen  atoms. 

Rectified. — Commuted,  or  caused  to  tako 
one  and  the  same  direction. 

Rectified  Currents.  —  Commuted  cur- 
rents. 

Rectifier. — A  name  sometimes  given  to  a 
commutator. 

Rectilinear  Co-Ordinates.  —  Co-ordi- 
nates measured  from  two  rectilinear  axes 
intersecting  in  the  plane  of  delineation 
at  a  point  called  the  origin. 

Rectilinear  Current.— A  current  flowing 
through  a  straight  or  rectilinear  portion 
of  a  circuit. 


Rectifying  Commutator. — A  term  some- 
times applied  to  a  commutator  which 
commutes  alternating  into  direct  cur- 
rents. 

Red  Candle. — A  photometric  candle  em- 
ployed in  connection  with  a  red  glass 
screen,  for  the  purpose  of  enabling  the 
unpracticed  eye  to  more  readily  compare 
it  with  the  source  whose  intensity  is  to  be 
measured. 

Red  Heat. — The  temperature  at  which  a 
body  begins  to  glow  or  to  emit  red  rays 
of  light. 

Red  Hot. — Possessing  the  temperature  of 
red  heat. 

"Red"  Magnetism.— A  name  formerly 
applied  to  the  magnetism  at  the  north 
pole  of  a  magnet,  as  distinguished  from 
the  so-called  ''blue"  magnetism  at  the 
south  pole. 

Redressed. — A  word  sometimes  employed 
for  commuted. 

Redressed  Currents.  —  Commuted  cur- 
rents. 

Reduced  Battery. — A  portion  only  of  a 
main-line  battery  employed  in  quadruplex 
telegraphy. 

Reduced      Deflection      Method.  —  A 

method  of  measuring  electromotive  force, 
resistance  or  current,  by  determinations 
based  upon  an  observed  reduction  in 
current  strength,  and  resulting  deflection 
of  a  galvanometer  in  the  circuit. 

Reducing  Clamp  for  Underground 
Tubing. — A  clamp  at  a  coupling  box 
clasping  an  underground  tube,  of  such 
dimensions  as  to  permit  of  a  change  in 
the  diameter  of  the  next  succeeding  tube. 

Reducing  Coupling. — A  flexible  coupling 
connecting  two  conductors  of  different 
diameters. 

Reducing  Switch.- -A  switch  so  con- 
nected with  a  circuit  as  to  bring  a  reduced 
or  lowered  pressure  upon  a  sub-circuit. 

Reducteur  Resistance  for  Volt-Meter. 

(1)  A  coil  of  known  resistance  as  com- 
pared with  the  resistance  of  the  coils  of 
a  voltmeter,  that  is  connected  with  them 
in  series  for  the  purpose  of  increasing  the 
range  of  the  instrument.     (2)  A  multi- 
plying coil,  or  multiplier  of  a  voltmeter. 

Reducteur  Shunt  for  Ammeter. — (1) 
A  shunt  coil  connected  in  multiple  with 
the  coils  of  an  ammeter  for  the  purpose 
of  changing  the  value  of  its  readings. 

(2)  A  multiplier. 

Reduction  Factor  of  Galvanometer.— 
The  ratio  between  the  horizontal  inten- 
sity of  the  field  of  a  galvanometer  and 
the  galvanometer  constant. 


Red.] 


901 


[Reg. 


Reduction  Gear. — Gear  employed  on  a 
street-car  for  suitably  reducing  the  speed 
of  the  car  below  that  of  the  motor  which 
drives  it. 

Reed  Interrupter. — A  form  of  automatic 
make-and-break  contact,  operated  by  the 
vibrations  of  a  reed. 

Reel  Insulator. — An  insulator  resembling 
a  reel  in  shape,  and  suitable  for  use  in 
connection  with  an  engine  plane  signal 
system. 

Re-Enforcement  of  Sound. — An  increase 
in  the  intensity  of  sound  by  the  use  of 
sounding  boards,  resonators,  or  reflectors. 

Re-Entrancy. — The  intersection  of  a  curve 
by  itself. 

Re-Entrancy  of  Armature  Winding. — 

The  condition  or  property  of  an  armature 
winding,  by  virtue  of  which  the  conduct- 
ing path  through  the  armature  repeats 
itself  or  re-enters  itself. 

Re-Entrant  Armature- Windings. — Ar- 
mature windings,  which,  when  followed 
in  either  direction,  lead  back  to  the  start- 
ing point. 

Refining,  Electric. — The  refining  of 
metals  by  the  application  of  electrolysis. 

Reflect. — To  throw  off  from  a  surface  ac- 
cording to  the  laws  of  reflection,  as  of 
waves  in  an  elastic  medium. 

Reflecting. — Throwing  off  from  a  surface 
in  accordance  with  the  laws  of  reflection. 

Reflecting  Galvanometer.  —  A  term 
sometimes  applied  to  a  mirror  galvano- 
meter. 

Reflection. — The  throwing  back  of  a  body 
or  wave  from  a  surface  at  an  angle  equal 
to  that  at  which  it  strikes  the  surface. 

Reflection  of  Electro-Magnetic  Waves. 
The  reflection  of  electro-magnetic 
waves  that  occurs  from  the  surfaces  of 
certain  substances  placed  in  the  path  of 
the  waves. 

Reflector. — A  reflecting  surface  suitably 
shaped  to  reflect  rays  of  light  in  any  de- 
sired direction. 

Reflector  Bracket. — A  bracket  for  sup- 
porting two  insulators  and  for  holding 
the  support  of  a  street  lamp,  with  or  with- 
out a  reflector. 

Reflector  Search-Light.— A  search-light 
consisting  of  a  focussing  lamp  placed  at 
the  focus  of  a  suitable  reflector. 

Reflector  Shade. — A  shade  surrounding 
an  arc-lamp,  a  portion  of  whose  surface 
is  covered  with  reflecting  material. 

Refract. — To  change  the  direction  of 
waves  in  any  elastic  media  in  accordance 
with  the  laws  of  refraction. 


Refracting. — Changing  the  direction  of 
waves  in  elastic  media  in  accordance 
with  the  laws  of  refraction. 

Refraction.— The  bending  of  a  ray  of  light, 
heat,  or  electro-magnetism,  at  the  inter- 
face of  any  two  transparent  media,  whose 
elasticity  and  density  differ. 

Refractive  Energy. — A  value  equal  to  the 
index  of  refraction  minus  unity. 

Refractory. — (1)  Possessing  the  power  of 
resisting  fusion  by  heat.  (2)  Fusible  only 
at  extraordinarily  high  temperatures. 

Refreshing  Action  of  Current.— The 
restoration,  after  fatigue,  of  muscular 
and  nervous  excitability  obtained  by  the 
action  of  voltaic  alternatives. 

Regenerable  Cell. — A  regenerative  cell. 

Regenerated  Cell. — A  cell  which  has  had 
its  ability  for  producing  current  restored 
by  a  charging  process. 

Regenerative  Armature.— A  word  pro- 
posed for  the  armature  of  a  dynamo  that 
is  capable  of  producing  its  own  magnetic 
field-flux,  when  commuted  with  a  back- 
ward lead. 

Regenerative  Cell.— (1)  A  name  some- 
times given  to  an  early  form  of  of  storage 
cell.  (2)  Any  cell  which  can  have  its 
energy  restored  by  the  action  of  a  charg- 
ing current. 

Regional  Magnetic  Disturbances.  —  A 
term  proposed  for  magnetic  disturbances 
that  are  apparently  confined  to  limited 
regions  of  the  earth's  surface. 

Register. — A  word  frequently  employed 
for  any  registering  apparatus. 

Registering  Apparatus,  Electric. — De- 
vices for  obtaining  permanent  records  by 
electrical  means. 

Registering  Declination-Magnetome- 
ter.— A  magnetometer  employed  for  au- 
tomatically registering  the  magnetic  de- 
clination. 

Registering  Electrometer. — An  electro- 
meter whose  indications  are  automatically 
registered. 

Registering  Photometer. — (1)  A  photo- 
meter which  registers  not  the  photometric 
but  the  actinic  or  chemical  action  of  light. 
(2)  A  recording  photometer. 

Regulating  Box. — (1)  A  rheostat  inserted 
in  the  field  circuit  of  a  generator  or 
motor  for  regulating  the  current  passing 
through  the  field-magnet  coils.  (2)  A 
rheostat. 

Regulating  Cell  for  Storage  Battery. — 
A  counter-electromotive  force  cell. 

Regulating  Lamp-Socket. — (1)  A  lamp 
socket  containing  a  device  controlled  by 


Beg.] 


902 


[Rem. 


a  key  or  switch  for  regulating  the  degree 
of  incandescence  of  the  filament.  (2)  A 
general  term  for  any  form  of  lamp  socket 
which  will  permit  the  light  to  be  econo- 
mically turned  down  or  lowered  in  in- 
tensity. 

Regulating  Wires. — Adjusting  the  ten- 
sion of  overhead  line  wires. 

Regulation  of  Dynamo. — Such  an  ad- 
justment of  a  dynamo  as  will  preserve 
constant  either  its  current  or  its  pres- 
sure. 

Regulation  of  Motor. — Such  an  adjust- 
ment of  a  motor  as  will  preserve  constant 
its  speed,  or  its  torque,  or  both. 

Regulator  for  Dynamo. — Any  device  by 
means  of  which  the  regulation  of  a  dy- 
namo is  effected. 

Regulator  for  Motor. — Any  device  by 
means  of  which  the  regulation  of  a  motor 
is  effected. 

Regulator  Magnet. — (1)  A  magnet  whose 
function  is  to  automatically  effect  any 
desired  regulation.  (2)  In  a  system  of 
automatic  constant-current  dynamo-reg- 
ulation, the  magnet  by  the  movements  of 
whose  armature  the  commutator  brushes 
are  automatically  shifted  to  such  posi- 
tions on  the  commutator  as  will  main- 
tain the  current  practically  constant, 
despite  changes  in  the  resistance  of  the 
circuit  external  to  the  machine. 

Reguline  Electro-Metallurgical  De- 
posit.— A  flexible,  adherent  and  strongly 
coherent  film  of  electrolytically  deposited 
metal. 

Rejuvenation  of  Luminescence. — Re- 
imparting,  by  exposure  to  light  or  other 
suitable  means,  the  power  of  lumines- 
cence to  a  substance  after  it  has  lost  this 
power. 

Relative  Inductivity.— The  ratio  of  the 
inductivity  of  a  medium  to  the  induc- 
tivity  of  vacuum. 

Relative  Permittivity. — The  ratio  of  the 
permittivity  of  a  medium  to  the  permit- 
tivity of  vacuum. 

Relaxation  Distance. — The  distance  in 
which  an  electro-magnetic  wave  travel- 
ling along  the  surface  of  a  conductor, 
diminishes  in  amplitude  in  a  ratio  whose 
Naperian  logarithm  is  unity. 

Relaxation  Time.  —  The  time  during 
which  a  logarithmically  diminishing 
quantity  diminishes  in  a  ratio  whose  Na- 
perian logarithm  is  unity. 

Relay. — In  telegraphy,  an  electro-magnet 
provided  with  contact  points  placed  on  a 
delicately  supported  armature,  the  move- 


ments of  which  open  or  close  a  local  re- 
ceiver circuit. 

Relay  Bell. — An  electric  bell  in  which  a 
relay  magnet  is  employed  to  switch  a 
local  battery  into  the  circuit  of  the  bell. 

Relay  Contact.— (1)  A  term  frequently 
applied  to  a  form  of  electro-magnetic  in- 
strument by  means  of  which  a  local  cir- 
cuit is  completed  on  the  passage  of  a  cur- 
rent. (2)  The  contact  point  of  a  relay. 

Relay  Magnet. — (1)  A  term  sometimes 
given  to  a  relay.  (2)  The  permanent 
magnet  of  a  polarized  relay.  (3)  The 
electro-magnet  of  a  relay. 

Relief  Lamp.— (1)  An  incandescent  lamp 
whose  socket  is  provided  with  a  spring 
cut-out,  so  arranged  that  on  the  breaking 
of  the  lamp  the  circuit  is  automatically 
closed.  (2)  An  incandescent  lamp  held  in 
reserve  for  insertion  in  a  series  system  to 
take  the  place  of  a  lamp  that  has  been 
cut  out. 

Relief  Operators.— In  telegraphy  or  tele- 
phony, operators  coming  on  duty  to  re- 
lieve the  operators  at  work. 

Relief  Photometer. — The  name  given  to 
a  class  of  photometers  in  which  the  two 
divisions  of  the  screen  are  not  placed  in 
the  same  plane  but  at  right  angles  to  each 
other,  the  quality  of  the  illumination 
being  readily  determined  since  the  whole 
screen  then  appears  as  a  single  plane  il- 
lumined surface,  in  which  the  edge  of  a 
dihedral  angle  of  the  screen  is  no  longer 
perceptible. 

Relievo. — (1)  The  opposite  of  intaglio.  (2) 
A  stone,  electro,  or  other  solid  body,  in 
which  a  figure  is  so  represented  that  its 
outlines  project  or  stand  out  from  the 
surface. 

Reluctance. — (1)  A  term  applied  to  mag- 
netic resistance.  (2)  In  a  magnetic  cir- 
cuit the  ratio  of  the  M.  M.  F.  to  the  total 
magnetic  flux.  , 

Reluctancy.— -fir  term  proposed  for  re- 
luctivity. 

Reluctivity — The  specific  magnetic  re- 
sistance of  a  medium. 

Reluctivity  Constants. — The  constants 
which,  wh en  applied  according  to  a  form- 
ula to  the  magnetic  force  or  magnptic 
flux  density  in  iron  or  steel,  give  the  re- 
luctivity of  the  iron  or  steel. 

Remaining  Sockets. — The  sockets  of  a 
multiple  telephone  switchboard  in  circuit 
with  any  particular  socket. 

Remanence. — (1)  Magnetic  retentivity. 
(2)  The  property  of  magnetic  substances 
to  retain  part  of  their  magnetism  owing 
to  hysteresis.  (3)  The  magnetic  flux 


Rem.] 

density  in  a  magnetic  substance  when 
the  magnetic  force  is  reduced  to  zero. 

Remanent  Flux. — Renianent  magnetism. 

Remanent  Magnetism. — A  phrase  some- 
times used  in  place  of  residual  mag- 
netism. 

Remanent  Polarization. — (1)  A  term 
proposed  to  describe  the  condition  of  a 
voltameter  when  a  certain  number  of 
discharges  having  traversed  it,  all  in  the 
same  direction,  and  a  series  of  discharges 
exactly  equal  to  the  preceding  have  been 
established  in  the  opposite  direction,  the 
currents  of  polarization  are  less  in- 
tense in  the  second  than  in  the  first.  (2) 
Residual  polarization  of  immersed  elec- 
trodes after  a  passage  of  the  current. 

Removable  Key-Switch.  —  A  plug 
switch. 

Removable  Pole-Step.— A  pole  step  cap- 
able of  being  inserted  into  and  removed 
from  a  socket  for  the  equipment  of  a  line- 
man, to  enable  a  lineman  to  reach  the 
permanent  steps. 

Renovation  of  Secondary  or  Storage 
Cell. — The  recharging  of  a  run-down  or 
discharged  storage  cell. 

Renter. — A  term  sometimes  used  for  sub- 
scriber. 

Reofore. — A  rheophore. 

Repair- Wagon  for  Trolley  Line.— A 
wagon  provided  with  a  tower  or  telescopic 
support  employed  for  the  repair  of  trolley 
lines. 

Repeater. — The  name  sometimes  given  to 
a  telegraphic  repeater,  or  translator. 

Repeating  Relay.— (1)  A  relay  employed 
in  a  repeater.  (2)  The  relay  in  a  tele- 
graph circuit  which  repeats  the  signals 
into  another  circuit. 

Repeating  Sounder. —A  telegraphic 
sounder  whicn  repeats  a  telegraphic 
despatch  into  another  circuit. 

Repeating  Telegraphic  Station.— A 
station  situated  at  some  intermediate 
point  on  a  long  telegraphic  line  which  is 
divided  into  sections,  where  the  currents 
received  on  one  section  are  passed 
through  a  repeater  by  means  of  which 
they  are  sent  on  or  repeated  into  the  other 
section. 

Repeating  Telephone  Coil.— An  induc- 
tion coil  provided  with  two  windings, 
usualhr  of  an  equal  number  of  turns,  each 
winding  being  connected  to  a  telephone 
circuit,  so  that  the  two  circuits  are  placed 
in  intimate  inductive  association. 

Replenisher. — A  static  influence  machine 
employed  for  charging  a  quadrant  elec- 
trometer or  other  electrostatic  device. 


903 


[Res. 


Repulsion,  Electric.— The  mutual  driv- 
ing apart,  or  tendency  to  mutually  drive 
apart,  which  exists  between  two  similarly 
charged  bodies,  or  between  two  similar 
electric  charges. 

Repulsion  Electrometer.— An  electro- 
meter in  which  the  differences  of  poten- 
tial are  measured  by  means  of  the  repul- 
sion existing  between  two  similarly 
charged  bodies. 

Repulsion  Motor.— (1)  An  electric  motor 
deriving  its  power  from  the  repulsion  be- 
tween electric  charges.  (2)  An  alternat- 
ing-current motor  deriving  its  power 
from  the  repulsion  between  electric  cur- 
rents. (3)  An  alternating-current  motor 
in  which  the  armature  is  provided  with 
temporarily  short-circuited  windings  by 
means  of  a  commutator  and  brushes. 

Reserve-Cell  Switch.— A  switch  em- 
ployed in  a  storage-battery  installation 
for  the  purpose  of  maintaining  the  pres- 
sure of  discharge  by  introducing  reserve 
cells  into  the  circuit. 

Residual  Atmosphere.— The  traces  of 
air  or  other  gas  remaining  in  a  space 
which  has  been  nearly  exhausted  of  its 
gaseous  contents  by  a  pump  or  other 
means. 

Residual  Charge.— The  charge  remain- 
ing in  a  Leyden  jar  after  it  has  been  dis- 
ruptively  discharged. 

Residual  Flux.  —  Residual  magnetic 
flux. 

Residual  Magnetic-Flux.— (1)  Rema- 
nence.  (2)  Magnetic  flux  remaining  in  a 
magnetic  circuit  by  virtue  of  hysteresis 
after  the  withdrawal  of  the  magnetizing 
force. 

Residual  Magnetism. — (1)  The  magnet- 
ism remaining  in  a  core  of  an  electro- 
magnet on  the  opening  of  the  magnetiz- 
ing circuit.  (2)  The  small  amount  of 
magnetism  retained  by  soft  iron  when  re- 
moved from  any  magnetic  flux. 

Residue,  Electric. — A  term  proposed  for 
residual  charge. 

Resilience. — (1)  A  word  sometimes  em- 
ployed for  elasticity.  (2)  The  work  done 
in  deforming  a  bar  up  to  the  elastic 
limit. 

Resin. — A  general  term  applied  to  a 
variety  of  dried  juices  of  vegetable 
origin. 

Resinous  Electricity. — A  term  formerly 
employed  in  place  of  negative  electri- 
city. 

Resinous  Electrification. — A  name  for- 
merly applied  to  an  electrification  pro- 
duced in  resin  by  its  friction. 


Res.] 


904 


[Res. 


Resistance. — (1)  A  word  sometimes  used 
for  electric  resistance.  (2)  Obstruction 
to  flow.  (3)  Obstruction  to  force. 

Resistance  Balance. — A  duplex  or  quad- 
ruplex  balance  adjusted  for  the  resistance 
of  a  line  by  means  of  a  rheostat. 

Resistance  Balance  of  Duplex  System. 

(1)  A  balance  obtained  in  a  duplex  system 
by  inserting  in  the  artificial  line  a  resist- 
ance corresponding  to  that  of  the  sum 
of  the  resistances  of  the  main-line  wire, 
the  distant  relays,  and  the  distant  battery. 

(2)  A  balance  of  resistance  in  duplex  tele- 
graphy as  opposed  to  a  balance  of  capac- 
ity. 

Resistance  Board. — A  general  term  for  a 
board  on  which  resistances  are  so  placed 
as  to  be  capable  of  ready  adjustment,  con- 
nection, introduction,  or  removal  from  a 
circuit. 

Resistance  Box. — A  term  employed  for  a 
box  containing  graduated  resistance  coils. 

Resistance  Bridge. — A  name  frequently 
employed  for  a  Wheatstone's  resistance 
balance. 

Resistance  Bridge-Box. — A  box  form  of 
Wheatstone's  bridge. 

Resistance  Coefficient. — The  resistance 
factor. 

Resistance  Coil. — (1)  A  coil  of  wire,  strip, 
or  conductor,  possessing  electric  resist- 
ance. (2)  A  coil  of  wire,  of  known  elec- 
tric resistance,  employed  for  measuring 
an  unknown  electric  resistance. 

Resistance  Column. — A  name  given  to  a 
particular  form  of  resistance  coil  or 
rheostat. 

Resistance  Conductivity. — The  resist- 
ance offered  by  a  substance  to  electric 
conduction ,  or  to  the  passage  of  electricity 
through  its  mass. 

Resistance,  Electric. — (1)  The  ratio  be- 
tween the  electromotive  force  of  a  circuit 
and  the  current  that  passes  therein.  (2) 
The  reciprocal  of  electric  conductance. 

Resistance  Factor. — The  coefficient  of 
frictional  resistance  to  the  movements  of 
a  suspended  or  oscillatory  system. 

Resistance  Losses. — (1)  Losses  in  any 
system  for  the  transmission  or  the  trans- 
ference of  energy  occasioned  by  friction. 
(2)  Losses  in  an  electrical  distribution 
system  due  to  resistance. 

Resistance  of  Human  Body,  Electric. 
The  ohmic  resistance  which  the  human 
body  offers  to  the  passage  of  an  electric 
discharge  or  current. 

Resistance  of  Human  Skin,  Electric. 
The  ohmic  resistance  of  the  skin. 


Resistance  of  Liquid,  Electric.— The 
ohmic  resistance  of  a  mass  of  liquid. 

Resistance  of  Telegraphic  Leak. — The 
resistance  offered  by  a  leak  in  a  tele- 
graphic line  or  circuit. 

Resistance  of  Voltaic  Arc. — Resistance 
offered  by  a  voltaic  arc  to  the  passage  of 
a  current. 

Resistance  Slide. — (1)  A  rheostat  in  which 
the  separate  resistances  or  coils  are  placed 
in  or  removed  from  a  circuit  by  means  of 
a  sliding  contact  or  key.  (2)  Apparatus 
employed  in  telegraphy  for  charging  a 
conductor  to  a  given  fraction  of  the  max- 
imum potential  of  a  battery,  so  as  to  adjust 
its  charge  in  order  to  balance  the  vary- 
ing charge  of  the  cable.  (3)  A  set  of  coils 
by  which  a  potential  difference  applied  to 
the  terminals  is  virtually  divided  into 
10,000  parts,  so  that  any  ratio  may  be  in- 
stantly selected. 

Resistance  Thermometer,  Electric. — A 
thermometer  whose  indications  are  based 
on  the  change  in  the  electric  resistance  of 
a  metallic  substance  with  changes  of 
temperature. 

Resistance  to  Shearing. — The  quotient 
of  the  shearing  stress  by  the  shear  pro- 
duced. 

Resistants. — Bodies  possessing  the  power 
of  resistance. 

Resister. — A  name  sometimes  given  to  a 
float  or  buoy  connected  with  a  cable  while 
it  is  being  paid  out,  in  order  to  diminish 
the  risk  of  injury  from  tension. 

Resisting  Torque.— (1)  The  torque  which 
it  is  necessary  to  give  to  a  motor  in  order 
to  enable  it  to  move.  (2)  The  torque  of 
retarding  or  opposing  forces. 

Resistive. — (1)  Possessing  the  property  of 
resistance.  (2)  Offering  resistance. 

Resistivity. — (1)  The  specific  resistance  of 
a  substance  referred  to  the  resistance  of 
a  cube  of  unit  volume.  (2)  Specific  re- 
sistance, or  the  inverse  of  specific  con- 
ductivity. (3)  A  quantity  in  the  C.  G.  S. 
electro-magnetic  system  represented  di- 
mensionally  in  square  centimetres  per 
second. 

Resolution  of  Force.— The  separation  of 
a  single  force  acting  with  a  given  inten- 
sity in  a  given  direction,  into  a  number  of 
separate  forces  acting  in  other  directions. 

Resonance. — (1)  In  a  simple-harmonic  cur- 
rent, circuit,  or  branch,  containing  both 
inductance  and  capacity,  the  neutraliza- 
tion or  annulment  of  inductance-reactance 
by  capacity-reactance,  whereby  the  imped- 
ance of  the  circuit  or  branch  is  reduced  to 
the  ohmic  resistance.  (2)  In  an  alternat- 


Res.] 


905 


[Ret. 


ing-current  circuit,  or  branch,  containing 
localized  inductance  and  capacity,  the  re- 
enforcement  of  condenser  pressure,  in- 
ductance pressure,  or  current  strength, 
due  to  the  mutual  neutralization  or  oppo- 
sition of  inductance  and  capacity-react- 
ances. (3)  In  an  alternating-current 
circuit,  or  branch,  the  attunement  of  a 
circuit  containing  a  condenser  to  the  same 
natural  undamped  frequency  of  oscil- 
lation as  the  frequency  of  impressed  E.  M. 
F.  whereby  the  circuit  responds  to  this 
frequency  more  than  to  any  other.  (4)  In 
an  alternating-current  circuit,  or  branch, 
the  annulment  of  inductance-reactance  by 
capacity-reactance,  whereby  the  imped- 
ance of  the  circuit  or  branch  is  not  only 
reduced  to  its  ohmic  resistance,  but  its 
current  is  in  phase  with  its  impressed 
E.  M.  F.  (5)  In  a  secondary  alternating- 
current  circuit  containing  localized  in- 
ductance and  reactance,  the  attunement 
of  the  natural  undamped  frequency  of 
oscillation  to  the  frequency  of  the  pres- 
sure impressed  upon  the  primary  circuit, 
whereby  the  secondary  impedance  is  re- 
duced to  its  ohinic  resistance,  the  second- 
ary current  is  a  maximum  for  any  given 
primary  current  strength,  and  the  second- 
ary current  is  in  phase  with  the  induced 
secondary  E.  M.  F. 

Resonant  Capacity. — The  capacity  of  a 
resonant  circuit,  or  such  a  capacity  as 
will  render  an  alternating-current  circuit 
resonant. 

Resonant  Circuit. — (1)  A  circuit  whose 
dimensions  are  such  as  to  bring  it  into 
resonance  with  a  neighboring  circuit. 
(2j  A  circuit  containing  distributed  in- 
ductance and  capacity,  in  which  resonant 
effects  are  thereby  produced. 

Resonant  Inductance. — The  inductance 
of  a  resonant  circuit,  or  the  inductance 
which  will  render  it  resonant. 

Resonant  Rise  of  Potential. — A  rise  of 
potential  in  a  circuit  due  to  its  resonance. 

Resonator,  Electric.— (1)  An  open-cir- 
.cuited  conductor  whose  dimensions  are 
such  that  electro-magnetic  waves  or 
pulses  are  propagated  through  it  at  the 
same  rate  as  they  are  taking  place  in  a 
neighboring  circuit,  and  which,  conse- 
quently, has  electro- magnetic  pulses  set  up 
sympathetically  in  it  by  resonance.  (2)  A 
circuit  tuned  to  oscillate  in  synchronism 
with  another  oscillating  or  alternating 
circuit. 

Rest.-^l)  Freedom  from  motion.  (2)  The 
condition  of  a  body  in  which  it  maintains 
an  unchanged  relative  position  with  re- 
spect to  neighboring  bodies. 


Restoring-Coil  Battery.— In  a  telephone 
exchange  the  battery  which  operates  the 
self-restoring  annunciators. 

Restoring-Coil  Circuit. — In  a  telephone 
switchboard,  the  local  circuit  of  the  coil 
of  a  self-restoring  annunciator. 

Restored  Cell. — A  charged  storage  cell. 

Resultant. — In  mechanics,  a  single  force 
that  represents  in  direction  and  intensity 
the  effects  of  two  or  more  separate  forces, 

Resultant  Fault. — The  apparent  position 
and  magnitude  of  a  fault  in  a  cable  due 
to  the  resultant  of  all  its  leakage,  or  faults 
compounded  by  the  rules  of  parallel 
forces,  or  as  represented  by  finding  the 
centre  of  gravity  of  an  unequally  loaded 
rod. 

Resultant  Induction. —  The  magnetic 
induction  in  an  armature  of  a  dynamo  or 
other  magnetized  body  which  is  the  re- 
sultant of  several  components  of  magnetic 
induction. 

Resultant  Magnetic  Field. — A  single 
magnetic  field  produced  by  two  or  more 
co-existing  magnetic  fields. 

Resultant  Magnetic  Field  of  Dynamo. 
The  magnetic  field  which  is  the  result 
of  both  the  field  due  to  the  field  magnets 
and  to  the  current  passing  through  the 
armature  coils. 

Resultant  Magnetic  Pole. —  A  term 
sometimes  employed  for  a  consequent 
pole. 

Resultant  Reactance. — The  total  react- 
ance in  a  circuit  or  conductor. 

Resuscitating  Power  of  Secondary  or 
Storage  Cell. — The  ability  possessed  by 
a  storage  cell  to  regain  its  normal  condi- 
tion under  the  influence  of  the  charging 
current. 

Retardance. — In  a  telephone  circuit,  a 
quantity  alleged  to  represent  the  limita- 
tion of  "the  circuit  in  regard  to  the  trans* 
mission  of  speech,  and  equal  to  the  prod- 
uct of  the  total  capacity  of  the  line  andi 
the  total  ohmic  resistance. 

Retarding  Coil. — A  choking  coil. 

Retarding  Disc. — A  copper  disc  supported' 
on  a  rotating  shaft  so  placed  as  to  cut 
magnetic  flux,  and  be  thereby  retarded 
in  its  speed  of  rotation. 

Retardation. — A  decrease  in  the  speed  of 
telegraphic  signalling  caused  by  distrib- 
uted electrostatic  induction  and  resist- 
ance. 

Retardation  Coil. — (1)  A  term  sometimes 
used  for  choking  coil.  (2)  An  induction 
coil.  (3)  A  retarding  coil. 

Retardation,  Electric. — A  retardation  in. 


Ret.] 


906 


[Rev. 


the  starting  or  stopping  of  an  electric 
current  due  to  self-induction. 

Retarded  Quadrature. —  In  a  simple- 
harmonic-current  circuit  the  condition  of 
lagging  in  quadrature,  or  of  phase  differ- 
ence amounting  to  90°  in  lag. 

Retentiveness. — Possessing  the  property 
of  retentivity. 

Retentivity. — Possessing  the  power  of  re- 
taining magnetization  or  of  resisting  de- 
magnetization. 

Retort  Carbon. — Carbon  obtained  from 
a  deposit  on  the  interior  of  a  gas  retort, 
and  formerly  used  for  the  production  of 
arc-light  carbons. 

Return-Call  Annunciator. — An  annun- 
ciator connected  with  an  answering  call- 
box  for  showing  that  a  call  sent  out  has 
been  received  at  the  central  station, 

Return  Charge. — (1)  A  charge  produced 
by  an  oscillatory  return  or  back  stroke  of 
lightning.  (2)  A  charge  produced  induc- 
tively by  a  lightning  discharge. 

Return  Circuit. — That  part  of  a  circuit 
by  which  an  electric  current  returns  to 
the  source. 

Return  Conductor. — The  return  wire. 

Return  Current. — In  telegraphy  the  elec- 
trostatic discharge  from  a  cable  or  under- 
ground wire. 

Return  Current. — The  discharge  current 
from  a  telegraph  line  passing  to  ground 
at  the  sending  end. 

Return  Feeders. — (1)  The  feeders  through 
which  a  current  returns  to  a  central  sta- 
tion. (2)  Negative  feeders.  (3)  The 
feeders  connected  with  the  track  in  a 
trolley  system.  (4)  Ground  feeders. 

Return  Feeders  for  Railway  Circuits. 
Copper  conductors  employed  in  rail- 
way circuits  for  re-enforcing  ground-re- 
turn circuits,  and  usually  insulated. 

Return  Ground.— (1)  That  part  of  the 
ground  employed  as  a  return.  (2)  The 
ground-return. 

Return-Signal  Call-Box . — An  answer- 
ing call-box. 

Return  Stroke  of  Lightning.  —  An 
electric  discharge  induced  by  the  direct 
discharge  of  a  lightning  flash,  as  distin- 
guished from  the  direct  discharge  itself. 

Return-Track  Feeder. — A  feeder  in  a 
trolley  system  connected  to  the  track. 

Return  Wire. — The  wire  or  conductor  by 
means  of  which  the  current  returns  to 
the  electric  source  after  having  passed 
through  the  electro-receptive  devices. 

Returns. — In  a  system  of  distribution, 
those  conductors  through  which  the  cur- 


rent flows  back  from  the  electro-receptive 
devices  to  the  sources.    ' 

Reversal. —  (1)  A  change  in  direction. 
(2)  A  semi-wave. 

Reversal  of  Phase. — A  change  in  the 
phase  of  a  current  due  either  to  the  re- 
versal of  the  current  or  of  the  conductor 
in  which  it  is  produced. 

Reversals. — In  telegraphy,  alternate-cur- 
rent signals  transmitted  for  the  purpose 
of  adjustment  or  for  clearing  the  line  of 
a  charge. 

Reverse  -  Current  Working.  —  Teleg- 
raphic transmission  by  means  of  reverse 
currents,  or  double  currents. 

Reverse  Currents. — (1)  A  name  some- 
times applied  to  alternating  currents. 
(2)  A  name  sometimes  applied  to  double- 
currents. 

Reverse-Induced  Current.— (1)  The  cur- 
rent induced  by  a  current  in  its  own  cir- 
cuit at  the  moment  of  making  or  closing 
the  circuit.  (2)  The  current  induced  in  a 
secondary  circuit  on  making  or  clos- 
ing a  primary  circuit. 

Reverser. — Any  device  for  reversing  or 
changing  the  direction  of  a  current. 

Reverser  Bars. — The  commutator  con- 
nection employed  in  Sayer's  armature 
winding  which  carries  the  current  during 
the  short  time  that  the  corresponding 
sections  are  passing  under  the  brushes. 

Reversible  Bridge. — A  bridge  or  balance 
so  arranged  that  the  proportionate  coils 
can  be  readily  interchanged,  thus  per- 
mitting the  bridge  coils  to  be  readily 
tested  by  reversing. 

Reversible  Electric  Motor. — (1)  A  mo- 
tor whose  direction  of  motion  is  readily 
reversed.  (2)  A  motor  which  is  so  ar- 
ranged as  to  be  readily  operated  as  a  gen- 
erator. 

Reversible  Heat. — The  heat  produced  in 
a  heterogeneous  conductor  by  the  passage 
through  it  of  an  electric  current. 

Reversible  Heating  Effect  of  Elec- 
tricity.— A  term  sometimes  employed  in 
place  of  the  Peltier  effect. 

Reversible  Regenerative  Armature.— 
A  regenerative  armature  that  is  capable 
of  generating  electromotive  forces  when 
the  direction  of  its  rotation  is  reversed. 

Reversibility  of  Dynamo. — The  ability 
of  a  dynamo  to  operate  as  a  motor  when 
traversed  by  an  electric  current. 

Reversing. — Changing  any  direction  to  its 
opposite. 

Reversing  a  Current. — Changing  the  di- 
rection of  a  current. 


Rev.] 


907 


[Bib, 


Reversing  Cell. — A  voltaic  cell  whose 
couple  and  electrolyte  are  contained  in  a 
hermetically  closed  vessel  so  arranged 
that  when  the  cell  is  placed  in  one  posi- 
tion the  electrolyte  does  not  touch  the 
couple,  and  when  reversed  the  electrolyte 
surrounds  the  couple. 

Reversing  Controlling-Box. — A  motor 
controlling-box  which  enables  the  direc- 
tion of  rotation  of  the  motor  to  be  re- 
versed. 

Reversing  Cylinder. — (1)  The  cylinder  in 
a  motor-controlling  apparatus  carrying 
the  reversing  contacts.  (2)  The  contact 
cylinder  of  a  reversing  switch. 

Reversing-Gear  of  Electric  Motor. — 
Apparatus  for  obtaining  a  reversal  in  the 
direction  of  rotation  of  a  motor. 

Reversing-Handle  of  Car  Controller.— 
(1)  A  switch  handle  placed  on  a  car  con- 
troller for  the  purpose  of  changing  its 
direction  of  motion.  (2)  The  handle  of 
an  emergency  switch  in  a  street-car  con- 
troller. 

Reversing  Key. — (I)  A  key  inserted  in 
the  circuit  of  a  galvanometer  for  obtain- 
ing deflections  of  the  needle  on  either  side 
of  the  galvanometer  scale.  (2)  A  key 
which  serves  to  reverse  the  current  sup- 
plied to  a  circuit. 

Reversing  Key  of  Quadruplex  Tele- 
graphic System. — The  key  in  a  quadru- 
plex  system  which  reverses  the  direction 
of  the  current  and  so  operates  one  of  the 
distant  instruments. 

Reversing  Magnetic-Field. — That  por- 
tion of  the  field  of  a  dynamo  produced  by 
the  field-magnet  coils,  in  which  the  cur- 
rents flowing  in  the  armature  coils  are 
stopped  or  reversed  after  the  coil  has 
passed  its  theoretical  position  of  neu- 
trality. 

Reversing  Switch. — A  switch  employed 
in  reversing  a  circuit  or  current. 

Revolving  Primary  of  Induction 
Motor. — (1)  A  rotor  primary.  (2)  In  an 
induction  motor,  a  revolving  element 
connected  with  the  line. 

Revolving  System. — The  twist  system  of 
erecting  telegraph  or  telephone  wires,  so 
as  to  avoid  induction. 

Rheocord. — A  word  formerly  employed 
for  rheostat.  (Obsolete.) 

Rheometer. — A  word  formerly  employed 
for  any  device  for  measuring  the  strength 
of  a  current.  (Obsolete.) 

Rheomotor. — A  word  formerly  employed 
to  designate  any  electric  source.  (Obso- 
lete.) 

Rheophore. — A  word  formerly  employed 


to  indicate  a  portion  of  a  circuit  convey- 
ing a  current  and  capable  of  deflecting  a 
magnetic  needle  placed  near  it.  (Obso- 
lete.) 

Rheoscope. — A  word  formerly  employed 
in  place  of  galvanoscope.  (Obsolete.) 

Rhebscopic  Limb. — A  word  sometimes 
employed  for  a  physiological  rheoscope, 
such  as  the  galvanoscopic  frog. 

Rheostat. — An  adjustable  resistance. 

Rheostat  Frame. — A  perforated  frame  or 
casing  in  which  the  separate  resistances 
of  a  rheostat  are  placed. 

Rheostat  Handle  of  Car-Controller.— 
The  main  switch  of  a  car-controller. 

Rheostat  Panel. — A  panel  in  any  switch- 
board to  which  the  rheostat  circuits  are 
connected. 

Rheostatic  Machine. — A  machine  de- 
vised by  Plante  in  which  continuous  static 
effects  of  considerable  intensity  are  ob- 
tained by  charging  a  number  of  con- 
densers from  storage  cells  connected  in 
multiple-arc,  and  then  discharging  the 
condensers  in  series. 

Rheotome. — A  word  formerly  employed 

for  interrupter.    (Obsolete. ) 
Rheotometer. — A  compound  bridge  and 

rheostat. 

Rheotrope. — A  word  formerly  employed 
for  commutator  or  current  reverser. 

Rhigolene. — A  highly  volatile  hydro-car- 
bon obtained  during  the  distillation  of 
coal-oil,  and  sometimes  employed  in  the 
flashing  treatment  of  incandescent  lamp 
filaments. 

Rhumbs  of  Compass. — The  points  of  a 
mariner's  compass. 

Ribbed  Armature-Core. — A  cylindrical 
armature  core  provided  with  longitudinal 
projections  or  ribs  which  serve  as  grooves 
for  the  reception  of  the  armature  coils. 

Ribbon  Conductor. — A  flat,  ribbon- 
shaped  conductor. 

Ribbon  Copper.— A  copper  strip  or  rib- 
bon-shaped copper  conductor. 

Ribbon  Core. — A  form  of  laminated  core 

made  by  iron  ribbons. 
Ribbon  Fuse. — A  fuse  in  the  shape  of  a 

ribbon. 

Ribbon  Induction-Coil. — An  induction- 
coil  whose  primary  and  secondary  circuits 
are  formed  of  metallic  ribbons  instead  of 
wires. 

Ribbon  Vibrator. — An  electro-magnetic 
contact-breaker  consisting  of  a  horizontal 
steel  ribbon,  the  rate  of  vibration  of 


908 


[Kin. 


which  can  be  varied  by  varying  its  ten- 
sion. 

Bight  -  Angled  Trolley  -  Crossing.— A 
trolley  crossing  placed  at  a  point  where 
two  streets  intersect  at  right  angles. 

Bight-Hand  Trolley-Prog.— A  trolley 
frog  used  at  a  point  where  a  branched 
trolley  wire  leaves  the  main  line  on  the 
right  hand  in  the  direction  of  advance. 

Bight-Hand  Trolley-Switch.— A  term 
sometimes  used  for  a  right-hand  trolley 
frog. 

Bight-Handed  Armature  Winding.— 
An  armature  winding  applied  to  the  core 
in  a  right-handed  or  dextrorsal  helix. 

Bight-Handed  Dynamo. — A  dynamo 
whose  proper  direction  of  rotation  is 
right-handed  regarded  from  the  pulley 
end. 

Bight-Handed  Helix.— (1)  A  right- 
handed  solenoid.  (2)  A  helix  wound 
right-handedly  when  regarded  from  either 
end. 

Bight-Handed  Motor. — A  motor  ar- 
ranged to  run  right-handedly  or  clock- 
wise when  regarded  from  the  pulley  end. 

Bight-Handed  Botation. — (1)  A  direction 
of  rotation  which  is  the  same  as  that  of 
the  hands  of  a  watch,  when  one  looks 
directly  at  the  face  of  the  watch.  (2)  Neg- 
ative rotation. 

Bight-Handed  Solenoid. — A  dextrorsal 
solenoid  or  one  whose  winding  is  right- 
handed. 

Bight-Handed  Spiral. — A  term  some- 
times used  for  right-handed  solenoid. 

Bight-Handed  Winding.— A  winding 
applied  in  a  right-handed  direction. 

Ring  Armature. — An  armature  provided 
with  a  ring-shaped  core. 

Bing-Armature  Core.— A  ring-shaped 
armature  core. 

Bing  Clutch. — A  form  of  clutch  employed 
for  gripping  the  lamp  rod  of  an  arc-lamp 
when  slightly  moved  from  a  horizontal 
position. 

Bing  Clutch  for  Arc-Lamp.— A  ring- 
shaped  clutch  embracing  the  lamp  rod, 
which  grips  or  holds  the  rod  when  tilted 
or  inclined,  but  permits  it  to  fall  when  in 
a  horizontal  position. 

Bing-Connected  Armature.— An  arma- 
ture provided  with  ring  connections. 

Bing-Connected  Generator.— A  gener- 
ator provided  with  an  armature  winding, 
in  which  corresponding  points  are  con- 
nected to  ring  conductors  for  the  purpose 
of  equalizing  the  magnetic  flux  and  the 
current  distribution  around  the  armature. 


Bing  Connections  of  Armature — Con- 
ductors  in  the  form  of  rings  in  a  multi- 
polar  armature  to  each  of  which  are  con- 
nected corresponding  points  of  the  arma- 
ture winding  for  the  purpose  of  equaliz- 
ing the  current  and  magnetic  flux  in  the 
machine. 

Bing  Core. — A  ring-armature  core. 

Bing  Current  of  Triphase  System. — 
The  current  flowing  between  adjacent 
wires  or  terminals  of  a  triphase  system. 

Bing  Magnet. — A  uniformly  magnetized 
rod  bent  into  a  closed  ring. 

Bing  Main. — A  ring-shaped  distributing 
main. 

Bing-Off. — A  term  employed  for  a  signal 
sent  by  a  telephone  correspondent  when 
the  conversation  is  finished. 

Bing-Off  Drop. — (1)  A  telephone  drop  re- 
leased by  a  ring-off  signal.  (2)  A  drop 
placed  at  a  central  telephone  station,  and 
operated  by  a  subscriber  when  he  rings 
off  or  hangs  up  his  telephone. 

Bing-Off  Signal.— A  signal  given  by  a 
subscriber  at  the  close  of  his  conversation, 
to  inform  the  central  station  that  the 
connection  may  be  discontinued. 

Bing-Off  Telephone-Indicator.  —  Any 

indicator  on  a  telephone  switchboard  that 
is  operated  by  a  ring-off  signal. 

Bing  Potential  of  Triphase  System. — 
The  effective  difference  of  potential  or 
voltmeter  pressure  between  adjacent 
lines  or  terminals  of  a  triphase  system. 

Bing-Up. — (1)  In  telephony,  to  actuate  the 
call-bell  of  a  subscriber  wanted.  (2)  To 
call  up  an  operator  at  an  exchange  or  a 
distant  subscriber. 

Bing  Windings. — Windings  suitable  for 
use  in  a  ring-wound  armature. 

Bing  -  Wound  Armature. — An  arma- 
ture consisting  of  a  ring  core  with  coils  of 
wire  wound  thereon. 

Binger. — A  telephone  magnet. 

Binger  Coils. — The  coils  or  winding  of  a 
telephone  magneto. 

Binger  Magnet. — A  permanent  magnet 
employed  in  a  telephone  magneto  or 
ringer. 

Binging  Keys. — In  a  telephone  switch- 
board, keys  for  closing  a  generator  upon 
a  subscriber's  circuit  to  ring  his  bell. 

Binging  Key. — In  a  telephone  switch- 
board, a  key  employed  to  ring  up  a  sub- 
scriber. 

Binging  Key-Bars.  —  In  a  telephone 
switchboard,  metallic  bars  connecting  the 
ringing  keys  with  the  instrument  bara 
and  generator. 


Kin.] 


909 


[Roo. 


Kings,  Electric. — A  term  sometimes  used 
instead  of  Nobili's  rings. 

Ripple  Marks,  Electric. — Wave  marks 
produced  in  a  fine  powder  by  a  neighbor- 
ing Leyden-jar  discharge. 

Risers. — (1)  Supply  wires  which  lead  the 
current  from  the  service  wires  to  the  dif- 
ferent floors  of  a  building.  (2)  The  supply 
wires  which  rise  to  the  various  floors,  as 
distinguished  from  floor  mains,  submains, 
or  branches,  which  run  along  each  floor. 

River  Cable. — (1)  A  cable  suitable  for  use 
in  a  river.  (2)  A  form  of  sub-aqueous 
cable. 

Riveted  Railway-Joint. — A  rail-bond  in 
which  the  connection  between  two  con- 
tiguous rails  is  obtained  by  riveting  spe- 
cially heavy  fish-plates  to  each  end  of  the 
rail. 

Riveting  Apparatus.  Electric. — A  rivet- 
ing apparatus  employing  electrically  gen- 
erated heat. 

Roaring  of  Arc. — A  roaring  sound  attend- 
ing the  formation  of  a  powerful  voltaic 
arc  when  the  carbons  are  too  near  to- 
gether. 

Rock-Drill,  Electric. — An  electrically 
operated  rock-drill. 

Rocker  Arm. — An  arm  on  which  the 
brushes  of  a  dynamo  or  motor  are  mount- 
ed for  the  purpose  of  shifting  their  posi- 
tion on  the  commutator. 

Rocker-Arm  Circle. — The  frame  of  a 
dynamo-electric  machine  which  supports 
the  brush  arms  and  is  capable  of  adjust- 
ment in  angular  position. 

Rocking  Switch. — An  automatic  throw- 
over  switch. 

Rod  Clamp. — A  clamp  employed  in  the 
lamp-rod  of  an  arc-lamp. 

Rod  Clutch. — The  clutch  .employed  for 
gripping  an  arc-lamp  rod. 

Rod  Switch. — A  switch  provided  for 
lighting  and  extinguishing  a  lamp,  so  ar- 
ranged that  it  can  readily  be  pushed  to  its 
off  or  on  position  by  means  of  a  rod. 

Rodding  a  Conduit. — The  process  of  in- 
troducing a  drawing-in  wire  through  the 
ducts  of  an  underground  conduit  by 
pushing  a  number  of  short  sections  of 
jointed  rods  through  such  ducts. 

Roentgen  Effects. — The  peculiar  effects 
produced  by  Roentgen  or  X-rays. 

Roentgen  Ether  Waves. — A  term  some- 
times employed  for  Rontgen  rays. 

Roentgen  Radiograph. — A  word  pro- 
posed for  radiograph. 


Roentgen-Ray  Picture. — A  word  pro- 
posed for  radiograph. 

Roentgen-Ray  Screen . — ( 1 )  A  screen  cov- 
ered with  fluorescent  material  intended 
to  receive  a  visible  Roentgen  picture. 
(2)  A  fluoroscopic  screen. 

Roentgen  Ray  Transformer. — An  alter- 
nating-current  transformer  suitable  for 
operating  a  Roentgen  ray  tube. 

Roentgen-Ray  Tube. — A  vacuum  tube 
for  the  production  of  Roentgen  rays,  or 
X-rays. 

Roentgen  Rays. — A  peculiar  radiation 
emitted  in  the  neighborhood  of  that  por- 
tion of  a  high  vacuum  tube  on  which  the 
cathode  rays  fall. 

Roentgen  Shadow  Print. —  A  radio- 
graph. 

Roentgen  Streams. — (1)  Roentgen  or 
X-rays.  (2)  A  term  applied  to  the  Roent- 
gen rays,  by  those  who  regard  them 
as  consisting  of  actual  streams  of  matter 
thrown  off,  either  from  the  cathode,  or 
from  the  residual  atmosphere  of  the 
vacuum  tube. 

Roentgen  Tube. — Any  high-vacuum  tube 
capable  of  producing  Roentgen  rays. 

Roentgengram. — A  word  proposed  for 
radiograph. 

Roentgengraph. — A  word  proposed  for 
radiograph. 

Roget's  Spiral.  —  (1)  A  spiral,  helix  or 
solenoid,  freely  suspended  at  its  upper 
end  so  that  its  lower  end  shall  dip  in  a 
mercury  surface,  which  when  traversed 
by  a  sufficiently  powerful  current  will 
break  its  own  circuit  by  the  attraction 
produced  by  its  adjacent  convolutions 
when  by  its  weight  it  will  complete  the 
circuit,  and  thus  be  alternately  opened 
and  closed.  (2)  A  form  of  automatic  con- 
tact-breaker. 

Roman  Vitriol. — A  name  formerly  applied 
to  blue-stone  or  copper  sulphate. 

Rontgram. — A  word  proposed  for  radio- 
graph. 

Rontgraph. — A  word  proposed  for  radio- 
graph. 

Rontgraphy. — A  word  proposed  for  radio- 
graphy. 

Roof  Box  of  Push. — A  term  sometimes 
employed  for  the  upper  covering  of  the 
box  of  a  push-button. 

Roof  Bracket. — (1)  An  insulator  bracket, 
either  straight  or  offset  for  attachment  to 
a  roof.  (2)  A  form  of  house  fixture  pro- 
vided for  the  support  of  overhead  wires. 

Roof  Standard.— A  form  of  house  fixture 
provided  for  overhead  wires. 


Roo.] 


910 


[Rub. 


Room  Call,  Electric. — Any  device  placed 
in  the  room  of  a  hotel  for  the  purpose  of 
automatically  sending  calls  to  the  office. 

Hope  Transmission.  —  Transmission  of 
power  by  means  of  ropes  or  cables. 

Rosette. — (1)  An  ornamental  plate  pro- 
vided with  service  wires  and  placed  in  a 
,  wall  or  ceiling  for  the  ready  attachment 
of  an  electric  lamp  or  electrolier.  (2)  A 
word  sometimes  used  in  place  of  ceiling 
rose. 

Rosette  Cut-Out. — A  rosette  for  an  elec- 
trolier, provided  with  a  cut-out. 

Rotary  Converter. — A  secondary  gener- 
ator for  transforming  alternating  into 
continuous  currents  or  vice-versd,  con- 
sisting of  an  alternating-current  machine 
whose  armature  winding  is  connected 
with  a  commutator  ;  or  of  a  continuous- 
current  machine,  whose  armature  is 
tapped  at  symmetrical  points  and  con- 
nected to  collector  rings ;  so  that,  when 
the  armature  runs  it  is  an  alternator  on 
one  side  and  a  direct  current  machine  on 
the  other.  (2)  A  rotary  transformer. 

Rotary  Current. — (1)  A  name  applied  to 
any  system  of  polyphase  currents  which 
are  capable  of  producing  a  rotary  field. 
(2)  A  rota  ting-current  distribution. 

Rotary-Current  Transformer.  —  A 
transformer  capable  of  being  operated  by 
a  rotary  current. 

Rotary  Electric  Field. — A  rotary  elec* 
trostatic  field. 

Rotary  Electro-Type. — (1)  A  term  some- 
times used  for  a  turtle-back.  (2)  Any 
electro-type  with  a  curved  surface  suit- 
able for  printing  in  a  cylinder  press. 

Rotary-Field  Induction-Motor. —  An 
induction  motor  operated  by  a  rotary 
field. 

Rotary -Field  Motor. — A  rotary-field  in- 
duction-motor. 

Rotary  Induction  Transformer.  —  A 
rotary-current  transformer. 

Rotary-Magnetic  Field.— (1)  A  field 
produced  by  a  rotary  current.  (2)  A  mag- 
netic field  in  which  a  set  of  magnet 
poles  is  produced,  whose  successive  posi- 
tions are  such  that  a  rotation  of  the  field 
is  effected. 

Rotary -Magnetic  Polarization.  —  The 
rotation  of  the  plane  of  polarization  of  a 
beam  of  plane-polarized  light,  consequent 
on  its  passage  through  a  medium  sub- 
jected to  the  stress  of  a  magnetic  field. 

Rotary  Magnetism.  —  The  magnetism 
produced  by  a  rotary  magnetic  field. 

Rotary-Phase  Alternating-Currents. 
Rotary-phase  currents. 


Rotary-Phase  Currents. — A  term  some- 
times employed  for  a  rotating  electrio 
current  distribution. 

Rotary -Phase  Dynamo.— A  term  some- 
times employed  for  a  rotating-current 
dynamo. 

Rotary  Transformer.— (1)  A  term  gener- 
ally employed  for  the  combination  of  a 
motor  and  generator  in  one  machine 
having  a  single  armature-winding  trav- 
ersed both  by  alternating  and  continuous 
currents.  (2)  A  secondary  generator  for 
transforming  from  alternating  to  contin- 
uous currents  or  vice-versd.  (8)  A  rotary 
converter. 

Rotating  Brushes  of  Dynamo.— (1)  Eo- 
tating  discs  of  metal  employed  in  place  of 
the  ordinary  brushes  for  carrying  off  the 
current  from  the  armature  of  a  dynamo. 
(2)  Brushes  revolved  around  the  periphery 
of  a  commutator. 

Rotating  Current. — (1)  A  term  applied 
to  the  current  which  results  by  combining 
a  number  of  alternating  currents,  whose 
phases  are  definitely  displaced  with  re- 
spect to  one  another.  (2)  A  polyphase  or 
multiphase  current. 

Rotating-Current  Field. — A  magnetic 
field  produced  by  a  rotating  current. 

Rotating-Current  Motor.  —  A  motor 
operated  by  a  rotating  current. 

Rotating-Current  Transformer.— A  ro- 
tary-current transformer. 

Rotating  Transformer.— (1)  A  rotary 
transformer.  (2)  An  induction  motor. 

Rotating  Vector.  —  A  line  or  vector 
quantity  which  rotates  about  a  fixed 
point. 

Rotometer. — A  form  of  cyclometer  at- 
tached to  a  drum  for  measuring  the 
amount  of  cable  passing  over  the  drum  in 
picking  up  or  paying  out  a  submarine 
cable. 

Rotor. — That  portion  of  a  dynamo-electric 
machine  which  rotates. 

Rotor  Armature. — An  armature  which 
rotates. 

Rotor  Circuit. — The  circuit  of  a  rotor. 

Rotor  Coils. — The  coils  placed  on  a  rotor. 

Rotor  Currents. — The  currents  produced 
in  the  rotor  coils. 

Rotor  Field.— The  field  of  a  rotor. 

Round  Wire-Gauge. — A.  wire  gauge  con- 
sisting of  a  circular  plate  provided  on  its 
circumference  with  slots  of  various  sizes. 

Rubber  of  Electric  Machine.  —  That 
portion  of  a  frictional  machine  which 
produces  the  electricity  by  rubbing  against 
a  disc  or  plate. 


Rul).] 


911 


[Saf. 


Rubber  Tape. — A  form  of  adhesive,  in- 
sulating tape  made  of  rubber. 

Rubbing  Contact.— A  contact  effected 
by  means  of  a  rubbing  motion. 

Rubbing  Contact  Key. — A  key  provided 
with  a  rubbing  contact. 

Ruhmkorff  Coil. — (1)  An  early  form  of 
induction  coil  or  step-up  transformer. 
(2)  An  induction  coil  having  an  iron-wire 
core,  and  a  fine  wire  secondary  coil  of 
many  turns  for  the  production  of  power- 
ful induced  E.  M.  F.'s,  usually  excited 
from  a  battery  or  continuous  -  current 
source  through  a  suitable  current  breaker. 

Ruhmkorff  Commutator.  —  A  com- 
mutator employed  in  a  Ruhmkorff  coil 
for  reversing  the  direction  of  the  current 
through  the  primary. 

Rumble. — A  barrel,  or  hollow  box,  rotated 
by  mechanical  power,  in  which  small 
articles  are  prepared  for  electro-plating 
by  the  polishing  obtained  by  their  attrition 
against  one  another,  or  against  hard  ob- 
jects placed  therein. 

Run-Down  Cell. — An  exhausted  cell. 

Running-Board. — A  device  employed  in 
the  construction  of  a  heavy  overhead  line, 


.  consisting  in  placing  a  number  of  reels 
of  wire,  usually  ten  or  more,  on  a  spindle, 
and  arranging  a  piece  of  wood  as  a  cross- 
arm  to  which  ten  or  more  wires  are  at- 
tached, harnessing  horses  to  the  cross- 
piece,  and  then  dragging  the  running 
board  away  as  the  wires  are  paid  out 
from  the  reels,  and  passing  them  over 
their  appropriate  cross-arms,  where  they 
are  at  once  secured  to  the  insulators  by 
line-men. 

Running  Guard- Wire. — A  wire  provided 
in  a  system  of  aerial  trolley  circuits,  ex- 
tending parallel  to  and  immediately  above 
the  trolley  wire,  intended  to  intercept  any 
wire  falling  on  the  line  from  above. 

Running  Position  of  Street-Car  Con- 
troller.— A  position  of  the  switch-handle 
of  a  street-car  controller  at  which  current 
is  supplied  to  the  car-motors  and  they  are 

.  kept  in  I'otation,  as  distinguished  from  a 
position  in  which  the  current  is  cut-off. 

Running  Rope. — A  rope  attached  to  the 
running-board  employed  in  the  stringing 
of  aerial  wires. 

Running  Torque  of  Motor.— The  torque 
exerted  by  a  motor  while  running,  as 
distinguished  from  the  starting  torque. 


S. — A  contraction  proposed  for  surface. 

S. — A  contraction  proposed  for  second. 

8. — An  abbreviation  for  second,  the  C.  G.  S. 
unit  of  time. 

S.  C. — A  contraction  for  secondaiy  current. 

S.  G. — In  submarine  telegraphy,  the  prefix 
for  a  service  message,  or  a  message  relat- 
ing to  the  business  of  the  company  only. 

S.  H.  M. — A  contraction  for  simple-har- 
monic motion. 

S.  P.  D. — A  contractive  for  secondary  pot- 
ential difference. 

S.  N.  Code.  —  A  contraction  for  single- 
needle  code. 

S.  N.  Telegraphic-Instrument.— A  con- 
traction employed  for  single-needle  tele- 
graphic instrument. 

S.  P.  Cut-Out. — A  contraction  for  single- 
pole  cut-out. 

S.  R.  G. — A  contraction  for  standard  rail- 
road gauge  or  4'.8i''. 

S.  W.  G. — A  contraction  for  the  British 
standard  wire  gauge. 

S.  W.  G. — A  contraction  for  Stubb's  wire 
gauge. 


Saddle  Bracket. — A  bracket  holding  an 
insulator  and  fastened  to  the  top  of  a  tele- 
graph or  telephone  pole. 

Safe  Alarm. — An  electro-magnetic  alarm 
connected  with  a  safe  and  designed  to 
give  notice  of  an  attempt  to  force  the  same. 

Safe  Carrying  Capacity  of  a  Conduc- 
tor.— The  maximum  electric  current  a 
conductor  will  carry  without  becoming 
unduly  heated. 

Safety  Catch. — A  safety  fuse. 

Safety-Catch  Holder.— A  holder  for  a 
safety  fuse. 

Safety  Cut-Out.— A  safety  fuse. 

Safety  Device. — Any  device  by  means  of 
which  a  circuit  is  automatically  opened 
or  short-circuited  when  the  current  pass- 
ing through  it  exceeds  certain  pre-deter- 
mined  limits. 

Safety  Device  for  Arc-Lamps  or  Series 
Circuit. — Any  mechanical  device  which 
automatically  provides  a  path  for  a  cur- 
rent around  a  lamp,  or  other  faulty  re- 
ceptive device  in  a  series  circuit,  and  thus 
prevents  the  opening  of  the  entire  circuit 
on  the  failure  of  such  device. 


912 


[Sea. 


Safety  Device  for  Multiple  Circuit.— 

(1)  A  safety  fuse.  (2)  A  fuse  wire  or  strip. 
(3)  Any  device  for  protecting  a  branch 
circuit,  instrument  or  conductor  from  an 
excessive  current. 

Safety  Factor  of  Transformer.— The 
ratio  of  the  voltage  with  which  a  trans- 
former has  been  tested,  to  the  voltage  at 
which  it  is  operated. 

Safety  Fuse. — A  wire,  bar,  plate  or  strip 
of  readily  fusible  metal,  capable  of  con- 
ducting, without  fusing,  the  current  or- 
dinarily employed  on  the  circuit,  but 
which  fuses  and  thus  automatically 
breaks  the  circuit  on  the  passage  of  an 
abnormally  strong  current. 

Safety  Fuse-Block. — A  block  provided 
for  the  reception  of  a  safety  fuse. 

Safety  Lamp,  Electric. — (1)  An  incan- 
descent lamp,  provided  with  thoroughly 
insulated  leads,employed  in  mines  or  other 
similar  places,  where  the  explosive  effects 
of  readily  ignited  substances  are  to  be 
feared.  (2)  A  portable  electric  incandes- 
cent lamp  and  battery  for  use  in  mines 
where  explosive  gases  may  be  found. 

Safety  Link. — A  link-shaped  safety-fuse. 

Safety  Plug.— (1)  A  safety  fuse.  (2)  An 
insulating  screw-plug  containing  a  safety 
fuse,  which  by  its  insertion  in  a  suitably 
prepared  socket,  automatically  closes  the 
circuit  through  such  fuse. 

Safety  Strip. — A  strip  of  fusible  metal 
employed  as  a  safety  fuse. 

Sag  of  Conductor  or  Line  Wire. — The 
dip  of  an  aerial  wire  or  conductor,  be- 
tween two  adjacent  supports,  due  to  its 
weight. 

Sag  Error. — (1)  Any  error  in  installing  an 
serial  wire  due  to  insufficient  allowance 
for  sag  with  change  of  temperature.  (2) 
Any  error  in  computing  the  length  of  an 
aerial  wire  due  to  insufficient  allowance 
for  sag. 

Saint  Elmo's  Fire. — Tongues  of  faintly 
luminous  flame  which  sometimes  appear 
on  the  pointed  ends  of  earth-connected 
bodies,  such  as  the  tops  of  church  stee- 
ples, or  the  masts  of  ships. 

Salient  Magnetic  Poles. — A  term  some- 
times applied  to  the  single  poles  located 
at  the  extremities  of  an  anomalous  mag- 
net, in  order  to  distinguish  them  from 
the  double  or  consequent  poles  formed  by 
the  juxta-position  of  two  similar  mag- 
netic poles. 

Salimeter. — A  form  of  hydrometer  suit- 
able for  measuring  the  density  of  a  saline 
solution. 

Saline  Creeping. — The  fonnation,by  efflo- 


rescence, of  salts  on  the  walls  of  a  solid 
immersed  in  a  saline  solution. 

Saline  Solution. — A  solution  of  a  salt  in 
a  liquid. 

Sand-Barrel  Setting  for  Pole. — A  stout 
barrel  or  cask,  placed  in  the  bottom  of 
an  excavation  in  a  loose,  sandy  soil,  as  a 
pole  foundation  in  which  the  butt  of  the 
pole  is  placed,  and  a  firm  loam  or  clay 
tightly  packed  into  the  barrel  around  the 
pole. 

Sand-Box  for  Electric  Car. — A  box  em- 
ployed for  holding  sand,  so  arranged  as 
to  distribute  it  over  a  track  as  desired, 
for  the  purpose  of  increasing  the  friction. 

Sanding  Device. — A  device  employed  for 
sprinkling  sand  over  a  car-track. 

Sandy  Electro-Metallurgical  Deposit. 
A  non-coherent  electro-metallurgical  de- 
posit, which  occurs  when  the  current 
density  exceeds  its  normal  value. 

Sash  Lines. — Ropes  employed  in  raising 
telegraph  poles  to  the  vertical  position. 

Saturated  Solution.  —  A  solution  in 
which  as  much  of  the  solid  has  been  dis- 
solved as  the  solvent  will  take  at  a  given 
temperature. 

Saturating  Flux. — The  flux  required  to 
produce  magnetic  saturation  in  any  cir- 
cuit. 

Saw,  Electric. — An  electrically  operated 
saw. 

Saw  -  Tooth  Lightning  -  Arrester.  —  A 
name  sometimes  applied  to  a  comb  light- 
ning-arrester. 

Sayers  Armature  Winding. — An  arma- 
ture winding  provided  with  additional 
coils  called  commutator  coils  which  are 
subjected  to  the  influence  of  an  auxiliary 
pole  and  which  are  introduced  into  the 
main  circuit  to  obtain  sparkless  commu- 
tation. 

Scalar. — The  name  given  to  a  quantity 
which  has  no  directive  property,  or  which 
has  numerical  magnitude  only,  such  as 
temperature,  or  energy,  as  distinguished 
from  a  vector  quantity. 

Scalar  Potential. — A  potential  possessing 
magnitude  and  sign  without  direction,  as 
distinguished  from  a  vector  potential 
which  possesses  both  direction  and  mag- 
nitude. 

Scale  Zero. — (1)  An  instrument  zero.  (2) 
A  zero  selected  at  the  zero  mark  of  a  scale. 

Scarf  Joint  of  Conductors. — A  joint  be- 
tween the  ends  of  conductors  in  which 
the  ends  are  prepared  by  filing  them  diag- 
onally, so  that  when  laid  together  and 
soldered,  the  joint  is  cylindrical  in  shape, 


Sch. 


913 


[Sec. 


presents  no  rough  edge,  and,  unlike  a 
butt  joint,  extends  over  an  appreciable 
length. 

Schiseophone.  —  An  electro  -  mechanical 
appliance  for  detecting  flaws  or  internal 
defects  in  rails  or  other  metallic  masses. 

Schweigger's  Multiplier.  —  A  name 
formerly  given  to  a  coil  consisting  of  a 
number  of  turns  of  insulated  wire,  pro- 
vided for  the  purpose  of  increasing  the 
strength  of  the  magnetic  field  produced 
by  an  electric  current,  and  so  increasing 
the  amount  of  its  deflecting  power  on  a 
magnetic  needle. 

Sciagraph. — A  word  proposed  for  radio- 
graph. 

Sciagraphic  Print. — A  word  sometimes 
used  for  radiograph. 

Sciagraphy.— A  word  proposed  for  radi- 
ography. 

Scintillating  Jar. — A  Ley  den  jar  whose 
coatings,  instead  of  being  formed  of  con- 
tinuous sheets  of  tin-foil,  are  formed  of 
small  pieces,  placed  at  regular  intervals 
on  the  glass  or  dielectric,  so  as  to  leave  a 
small  space  between  them. 

Scratch  Brush. — A  brush  made  of  wires, 
or  of  stiff  bristles,  employed  for  cleansing 
the  surfaces  of  metallic  objects  before  sub- 
jecting them  to  the  electro-plating  proc- 
ess. 

Scratch  Brushing. — Cleansing  the  sur- 
faces of  articles  to  be  electro-plated  by 
friction  with  a  scratch  brush. 

Screen,  Electric.— A  closed  conductor 
placed  over  a  body  in  order  to  protect  or 
screen  it  from  the  effects  of  external 
electro-static  fields. 

Screening. — Protecting  a  body  from  the 
effect  of  an  electrostatic  or  electro-mag- 
netic field  by  means  of  a  screen. 

Screening  Effect  of  Eddy  Currents.— 

A  term  sometimes  used  for  the  effect  pro- 
duced by  eddy  currents  in  a  solid  mass  of 
iron  or  steel,  of  shielding  the  interior  of 
the  mass  from  an  externally  applied 
alternating  magnetic  field. 
Screw  Block-Fuse.— (1)  A  form  of  plug 
cut-out.  (2)  A  screw-plug  in  a  receptacle 
or  block  containing  a  fuse. 

Screw  Cleat. — A  cleat  provided  with  a 
screw  for  its  ready  attachment  to  wood- 
work. 

Sea  Cell  Test. — In  a  sub-marine  system  of 
electric  torpedoes,  a  circuit  test  by  means 
of  a  single  voltaic  cell  in  which  sea  water 
is  the  electrolyte. 

Sea  Telegraphy.—  (1)  Submarine  Teleg- 
58 


raphy.  (2)  Telegraphy  carried  on  at 
sea  either  between  neighboring  vessels  or 
between  different  parts  of  the  same  ves- 
sel. 

Seal  of  Meter. — A  leaden  seal  placed  on  a 
meter,  after  it  has  been  properly  installed, 
for  preventing  its  being  tampered  with. 

Sealing-In  of  Filament.— Effecting  a 
hermetical  seal  between  the  support  of 
the  filament  of  an  in  candescent  lamp  and 
the  lamp  chamber  in  which  it  is  placed. 

Sealing-Off  of  Lamp  Chamber.— Her- 
metically closing  a  lamp  chamber  while 
it  is  connected  with  the  pumps,  by  the 
fusing  of  the  glass. 

Sealing  Tools. — Tools  employed  for  place 
ing  a  seal  on  a  meter. 

Sealing  Wires.— Wires  employed  for 
forming  part  of  the  seal  of  a  meter. 

Search-Light,  Electric.  —  A  focussing 
arc  light  placed  in  front  of  a  reflector 
or  lens,  for  the  purpose  of  obtaining  an 
approximately  parallel  beam  of  light  for 
lighting  the  surrounding  space. 

Searching  Coil. — A  term  sometimes  ap- 
plied to  an  exploring  coil. 

Secohm. — (1)  The  practical  unit  of  self- 
induction,  or  of  inductance.  (2)  A  length 
equal  by  definition  to  that  of  an  earth 
quadrant,  or  very  nearly  109  centimetres. 

(3)  A  henry. 

Secohmmeter. — An  apparatus  for  measur- 
ing the  self-inductance,  the  mutual  in- 
ductance, or  the  capacity  of  conductors. 

Secondary. — A  word  frequently  employed 
for  the  secondary  coil  of  a  transformer  or 
induction  coil. 

Secondary  Accumulator. — A  storage- 
cell  accumulator. 

Secondary  Ampere-Turns.  —  Ampere- 
turns  in  the  secondary  of  a  transformer 
or  induction  coil. 

Secondary  Admittance.  —  The  admit- 
tance of  a  secondary  circuit. 

Secondary  Battery. — A  word  frequently 
used  for  storage  battery. 

Secondary  Cell. — A  word  frequently  used 
for  storage  cell. 

Secondary  Clock. — Any  clock  in  a  system 
of  time  telegraphy  that  is  controlled  by 
a  master  clock. 

Secondary  Coil    of     Transformer.— 

(1)  The  coil  of  a  transformer  into  which 
energy  is  transferred  from  the  primary 
line  and  primary  coil.  (2)  The  secondary 
winding  of  a  transformer  or  induction 
coil.  (3)  The  driven  coil  of  a  transformer. 

(4)  The  coil  in  the  external  circuit  of 


Sec.] 


914 


[Sec. 


which  there  is  no  directly  impressed  E. 
M.  F. 

Secondary  Currents. — (1)  The  currents 
produced  in  the  secondary  of  a  trans- 
former. (2)  The  currents  produced  by 
secondary  batteries.  (3)  Currents  in  any 
secondary  circuit. 

Secondary  Electromotive  Forces. — A 
name  sometimes  given  to  the  electromo- 
tive forces  produced  by  a  secondary  cell 
or  battery. 

Secondary  Element  of  Induction 
Motor. — Those  portions  of  an  induc- 
tion motor,  closed  upon  themselves,  in 
which  currents  are  induced. 

Secondary  Frequency  of  Induction 
Motor. — The  frequency  of  the  alternat- 
ing currents  induced  in  the  secondary 
circuits  of  an  induction  motor,  compris- 
ing only  a  small  fraction  of  the  frequency 
in  the  primary  circuit  or  circuits. 

Secondary  Fuse-Box. — A  fuse  box  placed 
in  the  secondary  circuit  of  a  transformer 
or  induction  coil. 

Secondary  Generator. — (1)  A  generator 
which  is  not  a  prime  source  of  energy, 
but  receives  its  energy  from  some  other 
electrical  circuit  either  at  some  anteced- 
ent period,  as  in  the  case  of  a  storage  cell, 
or  coincidently,  as  in  the  case  of  a  trans- 
former. (2)  A  term  sometimes  employed 
for  transformer. 

Secondary  Generator. — A  device  em- 
ployed in  alternating-current  circuits  for 
obtaining  the  working  pressure  on  one 
circuit  by  induction  from  a  neighboring 
circuit. 

Secondary  Impressed  Electromotive 
Force. — The  E.  M.  F.  impressed  upon  a 
secondary  circuit,  as  distinguished  from 
the  E.  M.  F.  that  is  active  in  producing 
current,  or  the  E.  M.  F.  exerted  in  over- 
coming self-induction. 

Secondary  Impedance.— In  a  secondary 
circuit,  the  impedance,  either  of  part,  or 
of  all  of  the  circuit. 

Secondary  Movers. — The  driven  shafts 
or  machines,  as  distinguished  from  the 
driving  shafts  or  machines. 

Secondary  Plate  of  Condenser.— That 
plate  of  a  condenser  in  which  a  charge  is 
induced  by  the  presence  of  a  charge  on 
the  opposite  plate. 

Secondary  Primary.— A  winding  on  an 
induction  coil  intermediate  between  the 
secondary  and  primary  windings,  ar- 
ranged with  the  aid  of  revolving  contacts 
to  serve,  in  each  cycle,  first  as  a  secondary, 
and  next  as  a  primary  winding,  for  the 
purpose  of  reducing  the  sparking  at  the 


contact  wheel  of  the  primary  coil  when 
excited    from    an    incandescent-lighting 
continuous-current  circuit. 
Secondary  Resistance. — The  resistance 
of  a  secondary  coil  or  circuit. 

Secondary  Spiral  of  Induction  Coil. — 
A  term  sometimes  employed  for  the  sec- 
ondary winding  of  an  induction  coil. 

Secondary  Standard  of  Light. — Any 
standard  of  photometric  intensity  of  light 
that  is  not  a  fundamental  standard,  but 
which  is  used  as  an  intermediary  to,  or 
with  reference  to,  a  fundamental  stand- 
ard. 

Secret  Telephone  System. — A  domestic 
telephone  system  arranged  so  that  tele- 
phonic communication  can  be  obtained 
between  any  two  stations  without  being 
overheard  by  a  person  at  any  other  sta- 
tion, and  without  the  aid  of  an  attendant 
or  exchange. 

Secretion  Current. — A  current  following 
electric  stimulation  of  the  secretoiy 
nerves. 

Section. — (1)  Apart.    (2)  A  cutting  plane. 

(3)  A  graphical  representation  of  the  ap- 
pearance that  is,  or  would  be,  presented  by 
a  body  when  exposed  at  a  cutting  plane. 

(4)  In  a  trolley  system,  a  portion  or  length 
of  trolley  conductor  insulated  from  ad- 
jacent portions. 

Section  Box. — In  a  trolley  system,  a  box 
containing  the  connection  to  a  section 
and  the  switch  by  which  it  is  connected 
to  a  feeder. 

Section  Circuit-Breaker. — A  magnetic 
circuit-breaker  controlling  a  trolley-wire 
section. 

Section  of  Multiple  Switchboard. — A 
complete  division  or  reduplicating  unit  of 
a  switchboard,  in  which  every  jack  ap- 
pears once. 

Section  of  Switchboard. — A  term  some- 
times used  for  a  panel  or  a  part  of  a 
panal  of  a  switchboard. 

Section  Insulator. — An  insulator  in  a 
trolley-wire  system,  which  electrically 
disconnects  one  trolley  section  from  an- 
other. 

Sectional  Feeding-Point. — In  a  street- 
railway  system,  a  point  where  a  feeder 
connects  with  a  section  of  trolley  wire  or 
main-supply  conductor. 

Sectional  Plating. — Plating  an  article 
with  a  greater  thickness  of  metal  at  cer- 
tain points  than  at  the  rest  of  the  surface. 

Sectional  Plating-Frame. — A  frame  em- 
ployed for  holding  an  object  to  be  electro- 
plated so  that  it  shall  receive  a  greater 


Sec.] 


915 


[Sel. 


depth  of  deposit  on  certain  portions  of  its 
surface  than  elsewhere. 

Sectional  Trolley-Line.— A  system  of 
trolley  wires  divided  into  sections. 

Sectioned  Coils  for  Magnet. — (1)  A  term 
employed  for  a  method  of  winding  a 
magnetizing  coil,  in  separate  compart- 
ments. (2)  Dividing  a  winding  space 
into  short  axial  sections,  and  filling  each 
with  wire. 

Secular. — Of  or  pertaining  to  cycles  of 
time. 

Section  Switch. — In  a  system  of  railway 
or  power-distribution,  a  switch  control- 
ling and  supplying  a  section. 

Secular  Variation. — A  variation  in  the 
magnetic  declination,  which  occurs  at 
cycles  or  great  intervals  of  time,  as  op- 
posed to  diurnal  or  annual  variations. 

Seebeck  Effect. — A  term  sometimes  em- 
ployed for  thermo-electric  effect. 

See-Sawing. — A  term  employed  to  char- 
acterize the  condition  of  two  parallel-con- 
nected alternators  when  they  do  not  syn- 
chronize properly. 

See-Sawing  of  Parallel-Connected 
Generators. — (1)  A  term  sometimes  ap- 
plied to  the  hunting  of  generators.  (2) 
Imperfect  synchronism  between  gener- 
ators. 

Segment  Switch. — A  switch  in  which  a 
pivoted  strip  or  lever  moves  over  the  arc 
of  a  circle  divided  into  insulating  seg- 
ments. 

Segments!  Core-Disc. — A  dynamo  core- 
disc  which,  instead  of  being  made  in  one 
piece,  is  formed  of  suitable  joined  seg- 
ments. 

Seismic  Photo-Chronograph.— A  chro- 
nograph that  photographically  records 
seismic  disturbances. 

Seismograph,  Electric. — An  apparatus 
for  electrically  recording  the  direction 
and  intensity  of  earthquake  shocks. 

Selectance.— The  property  by  virtue  of 
which  resonant  electric  circuits  respond 
more  to  one  frequency  of  alternating  cur- 
rent than  to  another. 

Selective  Absorption.— The  absorption 
of  a  particular  or  selected  character  of  the 
waves  of  sound,  light,  heat  or  electricity. 

Selective  Consonance. — That  property 
of  a  consonant  alternating-current  circuit 
by  virtue  of  which  it  responds  more  to 
one  frequency  than  to  another. 

Selective  Emission. —  Selective  radia- 
tion. 

Selective  Opacity.— (1)  Opacity  limited  to 


certain  frequencies  only.     (2)  Selectivity 
as  regards  transparency. 
Selective     Radiation.  —  (1)    Radiation 
limited  to  certain  frequencies.    (2)  Selec 
tivity  as  regards  radiation. 

Selective  Resonance.— The  property  of  a 
resonant  circuit  which  renders  it  selective 
to  a  definite  frequency  of  alternating 
current. 

Selective  Signal.-^l)  A  term  sometimes 
employed  for  an  individual  signal.  (2) 
A  signal  which  affects  one  only  of  a 
plurality  of  translating  devices  connected 
to  a  circuit. 

Selective-Signal  Pendulum.— A  system 
of  selective  signalling  in  which  the  re- 
ceiving bells  respond  each  to  a  single 
alternating-current  frequency,  and  the 
transmitting  frequency  is  adjusted  cor- 
respondingly by  altering  the  virtual 
length  of  a  pendulum  swinging  in  the 
transmitter. 

Selective  Signalling  -  Apparatus.  —  A 
term  sometimes  employed  for  individual 
signalling-apparatus. 

Selectivity.— (1)  The  capability  for  devel- 
oping selective  action.  (2)  The  degree 
of  capability  for  effecting  selection. 

Selenium. — A  comparatively  rare  element, 
generally  found  associated  with  sulphur, 
the  electric  resistance  of  which  is  affected 
by  light. 

Selenium  Battery. — A  number  of  sepa- 
rate selenium  cells  connected  so  as  to 
form  a  single  cell  or  battery. 

Selenium  Cell.— A  cell  consisting  of  a 
mass  of  selenium  fused  in  between  two 
conducting  wires  or  electrodes  of  platin- 
ized silver,  or  other  suitable  metal. 

Selenium  Eye. — A  rough  model  of  the 
human  eye  in  which  a  selenium  resist- 
ance takes  the  place  of  'a  retina  and  two 
slides  the  place  of  the  eyelids. 

Selenium  Photometer.^-(l)  A  photo- 
meter in  which  the  intensity  of  the  light  is 
estimated  by  the  comparison  of  the 
changes  in  the  resistance  of  a  selenium 
resistance,  successively  exposed  under 
similar  conditions  to  the  light  to  be 
measured  and  to  a  standard  light.  (2)  A 
photometer  employing  the  photo-electric 
properties  of  selenium. 

Selenium  Resistance.— A  mass  of  sele- 
nium employed  as  a  resistance,  whose 
value  varies  with  the  variations  in  the  in- 
tensity of  the  light  to  which  it  is  exposed. 

Self-Acting  Make-and-Break. — A  term 
sometimes  employed  for  an  automatic 
make-and-break. 

Self- Aligning-Bearings. —  Journal  bear- 


Sel.] 


916 


[Sel. 


ings  so  constructed  and  adjusted  as  to 
permit  of  a  slight  angular  range  of  move- 
ment in  order  to  conform  to  the  surface  of 
the  shaft. 

Self-Cleaning  Contact  Key.— A.  name 
sometimes  given  to  a  key  provided  with  a 
rubbing  contact. 

Self-Closing  Telegraphic  Key.— A  tele- 
graphic key  provided  with  an  automatic 
switch  in  its  knob,  so  that  pressing  the 
key  opens  the  switch,  and  releasing  the 
key  automatically  closes  the  switch. 

Self-Compounding  Polyphase  Gen- 
erator.— A  polyphase  generator  whose 
field  magnets  are  compound-wound,  and 
which  supplies  the  series  winding  with 
currents  conductively  or  inductively  as- 
sociated with  those  in  the  line. 

Self-Contained  Engine  or  Machine. — 
An  engine  or  machine  all  of  whose  work- 
ing parts  are  within  the  said  engine  or 
machine. 

Self-Cooling  Transformer. — (1)  A  trans- 
former which  maintains  its  temperature 
within  the  necessary  safe  limits  by  natural 
radiation  and  conduction, without  the  use 
of  any  external  cooling  apparatus.  (2) 
An  oil  or  air-insulated  transformer  in 
which  no  forced  circulation  of  the  air  or 
oil  is  employed. 

Self-Demagnetizing  Force. — The  force 
exerted  by  a  permanent  bar  magnet  tend- 
ing to  demagnetize  itself,  owing  to  the 
passage  of  some  of  its  flux  back  through 
the  bar  in  the  opposite  direction  to  the 
magnetization  through  the  substance  of 
the  steel. 

Self-Excitation. — An  excitation  of  the 
field  magnets  of  a  generator  obtained 
by  leading  a  portion  or  all  of  its  own  cur- 
rent through  its  field  coils,  as  distin- 
guished from  separate  excitation. 

Self-Excited.— Excited  by  means  of  its 
own  current. 

Self-Excited  Alternator. — An  alternator 
whose  fields  are  self -excited. 

Self-Excited  Dynamo.  —  A  dynamo 
whose  field  is  self-excited. 

Self-Excited  Series-Wound  Contin- 
uous-Current Generator. — A  contin- 
uous-current generator  having  a  series- 
wound  field  which  is  excited  by  the  cur- 
rent supplied  from  the  armature  of  the 
generator. 

Self-Excited  Shunt-Wound  Contin- 
uous-Current Generator. — A  contin- 
uous-current generator  having  a  shunt- 
wound  field  which  is  excited  by  a  small 
part  of  the  current  supplied  by  the  arma- 


ture and  diverted  from  the  external  cir- 
cuit for  that  purpose. 

Self-Induced  Current. — A  current  in- 
duced in  a  circuit,  on  the  opening  or 
closing  of  the  circuit,  by  changes  in  its 
own  strength. 

Self-induction. — Induction  produced  in 
a  circuit  by  the  induction  of  the  current 
on  itself  at  the  moment  of  starting  or 
stopping  the  current  therein. 

Self-induction  Coil. — (1)  A  coil  of  wire 
possessing  self-induction.  (2)  A  choking 
coil. 

Self-Locking  Annunciator  Drop. — 
A  name  sometimes  given  to  a  self-restor- 
ing telephone  drop. 

Self-Locking  Pole  Ratchet. — A  ratchet- 
winder  for  raising  and  lowering  an  arc- 
lamp  on  a  pole,  and  provided  with  a  self- 
locking  attachment. 

Self-Oiling  Bearings. — (1)  Bearings  pro- 
vided with  automatic  oilers.  (2)  Bear- 
ings which  lubricate  themselves  when 
the  shaft  is  rotating. 

Self-Oiling  Journal. — A  journal  pro- 
vided with  automatic  oilers. 

Self-Polarizing  Relay. — A  relay  provided 
not  only  with  the  ordinary  set  of  magnet- 
izing coils,  but  also  with  an  additional 
magnetizing  coil  for  the  magnetization  of 
its  tongue,  so  that  the  magnetism  of  the 
tongue  is  reversed  when  the  current  re- 
verses. 

Self-Recording  Magnetometer.  —  A 
magnetometer  which  is  capable  of  con- 
tinuously recording  the  daily  and  hourly 
variations  of  the  earth's  magnetic  field. 

Self-Registering  Tachometer. — A  ta- 
chometer that  provides  a  permanent  re- 
cord of  the  varying  speed  of  the  machine 
to  which  it  is  connected. 

Self-Registering  Wire-Gauge.— A  wire- 
gauge  arranged  so  as  to  register  the  dia- 
meter of  the  wire  to  be  measured. 

Self-Regulating  Dynamo. — A  self-regu- 
lating generator. 

Self-Regulating  Generator.— A  gener- 
ator so  wound  as  to  automatically  main- 
tain either  a  constant-current  in  the  cir- 
cuit, or  a  constant  difference  of  potential 
between  its  terminals,  despite  changes  in 
the  resistance  of  its  load. 

Self-Regulating  X-Ray  Tube.— An  X- 
ray  tube  provided  with  an  automatic 
means  of  adjusting  the  degree  of  vacuum, 
and,  therefore,  the  electric  pressure  at 
its  terminals. 

Self-Regulation. — Any  form  of  automatic 
regulation. 


Sel.] 


917 


[Sen. 


Self-Restoring  Annunciator  Drop.— 
An  annunciator  drop  so  arranged  as  to  be 
capable  of  replacing  itself,  thus  dispens- 
ing with  a  manual  replacement. 

Self-Restoring  Indicator. — (1)  An  in- 
dicator which  will  automatically  resume 
its  proper  position.  (2)  A  self-restoring 
drop  or  annunciator. 

Self-  Starting  Alternating  -  Current 
Motor. — (1)  An  alternating-current  mo- 
tor which  is  capable  of  starting  at  any 
normal  load.  (2)  A  non-synchronous 
motor. 

Self-Starting  Synchronous  Motor. — 
.  An  alternating-current  synchronous  mo- 
tor which  is  in  any  way  enabled  to  be 
self -starting  when  connected  with  the 
mains. 

Self-Winding  Clock. — A  clock  that  is 
automatically  wound  at  regular  intervals 
by  the  action  of  a  small  electro-magnetic 
motor,  contained  within  the  clock,  and 
operated  by  one  or  more  voltaic  cells  con- 
cealed in  the  case  of  the  clock. 

Semaphore. — A  variety  of  visual  signal 
apparatus  employed  in  railroad  block  sys- 
tems. 

Semaphore  Arm. — A  movable  arm  of  a 
signal  apparatus  employed  in  block  sys- 
tems for  railroads,  for  the  purpose  of  in- 
dicating the  condition  of  the  road  as  re- 
gards other  trains. 

Semaphore  Indicator. — (1)  An  annunci- 
ator in  which  a  gravity  drop  or  shutter  is 
caused  to  fall  by  the  action  of  an  electric 
cmrent,  thus  exposing  a  number  or  other 
signal  back  of  the  drop  or  shutter.  (2) 
An  indicator  employed  in  a  semaphoric 
signalling  apparatus.  (3)  The  movable 
shutter  or  drop  employed  in  a  semaphore. 

Semaphoric  Electroscope.  —  A  name 
sometimes  given  to  a  particular  form  of 
quadrant  electroscope. 

Semi-Circular. — Of  or  pertaining  to  a 
semi-circle  or  half  a  circle. 

Semi-Circular  Deviation  of  Mariner's 
Compass. — A  term  employed  in  contra- 
distinction to  the  quadrantal  deviation 
for  the  deviation  of  a  magnetic  needle, 
due  to  the  permanent  magnetism  of  the 
ship,  having  its  resultant  in  a  horizontal 
plane,  and  changing  sign  twice  in  a 
complete"  revolution  of  the  ship. 

Semi  -  Circular  Error  of  Compass 
Needle. — The  semi-circular  deviation  of 
the  mariner's  compass. 

Semi-Conductor. — A  name  applied  to  a 
group  of  bodies  whose  conducting  power 
is,  roughly,  midway  between  that  of  good 
conductors  and  insulators. 


Semi-Incandescent  Electric  Lamp. — 
An  electric  lamp  in  which  the  light  is  due 
to  the  combined  effects  of  an  electric  aro 
and  of  incandescence. 

Semi-Period.— (1)  A  half  period.  (2)  Th» 
time  occupied  by  a  reversal  or  alterna- 
tion. 

Semi -Permanent  Telegraph  Line.— 
In  military  telegraphy,  a  line  interme- 
diate in  character  and  method  of  con- 
struction between  a  permanent  line  and  a 
temporary  line. 

Semi-Permeable  Septum. — A  septum 
which  will  permit  the  passage  through  it 
of  a  solvent,  but  not  of  the  dissolved  sub- 
stance. 

Sending  End  of  Line.— The  end  of  a 
telegraphic  line  from  which  the  signals 
are  sent. 

Sending  Leg  of  Telegraphic  Loop. — 
The  wire  of  a  telegraphic  loop  upon  which 
messages  are  sent,  as  distinguished  from 
the  receiving  leg. 

Sending  Signaller. — The  operator  on  a 
telegraphic  line  who  is  sending  the  sig- 
nals as  distinguished  from  one  at  the 
other  end  who  is  receiving  them. 

Sense  of  Magnetic  Force. — A  word  some- 
times used  for  direction  of  magnetic 
force. 

Sensibility  of  Galvanometer. — (1)  The 
readiness  and  degree  to  which  the  needle 
of  a  galvanometer  will  respond  to  the  pas- 
sage of  an  electric  current  through  its 
coils.  (2)  The  reciprocal  of  the  current 
required  to  produce  a  definite  small  angu- 
lar deflection.  (3)  The  deflection  pro- 
duced by  a  definite  small  current  strength. 
(4)  The  figure  of  merit  of  a  galvanometer. 

Sensitive  Flame. — A  flame  which  alters  its 
shape  or  size  on  the  sounding  of  notes 
possessing  the  same  frequency  as  that 
which  it  is  capable  of  producing. 

Sensitive  Discharge. — A  thin,  thread-like 
discharge  that  occurs  between  the  termi- 
nals of  a  high-frequency  induction  coil. 

Sensitive  Telephone. — A  telephone  that 
is  able  to  properly  respond  to  currents 
smaller  than  those  ordinarily  employed 
in  telephone  apparatus. 

Sensitive  Tube. — A  coherer. 

Sensitiveness  of  Wheatstone's  Bal- 
ance.—  The  minimum  change  in  the 
measured  resistance  which,  under  the  con- 
ditions of  the  test  and  with  the  apparatus 
employed,  is  capable  of  either  being  de- 
tected, or  of  producing  the  unit  of  scale 
deflection  in  the  galvanometer. 

Sent  Current. — The  current  employed  u» 
transmitting  a  signal. 


Sep.] 


918 


[Ser. 


Separable  Conducting  Cord  Tip.— A 
telephone  plug  arranged  for  ready  con- 
nection with,  or  disconnection  from,  a 
flexible  conducting  cord. 

Separable  Iron  Core.  —  An  iron  core 
which  can  be  removed  from  the  appara- 
tus in  which  it  is  used. 

Separate-Circuit  Dynamo. — (1)  A  term 
sometimes  employed  for  a  self-exciting 
dynamo  in  which  a  special  or  separate 
armature  circuit  is  connected  to  the  fields. 
(2)  A  dynamo  capab'e  of  supplying  a  plur- 
ality of  separate  circuits. 

Separate-Circuit  Motor. — A  term  some- 
times applied  to  a  motor  whose  armature 
is  provided  with  two  windings  having  two 
separate  commutators,  the  main  one  be- 
ing supplied  with  the  driving  current. 

Separate-Coil  Alternator. — An  alterna- 
tor whose  field  magnets  are  excited  by 
means  of  current  taken  from  the  coils  of 
the  armature  after  it  has  been  commuted. 

Separate-Coil  Dynamo-Electric  Ma- 
chine.— A  term  sometimes  used  for  a  sep- 
arate-coil alternator. 

Separate-Coil  Machine. — (1)  A  machine 
in  which  the  armature  coils  are  mechani- 
cally separated  from  each  other,  as  dis- 
tinguished from  a  machine  in  wiiich  the 
coils  are  interlaced.  (2;  A  dynamo-elec- 
tric machine  in  the  armature  of  which 
there  exists  a  separate  coil  or  winding  for 
the  special  purpose  of  exciting  the  field 
magnets. 

Separate  Excitation. — The  excitation  of 
the  field  magnets  produced  by  a  source 
external  to  the  machine. 

Separate  Touch. — A  phrase  sometimes 
employed  for  magnetization  by  separate 
touch. 

Separately -Excited  Alternator.  —  An 
alternator  whose  field  magnets  are  sep- 
arately excited. 

Separately-Excited  Dynamo-Electric 
Machine. — A  dynamo-electric  machine 
whose  field  coils  are  separately  excited. 

Separately-Excited  Field.— The  field  of 
a  dynamo  that  receives  its  magnetizing 
current  from  a  source  outside  or  separate 
from  the  dynamo. 

Separator. — A  corrugated  and  perforated 
insulating  sheet  of  ebonite  or  other  simi- 
lar substance,  shaped  so  as  to  conform  to 
the  outlines  of  the  plates  of  a  storage  bat- 
tery, and  placed  between  them  at  suitable 
intervals  in  such  a  manner  as  to  prevent 
their  short-circuiting,  but  without  imped- 
ing the  free  circulation  of  the  liquid. 

Septum. — The  porous  partition  of  an  en- 
dosmometer. 


Series  and  Magneto  Dynamo-Electric 
Machine. — A  compound-wound  dynamo 
in  which  the  armature  circuit  of  a  mag- 
neto-electric machine  is  connected  with 
and  excites  the  fine  winding  on  the  field 
magnets. 

Series-and-Separately-Excited  Dyna- 
mo-Electric Machine. — A  compound- 
wound  dynamo  whose  field-magnet  cores 
are  wound  with  two  separate  circuits,  one 
connected  in  series  with  the  field  magnets 
and  the  external  circuit,  and  the  other 
with  some  source  by  means  of  which  it  is 
separately  excited. 

Series  -  and  -  Shunt  -  Wound  Dynamo- 
Electric  Machine.  —  A  compound- 
wound  dynamo  whose  field  magnets  are 
wound  with  two  separate  coils,  one  in 
series  with  the  armature  and  the  external 
circuit,  and  the  other  in  shunt  with  the 
armature. 

Series-Arc  Cut-Out.— A  device  for  auto- 
matically providing  a  short-circuit  past  a 
faulty  lamp  in  a  series-connected  circuit, 
so  that  the  failure  of  a  lamp  to  operate 
may  not  interfere  with  the  operation  of 
the  rest  of  the  lamps. 

Series  Board. — A  series-connected  multi- 
ple telephone  switchboard. 

Series  Circuit. — A  circuit  in  which  the 
separate  sources  or  separate  electro-recep- 
tive devices,  or  both,  are  so  placed  that 
the  current  produced  in  it  or  passed 
through  it  passes  successively  through  the 
entire  circuit  from  the  first  to  the  last. 

Series-Connected  Battery. — A  battery 
of  series-connected  cells. 

Series-Connected  Incandescent 
Lamps. — A  number  of  lamps  connected 
to  a  circuit  in  series  and  provided  with  a 
film  or  other  similar  cut-out,  to  prevent 
the  failure  of  a  single  lamp  from  extin- 
guishing all  the  rest. 

Series-Connected  Electro-Receptive 
Devices. — A  number  of  electro- receptive 
devices  connected  to  a  circuit  in  series. 

Series-Connected  Sources. — A  number 
of  separate  sources  so  connected  in  series 
as  to  act  as  a  single  source. 

Series-Connected  Translating  Devices. 
A  term  sometimes  used  for  series-con- 
nected electro-receptive  devices. 

Series-Connected  Voltaic  Cells.  —  A 
number  of  voltaic  cells  so  connected  in 
series  as  to  be  capable  of  acting  as  a  single 
source  or  battery. 

Series  Connection. — Such  a  connection 
of  a  number  of  separate  electric  sources 
or  electro-receptive  devices  or  circuits 


Ser.] 


919 


[Ser. 


that  the  current  passes  successively  from 

the  first  to  the  last  in  the  circuit. 
Series-Connection   for    Condensers. — 

The  connection  of  a  number  of  condensers 

in  series. 
Series-Connection  of  Alternator  s . — The 

connection  of  two  or  more  alternators  in 

series. 

Series  Converter. — A  series  transformer. 

Series  Distribution. — A  distribution  of 
electric  energy  in  which  the  receptive 
devices  are  placed  one  after  another  in 
succession  upon  a  single  conductor,  ex- 
tending throughout  the  entire  circuit 
from  pole  to  pole. 

Series  Dynamo. — A  series-wound  dynamo. 

Series  Field-Terminals  of  Motor.— The 
terminals  of  a  compound-wound  motor 
which  are  connected  to  the  ends  of  a  series 
field-winding. 

Series  Grouping  of  Armature  Con- 
ductors.— (1)  A  two-circuit  multipolar 
winding.  (2)  A  winding  for  a  multipo- 
lar armature  in  which  only  two  paths 
are  provided  for  the  current  between  the 
brushes. 

Series  Incandescent  Lamp. — An  incan- 
descent lamp  suitable  for  use  in  a  series 
circuit. 

Series  Incandescent  Lighting  System. 
A  system  of  incandescent  lighting  in 
which  the  lamps  are  connected  in  series, 
as  distinguished  from  a  multiple  system 
in  which  they  are  connected  in  parallel. 

Series  Motor.-^l)  A  motor  suitable  for  use 
in  a  series  circuit.  (2)  A  series-wound 
motor. 

Series-Multiple.— A  series-multiple  con- 
nection. 

Series-Multiple  Car-Controller.  —  A 
controller  provided  for  starting  and  stop- 
ping a  double  motor  car,  for  varying  its 
speed,  or  the  torque  of  its  motors,  by  con- 
necting the  motors  either  in  series  or  in 
parallel  with  or  without  resistances. 

Series-Multiple  Circuit.— A  compound 
circuit  in  which  a  number  of  separate 
sources,  or  separate  electro-receptive 
devices,  or  both,  are  connected  in  a 
number  of  separate  groups  in  multiple 
arc,  and  these  separate  groups  sub- 
sequently connected  in  series. 

Series-Multiple-Connected  Electro- 
Receptive  Devices. — A  connected  sys- 
tem in  which  a  number  of  separate  elec- 
tro-receptive devices  are  joined  in  parallel 
in  separate  groups,  and  all  of  these  groups 
subsequently  connected  in  series. 

Series-Multiple-Connected  Sources. — 
The  connection  of  a  number  of  separate 


electric  sources  so  as  to  form  a  single 
source,  in  which  the  separate  sources  are 
connected  in  a  number  of  separate  mul- 
tiple groups  or  circuits,  and  these  groups 
or  circuits  separately  connected  together 
in  series. 

Series-Multiple-Connected  Translat- 
ing Devices. — Series-multiple-connected 
electro-receptive  devices. 

Series-Multiple  Connection.— Such  a 
connection  of  a  number  of  separate  electro- 
receptive  devices  that  the  devices  are 
placed  in  multiple  groups  or  circuits  and 
these  separate  groups  afterwards  con- 
nected with  one  another  in  series. 

Series-Multiple  Switchboard.— A  tele- 
phone switchboard,  in  which  a  subscriber's 
jacks  are  connected  in  series,  while  plug 
connections  are  made  in  parallel  or  across 
the  circuit. 

Series-Parallel  Controller.— A  series- 
multiple  car-controller. 

Series  Tranformer.— A  term  sometimes 
applied  to  a  converter  whose  primary  coil 
is  connected  in  series  with  the  primary 
coils  of  other  similar  transformers  in  the 
primary  circuit. 

Series  Turns  of  Dynamo  -  Electric 
Machine. — The  magnetizing  field-mag- 
net coils  of  a  dynamo  that  are  connected 
in  series  with  the  armature  circuit. 

Series  Winding. — A  winding  of  a  dynamo 
electric  machine  in  which  a  single  set  of 
magnetizing  coils  are  placed  on  the  field- 
magnet  cores  and  connected  in  series  with 
the  armature  and  the  external  circuit. 

Series- Wound  Dynamo-Electric  Ma- 
chine.— A  dynamo-electric  machine  in 
which  the  field  circuit  and  the  external 
circuit  are  connected  in  series  with  the 
armature  circuit,  so  that  the  armature 
current  passes  through  the  field  winding 
into  the  external  circuit. 

Series- Working  of  Dynamo-Electric 
Machines. — Such  a  coupling  of  several 
dynamo-electric  machines  as  will  deliver 
in  series  the  current  supplied  by  them. 

Series- Wound  Field.— The  field  of  a  dyn- 
amo in  which  the  armature  current  passes 
through  the  magnetizing  coil. 

Series- Wound  Laminated  Synchro- 
nous Motor. — A  series-wound  syncho- 
nous  motor  provided  with  a  laminated 
core. 

Series- Wound  Motor. — A  motor  provided 
with  a  series- wound  field. 

Serrated  Lightning  Arrester. — A  terra 
sometimes  applied  to  a  saw-tooth  light- 
ning arrester. 


Ser.j 


920 


[She. 


Service. — A  conductor  or  set  of  conductors 
supplying  electric  energy  from  electric 
mains  to  the  premises  of  a  consumer. 

Service  Block.— (1)  A  block  connected 
with  service  wires.  (2)  A  block  for  sup- 
porting and  connecting  service  wires. 

Service  Conductors. — Service  wires. 

Service  Line. — (1)  A  service  wire.  (2) 
In  telephony,  a  line  or  circuit  connecting 
a  switchboard  with  a  subscriber. 

Service  Tube. — A  tube  provided  for  the 
introduction  of  service  wires. 

Service  Wires. — (1)  The  wires  which  lead 
into  a  building  and  which  are  connected  to 
the  supply  mains  or  supply  circuit.  (2) 
The  wires  through  which  service  is  given 
to  a  consumer.  (3)  Delivery  wires. 

Serving  Mallet. — A  tool  employed  for 
placing  the  tarred  yarn  serving  on  a  cable 
splice. 

Serving  of  Cable. — The  bedding  of  tape, 
yarn,  jute  or  compound  in  a  cable  as  dis- 
tinguished from  the  core  or  the  sheathing. 

Serving  Tool. — A  tool  employed  in  placing 
the  serving  on  a  cable. 

Seven-Point  Jacks. — In  a  multiple  tele- 
phone switchboard,  jacks  having  each 
seven  different  points  of  contact. 

Sextant. — An  optical  device  consisting  of 
a  fixed  and  movable  mirror,  employed  for 
measuring  the  angular  distance  between 
any  two  objects. 

Sextaplex  Telegraph. — A  general  term 
embracing  the  apparatus  used  in  sex- 
taplex  telegraphy. 

Sextaplex  Telegraphy.— A  system  of 
telegraphy  whereby  six  distinct  messages 
can  be  simultaneously  transmitted  over 
the  same  line,  three  in  one  direction  and 
three  in  the  opposite  direction. 

Sextaplex  Transmission.— Transmitting 
intelligence  by  means  of  sextaplex  teleg- 
raphy. 

Sextipolar. — Possessing  six  poles. 

Sextipolar  Dynamo. — A  dynamo  posses- 
sing a  sextipolar  field. 

Sextipolar  Field. — A  field  produced  by 
six  magnet  poles. 

Sextuple  Telegraph. — A  general  term  for 
the  appratus  employed  in  sextuple  teleg- 
raphy. 

Sextuple  Telegraphy.— A  system  of 
telegraphic  communication  in  which  six 
separate  messages  are  simultaneously  sent 
over  a  line  in  the  same  direction. 

Sextuple  Transmission. — The  transmis- 
sion of  intelligence  by  sextuple  teleg- 
raphy. 


Sextuply  Re-Entrant.  —  An  armature 
provided  with  six  separate  conducting 
paths  or  windings,  each  of  which  is  inde- 
pendently re-entrant. 

Shackle  Insulator.— A  term  applied  to 
any  form  of  insulator  used  for  shackling 
a  wire,  as  distinguished  from  an  insulator 
which  merely  supports  a  wire. 

Shackling  a  Wire.— (1)  Inserting  an  insu- 
lator between  the  two  ends  of  a  cut  wire. 
(2)  Securing  the  end  of  a  telegraph  or 
telephone  wire  to  a  shackle. 

Shaded. — (1)  Cut  off  or  screened  from  the 
effects  of  an  electro-static  or  magnetic 
field.  (2)  Screened. 

Shaded-Pole  Motor. — An  alternating- 
current  motor  in  which  the  rotary  effort 
is  obtained  by  placing  short  circuited 
coils  on  a  portion  of  the  polar  faces. 

Shade-Holder. — A  ring  or  circle  clamped 
to  the  socket  of  an  incandescent  lamp  for 
supporting  a  shade. 

Shading  Coil  of  Alternating-Current 
Motor. — A  conducting  coil  or  loop  cover- 
ing part  of  one  or  more  poles  in  an  alter- 
nating-current motor,  for  the  purpose  of 
retarding  the  magnetic  flux  through  that 
portion  of  the  pole,  and  thereby  exerting 
a  tangential  drag  on  the  armature. 

Shadow,  Electric. —  A  term  sometimes 
used  for  molecular  shadow. 

Shadowgram. —  A  term  sometimes  used 
for  radiograph.  (Not  in  general  use.) 

Shadowgraph. — A  word  frequently  used 
for  radiograph. 

Shadow  Photometer. — A  photometer  in 
which  the  intensity  of  the  light  to  be 
measured  is  estimated  by  a  comparison  of 
the  distance  at  which  it  and  the  standard 
light  produce  shadows  of  the  same  inten- 
sity. 

Shallow- Water  Submarine  Cable.— A 
submarine  cable  intended  for  use  in  shal- 
low water,  where  the  cable  is  apt  to  be 
injured  by  friction  against  a  rocky  bot- 
tom, and  therefore  provided  with  heavier 
armor  than  a  deep-sea  cable. 

Shear. — A  strain  consisting  of  an  extension 
in  one  direction  combined  with  an  equal 
compression  perpendicular  thereto. 

Shearing  Stress.— A  stress  producing  a 
shear. 

Sheathing  of  Cable. — The  armor  or  pro- 
tecting covering  employed  for  surround- 
ing the  core  of  a  cable. 

Sheathing  Wires. —  The  metallic  wires 
which  form  the  armor  of  a  submarine 
cable. 


She.] 


921 


[Sho. 


Shed  of  Insulator. — A  petticoat  or  in- 
verted cone  of  a  telegraph  insulator. 

Sheer. — The  curve  which  the  line  of  ports 
or  the  deck  of  a  ship  presents  to  the  eye, 
when  observed  from  one  side. 

Sheet  Lightning. — A  variety  of  lightning 
flash,  unaccompanied  by  thunder  audible 
to  an  observer,  in  which  the  surfaces  of 
clouds  are  illumined. 

Shell  of  Arc-Lamp. — The  outside  casing 
of  an  arc-lamp. 

Shell  of  Commutator. — A  term  some- 
times employed  for  the  commutator  form, 
separated  from  its  shaft. 

Shell  of  Fixture. — A  light  ornamental 
metallic  casing  covering  some  part  of  an 
electrolier. 

Shell  Transformer. — (1)  A  transformer 
whose  primary  and  secondary  coils  are 
laid  on  each  other,  and  the  iron  core  is 
then  wound  through  and  over  them,  so  as 
to  completely  enclose  them.  (2)  A  form 
of  iron-clad  transformer. 

Shellac. — A  resinous  substance  obtained 
from  the  roots  and  branches  of  certain 
tropical  plants,  which  possesses  high  insu- 
lating powers,  and  high  specific  inductive 
capacity. 

Shifting  Magnetic  Field.— (1)  A  magnet- 
ic field  whose  lines  of  magnetic  force  are 
changing  position  with  respect  to  the 
axis  of  the  magnet  pole  from  which  they 
emanate.  (2)  A  rotary  magnetic  field. 

Shifting  of  Phase  of  Alternating  Cur- 
rent.— In  an  alternating-current  circuit 
the  changes  in  the  phase  relation  of  cur- 
rent strengtli  to  impressed  E.  M.  F.  de- 
pending upon  variations  in  the  frequency 
or  in  the  impedance. 

Shifting  of  Spot  of  Light.— Any  move- 
ment of  a  spot  of  light  on  a  scale  causing 
that  spot  to  move  away  from  its  true  zero 
position,  produced  by  causes  other  than 
those  acting  during  the  proper  operation 
of  the  instrument. 

Shifting  Zero.-^l)  A  zero  that  changes  or 
shifts  its  position.  (2)  A  false  zero  in 
measuring  instruments. 

Ship  Dynamometer. — A  dynamometer 
employed  on  board  a  cable  ship  for  the 
purpose  of  indicating  the  strain  on  a 
grappling  rope  or  on  a  cable. 

Ship  Return-Circuit  System.— A  name 
applied  to  a  single- wire  system  or  form  of 
circuit  in  which  the  hull  of  the  ship  forms 
the  return  wire. 

Shock. — (1)  Objectively,  a  concussion  or 
blow.  (2)  Subjectively,  a  violent  nervous 
stimulus. 

14- 


Shock,  Electric. — A  physiological  shock 
produced  in  an  animal  by  an  electric  dis- 
charge. 

Shoe  of  Contact  for  Street  Railway.— 
The  metallic  contact  piece  which  rubg 
against  a  surface  rail  or  conduit  rail  in  a 
street  railway  system. 

Shoe  Plug. — A  form  of  sliding  contact- 
plug  for  insertion  in  a  jack  of  a  telephone 
switchboard. 

Shore-End  of  Telegraphic  Cable.— (1) 
A  shallow-water  section  of  submarine 
cable.  (2)  The  end  of  a  submarine  cable 
landed  on  a  shore. 

Short  Arc  System  of  Electric  Light 
ing. — A  system  of  electric  lighting  in 
which  short  voltaic  arcs  are  maintained 
between  carbon  electrodes. 

Short  Circuit. — (1)  A  shunt  or  by-path  of 
negligible  or  comparatively  small  resist- 
ance, placed  around  any  part  of  an 
electric  circuit  through  which  so  much  of 
the  current  passes  as  to  virtually  cut  out 
the  parts  of  the  circuit  to  which  it  acts  as 
a  shunt.  (2)  An  accidental  direct  con- 
nection between  the  mains  or  main  ter- 
minals of  a  dynamo  or  system  producing 
a  heavy  overload  of  current.  (3)  To  cut 
out  of  circuit  by  a  short  conductor.  (4) 
To  accidentally  produce  a  short  circuit. 

Short-Circuit-Key. — A  key  which  in  its 
normal  position  short-circuits  a  galvan- 
ometer, or  other  device  with  which  it  is 
connected. 

Short-Circuited. — (1)  Placed  on  a  short- 
circuit.  (2)  Cut  out  by  means  of  a  short- 
circuit. 

Short-Circuited  Conductor. —  A  con- 
ductor which  has  a  short-circuit  estab- 
lished past  it. 

Short  Circuiting. —  (1)  Cutting  out  of 
circuit  by  means  of  a  short-circuit.  (2) 
Establishing  a  direct  connection  between 
the  terminals  of  a  source  or  device,  or 
between  mains  connected  to  them. 

Short-Circuiting  a  Dynamo-Electric 
Machine. — (1)  Cutting  out  the  external 
circuit  of  a  dynamo  by  means  of  a  short- 
circuit.  (2)  Connecting  the  poles  or  ter- 
minals of  a  dynamo  by  a  circuit  of  negli- 
gibly small  resistance.  (3)  Greatly  over- 
loading a  constant-potential  machine,  and 
underloading  a  constant-current  ma- 
chine. 

Short-Circuiting  Plug. — (1)A  plug  which 
when  inserted  in  its  receptacle  short  cir- 
cuits the  device  connected  therewith. 
(2)  A  plug  employed  in  short-circuiting  a 
coil  or  other  resistance. 

Short-Closed  Circuit. — In  a  series  dis* 
-Vol.  2 


Sho.] 


922 


[Shu. 


tribution  circuit,  the  condition  of 'having 
short-circuited  devices,  as  distinguished 
from  a  long-closed  circuit  from  which  all 
short  circuits  have  been  removed. 
Short-Coil  Magnet.— A  magnet  whose 
magnetizing  coil  consists  of  a  few  turns 
of  short  thick  wire. 

Short  Connection  of  Two-Circuit 
G-  r  a  m  m  e-W  i  n  d  i  n  g. — A  form  of 
Gramme  winding  in  which  the  circuits 
from  brush  to  brush  consist  of  conduc- 
tors influenced  by  all  the  poles,  so  that  the 
E.  M.  F.'s  generated  in  the  two  circuits 
are  necessarily  equal. 

flhort-Connection  Two-Circuit  Arma- 
ture Winding. — (1)  Such  a  two-circuit 
winding  that  in  each  circuit  between  the 
brushes  electromotive  forces  are  induced 
by  each  and  all  the  poles  of  the  field 
frame.  (2)  Such  a  type  of  two-circuit 
winding  as  connects  coils  together  lying 
in  adjacent  fields. 

Short-Core  Electro-Magnet. — An  elec- 
tro-magnet provided  with  a  short  core. 

Short-End  of  Quadruplex  Battery.— 
The  end  of  a  quadruplex  battery,  the 
smaller  portion  of  which  is  always  in 
circuit,  as  opposed  to  the  end  of  the  extra 
battery  thrown  in  circuit  by  the  depres- 
sion of  the  increment  key. 

Short-Shunt  Compound- Winding. — A 
compound  winding  of  a  dynamo-electric 
machine  in  which  the  shunt  coil  is  connect- 
ed directly,  or  through  resistance,  with 
the  armature  brushes,  as  distinguished 
from  a  long-shunt  com  pound- winding. 

Short-Shunt  Compound-Wound  Dy- 
namo -  Electric  Machine.  —  A  com- 
pound-wound dynamo  whose  field-magnet 
eoils  form  a  shunt  to  the  armature  only, 
as  distinguished  from  a  shunt  to  the 
armature  and  series  coils  combined. 

Short-Sightedness.— (1)  The  condition  of 
'  the  eye  in  which  distinct  images  are 
formed  of  those  objects  only  which  are 
near  to  the  eye.  (2)  Myopia.  (3)  The 
condition  of  sight  pertaining  to  an  elon- 
gated eyeball. 

Short  Timber.  —  A  term  applied  to 
timber  that  has  been  improperly  subjected 
to  preservative  processes,  and  has  thereby 
been  rendered  brittle. 

Short  Wire  Repeater.— A  repeater  be- 
tween a  duplex  or  quadruplex  and  a 
branch  office  wire. 

Shower-Bath,  Electric. — A  device  for 
carrying  an  electric  charge  to  the  body  of 
a  patient  by  the  falling  water. 

Shunt. — An  additional,  or  by-path  estab- 


lished for  the  passage  of  an  electric  cur- 
rent or  discharge. 

Shunt. — To  establish  an  additional,  or  by- 
path for  the  passage  of  an  electric  current 
or  discharge. 

Shunt  -  and  -  Separately  -  Excited  Dy- 
namo -  Electric  Machine. — A  com- 
pound-wound dynamo  in  which  the  field 
is  excited  both  by  means  of  a  shunt  to  the 
armature  circuit,  and  by  a  current  pro- 
duced by  a  separate  source. 

Shunt  Bell,  Electric. — An  electric  bell 
whose  magnetizing  coils  are  connected  to 
the  line  wire  in  shunt. 

Shunt  Breaking  Resistance. — A  re- 
sistance for  insertion  in  the  field  of  a 
shunt  dynamo,  before  breaking  its  circuit, 
to  prevent  the  production  of  a  dangerously 
powerful  induced  pressure. 

Shunt  -  Circuit. —  (1)  A    derived    circuit. 

(2)  A  branch  or  additional  circuit,   pro- 
vided in  any  part  of  a  circuit,  through 
which  the  current   branches  or  divides, 
part  flowing  in  the  original   circuit  and 
part  through  the  new  branch  or  shunt. 

(3)  A  circuit  for  diverting  or  shunting  a 
portion  of  the  current. 

Shunt  Coil. — A  coil  placed  in  a  shunt 
circuit. 

Shunt  Dynamo.— A  shunt-wound  dy- 
namo-electric machine. 

Shunt-Field  Terminals  of  Motor.— The 
terminals  of  the  shunt  field  coils  of  an 
electric  motor. 

Shunt  for  Ammeter. — (1)A  shunt  coil  con- 
nection in  multiple  with  the  coils  of  an 
ammeter  for  the  purpose  of  changing  the 
value  of  the  readings.  (2)  A  reducteur. 

Shunt  Spool. — A  spool  or  coil  of  insulated 
wire  placed  in  a  shunt  circuit. 

Shunt  Street-Car  Motor.  —  A  shunt- 
wound  car  motor. 

Shunt  Ratio. —  (1)  The  ratio  existing 
between  a  shunt  and  the  circuit  it  shunts. 
(2)  The  ratio  existing  between  the  total 
current  strength  and  the  current  strength 
in  the  branch  to  which  the  shunt  is  ap- 
plied. 

Shunt  Rheostat.— A  rheostat  placed  in  a 
shunt-circuit. 

Shunt  Turns  of  Dynamo. — The  ampere 
turns  in  the  shunt  circuit  of  a  shunt- 
wound  or  compound-wound  dynamo. 

Shunt  Winding. — A  term  sometimes  em- 
ployed for  the  shunt  field  coils  on  a  shunt- 
wound  dynamo  or  motor. 

Shunt- Wound  Dynamo-Electric  Ma- 
chine. —  A  dynamo  -  electric  machine 
whose  field-magnet  coils  are  placed  in 


Shu.] 


923 


[Sie. 


shunt  with  the  armature  circuit,  so  that 
only  a  portion  of  the  current  generated 
passes  through  the  field-magnet  coils,  but 
all  the  difference  of  potential  of  the 
armature  acts  at  the  terminals  of  the 
field  circuit. 

Shunt-Wound  Field.— The  field  of  a 
dynamo  in  •which  the  field-magnet  coils 
are  placed  in  shunt  with  the  armature 
and  external  circuit. 

Shunt- Wound  Motor. — A  motor  whose 
field-magnet  coils  are  placed  in  shunt  to 
the  armature  circuit. 

Shunted. — Provided  with  a  shunt. 

Shunting. — Providing  with  a  shunt. 

Shunting  Air-Gap . — (1)  An  air-gap  in  a 
circuit  placed  around  a  galvanometer  or 
other  instrument,  for  the  purpose  of  pro- 
tecting it  from  the  effects  of  a  powerful 
disruptive  discharge.  (2)  An  air-gap 
shunt  in  a  magnetic  circuit. 

Shutter  Apparatus. — In  a  system  of 
visual  telegraphy,  an  apparatus  for  sud- 
denly displaying  and  obscuring  a  light 
by  means  of  hand-controlled  shutters. 

Shutter  Indicator  Armature. — The  ar- 
mature of  an  electro-magnet  so  arranged 
that  when  released  it  displays  an  in- 
dicator on  an  annunciator. 

Shuttle  Armature. — (1)  A  variety  of 
drum  armature  in  which  a  single  coil  of 
wire  is  wound  in  an  H-shaped  groove 
formed  in  a  bobbin-shaped  core.  (2)  The 
old  form  of  Siemens'  armature. 

Shuttle- Wound  Armature.  —  An  ar- 
mature whose  coils  are  placed  on  its  core 
by  first  winding  the  wire  on  a  shuttle  and 
passing  the  same  through  the  opening  or 
gap  provided  for  the  coil. 

Side  A  of  Quadruples  Table.— That 
side  of  a  quadfuplex  system  which  is 
worked  by  means  of  reversed  currents.' 

Side  B  of  Quadruples  Table.— That  side 
of  a  quadruplex  system  which  is  worked 
by  means  of  strengthened  currents. 

Side-Bar  Suspension  of  Motor. — In  a 
street  railway  car  truck,  a  method  of  sup- 
porting the  motors  which  consists  in  em- 
ploying a  pair  of  bars  or  light  girders 
mounted  on  springs  parallel  to  the  side 
frames  and  supporting  the  motors  from 
these  bars. 

Side  Bracket. — A  particular  form  of 
single  insulator  bracket. 

Side  Commutator. — The  commutator  of 
a  dynamo-electric  machine  placed  on  the 
side  of  the  revolving  armature. 

Side  Current. — A  term  applied  by  Hertz 
to  the  current  produced  in  the  side  cir- 
cuit of  a  micrometer. 


Side  Plash. — A  sparking  or  lateral  dis- 
charge taking  place  from  the  sides  of  a 
conductor  through  which  an  impulsive 
rush  of  electricity  is  passing. 

Side-Lights,  Electric. — Red  or  green 
lanterns  placed  on  permanent  fixtures  on 
either  side  of  a  ship. 

Side  of  Three-Wire  System.— <1)  A  term 
applied  to  the  positive  or  negative  con- 
ductors or  leads  in  the  three-wire  system 
of  distribution.  (2)  The  positive  or  the 
negative  half  of  a  three-wire  system. 

Side  Pole. — A  trolley-wire  pole  mounted 
at  the  side  of  a  track  as  distinguished  from 
a  central  pole. 

Side  Pole  Line. — An  aerial  line  supported 
from  poles  placed  on  the  side  of  a  street 
or  road,  as  distinguished  from  a  centre 
pole  line  or  from  one  supported  from 
poles  placed  in  the  centre  of  the  street  or 
road. 

Side-Pole  Trolley-Line  Construction. 
A  method  for  the  suspension  of  aerial 
trolley  lines  in  which  the  trolley  and  feed 
wires  are  suspended  from  poles  placed  on 
one  side  of  the  street  or  road. 

Side  Suspension  of  Motor. — A  side-bar 
suspension  of  a  motor  in  a  truck. 

Side  Telegraphic  Eepeater.— A  tele- 
graphic repeater  which  operates  adja- 
cent circuits  from  a  main  line. 

Sides  of  Three-Wire  System.— (1)  The 
portions  of  a  three-wire  system  which  have 
respectively  positive  and  negative  poten- 
tials. (2)  The  positive  and  negative  por- 
tions of  a  three-wire  system. 

Siderial. — Of  or  pertaining  to  the  stars. 

Sidero-Magnetic. — A  term  proposed  for 
ferro-magnetic. 

Siemens  Armature  Electro-Magnetic 
Bell. — A  form  of  electro-magnetic  bell, 
the  movements  of  whose  armature  are 
obtained  by  the  reversal  of  polarity  that 
occurs  when  alternating  currents  are 
passed  through  a  single-coil  Siemens  ar- 
mature. 

Siemens  Differential  Voltameter. — 
A  form  of  voltameter  employed  by 
Siemens  for  determining  the  resistance 
of  the  platinum  spiral  used  in  his  electro- 
pyrometer. 

Siemens  Electro  -  Dynamometer. — A 
form  of  galvanometer  employed  for  the 
measurement  of  electric  currents. 

Siemens  Electro-Pyrometer.— An  ap- 
paratus for  the  determination  of  temper- 
ature by  the  measurement  of  the  electric 
resistance  of  a  platinum  wire  exposed  to 
the  source  of  heat,  the  temperature  of 
which  is  to  be  measured. 


Sie.] 


924 


[Sim. 


Siemens-Halske  Voltaic  Cell. — A  zinc- 
copper  couple  whose  elements  are  em- 
ployed with  dilute  sulphuric  acid  and  a 
saturated  solution  of  copper  sulphate  re- 
spectively. 

'Siemens  Water  Pyrometer.— A  pyro- 
meter employed  for  determining  the  tem- 
perature of  a  furnace  or  other  intense 
source  of  heat,  by  the  increase  in  the  tem- 
perature of  a  known  weight  of  water  to 
which  a  metal  cylinder  of  a  given  weight 
has  been  put,  after  exposure  for  a  given 
time  to  the  som-ce  of  heat  to  be  measured. 

Signal  Arm. — A  semaphore  arm. 

.Signal-Service  System  for  Electric 
Railroad. — A  system  of  electric  signals 
used  on  railroads  for  ascertaining  the 
condition  of  the  road,  sending  instruc- 
tions to  engineers,  and  conveying  intelli- 
gence generally  from  stations  along  the 
road  to  running  trains. 

Sight-Feeding  Oiler. — A  glass  oil-cup 
which  permits  the  visible  feeding  of  lu- 
bricating oil  to  the  journal  bearings. 

Signature. — In  telegraphy,  a  name  of  the 
sender  of  a  message  as  it  appears  upon  the 
same. 

Silence  Telephone  Cabinet.— A  long- 
distance telephone  cabinet. 

Silent. — A  switch  device  for  preventing 
the  action  of  an  electric  alarm  by  short- 
circuiting  it. 

Silent  Discharge. — A  name  sometimes 
given  to  a  convective  discharge,  in  order 
to  distinguish  it  from  the  more  noisy  dis- 
ruptive discharge. 

Silhougraph. — A  word  proposed  for  ra- 
diograph. 

Silver  Bath. — An  electrolytic  bath  con- 
taining a  readily  electrolyzable  salt  of  sil- 
ver, and  a  plate  of  silver  acting  as  the 
anode,  placed  in  the  liquid  near  the 
object  to  be  coated  which  forms  the 
cathode. 

Silver  Chloride  Voltaic  Cell. — A  zinc- 
silver  couple  immersed  in  electrolytes  of 
sal-ammoniac  or  common  salt,  and  silver 
chloride,  respectively. 

Silver-Palladium  Alloy. — An  alloy  of 
silver  with  palladium  and  other  metals, 
employed  for  the  hair-springs,  escape- 
ments and  balance-wheels  of  watches,  on 
account  of  its  non-magnetic  properties. 

Silver  Plating. — Covering  the  surfaces  of 
the  baser  metals  with  an  adherent  coating 
of  silver  by  the  electric  current. 

Silver  Voltameter. — A  voltameter  in 
which  the  quantity  of  electricity  passing  is 
determined  by  the  weight  of  silver  depos- 
ited. 


Silvered  Plumbago. — Powdered  plum- 
bago covered  with  metallic  silver,  for  use 
in  the  metallization  of  objects  to  be  elec- 
tro-plated. 

Silurus  Electricus. — The  electric  eel. 

Similars. — Conductors  in  the  secondary 
winding  of  an  induction  machine  which 
are  similar  to  each  other  in  respect  to 
the  magnitude  of  their  induced  electro- 
motive forces  at  any  instant,  and  sym- 
metrically disposed  relatively  to  the  ro- 
tating poles. 

Simple  Alternating-Currents. — (1)  Sin- 
usoidal-alternating currents.  (2)  Simple- 
harmonic  currents. 

Simple  Arc. — A  voltaic  arc  formed  be- 
tween two  electrodes. 

Simple  Circuit. — A  term  sometimes  em- 
ployed for  a  circuit  containing  a  single 
electric  source  and  a  single  electro-recep- 
tive device. 

Simple   Electric    Candle   Burner.— A 

plain-pendant  electric  burner. 

Simple-Harmonic  Currents.— (1)  Cur- 
rents whose  flow  is  variable  both  in 
strength  and  duration,  and  in  which  the 
quantity  of  electricity  passing  by  any  sec- 
tion of  conductor  may  be  represented  by 
a  simple-harmonic  curve.  (2)  A  current 
of  such  a  nature  that  the  continuous  va- 
riation of  the  flow  of  electricity  past  any 
area  of  cross-section  of  the  conductor,  or 
the  continuous  variations  in  electromotive 
force,  may  be  expressed  by  a  simple-har- 
monic curve. 

Simple-Harmonic  Curve.— The  curve 
which  results  when  a  simple-harmonic 
motion  in  one  line  is  compounded  with 
uniform  motion  in  a  straight  line  at  right 
angles  thereto. 

Simple-Harmonic.  Electromotive 
Forces. —  Electi'omotive  forces  which 
vary  in  such  a  manner  as  to  produce 
simple-harmonic  currents  ;  or,  electromo- 
tive forces  whose  variations  can  be  cor- 
rectly represented  by  a  simple-harmonic 
curve. 

Simple-Harmonic  Motion.— (1)  Motion 
which  repeats  itself  at  regular  intervals 
in  one  line,  taking  place  backwards  or 
forwards,  and  which  is  the  orthogonal 
projection  of  the  path  of  a  point  moving 
uniformly  in  a  plane  circle  upon  a  diame- 
ter of  the  circle.  (2)  Motion  which  is  a 
simple-periodic  function  of  the  tim«.  (3) 
Simple-periodic  motion. 

Simple-Harmonic  Variation. — A  varia- 
tion of  current  or  electromotive  force 
which  takes  place  in  accordance  with 
simple-harmonic  law. 


Sim.] 


925 


[Sin. 


Simple  Immersion. — A  term  sometimes 
employed  for  an  electrolytic  deposit  ob- 
tained by  merely  dipping  a  metal  in  a  so- 
lution of  a  metallic  salt. 

Simple  Magnet. — A  simple  magnetized  bar. 

Simple  Magnetic  Shell. — A  magnetic 
shell  whose  strength  is  everywhere  the 
same. 

Simple  -  Periodic  Currents. — A  term 
sometimes  used  for  simple-harmonic  cur- 
rents. 

Simple-Periodic  Curve.— A  simple-har- 
monic curve. 

Simple-Periodic  Electromotive  Force. 
A  simple-harmonic  electromotive  force. 

Simple-Periodic  Motion. — Simple-har- 
monic motion. 

S  i  m  p  1  e-Periodic  Variation.— Simple- 
harmonic  variation. 

Simple  Radical.—  (1)  An  unsaturated 
atom  with  its  bond  or  bonds  free.  (2)  A 
single  unsaturated  atom,  as  distinguished 
from  an  unsaturated  group  of  atoms. 

Simple  Rigidity.— (1)  In  an  isotropic 
body  the  ratio  of  shearing  stress  to  the 
resulting  shear.  (2)  Resistance  to  shear- 
ing. (3)  In  an  isotropic  body  the  edges 
of  a  unit  cube  to  which  tangential  shear- 
ing stresses  are  applied,  the  ratio  of  the 
tangential  force  to  the  angular  distortion 
effected  in  the  cube. 

Simple    Shunt. — A    coil   arranged    as   a 

shunt,  and  unprovided  with  an  iron  core. 
Simple-Sine  Motion. — A  term  sometimes 

employed  for  simple-harmonic  motion. 
Simple  Voltaic  Cell.— A  term  sometimes 

used  for  a  single-fluid  cell. 
Simplex    Telegraph.— A   general    term 

embracing  the   apparatus    employed    in 

simplex  telegraphy. 

Simplex  Telegraphy  .—A  system  of  teleg- 
raphy in  which  a  single  message  only  can 
be  sent  over  the  line  wire. 

Simplex  Working.— (1)  Transmitting 
messages  by  simplex  telegraphy.  (2)  A 
word  sometimes  employed  for  simple 
telegraphic  transmission: 

Sims-Edison  Torpedo.— A  special  form 
of  torpedo  in  which  electricity  is  both  the 
propelling  and  directing  power,  but  the 
electric  source  is  situated  outside  the  tor- 
pedo, and  is  connected  with  the  same  by 
a  light  cable. 

Sine  Galvanometer. — A  galvanometer 
whose  deflecting  coil  is  placed  in  a  verti- 
cal plane  movable  about  a  vertical  axis, 
so  that  it  can  be  made  to  follow  the  mag- 
netic needle  in  its  deflections. 

Sine  Law. — (1)  A  law  of  magnitude  de- 


nned by  the  sines  of  angles.  (2)  A  mag- 
nitude which  follows  the  sines  of  succes- 
sive angles. 

Single  Brush-Rocker  Arm.— A  device 
by  means  of  which  a  single  pair  of  brushes 
are  so  situated  on  a  dynamo  or  motor  as 
to  be  capable  of  being  readily  shifted  into 
the  desired  position  on  the  commutator 
cylinder. 

Single-Brush  Yoke. — A  term  sometimes 
used  for  single  brush-rocker  arm. 

Single-Circuit.— An  undivided  circuit. 

Single-Contact  Carbon  Telephone. — 
A  form  of  microphonic  telephone  trans- 
mitter, in  which  a  single  contact  is  em- 
ployed. 

Single-Contact  Key. — Any  key  which 
makes  a  single  contact  only. 

Single-Cord  Multiple-T  elephone 
Switchboard.— (1)  A  multiple  telephone 
switchboard  employing  a  single  conduct- 
ing cord  in  establishing  connections. 
(2)  A  multiple-telephone  switchboard  in 
which  the  circuits  are  all  ground-return- 
circuits,  and  the  subscribers'  jacks  are  all 
connected  in  series. 

Single-Cord  Switchboard.— (1)  A  tele- 
phone switchboard  in  which  an  inter-con- 
nection between  two  subscribers  is  ef- 
fected through  a  single  cord.  (2)  A  tele- 
phone switchboard  in  which  each  line 
terminates  in  a  plug. 

Single-Cord  Telephone  Switchboard. 
A  telephone  switchboard  employing 
single  conducting  cords. 

Single-Cup  Insulator. — An  insulator 
consisting  of  a  single  inverted  cup. 

Single  Curb. — A  device  for  increasing  the 
speed  of  telegraphic  signalling  by  ridding 
the  line  of  its  previous  charge  by  means 
of  a  single  reversed  current  sent  through 
it  after  each  signal,  before  connecting  to 
the  ground,  as  distinguished  from  a 
double  curb  in  which  a  succession  of  two 
reversed  currents  follow  each  signal. 

Single-Curb  Signalling. — Signalling  by 
means  of  a  single  curb. 

Single-Current  Signalling.— Signalling 
by  means  of  makes  or  breaks  in  the  cir- 
cuit of  a  single  current. 

Single-Current  Closed-Circuited  Sig- 
nalling.— A  method  of  telegraphic  sig- 
nalling in  which  the  line  circuit  is  nor- 
mally closed,  being  only  broken  by  the 
sending  operator,  while  the  current  in  the 
circuit  has  only  one  direction. 

Single-Current  Key. — A  key  employed 
in  single-current  signalling. 

Single-Current  Open-Circuit   Signal- 


Sin,] 


926 


[Sin. 


ling. — A  method  of  telegraphic  signalling 
in  which  the  main-line  batteries  are  fixed 
at  each  station,  and  are  in  circuit  only 
when  signalling. 

Single-Current  Telegraphic  Working. 
A  term  sometimes  used  for  single-current 
signalling. 

Single-Current  Translator. — A  tele- 
graphic translator  suitable  for  use  in 
single-current  working. 

Single-Curve  Suspension. — (1)  A  sus- 
pension suitable  for  the  support  of  a  trol- 
ley wire  at  a  single  curve  in  the  line,  or 
single-track  curve.  (2)  A  form  of  suspen- 
sion having  a  single  curved  holder  or 
support. 

Single-Curve  Trolley  Hanger. — (1)  A 
hanger  supporting  a  single  curve  wire  or 
single-track  curve  wire.  (2)  A  trolley 
hanger  supported  by  a  single  curved 
holder. 

Single-Curve  Trolley-Suspension. — 
(1)  Suspension  of  a  trolley  wire  by  a  single- 
curve  trolley-hanger.  (2)  A  single-track 
trolley-suspension  at  a  curve  in  the  track. 

Single-Coil  Field  Dynamo.— A  dynamo 
whose  magnetic  field  is  obtained  from  a 
single  magnetizing  coil. 

Single  Field-Coil  Multipolar  Dynamo. 
A  multipolar  dynamo  having  a  single 
field  coil  on  a  single  core  provided  with  a 
plurality  of  polar  projections. 

Single-Fluid. — Pertaining  to  the  single- 
fluid  hypothesis  of  electricity  or  magnet- 
ism. 

Single -Fluid  Hypothesis  of  Elec- 
tricity.— A  hypothesis  which  endeavors 
to  explain  the  cause  of  electrical  phenom- 
ena by  the  assumption  of  the  existence  of 
a  single  electric  fluid. 

Single-Fluid  Voltaic  Cell.— A  voltaic 
cell  in  which  but  a  single  fluid  or  electro- 
lyte is  used. 

Single-Focus  X-Ray  Tube. — An  X-ray 
tube  suitable  for  use  in  connection  with 
pulsatory  currents,  and  provided  with  a 
single  deflecting  plate  or  anticathode  op- 
posite the  cathode. 

Single-Line  Repeater. — In  telegraphy,  a 
repeater  from  a  single  circuit  into  an- 
other. 

Single-Liquid  Voltaic  Cell. — A  single- 
fluid  voltaic  cell. 

Single-Loop  Armature. — An  armature 
consisting  of  a  closed  conducting  circuit 
containing  a  single  loop,  so  placed  as  to 
be  capable  of  revolving  in  a  magnetic 
field,  as  to  cut  its  magnetic  flux. 

Single-Magnet  Dynamo-Electric  Ma- 


chine.— A  term  sometimes  used  for  a 
single  field-coil  dynamo. 
Single-Needle  Telegraphy.— A  system 
of  telegraphy  in  which  the  transmitted 
signals  are  received  by  the  movements  of 
a  vertical  needle  suitably  suspended  be- 
fore a  dial. 

Single-Pair  Brush-Rocker.— A  term 
sometimes  used  for  single-pair  brush  yoke. 

Single-Pair  Brush  Yoke. — A  device  for 
so  holding  a  single  pair  of  collecting 
brushes  of  a  dynamo-electric  machine 
that  they  can  be  readily  moved  or  rotated 
on  the  commutator  cylinder. 

Single-Pair  Yoke.— A  single-pair  brusk 

yoke. 

Single  Peg. — A  peg  provided  with  but  a 

-  single  contact. 

Single  Phase.— (1)  Uniphase.  (2)  Mono- 
phase. (3)  Pertaining  to  ordinary  alter- 
nating currents  in  a  simple  alternating- 
current  system  as  distinguished  from 
multiphase  currents. 

Single-Phase  Alternating  Current. — 
A  uniphase  alternating  current. 

Single-Phase  Alternator. — An  alter- 
nator capable  of  producing  simple  »r 
single-phase  currents. 

Single-Phase  Armature  Windings. — 
Windings  employed  on  the  armature  of  a 
single-phase  alternator. 

Single-Phase  Armature  Windings.— 
Armature  windings  of  single-phase  ge»- 
erators. 

Single-Phase  Asynchronous  Motor. — 
A  single-phase  alternating-current  motor 
capable  of  running  otherwise  than  in 
synchronism  with  the  current  supplied  to 
it  from  the  circuit. 

Single-Phase  Bar  -  Armature  Wind- 
ings.— Such  a  bar  armature  winding  of 
an  alternator  as  is  capable  of  producing 
single-phase  currents. 

Single-Phase  Dynamo. — A  single-phaj* 
alternator. 

Single-Phase  Generator.  —  A  single- 
phase  alternator. 

Single-Phase  Motor.  —  A  uniphate 
motor. 

Single-Phase  Induction  Motor.— An 
induction  motor  operated  by  uniphase 
currents. 

Single-Phase  Induction  Motor. — An  in- 
duction motor  operated  or  intended  to  be 
operated  on  a  single-phase  alternating- 
current  circuit. 

Single-Phase  Synchronous  Motor. — A 
synchronous  motor  capable  of  being  opei* 
ated  by  uniphase  currents. 


Sin.] 


927 


[Sin. 


Single-Phase  Transformer. — A  transfor- 
mer suitable  for  supplying  or  transform- 
ing single-phase  currents. 

Single-Phase  Winding.— A  single-phase 
armature  winding. 

Single-Phaser. — (1)  An  alternating-cur- 
rent generator  of  single-phase  currents. 
(2)  A  uniphaser. 

Single-Pole  Cut-Out. — A  cut-out  by 
means  of  which  the  circuit  is  broken  or 
cut  in  one  of  the  two  leads  only. 

Single-Pole  Safety -Fuse. —A  single  pole 
cut-out  operated  by  a  safety  fuse. 

Single-Pole  Switch. — A  switch  which 
opens  or  closes  a  circuit  at  one  of  its 
leads  only. 

Single-Pole  Telephone  Receiver. — (1) 
A  bar-magnet  telephone  with  a  coil  on 
one  end  of  the  bar.  (2)  A  telephone  re- 
ceiver in  which  only  one  magnetic  pole  is 
presented  to  the  diaphragm,  as  distin- 
guished from  a  receiver  in  which  a  pair  of 
poles,  each  surrounded  by  a  coil,  is  pre- 
sented to  the  diaphragm. 

Single-Pole  Telephone  Switch.  —  A 
fcingle-pole  switch  employed  on  a  tele- 
phone circuit. 

Single  Pull-Off. — <!)' A  trolley  pull-off 
supported  on  a  single-curve  holder.  (2) 
A  single-curve  pull-off.  (3)  A  trolley 
pull-off  on  a  single-track  curve. 

Single-Reduction. — (1)  Having  but  a 
single  gear  wheel  for  reducing  speed. 
(2)  A  gearing  in  which  but  a  single  re- 
duction of  speed  takes  place  as  opposed 
to  a  double  gearing  in  which  two  separate 
reductions  are  effected. 

Single-Reduction  Street-Car  Motor. — 
A  street-car  motor  which  requires  a 
single  reduction  gear  connected  with  the 
car  axle  to  reduce  the  motion  of  the  car 
axle  as  opposed  to  i»  motor  geared  with 
the  car  axle  through  two  successive  gear 
wheels  and  therefore  one  intermediate 
shaft. 

Single-Reflection  Tube. — A  term  some- 
times applied  to  an  X-ray  tube  contain- 
ing but  a  single  deflecting  plate  or  anti- 
cathode. 

Single-Shackle  Insulator.— <1)  A  form 
of  insulator  employed  in  shackling  a 
single  wire.  (2)  A  form  of  single  shackle 
to  which  two  wires  can  be  fastened  at 
different  points  and  left  insulated. 

Single-Shed  Insulator.— An  insulator 
provided  with  a  single  inverted  cup. 

Single-Stroke  Electric  Bell.— An  elec- 
tric bell  that  gives  a  single  stroke  only  for 
each  closure  of  the  circuit. 


Single-Throw  Switch.— A  switch  having 
but  two  positions,  one  for  opening,  and  the 
other  for  closing  the  circuit  it  controls, 
as  distinguished  from  a  double-throw 
switch. 

Single-Touch. — A  phrase  sometimes  em* 
ployed  for  magnetization  by  single 
touch. 

Single-Track  Bracket  Trolley-Suspen- 
sion.— A  form  of  single-track  trolley- 
wire  suspension,  in  which  a  bracket  is 
supported  from  a  pole  placed  on  one  side 
of  the  street. 

Single-Trolley  System.  —  A  trolley 
system  in  which  a  single  conducting 
over-head  wire  is  employed,  the  track 
and  ground  being  used  for  a  return. 

Single-Trolley  System  Electric-Rail- 
road.— An  electric  railroad  operated  by  a 
single  trolley. 

Single-Truck  Car.— A  car  whose  body  is 
supported  on  a  single  truck. 

Single- Valued  Function. — A  function 
which  has  only  a  single  value  for  each 
value  of  the  variable. 

Single- Wire  Cable. — A  cable  whose  core 
contains  a  single  conducting  wire  only. 

Single- Wire  Circuit. — A  term  sometimes 
used  for  a  grounded  circuit. 

Single-Wire  Line. — A  term  sometimes 
used  for  a  single-wire  circuit. 

Single  -Wi  r  e  Multiple  Telephone 
Switchboard. — (1)  A  single-cord  mul- 
tiple telephone  switchboard.  (2)  A 
switchboard  connecting  ground-return 
subscribers'  lines,  the  jacks  of  which  are 
all  in  series  in  each  line. 

Single-Wire  Spring-Jack. — A  spring- 
jack  suitable  for  use  in  a  single-wire 
switchboard. 

Single -Wire  Switchboard.— (1)  A 
switchboard  devoted  to  the  connections 
of  a  single  line  with  various  sets  of  appa- 
ratus. (2)  A  telephone  switchboard  con- 
nected to  ground-return  circuits. 

Single -Wire  System  for  Electric 
Light  Leads. — A  term  sometimes  em- 
ployed for  a  ground-return  electric  light 
circuit. 

Single- Wire  Telephone  Switchboard. 
A  form  of  telephone  switchboard  connect- 
ing ground-return  circuits. 

S  i  ng  1  e- Wound  Gramme  Ring.  —  A 
Gramme  ring  provided  with  a  single 
winding,  the  number  of  whose  coils  is  a 
multiple  of  the  number  of  poles,  and  th« 
number  of  whose  commutator  segments 
is  equal  to  the  number  of  poles. 

Single-Wound  Multiple-Circuit  Mul 


Sin.] 


928 


[Ski, 


tipolar  Drum-Armature.— A  drum 
armature  wound  for  a  multipolar  field  in 
a  single  winding  and  affording  a  plur- 
ality of  paths  or  circuits  between  its 
brushes. 

Single-Wound  Two-Circuit  Drum- 
Armature. — A  drum  armature,  wound 
for  a  multipolar  field,  with  a  single  wind- 
ing and  affording  two  conducting  paths 
or  circuits  between  the  brushes. 

Single-Wound  Two-Circuit  Multipo- 
lar Ring- Armature. — A  ring  armature 
wound  for  a  multipolar  field,  with  a  single 
winding,  which  affords  but  two  conduct- 
ing paths  or  circuits  between  the  brushes. 

Single-Wound  Wire. — Wire  wound  or 
covered  with  a  single  layer  of  insulating 
material. 

Singly  Re-Entrant  Armature- Wind- 
ing.— (1)  A  single-winding  which  re-en- 
ters itself.  (2)  An  armature  provided 
with  a  single- winding  which  is  re-entrant. 

Singular  Polarization. — A  term  applied 
to  the  polarization  of  a  voltaic  cell  when 
the  depolarizing  current  is  many  times 
stronger  than  the  primary  current. 

Sinistrorsal  Helix. — A  sinistrorsal  sole- 
noid. 

Sinistrorsal  Solenoid. — A  solenoid  whose 

winding  is  left-handed. 
Sinuous    Current.— A    term    sometimes 

applied  to  a  current  flowing  through  a 

sinuous  conductor. 

Sinusoid. — A  name  frequently  given  to  a 
curve  of  sines. 

Sinusoidal. — Of  or  pertaining  to  a  sinu- 
soid. 

Sinusoidal  Alternating  Electromotive 
Forces. — (1)  Alternating  electromotive 
forces  whose  variations  in  strength 
are  correctly  represented  by  a  sinusoidal 
curve.  (2)  Simple-harmonic  E.  M.  F.'s. 
(3)  E.  M.  F.'s  which  are  simple-harmonic 
functions  of  time. 

Sinusoidal  Alternator. — An  alternator 
capable  of  producing  sinusoidal  electro- 
motive forces. 

Sinusoidal  Currents.  —  Simple-periodic 
currents  whose  strengths  are  correctly 
represented  by  sinusoids. 

Sinusoidal-Current  Circuit.— A  circuit 
conveying  sinusoidal  currents. 

Sinusoidal  Curve. — (1)  A  curve  of  sines. 
(2)  A  sinusoid.  (3)  A  curve  which  to 
rectangular  co-ordinates  has  an  ordinate 
at  each  point  proportionate  to  the  sine  of 
an  angle  proportionate  to  the  abscissa. 

Sinusoidal  Flux. — A  flux  which  varies 


sinusoidally  or  according  to  a    simple- 
harmonic  law. 

Sinusoidal  Generator.— A  sinusoidal  al- 
ternator or  generator  capable  of  deliver- 
ing a  simple-harmonic  E.  M.  F. 

Sinusoidal  Magnetic  Flux. — A  sinu- 
soidally varying  flux. 

Sinusoidal  Magnetomotive  Force. — 
A  magnetomotive  force  varying  sinw- 
soidally. 

Sinusoidal  Variation. — Such  a  variation 
of  an  electromotive  force,  current,  or  flux, 
as  may  be  correctly  represented  by  a  sin- 
usoid. 

Sinusoider. — A  name  sometimes  given  to 
a  sinusoidal  alternator. 

Siphon,  Electric.— A  siphon  in  which 
the  stoppage  of  the  flow  of  the  liquid  due 
to  the  gradual  accumulation  of  air,  is 
prevented  by  electrical  means. 

Siphon  Recorder. — An  apparatus  for  re- 
cording in  ink  on  a  strip  of  paper  a  mes- 
sage received  over  a  cable  by  means  of  a 
jet  of  ink  thrown  out  from  a  fine  glass 
tube  supported  on  a  fine  wire. 

Siphon-Recorder  Vibrator. — A  device 
employed  in  a  siphon  recorder  to  obtain 
the  vibrations  required  for  the  ejection 
of  the  ink  from  the  siphon  by  mechanical 
means  instead  of  by  electrical  means. 

Siphon  Writing.— A  record  obtained  by 
means  of  a  siphon  recorder. 

Siren. — An  acoustic  apparatus  employed 
for  measuring  the  frequency  of  sound 
waves. 

Six-Pole  Dynamo-Electric  Machine. — 

A  sextipolar  dynamo. 

Six- Wire  System. — A  system  of  distribu- 
tion similar  in  general  to  the  three-wire 
system,  in  which  five  dynamos  are  con- 
nected to  six  conductors  or  leads. 

Six- Wire  Triphase  System. — A  system 
for  the  production  of  triphase  currents, 
in  three  separate  circuits,  each  having  two 
wires. 

Skew  Adjustment  of  Carbons  in  Arc- 
Lamps. — The  adjustment  of  the  carbons 
of  an  arc  lamp  by  means  of  which  the 
positive  carbon  is  placed  a  short  distance 
in  front  of,  but  out  of  the  vertical  line 
with  the  negative  carbon. 

Skiagraph. — A  word  proposed  for  radio- 
graph. (Not  in  general  use.) 

Skiasmogram.  —  A  word  proposed  for 
radiograph.  (Not  in  use.) 

Skidding  of  Car  Wheels. — A  term  ex- 
pressing the  sliding  of  the  wheels  of  a  cal 
in  place  of  their  proper  rolling  motion. 


Ski.] 


929 


[Slo. 


Skin  Currents. — A  term  applied  to  rapid- 
ly alternating  currents  which  are  limited 
to  the  surface  of  a  conductor. 

Skin  Electromotive  Force. — The  E.  M. 
F.  which  is  active  in  producing  the  skin 
effect  in  a  conductor. 

Skin  Effect. — The  tendency  of  rapidly 
alternating  currents  to  avoid  the  central 
portions  of  solid  conductors  and  flow,  for 
the  greater  part,  through  the  superficial 
portions. 

Skipping  of  Pointer  of  Telegraph  In- 
strument.— In  a  dial  telegraph,  the  fail- 
ure of  the  dial  to  point  to  the  letter  in- 
tended, and  caused  by  its  skipping  one  or 
more  of  the  letters. 

Skodogram.  —  A  term  proposed  for 
radiograph.  (Not  in  use.) 

Skotograph. — A  term  proposed  for  radio- 
graph. (Not  in  use.) 

Slack. — Excess. 

Slack  Cable. — Extra  cable,  or  cable  paid 
out  in  excess  of  the  distance  covered, 
in  order  to  permit  of  the  subsequent  re- 
covery of  the  cable  without  undue  strain, 
and  also  to  allow  of  its  accommodating 
itself  to  irregularities  in  the  contour  of 
the  sea-bottom. 

Sled. — A  sliding  contact  drawn  after  a 
moving  railroad  car  through  the  slotted 
conduit  containing  the  wires  or  conduc- 
tors from  which  the  driving  current  is 
taken. 

Sleeve  Joint. — A  junction  of  the  ends  of 
conducting  wires  obtained  by  passing 
them  through  tubes,  and  subsequently 
twisting  and  soldering. 

Sleeve  of  Plug. — A  conducting  cylinder 
upon  a  telephone  plug,  making  contact 
with  the  barrel  or  socket  of  a  telephone 
jack. 

Slide  Bridge. — A  bridge  whose  propor- 
tionate arms  are  formed  of  a  single  thin 
wire,  of  uniform  diameter  and  of  compar- 
atively high  resistance,  of  some  material 
whose  temperature  coefficient  is  low. 

Slide  Contact  Piece. — A  contact  piece  in 
which  the  circuit  is  completed  by  means 
of  a  sliding  or  wiping  joint. 

Slide  Form  of  Electric  Bridge. — A  slide 
bridge. 

Slide  Resistance. — (1)  A  rheostat  whose 
separate  resistances  or  coils  are  placed  in 
or  removed  from  a  circuit  by  means  of  a 
sliding  contact.  (2)  An  apparatus  em- 
ployed in  telegraphy  consisting  of  a  pair 
of  slide  rheostats  actually  subdivided  into 
100  parts  each,  but  forming  jointly  a 
rheostat  virtually  subdivided  into  10,000 
parts. 

59' 


Slide  Switchboard. — A  telephone  switch- 
board in  which  the  connections  are  made 
by  sliding  contacts. 

Slide  Wire. — A  wire  of  uniform  diameter 
employed  in  Wheatstone's  electric  bridge 
for  the  proportionate  arms  of  the  bridge. 

Sliding  Bed-Plate. — A  bed-plate  of  a 
belt-driven  dynamo,  motor,  or  other  sim- 
ilar apparatus,  provided  with  means  for 
moving  it,  so  as  to  tighten  the  belt. 

Sliding  Contact. — A  contact  connected 
with  one  part  of  a  circuit  that  closes  or 
completes  that  circuit  by  being  slid  over 
a  conductor  connected  \vith  another  part 
of  such  circuit. 

Sliding  Contact-Key. — A  key  employed 
in  the  slide  form  of  Wheatstone's  bridge 
to  make  contact  with  the  sliding  wire. 

Sliding  Joint. — An  expansion  joint. 

Slings. — Bright  copper  wires  employed  for 
hanging  an  object  to  be  electro-plated  to 
the  negative  rod  in  the  depositing  vessel. 

Slinging  Wires.  —  Erecting  wires  on 
aerial  poles. 

Slip. — To  release  a  buoy,  rope,  anchor  etc., 
in  cable  work. 

Slip  of  Induction  Motor. — The  propor- 
tional difference  between  the  speed  of  the 
rotary  magnetic  field  which  drives  the 
motor  and  the  speed  of  the  rotor. 

Slip  of  Rotor. — The  proportional  differ- 
ence between  the  speed  of  a  rotary 
magnetic  field  and  the  speed  of  the  rotor. 

Slip  Thimble. — In  cable  work,  a  device  for 
readily  disengaging  a  buoy  from  the  side 
of  a  vessel  or  from  its  buoy  rope. 

Slippage. — The  ratio,  subtracted  from 
unity,  of  the  speed  of  a  rotor  divided  by 
the  speed  of  a  rotatory  magnetic  field. 

Slipping  of  Belt. — The  loss  of  speed  of  a 
revolving  belt  on  its  pulley  due  to  slip- 
ping. 

Slope  of  Magneto-Motive  Force.— A 
term  sometimes  used  for  magnetizing 
force. 

Slope  of  Potential. — A  phrase  some.times 
used  for  drop  of  potential. 

Slots  on  Armature  Core.  —  Slots  or 
grooves  provided  in  an  armature  core  for 
the  reception  of  the  armature  coils. 

Slot- Wound  Armature.— (1)  An  arma- 
ture in  which  the  windings  are  buried  in 
slots.  (2)  An  ironclad  armature. 

Slotted  Armature. — (1)  An  armature  pro- 
vided with  slots  or  grooves  for  the  recep- 
tion of  the  wires.  (2)  An  iron-clad  arma- 
ture. 

Slotted  Armature-Core. — An  armature 
core  provided  with  longitudinal  grooves. 


Slo.] 


930 


[Sof. 


Slotted  Conduit. — An  underground  con- 
duit provided  with  a  slot  extending  to 
the  surface  of  the  road-bed,  through 
which  a  travelling  conductor  can  carry 
off  the  current  from  one  or  more  con- 
ductors supported  in  the  conduit. 

Slow-Speed  Electric  Motor.— (1)  An 
electric  motor  which  is  capable  of  efficient 
operation  at  a  comparatively  slow  speed. 
(2)  A  motor  designed  to  run  at  a  com- 
paratively slow  speed. 

Slow-Speed  Generator. — A  generator 
designed  to  be  run  at  a  slow  speed. 

Sluggish  Magnet. — A  magnet  that  ac- 
quires or  loses  its  magnetism  sluggishly. 
mashing  Point  of  Incandescent 
Electric  Lamp. — Such  a  period  in  the 
life  of  an  incandescent  lamp  which  has 
become  blackened,  when  it  will  be  more 
economical  to  break  the  lamp,  or  remove 
it  from  the  circuit  and  replace  it  by  a 
new  one,  than  to  continue  its  operation. 

Smee  Voltaic  Cell. — A  zinc-silver  couple 
employed  in  connection  with  an  electro- 
lyte of  dilute  sulphuric  acid. 

Smelting  of  Phosphorus,  Electric. — 
The  electric  separation  of  phosphorus  from 
any  of  its  compounds. 

Smooth-Body  Generator. — A  dynamo  or 
generator  provided  with  a  smooth-core 
armature. 

Smooth -Core  Armature. — (1)  An  ar- 
mature which  presents  a  continuously 
smooth  cylindrical  surface  before  the  ar- 
mature coils  are  wound  on  it.  (2)  A  sur- 
face-wound armature  as  distinguished 
from  an  iron-clad  armature. 

Snap  Switch. — A  switch  in  which  the 
transfer  of  the  contact  points  from  one 
position  to  another  is  accomplished  by  a 
quick  motion  obtained  by  the  operation 
of  a  spring. 

Snap  Welding  of  Bails. — A  welding 
joint  for  a  rail  bond  in  which  the  rails  are 
clamped  at  their  short  projections,  the 
ends  heated  as  rapidly  as  possible  and 
then  firmly  squeezed  together  when  the 
welding  temperature  has  been  reached. 

Snapper. — A  device  in  a  sounding-lead 
consisting  of  a  pair  of  metallic  jaws  which 
are  open  when  the  lead  is  lowered  but 
which  automatically  close  when  the  sea 
bottom  is  reached,  for  the  purpose  of 
securing  samples  of  the  sea  bottom. 

Snapper  Sounder. — A  mechanical  device 
for  producing,  by  the  flexure  of  a  spring, 
sounds  corresponding  to  Morse  characters 
as  heard  from  a  Morse  sounder. 

Sneak  Current. — (1)  A  relatively  weak 
current  accidentally  introduced  into  a 


telephonic  or  telegraphic  circuit,  which 
would  do  no  immediate  harm,  but  which 
continuing  to  circulate  in  a  bell  or  annun- 
ciator coil  would  generate  enough  heat 
in  a  comparatively  short  time  to  burn  it 
out.  (2)  A  current  of  sufficient  strength 
to  be  dangerous  if  maintained,  but  insuf- 
ficiently strong  to  melt  the  usual  safetj 
fuses. 

Sneak-Current  Arrester. — A  sneak-cur- 
rent protector  or  coil. 

Sneak-Current  Coil. — A  coil  of  German- 
silver  wire  inserted  in  a  telephone  circuit 
to  become  sufficiently  heated  by  a  sneak- 
current,  or  current  of  dangerous  strength, 
to  melt  a  drop  of  fusible  metal  placed 
within  it,  and  thereby  cut  the  telephone 
apparatus  out  of  circuit. 

Sneak-Current  Protector. — A  form  of 
protector  in  which  a  fine  fusible  wire  is 
inserted  between  the  end  of  a  line  andtha 
instruments. 

Snow-Sweeper,  Electric. — A  form  of 
snow-sweeper  operated  by  means  of  a*, 
electric  motor. 

Soakage. — A  term  sometimes  employed 
for  residual  charge. 

Spaking-In. — A  term  sometimes  employed 
for  the  gradual  penetration  of  an  electria 
charge  through  a  dielectric. 

Soaking-Out. — A  term  sometimes  em- 
ployed by  telegraphers  to  represent  th« 
gradual  discharge  which  occurs  after 
the  first  discharge  when  a  charged  cabl« 
conductor  is  put  to  earth. 

Socket. — (1)  In  a  telephone  switchboard  a 
jack  or  receptacle  for  a  plug.  (2)  Th« 
barrel  of  a  jack,  as  distinguished  from  th« 
contact  of  the  jack  placed  behind  tht 
barrel. 

Socket-Base. — A  lamp  base  provided  witk 
means  for  ready  introduction  into  a  lamp 
socket. 

Socket  for  Electric  Lamp. — A  support 
for  the  reception  of  an  incandescent 
lamp. 

Socket  Key. — A  key  provided  in  a  lamp 
socket  for  lighting  or  extinguishing  th« 
lamp. 

Socket  Lamp. — A  lamp  provided  with  a 
socket.  • 

Socket  Switch. — A  socket  key. 

Soft-Drawn  Copper  Wire.— Copper  wire 
that  is  softened  by  annealing  after  being 
drawn. 

Soft  Porous  Cell. — A  soft  baked  poroua 
cell,  whose  use  in  a  voltaic  cell  renders  its 
internal  resistance  comparatively  low. 

Softness. — That   property  of    a    body   in 


Sol.] 


931 


[Sou. 


virtue  of  which  it  is  readily  scratched,  or 
its  molecules  displaced. 

Solar  Telegraph. — A  name  sometimes  ap- 
plied to  a  heliograph. 

Solarizatioii. — A  term  used  in  photogra- 
phy for  the  effect  produced  by  exposure 
to  the  sun. 

Solder  Ear. — An  ear  or  hanger  in  a  trolley 
system  to  which  the  trolley  is  secured  by 
solder. 

Soldering,  Electric. — A  process  for  ob- 
taining metallic  joints,  in  which  electri- 
cally generated  heat  is  employed  to  melt 
the  solder. 

Soldering  Flux. — Any  chemical  suitable 
for  use  in  connection  with  solder  to  cleanse 
the  surfaces  of  the  articles  to  be  soldered. 

Soldering  Furnace. — A  portable  furnace 
for  melting  solder  and  heating  soldering 
irons. 

Solenoid. — (1)  A  cylindrical  coil  of  wire 
whose  convolutions  are  circular.  (2)  An 
electro-magnetic  helix.  (3)  Theoretically, 
a  series  of  coaxial  conducting  circles 
placed  side  by  side. 

Solenoid  Core. — A  core,  usually  of  soft 
iron,  placed  within  a  solenoid  and  mag- 
netized by  the  magnetic  flux  of  the  ma'g- 
netizing  current. 

Solenoid  Galvanometer.— A  galvano- 
meter whose  needle  consists  of  a  solenoid 
core. 

Solenoidal. — Of  or  pertaining  to  a  solenoid. 

Solenoid  al  Blow-Out.— A  magnetic 
blow-out  in  which  the  magnet  is  a  solenoid 
devoid  of  an  iron  core. 

Solenoidal  Distribution.— A  space  dis- 
tribution of  a  vector  quantity  devoid  of 
convergence. 

Solenoidal  Distribution  of  Magnetism. 

A  term  sometimes  applied  to  such  a  dis- 
tribution of  magnetism  in  a  bar  that  its 
particles  are  arranged  with  their  poles  in 
the  direction  of  the  length  of  the  bar,  the 
ends  of  which  are  of  opposite  magnetic 
polarities,  and  the  extent  of  whose  surface 
is  small  as  compared  with  the  length  of 
the  bar. 

Solenoidal  Magnet. — A  magnet  possess- 
ing a  solenoidal  distribution  of  magnetism. 

Solid  Angle. — (1)  The  opening  between 
three  or  more  planes  at  their  point  of 
common  intersection.  (2) 'The  area  of  a 
portion  of  spherical  surface  of  unit  radius 
as  traced  by  a  central  radius  vector  which 
traces  the  outline  of  the  solid  angle. 

Solid  Arc-Light  Carbons.— (1)  Carbon 
electrodes  for  arc  lights  unprovided  with 
a  core  of  softer  carbon.  (2)  A  carbon 


which  is  of  uniform  composition  through- 
out as  distinguished  from  a  cored  carbon. 
Solid-Back  Telephone  Transmitter.— 
A  term  applied  to  a  form  of  microphone 
transmitter,  largely  employed  in  long- 
distance telephony. 

Solid  Carbons. — Solid  arc-light  carbons. 

Solid  Conduit.— A  conduit  in  which  the 
insulating  material  is  cast  or  placed  around 
the  wires  or  conductors  so  that  they  can- 
not be  removed  from  the  conduit  with- 
out breaking. 

Solid  Depolarizer. — Any  solid  substance 
employed  in  connection  with  the  negative 
plate  of  a  voltaic  cell  for  the  purpose  of 
effecting  its  depolarization. 

Solid  Thermostat.— A  thermostat  whose 
operation  depends  on  the  expansion  of  a 
solid,  or  on  the  unequal  expansion  of  two 
different  solids. 

Solid  Wires. — Any  conductor  formed  of 
a  single  wire,  as  distinguished  from  a 
stranded  conductor,  or  one  formed  of  a 
number  of  parallel  wires. 

Soluble  Electrodes.  —  Electrodes  em- 
ployed in  metallic  electrolysis,  made  of 
copper,  iron  or  other  metals  which  are 
converted  into  metallic  salts  during  elec- 
trolysis. 

Solution. — A  liquid  in  which  a  solid,  gas 
or  another  liquid  is  dissolved. 

Sonometer. — A  single  wire  stretched  at 
its  ends,  provided  with  a  movable  bridge 
for  the  purpose  of  determining  the  rela- 
tion existing  between  the  frequencies  of 
the  successive  tones  of  any  gamut. 

Sonometer  Interrupter. — A  term  some- 
times employed  in  place  of  electro-dyna- 
mic interrupter. 

Sonorescence. — A  word  proposed  for  the 
sounds  produced  when  a  piece  of  vulcan- 
ite, or  other  solid  substance,  is  exposed  to 
a  rapid  succession  of  flashes  of  light. 

Sonorous. — Sounding  or  producing  sound. 

Soot  Cell. — In  radiophony,  a  name  some- 
times given  to  .a  carbon  cell. 

Sound. — (1)  The  sensation  produced  on  the 
brain  through  the  ear  by  the  vibrations 
of  a  sonorous  body.  (2)  The  sound  waves 
that  are  capable  of  producing  a  sensation 
of  sound  on  the  brain  through  the  ear. 

Sound  Error. — In  telegraphy,  an  error 
made  by  mistaking  the  sound  of  a  signal, 
syllable,  word  or  phrase,  as  distinguished 
from  an  error  made  by  mistaking  the 
sight  of  a  written  character  or  word. 

Sound  Wavos. — Waves  produced  in  the 
air  or  other  elastic  medium  by  the  vibra- 
tions of  a  sonorous  body. 


Sou.] 


932 


[Spa, 


Sounder  Resonator. — (1)  A  name  some- 
times given  to  a  sounder  surrounded  by  a 
resonant  case,  for  the  purpose  of  increas- 
ing the  intensity  of  its  sound  by  reso- 
nance. (2)  A  box-sounding  relay. 

Sounding  Board. — An  elastic  board  em- 
ployed in  a  stringed  musical  instrument 
for  the  purpose  of  increasing  the  intensity 
of  the  sounds  by  resonance. 

Sounding  Belay. — A  box-sounding  relay. 

Sounding  Tube. — A  tube  employed  in  a 
deep-sea  sounding-lead  for  the  purpose  of 
securing  a  sample  of  the  sea  bottom. 

Source,  Electric. — Any  arrangement  ca- 
pable of  maintaining  a  difference  of  po- 
tential or  electromotive  force. 

Southern  Light. — The  aurora  australis. 

South  Magnetic  Pole.— (1)  That  pole  of 
a  magnetic  needle  which  points  approxi- 
mately to  the  earth's  geographical  south. 
(2)  The  south-seeking  pole  of  a  magnetic 
needle. 

South-Seeking  Magnetic  Pole.  —  The 
south  magnetic  pole. 

Spacer. — In  a  double-current  Morse  trans- 
lator, an  electro-magnet  in  the  local  cir- 
cuit, sending  zinc,  negative,  or  spacing 
currents  on  the  circuit  to  which  the  cur- 
rent is  being  delivered. 

Spacing  Battery.— A  battery  in  double- 
current  telegraphy  employed  to  send  spac- 
ing currents. 

Spacing  Current. — (1)  The  current  em- 
ployed in  automatic  telegraphy  for  the 
purpose  of  leaving  a  space  on  the  record- 
ing paper,  as  distinguished  from  the 
marking  current,  or  the  current  that  is 
intended  to  record  a  dot  or  dash  on  the 
paper.  (2)  In  double-current  telegraphy, 
the  currents  in  one  direction  which  effect 
and  correspond  to  spaces  as  distinguished 
from  those  in  the  other  direction  which 
effect  and  correspond  to  marks  or  signals. 

Spacing  of  Armature  Conductors. — The 

pitch  of  an  armature  \vinding. 

Span  Cable- Way. — An-  overhead  cable 
suspended  from  poles,  and  intended  for 
supporting  an  electric  locomotor  in  a  sys- 
tem of  electric  haulage  or  telpherage. 

Span  Guard-Wire. — A  wire  strung  across 
the  street  over  a  trolley  wire  for  the  pur- 
pose of  preventing  a  wire  from  falling  on 
the  trolley  wire,  as  distinguished  from 
running  guard  wires  which  overhang  and 
follow  a  trolley  wire  along  the  street. 

Span  Wires.— Wires  tightly  stretched 
across  a  street  from  pole  to  pole,  for  the 
purpose  of  supporting  trolley  wires. 

Span- Wire  Hangers.— The  hangers  which 


suspend  the  trolley  wires  from  the  span 
wires. 

Span -Wire  Trolley  Line  Construction. 
A  method  for  the  suspension  of  an  aerial 
trolley  line,  in  which  the  trolley  and  feed 
wires  are  suspended  from  span  wires  sup- 
ported on  poles  placed  opposite  to  one 
another  on  each  side  of  the  street  or  road. 

Spanish  Spoon. — A  name  given  to  a  form 
of  shovel  employed  for  lifting  soil  out  of 
a  hole  in  the  ground  excavated  for  a  tele- 
graph pole. 

Spar  Torpedo.— A  torpedo  attached  to 
the  end  of  a  spar  and  designed  to  be  ex- 
ploded by  percussion  against  the  side  of 
an  enemy's  vessel  when  thrust  against  it. 

"Spare"  Machine.— An  extra  dynamo, 
motor  or  other  machine  reserved  in  an  in- 
stallation for  use  in  case  of  accidental 
break  down. 

Spark  Arrester. — A  device  for  preventing 
an  arc  lamp  from  scattering  sparks  or 
particles  of  incandescent  carbon. 

Spark  Chronograph.— A  form  of  electric 
chronograph  in  which  the  record  is  made 
of  the  time  of  a  certain  event  by  means 
of  a  spark  from  a  Ruhmkorff  or  spark 
.coil. 

Spark  Coil.— A  coil  of  insulated  wire  con- 
nected with  the  main  circuit  in  a  system 
of  electric  gas  lighting,  whose  extra  spark 
produced  on  breaking  the  circuit  is  em- 
ployed for  electrically  igniting  gas  jets. 

Spark  Discharge.— (1)  An  electric  dis- 
charge effected  by  a  spark.  (2)  A  dis- 
ruptive discharge. 

Spark,  Electric. — A  term  sometimes  ap- 
plied to  a  disruptive  discharge.  (2)  The 
phenomena  produced  by  a  disruptive  dis- 
charge in  the  air-space  or  gap  through 
which  the  discharge  passes. 

Spark  G-ap.-Kl)  The  air-space  or  gap 
through  which  a  disruptive  discharge 
passes.  (2)  A  gap  forming  part  of  a  cir- 
cuit between  two  opposing  conductors 
and  filled  with  air  or  other  dielectric, 
across  which  a  spark  passes  when  a  cer- 
tain difference  of  potential  has  been 
reached. 

Spark  Micrometer. — A  spark  gap  capable 
of  delicate  adjustment  and  measurement. 

Spark  Tube. — A  high-vacuum  tube  across 
which  the  epark  from  an  induction  coil 
will  not  pass,  if  the  vacuum  is  sufficiently 
high. 

Sparking. — Discharging  by  means  of  dis- 
ruptive sparks. 

Sparking  Discharge. — A  disruptive  di& 
charge. 


Spa.] 


933 


[Spe. 


Sparking  Distance.  —  The  distance 
through  which  electric  sparks  will  pass 
across  an  intervening  air-gap. 

Sparking  of  Dynamo-Electric  Ma- 
chine.— An  irregular  and  injurious  oper- 
ation of  a  dynamo  attended  with  sparks 
at  its  collecting  brushes. 

Sparking  Terminals. — (1)  The  terminals 
of  a  spark-gap.  (2)  The  points  or  ends  of 
a  spark-gap. 

Sparkless  Commutation.  —  Commuta- 
tion of  a  dynamo  accomplished  without 
sparking  at  the  brushes. 

Spasmodic  Governor. — A  name  given  to 
a  form  of  governor  for  electric  motors,  in 
which  the  current  is  automatically  cut 
off  in  proportion  as  the  work  is  cut  off. 

Speaking  Battery.  —  In  telegraphy  or 
telephony,  the  battery  employed  for 
speaking  or  signalling. 

Speaking  Key. — (1)  In  telegraphy,  a  key 
employed  in  speaking.  (2)  A  signalling 
key  as  distinguished  from  a  testing  key. 

Speaking  Mirror. — A  simple  form  of 
mirror  galvanometer  employed  in  cable 
telegraphy  for  the  reception  of  the  cur- 
rent impulses  or  signals. 

Speaking  Mirror  Plug. — A  closed  tube 
or  plug  for  insertion  into  a  speaking  mir- 
ror instrument,  and  containing  a  sus- 
pended mirror  and  magnet. 

Speaking  Switch.  —  In  telegraphy,  a 
switch  employed  in  speaking  or  signalling. 

Speaking  Telegraph. — A  term  sometimes 
employed  for  the  telephone. 

Speaking  Telegraphy. — A  term  some- 
times employed  for  telephony. 

Speaking-Tube  Annunciator. — An  oral 
annunciator. 

Speaking-Tube  Mouth-Piece  Alarm, 
Electric. — A  mouth-piece  for  a  speaking- 
tube,  so  arranged  that  the  movement  of 
a  pi  voted  plate  covering  the  mouth-piece 
automatically  rings  an  electric  bell  atthe 
other  end  of  the  tube. 

Speaking-Tube  Telephone  System.— A 
name  sometimes  employed  for  a  system 
of  telephone  communication  by  means  of 
which  a  number  of  offices  can  be  con- 
nected without  the  use  of  a  central  switch- 
board. 

Speaking  Wire. — In  a  system  of  tele- 
phony, a  wire  connecting  two  exchanges 
for  the  purpose  of  communicating:  instruc- 
tions between  operators,  as  distinguished 
from  a  wire  through  which  a  subscriber 
may  be  connected. 

Specific  Capacity. — Specific  inductive 
capacity. 


Specific  Conductance. — A  term    some- 
times used  for  specific  conductivity. 
Specific    Conduction    Resistance.  — 

(1)  Resistivity.      (2)   A    term    sometimes 
used  for  specific  resistance. 

Specific  Conductivity.— (1)  The  partic- 
ular conductivity  of  a  substance  for  elec- 
tricity. (2)  The  specific  or  particular  re- 
sistance of  a  given  length  and  area  of 
cross-section  of  a  substance,  as  compared 
with  the  same  length  and  area  of  cross- 
section  of  some  standard  substance. 
(3)  Conductivity  with  reference  to  Mat- 
thiessen's  standard  conductivity. 

Specific  Dielectric  Capacity. — A  term 
sometimes  employed  in  place  of  specific 
inductive  capacity. 

Specific  Energy. — (1)  Volumetric  energy. 

(2)  Energy  per  unit  of  volume. 
Specific  Gravity. — The  weight  of  a  given 

volume  of  a  substance,  as  compared  with 
an  equal  volume  of  some  standard  sub- 
stance, such  as  water. 

Specific  Heat. — The  capacity  of  a  sub- 
stance for  heat,  as  compared  with  an 
equal  quantity  of  some  other  substance 
taken  as  unity. 

Specific  Heat  of  Electricity.— A  term 
proposed  to  indicate  the  analogies  exist- 
ing between  the  absorption  and  emission 
of  heat  in  purely  thermal  phenomena, 
and  the  absorption  and  emission  of  heat 
in  thermo-electric  phenomena. 

Specific    Hysteretic    Dissipation.   — 

(1)  The  loss  of  energy  by  hysteresis  in  a 
particular  substance,  per  unit  of  volume. 

(2)  The  hysteretic  loss  of  energy  in  a  sub- 
stance under  given  conditions  compared 
•with  the  similar  loss  in  a  standard  sub- 
stance. 

Specific  Inductive  Capacity. — (1)  The 
ability  of  a  dielectric  to  permit  induction 
to  take  place  through  its  mass  as  compar- 
ed with  the  ability  possessed  by  a  vacuous 
space  of  the  same  dimensions,  under  pre- 
cisely the  same  conditions.  (2)  The  rela- 
tive power  of  bodies  for  transmitting  elec- 
trostatic stresses  and  strains,  analogous 
to  permeability  in  metals.  (3)  The  ratio 
of  the  capacity  of  a  condenser  whose  coat- 
ings are  separated  by  a  dielectric  of  a 
given  substance,  to  the  capacity  of  a 
similar  condenser  whose  plates  are  sep- 
arated by  a  vacuum .  (4)  The  ratio  of  the 
permittivity  of  a  substance  to  the  permit- 
tivity of  vacuum. 

Specific  Magnetic  Capacity.  —  (1)  A 
term  sometimes  employed  in  the  sense  of 
magnetic  permeability.  (2)  A  word  em- 
ployed for  conductibility  for  magnetic 


Spe.] 


934 


[Spe. 


flux,  in  the  same  sense  that  specific  capac- 
ity is  conductibility  for  electrostatic  flux. 

Specific  Magnetic  Conductivity. — The 
specific  or  particular  permeability  of  a 
substance  to  magnetic  flux. 

Specific  Magnetic  Induct! vity. — A  term 
sometinies  used  for  specific  magnetic  con- 
ductivity. 

Specific  Magnetic  Reluctance.  —  A 
term  sometimes  used  for  specific  magnetic 
resistance. 

Specific  Magnetic  Resistance. — A  term 
sometimes  used  for  reluctivity. 

Specific  Magnetism. — A  term  proposed 
for  the  quotient  of  the  magnetic  moment 
of  a  magnet  by  its  mass. 

Specific  Molecular  Conductivity. — 
Molecular  conductivity  as  referred  to  that 
of  some  standard  substance. 

Specific  Reluctance. — A  term  sometimes 
used  for  reluctivity. 

Specific  Resistance. — (1)  The  particular 
resistance  a  substance  offers  to  the  pas- 
sage of  electricity  through  it,  compared 
with  the  resistance  of  some  standard  sub- 
stance. (2)  In  absolute  measurements,  the 
resistance  in  absolute  units  between  op- 
posed faces  of  a  centimetre  cube  of  a 
given  substance.  (3)  In  the  practical 
system,  the  above  resistance  in  ohms.  (4) 
Resistivity,  expressed  in  electro-magnetic 
absolute  units  as  square-centimetres  per 
second. 

Specific  Resistance  of  Liquid.  — 
(I)  Tha  resistance  of  a  given  length  and 
area  of  cross-section  of  any  liquid  as  com- 
pared with  the  resistance  of  an  equal 
length  and  cross-section  of  pure  copper 
or  other  standard  conductor.  (2)  Resis- 
tivity of  a  liquid. 

Spectrograph. — A  word  proposed  for 
radiograph. 

Spectrophone. — An  instrument  employed 
for  the  exploration  of  the  ultra- red  por- 
tion of  the  spectrum. 

Spectro-Photometer.  —  (1)  A  form  of 
photometer  suitable  for  measuring  the 
relative  intensities  of  lights  of  different 
qualities.  (2)  A  photometer  which  com- 
pares luminous  intensities  in  successive 
'  portions  of  spectra,  frequency  by  fre- 
quency. (3)  A  spectroscope  so  arranged 
as  to  readily  permit  of  the  comparison  as  to 
brightness,  wave-length  by  wave-length, 
of  rays  from  two  different  luminous 
sources. 

Spectro-Photometric. — Of  or  pertaining 
to  the  spectro-photometer. 

Spectro-Photometry.  —  Photometry  by 
means  of  the  spectro-photometer. 


Spectroscope. — An  optical  instrument  for 
determining  the  composition  of  a  body 
by  the  character  of  the  light  it  emits,  as 
determined  by  its  component  frequencies. 

Spectroscopic. — Of  or  pertaining  to  the 
spectrum. 

Spectrum. — A  band  of  multicolored  light 
or  radiant  energy  of  different  frequencies, 
obtained  by  dispersion  in  a  prism  or  by  a 
diffraction  grating. 

Speed  Constant. — In  submarine  teleg.a- 
phy,  a  constant  quantity  which  divided 
by  the  product  of  the  capacity  and  resist- 
ance of  a  cable  gives  the  working  speed 
of  the  cable  in  letters  per  minute. 

Speed  Counter. — Any  apparatus  for  deter- 
mining the  number  of  revolutions  of  a 
shaft. 

Speed  and  Direction  Indicator.  —  A 
telegraph  on  board  ship  for  indicating  the 
speed  of  revolution  of  the  propeller  shaft 
and  the  direction  of  its  movement. 

Speed  Indicator. — A  form  of  speed 
counter. 

Speed  of  Rotation. — (1)  The  number  of 
revolutions  per  second,  per  minute,  hour 
or  unit  of  time  generally.  (2)  The  dis- 
tance passed  over  in  a  given  time  by  the 
circumference  of  a  rotating  wheel  or 
pulley.  (3)  The  angular  velocity  of  rota- 
tion in  degrees  or  radians  per  unit  of 
time. 

Speed  Recorder. — (1)  An  apparatus  for 
recording  the  instantaneous  values  of  the 
speed  of  any  machine.  (2)  An  instru- 
ment for  both  indicating  and  recording 
the  speed  of  a  trolley  car  from  moment 
to  moment. 

Speeding. — (1)  Varying  the  number  of 
revolutions  per  second.  (2)  Increasing  a 
speed  of  rotation. 

Speeding  of  Dynamo. — Varying  the 
speed  of  a  dynamo,  for  the  purpose  of  ob- 
taining the  proper  speed  required  to  oper- 
ate an  electro-receptive  device  placed  in 
its  circuit. 

Spelter. — A  name  sometimes  given  to  com- 
mercial zinc. 

Spent  Acid. — A  battery  or  other  acid  that 
has,  through  use,  become  too  weak  for 
efficient  action. 

Spent  Liquor. — Any  liquor  such  as  that 
used  in  an  acid  or  other  bath,  that  has 
through  use  become  too  weak  for  efficient 
action. 

Spewing  of  Cable  Core. — The  mechani- 
cal derangement  of  a  cable,  whereby  the 
sheathing  opens  and  the  core  appears  OB 
the  surface. 


935 


[SplL 


Spherical  Aberration. — A  defect  where- 
by a  lens  or  mirror  with  spherical  faces 
fails  to  produce  in  its  images  the  correct 
outlines  of  objects,  owing  to  the  fact  that 
the  curvature  of  one  or  both  of  its  faces 
should  slightly  depart  from  the  true 
spherical  form  in  order  to  produce  a  true 
image. 

Spherical  Armature. — An  armature  for 
a  dynamo,  the  coils  of  which  are  wound 
on  a  spherical  iron  core. 

Spherical  Bougie  Decimale. — (1)  A  unit 
of  luminous  flux  equal  to  that  which 
would  be  produced  by  a  point  source 
having  an  intensity  of  one  bougie  deci- 
male  in  all  directions.  (2)  A  luminous 
flux  equal  to  12.566  lumens. 

Spherical  Candle-Power. — (1)  The  total 
flux  of  light  emitted  by  a  luminous  source 
divided  by  12.566.  (2)  The  candle-power  of 
a  point-source,  which  emits  with  uniform 
intensity  in  all  directions,  as  much  light 
as  does  an  actual  lamp.  (&  The  average 
candle-power  of  a  luminous  source  taken 
in  all  directions,  or  considered  over  the 
entire  surface  of  an  enveloping  sphere. 

Spherical  Candle-Power  Measurer. — 
An  instrument  for  measuring,  or  ena- 
bling to  be  measured,  the  mean  spherical 
candle-power  of  a  source  of  light  from  a 
single  observation. 

Spherical  Candle-Power  Photometer. 
(1)  A  photometer  designed  to  measure 
the  mean  spherical  candle-power  of  a 
lamp.  (2)  A  photometer  designed  to 
measure  the  mean  spherical  candle-power 
of  a  luminous  source  from  a  single  ob- 
servation. 

Spherical  Harmonics.  —  Homogeneous 
functions  of  rectilinear  space-co-ordinates 
which  satisfy  Laplace's  equation. 

Spherical  Strain  Insulator. — An  insu- 
lator for  a  guy-wire  or  trolley  pull-off, 
spherical  in  form. 

Spherorneter. — An  apparatus  for  readily 
measuring  the  curvature  of  a  sphere. 

Sphygmogram. — A  record  made  by  a 
sphygmograph. 

Sphygmograph.— An  instrument  for  re- 
cording the  movements  of  the  pulse,  usu- 
ally of  the  radial  artery  at  the  wrist. 

Sphygmograph,  Electric.  —  An  instru- 
ment for  electrically  recording  the  pecul- 
iarities of  the  pulse. 

Sphygmophone. — An  apparatus  employ- 
ing a  microphone  for  the  medical  exam- 
ination of  the  pulse. 

Sphygmoscope. — An  apparatus  for  de- 
tecting, but  not  recording,  the  peculiari- 
ties of  the  pulse. 


Spider. — A  radial  bracket  or  support  fot 
supporting  an  armature  or  machine  on  a 
revolving  shaft. 

Spider  Arm. — One  of  the  projections  of  a 
spider  support. 

Spin. — (1)  The  curl  of  a  vector  point- 
function.  (2)  Eotation.  (3)  Vorticity. 

Spiral. — (1)  A  helix.  (2)  A  word  some- 
times  employed  in  electricity  and  mag- 
netism for  an  open  conducting  coil. 

Spiral  Accumulator.— An  accumulator 
whose  plates  consist  of  two  parallel  plates 
of  lead  insulated  from  each  other  and 
rolled  into  a  close  spiral. 

Spiral  Loop  System  of  Parallel  Distri- 
bution.— A  modified  form  of  loop  system 
for  parallel  distribution. 

Spiral  Loop  System  of  Distribution. — 

A  name  given  to  a  variety  of  parallel 
distribution  adopted  for  obtaining  a  com- 
paratively uniform  distribution  of  poten- 
tial, in  which  the  parallel  conductors  are 
extended  in  the  arcs  of  spirals  from  the 
generating  station  throughout  the  district 
to  be  served,  both  spirals  extending  from 
one  pole  of  the  generator  nearly  to  the 
other  pole. 

Spiral  Winding. — A  S9lenoidal  winding. 

Spiralled  Fours  of  Cable. — A  defect  In 
the  winding  of  a  telephone  cable,  in  which 
any  four  wires  are  so  wound  about  the 
core  that  one  pair  is  not  on  the  average 
midway  between  the  other  pair,  so  that 
cross-talk  is  sure  to  result. 

Splice  Bar. — A  fish  plate  employed  for 
connecting  together  the  ends  of  a  rail. 

Splice  Box. — A  box  provided  for  holding 
splice  joints  and  loops  so  arranged  as  to 
be  readily  accessible  for  examination,  re- 
arrangement, cross-connection,  etc. 

Splicing. — Connecting  the  sheathings  of 
the  two  ends  of  a  cable  at  a  joint. 

Splicing  Ear. — (1)  A  trolley  ear  for  uniting 
the  ends  of  a  trolley  wire.  (2)  A  splicing 
suspension  ear. 

Splicing  Mallet. — A  mallet  used  in  a  sub- 
marine cable  splice  for  laying  on  a  serv- 
ing of  yarn  under  tension. 

Splicing  Sleeve. — A  tube  of  conducting 
material  employed  for  covering  a  splice 
in  a  conducting  wire. 

Splicing  Suspension  Ear. —  A  metal 
piece  suitably  supported  on  an  insulator 
and  provided  in  a  system  of  overhead 
trolley  wires  for  connecting  two  separate 
ends  of  the  trolley  line. 

Splicing  Tool.  —  A  tool  employed  in 
making  a  cable  splice,  for  forcing  the 
sheave  wires  around  the  cable  in  their 


Spli.] 


936 


[Spr. 


proper  spiral  position  corresponding  to 
that  which  they  have  on  other  parts  of 
the  cable. 

Splicing  Tube. — A  name  sometimes  given 
to  a  connector  employed  in  making  a 
joint  in  a  trolley  wire. 

Split  Battery. — A  voltaic  battery  connect- 
ed in  series  and  having  one  of  its  middle- 
plates  connected  to  the  ground. 

Split  Condenser. — (1)  A  condenser  so  ar- 
ranged that  its  different  sections  can  be 
readily  inter-connected  in  the  same  cir- 
cuit or  employed  in  different  circuits  as 
may  be  required.  (2)  A  subdivided  con- 
denser. 

Split  Current. — (1)  A  divided  current. 
(2)  A  current  tapped  from  a  main  tele- 
graph wire. 

Split  Dynamometer. — A  dynamometer 
employed  in  connection  with  alternating 
currents  provided  with  two  coils,  so  ar- 
ranged that  separate  currents  of  the  same 
frequency  can  be  passed  independently 
through  each. 

Split  Lead-Tee. — A  T-shaped  lead  tube 
that  is  split  for  readily  covering  a  joint  at 
a  branch  in  a  cable. 

Split  Phase. — A  difference  produced  be- 
tween the  phased  of  two  or  more  alter- 
nating currents  into  which  a  Uniphase 
alternating  current  has  divided. 

Split-Phase  Motor. — (1)  A  multiphase 
motor  operated  from  a  uniphase  alternat- 
ing-current circuit  by  the  introduction  of 
a  phase-splitting  device.  (2)  A  multiphase 
motor  in  which  the  multiphase  currents 
are  locally  produced  from  a  single-phase 
circuit. 

Split-Pin  Plug.  —  A  plug  having  two 
halves  or  two  sleeves  insulated  from  each 
other,  employed  for  readily  introducing  a 
loop  into  a  circuit. 

Split-Ring  Magnet. — A  ring-core  magnet 
provided  with  an  air-gap. 

Split-Secondary  of  Induction  Coil. — 
The  secondary  of  an  induction  coil  which 
is  divided  into  two  equal  portions. 

Spluttering  of  Arc. — A  spluttering  sound 
attending  the  formation  of  a  voltaic  arc. 

Spokes  of  Armature  Core. — Radial  pro- 
jections on  a  spider  in  an  armature  core, 
on  which  coils  are  sometimes  wound. 

Sponge  Electrode. — A  therapeutic  elec- 
trode provided  with  a  sponge. 

Spontaneous  Electricity. — A  term  for- 
merly employed  for  the  electricity  pro- 
duced by  the  melting  of  sulphur. 

Spot. — The   reflected  image  or  luminous 


patch  of  light  on  a  mirror  galvanometer 
scale. 

Spotty  Filament.— The  filament  of  an 
incandescent  lamp  possessing  such  local 
variations  in  resistance  that  when  ren- 
dered luminous  by  the  passage  of  the  cur- 
rent, it  possesses  points  of  unequal  brill- 
iancy. 

Spreader  Bracket. — A  name  sometimes 
given  to  a  loop  bracket. 

Spreader  for  Arc  Wires.— A  form  of 
loop  bracket  employed  on  arc  circuits. 

Spreading  of  Magnetic  Field. — A  term 
sometimes  employed  for  divergence  of  a 
magnetic  field. 

Sprengel  Mercury  Pump. — A  mercurial 
air  pump  in  which  the  vacuum  is  obtained 
by  means  of  the  fall  of  a  stream  of 
mercury  through  a  tube  in  such  a  manner 
as  to  entangle  portions  or  bubbles  of 
residual  air. 

Spring  Ammeter. — A  form  of  ammeter 
in  which  a  magnetic  core  or  needle  is 
moved  against  the  action  of  a  spring  by 
the  field  of  the  current  it  is  measuring. 

Spring  Clips  of  Switch. — Spring  jaws  of 
a  switch  which  grasp  the  blade  or  blades 
in  the  closed  position. 

Spring  Contact. — (1)  A  contact  which 
either  opens  or  closes  under  the  action  of 
a  spring.  (2)  A  spring-supported  contact, 
connected  with  one  part  of  a  circuit,  that 
completes  the  circuit  on  being  moved  so 
as  to  touch  another  contact  connected 
with  the  other  part  of  the  circuit.  (3)  A 
circuit-closing  or  circuit-opening  device 
normally  maintained  in  one  position  and 
condition  by  the  action  of  a  spring. 

Spring  Dynamometer. — A  dynamometer 
whose  operation  is  dependent  on  the 
action  of  a  spring. 

Spring  Jack. — A  form  of  spring  contact 
provided  with  a  hole  for  the  insertion  of 
a  plug. 

Spring- Jack  Cut-Out. — A  cut-out  operat- 
ed by  a  spring  jack. 

Spring-Jack  Telephone  Switchboard. 
A  form  of  telephone  switchboard  pro- 
vided with  calling  drops,  clearing  out 
drops,  and  spring  jacks,  so  arranged  as  to 
readily  enable  a  number  of  subscribers  to 
be  placed  in  inter-communication. 

Spring  Manometer. — A  manometer 
whose  operation  is  dependent  on  the  de- 
formation of  an  elastic  solid. 

Spring  Relay-Contact. — A  form  of  relay 
contact  which  is  interrupted  by  the  action 
of  a  spring  as  soon  as  the  circuit  is 
broken. 


Spr.] 


937 


[Sta. 


Spring-Snag  Lever-Switch.— A  form  of 
switch  operated  by  a  spring  snap  lever. 

Spring  -  Suspended  Street- Bail  way 
Motor. — A  street-railway  car  motor  sus- 
pended from  the  car  truck  by  means  of 
springs. 

Spring  Voltmeter. — A  form  of  voltmeter 
in  which  the  potential  difference  is 
measured  by  the  movement  of  a  magnetic 
needle,  coil,  or  core,  against  the  pull  of  a 
spring. 

Spurious  Hall  Effect.  —  An  apparent 
transverse  electromotive  force  in  conduc- 
tors carrying  electric  currents  in  magnet- 
ic fields,  by  changes,  produced  by  magnet- 
ism, in  the  conductivity  of  the  metals 
and  the  consequent  production  of  local 
disturbances  in  the  electrical  flow,  thus 
resulting  in  an  apparent  transverse  elec- 
tromotive force. 

Spurious  Resistance. — A  false  or  ap- 
parent resistance  arising,  from  the  devel- 
opment of  a  counter-electromotive  force. 

Square  Conductor. — A  form  of  power 
conductor  with  rectilinear  cross-section. 

Square  Mil. — (1)  A  unit  of  area  employed 
in  measuring  the  areas  of  cross-section  of 
wires,  equal  to  .000001  square  inch. 
(2)  A  unit  of  area  equal  to  1.2732  circular 
mils. 

"  Squeeze." — In  electro-typing  the  im- 
pression obtained  by  subjecting  a  type,  or 
woodcut,  to  a  plate  or  mass  or  soft  wax. 

Squeezer. — A  device  for  testing  the  duc- 
tility of  a  wire,  consisting  in  a  receptacle, 
somewhat  resembling  a  lemon  squeezer, 
in  which  the  wire  is  placed  and  clamped 
and  the  device  opened  and  closed  until 
the  wire  breaks. 

Squirted  Filament.— A  filament  for  an 
incandescent  lamp  made  by  the  carboni- 
zation of  a  carbonaceous  paste,  that  is 
shaped  by  being  squirted  by  pressure 
through  a  suitably  shaped  die  hole. 

Stabile  Galvanization.  —  A  term  em- 
ployed in  electro-therapeutics  in  which 
the  current  is  caused  to  pass  continuously 
and  steadily  through  the  portions  of  the 
body  undergoing  galvanization. 

Stable  Equilibrium. — (1)  The  equilib- 
rium of  a  body  supported  on  a  base,  such 
that  in  order  to  overturn  it,  its  centre  of 
gravity  must  be  raised.  (2)  The  equilib- 
rium of  a  body  so  supported  that  any 
small  displacement  raises  its  centre  of 
gravity. 

Stable  Period  9f  Circuit.  —  (1)  That 
condition  of  a  circuit  in  which  the  cur- 
rent- passing  through  it  has  reached  its 


full  strength,  and  is  no  longer  undergoing 
variations.     (2)  The  permanent  state. 

Stage  Regulator.— A  controller  of  incan- 
descent lamps  in  a  theatre,  placed  near 
the  stage,  whereby  they  may  be  lighted, 
extinguished,  or  dimmed. 

Staggered  Armature. — An  armature  in 
which  the  conductors  do  not  lie  on  ita 
surface  in  a  direction  parallel  to  the  axis 
of  rotation,  but  cross  its  surface  diag- 
onally. 

Staggering  of  Dynamo  Brushes.— A 
term  sometimes  applied  to  the  position  of 
the  brushes  on  a  commutator  cylinder,  in 
which  one  brush  is  placed  slightly  in  ad- 
vance of  the  other,  so  as  to  wear  the 
commutator  surface  smoothly,  and  pre- 
vent the  formation  of  grooves. 

Stalk  of  Insulator. — The  support  or  inner 
metal  cylinder  of  an  aerial  line  insulator. 

Standard. — A  metallic  pole  supported  on 
the  roof  of  a  house  for  carrying  overhead 
wires. 

Standard  Candle.— (1)  A  candle  of  defi- 
nite composition,  which,  when  burned  at 
the  rate  of  two  grains  per  minute,  will 
produce  a  light  of  a  definite  and  fixed 
brightness.  (2)  A  legal  standard  of  light 
in  Great  Britain. 

Standard  Cell. — A  standard  voltaic  cell. 

Standard  Clock. — A  clock  employed  for 
the  comparison  of  other  clocks. 

Standard  Coil. — A  standard  resistance 
coil. 

Standard  Compass. — A  compass  on  board- 
ship  which  is  used  as  a  standard  and  by 
which  other  compasses  may  be  checked- 
or  compared. 

Standard  Cross-Arms. — Wooden  cross- 
arms  of  standard  dimensions  for  support- 
ing aerial  wires  on  poles. 

Standard  Earth  -  Quadrant.  —  (1)  A- 
length  approximately  equal  to  10,000 
kilometres.  (2)  One  quarter  of  the  mend* 
ian  circle  of  the  earth  taken  through  Paris, 
(3)  A  standard  unit  of  inductance. 

Standard  Feeder. — A  term  sometimes 
applied  to  a  principal  feeder,  operated  at 
standard  pressure. 

Standard  Luminous  Intensity.  — 
(1)  Any  unit  of  luminous  intensity  em- 
ployed as  a  standard.  (2)  A  luminous 
intensity  of  one  violle,  bougie-decimale, 
Hefner- Alteneck,  carcel,  British  standard 
candle,  etc. 

Standard  Megohm. — A  resistance  equal 
to  one  million  ohms,  employed  as  a. 
standard. 

Standard  Ohm. — A  length  of  wire  having 


Sta.] 

a  resistance  of  the  value  of  one  ohm,  em- 
ployed in  standardizing  resistance  coils. 

Standard  Quadrant.— (1)  The  standard 
earth  quadrant.  (2)  A  standard  induct- 
ance equal  to  one  quadrant. 

Standard  Resistance. — A  known  resist- 
ance used  for  comparison  with,  or  deter- 
mination of,  an  unknown  resistance. 

Standard  Resistance  Coil. — A  coil  whose 
resistance  is  that  of  a  standard  ohm  or 
some  multiple  or  sub-multiple  thereof. 

Standard  Telephone  Switchboard.— 
A  name  applied  to  a  foi-m  of  multiple 
switchboard  commonly  employed  in  the 
United  States. 

Standard  Time. — Mean  solar  time  used 
in  telegraphy,  and  referred  either  to  the 
meridian  of  Greenwich,  or  to  some  other 
meridian  west  of  Greenwich,  an  exact 
number  of  hours. 

Standard  Voltaic  Cell.— A  voltaic  cell 
whose  electromotive  force  is  practically 
constant,  and  which  can,  therefore,  be 
used  as  a  standard  in  the  measurement  of 
an  unknown  electromotive  force. 

Standard  Wire  Gauge. — A  wire  gauge 
adopted  by  the  National  Telephone  Ex- 
change Association  and  the  National 
Electric  Light  Association  of  America. 

.Standards.— (1)  Telegraphic  or  telephonic 
supports  placed  on  the  roof  of  a  building 
for  the  purpose  of  supporting  the  wires  or 
conductors.  ^  (2)  A  general  term  for  a 
resistance  coil,  voltaic  cell  or  other  stand- 
ard employed  for  purposes  of  comparison. 
(3)  A  term  applied  to  the  support  of  the 
bearings  of  a  dynamo  or  motor. 

Standardized  Resistance  Coil.— A  coil 
whose  resistance  has  been  carefully  ob- 
tained by  comparison  with  a  standard. 

Standardizing  a  Voltaic  Cell. — Deter- 
mining the  exact  value  of  the  electromo- 
tive force  of  a  voltaic  cell,  in  order  to 
permit  it  to  be  used  as  a  standard  in  ob- 
taining the  electromotive  force  of  any 
electric  source. 

Standing  Torque.— Starting  torque. 

Star  Current  in  Polyphase  System.— 
(1)  A  current  between  any  line  or  terminal 
of  a  polyphase  system  and  the  neutral 
point.  (2)  The  current  in  any  branch  of 
a  star  polyphase  system. 

Star  Grouping  of  Polyphase  Circuits. 
A  method  of  grouping  a  triphase  circuit 
consisting  of  making  a  common  junction 
at  one  point  and  branching  them  star- 
wise. 

Star  Potential  in  Polyphase  System. — 
The  effective  difference  of  potential  or 


[Sta. 

voltmeter  pressure  between  any  line  or 
terminal  of  a  polyphase  system  and  tka 
neutral  point. 

Star  Triphase- Winding.— A  connectio* 
of  three  triphase  windings  in  which  all 
three  are  connected  together  at  a  common 
point  or  junction  point,  and  the  three 
free  ends  connected  to  the  terminals. 

Star  Triphaser. — A  triphaser  possessing 
a  star  triphase  winding. 

Starting  Box. — A  name  sometimes  applied 
to  a  starting  resistance. 

Starting  Box  for  Electric  Motor. — A 
resistance  provided  for  starting  an  elec- 
tric motor. 

Starting  Box  of  Shunt- Wound  Motor. 
A  box  provided  with  a  rheostat  of  variable 
resistance,  introduced  into  the  armature 
circuit  of  a  shunt-wound  motor  for  the 
purpose  of  preventing  the  rush  of  current 
made  on  first  connecting  the  motor  with 
the  driving-circuit. 

Starting  Coil  of  Motor. — A  coil  employed 
as  a  starting  resistance  for  an  electric 
motor. 

Starting  Current  of  Motor.— The  cur- 
rent traversing  the  coils  of  a  motor  at 
its  moment  of  starting. 

Starting  Motor  for  Synchronous 
Motor. — A  small  electric  motor  some- 
times employed  for  bringing  the  arma- 
ture, of  a  synchronous  singlerphase  motor 
up  to  its  proper  speed  before  connecting 
it  with  the  driving-current  circuit. 

Starting  Position  of  Street-Car  Con- 
troller.—(1)  The  position  of  a  street-car 
controller  switch  at  which  the  current  is 
cut  off  from  the  motors.  (2)  The  position 
of  a  street-car  controller  switch,  at  which 
the  current  is  first  admitted  to  the  motors 
when  starting. 

Starting  Resistance. — A  resistance  em- 
ployed in  the  starting  box  for  an  electric 
motor. 

Starting  Rheostat. — Coils  of  wire  mount- 
ed in  a  suitable  manner,  and  so  connected 
as  to  be  successively  placed  in  the  circuit 
of  a  motor  while  it  is  being  started. 

Starting  Torque  of  Motor.— (1)  The 
torque  required  in  starting  a  motor.  (2) 
The  torque  developed  by  a  motor  in  start- 
ing. 

Static  Balance. — A  duplex  or  quadruplex 
balance  ad  justed  for  the  capacity  of  a  line 
by  the  use  of  a  condenser. 

Static  Balance  of  Duplex   System.— 

(1)  The  capacity  balance  of  a  duplex  sys- 
tem as  distinguished  from  the  resistance 
balance.  (2)  A  balance  for  charging  and 


Sta.] 


939 


[Sta. 


discharging  as  distinguished  from  a  bal- 
ance for  steady  currents. 
Static   Breeze. — An    electric   breeze   ob- 
tained by  a  cpnvective  discharge  or  an 
electrostatic  discharge. 

Static  Compensating  Condenser. — A 
condenser  employed  in  the  artificial  line 
of  duplex  or  quadruplex  telegraphy. 

Static  Compensator. — A  condenser  em- 
ployed for  compensating  the  electro-static 
capacity  of  a  line  in  the  duplex  system. 

Static  Discharge. — A  name  sometimes 
given  to  a  disruptive  discharge. 

Static  Electricity. — A  term  applied  to 
electricity  produced  by  friction. 

Static  Electro-Motor. — An  electro-motor 
operated  by  the  repulsion  of  electric 
charges. 

Static  Energy. — (1)  A  term  used  to  ex- 
press the  energy  possessed  by  a  body  at 
rest,  resulting  from  its  position  as  regards 
other  bodies,  in  contradistinction  to  ki- 
netic energy,  or  the  energy  possessed  by  a 
body  whose  atoms,  molecules  and  masses 
are  in  actual  motion.  (2)  Potential  en- 
ergy. 

Static  Hysteresis. — (1)  A  term  sometimes 
applied  to  that  quality  in  iron  or  other 
paramagnetic  substance,  by  virtue  of 
which  energy  is  dissipated  during  every 
reversal  in  its  magnetization,  in  contra- 
distinction to  viscous  hysteresis.  (2)  Elec- 
trostatic dielectric  hysteresis. 

Static  Induction. — A  term  sometimes 
employed  for  electrostatic  induction. 

Static  Insulation. — A  term  employed  in 
electro-therapeutics  for  a  method  of  treat- 
ment by  convection  streams  or  discharges, 
in  which  the  patient  is  seated  on  an  insu- 
lated stool  connected  to  one  pole  or  elec- 
trode of  an  influence  machine,  while  the 
other  pole  or  electrode  is  connected  to  the 
ground. 

Static  Magnetic  Induction. — The  in- 
duction which  takes  place  in  the  field  of 
a  magnet  whose  flux  is  stationary  as  re- 
gards the  body  in  which  the  induction  is 
occurring. 

Static  Shock. — (1)  A  term  employed  in 
electro-therapeutics  for  a  mode  of  apply- 
ing Franklinic  currents  or  discharges  by 
placing  the  patient  on  an  insulating  stool 
and  applying  one  pole  of  a  static  machine 
provided  with  small  condensers  or  Leyden 
jars,  while  the  other  pole  is  connected  to 
the  body  of  the  patient.  (2)  An  electro- 
static shock. 

Static  System  of  Induction  Teleg- 
raphy.— A  system  of  induction  teleg- 
raphy depending  on  static  induction  be- 


tween the  sending  and  the  receiving  in- 
strument. 

Static  Time  Constant.— The  electrostatic 
time  constant  of  a  circuit. 

Static  Transformer. — A  term  sometimes 
employed  for  an  ordinary  transformer, 
to  distinguish  it  from  a  rotary  trans- 
former. 

Static  Voltmeter.— (1)  A  voltmeter  oper- 
ating by  electrostatic  action,  as  opposed 
to  a  voltmeter  operating  electro-magneti- 
cally.  (2)  A  voltmeter  in  which  the  mov- 
ing system  is  displaced  by  electrostatic 
forces.  (3)  A  voltmeter  of  the  electro- 
scope or  electrometer  type. 

Statics. — (1)  That  branch  of  science  which 
treats  of  the  relations  that  must  exist  be- 
tween the  points  of  application  of  forces 
and  their  direction  and  intensity,  in  order 
that  equilibrium  may  result.  (2)  The 
science  of  forces  at  rest. 

Station  Circuit  -  Breaker.— A  circuit- 
breaker  in  a  central  station. 

Station  Indicator.— (1)  A  name  some- 
times given  to  a  station  voltmeter.  (2) 
Any  indicator  situated  at  a  central  station. 

Station  Load. — The  total  load  existing  on 
a  central  station  at  any  time. 

Station  Load-Curve. — A  curve  repre- 
senting the  station  load  at  different 
times. 

Station  Panel. — (1)  A  panel  in  a  central- 
station  switchboard.  (2)  A  load  panel  in 
a  central-station  switchboard  showing  the 
total  load  of  the  station.  (3)  A  panel  in 
a  central-station  switchboard  connecting^ 
a  feeder  running  to  some  other  station  or 
sub-station. 

Station  Recording- Wattmeter. — A 
wattmeter  suitable  for  use  in  a  central 
station  for  recording  the  energy  delivered 
bv  the  station. 

Station  Switch.— (1)  A  switch  in  a  sta- 
tion. (2)  A  switch  for  connecting  an 
auxiliary  station  to  a  system.  (3)  A 
switch  supplying  an  auxiliary  station. 
(4)  A  switch  for  connecting  the  lighting 
or  other  local  wires  in  a  central  station  to 
the  system  of  distribution. 

Station  Transformer. — (1)  A  transform- 
er placed  in  a  central  station.  (2)  A 
transformer  which  supplies  a  load  in  a 
station.  (3)  A  transformer  intended  to 
supply  current  to  lamps  and  potential 
indicators  on  the  switchboard  in  the 
station. 

Stationary  Transformers. — A  word 
sometimes  applied  to  ordinary  alternat- 
ing-current transformers,  in  contradis- 
tinction to  rotary  transformers. 


:Sta.] 


940 


[Ste. 


Stationary  Electric  Motor.— An  electric 
motor  that  is  fixed  to  the  floor  or  ground, 
in  contradistinction  to  a  travelling  or 
locomotor. 

^Stationary  Fare-Register  for  Street 
Car. — A  register  placed  permanently  in 
a  car,  for  the  purpose  of  recording  the 
fare  received  by  a  conductor. 

Stationary  Floor-Key. — A  name  some- 
times applied  to  a  floor  push. 

Stationary  Hook  of  Telephone.  —  A 
fixed  hook  provided  for  holding  a  tele- 
phone. 

Stationary  Motor. — A  motor  that  is  fixed 
in  place,  in  contradistinction  to  a  loco- 
motor. 

Stationary  Secondary  of  Induction 
Motor. — An  induction  motor  whose  sec- 
ondary coils  form  the  stator. 

Stationary  Tachometer. — Any  tacho- 
meter employed  for  indicating  the  num- 
ber of  revolutions  per  minute  of  a  snaft 
in  a  stationary  rotating  machine. 

Stationary  Torpedo. — A  term  sometimes 
employed  for  a  submarine  mine. 

Stator. — That  part  of  a  dynamo  or  motor, 
whether  the  armature  or  the  field,  which 
remains  at  rest  or  stands  still  during  the 
operation  of  the  machine,  as  distinguished 
from  the  rotor  or  part  which  rotates. 

Stator  Armature. — (1)  An  armature  of  a 
dynamo  or  motor  that  remains  at  rest 
during  the  operation  of  the  machine. 
(2)  An  immovable  element  of  a  machine 
which  is  also  its  armature. 

Stator  Circuit. — The  circuit  of  the  stator 
coils. 

Stator  Coils. — The  coils  placed  on  the  sta- 
tor of  a  dynamo  or  motor. 

Stator  Currents. — Currents  that  flow  in 
the  stator  of  a  dynamo  or  motor. 

Stator  Field. — A  field  of  a  dynamo  or  mo- 
tor that  remains  at  rest  during  operation. 

Statute  Mile. — A  length  employed  in 
Great  Britain  equal,  by  statute,  to  5280 
feet. 

Stauroscope. — A  form  of  polariscope  for 
investigating  the  effects  of  polarized  light 
on  crystals. 

Stay-Eye  Clip.— An  iron  band  rigidly 
clamped  to  roof  beams  or  other  strong 
supports  and  carrying  an  iron  ring  for  the 
attachment  of  a  stay -rod. 

Stay  Rod. — A  rod  of  iron  or  steel,  used  to 
stay  or  support  a  telegraph  or  telephone 
pole. 

Stay  Tightner.— A  swivel  for  taking  up 
slack  in  a  stay. 


Steady  Current. — A  current  whose 
strength  does  not  vary  from  time  to  time. 

Steam  Dynamo.— (1)  A  name  applied  to 
a  steam-turbine  dynamo.  (2)  A  dynamo 
direct-connected  to  a  steam  engine. 

Steam  Governor,  Electric. — A  device 
used  in  connection  with  a  valve  to  so 
electrically  regulate  the  supply  of  steam 
to  an  engine  that  the  engine  shall  be 
driven  at  such  a  speed  as  will  maintain 
either  a  constant  current,  or  constant 
potential. 

Steam-Turbine  Dynamo.— A  high-speed 
dynamo  whose  armature  is  driven  by 
means  of  a  steam  turbine. 

Steaming  Lights,  Electric. — A  term 
sometimes  applied  to  the  side  lights  of  a 
ship. 

Steam's  Relay  Shunt. — A  shunt  em- 
ployed in  the  differential  method  of  du- 
plex telegraphy  to  short-circuit  the  relay 
and  then  permit  the  line  current  to  be  cut 
off  directly  after  it  has  completed  its  work 
in  closing  the  local  circuit. 

Steel  Facing  of  Electro-Type. — A  thin 
electrolytic  deposit  of  iron  placed  on  the 
surface  of  an  electro-type  for  the  purpose 
of  hardening  it. 

Steel-Yard  Ammeter. — A  form  of  am- 
meter in  which  the  strength  of  a  current 
is  measured  by  means  of  the  electro-mag- 
netic forces  applied  to  one  extremity  of  a 
steel-yard  lever,  provided  with  sliding 
weights  for  balancing  these  forces. 

Steeps. — A  word  sometimes  employed  in 
electro-plating  for  dips  or  dipping  liquids 
or  solutions. 

Steering  Compass. — A  compass  employed 
for  the  steering  of  a  ship. 

Steering,  Electric. — Steering  effected 
electrically. 

Steering  Telegraph. — A  telegraph  on 
board  ship  for  communicating  steering 
orders  from  some  point  such  as  the  bridge 
or  conning  tower. 

Steno-Telegraphy. — A  system  of  tele- 
graphy in  which  the  sounds  of  a  word  are 
represented  by  characters  instead  of  by 
letters. 

Step-by-Step  Annunciator.  —  An  an- 
nunciator operated  on  the  step-by-step 
principle. 

Step-by-Step  Telegraphy.— (1)  A  sys- 
tem of  telegraphy  in  which  the  signals 
are  registered  by  the  movements  of  a 
needle  over  a  dial  on  which  the  letters  of 
the  alphabet  are  marked.  (2)  Dial  teleg- 
raphy. 


Ste.J  S 

Step-Down  Converter.— A  step-down 
transformer. 

Step-Down  Transformer. — (1)  A  trans- 
former in  which  a  small  current  of  com- 
paratively great  difference  of  potential  is 
converted  into  a  large  current  of  com- 
paratively small  difference  of  potential. 
(2)  An  inverted  Rulimkorff  induction  coil. 

Step-Up  Converter. — A  step-up  trans- 
former. 

Step-Up  Transformer. — A  transformer 
in  which  a  large  current  of  comparatively 
small  difference  of  potential  is  converted 
into  a  small  current  of  comparatively 
great  difference  of  potential. 

Steradian. — (1)  A  unit  of  solid  angle.  (2) 
The  solid  angle  subtended  at  the  centre 
of  a  sphere  of  unit  radius  by  a  unit  of 
spherical  area,  or  unit  of  surface  on  the 
sphere. 

Stereopticon. — A  lantern  apparatus  for 
projecting  on  a  screen  a  stereoscopic 
picture. 

Stereoscope. — An  optical  apparatus  for 
obtaining  from  two  photographic  pic- 
tures, taken  in  slightly  different  positions, 
pictures  correctly  representing  solid  ob- 
jects. 

Stereoscopic. — Of  or  pertaining  to  a  ster- 
eoscope. 

Stereotype. — A  fac-simile  or  duplication 
of  a  page  of  movable  types  or  of  engrav- 
ings, effected  by  obtaining  a  moulding  of 
the  original  in  some  suitable  material,  and 
then  immersing  the  mould  in  melted  type 
metal. 

Sterilization,  Electric. — Sterilizing  a  so- 
lution by  depriving  it,  by  means  of  elec- 
tric currents,  of  whatever  germs  it  may 
contain. 

Stern  Sheave. — (1)  A  large  sheave  on  the 
stern  of  a  cable-ship  for  paying  out  cable. 
(2)  Any  sheave  at  the  stern  of  a  boat  or 
vessel  used  in  paying  out  cable. 

Stethoscope. — An  instrument  for  ascer- 
taining the  condition  of  the  organs  of  cir- 
culation and  respiration  by  the  sounds 
they  produce. 

Sticking. — (1)  A  name  given  by  teleg- 
raphers to  the  failure  of  a  relay  arma- 
ture to  leave  the  magnet  pole  and  break 
contact  on  the  cessation  of  the  current. 
(2)  Undue  adhesion  between  the  contacts 
of  a  relay. 

Sticking  of  Magnetic  Armature. — The 
adherence  of  the  armature  of  any  electro- 
magnet to  its  poles  after  the  current  has 
ceased  to  pass  through  the  magnetizing 
coils. 


[Sto. 

"  Stiff  Field."— A  magnetic  field  of  com- 
paratively  high  density. 

Stilography. — A  modified  form  of  glyph- 
ography. 

Stimulus  of  Nerve,  Electric.— The  effect 
which  electricity  produces  by  its  passage 
through  a  nerve. 

Stock  Ticker.— A  step-by-step  printing 
telegraphic  instrument,  employed  in 
transmitting  stock  quotations  to  brokers' 
offices  from  stock  exchanges. 

Stock-Ticker  Service.— A  term  em- 
ployed for  the  transmission  of  stock  quo- 
tations from  stock  exchanges  to  sub- 
scribers. 

Stoneware  Dipping-Bowl.— A  perfo- 
rated bowl  made  of  stoneware,  in  which 
articles  are  placed  that  are  to  be  subjected 
to  the  dipping  process  in  electro-metal- 
lurgy. 

Stoneware  Dipping-Basket.— A  stone- 
ware dipping  bowl. 

Stopped-Off.— Subjected  to  the  stopping- 
off  process. 

Stopper  Incandescent  Lamp.— An  in- 
candescent lamp  in  which  the  mounted 
filament,  instead  of  being  hermetically 
sealed  in  the  lamp  chamber,  is  placed 
therein  by  means  of  a  tightly  fitting 
stopper. 

Stopper  Lamp. — A  stopper  incandescent 
lamp. 

Stopping-Off— A  process  employed  in 
electro-plating,in  which  a  metallic  article, 

.  already  electro-plated  over  its  entire  sur- 
face, is  electro-plated  with  another  metal 
over  certain  parts  only. 

Stopping-Off  Process. — A  process  em- 
ployed in  electro-plating  by  means  of 
which  an  article  which  is  to  be  electro- 
plated on  portions  of  its  surface  only  with 
one  metal,  and  on  other  portions  with 
another  metal,  is  first  completely  covered 
by  an  electro-plating  of  the  cheaper  metal, 
and  then  stopped-off  by  covering,  with  a 
coating  of  non-conducting  varnish,  such 
portions  only  of  its  surface  as  are  not  to 
receive  the  deposit  of  the  more  precious 
metal. 

Stopping-Off  Varnish. — A  varnish  used 
in  electro-plating  to  cover  portions  which 
are  not  to  receive  the  metallic  coating. 

Stopping-Out  Process.— A  process  em- 
ployed in  electro-typing,  by  means  of 
which  those  parts  of  an  electro-type 
mould  that  are  not  to  be  copied  in  the 
electro-type  are  covered  with  clean  hot 
wax. 

Storage  Accumulator. — A  term  some- 
tunes  used  for  storage  battery. 


Sto.] 


942 


[Str. 


Storage  Battery. — A  number  of  separate 
storage  cells  connected  so  as  to  form  a 
single  electric  source. 

Storage-Battery  Car. — An  electric  car 
which  carries  the  storage  battery  em- 
ployed for  its  propulsion. 

Storage-Battery  Meter. — A  meter  con- 
nected with  a  storage  battery  for  the  pur- 
pose of  indicating  the  electric  quantity, 
or  energy,  left  in  the  same. 

Storage-Battery  Traction. — Electric  car 
traction  obtained  by  means  of  storage 
batteries. 

Storage  Capacity. — The  capacity  of  a 
storage  battery,  as  measured  in  ampere- 
hours. 

Storage  Cell. — (1)  Two  relatively  inert 
plates  of  metals  or  metallic  compounds 
immersed  in  an  electrolyte  incapable  of 
acting  on  them  until  after  an  electric  cur- 
rent has  been  passed  through  the  liquid 
from  one  plate  to  the  other,  and  has  thus 
changed  their  chemical  relations.  (2) 
One  of  the  cells  required  to  form  a  sec- 

•  ondary  battery.  (§)  A  term  sometimes 
given  to  the  jar  containing  a  single  cell. 

Storage-Cell  Tester. — A  convenient  form 
of  electrode  provided  for  ready  attach- 
ment to  the  individual  cells  of  a  storage 
battery,  for  the  purpose  of  ascertaining 
their  electromotive  forces  from  time  to 
time. 

Storage  of  Electricity. — A  term  improp- 
erly employed  to  indicate  such  a  storage 
of  energy  as  will  enable  it  to  directly  re- 
produce electric  energy. 

Storage  of  Energy. — The  change  from 
any  form  of  kinetic  energy  to  any  form 
of  potential  energy. 

Storm,  Electric. — (1)  Any  unusual  con- 
dition of  the  atmosphere  as  regards  the 
quantity  or  distribution  of  its  free  elec- 
tricity. (2)  A  thunder  storm. 

Stove-Plate,   Electric. — An  electrically 

heated  stove-plate. 
Straggling  Flux. — Leakage  flux. 
Straight    Connector. — A  connector  for 

coupling  two  wires  in  the  same  straight 

line. 
Straight-  Filament     Incandescent 

Lamp. — An  incandescent  lamp  provided 

with  a  straight  filament. 
Straight-Line  Insulator. — An  insulator 

employed  for  a  trolley  line,  where  the 

conductor    is    supported    by  transverse 

wires  from  poles  placed  on  either  side  of 

the  roadway. 
Straight-Line  Suspension . — Suspension 

by  means  of  a  straight-line  trolley  hanger. 


Straight-Line  Trolley  Hanger.— A  trol- 
ley hanger  employed  on  a  straight  trolley 
line,  suitably  supported  by  a  span  wire  sa 
as  to  have  a  vertical  strain  only. 

Straightaway  Bunched  Cable.  —  A 
bunched  cable,  the  separate  conductors 
of  which  are  placed  in  successive  layers, 
and  extend  in  the  direction  of  the  length 
of  the  cable  without  any  twisting,  as  dis- 
tinguished from  a  helically  wound  cable. 

Strain. — The  deformation  produced  by  the 
action  of  a  stress. 

Stranded  Conductor.— A  conductor 
formed  of  a  number  of  smaller  interlaced 
or  twisted  conductors,  either  for  the  pur- 
pose of  reducing  self-induction,  or  eddy 
currents,  or  for  increasing  its  flexibility. 

Stranded  Core. — A  core  whose  conductor 
is  stranded,  as  opposed  to  a  core  whose 
conductor  is  a  solid  wire. 

Stranded  Feeder  Conductor. — A  feeder 
conductor  formed  of  stranded  wires. 

Stranded  Line. — A  line  formed  of  a 
stranded  conductor. 

Stranding  of  Conductor. — Forming  a 
conductor  of  a  number  of  separate  con- 
ductors or  strands. 

Strap  Coppers.  —  Copper  conductors 
formed  of  bars  or  straps,  employed  in  con- 
nection with  a  bar-armature  winding. 

Strap-Driven. — A  term  sometimes  em- 
ployed for  belt-driven. 

Strap  Key. — A  Tjey  made  from  an  elastic 
strip  or  strap  of  metal. 

Strap  Switch. — A  switch  made  from  a 
strip  or  strap  of  metal. 

Straps  and  Climbers. — A  device  em- 
ployed by  line-men  for  climbing  wooden 
telegraph  poles. 

Stratham's  Electric  Fuse.— A  form  of 
fuse  in  which  the  ignition  is  effected  by 
an  electric  spark. 

Stratification  Tube. — A  vacuum  tube 
whose  residual  atmosphere  displays  alter- 
nate dark  and  light  striae,  or  stratifications, 
on  the  passage  through  it  of  an  induction- 
coil  discharge. 

Stratified. — Arranged  in  separate  layers 
or  strata. 

Stratified  Discharge.  —  The  alternate 
light  and  dark  spaces  assumed  by  the  dis- 
charge of  an  induction  coil  through  a 
partially  exhausted  gas. 

Stray  Chain. — In  submarine  cable-work, 
a  length  of  chain  which  attaches  the  end 
of  a  buoyed  cable  to  the  mushroom  anchor 
mooring  chain. 

Stray  Currents. — A  term  sometimes  used 
for  eddy  currents. 


Stp.] 


943 


[Str. 


Stray  Field.y-(l)  Leakage  magnetic  flux. 

(2)  That  portion  of  a  magnetic  field  which 

does   not   pass  through  an  armature  or 

other  magneto-receptive  device. 
Stray  Flux.— The  flux  of  a  stray  field. 
Stray  Power. — That  portion  of  the  power 

applied  to  drive  a  machine  which  is  lost 

by  various  frictions. 
Stream-Lines    of   Escaping   Fluid. — 

Lines  which  show  the  actual  paths  of  the 

particles  of  an  escaping  fluid. 
Streamers. — Pillars    or  parallel    flashing 

columns  of  light  frequently  seen  during 

the  prevalence  of  an  aurora. 

Streaming  Discharge. — A  form  assumed 
by  a  flaming  discharge  between  the  sec- 
ondary terminals  of  an  induction  coil, 
when  the  frequencies  of  the  alternations 
increase  beyond  a  certain  limit,  and  the 
potential  is  consequently  increased. 

Streamings. — (1)  A  term  sometimes  em- 
ployed for  electrostatic  or  electro-mag- 
netic flux.  (2)  X-ray  streamings. 

Street  Call-Point  in  Fire  Telegraphy. 
Any  point  in  a  street  where  an  alarm 
call-box  is  placed. 

Street- Car  Controller.— (1)  An  electric 
switching  apparatus  contained  in  a  box 
placed  on  the  platform  of  an  electric 
street-car,  and  employed  to  control  the 
speed  of  the  car.  (2)  A  car-controller. 

Street-Car  Lamp. — An  incandescent  lamp 
provided  with  an  anchored  filament,  suit- 
able for  use  in  a  street-car. 

Street-Car  Motor. — A  motor  employed 
for  the  propulsion  of  a  trolley  car. 

Street-Car  Recording  Watt-Meter. — A 

wattmeter  designed  for  use  on  a  street- 
car for  registering  the  amount  of  electric 
energy  delivered  to  a  car  in  a  given  time. 

Street  Load-Diagram. — A  diagram  show- 
ing the  electric  load  on  each  street  of  any 
particular  district  of  electric  supply. 

Street  Mains. — In  any  system  of  electric 
distribution,  the  conductors  extending 
through  the  streets  from  junction  box  to 
junction  box,  through  which  the  current 
is  distributed  from  the  feeders,  and  from 
which  service  wires  are  taken. 

Street  Railway,  Electric,— (1)  Any  elec- 
trically propelled  street  railway.  (2)  The 
ordinary  trolley  system  of  electric  car 
propulsion. 

Street  Service.— <1)  In  a  system  of  in- 
candescent-lamp distribution  that  portion 
of  the  circuit  which  is  included  between 
a  main  and  the  service  cut-out.  (2)  That 
portion  of  service  conductors  which  lies 
outside  of  the  building  served.  (3)  In  a 


system  of  electric  distribution  including 
street  lighting,  service  wires  supplying 
street  lamps. 

Strength  of  Current.— (1)  A  general  term 
for  the  magnitude  of  the  current  in  a  cir- 
cuit. (2)  Amperage. 

Strength  of  Magnetic  Field. — The  mag- 
netic force  acting  on  a  free  unit  magnetic 
pole  placed  in  any  magnetic  field. 

Strength  of  Magnetism. — A  term  some- 
times used  for  intensity  of  magnetization. 

Stress. — The  pressure,  pull  or  other  force, 
producing  a  deformation  or  strain. 

Stress  Flux. — (1)  A  general  term  for  the 
flux  producing  any  stress.  (2)  The  sur- 
face integral  of  stress  passing  through  a 
surface. 

Stretching  Insulator. — An  insulator  of 
extra  mechanical  strength  provided  with 
means  for  carrying  a  short  extra  length 
of  wire,  twisted  around  a  stem  such  that 
the  excess  can  be  employed  for  making  a 
joint,  o.r  for  other  purposes. 

Striae,  Electric. — Parallel  streaked  bands, 
consisting  of  alternate  light  and  dark 
spaces,  produced  in  low-vacuum  tubes  by 
an  electric  discharge  through  them. 

Striking. — Subjecting  an  article  to  ttie 
action  of  a  striking  bath. 

Striking  an  Arc. — Separating  the  carbon 
electrodes  for  the  formation  of  an  arc  be- 
tween them. 

Striking  Bath. — A  bath  containing  less 
silver  and  a  greater  proportion  of  free 
cyanide,  employed  in  silver  plating,  for 
obtaining  an  almost  instantaneous  deposit 
of  silver  before  subjecting  the  object  to 
the  regular  plating  bath. 

Striking  Distance. — A  term  sometimes 
employed  for  sparking  distance,  or  the 
distance  through  which  a  disruptive  dis- 
charge will  pass. 

Striking  Mechanism  of  Arc  Lamp.— 
The  mechanism  employed  in  an  arc-lamp 
to  separate  the  carbons  on  the  establish- 
ment of  the  arc. 

Stringing  Wires. — Placing  aerial  wires  on 
poles  or  other  supports. 

Strip  Commutator.  —  A  commutator 
formed  of  plates  or  flat  strips  as  opposed 
to  a  commutator  whose  segments  are 
strips  placed  edgewise. 

Strip  Fuse. — A  name  sometimes  applied 
to  a  safety  strip. 

Strip  Resistance. — A  resistance  formed 
of  strip  or  strap  conductors. 

Stripping?. — Dissolving  the  metal  coating 
from  a  silver,  gold  or  other  plated  article 


Str.] 


944 


[Sub. 


Stripping  Bath. — A  bath  employed  for 
removing  an  electro-plating  of  gold,  silver 
or  other  metal,  either  by  simple  dipping 
or  by  electric  action. 

Stripping  Liquid.^(l)  The  liquid  em- 
ployed in  a  stripping  bath.  (2)  The 
liquid  employed  to  remove  the  coating  of 
one  metal  from  the  surface  of  another 
without  affecting  the  other  metal. 

Stroboscope. — An  instrument  employed 
in  the  study  of  periodic  motion. 

Stroboscopic. — Of  or  pertaining  to  the 
stroboscope. 

Stroboscopic  Disc. — A  disc  employed  in 
a  stroboscope. 

Strong-Current  Arrester. — Any  form  of 
arrester  suitable  for  protecting  a  line 
from  a  strong  current  produced  by  ac- 
cidental contact  with  a  trolley,  power  or 
lamp  circuit. 

Struck. — A  word  employed  in  electro-plat- 
ing to  characterize  a  surface  that  has  been 
covered  with  a  film  of  electrolytically  de- 
posited silver  or  nickel,  by  being  placed 
in  a  bath  and  exposed  for  a  few  moments 
to  the  action  of  a  strong  current. 

Structural  Carbon. — A  term  applied  to  a 
carbon  lamp-filament  obtained  by  the  car- 
bonization of  any  structural  carbonizable 
material  such  as  bamboo. 

Structural  Magnetic  Flux.— (1)  Mag- 
netic flux  produced  by  the  alignment  of 
the  individual  molecular  magnets  in  iron, 
steel  or  other  magnetic  substance.  (2) 
Magnetic  flux  produced  by  means  of  a 
structural  magneto-motive  force.  (3) 
Magnetic  flux  produced  by  iron  or  other 
magnetic  metal  as  opposed  to  flux  pro- 
duced by  electric  currents. 

Structural  Magneto-Motive  Force. — 
(1)  A  name  sometimes  given  to  an  aligned 
or  induced  magneto-motive  force,  in  order 
to  distinguish  it  from  the  prime  magneto- 
motive force.  (2)  A  magneto-motive 
force  produced  by  aligning  or  structurally 
arranging  the  molecular  magneto-motive 
forces  inherent  in  iron,  steel,  or  other 
magnetic  substance. 

Structureless  Carbons. — A  term  some- 
times applied  to  carbon  filaments  that  are 
obtained  by  the  carbonization  of  a  struct- 
ureless material,  such  as  tamadine  or 
celluloid. 

Struts  for  Telegraph  Poles. — Inclined 
wooden  or  iron  props  applied  to  telegraph 
poles  in  order  to  resist  thrusts  or  pressures. 

Sturgeon's  Wheel. — A  name  sometimes 
applied  to  Barlow's  wheel. 

Sub- Aqueous. — Under  water. 

Sub-Aqueous  Cable.— (1)  A  cable  em- 


ployed for  use  under  water,  generally 
under  fresh  water,  as  in  crossing  a  river. 
(2)  A  river  cable  as  distinguished  from  a 
sea  cable. 

Sub-Branch. — A  term  sometimes  em- 
ployed for  a  branch  taken  out  of  or  tapped 
from  a  branch. 

Sub-Centre  Transformer.  —  A  trans- 
former placed  at,  and  supplying  secondary 
circuits  radiating  from,  a  sub-centre  of 
distribution. 

S u b-D ivided  Conducto r.— (1)  A 

stranded  conductor.  (2)  A  compositely 
formed  conductor.  (3)  A  multiple-wire 
conductor. 

Sub-Divided  Transformer. — (1)  A  trans- 
former having  subdivisions  in  its  primary 
or  secondary  coils.  (2)  A  transformer 
having  a  sub-divided  magnetic  circuit. 

Sub-Exchange  for  Telephones.  —  A 
local  exchange  in  connection  with  a  cen- 
tral exchange. 

Sub-Mains. — (1)  Conductors  which  branch 
off  from  the  mains.  (2)  Mains  which  are 
themselves  branches  of  mains. 

Sub-Marine. — Under  the  sea. 

Sub-Marine  B^at,  Electric.— A  boat 
capable  of  being  propelled  and  steered 
while  under  water. 

Sub-Marine  Board.-  (1)  A  complete  set 
of  sub-marine  cable  telegraphic  instru- 
ments mounted  on  a  board.  (2)  A  sub- 
marine cable  testing  board. 

Sub-Marine  Cable. — A  cable  designed  for 
use  under  water,  generally  under  the 
ocean. 

Sub-Marine  Finder. — A  form  of  induc- 
tion balance  proposed  for  the  location  of 
torpedoes,  anchors,  iron  ships  or  other 
metallic  submerged  articles. 

Sub-Marine  Fuse. — A  fuse  employed  for 
the  ignition  of  a  sub-marine  mine. 

Sub-Marine  Key. — A  key  suitable  for  use 
in  sub-marine  telegraphy. 

Sub-Marine  Mine. — A  mass  of  gun-cot- 
ton or  other  explosive  material  contained 
in  a  water-tight  vessel  and  placed  under 
water  so  as  to  explode  on  the  passage  of 
an  enemy's  vessel  over  it. 

Sub-Marine  Search  Light. — A.n  incan- 
descent light  employed  for  sub-marine 
exploration. 

Sub-Marine  Sentry.— A  device  sometimes 
employed  in  sub-marine  cable  work  for 
indicating  the  presence  of  very  shallow 
water,  and  consisting  of  a  water  kite 
which  is  below  the  vessel  and  which  rises 
to  the  surface  when  it  strikes  the  sea-bot- 
tom. 


Sub.] 


945 


[Sup. 


Sub-Marine  Telegraph.— A  general  term 
for  the  apparatus  employed  in  sub-marine 
telegraphy. 

Sub-Marine  Telegraphy.— (1)  A  system 
of  telegraphy  in  which  the  line  wire  con- 
sists of  a  sub-marine  cable.  (2)  A  system 
of  telegraphy  across  oceans. 

Sub-Marine  Telephony.  —  Telephony 
carried  on  by  means  of  sub-marine  cables. 

Sub-Permanent  Magnetism.— A  term 
sometimes  employed  for  the  character 
of  the  magnetism  in  an  iron  ship,  as  dis- 
tinguished from  that  of  a  magnetized  steel 
bar,  and  as  indicating  that  the  perman- 
ence in  the  magnetism  of  the  former  is 
not  as  marked  as  in  that  of  the  latter. 

Subscriber's  Indicator.— In  a  telephone 
switchboard,  the  indicator  or  drop  con- 
nected in  a  subscriber's  circuit  and  oper- 
ated by  his  call. 

Subsidiary  Distributing  Board.— A  dis- 
tributing board  auxiliary  to  a  multiple 
telephone  switchboard,  and  from  which 
the  subscribers'  lines  are  portioned  to  the 
local  spring  jacks  for  the  various  opera- 
tors, in  order  to  equally  distribute  their 
work. 

Sub-Station. — An  auxiliary  station. 

Sub-Station  Accumulator. — An  accum- 
ulator employed  at  sub-stations,  or  aux- 
iliary centres  of  distribution. 

Sub-Station  Transformer.  —  A  trans- 
former employed  at  an  auxiliary  station 
or  sub-station. 

Substitute  Primary  Coil.-^l)  A  secon- 
dary-primary coil.  (2)  An  intermediate 
coil  in  a  transformer  which  alternately 
takes  the  part  of  a  secondary  and  primary. 

Substitution  Method. — A  method  of 
measuring  resistances,  currents,  electro- 
motive forces,  etc.,  by  removing  them 
from  a  circuit  and  replacing  them  by  a 
known  or  adjustable  corresponding  resist- 
ance, current  or  electromotive  force. 

Subterranean. — Under  the  earth. 

Subterranean  Mine.  —  An  underground 
mass  of  gunpowder,  or  gun-cotton  or 
other  high  explosive,  placed  in  suitable 
vessels  for  protection  against  moisture, 
provided  with  an  electrically  connected 
fuse,  which  is  either  exploded  automati- 
cally on  the  movement  of  an  enemy  over 
it,  or  by  a  distant  operator. 

Sub-Transformer  Station.— In  a  system 
of  electric  distribution  by  alternating  cur- 
rents, an  auxiliary  station  at  which  trans- 
formers are  placed  for  local  secondary  dis- 
tribution. 

Sub-Trunk   Telephone   Line.— (1)  An 
•60 


auxiliary  trunk  telephone  line.  (2)  A 
trunk  line  connecting  telephone  ex- 
changes and  used  for  making  connections 
with  trunk  lines. 

Suburban  Communication.  —  Tele- 
phonic or  telegraphic  communication  be- 
tween the  suburbs  and  central  portions  of 
a  city. 

Suburban  Electric  Railway. — An  elec- 
tric railway  connecting  the  centre  of  a 
city  with  the  suburbs. 

Subway,  Electric. — An  accessible  under- 
ground way  or  passage  provided  for  the 
reception  of  electric-light  wires  or  cables. 

Successive-Contact  Key. — Any  form  of 
key  employed  to  make  two  or  more  suc- 
cessive contacts. 

Sugg. — A  name  sometimes  given  to  a  stand- 
ard British  candle. 

Sulphating. — A  name  applied  to  one  of  the 
sources  of  loss  in  the  operation  of  a  stor- 
age cell,  by  means  of  the  formation  of  an 
inert  coating  of  lead  sulphate  on  the  sur- 
face of  the  battery  plates. 

Summer  Lightning. — A  name  sometimes 
given  to  heat  lightning. 

Sunflower  Commutator. — (1)  A  com- 
mutator resembling  a  sunflower  in  ap- 
pearance. (2)  A  form  of  flat  or  disc  com- 
mutator. 

Sun-Light  Color- Values. — Such  lumin- 
ous frequencies  in  a  source  of  artificial 
light  as  will  give  to  its  light  the  same 
effects  as  are  produced  by  sunlight. 

Sunshine. — The  luminous  radiant  energy 
emitted  by  the  sun. 

Sun-Spot  Disturbance. — Any  disturb- 
ance due  to,  attributed  to,  or  accompany- 
ing, the  presence  of  spots  on  the  sun. 

Sun-Spots. — Dark  spaces,  varying  in  num- 
ber and  position,  which  appear  on  the  sur- 
face of  the  sun. 

Sun-Stroke,  Electric. — (1)  Electric  pros- 
tration produced  by  exposure  to  the  light 
of  an  electric  arc.  (2)  Physiological  ef- 
fects similar  to  those  produced  by  ex- 
posure to  the  sun,  experienced  by  those 
exposed  for  a  long  time  to  the  intense  light 
and  heat  of  the  voltaic  arc. 

Sun  Telegraph. — A  name  sometimes  ap- 
plied to  the  heliograph. 

Sunk  Winding.— (1)  A  name  sometimes 
employed  for  an  iron-clad  winding.  (2) 
A  winding  sunk  below  the  surface  of  an 
armature  or  other  device. 

Superficial  Eddy-Currents. — Eddy  cur- 
rents produced  in  conducting  substances 
that  are  limited  to  the  outer  layers 
thereof. 


Sup,] 


946 


[Sus, 


Superficial  Field.— A  field  produced  by 
the  super-position  of  two  or  more  sep- 
arate fields. 

Superposed  Magnetism. — A  term  ap- 
plied to  a  magnetism  impressed  on  an 
already  magnetized  substance. 

Super-Saturation.  —  A  condition  of  a 
solution  which  has  been  allowed  to  cool, 
while  out  of  contact  with  air,  below  its 
point  of  crystallization  or  solidification. 

Super-Saturation  of  Solution.  —  The 
condition  assumed  by  a  warmed  saturated 
solution  of  a  salt  when  placed  in  a  closed 
vessel  out  of  contact  with  the  air,  and  al- 
lowed to  cool,  without  being  shaken. 

Supervising  Operators. — In  telephony, 
or  telegraphy,  operators  whose  duty  it  is 
to  supervise  the  work  of  other  operators. 

Supplement  of  Angle. — What  an  angle 
needs  to  bring  its  value  to  180°. 

Supplementary  Dynamo.  —  A  word 
sometimes  used  for  a  booster  dynamo. 

Supply  Conductors. — (1)  A  term  some- 
times applied  to  the  sub-mains  in  a  system 
of  incandescent  light  distribution.  (2) 
Conductors  which  convey  electric  energy. 

Supply  Mains. — A  term  sometimes  ap- 
plied to  the  mains  in  a  system  of  incan- 
descent light  or  power  distribution. 

Supply  Meter,  Electric. — A  meter  which 
indicates  or  measures  the  electricity  or 
electric  energy  supplied  to  a  given  cus- 
tomer or  machine. 

Supply  Unit. — A  name  proposed  for  the 
Board  of  Trade  unit. 

Support  Plate  of  Storage  Cell. — A  term 
sometimes  employed  for  the  grid  of  a 
storage  cell. 

Surface  Action. — Any  action  limited  to 
a  surface. 

Surface  Contact  of  Street-Railway 
Car. — A  contact,  flush  with  the  surface 
of  a  street,  and  intended  for  use  in  con- 
nection with  the  electric  propulsion  of  a 
street-railway  car. 

Surface  Contact-Resistance  between 
Metal  and  Liquid. — The  resistance  in- 
troduced into  a  primary  or  secondary  cell 
at  the  contact  between  the  metal  and 
liquid. 

Surface  Contact  Street  Railway  Sys- 
tem.— A  system  of  street-railway  pro- 
pulsion employing  surface  contacts. 

Surface  Density. — The  quantity  of  elec- 
tricity-per-unit-of-area  at  any  point  on  a 
charged  surface. 

Surface-Efficiency  of  Filament.— (1) 
The  efficacy  of  a  particular  character  of 
surface  for  luminous  radiation.  (2)  The 


luminous  efficiency  of  a  particular  charac- 
ter of  surface  in  a  filament. 
Surface  Integral.— (1)  The  sum  of  all 
the  products  of  a  point  function  and  its 
associated  element  of  area,  lying  on  a 
surface,  when  the  elements  are  all  in- 
definitely small.  (2)  The  integral  of  a 
quantity  taken  over  a  surface. 

Surface  Integral  of  Magnetic  Induc- 
tion.— The  total  magnetic  flux  passing 
through  a  surface. 

Surface  Magnetization. — In  the  distri- 
bution of  imaginary  magnetic  matter, 
the  magnetism  residing  on  a  surface,  or 
the  so-called  free  magnetism. 

Surface-Wound  Armature. — (1)  An  ar- 
mature wound  on  its  surface,  as  distin- 
guished from  an  iron-clad  armature.  (2) 
An  armature  in  which  the  conductors  lie 
over  the  surface  of  the  core,  instead  of 
being  placed  in  grooves  or  slots  formed 
therein. 

Surfusion. — A  word  sometimes  employed 
for  super-saturation. 

Surgical  Lamp. — A  lamp  employed  in 
surgical  exploration,  examination,  or  oper- 
ation. 

Surging  Circuit. — Any  circuit  through 
which  a  surging  discharge  is  passing. 

Surging  Discharge. — (1)  A  discharge  ac- 
companied by  electric  surgings.  (2)  An 
oscillatory  discharge. 

Surgings,  Electric. — (1)  Electric  oscilla- 
tions set  up  in  a  conductor  that  is  under- 
going rapid  discharging,  or  in  neighbor- 
ing conductors  that  are  being  rapidly 
charged  and  discharged.  (2)  Electric 
oscillations,  direct  or  induced. 

Susceptance. — In  an  alternating-current 
circuit,  branch,  or  conductor,  the  quan- 
tity whose  square  added  to  the  square  of 
the  conductance  is  equal  to  the  square  of 
the  admittance. 

Susceptibility. — A  word  sometimes  used 
for  magnetic  susceptibility. 

Suspended  Cable-Way.— A  modification 
of  the  telpherage  system,  in  which  a  car- 
riage provided  with  one  or  more  grooved 
wheels  is  electrically  driven  over  a  sus- 
pended cable. 

Suspended-Coil  Galvanometer.— Any 
form  of  galvanometer  in  which  the  cur- 
rent passing  is  measured  by  the  move- 
ments of  a  suspended  coil. 

Suspended  Trolley-Way. — (1)  A  sus- 
pended cable- way.  (2)  A  form  of  tele- 
pherage  system. 

Suspender. — A  word  sometimes  used  fof 
a  cable  suspender. 


Sus.] 


947 


[Swi. 


Suspender  for  Telephone  Cable. — (1) 
A  word  sometimes  employed  for  cable 
hanger.  (2)  A  hook  or  support  for  a 
telephone  cable. 

Suspending  Hook  for  Telephone 
Cable. — A  cable  hanger. 

Suspending  Wire  of  Aerial  Cable.— (1) 
The  wire  from  which  an  aerial  cable  is 
strung  or  suspended.  (2)  A  messenger 
wire. 

Suspension.— (1)  The  mechanism  for  sus- 
pending a  thing,  with  or  without  the 
thing  suspended.  (2)  The  means  employed 
in  suspending  any  system,  such  as  a 
needle,  a  pendulum,  or  a  car  motor. 

Suspension  for  Car-Motor. — The  means 
employed  for  supporting  a  car-motor  on 
a  car  truck. 

Sustained  Currents,  Electromotive 
Forces  or  Fluxes. — Any  electromotive 
force,  current  or  flux,  whose  effect  is  con- 
tinued, as  distinguished  from  one  whose 
effect  is  temporary. 

Swage. — A  particular  form  of  anvil  on 
which  highly  heated  metallic  plates  are 
shaped  by  hammering  them  into  forms 
the  same  as  that  of  the  anvil  on  which 
they  are  placed. 

Swage. — To  fashion  heated  metallic  plates 
by  hammering  them  into  the  form  of  the 
anvil  on  which  they  are  supported. 

Swaging. — Fashioning  highly  heated  me- 
tallic plates  into  any  desired  form  by  ham- 
mering, while  on  suitable  dies. 

Swaging,  Electric. — Forming  or  shaping 
of  metallic  plates  by  hammering  them 
against  suitable  anvils  or  dies  while  soft- 
ened by  electric  heat. 

Sweating. — A  term  employed  for  the  proc- 
ess of  soldering  together  the  ends  of 
electric-light  cables. 

Swelling  Current.  —  In  electro-thera- 
peutics, a  current  that  begins  weak  and 
is  then  periodically  made  stronger  and 
weaker. 

Swelling  Faradic-Currents.— A  term 
employed  in  electro-therapeutics  for 
Faradic  currents  that  are  caused  to  grad- 
ually increase  in  strength  and  then  to 
gradually  decrease  to  zero  strength. 

Sweep, — (1)  In  submarine  cable  work,  a 
drag.  (2)  In  submarine  cable  work,  a 
haul  made  with  a  grapnel  across  a  line  of 
cable. 

Sweeper,  Electric. — A  term  employed 
for  an  electrically -driven  sweeper. 

•Sweeping-Out  Charge.— A  phrase  em- 
ployed in  double-current  signalling  for 
freeing  the  line  from  a  charge  produced  in 


sending  one  signal,  by  reversing  the  di- 
rection of  the  current  through  the  line 
before  sending  the  next  signal. 

Swinging  Annunciator.— A  pendulum 
annunciator. 

Swinging    Cross.— A    term     sometimes 

given  to  an  intermittent  cross. 
Swinging  Earth. — A  name  sometimes 

given  to  an  intermittent  earth. 
Swinging  Voltmeter.— A  voltmeter 

mounted  upon  a  swinging  bracket  of  a 

switchboard,  so  as  to  be  capable  of  being 

read  from  any  direction. 

Swiss  Commutator   Switchboard. — A 

switchboard  having  cross-bars  after  the 
type  of  a  Swiss  commutator. 
Switch. — (1)  Any  device  for  readily  open- 
ing or  closing  an  electric  circuit.  (2)  -In 
telephony,  a  name  sometimes  given  to  a 
switchboard. 

Switch-Bell.— (1)  A  bell  switch.  (2)  A 
combination  of  a  bell  and  switch. 

Switch  Blade. — A  conducting  strip  or 
knife-blade  of  a  switch. 

Switch-Board. — (1)  A  board,  base,  slab  or 
frame  of  insulating  material,  upon  which 
are  supported  conducting  bars,  pieces, 
frames  or  masses,  with  or  without  switches 
and  instruments,  for  the  ready  establish- 
ment of  electrical  connections  between 
circuits  connected  therewith.  (2)  A  board 
carrying  switches  and  instruments  for 
controlling  a  distribution  system  and  the 
generators  connected  therewith.  (3)  A 
board  provided  with  a  switch  or  switches 
by  means  of  which  electric  circuits  con- 
nected therewith  may  be  opened,  closed 
or  interchanged.  (4)  In  a  central  station 
for  telegraphy,  telephony,  light  or  power 
distribution,  the  electric  controlling  me- 
chanism. 

Switch  Cord. — An  insulated  conducting 
cord  connected  with  a  switch. 

Switch-Board  Arrester. — A  device  in- 
tended for  use  on  switchboards,  consist- 
ing either  of  some  form  of  lightning  ar- 
i  ester  or  of  a  sneak-current  arrester. 

Switch-Board  Bolt. — A  bolt  for  mechan- 
ically fastening  apparatus  to  a  switch- 
board or  the  panels  of  a  switchboard  to  a 
frame. 

Switch-Board  Bracket. — A  bracket  on  a 
switchboard  for  supporting  an  incandes- 
cent lamp  or  other  device. 

Switch-Board  Cable. — Any  cable  con- 
nected with  a  switchboard. 

Switchboard  Fittings.— A  general  term 
embracing  the  connectors,  set  screws, 
wire-holders  or  bus-bar  connections,  em 


Swi.] 


948 


[Syn. 


ployed  in  placing  the  different  apparatus 
on  a  switchboard. 

Switch-Board  Protector.— (1)  A  pro- 
tector provided  with  a  suitable  electro- 
magnetic safety  device,  or  with  a  fuse  wire 
or  safety  catch,  placed  at  cable  heads,  at 
the  junction  between  aerial-land  and  un- 
derground lines,  for  the  purpose  of  pro- 
tecting the  cable  from  a  too  powerful 
electric  discharge  or  current.  (2)  Any 
lightning,  or  circuit  protector,  placed  on 
a  switchboard. 

Switchboard  Transformers.— Trans- 
formers on  an  alternating-current  switch- 
board for  locally  supplying  alternating- 
currents  of  reduced  pressure. 

Switch-Board  Wattmeter. — A  wattme- 
ter placed  on  a  switchboard  to  determine 
the  out-put,  or  the  intake,  of  some  circuit 
connected  therewith. 

Switch-Box. — Any  box  containing  one  or 
more  switches. 

Switch-Finger. — A  contact-finger,  or  pro- 
jecting metallic  contact  on  the  cylinder 
of  a  street-car  controlling-switch,  or  on 
similar  apparatus. 

Switch-Handle,  Electric. — In  electric 
railway  block-signalling,  a  miniature  rail- 
way electric  switch  handle  for  closing 
and  opening  an  electric  circuit. 

Switch  Hole. — A  hole  provided  in  a 
switch  key  for  the  insertion  of  a  plug. 

Switch  Hook. — (1)  An  automatic  tele- 
phone hook.  (2)  A  hook  which  serves 
the  purpose  of  a  switch. 

Switch  Jack. — A  spring  jack. 

Switch  Pin. — A  metallic  pin  or  plug  pro- 
vided for  insertion  in  a  switchboard. 

Switch  Room. — The  room  or  hall  in  a 
central  telephone  exchange  in  which  a 
switchboard  is  placed. 

Switch  Spring. — A  spring  placed  in  a 
switch  for  its  mechanical  operation,  or  for 
securing  electric  connection. 

Switched-In. — Thrown  into  a  circuit  by 
means  of  a  switch. 

Switched-Out. — Removed  from  a  circuit 
by  means  of  a  switch. 

Swivel  Clevis. — A  device  consisting  es- 
sentially of  a  nut  and  bolt,  by  means  of 
which  any  slack  in  a  guy -rod  may  be  taken 
up. 

Symmetrical  Alternating  Current. — 
Any  alternating  current  whose  successive 
semi-periods,  waves,  or  alternations  pos- 
sess opposite  but  equal  values,  or  corre- 
spond in  all  respects  save  in  direction. 

Symmetrical  Alternating  Electro- 
motive Forces. — Electromotive  forces 


whose  successive  semi-waves  or  alterna- 
tions possess  equal  but  opposite  values,  or 
correspond  in  all  respects  save  in  direc- 
tion. 

Symmetrical  Induction  of  Armature. 
— (1)  An  induction  produced  by  the  sim- 
ultaneous passage  of  the  same  quantity 
of  magnetic  flux  through  adjoining 
halves  of  the  armature.  (2)  A  sym- 
metrical magnetization  in  an  armature. 

Symmetrical  Magnetic  Field.— A  field 
whose  magnetic  flux  is  symmetrically 
distributed. 

Symmetrical  Polyphase  System. — 
A  polyphase  system  symmetrically  ar- 
ranged in  regard  to  conductors,  pressures, 
currents  and  loads. 

Sympathetic  Electric  Vibrations.— 
(1)  Electric  vibrations  produced  in  a  cir- 
cuit by  the  electro-magnetic  waves  given 
off  by  a  neighboring  circuit.  (2)  Electric 
vibrations  that  are  produced  by  reso- 
nance. 

Sympathetic  Generator. — An  induction 
generator. 

Sympathetic  Vibrations.  — Vibrations 
set  up  in  bodies,  and  having  the  same 
frequency  as  that  produced  by  the  excit- 
ing body. 

Symphonance. — A  word  proposed  in  place 
of  resonance. 

Synchronism. — (1)  Unison  of  frequencies 
in  alternating-current  systems  or  appara- 
tus. (2)  The  simultaneous  occurrence  of 
any  two  events.  (3)  Generally,  the  co- 
periodicity  and  co-phase  of  two  periodi- 
cally recurring  events.  (4)  The  coinci- 
dence in  cyclic  recurrence  of  two  or  more 
periodic  variables,  without  regard  to  am- 
plitude. 

Synchronizable. — Capable  of  being  syn- 
chronized. 

Synchronize. — (1)  To  cause  to  occur  or 
act  simultaneously.  (2)  To  bring  two 
alternating-current  machines  into  unison 
or  co-periodicity,  and  into  practical  coin- 
cidence of  phase,  so  that  they  may  be  con- 
nected together. 

Synchronized. — Caused  to  occur  or  act 
simultaneously. 

Synchronizer. — (1)  Anything  causing  or 
tending  to  cause  synchronism.  (2)  A 
phase  indicator.  (3)  A  device  for  indi- 
cating when  synchronism  is  attained  be- 
tween alternators  that  are  to  be  connect- 
ed in  parallel. 

Synchronizing  Dynamo-Electric  Ma- 
chines.— Adjusting  the  frequencies  and 
phases  of  two  alternating-current  dyna- 


949 


[Tai. 


mos  so  as  to  permit  of  their  being  coupled 
or  joined  in  parallel. 

Synchronizing  Torque. — The  torque  of 
an  alternating-current  generator  or  motor 
armature  tending  to  bring  it  into  syn- 
chronism with  some  other  armature  oper- 
ated with  it. 

Synchronograph. — A  name  given  to  a 
record  obtained  by  a  polarizing  photo- 
electric apparatus.  ' 

Synchronous. — (1)  Occurring  simulta- 
neously in  point  of  time.  (2)  Generally, 
co-periodic  and  co-phasal,  as  distin- 
guished from  isochronous,  which  connotes 
agreement  in  period  only. 

Synchronous  Generator. — A  generator 
of  alternating  currents,  operating  or 
capable' of  operating  in  synchronism  with 
another  generator. 

Synchronous  Motor. — A  form  of  alter- 
nating-current motor  which  requires  to  be 
brought  into  step  with  the  driving  cur- 
rent before  it  will  properly  operate. 

Synchronous  Multiphase  Motor. — 
A  multiphase  motor  designed  to  operate 
in  isochronism  with  the  generator  or  gen- 
erators connected  with  it. 

Synchronous  Multiplex  Telegraph. — 
A  general  term  for  the  apparatus  em- 
ployed in  synchronous  multiplex  teleg- 
graphy. 


Synchronous  Multiplex  Telegraphy.— 
A  system  of  simultaneous  telegraphic 
transmission  in  which  a  number  of  mes- 
sages, either  all  in  the  same  direction,  or 
part  in  one  and  the  remainder  in  the  op- 
posite direction,  can  be  simultaneously 
transmitted  over  a  single  line  wire. 

Synchronous  Reactance.— (1)  The  ap- 
parent reactance  of  a  synchronous  motor 
armature  under  working  conditions 
(2)  The  combined  apparent  reactance  of 
self-induction  and  armature  reactance  of 
a  synchronous  motor  armature  under 
working  conditions. 

Synchronous  Speed. — The  speed  of  a 
motor  or  generator  at  which  it  is  in  syn- 
chronism with  the  current  in  the  system 
to  which  it  is  connected. 

Synchronous  Vibrations. — Vibrations 
produced  by  two  or  more  separate  sys- 
tems that  exactly  coincide,  both  in  fre- 
quency and  in  phase. 

Synthesis. — (1)  Indirect  analysis  or  the 
formation  of  a  chemical  substance  by  the 
combination  of  its  constituent  parts. 
(2)  The  building-up  or  combination  of 
atoms  into  molecules. 

System  of  Electric  Lighting.— (1)  A 
term  sometimes  applied  to  an  electric 
light  installation.  (2)  An  electric  light 
plant. 


t. — A  symbol  employed  for  time, 
t  :  m. — An  abbreviation  for  turns-per-min- 
ute,  a  practical  unit  of  angular  velocity. 

T.  P.  Switch. — A  contraction  for  triple- 
pole  switch. 

T-Connector. — A  connector  provided  for 
connecting  a  wire  with  two  branch  wires, 
and  resembling  the  letter  T  in  shape. 

T-Shaped  Spark.— A  variety  of  three- 
branched  spark  obtained  by  the  discharge 
of  a  Leyden  jar  through  a  peculiar  form 
of  induction  coil. 

Table-Key. — A  key  placed  on  the  table  of 
a  telephone  exchange  for  effecting  the 
connections  with  an  operator. 

Table  Push. — A  push-button  connected 
with  a  table  for  ease  in  ringing  a  call-bell. 

Table  Switch.— A  switch  on  the  table  of 
a  telephone  switchboard. 

Tablet  Board. — A  switchboard  divided 
into  panels  or  tablets. 

Tablet  Check.— In  telegraphy,  a  tabulat- 
ed form  upon  which  messages  sent  and 


received  are  checked  off  for  the  purpose 
of  recording  the  traffic  and  ensuring 
against  the  loss  of  a  message. 

Tachograph. — An  apparatus  for  recording 
the  number  of  revolutions  per  minute  of 
a  machine  or  shaft. 

Tachometer. — (1)  An  apparatus  for  indi- 
cating at  any  moment  on  a  dial  the  num- 
ber of  revolutions  per  minute  of  a  shaft 
or  machine  with  which  it  is  connected. 
(2)  A  speed  indicator. 

Tachyphore. — (1)  A  name  proposed  for  a 
system  of  electric  transportation  in  which 
a  carriage  formed  of  magnetic  material  is 
propelled  by  the  sucking  action  of  sole- 
noids placed  along  the  tracks,  and  ener- 
gized in  succession  during  the  passage  of 
the  car.  (2)  A  port-electric  system. 

Tail  Light. — A  light  displayed  at  the  rear 
of  a  train,  in  order  to  avoid  rear-end  col- 
lisions. 

Tail  of  Mercury.— An  elongation  or  tail, 
of  grayish  color,  due  to  the  presence  of 


Tai.] 


950 


[Tea, 


oxides,  left  behind  a  drop  of  impure  mer- 
cury, when  moved  over  smooth  surface. 

Tailings. — (1)  In  telegraphy,  residual  dis- 
charges from  the  line  through  the  receiv- 
ing instrument,  following  each  signal,  and 
thus  tending  to  make  the  signals  run  to- 
gether. (2)  Residual  or  return  charges  or 
currents  in  the  transmission  of  electro- 
magnetic waves  through  a  dielectric. 

Talantoscope. — A  low-vacuum  tube  em- 
ployed in  connection  with  a  Hertzian  os- 
cillator to  determine  when  it  is  sending 
forth  waves,  and  when  it  is  under  the  in- 
fluence of  undirectional  discharges  and 
is  not  sending  forth  waves. 

Talking  Circuit. — In  telephony,  a  circuit 
employed  by  a  subscriber  during  conver- 
sion, as  distinguished  from  a  calling  cir- 
cuit. 

Tamadine. — A  modified  form  of  tri-nitro 
cellulose,  employed,  when  cut  into  suit- 
able shapes  and  subsequently  carbonized, 
for  the  filaments  of  incandescent  lamps. 

Tangent. — (1)  One  of  the  trigonometrical 
functions.  (2)  In  a  right-angled  triangle 
formed  by  a  radius-vector,  base,  and  per- 
pendicular, the  ratio  of  the  perpendicular 
to  the  base. 

Tangent  and  Sine  Galvanometer. — A 
galvanometer  furnished  with  two  mag- 
netic needles  of  different  lengths,  the 
small  one  being  used  for  tangent  meas- 
urements, and  the  long  one  for  sine 
measurements  of  current  strength. 

Tangent  Galvanometer. — An  instrument 
in  which  the  deflecting  coil  consists  of  a 
coil  of  wire  within  which  is  placed  a 
needle,  supported  at  the  centre  of  the 
coil,  and  very  short  by  comparison  with 
the  diameter  of  the  coil. 

Tangent  Scale. — A  scale  designed  for  use 
with  a  tangent  galvanometer  on  which 
the  values  of  the  tangents  are  directly 
marked,  instead  of  degrees  of  the  circle 
as  ordinarily,  thus  avoiding  the  necessity 
of  finding  from  tables,  tangents  corre- 
sponding to  the  degrees. 

Tangentially  -  Laminated  Armature 
Core. — An  armature  core  consisting  of  a 
closely-coiled  ribbon  of  sheet  iron. 

Tank-Heater,  Electric.— A  form  of  elec- 
tric heater  for  heating  liquids,  consisting 
essentially  of  a  heating  coil  immersed  in 
a  liquid  contained  in  a  tank. 

Tanning,  Electric.— The  application  of 
electric  currents  to  the  tanning  of  leather. 

Tap. — (1)  A  conductor  attached  as  a  shunt 
to  a  larger  conductor.  (2)  A  derived 
circuit  for  carrying  off  a  share  of  the 
main  current.  (3)  A  wire  taken  from  the 


junction  between  the  short  and  long  sec- 
tions of  a  quadruplex  battery. 

Tap  Wire  in  Quadruplex  Telegraphy. 
The  intermediate  wire  or  conductor  in  a 
system  of  quadruplex  telegraphy,  which 
divides  the  battery  into  two  unequal 
parts,  called  respectively  the  long  side 
and  the  short  side. 

Tap  Wires. — The  wires  or  conductors  em- 
ployed in  trolley  systems  to  carry  the 
current  from  the  feeders  or  mains  at  a 
pole  to  a  near  point  on  the  trolley  wire. 

Taped  Conductor.— A  taped  wire. 

Taped  Wire. — (1)  A  conducting  wire  cov- 
ered witli  an  insulating  material  in  the 
shape  of  a  tape.  (2)  A  wire  covered  with 
an  insulating  material  and  subsequently 
taped. 

Tapered  Mains. — Mains  in  the  tree  sys- 
tem whose  diameters  diminish  in  succes- 
sive sections. 

Taping. — (1)  Covering  a  wire  or  a  joint 
with  an  insulating  tape.  (2)  A  covering 
of  tape  applied  to  a  cable  sheathing. 

Tapers. — Wires  tapering  in  diameter  for 
the  purpose  of  effecting  a  splice  between 
two  different  types  of  submarine  cables. 

Tapper  Bell.  —  A  single-stroke  electric 
bell  provided  with  a  suitable  key  for  sig- 
nalling purposes. 

Tapper  Key. — A  term  sometimes  em- 
ployed in  place  of  a  Morse  tapper. 

Tapper  Signal. — In  a  system  of  mining 
signals,  signals  sent  or  received  by  meaas 
of  tapper  bells. 

Tapping  a  Circuit. — Introducing  a  loop 
or  branch  in  a  telegraphic  or  telephonic 
circuit,  for  the  purpose  of  intercepting 
the  messages  sent  over  the  circuit. 

Taps. — A  general  term  employed,  in  a  sys- 
tem of  incandescent  lamp  distribution, 
for  branches  or  sub-branches  that  are 
carried  from  the  mains  into  the  rooms  ef 
a  building  or  to  the  fixtures  in  the  halls. 

Target,  Electric. — A  target  in  which  the 
point  struck  by  the  ball  is  automatically 
registered  by  means  of  electric  devices. 

Tasimeter. — An  apparatus  designed  by 
Edison  for  the  purpose  of  detecting 
minute  heat  changes  by  variations  in  the 
resistance  of  a  soft-carbon  disc,  resulting 
from  changes  of  pressure  due  to  the  ex- 
pansion of  a  substance  exposed  to  the 
heat  to  be  measured. 

Teaser. — An  electric  current  teaser. 

Teaser,  Electric.  —  (1)  A  coil  of  fine 
wire  placed  on  the  field  magnets  of  a 
dynamo  in  a  shunt  across  the  main  cir* 
cuit,  in  addition  to  the  field  magnet  series 


Tea,  ]  951 

coil.  (2)  A  series  coil  placed  on  a  field 
magnet,  in  addition  to  a  regular  shunt 
field,  for  the  purpose  of  preliminary  ex- 
citation. 

Teaser  "Winding.  —  An  additional  coil 
wound  on  the  armature  of  a  monocyclic 
generator  of  smaller  cross-section  and 
fewer  turns  than  the  main  winding,  one 
end  of  which  is  connected  at  the  centre 
of  the  main  winding,  and  the  other  to  a 
collecting  ring. 

Tee  Box  for  Underground  Cables  or 
Conductors. — A  box,  shaped  like  a  letter 
T,  and  containing  a  joint  or  joints  between 
a  main  line  and  an  offset,  branch,  lateral, 
or  service  conductor. 

Tee  Connector. — A  T-shaped  connector 
employed  for  readily  connecting  a  wire 
at  right  angles  to  another  wire. 

Teeth  of  Armature. — Polar  projections 
or  ridges  on  the  surface  of  an  armature- 
core,  between  which  lie  the  armature 
windings  or  conductors. 

Tele-Anemograph. — A  device  for  record- 
ing the  indications  of  an  anemograph  at 
a  distance. 

Tel-Autogram. — A  recorded  message  ob- 
tained by  means  of  a  tel-autograph. 

Tel-Autograph. — A  telegraphic  system 
for  the  fac-simile  reproduction  of  writing 
at  a  distance. 

Tele- Autograph. — An  orthography  some- 
times employed  for  tel-autograph. 

Tele-Barograph. — A  device  for  recording 
the  indications  of  a  barometer  at  a  dis- 
tance. 

Tele-Barometer,  Electric. — An  electric 
recording  barometer,  for  indicating  and 
recording  barometric  pressures  at  a  dis- 
tance. 

Telegram. — Any  despatch  received  by 
means  of  a  telegraph. 

Telegraph. — (1)  A  general  name  for  the 
instrument  or  combination  of  instru- 
ments employed  for  conveying  a  commu- 
nication or  despatch  to  a  distance  by 
means  other  than  that  of  the  unassisted 
voice.  (2)  A  general  term  for  any  appa- 
ratus employed  in  telegraphy. 

Telegraph. — To  transmit  a  message  by 
means  of  a  telegraph. 

Telegraph  Circuit.— (1)  An  electric  cir- 
cuit employed  in  telegraphy.  (2)  An  in- 
sulated line  apparatus  at  one  or  more  tele- 
graph stations  and  a  ground  return  cir- 
cuit. 

Telegraph,  Electric. — A  general  term 
for  any  apparatus  employed  in  electric 
telegraphy. 


Telegraph  Line-Adjuster.— A  general 
term  given  to  apparatus  by  means  of 
which  the  adjustment  of  a  telegraph  line 
is  facilitated. 

Telegraph  Loop.— A  pair  of  wires  ex- 
tending from  a  telegraphic  station  to  a 
branch  office. 

Telegraph  Posts.— A  term  sometimes 
employed  for  telegraph  poles. 

Telegrapher.— A  telegraphic  operator. 

Telegrapher's  Cramp.— An  affection  of 
the  hand  of  a  telegrapher,  due  to  con- 
tinuous excessive  use  of  the  same  muscles, 
somewhat  similar  to  the  disease  known  as 
writer's  cramp. 

Telegraphic.— Of  or  pertaining  to  a  tele- 
graph. 

Telegraphic  Alarm.— An  alarm  bell  for 
calling  the  attention  of  an  operator  to  a 
telegraphic  instrument  when  the  latter  is 
of  the  non-acoustic  or  needle  type. 

Telegraphic  Alphabet.— The  code  em- 
ployed for  letters  and  other  characters  in 
telegraphy. 

Telegraphic  Arm.— A  cross-arm  placed 
on  a  telegraphic  pole  for  the  support  of 
the  insulators. 

Telegraphic  Box-Sounder.— A  sounder 
whose  receiving  magnets  are  enclosed  in 
a  hollow  box,  for  the  purpose  of  increas- 
ing the  intensity  of  the  sound  by  reso- 
nance. 

Telegraphic  Bracket.— A  support  or 
cross-piece  placed  on  a  telegraph  pole, 
tree,  wall  or  roof,  for  the  support  of  a 
telegraphic  line-insulator. 

Telegraphic  Cable. — A  cable  designed 
to  establish  telegraphic  communication 
between  different  points. 

Telegraphic  Clock. — A  name  sometimes 
applied  to  a  master  clock. 

Telegraphic  Code. —  The  pre-arranged 
system  of  signals  employed  in  any  system 
of  telegraphy. 

Telegraphic  Cross- Arm. — A  term  some- 
times employed  for  telegraphic  arm. 

Telegraphic  Dial. — A  dial  board  contain- 
ing letters  of  the  alphabet  and  figures, 
employed  in  dial  telegraphy. 

Telegraphic  Dynamo. — A  dynamo  em- 
ployed for  generating  the  currents  used 
in  telegraphic  transmission. 

Telegraphic  Earth-Circuit. — That  por- 
tion of  a  telegraphic  circuit  which  is  com- 
pleted through  the  earth  or  ground. 

Telegraphic  Embosser. — An  apparatus 
for  recording  a  telegraphic  message  on  a 
paper  strip  in  raised  or  embossed  char- 
acters. 


Tel,] 


952 


TTel. 


Telegraphic  Fixtures. — A  term  gener- 
ally limited  to  the  various  supports  pro- 
vided for  the  attachment  of  telegraphic 
wires. 

Telegraphic  Ground-Circuit. — An  earth 
circuit  used  in  any  system  of  telegraphy. 

Telegraphic  House-Top  Fixtures.— 
Telegraphic  fixtures  placed  on  the  roofs 
of  buildings  for  the  support  of  the  lines. 

Telegraphic  Ink- Writer.— (1)  A  device 
employed  for  recording  the  dots  and 
dashes  of  a  telegraphic  message  in  ink  on 
a  strip  of  paper.  (2)  A  Morse  inker. 

Telegraphic  Insulator. — An  insulator 
employed  on  telegraphic  lines. 

Telegraphic  Interrupter.— (1)  A  device 
for  making  and  breaking  a  circuit  at  a 
definite  rate.  (2)  A  telegraphic  key,  or 
other  analogous  device. 

Telegraphic  Interruption.—  (1)  Any 
fault  in  a  line  or  apparatus  which  pre- 
vents telegraphic  transmission.  (2)  A 
term  sometimes  employed  in  telegraphy 
for  faults  in  general.  (3)  A  break  or 
total  stoppage  of  signals  in  a  submarine 
cable. 

Telegraphic  Joint. — A  permanent  con- 
tact or  junction  between  the  ends  of  two 
electric  conductors. 

Telegraphic  Key. — The  key  employed 
for  sending  over  the  line  the  successive 
makes-and-breaks  corresponding  to  the 
dots  and  dashes  of  the  Morse  alphabet,  or 
to  the  deflections  of  the  needle  in  a  needle 
telegraph. 

Telegraphic  Line. — A  conducting  circuit 
employed  in  any  telegraphic  system  for 
the  transmission  of  electric  impulses  or 
currents. 

Telegraphic  Line-Circuit. — The  conduc- 
tor or  line  connecting  different  tele- 
graphic stations. 

Telegraphic  Needle. — A  needle  em- 
ployed in  telegraphy  to  represent  by  its 
movements  to  the  right  or  left,  respec- 
tively, the  dots  and  dashes  of  the  Morse 
alphabet. 

Telegraphic  Paper-Winder. — An  appa- 
ratus for  winding  or  coiling  the  paper 
fillet  used  on  a  telegraphic  register. 

Telegraphic  Photography. —  A  term 
sometimes  used  for  means  whereby  an 
image  of  a  photographic  object  may  be 
telegraphically  transmitted  to  a  distant 
station. 

Telegraphic  Pocket-Belay.— A  form  of 
telegraphic  relay  of  such  small  dimen- 
sions as  to  permit  it  to  be  readily  carried 
in  the  pocket. 


Telegraphic  Polar  -  Belay . —  A  tele- 
graphic  relay  provided  with  a  polarized 
armature. 

Telegraphic  Pole. — A  wooden  or  iron 
pole  provided  with  suitable  insulators  for 
the  support  of  an  overhead  telegraphic 
line  or  lines. 

Telegraphic  Begister. — (1)  An  apparatus 
employed  at  the  receiving  end  of  a  tele- 
graphic line  for  the  purpose  of  obtaining 
a  permanent  record  of  the  telegraphic 
despatch.  (2)  A  Morse  register. 

Telegraphic   Begistering  Apparatus. 

(1)  A  name  sometimes  given  to  a  tele- 
graphic recorder.     (2)  A  Morse  register. 

Telegraphic  Bepeater.— (1)  Any  telegra- 
phic device  whereby  the  relay,  sounder  or 
registering  apparatus  is  caused  to  repeat 
into  another  circuit  the  signals  received. 

(2)  An  apparatus  for  maintaining  telegra- 
phic communication  between  two  circuits 
not  in  conductive  connection. 

Telegraphic  Saddle. — A  bracket  of  spe- 
cial shape,  placed  astride,  on  the  top  of 
a  telegraph  pole,  for  the  support  of  an 
insulator. 

Telegraphic  Splice. — A  sheath  connec- 
tion made  between  two  cable  ends,  and 
overlying  a  joint. 

Telegraphic  Stay-Bods. — Guy  rods  sup- 
porting telegraph  poles. 

Telegraphic  Stock-Printer. — A  form  of 
printing  telegraph  employed  for  printing 
on  a  strip  of  paper  the  quotations  of  stocks, 
received  from  a  stock  exchange. 

Telegraphic  Switchboard. — (1)  A  device 
employed  at  a  telegraphic  station,  by 
means  of  which  any  one  of  a  number  of 
telegraphic  instruments  in  use  at  that 
station  may  be  placed  in  or  removed 
from  any  line  connected  with  the  station, 
or  by  means  of  which  one  wire  may  be 
connected  to  another.  (2)  A  switchboard 
for  conveniently  effecting  and  changing 
telegraphic  connections. 

Telegraphic  Through-Traffic.— A  gen- 
eral term  for  the  telegraphic  messages 
sent  directly  between  the  terminal  sta- 
tions, as  distinguished  from  way  traffic, 
which  includes  some  intermediate  sta- 
tion. 

Telegraphic  Time-Service.  —  (1)  Any 
telegraphic  distribution  of  time.  (2)  The 
telegraphic  distribution  of  time  to  jewel- 
lers, railroad  time-keepers,  or  others  in 
need  of  frequent  imfprmation  as  to  the 
precise  time,  in  which  electric  signals 
are  sent  out  from  a  standard  clock,  through 
relays,  at  two  second  intervals,  with  spe- 
cial signals  at  minute,  five-minute,  and 
hour  intervals. 


Tel.] 


953 


[Tel. 


Telegraphic  Transmitter.—  A  tablet 
having  suitable  contact  marks  placed  on 
its  surface,  such  that  by  moving  a  metal- 
lic rod  over  it  proper  signals  are  sent. 

Telegraphic  Translator. — A  term  some- 
times applied  to  a  telegraphic  repeater. 

Telegraphic  Way-Traffic.— Telegraphic 
messages  sent  from  one  ofKce  to  another, 
as  distinguished  from  messages  between 
terminal  offices  only. 

Telegraphic  Wire.— The  wires  employed 

in  telegraphic  line  circuits. 
Telegraphical. — Of  or  pertaining  to  the 

telegraph. 

Telegraphically. — In  a  telegraphic  man- 
ner. 

Telegraphing. — Sending   a    communica- 
tion by  means  of  a  telegraph. 
Telegraphist. — A  telegraphic  operator. 

Telegraphone. — An  instrument  whereby 
the  indentations  on  the  cylinder  of  a  graph- 
ophone  can  be  reproduced  upon  another 
cylinder,  at  the  same  time  that  the  vocal 
sounds  represented  by  the  indentations 
are  being  rendered  audible. 

Telegraphy.— Any  system  by  means  of 
which  a  communication  or  despatch  is 
transmitted  to  a  distance,  by  means  other 
than  that  of  the  unassisted  voice. 

Tele  -  Hydro  -  Barometer.—  An  in  stru- 
ment  for  indicating  and  recording  at  a 
distance  the  height  of  water  or  other 
liquid  in  a  vessel  or  reservoir. 

Tele-Hydro-Barometer,  Electric.— An 

apparatus  for  electrically  transmitting  to, 
and  recording  at  a  distant  station,  the 
height  of  water  or  other  liquid. 

Tele-Indicator. — A  term  sometimes  em- 
ployed for  telemeter. 

Tele-Intensity  of  Projector.— The  ap- 
parent luminous  intensity  of  a  search 
light  at  a  distance. 

Tele-Manometer,  Electric.— A  gauge 
for  electrically  indicating  and  recording 
pressures  at  a  distance. 

Tele-Meteorograph.— A  form  of  meteor- 
ograph, registering  at  a  distance  by  the 
aid  of  electricity. 

Telemeter. — An  apparatus  for  electrically 
indicating  and  recording  at  a  distance 
the  pressure  on  a  gauge,  the  reading  of  a 
thermometer,  or  the  indications  of  a 
similar  instrument. 

Tele-Metric.— Of  or  pertaining  to  a  tele- 
meter. 


Telephone. — To  communicate   by  means 
of  a  telephone. 

15— Vol. 


Telephone. — An  instrument  for  the  elec- 
tric transmission  of  articulate  speech. 

Telephone  Battery.— Any  form  of  open- 
circuit  battery,  suitable  for  use  in  connec- 
tion with  a  telephone. 

Telephone  Booth.— A  telephone  cabinet 
booth. 

Telephone  Cabinet-Booth.— A  silence 
telephone  cabinet. 

Telephone  Cable.— (1)  A  cable,  either 
aerial  or  subterranean,  suitable  for  the 
transmission  of  telephonic  despatches. 
(2)  Generally,  a  cable  whose  conductors 
are  twisted  in  pairs,  for  the  purpose  of 
avoiding  the  disturbance  produced  by 
cross-talk. 

Telephone  Call-Bell.— A  bell  employed 
in  connection  with  a  telephone  circuit 
for  calling  a  correspondent  at  the  other 
end  of  the  line  to  his  telephone. 

Telephone  Call-Wire.— (1)  A  wire  em- 
ployed in  certain  telephone  systems,  by 
the  subscriber,  for  the  purpose  of  calling 
the  central  office.  (2)  A  special  calling 
wire  in  a  telephone  system. 

Telephone  Circuit. — An  electric  circuit 
for  the  transmission  of  telephonic  mes- 
sages. 

Telephone  Cords.— (1)  Flexible  conduc- 
tors provided  for  use  in  connection  with  a 
telephone.  (2)  Flexible  conducting  cords 
provided  with  a  telephone  switchboard 
for  making  connections  between  sub- 
scribers. 

Telephone  Cross-Talk.— A  disturbance 
produced  in  a  telephone  circuit  by  induc- 
tion or  leakage  from  a  neighboring  circuit. 

Telephone  Drop. — An  annunciator  drop 
used  on  a  telephone  switchboard. 

Telephone  Exchange. — A  central  office 
provided  with  circuits,  switches  and  other 
devices,  by  means  of  which  any  one  of  a 
number  of  subscribers,  connected  either 
directly  or  indirectly  with  the  exchange, 
may  be  placed  in  communication  with 
any  other  subscriber,  or  with  some  other 
exchange. 

Telephone-Exchange  Switchboard.— 
A  switchboard  employed  in  a  central 
telephone  exchange  for  the  purpose  of 
readily  placing  any  subscriber  in  connec- 
tion with  any  other  subscriber  connected 
with  that  system. 

Telephone  Galvanometer. —  A  high- 
resistance  galvanometer  consisting  of  ail 
electro-magnet,  provided  with  a  soft-iron 
disc  delicately  mounted  between  its  poles, 
and  permanently  bridged  across  a  tele- 
phone circuit  for  the  purpose  of  giving  a 
visual  call-signal. 
2 


Tel.i 


[Tel. 


Telephone  Head-Gear. — Any  apparatus 
placed  on  the  head  for  readily  attaching 
a  telephone  receiver  to  the  ear  of  the 
operator. 

"Telephone  Indicator. — (1)  An  indicator 
employed  on  a  telephone  circuit  to  in- 
dicate the  number  of  the  correspondent 
calling.  (2)  A  telephone  drop  annuncia- 
tor. 

Telephone  Indicator-Coil. — A  coil  em- 
ployed on  a  telephone  indicator. 

Telephone  Meter. — (1)  An  apparatus  em- 
ployed on  telephone  circuits  for  register- 
ing the  number  of  connections  between 
subscribers  and  the  time  or  duration  of 
the  same.  (2)  A  calculagraph. 

Telephone  Relay. — An  electro-magnetic 
relay  employed  to  close  an  indicator  cir- 
cuit or  a  call-bell  circuit  in  a  telephone 
system. 

Telephone  Repeating-Coil. — (1)  A  form 
of  induction  coil  employed  for  repeating 
a  telephonic  message.  (~)  An  induction 
coil  having  two  insulated  windings,  one 
in  each  of  the  two  telephone  circuits  to 
be  connected. 

Telephone  Set. — A  general  term  for  the 
apparatus  employed  by  a  telephone  sub- 
scriber at  his  office. 

Telephone  Side  Tone. — The  tone  obtained 
in  a  telephone  receiver  by  talking  to  or 
tapping  at  its  own  transmitter. 

Telephone  Subscriber. — A  term  applied 
to  a  person  who  is  connected  with  a  cen- 
tral telephone  station. 

Telephone  Subway. — A  subway  provided 
for  the  reception  of  telephone  cables  or 
wires. 

Telephone  Switch. — (1)  Any  switch  em- 
ployed in  connection  with  a  telephone. 
(2)  A  switch  employed  to  place  either  a 
call-bell  or  a  telephone  in  a  telephone 
circuit. 

Telephone  Test-Board.— A  board  pro- 
vided in  a  central-telephone  exchange 
for  the  leading-in  and  orderly  arrange- 
ment of  the  line  wires,  between  the  out- 
side line  and  the  switchboard,  for  identi- 
fication and  testing. 

Telephone  Time-Check. — A  clock  in  a 
•  telephone  exchange  by  means  of  which 
a  drop  shutter  is  automatically  released, 
at  a  particular  trunk-  wire  indicator,  at 
the  expiration  of  the  allotted  time  that  a 
subscriber  is  given  the  use  of  the  trunk 
line,  and  by  which  the  central-station 
operator's  attention  is  called  to  the  fact 
01  such  expiration.  (2)  A  telephone 
meter. 

Telephone  Tinnitus. — (1)  A  professional 


neurosis  of  the  auditory  mechanism  as- 
cribed to  the  constant  use  of  the  tele- 
phone. (2)  A  nervous  auditory  disorder 
attributed  to  constant  use  of  the  tele- 
phone. 

Telephone  Transformer.— (1)  An  appa- 
ratus for  repeating  into  one  circuit  a 
telephonic  message  received  on  another 
circuit.  (2)  A  telephone  repeating  coil. 

Telephone  Translator. — A  telephone  re- 
peater. 

Telephoner. — (1)  A  term  sometimes  ap- 
plied to  a  person  at  one  end  of  a  simple 
telephone  line,  in  contradistinction  to  a 
telephone  subscriber  at  the  end  of  a  cir- 
cuit connected  with  any  telephone  ex- 
change. (2)  Any  one  carrying  on  a  con- 
versation by  means  of  a  telephone. 

Telephonic. — Of  or  pertaining  to  a  tele- 
phone. 

Telephonic  Alarm. — (1)  An  alarm  bell 
for  calling  a  correspondent  to  his  tele- 
phone. (2)  A  call  bell. 

Telephonic  Cable. — A  telephone  cable. 

Telephonic  Cross-Connection.  — Tele- 
phonic transposition. 

Telephonic  Exchange. — A  telephone  ex- 
change. 

Telephonic  Insulator.  —  Any  insulator 
employed  in  connection  with  a  telephone 
line. 

Telephonic  Line. — The  line  wire  or  cir- 
cuit employed  in  telephonic  transmission. 

Telephonic  Joint. — A  joint  effected  be- 
tween the  ends  of  two  wires  in  a  tele- 
phone circuit. 

Telephonic  Meter. — A  telephone  meter. 

Telephonic  Receiver.  —  (1)  The  instru- 
ment employed  in  receiving  a  telephonic 
message.  (2)  The  instrument  held  to  the 
ear  for  the  purpose  of  receiving  a  tele- 
phonic message. 

Telephonically. — By  means  of  a  tele- 
phone. 

Telephonist. — Any  one  employing  a  tele- 
phone. 

Telephony. — The  art  of  transmitting  ar- 
ticulate speech  by  means  of  a  telephone. 

Telephote.  —  (1)  An  apparatus  for  the 
telegraphic  transmission  of  pictures  by 
means  of  the  action  of  light  on  selenium. 
(2)  The  pherope. 

Tele-Photography.  —  A  system  of  fac- 
simile transmission  by  dots  and  dashes 
transmitted  by  means  of  a  continuous  cur- 
rent, whose  intensity  is  varied  by  a  trans- 
mitting instrument  containing  a  selenium 
resistance. 


Tel.] 


955 


[Tern. 


Tele-Radiophone. — A  form  of  radiophone 
arranged  for  the  simultaneous  transmis- 
sion of  telegraphic  and  telephonic  mes- 
sages. 

Telescope.  —  An  optical  instrument  for 
rendering  distant  objects  visible  by  en- 
larging their  apparent  dimensions  and  by 
increasing  the  amount  of  the  light  emitted 
by  them  that  reaches  the  eye. 

Telescopic. — Of  or  pertaining  to  the  tele- 
scope. 

Telescriptor. — A  name  given  to  a  particu- 
lar form  of  printing  telegraph. 

Teleseme.  —  A  self-registering  hotel  an- 
nunciator by  means  of  which  a  dial 
operated  in  a  room  indicates  the  charac- 
ter of  the  service  required. 

Telestereoscope. — An  optical  instrument 
for  causing  distant  objects  to  appear  in 
relief. 

Tele-Thermograph.— (1)  A  registering 
tele-thermometer.  (2)  The  record  made 
by  a  tele-thermometer. 

Tele-Thermometer,  Electric. — An  elec- 
trical recording  thermometer,  for  indicat- 
ing and  recording  temperature  at  a  dis- 
tance. 

Telluric  Magnetic  Force. — A  term  some- 
times employed  for  the  earth's  magnetic 
force. 

Telluric  Mines. — Explosive  mines  under- 
ground ,  as  distinguished  from  sub-aqueous, 
or  sub-marine  explosive  mines. 

Telpher. — A  general  name  for  the  appara- 
tus employed  in  systems  of  telpherage. 

Telpher  Line. — The  electric  circuit  em- 
ployed in  a  telpherage  system. 

Telpher  Locomotion. — The  transporta- 
tion of  merchandise  by  means  of  a  telpher 
system,  or  telpherage. 

Telpher  Locomotive. — An  electric  motor 
by  means  of  which  telpher  cars  are  drawn 
on  a  telpher  line. 

Telpherage. — A  system  for  the  convey- 
ance of  carriages  suspended  from  electric 
conductors,  driven  by  means  of  electric 
motors,  that  take  the  current  required  to 
energizo  them  directly  from  the  conduct- 
ors on  which  they  are  suspended. 

Temper. — To  obtain  the  requisite  degree 
of  hardness  and  elasticity  of  a  metal  by 
cooling  IT;  while  heated. 

Temperature. — The  thermal  condition  of 
a  body  considered  with  reference  to  its 
capability  to  communicate  heat  to  other 
bodies. 

Temperature  Alarm,  Electric.  — An 
electric  alarm  automatically  operated  by 
a  change  of  temperature. 


Temperature  Coefficient.— <1)  A  coef- 
ficient of  variation  in  a  quantity,  per  de- 
gree of  change  in  temperature.  (2)  The 
coefficient  by  which  a  change  of  tempera- 
ture must  be  multiplied  in  order  to  arrive 
at  the  change  in  a  quantity  due  to  the 
change  of  temperature. 

Temperature  Elevation. — (1)  The  excess 
of  temperature  of  a  heated  body  over  the 
temperature  of  its  environment.  (2)  The 
excess  of  temperature  acquired  by  a  con- 
ductor traversed  by  a  current  over  the 
surrounding  air. 

Temperature  Gradient. — (1)  A  line  rep- 
resenting the  rate-of-change  of  tempera- 
ture in  a  body  through  which  heat  is  flow- 
ing. (2)  A  space-rate-of-change  in  tem- 
perature. (3)  A  rate-of-change  in  any 
quantity  varying  with  temperature. 

Temperature  Regulating-Switch  for 
Electric  Car  Heater. — A  switch  em- 
ployed in  systems  of  car  heating,  whereby 
the  separate  heaters  may  be  connected  in 
series,  or  in  parallel  groups,  between  the 
trolley  and  the  track,  or  by  means  of 
which  one  or  more  of  the  heaters  may  be 
removed  at  will. 

Tempering. — Obtaining  a  change  in  the 
hardness  and  elasticity  of  a  metal  by  sud- 
denly cooling  it  while  heated. 

Tempering,  Electric. — A  process  for 
temperii  g  metals  in  which  heat  of  electric 
origin  is.  employed  instead  of  ordinary 
heat. 

Temporary. — Lasting  but  for  a  while. 
Temporary  Charge  by  Induction.— An 

electric  charge  of  a  temporary  character 

produced  on  a  conductor  by  induction,  as- 

distinguished  from  a  permanent  charge 

so  obtained. 
Temporary    Currents. — Currents    that 

continue  but  for  a  brief  interval  of  time. 
Temporary   Electromotive   Forces. — 

Electromotive  forces  which  continue  but 

for  a  brief  interval  of  time. 

Temporary  Intensity  of  Magnetiza- 
tion.— The  intensity  of  the  magnetization, 
temporarily  induced  in  a  bar  of  soft  iron, 
as  distinguished  from  permanent  mag- 
netization induced  in  hard  steel. 

Temporary  Magnetization. — (1)  A  word 
employed  for  the  magnetization  produced 
in  a  mass  of  soft  iron,  when  brought  into 
a  magnetic  field.  (2)  Magnetization  which 
is  temporary  in  character. 

Temporary  Magneto-Motive  Forces. 

Magneto-motive  forces  that  continue  but 

for  a  brief  interval  of  time. 
Temporary  Socket.— A  socket  provided. 


Ten.} 


956 


[Tes. 


for  an  incandescent  lamp  that  is  not  in- 
tended to  be  permanently  installed. 

Tenacity. — (1)  The  stress  required  to  pro- 
duce a  rupture  in  a  mass  of  given  cross 
section  of  any  material.  (2)  The  power  of 
a  material  to  resist  rupture. 

Tension.-^-(l)  An  elongating  stress.  (2) 
The  strain  produced  in  a  substance  by  the 
action  of  a  stress.  (3)  The  pressure  pro- 
duced by  a  confined  gas  against  the  walls 
of  the  containing  vessel,  due  to  molecular 
impact. 

Tension,  Electric. — A  term  loosely  ap- 
plied to  signify  indifferently  surface  den- 
sity, electromotive  force,  electromotive" 
intensity,  dielectric  stress,  or  difference 
of  potential. 

Tension-Ratchet. — A  name  sometimes 
given  to  a  line-dynamometer. 

Terminal  Board. — A  switchboard  situat- 
ed on  a  dynamo. 

Terminal  Branch  Cut-Out. — A  cut-out 
for  a  branch  taken  from  the  end  of  a  main 
line. 

Terminal  Electromotive   Force. — The 

electromotive  force  of  a  dynamo  taken  at 
the  terminals  of  the  machine. 

Terminal  Insulator. — (1)  An  insulator 
at  the  terminus  of  a  line.  (2)  A  telegraph 
line  insulator  provided  with  two  grooves 
for  the  reception  of  two  ends  which  may 
be  kept  insulated  from  each  other. 

Terminal  Pole. — (1)  The  last  pole  of  a  line. 
(2)  A  pole  of  greater  dimensions  and  more 
securely  anchored  than  the  rest,  erected 
at  the  end  of  a  telegraphic,  telephonic, 
trolley,  or  power  line,  or  where  aerial  wires 
join  subterranean  cables,  and  intended  to 
safely  resist  the  lateral  tension  of  the  line. 

Terminal  Pressure. — The  pressure  at  the 
terminals  of  any  electric  apparatus. 

Terminal  Reflection. — A  term  applied 
to  the  reflection  of  electro-magnetic  waves 
from  the  end  of  an  open-circuited  con- 
ductor. 

Terminal  Telegraphic  Station. — The 
telegraphic  station  at  either  terminus  of 
a  line. 

Terminal  Voltage. — The  terminal  elec- 
tromotive force. 

Terminals. — A  name  indifferently  applied 
to  the  poles  or  to  the  electrodes  of  a  vol- 
taic battery. 

Terra-Cotta  Conduit. — An  earthenware 
conduit.  • 

**  Terra  Voltaism." — The  operation  of  a 
telegraph  system  by  a  single  voltaic  ele- 
ment, consisting  of  a  pair  of  dissimilar 


metals  buried  in  the  earth  at  opposite 
ends  of  the  line. 

Terella. — A  sphere  of  hardened  steel,  or  of 
lode-stone,  magnetized  so  that  the  distri- 
bution of  its  magnetism  shall  resemble 
that  of  the  earth. 

Terrestrial  Electricity. — A  term  pro* 
posed  for  atmospheric  electricity. 

Terrestrial  Magnetic  Induction. — The 
production  of  magnetism  by  the  action  of 
the  earth's  field. 

Terrestrial  Magnetism. — A  name  ap- 
plied to  the  magnetism  of  the  earth. 

Tesla  Coil. — A  form  of  oil-insulated  in- 
duction  coil  or  transformer. 

Tesla  Discharge. — A  variety  of  high-fre- 
quency, high-pressure  discharge. 

Tesla  Frequencies.— A  term  sometimes 
applied  to  frequencies  which  are  much 
higher  than  those  ordinarily  employed. 

Tesla  Transformer. — A  step-up,  oil-in- 
sulated transformer,  employed  by  Tesla 
in  obtaining  high-frequency  discharges. 

Test  Board.— (1)  A  board  employed  in  a 
telegraphic,  telephonic,  or  transmission  cir- 
cuits, generally,  provided  with  the  measur- 
ing instruments  required  for  testing  its 
insulation  and  other  electrical  properties. 
(2)  A  board  in  a  telephone  station  to 
which  telephone  lines  are  connected,  for 
the  purpose  of  quickly  connecting  the 
testing  instruments  to  such  lines. 

Test  Cell. — A  voltaic  cell  employed  for 
the  busy  or  engaged  test  in  a  multiple 
telephone  switchboard. 

Test  Circuit. — In  a  multiple-telephone 
switchboard  the  circuit  for  the  busy  test. 

Test  Clerk. — A  clerk  to  whom  the  duties 
of  testing  the  telephone  lines  are  assigned. 

Test  Loop. — A  loop  running  to  a  test 
board. 

Test  Plugs. — (1)  Plugs  used  in  testing. 
(2)  Plugs  for  insertion  in  testing  jacks. 

Test  Ring. — (1)  A  call  made  by  the  central 
station  to  each  subscriber  to  ascertain 
whether  the  line  is  in  good  operating  con- 
dition. (2)  A  ring  in  front  of  each  jack 
in  a  multiple  telephone  switchboard,  and 
supplying  a  contact  for  the  busy  test. 

Test  Room. — A  testing  room. 

Test  Thimble. — A  thimble  at  a  central 
telephone  exchange  carrying  a  contact, 
and  employed  for  making  a  busy  test  at  9> 
multiple  telephone  switchboard. 

Test  Wire  for  Multiple  Switchboard. 
A  wire  running  to  a  multiple  switchboard 
and  connecting  all  the  jacks  of  the  same 
number  in  the  different  sections  for  the- 


Tes,] 


957 


[The. 


purpose  of  enabling  the  operator  to  ascer- 
tain whether  the  subscriber  needed  is 
busy. 

Test  Wire  of  Metallic  Circuit.— (1)  The 
return-wire  of  a  metallic  circuit.  (2)  In 
telephony,  that  wire  in  a  subscriber's  me- 
tallic-circuit loop  which  serves  for  the 

'  busy  test  at  the  switchboard. 

Test  Wires. — (1)  The  wires  in  a  multiple 
telephone  switchboard,  by  which  the 
busy  test  is  made.  (2)  Any  wires  or  cir- 
cuits used  in  making  a  test.  (3)  Wires 
to  be  tested  or  undergoing  a  test. 

Testing. — (1)  Submitting  to  trial  for  elec- 
tric capabilities.  (2)  Determining  the 
value  of  the  current  strength,  the  dif- 
ference of  potential,  the  resistance,  the 
coulombs,  the  farads  the  joules,  the  watts, 
etc.,  in  any  circuit.  (3)  Making  electrical 
measurements,  generally. 

Testing  Bank. — A  bank  of  lamps,  or  otner 
inductionless  resistances,  employed  in 
testing  a  circuit. 

Testing  Board. — A  board  employed  in  a 
telephone  switchboard  for  the  purpose  of 
testing  the  condition  of  the  lines. 

Testing  Car  for  Railway  Circuits. — 

An  electric  trolley-car  provided  for  mak- 
ing electric  tests  along  a  line  of  street 
railway  while  the  car  is  in  motion. 

Testing  Jacks. — In  a  multiple  telephone 
switchboard,  or  distributing  board,  special 
jacks  sometimes  inserted  in  any  circuit 
for  testing  such  circuit. 

Testing  Magneto. — A  magneto-electric 
machine  employed  to  produce  the  high 
electromotive  force  required  in  testing 
high-resistance  circuits. 

Testing  of  Joints. — (1)  Determining  the 
insulation  or  conductor  resistance  of  a 
joint  in  any  circuit.  (2)  Ascertaining  the 
resistance  of  the  insulating  material 
around  a  joint  in  a  cable. 

Testing  Point  of  Spring  Jack.— The 
tip  of  a  spring  jack. 

Testing  Pole. — A  term  sometimes  em- 
ployed in  electro-therapeutics  for  the  in- 
different pole  or  electrode. 

Testing  Posts.  — Hollow  posts  provided 
with  a  door,  placed  above  an  underground 
cable,  into  which  the  wires  are  sometimes 
led,  employed  for  ease  in  opening  and 
testing. 

'1'esting  Rod. — An  insulated  conducting 
rod  employed  in  testing  insulators  for 
dipping  into  the  liquid  contained  in  their 
sheds,  when  inverted  in  a  testing  bath. 

Testing  Room. — (1)  A  room  on  board  a 
cable-ship  provided  with  instruments  for 


cable  testing  and  signalling.  (2)  A  room 
fitted  with  tables  and  apparatus  for  mak- 
ing electrical  tests.  (3)  In  a  telephone 
exchange,  a  room  usually  near  the  switch 
room  through  which  all  telephone  lines 
pass  and  arranged  for  conveniently  test- 
ing such  lines. 

Testing  Switch.— In  a  quadruples  tele- 
graphic system,  a  switch  for  throwing 
the  line  from  the  sending  battery  to 
ground  through  a  suitable  resistance,  for 
the  purpose  of  enabling  the  distant  sta- 
tion to  obtain  a  balance. 

Testing  Transformer.— (1)  A  transformer 
employed  in  any  system  of  distribution 
for  the  purpose  of  testing  for  grounds,  for 
the  condition  of  the  line,  for  drop  of  po- 
tential, etc.  (2)  A  transformer  employed 
in  testing. 

Tetanus. — Continuous  spasmodic  contrac- 
tion of  the  muscles. 

Tetrad  Atom. — An  atom  whose  valency 
or  atomicity  is  four. 

Tetrivalent.  —  Possessing  a  valency  or 
atomicity  of  four. 

Tetrode  Working. — A  term  applied  to  a 
four-way  mode  of  working  the  Delany 
synchronous  multiple  telegraph. 

Thaumatrope. — An  optical  toy  depending 
on  the  persistence  of  the  retinal  image, 
in  which  two  different  pictures  placed 
upon  the  opposite  sides  of  a  card  are 
caused,  by  the  rapid  rotation  of  the  card, 
to  appear  as  a  single  picture. 

Theatre  Dimmer.— (1)  A  dimmer  employ- 
ed in  theatres  for  varying  the  intensity  of 
the  illumination.  (2)  A  rheostat  or  chok- 
ing coil  employed  in  a  theatre-lighting 
circuit. 

Theatre  Dimming  Rheostat. — A  rheo- 
stat employed  in  connection  with  a  theatre 
dimmer. 

Theatrophone. — A  sytem  of  telephonic 
communication  between  theatres  or  opera- 
houses  and  subscribers. 

Theodolite. — An  instrument  employed  for 
measuring  angles  in  vertical  or  horizon- 
tal planes. 

Theoretical  Magnet.  —  A  hypothetical 
magnet,  assumed  for  the  purpose  of 
mathematical  discussion  as  possessing  in- 
finite length  and  thinness,  and  uniform 
magnetization. 

Therapeutic  Adapter. — An  adapter  em- 
ployed in  electro-therapeutic  work. 

Therapeutical  Electrization. — Subject- 
ing different  parts  of  the  human  body  to 
the  action  of  electric  currents  for  the  cure 
of  a  diseased  condition. 


The.] 


958 


[The. 


Therm. — (1)  A  heat  unit  equal  to  the 
amount  of  heat  required  to  raise  the  tem- 
perature of  a  gramme  of  water,  at  the 
temperature  of  its  greatest  density,  one 
degree  Centigrade.  (2)  The  smaller 
calorie. 

Therm  Calorie. — A  word  sometimes  used 
for  the  smaller  calorie. 

Thermsethesiometer.  —  An  instrument 
employed  in  electro-therapeutics  for  test- 
ing the  temperature  sense  in  nervous 
diseases. 

Thermal. — Of  or  pertaining  to  heat. 

Thermal  Absorption. — The  absorption  of 
heat  energy  during  its  passage  through  a 
body. 

Thermal  Activity.— (1)  The  activity  pos- 
sessed by  a  body,  arising  from  its  heat 
energy.  (2)  The  rate  of  doing  thermal 
work.  (3)  The  rate  of  generating  heat. 

Thermal  Balance.  —  (1)  A  differential 
galvanometer  employed  for  determining 
small  differences  of  temperature.  (2)  The 
bolometer. 

Thermal  Batteries. —  (1)  Thermo-piles. 
(2)  Thermo-electric  batteries.  (3)  An  elec- 
tric source  operated  by  heat  energy. 

Thermal  Cautery. — A  cautery  heated  by 
ordinary  heat,  as  distinguished  from  an 
electric  cautery,  or  one  heated  by  heat  of 
electric  origin. 

Thermal  Circuit  Closer. —  A  circuit- 
closer  operated  by  changes  of  tempera- 
ture. 

Thermal  Coil  of  Resistance  Box.— A 
coil  of  wire  inserted  in  a  resistance  box, 
and  possessing  a  high  temperature  suffi- 
cient, for  the  purpose  of  indicating  by  its 
resistance  the  temperature  within  the 
box. 

Thermal  Current. — A  heat  current,  or 
one  due  to  the  flow  or  transference  of 
heat  through  a  conductor. 

Thermal  Current-Strength. — The  quan- 
tity of  heat  per  second  transmitted  across 
any  area  of  normal  cross-section  of  a  con- 
ductor. 

Thermal  Diffusiyity. — A  term  proposed 
for  thermometric  conductivity,  or  the 
ratio  of  the  calorimetrical  conductivity 
to  the  specific  heat  per  unit  volume. 

Thermal  Electromotive  Force  of  Re- 
sistance  Coils . — A  thermo-electric 
couple  inserted  in  a  resistance  box,  for 
the  purpose  of  determining  the  tempera- 
ture within  it. 

Thermal  Equivalent  of  Work.— The 
equivalent,  in  heat  units,  of  a  given 
quantity  of  mechanical  work. 


Thermal  Incandescence. — The  shining 
or  glowing  of  a  substance,  generally  a 
solid,  by  means  of  heat  other  than  that  ot 
electric  origin. 

Thermal  Resistance.  —  The  resistance 
.  offered  by  a  substance  to  the  passage  of 
heat. 

Thermal  Resistivity. — (1)  Specific  ther- 
mal resistance.  (2)  The  specific  thermal 
resistance  of  a  substance  referred  to  the 
thermal  resistance  of  a  unit  cube  between 
any  pair  of  parallel  faces. 

Thermally  Effective  Value.— (1)  In  an 
alternating-current  circuit,  the  effective 
values  from  thermal  measurements  or 
considerations.  (2)  The  square-root-of- 
mean-square  values. 

Thermic  Balance. — A  bolometer. 

Thermic  Interrupter. — A  device  operat- 
ed by  the  expansion  of  a  metallic  wire 
employed  for  the  purpose  of  preventing 
more  than  a  certain  number  of  arc-lamps 
being  used  in  a  circuit  where  the  current 
is  paid  for  by  the  number  of  lights,  rather 
than  by  the  current  supplied. 

Thermo-Barometer. — (1)    A  device  for 

.  determining  the  elevation  of  a  mountain 
by  observing  the  temperature  at  which 
water  boils  on  that  elevation.  (2)  A 
hypsometer. 

Thermo-Battery. — A  term  sometimes  ap- 
plied for  a  thermo-electric  battery. 

Thermo-Call. — A  thermo-electric  call. 

Thermo-Cell. — A  thermo-electric  cell. 

Thermo-Chemical  Cell.  —  An  electric 
cell,  in  which  a  difference  of  potential  is 
produced  by  the  combined  action  of  heat 
and  chemical  action. 

Thermo-Chemistry.  —  That  branch  of 
chemistry  which  treats  of  the  measure- 
ment of  chemical  energy  in  thermal  units. 

Thermochrosy. — (1)  A  word  expressive 
of  the  fact  that  ordinary  radiant  heat, 
like  light,  consists  of  an  assemblage  of 
waves  of  different  frequencies.  (2)  Heat 
coloration. 

Thermo-Electric  Battery. — A  combina- 
tion, as  a  single  thermo-electric  source,  of 
a  number  of  separate  thermo-electric  cells 
or  couples. 

Thermo-Electric  Call. — An  instrument 
for  electrically  sounding  an  alarm  when 
the  temperature  rises  above  or  falls  below 
a  fixed  point. 

Thermo-Electric  Cell. — A  name  applied 
to  a  thermo-electric  couple. 

Thermo-Electric  Couple. — Any  two  dis- 
similar metals  which,  when  connected  at 
their  ends  only,  so  as  to  form  a  complete 


The.] 


959 


[The. 


electric  circuit,  will  produce  an  electric 
current  when  one  end  is  more  highly 
heated  than  the  other. 

Thermo-Electric  Current. — A  current 
produced  by  a  thermo-electromotive 
force. 

Thermo-Electric  Diagram. — A  diagram 
in  which  the  thermo-electric  power  be- 
tween different  metals  is  given  for  dif- 
ferent temperatures. 

Thermo-Electric  Effect. — The  produc- 
tion of  an  electromotive  force  at  a  thermo- 
electric junction  by  reason  of  the  differ- 
ence of  temperature  between  that  junc- 
tion and  the  other  junction  of  the  couple. 

Thermo-Electrio  Electromotive  Force 
of  Voltaic  Cell. — The  thermo-electro- 
motive force  produced  by  a  voltaic  couple. 

Thermo-Electric  Element. — A  name  ap- 
plied to  either  of  the  metals  that  form  a 
thermo-electric  couple. 

Thermo-Electrio  Force. — (1)  The  force 
produced  by  a  thermo-electric  couple. 
(2)  The  electromotive  force  of  a  thermo- 
electric circuit. 

Thermo-Electric  Generator. — A  ther- 
mo-electric pile. 

Thermo-Electric  Inversion. — An  inver- 
sion of  the  thermo-electromotive  force  of 
a  couple  at  certain  temperatures. 

Thermo-Electric  Junction. — A  junction 
of  a  thermo-electric  couple. 

Thermo-Electric  Neutral  Point. — A 
temperature  at  which  two  thermo-elec- 
tric forces  are  equal.  (2)  A  temperature 
at  which  a  junction  of  two  metals  has  no 
thermal  E.  M.  F. 

Thermo-Electric  Pair. — A  thermo-elec- 
tric couple. 

Thermo-Electric  Pile. — A  thermo-elec- 
tric battery. 

Thermo  -Electric  Potential-Difference. 
Difference  of  potential  produced  by  a 
thermo-electric  cell  or  pile. 

Thermo-Electric  Power.  —  A  number 
which,  when  multiplied  by  the  difference 
of  temperatures  of  a  thermo-electric 
couple,  will  give  the  difference  of  poten- 
tial generated  thereby. 

Thermo-Electric  Series.  —  A  list  of 
metals,  so  arranged  as  to  their  thermo- 
electric powers,  that  each  in  the  series  is 
electro-positive  to  any  lower  in  the  list. 

Thermo-Electricity.  —  (1)  The  electro- 
motive forces  developed  by  a  thermo- 
electric cell  or  battery.  (2)  Electricity 
produced  by  differences  of  temperature 
at  the  junction  of  dissimilar  metals. 

Thermo-Electriflcation. — E  lectrifica- 


tion  produced  by  differences  of  tempera- 
ture in  a  thermo-electric  couple. 
Thermo-Electrometer.— A  name  some- 
times, though  not  happily,  given  to  an 
electric  thermometer. 

Thermo  -  Electromotive    Force.  —  An 

electromotive  force  or  difference  of  poten- 
tial produced  by  differences  of  tempera- 
ture at  a  thermo-electric  junction. 

Thermo-Element. —  A  name  sometimes 
employed  for  a  thermo-couple 

Thermo-Galvanometer. — A  galvanome- 
ter employed  in  connection  with  a  thermo- 
pile for  the  purpose  of  showing  difference, 
of  temperature  by  means  of  the  currents 
developed. 

Thermo-Luminescence. — Luminescence 
produced  in  a  substance  by  heat  at  a 
temperature  below  that  of  luminosity. 

Thermolysis. — The  decomposition  of  a 
molecule  by  heat. 

Thermo-Magnetic  Generator.— (1)  A  de- 
vice for  producing  electricity  by  the  com- 
bined influence  of  heat  and  magnetism. 
(2)  A  pyro-magnetic  generator. 

Thermo-Magnetic  Motor.  —  A  pyro- 
magnetic  motor. 

Thermometer,  Electric. — A  device  for. 
determining  the  effects  of  an  electric  dis- 
charge by  the  movements  of  a  liquid 
column  due  to  the  expansion  of  a  con- 
fined mass  of  air  through  which  the  dis- 
charge is  passed. 

Thermometric  Conductivity.  —  The. 
ratio  of  the  calorimetric  conductivity  to, 
the  specific  heat  of  unit  volume. 

Thermometric  Heat. — A  term  proposed 
for  heat  in  gross  matter,  as  distinguished 
from  radiant  heat,  or  wave  motion  in  the. 
ether. 

Thermometric  Resistance  Coil. — A  coil 
whose  resistance  is  known  at  a  given 
temperature,  and  employed  to  determine, 
an  unknown  temperature  to  which  it  is 
exposed,  from  the  change  in  its  resistance. 

Thermometry. — That  branch  of  science 
which  treats  of  the  determination  of 
temperature. 

Thermo-Multiplier. — (1)  A  word  some- 
times used  for  thermo-pile.  (2)  A  form 
of  low-resistance  galvanometer  suitable 
for  use  in  connection  with  a  thermo-pile. 

Thermo-Pair. — A  thermo-electric  couple. 

Thermophone.  —  (1)  An  electric  instru- 
ment for  producing  sound  by  means  of 
electricity.  (2)  Any  instrument  by  means, 
of  which  sounds  are  produced  by  the  ab- 
sorption of  radiant  energy. 

Thermo-Pile. — A  thermo-electric  battery.^ 


The.] 


960 


[Thr. 


Thermo-Pile  Galvanometer. — A  form 
of  galvanometer  for  detecting  small  dif- 
ferences of  temperature,  in  which  the 
thermo-pile  is  placed  within  the  instru- 
ment. 

Thermoscopie  Receiver. — A  name  some- 
times given  to  a  microphonic  receiver. 

Thermostat. — An  instrument  for  auto- 
matically maintaining  a  given  tempera- 
ture by  closing  an  electric  circuit  through 
the  expansion  of  a  solid  or  liquid. 

Thermostatic  Alarm,  Electric. — Any 
electric  alarm  operated  by  the  action  of  a 
thermostat. 

Thermostatic. — Of  or  relating  to  a  ther- 
mostat. 

Thermostatic  Regulation. — Any  regula- 
tion, such  as  in  the  temperature  of  a  room, 
effected  by  the  action  of  a  thermostat. 

Thermostatic  Regulator. — A  regulator 
whose  action  is  dependent  on  a  ther- 
mostat. 

Thermo  -  Telephone. — (1)  A  telephone 
transmitter  consisting  of  a  continuous 
wire,one  end  of  which  is  connected  with  a 
transmitting  diaphragm  placed  in  circuit 
with  the  receiving  telephone  battery,  and 
having  a  current  passed  through  it  of 
sufficient  strength  to  heat  the  wire.  (2)  A 
telephone  receiver  in  which  the  dia- 
phragm is  set  in  vibration  by  thermally- 
produced  changes  in  the  length  of  an  at- 
tached wire. 

Thermo-Tropic  Battery. — A  name  pro- 
posed for  a  form  of  carbon  batteiy,  in 
which  the  E.  M.  F.  is  produced  by  the  ac- 
tion of  heat. 

Thermo-Tropic  Current. — The  currents 
produced  by  a  thermo-tropic  battery. 

Thief  Alarm. — A  term  sometimes  em- 
ployed for  a  burglar  alarm. 

Third -Rail  Electric  Railway. — An 
electric  street-car  railway  in  which  a  third 
rail,  insulated  from  the  track,  is  employed 
for  one  side  of  the  circuit,  the  outside 
rails,  together  with  return  feeders,  being 
employed  for  the  other  side  of  the  circuit. 

Thimble  Brush.  —  A  suitably  shaped 
brush  employed  for  cleansing  such  sur- 
faces as  the  inside  of  a  thimble,  and  so 
preparing  them  for  electro-plating. 

Thomson.  —  A  name  proposed,  but  not 
adopted,  for  a  unit  of  electric  conduc- 
tivity. 

Thomson  Effect. — (1)  The  production  of 
an  electromotive  force  in  unequally 
heated  homogeneous  conducting  sub- 
stances. (2)  The  increase  or  decrease  in 
the  differences  of  temperature  in  an  un- 


equally heated  conductor,  produced  by 
the  passage  of  an  electric  current  through 
the  conductor. 

Thomson's  Bridge. — A  modified  form  of 
Wheatstone's  bridge  employed  for  the 
measurement  of  very  small  resistances. 

Three  Ammeter  Method  of  Measure- 
ment.— A  method  of  measuring  activity 
in  an  alternating-current  circuit  by  the 
combined  use  of  three  ammeters  in  a 
main  and  branch  circuits  respectively. 

Three-Bearing  Generator. — (1)  A  belt- 
driven  dynamo-electric  generator,  pro- 
vided with  a  third  shaft  bearing  situated 
between  the  armature  and  the  pulley. 
(2)  A  generator  whose  rotor  shaft  has 
three  bearings. 

Three-Bearing  Motor. — (1)  A  belt-driv- 
ing motor  provided  with  a  third  shaft 
bearing  between  the  pulley  and  the  ar- 
mature. (2)  A  motor  whose  rotor  shaft 
has  .three  bearings. 

Three-Bearing  Railway  Generator. — 
A  railway-generator  having  three  bear- 
ings for  its  rotor  shaft. 

Three-Bladed  Switch.— (1)  A  switch 
provided  with  three  blades.  (2)  A  switch 
closing  three  circuits  simultaneously. 

Three-Branched  Spark.  —  A  form  of 
branched  spark  obtained  by  the  discharge 
of  a  Leyden  jar  through  a  peculiar  form 
of  induction  coil. 

Three  -  Circuit  Way  -  Telegraphic 
Switchboard. — A  form  of  telegraphic 
switchboard  suitable  for  use  at  a  way 
station. 

Three-Coil  Armature  Winding  of  Al- 
ternator.— An  armature  winding  pro- 
viding three  coils  in  a  ring  armature  or 
three  slots  in  a  drum  armature  for  each 
and  every  pole  in  the  field  frame. 

Three-Coil  Armature  Winding  of 
Multiphase  Alternator. — An  armature 
winding  providing  three  coils  in  a  ring 
armature  or  three  slots  in  a  drum  arma- 
ture, per  phase,  for  each  and  every  pole 
in  the  field  frame. 

Three  Corner  Telegraphic  Repeater. 
A  telegraphic  repeater  which  repeats  from 
one  circuit  to  two  circuits. 

Three-Current  Test  to  Instrumental 
Zero. — A  localization  submarine  cable 
test,  in  which  three  separate  measure- 
ments of  resistance  are  made  with  differ- 
ent current  strengths  in  succession,  the 
Wheatstone  bridge  balance  being  taken 
to  instrument  zero. 

Three-Filament  Incandescent  Lamp 
for  Triphase  Circuits. — An  incandes- 
cent lamp  intended  for  use  on  triphas* 


Thr.] 


961 


[Thr. 


circuits  provided  with  three  leading-in 
wires  connected  to  the  free  ends  of  three 
filaments  which  are  connected  in  a  com- 
mon joint. 

Three-Part  Commutator. — A  commuta- 
tor made  up  of  three  insulated  segments. 

Three-Phase  Armature. — An  armature 
possessing  a  three-phase  winding. 

Three-Phase  Armature- Winding. —An 
armature  winding  such  as  will  enable  it 
to  produce  three-phase  currents. 

Three-Phase  Bar- Winding  for  Arma- 
ture.— A  bar  winding  for  an  armature, 
such  as  will  enable  it  to  produce  three- 
phase  currents. 

Three-Phase  Circuit. — Any  circuit  suit- 
able for  the  transmission  of  three-phase 
currents. 

Three-Phase  Coil-Winding  for  Arma- 
ture.— A  coil  winding  for  an  armature, 
such  as  will  enable  it  to  produce  three- 
phase  currents. 

Three  -  Phase  Continuous  -  Current 
Commutating  Machine.  —  A  trans- 
former from  triphase  alternating  to  con- 
tinuous currents,  employing  a  revolving 
armature  provided  with  a  commutator. 
(2)  A  triphase  rotary  transformer. 

Three-Phase  Currents. — Three  alternat- 
ing-currents differing  in  phase  from  one 
another  by  one-third  of  a  cycle. 

Three-Phase  Dynamo. — A  three-phase 
generator. 

Three-Phase  Generator. — Any  generator 
capable  of  producing  three-phase  cur- 
rents. 

Three-Phaser. — A  three-phase  generator. 

Three-Phase  Meter. — A  meter  suitable 
for  operation  on  a  three-phase  system,  for 
recording  the  energy  delivered  on  all 
three  branches. 

Three-Phase  Motor. — Any  motor  suitable 
for  operation  by  three-phase  currents. 

Three-Phase  Rotary-Converter. — A  ro- 
tary converter  suitable  for  use  in  connec- 
tion with  three-phase  currents. 
,  Three  -  Phase  Rotating  -  Magnetic 
Field. — A  rotating  field  produced  by  the 
action  of  a  three-phase  current. 

Three-Phase  System. — A  system  for  the 
transmission  of  electric  energy  by  means 
of  three-phase  currents. 

Three-Phase  Transformer. — Three  sep- 
arate transformers  employed  for  the 
transformation  of  triphase  currents. 

Three-Phase  Transmission. — Transmis- 
sion by  means  of  three-phase  currents. 


Three-Phase  Two-Phase  Transformer. 
An  alternating-current  transformer  for 
transforming  from  three-phase  currents 
to  two-phase  currents. 

Three-Phase  Working.  —  Three-phase 
transmission. 

Three-Phaser.-y<l)  A  three-phase  gener- 
ator. (2)  A  triphaser. 

Three-Point  Switch.— (1)  A  switch  by 
means  of  which  a  circuit  can  be  com- 
pleted through  three  different  contact 
points.  (2)  A  switch  designed  to  make 
three  distinct  contacts. 

Three-Point  Trolley  Switch. — A  trolley 
switch  provided  for  a  bifurcation  in  a 
road,  or  where  a  road  divides  into  three 
branches. 

Three-Voltmeter  Method  of  Measure- 
ment.— A  method  of  measuring  activity 
in  an  alternating-current  circuit,  employ- 
ing three  voltmeters  simultaneously. 

Three- Way  Frog. — A  three-way  trolley 
frog. 

Three- Way  Plug. — A  multiple  telephone 
switchboard  plug  making  three  contacts 
at  sleeve,  ring  and  tip  respectively. 

Three-Way  Switch.  —  A  three-point 
switch. 

Three-Way  Trolley -Frog.  —  A  trolley 
frog  used  where  a  trolley  line  branches 
in  three  directions. 

Three- Way  Trolley-Switch.  —  (1)  A 
trolley  switch  designed  for  use  at  a  point 
where  the  line  branches  in  three  direc- 
tions. (2)  A  trolley  switch  with  three 
connections. 

Three- Wire  Circuit. — (1)  A  circuit  em- 
ployed in  a  three-wire  system.  (2)  A 
three-wire  diphase  system.  (3)  A  three- 
wire  triphase  system. 

Three- Wire  Diphase. — A  form  of  diphase 
circuit  containing  three  wires,  in  which 
one  of  the  wires  is  usually  provided  with 
a  greater  area  of  cross-section  and  is  em- 
ployed as  the  common  return. 

Three-Wire    Distribution    Board. — A 

distribution  board  in  a  three-wire  system. 

Three-Wire  Mains. — The  mains  employed 
in  a  three-wire  system  of  distribution. 

Three-Wire  Meter. — A  meter  suitable 
for  operation  on  a  three-wire  system  for 
recording  the  power  delivered  on  both 
sides  of  the  system. 

Three-Wire  Moulding.— Moulding  em- 
ployed in  a  three- wire  distribution  system. 

Three-Wire  Multiple  Switchboard.— 
A  multiple  telephone  switchboard  in 
which  the  jacks  in  a  subscriber's  line  are 


Thr.] 


962 


[Tinu 


connected  in  multiple,  and  in  which  three 
wires  run  to  all  jacks. 

Three-Wire  Switchboard. — (1)  A  tele- 
phone switchboard  with  three  wires  to 
each  jack.  (2)  A  switchboard  employed 
in  a  three-wire  system  of  electric  distri- 
bution. 

Three- Wire  Switchboard. — A  switch- 
board suitable  for  use  in  connection  with 
a  three-wire  system  of  distribution. 

Three-Wire  System. — A  system  of  elec- 
tric distribution  for  lamps  or  other  mul- 
tiple-connected translating  devicas,  in 
which  three  conductors  are  employed  in 
connection  with  two  dynamos  connected 
in  series,  the  central  or  neutral  conductor 
being  connected  to  the  junction  of  the 
dynamos,  and  the  two  other  conductors  to 
the  remaining  free  terminal  of  each. 

Three- Wire  Transmission. — (1)  Trans- 
mission by  the  three-wire  system.  (2) 
Transmission  by  means  of  the  three-wire 
diphase  or  three-wire  triphase  systems. 

Three- Wire  Telephone  Switchboard. 
A  branched  terminal  telephone  switch- 
board. 

Throttling. — Partially  or  completely  cut- 
ting off. 

Throttling  of  Lines  of  Magnetic  Force. 
Any  decrease  in  the  density  of  magnetic 
flux  due  to  a  magnetic  joint,  or  to  any 
decrease  in  the  magnetic  permeability  of 
any  portion  of  a  circuit.  (2)  Saturation. 

Through.-^-(l)  In  communication  with, 
telegraphically.  (2)  Directly  connected 
telegraphically,  without  intermediate 
stations.  (3)  Completed  or  ended. 

Through  Circuit. — A  telephonic  or  tele- 
graphic circuit  that  has  been  completed 
through  to  a  given  station,  by  cutting  out 
interruptions  or  breaks  in  a  line,  by  the 
connection  together  of  sections  of  dif- 
ferent wires. 

Through  Line. — A  line  extending  be- 
tween two  terminal  stations,  as  distin- 
guished from  a  line  containing  way  sta- 
tions. 

Through  Telephone  Tablets. — Panels 
placed  in  a  telephone  switchboard  for 
connecting  subscribers  on  different 
switchboards. 

Throw. — A  term  sometimes  employed  for 
the  excursion  or  throw  of  a  needle. 

Throw  of  Needle. — A  phrase  sometimes 
employed  for  the  angular  deflection  of  a 
needle,  particularly  when  the  needle 
makes  its  first  swing. 

Throw-Back-Indicator,  Electric. — An 
annunciator  with  a  drop  that  is  automati- 
cally replaced. 


Throw-Over  Reversing  Switch.— A  re- 
versing switch  which  is  operated  by 
throwing  it  over  from  one  side  to  the 
other. 

Throw-  Over  Starting  Switch.—  A 
throw-over  switch  employed  for  starting 
an  electric  motor. 

Throw-Over  Switch.— (1)  A  switch  for 
readily  and  rapidly  changing  a  circuit 
from  one  source  to  another  or  one  system 
to  another.  (2)  A  switch  which  is 
thrown  over  from  one  set  of  contacts  to 
another,  by  movement  about  an  axis. 

Thumb-Cock    Electric   Burner.  —  An 

electric  gas-burner  in  which  the  turning 
of  an  ordinary  thumb-cock  turns  on  the- 
gas  and  ignites  it  by  a  spark  produced  by 
a  wiping  contact,  actuated  by  the  motion 
of  the  thumb-cock. 

Thunder. — The  loud  noise  accompanying 
a  disruptive  lightning  discharge. 

Thunder  Bod. — A  term  formerly  em- 
ployed for  lightning  rod. 

Thunder  Storm. — A  rain  storm  accom- 
panied by  thunder  and  lightning. 

Ticker. — A  word  sometimes  employed  for 
stock  ticker,  or  printing  telegraph. 

Ticket  Operator. — In  telephony,  an  oper- 
ator at  a  central  exchange  whose  duty  it 
is  to  record  calls  on  tickets  for  that  pur- 
pose. 

Tie  Bar. — A  bar  extending  across  the  track 
at  suitable  intervals  between  two  opposite 
rails,  and  employed  to  prevent  the  spread- 
ing of  the  rails. 

Tie  Feeder. —  A  feeder  connecting  two 
stations,  two  feeders,  or  two  feeding 
points. 

Tie  Line. — (1)  In  an  electric  distributing 
system,  a  conductor  free  from  translating 
devices  and  employed  to  equalize  poten- 
tial. (2)  A  conductor  connecting  two 
points  in  a  distributing  system  for  the 
purpose  of  equalizing  their  potentials. 

Tie  Sleeper. — A  sleeper  laid  transversely 
to  a  track  and  serving  to  retain  in  place 
the  rails  which  are  fastened  to  it. 

Tie  Wire. — (1)  Binding  wire  of  an  insu- 
lator. (2)  Wire  which  binds  an  overhead 
wire  to  the  groove  of  its  insulator. 

Time  Annunciator. — An  alarm  clock. 

Time-Ball,  Electric. — A  ball  suspended  in 
a  prominent  position  on  a  tall  pole  and 
caused  to  fall  at  the  exact  hour  of  noon, 
or  at  any  other  pre-determined  time,  for 
the  purpose  of  giving  a  visual  signal  of 
correct  time  to  an  entire  neighbor  hood. 

Time  Constant. — (1)  Irf  an  electric  circuit 
the  ratio  of  the  inductance  to  the  con 


Tim.] 


963 


[Too. 


ductor  resistance.  (2)  In  an  electric  cir- 
cuit containing  a  condenser  the  product 
of  the  capacity  of  the  condenser,  and  the 
resistance  of  its  discharging  circuit. 

Time-Constant  of  Circuit. — (1)  The  time 
in  which  a  current  will  fall  in  a  circuit 
when  the  E.  M.  F.  is  suddenly  removed,  in 
a  ratio  whose  Naperian  logarithm  is  unity. 
(2)  The  ratio  of  the  inductance  of  a  cir- 
cuit to  its  resistance. 

Time-Constant  oi  Condenser. — The  time 
in  which  the  charge  of  a  condenser  falls 
in  a  ratio  whose  Naperian  logarithm  is 
unity. 

Time-Constant  of  Electro-Magnet. — 
The  time  required  for  the  current  to  fall, 
when  the  E.  M.  F.  is  suddenly  withdrawn, 
to  a  ratio  whose  naperian  logarithm  is 
unity. 

Time  Cut-Out. — An  automatic  cut-out  ar- 
ranged so  as  to  permit  a  translating  de- 
vice to  operate  for  a  certain  time,  after 
which  it  is  cut  cu  ,  of  the  circuit. 

Time  Detector,  Electric. — An  electri- 
cally operated  v  .tchman's  clock.  An  ap- 
paratus for  electrically  registering  the 
time  at  which  a  watchman  visits  one  or 
more  stations  and  closes  or  opens  a  cir- 
cuit connected  with  the  register. 

Time  Fall  ot  Electromotive  Force  of 
Secondary  Cell. — A  gradual  decrease  in 
the  potential  difference  of  a  secondary  or 
storage  cell  observed  during  its  discharge. 

Time  Flow. — The  ratio  expressed  in  ergs- 
per-square-centi metre,  of  the  amount  of 
energy  which  is  passed  through  a  normal 
area  of  cross -section,  to  that  cross-section. 

"Time  Gun. — A  gun  that  is  automatically 
fired  by  a  standard  clock,  for  the  purpose 
of  giving  a  time  signal  to  an  entire  neigh- 
borhood. 

Time  Hysteresis. — A  term  sometimes  in- 
correctly employed  for  magnetic  creep- 
ing. 

Time-Illumination. — (1)  A  given  illumi- 
nation that  is  continued  for  a  given  time. 
(2)  The  effect  produced  by  an  illumina- 
tion continued  for  a  time.  (3)  The  pro- 
duct of  illumination  and  time. 

•Time-Lag  of  Magnetization.— (1)  A  lag 
which  appears  to  exist  between  the  time 
of  the  action  of  the  magnetizing  force, 
and  the  appearance  of  the  rriagnetism. 
\2)  In  an  alternating-current  choking-coil 
or  transformer,  the  lag  of  magnetization 
due  to  hysteresis,  expressed  as  a  time  or 
fraction  of  a  period. 

Time  Meter,  Electric. — An  electric  meter 
whose  operation  is  based  on  a  record  of 


time  during  which  an  electric  current  ia 
passing. 

Time  of  Oscillation. — The  time  of  vi- 
bration. 

Time  of  Vibration. — The  time  required 
for  a  complete  to-and-fro  motion  of  the 
particles  of  an  elastic  medium. 

Time  Register. — Any  device  for  register- 
ing a  lapse  of  time. 

Time  Register  for  Railroads. — A  tele- 
graphic apparatus  or  register  designed  to 
record  a  telegraphic  message  transmitted 
over  a  line. 

Time  Relay. — (1)  A  relay  employed  in  a 
form  of  stock  ticker  for  momentarily  de- 
laying the  releasing  of  a  clutch  and  the 
closing  of  a  transmitter,  until  the  print- 
ing of  a  given  letter  has  been  assured. 
(2)  A  relay  employed  in  a  system  of  time 
signalling. 

Time-Rise  of  Electromotive  Force  of 
Secondary  Cell. — A  gradual  increase  in 
the  potential  difference  of  a  secondary  or 
storage  cell  observed  during  charge. 

Time  Switch. — (1)  A  switch  arranged  to 
open  or  close  a  circuit  at  a  certain  time 
or  after  the  lapse  of  a  certain  time 
(2)  An  automatic  switch  in  which  a  pre- 
determined time  is  required  either  to  in- 
sert a  resistance  into  or  remove  it  from 
a  circuit. 

Time  Telegraph. — A  general  term  for  the 
apparatus  employed  in  time  telegraphy. 

Time  Telegraphy. — A  system  for  the  tel- 
egraphic transmission  of  time. 

Tinned  Wire. — Wire  electro-plated  with 
tin. 

Tinning  Metal. — The  solder  employed  in 
joining  electrotype  shells  or  for  preparing 
their  backs  for  the  reception  of  the  back- 
ing metal. 

Toe  of  Grapnel. — A  prong  of  a  cable 
grapnel. 

Toll  Station. — A  pay  telephone  or  tele- 
graph station. 

Toll  System. — A  system  of  charging  for 
telephone  communications  based  upon 
telephone  calls,  as  distinguished  from  a 
charge  based  upon  rental. 

Tone. — Any  musical  note  of  a  definite  fre- 
quency. 

Tongue  of  Relay. — The  tip  or  extremity 
of  the  armature,  carrying  a  contact  point. 

Tooling. — The  operation  of  shaping  a 
gutta-percha  covered  joint  by  the  appli- 
cation of  a  warm  tool  to  its  surface. 

Toothed-Core  Armature. — A  laminated 
armature-core  whose  toothed  discs  pro- 


Too.] 


964 


[Toil. 


vide  longitudinal  grooves  on  the  surface 
of  the  armature  for  the  reception  of  the 
armature  coils. 

Toothed-Core  Discs.— The  discs  employed 
in  a  toothed-core  armature. 

Toothed-Drum  Armature.  —  A  drum- 
shaped  form  of  toothed-core  armature. 

Toothed-Ring  Armature.  —  A  ring- 
shaped  form  of  toothed-core  armature. 

Top-Hat  Curve. — A  curve  of  electro- 
motive force,  current  or  flux  •which  lias 
the  shape  of  a  top  hat,  that  is,  in  which 
the  value  is  fairly  constant  for  a  consid- 
erable time  at  its  maximum  rise  and  fall. 

Topler-Holtz  Machine. — A  form  of  elec- 
trostatic induction,  or  influence,  machine. 

Torch  Signalling.— A  form  of  flash  sig- 
nalling. 

Tore. — A  toroid. 

Toroid. — A  solid  of  revolution  bounded  by 
a  surface  generated  by  revolving  any 
closed  plane  curve  about  an  axis  in  its 
plane  which  does  not  cut  it. 

Toroidal  Coil.— <1)  A  coil  wound  in  the 
form  of  a  toroid.  (2)  A  closed  circular 
solenoid. 

Toroidal  Current-Sheet.  —  A  uniform 
current-sheet  having  the  form  of  a 
toroid. 

Torpedo  Boat. — A  boat  used  for  carrying 
and  discharging  torpedoes. 

Torpedo  Cable. — (1)  A  cable  in  the  circuit 
of  which  a  torpedo  fuse  is  placed.  (2)  A 
cable  designed  for  use  with  a  torpedo. 

Torpedo,  Electric. — (1)  A  name  some- 
times given  to  an  electric  ray.  (2)  An 
electrically  operated  torpedo. 

Torpedo  Nets. — Steel-wire  netting  sus- 
pended from  or  attached  to  a  ship's  side 
for  the  purpose  of  ensuring  protection 
against  moving  torpedoes. 

Torque. — (1)  The  moment  of  a  force  ap- 
plied to  a  dynamo  or  other  machine  which 
causes  its  rotation.  (2)  The  mechanical 
rotary  or  turning  force  which  acts  on  the 
armature  of  a  dynamo-electric  machine, 
or  motor,  and  causes  it  to  rotate.  (3)  The 
ratio  of  the  mechanical  activity  of  a 
motor,  at  its  belt  or  pulley,  to  the  angular 
velocity. 

Torque  Efficiency.— The  ratio  of  the 
torque  exerted  by  a  motor  at  a  given  in- 
put or  terminal  electric  activity,  to  the 
torque  it  would  exert  if  it  were  a  perfect 
machine  and  had  no  loss  of  energy. 

Torqueless  Stress. — A  twistless  stress,  or 
stress  which  produces  no  torque. 

Torricellian  Vacuum.  —  The  vacuum 
which  exists  above  the  surface  of  the 


mercury  in  a  barometer  tube,  or  other 
vessel  over  thirty  inches  in  vertical 
height,  which  has  been  filled  with  boiled 
mercury  and  inverted  below  the,  surface 
of  the  mercury  in  a  vessel. 

Torsibility. — Possessing  the  ability  of  be- 
ing torsed  or  twisted. 

Torsion. — The  twisting  of  a  body  by  the 
application  of  a  torsional  force. 

Torsion  Galvanometer. — A  galvanom- 
eter in  which  the  strength  of  a  deflecting 
current  is  measured  by  the  torsion  exerted 
on  the  suspension  system. 

Torsional  Rigidity  of  Fibres. — The 
elastic  couple  set  up  in  a  fibre  per  unit  of 
twist. 

Torsional  Vibration. — The  vibration  pro- 
duced in  a  solid  body  by  torsion. 

Total  Candle-Power. — A  term  some- 
times used  for  the  total  quantity  of 
light  emitted  by  any  luminous  source. 

Total  Contact. — A  full  or  metallic  contact. 

Total-Current-Panel  of  Switchboard. 
That  panel  of  a  switchboard  which  is  pro- 
vided with  devices  for  measuring  and  con- 
trolling the  total  current  generated  by  a 
station. 

Total  Disconnection.— (1)  Any  discon- 
nection effected  by  the  opening  of  a 
switch  or  the  actual  breaking  of  a  circuit. 
(2)  A  complete  loss  of  continuity  in  a  cir- 
cuit. 

Total  Earth. — A  term  sometimes  used  for 
dead  earth. 

Total  Efficiency  of  Luminous  Source. 
The  ratio  of  the  luminous  rays  to  the 
total  energy  expended. 

Total  Intensity  of  Earth's  Magnetism. 

(1)  The  resultant  or  entire  force  of  the 
earth's  magnetism,  as  distinguished  from 
the  horizontal  or  vertical   components. 

(2)  The  flux  density  of  the  earth's  mag- 
netism. 

Total  Magnetic  Induction. — (1)  The 
number  of  lines  of  magnetizing  force 
which  pass  through  any  space  where 
magnetizable  material  is  ,_iaced.  to- 
gether with  the  lines  added  by  the  mag- 
netization of  the  magnetic  material. 
(2)  Total  magnetic  intensity,  or  in- 
duction density,  in  a  magnetized  sub- 
stance. 

Total  Resistance. — The  sum  <A  Mie  re- 
sistances of  a  circuit. 

Tourmaline. — A  crystalline  body  consist-- 
ing of  natural  silicates  and  borates  of 
alumina,  lime,  iron,  etc. ,  possessing  pyro- 
electric  properties. 


Tou.] 


965 


[Tra. 


Tourniquet,  Electric. — A  term  some- 
times used  for  an  electric  flyer. 

Tower,  Electric. — A  high  tower,  provided 
in  systems  of  tower  illumination,  for  the 
support  of  a  number  of  electric  arc-lamps. 

Tower-System  of  Electric  Lighting.— 

The  lighting  of  extended  areas  by  means 
of  arc  lights  placed  on  the  tops  of  tall 
towers. 

Tower  Wagon. — The  repair  wagon  em- 
ployed on  trolley  lines,  and  provided  with 
a  structure  for  enabling  the  workmen  to 
conveniently  reach  the  trolley  wires. 

Towing,  Electric. — Electric  hauling  of 
canal  boats.  . 

Towing  Torpedo. — A  torpedo  arranged 
to  be  towed  after  a  vessel,  and  exploded 
when  it  strikes  the  side  of  an  enemy's 
vessel. 

Track  Bond. — A  rail  bond. 

Track  Instrument.— An  electric  contact 
capable  of  being  closed  by  a  train  moving 
over  it,  placed  by  the  side  of  a  railroad 
track,  and  employed  to  sound  an  alarm 
or  indicate  at  a  distance  the  presence  of 
the  train. 

Track  Joint. — A  rail  joint. 

Track  Switch. — (1)  A  switch  for  leading  a 
car  from  one  track  to  another.  (2)  A 
mechanical  switch  in  the  rail  of  a  street- 
car track  for  changing  the  route  of  a  car. 

Track-to-Dynamo  Bonding. — A  method 
of  bonding  in  which  a  track  of  positive 
polarity  is  bonded  to  the  negative  side  of 
a  dynamo. 

Traction,  Electric. — The  propulsion  of  a 
car,  or  other  vehicle,  by  the  action  of  an 
electric  motor. 

Trailer. — (1)  An  ordinary  car  attached  to 
a  trolley  car  and  drawn  after  it.  (2)  Any 
car  hauled  by  a  motor  car. 

Trailer  Grapnel. — A  second  or  following 
grapnel  attached  to  and  travelling  behind 
an  ordinary  grapnel. 

Trailing  Pole. — (1)  The  following  pole 
edges  of  a  dynamo-electric  machine.  (2) 
The  pole  edges  of  a  dynamo-electric  ma- 
chine, from  which  a  point  on  the  surface 
of  the  armature  moves  when  midway  be- 
tween the  poles. 

Train  Describer. — (1)  An  electric  contriv- 
ance arranged  for  automatically  indicat- 

,  ing  the  position  of  trains  on  a  railroad. 
(2)  In  a  system  of  block  signalling  by 
electricity,  an  instrument  for  indicating 
at  a  distance  the  character  of  a  train 
which  is  being  sent  along  the  line. 

Train  Wire. — A  line  wire  connected  with 
the  general  despatcher's  office,  employed 


in  a  block  system  of  railroads,  and  used 
for  sending  train  orders  only. 

Trajectory. — (1)  The  curve  described  by  a 
pi'ojectile  thrown  obliquely  upwards.  (2) 
A  curve  which  cuts,  according  to  a  given 
law,  a  system  of  curves  obtained  by  vary- 
ing a  parameter. 

Tramcar,  Electric. — A  term  applied  to 
an  electric  trolley  car. 

Tramway,  Electric. — A  term  applied  tc 
an  electric  railway . 

Trans-Continental  1'elephony.— Tele- 
phonic communication  established  across 
a  continent. 

Transfer  Board. — In  telephony,  a  switch- 
board at  which  calls  are  transferred  from 
one  junction  line  to  another. 

Transfer  Bus-Bar. — A  bus-bar  that  is  em- 
ployed to  gradually  transfer  a  feeder 
from  one  bus-bar  to  another,  without  the 
sudden  variation  of  potential  which 
would  occur  if  it  were  thrown  over  di- 
rectly. 

Transfer  Operator. — In  telephony,  an  op- 
erator at  a  transfer  board. 

Transform. — (1)  To  change  or  convert. 
(2)  To  change  or  convert  the  electromo- 
tive force,  and,  consequently,  the  current 
strength  in  a  circuit,  by  any  means.  (3) 
To  change  the  type  of  a  current,  as  from 
an  alternating  into  a  continuous  current. 

Transformation. — The  act  of  transform- 
ing or  changing. 

Transformation  of  Electromotive 
Force  or  Current. — A  change  in  the 
value  of  an  electromotive  force  or  current 
by  any  means. 

Transformation  of  Electric  Force. — 
(1 )  Transformation  of  electromotive 
force.  (2)  Transformation  of  electric  en- 
ergy into  some  other  form  of  energy. 

Transformation  of  Heat. — Transforma- 
tion of  heat  energy  into  any  other  form, 
of  energy. 

Transformer. — An  induction  coil  em- 
ployed either  for  raising  or  for  lowering 
electric  pressure. 

Transformer  Connection  Board. — A 
board  employed  on  a  transformer  for  ease 
in  changing  or  inter-connecting  its  cir- 
cuits. 

Transformer  Controller. — (1)  An  appa- 
ratus for  operating  or  controlling  a  trans- 
former. (2)  A  controller  of  pressure  op- 
erated on  the  principle  of  an  alternating* 
current  transformer. 

Transformer  Fuse. — A  fuse  employed 
either  in  the  primary  or  secondary  circuit 
of  a  transformer. 


Tra.] 


966 


[Tra. 


Transformer  Fuse-Block. — A  fuse-block 
in  or  near  a  transformer  case. 

Transformer  Guard. — (1)  A  transformer 
lightning-guard.  (2)  Any  device  for 
automatically  grounding  the  secondary  of 
a  transformer  on  its  accidental  contact 
with  the  primary. 

Transformer     Indicator-Diagram. — A 

set  of  diagrams  automatically  recorded  on 
a  card,  which  give  the  instantaneous 
values  of  the  current  and  electromotive 
force  of  a  transformer  circuit. 

transformer  Lightning- Arrester. — A 
form  of  lightning  arrester  designed  for 
the  protection  of  transformers. 

Transformer  Lightning  Guard. — A 
transformer  lightning-arrester. 

Transformer  Motor. — An  induction  mo- 
tor. 

Transformer  Secondary  Connection 
Board. — A  separate  transformer  connec- 
tion board  provided  for  its  secondary 
circuits. 

Transformer  Stampings. —  Sheet  steel 
stampings  of  such  shape  as  is  suitable  for 
building  up  the  laminated  core  of  a  trans- 
former. 

Transformer  Sub-Station. — A  sub-sta- 
tion where  a  number  of  transformers  are 
grouped,  designed  as  a  sub-centre  of  dis- 
tribution. 

Transforming.— (1)  Changing  electric  en- 
ergy from  lower  pressure  and  higher  cur- 
rent to  higher  pressure  and  lower  current 
or  vice-versA.  (2)  Changing  the  charac- 
ter of  a  current. 

Transforming  Currents. — Changing  the 
value  of  the  current  strength  in  any 
circuit,  with  a  corresponding  opposite 
change  in  pressure. 

Transforming  Down.  —  Lowering  the 
pressure  in  a  distribution  circuit  by  means 
of  a  step-down  transformer. 

Transforming  Station. — (1)  In  a  system 
of  distribution  by  transformers,  a  station 
other  than  a  central  station,  where  a  num- 
ber of  transformers  are  placed  in  order  to 
supply  a  group  of  houses  in  that  neighbor- 
hood. (2)  A  transformer  sub-station. 

Transforming  Up. — Raising  the  pressure 
in  a  distribution  circuit,  by  means  of  a 
step-up  transformer. 

Transient. — (1)  Momentary.  (2)  Lasting 
or  enduring  but  for  a  short  time. 

Transient  Currents. — Currents  that  are 
of  but  momentary  duration. 

Transient  Magnetomotive  Force. — (1) 
A  momentary  magnetomotive  force.  (2) 


A  magneto-motive  force  produced  by  the 
momentary  passage  of  an  electric  current. 

Trans-Illumination. — Such  an  illumina- 
tion of  an  interior  cavity  of  the  body  as 
to  permit  it  to  be  visible  through  the  in- 
tervening portions  of  the  body  as  a  trans 
lucent  screen. 

Transition  Layer. — A  layer  marking  the 
separation  of  two  homogeneous  bodies  at 
which  the  electric  or  magnetic  proper- 
ties pass  with  great  rapidity  from  one 
value  to  another. 

Transition  Resistance.— (1)  A  term 
sometimes  used  in  electro-therapeutics 
for  a  change  in  the  value  of  a  resistance 
caused  by  polarization.  (2)  Resistance 
residing  in  the  contact  surface  between  a 
solid  and  a  liquid,  or  between  two  solids. 

Translator. — A  telegraphic  translator  or 
repeater. 

Translating  Commutator.—  A  term 
sometimes  used  for  translation  commu- 
tator. 

Translating  Device. — A  name  frequently 
given  to  an  electro-receptive  device. 

Translating  Telegraphic  Station. — 
(1)  A  receiving  station.  (2)  Any  station 
at  which  a  telegraphic  message  is  auto- 
matically repeated  into  another  circuit. 

Translation  Commutator. —  A  name 
sometimes  given  to  a  switch  on  a  trans- 
lating board. 

Translation  Lag. — A  lag  due  to  the 
traverse  of  an  active  conductor  past  a 
magnet  pole,  whereby  the  current  in  the 
conductor  is  displaced  in  the  direction  of 
the  motion,  and  produces  a  moving  field, 
the  iron  mass  or  body  tending  to  accom- 
modate itself  to  the  direction  of  the  flux 
in  the  moving  field. 

Translator. — An  orthography  for  tran- 
slator. 

Translator  Keys. — Keys  employed  in  a 
translator  for  signalling  on  either  circuit. 

Translucence. — Possessing  the  property 
of  transmitting  light  but  of  preventing 
the  outlines  of  objects  from  being  seen. 

Translucent. — Possessing  the  property  of 
translucence. 

Translucent-Disc  Photometer.— A 
photometer  in  which  the  light  to  be  meas- 
ured is  placed  on  one  side  of  a  partly 
translucent  and  partly  opaque  disc,  and 
the  standard  candle,  or  other  photometric 
standard,  is  placed  on  the  opposite  side, 
the  intensity  of  the  light  being  estimated 
by  the  distance  of  the  lights  from  the  disc, 
when  an  equal  illumination  is  obtained 
over  both  surfaces. 


Tra.] 


967 


[Tre. 


Transmission  Circuit,  Electric.— The 
circuit  employed  to  receive  the  apparatus 
necessary  in  any  transfer  of  electric  en- 
ergy from  the  generators  to  the  receptive 
devices. 

Transmission  Dynamometer.— A  dyna- 
mometer in  which  the  mechanical  power 
that  is  measured  is  transmitted  to  some 
machine,  as  distinguished  from  a  dyna- 
mometer which  measures  and  at  the  same 
time  absorbs  the  energy. 

Transmission,  Electric. — The  transfer- 
ence of  energy  from  one  po^nt  to  another 
by  means  of  electric  currents. 

Transmission  Insulator.— (1)  An  insu- 
lator employed  on  transmission  lines.  (2) 
A  high-tension  insulator. 

Transmission  Line. — A  transmission  cir- 
cuit. 

Transmission  of  Energy. — The  trans- 
ference of  energy  from  one  point  to  an- 
other. 

Transmission  of  Electric  Energy. — The 
transference  of  electric  energy  from  one 
point  to  another. 

Transmitted  Power. — Power  that  is 
transferred  from  one  point  to  another. 

Transmitter,  Electric. — (1)  A  general 
name  applied  to  the  various  electric  ap- 
paratus employed  in  telegraphy  or  tele- 
phony to  transmit  or  send  electric  im- 
pulses over  a  line  wire  or  conductor. 
(2)  Any  electric-transmitting  instrument, 
as  distinguished  from  a  receiving  instru- 
ment. 

Transmitting  Magnet. — The  magnet  em- 
ployed in  any  transmitting  instrument. 

Transmitting  Station. — A  station  from 
which  any  electric  signals  or  impulses  are 
sent. 

Transposing. — In  a  system  of  telephonic 
communication,  a  device  for  avoiding  the 
bad  effects  of  mutual  induction,  by  alter- 
nately crossing  equal  lengths  of  consecu- 
tive sections  of  the  line. 

Transposition. — The  transposing  of  a  tele- 
graph or  telephone  circuit. 

Transposition  Insulator. — A  special 
form  of  insulator  provided  for  the  ready 
transposition  of  a  telephone  circuit. 

Transposition  Joints  of  Telephone 
Circuit. — The  joints  employed  on  a  tele- 
phone circuit  at  the  transposition  in- 
sulators. 

Transverse  Electromotive  Force.— An 
electromotive  force  excited  by  a  magnetic 
field  in  a  substance  in  which  electric  dis- 
placement is  occurring. 

Transverse  Vibration.— A  vibration  in 


an  elastic  medium  in  which  the  successive 
particles  move  at  right  angles  to  the  direc- 
tion in  which  the  wave  is  progressing 
through  the  medium. 

Travelling  Derrick.— A  derrick  sup- 
ported on  guideways,  on  a  platform  over 
which  it  is  movable,  provided  for  shifting 
or  moving  heavy  masses  through  short 
distances. 

Travelling  Dynamo. — A  dynamo  mount- 
ed on  a  movable  platform. 

Travelling  Motor.— (1)  A  motor  placed 
on  a  movable  car  or  carriage,  as  distin- 
guished from  a  stationary  motor.  (2)  A 
locomotor. 

Travelling  of  Arc. — An  unsteadiness  pro- 
duced in  the  light  of  a  carbon  arc  occa- 
sioned by  the  shifting  of  the  position  of 
the  arc  between  the  electrodes. 

Traversing  Motor,  Electric.— (1)  A  mo- 
tor which  moves  regularly  to-and-fro, 
through  a  limited  distance.  (2)  In  an 
electrically  operated  crane,  the  motor 
which  operates  the  traverse. 

Tread  of  Car  Wheel.— The  running  face 
of  a  car  wheel,  or  the  part  that  comes  in 
contact  with  the  surface  of  the  track. 

Treated  Coke  Filament. — A  coke  fila- 
ment of  an  incandescent  lamp  that  has 
been  subjected  to  the  flashing  process. 

Tree-System  of  Parallel  Distribution. 
A  system  of  parallel  distribution  of  in- 
candescent lamps,  in  which  the  main 
conductors  of  the  system  resemble  the 
trunk  of  a  tree,  and  the  auxiliary  leads 
branch  in  various  directions,  somewhat 
after  the  fashion  of  a  spreading  tree,  the 
lamps  occupying  the  place  of  the  twigs, 
leaves  and  fruit. 

Tree  Insulator. — (1)  An  insulator  placed 
on  a  tree  for  the  support  of  an  aerial  wire. 
(2)  A  variety  of  insulator  suitable  for  at- 
tachment to  trees,  and  designed  so  as  to 
keep  the  conductor  in  normal  position, 
despite  the  movement  of  the  tree. 

Tree  Wire. — A  special  form  of  insulated 
wire  designed  to  resist  the  abrasion  of 
the  insulating  substance,  when  rubbed 
against  a  rough  surface,  like  the  bark  of 
a  tree. 

Trega. — A  prefix  for  a  trillion,  or  one  mil- 
lion millien,  or  1012. 

Tregadyne. — A  trillion  dynes,  or  roughly 
the  weight  of  a  thousand  tons. 

Tregerg. — One  trillion  ergs,  or  73,730  foot- 
pounds at  Greenwich  ;  or,  approximately. 
33  foot-tons. 

Tregohm. — One  trillion  ohms,  or  one  mil- 
lion megohms. 


Tre.J 


968 


[Tri. 


Tregohm  Galvanometer. —  A  galvano- 
meter which  gives  unit  deflection  through 
a  resistance  of  one  tregohm,  in  circuit 
with  one  volt. 

Trembler. — A  name  sometimes  applied  to 
a  trembling  bell. 

Trembler  Bell. — A  trembling  bell. 

Trembling  Bell. — A  form  of  vibrating  or 
automatic  make-and-break  contact  bell. 

Trevelyan  Effect. — A  musical  note 
emitted  under  certain  circumstances 
when  a  mass  of  heated  copper  is  supported 
on  thin  edges  on  a  block  of  cold  lead. 

Triad  Atom. — An  atom  whose  valency  or 
atomicity  is  three. 

Triangular  Trip  base  Winding.  —  A 
word  sometimes  employed  for  the  inter- 
linked or  three-wire  triphase. 

Triangular  Triphaser. — A  triangularly 
wound  triphaser. 

Tricro. — A  prefix  signifying  one  trillionth 
part,  or  1CM2. 

Tricro- Ampere. — The  one  trillionth  of  an 
ampere. 

Tricro-Farad. — The  one  trillionth  of  a 
farad. 

Tricron. — One  trillionth  of  a  metre,  or 
KM2  metre. 

Tricrohm. — The  one  trillionth  of  an  ohm. 

Trifilar  Suspension. — A  suspension  sup- 
ported by  three  parallel  fibres. 

Trigonometrical. — Of  or  pertaining  to 
trigonometry,  or  the  science  of  angles, 
their  relations,  and  properties. 

Trigonometrical  Functions.  —  Certain 
quantities  definitely  related  to  angles 
considered  as  independent  variables. 

Trigonometrically. — In  a  trigonometri- 
cal manner. 

Trigonometry. — That  branch  of  mathe- 
matical science  which  treats  of  angles  and 
their  properties,  in  triangles  or  otherwise. 

Trimmer. — A  name  sometimes  given  to  a 
man  who  recarbons  electric  arc-lamps. 

Trimming  a  Lamp. — Re-carboning  an 
arc  lamp. 

Trimming  a  Wire. — (1)  Preparing  a  wire 
for  jointing  or  connecting  to  an  instru- 
ment. (2)  Baring  a  wire  of  insulation 
and  cleansing  its  conducting  surface. 

Triode  Working. — A  three-way  mode  of 
telegraphic  working  by  the  Delany  syn- 
chronous multiplex  telegraphic  system. 

Trip  Indicator. — A  form  of  indicator  in 
which  the  indicator  arm  or  drop  is  disen- 
gaged by  the  tripping  action  produced  by 


the  movement  of  the  armature  of  an  elec« 
tro-magnet. 

Triphase. — A  word  frequently  employed 
for  three-phase. 

Triphase  Armature.  —  A  three-phase 
armature. 

Triphase  Armature- Windings.— Three- 
phase  armature  windings. 

Triphase  Circuit. — A  three-phase  circuit. 
Triphase-Current. — A   three-phase  cur- 
rent. 

Triphase  Dynamo. — A  dynamo  capable 

of  producing  three-phase  currents. 
Triphase      Generator.  —  A      triphase 

dynamo. 
Triphase  Motor. — A   motor  capable   of 

being  operated  by  triphase  currents. 
Triphase  Rotary-Field. — A  rotary  field 

produced  by  the  simultaneous  action  of 

triphase  currents. 

Triphase  Rotary-Transformer. — A  ro- 
tary transformer  operated  by,  or  produc- 
ing three-phase  currents. 

Triphase  Rotating-Magnetic  Field.— 
A  triphase  rotary  field. 

Triphase  Transformers. — (1)  Three  sep- 
arate transformers  employed  for  chang- 
ing the  pressure  on  triphase  circuits. 

(2)  A  single  transformer  having    three 
separate  triphase  windings. 

Triphase  Alternating-Currents.  — 
Three  uniphase  alternating-currents 
whose  phases  are  displaced  with  regard 
to  one  another  by  one-third  of  a  cycle. 

Triphaser. — A  triphase  generator. 

Triple-Carbon  Arc-Lamp.  —  An  arc- 
lamp  in  which  three  carbon  electrodes 
are  used. 

Triple  Connector. — A  connector  suitable 
for  uniting  the  ends  of  three  wires. 

Triple  Petticoat  Insulator. — An  aerial 
line  insulator  provided  with  a  triple  pet- 
ticoat. 

Triple-Pole  Single-Throw  Switch. — 
A  single-throw  switch  having  three 
blades,  and  intended  for  closing  three 
circuits  simultaneously. 

Triple-Pole  Switch. — (1)  A  switch  consist- 
ing of  a  combination  of  three  separate- 
switches  for  opening  or  closing  three  cir- 
cuits at  the  same  instant.  (2)  A  switch 
employed  to  open  or  close  three  contacts. 

(3)  A  switch  employed  to  open  or  close 
triphase  circuits. 

Triple-Truck  Support. — (1)   A  support 
for  a  car  body,  consisting  of  three  sep» 
rate  trucks.     (2)  A  radial-truot  supportt 


Tri,] 


969 


[Tro, 


Triplex  Telephony.— (1)  The  simultan- 
eous telephonic  transmission  of  three 
distinct  messages  over  the  same  wire  in 
the  same  direction. 

Triply  He-Entrant  Armature  Wind- 
ing. —  An  armature  winding  provided 
with  three  independent  conducting  paths 
or  windings  each  of  which  is  separately 
re-entrant. 

Tripod  Roof  Support. — A  roof-top  sup- 
port for  a  telegraph  line,  in  the  shape  of 
a  tripod. 

Tripping  Coil. — A  coil  forming  part  of  the 
mechanism  of  a  circuit-breaker  on  the 
switchboard  of  a  central  railroad  station, 
so  arranged  that  when  the  current  has 
reached  a  certain  predetermined  value, 
limited  by  the  action  of  a  spring,  the  trip- 
ping mechanism  is  operated,  thus  break- 
ing the  circuit. 

Trivalent. — Possessing  an  atomicity  or 
valency  of  three. 

Trolley. — A  rolling  contact-wheel  that 
moves  over  a  trolley  line  and  carries  off 
the  current  required  to  drive  the  motor 
cars. 

Trolley  Base. — A  base  provided  for  the 
support  of  a  trolley  pole,  and  furnished 
with  springs  to  preserve  a  firm  contact 
between  the  trolley  and  the  trolley  wire, 
and  also  provided  with  a  swivel  joint  for 
readily  reversing  the  direction  of  the 
trolley  pole. 

Trolley  Base-Frame. — A  trolley  base. 

Trolley  Bus-Bar. — In  a  railway  power 
station,  the  bus-bar  connected  with  the 
trolley  system,  as  distinguished  from  the 
bus-bar  connected  with  the  ground. 

Trolley  Car. — A  motor  car  in  a  system  of 
electric  railroads  employing  a  trolley 
system. 

Trolley  Car-Controller. — (1)  A  series-par- 
allel controller.  (2)  A  car-controller. 

Trolley-Contact. — The  contact  secured 
between  a  trolley  and  the  trolley  wire. 

Trolley-Cord. — The  cord  attached  to  the 
trolley  pole  or  mast  for  removing  it  from 
and  placing  it  on  the  line. 

Trolley-Crossing. — (1)  An  insulating  de- 
vice, placed  at  the  crossing  of  two  trolley 
wires,  by  which  the  trolley,  while  run- 
ning on  one  line  may  cross  the  other  with- 
out coming  into  electrical  contact  with  it. 
(2)  A  plate  supported  at  the  crossing  of 
two  trolley  wires  with  guides  to  assist 
the  trolley  wheel  across  it. 

Trolley  Crossing-Ear. — An  ear  employed 
at  a  trolley  crossing. 

Trolley  Cross-Over. — (1)  An  arrangement 


for    suspending    the  trolley  wires  at  a 
trolley  crossing.     (2)  A  trolley  crossing. 
Trolley  Ear. — A  metal  piece  supported  by 
an  insulator,  to  which  the  trolley  wire  ia 
fastened. 

Trolley  Fork.— The  mechanism  which 
mechanically  connects  the  trolley  wheel 
to  the  trolley  pole. 

Trolley  Frog.— (1)  The  device  to  which 
the  trolley  wire  is  attached,  employed  for 
causing  a  car  to  deviate  from  one  line  to 
another.  (2)  A  name  given  to  the  device 
employed  in  fastening  or  holding  together 
the  trolley  wires  at  any  point  where  the 
wires  branch,  and  properly  guiding  the 
trolley  along  the  trolley  wire  on  the 
movement  of  the  car  over  the  track, 
under  the  action  of  the  track  switch. 

Trolley  Guard. — A  trolley  wire  guard. 

Trolley  Hanger. — A  device  for  support- 
ing and  properly  insulating  a  trolley  wire. 

Trolley  Harp.— The  metallic  frame  placed 
on  a  trolley  fork  for  supporting  the  trolley 
wheel. 

Trolley  Ice-Clearer. — A  form  of  trolley 
wheel  suitable  for  removing  ice  or  sleet 
from  a  trolley  wire. 

Trolley  Insulator. — A  name  sometimes 
applied  to  a  trolley  ear. 

Trolley  Insulated  Crossing. — An  insu- 
lated trolley  crossing. 

Trolley  Mast.— A  term  frequently  used 
for  trolley  pole. 

Trolley  Mechanism. — (1)  The  device  em- 
ployed for  carrying  the  current  from  the 
trolley  line  to  the  motor  in  the  car.  (2) 
A  general  mechanism,  including  the 
trolley  base,  pole,  wheel  and  rope. 

Trolley  Pole. — A  pole,  or  mast,  of  wood 
or  metal  supporting  the  trolley  and  em- 
ployed to  carry  a  conductor  from  the  car 
to  the  trolley  wire. 

Trolley  Section. — (1)  A  single  continuous 
length  of  trolley  wire.  (2)  A  portion  of  a 
trolley  line  insulated  from  adjoining  por 
tions  and  furnished  with  separate  feed 
wires. 

Trolley  Railway. — An  electrically  oper 
ated  railroad  employing  a  trolley. 

Trolley  Stand. — (1)  A  word  sometimes 
used  for  a  trolley  base.  (2)  A  support 
provided  for  a  trolley  pole. 

Trolley  Strain-Insulator. — An  insulator 
provided  for  the  support  of  the  strain 
wires. 

Trolley  Strain- Wires. — Wires  employed 
for  attachment  to  lugs  in  the  anchor 
strain  ear,  for  the  purpose  of  maintaining 
the  trolley  line  taut. 


Tro.J 


970 


LTru, 


Trolley  Switch. — (1)  A  switch  placed  on  a 
track  for  the  purpose  of  changing  the 
car  from  one  track  to  another.  (2)  An 
overhead  switch  provided  at  a  turn  of  a 
trolley  road  for  guiding  the  trolley  to 
another  line  when  the  frogs  on  the  track 
beneath  have  thrown  the  wheels  of  the 
car  into  another  track. 

Trolley  Three-Way  Prog.— A  trolley 
frog  used  where  the  line  branches  in 
three  directions. 

Trolley  Traction. — Electric  traction  by 
the  trolley  system. 

Trolley  Truck.  —  The  truck  supporting 
a  trolley  car  and  containing  the  car 
motors. 

Trolley  Two-Way  Frog. — The  ordinary 
V-shaped  trolley  frog. 

Trolley  Wheel. — (1)  A  metallic  wheel 
connected  with  the  trolley  pole  and  moved 
over  the  trolley  wire,  for  the  purpose  of 
taking  therefrom  the  current  required 
for  driving  the  motor  car.  (2)  The  trolley. 

Trolley  Wire. — The  bare  overhead  wire 
employed  in  a  trolley  system  for  supply- 
ing the  driving  current  to  the  car  motors 
through  the  intervention  of  the  trolley 
mechanism. 

Trolley  Wire  Insulator. — The  insulator 
provided  for  the  support  of  a  trolley  wire. 

Trolley  Wire  Splice. — A  joint  or  splice 
employed  in  joining  two  ends  of  trolley 
wires,  consisting  essentially  in  slipping 
the  ends  in  a  tubular  conductor  and 
then  brazing  them. 

Trop. — A  proposed  unit  of  entropy  equal 
to  the  quotient  of  one  joule  divided  by  one 
degree  Centigrade. 

Truck  for  Car  Motor. — A  support  pro- 
vided with  wheels,  and  employed  either 
singly,  or  in  connection  with  one  or  more 
similar  trucks,  for  the  support  of  the  car 
body. 

True  Contact  Force. — The  force  or  effect, 
distinguished  from  the  voltaic  effect 
which  exists  at  the  points  of  contact  be- 
tween two  dissimilar  metals. 

True  Galvanometer  Constant. — The 
intensity  of  the  field  produced  at  the 
centre  of  a  galvanometer  coil  by  a  unit 
current  flowing  through  the  coil. 

True  Ohm. — (1)  An  ideal  ohm  having  the 
true  theoretical  value.  (2)  A  term  some- 
times applied  to  the  International  ohm  in 
contradistinction  to  the  B.  A.  or  legal 
ohm. 

True  Power. — In  an  alternating-current 
circuit  the  power  which  is  represented 
by  the  true  watts,  as  distinguished  from 


the  apparent  power,  or  that  represented  by 
the  apparent  watts. 

True  Resistance. — The  resistance  which 
a  conductor  offers  to  the  passage  of  a  cur- 
rent, by  reason  of  its  dimensions  and 
resistivity,  as  distinguished  from  the 
spurious  resistance  produced  by  a  counter 
electromotive  force. 

True  Watts. — The  activity  in  an  alternat- 
ing-current circuit,  as  given  by  the  read- 
ing of  a  correctly  calibrated  wattmeter 
connected  with  such  circuit. 

True  Zero. — An  instrument  or  scale  zero, 
as  distinguished  from  a  false  zero  of  a 
galvanometer. 

Trumpet,  Electric.— An  electro-magnetic 
buzzer  whose  sound  is  strengthened  by  a 
trumpet- shaped  resonator. 

Trunion  Screws. — A  pair  of  screws  whose 
opposed  points  form  the  pivots  of  a  mov- 
able shutter,  armature,  or  other  rotating 
device. 

Trunk  Call. — A  telephone  call  transmitted 
through  a  trunk  wire. 

Trunk  Connection. — A  telephonic  con- 
nection established  through  a  trunk  wire. 

Trunk  Junction -Board. — A  junction 
telephone  switchboard  for  trunk  wires. 

Trunk-Line  Wires.— (1)  Through  wires 
extended  between  two  distant  stations, 
provided  with  receiving  and  transmitting 
instruments  aj.  their  ends  only.  (&)  In 
telephony,main  line  wires  connecting  two 
terminal  offices  for  connection  to  sub- 
offices  or  subscribers.  (3)  A  main  line 
wire  connecting  two  important  terminals 
for  receiving  telephone  traffic. 

Trunk-Line  Working. — Telephone  work- 
ing embracing  the  use  of  trunk  lines  be- 
tween central  stations,  as  distinguished 
from  lines  connecting  a  central  station 
with  subscribers. 

Trunk  Operator.— In  telephony,  an  oper- 
ator at  a  trunk  switchboard. 

Trunk  Switchboard. — In  telephony,  a 
switchboard  at  which  trunk  lines  termi- 
nate. 

Trunk  Wire. — (1)  A  trunk  line  wire.  (2) 
A  main  telephone  wire.  (3)  A  connect- 
ing wire  running  from  town  to  town,  or 
exchange  to  exchange,  as  distinguished 
from  a  wire  connected  permanently  tc  a 
subscriber. 

Trunk  Working. — Telephonic  or  tele- 
graphic transmission  by  means  of  trunk 
line-wires. 

Trunking  -  Out  Telephone  Switch- 
board.— A  form  of  telephone  switch* 
board  employed  in  long-distance  working, 


Tru.] 


971 


[Twi. 


Trunking  Switchboard. — A  switchboard 
in  which  a  few  subscribers  only  are  con- 
nected to  the  operator,  thus  enabling  him 
to  obtain  any  other  subscriber  by  means 
of  trunk  wires  extending  to  other  sec- 
tions. 

Trunking  Telephone  System. — (1)  A 
system  of  telephony  employing  trunk 
wires.  (2)  A  system  of  telephony  in  which 
multiple  switchboards  are  dispensed  with, 
and  all  calls  are  trunked  from  the  in- 
coming to  the  outgoing  panel. 

Trussed  Pole. — A  pole  which  has  been 
strengthened  against  lateral  pull  by  the 
use  of  an  outrigger  and  stays. 

Trussed  Standard. — A  standard  which 
has  been  strengthened  to  resist  lateral 
stresses  by  the  use  of  an  outrigger  and 
stays. 

Tube  of  Flow. — A  word  sometimes  used 
for  a  tube  of  force. 

Tube  of  Force. — An  imaginary  tube  in 
electrified  or  magnetized  space,  bounded 
by  lines  of  electrostatic  or  magnetic  force, 
and  intersected  by  equipotential  surfaces. 

Tube  of  Induction. — In  a  space  occupied 
by  magnetic  induction,  an  imaginary  tube 
of  induction  flux  bounded  by  induction 
lines. 

Tube  of  Magnetic  Force. — In  magnet- 
ized space,  a  tube  bounded  by  lines  of 
magnetic  force. 

Tubular  Annunciator  Drop. — A  special 
form  of  telephone  annunciator-drop  in 
the  shape  of  a  tube,  and  provided  with 
an  iron-clad  magnet. 

Tubular  Braid. — A  braid  of  fibrous  insu- 
lating material,  woven  in  the  form  of  a 
tube,  and  provided  for  drawing  over  a 
joint  after  the  two  wires  have  been  con- 
nected. 

Tubular  Conductors. — Conductors  in  the 
shape  of  tubes. 

Tubular  Connectors. — Connectors  in  the 
shape  of  tubes. 

Tubular  Current. — (1)  A  term  sometimes 
applied  to  the  current  that  traverses  the 
superficial  portions  only  of  a  solid  con- 
ductor. (2)  A  current  flowing  through  a 
tube,  or  having  a  distribution  such  as 
would  be  produced  by  flow  through  a 
tube. 

Tubular  Electro-Magnet. — An  electro- 
magnet of  a  tubular  form. 

Tubular  Magnet. — (1)  A  magnet  in  which 
a  single  coil  enclosing  a  core  is  surrounded 
by  an  iron  cylinder  connected  to  the  core 
at  one  end  by  an  iron  base  or  yoke.  (2) 
A  form  of  iron-clad  magnet. 


Tumbler  Switch. — A  switch  provided 
with  a  double-contact  knife-blade  which 
can  be  readily  depressed  by  the  movement 
of  a  bolt  lever  placed  at  the  top. 

Tumbling  Box. — (1)  A  rotating  box  in 
which  metallic  articles  that  are  to  be 
electro-plated  are  placed,  so  as  to  be 
polished  by  attrition  against  one  another. 
(2)  A  rotating  box  in  which  rough  cast- 
ings are  placed  for  smoothing  their  sur- 
faces by  attrition. 

Tuning-Fork  Dynamo. — An  oscillatory 
dynamo. 

Tuning-Fork  Interrupter. — A  reed  in- 
interrupter. 

Tuning  of  Electric  Circuit.— Altering 
the  period  of  a  circuit,  or  varying  either 
its  capacity  or  self-induction,  so  as  to 
bring  it  in  resonance  with  another  circuit. 

Tunnel  Armature. — An  armature  of  a 
dynamo-electric  machine  in  which  the 
conductors  are  placed  in  holes,  or  nearly 
closed  grooves,  beneath  the  external 
surface  of  the  core. 

Turnbuckle. — (1)  An  appliance  for  strain- 
ing span  wires.  (2)  A  screw  tightener 
for  a  rod,  guy,  or  line. 

Turn-Out. — (1)  A  short  section  of  single 
track  which  allows  two  cars  to  pass  one 
another  on  a  single  track  line .  (2)  A  short 
side  section  placed  at  a  station  on  a  single- 
track  road  for  switching  a  car  off  the  main 
line  so  as  to  leave  it  clear. 

Turn-Table,  Electric. — A  table  suitable 
for  show-windows  revolved  around  a  ver- 
tical axis  by  means  of  an  electric  motor. 

Turret-Turning  Motor. — A  motor  em- 
ployed on  board  a  war-ship  for  turning  a 
gun  turret. 

Turtle-Back  Electro. — A  curved  electro- 
type employed  for  use  in  cylindrical 
presses. 

Twigs. — (1)  A  term  sometimes  applied  te 
the  branches  or  conductors  connected 
with  the  sub-mains  in  a  system  of  incan- 
descent distribution.  (2)  Sub-branches, 

Twin-Carbon  Arc-Lamp. — A  double-car- 
bon arc-lamp. 

Twin  Conductors. — Two  parallel  con- 
ductors, laid  side-by-side,  and  covered  by 
a  simple  coating  of  braid. 

Twin  Filament  Lamp. — A  double-fila- 
ment lamp. 

Twin  Wire. — A  conductor  consisting  of 
two  separate  conductors  bound  together 
by  an  insulating  covering. 

Twin- Wire  Circuit. — A  circuit  formed 
of  twin  conductors. 


Twi.] 


972 


[Two. 


Twist  System. — A  system  of  running 
overhead  wires  for  the  purpose  of  destroy- 
ing mutual  inductive  disturbances,  and 
consisting  in  giving  to  the  wires  a  helical 
twist  as  they  run. 

Twist  in  Armature  Leads. — A  displace- 
ment of  the  ends  of  the  armature  wires 
connected  with  the  commutator  seg- 
ments, as  regards  the  position  of  the  coils 
on  the  armature,  for  the  purpose  of  ob- 
taining a  more  convenient  position  for 
the  diameter  of  commutation,  and,  con- 
sequently, for  the  points  of  contact  of  the 
collecting  brushes  on  the  commutator. 

Twist  in  Leads. — A  twist  given  at  regu- 
lar intervals,  to  the  leads  of  twin  con- 
ductors, for  the  purpose  of  avoiding  the 
effects  of  induction. 

Twisted  Bunched-Cable.— A  bunched 
cable,  the  separate  conductors  of  which 
consist  of  twisted  pairs  placed  in  succes- 
sive layers. 

Twisted  Double-Conductors.— A  pair 
or  a  number  of  pairs  of  twisted  twin  con- 
ductors. 

Twisted  Pair  Cable.— A  cable  contain- 
ing one,  several,  or  many  twisted  pairs  of 
conductors,  suitable  for  metallic  circuits. 

Twisted  Pairs  of  Conductors.  —  An 
assemblage  of  twisted  pairs  of  con- 
ductors, for  metallic  circuits. 

Twisted  Strip- Voltmeter.— A  voltmeter 
consisting  of  a  twisted  strip  of  platinum- 
silver,  and  operating  by  the  tendency  of 
the  strip  to  coil  or  uncoil  when  its  tempera- 
ture is  changed  by  the  passage  through 
it  of  the  current  to  be  measured. 

Twisted  Wire-Clip.— A  clip  formed  of  a 
twisted  wire. 

Twisted  Wires. — A  term  sometimes  em- 
ployed for  transposed  aerial  telephone 
wires. 

Twisting  Force. — A  term  sometimes  used 
for  torque. 

Two-Bearing  Generator.— A  generator 
whose  rotor  is  provided  with  but  two 
bearings,  as  distinguished  from  a  three- 
bearing  generator. 

Two-Bearing  Motor. — A  motor  whose 
rotor  is  provided  with  but  two  bearings, 
as  distinguished  from  a  three-bearing 
motor. 

Two-Circuit  Armature-Winding.— An 
armature  winding  which  provides  only 
two  circuits  through  an  armature  be- 
tween the  commutator  brushes,  no  matter 
how  great  may  be  the  number  of  poles. 

Two-Circuit  Dynamo. — A  dynamo  pro- 
vided with  a  two-circuit  armature  wmdr 
ing. 


Two-Circuit  Multiple  -  Winding.  —  A 
multiple  winding  on  an  armature,  each 
component  of  which  offers  two  circuits 
to  the  current. 

Two-Circuit  Single-Wound  Armature. 
A  single-wound  armature  possessing  two 
circuits  independently  of  the  number  of 
poles  and  distinguished  by  the  fact  that 
the  pitch  is  always  forward. 

Two-Coil  Armature- Win  ding  of  Alter 
nator. — A  winding  providing  two  slots 
in  drum  armatures  or  two  coils  in  ring 
armature,  for  each  and  every  pole  in  the 
field  frame. 

Two-Coil  Armature- Winding  of  Mul- 
tiphase Alternator. — A  winding  pro- 
viding two  slots  in  drum  armatures,  or  two 
coils  in  ring  armatures,  per  phase,  for 
each  and  every  pole  in  the  field  frame. 

Two-Fluid  Voltaic  Cell.— A  double-fluid 
voltaic  cell. 

Two-Layer  Amature- Winding.— (1)  A 
winding  which  is  essentially  applied  in 
two  layers.  (2)  A  winding  having  more 
than  two  layers,  but  which  would  be 
capable  of  application  in  two  layers  only. 

Two-Liquid  Cell.— A  term  sometimes 
used  for  double-fluid  cell. 

Two-Part  Commutator. — A  commutator 
containing  two  segments  suitable  for  com- 
muting currents  in  a  single  coil  rotated 
in  a  bipolar  field. 

Two-Phase  Alternator.— A  diphase  al- 
ternator. 

Two-Phase  Armature. — A  diphase  arma- 
ture. 

Two-Phase  Circuit. — A  diphase  circuit. 
Two-Phase  Dynamo  or  Generator. — 
A  diphase  generator. 

Two-Phase  Motor. — A  diphase  motor. 
Two-Phase   Rotary  -  Transformer. — A 

diphase  rotary  transformer. 

Two-Phase-Three-Phase  Transformer. 
An  alternating-current  transformer  for 
transforming  from  two-phase  currents  to 
three-phase  currents. 

Two-Phase  Transformer. — A  diphase 
transformer. 

Two-Phase  Working.  —  Transmitting 
electric  power  by  means  of  diphase  cur- 
rents. 

Two-Phaser. — (1)  A  generator  of  diphase 
or  quarter-phase  alternating-currents. 
(2)  A  diphaser. 

Two-Point  Switch. — A  switch  by  means 
of  which  a  circuit  can  be  completed 
through  two  different  contact  points. 

Two-Point  Trolley  Switch.— A  trolley 


Two.J 


973 


[Unb. 


switch  provided  for  a  bifurcation  in  a 
road. 

Two-Pole  Dynamo-Electric  Machine. 
A  dynamo-electric  machine  whose  field 
is  produced  by  two  poles. 

Two,  Three,  or  Pour-Conductor  Cable. 
A  cable  containing  two,  three  or  four 
separate  conducting  wires. 

Two-Way  Door-Trigger.  —  A  trigger 
which  operates  both  when  the  door  is 
opened  and  when  it  is  closed. 

Two- Way  Splice-Box.  —  A  splice  box 
provided  with  two  tubular  conduits  or 
ways. 

Two- Way  Switch. — A  switch  provided 
with  two  contacts  connected  with  two 
separate  and  distinct  circuits. 

Two- Wire  Distributing  Board. — A  dis- 
tributing board  for  metallic  circuits. 

Two- Wire  Incandescent  Lighting. — 
Incandescent  lighting  from  a  single  pair 
of  mains,  as  distinguished  from  three- 
wire  incandescent  lighting. 

Two-Wire  Mains.  —  A  name  for  the 
mains  employed  in  the  ordinary  system 
of  multiple  distribution,  as  distinguished 


from  a  three-wire  main,  or  that  used  in  a 
three-wire  system. 

Two- Wire  Moulding. — A  moulding  pro- 
vided with  two  grooves,  and  employed  for 
the  reception  of  two-wire  mains  or  bran- 
ches. 

Two-Wire  Multiple-Switchboard.— A 
multiple  telephone  switchboard  in  which 
the  jacks  of  a  subscriber's  circuit  are  con- 
nected by  two  wires. 

Two- Wire  Switchboard. — A  telephone 
switchboard  with  two-wire  connections. 

Tying-In  of  Line  Wire. — Securing  aline 
wire  to  its  insulator. 

Type-Printing  Telegraphy.  —  Printing 
telegraphy. 

Type-Printing  Telegraphic  Transmit- 
ter.— A  transmitter  employed  in  printing 
telegraphy. 

Typewriter,  Electric.  —  A  typewriting 
machine  in  which  the  keys  are  only  in- 
tended to  make  the  contacts  of  circuits 
of  electro-magnets,  the  attractions  of 
whose  armatures  cause  the  movement  of 
the  type  levers  required  for  the  work  of 
printing. 


u 


TJ. — A  contraction  sometimes  employed  for 

unit. 
Ultimate  Capacity  of  Switchboard. — 

The  total  number  of  subscribers  that  a 

multiple  telephone  switchboard  can  be 

made  to  accommodate. 

Ultimate  Optical  Efficiency. — A  term 
sometimes  employed  for  the  conditions 
required  to  ensure  the  greatest  efficiency 
in  the  observation  of  small  angular  de- 
flections of  a  suspended  mirror  by  prop- 
erly proportioning  the  dimensions  of  dif- 
ferent parts  of  the  system. 

Ultra-Gaseous  Matter. — (1)  The  peculiar 
condition  of  the  matter  which  consti- 
tutes the  residual  atmospheres  of  high 
vacua.  (2)  Radiant  matter. 

Ultra-Incandescent  Lamp. — An  incan- 
descent lamp  in  which  the  filament  is 
covered  with  oxides  of  thorium,  etc.,  so 
that  their  radiative  powers  are  utilized 
by  the  glowing  filament. 

Ultra-Thermal  Lightning  Arrester. — 
An  arrester  for  protecting  instruments 
from  unduly  powerful  currents,  operated 
by  the  expansion  of  a  metallic  wire  placed 
in  the  line  circuit. 


Ultra-Ultra- Violet. — A  term  proposed  If  ot 
luminous  frequencies  far  beyond  the  vio- 
let in  the  spectrum. 

Ultra- Violet  Bays. — A  term  proposed 
for  rays  whose  frequencies  are  greater 
than  that  of  violet  light. 

Ultra-Violet  Spectrum. — That  portion 
of  the  spectrum  which  lies  beyond  the 
violet,  or  whose  frequencies  are  greater 
than  that  of  the  violet. 

Umbrella  Type  of  Generator. — A  type 
of  generator  in  which  an  umbrella-shaped 
rotor  is  revolved  around  the  stator  or 
stationary  element. 

Umbrella  Springs. — In  telephone  switch- 
board plugs,  contact-springs  pressing  out 
sideways  from  the  plug,  like  umbrella 
springs. 

Unbalanced  Load. — In  a  system  of  elec- 
tric distribution,  a  load  whose  distribu- 
tion is  unsymmetrical. 

Unbalanced  Polyphase  System. — A 
polyphase  system  in  which  the  load  and, 
therefore,  the  pressures  and  currents,  are 
not  symmetrically  distributed. 

Unbattery . — <1)  To  disconnect  from  a  bat 
tery.  (2)  To  remove  a  battery  from  a  car. 


Unto.] 


974 


[Und. 


carriage,  boat,  building,  device  or  recep- 
tacle. 

Unbuilding  of  Dynamo. — The  loss  of 
magnetization  of  a  dynamo  field. 

Undemagnetizable.— A  term  applied  to 
an  electro-magnetic  railroad  signal,  whose 
signals  are  unreversible  by  atmospheric 
causes. 

Underframe. — A  truck  of  an  electric  mo- 
tor car. 

Underground  Cable. — A  cable  suitable 
for  being  placed  underground. 

Underground-Cable  Support. — (1)  Any 
support  provided  in  a  subway  for  holding 
an  underground  cable.  (2)  A  support 
provided  for  holding  a  cable  where  it 
passes  around  the  side  of  a  manhole,  un- 
derground conduit,  or  other  similar  loca- 
tion. 

Underground-Cable  Terminal.— (1)  The 
place  where  an  underground  cable 
emerges  from  the  ground.  (2)  A  cross- 
connecting  or  distributing  board  placed 
where  an  underground  cable  enters  or 
leaves  the  ground,  in  order  to  facilitate 
the  making  and  changing  of  the  connec- 
tions. 

Underground  Conductor. — An  electric 
conductor  placed  underground,  either  by 
actual  burial,  or  by  passing  it  through 
underground  conduits  or  subways. 

Underground  Electric  Conduit. — 
(1)  An  underground  pipe  or  tube  provided 
with  a  number  of  separate  ways  or  ducts 
for  the  reception  of  electric  wires  or 
cables.  (2)  An  underground  passage- way 
or  space  provided  for  the  reception  of 
electric  wires  or  cables. 

Underground  Electric  Tube.— An  iron 
pipe  containing  three  insulated  conduc- 
tors separated  from  one  another  and  from 
the  pipe  by  means  of  a  bituminous  insul- 
ating substance,  employed  in  connection 
with  the  Edison  three-wire  system  of  dis- 
tribution. 

Underground  Railway. — A  name  some- 
times applied  to  an  under-running  trolley 
system. 

Underground  Telegraph. — (1)  A  tele- 
graph, a  large  portion  of  whose  circuit 
consists  of  underground  wires  or  conduc- 
tors. (2)  A  telephone  cable  provided  for 
use  underground. 

Underground  Telephone  Cable.—  A 
subterranean  telephone  cable,  as  distin- 
guished from  an  aerial  telephone  cable. 

Underground  Trolley  System.— A 
system  of  car  propulsion  in  which  the 
trolley  wheel  is  replaced  by  a  plow  or 
sled  that  is  pushed  before,  or  drawn  after, 


the  car  along  a  trolley  wire  placed  inside 
a  slotted  underground  conduit. 

Underground  Tube. — An  underground 
electric  tube. 

Under-Running  of  Cable. — The  opera- 
tion of  passing  a  shallow-water  cable  over 
a  boat,  barge  or  vessel  for  the  purposes  of 
examination,  by  hauling  the  cable  in  at 
the  bows,  and  allowing  it  to  pass  out  at 
the  same  time  over  the  stern  ;  or,  simply 
allowing  it  to  run  over  a  sheave  while  the 
boat  is  urged  along  the  line  of  cable. 

Under -Running  of  Incandescent 
Lamps. — The  operation  of  incandescent 
lamps  at  a  pressure  below  the  normal. 

Under-Running  Sheave. — A  supported 
sheave  for  the  admission  of  a  bight  of 
cable,  and  suitable  for  use  in  underrunning 
as  distinguished  from  a  sheave  through 
which  an  end  must  be  passed. 

Under-Running  Trolley. — (1)  A  trolley 
wheel  running  under  a  wire  in  the  usual 
way.  (2)  A  word  sometimes  used  for  un- 
derground underrunning  trolley. 

Under-Running  Trolley. — A  system  of 
street-car  propulsion  in  which  the  trolley 
wire  is  suitably  supported  in  an  under- 
ground slotted  conduit,  the  current  being 
taken  off  by  means  of  a  sled  or  shoe, 
pushed  before  or  drawn  after  the  car. 

Undertaker. — (1)  One  who  supplies  elec- 
tric energy  to  consumers.  (2)  A  word 
sometimes  used  in  electric  lighting  litera- 
ture for  those  who  are  ready  to  deliver 
electric  energy  to  consumers. 

Under-Type  Magnet. — A  horse-shoe 
magnet  of  the  vertical  type,  whose  arma- 
ture is  placed  near  the  lower  end. 

Undulating  Current. — (1)  A  name  some- 
times given  to  an  undulatory  current.  (2) 
V  current  of  constant  direction  but  contin- 
uously varying  strength. 

Undulation. — A  wave  or  vibration,  es- 
pecially electric. 

Undulator. — A  form  of  rotating  commu- 
tator employed  for  the  use  of  transform- 
ers on  continuous-current  circuits.  (2)  A 
commutating  device  for  the  operation  of 
alternating-current  apparatus  from  a 
continuous-current  circuit. 

Undulatory  Currents.— Currents  of  con- 
stant direction  whose  strength  gradually 
changes. 

Undulatory  Discharge.— (1)  A  discharge 
whose  strength  gradually  changes  with- 
out change  of  direction.  (2)  A  term 
sometimes  used  for  an  oscillatory  dis- 
charge. 

Undulatory  "Winding.— A  name  fre- 
quently given  to  a  wave  winding. 


line. 


975 


[Uni. 


Unevenly  Distributed  Armature 
Winding. — A  winding  in  which  the 
slots  do  not  recur  at  equal  intervals 
around  the  periphery  of  the  armature. 

Unflashed  Filament. — A  lamp  filament 
that  has  not  been  subjected  to  the  flashing 
process. 

Hnfooting. — A  layer  of  broken  stone, 
gravel  and  concrete,  placed  in  layers  and 
rammed,  and  employed  at  the  bottom  of  a 
foundation  trench  for  receiving  the  ma- 
sonry work. 

TTngilding  Bath. — A  stripping  bath  suit- 
able for  the  removal  of  a  coating  of  gold. 

Uni-Coil  Alternating-Current  Arma- 
ture-Winding.— A  winding  providing 
one  slot  or  coil  on  the  armature  for  each 
and  every  pole  in  the  field  frame. 

Uni-Coil  Multiphase  Armature- Wind- 
ing.— A  multiphase  armature  winding 
providing  one  slot  or  coil  per  phase  for 
each  and  every  pole  in  the  field  frame. 

Uni-Directed  Currents. — (1)  Currents 
that  have  been  caused  to  take  the  same 
direction  by  means  of  a  commutator. 
(2)  Commuted  currents. 

Uni-Directed   Electromotive  Forces. 

Unidirectional  electromotive  forces. 
Unidirectional.  —  Possessing    the    same 
direction. 

Unidirectional  Discharge. — An  electric 
discharge  which  preserves  the  same  direc- 
tion from  the  beginning  to  the  end  of  the 
discharge. 

Unidirectional  Electromotive  Forces. 
Similarly  directed  electromotive  forces. 

Unidirectional  Leak. — A  gradual  loss 
or  leakage  of  electricity  which  takes  place 
in  the  same  direction. 

Unifilar  Suspension. — Suspension  by 
means  of  a  single  wire  or  thread. 

Uniform  Density  of  Field. — A  field  in 
which  the  density  is  the  same  in  all  equal 
areas  of  similar  cross-section, 

Uniform  Flux. — Uniform  magnetic-flux. 

Uniform  Magnetic-Field.— (1)  A  field 
of  uniform  density.  (2)  A  field  traversed 
by  the  same  number  of  lines  of  magnetic 
flux  in  all  portions  of  area  of  normal 
cross-section.  (3)  Magnetic  flux  in 
straight  lines  and  of  uniform  density. 

Uniform  Magnetic  Filament. — A  term 
sometimes  applied  to  a  magnetic  fila- 
ment. 

Uniform  Magnetic  Flux. — (1)  A  mag- 
netic flux  whose  density  is  everywhere 
the  same.  (2)  The  flux  of  a  uniform 
magnetic-field. 


Uniform  Magnetization. — Such  a  mag- 
netization of  a  rectangular  or  cylindrical 
bar  that  equal  areas  of  normal  cross- 
section  are  traversed  by  the  same  quan- 
tity of  magnetic  flux. 

Uniform  Potential.  —  (1)  A  potential 
whose  value  does  not  vary  from  point  to 
point.  (2)  A  constant  potential. 

Uniformly  Distributed  Current.— (1)  A 
term  sometimes  employed  in  the  sense  of 
a  steady  current.  (2)  A  current  having 
the  same  density  at  all  points  in  a  cross- 
section  of  a  conductor. 

Unigraph. — A  portable  form  of  sending 
and  receiving  Morse  instrument  in  one 
piece. 

Uninsulated  Return.— (1)  A  return  which 
employs  the  earth  only  as  a  return  cir- 
cuit. (2)  An  earth-return. 

Uni-Periodic  Current. — An  alternating 
current  of  a  single  frequency,  as  distin- 
guished from  a  multi-periodic  current. 

Uniphase. — Single  phase. 

Uniphase  Alternator. — An  alternator 
that  produces  uniphase  currents. 

Uniphase  Armature. — The  armature  of 
a  uniphase  alternator. 

Uniphase  Armature-Winding. — Such 
an  armature-winding  as  will  produce  uni- 
phase alternating-currents. 

CJniphase  Circuit. — Any  circuit  through 
which  uniphase  or  single-phase  currents 
are  passing. 

Uniphase  Dynamo. — A  uniphase  alter- 
nator. 

Uniphase  Generator.— A  uniphase  al- 
ternator. 

Uniphase  Motor. — An  electric  motor 
capable  of  being  operated  by  uniphase 
currents. 

Uniphaser. — A  term  sometimes  employed 
for  a  uniphase  alternator. 

Uniplanar. — Confined  to  a  single  plane. 

Unipolar. — Possessing  a  single  pole. 

Unipolar  Alternator. — An  alternator 
provided  with  a  so-called  single  magnetic 
pole. 

Unipolar  Armature. — A  dynamo-electric 
machine  armature  whose  polarity  is  not 
reversed  during  its  rotation  in  the  field  of 
the  machine. 

Unipolar  Dynamo. — (1)  A  dynamo  pro- 
vided with  a  unipolar  armature.  (2)  A 
commutatorless,  continuous-current  dy- 
namo. 

Unipolar  Electric  Bath. — An  electro- 
therapeutic  bath  in  which  the  water 
forms  one  of  the  electrodes  of  the  source. 


Uni.] 


976 


[Uni, 


and  the  other  electrode  is  attached  to  a 
metal  rod  fixed  at  a  convenient  height 
above  the  body. 

Unipolar  Induction. — (1)  A  term  some- 
times applied  to  the  induction  that  occurs 
when  a  conductor  is  so  moved  through  a 
magnetic  field  as  to  continuously  cut  its 
lines  of  force.  (2)  The  induction  that 
occurs  in  a  commutatorless,  continuous- 
current  dynamo. 

Unipolar  Magnet. — A  term  proposed  for 
a  magnet  in  the  shape  of  a  long  bar,  one 
pole  of  which  lies  in  the  axis  of  rotation, 
the  axis  being  placed  near  to  the  other 
pole  which  is  balanced  by  a  counterpoise. 

Unipolar  Stimulation  of  Nerve. — The 
stimulation  of  a  nerve  produced  by  the 
application  of  a  single  electrode  to  that 
nerve. 

Uni-Slot  Armature- Winding  or  Al- 
ternator.—  An  alternator  armature- 
winding  in  which  a  single  slot  is  provided 
for  each  and  every  pole  in  the  armature 
frame. 

Unit  Angle. — (1)  A  radian.  (2)  An  angle 
equal  to  57.29578° ;  or,  57°  17' 44.8"  nearly. 
(3)  A  degree,  minute,  second,  grad,  radian 
or  other  unit  of  angular  measure. 

Unit  Angular  Velocity. — (1)  A  radian 
per  second.  (2)  The  velocity  under  which 
a  particle  moving  in  a  circular  path 
whose  radius  is  equal  to  unity,  would 
traverse  unit  angle  in  unit  time.  (3)  Any 
angular  velocity  which  describes  a  unit 
angle  in  unit  time. 

Unit  Difference  or  Potential  of  Elec- 
tromotive Force. — (1)  Such  a  differ- 
ence of  potential  between  two  points  that 
requires  the  expenditure  of  one  erg  of 
work  to  bring  a  unit  of  positive  electricity 
from  one  of  these  points  to  the  other, 
against  the  electric  force.  (2)  In  the 
practical  system  of  units,  the  volt. 

Unit  Jar. — A  small  Leyden  jar  sometimes 
employed  to  measure,  approximately,  the 
quantity  of  electricity  passing  into  a  Ley- 
den  battery  or  condenser. 

Unit  Magnetic-Pole. —  (1)  A  magnetic 
pole  whose  strength  is  such  that  it  would 
act  on  a  similar  pole  at  a  distance  of  one 
centimetre  with  a  force  of  a  dyne.  (2) 
A  magnetic  pole  of  unit  strength. 

Unit  of  Acceleration. — That  accelera- 
tion which  will  give  to  a  body  unit  ve- 
locity in  unit  time,  as  for  example,  a 
centimetre-per-second  per-second. 

Unit  of  Activity. — (1)  A  rate-of-doing- 
work  that  will  perform  one  unit  of  work 
in  each  second.  (2)  In  the  C.  G.  S.  sys- 


tem, an  activity  of  one  erg-per-second. 
(3)  In  the  practical  system,  the  watt. 

Unit  of  Diviance. — A  term  proposed  for 
unit  of  resistance  to  lines  of  electrostatic 
force. 

Unit  of  Electric  Quantity. — (1)  A  unit 
quantity  of  electricity.  (2)  The  quantity 
of  electricity  conveyed  by  unit  current 
per  second.  (3)  In  the  practical  system 
of  units,  the  coulomb. 

Unit  of  Electric  Supply.— (1)  A  unit, 
provisionally  adopted  in  England  by  the 
Board  of  Trade,  equal  to  a  supply  of  one 
thousand  amperes  flowing  for  one  hour 
under  an  electromotive  force  of  one  volt. 

(2)  The  Board  of  Trade  unit,  or  kilowatt- 
hour.     (3)  An  amount  of  electric  energy 
equal  to  3,600,000  joules. 

Unit  of  Electric  Work.— The  joule. 

Unit  of  Electrostatic  Capacity. — (1) 
Such  a  capacity  of  a  condenser,  or  con- 
ductor, that  an  electromotive  force  of  one 
volt  will  charge  it  with  a  quantity  of 
electricity  equal  to  one  coulomb.  (2) 
The  farad. 

Unit  of  Force. — (1)  A  force  which  acting 
for  one  second  on  a  mass  of  one  gramme 
will  give  it  a  velocity  of  a  centimetre-per- 
second.  (2)  In  the  C.  G.  S.  system,  the 
dyne. 

Unit  of  Heat. — (1)  The  quantity  of  heat 
required  to  raise  a  given  weight  of  water 
through  one  degree  of  the  thermometric 
scale.  (2)  The  British,  thermal  unit  or 
the  pound-degree-Fahrenbeit  ;  i.  e.,  the 
amount  of  heat  required  to  raise  one 
pound  of  water  one  degree  Fahrenheit. 

(3)  The  greater  calorie,  or  the  amount  of 
heat  required  to  raise  the  temperature  of 
one  thousand  grammes  of  water  one  de- 
gree centigrade.    (4)  The  smaller  calorie, 
or  the  amount  of  heat  required  to  raise 
the  temperature  of  one  gramme  of  water 
one  degree  centigrade.     (5)  The  joule  ;  or 
the  quantity  of  heat  energy  developed  in  a 
second  by  the  passage  of  a  current  of  one 
ampere    through    the  resistance  of  one 
ohm. 

Unit  of  Illumination. — The  lux. 

Unit  of  Inductance.—  (1)  A  unit  of 
length  equal  to  one  centimetre.  (2)  In 
the  practical  system  of  units,  a  secohn?  or 
quadrant.  (3)  The  henry. 

Unit  of  Light. — Such  a  light  that  collect- 
ed at  a  single  point,  would  produce  unit 
illumination  at  unit  distance  from  such 
point. 

Unit  of  Luminous  Intensity. —  The 
British  candle :  or  the  intensity  of  light 
emitted  by  a  candle,  of  definite  dimen- 


Uni.] 


977 


[Up-C. 


sions  and  composition,  burning  at  the 
rate  of  two  grains  per  minute. 
Unit  of  Magnetic-Flux. — The  weber ;  or, 
the  amount  of  flux  which  would  pass 
through  a  magnetic  circuit  whose  reluc- 
tance is  one  oersted,  under  a  magne to- 
motive  force  of  one  gelbert. 

Unit  of  Magnetic  Intensity. — The  gauss ; 
or,  a  flux  density  of  one  weber-per-square- 
centimetre  of  normal  cross-section. 

Unit  of  Magnetic  Reluctance. — The 
oersted;  or,  the  reluctance  which  is  offered 
to  the  passage  of  magnetic  flux  by  a  cubic 
centimetre  of  air,  when  measured  between 
parallel  faces. 

Unit  of  Magneto-Motive  Force. — The 
gilbert ;  or,  the  magneto-motive  force 
which  is  required  to  act  on  a  circuit  in 
order  to  cause  one  weber  of  flux  to  pass 
through  it  against  a  reluctance,  or  mag- 
netic resistance  of  one  oersted. 

Unit  of  Mass. — The  quantity  of  matter 
in  a  standard  gramme. 

"Unit  of  Out-Put  of  Dynamo-Electric 
Machine. — (1)  The  unit  of  electric  power 
furnished  by  the  current  of  a  dynamo- 
electric  machine.  (2)  The  kilowatt. 

Unit  of  Photometric  Intensity.— The 
intensity  of  light  produced  by  a  candle  of 
given  dimensions  and  composition  that 
consumes  two  grains  per  minute. 

Unit  of  Resistance. — (1)  Such  a  resistance 
that  unit  difference  of  potential  is  re- 
quired to  cause  the  passage  of  unit  cur- 
rent strength  through  it.  (2)  In  the 
practical  system  of  units,  the  ohm. 

Unit  of  Self-induction.— The  unit  of  in- 
ductance. 

Unit  Quantity  of  Electricity . — (l)Such 
a  quantity  of  electricity  as  would  pass 
in  one  second  through  a  circuit  whose  re- 
sistance is  one  ohm  under  an  electromotive 
force  of  one  volt.  (2)  The  coulomb. 

Unit  Strength  of  Current.— (1)  Such  a 
strength  of  current  that  when  passed 
through  a  circuit  one  centimetre  in  length 
arranged  in  an  arc  of  a  circle  one  centi- 
metre in  radius,  will  exert  a  force  of  one 
dyne  on  a  unit  magnetic  pole  placed  at 
the  centre.  (2)  In  the  practical  system 
of  units,  the  ampere.  (3)  In  the  C.  G.  S. 
system  of  units,  ten  amperes. 

Unit  of  Power. — Any  unit  which  meas- 
ures the  rate  at  which  energy  is  expended, 
such  as  the  erg-per-second,  the  foot- 
pound-per-minute,  the  kilogramme- metre- 
per-minute,  the  horse-power,  etc. 

Unit  of  Twist  of  a  Fibre.— Such  a  twist 
that   in    unit   of  length  of  fibre  a  unit 
angular  twist  is  produced. 
62 


Units  of  Work.— (1)  The  erg.  (2)  A  dyne- 
centimetre,  or  the  amount  of  work  done 
when  a  force  of  one  dyne  acts  through 
a  distance  of  one  centimetre.  (3)  A  foot- 
pound, or  the  amount  of  work  required  to 
raise  one  pound  vertically  through  the 
distance  of  one  foot. 

Univalent. — (1)  Possessing  a  valency  or 
atomicity  of  one.  (2)  Monovalent. 

Universal  Battery  System. — In  teleg- 
raphy or  telephony,  a  system  of  employ- 
ing one  battery  for  the  supply  of  a  plur- 
ality of  circuits. 

Universal  Discharger. — An  apparatus 
for  sending  the  discharge  of  a  Leyden 
jar,  or  condenser,  through  any  desired 
circuit. 

Universal  Ether. — (1)  The  luminiferous 
ether.  (2)  The  ether. 

Universal  Switch. — A  pin  switchboard 
composed  of  horizontal  and  vertical  me- 
tallic bars  capable  of  inter-connection  by 
means  of  pins. 

Unlighted  Segment  of  Aurora. — A  term 
frequently  applied  to  the  dark  segment  of 
an  aurora. 

Unmarked  End  of  Magnet. — A  name 
formerly  applied  to  the  south-seeking  pole 
of  a  magnet. 

Unmarked  Pole  of  Magnet. — The  south- 
seeking  pole  of  a  magnet. 

Unmarked  Magnet  Pole. — A  name  some- 
times given  to  the  south  pole  of  a  magnet. 

Unplugging. — Introducing  the  resistance 
of  a  resistance  box  into  a  circuit  by  the 
removal  of  the  plug  keys, 

Unpolarized. — Devoid  of  polarization. 

Unsilvering  Bath. — A  stripping  bath, 
suitable  for  the  removal  of  a  coating  of 
silver. 

Unsymmetrical  Polyphase  Motor. — A 
polyphase  motor  provided  with  unsym- 
metrical  windings. 

Untreated  Filament.— The  filament  of  an 
incandescent  lamp  that  has  not  been  sub- 
jected to  the  flashing  process. 

Unvaring  Current. — (1)  A  current  whose 
strength  does  not  vary  from  time  to  time. 
(2)  A  current  of  constant  strength  and 
direction. 

Up-and  -  Down  -  "Working.  —  In  teleg- 
raphy, a  method  of  operating  consisting 
of  sending  a  message  over  the  line  from 
each  end  alternately,  as  distinguished 
from  batch  working. 

Up-Contact  of  Switch. — A  contact  which 
is  made  by  the  upward  movement  of  a 
switch. 


Up.] 


978 


[Tar. 


Tip  Lines. — In  Great  Britain,  lines  in  the 
direction  of  the  principal  station  on  a 
circuit,  as  distinguished  from  the  down 
lines. 

Tip  Side. — In  telegraphy  in  Great  Britain, 
that  side  nearer  to  the  principal  station  of 
a  circuit,  as  distinguished  from  the  down 
side. 

Upper  Harmonics  of  Current.— The 
higher  frequencies  of  a  simple-periodic  or 
alternating  current. 

Upright  Board. — A  telephone  switch- 
board whose  surface  is  vertical,  as  dis- 
tinguished from  a  flat  board. 

Upright  Galvanometer. — A  galvano- 
meter whose  needle  moves  in  a  vertical 
plane. 


Uranium  Rays.— A  phrase  sometimes 
employed  for  Becquerel  rays. 

Urban  Telephony. — Telephonic  com- 
munication between  different  portions  of 
the  same  city. 

Urethral  Electrode.— An  electro-thera- 
peutic electrode  suitable  for  treatment  of 
the  urethra. 

Useful  Current. — A  name  proposed  for 
the  effective  current  in  an  alternating- 
current  circuit. 

Useful  Life  of  Incandescent  Lamp. — 
The  time  during  which  an  incandescent 
lamp  can  furnish  practical  and  operative 
illumination. 

Utilizing  Apparatus.— Any  device  by 
means  of  which  energy  may  be  utilized. 


V. — A  contraction  for  volt. 

V. — A  contraction  for  volume. 

V. — A  contraction  sometimes  used  for  ve- 
locity. 

v. — (1)  A  symbol  employed  for  the  ratio 
existing  between  the  units  of  resistance 
in  the  electrostatic  and  magnetic  C.  G.  S. 
system  of  units.  (2)  A  velocity  ratio. 

V.  A. — A  contraction  sometimes  used  for 
voltaic  alternatives. 

Vacuum. — A  space  from  which  all,  or 
nearly  all,  traces  of  gas  have  been  re- 
moved. 

Vacuum  Lightning-Discharger.  —  A 
vacuum  lightning  protector. 

Vacuum  Lightning -Protector.  —  A 
lightning  protector  employing  a  vacuum 
tube  for  carrying  off  high-pressure  dis- 
charges. 

Vacuum  Manometer. — Any  manometer 
whose  operation  is  independent  of  at- 
mospheric pressure. 

Vaccuum  Pump. — An  air  pump. 

Vacuum -Tube  Lighting.  —  Artificial 
illumination  obtained  by  the  passage  of 
electric  discharges  through  vacuum 
tubes. 

Vacuum  Tubes.  —  (1)  Glass  tubes  in 
which  the  air  or  other  gas  has  been  par- 
tially removed,  and  through  which  electric 
discharges  are  passed  for  the  production 
of  luminous  effects.  (2)  A  name  some- 
times applied  to  Crookes,  Roentgen,  or 
other  high-vacuum  tubes. 

Vaginal   Electrode. — An   electro-thera- 


peutical electrode  suitably  shaped  for  the 
treatment  of  the  vagina. 
Valency.  —  The  combining  value  of  a 
chemical  atom,  as  regards  its  power  of 
displacing  other  atoms  in  chemical  com- 
pounds. 

Valve,  Electric.  —  An  electrically-con- 
trolled or  operated  valve. 

Vapor. — A  gaseous  substance  produced  by 
the  action  of  heat,  or  by  reduction  of  pres- 
sure, on  a  vaporizable  liquid. 

Vapor  Globe  of  Incandescent  Lamp. 
A  glass  globe  surrounding  the  chamber 
of  an  incandescent  lamp,  for  the  purpose 
of  enabling  it  to  be  safely  employed  in  an 
explosive  atmosphere,  or  to  permit  it  to 
be  exposed  in  places  where  water  is  liable 
to  fall  on  it. 

Vapor  Pressure.— The  pressure  at  which 
a  liquid  changes  into  a  vapor. 

Vaporization. — The  conversion  of  a  vola- 
tile liquid  into  a  vapor,  either  as  in  evap- 
oration at  the  surface  of  a  liquid,  or 
throughout  its  mass,  as  in  ebullition. 

Variable  Condenser. — A  term  sometimes 
employed  for  an  adjustable  condenser. 

Variable  Inductance.  —  (1)  The  induc- 
tance of  a  substance  whose  magnetic  per- 
meability is  not  constant.  (2)  An  adjust- 
able inductance. 

Variable  Period  of  Electric  Circuit.— 
That  period  during  whicli  the  current 
strength  is  rising  or  falling  in  a  circuit, 
after  the  making  or  breaking  of  the  same, 
until  the  current  strength  is  reached  or 


Tar.] 


979 


[Ten. 


until  the  line  has  been  completely  dis- 
charged. 

Variable  Period  of  Electric  Current. 
The  time  which  is  required  for  an  electric 
current  to  reach  its  full  strength  after 
the  circuit  is  made,  or  for  reaching  zero 
strength  when  its  circuit  has  been  opened. 

Variable  Period  of  Telegraph  Line.— 
The  time  required  for  the  current  in  a 
telegraphic  line  to  reach  a  constant 
strength  after  the  circuit  through  it  has 
been  closed. 

Variable  Ratio  Transformer. — An  alter- 
nating-current transformer  whose  ratio  of 
transformation  is  subject  to  variation. 

Variable  Resistance.  —  (1)  A  resistance, 
the  value  of  which  can  be  readily  varied 
or  changed.  (2)  An  adjustable  resist- 
ance. 

Variable  State  of  Charge  on  Telegraph 
Line. — The  condition  of  the  charge  on  a 
telegraph  wire,  while  the  strength  of  the 
current  is  increasing  up  to  its  full 
strength  in  all  parts,  or  diminishing  to 
zero. 

Variation  Chart  or  Map. — (1)  A  chart  or 
map  on  which  the  variations  of  the  earth's 
magnetism  are  marked.  (2)  An  isogonic 
chart. 

Variation  Magnetometer. — A  form  of 
magnetometer  suitable  for  measuring 
changes  in  the  earth's  magnetic  variation 
at  any  place. 

Variation  of  Declination. — A  variation 
in  the  magnetic  declination  of  the  earth 
at  any  place. 

Variation  of  Earth's  Magnetism. — Any 
variation  in  the  value  of  the  magnetic 
declination  or  inclination  that  occurs 
simultaneously  over  all  parts  of  the  earth. 

Variation  of  Magnetic  Needle.^-(l)  The 
angular  deviation  of  the  magnetic  needle 
from  the  true  geographical  north.  (2)  The 
declination  of  the  magnetic  needle. 

Variometer. — (1)  An  instrument  for  com- 
paring the  horizontal  component  of  the 
earth's  magnetism  in  different  localities. 
(2)  The  magnetic  variometer. 

Varnish,  Electric. — A  varnish  formed  of 
any  good  insulating  material. 

Varley's  Photometer. — A  form  of  pho- 
tometer in  which  the  intensity  of  the 
light  to  be  measured  is  determined  from 
the  relative  openings  of  two  concentric 
circular  diaphragms  placed  in  two  rotat- 
ing discs  through  which  the  standard  light 
and  the  light  to  be  measured  respectively 
pass. 

Varley's  "Unit  of  Resistance.— The  re- 
sistance of  one  statute  mile  of  a  special 


copper  wire  ^th  of  an  inch  in  diameter. 
(No  longer  in  use.) 

Varying  Continuous  -  Current.— A  di- 
rect current  whose  strength  varies  from 
time  to  time. 

Varying  Undirectional  -  Current. — A 
varying  continuous  or  direct  current. 

Vector. — (1)  A  directed  quantity.  (2)  A 
quantity  possessing  both  direction  and 
magnitude. 

Vector  Diagram. — A  diagram  represent- 
ing the  relations  of  vector  quantities. 

Vector  Equations. — Equations  connect- 
ing vector  quantities. 

Vector  Formula. — A  formula  containing 
vector  quantities. 

Vector  Impedance. — The  impedance  of 
an  alternating-current  circuit  considered 
as  a  vector  or  directed  quantity. 

Vector  Potential. — A  potential  possessing 
direction,  as  well  as  magnitude,  derived 
by  the  process  of  summation  of  vectors 
or  elementary  directed  quantities,  as  op- 
posed to  a  scalar  potential,  or  one  pos- 
sessing undirected  magnitude. 

Vector  Quantity. — A  quantity  possessing 
both  direction  and  magnitude. 

Vector  Sum. — The  geometrical  sum  of 
two  or  more  vector  quantities. 

Vectorial  Algebra. — The  algebra  of  vec- 
tors or  directed  quantities. 

Vehicle,  Electric. — (1)  An  electrically- 
propelled  vehicle.  (2)  An  automobile 
carriage. 

Velocimeter. — Any  apparatus  for  measur- 
ing the  speed  of  a  machine,  or  velocity 
generally. 

Velocity. — The  distance  traversed  by  a 
body  in  any  time. 

Velocity  of  Discharge.— (1)  The  veloc- 
ity with  which  a  liquid  or  gas  escapes 
from  an  orifice  in  a  given  time.  (2)  The 
time  required  for  the  passage  of  a  dis- 
charge from  a  given  length  of  conductor. 

Velocity  of  Transmission  of  Signal- 
ling.— The  apparent  speed  of  transmis- 
sion of  signals  over  a  telegraph  circuit. 

Velocity  Ratio.— (1)  A  ratio  of  the  na- 
ture of  a  velocity  that  exists  between  the 
dimensions  of  the  electrostatic  and  elec- 
tro-magnetic units.  (2)  The  ratio  between 
the  velocities  of  two  mutually  associated 
or  interconnected  bodies  or  parts  in 
a  machine. 

Vena-Contracta. — A  contracted  vein  or 
conical  jet  that  exists  in  a  jet  of  ^  water 
escaping  from  a  circular  orifice  in  the 
wall  of  a  containing  vessel. 


Ven,] 


980 


[Yir. 


Ventilated  Armature- Windings.— Ar- 
mature windings  provided  with  means 
for  cooling  by  forcing  currents  of  air  over 
them. 

Ventilating  Duct. — A  ventilating  space. 
Ventilating  Groove. — A  ventilating  space 
or  duct  in  an  armature  core. 

Ventilation  of  Armature  of  Dynamo 
or  Motor. — The  renewal  of  air  in  the 
armature  chamber,  due  to  the  passage 
through  it  of  a  stream  of  air  employed 
for  the  purpose  of  preventing  too  high  a 
temperature  elevation  during  operation. 

Verdet's  Constant. — The  magneto-optic 
constant  of  a  transparent  magnetized 
substance,  expressed  in  angular  rotation 
of  the  plane  of  polarization,  for  a  lumin- 
ous ray  of  definite  frequency  at  a  definite 
temperature,  between  points  on  the  ray 
path  whose  magnetic  potential  differs  by 
unity. 

Veriscope. — A  form  of  bioscope. 

Vernier. — A  device  for  the  more  accurate 
measurement  of  smaller  differences  of 
length  or  angle  than  could  be  detected  by 
the  eye  alone,  by  means  of  the  direct  read- 
ing of  the  position  of  a  mark  on  a  slid- 
ing scale. 

Vernier  Caliper. — A  caliper  possessing  a 
vernier  scale  provided  for  greater  precis- 
ion in  observation. 

Vernier  Slides. — A  pair  of  resistance 
slides  one  of  which  is  connected  in  shunt 
to  a  pair  of  contacts  on  the  other. 

Vernier  Wire-Gauge.  —  A  micrometer 
wire-gauge. 

Vertical  Component  of  Earth's  Mag- 
netism.— That  component  of  the  earth's 
directive  force  which  acts  in  a  vertical 
direction.  . 

Vertical  Electrostatic  Voltmeter.  — 
A  form  of  voltmeter  the  needle  of  which 
moves  in  a  vertical  instead  of  in  a  hori- 
zontal plane. 

Vertical  Galvanometer.— A  galvanome- 
ter whose  needle  is  capable  of  motion  in 
a  vertical  plane  only. 

Vertical  Intensity  of  Earth's  Mag- 
netism.— (1)  The  vertical  component  of 
the  earth's  magnetism.  (2)  The  -force 
which  tends  to  cause  a  magnetic  needle 
to  assume  a  vertical  position. 

Vertical  Magnetic  Needle.— A  magnetic 
needle  free  to  move  in  a  vertical  plane 
only. 

V.  Frog. — A  trolley  frog  shaped  like  a 
letter  V. 

Vibrating. — Periodically  moving  to-and- 
fro. 


Vibrating  Bell.  —  A  name  sometimes 
given  to  a  trembling  bell. 

Vibrating  Contact.— (1)  A  spring  con- 
tact connected  with  one  part  of  a  circuit, 
and  so  supported  as  to  be  able  to  vibrate 
towards  and  from  another  part  of  the 
circuit,  thus  automatically  closing  and 
opening  the  same.  (2)  A  form  of  auto- 
matic contact-breaker. 

Vibrating  Electric  Doublet. — A  source 
of  electro-magnetic  waves  consisting  of 
two  equal  and  opposite  oscillating  charges 
concentrated  on  two  small  conductors 
whose  distance  from  each  other  is  indefi- 
nitely small  in  comparison  with  the  dis- 
tance at  which  the  resulting  wave  disturb- 
ance is  considered. 

Vibrating  Electrotome.  —  An  auto- 
matic circuit-breaker  producing  a  musi- 
cal note. 

Vibration. — A  complete  to-and-fro  move- 
ment of  a  vibrating  body. 

Vibration  Frequency. — The  number  of 
vibrations  produced  per  second. 

Vibration  Needle. — A  tube  containing 
cylindrical  weights  for  attachment  to  a 
suspension  for  measuring  the  torsional 
rigidity  of  the  same. 

Vibration  Period. — The  period  of  a  single 
or  whole  vibration  in  a  conductor  in 
which  an  oscillatory  vibration  is  being 
produced. 

Vibrator.  —  An  electro-magnetic  device 
provided  on  a  siphon  recorder  for  main- 
taining the  siphon  in  continual  vibra- 
tion, so  that  ink  is  thrown  from  it  on  a 
fillet  of  paper  beneath. 

Villari  Critical  Point. — A  term  proposed 
for  that  strength  of  magnetic  field  at 
which  the  reversal  of  the  effects  of  ten- 
sion occurs. 

Vine  System  of  Space  Relations.— A 
system  of  space  relations,  usually  adopted 
by  electrical  writers,  which  follows  the 
vine  tendril ;  i.  e.,  which  considers  ad- 
vance in  the  direction  of  a  right-handed 
rotation  as  positive. 

Violle. — A  unit  of  luminous  intensity  pro- 
duced in  a  perpendicular  direction  by  one 
square  centimetre  of  platinum  at  the  tem- 
perature of  its  solidification. 

Violle  Lamp. — The  violle. 
Virgin  Iron. — Iron  that  has  never  been 
subjected  to  magnetization. 

Virtual  Amperes. — (1)  Amperes  meas- 
ured in  an  alternating-current  as  the 
square  root  of  the  mean  square  of  the 
current,  and  determined  by  an  ammeter 


Vir.] 


981 


[Vol. 


calibrated  by  constant  currents.  (2)  Ef- 
fective amperes. 

Virtual  Conductance. — A  term  some- 
times employed  for  equivalent  conduct- 
ance. 

Virtual  Counter  Electromotive  Force. 
Effective  C.  E.  M.  F.  in  an  alternating- 
current  circuit. 

Virtual  Current. — The  virtual  amperes. 

Virtual  Resistance. — The  apparent  re- 
sistance of  a  circuit. 

Virtual  Voltage. — Voltage  measured  in 
an  alternating-current  circuit  as  the 
square  root  of  the  mean  square  of  the 
value  in  volts,  as  obtained  by  a  voltmeter 
calibrated  by  continuous  currents. 

Virtual  Work. — In  a  system  of  bodies  or 
material  points,  the  amount  of  work 
which  would  be  done  by  the  force  acting 
upon  the  bodies  in  an  indefinitely  small 
displacement,  and  which  work  vanishes 
when  the  system  is  in  equilibrium. 

Viscous  Hysteresis. — (1)  The  time  lag 
observed  in  magnetizing  a  bar  of  iron 
which  is  neither  referable  to  the  induc- 
tion in  the  iron  nor  to  self-induction  in 
the  magnetizing  current,  but  to  the  mag- 
netic viscosity  of  a  substance.  (2)  A 
sluggishness  exhibited  by  iron  for  mag- 
netization or  demagnetization,  due  to 
magnetic  viscosity. 

Visual. — Of  or  pertaining  to  vision. 

Visual  Angle. — An  angle  subtended  be- 
tween two  lines  drawn  from  an  eye  to 
opposite  extremities  of  an  object. 

Visual  Clearing-Indicator.— (1)  An  in- 
dicator at  a  telephone  exchange  for  in- 
forming the  operator  that  a  conversation 
has  ended,  by  the  lighting  up  of  a  little 
incandescent  lamp  through  a  relay  con- 
tact. (2)  A  clearing  indicator  appealing 
to  the  eye,  as  distinguished  from  an  in- 
dicator which  releases  a  drop. 

Visual  Telegraphic  Signals. — Telegra- 
phic signals  that  can  be  seen,  as  distin- 
guished from  those  which  can  be  heard. 

Visual  Telegraphy.— (1)  Any  system  of 
telegraphy  whose  receiving  instruments 
give  visual  signals.  (2)  Needle  telegraphy. 

Vis- Viva. — (1)  The  energy  stored  in  a  mov- 
ing body.  (2)  The  measure  of  the  amount 
of  work  that  must  be  perfonned  in  order 
to  bring  a  moving  body  to  rest. 

Vitreous. — Of  or  pertaining  to  glass. 

Vitreous  Electricity. — A  term  formerly 
employed  for  positive  electricity. 

Vitreous  Electrification. — A  term  for- 
merly employed  for  positive  electrifica- 
tion. 


Vitrite. — A  variety  of  insulating  sub- 
stance. 

Volatilization,  Electric. — (1)  A  term 
sometimes  used  instead  of  electric  evap- 
oration. (2)  The  volatilization  of  a  con- 
ductor under  the  influence  of  heat  of 
electric  origin. 

Volatilization  of  Electric  Conductor.— 
The  deflagration  of  an  electric  conductor 
by  electrically  generated  heat. 

Volcanic  Lightning. — The  lightning  dis- 
charges that  attend  most  volcanic  erup- 
tions. 

Volt. — (1)  The  practical  unit  of  electro- 
motive force.  (2)  Such  an  electromotive 
force  as  is  induced  in  a  conductor  which 
cuts  lines  of  magnetic  flux  at  the  rate  of 
100,000,000  per  second.  (3)  Such  an  elec- 
tromotive force  as  would  cause  a  current 
of  one  ampere  to  flow  against  a  resistance 
of  one  ohm.  (4)  Such  an  electromotive 
force  as  would  charge  a  condenser  of  the 
capacity  of  one  farad  with  a  quantity  of 
electricity  equal  to  one  coulomb.  (5) 
108  absolute  electro-magnetic  units  of  elec- 
tromotive force. 

Volt-Ammeter. — (1)  A  name  sometimes 
given  to  any  instrument  capable  of  meas- 
uring either  the  volts  or  the  amperes  in  a 
circuit,  or  both.  (2)  The  measurer  of  the 
volt-amperes  or  watts.  (3)  A  wattmeter. 

Volt- Ampere. — The  watt. 

Volt  Box. — The  name  sometimes  given  to 
a  divided  wire  placed  across  the  terminals 
of  a  voltmeter  to  be  tested.  (2)  A  name 
sometimes  given  to  a  resistance  divided 
into  such  sections  that  any  suitable  frac- 
tional drop  in  potential  in  the  entire  re- 
sistance can  be  readily  measured  by  a  po- 
tentiometer. 

Volt  Indicator. — A  name  sometimes  given 
to  a  voltmeter. 

Voltage. — The  value  of  the  electromotive 
force  or  difference  of  potential  of  any  part 
of  a  circuit,  expressed  in  volts. 

Volta-Electric. — Of  or  pertaining  to  volta- 
electricity. 

Volta-Electric  Induction. — A  term 
sometimes  used  for  voltaic  induction. 

Volta-Electricity. — A  word  sometimes 
used  for  voltaic  electricity. 

Volta-Electrometer. — A  word  sometimes 
used  for  voltameter. 

Volta  -Electrometric.— Of  or  pertaining 
to  a  voltameter  or  to  voltaic  electricity. 

Volta-Electr  emotive  Force . — Voltaic 
electromotive  force. 

Volta-Force. — Contact  force  between  dif- 
ferent metals. 


Vol.] 


982 


[Vol. 


Volta-Plast. — An  unnecessary  word  pro- 
posed for  a  voltaic  battery,  used  in  electro- 
plating. 

Volta-Type. — An  unnecessary  word  pro- 
posed for  electro-type. 

Volta's  Law. — The  difference  of  potential 
between  any  two  metals  is  equal  to  the 
sum  of  the  difference  of  potential  between 
the  intervening  substances  in  the  contact 
series. 

Voltagraphy. — An  unnecessary  word 
sometimes  used  for  electro-typing. 

Voltaic  Accumulator. — A  term  some- 
times used  for  a  secondary  cell. 

Voltaic  Alternatives. — (1)  A  term  used 
in  medical  electricity  for  the  sudden  re- 
versals in  the  polarity  of  the  electrodes  of 
a  voltaic  battery  employed  in  electro- 
therapeutics. (2)  An  alternating  current 
obtained  from  a  voltaic  battery  by  the  use 
of  a  suitable  commutator. 

Voltaic  Arc. — (1)  A  brilliant  arc  or  bow  of 
light  which  appears  between  the  elec- 
trodes or  terminals  of  a  sufficiently  power- 
ful source  of  electricity,  when  placed  in 
contact  and  then  separated  a  short  dis- 
tance from  each  other.  (2)  The  source  of 
light  of  the  electric  arc-lamp. 

Voltaic  Balance.— An  apparatus  employed 
to  measure  the  voltaic  energy  present  in 
any  aqueous  solution  by  balancing  the 
electromotive  forces  produced  by  two 
small  zinc-platinum  couples  immersed  in 
water  and  placed  in  series  with  the  circuit 
of  a  sensitive  galvanometer,  so  as  to  bal- 
ance one  another,  and  then  applying  a  solu- 
tion of  the  substance  whose  energy  is  to  be 
measured  to  the  liquid  in  one  of  the  solu- 
tions. 

Voltaic  Battery. — The  combination  as  a 
single  source  of  a  number  of  separate  vol- 
taic cells. 

Voltaic  Battery  Indicator. — A  device  for 
indicating  the  condition  of  a  voltaic  bat- 
tery. 

Voltaic  Battery  Protector. — A  device 
for  automatically  opening  the  circuit  of  a 
voltaic  battery,  whenever  it  becomes 
accidentally  grounded. 

Voltaic  Bow. — A  word  sometimes  used 
for  a  voltaic  arc. 

Voltaic  Capacity  of  Accumulator. — A 
term  sometimes  applied  to  the  storage 
capacity  of  an  accumulator. 

Voltaic  Cell. — (1)  The  combination  of  two 
metals,  or  of  a  metal  and  a  metalloid, 
which ,  when  dipped  into  a  liquid  or  liquids 
called  electrolytes,  and  connected  by  a 
conductor,  will  produce  a  current  of  elec- 


tricity. (2)  A  voltaic  couple  and  ita 
accompanying  electrolytes. 

Voltaic  Circle. — A  name  formerly  em- 
ployed for  voltaic  cell  or  circuit. 

Voltaic  Circuit. — The  patli  through  which 
the  current  flows  from  a  voltaic  cell  or 
battery  through  the  translating  devices 
and  back  again  through  the  cell  or 
battery. 

Voltaic  Couple. — Any  two  materials,  gen- 
erally dissimilar  metals,  which  are  capa' 
ble  of  acting  as  an  electric  source  wheii 
dipped  into  an  electrolyte. 

Voltaic  Coupler. — Any  device  by  means 
of  which  voltaic  cells  may  be  readily 
coupled  or  connected  in  different  varieties 
of  circuits. 

Voltaic  Effect.— The  difference  of  poten- 
tial observed  at  the  point  of  contact  of 
dissimilar  metals. 

Voltaic  Electricity. — The  difference  of 
potential  produced  by  a  voltaic  cell  or 
battery. 

Voltaic  Electromotive  Force.— A  term 
sometimes  used  for  the  electromotive 
force  generated  at  the  electrodes  of  an 
electrolytic  cell  in  contradistinction  to 
the  counter-electromotive  force  produced 
at  such  electrodes  before  polarization. 

Voltaic  Elements. — Two  metals  or  sub- 
stances which  form  a  voltaic  couple. 

Voltaic  Endosmose. — A  term  sometimes 
used  for  electric  osmose  or  endosmose. 

Voltaic  Force.— A  word  sometimes  used 
for  voltaic  electromotive  force. 

Voltaic  Heat  Cell. — A  cell  by  means  of 

which  heat  energy  is  changed  or  converted 

into  electric  energy. 
Voltaic    Impulse. — A  word    sometimes 

used  for  the  electromotive  impulse  of  a 

voltaic  couple. 
Voltaic  Induction. — A  word  sometimes 

used  for  current  induction. 

Voltaic  Magnet. — An  unnecessary  term 
sometimes  employed  for  a  solenoid  or 
electro-magnetic  helix. 

Voltaic  Pair. — A  voltaic  couple. 

Voltaic  Pile. — A  word  sometimes  used 
for  voltaic  battery. 

Voltaism. — (1)  A  word  sometimes  em- 
ployed in  electro-therapeutics  for  treat- 
ment by  means  of  the  voltaic  current. 
(2)  The  production  of  electricity  by  means 
of  voltaic  couples. 

Voltameter. — An  electrolytic  cell  em- 
ployed for  measuring  the  quantity  of 
electric  current  passing  through  it,  by 
the  amount  of  chemical  decomposition 
affected  in  a  given  time. 


Vol.] 


983 


[Wai. 


Voltameter  Law.— The  amount  of  chemi- 
cal action  produced  by  electrolysis  in  any 
electrolyte  is  proportional  to  the  quantity 
of  electricity  which  passes  through  that 
electrolyte. 

Volta's  Condensing  Electroscope. — An 
electroscope  whose  leaves  are  charged  by 
means  of  a  condenser,  employed  for  the 
detection  of  feeble  charges. 

Voltmeter. — Any  instrument  employed 
for  measuring  differences  of  potential. 

Voltmeter  Panel  of  Switchboard. — The 
panel  of  a  switchboard  containing  a  volt- 
meter or  voltmeters. 

Voltmeter  Switch. — A  switch  for  readily 
and  safely  connecting  a  voltmeter  with 
any  one  of  a  number  of  circuits  whose 
pressures  may  have  to  be  measured. 

Volume  Density,  Electric. — The  amount 
of  electricity  per  unit  of  volume. 

Volume  Density  of  Charge.— The  elec- 
tric volume-density. 

Volume  of  Illumination. — A  term  pro- 
posed for  a  total  quantity  of  illumination 
comprised  between  a  surface  on  a  hori- 
zontal plane,  and  the  locus  of  the  extremi- 
ties of  ordinates  drawn  vertically  to  each 
part  of  that  surface,  in  values  represent- 
ing the  intensity  of  illumination  at  that 
point. 

Volume  Specific  Resistance.-^!)  The 
electric  resistance  of  a  cubic  centimetre  of 
material  measured  between  opposite  faces 
of  the  cube,  and  expressed  in  the  C.  G.  S. 
absolute  system  of  units.  (2)  Volume  re- 
sistivity. (3)  Specific  resistance  by  vol- 
ume as  compared  with  the  volume  resist- 
ance of  a  standard  substance. 

Volume  Voltameter. — A  voltameter  in 


which  the  quantity  of  current  passing  is 
determined  by  the  volume  of  gas  evolved. 

Volumetric  Energy.— (1)  Energy  per 
unit  of  volume.  (2)  The  energy  in  any 
substance  or  space  divided  by  the  volume 
of  the  substance  or  space. 

Vortex  Atom. — A  hypothetical  vortex  in 
the  ether  constituting  an  atom  of  a  ma- 
terial substance. 

Vortex  Cylinder. — A  cylindrically  shaped 
vortex  ring. 

Vortex  Ether. — An  ether  possessing  in- 
ertia and  capable  of  forming  vortices  like 
a  frictionless  liquid. 

Vortex  Ring. — (1)  A  ring  of  vertically 
moving  matter.  (2)  A  name  sometimes 
given  to  a  motion  in  the  air  or  other  gross 
matter,  similar  to  that  which  is  supposed 
to  constitute  a  vortex  atom. 

Vortex-Ring  Field.— The  field  of  influ- 
ence possessed  by  a  vortex  ring. 

Vortex  Stream  Lines. — Stream  lines  in 
the  ether  or  matter,  constituting  a  vortex 
atom  or  ring. 

Vulca. — A  variety  of  insulating  material. 

Vulcabeston. — A  variety  of  insulating 
substance  composed  of  asbestos  _  and  rub- 
ber. 

Vulcanite. — (1)  A  variety  of  vulcanized 
rubber,  possessing  high  powers  of  insula- 
tion and  specific  inductive  capacity.  (2) 
Ebonite. 

Vulcanized  Fibre. — A  variety  of  insulat- 
ing material  suitable  for  purposes  requir- 
ing the  highest  insulation. 

Vulcanizing  Wooden  Poles. — Subject- 
ing poles  to  the  action  of  heat  while  in  a 
closed  cylinder. 


w 


W. — A  contraction  for  watt. 

"W. — A  contraction  for  work. 

W. — A  contraction  for  weight. 

W. — A  contraction  for  physical  energy, 
whether  electrical,  thermal,  mechanical 
or  chemical ;  or,  in  general,  for  the  pro- 
duct of  the  force  acting,  and  the  distance 
through  which  it  acts. 

W. — A  symbol  for  electric  energy. 

W. — A  symbol  proposed  for  moment  of  a 
couple. 

W.  H.  E.— A  contraction  for  watt-hour 

efficiency. 
W.  P. — A  contraction  for  waterproof. 


w.  h. — An  abbreviation  for  watt-hour,  a 
practical  unit  of  electric  energy. 

Wall  Box  for  Flush  Switch.— A  box 
sunk  in  a  wall  for  the  reception  of  a  flush 
switch. 

Wall  Bracket. — (1)  An  insulator  bracket 
attached  to  a  wall.-  (2)  A  more  or  less 
ornamental  support  for  one  or  more  in- 
candescent lamps  attached  to  the  wall  of 
a  room,  hall,  or  corridor. 

Wall  Frame  for  Flush  Switch.— A  term 
sometimes  used  for  the  wall  box  of  a  flush 
switch. 

Wall  Plug.— A  plug  provided  for  the  in- 
sertion of  a  lamp  or  other  electro-recep- 


Wai.] 


984 


[Wat. 


tive  device  in  a  wall  socket,  thus  connect- 
ing it  with  the  lead. 

Wall  Set. — Telephone  apparatus  arranged 
for  use  when  supported  on  or  against  a 
wall. 

Wall  Socket. — A  socket  placed  in  a  wall 
and  provided  with  openings  for  the  inser- 
tion of  a  wall  plug  with  which  the  ends 
of  a  flexible  twin-lead  are  connected. 

Wand,  Electric. — A  term  sometimes  used 
for  an  electrophorus  in  the  form  of  a  torch. 

Wandering  of  Electric  Spark.— A  dis- 
charge possessing  the  appearance  of  a 
brilliant  luminous  globule,  which  moves 
slowly,  in  an  irregular  path,  over  the  sur- 
face of  the  tin-foil  on  a  condenser  to 
which  the  terminals  of  a  powerful  rheo- 
static  machine  is  placed,  when  a  portion 
of  the  mica  plate  in  the  condenser  is  ac- 
cidentally pierced. 

Wanted  Station. — A  word  sometimes  em- 
ployed for  a  station  that  is  desired  by  a 
telephone  subscriber. 

Ward. — A  term  proposed  for  a  line  and 
direction  in  a  line. 

Waring  Anti-Induction  Cable.  —  A 
form  of  lead-covered  anti-induction  cable. 

Washer  Plate. — A  buried  metallic  plate 
for  supporting  the  tension  of  a  stay-rod. 

Waste  Magnetic  Field. — A  term  fre- 
quently employed  for  stray  field. 

Watch-Case  Telephone  Beceiver. — A 
name  sometimes  given  to  a  small  tele- 
phone receiver  in  the  shape  of  a  watch- 
case. 

Watchman's  Electric  Clock. — A  name 
sometimes  given  to  a  watchman's  electric 
register. 

Watchman's  Electric  Register.— A 
clock  device  for  permanently  recording 
the  time  of  a  watchman's  visit  to  each  of 
the  different  localities  he  is  required  to 
visit  at  stated  intervals. 

Water  Battery.— A  battery  formed  of 
zinc-copper  couples  immersed  in  an  elec- 
trolyte of  ordinary  water. 

Water-Cooled  Transformer. — A  trans- 
former that  is  cooled  by  the  forced  circu- 
lation of  water  through  it. 

Water-Dropping  Accumulator.— A  de- 
vice tor  increasing  the  difference  of  po- 
;     tential  between  two  electric  charges,  by 
the  dropping  of  water  through  electrified 
funnels. 

,  Water-Dropping  Collector.  —  A  term 
sometimes  employed  for  a  water-drop- 
ping accumulator. 

Water-Gramme-Degree  Centigrade.— 
(1)  A  heat  unit  equal  to  the  quantity  of 


heat  required  to  raise  a  gramme  of  water 
one  degree  Centigrade.  (2)  The  small 
calorie. 

Water  Horse-Power. — A  term  employed 
by  the  Indian  Government  for  a  horse- 
power developed  by  falling  water,  and 
estimated  as  being  equal  to  15  cubic  feet 
of  water  falling  per  second,  through  a  dis- 
tance of  one  foot. 

Water    Telephone    Transmitter.  —  A 

telephone  transmitter  consisting  of  a  jet 
of  water  issuing  vertically  downwards 
from  a  small  orifice. 

Water-Level  Alarm,  Electric.— (1)  A 
device  for  electrically  sounding  an  alarm 
when  a  water  level  varies  materially  from 
a  given  level.  (2)  A  liquid-level  alarm. 

Water-Pipe  Besistance.— The  resistance 
which  any  pipe  offers  to  the  flow  of  water 
through  it. 

Water-Proof  Wire. — Wire  covered  by  a 
water-proof  material. 

Water  Pyrometer. — A  pyrometer  em- 
ployed for  determining  the  temperature 
of  a  furnace,  or  other  intense  source  of 
heat,  by  the  increase  in  temperature  of  a 
known  weight  of  water,  into  which  a 
metal  cylinder  of  a  given  weight  has 
been  put,  after  having  been  exposed  for  a 
given  time  to  the  source  of  heat  to  be 
measured. 

Water  Bheostat.— A  rheostat  whose  resist- 
ance is  obtained  by  means  of  a  mass  of 
water  of  fixed  dimensions. 

Water-Tube  Dead-Beat  Suspension.— 
A  dead-beat  suspension  obtained  for  the 
mirror  of  a  sensitive  galvanometer  by  the 
resistance  offered  by  water  in  a  tube  to 
the  movement  of  a  vane  attached  to  the 
suspension  axis. 

Water  Voltaic  Cell. — A  cell  consisting 
of  a  couple  immersed  in  ordinary  water. 

Water  Voltameter. — A  name  sometimes 
given  to  a  dilute  sulphuric  acid  volta- 
meter. 

Watt.— (1)  A  unit  of  electric  power.  (2)  A 
volt-ampere.  (3)  The  power  developed 
when  44.25  foot  pounds  of  work  are  done 
in  a  minute,  or  0.7375  foot-pound  of  work 
is  done  in  a  second. 

Watt  Arc. — A  voltaic  arc,  the  electric 
power  of  which  is  estimated  in  watts. 

Watt  Balance. — A  form  of  electric  balance 
suitable  for  measuring  in  watts  the  elec- 
tric energy  developed  in  any  circuit. 

Watt  Generator. — A  term  sometimes  em- 
ployed for  the  power  in  watts  that  any 
electric  source  is  capable  of  producing. 

Watt-Hour.— (1)  A  unit  of  electric  work. 


Wat.] 


985 


(2)  A  term  employed  to  indicate  the  ex- 
penditure of  an  electric  power  of  one 
watt  for  an  hour. 

Watt-Hour  Efficiency  of  Storage  Bat- 
tery.— The  ratio  between  the  amount  of 
electric  work  in  watt-hours  a  battery 
will  yield  after  being  charged,  and  the 
amount  of  work  in  watt-hours  expended 
in  charging  it. 

Watt-Hour  Meter. — A  form  of  recording 
watt-meter. 

Wattless  Component.  —  A  component 
of  E.  M.  F.  or  current,  in  quadrature  with 
the  working  component. 

Wattless  Component  of  Current. — (1) 
In  an  alternating-current  circuit  that 
component  of  the  current  which  is  in 
quadrature  with  the  impressed  E.  M.  F. 
and  which,  therefore,  takes  from  or  gives 
no  energy  to  the  circuit.  (2)  In  an  alter- 
nating-current circuit  the  product  of  the 

E.  M.  F.  and  the  effective  susceptance. 

Wattless  Component  of  Electromo- 
tive Force. — (1)  In  an  alternating-cur- 
rent circuit,  that  component  of  the  E.  M. 

F.  which  is  in  quadrature  with  the  cur- 
rent   strength,    and,   therefore,  does  no 
work  on  the  current.     (2)  In  an  alternat- 
ing-current   circuit   the  product  of  the 
current  and  the  effective  reactance. 

Wattless  Current. — (1)  That  component 
of  an  alternating  electric  current  which  is 
in  quadrature  with  the  pressure  and 
which,  therefore,  does  no  work.  (2)  The 
idle  current.  (3)  In  an  alternating-cur- 
rent circuit  the  product  of  the  effective 
susceptance  and  the  E.  M.  F. 

Wattless  E.  M.F.— (1)  The  wattless  com- 
ponent of  E.  M.  F.  in  an  alternating-cur- 
rent circuit.  (2)  The  reactive  E.  M.  F., 
as  distinguished  from  the  active  E.  M.  F. 
of  an  alternating-current  circuit.  (3)  In 
an  alternating-current  circuit,  the  pro- 
duct of  the  E.  M.  F.  and  the  effective  or 
apparent  conductance. 

Wattless  Magnetizing  Current. — (1)  A 
component  of  the  magnetizing  current 
•which  consumes  no  power  on  the  average. 
(2)  That  component  of  the  current  which 
flows  through  the  primary  of  a  trans- 
former, which  serves  for  magnetizing 
only,  and  which  is  in  quadrature  with  the 
pressure,  as  distinguished  from  the  com- 
ponent of  magnetizing  current  which 
expends  energy  in  the  iron  core. 

Wattmeter.  — An  instrument  for  measur- 
ing the  power  in  any  circuit. 

Watt-Minute. — (1)  A  unit  of  electric 
work.  (2)  An  expenditure  of  electric 
power  of  one  watt  for  one  minute. 

16— 


Watt-Second. — (1)  A  unit  of  electric  work. 
(2)  An  expenditure  of  electric  power  of ! 
one  watt  for  one  second.  (3)  A  joule. 

Wave. — An  oscillatory  motion  in  an  elastic' 
medium,  periodic  in  time. 

Wave  Bisector. — An  electric  chronograph 
for  determining  the  current  or  potential 
in  a  telegraph  circuit  or  line  at  any  given 
small  interval  of  time  after  the  applica- 
tion of  the  sending  current. 

Wave,  Electric. — An  electric  periodic  dis- 
turbance in  an  elastic  medium. 

Wave  Form  of  Alternating  Current. — 
Any  particular  type  of  an  alternating- 
current  wave. 

Wave  Form  of  Alternating  Current. 
A  graphical  type  of  an  alternating-cur- 
rent wave. 

Wave  Winding. — (1)  Undulatory  wind- 
ing. (2)  Continuous  winding.  (3)  A  wind- 
ing which,  when  developed,  has  the  form 
of  a  wave. 

Waves  of  Condensation  and  Rarefac- 
tion.— (1)  The  alternate  spheres  of  con- 
densed and  rarified  air  by  means  of  which 
sound  is  propagated.  (2)  Sound  waves. 

Way. — A  term  sometimes  employed  for 
cable  way. 

Way  Lease. — A  permit  obtained  from  the 
owner  of  a  property  for  the  erection  of 
poles  or  other  attachments  for  telephonic 
or  telegraphic  lines. 

Way  Leave. — A  word  sometimes  used  for 
way  lease. 

Way  Leave. — (1)  A  right  of  way.  (2) 
An  easement. 

Way  Line. — A  line  communicating  with 
way  stations. 

Way  Office  Cut-Out. — A  cut-out  em- 
ployed for  inserting  or  removing  a  way 
office  in  a  telegraphic  line,  by  the  aid  of 
a  plug. 

Way  Telegraphic  Station. — Any  station 
intermediate  between  the  terminal  sta- 
tions. 

Ways  for  Dynamo-Electric  Machine. 
Slides  on  the  base  of  a  dynamo-electrio 
machine  for  moving  part  of  its  frame. 

Weather  Contact. — (1)  A  weather  cross. 
(2)  A  partial  contact  between  wires  ow- 
ing to  leakage  in  bad  weather. 

Weather  Cross. — A  contact  or  leak  occur- 
ring in  a  telegraphic  or  other  line  during 
wet  weather,  from  a  defective  action  of 
the  insulators. 

Weather  Proof  Insulation. — A  trade- 
name  for  a  character  of  insulation  con- 
sisting of  one  or  more  layers  of  braided 
Vol.  2 


Wea.] 


986 


[Wim. 


material  soaked  in    an    insulating    com- 
pound. 

"Weather-Proof  Wire. — A  wire  provided 
with  weather-proof  insulation. 

Weber. — (1)  The  practical  unit  of  magnetic 
flux.  (2)  A  unit  of  magnetic  flux  having 
the  value  of  one  absolute  unit  or  line. 
(3)  A  term  formerly  employed  for  unit  of 
current,  but  now  replaced  by  ampere.  (4) 
A  term  proposed  by  Clausius  and  Siemens, 
but  not  adopted,  for  a  magnetic  pole  of 
unit  strength. 

Weber  Turns. — Flux  linkages  in  C.  G.  S. 
units  of  flux  and  the  turns  through  which 
they  pass. 

Weber's  Theory  of  Diamagnetism.— A 
theory  which  endeavors  to  account  for  the 
phenomena  of  diamagnetism  on  the  as- 
sumption of  originally  magnetized  parti- 
cles, molecules,  or  atoms. 

Wedge  Battery.-— In  a  telegraph  station, 
a  battery  whose  terminals  are  connected 
with  a  wedge  for  insertion  in  a  jack. 

Wedge  Cut-Out. — A  form  of  cut-out  em- 
ployed on  telegraphic  circuits. 

Weeding-Out  of  Harmonics  by  Elec- 
tric Resonance. — Gradually  removing 
the  upper  harmonics  from  a  complex- 
harmonic  current  by  altering  the  natural 
period  of  the  system,  until  it  is  in  unison 
or  resonance  with  the  fundamental  fre- 
quency. 

Weight  of  Observations. — The  relative 
numerical  reliability  of  observations. 

Weight  Efficiency  of  Transformer. — 
The  specific  output  or  activity  of  a  trans- 
former. 

Weight  Voltameter  —  A  voltameter  in 
which  the  quantity  of  current  passing  is 
determined  by  the  difference  of  weight  of 
the  instrument  after  the  current  has 
passed  for  a  given  time. 

Weight  Voltmeter.  —  A  voltmeter  in 
which  the  potential  difference  to  be  meas- 
ured is  determined  by  the  movement  of 
a  magnetic  needle  under  the  influence  of 
the  current,  against  the  action  of  a 
weight. 

Weight-Per-Mile-Ohm. — (1)  A  standard 
of  conductivity  of  wires.  (2)  The  weight 
per  mile  of  a  wire,  multiplied  by  its  re- 
sistance per  mile  at  a  given  temperature. 

Welded  Bail  Bond.— A  rail  bond  ef- 
fected by  electrically  welding  together 
the  ends  of  the  rails. 

Welder. — A  name  sometimes  applied  to  an 
electric  welder 

Welding. — Uniting,  generally  at  a  high 


temperature,  two  pieces  of  metal  in  one 
without  the  appearance  of  a  junction. 

Welding  Converter.— A  welding  trans- 
former. 

Welding,  Electric.— Effecting  the  weld- 
ing union  of  metals  by  means  of  heat  of 
electric  origin. 

Welding  Transformer.— A  step-down 
transformer  employed  in  electric  welding. 

Welsbach  Burner. — A  form  of  incandes- 
cent mantel  burner  whose  light  ig  due  to 
the  incandescence  under  the  action  of  a 
Bunsen  flame  of  a  mantel  covered  with 
refractory  materials. 

Western  Union  Splice. — A  term  some- 
times employed  for  an  American  wire 
joint. 

Wheatstone's  Electric  Balance.  —  A 
name  sometimes  given  to  an  electric 
bridge  or  balance. 

Wheatstone's   Electric    Bridge.  —  A 

Wheatstone's  electric  balance. 
Wheel  Brush. — A    name  given  to  any 

rotary  brush. 
Wheel  Printing  Telegraph. — A  printing 

telegraph   in   which  a  printing  wheel  is 

employed. 
Whip. — A  vibrating  contact-maker. 

Whirl,  Electric. — (1)  A  term  employed  to 
indicate  the  circular  directions  of  the 
lines  of  magnetic  fcrce  surrounding  a 
conductor  conveying  an  electric  current. 
(2)  A  magnetic  whirl. 

Whistle,  Electric. — An  automatic  electric 
whistle. 

Whistling  Effect.— (1)  An  effect  produced 
with  a  carbon  transmitter  and  telephone 
receiver  in  a  line,  such  that  if  the  trans- 
mitter be  close  to  the  receiver  and  then 
slightly  jarred,  a  musical  note  will  be 
emitted  by  the  receiver  which  will  react 
upon  the  transmitter  and  produce  similar 
sounds  in  other  receivers  on  the  same 
circuit.  (2)  A  means  sometimes  em- 
ployed to  call  a  subscriber's  attention 
when  his  receiver  has  been  accidentally 
left  in  the  line  circuit,  instead  of  the  bell. 

White. — Containing  all  the  frequencies  of 
the  sun's  radiation. 

White  Heat. — A  temperature  of  a  heated 
body,  at  which  it  emits  all  visible  fre 
quencies  from  the  red  to  the  violet,  and 
therefore  glows  with  a  white  light. 

Wig- Wag  Signalling. — A  term  sometimes 
used  for  torch  signalling. 

Wimshust's  Electrostatic  Machine.— A 
form  of  influence  electric  machine. 


Win.] 


987 


[Woo. 


Wind  and  Water  Line  of  Telegraph 
Pole. — The  surface  of  a  telegraph  pole  at 
the  level  of  the  ground,  where  it  is  ex- 
posed to  the  destructive  action  of  air  and 
water. 

Wind,  Electric. — The  convection  streams 
of  air  particles  produced  at  the  extremi- 
ties of  points  attached  to  the  surface  of 
charged  insulated  conductors. 

Windage  of  Dynamo  Armature. — A 
term  proposed  for  the  air-gap  between 
the  armature  and  the  pole-pieces  of  a 
dynamo.  (Not  ill  general  use.) 

Winding  Space. — The  space  provided  on 
an  armature  or  magnet  core  for  its  mag- 
netizing coils. 

Windings. — A  .general  name  applied  to 
the  coils  placed  on  an  armature  of  a 
dynamo  or  motor,  or  on  the  core  of  an 
electro-magnet. 

Wind-Mill  Electric. — A  term  sometimes 
used  for  an  electric  flyer. 

Wind-Mill  Meter. — An  alternating-cur- 
rent meter  whose  operation  is  dependent 
on  the  motion  of  a  wind-mill,  by  currents 
of  air  set  up  by  the  heat  emitted  from  a 
conductor  through  which  the  current  to 
be  measured  is  passing. 

Window  Contact. — A  variety  of  burglar- 
alarm  contact,  by  means  of  which  an 
alarm  bell  is  rung  by  a  slight  pressure 
against  a  blind  contact,  on  any  attempt 
from  without,  after  the  breaking  of  the 
glass  in  the  window. 

Window-Tube  Insulator.— A  tube  of 
vulcanite,  or  other  insulating  material, 
provided  for  the  insulation  of  a  wire 
entering  a  room  through  a  window. 

Wings. — The  conducting  plates,  flaps,  or 
extensions,  of  an  electric  resonator  or 
oscillator. 

Wipe  Spark. — A  spark  obtained  from  a 
spark  coil  by  the  wiping  contact  of  a 
spring. 

Wiped  Joint. — (1)  A  wiped  solder  or 
plumber's  joint.  (2)  A  joint  in  the  lead 
sheathing  of  a  cable  formed  by  adding  free 
surface  metal,  as  in  a  plumber's  joint  in 
lead  pipes. 

Wiping  Contact. — A  contact  obtained  by 
a  wiping  movement  of  one  conductor 
against  another. 

Wippe. — An  orthography  sometimes  em- 
ployed for  whip. 

Wire. — (1)  To  provide  with  a  conduct- 
ing circuit.  (2)  To  send  a  telegram. 

Wire. — (1)  A  conductor  that  forms  part  of 
a  circuit.  (2)  A  telegram. 

Wire  Core. — A  form  of  laminated  core  ob- 


tained by  the  use  of  a  number  of  iron 
wires. 

Wire  Drum.— A  drum  for  holding  over- 
head wires  in  process  of  erection. 

Wire  Dynamometer. — A  line  dynamo- 
meter. 

Wire  Finder. — Any  form  of  galvanometer 
used  to  locate  or  find  the  corresponding 
ends  of  different  wires  in  a  bunched  cable. 

Wire-Grating  Polarizer.— A  series  of 
parallel  wires  set  in  a  frame  and  em- 
ployed for  polarizing  electro-magnetic 
waves. 

Wire  Guard. — A  wire  netting  placed  over 
an  incandescent  lamp  chamber,  acting  as 
a  guard  or  protection  for  it. 

Wire  Holder.— (1)  A  form  of  insulator 
suitable  for  holding  or  supporting  a  wire. 
(2)  A  reel  or  cross  suitable  for  holding  a 
roll  of  wire. 

Wire  Joint. — (1)  Any  joint  connecting 
two  pieces  of  line  wire.  (2)  A  telegraphic 
joint. 

Wire  Rail-Bond. — A  bond  between  con- 
tiguous or  opposite  rails  effected  by 
means  of  a  conducting  wire. 

Wire  Selector.— A  wire  finder. 

Wire  Shade-Guard.— A  wire  guard  pro- 
vided for  the  shade  of  an  incandescent 
lamp. 

Wire  Shield  for  Incandescent  Lamp.— 
A  wire  lamp-guard. 

Wire  Splice.— A  splice  effected  between 
two  pieces  of  wire. 

Wire  Terminals.— Metal  eyes  for  solder- 
ing to  the  ends  of  wires  and  for  connec- 
tions to  switchboards. 

Wire- Wound  Armature. — An  armature 
which  is  wound  with  wire,  as  distin- 

fuished  from  an  armature  wound  with 
ars. 

Wired. — Provided  with  a  conducting  wire 
or  wires. 

Wireless  Telegraphy.  —  (1)  A  general 
term  for  any  form  of  telegraphic  com- 
munication which  can  be  effected  with- 
out wire  circuits.  (2)  Induction  teleg- 
raphy. (3)  Conduction  telegraphy  through 
the  medium  of  the  earth. 

Wiring.  — (1)  Placing  or  installing  the 
wires  required  in  any  circuit.  (2)  Col- 
lectively, the  wires  or  electric  conductors 
employed  in  any  circuit  of  electric  dis- 
tribution. 

Wood  Mouldings,  Electric.— Mouldings 
of  dried  non-conducting  wood  provided 
with  longitudinal  grooves  for  the  recep- 


Woo.] 


988 


[X-Ra. 


tion  and  support  of  electric  wires  or  con- 
ductors. 

Wood's  Button-Repeater.— A  form  of 
manual  telegraphic  repeater. 

"Work. — The  product  of  the  force  by  the 
distance  through  which  it  acts. 

Work,  Electric.— (1)  The  joule.  (2)  A 
volt-coulomb,  or  the  work  done  by  the 
passage  of  one  conduct  through  one  volt. 

Work-Meter. — A  word  sometimes  used 
for  energy  meter. 

Working  Current. — (1)  In  an  alternating- 
current  circuit,  a  name  sometimes  given 
to  an  active  current,  or  that  component 
of  the  current  which  is  in  phase  with  the 
pressure.  (2)  Any  current  in  a  circuit, 
which  does  work.  (3)  A  current  operat- 
ing a  translating  device. 

Working  Current  of  Motor. — The  active 
current  of  an  alternatirg-current  motor. 

Working  Efficiency  of  Telegraphic 
Circuit. — The  variation  or  margin  be- 
tween the  joint  resistance  of  the  line 
conductor  and  the  resistance  of  the  in- 
sulators supporting  such  conductor. 

Working  Galvanometer-Constant.— A 
term  sometimes  employed  for  galvano- 
meter constant. 


Wprking  Position  of  Switch..— The  po- 
sition of  a  switch  when  closed. 

Working  Speed  of  Cable. — A  term  em- 
ployed for  the  number  of  signals  that  can 
be  sent  over  a  cable  in  a  given  time. 

Working  Substance  of  Storage  Bat- 
tery.— A  name  sometimes  given  to  the 
active  material  of  a  storage  battery. 

Woven-Wire  Dynamo  or  Motor 
Brushes. — Gauze  brushes  for  dynamos 
or  motors. 

Wrapped  Wire.— Wire  covered  with  a 
wrapping  of  insulating  material. 

Wrecking  Wagon  for  Trolley  Line.— A 
word  sometimes  used  for  repair  wagon. 

Writing  Error. — In  telegraphy  an  error 
made  in  writing  a  message. 

Writing  Telegraph. — A  general  name 
for  the  apparatus  used  in  writing  tele- 
graphy. 

Writing  Telegraphy. — A  species  of  fac- 
simile telegraphy,  by  means  of  which  the 
motions  of  a  transmitting  pen  so  vary 
the  resistance  of  two  lines  connected  with 
the  receiving  instrument,  as  to  cause 
a  receiving  pen  or  stylus  to  reproduce 
them. 


X 


X-G-raph. — A  word  sometimes  employed 
for  radiograph. 

X-Radiation. — A  term  sometimes  used 
for  Roentgen  radiation. 

X-Ray  Field.— The  field  of  activity  of 
X-rays. 

X-Ray  Pluoroscopy.— The  study  of  flu- 
oroscopic  effects  obtained  by  means  of 
the  X-rays. 

X-Ray  Lamp. — A  lamp  consisting  essen- 
tially of  a  high-vacuum  tube,  the  inner 
walls  of  which  are  covered  with  crystals 
of  calcium  tungstate  or  other  fluorescent 
substance,  which  emits  fluorescent  light 
when  exposed  to  X-rays. 

X-Ray  Photograph. — A  term  sometimes 
employed  for  radiograph. 

X-Ray  Photography. — Photography  ef- 
fected by  means  of  the  X-rays. 

X-Ray  Picture. — A  term  sometimes  em- 
ployed for  radiograph. 


X-Ray  Source.  —  Any  source  capable  of 
producing  X-rays. 

X-Ray  Transformer.  —  A  transformer 
employed  for  obtaining  the  high-potentia', 
discharges  employed  in  Roentgen  or  X 
ray  tubes. 

X-Ray  Transformer-Coil.  —  A  form  of 
induction  coil  employed  for  the  produc- 
tion of  X-rays. 

X-Ray  Tube.  —  A  name  sometimes  given 
to  a  Roentgen  ray  tube. 


X-Rays.—  ^(1)  A  name  frequently  given  to 
X-radiation.  (2)  The  invisible  rays  emit- 
ted by  an  electrically  excited  Crookes 
tube,  and  which  are  capable  of  penetrat- 
ing many  substances  opaque  to  light,  and 
of  producing  actinic  or  fluorescent  effects. 
(3)  The  unknown  rays  emitted  by  an  X- 
ray  tube  from  some  point,  generally  op- 
posite the  cathode,  which  receives  cath- 
ode-ray bombardment. 


Y-Co,] 


[Zin. 


Y-Connection  of  Three-Phaser.— (1)  The 
connection,  resembling  the  letter  Y,  of  the 
three  circuits  of  a  triphaser  to  a  common 
junction.  (2)  Star  connection. 

Y-Connected  Three-Phaser  Armature. 
(1)  A  triphase  armature  having  three  cir- 
cuits connected  to  a  common  point.  (2)  A 
star-connected  triphase  armature. 

Y-Connector. — A  connector  resembling 
the  letter  Y  in  shape  for  joining  a  con- 
ductor to  two  branch  wires. 

Y-Current. — The  current  between  any 
wire  of  a  triphase  system  and  the  neutral 
point. 

Y-Guy  for  Telegraph  Pole.— A  Y-shaped 
guy  attached  to  a  telegraph  pole  for  pre- 
venting it  from  bending  near  the  top. 

Y-Potential  of-Triphase  System.— The 
effective  difference  of  potential  or  volt- 
meter pressure  between  one  terminal  or 


conductor  of  a  triphase  system  and  the 
neutral  point. 

Y-Shaped  Spark. — A  variety  of  three- 
branched  spark  obtained  by  the  discharge 
of  a  Ley  den  jar  through  a  peculiar  form 
of  induction  coil. 

Yale-Lock-Switch  Burglar-Alarm.— 
An  apparatus  whereby  the  opening  of  a 
door  by  an  authorized  party  provided  with 
a  regular  key,  will  not  sound  an  alarm, 
but  any  other  opening  will  sound  an  alarm. 

Yacht-Tender,  Electric. — An  electrically 
propelled  tender  provided  for  use  in  con- 
nection with  a  yacht. 

Yoke. — That  portion  of  the  iron  of  an  elec- 
tro-magnet that  joins  the  two  cores. 

Yoke  Horse-Shoe  Electro-Magnet.— A 
horse-shoe  electro-magnet  whose  two 
straight  limbs  are  formed  of  two  straight 
rods  or  bars  connected  together  at  one 
pair  of  ends  by  a  yoke. 


Z. — A  symbol  sometimes  employed  in  elec- 
tro-therapeutics for  muscular  contraction. 

Z. — A  symbol  for  electro-chemical  equiv- 
alent. 

Z-Insulator. — A  simple  form  of  single- 
shed  earthenware  overhead  line  insul- 
ator. 

Zamboni's  Dry  Pile. — A  form  of  dry  pile 
consisting  of  discs  of  paper,  silvered  on 
one  side  and  tinned  on  the  other,  placed 
together  alternately  with  slightly  moist- 
ened bin-oxide  of  manganese. 

Zeeman  Effect. — The  broadening  of  the 
lines  in  the  spectrum  of  a  heated  sub- 
stance when  placed  in  the  flux  of  a  power- 
ful magnetic  field. 

Zero  Method.— (1)  Any  method  employed 
in  electrical  measurement,  in  which  the 
value  of  the  electromotive  force,  the  resist- 
ance, current,  or  other  similar  quantities, 
are  determined  by  balancing  against  such 
quantities  equal  values  of  the  same  units, 
and  ascertaining  the  equality,  not  by  the 
deflection  of  a  needle  of  a  galvanometer  or 
electrometer,  but  by  the  absence  of  such 
deflections.  (2)  A  null  method. 

Zero  Potential. — (1)  An  arbitrary  poten- 
tial-level from  which  electric  levels  are 
measured.  (2)  The  earth's  potential. 


Zigzag  Electro-Magnet. — A  multipolar 
electro-magnet  whose  magnetizing  coils 
are  separately  wound  in  grooves  cut  in 
the  face  of  straight  or  curved  bars. 

Zigzag  Electromotive  Force. — An  elec- 
tromotive force,  the  curve  of  which  would 
have  the  general  form  of  a  zigzag. 

Zigzag  Lightning.— (1)  A  common  vari- 
ety of  lightning  flash,  in  which  the  dis- 
charge assumes  a  forked  or  zigzag  ap- 
pearance. (2)  Forked  lightning. 

Zigzag  Periodic  Electromotive 
Force. — A  zigzag  alternating  electro- 
motive force. 

Zigzag  Type  of  Periodically  Alter- 
nating Electromotive  Force. — An 
alternating  electromotive  force  whose 
graphic  representation  is  a  zig-zag  curve. 

Zinc  Battery. — A  battery  employed  in 
sending  zinc  currents  to  line, 

Zinc-Carbon  Voltaic  Cell. — A  voltaic 
cell  consisting  of  a  zinc-carbon  couple 
immersed  in  a  suitable  electrolyte. 

Zinc-Copper  Voltaic  Cell. — A  voltaic 
cell  consisting  of  a  zinc-copper  couple  im- 
mersed in  a  suitable  electrolyte. 

Zinc-Lead  Accumulator. — A  secondary 
cell  employing  plates  of  lead  and  zinc. 


Zin.] 


990 


[Zon. 


Zinc  Currents. — A  term  sometimes  used 
for  negative  currents. 

Zinc-Lead  Voltaic  Cell. — A  voltaic  cell 
consisting  of  a  zinc-lead  couple  immersed 
in  a  suitable  electrolyte. 

Zinc  Plating. — Electro-plating  with  zinc. 

Zinc  Sender. — A  device  employed  in  tele- 
graphic circuits  in  order  to  counteract 
the  retardation  produced  by  the  charge 
given  to  the  line,  in  which  a  momentary 
reverse  current  is  sent  into  the  line  after 
each  signal. 

Zincs. — A  general  term  applied  to  the  zino 
elements  of  voltaic  cells. 

Zincode  of  Voltaic  Ceil.— A  name  for- 


merly given  to  the  zinc  terminal  or  elec- 
trode of  a  voltaic  cell. 

Zootrope. — An  optical  toy  depending  on 
the  persistence  of  vision,  in  which  a  num- 
ber of  pictures  of  animals  are  so  caused 
to  pass  before  the  eye  as  to  produce  the 
appearance  of  the  motions  of  life. 

Zonal  Harmonic. — A  zonal  surface  har- 
monic. 

Zonal  Surface  Harmonic. — A  spherical 
harmonic  which  is  symmetrical  about  an 
axis. 

Zone  Lamp. — A  lamp  provided  with  a 
lens-shaped  chamber  so  as  to  cause  it  to 
throw  out  its  light  in  a  single  zone  only. 


IBtS 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


